Cerebrovascular hemodynamic inefficiency of premature ventricular contractions.

Transcranial Doppler (TCD) measurements of middle cerebral artery (MCA) blood flow velocities were recorded and synchronized with electrocardiographic (EKG) recordings in 52 EKG/TCD complexes in 4 patients. Thirty-seven normal sinus beats and 13 conductive and 2 nonconductive premature ventricular contractions (PVCs) were examined. Mean velocities averaged 45 +/- 4 cm/sec for normal sinus rhythm (NSR) vs 26 +/- 4 cm/sec in the PVC group (P = 0.007). Peak systolic velocities averaged 74 +/- 6 cm/sec for the NSR and 45 +/- 7 cm/sec in the PVC group (P = 0.016). The latency between the QRS complexes and corresponding TCD wave forms (QRS-SU) averaged 0.12 +/- 0.03 sec in NSR AND 0.17 +/- 0.04 sec for the PVC group (P < 0.001). In addition, QRS-SU was inversely related to all velocities. PVCs appeared to be less hemodynamically efficient than NSR. The lower blood flow velocities and increased QRS-SU may result from lower stroke volume and delayed ventricular contraction associated with the aberrant QRS complex.