Mechanisms of Ventricular Arrhythmias Induced by Myocardial Contusion

2000 ◽  
Vol 92 (4) ◽  
pp. 1132-1143 ◽  
Author(s):  
Emmanuelle Robert ◽  
Jean E. de La Coussaye ◽  
Antoine G. M. Aya ◽  
Jean-Pierre Bertinchant ◽  
Anne Polge ◽  
...  
Keyword(s):  
Kinetic Energy ◽  
Conduction Block ◽  
Rabbit Heart ◽  
Control Group ◽  
Myocardial Contusion ◽  
Refractory Periods ◽  
Heart Study ◽  
Resolution Mapping ◽  
Ventricular Tachycardias ◽  
Intact Heart

Background The aims of the Langendorff-perfused rabbit heart study were to evaluate the arrhythmogenic consequences of myocardial contusion and to determine the mechanism of arrhythmia. Methods Six hearts were in the control group, and 24 hearts (intact heart protocol) were submitted to one of four different contusion kinetic energies (75, 100, 150, or 200 millijoules [mJ]; n = 6). Occurrence of arrhythmia, of an electrically silent area (i.e., area with no electrical activity), and of line of fixed conduction block were reported before and for 1 h after contusion. In 16 hearts (frozen hearts) submitted to cryoprocedure and contusion impact of 100 or 200 mJ, ventricular conduction velocities, anisotropic ratio, wavelengths, ventricular effective refractory period, and its dispersion were measured before and for 1 h after contusion. Using high-resolution mapping, arrhythmias were recorded and analyzed. Results The intact heart study showed that the number and seriousness of contusion-induced arrhythmias increased with increasing contusion kinetic energy, as did the number of electrically silent areas (five of six ventricular fibrillations and five of six electrically silent areas at 200 mJ). In the frozen heart study, immediately after contusion ventricular effective refractory periods were shortened and dispersed, and wavelengths were also shortened. The arrhythmia analysis showed that all ventricular tachycardias but one were based on reentry developed around an electrically silent area or a line of fixed conduction block. Conclusions Myocardial contusion has direct arrhythmogenic effects, and the seriousness of arrhythmia increases with the level of contusion kinetic energy. The mechanism of arrhythmia was mainly based on reentrant circuit around a fixed obstacle.

Vulnerability of rabbit atrium to reentry by hypoxia. Role of inhomogeneity in conduction and wavelength

1992 ◽  
Vol 262 (1) ◽  
pp. H47-H55 ◽  
Author(s):  
W. J. Lammers ◽  
C. Kirchhof ◽  
F. I. Bonke ◽  
M. A. Allessie
Keyword(s):  
Conduction Block ◽  
Refractory Periods ◽  
High Resolution Mapping ◽  
Circus Movement ◽  
Resolution Mapping ◽  
Slow Rhythm ◽  
Inhomogeneity Index ◽  
Reentrant Arrhythmias ◽  
Rabbit Atrium

In isolated superfused left atria of the rabbit, the inducibility of tachyarrhythmias by single early premature stimuli was highly increased by hypoxia. High-resolution mapping showed that these arrhythmias were caused by circus movement around a functional arc of conduction block (leading circle reentry). To determine the electrophysiological changes by hypoxia responsible for the higher vulnerability to intra-atrial reentry, the wavelength of the atrial impulse and spatial inhomogeneities in refractory periods and local conduction delays were measured. Hypoxia caused a transient increase in refractory periods during the first 10-15 min of hypoxia. After this period, refractory periods shortened again to values slightly lower than during control. During the whole period of hypoxia, local differences in refractory periods were enlarged. Conduction velocity was significantly depressed by hypoxia. As a result, the wavelength of the atrial impulse gradually shortened during hypoxia to approximately 80% of control. Inhomogeneity in conduction was quantified by phase maps in which the maximal local delays in conduction are plotted. Hypoxia caused a marked increase in inhomogeneity in conduction both during slow rhythm (inhomogeneity index increased from 2.3 to 3.4) and premature activation (from 3.1 to 4.7). We conclude that the higher vulnerability of the atrium for reentrant arrhythmias by hypoxia is based on a combination of a moderate shortening of the wavelength and an increase in inhomogeneity in conduction of premature wavefronts.

Cardioprotection with Captopril added to Bretschneider-Solution: An in vitro rabbit heart study

2014 ◽  
Vol 62 (S 01) ◽  
Author(s):  
A. Hoyer ◽  
P. Pritzwald-Stegmann ◽  
J. Kempfert ◽  
C. Etz ◽  
F.W. Mohr ◽  
...  
Keyword(s):  
Rabbit Heart ◽  
Heart Study

Abstract 115: Results of a Twelve Month Randomized Trial of an Internet Based Lifestyle Intervention in High Cardio Metabolic Risk Individuals: The Baptist Employee Healthy Heart Study (BEHHS)

2018 ◽  
Vol 11 (suppl_1) ◽  
Author(s):  
Ehimen Aneni ◽  
Lara Arias ◽  
Janisse Post ◽  
Shozab S Ali ◽  
Chukwuemeka U Osondu ◽  
...  
Keyword(s):  
Physical Activity ◽  
Blood Pressure ◽  
Cardiometabolic Risk ◽  
Laboratory Data ◽  
Control Group ◽  
Wellness Program ◽  
Web Based ◽  
Lifestyle Program ◽  
Heart Study ◽  
Diet And Physical Activity

Background: Web-based platforms have been proposed as tools to facilitate lifestyle improvement, however, their efficacy in individuals with high cardiometabolic risk has not been adequately tested. The Baptist Employee Healthy Heart Study (BEHHS) was designed to assess the addition of a personalized, interactive, web-based, lifestyle-management program to the existing health-expertise web platform available to BHSF employees with metabolic syndrome (METS) or type 2 diabetes (DM2) Methods: In this 1:1 randomized, non-blinded trial, the intervention arm was provided access to a web-based personalized and interactive lifestyle program that provided targeted and personalized dietary, weight management and physical activity counseling. The intervention was in addition to access to an online wellness program, a non-interactive website that provided information on healthy diet and physical activity. The control group only had access to the online wellness program. At baseline, each participant had their demographic data collected via questionnaire. At each study visit (baseline, 4 months and 12 months) participants completed questionnaires on lifestyle indices such as diet and physical activity, had their weight, height, waist circumference, body fat (by plethysmography) and blood pressure measured. Laboratory testing was done for traditional lipids and glucose at each visit. Results: Of the 182 participants that were randomized, 163 (82 in the intervention arm and 81 in the control arm) completed the baseline survey and had complete laboratory data at baseline. Loss to follow-up was 12% at 4 months 34% at 12 months. As shown the table, intention to treat analysis using both single imputation (last observation carried forward) and multiple imputation techniques showed no difference in BMI, other measures of adiposity, blood pressure, lipids, physical activity and diet scores. When analyses were restricted to completers alone, no significant change in the results were observed. Conclusion: The addition of web-based, personalized lifestyle program to an already existing lifestyle educational platform did not significantly impact healthy lifestyle promotion and cardiometabolic risk in employees with MetS or DM2.

PEG-SOD improves postischemic functional recovery and antioxidant status in blood-perfused rabbit hearts

1992 ◽  
Vol 263 (4) ◽  
pp. H1243-H1249
Author(s):  
Y. Qiu ◽  
M. Galinanes ◽  
R. Ferrari ◽  
A. Cargnoni ◽  
A. Ezrin ◽  
...  
Keyword(s):  
Redox State ◽  
Additive Group ◽  
Rabbit Heart ◽  
Left Ventricular ◽  
Control Group ◽  
Sod Activity ◽  
Group A ◽  
Group B ◽  
Developed Pressure ◽  
Postischemic Recovery

The isolated blood-perfused rabbit heart, subjected to 60 min of cardioplegic arrest and 60 min of reperfusion, was used to assess the effects of polyethylene glycol-conjugated superoxide dismutase (PEG-SOD) on postischemic recovery of left ventricular developed pressure (LVDP), the tissue activity of SOD, and tissue redox state. The five groups studied were the following: PEG-SOD-free control (group A), PEG-SOD as a pretreatment and as an additive during cardioplegia and reperfusion (group B), PEG-SOD as a pretreatment and a cardioplegic additive (group C), PEG-SOD in cardioplegia alone (group D), and PEG-SOD in reperfusion alone (group E). The results show that pretreatment with PEG-SOD improves postischemic recovery of LVDP (72 +/- 2% and 66 +/- 7 vs. 47 +/- 4% in groups B, C, and A, respectively). This protection was associated with an improved tissue redox state. Thus the ischemia-induced rise in oxidized glutathione was reduced from 313 +/- 26% (group A) to 162 +/- 15 and 138 +/- 14% (groups B and C, respectively), and the fall in reduced glutathione was attenuated from 51 +/- 5% to 35 +/- 6 and 13 +/- 5%, respectively. Tissue Mn-SOD activity was also conserved from 36 +/- 4% (group A) to 71 +/- 6 and 94 +/- 4% (groups B and C, respectively). No significant effect was seen when PEG-SOD was applied in cardioplegia or during reperfusion alone.

scholarly journals Atrial Tachycardias and Atypical Atrial Flutters: Mechanisms and Approaches to Ablation

2019 ◽  
Vol 8 (2) ◽  
pp. 131-137 ◽  
Author(s):  
Steven M Markowitz ◽  
George Thomas ◽  
Christopher F Liu ◽  
Jim W Cheung ◽  
James E Ip ◽  
...  
Keyword(s):  
Catheter Ablation ◽  
De Novo ◽  
Pulmonary Veins ◽  
Conduction Block ◽  
Small Diameter ◽  
Structural Heart Disease ◽  
Crista Terminalis ◽  
Slow Conduction ◽  
Resolution Mapping ◽  
Mapping Techniques

Atrial tachycardias (ATs) may be classified into three broad categories: focal ATs, macroreentry and localised reentry – also known as ‘microreentry’. Features that distinguish these AT mechanisms include electrogram characteristics, responses to entrainment and pharmacological sensitivities. Focal ATs may occur in structurally normal hearts but can also occur in patients with structural heart disease. These typically arise from preferential sites such as the valve annuli, crista terminalis and pulmonary veins. Macro-reentrant ATs occur in the setting of atrial fibrosis, often after prior catheter ablation or post atriotomy, but also de novo in patients with atrial myopathy. High-resolution mapping techniques have defined details of macro-reentrant circuits, including zones of conduction block, scar and slow conduction. Localised reentry occurs in the setting of diseased atrial myocardium that supports very slow conduction. A characteristic feature of localised reentry is highly fractionated, low-amplitude electrograms that encompass most of the tachycardia cycle length over a small diameter. Advances in understanding the mechanisms of ATs and their signature electrogram characteristics have improved the efficacy and efficiency of catheter ablation.

scholarly journals Changes of electrophysiological parameters in patients with atrial flutter

Medicina ◽  
2007 ◽  
Vol 43 (8) ◽  
pp. 614 ◽  
Author(s):  
Diana Žaliaduonytė-Pekšienė ◽  
Tomas Kazakevičius ◽  
Vytautas Zabiela ◽  
Vytautas Šileikis ◽  
Remigijus Vaičiulis ◽  
...  
Keyword(s):  
Response Time ◽  
Atrial Flutter ◽  
Right Atrium ◽  
Propagation Speed ◽  
Control Group ◽  
Type I ◽  
Stimulus Response ◽  
Refractory Periods ◽  
Impulse Propagation ◽  
The Right

Objectives. The aim of the study was to study some anatomic and electrophysiological features of the right atrium, related to the presence of atrial flutter. Materials and methods. A total 23 patients with type I atrial flutter and 22 patients without atrial flutter were studied. Right atrium size was assessed using echocardiography before intracardiac examination and radiofrequency ablation. Results. Effective refractory periods of coronary sinus, high right atrium, low right atrium were different comparing with the control group (P<0.05). A stimulus–response time between high right atrium and low right atrium positions in anterograde and retrograde ways, an impulse propagation speed along the lateral wall of the right atrium were statistically different comparing both groups (P<0.05). There was a significant correlation among effective refractory periods measured in different sites of the right atrium (r²=0.64, 0.44, 0.44, respectively). All measured effective refractory periods also correlated with stimulus–response time in anterograde way (P<0.05) and impulse propagation speed (P<0.05). Right atrium dimensions were significantly larger in atrial flutter group. There was no correlation between the right atrium dimensions and measured electrophysiological parameters in both groups.Conclusions. The presence of atrial flutter associates with diffuse alterations of the right atrium, but not the focal or single changes of refractoriness.

Increases in myocardial cyclic GMP attenuate contractile delay in myocardial stunning

2002 ◽  
Vol 80 (8) ◽  
pp. 804-810 ◽  
Author(s):  
Mark W Huang ◽  
Peter M Scholz ◽  
Harvey R Weiss
Keyword(s):  
Cyclic Gmp ◽  
Myocardial Stunning ◽  
Ischemia Reperfusion ◽  
Rabbit Heart ◽  
Left Ventricular ◽  
Control Group ◽  
Wall Thickening ◽  
Maximal Rate ◽  
Myocardial Wall ◽  
New Zealand White Rabbits

We tested the hypothesis that the effects of myocardial stunning would be reduced by cyclic GMP in rabbit hearts. In three groups of anesthetized open-chest New Zealand white rabbits, myocardial stunning was produced by 15 min of occlusion of the left anterior descending coronary artery followed by 15 min of reperfusion repeated twice. Either control vehicle (saline plus 1% dimethyl sulfoxide) or 8-bromo-cyclic GMP (8-Br-cGMP (10–4 and 10–3 M)) was topically applied to the left ventricular surface. Hemodynamic (left ventricular and aortic pressures) and functional parameters (wall thickening, delay in onset of wall thickening, and rate of wall thickening) were determined. Coronary blood flow (microspheres) and O2 extraction (microspectrophotometry) were used to determine myocardial O2 consumption (VO2). Myocardial stunning was observed in the control group through an increased delay in onset of myocardial wall thickening (29 ± 7 versus 55 ± 16 ms) and decreased maximal rate of wall thickening (20 ± 8 versus 11 ± 3 mm·s–1). After treatment with 8-Br-cGMP 10–4 and 10–3 M, stunning did not increase the delay (37 ± 5 versus 39 ± 7 and 39 ± 7 versus 28 ± 8 ms). Myocardial stunning did not significantly alter V02. 8-Br-cGMP 10–3 M significantly decreased subepicardial V02 (6.2 ± 0.8 versus 3.7 ± 0.6 mL O2·min–1·100 g–1) and insignificantly decreased subendocardial V02 (8.6 ± 0.9 versus 6.3 ± 1.2 mL O2·min–1·100 g–1) when compared with the vehicle-treated rabbits. We conclude that increasing cyclic GMP reduced the effects of myocardial stunning in the rabbit heart by ameliorating the delay in onset of wall thickening and decreasing the local O2 costs in the stunned region. Key words: cyclic GMP, myocardial stunning, O2 consumption, ischemia, reperfusion, wall thickening, rabbit.

Effect of work on intracellular calcium of the intact heart

1991 ◽  
Vol 261 (4) ◽  
pp. 54-59
Author(s):  
Teresa A. Fralix ◽  
Frederick W. Heineman ◽  
Robert S. Balaban
Keyword(s):  
Oxygen Consumption ◽  
Oxidative Phosphorylation ◽  
Intracellular Calcium ◽  
Myocardial Oxygen Consumption ◽  
Contractile Activity ◽  
Rabbit Heart ◽  
Metabolic Process ◽  
Contractile Apparatus ◽  
Cardiac Work ◽  
Intact Heart

Intracellular calcium has been proposed to play a key role in the orchestration of metabolic rate with contractile activity in the mammalian heart. Calcium is believed to accomplish this task by modulating the contractile apparatus as well as the metabolic process directly, and perhaps simultaneously, during alterations in cardiac work. The purpose of this study was to evaluate whether appropriate changes in intracellular calcium accompany alterations in cardiac work in the intact working rabbit heart. A range of myocardial oxygen consumption was obtained from 0.94 to 6.51 μmol·g LV wt-1·min-1 by changing afterload or -agonist addition. With the increase in work and associated increase in respiration, an increase in intracellular calcium was observed, on the basis of indo-1 fluorescence. These results indicate that intracellular calcium is a valid candidate as a cytosolic transducer contributing to the orchestration of myofibril adenosinetriphosphatase activity and oxidative phosphorylation in the intact heart. oxygen consumption; indo-1; fluorescence; rabbit; afterload; isoproterenol

Intrinsic changes on automatism, conduction, and refractoriness by exercise in isolated rabbit heart

2002 ◽  
Vol 92 (1) ◽  
pp. 225-229 ◽  
Author(s):  
L. Such ◽  
A. Rodriguez ◽  
A. Alberola ◽  
L. Lopez ◽  
R. Ruiz ◽  
...  
Keyword(s):  
Left Ventricle ◽  
Coronary Flow ◽  
Sinus Node ◽  
Thiobarbituric Acid ◽  
Rabbit Heart ◽  
Conduction Time ◽  
Refractory Periods ◽  
Liver And Kidney ◽  
Acid Reagent ◽  
Retrograde Conduction

We have studied the intrinsic modifications on myocardial automatism, conduction, and refractoriness produced by chronic exercise. Experiments were performed on isolated rabbit hearts. Trained animals were submitted to exercise on a treadmill. The parameters investigated were 1) R-R interval, noncorrected and corrected sinus node recovery time (SNRT) as automatism index; 2) sinoatrial conduction time; 3) Wenckebach cycle length (WCL) and retrograde WCL, as atrioventricular (A-V) and ventriculoatrial conduction index; and 4) effective and functional refractory periods of left ventricle, A-V node, and ventriculoatrial retrograde conduction system. Measurements were also performed on coronary flow, weight of the hearts, and thiobarbituric acid reagent substances and glutathione in myocardium, quadriceps femoris muscle, liver, and kidney, to analyze whether these substances related to oxidative stress were modified by training. The following parameters were larger ( P < 0.05) in trained vs. untrained animals: R-R interval (365 ± 49 vs. 286 ± 60 ms), WCL (177 ± 20 vs. 146 ± 32 ms), and functional refractory period of the left ventricle (172 ± 27 vs. 141 ± 5 ms). Corrected SNRT was not different between groups despite the larger noncorrected SNRT obtained in trained animals. Thus training depresses sinus chronotropism, A-V nodal conduction, and increases ventricular refractoriness by intrinsic mechanisms, which do not involve changes in myocardial mass and/or coronary flow.

Abstract MP164: Electrophysiologic Conservation of Epicardial Conduction Dynamics After Myocardial Infarction in Newborn Piglets

2020 ◽  
Vol 127 (Suppl_1) ◽  
Author(s):  
Hanjay Wang ◽  
Terrence Pong ◽  
Haley Lucian ◽  
Joy Aparicio-Valenzuela ◽  
Yuko Tada ◽  
...  
Keyword(s):  
Myocardial Infarction ◽  
High Resolution ◽  
Electrical Conduction ◽  
Conduction Block ◽  
Cardiac Regeneration ◽  
Coronary Artery Ligation ◽  
Artery Ligation ◽  
Newborn Piglets ◽  
High Resolution Mapping ◽  
Resolution Mapping

Introduction: Newborn piglets reportedly exhibit natural heart regeneration after myocardial infarction (MI). However, the electrophysiologic properties of this regenerated muscle have not been examined. We hypothesized that epicardial electrical conduction is preserved after MI in newborn piglets. Methods: Yorkshire-Landrace piglets underwent left anterior descending coronary artery ligation on postnatal day 1 (P1, n=4) or postnatal day 7 (P7, n=7), infarcting the anteroseptal left ventricle through which the Purkinje conduction system passes. After 7 weeks, cardiac magnetic resonance imaging (MRI) was performed with late gadolinium enhancement for fibrosis analysis. Epicardial conduction mapping was performed using custom 3D-printed, 256-channel high-resolution mapping arrays (Fig 1A). Age- and weight-matched healthy pigs served as controls (n=7). Data are expressed as mean±SD. Results: MRI analysis revealed significant differences between the control, P1, and P7 groups in ejection fraction (47.6±3.1% vs 37.6±3.3% vs 30.2±6.6%, p<0.001, Fig 1B) and the degree of transmural anteroseptal LV scar (0.0±0.0% vs 9.1±5.4% vs 15.4±4.2%, p<0.001), respectively. Evidence of infarcted myocardium was identified with high-resolution mapping in the P1 and P7 piglets (black arrows, Fig 1C-F). Epicardial electrical conduction was preserved in control and all P1 pigs (Figs 1C-D), whereas variable conduction block or aberrant propagation were observed in all P7 pigs (Fig 1E-F, p=0.001). Conclusion: P1 piglets exhibited incomplete natural cardiac regeneration after MI but nevertheless demonstrated electrophysiologic conservation of epicardial conduction dynamics.

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