Robotic internal thoracic artery harvesting: the learning curve and graft patency

Abstract

Since the first report of totally endoscopic coronary artery bypass graft (CABG) using da Vinci Surgical System (Intuitive Surgical, Sunnyvale, CA, USA) in 1999, the robotic technology has been applied to internal thoracic artery (ITA) harvesting for more than 10 years. We present the experience of robotic ITA skeletonized harvesting in 200 cases using the da Vinci S or da Vinci SI Surgical System. The learning curves of ITA harvesting time and the results of ITA graft patency were evaluated. METHODS Patients Between January 2007 and August 2012, a total of 200 patients underwent totally robotic ITA takedown, including 154 males and 46 females aged 33-79 years (mean 58 years). The procedures of robotic-assisted CABG on beating heart were completed in two ways:1, 2 to harvest the ITA, followed by a minimally invasive direct coronary artery bypass graft (MIDCAB); and to harvest the ITA, followed by totally endoscopic coronary artery bypass graft (BH-TECAB). The performance of robotic ITA harvesting, MIDCAB and TECAB was approved by the Institutional Review Board of People's Liberation Army General Hospital and informed consent was obtained. Surgical methods After routine induction of anesthesia, double-lumen intubation was carried out for single right lung ventilation. Three 0.8 to 1.0-cm incisions were made in the 3rd, 5th and 7th intercostal spaces that located about 3 cm lateral of the midclavicular line. After deflation of the left lung, carbon dioxide insufflation was initialed through the cameral port and maintained at an average pressure of 6 to 8 mmHg (1 mmHg=0.133 kPa). The surgical cart of robotic surgical system docked to the camera and instrument ports. A 30-degree angle upward camera and micro-instruments were inserted. First, the fascia and muscles covering the ITA were transected along the entire length. The skeletonized ITA was developed from the lateral edge medially using blunt dissection and short bursts of low power monopolar cautery to mobilize the anterior attachments (Figure 1). Small intercostal branches were ligated with monopolar energy and the large intercostal branches were clipped for hemostasis. The entire length of ITA was dissected from the first intercostal branch to the diaphragm. The right ITA can be harvested after dissecting the anterior mediastinum. The left ITA was harvested followed the right ITA harvesting in double ITAs harvesting. The ITA harvesting time was defined from completed port placement to completed ITA detachment from thoracic wall. For calculation of the learning curve, regression analysis with logarithmic curve fit was used.Figure 1.: The robotic skeletonized ITA was harvested using monopolar cautery.RESULTS All the ITAs were harvested successfully in a skeletonized fashion. There were no major technical failures of the robotic system. One hundred and ninety-one left ITAs, 5 right ITAs and 4 double-ITAs were harvested. After robotic ITA harvesting, 120 patients underwent MIDCAB and 80 patients underwent BH-TECAB. The mean time of single ITA harvesting was (35.8±10.7) minutes (18 to 70). A significant learning curve was observed: y(min) = 58.0-5.3×ln(x), x = ITA takedown number; P<0.01, r2 = 0.33 (Figure 2). Harvesting time decreased from 41 minutes (median) in the first 30 cases to 29 minutes (median) in the last 30 cases.Figure 2.: The learning curve for robotic ITA harvesting. Followed the formula: y (min) = 58.0-5.3×ln (x).One hundred and ninety-five patients (97.5%) accepted the follow-up of graft patency before discharging, including 130 cases of CT angiography (CTA) scan and 65 patients coronary angiography. Both coronary angiography and CTA scan showed 100.0% graft patency. Unexpectedly, the angiography showed that left ITA graft in the middle segment developed a collateral branch in 2 patients. However, the patients were asymptomatic. One left ITA graft stenosis in TECAB group at 1year, and one in MIDCAB group at 2 years were found. The graft patency decreased as tim