Idiopathic restrictive cardiomyopathy in childhood. A diastolic disorder characterized by delayed relaxation.

Six children with idiopathic restrictive cardiomyopathy were evaluated. Electrocardiographic evaluation disclosed left atrial dilatation and repolarization abnormalities. Echocardiographic examination showed gross left atrial enlargement (182 +/- 29% of predicted values, P < 0.001) in the presence of normal left ventricular cavity dimensions (99 +/- 6%, P: ns). Left ventricular wall thickness varied from normal to mild concentric hypertrophy (septum: 116 +/- 16%, P < 0.05). Global left ventricular systolic function was normal or slightly subnormal; however, the relaxation was significantly delayed throughout diastole. E/A ratio was 4.1 +/- 1.4 and deceleration time 94 +/- 7 ms. Marked ventricular filling occurred in mid-diastole as could be deduced from a prominent mid-diastolic mitral L wave on the Doppler flow tracing. Early filling contributed 56 +/- 6%, mid-diastolic filling 28 +/- 4% and atrial contraction 16 +/- 3% to total ventricular filling as estimated by determining E-area, L-area and A-area, respectively. The left ventricular pressure curve showed a steady decline during mid-diastolic filling. This implies that the driving force for mid-diastolic filling is not the increased left atrial pressure but suction by the ventricle. The restrictive haemodynamics are therefore not caused by increased intrinsic stiffness of the ventricular wall, but most likely result from serious dysfunction and delay of the active relaxation of the ventricle. Progression of the disease was observed in three out of six patients, resulting in death or extreme low cardiac output. The three other patients remained clinically stable during the follow-up period of 6-10 years.