Occurrence and significance of progressive left ventricular wall thinning and relative cavity dilatation in hypertrophic cardiomyopathy

This investigation was undertaken to assess the prevalence of systolic dysfunction, left ventricular (LV) wall thinning and cavity enlargement in a large population of patients with hypertrophic cardiomyopathy (HC), and to determine the role of these conditions in the natural-history of this disease. Of 217 consecutively studied patients with HC, most of whom were severely symptomatic, 197 (91 %) had an LV ejection fraction of 50% or more and 20 (9%) had an ejection fraction of less than 50% as assessed with radionuclide anglography. Changes in LV wall thickness and cavity dimension were evaluated using serial M-mode and 2-dimensional echocardiography over an average follow-up of 3.6 years in 67 of the 217 patients (54 with ejection fraction of ≥ 50 % and 13 with ejection fraction <50%). A substantial decrease (at least 5 mm) in LV wall thickness was seen in 8 of the 13 patients (62%) with an ejection fraction {succeeds above single-line equals sign} 50%, but in only 2 of the 54 patients (4%) with an ejection fraction ≥ 50 % (p <0.001). LV cavity dimension increased significantly over the period of follow-up in the 13 patients with depressed ejection fraction (from 44 ± 5 to 49 ± 7 mm, p <0.005); however, absolute cavity size remained normal (≤52 mm or less) in 10 of these 13 patients. The clinical course was poor in each of the 8 patients who showed LV systolic dysfunction, wall thinning and an enlarging cavity; all had severe symptoms, including 4 who died of congestive cardiac failure, and 1 who underwent cardiac transplantation. It is concluded that LV systolic impairment, associated with progressive LV wall thinning and relative cavity enlargement, are present in almost 10 % of patients with HC and severe symptoms. These functional and morphologic changes are usually associated with refractory cardiac failure and poor prognosis, and appear to identify a subset of patients with HC who have a distinctive and well defined natural history.