Sinus Bradycardia

Sinus Bradycardia



Basic Information image



Definition


A sinus rhythm with a heart rate of less than 24 beats/min



Epidemiology



Risk Factors


High vagal tone



Associated Conditions and Disorders


Other arrhythmias associated with a high vagal tone such as sinus arrhythmia, sinoatrial block, first- or second-degree atrioventricular (AV) block



Clinical Presentation



Disease Forms/Subtypes




• Physiologic form caused by the horse’s vagal tone: Asymptomatic, and bradycardia disappears with stress or exercise


• Pathologic form caused by underlying disease: May or may not be associated with clinical signs



History, Chief Complaint




• Usually incidental finding; asymptomatic


• Administration of drugs


• Poor performance, exercise intolerance


• Head trauma (increased intracranial pressure [ICP])


• Systemic disease


• Syncope



Physical Exam Findings




• Normal, alert animal or depression and weakness if bradycardia is severe


• Slow heart rate (<24 beats/min), which can be regular or irregular (if associated with other vagally induced arrhythmias)


• Signs of head trauma


• Hypothermia



Etiology and Pathophysiology




• High vagal tone (caused by eye pressure during ophthalmic surgery, increased ICP, hypothermia)


• Systemic disease


• Electrolyte disturbances (calcium, magnesium, and especially potassium). Foals with urinary bladder rupture and hyperkalemia are at an increased risk of developing bradycardia during anesthesia.


• Sinoatrial node disease


• Administration of drugs (digoxin, verapamil, diltiazem, sedatives, and anesthetics)


• Hypothyroidism



Diagnosis image


Diagnosis is made by electrocardiography. Further tests (blood examination, echocardiography, are necessary to look for underlying disease.



Differential Diagnosis




• Sinus block, sinus arrest


• Second-degree AV block


• Third-degree AV block

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Jul 24, 2016 | Posted by in SMALL ANIMAL | Comments Off on Sinus Bradycardia
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