Q waves in ischemic cardiomyopathy

Abstract

Q waves may be observed in the absence of non-viable tissue. However, their scintigraphic translation in patients with ischemic cardiomyopathy (ICM) has not been properly assessed. This study sought to establish the determinants of Q waves in the absence of non-viable tissue and the diagnostic accuracy in this population. A retrospective study enrolling 487 consecutive patients (67.0 [57.4 - 75.4] years), with ICM, LVEF < 40% and narrow QRS who underwent stress-rest 99 m-Tc SPECT was conducted. A 17-segment model for myocardium was used: Myocardium was divided in basal (1 to 6), mid (7 to 12), apical (13 to 16) and apex (17) segments. Non-viable tissue was defined as a severe perfusion defect without systolic thickening. Patients with Q waves (65.7%) had more non-viable tissue, more extensive scar and less ischemia. Q waves had a moderate correlation with non-viable tissue (AUC = 0.63) and were associated with the extension of the scar. After excluding patients with non-viable tissue in any myocardial segment, Q waves were observed in 51.9% of the patients, of which 78.1% had a scar fulfilling viability criteria. The presence of Q waves was associated with the location of these scars in a base-to-apex axis (OR = 1.88 [1.35-2.62] for segment towards the apex) and their extent (OR = 1.19 [1.05 - 1.35] for each segment). In patients with ICM, Q waves discriminate poorly viable from non-viable tissue. Q waves in this population may be due to extensive scars fulfilling viability criteria located in apical segments.

Keywords: Ischemic cardiomyopathy; Q wave; SPECT; Viability.