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- Title
Electrophysiologic Mechanism of Typical Atrial Flutter Termination by Nifekalant: Effect of a Pure I<sub>Kr</sub>-Selective Blocking Agent.
- Authors
YAMABE, HIROSHIGE; TANAKA, YASUAKI; MORIHISA, KENJI; UEMURA, TAKASHI; KOYAMA, JUNJIROH; KANAZAWA, HISANORI; HOSHIYAMA, TADASHI; OGAWA, HISAO
- Abstract
Background Little is known about the effect of nifekalant, a pure IKr-selective blocker, on typical atrial flutter (AFL) and its termination mechanism. Methods The effects of nifekalant on AFL were elucidated in 17 patients. During AFL, the conduction time from the lateral to septal cavotricuspid isthmus (IS) and that through the reminder of the right atrium (nIS); AFL-cycle length (CL) variability, which was quantified by the standard deviation; and the maximum difference in AFL-CL were measured before and after administration of nifekalant (0.2-0.3 mg/kg). A single extrastimulus was delivered from the lateral cavotricuspid isthmus to elucidate the resetting response curves and atrial effective refractory period (AERP) before and after administration of nifekalant. Results There was no significant difference in AFL-CL, IS, and nIS before and after nifekalant; however, AERP was increased after nifekalant (155 ± 22 ms vs 184 ± 32 ms, P < 0.001). The standard deviation and the maximum difference in AFL-CL were both increased after nifekalant (1.7 ± 0.7 ms vs 3.6 ± 2.3 ms, P < 0.001 and 4.1 ± 1.9 ms vs 8.5 ± 5.2 ms, P < 0.001). The total excitable gap decreased (94 ± 17 ms vs 66 ± 21 ms, P < 0.001) with rightward shift of the resetting response curves and loss of full excitability after nifekalant. In 11 patients (65%), AFL was terminated spontaneously (n = 7) or by a single extrastimulus (n = 4), which was not observed before nifekalant. Termination was associated with orthodromic block in the cavotricuspid isthmus in all patients. Conclusions Nifekalant increases AERP and AFL-CL variability by abolishing a fully excitable gap, without prolongation of AFL-CL. These unique effects facilitate the termination of AFL.
- Subjects
MYOCARDIAL depressants; POTASSIUM antagonists; BIOLOGICAL models; BODY surface mapping; CHI-squared test; HEART conduction system; HEALTH outcome assessment; POTASSIUM; PROBABILITY theory; T-test (Statistics); ATRIAL flutter; EVALUATION research; TREATMENT effectiveness; DESCRIPTIVE statistics; THERAPEUTICS
- Publication
Pacing & Clinical Electrophysiology, 2013, Vol 36, Issue 9, p1123
- ISSN
0147-8389
- Publication type
Article
- DOI
10.1111/pace.12147