[Hemodynamic and electrophysiologic changes in hypertrophic cardiomyopathy].
Hypertrophic cardiomyopathy is characterized by abnormalities of the myocardium, and the activation and conduction tissues, that may have separate manifestations, but often occur together in complex clinical pictures. The subaortic gradient, although not always present, is the most classical manifestation of the disease, with its typical dynamic behavior, changing with preload, afterload and contractility. In most cases it is due to systolic motion of the mitral valve against the septum in systole, but in a few it is caused by midventricular "constriction". Alteration of diastolic ventricular function is important, and probably the main cause of heart failure, that is usually accompanied by normal systolic function. Mitral insufficiency is common in the obstructive forms, due to the abnormal mitral valve motion, but in some cases it may be due to structural abnormalities of the valve. There may be systolic constriction, or nonatherosclerotic occlusion of the intramyocardial coronary arteries, causing myocardial infarction and ventricular aneurysms, that may lead to systolic dysfunction. The electrocardiogram is rarely normal. Hypertrophy patterns, deeply inverted T waves, deep Q waves, QRS slurring suggestive of WPW syndrome without true preexcitation are the most common manifestations. Rhythm disturbances are common and include sinus node dysfunction, superconductor atrioventricular node or heart block. Atrial fibrillation is frequent and may have catastrophic consequences, including systemic embolism. Non-sustained ventricular arrhythmias are often present, but its predictive value for sudden death is unclear. Monomorphic ventricular tachycardia is infrequent, and programmed stimulation is more likely to precipitate polymorphic ventricular tachycardia of difficult clinical interpretation. Sudden death may be due to multiple mechanisms, and it is difficult to predict and prevent.