Functional role of the epicardium in postinfarction ventricular tachycardia. Observations derived from computerized epicardial activation mapping, entrainment, and epicardial laser photoablation.

Abstract

BACKGROUND Conventionally, monomorphic sustained ventricular tachycardia in patients with remote myocardial infarction is believed to originate from the subendocardium. In a previous study, we demonstrated that electrical activation patterns during ventricular tachycardia occasionally suggest a subepicardial rather than subendocardial reentry. METHODS AND RESULTS This study prospectively evaluated the functional role of the epicardium in postinfarction ventricular tachycardia with complex intraoperative techniques including computerized electrical activation mapping, entrainment, observation of changes in activation pattern during successful epicardial laser photoblation, and histological study. Five of 10 consecutive patients undergoing intraoperative computerized activation mapping had 10 ventricular tachycardia morphologies displaying epicardial diastolic activation These 10 "epicardial" ventricular tachycardias revealed the following global activation patterns: monoregional spread (two), figure-eight activation (five), and circular macroreentry (three). Entrainment of ventricular tachycardia using epicardial stimulation was successfully performed from an area of slow diastolic conduction in four tachycardia morphologies. During entrainment, global activation remained undisturbed with recordings showing a long stimulus to QRS interval, unchanged QRS morphology, and pacing capture of all components of the reentry circuit. Neodymium:yttrium aluminum garnet laser photocoagulation was delivered during ventricular tachycardia to epicardial sites of presumed reentry. Epicardial photoablation terminated five of five figure-eight tachycardias, two of three circular macroreentry tachycardias but not the monoregional tachycardias. Electrophysiological recordings during epicardial laser photocoagulation demonstrated progressive prolongation of ventricular tachycardia cycle length and apparent interruption of the presumed reentrant circuit. Histological evaluation of the reentrant region (three patients) showed a rim of surviving myocardium under the epicardial surface. CONCLUSIONS This study suggests that 1) chronic postinfarction ventricular tachycardia may result from subepicardial macroreentry, 2) slow conduction within the reentry circuit can be localized by computerized mapping and epicardial entrainment, and 3) ventricular tachycardia interruption by laser photocoagulation results from conduction delay and block within critical elements of the reentrant pathway. Viable subepicardial muscle fibers may constitute the underlying pathology.

Characteristics and identification of sites of chagasic ventricular tachycardia by endocardial mapping

“…Intraoperative mappings and computer simulations of endocardial mappings of patients with ischemic heart disease showed that concealed entrainment could be obtained through stimulation of a region of the reentrant circuit. This results in antidromic blockade of the depolarizing wave by the wave front of the tachycardia, preventing depolarization of adjacent regions and also causes the orthodromic conduction of the depolarizing wave in a similar manner to SVT activation 34,35 . In rare situations, blockade of the stimulation wave may occur orthodromically, allowing antidromic conduction and, consequently, change of the outlet site of the circuit and of SVT morphology.…”

2015 ESC Guidelines for the management of patients with ventricular arrhythmias and the prevention of sudden cardiac death

“…Celem ablacji przezcewnikowej jest cieśń wolnego przewodzenia (cieśń krytyczna) w obrębie obwodu pobudzeń nawrotnych generującego VT. Ten obwód pobudzeń nawrotnych może mieć wielkość kilku centymetrów i obejmować wsierdzie, śródsierdzie lub nasierdzie w obrębie złożonej trójwymiaro-wej struktury [192,193]. Częstoskurcz komorowy związany z blizną w mięśniu sercowym jest typowo jednokształtny, ale u tego samego pacjenta może występować VT o wielu różnych morfologiach.…”

Endo-Epicardial Versus Only-Endocardial Ablation as a First Line Strategy for the Treatment of Ventricular Tachycardia in Patients With Ischemic Heart Disease

“…However, the main limitation of the study of Di Biase et al was that the ablation technique differed between groups: scar homogenization in the epi-group versus limited substrate ablation in the historical cohort. Our series includes not only electrical storms but all patients with sustained monomorphic VTs, and the same ablation technique was used in both groups.This systematic endo-epicardial approach in IHD patients could be justified by some arguments: (a) different data point to increased electrophysiologists confidence with the technique that probably reflects the improvement in terms of security and the awareness of the extent of epicardial involvement 7 ; (b) epicardial and intramural re-entry circuit locations are well recognized in the literature [12][13][14] and are an important cause of failure of endocardial ablation 6 ; (c) improvements in outcome have been demonstrated when patients undergo an endo-epicardial ablation in a second procedure after a first only endocardial ablation has failed 5 ; (d) clinical and EKG characteristics have failed to reliably identify endocardial or epicardial components of VT circuit in IHD. 15 So we speculated that an appropriate choice of a combined endo-epicardial approach as a first line mapping, and ablation strategy may avoid a substantial number of repeated procedures and improve ablation outcome, as it has been demonstrated.…”