Systolic heterogeneity of transmural myocardial function in normal subjects: Physiological functional heterogeneity

Because of the lack of a clinical method for assessing the transmural myocardial function, few studies on the heterogeneity during the myocardial contraction/relaxation sequence inside the human ventricular wall have been reported, despite the fact that the importance of the pathophysiology in the transmural heterogeneity has been stressed in previous experimental studies. We studied the transmyocardial functional heterogeneity of the basal antero-septal segment in normal subjects (n=8, 40.0±12.8 year, male), adopting the novel high resolution Doppler measurement "Phased Tracking Method". Each transmural layer of 0.75 mm thickness showed functional heterogeneity (physiological transmural functional heterogeneity), namely larger thickening occurred in the left ventricular endocardial side (right side 1/3: 26.1±5.2% of the total wall thickness, middle 1/3: 31.9± 2.7%, left side 1/3: 42.1± 6.4%) and the peak thickening shifted smoothly in time from the middle layers to the left subendocardial side during the contraction period. We concluded that transmural functional heterogeneity does exist in normal subjects as well as in the experimental animals of previous reports. Smooth and coordinate myocardial layer contraction across the ventricular wall (physiological transmural functional heterogeneity) is fundamental to maintain the normal ventricular function.