Innovations: Technology & Techniques in Cardiothoracic & Vascular Surgery:
Evolution of Off-Pump Coronary Artery Bypass Grafting over 15 Years: A Single-Institution Experience of 14,030 Cases
Mishra, Yugal K. PhD*; Mishra, Manisha MD†; Malhotra, Rajneesh MCh*; Meharwal, Zile Singh MCh*; Kohli, Vijay MCh*; Trehan, Naresh MD*
Departments of *Cardiothoracic and Vascular Surgery and †Anaesthesiology and Intensive Care, Escorts Heart Institute and Research Centre, New Delhi, India.
Presented at the International Society For Minimally Invasive Cardiothoracic Surgery (ISMICS) Scientific Meeting, June 1–4, 2005, New York, NY.
Address correspondence and reprint requests to Yugal K Mishra, PhD, Escorts Heart Institute and Research Centre, Okhla Road, New Delhi 110025, India; e-mail: firstname.lastname@example.org.
Background: Off-pump coronary artery bypass grafting for multivessel disease is an important alternative to conventional myocardial revascularization using cardiopulmonary bypass. The development of exposure and stabilization techniques has made this surgery simple, safe, and routine. Experience with the technique, its evolution, the learning curve, and the pitfalls is presented.
Methods: A retrospective analysis was made of 28,216 patients who underwent elective coronary artery bypass grafting over a 15-year period from January 1990 through December 2004. Isolated off-pump coronary artery bypass grafting was performed in 14,030 patients and on-pump coronary artery bypass grafting in 14,186 patients. The overall period was divided into 3 groups of 5 years each: group I (1990-1994), group II (1995–1999), and group III (2000–2004). Initially, off-pump coronary artery bypass grafting was performed selectively in high-risk patients (eg, atheromatous aorta, severe systemic impairment, chronic obstructive pulmonary disease, octogenarian). Recently (2000–2004), multivessel off-pump coronary artery bypass grafting has been performed electively in 96% to 98% of patients undergoing coronary artery bypass grafting. Patients’ medical charts were reviewed for age, preoperative risk factors, operative findings, intraoperative conversion rate to cardiopulmonary bypass, postoperative complications, and length of hospital stay.
Results: In the years 1990–1994 (group I), mostly high-risk cases and cases with left anterior descending coronary artery lesions were included for off-pump coronary artery surgery. In the years 1995–1999 (group II), patients with double and triple vessel disease presenting for coronary artery bypass surgery were accepted for off-pump surgery irrespective of preoperative risk factors. However, in the years 2000–2004 (group III), off-pump coronary artery bypass surgery was the first choice of approach for any patient presenting for coronary artery bypass surgery. The mean number of grafts was lower in off-pump cases than in on-pump cases in group I (2.0 ± 0.4 vs. 3.2 ± 0.80) and group II (2.6 ± 0.6 vs. 3.3 ± 0.4), whereas the mean number of grafts was higher in off-pump cases than in on-pump cases in group III (3.5 ± 0.2 vs. 3.4 ± 0.8). In groups I and II, the conversion to cardiopulmonary bypass was 5.2% and 5.9%, respectively. The conversion to cardiopulmonary bypass decreased to 1.7% in group III, which was statistically significant. Perioperative myocardial infarction was 5.2% in group I, 1.7% in group II, and 1.5% in group III. The difference between groups II and III was not statistically significant. Hospital mortality was higher in group I (5.2%) than in group II (1.2%) or III (1.1%). The difference between groups II and III was not statistically significant. Length of intensive care unit stay was 36 ± 8 hours in group I, 28 ± 7 hours in group II, and 20 ± 8 hours in group III. These differences were statistically significant. Length of postoperative hospital stay was 8 ± 2 days in group I, 7 ± 2 days in group II, and 5 ± 2 days in group III These differences were statistically significant.
Conclusions: As surgeons’ experience matures, off-pump coronary artery bypass surgery permits total myocardial revascularization in virtually all patients with multivessel coronary artery disease. Despite a significant learning curve, evolution to routine off-pump coronary artery bypass with good patient outcomes can be achieved with careful patient selection during the “learning curve.” The method is safe and reproducible, and patients benefit with shorter intensive care unit and hospital stays.
Cardiopulmonary bypass (CPB) has long been recognized as one of the major causes of systemic inflammatory response, which may contribute to postoperative complications and even multiorgan dysfunction.1 The mortality and significant morbidity of coronary artery bypass grafting (CABG) is largely attributed to the use of CPB, global cardiac arrest, hypothermia, median sternotomy, and manipulation of the aorta. In the last decade of the 20th century, off-pump CABG emerged as an effective alternative technique allowing coronary revascularization without the use of CPB.2,3 Off-pump coronary artery bypass (OPCAB) is associated with decreased postoperative morbidity, shorter hospital stay, reduced cost,2,4 and reduced operative mortality in some studies.3,5
Early experience with OPCAB was confined to easily accessible anterior vessels and was not recommended for circumflex or lateral marginal grafting.6 But subsequent developments in the technique of coronary artery exposure and myocardial revascularization have allowed the use of OPCAB in multivessel coronary artery disease with encouraging results.7,8
We started using OPCAB in 1990 in high-risk groups (eg, atheromatous aorta, severe obstructive pulmonary disease, octogenarians). As our experience has grown, currently all patients requiring isolated coronary artery bypass are considered for OPCAB. In the present study, we retrospectively analyzed the evolution of OPCAB in our institute in the last 15 years and evaluated how experience has affected the outcome of OPCAB.
MATERIALS AND METHODS
A retrospective analysis of 28,216 patients who underwent elective CABG over a 15-year period from January 1990 through December 2004 was done. In this group of patients, Conventional Coronary Artery Bypass Surgery (CCAB) was performed in 14,186 and OPCAB in 14,030 consecutive cases. We divided the overall period into 3 groups of 5 years each: group I (1990–1994), group II (1995–1999), and group III (2000–2004).
From 1990 to 1994, 19 patients underwent OPCAB compared with 5213 CCAB cases in the same time frame. Patients who underwent OPCAB in this period were high-risk cases for CCAB due to atheromatous aorta or severe systemic impairment, or were those patients who needed bypass grafting to the left anterior descending artery only. These cases underwent OPCAB without commercially available stabilization devices and intracoronary shunts. Stabilization involved manual compression of the adjoining myocardial territory and the use of traction slings.
From 1995 to 1999, the number of OPCAB cases exponentially increased to 1412, whereas CCAB was performed in 7929 cases (Fig. 1). This increase in the number of OPCAB cases was due to the availability of myocardial stabilizers. We started using the Octopus I (Medtronic Inc., Minneapolis MI) in early 1996 and Genzyme (Genzyme Surgical Products Corp., Fall River, MA) stabilizers in late 1997. Because of availability of these commercial stabilizers, grafting of the posterior and inferior wall vessels became feasible with acceptable results. Because of increased experience of our team, more and more cases were enrolled for OPCAB than for CCAB. We also started enrolling low-ejection-fraction cases for OPCAB with good outcome, whereas low-ejection-fraction cases were managed with CCAB.9 In 1999, we also started using OPCAB for patients with left main disease, which had formerly been considered a contradiction for OPCAB.10
From 2000 to 2004, all patients who presented for elective CABG were considered for OPCAB irrespective of risk factors, low ejection fraction, or left main disease. Hence, only 1044 patients received CCAB, whereas12 599 received OPCAB. This increase in number of OPCAB cases was due to the availability of better myocardial stabilizers (Octopus II, III & IV, Medtronic) and other commercially available stabilizers and exposer devices, as well as intracoronary shunts. In this era, very few cases required conversion to CPB. In this period, we started assessing the quality of anastomosis intraoperatively in 80% of cases using a transonic flow meter (Transonic Inc., Ithaca, NY).
As shown in Table 1, the mean age of patients in groups I, II, and III was similar. There was steady increase in the number of female patients from group I to group III. In group I, 26% of patients had preoperative neurologic dysfunction. In group II, 11% of OPCAB patients experienced neurologic dysfunction preoperatively. In both groups I and II, the number of OPCAB patients with neurologic dysfunction was much higher than that of CCAB patients operated in same time frame. In group III, only 2.6% of patients had preoperative neurologic dysfunction, and these numbers were similar to the CCAB group (2.6%). In groups I and II, renal dysfunction with OPCAB was present in 21% and 16.7% of cases, respectively, which was much higher than the number of cases in the CCAB patients in the same time frame. However, in group III, only 1.5% of patients had preoperative renal dysfunction as compared with 2.8% of CCAB patients. The number of patients with a left ventricular ejection fraction below 30% was quite different among OPCAB patients (group I: 10%, group II: 23.2%, group III: 36.7%). Similarly, the number of patients with left main stenosis was different in all OPCAB groups (group I: 0%, group II: 3.7%, group: III 14%). Analysis of the mean number of grafts used in all 3 OPCAB groups revealed a steady increase from 2.0 ± 0.4 grafts per patient in group I, 2.6 ± 0.6 grafts in group II, and 3.5 ± 0.2 grafts in group III. There was significant drop in conversion to CPB in these OPCAB groups from 5.2% in group I and 5.9 in group II to only 1.7% in group III (Fig. 2). The number of patients with perioperative myocardial infarction also decreased from group I to group III (group I: 5.2%, group II: 1.7%, group III: 1.5%). There was a gradual reduction in the duration of intensive care unit stay in these groups of OPCAB patients (group I: 36 ± 8 hours, group II: 28 ± 7 hours, group III: 20 ± 8 hours) (Fig. 3). Hospital mortality decreased from 5.2% in group I OPCAB patients to 1.2% in group II and 1.1% in group III patients. There was also a gradual decrease in postoperative hospital stay in OPCAB cases from 8 ± 2 days in group I to 7 ± 2 days in group II and only 5 ± 2 days in group III.
Coronary artery bypass grafting without CPB, which was introduced as early as 1967,11 was overshadowed by CABG on CPB with technologic advances of CPB and cardioplegic arrest, which provided a quiet bloodless field. A resurgence in beating heart surgery began in the early 1990, though it was practiced by few surgeons.12,13 In the terminal years of the 20th century, OPCAB gained wider acceptance with good short-term results.2,3 Initial experience with OPCAB was limited to single or double vessel disease.3,14 With the availability of better stabilization techniques and increasing experience, OPCAB was used for patients with multivessel disease.8,15
Refinements in off-pump technology and new mechanical stabilizers have led to the widespread application of coronary revascularization without CPB. Several studies conducted in the last decade of the 20th century describe the success of complete revascularization in beating heart surgery.16–18
Today, myocardial revascularization without CPB is an accepted surgical strategy. Its benefit is considered higher in patients in whom CPB may have potential complications, such as in the elderly or in patients with severe preoperative organ failure. We started OPCAB at our institution in 1990 mostly in high-risk groups (eg, atheromatous aorta,severe systemic disease, octogenarians). As our experience grew, we extended this technology to patients with single and double vessel disease presenting for isolated CABGs. As we gained more experience and the results of OPCAB became equal to those of CCAB, we extended the procedure to all patients presenting for CABG. In the present study, we retrospectively analyzed patients’ preoperative profile, changes in the strategy of intraoperative management, and postoperative outcome from 1990 to 2004. The spectrum of patients accepted for surgical myocardial revascularization without CPB has changed considerably during these 15 years. Now we are performing OPCAB in every patient who presents for elective CABG who is not at high risk due to underlying comorbidities or poor left ventricular function. In present series, only 10% of patients had OPCAB with a left ventricular ejection fraction (LVEF) below 30% between 1990 and 1994. Between 1995 and 1999, 23.2% of patients had an LVEF below 10%, and between 2000 and 2004 36.7% of patients with an LVEF below 30% had OPCAB. Similarly, we are now accepting all patients with left main disease for OPCAB, which was not true in earlier years (between 1990 and 1999). The technique of OPCAB has evolved in our institution over the last 15 years largely due to the introduction of mechanical stabilizers, which led to an increased number of OPCAB operations with time. There was a higher mean number of grafts used per patient between 2000 and 2004 compared with previous years, along with a drop in the conversion rate to CPB. During this time, patients who were candidates for conventional CABG could undergo OPCAB with equal safety.
We have also seen a significant improvement in the outcome of OPCAB over the period of this study, as evidenced by fewer perioperative myocardial infarctions and fewer postoperative deaths than observed 5 or 10 years ago. The most remarkable difference seen in OPCAB cases in recent years is a shorter intensive care unit stay and postoperative hospital stay in comparison with CCAB cases and with OPCAB cases performed between 1990 and 1999.
In summary, a retrospective analysis of last the 15 years of cases done without CPB revealed a change in the profile of patients accepted for OPCAB with time and a significant improvement in surgical outcomes for these patient, which led to shorter intensive care unit and hospital stays.
The authors thank Mr. Sudhir Shekhawat for his statistical assistance and Mrs. Preeti Saxena for her secretarial assistance.
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OPCAB; C-CAB; CABG; Evolution
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