title: ECG morphological variability in beat space for risk stratification after acute coronary syndrome.
abstract: BACKGROUND
  Identification of patients who are at high risk of adverse cardiovascular events after an acute coronary syndrome (ACS) remains a major challenge in clinical cardiology. We hypothesized that quantifying variability in electrocardiogram (ECG) morphology may improve risk stratification post-ACS.
  
  
  RESULTS
  We developed a new metric to quantify beat-to-beat morphologic changes in the ECG: morphologic variability in beat space (MVB), and compared our metric to published ECG metrics (heart rate variability [HRV], deceleration capacity [DC], T-wave alternans, heart rate turbulence, and severe autonomic failure). We tested the ability of these metrics to identify patients at high risk of cardiovascular death (CVD) using 1082 patients (1-year CVD rate, 4.5%) from the MERLIN-TIMI 36 (Metabolic Efficiency with Ranolazine for Less Ischemia in Non-ST-Elevation Acute Coronary Syndrome-Thrombolysis in Myocardial Infarction 36) clinical trial. DC, HRV/low frequency-high frequency, and MVB were all associated with CVD (hazard ratios [HRs] from 2.1 to 2.3 [P<0.05 for all] after adjusting for the TIMI risk score [TRS], left ventricular ejection fraction [LVEF], and B-type natriuretic peptide [BNP]). In a cohort with low-to-moderate TRS (N=864; 1-year CVD rate, 2.7%), only MVB was significantly associated with CVD (HR, 3.0; P=0.01, after adjusting for LVEF and BNP).
  
  
  CONCLUSIONS
  ECG morphological variability in beat space contains prognostic information complementary to the clinical variables, LVEF and BNP, in patients with low-to-moderate TRS. ECG metrics could help to risk stratify patients who might not otherwise be considered at high risk of CVD post-ACS.
authors: Institute for Medical Engineering and Sciences, Massachusetts Institute of Technology and Harvard-MIT Division of Health Sciences and Technology, Cambridge, MA (Y.L., C.M.S.).
authors: Yun
authors: Y
authors: Liu
authors: Electrical and Computer Engineering, University of Michigan, Ann Arbor, MI (Z.S.).
authors: Zeeshan
authors: Z
authors: Syed
authors: TIMI Study Group, Cardiovascular Division, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA (B.M.S., D.A.M.).
authors: Benjamin M
authors: BM
authors: Scirica
authors: TIMI Study Group, Cardiovascular Division, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA (B.M.S., D.A.M.).
authors: David A
authors: DA
authors: Morrow
authors: MIT Department of Electrical Engineering and Computer Science, Cambridge, MA (J.V.G., C.M.S.).
authors: John V
authors: JV
authors: Guttag
authors: Institute for Medical Engineering and Sciences, Massachusetts Institute of Technology and Harvard-MIT Division of Health Sciences and Technology, Cambridge, MA (Y.L., C.M.S.) MIT Department of Electrical Engineering and Computer Science, Cambridge, MA (J.V.G., C.M.S.).
authors: Collin M
authors: CM
authors: Stultz
mesh_terms: D054058:Acute Coronary Syndrome / Q000150:complications / Q000503:physiopathology*; D000368:Aged; D002318:Cardiovascular Diseases / Q000175:diagnosis / Q000401:mortality; D015331:Cohort Studies; D004562:Electrocardiography; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D053208:Kaplan-Meier Estimate; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000175:diagnosis / Q000209:etiology; D020097:Natriuretic Peptide, Brain / Q000097:blood; D011379:Prognosis; D016016:Proportional Hazards Models; D018570:Risk Assessment; D012307:Risk Factors; D013318:Stroke Volume / Q000502:physiology
chemical_list: D020097:Natriuretic Peptide, Brain
keywords: morphological variability; risk stratification acute coronary syndrome