Effect of Sustained Load on Dispersion of Ventricular Repolarization and Conduction Time in the Isolated Intact Rabbit Heart

Zabel, Markus; Portnoy, Stuart; Franz, Michael R.

doi:10.1111/j.1540-8167.1996.tb00455.x

Cited by 65 publications

(47 citation statements)

References 37 publications

(1 reference statement)

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“…Previous studies on refractoriness resting membrane potential between successive activations. This is supported by the demonstration of a close correlaSeveral studies using isolated hearts under isovolumetric tion between VF interval and effective refractory period [8,9,12,19,20] or ejecting [10,21,22] conditions have [15]. However, Janse et al [28] have recently challenged shown a significant (7-22%) shortening in monophasic the multiple wavelet assumption, based on the observation action potential duration and refractory period during a that several single wandering spiral waves and two insustained increase in left ventricular volume, consistent dependent wandering reentrant wavefronts, in addition to with our findings, although Calkins [23,24] reported only multiple wavelets, may give rise to similar epicardial minor (,2%) changes in these parameters in blood-perelectrograms.…”

Section: Discussionmentioning

confidence: 69%

“…Numerous factors predispose to arrhythof conduction velocity and refractory period [11]. mias, including increased sympathetic tone, ionic disturChanges in refractoriness due to stretch vary in magbances, ischaemia and structural abnormalities associated nitude in different regions of the left ventricle [12], and with infarction and fibrosis [3]. However, alterations in between left and right ventricles [9].…”

Section: Introductionmentioning

confidence: 99%

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Effect of sustained stretch on dispersion of ventricular fibrillation intervals in normal rabbit hearts

Burton

1998

Cardiovascular Research

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Objective: To determine the effect of acute left ventricular dilatation on refractoriness in normal hearts. Methods: During sustained ventricular fibrillation (VF) in isolated perfused hearts, recording of local activation time yields VF intervals which provide an index of local refractoriness. Simultaneous measurement from multiple sites enables study of spatial aspects of changes in refractoriness. We studied the effects of stretch on the magnitude and dispersion of changes in VF interval in 10 isolated, Langendorff-perfused rabbit hearts using a flexible epicardial array containing 240 unipolar electrodes. The left ventricular pressure was increased from 0 to 40 mmHg by inflation of an intraventricular balloon during sustained VF. Results: The current threshold for VF induction fell from 64611 mA to 43611 mA (mean6SE, P,0.01) following ventricular dilatation. Mean VF interval at 0 mmHg was 79.861.3 ms and fell to 70.261.7 ms (P,0.01) at 40 mmHg. There was a corresponding increase in dispersion of VF interval (coefficient of variation) from 8.1360.8 to 13.360.8 (P,0.01). There was regional heterogeneity in the areas of greatest reduction in VF interval, which varied between hearts. Following balloon inflation there was an increase in the number of activation waves. Conclusions: Acute ventricular dilatation produces spatially heterogeneous changes in refractoriness which would predispose to the maintenance of reentrant arrhythmias.

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Section: Discussionmentioning

confidence: 69%

Section: Introductionmentioning

confidence: 99%

Effect of sustained stretch on dispersion of ventricular fibrillation intervals in normal rabbit hearts

Burton

1998

Cardiovascular Research

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“…Furthermore, Franz et al 3 have reported that myocardial stretch induces ventricular arrhythmias triggered by early afterdepolarizations (EADs). Also, they showed that sustained load increases the dispersion of ventricular repolarization, suggesting reentry as an another mechanism of stretch-induced arrhythmias, 5 although development of the arrhythmias was not quantified.…”

Section: Echano-electrical Feedback Phenomenon (Mef)mentioning

confidence: 99%

“…These studies suggest that stretch-induced arrhythmias occur due to depolarization-induced automaticity and/or triggered activity. Also, Franz et al 5 have shown that sustained load increases the dispersion of epicardial ventricular repolarization, and suggested reentry as another mechanism of stretch-induced arrhythmias. The present results suggest that acute pressure overloading of the LV increases the spatial dispersion of epicardial and endocardial MAP durations and may cause reentrant arrhythmias because arrhythmias developed in association with the increased difference in MAP durations and were suppressed by Gd 3+ in accordance with elimination of the increase in the difference.…”

Section: Mechanisms Of Stretch-induced Arrhythmiasmentioning

confidence: 99%

Gadolinium Suppresses Stretch-Induced Increases in the Differences in Epicardial and Endocardial Monophasic Action Potential Durations and Ventricular Arrhythmias in Dogs

et al. 1999

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echano-electrical feedback phenomenon (MEF)is the concept that myocardial stretch modulates the electrophysiological properties of the heart. 1,2 MEF appears to be an important mechanism that causes arrhythmias. Myocardial stretch causes shortening of the action potential duration, 1 and mild decreases in the action potential amplitude 3 and resting membrane potential. 4 These changes may be arrhythmogenic by facilitating a variety of mechanisms, including reentry and abnormal automaticity. Furthermore, Franz et al 3 have reported that myocardial stretch induces ventricular arrhythmias triggered by early afterdepolarizations (EADs). Also, they showed that sustained load increases the dispersion of ventricular repolarization, suggesting reentry as an another mechanism of stretch-induced arrhythmias, 5 although development of the arrhythmias was not quantified.In the present study, we examined the temporal correlation between the dispersion of epicardial and endocardial monophasic action potential (MAP) durations with the occurrence of ventricular arrhythmias during acute pressure overloading of the left ventricle (LV) in intact canine hearts. We also examined the effects of gadolinium (Gd 3+ ), 6 a non-specific blocker of stretch-activated channels (SACs). 7,8 Methods InstrumentationSeventeen mongrel dogs weighing 12 to 20 kg were anesthetized with a single intravenous dose of 30 mg/kg sodium pentobarbital. Additional doses were given as needed to maintain anesthesia. The dogs were intubated and ventilated with room air using a constant-volume respirator (Harvard Apparatus, model 607). A fluid-filled cannula was inserted into the right femoral artery and connected to a transducer (Nihon Koden, model TP400T) to monitor arterial blood pressure. A femoral venous cannula was used to infuse normal saline at a rate of 100-200 ml/h to replace spontaneous fluid losses and to inject drugs.After left thoracotomy and pericardotomy, the ascending aorta was dissected free at a site distal to the branching of the coronary arteries. A silk ribbon was positioned around the ascending aorta, passed through a plastic tube, and used as a noose to obtain complete occlusion and release of the aorta by tightening and releasing the ribbon.A digital thermistor was used to monitor epicardial temperature, which was maintained between 36 and 38°C by an overhead heating lamp. Heart rate was kept constant by left atrial pacing at a cycle length slightly shorter than Jpn Circ J 1999; 63: 296 -302 (Received October 19, 1998; revised manuscript received December 24, 1998; accepted January 6, 1999 We tested whether acute pressure overloading of the left ventricle (LV) had spatially different effects on repolarization, thereby causing arrhythmias. The effects of gadolinium (Gd 3+ ), a nonspecific blocker of stretch-activated channels were also examined. In anesthetized dogs, 5 s clamping of the ascending aorta (AC), separated by 5-min intervals, was repeated while monophasic action potentials (MAPs) were recorded from the LV endocardium and epic...

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“…27,32 Mechanical stretch can facilitate arrhythmias by depolarisation of the membrane potential, premature depolarisations and dispersion in refractoriness. 33,34 Furthermore, the increase in heart rate during pregnancy may act as a trigger in susceptible patients. 35 There are also indications that oestrogen and progesterone may contribute to altered cardiac repolarisation facilitating arrhythmias.…”

Section: Haemodynamic Alterations During Pregnancymentioning

confidence: 99%

Pharmacological Therapy of Tachyarrhythmias During Pregnancy

Yaksh

Does

Lanters

et al. 2016

Arrhythmia &Amp; Electrophysiology Review

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Tachyarrhythmias are the most frequently observed cardiac complications during pregnancy. The majority of these maternal and foetal arrhythmias are supraventricular tachyarrhythmias; ventricular tachyarrhythmias are rare. The use of anti-arrhythmic drugs (AADs) during pregnancy is challenging due to potential foetal teratogenic effects. Maintaining stable and effective therapeutic maternal drug levels is difficult due to haemodynamic and metabolic alterations. Pharmacological treatment of tachyarrhythmias is indicated in case of maternal haemodynamic instability or hydrops fetalis. Evidenc e regarding the efficacy and safety of AAD therapy during pregnancy is scarce and the choice of AAD should be based on individual risk assessments for both mother and foetus. This review outlines the current knowledge on the development of tachyarrhythmias during pregnancy, the indications for and considerations of pharmacological treatment and its potential side-effects. KeywordsPregnancy, tachyarrhythmia, anti-arrhythmic drugs, teratogenicity, foetus 1,2 They also develop de novo or occur in women without apparent heart diseases.Tachyarrhythmias, including both supraventricular and ventricular tachycardias, are the most common cardiac complications observed during pregnancy. Not only the mother, but also the foetus may develop tachyarrhythmias. 3 The exact mechanisms underlying the development of cardiac arrhythmias during pregnancy are unknown, and selection of the appropriate treatment modality is hampered by the lack of randomised studies in pregnant women. 1,4,5 This review outlines the current knowledge on the development of tachyarrhythmias during pregnancy, the indications for and considerations of pharmacological treatment and its potential side-effects. Incidences of Cardiac Arrhythmia During PregnancyMaternal Arrhythmias (Supra)ventricular premature beats are the most frequently observed arrhythmias during pregnancy followed by paroxysmal supraventricular tachycardias (SVT); incidences are 33 and 24 per 100,000 pregnancies respectively.6 Atrioventricular nodal reentrant tachycardia (AVNRT) and atrioventricular reentry tachycardia (AVRT) are the most common supraventricular tachycardias both in pregnant and non-pregnant women with structurally normal hearts and usually do not cause haemodynamic deterioration. 7,8 Studies investigating the risk of first onset paroxysmal SVT have shown inconsistent results.7,9-12 Tawam et al. This is in contrast to a study by Lee et al. 7 who reported development of de novo paroxysmal SVT in only 3.9 % of the pregnancies. Recurrences were observed in 55 out of 65 (85 %) pregnant women with a history of paroxysmal SVT. 7 In women with congenital heart disease (CHD) arrhythmias, mainly SVT, occurred in 4.5 % and were associated with multiple factors, including the presence of cyanotic heart disease (corrected/uncorrected) and usage of cardiac medication prior to gestation.

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Effect of Sustained Load on Dispersion of Ventricular Repolarization and Conduction Time in the Isolated Intact Rabbit Heart

Abstract: Sustained load shortens the ERP and the mean APD90, and at the same time increases dispersion of APD90 and prolongs activation times. These findings provide additional insight into the arrhythmogenic mechanisms of sustained mechanical load.

Cited by 65 publications

References 37 publications

Effect of sustained stretch on dispersion of ventricular fibrillation intervals in normal rabbit hearts

Effect of sustained stretch on dispersion of ventricular fibrillation intervals in normal rabbit hearts

Gadolinium Suppresses Stretch-Induced Increases in the Differences in Epicardial and Endocardial Monophasic Action Potential Durations and Ventricular Arrhythmias in Dogs

Pharmacological Therapy of Tachyarrhythmias During Pregnancy

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