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Hemodynamics of in situ saphenous vein arterial bypass
D F Bandyk1, H W Kaebnick, T M Bergamini
1Department of Surgery, Medical College of Wisconsin, Milwaukee.
Insights
Graft blood flow velocity predicts bypass success. High velocities in small grafts initially lower limb pressure but resolve symptoms and maintain patency, crucial for interpreting noninvasive diagnostics.
Area of Science:
- Vascular Surgery
- Hemodynamics
- Noninvasive Diagnostics
Background:
- In situ saphenous vein arterial bypass grafting is a common procedure.
- Assessing graft hemodynamics is vital for predicting clinical outcomes and ensuring graft patency.
Purpose of the Study:
- To characterize hemodynamics of in situ saphenous vein arterial bypasses using Doppler-derived blood flow velocity and limb blood pressure.
- To identify hemodynamic parameters that predict clinical outcome and technical success.
Main Methods:
- Doppler-derived blood flow velocity and limb blood pressure measurements were performed on 128 in situ saphenous vein arterial bypasses.
- Graft velocity waveform, flow velocity, and ankle-brachial pressure index were analyzed.
Main Results:
- Graft velocity waveform magnitude and configuration were the best predictors of clinical outcome.
- Successful bypasses exhibited antegrade flow and velocities >40 cm/s; low velocities (<40 cm/s) indicated technical issues or poor runoff.
- High systolic (102±20 cm/s) and diastolic (35±11 cm/s) velocities in small grafts (<4mm) initially lowered limb pressure (ABI=0.68) but resolved symptoms and maintained patency.
Conclusions:
- Doppler-derived blood flow velocity is a critical noninvasive parameter for assessing technical adequacy and postoperative surveillance of in situ saphenous vein bypasses.
- Understanding graft and limb hemodynamics is essential for interpreting noninvasive diagnostic findings and managing patients postoperatively.
Abstract:
Doppler-derived blood flow velocity and limb blood pressure measurements were used to characterize the hemodynamics of 128 in situ saphenous vein arterial bypasses. The magnitude and configuration of the graft velocity waveform was the best predictor of clinical outcome. Successful bypasses had antegrade flow throughout the pulse cycle and a blood flow velocity above 40 cm/s. A low graft blood flow velocity (less than 40 cm/s) was associated with technical error or early graft failure due to poor runoff. The return of normal limb blood pressure correlated with a technically satisfactory bypass but was measured in only 50% of limbs on the first day after surgery. In 28 bypasses with high blood flow velocity (mean +/- SD) in systole (102 +/- 20 cm/s) and diastole (35 +/- 11 cm/s), postoperative limb blood pressure was initially low (mean ankle-brachial pressure index = 0.68) due to restriction of blood flow through small-diameter (less than 4-mm) venous conduits. As revascularization hyperemia abated, diastolic blood flow velocity decreased and limb blood pressure normalized. Despite the high blood flow velocity and pressure gradient associated with flow-restrictive venous conduits, limb ischemic symptoms resolved, and graft patency was not decreased. An understanding of graft and limb hemodynamics after in situ bypass grafting is critical when noninvasive diagnostic techniques are used to document technical adequacy and for postoperative surveillance.