Electrophysiologic changes in ischemic ventricular myocardium: 1. Influence of ionic, metabolic, and energetic changes

Author(s): Johnson, T. A., Gettes, L. S.

Journal/Book: J Cardiovasc Electrophysiol. 1995; 6: 135 Bedford Rd, PO Box 418, Armonk, NY 10504-0418. Futura Publ Co. 1039-1062.

Abstract: Myocardial ischemia leads to significant changes in the intracellular and extracellular ionic milieu, high-energy phosphate compounds, and accumulation of metabolic by-products, Changes are measured in extracellular pH and K+, and intracellular pH, Ca2+, Na+, Mg2+, ATP, ADP, and inorganic phosphate, Alterations of membrane currents occur as a consequence of these ionic changes, adrenergic receptor stimulation, and accumulation of lactate, amphipathic compounds, and adenosine, Changes in the volume of the extracellular and intracellular spaces contribute further to the ultimate perturbations of active and passive membrane properties that underlie alterations in excitability, abnormal automaticity, refractoriness, and conduction, These characteristic changes of electrophysiologic properties culminate in loss of excitability and failure of impulse propagation and form the substrate for ventricular arrhythmias mediated through abnormal impulse formation and reentry, The ability to detail the changes in ions, metabolites, and high-energy phosphate compounds in both the extracellular and intracellular spaces and to correlate them directly with the simultaneously occurring electrophysiologic changes have greatly enhanced our understanding of the electrical events that characterize the ischemic process and hold promise for permitting studies aimed at developing interventions that may lessen the lethal consequences of ischemia.

Note: Review WE Cascio, Univ N Carolina, Sch Med, Dept Med, Div Cardiol, CB 7075, Burnett Womack Bldg 229H, Chapel Hill, NC 27599 USA

Keyword(s): heart; ionic homeostasis; ischemic metabolism; impulse propagation; arrhythmias; cell-to-cell coupling; SENSITIVE K+ CHANNELS; CARDIAC PURKINJE-FIBERS; INTRACELLULAR SODIUM ACTIVITY; FREE CALCIUM-CONCENTRATION; RABBIT PAPILLARY-MUSCLE; CYTOSOLIC FREE CALCIUM; ACUTE GLOBAL-ISCHEMIA; GAP JUNCTIONAL CONDUCTANCE; CORONARY-ARTERY OCCLUSION; LONG-CHAIN ACYLCARNITINES

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