MYOCARDIAL ELECTRICAL PROPAGATION IN PATIENTS WITH IDIOPATHIC DILATEDCARDIOMYOPATHY

Myocardial propagation may contribute to fatal arrhythmias in patients with idiopathic dilated cardiomyopathy (IDC). We examined this proper ty in 15 patients with IDC undergoing cardiac transplantation and in 1 4 control subjects. An 8 X 8 array with electrodes 2 mm apart was used to determine the electrical activation sequence over a small region o f the left ventricular surface. Tissue from the area beneath the elect rode array was examined in the patients with IDC. The patients with ID C could be divided into three groups. Group I (n = 7) had activation p atterns and estimates of longitudinal (theta(L) = 0.84+/-0.09 m/s) and transverse (theta(T) = 0.23+/-0.05 m/s) conduction velocities that we re no different from controls (theta(L) = 0.80+/-0.08 m/s, theta(L) 0. 23+/-0.03 m/s). Group II (n= 4) had fractionated electrograms and dist urbed transverse conduction with normal longitudinal activation, featu res characteristic of nonuniform anisotropic properties. Two of the co ntrol patients also had this pattern. Group III (n = 4) had fractionat ed potentials and severely disturbed transverse and longitudinal propa gation. The amount of myocardial fibrosis correlated with the severity of abnormal propagation. We conclude that (a) severe contractile dysf unction is not necessarily accompanied by changes in propagation, and (b) nonuniform anisotropic propagation is present in a large proportio n of patients with IDC and could underlie ventricular arrhythmias in t his disorder.