The ECG from page 7.4.8 is shown again here to review the features that characterize parasystole that in this case, is ventricular.
- The coupling intervals of the premature complexes are variable, ranging between 0.40 and 0.56 seconds.
- The interectopic intervals of 0.96, 2.0 and 2.9 seconds are approximate multiples of 1.0 second, suggesting that the rate of the ectopic focus is close to 60.
- The first premature QRS complex (#1) is preceded by a P wave and a PR interval of 0.16 seconds. It is a fusion of the non-premature sinus QRS complex and the ectopic QRS complex and its morphology is different from that of the second and third premature complexes. These are not fused with sinus beats and their right bundle branch block morphology suggests that they are arising from a focus located in the left ventricle. The fourth premature complex is also preceded by a P wave and, like beat #1, is a fusion beat. However, its PR interval is only 0.10 seconds and its wave form owes more to the ectopic depolarization that to the normally conducted impulse. Thus. its waveform is different from that of beat #1 and somewhat more like beats #2 and #3.