Submitted on February 7, 2008
Revised on May 8, 2008
Accepted on May 8, 2008
Intracellular Calcium Dynamics at the Core of Endocardial Stationary Spiral Waves in Langendorff-Perfused Rabbit Hearts
Liang Tang1, Gyo-Seung Hwang, Hideki Hayashi, Juan Song, Masahiro Ogawa, Kenzaburo Kobayashi, Boyoung Joung, Hrayr S Karagueuzian2, Peng-Sheng Chen3, and Shien-Fong Lin1*
1 Indiana University School of Medicine
2 UCLA Medical School
3 Krannert Institute of Cardiology
* To whom correspondence should be addressed. E-mail: linsf{at}iupui.edu.
In vitro models of sustained monomorphic ventricular tachycardia (MVT) are rare and do not usually show spiral reentry on the epicardium. We hypothesize that MVT is associated with spiral wave in the endocardium and this stable reentrant propagation is supported by a persistently elevated intracellular calcium transient (Cai) at the core of the spiral wave. We performed dual optical mapping of transmembrane potential (Vm) and Cai dynamics of the right ventricular (RV) endocardium in Langendorff-perfused rabbit hearts (n=12). Among 64 induced arrhythmias, 55% were sustained MVT (> 10 minutes). 80% of the MVT showed stationary spiral waves (>10 cycles, CL: 128±14.6 ms) in the endocardial mapped region, anchoring to the anatomic discontinuities. No reentry activity was observed in the epicardium. During reentry, the amplitudes of the Vm and Cai signals were higher in the periphery and gradually decreased toward the core. At the core, the maximal Vm and Cai amplitudes were 42.95±5.89% and 43.95±9.46% respectively of the control, (p<0.001). However, the trough of the Vm and Cai signals at the core were higher than the periphery, indicating persistent Vm and Cai elevations during reentry. BAPTA-AM, a calcium chelator, significantly reduced the maximal Cai transient amplitude and prevented sustained MVT and spiral wave formation in the mapped region. These findings indicate that endocardial spiral waves often anchor to anatomic discontinuities causing stable MVT in normal rabbit ventricles. The spiral core is characterized by diminished Vm and Cai amplitudes and persistent Vm and Cai elevations during reentry.
