Contractile Reserve in Segments With Nontransmural Infarction in Chronic Dysfunctional Myocardium Using Low-Dose Dobutamine CMR

Objectives This study sought to quantify contractile reserve of chronic dysfunctional myocardium, in particular in segments with intermediate transmural extent of infarction (TEI), using low-dose dobutamine cardiac magnetic resonance (CMR) in patients with a chronic total coronary occlusion (CTO). Background Recovery of dysfunctional segments with intermediate TEI after percutaneous coronary intervention is variable and difficult to predict, and may be related to contractility of the unenhanced rim. Methods Fifty-one patients (mean age 60 ± 9 years, 76% male) with a CTO underwent CMR at baseline and 35 patients underwent CMR at follow-up to quantify segmental wall thickening (SWT) at rest during 5 and 10 μg/kg/min dobutamine, and at follow-up. Delayed-enhancement CMR was performed to quantify TEI. Dysfunctional segments were stratified according to TEI, end-diastolic wall thickness (EDWT), or unenhanced rim thickness, and SWT was quantified. Segments with an intermediate TEI (25% to 75%) were further stratified according to baseline SWT of the unenhanced rim (SWTUR ) (45%), and SWT was quantified. For each parameter, odds ratio (OR) and diagnostic performance for the prediction of contractile reserve were calculated. Results Significant contractile reserve was present in dysfunctional segments with EDWT >6 mm, unenhanced rim thickness >3 mm, or TEI of