| Recovery curve and concealed conduction in the His-Purkinje system of the rabbit heart: effects of radiofrequency modification of the low AV junction. | |
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MedLine Citation:
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PMID: 8848374 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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The aim of this study was to analyze the recovery curve and concealed conduction in the normal His-Purkinje system and after delivering radiofrequency current in the low AV junction, in the perfused rabbit heart. Twenty-one rabbit hearts were studied. Radiofrequency current (5 W) was delivered in the low AV junction to induce an incomplete His-Purkinje AV block (HV prolongation with 1:1 AV conduction); this was achieved in 9 experiments (Group I), while 12 experiments developed a complete block (Group II). Atrial stimulation was performed in both Groups at baseline, and in Group I after radiofrequency delivery, as follows: (1) pacing at increasing rates to determine the His-Purkinje AV block cycle length; (2) atrial extrastimulus test (A1A2) to calculate the His-Purkinje effective refractory period and the fitting of the recovery curve (H1H2 vs H2V2) to the exponential equation delta HV = a.e(-b)x(H1H2); (3) concealed conduction protocol (in 15 experiments) consisting of an atrial extrastimulus test with an interposed beat (A1-A0-A2) at a fixed A1A0 coupling interval. The baseline recovery curve fitted an exponential equation in 17 experiments (with a 93% +/- 42% maximum H2V2 increase at the shortest H1H2), but did not in 4 experiments (the maximum H2V2 increase being only 22% +/- 7%). Radiofrequency application prolonged the HV interval (25 +/- 6 ms vs 46 +/- 16 ms; P = 0.001) and His-Purkinje effective refractory period (167 +/- 28 ms vs 217 +/- 57 ms; P = 0.02). The percentage increment was greater for HV than for refractory period (99% +/- 65% vs 35% +/- 32%; P = 0.02); however, the increment of the His-Purkinje block cycle length (77% +/- 74%) only correlated with that of the refractory period (r = 0.95; P = 0.0001). The recovery curve after radiofrequency delivery fitted an exponential equation in all experiments, showing a rightward shift expressed by an increment of the constant ln a (2.7 +/- 1.9 vs 5.5 +/- 5.5; P = 0.02). Concealed conduction appeared in only three experiments at baseline. After radiofrequency, however, it was observed in all experiments, producing a rightward shift of the recovery curve and an ln a increase (2.87 +/- 1.2 vs 9.9 +/- 2.7; P = 0.0001). When Ho was conducted, the curve rightward shift and ln a increase (26 +/- 7.5; P = 0.0001) were greater. CONCLUSION: (1) His-Purkinje physiology, as in AV nodal physiology, can be described by a recovery curve that fits an exponential equation, especially if conduction becomes depressed with radiofrequency current. (2) Radiofrequency application in the low AV junction modifies His-Purkinje conduction more than refractoriness, though the refractoriness increase determines the degree of block at fast atrial rates. (3) Concealed conduction is uncommon in the normal His-Purkinje system during atrial pacing, but very frequent after modifying the low AV junction with radiofrequency current. |
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Authors:
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J Sanchis; F J Chorro; L Such; L Artal; V Bodí; F Atienza; E Llavador; J Llavador; V López Merino |
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Publication Detail:
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Type: Journal Article |
Journal Detail:
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Title: Pacing and clinical electrophysiology : PACE Volume: 19 ISSN: 0147-8389 ISO Abbreviation: Pacing Clin Electrophysiol Publication Date: 1996 Jan |
Date Detail:
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Created Date: 1996-10-24 Completed Date: 1996-10-24 Revised Date: 2003-11-14 |
Medline Journal Info:
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Nlm Unique ID: 7803944 Medline TA: Pacing Clin Electrophysiol Country: UNITED STATES |
Other Details:
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Languages: eng Pagination: 31-41 Citation Subset: IM |
Affiliation:
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Servicio de Cardiología, Hospital Clínico Universitario, Valencia, Spain. |
Export Citation:
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| MeSH Terms | |
Descriptor/Qualifier:
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Animals Atrioventricular Node / physiology*, surgery Bundle of His / physiology* Cardiac Pacing, Artificial Catheter Ablation* Electrocardiography Electrophysiology Heart Block / etiology, physiopathology* Perfusion Purkinje Fibers / physiology* Rabbits |
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