Temporal relation of changes in regional coronary flow and myocardial lactate and nucleoside metabolism during pacing-induced ischemia.

The temporal relation between myocardial lactate and hypoxanthine metabolism and regional changes in krypton-81m perfusion during pacing-induced ischemia was studied in 17 patients with coronary artery disease (CAD). During incremental atrial pacing, lactate production and hypoxanthine release occurred early and simultaneously, accompanied by ST-segment changes, but before angina and only few minutes after a significant (17%) reduction in krypton-81m perfusion in areas with more than 90% luminal diameter reduction. During maximal pacing heart rates, krypton-81m distribution decreased to 68 +/- 7% of control in areas with more than 90% diameter reduction and to 80 +/- 4% in 70 to 90% reduction (both p less than 0.05 vs control). Maximal lactate production occurred 15 seconds after pacing (extraction -15 +/- 7% vs 16 +/- 2% during control, p less than 0.05) and peak hypoxanthine release 1 minute after pacing (delta arteriovenous -2.64 +/- 0.8 microM vs 0.08 +/- 0.21 microM during control, p less than 0.05). Krypton-81m perfusion decreased in 20 of the 21 CAD areas. Angina, ST-segment changes, hemodynamic alterations and lactate production occurred in 15, 14, 9 and 15 patients, respectively. In contrast, hypoxanthine release was found in all cases. After pacing, lactate production and all general indexes of ischemia persisted for only 2 to 3 minutes. In contrast, krypton-81m perfusion was still significantly reduced 5 minutes after pacing and was only accompanied by hypoxanthine release (delta arteriovenous -1.41 +/- 0.6 microM, p less than 0.05 vs control).(ABSTRACT TRUNCATED AT 250 WORDS)