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Vascular outflow resistance and angiographic assessment of lower limb arterial reconstructive procedures
J Miller1, J A Walsh, R K Foreman
1Vascular Surgery Unit, Flinders Medical Centre, Bedford Park, South Australia.
Insights
Intra-operative outflow resistance measurement offers a highly specific method for predicting early lower limb bypass graft occlusion, outperforming angiographic assessment alone.
Area of Science:
- Vascular Surgery
- Surgical Outcomes
- Graft Patency Prediction
Background:
- Early graft occlusion in lower limb bypass procedures significantly impacts patient outcomes.
- Predicting graft failure, often due to poor distal run-off, remains a clinical challenge.
Purpose of the Study:
- To evaluate the efficacy of intra-operative outflow resistance measurement in predicting early graft occlusion.
- To compare the predictive accuracy of outflow resistance with intra-operative angiographic assessment.
Main Methods:
- Outflow resistance was measured intra-operatively in 50 lower limb bypass patients by infusing plasmalyte and measuring graft pressure.
- Angiograms were independently assessed to categorize run-off vessels and stenoses, predicting graft failure probability.
- Early graft failure was defined as graft cessation within 3 months of surgery.
Main Results:
- High outflow resistance ( > 1.1 mmHg/mL/min) was associated with graft occlusion.
- Outflow resistance measurements demonstrated 100% specificity and 22% sensitivity for predicting early graft failure.
- Angiographic assessment showed 78% specificity and 67% sensitivity for predicting graft failure.
Conclusions:
- Intra-operative outflow resistance measurement is a highly specific predictor of early lower limb bypass graft occlusion.
- While less sensitive than angiography, outflow resistance offers superior specificity in identifying grafts at high risk of failure.
Abstract:
In an attempt to predict early graft occlusion secondary to poor distal run-off, the outflow resistance was measured intra-operatively and compared with the intra-operative angiogram in 50 patients undergoing lower limb bypass procedures. With arterial inflow occluded, 60 mL of plasmalyte was infused via a catheter and the resultant pressure generated in the graft was measured through a second catheter connected to a pressure transducer and recorder. Using the infusion rate and integrated pressure value, outflow resistance was calculated. High resistance measurements were defined as grafts with outflow resistance greater than 1.1 mmHg/mL per min, low measurements were defined as values less than 0.5 mmHg/mL per min and intermediate measurements were those in the range 0.5-1.1 mmHg/mL per min. Angiograms were classified independently of resistance measurements by scoring the numbers of run-off vessels crossing the ankle and stenoses, with subsequent assignment of the patient to one of three groups with either low, intermediate, or high probability of graft failure. Early graft failure was defined as cessation of graft function within 3 months of surgery. Early graft failure occurred in both cases with high outflow resistance and in seven of 44 with low outflow resistance. Of these nine occluded bypasses, six had been placed in the high probability of occlusion category on angiographic appearance and three in the intermediate category. Assessment of angiographic appearance and prediction of patency on a prospective basis had a sensitivity rate of 67% and a specificity rate of 78%. The corresponding sensitivity and specificity rates with resistance measurements were 22% and 100%, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)