Abstract | BACKGROUND: In patients with sinoatrial nodal (SAN) dysfunction, atrial pauses lasting several seconds may follow rapid atrial pacing or paroxysmal tachycardia (tachy-brady arrhythmias). Clinical studies suggest that adenosine may play an important role in SAN dysfunction, but the mechanism remains unclear. OBJECTIVE: METHODS: We studied the mechanism of SAN dysfunction produced by a combination of adenosine and rapid atrial pacing in isolated coronary-perfused canine atrial preparations by using high-resolution optical mapping (n = 9). Sinus cycle length and sinoatrial conduction time (SACT) were measured during adenosine (1-100 μM) and DPCPX (1 μM; A1 receptor antagonist; n = 7) perfusion. Sinoatrial node recovery time was measured after 1 minute of "slow" pacing (3.3 Hz) or tachypacing (7-9 Hz). RESULTS:
Adenosine significantly increased sinus cycle length (477 ± 62 ms vs 778 ± 114 ms; P<.01) and SACT during sinus rhythm (41 ± 11 ms vs 86 ± 16 ms; P<.01) in a dose-dependent manner. Adenosine dramatically affected SACT of the first SAN beat after tachypacing (41 ± 5 ms vs 221 ± 98 ms; P<.01). Moreover, at high concentrations of adenosine (10-100 μM), termination of tachypacing or atrial flutter/fibrillation produced atrial pauses of 4.2 ± 3.4 seconds (n = 5) owing to conduction block between the SAN and the atria, despite a stable SAN intrinsic rate. Conduction block was preferentially related to depressed excitability in SAN conduction pathways. Adenosine-induced changes were reversible on washout or DPCPX treatment. CONCLUSIONS: These data directly demonstrate that adenosine contributes to post- tachycardia atrial pauses through SAN exit block rather than slowed pacemaker automaticity. Thus, these data suggest an important modulatory role of adenosine in tachy-brady syndrome.
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Authors | Qing Lou, Alexey V Glukhov, Brian Hansen, Lori Hage, Pedro Vargas-Pinto, George E Billman, Cynthia A Carnes, Vadim V Fedorov |
Journal | Heart rhythm
(Heart Rhythm)
Vol. 10
Issue 1
Pg. 110-8
(Jan 2013)
ISSN: 1556-3871 [Electronic] United States |
PMID | 22985657
(Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)
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Copyright | Copyright © 2013 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved. |
Chemical References |
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Topics |
- Action Potentials
(drug effects)
- Adenosine
(pharmacology)
- Analysis of Variance
- Animals
- Bradycardia
(drug therapy, physiopathology)
- Cardiac Pacing, Artificial
- Dogs
- Dose-Response Relationship, Drug
- Heart Block
(chemically induced, physiopathology)
- Heart Conduction System
(drug effects, physiopathology)
- Sinoatrial Node
(drug effects, physiopathology)
- Spectroscopy, Near-Infrared
- Tachycardia
(drug therapy, physiopathology)
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