Abstract 3094: Left Atrial Function Assessed During Cardiac Magnetic Resonance Dobutamine Stress Imaging is a Powerful Predictor of Cardiovascular Outcome
Objectives: Cardiac stress testing has traditionally concentrated on imaging of the left ventricle (LV). However, LV performance is intimately connected to left atrial (LA) function and size. Since diastolic dysfunction precedes systolic wall motion abnormalities in the ischemic cascade, we hypothesized that abnormalities of early LA emptying will reflect these diastolic changes and may be a powerful predictor of cardiovascular outcome during Dobutamine stress MRI.
Methods: We enrolled 122 consecutive patients referred for evaluation of coronary artery disease by MRI dobutamine stress testing. LA volumes were measured by the biplane area-length method at end systole (VOLmax) and prior to atrial contraction (VOLac). LA passive emptying fraction was defined as 100 x (VOLmax − VOLac)/ VOLmax. For each patient the maximum augmentation in LA passive emptying fraction (ΔLAPEF) during dobutamine infusion (10 – 40 mcg/kg/min) was calculated.
Results: A total of 29 major adverse cardiac events (MACE) occurred (16 deaths, 3 myocardial infarctions, 7 unstable angina and 3 congestive heart failure episodes requiring hospitalization) during a median follow up of 23 months (range 6 to 54 months). Kaplan-Meier curves illustrated that the risk of MACE was significantly less among patients with a ΔLAPEF≤10.8 (the median) compared with those with a ΔLAPEF<10.8 (p<0.01). By univariable analysis, ΔLAPEV was strongly associated with MACE (unadjusted HR 1.56, p<0.01). By multivariable analysis, every 10% decrease in ΔLAPEF, carried a 62% increase risk of MACE, adjusted to the combined effects of known predictors (patient age, LV ejection fraction, and presence of LV ischemia). Moreover, ΔLAPEV remained a powerful predictor of MACE even when adjusted for the presence of myocardial scar quantified by delayed enhancement imaging.
Conclusions: Quantitative evaluation of LA function during dobutamine stress MRI is clinically feasable and improves risk stratification of patients with suspected coronary artery disease beyond known risk predictors.