Multiform ventricular complexes: a transitional arrhythmia form?

This study was undertaken to better characterize the role of multiform premature ventricular complexes in the classification of ventricular arrhythmias based on form and frequency. Twenty inpatients with organic heart disease and multiform ventricular complexes underwent continuous electrocardiographic monitoring with full disclosure analysis of the number and morphology of single premature ventricular complexes, of repetitive forms of greater than or equal to 2 premature ventricular complexes, and of the variability of coupling intervals (greater than or equal to 40 msec). Multiform premature ventricular complexes were of 3 +/- 1.4 (mean +/- S.D.) different QRS morphologies. Nineteen patients (95%) had repetitive forms of greater than or equal to 2 premature ventricular complexes; 18 patients (90%) showed variable coupling (125 +/- 29 msec). Repetitive forms or variable coupling were present in each (100%) of the 20 patients studied. These data suggest that multiform premature ventricular complexes may be a transitional arrhythmia, since repetitive forms almost always coexist. Variability in coupling, rather than just form and frequency, may be an electrocardiographic characteristic linking single and repetitive forms.