Ventricular Premature Beats in the Diagnosis of Myocardial Infarction.

The importance of ventricular premature beats (VPB) in the clinical diagnosis of myocardial infarctions has been pointed out by several authors. Dressler (1943) reported a case in which the electrocardiographic signs of infarction were present in such beats (deep and slurred Q waves in lead III) and absent in the sinus beats. Simonson et al. (1945), Bellet (1953), Scherf and Schott (1953), Katz et al. (1958), Silverman and Salomon (1959), and Anttonen et al. (1959) recognized that myocardial infarctions can be diagnosed from VPB and, at times, even earlier from these cycles than from the sinus beats. The similarity of ventricular activation in VPB and in right bundle-branch block (RBBB) and left bundle-branch block (LBBB) has long been accepted. Consequently, VPB with unipolar patterns of LBBB are right VPB, and VPB with patterns of RBBB are left VPB. The same considerations apply also for supraventricular premature beats (SVPB) with aberrant conduction, since the aberration is due to some degree of either RBBB or LBBB (Bisteni et al., 1960). Thus, right VPB and SVPB with aberration similar to that in LBBB are analysed in the same manner as sinus beats with LBBB. In fact, in these three situations the process of ventricular activation follows a similar sequence: the right ventricle is activated before the left. This type of reasoning applies also for left VPB, RBBB, and SVPB with RBBB: in these three instances the left ventricle is activated before the right. A better knowledge of the ventricular activation process in normal conditions and in bundlebranch block has served for a new approach to the diagnosis and localization of myocardial infarctions. Sodi-Pallares et al. (1957, 1960) have shown that tracings with electrical signs of infarction are better understood when analysed in the light of recent studies concerning the ventricular activation process (Sodi-Pallares et al., 1955; Medrano et al., 1956, 1957, and 1958). It has been demonstrated also that septal infarctions may be more easily recognized in the presence of bundle-branch blocks (Sodi-Pallares, 1956), in contrast with the view generally held. On the basis of these considerations the significance of experimental and clinical VPB in the diagnosis of myocardial infarction is studied in this paper.