Cyclic bursts of ventricular premature contractions of more than one minute intervals

Ventricular premature contractions (VPCs) occasionally appear successively in the form of bigeminy, trigeminy or quadrigeminy associated with quiescen t periods. However, details of these rhythmic VPC bursts have not been well documented. We analyzed the incidence, periodicity and interval of VPC bur sts exhibiting bigeminy or trigeminy using ambulatory ECG monitoring and co mputer analysis. We defined VPC bursts as more than 5 successive groups of VPCs each containing more than 20 VPCs in the form of bigeminy or trigeminy that were interrupted by normal sinus rhythm lasting for more than 60 seco nds. Bursts thus defined were observed transiently or continuously in 78 ou t of 500 consecutive patients showing > 3000 VPCs a day. Their age ranged f rom 14 to 76 years (mean 48). Forty patients were men and 38 were women. We could discriminate between two types of bursts on the instantaneous heart rate tachograms. Dome type bursts (n = 48) showed gradual shortening of the VPC coupling intervals whereas horizontal type bursts (n = 30) demonstrate d fixed coupling intervals during the bursts. Cycle length of the dome type burst was 185 +/- 40 seconds and regular, whereas it was 210 +/- 63 second s and irregular in the horizontal type (NS). Duration of the VPC bursts was 101 +/- 31 seconds in the dome type and 98 +/- 41 seconds in the horizonta l type. Both burst types were associated with transient increases in sinus rate and abbreviated VPC-VPC intervals. We suspect ventricular parasystole to be the mechanism of these bursts especially in the dome type. Recognitio n of these two burst types from heart rate tachograms may be of value in th e suppression of VPCs.