Electrocardiographic signs of left ventricular hypertrophy and strain in hypertensive patients.

Electrocardiographic abnormalities in hypertensive patients can be divided into two main categories (Smirk, 1957). The first consists of abnormalities that can be directly ascribed to left ventricular "overload" (Sokolow and Lyon, 1949). The second category consists of a miscellaneous group of conditions that are less directly related to left ventricular " overload" and are rather to be considered as complications of vascular disease, such as arrhythmias, conduction defects, and myocardial infarction. The present study is concerned only with the first category, the intention being to investigate the relationship of the electrocardiographic signs of left ventricular hypertrophy and "strain" to the level of the diastolic blood pressure and to certain other clinical features. Since the advent of multiple-lead electrocardiography, several studies of the changes in hypertension have been reported. Evans et al. (1945) found some correlation between electrocardiographic changes in bipolar chest leads and the diastolic blood pressure. Leishman (1951) found some correlation with diastolic blood pressure, heart size, and retinal grade, but not between electrocardiographic changes and age, sex, body weight, or angina. Doyle (1953), in an investigation mainly concerned with the improvement obtained in the electrocardiograms of hypertensive patients during treatment with ganglion-blocking drugs, also found some correlation between electrocardiographic changes and diastolic blood pressure taken under basal conditions before treatment was started. Hay (1957) in another follow-up investigation on a series of treated patients (which included Doyle's (1953) group) mentions that the severity of the original cardiographic changes was related to the basal blood pressure and the retinal grade. These investigations have, however, not afforded any clear evidence of why patients with apparently comparable hypertension often have such different degrees of electrocardiographic abnormality. The present study has been made in an attempt to throw further light on this problem. The method of classification of the electrocardiograms used differs from that employed by previous workers and is based on a separate analysis of the incidence of each of three main changes seen in left ventricular hypertrophy and strain, namely high voltage in QRS complexes, S-T segment depression, and T wave diphasia or inversion.