Comparison of Epicardial and Endocardial Programmed Stimulation in Patients at Risk for Ventricular Arrhythmias After Cardiac Surgery

Abstract

Programmed ventricular stimulation was performed on 36 patients after recent cardiac surgery using implanted right ventricular epicardial temporary wires and with catheters positioned percutaneously at two right ventricular endocardial sites. Patients were followed for a mean of 18.5 months (range 3 to 36 months). Epicardial wires were nonfunctional in 10 patients (28%) due to excessively high pacing thresholds. Overall, 22 patients (61%) had inducible sustained ventricular tachycardia; epicardial wires were functional in 15 (68%) of these patients. Six patients without inducible ventricular tachycardia with epicardial stimulation were inducible using endocardial stimulation. Of the 24 patients in whom epicardial and endocardial ventricular stimulation could be performed, concordant results were obtained in only 17 (71%), despite similar epicardial and endocardial ventricular effective and functional refractory periods. A total of 14 arrhythmic events occurred during the follow-up period. Of the 22 patients with an inducible sustained ventricular tachycardia, 12 (64%) had subsequent arrhythmic events. Only 2 of the 14 noninducible patients had follow-up arrhythmic events, one of which was caused by medication proarrhythmia. Endocardial ventricular stimulation had a superior sensitivity (83% versus 30%, P < 0.0001) and an improved negative predictive value (86% versus 61%, P < 0.05) compared with epicardial ventricular stimulation. These results indicate that noninducibility using epicardial programmed ventricular stimulation does not reliably portend a low risk for recurrent ventricular tachyarrhythmias. Epicardial programmed stimulation, used alone, may be inadequate for postoperative electrophysiological evaluation of patients at risk for ventricular arrhythmias.

Na+ channel distribution and electrophysiological heterogeneities in guinea pig ventricular wall

“…In the present study, we used the guinea pig heart model to show greater endocardial than epicardial Na v protein expression levels, which is consistent with our previous findings in failing and nondiseased human ventricular tissue (72). We also replicate clinical findings on greater proarrhythmic potential of endocardial than epicardial pacing (9,70), as assessed by susceptibility to repolarization alternans and VT inducibility by rapid cardiac pacing, measuring VF threshold values following burst stimulation, and evaluating propensity to short-lasting tachyarrhythmia by extrasystolic stimulation. Furthermore, we explore the mechanisms staying behind these differences, to show that greater arrhythmic susceptibility to endocardial pacing may be related to greater excitability and steeper ERP restitution slopes at endocardium than epicardium.…”

“…Furthermore, pacemakerinduced VT has been detected in 26% of patients with an implantable cardioverter-defibrillator (34). VT inducibility by programmed stimulation as assessed after cardiac surgery is higher at RV endocardial than RV epicardial stimulation sites (70). Postoperative assessments of the efficacy of antitachyarrhythmia surgery suggest that epicardial stimulation implemented alone may underestimate the number of patients at risk for recurrent VT by 25%, thereby highlighting the important predictive value of endocardial testing (9).…”

“…Consistently, ventricular fibrillation (VF) thresholds were found to be lower at endocardial than epicardial stimulation sites in canine left ventricle (LV) (37). In cardiac patients at risk for ventricular tachyarrhythmia (VT), programmed ventricular endocardial stimulation has significantly higher sensitivity and better negative predictive value than epicardial stimulation over long-term follow-up (70).…”

“…There is a possibility that fatal outcomes in patients implanted with a permanent pacemaker are partly attributed to high vulnerability of the endocardial pacing site to electrical stimulation-induced tachyarrhythmias. Indeed, studies utilizing postoperative programmed ventricular stimulation in patients subjected to cardiac surgery suggest greater tachyarrhythmia inducibility at ventricular endocardial than epicardial stimulation sites (9,70). Consistently, ventricular fibrillation (VF) thresholds were found to be lower at endocardial than epicardial stimulation sites in canine left ventricle (LV) (37).…”

“…In the clinical setting, greater inducibility of tachyarrhythmias at ventricular endocardium has been observed in the presence of similar endocardial and epicardial effective refractory periods (ERPs) (70), thereby suggesting that VT induction may not be accounted for by large spatial repolarization gradients causing the propagating wave front to collide with refractory myocardial tissue upon upstream endocardial stimulation (8). Importantly, measurement of ventricular pacing thresholds reveals greater excitability of endocardium than epicardium in human hearts (9,23,53).…”