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Effects of hydrogen peroxide on isolated myocardium.

In a preliminary series of experiments, the mechanical responses of myocardium to dilute solutions of hydrogen peroxide were examined in 19 isolated rat papillary and 25 human atrial muscles under normoxic and hypoxic conditions. When a single dose (0.5 to 1..0 ml) of 3% hydrogen peroxide [final concentration 0.01% to 0.02%] was added to normoxic muscle, developed force rose significantly [P less than 0.05] followed by a gradual increase in resting force resulting in contracture. A similar result was obtained in normoxic hypodynamic human atrial muscle. Under hypoxic conditions a singly dose of hydrogen peroxide caused a significant [P less than 0.05] improvement in mechanical properties of both preparations: developed force increased while resting force decreased However, these changes were followed by a progressive irreversible contracture. In contrast, when a 0.06% solution of hydrogen peroxide was slowly infused at a constant rate [2 ml/min], human atrial muscle showed a significant [P less than 0.05] increase in developed force and a significant [p less than 0.05] decrease in resting force from the hypoxic state while the rat papillary muscle only showed a significant [P less than 0.05] increase in resting force. Contracture did not occur in either preparation. The authors conclude that controlled contact between cardiac muscle and dilute solutions of hydrogen peroxide can alter the mechanical characteristics of myocardial tissue.