[Liberation of inorganic phosphates in the coronary sinus as an indicator of human myocardial ischemia].

The effects of atrial pacing (A.P.) on the myocardial balance of inorganic phosphate (Pi) were studied in 11 patients with coronary atherosclerosis and pacing-induced angina (Group C) and in 5 normal subjects (Group N). During A.P. in group C 64% of patients had myocardial loss of Pi, statistically significant (p less than 0,025) always with concomitant reduced myocardial extraction or production of lactate, but only 70% of patients with reduced myocardial extraction or production of lactate had myocardial loss of Pi. In only 1 p. of group N myocardial loss of Pi with normal lactate extraction was observed. These data show that during pacing-induced ischemia there is a negative myocardial balance of Pi, that can be used as a metabolic indicator of ischemia, but less reliable than lactate reduced extraction or production.