Quality assessment of distal S2AS connector anastomosis by 13 MHz epicardial ultrasound

Objective: During application of a distal coronary bypass connector, we employed 13 MHz epicardial ultrasound to evaluate quantitative caliper measurements for vessel size matching and to assess anastomosis quality after connector deployment. Methods: Two S2AS connector anastomoses were constructed on ex vivo pressure-perfused porcine hearts. Epicardial ultrasound measurements of the connector ring and anastomosis were compared to intravascular ultrasound measurement and cast dimensions. In 21 pigs, anastomotic sites with internal diameter of 2.25–3.0 mm (internal mammary artery, IMA) and 1.8–2.2 mm (left anterior descending coronary artery, LAD) were selected using external caliper and epicardial ultrasound measurements. Anastomoses were visualized and assessed intraoperatively (beating heart, n = 21) and at 3 and 6 months’ follow-up (explanted heart, n = 10 each). Results: Epicardial ultrasound underestimated connector dimension by ≤5% versus intravascular ultrasound and deviated ≤13% from cast dimensions for other anastomotic measurements. Caliper estimates of internal IMA and LAD diameter differed from ultrasound by −3 ± 6% and −2 ± 7% (mean ± SD), respectively. Intraoperatively, the anastomotic orifice was flawless in all animals. It remained fully patent at 3 and 6 months by ultrasound, which was confirmed by histology. The connector to LAD percentage diameter stenosis changed from −12 ± 5% intraoperatively to −1 ± 7% at 3 months and from −5 ± 6% intraoperatively to −16 ± 13% at 6 months, in the growing pig model. Conclusions: In the pig, external caliper measurements provided a reliable quantitative estimate of inner graft and coronary diameter for connector size matching. Epicardial 13 MHz ultrasound is a promising method to assess coronary anastomosis quality even when connector metal is present.