Background: Fast ventricular tachycardias (VTs) have been historically attributed to shorter path lengths with smaller reentrant circuit dimensions in animal models. The relationship between the dimensions of the reentrant VT circuit and tachycardia cycle length (TCL) has not been examined in humans. This study aimed to analyze the determinants of the rate of human VT with comparison of circuit dimensions and conduction velocity (CV) across a wide range of both stable and unstable VTs delineated by high-resolution mapping. Methods: 54 VTs with complete circuit delineation (>90% TCL) by high-resolution multielectrode mapping were analyzed in 49 patients (male 88%, 65 years [58-71], nonischemic 47%). Fast VT was defined as TCL <333 ms (rate >180 bpm). Unstable VT was defined by hemodynamic deterioration with an intrinsic mean arterial pressure <60 mmHg during a sustained episode. Results: The median TCL of VT was 365 ms (306-443 ms) and 24 fast VTs with TCL<333ms (180 bpm) were characterized. A wide range of CV was observed within the entrance (0.03-0.55 m/s), common pathway (0.03-0.77 m/s), exit (0.03-0.53m/s), and outer loop (0.17-1.13 m/s). There were no significant differences in the median dimensions of the isthmus and path length between fast versus slow VTs and unstable versus stable VTs. The outer loop CV was the only circuit component that correlated with TCL both in ischemic cardiomyopathy (r=-0.5, p=0.006) and nonischemic cardiomyopathy(r=-0.45, p=0.028). The duration of the longest diastolic electrogram was inversely correlated with the dimensions of common pathway (length: r=-0.46, p=0.001, width: r=-0.3, p=0.047) and predictive of VT termination by a single radiofrequency application (r=-0.41, p=0.023). Conclusions: Due to a wide spectrum of CV observed within the reentrant path during human VT, the dimensions of the circuit were not predictive of VT cycle length. For the first time, we demonstrate that the CV of the outer loop, rather than isthmus, is the principal determinant of the rate of VT. The size of the circuit was similar between fast versus slow VTs and unstable versus stable VTs. Long, continuous electrograms were indicative of spatially confined isthmus dimensions, confirmed by rapid termination of VT during radiofrequency delivery.
Background: Fastventricular tachycardias (VTs) have been historically attributed to shorter path lengths with smaller reentrant circuit dimensions in animal models. The relationship between the dimensions of the reentrant VT circuit and tachycardia cycle length (TCL) has not been examined in humans. This study aimed to analyze the determinants of the rate of human VT with comparison of circuit dimensions and conduction velocity (CV) across a wide range of both stable and unstable VTs delineated by high-resolution mapping. Methods: 54 VTs with complete circuit delineation (>90% TCL) by high-resolution multielectrode mapping were analyzed in 49 patients (male 88%, 65 years [58-71], nonischemic 47%). FastVT was defined as TCL <333 ms (rate >180 bpm). Unstable VT was defined by hemodynamic deterioration with an intrinsic mean arterial pressure <60 mmHg during a sustained episode. Results: The median TCL of VT was 365 ms (306-443 ms) and 24 fast VTs with TCL<333ms (180 bpm) were characterized. A wide range of CV was observed within the entrance (0.03-0.55 m/s), common pathway (0.03-0.77 m/s), exit (0.03-0.53m/s), and outer loop (0.17-1.13 m/s). There were no significant differences in the median dimensions of the isthmus and path length between fast versus slow VTs and unstable versus stable VTs. The outer loop CV was the only circuit component that correlated with TCL both in ischemic cardiomyopathy (r=-0.5, p=0.006) and nonischemic cardiomyopathy(r=-0.45, p=0.028). The duration of the longest diastolic electrogram was inversely correlated with the dimensions of common pathway (length: r=-0.46, p=0.001, width: r=-0.3, p=0.047) and predictive of VT termination by a single radiofrequency application (r=-0.41, p=0.023). Conclusions: Due to a wide spectrum of CV observed within the reentrant path during human VT, the dimensions of the circuit were not predictive of VT cycle length. For the first time, we demonstrate that the CV of the outer loop, rather than isthmus, is the principal determinant of the rate of VT. The size of the circuit was similar between fast versus slow VTs and unstable versus stable VTs. Long, continuous electrograms were indicative of spatially confined isthmus dimensions, confirmed by rapid termination of VT during radiofrequency delivery.
Authors: Marc W Deyell; Steve Doucette; Ratika Parkash; Isabelle Nault; Lorne Gula; Christopher Gray; Martin Gardner; Laurence D Sterns; Jeff S Healey; Vidal Essebag; John L Sapp Journal: Europace Date: 2022-07-21 Impact factor: 5.486
Authors: Mehmet K Aktaş; Arwa Younis; Wojciech Zareba; Valentina Kutyifa; Helmut Klein; James P Daubert; Mark Estes; Scott McNitt; Bronislava Polonsky; Ilan Goldenberg Journal: J Am Coll Cardiol Date: 2021-05-25 Impact factor: 27.203