Haemodynamics of Acute and Chronic Atrioventricular Block in Dogs

Turina, Marko; Babotai, I; Bussmann, W.‐D.; Krayenbühl, H. P.

doi:10.1093/cvr/3.2.209

Cited by 17 publications

(7 citation statements)

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“…The results observed during vagally-mediated bradycardia in the absence of coronary stenosis are in general agreement with previous data obtained with traumatic heart block (8,26,27,28). The major purpose of the present study was to examine the effect of vagally-mediated bradycardias on the hemodynamic consequences of graded coronary stenosis.…”

Section: Discussionsupporting

confidence: 91%

“…Numerous clinical and experimental studies have convincingly demonstrated that in the presence of significant coronary stenosis the appearance of myocardial ischemia is greatly faciliThis work was supported by the Deutsche Forschungsgemeinschaft within the SFB "Kardiovaskul~res System" tated by gradual or sustained increase in heart rate (6,13,21), whereas brief bouts of paroxysmal tachycardia appear to be less effective (25). The effects of decrease in heart rate in the absence of coronary stenosis have also been extensively studied (8,26,27,28), but there is little information on the coronary events occurring during acute bradycardia in the presence of significant coronary stenosis (23).…”

Section: Introductionmentioning

confidence: 99%

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Effects of acute vagally-mediated bradycardia on systemic hemodynamics and coronary blood flow before and after coronary stenosis

et al. 1983

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The effects of short episodes (1 min) of vagally-mediated bradycardia were studied in 9 anesthetized dogs utilizing vagal stimulation and slow atrial pacing (120 and 80 beats/min) before and after graded coronary constriction of the left anterior descending (LAD) and the left circumflex (CCA). In the presence of 90% LAD stenosis, bradycardia tended to restore both the elevated total LAD coronary vascular resistance (CVR-LAD) and the reduced, total CVR-CCA towards control levels obtained at corresponding slow rates in the absence of coronary stenosis; as a result, LAD coronary flow (F-LAD) was relatively less reduced and the accessory rise of F-CCA disappeared. In the presence of combination of 90% LAD plus 70% CCA stenosis, the effects of bradycardia on total CVR-LAD and F-LAD were similar to those obtained with single 90% LAD stenosis, but the accessory flow through the CCA was abolished resulting in no significant difference of the rate-dependent alterations of total CVR-CCA and F-CCA as compared with those observed in the absence of coronary stenosis. In the presence of single or combined coronary stenosis, bradycardia restored the depressed aortic pressure and cardiac output towards control values obtained at comparable slow rates before coronary stenosis. The results support the concept that in the presence of 90% LAD stenosis vagally-mediated bradycardia 1) decreases the tension-time index (myocardial nutritional demand) shifting cardiac performance to less expensive "flow work" and 2) facilitates antegrade flow through the highly stenotic LAD thereby inhibiting accessory flow through the nonstenotic CCA.

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Section: Discussionsupporting

confidence: 91%

Section: Introductionmentioning

confidence: 99%

Effects of acute vagally-mediated bradycardia on systemic hemodynamics and coronary blood flow before and after coronary stenosis

et al. 1983

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“…(2) On the other hand, acute bradycardia without a change in cardiac output or mean arterial pressure causes a decrease in myocardial aerobic energy expen diture per minute but tends to increase the stroke energy expenditure. In line with this is the observation that chronic bradycardia produced by complete A-V block in dogs causes a moderate degree of hypertrophy of the ventricles [19,91].…”

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confidence: 57%

Development of Cardiomegaly

Badeer¹

1972

Cardiology

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Cardiomegaly results from the growth of muscle fibers, coronary vessels, connective tissue and other constituents of the myocardial wall. An attempt has been made to explain the growth of these tissues by a unifying concept, namely, a sustained increase in stroke energy expenditure per unit mass of myocardium. Myocardial growth seems to be initiated by the earliest biochemical change, namely, the increased production and utilization of energy-rich phosphates which are essential for protein synthesis. Coronary growth is considered to be the result of increased tangential stress in the vascular wall as a consequence of vasodilatation due to increased metabolites from the myocardium and decreased PΘ₂ in myocardial tissue fluids. Acceleration of the biosynthesis of collagenous protein is believed to be the result of decreased Po₂ in the interstitial fluids of the myocardium as a consequence of increased oxygen consumption of contractile elements. According to this concept, increased aerobic energy production of the myocardium per beat per unit mass of tissue plays a key role in the development of cardiomegaly.

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“…The mechanisms and consequences of atrial remodeling during chronic AVB are still incompletely understood. In an early study in dogs, RA pressures were increased during acute and chronic overload, 31 thus promoting dilatation and hypertrophy. In goats, progressive atrial dilatation has been demonstrated in chronic AVB along with atrial hypertrophy, prolongation of induced AF paroxysms, and local conduction delays.…”

Section: Johnson Et Al Azd1305 In the Remodeled Dog Heart 207mentioning

confidence: 99%

Reduced Ventricular Proarrhythmic Potential of the Novel Combined Ion-Channel Blocker AZD1305 Versus Dofetilide in Dogs With Remodeled Hearts

Johnson

Jong

Crijns

et al. 2012

Circ: Arrhythmia and Electrophysiology

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Background-AZD1305 is an investigational antiarrhythmic agent for management of atrial fibrillation. It blocks various cardiac ion currents at different potencies and has atrial-predominant electrophysiological effects. We investigated the electrophysiological and proarrhythmic effects of AZD1305 versus dofetilide in dogs with chronic complete atrioventricular block and myocardial hypertrophic remodeling. Methods and Results-AZD1305 was administered to anesthetized mongrel dogs before and Ͼ2 weeks after the induction of atrioventricular block and ventricular and atrial electrophysiological parameters were assessed. In all dogs, the selective I Kr blocker dofetilide was used to examine susceptibility to acquired torsades de pointes in chronic atrioventricular block and for comparison.

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Haemodynamics of Acute and Chronic Atrioventricular Block in Dogs

Cited by 17 publications

References 0 publications

Effects of acute vagally-mediated bradycardia on systemic hemodynamics and coronary blood flow before and after coronary stenosis

Effects of acute vagally-mediated bradycardia on systemic hemodynamics and coronary blood flow before and after coronary stenosis

Development of Cardiomegaly

Reduced Ventricular Proarrhythmic Potential of the Novel Combined Ion-Channel Blocker AZD1305 Versus Dofetilide in Dogs With Remodeled Hearts

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