Role of papillary muscle in the generation and maintenance of reentry during ventricular tachycardia and fibrillation in isolated swine right ventricle

Background-The role of papillary muscle (PM) in the generation and maintena nce of reentry is unclear. Methods and Results-Computerized mapping (477 bipolar electrodes, 1.6-mm re solution) was performed in fibrillating right ventricles (RVs) of swine in vitro. During ventricular fibrillation (VF), reentrant wave fronts often tr ansiently anchored to the PM. Tissue mass reduction was then performed in 1 0 RVs until VF converted to ventricular tachycardia (VT), In an additional 6 RVs, procainamide infusion converted VF to VT. Maps showed that 77% (34 o f 44) of all VT episodes were associated with a single reentrant wave front anchored to the PM. Purkinje fiber potentials preceded the local myocardia l activation, and these potentials were recorded mostly around the PM. When PM was trimmed to the level of endocardium (n = 4), sustained VT was no lo nger inducible, Transmembrane potential recordings (n = 5) at the PM reveal ed full action potential during pacing, without evidence of ischemia, Compu ter simulation studies confirmed the role of PM as a spiral wave anchoring site that stabilized wave conduction. Conclusions-We conclude that PM is important in the generation and maintena nce of reentry during VT and VF.