A technical review of optical mapping of intracellular calcium within myocardial tissue

Optical mapping of Ca2+ sensitive fluorescence probes has become an extremely useful approach and adopted by many cardiovascular research laboratories to study a spectrum of myocardial physiology and disease conditions. Optical mapping data are often displayed as detailed pseudocolor images, providing unique insight for interpreting mechanisms of ectopic activity, action potential and Ca2+ transient alternans, tachycardia, and fibrillation. Ca2+-sensitive fluorescent probes and optical mapping systems continue to evolve in the ongoing effort to improve therapies that ease the growing worldwide burden of cardiovascular disease. In this technical review we provide an updated overview of conventional approaches for optical mapping of Ca-i(2+) within intact myocardium. In doing so, a brief history of Ca-i(2+) probes is provided, and nonratiometric and ratiometric Ca2+ probes are discussed, including probes for imaging sarcoplasmic reticulum Ca2+ and probes compatible with potentiometric dyes for dual optical mapping. Typical measurements derived from optical Ca-i(2+) signals are explained, and the analytics used to compute them are presented. Last, recent studies using Ca-i(2+) optical mapping to study arrhythmias, heart failure, and metabolic perturbations are summarized.