Non-invasive Assessment of Regional Myocardial Function at Rest and during Exercise after Aorto-coronary Bypass Operation

Abstract

Fifty patients (mean age 53.9 years) with persistent severe ang na pectoris underwent aorto-coronary bypass surgery receiving an overall of 161 anastomosis. On an average 8.6 ± 1.3 months p.o. first pass radionuclide ventriculograms with 99 m Technetium-Pertechnetate were performed at rest and after maximum exercise. Regional ejection fractions (REF) was assessed defining REF as motion of a left ventricular piece of myocardium which is supplied by one main coronary artery and its branches.

All regions were classified using preoperative coronary angiograms and operative reports. Six groups evolved:

Group 1: (normally perfused areas; n = 14): Total group's REF increased after exercise by 11.6 percentage points.

Group 2 (completely revascularized regions without previous myocardial infarction (M.I.); (n=55): On an average REF improved by 11.0 points.

Group 3 (completely revascularized regions with previous M.I.; n=25): After exercise REF still rose by 4.1 percentage points. The results deteriorated further in the remaining three groups:

Group 4 (incompletely revascularized territories without previous M.I.; n=19), decrease of REF by —4.9 points,

Group 5 (incompletely revascularized territories with previous M.I.; n=8) deterioration by —8.1 points.

Group 6 (no revascularization but significant disease with or without previous M.I.; n=14) did not differ from group 5; REF deteriorated by —9.0 percentage points.

The findings show that complete revascularization improves REF significantly (p < 0.05). Areas without previous M.I. respond to exercise like normally perfused territories.

Angina pain relief subsequently to aorto-coronary bypass surgery is undisputed. Yet, up till now, improvement of left ventricular function seemed questionable. One reason for the ineptitude might be the global access to left ventricular function. Since coronary artery disease has segmental nature, global left ventricular parameters, like global ejection fraction e.g., may hide regional changes achieved by revascularization. Therefore, evidence of functional improvement should be done regionally. In the presented study regional ejection fraction was applied, defining that term as motion of a left ventricular portion, which is supplied by one main coronary artery and its branches.