Value of a radionuclide limb blood flow technique in the assessment of percutaneous balloon and...

European Journal of

Nuclear Medicine Original article

Value of a radionuclide limb blood flow technique in the assessment of percutaneous balloon and dynamic angioplasty A.A. Gehani 1, P. Thorley 2, K. Sheard 2, S. Ashley 1, S.G. BrookL and M.R. Rees ~

I Cardiac Research Unit and 2 Radionucl ide Unit, Ki l l ingbeck Hospital, Leeds LS14 6UQ, UK

Received 13 Apri l 1991 and in revised form 3 August 1991

Abstract. In a prospective study, a radionuclide technique was used to evaluate the limb blood flow (LBF) changes in 30 patients undergoing dynamic (n= 15) or balloon (n= 15) angioplasty for arterial occlusions or stenoses, respectively. The results were compared with Doppler Ankle Brachial Index (DABI) and treadmill exercise tests. Whilst LBF values (ml of blood flow per 100 ml of limb volume per rain) were significantly lower in limbs with arterial occlusion than stenosis (4.5 _+ 0.46 and 6.4_+ 0.74, respectively; P < 0.05), DABI provided no discrimination. Immediately after balloon angioplasty, there was a fall in DABI, from 0.60___ 0.05 to 0.47 _+ 0.04 (P<0.05), which rose 24 h later to 0.73_+0.02 (P< 0.01). Following dynamic angioplasty, DABI improved from 0.60_+0.05 to 0.66+0.02 (P<0.05). At 3 weeks, the LBF improved from 4.6___0.66 to 11.1-t-0.53 (P< 0.001) following dynamic angioplasty and from 6.2+ 0.68 to 8.53+0.81 (P<0.001) following balloon angioplasty. "Normal" LBF (> 10 ml/100 ml per rain) was achieved in 80% of patients who underwent successful dynamic angioplasty but in only 36% of the balloon group (P<0.05,)~Z-test). Reproducibility of repeated LBF measurements in control limbs was superior to that of DABI. This was indicated by a lower coefficient of variation, 13.8% compared with 25.2%, and a higher correlation coefficient, r=0.79 compared with 0.27. Treadmill exercise tests were invalid or impossible in 30% of all occasions. There was a good correlation between the improvement in maximum walking distance on the treadmill and that in LBF (r=0.84, P<0.05). In conclusion, measurement of LBF using radionuclide technique is a potentially valuable method for the assessment of patients undergoing percutaneous angioplasty. LBF results are reproducible and correlate well with the improvement in walking ability, which cannot always be assessed objectively.

Key words: Angioplasty - Radionuclide limb blood flow

Eur J Nucl Med (1992) 19:6-13

Offprint requests to: A.A. Gehani

Introduction

Balloon angioplasty is an established technique for non- operative treatment of stenotic arterial disease. In chronic total occlusions, however, persistent attempts to cross the lesion with a guide wire can be associated with vascular complications (Casarella 1986). Several laser and dynamic angioplasty techniques to overcome this prob- lem are under investigation. The Kensey catheter is an atherectomy device which is potentially useful since it does not require the leaf of a guide wire (Kensey et al. 1987).

Objective assessment of patients undergoing angioplasty is essential, particularly when the results of new techniques are compared. Many studies depend almost entirely on angiography and Doppler pressure measurements alone. Whilst it is a handy bedside technique, Doppler is relatively insensitive and suffers from poor reproducibility (Baker et al. 1980). It assesses the pressure in the main artery but gives no indication as to the collateral flow. The equipment for venous occlusion plethysmography is not widely available, and the signal to noise ratio is relatively poor, particularly in patients with low flow (Kester et al. 1981). The clearance rate of an intramuscular injection of radionuclides has been used by Angelides et al. (1978). Although a sensitive technique for the detection of peripheral vascular disease, blood flow is difficult to quantify. It also reflects the local vasculature around the injection site rather than that of the whole limb.

A radionuclide technique to overcome some of these problems was described by Parkin et al. (1986). Its value in the assessment of patients with intermittent claudication has been demonstrated (Wilkinson et al. 1987). In the present study, the technique was used to evaluate patients undergoing unilateral balloon or dynamic angioplasty. The limb blood flow (LBF) results were compared with those of Doppler and treadmill exercise tests. Finally, the reproducibility of the blood flow and Doppler measurements was examined in the untreated "control" limbs.

© Springer-Verlag 1992

Patients and methods

A total of 41 patients with peripheral vascular disease were recruit- ed and followed up for 3 months after balloon or dynamic angioplasty. The culprit lesion of each patient was treated. Balloon angioplasty was used to dilate 15 stenotic lesions (3 iliac, 8 femoral and 4 femoro-popliteal arteries) in 15 patients (11 male and 4 fe- male). Fifteen patients (all male) underwent dynamic angioplasty for total arterial occlusions (1 iliac, 6 femoral and 8 femoro-popliteal arteries). Eleven underwent a further vascular procedure to the same or other limb during the follow-up period and were therefore excluded.

In addition to clinical assessment and bilateral angiography, all patients had Doppler pressure and LBF measured and their walking ability assessed by treadmill exercise tests. All three measurements were performed in both legs prior to angioplasty and at 3 weeks and 3 months afterwards.

Limb bloodflow. The details of the procedure for LBF measurement have been described elsewhere (Parkin et al. 1987). In summa- ry, the patient's legs were placed over a gamma-camera (Siemens, Orbiter ZLC 7500) and prevented from moving by a foot-plate which also ensured identical positioning during subsequent follow- up. Marks were made on the skin to indicate the upper limit of the camera's field-of-view. A 12-cm wide blood pressure cuff was placed below each knee and was rapidly inflated to supra-systolic pressure (300 mmHg) to induce hyperaemia and isolate the blood pool in the legs from the rest of the body. Then 400 MBq of technetium-99m human serum albumin [C.I.S., UK] was injected into the upper pool via a cannula pre-placed in the antecubital vein. Three minutes were allowed to ensure equilibrium of the radionuclide in the body pool. Five seconds before deflation of the cuffs, a venous sample was taken, and data acquisition was started at one frame per second for 100 s. The acquisition during these 5 s was intended to ensure that no labelled bIood had leaked into the legs whilst the cuffs were still inflated. The cuffs were then suddenly deflated, and the rush of labelled blood into the legs was picked up by the camera. The area of interest was determined, and the images were analysed using a dedicated computer (Nodec- rest, System III). This produced a time-activity curve for each limb. The least squares gradient (x = counts, s - i s - 1) was calculated from the initial linear phase. A blood sample was placed in front of the camera to measure its radioactivity (y=coun t s - s - lml -1 ) , which was corrected for background activity. The blood flow was calculated from x/y x 60 (ml/min). Finally, each leg was immersed in water up to the skin mark to measure the volume of the limb. The LBF was expressed as ml/100 ml of tissue per rain.

Doppler ankle/brachial index. This was carried out using a non- directional Doppler flow device (Doppler-500). A blood pressure cuff was placed above the ankle and inflated to supra-systolic pressure. The Doppler probe was placed over the artery, and the cuff was deflated gradually at a rate of approximately 2 mmHg/s. The arterial pressure was noted at the first appearance of the Doppler flow signal. For the brachial pressure, the higher reading of both arms was recorded. Dorsalis pedis and posterior tibial artery pres- sures were measured at the ankle, and the higher value was used to calculate the DABI. All measurements were repeated twice, and the mean value was used.

Treadmill exercise test. This was carried out using a treadmill exercise machine (Marquette II) at a constant speed of 3 km/h, an incline of 10% and an ambient temperature of 22o-25 ° C. Patients were asked to report immediately the onset of pain in each leg.

If the patient stopped for any reason other than claudication, this was also noted. All tests were performed in the morning to avoid possible circadian variations. Most patients had already stopped smoking as a prerequisite for angioplasty; those who continued were required not to smoke on the day of the test.

Angiography. Angiography was performed through the transfemo- ral route using 5 Fr pig-tail catheter placed in the lower aorta. Lesions were classified as stenoses (>60% reduction in arterial diameter) or occlusions with no antegrade filling of the artery. Late films were used to measure the length of the occlusions. Each of the three vessels to the calf, namely the anterior and posterior tibial and peroneal, was scored as: 0 = totally occluded, 1 = patent but has significant stenotic disease (>60% stenosis), 2=patent with no significant stenotie disease. Therefore, 0 indicated that all three vessels were occluded and 6, all three vessels were patent with no significant stenosis.

Control limbs. In all patients, angioplasty was carried out on the limb with predominant symptoms. The other side acted as "con- t rol" to assess the reproducibility of Doppler and LBF measurements.

Angioplasty. Both balloon and dynamic angioplasty procedures were carried out percutaneously under local anaesthesia. Balloon angioplasty of stenoses (n = 15) was carried in the conventional "on-the-wire" technique. In all total occlusions (n = 15), however, an attempt to cross the lesion with a "steerable" guide wire had failed. Dynamic angioplasty was carried out using size 8 Fr (2.7 mm) Kensey catheter at a cam speed of 40000-80000 rpm. Fluid was injected at high pressure to exit under the cam as a strong vortex. The technique was approved by the ethical commit- tee, and informed consent was obtained from all patients. Recanal- ised occlusions were subsequently dilated using an appropriate size balloon.

All but two patients received 75 mg aspirin (once daily) and 100 mg dipyridamole (three times a day) starting I day before the procedure and continuing throughout the period of follow-up.

Statistics. All values were expressed as mean_+ SE of the mean. "Pa i red" and "unpaired" Student's t-tests were used to estimate the statistical significance of changes in measurements made in the same or independent groups, respectively. Proportional differ- ences between independent samples were tested using z~-test. One- way analyis of variance (ANOVA), coefficient of variation and correlation coefficient were applied to assess the reproducibility of LBF and DABI measurements in the "cont ro l" limbs, with P < 0.05 being considered significant.

Results

Angiography

T h e l eng ths o f the cu lp r i t o c c l u s i o n s a n d s t enoses w e r e

8.1___1.2 c m a n d 5.0_+0.7 cm, r e spec t ive ly ( P < 0 . 0 5 ) .

Success fu l d y n a m i c a n g i o p l a s t y (de f ined as r e c a n a l i z a -

t i on o f t he ful l l e n g t h o f the o c c l u d e d s e g m e n t ) was

a c h i e v e d in 10 o f 15 o c c l u s i o n s (Fig . 1), r e su l t i ng in a f ina l m e a n d i a m e t e r s tenos is o f 4 0 . 5 % _+3.1%. In 3 pa -

t ients , o n l y p a r t o f the o c c l u d e d s e g m e n t was r ecana l -

ised. In 2 a d d i t i o n a l pa t i en t s , ea r ly p e r f o r a t i o n p re -

c l u d e d a n y r e c a n a l i s a t i o n . T h e r e was n o c o r r e l a t i o n be-

A B

Fig. l A, B. Angiogram of a total occlusion of the superficial femoral artery before (A) and after (B) successful dynamic angioplasty

tween the length of the occlusion and the result of dynamic angioplasty.

Adequate balloon dilatation (final diameter stenosis of less than 60%) was achieved in 12 of 15 stenoses, reduced from 81.4%+3.7% to 49.6%-+2.4% (P< 0.001). Overall, there was no significant difference in the run-off score between successfully and unsuccessfully treated lesions, 3.57 _+ 0.41 and 3.86_+ 0.24, respectively.

Limb blood flow

A typical radionuclide time-activity curve before and after successful angioplasty is shown in Fig. 2A, B. Us- ing this technique, 10 ml/100 ml per rain has been shown to be the lower limit of LBF in normal limbs (Parkin et al. 1987). Prior to angioplasty, 80% (/2/15) of stenoses and all occlusions had a LBF of less than 10 ml/ 100 ml per min. Only 20% (3/15) of control legs exceeded this threshold.

LBF was significantly lower in treated than control limbs, 5.4_+ 0.46 and 6.85 -+ 0.53, respectively (P < 0.05). It was also lower in limbs with arterial occlusion than stenosis, 4.5 _+ 0.46 and 6.4 -+ 0.74, respectively (P < 0.05). Whilst over half (8/15) the stenotic lesions were associated with an LBF > 6 ml/100 ml per min, only 2/15 (13%) occlusions exceeded this level (P<0.05,)~Z-test) (Fig. 3). This was not due to a difference in the number of patent small vessels to the calf, since the run-off score was not significantly different between the two groups (4.2 -+ 0.38 and 3.45 _+ 0.25, respectively).

Before angioplasty, there was a poor correlation between LBF and run-off score (r = 0.15, NS). However, when the culprit lesions were successfully treated, the correlation improved (r = 0.69, P < 0.01).

LBF improved following successful dynamic and balloon angioplasty from 4.6___0.66 to 11.1_+0.53 (P< 0.001) and from 6.2_+0.68 to 8.53_+0.81 (P<0.001), respectively (Fig. 4). Some 80% (8/10) of patients who had undergone successful dynamic angioplasty and 36% (4/11) of patients in the balloon group achieved a "normal" LBF of greater than 10 ml/100 ml per min at 3 weeks (P<0.05, Z 2 test). By 3 months, there was a fall in LBF of the balloon group from 8.5_+0.9 to 7.1 __ 0.84 (16%, P<0.05). A smaller (10%) fall was observed following dynamic angioplasty during the same period, from 11.1 -+0.53 to 9.97___0.80 (NS).

In 3 patients (2 in the balloon and 1 in the Kensey catheter group), there was no significant change in LBF despite a good angiographic result. Early re-angiography demonstrated no evidence of re-occlusion. The run-off score was less than 4 in all 3 patients. There was no significant change in either LBF or DABI following unsuccessful dynamic or balloon angioplasty.

Pain during cuff inflation was infrequent and was only reported by 3 patients at 3 weeks, all of whom had suffered aterial perforation during dynamic angioplasty. In 2/90 occasions, LBF was invalidated by a leak of the radionuclide into the leg compartment whilst the cuffs were still inflated. This was indicated by a high "take-off" of the time activity curve during the 5 s of screening prior to the release of the cuffs (Fig. 2 C). The test had to be repeated a few days later.

Changes in limb volume

Prior to angioplasty, there was no significant difference between the volume of treated and control limbs, 2.84 + 0.86 and 2.85_+0.80 1, respectively, nor between limbs

V" 12

c o s B '

i i i i j ! I i

10 20 30 40 50 60 70 80 90 frames

cps C 8. YO~j~

I ,, i I i

liO 20 310 40 510 610 70 80 9; seconds

Fig. 2A-C. Time-activity curve of limb blood flow before A and after B successful dynamic angioplasty of an arterial occlusion. This resulted in considerable increase in the initial gradient (cps, counts/s). In patient C there was a high "take-off" of counts at zero time, indicating premature leakage of the radionuclide into the limb before the cuffs were released, which emphasises the value of starting data acquisition ahead of cuff release

10

L.B.F ( m l \ l OOml \min )

m

t;

O c c l u s i o n s S t e n o s e s

Fig. 3. Limb blood flow (LBF) values in patients with arterial stenoses and occlusions. The mean results were significantly different. The majority of occlusions were associated with LBF <6 ml/ 100 ml per rain

p <0.05 t

LBF ( m l / 1 0 0 m l / m i n ) 14

N = 2 1

n = l O

n = l l

12

10

cps A

10 20 30 40 50 60 70 80 90 frames

0 I I I

Pre 3 Wks 3 bits

Fig. 4. Follow-up results of limb blood flow (LBF) in patients who had successful balloon (*) and dynamic (o) angioplasty. There was a greater improvement in LBF following recanalisation of total occlusions. Wks, weeks; Mts, months

with arterial stenosis or occlusion, 2.82 ± 0.10 and 2.86 __+ 0.08 l, repectively. After angioplasty, however, the l imb volume in the dynamic angioplas ty g roup increased in 9/15 (60%) patients, f rom 2 .86±0 .11 to 3 . 0 3 ± 0 . 1 5 1 ( P < 0.05; mean increase o f 6% and m a x i m u m o f 21%).

This increase in limb volume caused a p ropor t iona l but artificial fall in the L B F calculated per unit volume o f tissue. The limb volume returned to normal at 3 months . In contrast , the volume o f ba l loon- t rea ted limbs re- mained unchanged t h r o u g h o u t the fol low-up period.

10

1

0.9

0.8

0.7

0 .6

0.5

0 .4

0 .3

0.2

0.1

0

A.B.I N = 2 1

n=lO

n = l l

I I I I I

Pre 2 Hrs I Day 3 Wks 3Mts

Fig. 5. Follow-up results of Doppler index (A.B.1) in patients who had undergone successful balloon (*) or dynamic (m) angioplasty. There was a small fall in ABI immediately following balloon dilatation. Maximum improvement was not seen until 3 weeks following a successful procedure

Table 1. Comparative reproducibility of Doppler index and limb blood flow measurements in untreated limbs. The values obtained on three occasions during the follow-up period were compared using ANOVA. The coefficient of variation and correlation coefficient between measurements obtained before and 3 weeks after angioplasty and means were calculated. The value in parentheses rep- resents the range of the smallest and largest values

Before 3 Weeks 3 Months

Doppler ankle brachial index

Mean + SE 0.76+0.04 0.65+0.03 ANOVA (One-way) P < 0.05 Mean correlation r = 0.58 coefficient Mean coefficient 25.2% (15%-54%) of variation

Limb blood flow

Mean_ SE 6.9___0.53 7.1 ___0.67 ANOVA (one-way) NS Mean correlation r = 0.86 coefficient Mean coefficient 13.8% (4%-39%) of variation

0.75_+ 0.03

7.0_+0.60


The DABI was significantly different between treated and control legs, 0.76 _+ 0.04 and 0.59 _+ 0.03, respectively (P < 0.001). However, Doppler provided no discrimination between occlusions and stenoses, 0.57+_0.02 and 0.62 +_ 0.05, respectively (NS).

Immediately after successful balloon angioplasty, there was a small but significant fall in DABI, from 0.60_+0.05 to 0.47+0.04 (P<0 .05) (Fig. 5). This was not observed following unsuccessful balloon procedures. A small rise in DABI was observed after successful dynamic angioplasty, from 0.53_+0.05 to 0.63_+0.05. By 24 h later, the DABI rose significantly, from 0.53-t-0.05 to 0.73___0.02 (P<0 .01) and from 0.60_+0.05 to 0.66___ 0.02 (P < 0.05) following successful dynamic and balloon angioplasty, respectively. Full improvement of DABI was not seen until 3weeks later, from 0.53+0.05 to 0.92_+0.05 (P<0.001) and from 0.64_+0.04 to 0.76_+ 0.05 (P<0.001) following dynamic and balloon angioplasty, respectively (Fig. 5).

There was some fall in DABI between 3 weeks and 3 months following successful angioplasty using both techniques. This was more pronounced in the balloon group, from 0.78+0.05 to 0.71+_0.04 (P<0.05) compared with 0.92 +_ 0.05 to 0.90 + 0.05 (NS) following dynamic angioplasty.

Calcification of the pedal arteries in a diabetic patient prevented proper Doppler assessment. The flow signal was not abolished even at very high cuff pressure. In the same patient, however, LBF was successfully performed. Scanning before the release of pressure cuffs showed no leak of the radionuclide.

Reproducibility o f measurement

Table 1 compares the reproducibility of LBF and DABI measurements in untreated " c o n t r o l " limbs. ANOVA indicated a small but significant difference between DABI readings over the 3-month follow-up period. The mean coefficient of variation of repeated measurements of DABI in control limbs was nearly twice that of LBF measurements in the same legs, 25.2% (range 15%- 54%) and 13.8% (range 4%-39%) , respectively. The poor reproducibility of DABI measurement was also highlighted by a lower mean correlation coefficient, r = 0.27 compared with 0.79 for concomitant measurements of LBF in the same limbs.

Treadmill exercise

The claudication distance estimated by each patient was compared with that measured during treadmill testing (paired t-test). The mean claudication distance (61.6+ • 4.0 m) was significantly different from both the treadmill "pa in- f ree" (40.8_+2.2m, P<0.001) and the "maxi- m u m " walking distances (78.4 + 4.2 m, P < 0.05) with a poor correlation of 0.35 and 0.25, respectively.

Following successful dynamic angioplasty, the pain- free walking distance improved from 41.1 _+ 2.2 to 92.5 __ 10.9 m (124%, P<0.001) and from 39.6_+4.3 to 66.7+ 5.7 (68%, P<0 .01 ) following balloon angioplasty. A similar improvement was witnessed in the patient's own assessment of the claudication distance, from 66.4+_5.8 to 119___9.2m (80%, P<0.001) and from 57.0___8.5 to 81.7+11.3 m (42%, P<0 .01) following successful dy-

11

namic and balloon angioplasty, respectively. Unlike DABI and LBF, the improvement in the walking ability was sustained over 3 months. There was a good correlation between the improvement in maximum walking distance and that in LBF (r = 0.84).

Exercise tests were impossible or invalid on 27 out of 90 occasions (30%). Three patients could not use the treadmill on all three occasions (n = 9 tests).

Discussion

The reliability of patient assessment following angioplasty is determined by the accuracy of the methods used. Angiography remains the standard technique of assess- ing the cosmetic result of angioplasty; however, it can be the subject of considerable error (Katritsis et al. 1988). This is particularly true immediately following the angioplasty procedure, when haziness caused by inti- mal flaps can make visual assessment that more difficult (Gehani et al. 1990). It gives a limited indication towards the ultimate functional result to be expected, which was highlighted by lack of improvement in LBF in some patients despite angiographically successful procedures. Equally, dissection and perforation during angioplasty did not preclude improvement in LBF, as long as the occluded segment was recanalised. Although the state of distal run-off did not affect the procedural outcome of angioplasty, it had a significant effect on the clinical and LBF results. This is in line with the experience of Walden et al. (1986), who found poor run-off to be the only factor to affect the long-term outcome of balloon angioplasty deleteriously.

Whilst the run-off score in the occlusion and stenosis groups was similar, a higher rise of LBF followed recan- alization of total occlusions. This suggests that a larger diameter was created during dynamic angioplasty; however, such a comparison is limited by the fact that the original lesions were different. Demopulos et al. (1988) produced experimental evidence to suggest that atheromatous arteries treated by Kensey atherectomy catheter alone had a significantly larger channel than those treated by balloon angioplasty in the same animals.

Limb blood flow

The measurement of LBF using radionuclide-labelled blood components was described by Parkin et al. (1986). They initially used labelled red blood cells and later sub- stituted human serum albumin. Measurement of LBF in the resting state has little diagnostic or prognostic value (Sumner and Strandness 1969). Clement (1979) demonstrated that peak flow following hyperaemia was a sensitive indicator of arterial disease. Ideally, hyperaemia should be induced by physiological exercise, but this is technically difficult to achieve and suffers from poor reproducibility.

Three phases can be identified in the radionuclide time-activity curve. The rush of the tracer from the body pool into the legs is indicated by a steep rise. This gradually gives way to a flat phase when equilibrium between the two pools is reached. The LBF is calculated from the least squares gradient of the initial linear phase.

Peripheral vascular disease is commonly bilateral; however, symptoms in the least affected leg can often be masked by limitation on the other side. Whereas claudication was reported in 20% (6/30) of "control" legs during exercise tests, 85% had a subnormal LBF. Laing and Greenhalgh (1981) found that 45% of control legs were functionally abnormal, as indicated by limited per- formance during I min of treadmill exercise. Of these, only 14% were detected by Doppler measurement at rest.

The improvement in LBF following successful treatment of occlusions cannot be attributed to dynamic angioplasty alone, since all such procedures were followed by balloon dilatation. Normalisation of LBF was achieved in twice as many patients treated by Kensey catheter than by balloon dilatation. The reason for this is not clear, since there was no significant difference in the run-off score between the two groups. Furthermore, patients in the balloon group had higher pre-angioplasty LBF values. LBF improvement following laser angioplasty of total occlusions has been shown to be similar to that obtained after mechanical atherectomy (Gehani et al. 1990).

Although changes in limb volume following angioplasty have not generally been significant, in some patients it was as great as 21%. This was more pronounced in the Kensey catheter group. This increase was confined to treated legs and does not seem to be due to a systemic cause nor to reproducibility type error, since no similar changes were seen in the control legs. In patients who suffered extravasation, the contrast medium may have provoked an inflammatory response leading to unilateral oedema; however, the etiology in the other patients is not clear. Caution should therefore be exercised when comparing LBF calculated under different limb volumes in the same patient since this may lead to false conclu- sions.

Cuff inflation for 3 min allows intravascular equilibrium with minimal clearance (Parkin et al. 1987). It was well tolerated by most patients. However, rapid inflation of the cuffs is particularly important. Gradual inflation causes painful engorgement of the limb, since occlusion of the veins occurs while the arterial flow into the limb continues. As well as arterial influx of labelled blood, the rate of venous return of non-active blood could affect the gradient of the linear phase. However, none of our patients had any history of venous insufficiency.

Cardiac output is an important determinant of re- gional blood flow (Folkow and Neil 1971). This was not assessed in the present study. The variation between repeated LBF measurements during the follow-up period may partly be due to fluctuation in cardiac output.

12

A study is underway to investigate the effects of changes in left ventricular ejection fraction measured at the same time as LBF.


In many studies, the DABI is the sole parameter used in the follow-up of patients undergoing peripheral angioplasty. Whilst providing an indication of the pressure in the main arteries around the ankle, DABI was unable to discriminate between proximal occlusions and stenoses. Of the three investigations used in the present study, DABI had the advantage of being available in a bedside test which was particularly valuable in the peri-operative period. This uncovered an early dip in the DABI a few hours following successful balloon angioplasty. Arterial spasm following balloon angioplasty has been well documented (Wilson et al. 1989). Although the reason for this is not clear, locally released vasoactive compounds from the vascular wall and/or occlusive ma- terial have been implicated (Bates et al. 1987).

DABI and LBF measurements have also shown that full improvement following angioplasty was not achieved immediately. However, the maximum effect was almost always accomplished by 3 weeks, probably due to slow post-angioplasty remoulding of the treated segments. This is supported by follow-up angiographic and pathological studies (Castaneda-Zuniga et al. 1981; Levine et al. 1985).

There was some fall in DABI and LBF values between 3 weeks and 3 months. Although this was greater following balloon than dynamic angioplasty, the groups are too small to suggest a difference in the restenosis rate between these techniques. However, there is some evidence to suggest that the incidence of restenosis may indeed be lower following atherectomy than balloon angioplasty (Hofling et al. 1988).

Treadmill exercise

Exercise tests are the most physiological method of as- sessing both the patient's disability and the success of angioplasty. Unfortunately, assessment of walking is not simple, and there is no universally accepted protocol. Many patients cannot use the treadmill or are limited by factors other than claudication. About 10% of patients who had a satisfactory exercise test prior to angioplasty were stopped by angina following successful treatment.

The data presented provide some insight into the patient's own estimation of claudication distance as compared with treadmill assessment. In almost all patients, the claudication distance was significantly different from objective measurements. Siggard-Anderson and Peter- son (1968) reported a similar conclusion. After successful angioplasty, patients continued to underestimate the improvement in their walking ability.

When patients who were limited by symptoms other than claudication were excluded and the improvement in exercise and LBF results were correlated, a mean- ingful relationship emerged. This is important, since it suggests that the LBF may provide an objective, albeit indirect, indication of the functional improvement even when assessment by treadmill is not possible.

Finally, although repeated exercise testing could in itself improve the walking ability, Creasy et al. (1990) demonstrated that a significant effect was not seen until 6 months of regular training. This is unlikely to have contributed to the improvement in our patients within the limited number of tests carried out.

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Value of a radionuclide limb blood flow technique in the assessment of percutaneous balloon and...

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