Progression of hypertrophic cardiomyopathy to dilated cardiomyopathy--a case reports and review of the literatures

Findings of Cardiac Magnetic Resonance Imaging in Hypertrophic Cardiomyopathy after 16 Years

A 58-year-old man had been diagnosed with non-obstructive hypertrophic cardiomyopathy (HCMP) according to echocardiography findings 16 years ago. Echocardiography showed ischemic cardiomyopathy (CMP)-like features with decreased systolic function but a non-dilated chamber. Coronary angiography was performed but showed a normal coronary artery. Cardiac magnetic resonance imaging (MRI) revealed multifocal transmural and subepicardial delayed-enhancing areas at the anteroseptal, septal, and inferoseptal left ventricular (LV) wall, and wall thinning and decreased motion of the anteroseptal LV wall. Findings of ischemic CMP-like features by echocardiography suggested microvascular dysfunction. This late stage of HCMP carries a high risk of sudden death. Cardiac MRI evaluation may be necessary in cases of ischemic CMP-like features in HCMP. In this case, the diagnosis of end-stage HCMP with microvascular dysfunction was confirmed by using cardiac MRI after a follow-up period of more than 16 years.

Pathology of End-stage Remodeling in a Family of Cats with Hypertrophic Cardiomyopathy

End-stage hypertrophic cardiomyopathy (ES-HCM), affecting 5-10% of human hypertrophic cardiomyopathy (HCM) patients, is characterized by relative thinning of the ventricular walls and septum with dilation of the ventricular lumen, decreased fractional shortening, and progression to heart failure. C. J. Baty and others recently documented similar progressive changes to ES-HCM in a family of four cats through serial echocardiograms. At the time of heart failure, these cats exhibited changes similar to those exhibited by human ES-HCM patients. Our objectives were to describe the pathologic alterations associated with ES-HCM and investigate the pathogenesis in three of the four cats. Grossly, there was left atrial dilation with relative thinning of the interventricular septum (IVS) and left ventricular free wall (LVFW). The left atrium contained large thrombi in two of the three cats, and all three cats died following thromboembolization of the aortic bifurcation. Histologically, all three cats had subendocardial and myocardial fibrosis, predominantly of the IVS and LVFW, and one cat had acute, multifocal, myocardial infarcts with mononuclear inflammatory cell infiltrates. The pathogenesis of ES-HCM is uncertain, but theories implicate occlusion of the coronary blood flow by thickening of the coronary vessels, coronary vascular thromboembolism or coronary vessel spasm, apoptosis of myocytes, and myocardial hypertrophy beyond the ability of the vasculature to supply blood. Apoptosis assays did not reveal any apoptotic myocytes. Considering the hypercoagulative state of these cats, coronary vascular thromboembolism could be a major contributing factor. We cannot exclude apoptosis or coronary vessel spasm on the basis of the data presented.

Hypertrophic cardiomyopathy: two homozygous cases with "typical" hypertrophic cardiomyopathy and three new mutations in cases with progression to dilated cardiomyopathy

About 10% of cases of hypertrophic cardiomyopathy (HCM) evolve into dilated cardiomyopathy (DCM) with unknown causes. We studied 11 unrelated patients (pts) with HCM who progressed to DCM (group A) and 11 who showed "typical" HCM (group B). Mutational analysis of the beta-myosin heavy chain (MYH7), myosin-binding protein C (MYBPC3), and cardiac troponin T (TNNT2) genes demonstrated eight mutations affecting MYH7 or MYBPC3 gene, five of which were new mutations. In group A-pts, the first new mutation occurred in the myosin head-rod junction and the second occurred in the light chain-binding site. The third new mutation leads to a MYBPC3 lacking titin and myosin binding sites. In group B, two pts with severe HCM carried two homozygous MYBPC3 mutations and one with moderate hypertrophy was a compound heterozygous for MYBPC3 gene. We identified five unreported mutations, potentially "malignant" defects as for the associated phenotypes, but no specific mutations of HCM/DCM.