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Prevalence of Regional Myocardial Thinning and Relationship With Myocardial Scarring in Patients With Coronary Artery Disease
Study Questions:
Does left ventricular wall thinning in patients with coronary artery disease (CAD) reliably represent scar tissue?
Methods:
The prospective multicenter study examined 1,055 patients with CAD who underwent cardiac magnetic resonance imaging (MRI) to evaluate viability, and evaluated the prevalence of myocardial wall thinning (end-diastolic thickness ≤5.5 mm in at least 5% of the total left ventricular circumference), the presence and extent of scarring in areas with thinning by delayed hyperenhancement imaging, and changes in contractility following revascularization in patients with wall thinning.
Results:
In this cohort of 1,055 individuals with CAD, 201 patients (19%) were noted to have myocardial wall thinning. The mean extent of scar tissue was 72 ± 25% of the area of thinning. Limited scar burden (≤50% of total extent of thinned myocardium) was observed in 18% of individuals. A total of 72 patients were revascularized in the artery that supplied a region with myocardial thinning, and follow-up cardiac MRI was performed in 42 (58%) of these individuals. In the subgroup with revascularization and follow-up MRI, there was an inverse relationship between the extent of scar and contractile improvement following revascularization (r = -0.72, p < 0.001), as well as improvement in left ventricular ejection fraction after revascularization (r = -0.53, p < 0.001). When patients were stratified by limited (≤50%) versus extensive scarring, only patients with limited scar burden were observed to have contractile improvement, with a mean increase in systolic wall thickening of 2.3 ± 1.1 mm. Finally, there was an inverse relationship between extent of scar and end-diastolic wall thickness after revascularization (r = -0.84, p < 0.001), and patients with limited scarring had a mean increase of 3.1 ± 1.1 mm in wall thickness (p < 0.001), with no change observed in patients with more extensive scarring. Using multivariable analysis, scar extent was independently associated with contractile improvement and reversal of thinning (p < 0.001 for each).
Conclusions:
The authors concluded that in patients with CAD noted to have myocardial wall thinning on MRI viability studies, 18% of individuals had scar burden that represented ≤50% of wall thickness. In the subgroup of patients undergoing revascularization and with follow-up MRI, limited scar burden was associated with improved contractility and increased end-diastolic wall thickness.
Perspective:
Myocardial wall thinning has typically been thought to represent a transmural infarct with nonviable scar tissue. This study finds that there may be a significant subset of these individuals with limited scar burden, who may potentially respond to revascularization with improved wall thickness, systolic contractility, and global left ventricular ejection fraction. These results suggest that wall thinning may be reversible in some cases, and prompt a need for future clinical trials to assess the potential benefit of revascularization in selected patients with wall thinning.
Keywords: Coronary Artery Disease, Follow-Up Studies, Ventricular Function, Left, Intracellular Signaling Peptides and Proteins, Magnetic Resonance Imaging, Systole, Heart Diseases, Prevalence, Cicatrix, Heart Failure, Stroke Volume, Heart Ventricles
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