MI and Robots at the Heart of Things

31 August 2005 (Last Updated August 31st, 2005 18:30)

The rise of minimally invasive surgery and robotic surgery for cardiac problems is continual and permanent. Dr Naresh Trehan runs through some specific usages and the benefits it brings.

Beating-heart surgery was originally the only approach to myocardial revascularisation. In 1967, Kolessov reported a left internal thoracic artery 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.

"Performing vascular anastomoses on small arteries of a beating heart can be a daunting and frustrating adventure."

Improvement in perioperative care, surgical technique and methods of attenuating the effects of CPB 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 devastating 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 (OPCABG), which now accounts for nearly 20% of all CABG operations performed in the USA. This is despite the lack of prospective randomised studies documenting mortality or morbidity benefits in the short- or long-term.

Performing vascular anastomoses on small arteries of a beating heart can be a daunting and frustrating adventure, and so far, no available method of target vessel stabilisation can achieve a steady bloodless field comparable to a cardioplegically arrested heart.

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 onpump CABG. Introduction of epicardial stabilisation systems resulted in a commanding improvement in early postoperative patency rates. Puskas and associates reported an impressive patency rate of 98.8% at the time of hospital discharge.

HIGH-RISK GROUPS

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 comorbidities.

Acute myocardial infarction and depressed left ventricular function constitute a high surgical risk with onpump CABG because the myocardial damaging effects of CPB and the often cumbersome and inefficient intraoperative myocardial protection do not prevent immediate postoperative cardiac dysfunction. OPCAB achieves 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.

Preoperative 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 problems for a better early clinical outcome.

"An increasing number of surgeons are expanding their OPCAB practice."

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. OPCAB has been shown to improve the clinical outcome in the growing population of surgical patients. The incidence of stroke, perioperative myocardial infarction, duration of mechanical ventilation, blood transfusion, lengthy intensive care and hospital stay, and mortality have all
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 a year, the freedom from death, stroke, myocardial infarction and coronary re-intervention for both techniques was similar, and there was no difference in graft patency rates.

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 being vigorously explored. An increasing number of surgeons are expanding their OPCAB practice and offering many more patients this technique.

MIDCAB AND OPCAB

Over the past few years, Minimally Invasive Direct Coronary Artery Bypass (MIDCAB) procedures have been introduced and are rapidly gaining acceptance. The MIDCAB procedure is typically done for Single Vessel Disease (SVD) on the beating heart through a small incision (left thoracotomy or partial sternotomy) without cardiopulmonary bypass. 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, coordinated team.

Currently, 96%–97% of patients who come for CABG are being operated upon with this technique. Our results confirm that single and multiple coronary revascularisations can be performed safely with good graft patency rates and event-free survival.

"Robotic devices have been demonstrated to enhance surgical dexterity during a microvascular anastomosis."

Postoperative morbidity in terms of renal dysfunction, stroke and perioperative MI are also significantly lower in the OPCAB group. 30-day mortality is 1% in the OPCAB group compared with 2.4% in CCAB groups.

Advances in OPCAB technology and the 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 and sutureless anastomosis will gain much wider acceptance, and lead to quicker turnaround and much shorter hospital stay.

ROBOTIC CARDIAC SURGERY

Several years ago, in the minds of a group of cardiac surgeons, there arose a dream of totally endoscopic coronary surgery. The influence also came from counterparts using robotics in general surgery for various procedures involving gastrointestinal and genitourinary procedures. The concept was purely based on thoracoscopic principles. The first-generation success of robotics was the voice controlled robotic arm (Aesop™ 3000).

Recently, surgical robotic systems have been developed to assist in endoscopic suturing. The Zeus from Computer Motion and the da Vinci system from Intuitive Surgical consist 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 that 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 over the conventional coronary artery surgery is a significant decrease in the trauma of surgery and therefore decreased morbidity related to the open procedures, which give 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 become the epitome of MI bypass procedures.

"Surgical robotic systems have been developed to assist in endoscopic suturing."

The robotic control of the surgeon is so perfect that the anastomosis is constructed in the customary fashion without sternal retraction: a bloody field and without a hand inside the chest cavity.

It is different to peer into the chest cavity with three-dimensional vision, absolute clarity and a ten times magnification of your 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 do the robotic procedures. From isolated Internal Mammary Artery (IMA) take down, to bilateral IMA take down followed by single vessel LIMA to LAD anastomosis, to multivessel 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. The patients who fulfil the inclusion criteria are those requiring CABG for stable angina, less than 80 years of age and willing to try a robotic cardiac procedure.

Escorts Heart Institute introduced the da Vinci robotic system in November 2002. In a short span of one year it performed 204 robotics-enhanced coronary surgeries. The average operating time was 208 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 the ventilator within four hours. The ICU stay for all the robotic patients was one to two days with a hospital stay of four to five days. In the future, multiple consoles may be added with additional arms to allow more than one surgeon to operate and assist in a totally robotic scenario.

Clinical trials are currently underway. This is a major step towards closed chest CABG, which will ultimately change cardiac surgery. In the near future CABG may be performed as an out-patient procedure.