Coronary blood flow reserve measured by contrast media injection depends on myocardial viability

Coronary blood flow reserve may be affected by several physiological variables besides hydraulic impediment to flow. A hyperaemic response induced by hyperosmolar radiopaque contrast medium was recorded in the left anterior descending and left circumflex arteries with a steerable pulsed Doppler system in four patients with Q wave anterior myocardial infarction chronic scar and non-stenotic coronary arteries. Resting flow velocities were similar in both arteries. The magnitude of the hyperaemic response induced by contrast media in the circumflex artery (mean flow velocity increase from 5.9 +/- 2.5 baseline to 12.2 +/- 0.6 cm s-1 at peak flow, P less than 0.05) was almost twice that induced in the left anterior descending artery (mean flow velocity increase from 6.1 +/- 2.2 baseline to 7.4 +/- 2.6 cm s-1 at peak flow, P = N.S.). The peak flow to baseline flow velocities ratios were 1.22 +/- 0.15 in the left anterior descending artery vs 2.23 +/- 0.75 in the circumflex artery. Thus when a post-myocardial infarction chronic scar is supplied by a non-stenotic coronary artery, the coronary blood flow hyperaemic response to contrast media-induced transient ischaemia is decreased, suggesting that coronary blood flow reserve depends on a myocardial metabolic stimulus which is impaired by ischaemic cell death.