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[Unclassified cardiomyopathies: subspecies and their transformation]
1Department of Internal Medicine, Jyuntendo University School of Medicine, Tokyo.
Insights
A novel phase of unclassified cardiomyopathy (UCM) may bridge hypertrophic cardiomyopathy (HCM) and dilated cardiomyopathy (DCM). Histopathological findings in UCM correlate with clinical deterioration, suggesting a transforming phase in heart muscle disease progression.
Area of Science:
- Cardiology
- Pathology
- Medical Research
Context:
- Hypertrophic cardiomyopathy (HCM) can progress to dilated cardiomyopathy (DCM).
- A potential transforming phase between HCM and DCM has not been clearly defined.
- Retrospective analysis of 471 cardiomyopathy patients undergoing myocardial biopsy between 1977-1995.
Purpose:
- To investigate the existence of a transforming-type phase between HCM and DCM.
- To classify patients into subgroups based on echocardiographic parameters: left ventricular hypertrophy, dilation, and systolic dysfunction.
- To compare clinical courses and histological findings in unclassified cardiomyopathy (UCM) subgroups.
Summary:
- Of 471 patients, 111 (24%) were classified as UCM, 240 as HCM, and 120 as DCM.
- Severe myocardial disarray was more frequent in UCM (15%) than DCM (6%) (p < 0.05).
- Deteriorating UCM patients showed positive pathological findings more often than non-deteriorating patients (p < 0.05).
Impact:
- Unclassified cardiomyopathy (UCM) may represent a transitional phase for patients progressing from HCM to DCM.
- Histopathological findings in UCM appear to correlate with the clinical course of the disease.
- This research provides insights into the dynamic nature of cardiomyopathy progression.
Abstract:
Some cases with hypertrophic cardiomyopathy (HCM) progress to dilated cardiomyopathy (DCM), therefore, we hypothesized that a transforming-type phase between HCM and DCM could exist. This study was made based on a retrospective analysis of 471 of 1,388 patients with cardiomyopathy who underwent diagnostic myocardial biopsy in several hospitals between 1977 to 1995, and who were not diagnosed with restrictive cardiomyopathy, arrhythmogenic right ventricular dysplasia, specific heart muscle diseases, or electrical disturbance type of heart muscle diseases. Based on echocardiographic measurements, the 471 patients were classified into eight subgroups according to the presence or absence of three parameters. A: left ventricular hypertrophy (septal or posterior wall thickness > 12 mm), B: left ventricular dilation (left ventricular end-diastolic dimension > 55 mm), C: systolic dysfunction (left ventricular ejection fraction < 50%), is signified by plus or minus ([ABC]). HCM, DCM and normal heart are defined as [+(-)-], [-(+2)] and [-(-)-], respectively. Unclassified cardiomyopathy (UCM) was indicated as cardiomyopathy not diagnosed as HCM or DCM. Therefore, unclassified cardiomyopathies are signified as either [+2-], [+(-)+], [+3], [-(+)-] or [-(-)+]. Patients in each subgroup of UCM were followed up for 6.4 +/- 6.0 years and their clinical courses compared with the histological findings. Of the 471 patients, 111 (24%) were classified as UCM, 240 as HCM, and 120 as DCM. Severe myocardial disarray was noted more frequently in UCM [17 of 111 cases (15%)] than in DCM [7 of 120 cases (6%)] (p < 0.05), and not significantly higher than in HCM [34 of 240 cases (14%)]. Patients with UCM whose conditions deteriorated had positive pathological findings (15 of 26 cases) more often than those without deterioration (8 of 29 cases; p < 0.05). UCM could be a transforming type of cardiomyopathy for some patients with HCM who progress to DCM. In addition, there may be a positive correlation between the histopathologic findings and the clinical course.