FLOW-FUNCTION RELATION IN PATIENTS WITH CHRONIC CORONARY-ARTERY DISEASE AND REDUCED REGIONAL FUNCTION - A POSITRON EMISSION TOMOGRAPHIC AND2-DIMENSIONAL ECHOCARDIOGRAPHIC STUDY WITH CORONARY VASODILATOR STRESS

Objectives. We sought to elucidate the flow-function relation in chron ic postischemic dysfunction during vasodilator stress. Background. In patients with ischemia and regional dysfunction, stress echocardiograp hy can elicit three responses in the dysfunctioning segments: no chang e, improvement or worsening. The physiology underlying these responses is unclear. Methods. Seventeen patients with ischemia and left ventri cular dysfunction underwent evaluation of regional function by two-dim ensional echocardiography and myocardial blood flow by positron emissi on tomography and N-13-ammonia. Flow (ml/min per g) and function (regi onal wall motion score [RWMS] from 1 = normal to 4 = dyskinetic) were evaluated both at rest and after dipyridamole (0.56 mg/kg body weight over 4 min). Results. Tn 45 normal segments, rest to dipyridamole how increased from 0.83 +/- 0.22 (mean +/- 1 SD) to 1.87 +/- 0.90 (p < 0.0 1) with a hyperkinetic contraction pattern, Among dysfunctioning segme nts, responders (n = 11) showed an upsloping flow-function curve durin g stress (i.e., increased function [RWMS rest 2.5 +/- 0.5 vs. dipyrida mole 1.2 +/- 0.4] and increased how [rest 0.69 +/- 0.30 vs. dipyridamo le 1.89 +/- 1.43, p < 0.01]); nonresponders (n = 20) had a hat flow-fu nction curve during dipyridamole (i.e., fixed function [RWMS rest and dipyridamole 2.6 +/- 0.5] and no how increase [rest 0.64 + 0.24 vs. di pyridamole 0.87 +/- 0.51, p = NS): Ischemic segments (n = 9) exhibited a downsloping flow-function curve during dipyridamole (i.e., worsened function [RWMS rest 2 + 0.5, dipyridamole 3.1 +/- 0.6] and no signifi cant how change [rest 0.67 +/- 0.29 vs. dipyridamole 0.79 + 0.23, p = NS]). Conclusions. Myocardial segments with rest dysfunction and a con tractile reserve elicitable by a vasodilator stress more often exhibit residual flow reserve, whereas segments with a fixed or worsening mec hanical response during stress show a flat flow response. (C) 1997 by the American College of Cardiology.