High-energy defibrillation impairs myocyte contractility and intracellular calcium dynamics

• Published in: Critical care medicine Vol. 36; no. 11 Suppl; p. S422
• Main Authors: Ristagno, Giuseppe, Wang, Tong, Tang, Wanchun, Sun, Shijie, Castillo, Carlos, Weil, Max Harry
• Format: Journal Article
• Language: English
• Published: United States 01.11.2008
• Subjects: Animals; Calcium - metabolism; Electric Countershock; Fura-2; In Vitro Techniques; Intracellular Fluid - metabolism; Male; Myocardial Contraction; Myocytes, Cardiac - physiology; Rats; Rats, Sprague-Dawley
• DOI: 10.1097/ccm.0b013e31818a84c5

We examined the effects of energy delivered with electrical defibrillation on myocyte contractility and intracellular Ca2+ dynamics. We hypothesized that increasing the defibrillation energy would produce correspondent reduction in myocyte contractility and intracellular Ca2+ dynamics. Randomized prospective study. University-affiliated research laboratory. Ventricular myocytes from male Sprague-Dawley rat hearts. Ventricular cardiomyocytes loaded with Fura-2/AM were placed in a chamber mounted on an inverted microscope and superfused with a buffer solution at 37 degrees C. The cells were field stimulated to contract and mechanical properties were assessed using a video-based edge-detection system. Intracellular Ca2+ dynamics were evaluated with a dual-excitation fluorescence photomultiplier system. Myocytes were then randomized to receive 1) a single 0.5-J biphasic shock; 2) a single 1-J biphasic shock; 3) a single 2-J biphasic shock; and 4) a control group without shock. After the shock, myocytes were paced for an additional 4 mins. A single 0.5-J shock did not have effects on contractility and intracellular Ca2+ dynamics. Higher energy shocks, i.e., 1- or 2-J shocks, significantly impaired contractility and intracellular Ca2+ dynamics. The adverse effects were greater after a 2-J shock compared with a 1-J shock. Higher defibrillation energy significantly impairs ventricular contractility at the myocyte level. Reductions in cardiomyocyte shortening and intracellular Ca2+ dynamics abnormalities were greater when higher energy shock was used.