Periaortic Ventricular Tachycardias in Nonischemic Cardiomyopathy: Substrate and Electrocardiographic Correlations

Background - Periaortic fibrotic ventricular tachycardia (VT) substrate is common in nonischemic cardiomyopathy (NICM), often intramural, and difficult to ablate. We sought to better characterize normal and abnormal periaortic voltage map parameters and NICM periaortic VTs. Methods - In 15 patients without heart disease, the 5 th percentile of endocardial voltage for increasing distance from the aortic valve ring was determined. In 53 consecutive NICM patients (64±11 years; left ventricular ejection fraction 31±10%) undergoing ablation of recurrent VT, periaortic electrogram voltage and VT characteristics were analyzed. Results - In healthy patients, the 5 th percentile of the bipolar voltage (BV) increased proportional to the distance from the aortic valve ring, from 1.0mV at 1cm to 1.5mV at 1.5cm; the corresponding unipolar voltage (UV) cutoffs were 5.0mV and 7.5mV. A total of 160 VTs were induced in 53 NICM patients, of which 28 VTs in 20 patients had periaortic origins. Periaortic VTs were associated with similar periaortic BV, but lower UVs consistent with intramural fibrosis as an important substrate. Periaortic VTs could be divided into left (LBBB) and right (RBBB) bundle branch block forms with mapping showing right septal and lateral exits. LBBB VTs were more often acutely abolished with ablation (100% vs. 69%; p=0.034), but with a 23% incidence of heart block. Greater extent of low voltage was associated with more induced VTs and worse acute outcome. Conclusions - Adjusting voltage parameters based on distance from the aortic valve may improve definition of LVOT arrhythmia substrate. Periaortic VTs are common in NICM, often associated with intramural substrate and can be divided into LBBB and RBBB types associated with different ablation outcomes and risks.

Impact of Left Atrial Bipolar Electrogram Voltage on First Pass Pulmonary Vein Isolation During Radiofrequency Catheter Ablation

BackgroundFirst pass pulmonary vein isolation (PVI) is associated with durable isolation and reduced recurrence of atrial fibrillation (AF).ObjectiveWe sought to investigate the relationship between left atrial electrogram voltage using multielectrode fast automated mapping (ME-FAM) and first pass isolation with radiofrequency ablation.MethodsWe included consecutive patients (pts) undergoing first time ablation for paroxysmal AF (pAF), and compared the voltage characteristics between patients with and without first pass isolation. Left atrium (LA) adjacent to PVs was divided into 6 regions, and mean voltages obtained with ME-FAM (Pentaray, Biosense Webster) in each region and compared. LA electrograms with marked low voltage (<0.5 mV) were identified and the voltage characteristics at the site of difficult isolation was compared to the voltage in adjacent region.ResultsTwenty consecutive patients (10 with first pass and 10 without) with a mean age of 63.3 ± 6.2 years, 65% males, were studied. Difficult isolation occurred on the right PVs in eight pts and left PVs in three pts. The mean voltage in pts without first pass isolation was lower in all 6 regions; posterior wall (1.93 ± 1.46 versus 2.99 ± 2.19; p < 0.001), roof (1.83 ± 2.29 versus 2.47 ± 1.99; p < 0.001), LA-LPV posterior (1.85 ± 3.09 versus 2.99 ± 2.19, p < 0.001), LA-LPV ridge (1.42 ± 1.04 versus 1.91 ± 1.61; p < 0.001), LA-RPV posterior (1.51 ± 1.11 versus 2.30 ± 1.77, p < 0.001) and LA-RPV septum (1.55 ± 1.23 versus 2.31 ± 1.40, p < 0.001). Patients without first pass isolation also had a larger percentage of signal with an amplitude of <0.5 mV for each of the six regions (12.8% versus 7.5%). In addition, the mean voltage at the site of difficult isolation was lower at 8 out of 11 sites compared to mean voltage for remaining electrograms in that region.ConclusionIn patients undergoing PVI for paroxysmal AF, failure in first pass isolation was associated with lower global LA voltage, more marked low amplitude signal (<0.5 mV) and lower local signal voltage at the site with difficult isolation. The results suggest that a greater degree of global and segmental fibrosis may play a role in ease of PV isolation with radiofrequency energy.