Organization of Myocardial Activation During Ventricular Fibrillation After Myocardial Infarction

Abstract

Background-Studies of ventricular fibrillation (VF) in small mammals have revealed localized sustained stationary reentry. However, studies in large mammals with surface mapping techniques have demonstrated only relatively short-lived rotors. The purpose of this study was to identify whether sustained high-frequency activation with low beat-to-beat variability was present at intramural sites in a postinfarct ovine model of VF. Methods and Results-VF was induced in 12 sheep 77Ϯ40 days after anterior myocardial infarction. Electrical activation was recorded with 20 multielectrode transmural plunge needles. Unipolar electrogram frequency content and local cycle duration variability were studied in 30-second recordings beginning 5 seconds after the onset of VF. Higher mean beat frequency was associated with lower SD of the cycle duration intervals (rϭϪ0.91, PϽ0.001). The mean beat frequency and the SD of cycle duration intervals of the highest-frequency electrode were 8.8Ϯ2.0 Hz and 17Ϯ11 ms. In 3 cases, a region with regular activation throughout the recording was identified (SD of the cycle duration interval, 6.0Ϯ0.7 ms). Two of these sites and 67% of all sites with low local cycle duration variability were intramural. They occurred within regions with a high dominant frequency as determined by fast Fourier transform of the unipolar electrogram. Conclusions-Regions with the highest frequency of activation during VF were always associated with a low local cycle duration variability and usually intramural in this chronic infarct model. In a minority of cases, a region of stable, rapid, and very regular activation could be identified. These findings support the hypothesis that relatively stable periodic sources form a component of the mechanism of VF in this model.

Ventricular fibrillation in myopathic human hearts: mechanistic insights from in vivo global endocardial and epicardial mapping

“…It is, however, explained by the current study that globally mapped the endocardium and epicardium to reveal that rotor activity and repeated wavefronts emanate from it. Our study in humans is consistent with recent studies in animal models of heart failure that suggest that dominant sources that are endocardial or intramural are seen during VF in myopathic animal hearts (9,29). In the hearts studied, there was a trend toward the presence of faster rotors and rotors that lasted longer on the endocardium compared with on the epicardium.…”

Regional Ion Channel Gene Expression Heterogeneity and Ventricular Fibrillation Dynamics in Human Hearts

“…Cell cultures [1] and animal models [2], [3], [4] have been utilized to test hypotheses regarding ionic currents and the spatiotemporal organization of VF. Although these models allow for elegant testing of the roles of single ion channels or currents [5], remodeling in myopathic human hearts involves multiple ion channels and requires a different investigative strategy.…”

Cell delivery and tracking in post-myocardial infarction cardiac stem cell therapy: an introduction for clinical researchers

“…At present, both contact and non-contact electrophysiological cardiac mapping systems such as the NOGA TM and the Endocardial Solutions (ESI) TM system, are being evaluated [37][38][39][40]. The NOGA system relies on body surface electrode patches to navigate electrophysiological catheters inside cardiac chamber [41][42][43][44]. NOGA endocardial mapping for manual intraendocardial injections is more established for stem cell transplantation and it has been used on human subjects [42,45] and ongoing clinical trials (www.clinicaltrials.gov).…”

“…The NOGA system relies on body surface electrode patches to navigate electrophysiological catheters inside cardiac chamber [41][42][43][44]. NOGA endocardial mapping for manual intraendocardial injections is more established for stem cell transplantation and it has been used on human subjects [42,45] and ongoing clinical trials (www.clinicaltrials.gov). Unlike the NOGA system, the ESI system is a noncontact-mapping system which employs catheter-based non-contact multi-electrode array (MEA) placed within the cardiac chamber to detect far field endocardial potential.…”