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

Axel Bauer, MD^_*,_*, Julinda Mehilli, MD^_*, Petra Barthel, MD^_*, Alexander Müller, Dipl Ing (FH)^_*, Adnan Kastrati, MD^_*, Kurt Ulm, PhD, Albert Schömig, MD^_*, Marek Malik, MD, PhD, Georg Schmidt, MD^_*

^_* 1. Medizinische Klinik und Deutsches Herzzentrum München, München, Germany
Institut für Medizinische Statitistk und Epidemiologie, Technischen Universität München, München, Germany
Division of Cardiac and Vascular Sciences, St. George's University of London, London, England

^_* Reprint requests and correspondence: Dr. Axel Bauer, 1. Medizinische Klinik der Technischen Universität München, Ismaninger Strasse 22, 81675 München, Germany (Email: axel.bauer{at}tum.de).

Objectives: The 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).

Background: Heart 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.

Methods: The 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).

Results: In 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.

Conclusions: In patients undergoing mechanical reperfusion therapy for acute MI, salvage index is an independent predictor of autonomic dysfunction but does not affect its prognostic value.

Key Words: autonomic function • myocardial infarction • myocardial salvage • reperfusion

Abbreviations and Acronyms   DC = deceleration capacity   HRT = heart rate turbulence   HRV = heart rate variability   MI = myocardial infarction   LV = left ventricular   LVEF = left ventricular ejection fraction   SDNN = standard deviation of all normal-to-normal intervals   TS = turbulence slope   VPC = ventricular premature complex