Advantages of OPCAB technology and adoption of creative techniques

Dr Naresh Trehan makes a powerful case for off-pump coronary artery bypass grafting (OPCAB)

The earliest attempts to myocardial revascularisation were done on a beating heart. In 1967, Kolessov reported a left internal thoracic artery (LITA) to left anterior descending (LAD) coronary artery anastomosis through a left thoracotomy on a beating heart, as a method of treatment for angina pectoris.

However, this was quickly abandoned in favour of coronary artery bypass grafting (CABG) via median sternotomy with modern cardiopulmonary bypass (CPB) techniques because of the improved safety and ease of suturing on a still, bloodless field. Improvement in peri-operative care, surgical technique and methods of attenuating the untoward effects of cardiopulmonary bypass have resulted in improved clinical outcome of on-pump myocardial revascularisation. Unfortunately, in doing so, it induces a whole body inflammatory response that is capable of causing increased morbidity and mortality.

The continuing drive to improve clinical outcome and compete with the ever evolving non-surgical methods of myocardial revascularisation has led to the rebirth of off-pump coronary artery bypass grafting (OPCAB) in 1994 and now accounts for nearly 65 per cent of all CABG operations performed.

Performing vascular anastomoses on small arteries on a beating heart used to be a daunting and frustrating adventure in the earlier years. However, with the application of effective target vessel stabilisation, and efficient visualisation systems, the early and mid-term patency of OPCAB is encouraging and comparable to on-pump CABG.

Introduction of epicardial stabilisation system resulted in a commanding improvement in early post-operative patency rates. Puskas and associates reported an impressive patency rate of 98.8 per cent at the time of hospital discharge.

OPCAB in high risk group of patients

OPCAB has been demonstrated to offer prognostic advantage over on-pump CABG in patients with exaggerated surgical risk from complicated coronary artery disease and/or debilitating co-morbidities. Acute myocardial infarction and depressed left ventricular function constitute a high surgical risk with on-pump CABG, because the myocardial damaging effects of CPB and the often cumbersome, inefficient and intraoperative myocardial protection do not prevent immediate post-operative cardiac dysfunction.

Table 1 Region wise distribution of CABGs in India, 2004

Bar diagram demonstrating the growth of OPCAB surgeries at EHIRC

OPCAB achieves comparatively better outcomes in patients who have myocardial revascularisation soon after recent AMI. OPCAB decreases the operative risk in the presence of impaired left ventricular function. Pre-operative renal impairment is an independent predictor of poor prognosis after on-pump CABG.

OPCAB preserves renal function better than on-pump CABG, and available evidence favours the preferential use of OPCAB for patients with chronic renal for a better early clinical outcome. Elderly patients are considered high risk surgical patients because of their reduced functional capacity and the presence of co-morbidities. Correspondingly, the outcome of on-pump CABG in this group is characterised by increased morbidity and mortality.

Interestingly, OPCAB has been shown to improve the clinical outcome in this growing population of surgical patients. Specifically, the incidence of stroke, peri-operative myocardial infarction, duration of mechanical ventilation, blood transfusion, length of intensive care, hospital stay and mortality are decreased.

Growing confidence in the techniques of OPCAB and the favourable influence on clinical outcome has provided the impetus for extension of this approach to intermediate and low-risk patients. After one year, the freedom from death, stroke, myocardial infarction and coronary re-intervention for both techniques were similar and there was no difference in graft patency rates.

However, both prospective and retrospective studies have reported a reduction in the need for mechanical ventilation, post-operative blood loss and need for transfusion, post-operative complications, length of intensive care and hospital stay and consequently the cost of treatment with OPCAB.

The early experience with OPCAB was bedraggled by incomplete revascularisation and consequently higher incidence of adverse cardiac events and re-intervention. Calafiore and their collaborators found a comparatively lower incidence of major adverse cardiac events and re-intervention with OPCAB, when equivalent extent of myocardial revascularisation with on-pump is achieved.

The rates of morbidity and mortality reported in most early observational studies and case-matched with risk-adjusted comparisons showed lower mortality with OPCAB. The techniques of OPCAB are constantly undergoing refinement and many areas of potential benefit are vigorously explored. Increasing number of surgeons are expanding their OPCAB practice and offering many more patients this technique of myocardial revascularisation. In India, the total number of CABGs performed is 41,000 per year approximately, of these 56.8 per cent are OPCABS. During the past five years, the number of OPCAB surgeries performed at the Escorts Heart Institute, New Delhi has significantly increased from 4.95 per cent in the initial period to 98 per cent recently.

Over the past few years, minimally invasive direct coronary artery bypass (MIDCAB) procedures have been introduced and are rapidly gaining acceptance. The MIDCAB procedure typically is conducted for single vessel disease (SVD) on the beating heart through a small incision (left thoracotomy or partial sternotomy) without cardiopulmonary bypass. With improved techniques and instrumentation, results have been excellent.

After establishing the surgical techniques for single or double vessel grafts by MIDCAB, experience and technology has evolved to permit safe and reliable multiple vessel anastomosis without the use of CPB. It has been made possible by the development of innovative techniques, stabilising platforms, intracoronary shunts, refined intraoperative monitoring and a skilled co-ordinated team.

Currently, almost 96- 97 per cent patients who come for CABG are being operated upon this technique including patients receiving total arterial revascularisation, multiple and sequential grafts. Our results confirm that single and multiple coronary revascularisations can be performed safely with excellent graft patency rates and long-term event free survival.

Post-operative morbidity in terms of renal dysfunction, stroke and peri-operative MI are also significantly lower in the OPCAB group. Thirty day mortality is one per cent in OPCAB group compared to 2.4 per cent in the CCAB group.

Advances in OPCAB technology and adoption of creative techniques will help to maximise the benefits of OPCAB. Concepts and budding practices like complete avoidance of the aorta (no touch technique), atraumatic anastomotic connection, complete arterial revascularisation, sutureless anastomosis and ultrashort hospital stay will gain wider acceptance. With the encouraging early to mid-term results demonstrated with OPCAB, the prospect is promising. OPCAB has journeyed through the past and now, by science shall take its place.

Robotic cardiac surgery

“The old order changth giving rise to new”

-William Shakespeare

Not many generations have seen a visible drastic change in technology involved with the present surgical procedures. Several years ago, from the inception in the minds of a group of cardiac surgeons, there arose a dream of totally endoscopic coronary surgery. The influence was also stimulated by the fellow counterparts using the robotics in general surgery for various procedures involving gastrointestinal and genitourinary procedures. The concept was purely based on thoracoscopic principles which had already developed by this time.

The first generation success of Robotics came with the voice controlled robotic arm (AesopTM 3000, computer motion Inc.). The voice controlled robotic arm moves precisely on surgeons command and remains stationary till the next command is given, giving a rock steady endoscopic view.

Since October 1998, we have at Escorts Heart Institute, performed Robot assisted minimally invasive procedures, ASD closures and mitral valve replacements. Recently, surgical robotic systems have been developed to assist in endoscopic suturing. The Zeus from Computer Motion and Da Vinci system from Intuitive Surgical, consists of three robotic arms that are attached to a platform. A complex master-console system is used for replicating the arm and hand movements of the surgeon.

The surgeon manipulates, traditional surgical instrument handles at the interface device. His movements are relayed in real-time by a computer to robotic arms which are attached to the operating room table. These robotic arms hold specially-designed endoscopic instruments which are placed through small ports. By the use of computer elimination of tremor and motion-scaling, robotics provide the precision necessary to perform total endoscopic coronary anastomoses (TECAB). These robotic devices have been demonstrated to enhance surgical dexterity during a microvascular anastomosis.

The first computer-assisted open-heart surgery was performed using the Intuitive system in May 1998 in France. The proposed advantage compared to the conventional coronary artery surgery was a significant decrease in the trauma of surgery and therefore decreased morbidity related to the open procedures which gave direct open access to heart and aorta.

It was also postulated that totally endoscopic beating heart coronary bypass surgery was likely to be superior to the current interventional approaches for coronary artery disease and may at the same time be an epitome of minimally invasive bypass procedures.

The robotic control of the surgeon just by sitting at the console is so perfect that the anastomosis is constructed in the customary fashion without sternal retraction, a bloody field and without a single hand inside the chest cavity. More to say, the surgeon enjoys a scrub free time while peering into the chest cavity with a 3-dimentional vision with absolute clarity and a ten time magnification of his work. With single lung ventilation and CO2 insufflated chest cavity the exposure of the surgical field is perfect.

As every procedure has a learning curve, so does the robotic procedures. From isolated internal mammary artery (IMA) take down to bilateral IMA take down followed by singel vessel LIMA to LAD anastomosis, to multi-vessel coronary artery bypass on a beating heart. It is a long process and requires not only patience but also zeal to learn and master the technique.

Escorts Heart Institute introduced the DaVinci robotic system in November 2002. In a short span of two years, we have performed 204 robotic enhanced coronary surgeries. The average operating time was 208 ñ 36 minutes. In patients for whom the IMA was taken down robotically and open anastomosis was performed, the IMA flow was checked by Echo Doppler.

Post operatively, the patients were weaned off from the ventilator extubated within four hour. The ICU stay for all our robotic patient was 1-2 days with a hospital stay of four to five days. There has been no late mortality till now and all our patients are doing well on follow up while doing routine physical activity. The prediction is that robotic cardiac surgery is here to stay. In the future, multiple consoles may be added with additional manipulation arms to allow more than one surgery to operate and assist in a totally robotic scenario.

Clinical trials are presently underway and this is a major step towards closed chest CABG, a procedure that will ultimately change the practice of cardiac surgery. In the foreseeable future, CABG may be performed as an outpatient procedure.

The writer is CEO, Escorts Heart Institute and Research Centre, New Delhi