Sick sinus syndrome causes

Many individuals, particularly those who partake in regular vigorous exercise, have heart rates less than 60 bpm. For those individuals, sinus bradycardia is normal and healthy, and does not require evaluation or treatment. However, some individuals develop symptomatic sinus node dysfunction. In the absence of correctable underlying causes, idiopathic sinus node dysfunction is referred to as sick sinus syndrome,12 and occurs with greater frequency with advancing age. The prevalence of sick sinus syndrome is approximately 1 in 600 individuals over the age of 65 years.12... 

Sick sinus syndrome leading to sinus bradycardia may be caused by degenerative changes in the sinus node that occur with advancing age. However, there are other possible etiologies of sinus bradycardia, including drugs (Table 6-2).13... 

Sick sinus syndrome Use only with extreme caution the drug may cause sinus bradycardia, sinus pause, or sinus arrest. The frequency probably increases with higher trough plasma levels. 

Sinus rhythm with a rate of less than 60/min is defined as sinus bradycardia. This bradycardia is usually a physiological response. Pathological and/or symptomatic sinus bradycardia may suggest sinus node dysfunction (see sick sinus syndrome). Vagally induced sinus bradycardia may be responsive to atropine, but only needs to be treated if symptomatic. Atropine doses of less than 0.5 mg may cause a paradoxical increase in vagal bradycardia. 

Propafenone is contraindicated in the presence of severe or uncontrolled congestive heart failure cardiogenic shock sinoatrial, A-V, and intraventricular disorders of conduction and sinus node dysfunction, such as sick sinus syndrome. Other contraindications include severe bradycardia, hypotension, obstructive pulmonary disease, and hepatic and renal failure. Because of its weak (3-blocking action, propafenone may cause possible dose-related bronchospasm. This problem is greatest in patients who are slow metaboUzers. 

Amiodarone is contraindicated in patients with sick sinus syndrome and may cause severe bradycardia and second-and third-degree atrioventricular block. Amiodarone crosses the placenta and will affect the fetus, as evidenced by bradycardia and thyroid abnormalities. The drug is secreted in breast milk. 

The common side effects seen in chronic therapy (Table 19.3) are mostly related to vasodilation—headaches, dizziness, facial flushing, hypotension, and so forth. High doses of verapamil in elderly patients are known to cause constipation. Serious side effects, especially following the intravenous use of verapamil, include marked negative inotropic effects and depression of preexisting sick sinus syndrome, A-V nodal disease, and... 

Contraindications are hypertrophic obstructive cardiomyopathy (increase in inotropism can increase outflow tract obstruction), AF in WPW syndrome (can cause precipitation of the arrhythmia to ventricular fibrillation (VF) by preferential conduction over the accessory pathway), significant AV-block or sick sinus syndrome, hypokalemia (causes increased digoxin sensitivity and supraventricular/ventricular arrhythmia), thyreotoxicosis, postinfarction status (increased mortality). Caution should be exerted in renal failure, and coadministration of other drugs depressing sinus node or AV-nodal function. 

Diltiazem (t) 5 h) is given thrice daily, or once or twice dcdly if a slow-release formulation is prescribed. It causes less myocardial depression and prolongation of AV conduction than does verapamil but should not be used where there is bradycardia, second or third degree heart block or sick sinus syndrome. 

Procainamide prolongs the QT interval (7) and can cause dysrhythmias. It can also impair cardiac conduction and can cause bradycardia and heart block (1). In the sick sinus syndrome it can alter sinus node recovery time (8), although the clinical significance of this is not clear. 

Sotalol should be used cautiously in pregnant patients and patients with renal failure or diabetes mellitus. Sotalol should be used with extreme caution in patients with sick-sinus syndrome associated with symptomatic arrhythmias, because the drug can cause sinus bradycardia, sinus pauses, or sinus arrest. 

Inferior-wall Ml or ischemia, hypoxia, vagal stimulation, and sick sinus syndrome. Acute rheumatic fever. Valve surgery. Digoxin toxicity. Correction of underlying cause. Atropine for symptomatic slow rate. Pacemaker insertion if patient doesn t respond to drugs. Discontinuation of digoxin if appropriate. 

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