title: The vasovagal tonus index as a prognostic indicator in dogs with dilated cardiomyopathy.
abstract: OBJECTIVE
  To investigate the prognostic and diagnostic value of heart rate variability (HRV) using the vasovagal tonus index (VVTI) in dogs suffering from idiopathic dilated cardiomyopathy (DCM).
  
  
  METHODS
  Electrocardiographic (ECG) recordings of 369 patients presented to a referral centre between 1993 and 2006 were reviewed.
  
  
  RESULTS
  VVTI values were calculated from 132 dogs. Lower VVTI values were found in patients in International Small Animal Cardiac Health Council (ISACHC) heart failure (HF) class 2 and 3 compared with class 1. VVTI was found to be positively correlated with survival time (ST) in class 2 and 3 patients. When a cut-off value of 7.59 for VVTI was used, the test could differentiate patients in ISACHC HF class 1 versus 2 and 3 with a sensitivity of 89 per cent and a specificity of 62.5 per cent. The ST for patients with VVTI values less than 7.59 was significantly lower.
  
  
  CONCLUSIONS
  The VVTI is a useful index, obtained from a standard ECG recording that estimates HRV in dogs and does not require any specific equipment for its calculation. It can be useful as a diagnostic tool to assess the severity of HF and is a useful prognostic tool in dogs with DCM.
authors.affiliation: Southern Animal Referral Centre, 248 Wickham Road, Highett, VIC 3190, Melbourne, Australia.
authors.forename: Y Martinez
authors.initials: YM
authors.lastname: Pereira
authors.forename: R
authors.initials: R
authors.lastname: Woolley
authors.forename: G
authors.initials: G
authors.lastname: Culshaw
authors.forename: A
authors.initials: A
authors.lastname: French
authors.forename: M
authors.initials: M
authors.lastname: Martin
mesh_terms: D000818:Animals; D002311:Cardiomyopathy, Dilated / Q000175:diagnosis / Q000401:mortality / Q000503:physiopathology / Q000662:veterinary*; D004283:Dog Diseases / Q000175:diagnosis* / Q000401:mortality / Q000503:physiopathology*; D004285:Dogs; D004562:Electrocardiography / Q000662:veterinary; D005260:Female; D006339:Heart Rate; D016014:Linear Models; D008297:Male; D011237:Predictive Value of Tests; D011379:Prognosis; D012372:ROC Curve; D012189:Retrospective Studies; D012720:Severity of Illness Index; D016019:Survival Analysis