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Components of outflow resistance and their correlation with graft patency in lower extremity arterial reconstructions
Insights
Measuring distal outflow resistance (OR) accurately predicts bypass graft success. A distal OR above 1.2 mm Hg/ml/min indicates likely failure, while below this threshold suggests patency. Pharmacologic manipulation does not improve prediction.
Area of Science:
- Vascular Surgery
- Hemodynamics
- Graft Patency
Background:
- Assessing bypass graft performance is crucial for patient outcomes.
- Outflow resistance (OR) is a key hemodynamic parameter influencing graft longevity.
- Predictive markers for early graft failure are needed.
Purpose of the Study:
- To establish a reproducible method for measuring total and component outflow resistance (OR).
- To determine the predictive accuracy of distal OR for femoropopliteal (FP) and femorodistal (FD) bypass graft success.
- To evaluate the role of vasospasm and papaverine infusion in OR and graft failure.
Main Methods:
- A simple, reproducible method was used to measure total, proximal, and distal OR in 101 bypasses (46 FP, 55 FD).
- Outflow resistance was measured before and after papaverine hydrochloride infusion in 60 bypasses to assess vasospasm.
- Graft patency was monitored for 3 months post-operatively.
Main Results:
- Bypass grafts with a distal OR > 1.2 mm Hg/ml/min failed within 3 months; those with distal OR < 1.2 mm Hg/ml/min remained patent.
- Papaverine infusion reduced mean total and distal OR by 30% and 31%, respectively, but did not alter predictive accuracy.
- In cases with high OR, sequential bypass extension to a second distal artery improved patency in 6 grafts.
Conclusions:
- Distal outflow resistance (OR) is a highly accurate predictor of early bypass graft success or failure.
- Pharmacologic manipulation with papaverine does not enhance the predictive value of OR measurements.
- OR measurement aids in selecting femorodistal bypass cases suitable for sequential bypass to improve patency.
Abstract:
We have used a simple reproducible method to measure total outflow resistance (OR) and its proximal and distal components in 101 bypasses (46 femoropopliteal [FP] and 55 femorodistal [FD]). All bypasses with a distal OR greater than 1.2 mm Hg/ml/min failed within 3 months and all with distal OR less than 1.2 mm Hg/ml/min remained patent for at least 3 months. To evaluate the contribution of vasospasm to OR and its role in graft failure, 60 bypasses (29 FP, 31 FD) had OR measurements before and after local infusion of papaverine hydrochloride (60 mg). Within 3 months, nine grafts (all FD) occluded and 51 remained patent. All nine failures had distal OR greater than 1.2 mm Hg/ml/min before papaverine infusion. After infusion, the mean percentage decrease in both total and distal OR for all grafts was 30% and 31%, respectively. However, there was no significant difference between these papaverine-induced decreases in OR and 3-month graft failure or success. Moreover, in three bypasses, even though papaverine lowered the distal OR from greater than 1.2 to less than 1.2 mm Hg/ml/min, early occlusion occurred. In six grafts (1 FP, 5 FD) when total and distal OR before and after papaverine was greater than 1.2 mm Hg/ml/min, the graft was extended to a second distal artery as a sequential bypass. These six grafts have remained patent over 3 months. Thus measurement of OR and particularly distal OR is a most accurate predictor of early graft success or failure. Pharmacologic manipulation does not enhance the predictive value of the OR measurement. OR measurements also help to select those FD bypass cases in which extension to a second distal artery as a sequential bypass improves patency.