Search

Background Cardiac resynchronization therapy (CRT) and atrial ablation procedures currently lack a noninvasive imaging modality for reliable treatment planning and monitoring. Electromechanical wave imaging (EWI) is an ultrasound-based method that has previously been shown to be capable of noninvasively and transmurally mapping the activation sequence of the heart in animal studies by estimating and imaging the electromechanical wave, that is, the transient strains occurring in response to the electrical activation, at both high temporal and spatial resolutions. Objective To demonstrate the feasibility of transthoracic EWI for mapping the activation sequence during different cardiac rhythms in humans. Methods EWI was perfor`med in patients undergoing CRT and a left bundle branch block (LBBB) during sinus rhythm, left ventricular pacing, and right ventricular pacing, as well as in patients with atrial flutter (AFL) before intervention, EWI findings from patients with AFL were subsequently correlated with results from invasive intracardiac electrical mapping studies during intervention. In addition, the feasibility of single-heartbeat EWI at 2000 frames/s is demonstrated in humans for the first time in a patient with both AFL and right bundle branch block (RBBB). Results The electromechanical activation maps demonstrated the capability of EWI to localize the pacing sites and characterize the bundle branch block activation sequence transmurally in patients with CRT. In patients with AFL, the EWI propagation patterns obtained with EWI were in excellent agreement with those obtained from invasive intracardiac mapping studies. Conclusions Our findings demonstrate the potential capability of EWI to aid in the assessment and follow-up of patients undergoing CRT pacing therapy and atrial ablation, with preliminary validation in vivo.

Steam pops are a risk of irrigated radiofrequency catheter ablation (RFA) and may cause cardiac perforation. Data to guide radiofrequency (RF) energy titration to avoid steam pops are limited.This study sought to assess the frequency and consequence of audible pops and to determine the feasibility of using the magnitude of impedance change to predict pops.We reviewed consecutive endocardial open-irrigated RFA for ventricular tachycardia (VT) with continuously recorded ablation data in 142 patients with structural heart disease. Steam pops were defined as an audible pop associated with a sudden spike in impedance. Ablation lesions before or after pops served as controls.From a total of 4,107 ablation lesions, 62 (1.5%) steam pops occurred in 42 procedures in 38 patients. Perforation with tamponade occurred with 1 of 62 (2%) pops. Applications with pops had a greater impedance decrease (22 +/- 7 Omega vs. 18 +/- 8 Omega, P = .001) and a higher maximum power (45 +/- 5 W vs. 43 +/- 6 W, P = .011), but did not differ in maximum catheter tip temperature (40 degrees C +/- 4 degrees C vs. 40 degrees C +/- 4 degrees C, P = .180) from applications without pops. Eighty percent of pops occurred after impedance decreased by at least 18 Omega.During VT ablation with open irrigation, audible pops are infrequent and do not usually cause perforation. Limiting RF power to achieve an impedance decrease of18 Omega is a feasible method of reducing the likelihood of a pop when perforation risk is of concern.