A Different Approach to the Analysis of Pure Ventricular Parasystole Agustin Castellanos, MD, FCCP, Federico Moleiro, MD, FCCP, Alberto Interian, MD, Robert J. Myerburg, MD  CHEST  Volume 107, Issue 5, Pages 1463-1464 (May 1995) DOI: 10.1378/chest.107.5.1463 Copyright © 1995 The American College of Chest Physicians Terms and Conditions

FIGURE 1 Artificial ventricular parasystole occurring when a nonsensing pacemaker (VVI) provided unintentional fixed rate (VOO) pacing. In both (noncontinuous) strips (lead 2), there was coexistence of sinus and parasystolic rhythms. Note that, consistently, there were three values for sinus beats interposed between consecutive manifest parasystolic beats (NISB). The corresponding values were 0, 2, and 3. TE=ectopic cycle length; TS=sinus cycle length; RP=ventricular refractory period. CHEST 1995 107, 1463-1464DOI: (10.1378/chest.107.5.1463) Copyright © 1995 The American College of Chest Physicians Terms and Conditions

FIGURE 2 Graph obtained from a mathematical model of pure ventricular parasystole showing the allowed number of sinus beats between manifest parasystolic beats in the so-called tE (ectopic cycle length)/ts (sinus cycle length); θ (ventricular refractory period)/ts plane. For each region, the allowed numbers are indicated by three integers separated by commas. The values expected from the calculations performed in Figure 1 fall in the site indicated by the X. The values obtained from the electrocardiographic tracings coincide with those predicted by the mathematical model (0,2,3) (from Gordon et al,3 with permission). CHEST 1995 107, 1463-1464DOI: (10.1378/chest.107.5.1463) Copyright © 1995 The American College of Chest Physicians Terms and Conditions