Depression of human myocardial contractility with "respiratory" and "metabolic" acidosis.

The effect of a similar degree of "respiratory" and "metabolic" acidosis was studied in seven isolated in vitro human pectinate muscles and eight ventricular muscle bundles. Either "respiratory" or "metabolic" acidosis (from 7.36 plus or minus 0.03 to 7.01 plus or minus 0.02 and 6.98 plus or minus 0.03, respectively) depressed in vitro contractility in human atrial or ventricular muscle to a similar extent. Previous contradictory responses of myocardial tissue to alterations in pH appear to be the result of species differences.