Leg haemodynamics during reconstructive vascular surgery

Impact of Bypass Flow Assessment on Long-Term Outcomes in Patients with Chronic Limb-Threatening Ischemia

BACKGROUND

Transit time flow meter (TTFM) allows quick and accurate intraoperative graft assessment. The main study goal is to evaluate the influence of graft flow measurements on long-term clinical outcomes in patients with chronic limb-threatening ischemia (CLTI) undergoing bellow the knee (BTK) vein bypass surgery.

METHODS

Between January 1st, 1999 and January 1st, 2006, 976 CLTI consecutive patients underwent lower extremity bypass surgery. When applying the exclusion criteria, 249 patients were included in the final analysis. Control measurements were performed at the end of the procedure. Patients were divided according to the mean (more/less than 100 ml/min) and diastolic graft flow (more/less than 40 ml/min) values in four groups. The primary endpoints were a major adverse limb event (male) and primary graft patency.

RESULTS

After the median follow-up of 68 months, a group with the mean graft flow below 100 ml/min and the diastolic graft flow below 40 ml/min had the highest rates of male (χ² = 36.60, DF = 1, P < 0.01, log-rank test) and the worst primary graft patency (χ² = 53.05, DF = 1, P < 0.01, log-rank test).

CONCLUSION

In patients with CLTI undergoing BTK vein bypass surgery, TTFM parameters, especially combined impact of mean graft flow less than 100 ml/min and diastolic graft flow less than 40 ml/min, were associated with an increased risk of poor long-term male and primary graft patency.

Laser Doppler Blood Flow Monitoring in Reconstructive Vascular Surgery: Case Studies

Laser Doppler flowmetric (LDF) measurements were performed preopera tively and postoperatively in patients undergoing arterial reconstruction in the lower limb, and intraoperatively in patients undergoing abdominal aortic re construction.

In 21 instances of successful arterial reconstruction in the lower limb, post operative LDF values from the skin of the foot were significantly higher than those obtained preoperatively. In 4 instances, depressed LDF values immedi ately after surgery clearly heralded thrombotic complications.

In 5 patients operated upon for occlusive disease of the aorta, LDF values from the skin of one foot were significantly higher at the end of surgery than those obtained when surgery was started. In 2 cases of aneurysm, LDF values decreased but distal pulses were normal. In 2 of these 7 patients, intraoperative embolization was instantly detected. In 1 case of severe microembolization from an aortic aneurysm, a low and unchanged LDF value was recorded throughout the reconstructive procedure, indicating thrombosis of the microvasculature.

These observations indicate that laser Doppler flowmetry is useful in recon structive vascular surgery to determine the patency of reconstructed vessels and also to detect thromboembolic complications during and after operation.

Preoperative angiographic score and intraoperative flow as predictors of the mid-term patency of infrapopliteal bypass grafts

OBJECTIVES

preoperative angiographic characteristics of the outflow tract have emerged as a predictive factor for the outcome of infrapopliteal reconstructions. Direct flow measurement can be routinely performed intraoperatively, but little is known regarding its impact on graft outcome. The present study was undertaken to compare the value of these parameters in predicting the mid-term patency of infrapopliteal bypass grafts.

DESIGN

retrospective clinical study.

PATIENTS

172 infrapopliteal reconstructions using autogenous vein were performed, of which 92 had a crural and 80 a pedal recipient artery.

METHODS

the preoperative angiogram was scored according to the SVS/ISCVS Ad Hoc Committee. At the end of the operation flow was measured with a transit-time flowmeter. Follow-up consisted of pressure measurements and duplex scanning.

RESULTS

the runoff score had no impact on femorocrural graft patency. For pedal grafts there was a tendency for inferior outcome with high runoff score, as the 1-year assisted primary patency for grafts with a completely occluded pedal arch was 11% compared with 52% for grafts with lower scores (p=0.056). Both intraoperative volume graft flow and maximum flow capacity had a highly significant influence on the outcome on crural reconstructions on univariate analysis. For pedal reconstructions only a a severely reduced maximum flow capacity after injection of papaverin was associated with an adverse outcome. Multivariate analysis revealed that maximum flow capacity was an independent significant factor affecting patency of femoroinfrapopliteal grafts (relative risk=0.53 per 30 ml/min increase, p<0.001). The runoff score was also a weak independent predictor of 1-year assisted primary patency in these grafts (relative risk=1.9 for a score >4 in crural and a score >5.5 in pedal grafts, p=0.036).

CONCLUSIONS

a completely occluded pedal arch in preoperative angiography was associated with poor infrapopliteal bypass outcome. Graft flow and maximal flow capacity are good predictors of the 1-year graft patency of femorocrural bypasses.

Prediction of early graft occlusion in femoropopliteal and femorodistal reconstruction by measurement of volume flow with a transit time flowmeter and calculation of peripheral resistance

A transit time flowmeter (Transonic TC101DTM, Transonic Inc., U.S.A.) was used for flow measurements and calculation of peripheral resistance in 48 primary femoropopliteal and femorodistal reconstructions. The results were correlated with primary graft occlusions during the first 90 postoperative days. There were 25 men and 23 women with a median age of 75 years (67-83). Eight were diabetic. Indications for surgery were rest pain (n = 23), ischaemic ulcer (n = 16), gangrene (n = 8) and popliteal aneurysm (n = 1). Measurements were made before reconstruction on the artery at the site of the distal anastomosis. After reconstruction flow measurements were made on the graft near the proximal and distal anastomoses together with a proximal graft pressure measurement. The peripheral resistance was calculated. Eleven grafts occluded and six patients died, four with patient grafts. Patients with graft occlusions had a significantly lower flow before (4 vs. 20 ml/min) and after (60 vs. 110 ml/min) reconstruction and a higher peripheral resistance, (1238 vs. 625 mPRU) than patients with patent grafts. The most significant differences were found in the femorodistal bypass grafts. The transit time flowmeter was easy to use. The flow before and after reconstruction as well as the peripheral resistance could be used for the prediction of graft function within 90 days of surgery.

The intraoperative measure of runoff resistance in the canine hindlimb

Long-term survival of femoro-popliteal grafts has been predicted on both graft function and distal vascular bed resistance. The purpose of this study was to demonstrate peripheral resistance as a function of the inherent elasticity (distensibility) of the distal vascular bed. The use of saline perfusate and maintenance of physiologic pressure will supplant such other factors as fluid viscosity, vasomotor tone, blood pressure, and tube dimensions. Our model consisted of Javid shunt insertion in the femoral artery of 13 female dogs distal to an occlusive tie. Saline was perfused in incremental fashion every 30 sec over a 5-min period; femoral pressure measurements were taken at each flow rate (Q) (cc/min). Results show that mean femoral pressure (MFP) varies with Q less than 125 (P less than 0.005) and Q greater than 200 (P less than 0.001). Furthermore, mean resistance (MR) declined precipitously with Q greater than 125 cc/min but at higher Q the MR plateaued (P less than 0.0001). We interpret these results to indicate that at Q less than 125 vasomotor tone is the predominant factor in MR and that saline perfusion abrogated this factor at 125 greater than Q less than 200. At Q greater than 200, MR declined only slightly and, therefore, MFP varied directly with Q indicating that vessel elasticity is the predominant feature of MR after vasomotor tone ablation and that pressure varies directly with flow in a distensible system. Pressure-flow graphs could be obtained prior to femoro-popliteal reconstruction via this quick, simple technique and rapid rises in pressure should indicate poor distal runoff.

Factors determining outcome of reversed saphenous vein femoropopliteal bypass grafts

The investigation was designed to study factors that might be of predictive value in femoropopliteal vein bypass grafting. A series of 146 grafts had a cumulative 5-year graft patency of 82.5 per cent. Five-year limb survival rate in salvage cases was 77.9 per cent. These results are encouraging. However, taking certain factors into account, the patency rates varied. In limbs with claudication, the 5-year graft patency rate was significantly higher than in salvage procedures (P < 0.05). Basal and maximal (during pharmacological vasodilatation) intraoperative graft flow rates were also significantly higher in claudicating limbs (P < 0.01). Reconstructions in limbs with a good run-off had better patency and flow rates than in limbs with a poor run-off (P < 0.001). This suggests that progression of distal atherosclerosis is a major factor for late graft thrombosis. The incidence of graft thrombosis was correlated with the flow rates (P < 0.01). Age, the presence of diabetes, graft diameter and the site of the distal anastomosis did not affect patency.