1. Volume 92, Issue 3, Pages 557-560 (September 1987)
Orthodromic Tachycardia Initiation Dependent on 1:2 Atrioventricular Conduction in the Presence of a Left Lateral Bypass Tract 
Peter C. Nalos, M.D., Mark Myers, M.D., Eli S. Gang, M.D., William J. Mandel, M.D. F.C.C.P., Thomas Peter, M.D. 
CHEST 
Volume 92, Issue 3, Pages (September 1987)
DOI: /chest
Copyright © 1987 The American College of Chest Physicians Terms and Conditions

2. FIGURE 1A
Twelve-lead ECG after conversion to sinus rhythm. Note the subtle ventricular preexcitation in the precordial leads with a sinus rate of 100 bpm. B. Twelve-lead ECG during distal coronary sinus pacing at 110 bpm, showing obvious preexcitation in the precordial and inferior leads.
CHEST  , DOI: ( /chest )
Copyright © 1987 The American College of Chest Physicians Terms and Conditions

3. FIGURE 2
Atrial extrasystoles from the high right atrium are introduced during atrial pacing at a drive cycle of 550 ms (A, B, C) and during sinus rhythm (D). Catheter-induced right bundle branch block is present in all four tracings. A. An atrial premature impulse at a coupling interval of 260 ms shows no evidence of a His bundle electrogram after the first preexcited QRS complex. B. His bundle depolarization is seen following a preexcited QRS complex with an atrial extrasystole, with a coupling interval of 250 ms. The interval between the stimulus artifact and His bundle deflection (S-H) is 420 ms. C. An atrial extrasystole at a coupling interval of 220 ms results in two ventricular responses. The first QRS complex is preexcited, and the second is conducted with a right bundle branch block which was present during sinus rhythm and is preceeded by His depolarization with an S-H interval of 490 ms. H-V interval with the second ventricular response is 30 ms and there is no shift in the frontal plane QRS axis. D. An atrial extrasystole during sinus rhythm (cycle length = 960 ms) shows splitting of the His bundle depolarization. S-H interval is 340 ms and the H-H′ interval is 90 ms. Note that a second ventricular depolarization following the first preexcited complex does not occur due to intra-Hisian conduction delay (Legends as in Figure 3).
CHEST  , DOI: ( /chest )
Copyright © 1987 The American College of Chest Physicians Terms and Conditions

4. FIGURE 3
Induction of orthodromic tachycardia with two ventricular complexes (short arrows) following a single atrial extrasystole from the mid-coronary sinus electrode at an atrial drive cycle length of 400 ms in the presence of: (A) resting right bundle branch block and (B) resolution of right bundle branch block. The A-H interval prior to the second ventricular response to an atrial extrasystole was 270 ms in both cases. However, with resting right bundle branch block (A), the second QRS complex during tachycardia is associated with a rightward axis shift and prolongation of the H-V interval to 60 ms compared, to 30 ms when conduction has normalized (B). Earliest retrograde atrial activation is seen in the distal coronary sinus electrogram and the tachycardia cycle length (360 to 370) does not change significantly in the presence of right bundle branch block. RV = right ventricular apex electrogram. CSp, CSm and CSd represent proximal, middle and distal coronary sinus electrograms. Long arrows indicate pacing stimuli.
CHEST  , DOI: ( /chest )
Copyright © 1987 The American College of Chest Physicians Terms and Conditions