Minimally invasive coronary artery bypass grafting in high-risk patients. Late follow-up with assessment of left internal mammary artery graft patency and flow by exercise transthoracic Doppler echocardiography

Patients with significant risk factors are at increased risk of higher mortality and morbidity (9–16%) after CABG-procedures with cardiopulmonary bypass (CPB). When catheter interventions are not applicable and conventional CABG with CPB are considered to have an unacceptable perioperative risk, these patients (n=35) were scheduled for minimally invasive coronary artery bypass grafting (MIDCAB).

Patients and methods: The risks leading to exclusion of conventional CABG procedures were: extremely impaired LV-function (EF<20%), severe pulmonary diseases, malignant carcinoma, compromised coagulation system, age >80 years with impaired physical constitution, redo-procedures after complicated initial operation, symptomatic descending thoracic aortic aneurysm, ongoing long-term intensive care treatment with unclear prognosis. All patients received the LIMA as a single graft to the LAD. One year follow-up was performed using transthoracic Doppler echocardiography at rest and during exercise.

Results: In 20 patients incomplete revascularization was accepted. There was no mortality, while signs for myocardial infarction were seen in two patients. Twenty-nine patients (82%) showed clear improvement of clinical symptoms, one patient needed further conventional CABG.

Nine to thirteen months postoperatively (mean 10.8±1.6 months), there were two deaths due to noncardiac reasons. Three of the survivors (n=33) had symptoms of angina pectoris. Exercise tests revealed an improved stress tolerance (NYHA class improved from preop. III–IV to postop. I–II). The IMA graft flow increased significantly with exercise in all patients. Flow patterns in both flow velocity and volume changed to diastolic-dominant, and the ratio of diastolic to systolic time–velocity integral of >1.5 excluded a graft stenosis.

Conclusions: In high-risk patients, with an increased likelihood of perioperative morbidity and mortality, the MIDCAB procedure can be performed accurately and safely. Even after incomplete revascularization of some high-risk patients, exercise tolerance was improved. Transthoracic Doppler echocardiography proved to be a clinically useful noninvasive method of assessing IMA graft function at rest and during exercise. Despite the small patient population, our late follow-up results suggest the potential benefit of MIDCAB for patients with otherwise inoperable heart disease.