Differentiation of wide QRS complex tachycardias on surface electrocardiograms is difficult for physicians and computers due in part to their inability to identify atrial activity, specifically atrioventricular (AV) dissociation. We studied 20 examples of AV associated rhythms and 17 examples of AV dissociated ventricular tachycardia. We
1028of ventricular tachycardias are AV dissociated and fewer than one-third had a 1: 1 ventriculoatrial conduction ratio. The percentage of AV dissociated ventricular tachycardias increases somewhat when the ventricular rate exceeds 200 beats/min. Historically, arrhythmia algorithms have determined atrial activity by searching the isoelectric region between the end of the T wave and the beginning of the following QRS complex for P wave candidates.>l9 P waves have been found by a variety of approaches, such as slope measurement,'6 difference functions,17' 18 and matched filters.'9 Some algorithms for interpretation of arrhythmias assume any detected P wave candidate a valid P wave, while in others additional criteria must be fulfilled (e.g., those relating to expected P wave width, slope, and PR interval) to validate a P wave candidate. All of these methods of P wave detection depend on detectable P waves occurring between the end of the T wave and the beginning of the following QRS complex. Such methods are unlikely to be reliable at rapid ventricular rates since little
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