[Effects of acute hypercapnia upon the myocardium: contractility, coronary resistance, oxygen consumption and potassium balance (author's transl)].

In the isolated perfused dog heart, at constant coronary blood flow and heart rate, we studied the effect of altering CO2 in the gas mixture from 5 to 15% on contractility, coronary resistance, myocardial O2 consumption and K balance. Contractility, assessed by the developed force, and its derivative through a strain-gauge arch sewed to the left ventricle decreased to 54 +/- 7% (p less than 0.01) and 59 +/- 6% (p less than 0.01), respectively from control values. Coronary resistance decreased to 79 +/- 3% of control ( less than 0.01). The negative inotropic effect of hypercapnia was accompanied by a decrease in myocardial O2 consumption to 68 +/- 11% (p less than 0.01) of control value and a net uptake of K by the heart. The possibility of an exchange of H+ by K+ is suggested as a possible mechanism involved in the negative inotropic effect of hypercapnia.