PATHOPHYSIOLOGY AND NATURAL HISTORY CARDIOMYOPATHY Mildly dilated congestive cardiomyopathy

Five patients with only mildly dilated ventricles but other features typical of congestive cardiomyopathy underwent cardiac transplantation for class IV NYHA heart failure. The findings of clinical studies, cardiac catheterization, endomyocardial biopsy, and pathologic examination of the removed hearts in this group with mildly dilated congestive cardiomyopathy (MDCM) were compared with similar data in four patients with idiopathic restrictive cardiomyopathy (IRCM) and in 10 patients with typical dilated congestive cardiomyopathy (DCM). In comparison with the other groups, patients with MDCM had a higher incidence of familial cardiomyopathy (p = .02) and a shorter symptomatic period than patients with IRCM (p < .02). Patients with both MDCM and DCM had globular hearts (with predominant left ventricular dilatation), congestive hemodynamics and poor left ventricular contractility (ejection fraction 12% to 1.9%), and high incidence of ventricular thrombi. Patients with IRCM showed normal ventricular size, marked atrial dilatation, restrictive hemodynamics, mild-tomoderate decrease in left ventricular contractility (ejection fraction 29% to 55%), and absence of ventricular thrombi. Cardiac index, ventricular wall thickness, and light microscopic findings were similar in the three groups of patients. Electron microscopy showed no myofibrillar loss in patients with IRCM but mild (partial) or moderate-to-severe (almost total) myofibrillar loss in those with MDCM and DCM, respectively. We conclude that (1) end-stage congestive cardiomyopathy may occur without significant ventricular dilatation and (2) patients with MDCM have heart sizes intermediate between those found in IRCM and DCM but their clinical, hemodynamic, and pathologic findings are virtually identical to those of patients with typical DCM. Circulation 72, No. 2, 302-309, 1985. CONGESTIVE and restrictive cardiomyopathies represent distinct entities with different hemodynamic and morphologic features.' Congestive cardiomyopathy is characterized by ventricular dilatation and poor systolic function with greatly reduced ejection fraction.' Dilatation of the ventricles usually occurs earlier than heart failure and is considered the most important manifestation of the disease. 5 For this reason, the terms "dilated"2'6 or "dilated congestive"3' 4 cardiomyopathy are currently preferred. Light and electron microscopic assessment show major but nonspecific abnormal changes.' 1. 6 Restrictive cardiomyopathy is characterized by normal or near normal ventricular size and systolic function but compromised ventricular relaxation leading to distinctive hemodynamic findings. 4 The term reFrom the Cardiology Division. Stanford University Medical Center, Stanford. CA. Supported in part by Fogarty Fellowship Grant FO5 TWO 3416-01B 1 from the National Institutes of Health. by the Israeli Heiden Fellowship, and by Clinical Heart and Heart-Lung Transplantation Grant HL13108-15 from the National Heart. Lung, and Blood Institute. Address for correspondence: Richard L. Popp, M.D., Cardiology Division. Stanford University Medical Center, Stanford, CA 94305. Received April 10. 1985; accepted May 16. 1985. 302 strictive (nondilated) cardiomyopathy is preferred by some authors to emphasize the absence of ventricular dilatation.4 Infiltrative processes or endomyocardial fibrosis, with or without eosinophilia, usually represent its pathologic basis.",6 Rarely has a primary7 or idiopathic8 form of the disease been reported in which histologic examination did not reveal specific changes.7-9 This study presents the clinical and morphologic data of patients who underwent cardiac transplantation in whom the characteristic features of congestive cardiomyopathy occurred without significant ventricular dilatation. For better characterization of these patients, with what we tentatively term "mildly dilated" congestive cardiomyopathy (MDCM), the findings of this group were compared with those of heart transplant recipients with idiopathic restrictive cardiomyopathy (IRCM) and with typical dilated congestive cardiomyopathy (DCM).