Characterization of warm saline-enhanced radiofrequency ablation lesions in the infarcted porcine ventricular myocardium.

BACKGROUND: Radiofrequency (RF) ablation of scar-mediated ventricular tachycardia is limited by the size of lesions achieved with conventional catheters. We examined the gross and histopathology characteristics of warm saline-enhanced radiofrequency (SERF) ablation delivered to left ventricular (LV) infarction scars via a novel catheter employing an extendable infusion needle electrode. METHODS AND RESULTS: Yorkshire pigs (n = 14) underwent LV infarction by left anterior descending artery balloon occlusion. After 4-6 weeks, baseline hemodynamic data were obtained and endocardial electroanatomic mapping was performed in 13 surviving animals. Following single, 40 Watt SERF ablations delivered endocardially to the center of infarctions, 4 were examined the same day (day 0). The rest underwent repeat measurements and were sacrificed at 1 week (n = 6), and at 4 weeks (n = 3). Average lesion depth and diameter were: 1.85 ± 0.7 cm and 2.33 ± 0.7 cm at day 0, 0.91 ± 0.1 cm and 1.9 ± 0.4 cm after 1 week, and 1.0 ± 0.2 cm and 1.89 ± 0.76 cm after 4 weeks, respectively. Histopathology at 1 week showed that ablation lesions covered 41 ± 10.6% of the infarct area. SERF ablation lesions extended 100%, 90%, and 68% of the total wall thickness at day 0, 1 week, and 4 weeks, respectively. Hemodynamic parameters were unchanged. There were no myocardial wall perforations or aneurysms. CONCLUSION: SERF ablation within myocardial infarct tissue produced large, near-transmural lesions, without evidence of myocardial perforation, wall thinning, or aneurysm formation. Ablations did not produce any negative hemodynamic effects in this small group of experiments.

Loss of pace capture after radiofrequency application predicts the formation of uniform transmural lesions.

AIMS: Lesion transmurality is critical to procedural success in radiofrequency catheter ablation. We sought to determine whether loss of pace capture (PC) with high-output unipolar and/or bipolar pacing predicts the formation of uniform transmural lesions. METHODS AND RESULTS: Ten juvenile swine were anaesthetized and prepped under sterile conditions. Seventy-seven isolated radiofrequency applications (RFAs) using a 3.5 mm tip-irrigated catheter were available for analysis. Pace capture was assessed before and after RFA at 10 mA/2 ms and catheter stability verified with a three-dimensional mapping system. Pace capture was defined as 1 : 1 or intermittent local capture per paced beat. Myocardial contact and catheter orientation were assessed using intracardiac echo. Endocardial and epicardial lesion areas were measured after sacrifice using 2,3,5-triphenyltetrazolium chloride staining. A uniform transmural lesion was defined as an epicardial-to-endocardial surface ratio (epi/endo) ≥ 76%. Seventy-four per cent of lesions were transmural and 55.8% of lesions had an epi/endo ratio ≥ 76%. In all, 79.2% of lesions associated with loss of bipolar PC were uniform whereas 20.8% of lesions with loss of bipolar PC were non-uniform (P = 0.006). Loss of bipolar PC was associated with higher mean epicardial/endocardial ratio compared with lesions with persistent PC (P = 0.019). Echocardiographic evidence of optimal catheter contact during RFA improved the predictive accuracy of uniform lesion formation when loss of bipolar PC was noted after RFA. CONCLUSION: Loss of bipolar PC after RFA is associated with the formation of uniform lesions in atrial tissue. Optimal catheter contact further improves the predictive accuracy associated with loss of PC.

Atrial electrograms improve the accuracy of tachycardia interpretation from ICD and pacemaker recordings: The RATE Registry.

BACKGROUND: Tachycardia diagnoses from implantable device recordings ultimately depend on the analysis of captured electrograms (EGMs). The degree to which atrial EGMs improve tachycardia discrimination, dependent on the level of expertise of the medical professional involved, remains uncertain. OBJECTIVE: The purpose of this article was to determine whether atrial EGM recordings improve tachycardia discrimination and whether this improvement, if any, varies for professionals with different levels of training. METHODS: Expert-adjudicated supraventricular tachycardia (SVT) and ventricular tachycardia (VT) dual-chamber EGMs (DEGMs) from the Registry of Atrial Tachycardia and Atrial Fibrillation Episodes in the Cardiac Rhythm Management Device Population were provided to electrophysiology specialists, electrophysiology fellows (EPF), and nurse practitioners or physician assistants (NPPA). Each participant diagnosed 112 EGM episodes presented in random sequence (61 VTs and 51 SVTs) and independently categorized each as "SVT," "VT," or "uncertain" in 2 stages. First, participants analyzed ventricular EGMs (VEGMs) alone (atrial channel covered). Second, the tracings were randomized and reanalyzed with atrial EGMs exposed. The diagnostic accuracy of VEGMs alone vs DEGMs was assessed for each group. RESULTS: For all 3 groups, diagnostic accuracy improved significantly (>20% for VTs and >15% for SVTs; P < .01 for all) when DEGMs were provided. Electrophysiology specialists diagnosed VTs more accurately than did EPF and NPPA (VEGM: 73.1%±7.6% vs 58.7%±15.5% and 56.1%±14.1%; P < .01; DEGM: 98.0%±2.7% vs 90.8%±16.0% and 80.3%±7.4%; P < .01). EPF diagnosed VTs more accurately than did NPPA only when DEGMs were provided. There was no significant intergroup difference in SVT diagnoses. CONCLUSION: DEGMs are superior to VEGMs alone for tachycardia discrimination at all levels of expertise. The level of training affects diagnostic accuracy with and without atrial EGMs.