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Quantitative morphologic findings of the myocardium in idiopathic dilated cardiomyopathy
Insights
In idiopathic dilated cardiomyopathy, reduced myofibrils and increased fibrosis correlate with impaired left ventricular function. Myocardial biopsy analysis reveals these key morphologic changes linked to ejection fraction.
Area of Science:
- Cardiology
- Pathology
- Biomedical Engineering
Background:
- Idiopathic dilated cardiomyopathy (IDCM) is characterized by impaired left ventricular (LV) contractile function.
- Quantitative morphologic analysis of myocardial tissue can provide insights into the structural basis of LV dysfunction.
Purpose of the Study:
- To investigate the relationship between quantitative myocardial morphologic findings and left ventricular contractile function in patients with IDCM.
- To identify specific structural changes associated with reduced ejection fraction in IDCM.
Main Methods:
- Endomyocardial biopsy specimens from 73 IDCM patients were analyzed using light and electron microscopic morphometry.
- Measurements included myocardial fiber diameter, interstitial fibrosis, and intracellular myofibril volume fraction.
- Correlation analysis was performed between morphometric parameters and ejection fraction.
Main Results:
- Myocardial fiber diameter and fibrosis showed a negative correlation with ejection fraction (p<0.01 and p<0.001, respectively).
- Volume fraction of myofibrils and myofibrillar mass positively correlated with ejection fraction (p<0.001).
- Sampling error was low for fiber diameter and myofibrils but high for fibrosis.
Conclusions:
- A reduction in myofibril volume fraction and an increase in interstitial fibrosis are significant morphologic correlates of left ventricular dysfunction in IDCM.
- Quantitative morphometry of myocardial biopsies can reveal structural abnormalities underlying impaired cardiac function in IDCM.
Abstract:
This study assesses the relation between quantitative morphologic findings and left ventricular contractile function in patients with idiopathic dilated cardiomyopathy. Left ventricular endomyocardial catheter biopsy specimens were obtained from 73 patients during diagnostic heart catheterization. All patients had normal coronary arteriograms but abnormal electrocardiograms. Twenty-six patients had normal left ventricular function (ejection fraction greater than or equal to 55%), whereas 47 patients had contractile dysfunction (ejection fraction less than or equal to 54%). Myocardial fiber diameter, volume fraction of interstitial fibrosis, and intracellular volume fraction of myofibrils were determined by light microscopic morphometry. Results of light microscopic morphometry were confirmed by electron microscopic morphometry in 12 patients. The coefficient of variation (analysis of several biopsies from the same patient) was 6% for determination of fiber diameter, 43% for interstitial fibrosis, and 3% for volume fraction of myofibrils. Fiber diameter (r = -0.32, p less than 0.01) and fibrosis (r = -0.47, p less than 0.001) showed a negative correlation, the volume fraction of myofibrils (r = 0.55, p less than 0.001) and calculated myofibrillar mass per 100 g of myocardium (r = 0.64, p less than 0.001) a positive correlation with the ejection fraction. Thus, (1) sampling error is low for determination of fiber diameter and myofibrils but high for evaluation of fibrosis, and (2) a reduction in the volume fraction of myofibrils and an increase in fibrosis are morphologic correlates of left ventricular dysfunction in patients with idiopathic dilated cardiomyopathy.