| [PMID]: | 28011584 |
| [Au] Autor: | Rossi S; Buccarello A; Ershler PR; Lux RL; Callegari S; Corradi D; Carnevali L; Sgoifo A; Miragoli M; Musso E; Macchi E |
| [Ad] Endereço: | Department of Life Sciences, Università degli Studi, Parma, Italy. |
| [Ti] Título: | Effect of anisotropy on ventricular vulnerability to unidirectional block and reentry by single premature stimulation during normal sinus rhythm in rat heart. |
| [So] Source: | Am J Physiol Heart Circ Physiol;312(3):H584-H607, 2017 Mar 01. |
| [Is] ISSN: | 1522-1539 |
| [Cp] País de publicação: | United States |
| [La] Idioma: | eng |
| [Ab] Resumo: | Single high-intensity premature stimuli when applied to the ventricles during ventricular drive of an ectopic site, as in Winfree's "pinwheel experiment," usually induce reentry arrhythmias in the normal heart, while single low-intensity stimuli barely do. Yet ventricular arrhythmia vulnerability during normal sinus rhythm remains largely unexplored. With a view to define the role of anisotropy on ventricular vulnerability to unidirectional conduction block and reentry, we revisited the pinwheel experiment with reduced constraints in the in situ rat heart. New features included single premature stimulation during normal sinus rhythm, stimulation and unipolar potential mapping from the same high-resolution epicardial electrode array, and progressive increase in stimulation strength and prematurity from diastolic threshold until arrhythmia induction. Measurements were performed with 1-ms cathodal stimuli at multiple test sites ( = 26) in seven rats. Stimulus-induced virtual electrode polarization during sinus beat recovery phase influenced premature ventricular responses. Specifically, gradual increase in stimulus strength and prematurity progressively induced make, break, and graded-response stimulation mechanisms. Hence unidirectional conduction block occurred as follows: ) along fiber direction, on right and left ventricular free walls ( = 23), initiating figure-eight reentry ( = 17) and tachycardia ( = 12), and ) across fiber direction, on lower interventricular septum ( = 3), initiating spiral wave reentry ( = 2) and tachycardia ( = 1). Critical time window (55.1 ± 4.7 ms, 68.2 ± 6.0 ms) and stimulus strength lower limit (4.9 ± 0.6 mA) defined vulnerability to reentry. A novel finding of this study was that ventricular tachycardia evolves and is maintained by episodes of scroll-like wave and focal activation couplets. We also found that single low-intensity premature stimuli can induce repetitive ventricular response ( = 13) characterized by focal activations. We performed ventricular cathodal point stimulation during sinus rhythm by progressively increasing stimulus strength and prematurity. Virtual electrode polarization and recovery gradient progressively induced make, break, and graded-response stimulation mechanisms. Unidirectional conduction block occurred along or across fiber direction, initiating figure-eight or spiral wave reentry, respectively, and tachycardia sustained by scroll wave and focal activations. |
| [Mh] Termos MeSH primário: |
Ventrículos do Coração/efeitos dos fármacos
Ventrículos do Coração/fisiopatologia
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| [Mh] Termos MeSH secundário: |
Animais
Anisotropia
Arritmia Sinusal
Estimulação Elétrica
Eletrodos
Mapeamento Epicárdico
Bloqueio Cardíaco/fisiopatologia
Sistema de Condução Cardíaco/efeitos dos fármacos
Septos Cardíacos/fisiopatologia
Ratos
Período Refratário Eletrofisiológico
Taquicardia por Reentrada no Nó Sinoatrial/fisiopatologia
Taquicardia Ventricular/fisiopatologia
Função Ventricular Esquerda
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| [Pt] Tipo de publicação: | JOURNAL ARTICLE |
| [Em] Mês de entrada: | 1707 |
| [Cu] Atualização por classe: | 170726 |
[Lr] Data última revisão:
| 170726 |
| [Sb] Subgrupo de revista: | IM |
| [Da] Data de entrada para processamento: | 161225 |
| [St] Status: | MEDLINE |
| [do] DOI: | 10.1152/ajpheart.00366.2016 |
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