Interrelation between Restitution Time-Constant and Alternating Myocardial Contractility in Dogs

1970 ◽  
Vol 39 (5) ◽  
pp. 625-639 ◽  
Author(s):  
Y. Mahler ◽  
S. Rogel
Keyword(s):  
Time Constant ◽  
Exponential Function ◽  
Myocardial Contractility ◽  
Heart Block ◽  
Complete Heart Block ◽  
General Rule ◽  
Single Equation ◽  
Time Interval ◽  
Force Of Contraction

1. In open chest dogs with complete heart block the ventricles were stimulated electrically at various steady rates, and a single premature or delayed beat was interposed to alter myocardial tension. This was followed by transient mechanical alternans. Steady alternans was induced by high stimulation frequencies. 2. It appeared that the recovery of the force of contraction of a beat could be approximated by an exponential function of the preceding time interval. We observed a correlation between the time-constant of this exponential curve and the force of contraction of the previous beat. 3. The results demonstrate that a general rule of mechanical alternans can be expressed by a single equation. This equation describes adequately (1) the duration of transient mechanical alternation produced by a delayed beat, (2) the production of steady alternation at rapid ventricular rates, and (3) the manifestations of post-extrasystolic potentiation during mechanical alternans. 4. Curves relating amplitude of one beat to the successive beat, based on experiments performed in in vivo dog hearts, corresponded to the results predicted by the equation.

Rendimiento de los Marcapasos Biológicos en Modelos Animales de Bloqueo AV: Una Revisión del Alcance

2021 ◽  
Author(s):  
◽  
M. J. Galeano Blanco
Keyword(s):  
Heart Rate ◽  
Animal Model ◽  
Heart Block ◽  
Complete Heart Block ◽  
Hybrid Approach ◽  
In Vivo Model ◽  
Screening Process ◽  
Physiological Values ◽  
Biological Pacemaker

The electronic pacemakers have some complications and limitations for which in the last two decades it has been investigated about biological pacemakers as an alternative treatment. The present study undertakes a scoping review of research on biological pacemakers assessed in an in vivo model of complete heart block to determine which approach has promoted the greatest restauration of heart rate. To achieve that, some databases were used to identify papers published 2011-2021, from which we retrieved 151 papers and after the identification and screening process only 6 articles were included. Of these articles, 4 articles had a pig as an animal model and 2 rats. The most common approach to design a biological pacemaker is gene therapy, alone or with cells in a hybrid approach. Only one study had a cell-based approach, which also achieved the heart rate closest to the normal physiological range of pigs. For rat’s models, the heart rate reported after the complete heart block were not physiologically relevant. In conclusion, the most promising therapy is the one based on cells, because it maintained the heart rate of the animal model within relevant physiological values over 2 weeks. In addition, to develop a permanent biological pacemaker is essential research about a better persistence of the expression for gene-based approach and long-term function assessment for any approach.

scholarly journals Biological pacemaker created by minimally invasive somatic reprogramming in pigs with complete heart block

2014 ◽  
Vol 6 (245) ◽  
pp. 245ra94-245ra94 ◽  
Author(s):  
Yu-Feng Hu ◽  
James Frederick Dawkins ◽  
Hee Cheol Cho ◽  
Eduardo Marbán ◽  
Eugenio Cingolani
Keyword(s):  
Gene Transfer ◽  
Minimally Invasive ◽  
Heart Block ◽  
Complete Heart Block ◽  
Large Animal Model ◽  
Pacemaker Activity ◽  
Large Animal ◽  
Intramyocardial Injection ◽  
Biological Pacemaker

Somatic reprogramming by reexpression of the embryonic transcription factor T-box 18 (TBX18) converts cardiomyocytes into pacemaker cells. We hypothesized that this could be a viable therapeutic avenue for pacemaker-dependent patients afflicted with device-related complications, and therefore tested whether adenoviralTBX18gene transfer could create biological pacemaker activity in vivo in a large-animal model of complete heart block. Biological pacemaker activity, originating from the intramyocardial injection site, was evident inTBX18-transduced animals starting at day 2 and persisted for the duration of the study (14 days) with minimal backup electronic pacemaker use. Relative to controls transduced with a reporter gene,TBX18-transduced animals exhibited enhanced autonomic responses and physiologically superior chronotropic support of physical activity. Induced sinoatrial node cells could be identified by their distinctive morphology at the site of injection inTBX18-transduced animals, but not in controls. No local or systemic safety concerns arose. Thus, minimally invasiveTBX18gene transfer creates physiologically relevant pacemaker activity in complete heart block, providing evidence for therapeutic somatic reprogramming in a clinically relevant disease model.

Congenital Complete Heart Block

2007 ◽  
Vol 3 (2) ◽  
pp. 111
Author(s):  
Robert Campbell ◽  
Peter Fischbach ◽  
Patricio Frias ◽  
Margaret Strieper ◽  
◽  
...  
Keyword(s):  
Heart Block ◽  
Complete Heart Block ◽  
Congenital Complete Heart Block

A Case of 2:1 Atrio-Ventricular Block- Unravelled by Exercise Testing

2020 ◽  
Vol 02 ◽  
Author(s):  
Sharada Sivaram Kalavakolanu ◽  
Madan Mohan Balakrishnan ◽  
Deepesh Venkatarama
Keyword(s):  
Exercise Testing ◽  
Exercise Test ◽  
Heart Block ◽  
Complete Heart Block ◽  
Pacemaker Implantation ◽  
Ecg Monitoring ◽  
Permanent Pacing ◽  
Mill Test

: We present a case of 75-year-old lady with effort intolerance and baseline ECG showing 2:1 atrio-ventricular block, in whom it was unclear as to requirement of permanent pacing, even after long term ECG monitoring. She underwent a tread mill test during which her QRS became wide and developed complete heart block within 2 minutes of the test. Thus, a simple exercise test helped in confirming level of block to be infra nodal without need for invasive study. In patients with exertional symptoms, even in elderly, and in those where ECG masquerades as a benign entity, exercise testing is useful to differentiate benign cases of atrio-ventricular block from the more serious cases that mandate a pacemaker implantation.

scholarly journals Expert’s Opinion–Challenging ECG

2020 ◽  
Vol 5 (04) ◽  
pp. 368-372
Author(s):  
Seema Kale
Keyword(s):  
Myocardial Ischaemia ◽  
Heart Block ◽  
Complete Heart Block ◽  
Conduction System ◽  
Av Block ◽  
Av Node ◽  
Purkinje System ◽  
Expert’S Opinion

AbstractVarying kinds of AV blocks can occur in the setting of myocardial ischaemia or due to degeneration of conduction system. Wenckebach AV block can present with typical Wenckebach periodicity or atypical periodicity. A variant of atypical Wenckebach periodicity may present like Mobitz II AV block. This is called Pseudo Mobitz II AV block. As we are aware that Mobitz II AV block is more dangerous and can suddenly convert into complete heart block, it is essential that we should try to differentiate between Mobitz and Pseudo Mobitz II blocks. Infact atypical Wenckebach cycles are quite common at both AV node and his Purkinje system.

scholarly journals B-PO03-011 COMPLETE HEART BLOCK. . .WHY NOW?

Heart Rhythm ◽  
2021 ◽  
Vol 18 (8) ◽  
pp. S193
Author(s):  
Angela L. Krebsbach ◽  
Nicholas James Abbott ◽  
Christopher M. Verdick ◽  
Peter M. Jessel ◽  
Charles A. Henrikson
Keyword(s):  
Heart Block ◽  
Complete Heart Block
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