Background: Reversibility of perfusion defects and left ventricular (LV) ejection fraction (LVEF) response to low-dose catecholamines may reflect complementary aspects of myocardial viability, in patients with CAD and LV dysfunction in whom revascularization is considered.
Objective: To evaluate the relationship between LVEF response to inotropic stimulation with adrenaline (delta LVEF) and myocardial perfusion.
Design and setting: Prospective study in a cardiology department with referral for revascularization and transplantation.
Patients: 45 patients (pt) with compromised LVEF (< 45%) after myocardial infarction (MI).
Methods: Radionuclide ventriculography at baseline and during graded adrenaline infusion until 12 micrograms/min: an empirical cut-off value of delta LVEF of 8% was used to define groups with (CR+) or without (CR-) contractile reserve. Stress-reinjection 201TI SPECT: perfusion was classified with a weighted score based on visual analysis of extent and intensity of thallium uptake in five major myocardial segments, with results expressed as percent of myocardium classified as normal (%N), with fixed defects (%F), and with reversibility (%R).
Main results: Groups CR+ (23 pt) and CR- (22 pt) had similar baseline LVEF (29.6 +/- 7.4 and 26.4 +/- 8.1), while delta LVEF was respectively 13.6 +/- 4.6 and 2.9 +/- 3.3. When compared to the other group, CR+ patients had, in average, 1.0 segment more with definite reversibility and 1.6 segments less with fixed defects; in terms of percentage of myocardium, CR+ patients had more extensive reversible areas (%R: 15.3 +/- 11.7 vs 4.7 +/- 5.0, p < 0.001), smaller irreversible areas (%F: 30.7 +/- 14.5 vs 45.6 +/- 16.1, p = 0.02) and similar extent of normal areas (54.0 +/- 14.6 vs 49.7 +/- 16.4). Patients with more extensive fixed defects had worse delta LVEF in response to adrenaline (p < 0.002, r = -0.45). Greater %R was positively correlated with delta LVEF (p < 0.02, r = 0.35). In all patients, delta LVEF with adrenaline was superior or equal to (%R/2)-10. No patient with %R > or = 15 had delta LVEF < 8%. However, ten patients had delta LVEF > or = 8% despite lesser degrees of %R.
Conclusion: Our data suggest a clear association between myocardial inotropic reserve and the extent of potentially viable myocardium (as evaluated by stress-reinjection thallium SPECT), in patients with left ventricular dysfunction after myocardial infarction. Further assessment is needed to clarify the relative role of radionuclide ventriculography with inotropic stimulation in viability evaluation, notably with inclusion of regional wall motion information and with reassessment of patients after revascularization, when performed.