Faculty Bibliography

BACKGROUND: -Arrhythmia origin in close proximity to the phrenic nerve (PN) can hinder successful catheter ablation. We describe our approach with epicardial PN displacement in such instances. METHODS AND RESULTS: -PN displacement via percutaneous pericardial access was attempted in 13 patients (age 49+/-16y, 9 females) with either atrial tachycardia (AT; 6 patients) or atrial fibrillation triggered from a superior vena cava focus (1 patient) adjacent to the right PN or epicardial ventricular tachycardia (VT) origin adjacent to the left PN (6 patients). An epicardially placed steerable sheath/4mm-catheter combination (5 patients) or a vascular or an esophageal balloon (8 patients) was ultimately successful. Balloon placement was often difficult requiring manipulation via a steerable sheath. In 2 VT cases, absence of PN capture was achieved only once the balloon was directly over the ablation catheter. In 3 AT patients, PN displacement was not possible with a balloon, however a steerable sheath/catheter combination was ultimately successful. PN displacement allowed acute abolishment of all targeted arrhythmias. No PN injury occurred acutely or in follow up. Two patients developed acute complications (pleuro-pericardial fistula 1, pericardial bleeding 1). Survival free of target arrhythmia was achieved in all AT patients, however a non-targeted VT recurred in 1 patient at a median of 13 months' follow up. CONCLUSIONS: -Arrhythmias originating in close proximity to the PN can be targeted successfully with PN displacement with an epicardially placed steerable sheath/catheter combination, or balloon, but this strategy can be difficult to implement. Better tools for phrenic nerve protection are desirable.

BACKGROUND: -Mapping to identify scar-related ventricular tachycardia (VT) reentry circuits during sinus rhythm focuses on sites with abnormal electrograms, or pace-mapping findings of QRS morphology and long stimulus to QRS (S-QRS) intervals. We hypothesized that 1. these methods do not necessarily identify the same sites and 2. some electrograms are "far-field" potentials that can be recognized by pacing. METHODS AND RESULTS: -From 12 patients with coronary disease and recurrent VT undergoing catheter ablation we retrospectively analyzed electrograms and pacing at 546 separate low bipolar voltage (<1.5mV) sites. Electrograms were characterized as showing evidence of slow conduction if late potentials (56%) or fractionated potentials (76%) were present. Neither was present at (13%) sites. Pacing from the ablation catheter captured 70% of all electrograms. Higher bipolar voltage and fractionation were independent predictors for pace capture. There was a linear correlation between the S-QRS duration during pacing and the lateness of a capturing electrogram (p<0.001), but electrogram and pacing markers of slow conduction were discordant at 40% of sites. Sites with far-field potentials, defined as those that remained visible and not captured by pacing stimuli, were identified at 48% of all pacing sites, especially in areas of low bipolar voltage and late potentials. Initial RF energy application rendered 74% of targeted sites electrically unexcitable. CONCLUSIONS: -Far-field potentials are common in scar areas. Combining analysis of electrogram characteristics and assessment of pace capture may refine identification of substrate targets for RF ablation.

One of the currently accepted paradigms for catheter ablation of persistent atrial fibrillation (AF) is wide antral pulmonary vein isolation, followed by some combination of adjunctive ablation that may include, but is not limited to, linear left atrial ablation, complex fractionated atrial electrogram ablation, rotor ablation, and box isolation of fibrosis until sinus rhythm is restored1-3 . These lesion sets often include establishment of perimitral conduction block, either as an empiric linear ablation, or to terminate and prevent perimitral flutter

BACKGROUND: -Ventricular tachycardia (VT) refractory to anti-arrhythmic drugs (AADs) and standard percutaneous catheter ablation techniques portends a poor prognosis. We characterized the reasons for ablation failure and describe alternative interventional procedures in this high-risk group. METHODS AND RESULTS: -67 patients with VT refractory to 4+/-2 AADs and 2+/-1 prior endocardial/epicardial catheter ablation attempts underwent transcoronary ethanol ablation (TCEA), surgical epicardial window (Epi-window) or surgical cryoablation (OR-Cryo; age 62+/-11 years, VT storm in 52%). Failure of endo/epicardial ablation attempts was due to VT of intramural origin (35 patients), non-endocardial origin with prohibitive epicardial access due to pericardial adhesions (16), and anatomic barriers to ablation (8). In 8 patients, VT was of non-endocardial origin with a co-existing condition also requiring cardiac surgery. TCEA alone was attempted in 37 patients, OR-Cryo alone in 21 patients; and a combination of TCEA and OR-Cryo (5 patients), or TCEA and Epi-window (4 patients) in the remainder. Overall, alternative interventional procedures abolished >/=1 inducible VT and terminated storm in 69% and 74% of patients, respectively although 25% of patients had at least one complication. By 6 months post procedures, there was a significant reduction in defibrillator shocks (from a median of 8 per month to 1, P<0.001) and AAD requirement, although 55% of patients had at least one VT recurrence, and mortality was 17%. CONCLUSIONS: -A collaborative strategy of alternative interventional procedures offers the possibility of achieving arrhythmia control in high-risk patients with VT that is otherwise uncontrollable with AADs and standard percutaneous catheter ablation techniques.

BACKGROUND: Ventricular arrhythmias (VAs) from the left ventricular outflow tract (LVOT) region can be inaccessible for ablation because of epicardial fat or overlying coronary arteries. OBJECTIVE: We describe surgical cryoablation of this type of VA. METHODS: From March 2009 to 2014, 190 consecutive patients with VAs originating from the LVOT underwent ablation at our institution. Four patients (2%) underwent surgical cryoablation for highly symptomatic VAs after failing catheter ablation. RESULTS: In all patients, endocardial or percutaneous epicardial mapping was consistent with origin in the LVOT. In 2 patients, the points of earliest activation during VAs were marked with a bipolar pacing lead in the overlying cardiac vein for guidance during surgery. Surgical cryoablation was successful in 3 of the 4 patients. The fourth patient subsequently had successful endocardial catheter ablation. During a mean follow-up of 22 +/- 16 months (range 4-42 months), all patients showed abolition of or marked reduction in symptomatic VA. However, 1 patient subsequently required percutaneous intervention to the left anterior descending coronary artery; another developed progressive left ventricular systolic dysfunction caused by nonischemic cardiomyopathy; and a third patient underwent permanent pacemaker implantation because of complete atrioventricular block after concomitant aortic valve replacement. CONCLUSION: Surgical cryoablation is an option for highly symptomatic drug-resistant VAs emanating from the LVOT region. Despite extensive preoperative mapping, the procedure is not effective for all patients, and coronary injury is a risk.

BACKGROUND: The initial impedance decrease during radiofrequency (RF) ablation is an indirect marker of catheter contact and lesion formation. We aimed to assess feasibility, efficacy, and safety of an ablation approach guided by initial impedance decrease. METHODS: A total of 25 patients with paroxysmal AF had point-by-point, wide antral pulmonary vein (PV) isolation. RF applications were aborted if a decrease of at least 5 Omega did not occur in the first 10 seconds; otherwise, ablation was continued for at least 20 seconds. Power was 30 Watts and reduced to 15-25 Watts on the posterior wall. RESULTS: A total of 28% of RF applications were terminated because of inadequate impedance decrease. The remaining lesions showed a median decrease of 7.6 Omega (IQR 5.0-10.7) at 10 seconds and median duration of RF lesions was 38 seconds. Note that, 100 PVs were isolated with 49 rings. PVI occurred before anatomic completion of the ablation ring of adequate lesions in 39/49 (80%) and concurrent with ring completion in 7/49 (14%). Additional lesions were required in 3/49 (6%) rings. After PVI, additional lesions were required to eliminate dormant conduction in 2/47 (4%) and pace-capture on the ablation line in 24/49 vein pairs (49%). During short-term follow-up, 3 nonfatal esophageal injuries and 2 late pericardial effusions occurred. During a mean follow-up of 431 +/- 87 days, 21/25 patients (84%) remained free of recurrent symptomatic atrial arrhythmias. CONCLUSIONS: PVI guided by initial impedance decrease is feasible and results in PVI concurrent with or before completion of the ablation ring in 94% of patients. Single procedure efficacy after one year of follow-up was 84%. Near-term complications suggest that deeper lesions are created, indicating that further reduction of RF-power and duration is warranted.

BACKGROUND: Cardiac sarcoid-related ventricular tachycardia (VT) is a rare disorder; the underlying substrate and response to ablation are poorly understood. We sought to examine the ventricular substrate and outcomes of catheter ablation in this population. METHODS AND RESULTS: Of 435 patients with nonischemic cardiomyopathy referred for VT ablation, 21 patients (5%) had cardiac sarcoidosis. Multiple inducible VTs were observed with mechanism consistent with scar-mediated re-entry in all VTs. Voltage maps showed widespread and confluent right ventricular scarring. Left ventricular scarring was patchy with a predilection for the basal septum, anterior wall, and perivalvular regions. Epicardial right ventricular scar overlay and exceeded the region of corresponding endocardial scar. After >/=1 procedures, ablation abolished >/=1 inducible VT in 90% and eliminated VT storm in 78% of patients; however, multiple residual VTs remained inducible. Failure to abolish all inducible VTs was because of septal intramural circuits or extensive right ventricular scarring. Multiple procedure VT-free survival was 37% at 1 year, but VT control was achievable in the majority of patients with fewer antiarrhythmic drugs compared with preablation (2.1+/-0.8 versus 1.1+/-0.8; P<0.001). CONCLUSIONS: Patients with cardiac sarcoidosis and VT exhibit ventricular substrate characterized by confluent right ventricular scarring and patchy left ventricular scarring capable of sustaining a large number of re-entrant circuits. Catheter ablation is effective in terminating VT storm and eliminating >/=1 inducible VT in the majority of patients, but recurrences are common. Ablation in conjunction with antiarrhythmic drugs can help palliate VT in this high-risk population.

BACKGROUND: Entrainment can be useful for mapping atrial tachycardias (ATs) after atrial fibrillation (AF) ablation but may result in AT alteration or termination. OBJECTIVE: We aimed to determine the incidence and risk factors for AT alteration or termination. METHODS: In 30 consecutive patients, 62 ATs (mean cycle length [CL] 268 +/- 53 ms) in which overdrive pacing for entrainment mapping was performed were retrospectively analyzed. AT was classified as altered if the CL or activation pattern remained altered 10 seconds after pacing. The variability in the PP intervals was determined over 10 beats from 2 measures: (1) the difference between the shortest and the longest CL expressed as a percentage of the CL and (2) the mean difference between sequential PP intervals expressed as a percentage of the AT CL (CLDmean). RESULTS: Of 386 total pacing attempts (tachycardia CL [TCL] - pacing CL [PCL] difference 15 +/- 6 ms), 5 (1.3%) altered or terminated AT and 381 did not change AT (98.7%). When the T