Prediction of unexpected sudden death among healthy dogs by a novel marker of autonomic neural activity.

Wetestedthehypothesisthataparametercombining BRS and HRV could predict risk for ventricular fibrillation (VF) during a first ischemic episode in otherwise healthy dogs. METHODS In 43 fully instrumented dogs, BRS and frequency do- main analysis of HRV were determined, as well as the occurrence (n 10, high-risk) or absence (n 33, low-risk) of VF during 2 minutes of myocardial ischemia superimposed on submaximal ex- ercise. TARVA (Tonic and Reflex Vagal Activity), expressed in units, is the parameter resulting from the multiplication of BRS by HF/LF (an index of tonic vagal activity).High-risk dogs had markedly lower TARVA values, re- flecting lower cardiac vagal activity, than low-risk animals (12 5 versus 56 43 units, P .001). The area under the receiver- operator characteristic curve for TARVA was 0.96 (95% confidence interval 0.86 to 0.99); its optimal cutoff had a 100% sensitivity and a 88% specificity with positive and negative predictive values of 71% and 100%, respectively. CONCLUSION Differencesincardiacautonomicactivity,presentin healthy dogs, allow prediction of arrhythmic risk during a first isch- emic episode. Increased risk is associated with reduced vagal activity. If confirmed in humans, this finding would open the way to the identification of those apparently healthy subjects at risk for sudden cardiac death during their first episode of myocardial ischemia.