Variability and reproducibility of morphologic findings in endomyocardial biopsies of patients with hypertrophic obstructive cardiomyopathy.

Morphometric investigations of endomyocardial catheter biopsies (EMCB) promise to give more insight in the morphologic-functional relationship in patients with hypertrophic obstructive cardiomyopathy (HOCM), and may disclose the morphologic course of the disease. Variability and reproducibility of morphologic findings in EMCB of patients with HOCM are still undefined. We investigated 112 right ventricular biopsies of 25 patients with HOCM of a mean age of 38.3 +/- 15.2 years (six women, 19 men). Mean EMCB size was 0.755 +/- 0.567 mm2. 28.6% of EMCB were not suitable for morphometric investigation. Variability of morphologic findings was investigated by analysis of variance and described by the coefficient of variation (CV). Sampling variabilities of muscle fiber diameter (CV = 5%), volume density of interstitium (CV = 9%) and fibrous tissue (CV = 17%) differed. Reproducibility in terms of intra- and interobserver variations for these variables reached a comparable level, diminishing observed differences between biopsies from the same heart, which became non-significant. Sampling variability of endocardial thickness (CV = 79%) and muscle fiber disarray (CV = 100%) were higher than intra- and interobserver variations. For an estimate of muscle fiber size, one EMCB specimen is sufficient, three for volume density of interstitium and nine for fibrous tissue. High sampling variability of endocardial thickness and muscle fiber disarray demand numerous biopsies; here the greatest measured value from a few biopsies may be of more clinical relevance. From our data, five EMBC are desirable, and give the most information at an acceptable strain.