THE BEHAVIOR OF ATRIO–VENTRICULAR NODAL RHYTHM FOLLOWING DIRECT PERFUSION OF THE SINUS NODE

1966 ◽  
Vol 44 (2) ◽  
pp. 317-324 ◽  
Author(s):  
R. A. Nadeau ◽  
T. N. James
Keyword(s):  
Sinus Node ◽  
Gradual Transition ◽  
Sinus Arrest ◽  
P Waves ◽  
Pharmacological Agents ◽  
Node Activity ◽  
Relaxation Oscillators ◽  
Sinus Node Artery ◽  
Chronotropic Effects ◽  
Sinus Node Activity

Direct perfusion of the canine sinus node with various pharmacological agents having negative chronotropic effects commonly leads either to abrupt sinus arrest or to a gradual transition from sinus to atrio–ventricular (A–V) nodal rhythm with progressive shortening of the P–R interval. The reappearance of sinus rhythm is usually preceded by a change in A–V nodal rate and a progressive lengthening of the P–R interval to a stable value. During A–V nodal rhythm, changes in heart rate are observed following injections into the sinus node artery. As perfusion of the sinus node is selective, these cannot be attributed to a direct pharmacological effect of the perfusates on the A–V node. Deliberate suppression of A–V nodal pacemaking dominance reveals the persistence of slow sinus node activity which is unapparent electrocardiographically during A–V nodal rhythm. It would seem that even in the absence of P waves, the sinus node may still influence the rate of the A–V node. These observations are consistent with the hypothesis that the sinus and A–V nodes behave as a system of coupled relaxation oscillators.

SIMULATION OF SINUS NODE ACTIVITY BY AN ELECTRONIC RELAXATION OSCILLATOR

1966 ◽  
Vol 44 (2) ◽  
pp. 301-315 ◽  
Author(s):  
F. A. Roberge ◽  
R. A. Nadeau
Keyword(s):  
Sinus Node ◽  
Relaxation Oscillator ◽  
Rhythmic Activity ◽  
Electronic Relaxation ◽  
Node Activity ◽  
Relaxation Oscillators ◽  
Ventricular Response ◽  
Sinus Node Activity ◽  
The Right ◽  
Intact Heart

After the sinus node was destroyed, its rhythmic activity was simulated by an electronic relaxation oscillator coupled to the beating heart. The output of the oscillator was used to stimulate the right atrium, and the ventricular response was returned to the input of the relaxation oscillator. By manually varying the frequency of this artificial pacemaker it was possible to produce changes in the rate of the atrio–ventricular (A–V) node similar to those obtained by perfusion of the intact sinus node with chronotropic agents. Particular attention was paid to the transitions from "oscillator" rhythm to A–V nodal rhythm, and vice versa. The results provide support for the following hypotheses relative to the intact heart: (i) some form of sinus node activity persists during A–V nodal rhythm, and (ii) the principal pacemakers of the heart, the sinus and A–V nodes, behave as a system of coupled relaxation oscillators.

Acute effects of amiodarone in the isolated dog heart

1983 ◽  
Vol 61 (4) ◽  
pp. 308-314 ◽  
Author(s):  
Miyoharu Kobayashi ◽  
Diane Godin ◽  
Réginald Nadeau
Keyword(s):  
Sinus Node ◽  
Direct Injection ◽  
Left Ventricular ◽  
Ventricular Muscle ◽  
Inotropic Effects ◽  
Percent Change ◽  
Sinus Node Artery ◽  
Arterial Blood ◽  
Chronotropic Effects ◽  
Dose Dependent

Direct injection of amiodarone (10–1000 μg) into the sinus node artery of the isolated blood-perfused dog atrium produced dose-dependent negative inotropic and chronotropic responses that were unaffected by atropine. Intraarterial amiodarone also had a negative inotropic action on isolated left ventricular muscle preparations electrically paced at 1.5 to 2.0 Hz. A continuous infusion of 100 μg/min of amiodarone significantly suppressed the positive chronotropic effect of norepinephrine whether expressed in percent change or in absolute values; its positive inotropic effect expressed in percent change was not suppressed but rather enhanced by amiodarone. Calcium chloride induced positive chronotropic and inotropic effects expressed in percent change were, respectively, slightly suppressed and enhanced by amiodarone. Intravenous injection of amiodarone (5 mg/kg) decreased the heart rate and blood pressure of the support dog and produced a negative inotropic response in the isolated left ventricular muscle preparation perfused with arterial blood from the support dog. These results suggest first, that amiodarone has direct negative inotropic and chronotropic effects that are not mediated by cholinergic mechanisms and second, that it has a depressive action on norepinephrine and calcium-induced positive chronotropic effects and an enhancing action on their positive inotropic effects.

Rate-Responsive Cardiac Pacemakers

1991 ◽  
Vol 2 (1) ◽  
pp. 140-149 ◽  
Author(s):  
Patricia Gonce Morton
Keyword(s):  
Clinical Experience ◽  
Sinus Node ◽  
Cardiac Pacing ◽  
Cardiac Pacemakers ◽  
Node Activity ◽  
Advantages And Disadvantages ◽  
New Form ◽  
Sinus Node Activity ◽  
Rate Responsive ◽  
The Ideal

Pacemaker technology continues to advance in the direction of restoring a normal hemodynamic response under varying physiologic conditions. Rate-responsive pacemakers meet this challenge by adjusting the pacing rate in response to a sensed physiologic variable other than sinus node activity. In an effort to design the ideal rate-responsive system, various physiologic cues have been tested. To translate shifts in the sensed physiologic indicator into an appropriate pacing rate, specialized sensor systems also have been developed and include mechanical, chemical, thermal, and electrical sensors. Although each sensor system offers advantages and disadvantages, continued research and clinical experience will determine the future of this exciting new form of cardiac pacing

scholarly journals Transient sinus arrest due to sinus node artery thrombus after revascularisation of the left circumflex artery

2019 ◽  
Vol 12 (2) ◽  
pp. e227878
Author(s):  
Muhammad Hamza Saad Shaukat ◽  
Alexey Tatusov ◽  
Anthony Nappi ◽  
Neil Yager
Keyword(s):  
Myocardial Infarction ◽  
Sinus Node ◽  
Posterior Wall ◽  
Sinus Arrest ◽  
Circumflex Artery ◽  
Left Circumflex Artery ◽  
Sinus Node Artery ◽  
Temporary Pacing ◽  
Escape Rhythm

We present a case of sinus arrest and junctional escape rhythm from sinus node artery (SNA) thrombus in a 55-year-old man after revascularisation of right coronary and proximal circumflex arteries for infero-posterior wall ST-segement elevation myocardial infarction (STEMI). Sinus arrest from occlusion of the SNA is uncommon. The ensuing bradycardia may have haemodynamic consequences requiring temporary pacing but is almost always self-limited.

Noninvasive Recording of Sinus Node Activity by P-Wave-Triggered Signal-Averaged Electrocardiogram: Validation Using Direct Intra-Atrial Recording of Sinus Node Electrogram

1993 ◽  
Vol 7 (3) ◽  
pp. 132-137 ◽  
Author(s):  
Anna Toso ◽  
Alessandro Mezzani ◽  
Luigi Padeletti ◽  
Mohamed Bamoshmoosh ◽  
Simone Salvi ◽  
...  
Keyword(s):  
Sinus Node ◽  
P Wave ◽  
Node Activity ◽  
Sinus Node Activity

Differential sensitivity to neurotransmitters in denervated canine sinus node

1977 ◽  
Vol 233 (2) ◽  
pp. H211-H216 ◽  
Author(s):  
G. R. Hageman ◽  
F. Urthaler ◽  
T. N. James
Keyword(s):  
Blood Pressure ◽  
Sinus Node ◽  
Differential Sensitivity ◽  
Electrical Stability ◽  
Extrinsic Denervation ◽  
Cardiac Denervation ◽  
Sinus Node Artery ◽  
Before And After ◽  
Selective Perfusion ◽  
Chronotropic Effects

This investigation determined the chronotropic effects of norepinephrine and acetylcholine (ACh) administered selectively into the canine sinus node artery after cardiac denervation. In 42 dogs the cervical vagi were isolated, the heart was exposed, and vagal stimulations were performed before and after sham procedure or extrinsic cardiac parasympathectomy. Four additional dogs underwent bilateral stellectomy. The dogs were reanesthetized 4-23 days later, and blood pressure, heart rate, ECG, and local cardiac electrograms were recorded. The vagi were again stimulated and the effectiveness of the parasympathectomy was verified in 11 of the dogs. On selective perfusion of the sinus node with 0.001- to 1-microgram doses of ACh, the sinus bradycardias of the parasympathectomized and the sham-operated dogs were not significantly different. The responses to norepinephrine (0.01 and 0.1 microgram/ml) administered via the same route in the stellectomized dogs were significantly greater than those in the sham-operated dogs, thus verifying this technique for the assessment of sinus node sensitivity to neurotrasmitters. We conclude that extrinsic denervation of the canine sinus node leads to development of a differential response between adrenergic and cholinergic neurotransmitters. These differential sensitivities may be important when considering the pharmacological responses and electrical stability of the denervated and/or transplanted heart.

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