Optical mapping of V m and Cai 2+ in a model of arrhythmias induced by local catecholamine application in patterned cell cultures

Abstract

Catecholamines are known to provoke cardiac arrhythmias, but important aspects such as localization of the arrhythmia source in multicellular tissue and exact ionic mechanisms are not well-known. In this work, a multicellular model of arrhythmias caused by local epinephrine application was developed; V (m) and Ca(i)(2+) changes at the arrhythmia source were measured using fluorescent dyes and high-resolution optical mapping. Cultured strands of neonatal rat myocytes (width approximately 0.4 mm) were produced by patterned growth. Epinephrine (1 micromol/l) was applied over an area of 0.3-0.6 mm via two micropipettes, and strands were stimulated by burst pacing. Local epinephrine application caused triggered arrhythmias with cycle lengths of 202-379 ms and duration of >10 s in 9 out of 16 preparations. Optical V(m) mapping demonstrated that in 78% of cases, the source of arrhythmia was located at the boundary of the locally perfused area. Staining with Ca(i)(2+)-sensitive dye Fluo-4 prevented arrhythmia induction in most cases (85%) likely due to Ca(2+) buffering by the dye. Optical Ca(i)(2+) mapping revealed non-propagated Ca(i)(2+) oscillations at the boundary of the locally perfused area in 45% cases. In conclusion, we developed a new model of catecholamine-dependent arrhythmias allowing mapping of V(m) and Ca(i)(2+) at the arrhythmia source with microscopic resolution. The arrhythmias typically originated from the boundary of the epinephrine-perfused area. The location of the arrhythmia source correlated with localized Ca(i)(2+) oscillations suggesting that arrhythmias were caused by Ca(i)(2+) overload at these locations.

Region of slowed conduction acts as core for spiral wave reentry in cardiac cell monolayers

“…Geometrically well-defined regions of heterogeneity can be achieved in cell cultures by restricting cell access to the bath by a glass coverslip (20) but are not easily reversed. Several groups have developed flow chambers that can selectively and reversibly superfuse a given area of a cell monolayer with drug (2,14,17,21). However, none of the designs resulted in the creation of a sharply defined, scalable island with uniform properties distinct from the remainder of the monolayer that would be valuable in the study of the initiation or maintenance of reentry.…”

Simultaneous Optical Mapping of Intracellular Free Calcium and Action Potentials from Langendorff Perfused Hearts

“…The method has been used to track the sequences of electrical activation and force generation as well as cardiac repolarization and relaxation as a function of rate and sympathetic activity and during electrically induced ventricular fibrillation (VF) and defibrillation. Dual optical mapping has been playing an important role in elucidating arrhythmia mechanisms in models of heart failure (London et al, ), long QT syndrome (Choi et al, ), and ischemia/reperfusion (Choi and Salama, ; Lakireddy et al, ; Choi et al, ,b; Lakireddy et al, ), and in genetically altered animal models of human cardiac diseases (Katra et al, ; Katra and Laurita, ; Lan et al, ; London et al, ; Roell et al, ; Hayashi et al, ; Laurita and Rosenbaum, ; Saba et al, ).…”

The Photodiode Array: A Critical Cornerstone in Cardiac Optical Mapping

“…These include high spatiotemporal resolutions systems (Choi et al, 2007), panoramic systems (Kay et al, 2004;Rogers et al, 2007), and systems which are capable of interrogating electrophysiological activity beneath the surface (Byars et al, 2003). In addition, several labs have used photodiodebased optical mapping systems to map V m and Ca i simultaneously, on both the whole heart (Choi & Salama, 2000;Lakireddy et al, 2006;Laurita & Singal, 2001;Pruvot et al, 2004) and in monolayer cell cultures of cardiac myocytes (Fast, 2005;Fast & Ideker, 2000;Lan et al, 2007). Cardiac optical mapping systems have greatly increased our understanding in nearly all areas of cardiac electrophysiology, from basic studies of conduction patterns (Cabo et al, 1994;Knisley & Hill, 1995) and effects of fiber geometry (Knisley & Baynham, 1997;Knisley et al, 1994;Knisley et al, 1999;Neunlist & Tung, 1995) to more clinical studies of defibrillation (Al-Khadra et al, 2000;Fast et al, 2002;Federov et al, 2008;Tung & Cysk, 2007) and ablation therapy (Himel et al, 2007;Perez et al, 2006).…”