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Right Ventricular Outflow Tract Septal Pacing: Long-Term Follow-Up of Ventricular Lead Performance
S130
Abstracts
ABSTRACTS
In the septum, there was no significant difference in mean CV (75 ± 44 cm/s vs. 95 ± 46 cm/s, p = 0.66); voltage (1.5 ± 1.4 mV vs. 1.8 ± 1.4 mV, p = 0.6); and % low voltage areas (23 ± 24% vs. 25 ± 20%, p = 0.9) in AA vs. controls. There were no regional differences in AA v controls in % of scar (lateral 4 ± 9% vs. 2 ± 5%, p = 0.4; septal 4 ± 7% vs. 3 ± 9%, p = 0.9) or in % of FS/DP (lateral 38 ± 21% vs. 32 ± 17%, p = 0.5; septal 17 ± 14% vs. 15 ± 13%, p = 0.9). Conclusion: In ASD patients, substrate abnormalities conducive to development of AA are most marked in the lateral wall cf. the septum and in patients with AA cf. ASD controls. This remodeling is out of proportion to extent of surgical intervention and may be due to the underlying defect and/or electrical remodeling. doi:10.1016/j.hlc.2008.05.308 308 Effect of Chronic Atrial Stretch on Pulmonary Vein Remodelling Bobby John ∗ , Martin Stiles, Dennis Lau, Hany Dimitri, Pawel Kuklik, Anthony Brooks, Lauren Wilson, Daryl Leong, Glenn Young, Prashanthan Sanders Cardiovascular Research Centre, Royal Adelaide Hospital and Disciplines of Medicine and Physiology, University of Adelaide, Adelaide, South Australia, Australia Introduction: Chronic stretch is known to modify the substrate of atrial fibrillation (AF). However, its role on the triggers of AF is not known. Methods: Ten (29 ± 8 years) patients with rheumatic mitral stenosis (MS) mitral valve area (MVA; 0.8 ± 0.1 cm2 ) having percutaneous mitral commissurotomy (MC) and ten age-matched controls undergoing ablation of left-sided accessory pathways (33 ± 8 years) underwent electrophysiological study of the pulmonary veins (PV) using a multi-electrode basket catheter. We determined effective refractory period (ERP) and conduction time (CT) while pacing the proximal and distal PV. Activation maps were created to identify regions of intra-PV conduction block (CB; ≥30 ms between adjacent bipoles) during the drive train (S1) and maximum pre-excited stimulus (S2). Results: Patients with MS had elevated left atrial mean pressure (31 ± 4 mmHg vs. 11 ± 5 mmHg, p = 0.04) associated with higher proximal PV but not distal PV ERP compared to controls. CT was prolonged both during sinus rhythm (41 ± 9 ms vs. 32 ± 8 ms, p = 0.02) and during the drive train (S1) in MS patients. Longer intra-PV CB was observed with distal S2 in MS patients compared to controls but did not differ from proximal PV. In addition, mean bipolar voltage was lower in MS (1.2 ± 0.4 mV vs. 1.8 ± 0.8 mV, p = 0.04). Conclusion: Patients with MS demonstrated significant electrical remodelling within the PV characterized chiefly by conduction delay, intra-PV CB and areas of low voltage. These abnormalities may result in circuitous activation within the veins contributing to triggers and maintenance of AF.
Heart, Lung and Circulation 2008;17S:S1–S209
MS
Controls
Proximal ERP (ms)
270 ± 39
231 ± 25
0.008
Distal ERP (ms)
278 ± 37
258 ± 50
0.3
Proximal conduction time, S1 (ms)
54 ± 15
40 ± 17
0.04
Distal conduction time, S1 (ms)
63 ± 8
42 ± 8
<0.0001
Proximal intra-PV CB, S2 (ms)
62 ± 26
50 ± 19
0.4
Distal intra-PV CB, S2 (ms)
61 ± 22
39 ± 24
0.04
P
doi:10.1016/j.hlc.2008.05.309 309 Right Ventricular Outflow Tract Septal Pacing: Long-Term Follow-Up of Ventricular Lead Performance Caroline Medi ∗ , Harry Mond The Royal Melbourne Hospital, Melbourne, VIC, Australia Introduction: The detrimental effects of right ventricular (RV) apical pacing on LV function has driven interest in selective site pacing, predominantly on the right ventricular outflow tract (RVOT) septum. There is currently no information on long-term ventricular lead electrical performance from this site. Methods: One hundred patients (mean age 73.4 year, range 16–92) with indications for single or dual chamber pacemaker implantation had ventricular lead positioning at the RVOT septum. Successful RVOT position was confirmed by four fluoroscopic views. Stimulation threshold, R wave sensing and bipolar lead impedance were assessed at implant, 24 h, 6 months and 1 year. Long-term follow up rate was 92%. Results: RVOT lead positioning was successful in all patients with no significant procedural complications. Electrical parameters at implant included: mean stimulation threshold of 0.84 V (±0.40 V), range 0.2–2.2 V; R wave sensing of 10.9 mV (±5.3 mV), range 3.0–24.5 mV; and impedance of 732 (±150 , range 350–1144 ). At 24 h, the ventricular lead pacing threshold fell to a mean of 0.55 V (±0.22 V), range 0.25–1.3 V. At the 1-year followup, the stimulation threshold had increased to a mean of 0.71 mV (±0.25 mV), range 0.25–1.50 mV (p < 0.001). Conclusion: The selection of the RVOT septum as the primary pacing site in the majority of patients with bradycardia indications is further supported by these results which indicates that the long-term electrical performance at this site is excellent. Long-term physiologic studies to prove if the RVOT septum is better than the RV apex are now required. doi:10.1016/j.hlc.2008.05.310
Abstracts
ABSTRACTS
In the septum, there was no significant difference in mean CV (75 ± 44 cm/s vs. 95 ± 46 cm/s, p = 0.66); voltage (1.5 ± 1.4 mV vs. 1.8 ± 1.4 mV, p = 0.6); and % low voltage areas (23 ± 24% vs. 25 ± 20%, p = 0.9) in AA vs. controls. There were no regional differences in AA v controls in % of scar (lateral 4 ± 9% vs. 2 ± 5%, p = 0.4; septal 4 ± 7% vs. 3 ± 9%, p = 0.9) or in % of FS/DP (lateral 38 ± 21% vs. 32 ± 17%, p = 0.5; septal 17 ± 14% vs. 15 ± 13%, p = 0.9). Conclusion: In ASD patients, substrate abnormalities conducive to development of AA are most marked in the lateral wall cf. the septum and in patients with AA cf. ASD controls. This remodeling is out of proportion to extent of surgical intervention and may be due to the underlying defect and/or electrical remodeling. doi:10.1016/j.hlc.2008.05.308 308 Effect of Chronic Atrial Stretch on Pulmonary Vein Remodelling Bobby John ∗ , Martin Stiles, Dennis Lau, Hany Dimitri, Pawel Kuklik, Anthony Brooks, Lauren Wilson, Daryl Leong, Glenn Young, Prashanthan Sanders Cardiovascular Research Centre, Royal Adelaide Hospital and Disciplines of Medicine and Physiology, University of Adelaide, Adelaide, South Australia, Australia Introduction: Chronic stretch is known to modify the substrate of atrial fibrillation (AF). However, its role on the triggers of AF is not known. Methods: Ten (29 ± 8 years) patients with rheumatic mitral stenosis (MS) mitral valve area (MVA; 0.8 ± 0.1 cm2 ) having percutaneous mitral commissurotomy (MC) and ten age-matched controls undergoing ablation of left-sided accessory pathways (33 ± 8 years) underwent electrophysiological study of the pulmonary veins (PV) using a multi-electrode basket catheter. We determined effective refractory period (ERP) and conduction time (CT) while pacing the proximal and distal PV. Activation maps were created to identify regions of intra-PV conduction block (CB; ≥30 ms between adjacent bipoles) during the drive train (S1) and maximum pre-excited stimulus (S2). Results: Patients with MS had elevated left atrial mean pressure (31 ± 4 mmHg vs. 11 ± 5 mmHg, p = 0.04) associated with higher proximal PV but not distal PV ERP compared to controls. CT was prolonged both during sinus rhythm (41 ± 9 ms vs. 32 ± 8 ms, p = 0.02) and during the drive train (S1) in MS patients. Longer intra-PV CB was observed with distal S2 in MS patients compared to controls but did not differ from proximal PV. In addition, mean bipolar voltage was lower in MS (1.2 ± 0.4 mV vs. 1.8 ± 0.8 mV, p = 0.04). Conclusion: Patients with MS demonstrated significant electrical remodelling within the PV characterized chiefly by conduction delay, intra-PV CB and areas of low voltage. These abnormalities may result in circuitous activation within the veins contributing to triggers and maintenance of AF.
Heart, Lung and Circulation 2008;17S:S1–S209
MS
Controls
Proximal ERP (ms)
270 ± 39
231 ± 25
0.008
Distal ERP (ms)
278 ± 37
258 ± 50
0.3
Proximal conduction time, S1 (ms)
54 ± 15
40 ± 17
0.04
Distal conduction time, S1 (ms)
63 ± 8
42 ± 8
<0.0001
Proximal intra-PV CB, S2 (ms)
62 ± 26
50 ± 19
0.4
Distal intra-PV CB, S2 (ms)
61 ± 22
39 ± 24
0.04
P
doi:10.1016/j.hlc.2008.05.309 309 Right Ventricular Outflow Tract Septal Pacing: Long-Term Follow-Up of Ventricular Lead Performance Caroline Medi ∗ , Harry Mond The Royal Melbourne Hospital, Melbourne, VIC, Australia Introduction: The detrimental effects of right ventricular (RV) apical pacing on LV function has driven interest in selective site pacing, predominantly on the right ventricular outflow tract (RVOT) septum. There is currently no information on long-term ventricular lead electrical performance from this site. Methods: One hundred patients (mean age 73.4 year, range 16–92) with indications for single or dual chamber pacemaker implantation had ventricular lead positioning at the RVOT septum. Successful RVOT position was confirmed by four fluoroscopic views. Stimulation threshold, R wave sensing and bipolar lead impedance were assessed at implant, 24 h, 6 months and 1 year. Long-term follow up rate was 92%. Results: RVOT lead positioning was successful in all patients with no significant procedural complications. Electrical parameters at implant included: mean stimulation threshold of 0.84 V (±0.40 V), range 0.2–2.2 V; R wave sensing of 10.9 mV (±5.3 mV), range 3.0–24.5 mV; and impedance of 732 (±150 , range 350–1144 ). At 24 h, the ventricular lead pacing threshold fell to a mean of 0.55 V (±0.22 V), range 0.25–1.3 V. At the 1-year followup, the stimulation threshold had increased to a mean of 0.71 mV (±0.25 mV), range 0.25–1.50 mV (p < 0.001). Conclusion: The selection of the RVOT septum as the primary pacing site in the majority of patients with bradycardia indications is further supported by these results which indicates that the long-term electrical performance at this site is excellent. Long-term physiologic studies to prove if the RVOT septum is better than the RV apex are now required. doi:10.1016/j.hlc.2008.05.310