Myocardial Effective Transverse Relaxation Time T 2 * is Elevated in Hypertrophic Cardiomyopathy: A 7.0 T Magnetic Resonance Imaging Study

Abstract

Hypertrophic cardiomyopathy (HCM) is the most common genetic disease of the myocardium and bares the risk of progression to heart failure or sudden cardiac death. Identifying patients at risk remains an unmet need. Recognizing the dependence of microscopic susceptibility on tissue microstructure and on cardiac macromorphology we hypothesized that myocardial T2* might be altered in HCM patients compared to healthy controls. To test this hypothesis, myocardial T2*-mapping was conducted at 7.0 Tesla to enhance T2*-contrast. 2D CINE T2*-mapping was performed in healthy controls and HCM patients. To ensure that T2* is not dominated by macroscopic magnetic field inhomogeneities, volume selective B0 shimming was applied. T2* changes in the interventricular septum across the cardiac cycle were analyzed together with left ventricular radius and ventricular septal wall thickness. The results show that myocardial T2* is elevated throughout the cardiac cycle in HCM patients compared to healthy controls. A mean septal T2* = 13.7 ± 1.1 ms (end-systole: T2*,systole = 15.0 ± 2.1, end-diastole: T2*,diastole = 13.4 ± 1.3 ms, T2*,systole/T2*,diastole ratio = 1.12) was observed in healthy controls. For HCM patients a mean septal T2* = 17.4 ± 1.4 ms (end-systole: T2*,systole = 17.7 ± 1.2 ms, end-diastole: T2*,diastole = 16.2 ± 2.5 ms, T2*,systole/T2*,diastole ratio = 1.09) was found. Our preliminary results provide encouragement that assessment of T2* and its changes across the cardiac cycle may benefit myocardial tissue characterization in HCM.

Cardiovascular magnetic resonance detects microvascular dysfunction in a mouse model of hypertrophic cardiomyopathy

“…Standard tests used to diagnose coronary artery disease are not designed to detect small vessel disease, so a better understanding of the factors associated with microvascular dysfunction and its relation to the development of HCM would represent a major step toward earlier diagnosis and better management of the disease. Our results can partially explain previous findings showing that HCM patients have lower myocardial blood volume than healthy counterparts [ 22 ]. In the presence of LVH, effective perfusion is critical to compensate for hypertrophy-induced micro-vessel restriction in the HCM heart.…”

“…Local myocardial blood volume and blood flow are important indicators of changes in micro-perfusion [ 21 ]. Recent work has investigated the relationship between hypertrophy and the myocardial microvascular network in HCM [ 22 ]. In these studies, the fractional tissue blood volume per cardiac tissue volume (Bvf), defined as the volume in the microvascular network, was directly probed by Bvf-sensitive CMR using blood oxygenation-weighted imaging contrast [ 22 ].…”

“…Recent work has investigated the relationship between hypertrophy and the myocardial microvascular network in HCM [ 22 ]. In these studies, the fractional tissue blood volume per cardiac tissue volume (Bvf), defined as the volume in the microvascular network, was directly probed by Bvf-sensitive CMR using blood oxygenation-weighted imaging contrast [ 22 ]. Myocardial regions with reduced Bvf were highly correlated with ventricular wall thickening [ 22 , 23 ].…”

“…In these studies, the fractional tissue blood volume per cardiac tissue volume (Bvf), defined as the volume in the microvascular network, was directly probed by Bvf-sensitive CMR using blood oxygenation-weighted imaging contrast [ 22 ]. Myocardial regions with reduced Bvf were highly correlated with ventricular wall thickening [ 22 , 23 ]. Yet the factors responsible for the reduction of microvascular network volume remain unknown.…”

Cardiac T2* mapping: Techniques and clinical applications

“…To link the T 2 * value acquired at 3.0T to its corresponding 1.5T T 2 * value, some studies proposed a conversion relationship 18,32 . Moreover, at 7.0T, acquisition techniques were introduced to reduce the influence of the substantial macroscopic magnetic field inhomogeneities in T 2 * measurement 33–35 . It is known that B 0 and B 1 inhomogeneities increase with the magnetic field strength 36 .…”