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Three distinct patterns of ventricular activation in infarcted human hearts. An intraoperative cardiac mapping study
R Hatala1, P Savard, G Tremblay
1Research Center, Hôpital du Sacré-Coeur de Montréal, Quebec, Canada.
Insights
This study maps ventricular activation in hearts after myocardial infarction, revealing distinct patterns related to infarct location. These findings improve understanding of surface ECG in patients with chronic myocardial infarction.
Area of Science:
- Electrophysiology
- Cardiology
- Medical Imaging
Background:
- Limited data exists on ventricular activation sequences in infarcted hearts during sinus rhythm.
- Understanding these sequences is crucial for interpreting electrophysiological data and surface ECG.
- This study addresses the gap by analyzing epicardial and endocardial activation patterns.
Purpose of the Study:
- To measure and analyze ventricular activation sequences on the epicardial and endocardial surfaces.
- To correlate specific activation patterns with the surface electrocardiogram (ECG).
- To provide a framework for interpreting electrophysiological data in post-myocardial infarction patients.
Main Methods:
- Computed isochronal maps from 127 endocardial and epicardial unipolar electrograms.
- Analyzed data from 45 post-myocardial infarction patients with recurrent ventricular tachycardia.
- Excluded patients with bundle-branch block; analyzed activation timing, breakthroughs, and total activation time.
Main Results:
- Identified three characteristic epicardial activation patterns: radial, counterclockwise rotation, and pincerlike encirclement.
- Pincerlike encirclement correlated with multiphasic, notched QRS complexes on surface ECG.
- Observed widespread initial breakthroughs on the anterior right ventricle and significant activation delays in most patients.
Conclusions:
- The study provides a foundation for precise interpretation of electrophysiological data in post-myocardial infarction patients.
- Established correlations between endocardial/epicardial activation patterns and surface ECG.
- Offers a framework for future research on ECG manifestations of myocardial infarction.
Background:
Comprehensive data based on single-beat analysis of the ventricular activation sequence during sinus rhythm in infarcted hearts are currently not available. It was the aim of our study (1) to measure and analyze these activation sequences on the epicardial surface of the right and left ventricles and on the left ventricular endocardial surface, and (2) to correlate specific activation patterns with the surface ECG.
Methods And Results:
Isochronal maps were computed from 127 endocardial and epicardial unipolar electrograms recorded simultaneously during sinus rhythm in 45 post-myocardial infarction patients operated on for recurrent ventricular tachycardia (age, 57 +/- 10 years [mean +/- SD], left ventricular ejection fraction, 29 +/- 9%). Patients with bundle-branch block, but not with intraventricular conduction defects, were excluded. Data such as the timing of initial and terminal activation, the number of breakthroughs, the total activation time, and the number of ventricular segments without activation were measured and analyzed according to location of the myocardial infarction. The global epicardial activation was characterized in all patients by a widespread initial breakthrough on the anterior right ventricle (16 +/- 8 milliseconds after QRS onset), which was followed by one or two other breakthroughs in 65% of patients. Subsequently, three characteristic epicardial patterns of the activation spread were found: (1) radial, from the right to the left ventricle, found in all patients with inferoposterior myocardial infarction; (2) counterclockwise rotation, in which posteroseptal crossing preceded the anteroseptal crossing, found in 38% of patients with anterior myocardial infarction; and (3) pincerlike encirclement, in which both septal crossings and/or breakthroughs occurred nearly simultaneously and merged at the left ventricular free wall (typical for apical involvement in anterior and combined myocardial infarction). The simultaneous presence of multiple major activation wave fronts typically found in patients with the pincerlike activation pattern was reflected on the surface ECG by multiphasic, notched QRS complexes. Activation delay was observed in 89% of patients, and terminal activation was topographically related to myocardial infarction in 94% of patients. Delayed activation exceeding the surface QRS was observed in 11% and 31% of cases on the endocardium and epicardium, respectively.
Conclusions:
These results offer a solid basis for a more precise interpretation of a wide range of electrophysiological data and provide a framework for future investigations of surface ECG reflections of endocardial and epicardial activation patterns recorded in patients with chronic myocardial infarction.