Abstract
The transition from healthy myocardium to hypertensive heart disease is characterized by a series of poorly understood changes in myocardial tissue microstructure. Incremental alterations in the orientation and integrity of myocardial fibers can be assessed using advanced ultrasonic image analysis. We used a modified algorithm to investigate left ventricular myocardial microstructure based on analysis of the reflection intensity at the myocardial-pericardial interface on B-mode echocardiographic images. We evaluated the extent to which the novel algorithm can differentiate between normal myocardium and hypertensive heart disease in humans as well as in a mouse model of afterload resistance. The algorithm significantly differentiated between individuals with uncomplicated essential hypertension (N = 30) and healthy controls (N = 28), even after adjusting for age and sex (P = 0.025). There was a trend in higher relative wall thickness in hypertensive individuals compared to controls (P = 0.08), but no difference between groups in left ventricular mass (P = 0.98) or total wall thickness (P = 0.37). In mice, algorithm measurements (P = 0.026) compared with left ventricular mass (P = 0.053) more clearly differentiated between animal groups that underwent fixed aortic banding, temporary aortic banding, or sham procedure, on echocardiography at 7 weeks after surgery. Based on sonographic signal intensity analysis, a novel imaging algorithm provides an accessible, non-invasive measure that appears to differentiate normal left ventricular microstructure from myocardium exposed to chronic afterload stress. The algorithm may represent a particularly sensitive measure of the myocardial changes that occur early in the course of disease progression.
Highlights
Hypertensive heart disease is characterized by remodeling of the myocardium in response to chronically elevated blood pressure and wall stress.[1]
Investigators have hypothesized that these properties alter tissue impedances, thereby changing sonographic signal reflections and yielding signal intensity distributions that are unique to the scattering properties of the imaged left ventricular (LV) wall
With respect to echocardiographic traits, there was no significant difference between groups in conventional measures of LV structure and systolic function; the conventional measures of diastolic function, E prime and E/e’ ratio, were worse in hypertensives than controls, as expected (Table 1)
Summary
Hypertensive heart disease is characterized by remodeling of the myocardium in response to chronically elevated blood pressure and wall stress.[1]. Prior studies have used sonographic image analysis, including integrated backscatter techniques, to characterize myocardial tissue alterations in a variety of clinical settings, including hypertension,[5] early myocardial infarction,[6] chronic coronary artery disease,[7] and hypothyroidism.[8,9] the use of previously established techniques has been limited by low sensitivity and specificity, in the setting of poorer quality images.[10] Integrated backscatter techniques, for example, depends predominantly on mean signal values and has demonstrated variability due to random noise,[11] susceptibility to time delays arising from the application of algorithms,[12,13] and limited correlation with the extent of myocardial fibrosis present.[10] we assessed the ability of a modified ultrasound-based image analysis algorithm to quantify LV wall microstructural alterations using distributions of sonographic signal intensity values We evaluated this algorithm in humans with variable exposure to elevated blood pressure, as well as in a mouse model of chronic afterload stress
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