3 DISTINCT PATTERNS OF VENTRICULAR ACTIVATION IN INFARCTED HUMAN HEARTS - AN INTRAOPERATIVE CARDIAC MAPPING STUDY DURING SINUS RHYTHM

Background Comprehensive data based on single-beat analysis of the ven tricular activation sequence during sinus rhythm in infarcted hearts a re currently not available. It was the aim of our study (1) to measure and analyze these activation sequences on the epicardial surface of t he right and left ventricles and on the left ventricular endocardial s urface, and (2) to correlate specific activation patterns with the sur face EGG. Methods and Results Isochronal maps were computed from 127 e ndocardial and epicardial unipolar electrograms recorded simultaneousl y during sinus rhythm in 45 post-myocardial infarction patients operat ed on for recurrent ventricular tachycardia (age, 57+/-10 years [mean/-SD], left ventricular ejection fraction, 29+/-9%). Patients with bun dle-branch block, but not with intraventricular conduction defects, we re excluded. Data such as the timing of initial and terminal activatio n, the number of breakthroughs, the total activation time, and the num ber of ventricular segments without activation were measured and analy zed according to location of the myocardial infarction. The global epi cardial activation was characterized in all patients by a widespread i nitial breakthrough on the anterior right ventricle (16+/-8 millisecon ds after QRS onset), which was followed by one or two other breakthrou ghs in 65% of patients. Subsequently, three characteristic epicardial patterns of the activation spread were found: (1) radial, from the rig ht to the left ventricle, found in all patients with inferoposterior m yocardial infarction; (2) counterclockwise rotation, in which posteros eptal crossing preceded the anteroseptal crossing, found in 38% of pat ients with anterior myocardial infarction; and (3) pincerlike encircle ment, in which both septal crossings and/or breakthroughs occurred nea rly simultaneously and merged at the left ventricular free wall (typic al for apical involvement in anterior and combined myocardial infarcti on). The simultaneous presence of multiple major activation wave front s typically found in patients with the pincerlike activation pattern w as reflected on the surface ECG by multiphasic, notched QRS complexes. Activation delay was observed in 89% of patients, and terminal activa tion was topographically related to myocardial infarction in 94% of pa tients. Delayed activation exceeding the surface QRS was observed in 1 1% and 31% of cases on the endocardium and epicardium, respectively. C onclusions These results offer a solid basis for a more precise interp retation of a wide range of electrophysiological data and provide a fr amework for future investigations of surface ECG reflections of endoca rdial and epicardial activation patterns recorded in patients with chr onic myocardial infarction.