Background: Periaortic (PA) scarring is one source of ventricular tachycardia (VT) in patients with nonischemic cardiomyopathy (NICM) and is often challenging to ablate.
Objective: To characterize periaortic VT in patients with NICM.
Methods: Consecutive patients with NICM undergoing VT ablation were studied.
Results: A total of 160 VTs were induced in 45 patients (65±11 years; left ventricular ejection fraction 31±11 %), of which 28 VTs in 20 patients had PA exit. PA VTs were divided into two forms: a septal form (left bundle branch block configuration in V1, left inferior axis, and early activation at the parahisian region (n= 14)), and a lateral form (right bundle branch block configuration in V1, right inferior axis, and early activation at the great cardiac vein (n=11)). Both forms were observed in 5 patients. Compared to lateral, septal VTs were associated with lower endocardial bipolar PA voltage (0.55±0.37 vs. 1.04±0.61 mV, p = 0.01) and more frequent observation of abnormal fractionated potentials (71% vs. 27%, p = 0.02) but similar unipolar PA voltage (2.80±1.33 vs. 2.51±1.46 mV, p = 0.40). Following LV endocardial ablation, 46% of VTs were still inducible—and required other techniques or additional sites of ablation (considered to be due to deep substrate)—including intramural needle ablation (4 VTs), left or right aortic sinus of Valsalva ablation (5 VTs), or right ventricular septal ablation (7 VTs). Compared to septal PA VTs, lateral PA VTs were more frequently associated with deep substrate (73% vs. 29%, p = 0.02) and appeared to have substrate further from the aortic ring (12.4±4.1 mm vs. 6.9±4.7, p = 0.008). With combined approaches, all septal and 91% of lateral PA VTs were rendered non-inducible acutely. However, 25% of patients with septal VT developed persistent heart block following ablation. During a median follow-up of 6 months, VT recurred in 7 % of patients with septal VT and 18 % with lateral VT.
Conclusion: Periaortic VT is common in NICM and can be divided into septal and lateral forms. Septal VTs were associated with more identifiable endocardial targets that could often be ablated, but with a significant risk of heart block, whereas lateral VTs were often associated with deep intramural substrate and appear to be at greater risk of recurrence.