Importance: Regional left ventricular (LV) wall thinning is believed to represent chronic transmural myocardial infarction and scar tissue. However, recent case reports using delayed-enhancement cardiovascular magnetic resonance (CMR) imaging raise the possibility that thinning may occur with little or no scarring.
Objective: To evaluate patients with regional myocardial wall thinning and to determine scar burden and potential for functional improvement.
Design, setting, and patients: Investigator-initiated, prospective, 3-center study conducted from August 2000 through January 2008 in 3 parts to determine (1) in patients with known coronary artery disease (CAD) undergoing CMR viability assessment, the prevalence of regional wall thinning (end-diastolic wall thickness ≤5.5 mm), (2) in patients with thinning, the presence and extent of scar burden, and (3) in patients with thinning undergoing coronary revascularization, any changes in myocardial morphology and contractility.
Main outcomes and measures: Scar burden in thinned regions assessed using delayed-enhancement CMR and changes in myocardial morphology and function assessed using cine-CMR after revascularization.
Results: Of 1055 consecutive patients with CAD screened, 201 (19% [95% CI, 17% to 21%]) had regional wall thinning. Wall thinning spanned a mean of 34% (95% CI, 32% to 37% [SD, 15%]) of LV surface area. Within these regions, the extent of scarring was 72% (95% CI, 69% to 76% [SD, 25%]); however, 18% (95% CI, 13% to 24%) of thinned regions had limited scar burden (≤50% of total extent). Among patients with thinning undergoing revascularization and follow-up cine-CMR (n = 42), scar extent within the thinned region was inversely related to regional (r = -0.72, P < .001) and global (r = -0.53, P < .001) contractile improvement. End-diastolic wall thickness in thinned regions with limited scar burden increased from 4.4 mm (95% CI, 4.1 to 4.7) to 7.5 mm (95% CI, 6.9 to 8.1) after revascularization (P < .001), resulting in resolution of wall thinning. On multivariable analysis, scar extent had the strongest association with contractile improvement (slope coefficient, -0.03 [95% CI, -0.04 to -0.02]; P < .001) and reversal of thinning (slope coefficient, -0.05 [95% CI, -0.06 to -0.04]; P < .001).
Conclusions and relevance: Among patients with CAD referred for CMR and found to have regional wall thinning, limited scar burden was present in 18% and was associated with improved contractility and resolution of wall thinning after revascularization. These findings, which are not consistent with common assumptions, warrant further investigation.