Intracardiac Echocardiography for the Detection of Arrhythmogenic Periaortic Ventricular Tachycardia Substrate:...

There is no established imaging technique to detect and diagnose periaortic scar, an increasingly prevalent and challenging substrate referred for ventricular tachycardia (VT) ablation. We hypothesized that wall thinning detected with intracardiac echocardiography (ICE) can identify periaortic arrhythmogenic substrate (PAS) in patients with structural heart disease.

This study sought to validate a new method of identifying PAS using ICE in comparison with electro-anatomic mapping and cardiac magnetic resonance (CMR).

A total of 84 VT ablation patients were analyzed (87% male, median age 72 years [Q1-Q3: 63-75 years], 61% with nonischemic cardiomyopathy) and categorized into 2 groups: PAS+ (n = 29) and PAS- (n = 55) based on voltage-defined scar and deceleration zones. Wall thickness of the basal anterior septum was measured by ICE and CMR at a standardized distance from the left ventricular ostium in diastole by an independent core lab. In 43 patients with CMR, correlation with late gadolinium enhancement (LGE) in the basal anterior septum was also assessed.

A significant difference in wall thickness measured at 1 cm from the left ventricular ostium with ICE was observed between PAS+ and PAS- patients (0.57 cm [Q1-Q3: 0.51-0.65 cm] vs 0.72 cm [Q1-Q3: 0.65-0.79 cm]; P < 0.001). Wall thickness by ICE had higher diagnostic performance than CMR, with only 50% of PAS+ patients exhibiting LGE. At a cutoff of <0.60 cm, the sensitivity and specificity of ICE predicting PAS+ were 58% and 87% (positive predictive value 71%, negative predictive value 80%) in comparison with 50% and 84% (positive predictive value 69%, negative predictive value 70%) with CMR-LGE, respectively.

ICE-detected wall thinning may be a novel imaging technique to identify arrhythmogenic periaortic VT substrate in this challenging anatomic region, which often eludes diagnosis with CMR. The absence of LGE on CMR does not rule out the presence of periaortic substrate in patients presenting with outflow tract VT.