Heart rate variability measurements and the prediction of ventricular arrhythmias.

Heart rate variability (HRV) is the temporal variationbetween sequences of consecutive heartbeats. It is possible that HRV confers a survival advantage.In normal subjects, a variable heart rate is the normal physiological state. A loss of variability is associated with an increased mortality in patients post myocardialinfarction.Initially, the focus of HRV investigation was its use in the prediction of long-term survival in patientswho had suffered myocardial infarction, or hadvalvular or congestive heart disease. More recently,work has concentrated on attempts to predict thetiming of onset of fatal VTAs. Given the poor resultscurrently achieved in out-of-hospital cardiac arrest,efforts directed towards the identification of VTAsare crucial.61 The area of HRV behaviour before theonset of life-threatening VTAs offers exciting possibilities.Newer improved analytical techniquessuch as wavelet analysis, together with improvedprocessing power, have simplified and speeded upsignal acquisition and analysis