Surgical Revascularization for Acute Total Occlusion of Left Main Coronary Artery

Abstract

We report our experience with emergency surgical revascularization in 3 patients who were in cardiogenic shock as a result of acute total occlusion of the left main coronary artery. Because they were in profound shock, 2 patients required mechanical support with extracorporeal membrane oxygenation before the operation. Another patient was given moderate inotropic support and treated with an intraaortic balloon pump before surgery, because he had a dominant right coronary artery with extensive collateral circulation to the left coronary artery. All 3 patients underwent surgical revascularization within 20 hours of acute occlusion. Two patients survived, although 1 of them required extracorporeal membrane oxygenation support for 5 days postoperatively. The 3rd patient, despite successful weaning from extracorporeal membrane oxygenation immediately after coronary revascularization, died of hypoxic encephalopathy due to prolonged preoperative resuscitation.

Immediate surgical revascularization was an effective treatment in our 3 patients who were in cardiogenic shock due to acute total occlusion of the left main coronary artery. Such factors as abundant collateral vessels from the right coronary artery to the left coronary artery, complete surgical revascularization within 20 hours of acute occlusion, and mechanical circulatory support were deemed important to recovery of left ventricular function. Two of our 3 patients survived.

Acute total occlusion of the left main coronary artery (LMCA) is a rare angiographic finding and is usually fatal. ^1–3 Patients who do not die during the acute phase of total occlusion usually have a dominant right coronary artery and extensive collateral circulation to the left coronary artery. ^4–6 Herein, we report our experience with surgical revascularization in 3 patients who were in cardiogenic shock due to acute total occlusion of the LMCA.

Case Reports

Patient 1

A 48-year-old man who had a history of smoking and hyperlipidemia was admitted to our coronary care unit 4 hours after experiencing an anteroseptal acute myocardial infarction. Emergency coronary angiography showed total occlusion of the LMCA. He had a dominant right coronary artery, with distal stenosis (80%) and extensive collateral circulation to the left coronary artery. Intraaortic balloon pumping and moderate inotropic support were applied to counteract the cardiogenic shock. Primary percutaneous transluminal coronary angioplasty (PTCA) with stent placement over the LMCA was performed, which initially relieved the patient's chest pain. However, he experienced recurrent chest pain and progressive lung edema 4 hours later. Moreover, a new Q wave formation appeared over the lateral leads (V₅, V₆, and I) on repeated electrocardiography. Stent occlusion was suspected, and the patient underwent immediate coronary artery bypass grafting (CABG). The duration from the onset of recurrent chest pain to complete revascularization was 10 hours. The patient was weaned from the intraaortic balloon pump and extubated 5 days later. The peak levels of cardiac enzymes 24 hours after CABG were 3,720 for creatine kinase and 131 for the MB isoenzyme of creatine kinase. During 13 months of follow-up, he has remained in New York Heart Association functional class I.

Patient 2

A 58-year-old man, previously physically active and in good health, presented at our emergency room with precordial chest pain and cold sweating of 3 hours' duration. Electrocardiography showed an anterior acute myocardial infarction. Emergency angiography revealed 90% stenosis of the LMCA and total occlusion of the proximal left anterior descending artery. There was no collateral circulation from the right coronary artery. The patient underwent primary PTCA with a left main stent, and the chest pain subsided initially. However, after 1 hour, he had recurrent chest pain and went into cardiogenic shock. He was intubated with multiple inotropic drips and treated by intraaortic balloon pumping. Because of refractory shock, the patient was placed on mechanical circulatory support by means of percutaneous extracorporeal membrane oxygenation (ECMO). Repeat coronary angiography showed total occlusion of the LMCA; therefore, the patient was taken to the operating room for immediate CABG. The duration from the recurrence of chest pain to complete revascularization was 20 hours. Postoperatively, he was supported by ECMO for 5 days before the ventricular function recovered. During 18 months of follow-up, the patient has remained in New York Heart Association functional class II.

Patient 3

A 41-year-old man was admitted to our institution for recurrent angina. Five months earlier, he had experienced acute inferior wall myocardial infarction and undergone successful primary PTCA of the right coronary artery. Coronary angiography showed double-vessel coronary artery disease with 80% stenosis of the proximal left anterior descending artery and 70% stenosis of the distal right coronary artery. There were no intracoronary collateral vessels. Percutaneous transluminal coronary angioplasty was attempted but was complicated by spasms of the LMCA, along with cardiogenic shock. Under continuous cardiopulmonary resuscitation, the patient underwent bailout PTCA to recanalize the LMCA, but this measure failed. He was placed on percutaneous ECMO and taken to the operating room for emergency CABG. The duration from the onset of acute LMCA occlusion to complete revascularization was 4 hours. The patient's heart function recovered and he was weaned from ECMO immediately after surgery. However, his course was complicated by hypoxic encephalopathy caused by prolonged (2-hour) resuscitation before the operation. He remained in a deep coma and died of sepsis 1 month after surgery.

Discussion

Most patients who have an acute total occlusion of the LMCA die of cardiogenic shock before angiography can be performed. Cases of patients surviving acute myocardial infarction with LMCA occlusion are more likely to be reported in the literature than those of patients not surviving this condition; consequently, a literature review does not allow an accurate calculation of survival probability. Successful treatment of acute total occlusion of the LMCA has only occasionally been reported. Treatments described in the literature include balloon pumping, intracoronary thrombolysis, ⁷ PTCA, ^2,8 and emergency CABG. 4,6,9–11 In 1993, Quigley and colleagues ¹ proposed that conservative treatment might be indicated for patients presenting with acute myocardial infarction, severe left main stenosis, and cardiogenic shock (left main shock syndrome), because the prognosis of such patients is quite grave regardless of their treatment. Chauhan and coworkers, ³ in 1997, recommended that no PTCA of the LMCA be performed in patients with both acute myocardial infarction and cardiogenic shock. However, the medical literature has revealed a growing number of such patients who survived with the aid of early reperfusion, ^2–11 most of whom underwent CABG, as well. 4,6,9–11 Although PTCA alone may be effective in some patients with left main shock syndrome, subsequent CABG is almost always necessary in order to achieve complete revascularization and to improve the probability of survival.

In the past, some studies ^4–6 have indicated that the presence of a dominant right coronary artery and substantial collateral circulation to the left coronary artery are crucial to the prognosis of patients with acute occlusion of the LMCA. Indeed, there are only a few reports ^9–11 of successful surgical revascularization in such patients who did not have collateral circulation. Most of those survivors underwent surgical revascularization within 6 hours of acute occlusion. Therefore, emergency surgical revascularization, if performed early, may save the patient's life in cases of acute total occlusion of the LMCA; this measure also enables myocardial salvage.

Of our 3 patients who experienced cardiogenic shock due to acute total occlusion of the LMCA, only 1 (Patient 1) had abundant intracoronary collateral vessels. In Patients 2 and 3, ECMO was necessary to treat refractory cardiogenic shock in order to stabilize the patients' conditions and enable surgical revascularization. Patients 1 and 2 survived; Patient 3 died of hypoxic encephalopathy despite recovered heart function. The intervals from acute LMCA occlusion to complete revascularization in the 3 patients were 10, 20, and 4 hours, respectively. Factors contributing to successful rescue of left ventricular function in our patients included the protective effect of abundant collateral vessels from the right coronary artery to the left coronary artery in Patient 1, early surgical revascularization (4 hours) in Patient 3, and mechanical circulatory support with ECMO in Patient 2. Emergency reperfusion with PTCA in Patients 1 and 2 was a preliminary step to stabilize the patients' conditions until they could undergo complete revascularization by CABG.

In our experience, immediate surgical revascularization was an effective treatment in 3 patients who were in cardiogenic shock due to acute total occlusion of the LMCA. Abundant collateral vessels from the right coronary artery to the left coronary artery, immediate surgical revascularization, and mechanical circulatory support were crucial to recovery of left ventricular function.