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Ann Thorac Surg 2000;70:1779-1781
© 2000 The Society of Thoracic Surgeons

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Supplement: outcomes 2000

Con: beating-heart surgery for coronary revascularization: is it the most important development since the introduction of the heart-lung machine?

^a Texas Heart Institute and University of Texas Medical School, Houston, Texas, USA

Address reprint requests to Dr Cooley, Texas Heart Institute, MC3-258, PO Box 20345, Houston, TX 77225-0345
e-mail: dcooley{at}heart.thi.tmc.edu

Presented at Outcomes 2000, "The Key West Meeting," Key West, FL, May 24–28, 2000.

Abstract

Contrary to what the media tend to suggest, beating-heart coronary artery bypass grafting (BHCABG) is not a new technique. It has been performed since the advent of coronary revascularization but, until recently, was largely abandoned in favor of cardiopulmonary bypass (CPB) and cardioplegic techniques. However, with the introduction of minimally invasive coronary surgery and mechanical methods for target-artery stabilization, interest in BHCABG has been renewed. In carefully selected cases, this approach has the advantages of simplicity, avoidance of the inflammatory response caused by CPB, and a decreased need for blood transfusion. Nevertheless, BHCABG may be technically difficult in some patients, and it involves a steep learning curve. Potential risks include incomplete revascularization, ischemia during temporary target-artery occlusion, and suboptimal anastomoses. Because of the need for special equipment, BHCABG can be expensive and time consuming. It may benefit older or sicker patients who are poor candidates for CPB, especially those with left anterior descending or right coronary artery lesions, but it should be used with discretion and not be considered for all coronary patients.

In taking a skeptical view of beating-heart coronary artery bypass grafting (BHCABG), let me begin by critiquing the title of the present debate, which implies that beating-heart surgery is a new concept. Indeed, in a 1999 issue of this same journal, Ascione and coauthors [1] stated that "operation on a beating heart is a relatively new surgical procedure," leading readers to conclude that this technique only recently became possible. Similarly, this impression was spread by U.S. News and World Report [2], which, in a feature story about heart disease, included BHCABG under "new surgical techniques." The author stated that, with this approach, the chest is opened "as in conventional surgery" (ie, by means of a full sternotomy), but "there’s no heart-lung machine." However, beating-heart surgery is not a modern innovation. In the 1950s, before cardiopulmonary bypass (CPB) came into widespread use, Murray and Longmire performed a coronary endarterectomy or segmental excision with saphenous vein or internal mammary artery (IMA) grafts [3]. The concept of myocardial revascularization by anastomosing the IMA to the coronary artery was propounded by Demikhov, who undertook a canine study of this technique in 1952 [4]; 4 of his dogs survived for more than 2 years with patent grafts. About the same time, Murray independently achieved similar results [3]. In 1962, Sabiston used a saphenous vein graft to bypass the right coronary artery, and, in 1964, Garrett bypassed the left anterior descending (LAD) coronary artery [5]. That same year, inspired by Demikhov’s experience, Kolesov [6] anastomosed the left IMA to a marginal branch of the circumflex artery. All of these procedures were done on the beating heart. After 1968, CABG with CPB was widely adopted, but BHCABG continued to be performed by some surgeons [7, 8]. Therefore, beating-heart surgery is not a revolutionary new approach. It was originally the only possible approach, and, after the advent of modern CPB techniques, was largely viewed as outmoded. Today, it is being revived, accounting for about 20% of CABG operations in the United States [9], and is usually done by means of a minimally invasive incision.

Beating-heart CABG has the advantages of simplicity, avoidance of the inflammatory response caused by CPB, and a decreased need for blood transfusion. Moreover, thanks to new mechanical devices for stabilizing the target artery, BHCABG is safer and easier than in the past. However, this approach entails a number of potential pitfalls, and its role in the cardiac surgical armamentarium has not yet been tested in randomized clinical trials. Like many others, I question whether BHCABG is truly as beneficial as its adherents claim.

Potential pitfalls

Technically demanding, with steep learning curve
Coronary artery bypass on the beating heart may be technically challenging in some patients and involves a steep learning curve, especially when performed through a minimally invasive incision, which provides reduced exposure. As Westaby [10] has pointed out, suturing a 1.5-mm artery to a 2-mm moving target vessel requires considerable surgical skill. Technical problems may be increased in patients who have excessive epicardial fat. In addition, harvesting of the IMA may be difficult and time consuming. Surgeons who aspire to BHCABG should master off-pump cases involving a conventional sternotomy before attempting limited-access beating-heart operations.

Incomplete revascularization
Beating-heart revascularization is appropriate mainly for well-collateralized lesions of the LAD or right coronary arteries. The circumflex and posterior descending arteries are hard to access and immobilize. Because of difficulties in creating the anastomoses, BHCABG is not suitable for diseased vessels that are small, intramyocardial, diffusely atherosclerotic, or calcified. If this approach is attempted and coronary disease turns out to be more extensive than expected, conversion to CPB may be necessary for complete revascularization. Moreover, if an endarterectomy is required (as it often is for smaller vessels), it cannot be satisfactorily done on the beating heart.

Consequently, BHCABG involves a risk of incomplete revascularization, even when the operation is performed through a full sternotomy. In many cases, the diseased circumflex coronary artery remains ungrafted, resulting in excessive morbidity and mortality [11, 12].

Intraoperative ischemia
To obtain a bloodless anastomotic field, the target artery must be occluded temporarily. Such occlusion appears to be well tolerated for up to 20 minutes. However, Calafiore and associates (who, by 1997, had the most extensive contemporary experience with LIMA-to-LAD grafting through a left anterior thoracotomy), reported a LAD occlusion time of 23 ± 7 minutes in 343 patients [13]. Such an occlusion time may place patients at risk for a perioperative myocardial infarction or for myocardial stunning and arrhythmias. To protect against these complications, ß-adrenergic antagonists may be used to reduce the myocardial oxygen demand. Other protective strategies include ischemic preconditioning and pretreatment with adenosine. Some surgeons use intraluminal coronary shunts to maintain distal perfusion during anastomosis, but these devices entail a risk of intimal damage, dissection, or loosening of atheromatous debris. With use of the latest mechanical stabilizing devices, these pharmacologic and mechanical adjuncts may not be necessary.

In patients with a moderately enlarged (4.0 to 4.5 cm) ascending aorta, the use of side clamps may pose a risk of dissection [14]. Also, in patients with patent but diseased grafts that feed blocked native vessels, partial aortic cross-clamping may lead to ischemia.

Suboptimal anastomoses
Clearly, surgeons are more comfortable performing an anastomosis on a quiet, bloodless field without the distractions caused by cardiac motion or pulmonary insufflation. One possible pitfall of BHCABG may be suboptimal anastomoses with the potential for early occlusion.

With conventional coronary artery bypass, the 15-year patency rate is >97% [15]. This is the gold standard that any new revascularization method must compete against. So far, however, few data are available regarding patency rates after BHCABG, and anastomotic failure may be under-reported. In their 343 patients, Califiore and associates [13] had a reintervention rate of 7.3% because of anastomotic failure of graft occlusion. In the 176 patients who underwent postoperative angiography, the overall patency rate was 89.8%, and the rate of "perfect" angiographic patency (stenosis <50%) was 85.2% [16], comparing unfavorably with the results of conventional LIMA-to-LAD grafting. In another series [15], a third of the patients had angiographic evidence of graft occlusion within 24 hours after undergoing BHCABG via a minimally invasive incision. McMahon and coauthors observed avulsion of the IMA 5 days after a similar procedure, and other surgeons have had unreported anecdotal instances of this complication [17].

In the early experience of Gundry and associates [18], BHCABG (with a full sternotomy) was considered for all patients in need of myocardial revascularization. Despite satisfactory in-hospital results, twice as many BHCABG patients as CPB patients needed recatheterization. The reintervention rate was 20% versus 7% in the two respective groups, and the cardiac-related mortality was 12% versus 9%.

Because of these problems, some experts recommend early postoperative angiographic or Doppler ultrasonographic evaluation, which adds to the length and expense of BHCABG.

Mediastinitis in diabetic patients
Pfister and associates [19] found that in diabetic patients BHCABG entailed a greater than twofold increase in the incidence of mediastinitis. The authors were unable to account for this phenomenon but stressed that "the risk of infection in diabetics may be increased off bypass."

Excessive operating room times and overall costs
Recently, new equipment became available that may alleviate some of the above-mentioned problems. For instance, with the use of several portals, the IMA can now be harvested laparoscopically. With the more elaborate devices and retractors, however, one can waste considerable time positioning the instruments, thereby increasing the operating room charge. Moreover, disposable items can cost up to $2,000 each, so the charge for these items may amount to $5,000 per case. For these reasons, I question where BHCABG confers a significant economic advantage.

Comment

Many cardiac surgeons remain skeptical of BHCABG, calling it "a triumph of technique over reason" [20]. Although it appears to have a distinct, but limited, role in some patients—particularly those who cannot tolerate CPB because of age or severe illness—it also seems largely market driven. Surgeons should not be intimidated into adopting this approach simply to remain competitive. We must rely on our own best judgment, make the patient’s well-being our primary consideration, and refuse to endorse innovation for its own sake. Any new revascularization technique must equal or surpass traditional CABG with respect to operative survival, low morbidity, cerebral protection, relief of angina, and long-term patency. When traditional CABG is performed properly, the brain is protected, and the adverse event rate is extremely low, so one must have an excellent reason for refusing to use CPB.

One of the chief reasons for contemporary interest in BHCABG is the desire to avoid the deleterious neurologic, renal, and systemic effects of CPB. However, BHCABG does not necessarily offer an improvement in this regard. In a recent comparison of the two techniques, Diegeler and associates [21] showed that changes in leukocyte subsets associated with a systemic inflammatory response were more related to surgical trauma than to CPB. Moreover, in patients undergoing single-vessel CABG, Andrew and colleagues [22] found that the elimination of CPB did not prevent postoperative neuropsychological dysfunction; they concluded that, in this subset of patients, minimally invasive BHCABG will have to provide other advantages before it can be regarded as an acceptable alternative to the traditional method. In addition, Malheiros and coworkers [23] found no difference in the early neurologic outcome of beating-heart versus CPB revascularization.

Some surgeons believe that, in high-risk patients, on-pump BHCABG is an appropriate compromise [24]. Sweeney and Frazier [25] have had good results after using a centrifugal ventricular assist device (the Hemopump and later the Biomedicus Bio-Pump) as an alternative to CPB/cardioplegia in severely ill patients. Broader application of these small, inexpensive, disposable pumps could yield better clinical and economic outcomes.

In conclusion, BHCABG should be performed only when it is clearly indicated and is in the patient’s best interests, not simply because of market-driven considerations or a desire for innovation.

References

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