Quadruple parametric optical mapping to measure cardiac metabolism-excitation-contraction coupling

Abstract

Metabolism-excitation-contraction coupling (MECC) refers to the interdependent facets of cardiac physiology working synchronously to generate each heartbeat. Simultaneous imaging of MECC parameters: transmembrane potential (Vm), intracellular calcium (Ca2+) and metabolic markers (NADH, FAD), provides a wholistic picture of cardiac physiology. Quadruple parametric optical mapping of Vm, Ca2+, NADH and FAD is performed during pharmacological (nifedipine, flecainide, FCCP) or pathological (ischemia/reperfusion) perturbations. Vm and Ca2+ are imaged using fluorescent dyes (RH237 and Rhod2-AM) along with NADH and FAD autofluorescence. While nifedipine alters only Ca2+-related parameters, flecainide and FCCP modulates all three aspects of MECC. The sequence of modulation of MECC parameters in response to FCCP and ischemia/reperfusion was also determined. Using this technique, we demonstrate known and novel cardiac responses to nifedipine and flecainide. We determine chronological changes in MECC with FCCP and ischemia/reperfusion to understand the interplay between electrical, mechanical, and metabolic functions in the heart and mechanisms underlying arrhythmogenesis.