Impact of Myocardial Salvage Assessed by 99mTc-Sestamibi Scintigraphy on Cardiac Autonomic Function in Patients Undergoing Mechanical Reperfusion Therapy for Acute Myocardial Infarction

ObjectivesThe purpose of this study was to analyze the impact of myocardial salvage on cardiac autonomic function in patients undergoing mechanical reperfusion therapy for acute myocardial infarction (MI).BackgroundHeart rate deceleration capacity (DC) and heart rate turbulence slope (TS) are strong predictors of post-MI mortality. Salvage of jeopardized myocardium is the main mechanism by which patients benefit from reperfusion therapy. The impact of myocardial salvage on DC and TS is unknown.MethodsThe study enrolled 854 consecutive patients undergoing mechanical reperfusion therapy for first MI. Paired 99mTc-sestamibi scintigraphy studies (acute and 7 to 14 days after reperfusion) were used to calculate myocardial salvage index. DC and TS were assessed from Holter recordings 7 to 14 days after reperfusion. Patients were categorized into 3 groups by salvage index: <30% (n = 244), 30% to 60% (n = 257), and ≥60% (n = 353).ResultsIn the 3 groups, DC was 5.2 (interquartile range 3.5 to 7.1) ms, 5.7 (4.1 to 7.3) ms, and 6.4 (5.0 to 8.0) ms, whereas TS was 5.3 (2.6 to 8.4) ms/R-R interval, 6.9 (3.2 to 11.7) ms/R-R interval, and 7.8 (4.1 to 13.2) ms/R-R interval, respectively (p < 0.0001 for both). After adjustment for left ventricular ejection fraction (LVEF), initial perfusion defect, creatine kinase, age, diabetes mellitus, sex, and medical therapy, patients with salvage index <30% had a 2.6-fold risk (95% confidence interval: 1.8 to 3.9, p < 0.001) of having abnormal DC (≤4.5 ms) or TS (≤2.5 ms/R-R interval) compared with patients with salvage index ≥60%. However, patients who had autonomic dysfunction defined by abnormal DC and TS had a poor prognosis independent of whether or not the salvage index was <30% (5-year mortality rates of 16.5% and 17.3%, respectively). In contrast, prognosis was excellent when both factors were normal (5-year mortality rates of 2.9% and 4.0%, respectively). Predictive value of impaired LVEF (≤40%) was also independent of salvage index. Multivariably, both autonomic dysfunction and impaired LVEF were independent predictors of 5-year mortality.ConclusionsIn patients undergoing mechanical reperfusion therapy for acute MI, salvage index is an independent predictor of autonomic dysfunction but does not affect its prognostic value.