title: ECG-derived spatial QRS-T angle is associated with ICD implantation, mortality and heart failure admissions in patients with LV systolic dysfunction.
abstract: BACKGROUND
  Increased spatial QRS-T angle has been shown to predict appropriate implantable cardioverter defibrilIator (ICD) therapy in patients with left ventricular systolic dysfunction (LVSD). We performed a retrospective cohort study in patients with left ventricular ejection fraction (LVEF) 31-40% to assess the relationship between the spatial QRS-T angle and other advanced ECG (A-ECG) as well as echocardiographic metadata, with all-cause mortality or ICD implantation for secondary prevention.
  
  
  METHODS
  534 patients ≤75 years of age with LVEF 31-40% were identified through an echocardiography reporting database. Digital 12-lead ECGs were retrospectively matched to 295 of these patients, for whom echocardiographic and A-ECG metadata were then generated. Data mining was applied to discover novel ECG and echocardiographic markers of risk. Machine learning was used to develop a model to predict possible outcomes.
  
  
  RESULTS
  49 patients (17%) had events, defined as either mortality (n = 16) or ICD implantation for secondary prevention (n = 33). 72 parameters (58 A-ECG, 14 echocardiographic) were univariately different (p<0.05) in those with vs. without events. After adjustment for multiplicity, 24 A-ECG parameters and 3 echocardiographic parameters remained different (p<2x10-3). These included the posterior-to-leftward QRS loop ratio from the derived vectorcardiographic horizontal plane (previously associated with pulmonary artery pressure, p = 2x10-6); spatial mean QRS-T angle (134 vs. 112°, p = 1.6x10-4); various repolarisation vectors; and a previously described 5-parameter A-ECG score for LVSD (p = 4x10-6) that also correlated with echocardiographic global longitudinal strain (R2 = - 0.51, P < 0.0001). A spatial QRS-T angle >110° had an adjusted HR of 3.4 (95% CI 1.6 to 7.4) for secondary ICD implantation or all-cause death and adjusted HR of 4.1 (95% CI 1.2 to 13.9) for future heart failure admission. There was a loss of complexity between A-ECG and echocardiographic variables with an increasing degree of disease.
  
  
  CONCLUSIONS
  Spatial QRS-T angle >110° was strongly associated with arrhythmic events and all-cause death. Deep analysis of global ECG and echocardiographic metadata revealed underlying relationships, which otherwise would not have been appreciated. Delivered at scale such techniques may prove useful in clinical decision making in the future.
authors.affiliation: Department of Cardiology, North Shore Hospital, Waitemata District Health Board, Auckland, New Zealand.
authors.forename: Sarah
authors.initials: S
authors.lastname: Gleeson
authors.affiliation: Department of Cardiology, North Shore Hospital, Waitemata District Health Board, Auckland, New Zealand.
authors.forename: Yi-Wen
authors.initials: YW
authors.lastname: Liao
authors.affiliation: Department of Cardiology, North Shore Hospital, Waitemata District Health Board, Auckland, New Zealand.|Division of Cardiology, Azienda Ospedaliera Universitaria Integrata, Verona, Italy.
authors.forename: Clementina
authors.initials: C
authors.lastname: Dugo
authors.affiliation: Department of Cardiology, North Shore Hospital, Waitemata District Health Board, Auckland, New Zealand.
authors.forename: Andrew
authors.initials: A
authors.lastname: Cave
authors.affiliation: Department of Epidemiology and Public Health, North Shore Hospital, Waitemata District Health Board, Auckland, New Zealand.
authors.forename: Lifeng
authors.initials: L
authors.lastname: Zhou
authors.affiliation: Deparment of Clinical Informatics, North Shore Hospital, Waitemata District Health Board, Auckland, New Zealand.
authors.forename: Zina
authors.initials: Z
authors.lastname: Ayar
authors.affiliation: Department of Cardiology, North Shore Hospital, Waitemata District Health Board, Auckland, New Zealand.
authors.forename: Jonathan
authors.initials: J
authors.lastname: Christiansen
authors.affiliation: Department of Cardiology, North Shore Hospital, Waitemata District Health Board, Auckland, New Zealand.
authors.forename: Tony
authors.initials: T
authors.lastname: Scott
authors.affiliation: Department of Cardiology, North Shore Hospital, Waitemata District Health Board, Auckland, New Zealand.
authors.forename: Liane
authors.initials: L
authors.lastname: Dawson
authors.affiliation: Department of Cardiology, North Shore Hospital, Waitemata District Health Board, Auckland, New Zealand.
authors.forename: Andrew
authors.initials: A
authors.lastname: Gavin
authors.affiliation: Department of Clinical Physiology, Karolinska Institutet, Stockholm, Sweden.|Nicollier-Schlegel Sàrl, Trélex, Switzerland.
authors.forename: Todd T
authors.initials: TT
authors.lastname: Schlegel
authors.affiliation: Department of Cardiology, North Shore Hospital, Waitemata District Health Board, Auckland, New Zealand.|Theranostics Laboratory, North Shore Hospital, Waitemata District Health Board, Auckland, New Zealand.
authors.forename: Patrick
authors.initials: P
authors.lastname: Gladding
mesh_terms: D000368:Aged; D009202:Cardiomyopathies / Q000401:mortality / Q000503:physiopathology* / Q000628:therapy; D057225:Data Mining; D016757:Death, Sudden, Cardiac; D017147:Defibrillators, Implantable; D004452:Echocardiography; D005260:Female; D006333:Heart Failure / Q000401:mortality / Q000503:physiopathology* / Q000628:therapy; D006801:Humans; D000069550:Machine Learning; D008297:Male; D008875:Middle Aged; D012307:Risk Factors; D018487:Ventricular Dysfunction, Left / Q000401:mortality / Q000503:physiopathology* / Q000628:therapy