Experimental and clinical cases have been described in which bradycardia, i.e., heart rates below 60 beats/min or slowing of the heart rate, resulted in lethal ventricular arrhythmias during various stages of myocardial ischemia and infarction. The present study was designed to determine the relationship of lethal ventricular arrhythmias and slow heart rates. In 18 dogs anesthetized with sodium...

Patients carrying the heterozygous A414G mutation in HCN4 gene, which encodes protein, demonstrate moderate to severe bradycardia of heart. Tetramers subunits compose ion channels sinus node that carry hyperpolarization-activated ‘funny’ current (If), also named ‘pacemaker current’. If plays an essential modulating role pacemaker activity. To assess mechanism by results bradycardia, we first pe...

Evidence has been presented to show that a second dose of suxamethonium is capable of producing a severe bradycardia in man. This response may be effectively prevented by the prior administration of certain non-depolarizing muscle relaxants namely tubocurarine, alcuronium, c-toxiferine and pancuronium in quantities of one-quarter or less of their muscle relaxant level. It is suggested that suxa...

An elderly woman who presented with Adams-Stokes attacks that were preceded by paroxysms of neuralgia was successfully treated with carbamazepine. Ventricular asystole was provoked by pharyngeal pain and coincided with loss of consciousness. Vagal reflexes are probably responsible for the bradycardia that causes the cardiac symptoms of glossopharyngeal neuralgia. Carbamazepine (600 mg/day) abol...

Vasovagal episodes occur frequently in young healthy patients undergoing venous cannulation and loco-regional anaesthesia. We report two cases of severe coronary vasospasm and non-Q-wave infarction in healthy young women after administration of ephedrine for vasovagal symptoms at the onset of spinal anaesthesia. In the light of unopposed vagal predominance pre-disposing patients to coronary vas...

1. During normoxia, heart rate was governed by a vagal tone which increased at higher acclimation temperatures. This tonic influence was exerted predominantly via the branchial cardiac nerves. The increase in heart rate following atropinization or cardiac vagotomy was associated with a reduction in stroke flow in the ventral aorta in accordance with Starling's Law of the heart. 2. During slowly...

The parasubthalamic nucleus (PSTN) projects extensively to the nucleus of the solitary tract (NTS); however, the function of PSTN in cardiovascular regulation is unknown. Experiments were done in alpha-chloralose anesthetized, paralyzed, and artificially ventilated rats to investigate the effect of glutamate (10 nl, 0.25 M) activation of PSTN neurons on mean arterial pressure (MAP), heart rate ...

The delay τ between rising systolic blood pressure (SBP) and baroreflex bradycardia has been found to increase when vagal tone is low. The α(2)-agonist clonidine increases cardiac vagal tone, and this study tested how it affects τ. In eight conscious supine human volunteers clonidine (6 μg/kg po) reduced τ, assessed both by cross correlation baroreflex sensitivity and sequence methods (both P <...

BACKGROUND In patients with Brugada syndrome (BS), ventricular fibrillation (VF) occurs mainly during sleep; therefore, not only vagal activity but also bradycardia dependent changes in ECG may relate to the nighttime occurrence of VF. The present study aimed to examine the difference in bradycardia-dependent changes in the ECG of symptomatic and asymptomatic BS patients. METHODS AND RESULTS ...

Basically similar physiological adjustments occur in diving amniote vertebrates and in fish removed from water (Andersen, 1966; and additional reviews by Irving, 1939, 1964; Scholander, 1940, 1961-62, 1963, 1964; and Andersen, 1964). In these vertebrates there is a pronounced, vagally induced bradycardia (slow heart rate) which generally is achieved in a few seconds or a few minutes. Jones & Sh...