What is the natural history of sinus node dysfunction (SND)?

Updated: Nov 30, 2018
  • Author: Bharat K Kantharia, MD, FRCP, FAHA, FACC, FESC, FHRS; Chief Editor: Mikhael F El-Chami, MD  more...
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The natural history of SND typically involves intermittent and/or progressive cardiac rhythm disorders, which have been associated with higher rates of other cardiovascular events and higher mortality. There is a tendency for the rhythm disturbances associated with SND to evolve over time, along with a higher likelihood of thromboembolic events and other cardiovascular events.

For many patients with SND, there are variable, and often long, periods of normal SN function. However, once present, in due course, SND progresses in most patients, accompanied by a greater likelihood of developing atrial tachyarrhythmias. However, the time course of disease progression is difficult to predict; hence, most patients with symptomatic SND are treated earlier in an attempt to alleviate symptoms.

As noted, SND usually progresses over time. In a study of 52 patients with SND and sinus bradycardia associated with sinoatrial (SA) block or sinus arrest, it took an average of 13 years (range, 7-29 years) for progression to total sinus arrest and an escape rhythm. [6]

The incidence of atrial arrhythmias and conduction disturbances occurs more frequently over time, which may be due in part to a progressive pathologic process that affects the entire atrium and other parts of the heart. In a study comprising 213 patients with a history of symptomatic SND who were treated with atrial pacing and followed for a median of 5 years, 7% developed atrial fibrillation and 8.5% developed high-grade atrioventricular block. [7]

Patients with SND, especially those with tachycardia-bradycardia, are at higher risk for thromboembolic events—even after pacemaker implantation. Asymptomatic episodes of atrial fibrillation resulting in thromboembolic events may contribute to cardiovascular events following pacemaker implantation.

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