Predicting imminent episodes of ventricular tachyarrhythmia--retrospective analysis of short R-R records from ICD

A predictor of an imminent episode of ventricular tachyarrhythmia, namely ventricular tachycardia and ventricular fibrillation has been developed. It only uses R-R records. The previous work was based on long R-R records stored in the memory of implantable cardioverter-defibrillators. With 1.8 hour of data, sensitivity of 53-83% can be achieved with corresponding specificity of 57-91%, depending on which set of criteria are used. The Medtronic ICD data series was made available to us. This consists of 135 pairs of files with 1024 R-R intervals. Each pair consists of a record that ends with the detection of the tachyarrhythmia, and a 'most recent' record just prior to the interrogation of the device. It was hoped that the 'most recent' record can be used to improve the specificity of the prediction algorithm. The predictor pattern was found in 29% of the arrhythmic records, and in 38% of the records with heart rate variability, namely SDNN, greater than 20 ms. This is comparable to the 40% results for similar conditions found earlier for records only 0.2 hr long. Unfortunately, due to a 'white coat effect', the predictor pattern was found in 40% of the 'most recent' records. While this new set of data has confirmed the sensitivity of the arrhythmia predictor, a fault in the data collection process this data set did not add to our understanding of the predictor behavior with a normal heart rhythm.