Relationship between myocardial viability and improvement in left ventricular function and heart failure symptoms after coronary artery bypass surgery

Abstract

Background: The evaluation of myocardial viability is an important preoperative parameter, predictive of improvement in regional and global left ventricular (LV) function after coronary artery bypass surgery (CABG). However, whether the presence of viability is also associated with relief of heart failure symptoms after revascularization is not always certain. The aims of the study were to define the relationship between extent of viable myocardium and improvement in LV function after CABG and to determine whether preoperative viability testing can predict improvement in heart failure symptoms.

Methods: Eighty-five consecutive patients with ischemic cardiomyopathy (mean LVEF 35%) undergoing surgical revascularization were studied with a Tc-99m sestamibi one-day rest/nitrate enhanced myocardial perfusion SPECT imaging (MPI) to assess viability. Regional and global function were measured before and 16 -/+ 6 months after revascularization. We have used the Bull's eye quantitative analysis of MPI scans and 17 segment model of LV function and perfusion evaluation. Heart failure symptoms were graded according to the New York Heart Association (NYHA) criteria, before and 16 -/+ 6 months after revascularization.

Results: The number of viable segments per patient was directly related to the improvement in LVEF after revascularization (r 0.79, P < 0.01). Patients with > 4 viable segments representing 24% of the left ventricle yielded the sensitivity of 83% and specificity of 79% respectively for predicting improvement in LVEF. Furthermore, the presence of four or more viable segments predicted improvement in heart failure symptoms after revascularization, with positive and negative predictive values of 79% and 74%, respectively.

Conclusion: The presence of substantial viability (four or more viable segments, 24% of the left ventricle) on myocardial perfusion gated SPECT imaging in patients with ischemic heart failure before CABG surgery has significant correlation with the improvement in LVEF and heart failure symptoms postoperatively.