... or placebo. 3. Coronary vein pH decreased to 6.91 ± 0.06 units (mean ± sem ) with concurrent increases in P co 2 to levels exceeding 100 mmHg. Coronary vein lactate increased to a maximum of 7.5 ± 0.6 mmol/l. Coronary vein acidaemia was accompanied by decreases in intramyocardial pH to 6.64 ± 0.06 units...