Attenuating loss of cardiac conduction during no-flow ischemia through changes in perfusate sodium and calcium.

Attenuating loss of cardiac conduction during no-flow ischemia through changes in perfusate sodium and calcium. Am J Physiol Heart Circ Physiol. 2020 Jul 17;: Authors: Hoeker GS, James CC, Tegge AN, Gourdie RG, Smyth JW, Poelzing S Abstract Myocardial ischemia leads to conduction slowing, cell-to-cell uncoupling, and arrhythmias. We previously demonstrated that varying perfusate sodium (Na+) and calcium (Ca2+) attenuates conduction slowing and arrhythmias during simulated ischemia with continuous perfusion. Cardioprotection was selectively associated with widening of the perinexus, a gap junction adjacent nanodomain important to ephaptic coupling. It is unknown whether perfusate composition affects the perinexus or ischemic conduction during non-simulated ischemia, when coronary flow is reduced or halted. We hypothesized that altering pre-ischemic perfusate composition could facilitate perinexal expansion and attenuate conduction slowing during global ischemia. To test this hypothesis, ex vivo guinea pig hearts (n=49) were Langendorff-perfused with 145 or 153mM Na+and 1.25 or 2.0mM Ca2+, and optically mapped during 30 minutes of no-flow ischemia. Altering Na+ and Ca2+ did not significantly affect baseline conduction velocity (CV). Increasing Na+ and decreasing Ca2+ both lowered pacing thresholds, while increasing Ca2+ narrowed perinexal width (WP). A least squared means estimate revealed that reduced Na+ and Ca2+ slowed CV by 2.20 (c...
Source: American Journal of Physiology. Heart and Circulatory Physiology - Category: Physiology Authors: Tags: Am J Physiol Heart Circ Physiol Source Type: research