1. Date of download: 6/26/2016 Copyright © The American College of Cardiology. All rights reserved. From: Mechanism and Location of Atrial Flutter in Transplanted Hearts: Observations During Transient Entrainment From Distant Sites J Am Coll Cardiol. 1997;30(2):539-546. doi:10.1016/S0735-1097(97)00186-1 A, Transplanted atrium. This view of the right atrium from the tricuspid ring shows the locations of pacing sites C (close to the TA) and D (distant from the TA). The shaded area represents the orifice created by the inferior vena cava (IVC) and the surgical incision. B, Nontransplanted atrium. The pacing sites separated from the TA were close to the CT in the lateral wall and in the interatrial septum close junction with the posterior wall. SVC = superior vena cava. Dashed lines = fossa ovalis. Figure Legend:

2. Date of download: 6/26/2016 Copyright © The American College of Cardiology. All rights reserved. From: Mechanism and Location of Atrial Flutter in Transplanted Hearts: Observations During Transient Entrainment From Distant Sites J Am Coll Cardiol. 1997;30(2):539-546. doi:10.1016/S0735-1097(97)00186-1 Right (left panel) and left (right panel) anterior oblique fluoroscopic projections showing catheter positioning. The halo catheter (HALO) spans the area from the 4 o’clock (distal pair) to the 8 o’clock position (proximal pair) on the TA. The roving catheter (ROVE) is situated at the 5 o’clock position near the TA. 1 ∗, 5 ∗, 7 ∗ and 11 ∗ = 1, 5, 7 and 11 o’clock positions along the tricuspid ring (see text for details). Figure Legend:

3. Date of download: 6/26/2016 Copyright © The American College of Cardiology. All rights reserved. From: Mechanism and Location of Atrial Flutter in Transplanted Hearts: Observations During Transient Entrainment From Distant Sites J Am Coll Cardiol. 1997;30(2):539-546. doi:10.1016/S0735-1097(97)00186-1 Donor right atrium activation sequence recorded during atrial flutter with use of a halo catheter located along the TA. The activation is caudocranial in the septum and craniocaudal in the lateral wall. The electrograms span the entire flutter cycle, suggesting a circus movement. Low amplitude electrograms are recorded in the low septum. IS = interatrial septum (IS 1-2 = the low interatrial septum and IS 7-8 = the high septum); LRA = lateral right atrium (LRA 1-2 = the high lateral wall and LRA 7-8 = the low lateral wall); II = ECG lead II; time lines are at 50-ms intervals. Figure Legend:

4. Date of download: 6/26/2016 Copyright © The American College of Cardiology. All rights reserved. From: Mechanism and Location of Atrial Flutter in Transplanted Hearts: Observations During Transient Entrainment From Distant Sites J Am Coll Cardiol. 1997;30(2):539-546. doi:10.1016/S0735-1097(97)00186-1 ECG surface leads II and V 1 and nine intracardiac electrograms (IS 1-2 = the low interatrial septum and IS 5-6 = the high septum; HRA = the high right atrium; LRA 1-2 = the high lateral right atrial wall and LRA 7-8 = the low lateral wall; MAP = the pacing and mapping catheter) recorded during pacing with entrainment from the low LRA. Top panel, The pacing site is close to the TA. The FPPI at the stimulation site is equal to the FCL, suggesting that this site belongs to the flutter circuit. The stimuli are delivered when LRA 1-2, 3-4 and 5-6 are being activated orthodromically by the preceding stimulus. Therefore, the right atrium is simultaneously activated by two activation wave fronts. The electrogram morphology and activation sequence are identical during pacing and flutter. Only the morphology of LRA 7-8, which is activated antidromically, changes during pacing; this site is also captured orthodromically by the last stimulus. The dashed lines and the numbers bracketed between signs help to compare the activation sequences showing the time intervals in reference to the last stimulus artifact and to the local electrogram at the pacing site. Unbracketed numbers indicate time intervals between local electrograms. Bottom panel, The pacing site is close to the receptor atrium (RA), which is recorded along with the donor atrium. The FPPI is 50 ms longer than the FCL, suggesting that this point is out of the flutter circuit. The electrogram morphology and activation sequence are clearly different during pacing. The conduction time from the pacing catheter to LRA from 1-2 to LRA 7-8 is short. Additionally, the activation of these sites is simultaneous. These observations refute the possibility that the CT acts as a line of block between the pacing site and the TA. A and V = atrial and ventricular electrograms, respectively. Figure Legend:

5. Date of download: 6/26/2016 Copyright © The American College of Cardiology. All rights reserved. From: Mechanism and Location of Atrial Flutter in Transplanted Hearts: Observations During Transient Entrainment From Distant Sites J Am Coll Cardiol. 1997;30(2):539-546. doi:10.1016/S0735-1097(97)00186-1 Same heart as in Fig. 4 during entrainment from the low septum. Top panel, As in Fig. 4, pacing near the TA reproduces the flutter activation sequence, and the FPPI is equal to the FCL. Bottom panel, The mapping catheter has been pulled back from the TA until the ventricular electrogram almost disappeared (a small ventricular electrogram compared with a larger atrial electrogram). At this site the FPPI and FCL differ by 35 ms, suggesting that this point is out of the circuit. The activation sequence is clearly different from that during atrial flutter. Format and abbreviations as in Fig. 4. Figure Legend:

6. Date of download: 6/26/2016 Copyright © The American College of Cardiology. All rights reserved. From: Mechanism and Location of Atrial Flutter in Transplanted Hearts: Observations During Transient Entrainment From Distant Sites J Am Coll Cardiol. 1997;30(2):539-546. doi:10.1016/S0735-1097(97)00186-1 Twelve right atrial bipolar electrograms (IS 1-2 = the low interatrial septum and IS 7-8 the high septum; LRA 1-2 = the high lateral right atrial wall and LRA 9-10 = the low lateral wall, MAP = the pacing and mapping catheter) are depicted along with ECG surface leads II and V 1 in a nontransplanted heart. Top panel, Entrainment from a site of the LRA close to the TA (a large ventricular electrogram is recorded) at which the FPPI is longer than the FCL. Note that the LRA 7-8 and 9-10 are captured antidromically, whereas the interatrial septum is captured orthodromically. In this case, it was possible to record the local electrograms with the distal (pacing) pair, which permits us to observe that the first rapid deflections are simultaneously recorded with both the proximal and the distal pairs of electrodes. Bottom panel, Same heart during entrainment from a site separated from the TA. The FPPI is equal to the FCL. Format and abbreviations as in Fig. 4. Figure Legend: