Regional nonuniformity of normal adult human left ventricle

TLDR

Regional nonuniformity is a feature of both diseased and normal left ventricles, likely driven by differences in regional LV architecture and local stress. The study used MR myocardial tagging to perform 3‑D strain analysis on 87 healthy adults, aiming to characterize normal LV nonuniformities and evaluate wall thickening as a regional function metric. The authors measured regional wall thickness and radii of curvature, and performed 3‑D strain analysis in local cardiac and fiber coordinate systems using MR myocardial tagging. Strain analysis revealed transmural nonuniformity with subendocardial strains exceeding subepicardial strains, base‑to‑apex gradients in wall thickness and curvature, apex‑higher EF, and regional variations in wall thickening and EF, indicating that wall thickening alone does not fully characterize LV regional contribution to ejection.

Abstract

Regional nonuniformity is a feature of both diseased and normal left ventricles (LV). With the use of magnetic resonance (MR) myocardial tagging, we performed three-dimensional strain analysis on 87 healthy adults in local cardiac and fiber coordinate systems (radial, circumferential, longitudinal, and fiber strains) to characterize normal nonuniformities and to test the validity of wall thickening as a parameter of regional function. Regional morphology included wall thickness and radii of curvature measurements. With respect to transmural nonuniformity, subendocardial strains exceeded subepicardial strains. Going from base to apex, wall thickness and circumferential radii of curvature decreased, whereas longitudinal radii of curvature increased. All of the strains increased from LV base to apex, resulting in a higher ejection fraction (EF) at the apex than at the base (70.9 ± 0.4 vs. 62.4 ± 0.4%; means ± SE, P < 0.0001). When we looked around the circumference of the ventricle, the anterior part of the LV was the flattest and thinnest and showed the largest wall thickening (46.6 ± 1.2%) but the lowest EF (64.7 ± 0.5%). The posterior LV wall was thicker, more curved, and showed a lower wall thickening (32.8 ± 1.0%) but a higher EF (71.3 ± 0.5%). The regional contribution of the LV wall to the ejection of blood is thus highly variable and is not fully characterized by wall thickening alone. Differences in regional LV architecture and probably local stress are possible explanations for this marked functional nonuniformity.