Fractionated electrical activity and continuous electrical activity: fact or artifact?

ENDOCAVITARY MAPPING during chronic ventricular tachycardia in patients with healed myocardial infarction and/or ventricular aneurysms has been used to locate the region from which ventricular tachycardia originates. During the process of mapping, bipolar electrograms with unusual configurations have been recorded from the chronically ischemic or healed infarcted regions, both with electrode catheters and with hand-held probes. Electrograms consisting of multiple "high-frequency" components with low amplitudes (< 1 mV) and long durations that may exceed 100 msec have been termed "fractionated." Although fractionated electrograms have these qualitative descriptors, quantitative criteria to distinguish among various types of electrograms have not been established. Such quantification, however, is limited by the fact that electrogram amplitude and width can vary depending on the interelectrode distance, contact, and degree to which the signal is amplified. We have recently undertaken studies in normal subjects and in patients with infarction and ventricular tachycardia to develop such criteria using a 1 cm interelectrode distance and a fixed gain of I mV = 1 cm. With these methods normal electrograms had amplitudes greater than 3 mV, durations of 70 msec or less, and amplitude/duration ratios of 0.046 or more. Electrograms outside these values were termed "abnormal." Multicomponent electrograms that fell beyond 1 SD from mean values of abnormal electrograms (amplitude 1.4 ± 0.9 mV, duration 93 + 40 msec, ratio 0.017 + 0.012) were termed "fractionated." Although the pathophysiologic significance of the relationship between multicomponent "abnor-