SURGICAL MANAGEMENT OF HEART FAILURE

HEART FAILURE IN THE ELDERLY 0749-0690/00 $15.00 + .OO

SURGICAL MANAGEMENT OF HEART FAILURE

Mark S. Slaughter, MD, and Herbert B. Ward, MD, PhD

The prevalence of congestive heart failure (CHF) in elderly patients is increasing. Aging of the population, early reperfusion after acute myocardial infarction, improved medical therapy for heart failure, and enhanced management of valvular heart disease are all partially responsible for the increase in the absolute number of patients with CHF.lz4 Currently, there are approximately 5 million Americans with CHF and 400,000 new cases diagnosed each The incidence of CHF increases with age, peaking at 1 in 10 for those patients older than 85 years. Besides being associated with poor functional capacity and decreased quality of life, the diagnosis of CHF carries with it signrficant morbidity and mortality. Recent reports document mortality rates in excess of 40% within 2 years of initial diagnosis.68J08 The cost of treating CHF is also a concern and is estimated to be $10 to 40 billion per year.98 Although the vast majority of patients are man- aged using pharmacologic and rehabilitative strategies, there are subsets of patients for whom operative intervention offers enhanced quality of life and relative freedom from intense and restrictive medical regimens.lZ4

Chronic CHF results in myocardial hypertrophy and ventricular dilation in response to ventricular work This remodeled ventricle has a larger chamber with increased curvature, increased wall stress, increased myocardial energetics, and increased risk of The most common cause of CHF is ischemic heart disease followed by idiopathic dilated cardiomyopathy and hypertension. It is possible to reverse the remodeling process, restoring more normal geometry and function. Pharmacologic therapy including digoxin, diuretics, an- giotensin-converting enzyme inhibition, and P-blockers has been shown to improve symptoms and extend life, but there are subsets of patients who clearly

From the Mechanical Assist Device Program and Surgery for Congestive Heart Failure, Christ Hospital and Medical Center, Oak Lawn, Illinois (MSS); the Division of Cardio- vascular and Thoracic Surgery, Department of Surgery, University of Minnesota; and the Section of Cardiothoracic Surgery, Surgical Service, Veterans Affairs Medical Center, Minneapolis, Minnesota

CLINICS IN GERIATRIC MEDICINE

VOLUME 16 -NUMBER 3 AUGUST 2000 567

568 SLAUGHTER & WARD

benefit from surgical intervention. These groups include ischemic cardiomyopathy in patients with viable myocardial tissue with or possibly without adequate target vessels; aortic stenosis (AS) with or without coronary artery disease; aortic regurgitation with or without a dilated aortic root; mitral regurgitation (MR) associated with dilated or ischemic cardiomyopathy; remodeled ventricles in which operations that alter geometry provide improved function; end-stage cardiomyopathy in which transplantation is a viable alternative; and end-stage cardiomyopathy in which ventricular assist devices are used as (1) a bridge to transplantation, (2) a bridge to recovery, or (3) a permanent solution. This last is an exciting and innovative new field, which has enormous potential for improvement in quality and duration of life.

Cardiac surgery in patients over 70 years of age has changed dramatically during the past three decades. In 1971, only 2% of a large series of patients undergoing heart surgery at the Texas Heart Institute were over 70 years of age.& By 1982 the frequency had increased to 9%. In 1991, at the Minneapolis Veterans Affairs Medical Center, we reported that 31% of patients having open heart surgery were over 70 years of age.111 Of 572 open heart procedures performed in 1998 to 1999,265 (46%) patients were 70 years of age or older. This represents a startling shift in age demographics in the past 7 years. Although it is not euphemistic to say that physiologic age is more important than chronologic age, it is also true that patients look and act more like their chronologic age in the postoperative period.

A careful and extensive evaluation of elderly patients with cardiomyopathy is of critical importance if an honest appraisal of risk-benefit ratios is to be presented to those considered for surgical intervention. Most important is the consideration of comorbid diseases, especially cerebrovascular disease. The incidence of stroke in patients over age 70 years who had heart operations at the Cleveland Clinic between 1970 and 1982 was 4.5%.% From 1974 to 1983, the incidence of stroke in patients undergoing coronary artery bypass grafting (CABG) at The Johns Hopkins Hospital increased significantly with age.59 Patients aged 51 to 60 years had a 1% risk of stroke, whereas patients over age 75 years had a 7% risk. In this group, CHF was identified along with preoperative transient ischemic at- tacks and peripheral vascular disease as being predictive of postoperative stroke.

The increased risk of stroke in elderly patients undergoing open heart surgery is most commonly caused by severe atherosclerosis in the ascending aorta.78 Echo- cardiography, either by the transesophageal or the direct hand-held approach, is far superior to radiograph or direct palpation of the aorta in idenhfymg the soft protuberant mobile-type of aortic plaque most likely to embolize. Localization of these plaques allows the surgeon to alter cannulation techniques, alter graft place- ment, or even radically debride the aorta in an effort to reduce the incidence of

Because of the high incidence of stroke in the elderly, techniques of myocardial revascularization that avoid the use of cardiopulmonary bypass are gaining favor. The contribution of extracranial large artery stenosis to the incidence of stroke during cardiac operations and the timing of surgical management of these lesions remains controversial.61

ISCHEMIC CARDIOMYOPATHY

Evaluation

Tests that identlfy viable myocardium in patients with ischemic cardiomyopathy may predict positive outcomes following surgical revascularization and

SURGICAL MANAGEMENT OF HEART FAIL,URE 569

include positron emission tomography (PET), dobutamine echo, dobutamine M R imaging, thallium-201 single photon emission computed tomography, and Tc99m tetrofosmin single photon emission CT.43,48,52,63,83,84.86,90,94,102,120 These positive outcomes include improvements in mortality, New York Heart Association (NYHA) functional class, exercise capacity, quality of life, and left ventricular ejection fraction (LVEF). The different tests have different sensitivities and specificities in predicting these outcomes and may also be site specific. Test availability and local expertise are most important. Our own data suggest that a greater uptake of Wuo- rodeoxyglucose in the anterior wall of the left ventricle as assessed by PET is associated with improved postoperative ejection fraction.94 Others, however, have reported that failure to improve left ventricular function after coronary revascularization is not necessarily associated with worse outcomes.11o In the latter study, patients with no postoperative improvement in ejection fraction still had signhcant improvements in angina and heart failure scores and no difference in mor-

Clinical acumen still plays an important role in selecting patients with ischemic cardiomyopathy for surgical revascularization. According to the literature and in our own experience, when anginal symptoms predominate, when surgery is elective, and when there is evidence of viability, the results are uniformly good. The presence of overt heart failure in the absence of ischemic symptoms or evidence of viability, especially in an unstable (urgent) setting, identifies the highest- risk patient who is least likely to benefit from surgical revascularization. The absolute ejection fraction tends to be less important than these factors.

tality.

Revascularization

In the Coronary Artery Surgery Study, surgical revascularization for ischemic cardiomyopathy was associated with improved survival and quality of life? The surgical benefit was most profound in patients with ejection fractions below 26%, in whom there was a 63% 5-year survival with surgery versus 43% with medical treatment. Surgically treated patients experienced substantial symptomatic benefit compared with medically treated patients if their presenting symptoms were predominantly angina; however, there was no improvement in symptoms attributed primarily to heart failure.

Combined series of surgical revascularization in the elderly suggest hospital survival rates of 92% to 97% for patients over 70 years of age and 88% to 94% for patients over 80 years of age (Table 1). In our own series from 1988 to 1999, we had a 95% hospital survival in 946 patients 70 years of age and older and a 91% hospital survival in 67 patients 80 years of age and older. Other combined series reveal, on average, a two-class improvement in NYHA functional class in patients 80 years old and older (Table 2). Perioperative morbidity remains higher in the elderly and includes stroke, atrial arrhythmias in 20% to 60%, renal insufficiency in 5% to 13%, prolonged ventilatory support in 4% to 13%, reoperation for hem- orrhage in 5% to 12%, and CHF requiring inotropic support in 11% to 29%.4,49,56 Length of stay is prolonged si@cantly by advanced age, prior history of stroke, and the presence and severity of heart failure."

Despite the higher morbidity and mortality seen in elderly patients undergoing CABG, symptom relief and functional recovery are quite good. Multiple studies report signhcant reductions in angina and improvements in quality of life.25,56,82,118 In a group of 121 octogenarians undergoing CABG, 92% were discharged home, with only 6% requiring transfer to a nursing facility.27 Actuarial


Table 1. HOSPITAL SURVIVAL FOLLOWING CORONARY REVASCULARIZATION BY AGE

Author Year (Years) Number Deaths Survival (%) Age Hospital Hospital

Salomon et allw KO et aP2 Edwards et a149 Cane et aP7 Talwalker et alns Canver et a P Ward* Total

1989 2 75 469 1990 280 100 1991 270 121 1995 280 84 1996 280 100 1996 280 218 1997 270 733

1825

32 12 9 5 8 7

38 111

93.2 88 92.6 94 92 96.8 95 93.9

*Unpublished data, Minneapolis VA Medical Center (1988-1997), includes 11.3% reoperative cornary artery bypass grafting.

survival of patients discharged from the hospital is reported to be better than age- matched controls.1w In a series of 100 consecutive octogenarians undergoing CABG, the actuarial survival was 87%, 80%, 77%, and 73% at 1,2,3, and 4 years, respectively.118

Mortality statistics from recent series of elderly patients with CI-P vary con- siderably, most likely reflecting differences in the cause and severity of CHF and the extent of viable myocardium. In a series of 241 patients with CHF, 153 had PET assessment of viability and 88 patients had no viability study.% Of the 153 patients undergoing PET, 110 had viable tissue. These patients were referred for CABG and the operative mortality was 0.9%. The 43 patients without evidence of viability were treated medically. In contrast, 86 of 88 patients not studied with PET underwent surgery, and the operative mortality in this group was 19.8%. In another series, 93 elderly patients with ischemic cardiomyopathy were studied with PET." A total of 43 patients with a flow-metabolic mismatch (viable tissue) had surgical revascularization and 50 patients were treated medically. The surgical group had a 75% 4-year survival compared with 30% in the medically treated arm.

In an impressive series from France, Dreyfus et ale evaluated 50 patients with ischemic cardiomyopathy (mean LVEF of 23 2 6%) referred for heart transplantation. Twenty-eight of the 50 had evidence of viable myocardium by thallium scintigraphy. When the thallium results were negative, PET was performed and showed viability in an additional 20 patients. Myocardial revascularization was performed in 46 patients with one early death and three late deaths (mean follow- up of 18 months). These authors recommend CABG if myocardial viability is de-

Table 2. RESULTS OF CORONARY REVASCULARIZATION IN THE ELDERLY

Follow-up Patients period Evaluated NYHA Functional Class

Author Age (Months) (Number) Preoperative Postoperative p value

Freeman et a156 280 22.6 54 3.6 1.6 p < 0.001 KO et aP2 280 22 63 3.8 1.1 p < 0.001 Boucher et aP 270 31.2 266 3.2 1.6 p < 0.001

NYHA = New York Heart Association.

SURGICAL MANAGEMENT OF HEART FAILURE 571

tected by PET or thallium, and if the cardiac index is greater than or equal to 1.5 L/min/mz and the mean pulmonary artery pressure is less than 40 mm Hg.

Three recent studies help elucidate the criteria for offering surgical revascularization to elderly patients with ischemic cardiomyopathy. In the CABG Patch Trial, 900 patients with ischemic cardiomyopathy and symptomatic CHF or angina underwent surgical revascularization.ll Surgical mortality was 3.5% in 454 patients without clinical heart failure and 7.7% in 443 patients with NYHA class I to IV heart failure. CHF and redo operations increased the odds of dying by factors of 2.4 and 3.8, respectively, and length of stay was increased by 0.7 days per NYHA class. Another study of 210 patients with ejection fractions less than or equal to 20% demonstrated a 5-year actuarial survival of 73%.79 As in the CABG Patch Trial, mortality was signhcantly higher throughout follow-up in patients with congestive symptoms or redo bypass grafting. A third study analyzed 203 patients with CHF (NYHA functional class 111 to IV) and no angina who had CABG.8 Hospital mortality was 6% and 5-year survival was 59%. Seventy-five percent of patients had a mean functional improvement of 1.6 2 0.6 NYHA classes.

Total Arterial Revascularization. The patency of left internal mammary artery (LIMA) to left anterior descending artery (LAD) grafts approaches 95% at 10 years, whereas the patency of saphenous vein grafts to other coronary arteries is about 70% to 75% at 5 years. These data have led surgeons to use more arterial grafts to decrease the need for reoperation. Possible conduits include the right internal mammary artery, the right gastroepiploic artery, the inferior epigastric artery, and the radial artery. The inferior epigastric artery is not a good conduit and is rarely used. The gastroepiploic artery can be used to the posterior descending artery or distal LAD and appears to have satisfactory patency. The patency of the right internal mammary artery as a free graft is intermediate to the LIMA and saphenous veins and approaches 85% at 5 years. The radial artery is the current choice of many groups and has a 5-year patency of 83% to 87%.l,'05 The radial artery has a thick media and is prone to spasm, so calcium channel blockers are frequently used during surgery and postoperatively. Several groups are using the radial artery in combination with the LIMA to perform multiple distal anasto- m o s e ~ . ~ ~ ~ , ' ~ In these reports, early patency of the LIMA was loo%, but one group reported only an 82% patency of the radial anastomosis.117

Minimally Invasive Direct Coronary Bypass-Off-Pump Coronary Bypass. Minimally invasive direct coronary bypass (MIDCAB) refers to coronary artery bypass operations performed without cardiopulmonary bypass, usually through a small, left lateral thoracotomy incision. Most often the LIMA is anastomosed to the LAD. Off-pump coronary bypass (OPCAB) refers to CABG operations without cardiopulmonary bypass, but with a standard sternotomy. With this approach, multivessel CABG can be performed including a LIMA to the LAD. Both types of operation are also called beating-heart surgery. These operations were developed potentially to decrease stroke, postoperative confusion, operating time, blood us- age, ICU time, length of stay, and cost. The unknown has always been the anas- tomotic patency.

Beating-heart surgery is both feasible and effective. Some groups are doing the majority of their CABG surgeries in this manner, but there is a steep learning curve. In experienced hands, anastornotic patency is equivalent to conventional CABG, but anastomoses performed with the use of specialized instruments have a higher patency rate than those performed with conventional instrumenta- tion.",lffi MIDCAB is most often performed for a single vessel CABG, whereas OPCAB is usually used for two to three grafts. MIDCAB anastomoses take longer, but operating times, blood loss, length of stay, and cost are less than for conventional CABG.12,*4J05 Obesity, an intramyocardial or diffusely diseased LAD, chronic


obstructive pulmonary disease (COPD), unstable angina, and emergency operation are all relative contraindications to beating-heart surgery.44 No study has demonstrated a decrease in stroke rate or postoperative confusion. These techniques are particularly effective for redo surgery to the LAD or right coronary artery when only one or two grafts are required.

Angiogenesis

There is a subset of elderly patients with ischemic cardiomyopathy who do not have adequate target coronary vessels for conventional revascularization by either CABG or percutaneous techniques. Methods for promoting angiogenesis are currently in clinical trials. Two families of growth factors, fibroblast growth factor and vascular growth factor, are being studied. The growth factor is delivered to the myocardium by intra-artenal, perivascular, or intramuscular routes. Al- though some animal studies have shown improved cardiac function and decreased infarct size in animals, clinical trials to date have been inconclusive or showed no improvement.81

Equally controversial, and having a significant economic impact, are the techniques of transmyocardial laser and percutaneous myocardial laser revascularization. These techniques involve boring holes into the myocardium using laser in the hope that channels will form between the left ventricular cavity and venous sinusoids, thereby providing more blood directly to ischemic myocardium. Hu- man and animal studies have failed to show persistent channels, but there is evidence of angiogenesis. Frazier et a153 recently reported that myocardial perfusion increased by 20% in the transmyocardial laser group compared with medically treated patients as assessed by thallium scanning. Others have also reported improvement in Canadian Cardiovascular Society angina scores, increased exercise tolerance, improved quality of life, and increased survival free of cardiac events and cardiac-related hospitalizations, but no evidence of improved myocardial perfusion.5,26,~,87,107

Ventricular Remodeling

Aneurysmectomy. The classic corrective surgery for cardiomyopathy involving ventricular remodeling is aneurysmectomy? Volume-accepting aneurysms (dyskinetic segments) that cause CHF are usually anterior or apical because of occlusion of the LAD, and are repairable with low morbidity and mortality (8% to 16%, Veterans Administration database). The repair can be combined with en- docardial resection and cryoablation if ventricular tachyarrhythmias are present. A far more difficult and dangerous repair is required if the aneurysm is posterior and involves the mitral valve or papillary muscles. The prevalence of CHF caused by localized dyskinetic myocardium that is amenable to surgical resection is low when compared with idiopathic, globally ischemic, or infectious cardiomyopathy. Surgery for heart failure caused by these latter conditions is newer and less well understood.

Batista Procedure. Partial left ventriculectomy as treatment for dilated cardiomyopathy was first described by Batista et all5 in 1997 and was used in patients with idiopathic cardiomyopathy, regurgitant valve-induced cardiomyopathy, and Chagas’ disease. In this operation, reducing left ventricular diameter improves ventricular function (Laplace’s law). Initial enthusiasm for this procedure, which


showed a two-class functional improvement and a mean increase in ejection fraction of 13%, was tempered by an 8.7% early and 13% late mortality.116 More recent studies have shown a 3% early mortality, but 16% of patients needed ventricular assist devices postoperati~ely.~~ Survival at 1 and 2 years was 80% and 71%, respectively. Numerous less favorable reports, however, have led one investigator to conclude that the Batista procedure has hastened the demise of more patients than it has helped:24 and the Cleveland Clinic Foundation has recently discontin- ued partial left ventriculectomy as a treatment for CHF.

Dor Procedure. A less drastic procedure for the treatment of ischemic ventricular dilatation associated with CHF was proposed by Dor et al& in 1985. The procedure involves resection of akinetic apical and septa1 myocardium, cryoablation of ventricular ischemic zones, and reconstruction with a patch designed to restore ventricular geometry. Dor et al" reported a 12% mortality, a mean increase in ejection fraction of 8%, and a reduction in ventricular arrhythmias. These results were improved on by the Cleveland Clinic group who reported a 6% mortality, a mean increase in ejection fraction of 12%, a decrease in left ventricular volume, and no late failures?z

Dynamic Cardiomyoplasty. The idea of using skeletal muscle to replace or augment the failing heart is not new. Skeletal muscle was used in the 1930s to repair injured myocardium after infarction or trauma.16,a,62 It also has been used successfully to patch the ventricular wall following aneurysmectomy or resection of cardiac tumors.1o4 In 1959, Kantrowitz and M~Kinnon~~ reported the experimental use of electrically stimulated diaphragm to augment the heart or aorta in animals. Over the years, tremendous insights into the histologic and clinical differences between skeletal and cardiac muscles have been achieved. This growth of knowledge has allowed the clinical application of skeletal muscle not only as a biologic patch but also to augment the failing heart and as a potential power source for mechanical assist devices.

The first cardiomyoplasty was performed in 1985.29 Clinical trials were begun the same year and knowledge and experience continue to accumulate. With cardiomyoplasty, the latissimus dorsi muscle is mobilized and detached from its insertion on the back. The muscle is then passed into the chest after resection of a portion of rib, and wrapped around the outer surface of the left and right ventricles. Electrodes are placed on the heart and latissimus dorsi muscle for synchro- nization. The muscle is then converted to its fatigue-resistant state through elec- trical stimulation over a 10- to 12-week period. Shorter training periods may result in overworking the muscle before it has developed sufficient blood flow. This can result in fibrosis and loss of muscle function.89 At this point the latissimus dorsi muscle is ready for chronic stimulation.

Since 1985 more than 600 patients have undergone dynamic cardiomyoplasty.2 There has been a significant improvement in operative mortality since the initial phase I study. The hospital mortality is now less than 3% in the current phase III trial involving very sick patients. Clinical improvement has been noted in 80% to 85% of hospital survivors. Most patients have an improvement in NYHA functional class and other quality of life measures. Hemodynamically small but statis- tically s i w c a n t improvements in LVEF and left ventricular stroke work index have been documented.58 No improvements in cardiac index, pulmonary capillary wedge pressure, right ventricular ejection fraction, or maximal oxygen consumption, however, have been noted. In addition, although the overwhelming majority of patients have improvements in NYHA functional class and quality of life, there has been no sigruficant survival advantage over medical therapy alone.

Several different theories exist as to how dynamic cardiomyoplasty works. Initially, it was thought that there would be direct mechanical assistance (i.e.,


squeezing) that would assist the failing heart on a beat-to-beat basis. Clinically important direct systolic assist is hard to document, however, and may not be present at all.n Another potential mechanism involves a g'idling effect and the prevention of further dilatation and remodeling.*

It may be possible to use skeletal muscle as a power source for mechanical assist devices. Left ventricular assist devices (LVADs) have proved their clinical use as a bridge to transplant, in providing temporary support for postcardiotomy cardiogenic shock, and possibly as long-term therapy for end-stage heart failure. Thoratec Laboratories (Pleasanton, CA) has developed a novel method of using skeletal muscle to power an implantable LVAD (Fig. 1). The muscle-powered ventricular assist device uses linear contracting latissimus dorsi muscle connected to a hydraulic piston energy converter coupled to a Thoratec LVAD. The result is a completely implantable circulatory support system with no need for batteries or percutaneous drive line^.^' The muscle-powered ventricular assist device is designed as a possible alternative to transplantation.

compensation

Figure 1. A muscle-powered ventricular assist device using the linear contracting latissimus dorsi muscle, which is removed from its insertion at the humerus and reattached to a mechanical-to-hydraulic energy converter that provides hydraulic energy to power the ventricular- assist device. (Courtesy of Thoratec Laboratories, Pleasanton, CA.)


Passive Ventricular Constraint. A new device developed by Acorn Medical Systems (St. Paul, MN) is a soft cloth jacket that conforms to the outside of the ventricles and becomes a passive mechanical constraint that prevents ventricular remodeling. The device has had excellent success in animal models and phase I trials are underway in

AORTIC STENOSIS AND REGURGITATION

Evaluation

The assessment of elderly patients with heart failure and AS is challenging. In all cases, comorbid diseases, such as COPD, should be thoroughly evaluated because the symptoms may mimic those of AS. Direct measurement of the aortic valve gradient with determination of cardiac output by the Fick method and cal- culation of the aortic valve area by the Gorlin formula has been the gold standard for defining the severity of AS, but two-dimensional echocardiography has largely supplanted this technique. Recent reports indicate a high degree of correlation among several methods for determining aortic valve area, venfymg that direct planimetry using transesophageal echocardiography, the continuity equation and velocity-time integral ratio with transthoracic echocardiography, and the Gorlin formula are equally accurate and may be used inter~hangeably.~~~~~~'~~

Low-gradient AS in association with CHF is an especially difficult pr~blem.'~ When the mean gradient is high (e.g., > 30 to 50 mm Hg), aortic valve replacement (AVR) markedly decreases the gradient (e.g., to about 15 mm Hg), thereby im- proving left ventricular performance. Conversely, when the mean gradient is low, the reduction in gradient is less (e.g., from 25 to 15 mm Hg) and the performance benefit is decreased. In patients with low-gradient AS, it is important to determine if the ventricle is failing as a result of ischemic cardiomyopathy, in which case it no longer has the power to open a modestly stenotic aortic valve, or if the ventricle is failing as a result of severe AS. In the former case, AVR alone may not solve the problem. In the latter case, special consideration should be given to picking an aortic valve prosthesis with a very low intrinsic gradient. Dobutamine stress echocardiography may be helpful in distinguishing ventricular failure caused by AS from that caused by ischemic, alcoholic, hypertensive, or idiopathic cardiomyopathy, thereby predicting the response to AVR in patients with low-gradient AS.=

Results

Short- and long-term survival for elderly patients undergoing AVR is excellent, and equals or even exceeds survival in age- and sex-matched controls."' Hospital mortality is higher in the aged patient, however, and increases incre- mentally with advancing age.60 Hospital and 5-year survival rates for patients 70 years and older are 97% and 75%, respectively; comparable rates for patients 80 years and older are 86% and 70%.60J11 In a study of 322. patients 80 years and older undergoing AVR, Gehlot et a P reported independent predictors of operative mortality to be female gender, renal impairment, concomitant coronary bypass grafting, CHF, and COPD. In the study by Gehlot et al,@I the operative mortality was 18% in octogenarians undergoing combined CABG and AVR, as compared with 10% in those undergoing isolated AVR.


Prostheses

The choice of aortic valve prosthesis in elderly patients with heart failure and AS is relatively simple. The ideal prosthesis should have a low intrinsic gradient, be easy to implant, and not require anticoagulation. Stented porcine or bovine pericardial aortic valves are easy to implant, do not require anticoagulation, and have 93% to 100% freedom from valve deterioration at 10 years; however, they tend to have a relatively high resting gradient in smaller sizes.39,n,103 Stentless aortic valves have a low transvalvar gradient, a large effective orifice area, and good hemodynamic efficacy, but implantation requires greater technical exper- t i ~ e . ~ ~ Although the rate of valve deterioration in stentless valves is similar to that in stented valves, long-term survival has been reported to be better with the stentless valve probably as a result of greater regression in left ventricular mass.13,36,a,91 In patients who already require anticoagulation for other reasons, low-profile metallic valves are a good choice because they are simple to implant, have excellent hemodynamic profiles, and rarely fail.10,119

Repair

The indications for surgery in elderly patients with aortic regurgitation are similar to those in younger patients, and include evidence of symptomatic ventricular failure, left ventricular chamber dilatation, and falling ejection fraction at rest or with exercise. When severe aortic regurgitation is associated with a relatively normal aortic root, the choice of prosthesis is the same as for AS. It is not uncommon in elderly patients, however, for the regurgitation to be associated with loss of the sinotubular ridge and aortic root enlargement. In these cases, either a composite graft (metallic valve inserted into a dacron graft) or a homograft (human) valve and aorta can be used to replace the native valve and root. Recent reports indicate that in selected cases, the native aortic valve can be preserved and the aortic root replaced with a dacron graft.37,ffi,1z

MITRAL REGURGITATION

Patients with severe MR caused by intrinsic structural abnormalities of the mitral valve, including myxomatous degeneration, ruptured chordae, ruptured papillary muscle, endocarditis, or rheumatic valvular disease, should undergo valve repair or replacement based on standard indications. These patients have low operative morbidity and mortality with improved symptoms and long-term survival, especially in the absence of coronary artery disease. Generally, mitral valve repair should be performed as the first choice if technically feasible. If a mitral valve replacement is necessary it should be done with preservation of the annular-papillary muscle apparatus.

Patients with dilated cardiomyopathy and severe mitral insufficiency repre- sent a special subset with a very high mortality that is directly related to the degree of ventricular The mitral valve in these patients is structurally intact, but with abnormal leaflet coaptation resulting in a centrally located jet of regurgitation. Several factors contribute to poor leaflet coaptation, including ventricular dilatation and altered ventricular geometry, papillary muscle dysfunction, dilated mitral annulus, and restricted leaflet motion. The 1-year mortality for these patients has been reported to be as high as 70% with medical therapy


Until recently, cardiac transplantation was the only surgical alternative for these patients. Several centers, however, have now reported excellent outcomes with mitral valve repair. Bolling et a P reported on 100 elderly patients (mean age 73 years) with severe ischemic cardiomyopathy. The average preoperative ejection fraction was 32% and all patients had severe MR and NYHA class I11 or IV heart failure. All patients had CABG and a mitral ring annuloplasty. At 2 years, 90% of the patients were alive with minimal M R and NYHA functional class I or II. We recently reported on 30 patients (mean age 70 years) with severe ischemic cardiomyopathy (mean ejection fraction 25%; 77% with NYHA class IV failure) and MR. All patients had CABG and mitral ring annuloplasty. There were three (10%) operative deaths and long-term follow-up was complete up to 70 months. Repeat echocardiography revealed no recurrent MR. All survivors remain in NYHA functional class I with significant improvements in quality of life. The survival curve in this group versus that for transplantation is similar at 5 and 10 years. Most patients hb both of these series would have been excluded from transplantation based on Age alone.

Patients with nonischemic dilated cardiomyopathy and severe MR are a more difficult group. Because of the inherent myocyte abnormality, these patients have both right and left ventricular dysfunction. Although they have normal epicardial coronary arteries, s i m c a n t subendocardial ischemia is present, which contrib- utes to the myocardial fibrosis seen in later stages. Bolling et al’ reported the results of mitral valve reconstruction in patients with idiopathic dilated cardiomyopathy. These patients had severe MR, an average ejection fraction of 16%, and NYHA class III or IV heart failure. All patients had an undersized mitral ring annuloplasty and 23% required tricuspid valve repair. There was one operative death that was secondary to right heart failure, and one patient eventually required cardiac transplantation. One- and 2-year actuarial survival rates were 82% and 71%, and surviving patients were in NYHA functional class I or 11.

Recently, we reported on eight patients with dilated cardiomyopathy and severe MR214 All patients had NYHA class IV failure, pulmonary hypertension, ejection fractions less than 20%, and required intermittent or continuous intrave- nous inotropic support preoperatively. All patients had a mitral ring annuloplasty, but required an LVAD for failure to wean from bypass. Duration of LVAD support ranged from 4 to 16 weeks. At the time of device removal all patients underwent a modified ventricular reduction procedure. All patients were alive at 1 year and remained in NYHA class I with significant improvements in quality of life. For patients with severe M R who are not transplant candidates, these procedures offer hope for improved quality of life and long-term survival.

CARDIAC TRANSPLANTATION

Since the first successful heart transplant by Barnard14 approximately 30 years ago, many refinements have been made in recipient and donor selection, immu- nosuppression, identification of rejection, and treatment of rejection and infection. The surgical procedure is now routinely performed with reproducible results in many centers around the world. In the United States alone, there are about 135 programs that offer cardiac transplant services. Cardiac transplantation continues to be the surgical treatment of choice for patients with end-stage CHF. Also, it is the standard by which alternative surgical therapies for CHF are evaluated and compared.


The number of heart transplants performed in the world plateaued in the early 1990s at approximately 4000 per year, and has been declining since 1995 (Fig. 2). In the United States, volume peaked at 2500 per year and has remained constant because of lack of donors. Clearly, these numbers do not come close to meeting the needs of people dying from heart failure (over 40,000 per year in the United States alone). Attempts have been made to standardize criteria for listing patients for heart transplantation. The latest effort emphasizes the need for maximal state- of-the-art medical therapy combined with an objective assessment of the patient's functional capacity. Exercise testing with peak oxygen uptake is still the best objective method for predicting outcome in patients with severe CHF.% Patients with the lowest probability of survival with continued medical therapy are potential candidates for transplantation. Specific selection criteria vary between centers, but in general include the presence of severe symptomatic CHF despite maximal medical therapy and no contraindications to transplantation.

The most common causes of CHF among patients referred for transplantation are coronary artery disease and nonischemic dilated cardiomyopathy. The majority of patients undergoing cardiac transplantation are between the ages of 35 and 64 (Fig. 3). Survival after transplantation is 79% at 1 year with a constant mortality of 4% per year thereafter (Fig. 4). Approximately 5% to 10% of patients die awaiting transplant. The most common cause of early death following transplantation is donor organ dysfunction. Intermediate-term deaths (i.e., 1 to 3 years posttransplant) are usually related to rejection or infection. Cardiac transplant recipients exist on a fine line between overimmunosuppression and underimmunosuppression. Underimmunosuppression can result in graft rejection, whereas oversup- pression increases susceptibility to opportunistic infections. The risk of rejection is greatest within the first year and diminishes with time. Late deaths (>3 years

Figure 2. Heart transplant volumes and donor age by year. (Reprinted from Hosenpud JD, Bennett LE, Keck BB, et al: The Registry of the International Society of Heart and Lung Tranplantation: 16th official report-1999. J Heart Lung Transplant 18:611, 1999; with permission from Elsevier Science.)


20

0

Figure 3. Age distribution of heart transplant recipients. (Reprinted from Hosenpud JD, Ben- nett LE, Keck BB, et al: The Registry of the International Society of Heart and Lung Trans- plantation: 16th official report-1 999. J Heart Lung Transplant 18:611,1999; with permission from Elsevier Science.)

I I I I I I I I I I I I I I

posttransplant) are often the result of graft coronary artery disease or malignancy. Graft coronary artery disease tends to be diffuse and obliterative and is present in approximately 50% of patients by 5 years.lZ1 Malignancies account for approximately 19% of late deaths and are the second most common cause of death after 4 years.

Figure 4. Total heart transplant actuarial survival rate among 43,936 patients. Half-life = 8.8 years; conditional half-life = 11.5 years. (Reprinted from Hosenpud JD, Bennett LE, Keck BB, et al: The Registry of the International Society of Heart and Lung Transplantation: 16th official report-1999. J Heart Lung Transplant 18:611, 1999; with permission from Elsevier Science.)


Patients chosen for transplantation are those at greatest risk for death from CHF. As a result, these patients derive the greatest survival benefit from the procedure. Approximately 50% of all cardiac transplant recipients are alive at 10 years and the majority return to NYHA class I functional status. Registry data indicate that about 90% of patients consider themselves to have no activity limitations at 1-year follow-up, which represents a sigruficant improvement in quality of life for these individuals.@

Older age, although not an absolute contraindication, is a relative contraindication to transplantation in most programs. Physiologic age is more important than chronologic age, however, and the majority of programs evaluate elderly patients on a case-by-case basis. Despite efforts to consider elderly patients for transplantation, only 8.4% of all cardiac transplants are in patients over the age of 65.@ Based on registry data, advancing age is associated with increased mortality risk. Overall survival after transplantation declines with each 10-year increment in age, and there is a clinically sigruficant decrease in survival for patients older than 65 years (Fig. 5). Despite this seemingly unavoidable decrease in survival for elderly patients, many centers continue transplantation in patients over 60 years of age with very good results. These experienced centers report 1- and 5-year survival rates equal to or better than in the younger age g r o ~ p s . ~ , ~ , ~ ~ Although few centers perfom transplantation in patients over age 70, Blanche et aPo reported on six patients 70 years of age or older, all of whom were alive and clinically well at a mean follow-up of 12 months. In addition to excellent survival statistics, these centers also document improved quality of life for their elderly transplant recipients. Moreover, Chang et a130 have provided objective evidence of enhanced physical performance by using cardiopulmonary exercise testing to show that improved functional status and exercise capacity are related to increases in peak oxygen consumption.

Cardiac transplantation has evolved into a safe, reliable, and reproducible surgical option for patients with end-stage CHE71 The number of patients who are

2 .o

1.5 .- +I

(II

U : 1.0

8 0.5

0 I I I I I I I I I

20 25 30 35 40 45 50 55 60 65 70 Recipient age (y)

Figure 5. Five-year mortality risk after heart transplantation by increasing recipient age (adults, multivariate analysis). (Reprinted from Hosenpud JD, Bennett LE, Keck BB, et al: The Registry of the International Society of Heart and Lung Transplantation: 16th official report- 1999. J Heart Lung Transplant 18:611, 1999; with permission from Elsevier Science.)


potential candidates for cardiac transplantation, however, is much greater than the number of donors. This has provided the impetus for the development of implantable mechanical assist devices, innovative uses of auxiliary muscles, myocyte cell transplants, and chronic mechanical unloading of the left ventricle to promote myocardial recovery.

MECHANICAL CIRCULATORY SUPPORT

Since the development of the cardiopulmonary bypass machine by Gibbon in the 1950s there has been an ongoing effort to devise a more portable, safe, and efficient means of supporting the failing human heart. The first clinical implantation of an LVAD was in 1963M and the first successful implantation occurred in 1966 when a patient was supported for 10 days after a failed double valve replacement.41fM The intra-aortic balloon pump, introduced clinically in 1967,” has been used extensively with excellent clinical outcomes in patients with reversible acute heart failure. In 1978, the first patient was successfully bridged to cardiac transplantation with a ventricular assist device.” Over the years sigruficant improvements have been made in implantable mechanical circulatory support systems. Many patients with end-stage CHF have been supported for over a year and because of the portability of the current systems some patients may return home or even to their jobs while awaiting transplantation.

Bridge to Transplantation

As cardiac transplantation became more successful it placed great demands on the limited supply of donor organs. This created the need to support these patients successfully until a donor heart became available. One indication for LVAD support is bridge to transplantation. Years of experience have demonstrated that the LVAD not only provides hemodynamic support but also improves function of other organs and allows for physical and nutritional rehabilitation. Overall, approximately 70% of LVAD patients are successfully bridged to transplantation with an 80% actuarial survival at 1 year.19 Three systems currently approved by the Food and Drug Administration for bridge to transplantation are (1) Novacor implantable LVAD, (2) HeartMate pneumatic IP-LVAD and HeartMate VE-LVAD, and (3) Thoratec extracorporeal VAD.

The Thoratec VAD (Thoratec Laboratories, Pleasanton, CA) is a pneumatically driven pump with a stroke volume of 65 mL and a maximum pump output of approximately 7 L/min (Fig. 6). The pump chamber is a smooth seamless polyurethane sac and it uses mechanical tilting disc valves to ensure unidirectional flow. The pump itself is paracorporeal and rests on the abdominal wall that allows direct inspection of the actual filling and emptying of the pump. Anticoagulation with warfarin is required to maintain an International Normalized Ratio (INRI of 2.5 to 3.5. The Thoratec VAD is versatile and can be used for either left or right ventricular support. Also, because of its paracorporeal position, it can be used in adolescents and small-stature adults with body surface areas as low as 0.8 m2. The Thoratec VAD is approved by the Food and Drug Administration for myocardial recovery after failure to wean from cardiopulmonary bypass and for bridge to transplantation, and it has been implanted in more than 800 patients.

The HeartMate left ventricular assist systems (Thermo Cardiosystems, Wo- burn, MA) are driven either pneumatically (IP) or electrically (VE). The HeartMate VE is shown in Figure 7. The pump is made from a titanium alloy with a textured


Figure 6. Thoratec extracorporeal ventricular assist device. (Courtesy of Thoratec Labora- tories, Pleasanton, CA.)

polyurethane diaphragm. It has a maximum stroke volume of 85 mL and a maximal flow of 10 to 11 L/min. It uses porcine bioprosthetic valves and requires no coumadin under normal conditions. The pump is placed either intra-abdominally or in the preperitoneal space. This requires that the patient has sufficient body size (body surface area > 1.5 mz) to allow implantation. Many patients with the VE model are able to return home where they can continue their rehabilitation while awaiting transplantation. HeartMate LVADs have been used in more than 1500 patients.

The Novacor LVAD (Baxter Healthcare Corp., Oakland, CA) was the first electrically powered, totally implantable ventricular assist system (Fig. 8). It uses bioprosthetic valved conduits and the pumping chamber is a smooth polyurethane sac. The pump is implanted beneath the abdominal wall musculature in the left upper quadrant. The Novacor LVAD requires anticoagulation with warfarin and has similar size requirements as the HeartMate (body surface area > 1.5 mz). The Novacor LVAD has been implanted in over 1000 patients and 60% of recent recipients have returned home after device insertion.lM

Bridge to Recovery

Once an LVAD has been implanted as a bridge to transplantation the duration of support is determined predominantly by donor organ availability. Many pa-


Air Vent System Controller

Figure 7. HeartMate implantable vented electric left ventricular assist device (LVAD). (Cour- tesy of Therrno Cardiosystems, Inc., Woburn, MA.)

tients have been supported for 6 months or more and some have remained on the device for over a year. When some of these patients finally underwent cardiac transplantation, it was noted that the function of the native heart appeared to have improved. Subsequently, many investigators began to study the effect of chronic mechanical unloading on the native heart. Improvements that occur during chronic mechanical unloading with an LVAD include a decrease in myocardial cytokines, decreased neurohormonal activity, upregulation of b-receptor density, normalization of calcium transport of the sarcoplasmic reticulum, and an improvement in myocyte h i ~ t ~ l ~ g y . ~ , ~ * , ~ , ~ ~ , ~ , ~ ~ ~ Frazier and Myers” and Hetzer et aF7 have both recently reported their experiences with LVAD removal after myocardial recovery in nontransplanted patients. Remarkably, the majority continue to have no functional limitations with follow-up extending beyond 2 years in some patients. Despite these findings, there remain several sigruficant issues with bridge to recovery. One is idenhfymg clinical, hormonal, or histologic markers that are predictive of sustained recovery of the native heart. Also, the best approach to wean-


Figure 8. Novacor implantable left ventricular assist device. (Courtesy of Baxter Healthcare Corp., Oakland, CA.)

ing the LVAD and reloading the native ventricle is still under investigation. It is clear that some patients with severe CHF have s i d c a n t myocardial recovery while being supported with an LVAD. Iden-g these patients permits device removal, thereby avoiding or at least delaying the need for cardiac transplantation.

Permanent Implantation

As noted previously, there are up to 70,000 patients per year who are potential candidates for mechanical assist device support. The majority have contraindications to cardiac transplantation, however, making them also ineligible for LVAD implantation. Encouraged by data from the bridge to transplantation population, trials are now underway to evaluate the permanent implantation of LVADs. Per- manent implantation or destination therapy could be a potential alternative to cardiac transplantation. This would sigruficantly relieve the current donor organ shortage and provide a possible solution for those patients who are not cardiac transplant candidates but are dying of heart failure.


The first trial to evaluate permanent implantation is the Randomized Evalu- ation of Mechanical Assistance for the Treatment of Congestive Heart Failure. This is a multicenter study supported by the National Heart, Lung and Blood Institute. It is a prospective randomized trial comparing optimal medical therapy versus permanent LVAD implantation in patients with end-stage CHF who require but do not quahfy for cardiac transplantation. Patients randomized to LVAD therapy receive a HeartMate VE device. The trial is currently ongoing and no results are available.

The only other current study is the Pneumatic EeartMate Assist as Destina- tion Evaluation (PHADE) trial. PHADE is a single-center, nonrandomized safety study of permanent implantation of the HeartMate IP-LVAD. This study is open to 50 patients with end-stage heart disease who are not transplantation candidates. The PHADE trial is also ongoing with no results available.

Future Mechanical Assist Devices. Axial blood flow pumps have been successfully developed and will soon come to clinical trial. Axial flow pumps have several advantages over the currently available implantable LVADs. The Jarvik 2000 axial flow pump is shown in Figure 9 with a schematic diagram of its implantation in Figure 10. As can be seen these pumps are much smaller than those currently available, allowing implantation in patients with a body surface area less than 1.5 m2. Also, the simple design results in few moving parts, a small surface area for the blood-pump interface, and no valves. Axial flow pumps currently approaching clinical application include the Jarvik 2000 axial flow impeller, United States Surgical axial flow cannula pump, Nimbus/University of Pittsburgh axial flow system, and the DeBakey/NASA axial flow pump.

The HeartSaver VAD (Fig. ll), a fully implantable LVAD for long-term support, is also nearing clinical trials. Several innovative developments by the team at the University of Ottawa Heart Institute make this a very promising device. All percutaneous lines have been eliminated, making the device truly totally implantable and avoiding the infectious complications associated with percutaneous lines. The need for percutaneous venting has also been eliminated by developing a volume displacement chamber integrated into the unit, which also helps with heat dissipation. The pump is powered by a transcutaneous energy transfer system

Figure 9. Jarvik 2000 (Jarvik Heart, Inc., New York) axial flow impeller pump. (Courtesy of 0. H. Frazier, MD, Texas Heart Institute, Houston, TX.)


Figure 10. Implantation of the Jarvik 2000 with apical left ventricular inflow and outflow by dacron graft anastomosed to the descending thoracic aorta. Electric cables are delivered percutaneously through the abdominal wall and attached to the power supply. (Courtesy of 0. H. Frazier, MD, Texas Heart Institute, Houston, TX.)

Figure 11. Connection of the developed device to the natural heart and systemic circulation. (Courtesy of T. Mussivand, Ottawa Heart Institute, Ottawa, Canada.)


and the device can be monitored at a remote location by a biotelemety system, which uses infrared communication modules. These enhancements offer many advantages to the patient who needs long-term mechanical assistance and wants an untethered active lifestyle.

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Address reprint requests to Herbert B. Ward, MD, PhD

Cardiothoracic Surgery (112) Veterans Affairs Medical Center

One Veterans Drive Minneapolis, MN 55417

e-mail: wardx0200tc.umn.edu

SURGICAL MANAGEMENT OF HEART FAILURE

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