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Ann Thorac Surg 1998;66:1113-1118
© 1998 The Society of Thoracic Surgeons
a Escorts Heart Institute and Research Centre, New Delhi, India
Address reprint requests to Dr Mishra, Escorts Heart Institute and Research Center, Okhla Rd, New Delhi, 110 025, India
e-mail: (ehirc{at}giasdlOl.vsnl.net.in)
Presented at "Facts and Myths of Minimally Invasive Cardiac Surgery: Current Trends in Thoracic Surgery IV," New Orleans, LA, Jan 24, 1998.
Abstract
Background. To achieve complete myocardial revascularization in patients with diffuse coronary artery disease and patients at high risk if they undergo cardiopulmonary bypass such as severe systemic disease or diffuse arteriosclerosis of the aorta, we have adopted the technique of combining direct coronary artery bypass grafting without cardiopulmonary bypass with transmyocardial laser revascularization.
Methods. From April 1995 to September 1997 this technique was used in 77 patients. Ages ranged from 37 to 85 years with a mean of 56 ± 17 years. Diffuse coronary artery lesions were present in 46 patients, 10 had severely deranged renal function, 7 had diffuse carotid artery lesions, and 7 had aortic arch atheromas. Liver dysfunction was present in 4 patients and severe obstructive airway disease in 3. The mean left ventricular ejection fraction was 0.45 ± 0.05. Midsternotomy approach was used in 65 patients and anterior minithoracotomy in 12. Direct coronary artery bypass grafting without cardiopulmonary bypass was done to the left anterior descending coronary artery or right coronary artery or both. Transmyocardial laser revascularization using a 1,000-W CO2 laser machine was performed on the areas supplied by ungraftable coronary arteries or even in graftable distal targets in the posterolateral or inferior wall in patients who were at high risk if they underwent cardiopulmonary bypass.
Results. The mean number of vessels bypassed was 1.12. One patient died of intractable ventricular arrhythmia in the early postoperative phase. Mean follow-up was 16.6 months. At 12 months 89% of the patients were angina free. Metabolic stress test demonstrated an average increase in exercise tolerance from 5.2 at baseline to 9.7 minutes at 12 months. Myocardial thallium scanning done at 3-, 6-, and 12-month intervals postoperatively revealed that myocardial perfusion in grafted segments had an exponential trend of improvement, and perfusion in transmyocardial laser revascularization segments showed a linear trend in the same period with a total gain of 28.4%.
Conclusions. Transmyocardial laser revascularization is an excellent adjunct to minimally invasive coronary artery bypass grafting to achieve complete myocardial revascularization in patients with graftable vessels in the anterior wall and ungraftable vessels in the posterior and inferior wall. This achieves complete myocardial revascularization without compromising safety in patients who are at high risk if they undergo cardiopulmonary bypass. Minimal morbidity and mortality in the present series revealed that this procedure is safe, and postoperative follow-up of these patients showed significant functional improvement as well as an improvement in myocardial perfusion scan.
Although current methods of cardiopulmonary bypass (CPB) are remarkably safe, there is evidence that various damaging effects of CPB do occur [1]. In the majority of patients the adverse effects of CPB are minor and reversible; however, patients with significant functional impairment of various organ systems may not tolerate the added deleterious effects of CPB, which may be irreversible and even fatal [2].
The first operation for coronary artery disease in which the internal mammary artery (IMA) was anastomosed on a beating heart to the left anterior descending coronary artery (LAD) was done by Kolessov [3]. Subsequently the technique was developed and improved mainly by Benetti and associates [4] and Buffolo and colleagues [5]. In an attempt to further reduce the invasiveness of coronary artery bypass grafting (CABG) and retain the benefit of mammary artery grafting, the minianterior mediastinal approach [6], partial sternotomy approach, a minilateral thoracotomy [7], and minithoracotomy [8, 9] approach have recently been described. There has also been some apprehension that in the overenthusiasm to perform CABG off-pump, there may be, in some patients, an incomplete revascularization [10]. This holds true especially for patients who have multivessel disease but are at high risk if they undergo cardiopulmonary bypass because of severe systemic disease, aortic arteriosclerosis, advanced age, or other conditions [11].
Mirhoseini and Cayton [12] first proposed using a laser to create transmyocardial channels to provide direct perfusion of the myocardium with ventricular blood. Initially they performed transmyocardial laser revascularization (TMLR) clinically as an adjunct to CABG, using an 80-W CO2 laser on a cardioplegia-arrested heart. In 1991 Mirhoseini and Cayton [12] began clinical studies of TMLR with a high-powered CO2 laser (1,000 W) that could transect the entire thickness of the myocardium without interfering with the electrical activity of the heart. The emergence of TMLR as a therapeutic modality has added another dimension to coronary revascularization. Although the long-term efficacy of TMLR for myocardial revascularization has yet to be proved, early clinical evidence [13] along with radionuclide studies [14] does suggest that TMLR improves myocardial perfusion and ameliorates anginal symptoms. Thus even patients with triple-vessel disease, who are unsuitable for cardiopulmonary bypass, can be offered complete myocardial revascularization after bypassing the LAD or right coronary artery (RCA) on a beating heart without CPB, and simultaneously performing TMLR to the posterolateral surface of the heart in the territory of the left circumflex (LCX) or posterior descending coronary artery.
This study has been undertaken to evaluate the suitability of the procedure in patients who have symptomatic coronary artery disease and are at a high risk if they undergo CPB, and to evaluate the adequacy of myocardial revascularization by TMLR combined with CABG in patients who have graftable vessels in the posterior or inferior wall.
Material and methods
Between April 1995 and September 1997, 77 patients had undergone TMLR combined with CABG without CPB. During the same time frame 254 patients had undergone TMLR combined with CABG on CPB. Patients’ ages ranged from 37 to 81 years (mean, 56.17 years). Twelve patients were older than 70 years. There were 49 men and 28 women. Forty-one patients (53.2%) suffered previous myocardial infarction (Table 1). The mean left ventricular ejection fraction of the group was 0.45 (range, 0.18 to 0.60). Eighteen patients had unstable angina. Preoperatively 41 patients (53.2%) were in the Canadian Cardiovascular Society (CCS) class 3 angina whereas 10 patients (12.9%) were in class 4 (Table 2). Four patients required intraaortic balloon pump support for unstable angina preoperatively. Two patients had undergone prior CABG. On coronary angiography, 25 patients (32.5%) had double-vessel disease and 52 patients (67.21%) triple-vessel disease. In 4 patients, in addition to TMLR combined with CABG on the beating heart without CPB, carotid endarterectomy was also performed.
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Patients with bleeding diathesis, intractable arrhythmias, and coronary artery disease with left ventricular aneurysm were considered to have absolute contraindications for the procedures.
Surgical technique
The target areas for TMLR and CABG were planned on the basis of the coronary angiography and stress thallium scan. During the operation all patients were monitored with direct arterial and pulmonary artery catheters. After endotracheal intubation a multiplane phased-array dual-frequency (3.7/5 MHz) transesophageal echocardiography transducer was inserted. A baseline transesophageal echocardiography study was performed to evaluate the regional and global left ventricular function and the cardiac valves.
In 65 patients a midsternotomy approach was used whereas a left anterior thoracotomy was done in 12 patients. The pericardium was opened and the vessels examined to confirm the angiographic assessment of their size and diffuse nature of disease. The appropriate conduits were harvested before TMLR. A 1,000-W CO2 heart laser machine (PLC System) was made ready and laser channels were created 1 cm apart in the target areas. On average it was desirable to make 10 to 12 channels in the lateral wall. The laser energy delivered was 35 to 45 J. Bleeding from the TMLR site was stopped most of the time by applying external digital pressure. Occasionally epicardial stitching was required to stop the bleeding. We use heparin in a dose of 1.5 mg/kg body weight before dividing the arterial conduits for grafting. The distal anastomoses to the LAD and RCA were constructed with 8-0 polypropylene sutures. The target vessel was occluded with a 3-0 polypropylene sling and silicone elastomer bolster proximal to the proposed site of arteriotomy.
In patients who underwent anterior thoracotomy, a Cardiothoracic Systems (Cupertino, CA) mammary retractor and stabilizer were used for the procedure.
Analysis of myocardial injury was done by serial electrocardiograms and estimation of creatine kinase MB and troponin T levels in the postoperative period.
Follow-up
The patients were examined 3, 6, and 12 months after the operation. They were assessed for angina class, activity level, medications, and hospitalizations since the procedure. All patients had to undergo a thallium perfusion scintigraphic study and an exercise tolerance test.
The scintography results were based on counting the number of segments with fixed ischemia and the number of segments with reversible ischemia as viewed on the polar plots. The follow-up studies were compared with the baseline scans and the change in the number of involved segments was calculated.
Results
In this series of 77 patients the average number of grafts was 1.12. Internal mammary artery was used in 74 patients (95.1%). Vein graft to the LAD was used in 3 patients who had severe obstructive airway disease. Seventy-two patients received a single graft to the LAD, and 5 patients received an additional graft to the RCA as well (Table 4).
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Postoperatively 5 patients (6.4%) showed elevation of creatine kinase-MB levels, whereas 3 patients (3.8%) had increased troponin T levels. At this time there were no associated electrocardiographic changes, and no segmental wall motion abnormalities were detected on transesophageal echocardiography. Two patients underwent reexploration for postoperative bleeding from TMLR holes (Table 5). One patient died of intractable arrhythmia on the second postoperative day. The mean duration of hospital stay was 6 days. All patients were angina free when they left the hospital. The mean follow-up has been 16.6 months. Sixteen patients have completed 12 months of follow-up. At 12 months 89% of the patients were angina free. Metabolic stress tests demonstrated an average increase in exercise tolerance from 5.2 minutes at baseline to 9.7 minutes at 12 months. Similarly the metabolic equivalents increased from 4.7 at baseline to 9.4 at 12 months (Table 6). The average Karnofsky score of 44% also increased to 86% at 12 months.
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Figure 1 shows the angiogram of a 68-year-old man with a critically occluded LAD and diffusely diseased LCX and RCA who had angina at rest. He received a LIMA graft to the LAD and TMLR to the LCX and posterior descending coronary artery territory. The patient was discharged from the hospital on the sixth postoperative day. Figure 2 shows his perfusion scan preoperatively and 3, 6, and 12 months postoperatively. At 1 year, the patient had marked improvement in symptomatic status and was in CCS class 1 angina.
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Performing CABG without CPB is a technical solution to be considered in every patient in whom CPB is likely to be associated with increased morbidity. However, there is always a possibility of incomplete revascularization in patients with multivessel disease. To overcome this limitation of CABG without CPB in multivessel disease in patients who are at high risk if they undergo CPB, TMLR can be used as an adjunct to achieve complete myocardial revascularization. Early results from many centers indicate that TMLR provides substantial benefit to patients. Cooley and associates [15] evaluated 21 patients and found that TMLR improved the clinical status and produced objective benefits. They noted that relief from angina occurred immediately. The mean resting left ventricular ejection fraction increased from 0.48 ± 0.10 before the operation to 0.50 ± 0.08. The resting mean subendocardial to subepicardial perfusion ratio also increased by 20% ± 9% during the subsequent 12 months. Horvath and coworkers [13] treated 20 patients with transmyocardial laser. The angina class improved markedly in all patients available for follow-up. They were all in angina class 0, 1, or 2 postoperatively compared with 14 patients in class 4 and 6 in class 2 preoperatively. Their report was based on the use of TMLR as the sole therapy.
In the absence of irrefutable evidence of long-term efficacy of TMLR, CABG still remains the gold standard for surgical myocardial revascularization. Thus if there is even one graftable vessel in a patient, the other being diffusely diseased, it should be used for the bypass graft procedure. Incomplete revascularization may not affect early mortality, but failure to effectively bypass severe arterial narrowing profoundly affects late cardiac events [16, 17]. In one report in which 500 surgical patients were followed up for 10 to 12 years, the presence of disease in ungraftable arteries was the most significant predictor of late cardiac events, including cardiac-related deaths, recurrence of angina, and myocardial infarction [18].
We have combined TMLR with CABG to provide complete myocardial revascularization in patients who had graftable vessels in the anterior wall and ungraftable vessels in the posterior and inferior wall. In these patients CABG without CPB was done to the LAD or RCA and TMLR was done to the posterolateral or inferior wall depending on the quality of distal targets. We have also combined TMLR with CABG to provide complete myocardial revascularization in territories that could be revascularized by grafts, as well as in territories where revascularization by conventional grafting was not feasible, without using extracorporeal circulation. Through a median sternotomy it is easy to approach and perform an anastomosis on the LAD, diagonal branch, and RCA but not on the LCX and posterior descending coronary artery. Hence, TMLR performed on the LCX territory is the most logical option.
Technically the anastomosis performed on a beating heart is more difficult and demands greater surgical skill [1, 5]. But among the advantages of performing CABG without CPB are the safety of the procedure, almost total nonuse of blood products, and a dramatic reduction in the cost and hospital stay [5]. Patients with preoperative renal failure are at increased risk for acute renal shutdown after CABG because of decreased renal perfusion, absence of pulsatile flow, excessive hemolysis, and platelet–fibrin microemboli [19]. Our experience of CABG without CPB shows a temporary increase in blood urea nitrogen and creatinine levels in patients with preoperative abnormal renal function. But before hospital discharge their blood urea nitrogen and creatinine returned to baseline levels and none of them needed dialysis.
Coronary artery bypass grafting without CPB should address some of the problematic issues of aortic atheroma and calcified aorta [20]. In the current series, 7 patients had aortic atheroma in the arch. All of these patients tolerated the operation well without any neurologic problems. We achieved this with our current practice of making every effort to avoid manipulation of the aorta and prefer using arterial conduits in these patients.
Coronary anastomosis requires a meticulous technique. It appears to be much more difficult to perform a perfect distal anastomosis with a beating heart. Doppler flow examination of the LIMA to LAD anastomosis was done in 12 patients who had grafting done through an anterior minithoracotomy, and all of them showed excellent flow dynamics. In the early part of our study we subjected most of our minithoracotomy patients to a postoperative check angiogram to evaluate the LIMA to LAD anastomosis. All of the 12 patients in this series had excellent flow across the LIMA to LAD anastomosis (Fig 3). This observation supports the view that a good quality IMA anastomosis can be achieved even on a beating heart.
In summary, it is evident from our series that TMLR is an excellent adjunct to minimally invasive CABG to achieve complete myocardial revascularization in patients with graftable vessels in the anterior wall and ungraftable diffusely diseased vessels in the posterior and inferior wall. Performing TMLR and CABG without CPB is the appropriate procedure to achieve complete myocardial revascularization without compromising the safety in patients who are at high risk if they undergo CPB. Minimal morbidity and mortality in this study revealed that the procedure is safe. Postoperative follow-up showed significant functional improvement with improvement in the myocardial perfusion on thallium scan.
References
This article has been cited by other articles:
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  S. W Sutton, M. A Duncan, V. A Chase, B. L Hamman, and E. H Cheung Perfusion-assisted beating heart support with a miniature extracorporeal circuit and leukocyte filtration: a 58-year-old patient with severe COPD Perfusion, December 1, 2004; 19(6): 369 - 373. [Abstract] [PDF]
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 M. Ruel, R. A. Kelly, and F. W. Sellke Therapeutic Angiogenesis, Transmyocardial Laser Revascularization, and Cell Therapy Card. Surg. Adult, January 1, 2003; 2(2003): 715 - 750. [Full Text]
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 K. Minami Surgical Treatments for Endstage Heart Failure Due to Dilated Cardiomyopathy Asian Cardiovasc Thorac Ann, September 1, 2001; 9(3): 159 - 166. [Full Text] [PDF]
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 C. R. Bridges Myocardial laser revascularization: the controversy and the data Ann. Thorac. Surg., February 1, 2000; 69(2): 655 - 662. [Abstract] [Full Text] [PDF]
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 J. T. Beranek Emerging new concepts of myocardial laser revascularization J. Thorac. Cardiovasc. Surg., November 1, 1999; 118(5): 977 - 977. [Full Text] [PDF]
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 T. M. McLoitghlin JR Complications of Minimally Invasive Cardiac Surgical Procedures Seminars in Cardiothoracic and Vascular Anesthesia, July 1, 1999; 3(2): 136 - 142. [Abstract] [PDF]
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