4.1. The development of SSS in patients with AF
The prevalence of SSS is estimated to be 1 in 1000 in adults over 45
years of age,13 with
the incidence rate increasing with age, up to 1 in 600 patients over 65
years of age. SSS accounts for significant healthcare use, including
hospitalization and pacemaker implantation (about half of implant
indications in the United
States).13 However, a
characteristic feature of SSS is the development of supraventricular
arrhythmias, among which, AF is the most
common.9,
14, 15 In
a large population study, the estimated HR for new-onset AF in patients
with SSS was 4.14 At
initial diagnosis of SSS, AF can appear simultaneously in 40–70% of
patients.9,
14, 15 In
patients without clinical AF, incident AF occurs in 4–22% of patients
during follow-up.9,
14, 15During long-term follow-up, 68% of patients had AF recorded in their
pacemakers.14
AF can change a normal SAN or promote preexisting SSS. However, the
incident of SSS in patients with incident AF has not been well
elucidated. This study showed that about a third of SSS occurred before
or after 30 days of incident AF. After regarding AF as time-varying
covariate, the estimated HR for the newly developed SSS in patients with
incident AF was 8.2 and 13.4, compared with the overall and PS-matched
patients without AF. The concept of a single pacemaker dominating the
cardiac rhythm of the atria is effective wherein AF blocks the SAN by
long-term overdrive suppression of its activity. Patients with
paroxysmal AF and prolonged sinus pauses (>3 s) had
improved SAN function after ablation of AF. Sinus pauses were caused by
long-term suppression of the SAN
activity.16