Effect of anisotropy on ventricular vulnerability to unidirectional block and reentry by single premature stimulation during normal sinus rhythm in rat heart

被引:3
|
作者
Rossi, S. [1 ,5 ]
Buccarello, A. [1 ]
Ershler, P. R. [2 ]
Lux, R. L. [2 ]
Callegari, S. [3 ]
Corradi, D. [4 ,5 ]
Carnevali, L. [1 ]
Sgoifo, A. [1 ]
Miragoli, M. [5 ,6 ]
Musso, E. [1 ,7 ]
Macchi, E. [1 ,5 ,7 ]
机构
[1] Univ Parma, Dept Life Sci, Parma, Italy
[2] Univ Utah, Nora Eccles harrison Cardiovasc Res & Training In, Salt Lake City, UT USA
[3] Azienda Unita Sanitaria Locale, Unit Cardiol, Parma, Italy
[4] Univ Parma, Unit Pathol, Dept Biomed Biotechnol & Translat Sci, Parma, Italy
[5] Univ Parma, CERT, Ctr Excellence Toxicol Res, Dept Clin & Expt Med, Parma, Italy
[6] Humanitas Clin & Res Ctr, Milan, Italy
[7] Univ Parma, Cardiac Stem Cell Interdept Ctr CISTAC, Parma, Italy
来源
AMERICAN JOURNAL OF PHYSIOLOGY-HEART AND CIRCULATORY PHYSIOLOGY | 2017年 / 312卷 / 03期
关键词
unidirectional conduction block and reentry; pinwheel experiment; myocardial anisotropy; arrhythmia vulnerability; single premature stimulation during sinus rhythm; CARDIAC TISSUE; ELECTRICAL-STIMULATION; VIRTUAL ELECTRODES; CATHODAL STIMULATION; CONDUCTION-VELOCITY; CURRENT INJECTION; GRADED RESPONSES; PURKINJE SYSTEM; CANINE HEART; MECHANISM;
D O I
10.1152/ajpheart.00366.2016
中图分类号
R5 [内科学];
学科分类号
1002 ; 100201 ;
摘要
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 (n = 26) in seven rats. Stimulusinduced 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: 1) along fiber direction, on right and left ventricular free walls (n = 23), initiating figure-eight reentry (n = 17) and tachycardia (n = 12), and 2) across fiber direction, on lower interventricular septum (n = 3), initiating spiral wave reentry (n = 2) and tachycardia (n = 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 (n = 13) characterized by focal activations. NEW & NOTEWORTHY 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.
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页码:H584 / H607
页数:24
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