Wave-front pivoting during reentrant propagation significantly shortened cardiac wavelength compared to plane wave propagation (10.6 vs 32.8 mm, P<0.02) due to increased current load.
Absolute Event Rate: 10.6% vs 32.8%
p-value: p=<.02
BACKGROUND: Although the relationship between cardiac wavelength (lambda) and path length importantly determines the stability of reentrant arrhythmias, the physiological determinants of lambda are poorly understood. To investigate the cellular mechanisms that control lambda during reentry, we developed an experimental system for continuously monitoring lambda within a reentrant circuit with the use of voltage-sensitive dyes and a new guinea pig model of ventricular tachycardia (VT). METHODS AND RESULTS: Action potentials were recorded simultaneously from 128 ventricular sites in Langendorff-perfused hearts (n = 15) in which propagation was confined to a two-dimensional rim of epicardium by an endocardial cryoablating procedure. The reentrant path was precisely controlled by creating an epicardial obstacle (2 x 10 mm) with an argon laser. To control for fiber orientation and rate-dependent membrane properties, lambda during reentry was compared with lambda during plane wave propagation transverse and longitudinal to cardiac fibers at a stimulus cycle length (CL) comparable to the VT CL. Reentrant VT (CL = 97.0 +/- 6.2 ms) was reproducibly induced by programmed stimulation in 93% of preparations. lambda varied considerably within the reentrant circuit (range, 10.6 to 22.5 mm), because of heterogeneities of conduction rather than action potential duration. lambda was significantly shorter during reentrant propagation (ie, with pivoting) parallel to fibers (10.6 +/- 4.2 mm) compared with plane wave propagation (ie, without pivoting) parallel to fibers (32.8 +/- 6.5 mm, P < .02), indicating that wave-front pivoting was primarily responsible for shortening of lambda during reentry. The mechanism of lambda shortening was conduction slowing from increased current load experienced by the pivoting wave front. CONCLUSIONS: We provide direct experimental evidence that multiple wavelengths are present even within a relatively simple reentrant circuit. Abrupt changes in loading during wave-front pivoting, rather than membrane ionic properties or fiber structure, were a major determinant of lambda and, therefore, may play an important role in the stability of reentry.
Girouard et al. (Thu,) conducted a other in Ventricular tachycardia (n=15). Reentrant propagation (with pivoting) parallel to fibers vs. Plane wave propagation (without pivoting) parallel to fibers was evaluated on Cardiac wavelength (lambda) (p=<.02). Wave-front pivoting during reentrant propagation significantly shortened cardiac wavelength compared to plane wave propagation (10.6 vs 32.8 mm, P<0.02) due to increased current load.