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Using CT Angio to Predict Sternotomy or Complicated Anastomosis in Patients Undergoing Robotically-Assisted MIDCAB
Objective: Robotically-assisted minimally invasive direct coronary artery bypass (RA-MIDCAB) is an alternative to sternotomy-based surgery in properly selected patients. Some patients are more complicated, or require conversion to sternotomy. Identifying the left anterior descending artery (LAD) when it is deep in the epicardial fat can be particularly challenging through a 5 – 6cm mini-thoracotomy incision. The objective of this study was to evaluate a technique for predicting conversion to sternotomy or complicated LAD anastomosis using pre-operative cardiac-gated computed tomography angiograms (CTA).
Methods: Retrospective review of 75 patients who underwent RA-MIDCAB for whom a pre-operative CTA was available. The distance from the LAD to the myocardium (LTM) was measured on a standardized “5-chamber” axial CT view (Figure 1). The relative risk of sternotomy or complicated anastomosis was compared between patients whose LAD was resting directly on the myocardium (LTM distance = 0mm) with those whose LAD was resting above (LTM distance > 0mm).
Results: The average LTM distance was 3.2+/-2.6mm (range 0 – 11.5mm). Fourteen patients (18.7%) had an LTM distance = 0mm. Of the entire group of 75 patients, 6 (8.0%) required conversion to sternotomy. Four others (5.3%) were reported to have a complication with the anastomosis intra-operatively. For patients with LTM distance = 0mm, the relative risk of sternotomy or complicated anastomosis was 18.0 (95% CI: 4.3 – 75.6, p = 0.0001).
Conclusions: In our experience, patients with LTM distance = 0mm were at significantly higher risk of either conversion to sternotomy or technically challenging anastomosis, with 8 of 14 patients (57.1%) in this group experiencing either endpoint. This novel measurement may be useful to identify patients who may have anatomy which is not well suited to the RA-MIDCAB approach.
Figure 1. “5-chamber” view used to measure LTM. PA:pulmonary artery, RA:right atrium, LVOT:left ventricular outflow tract, Ao:aortic root, LA:left atrium.