Introduction: Sick sinus syndrome (SSS) is one of the major indications of pacemaker implantations. Aim: We evaluated the usefulness of rapid atrial pacing in patients with suspected SSS, regarding the diagnosis and the indication of permanent pacing.
Methods: Sinus node recovery time (SNRT) was measured by atrial overdrive pacing in 21 patients with clinical and electrocardiographic evidence of sick sinus syndrome. There were 11 men and 10 women with an age range 52 to 82 years and a mean age of 68±6 years. Seven had sinus bradycardia, 5 had second degree sino-atrial block and 9 had a bradycardia-tachycardia syndrome. Underlying heart disease included ischemic heart disease in 13 patients, dilated cardiomyopathy in 1 and no detectable heart disease in 7 patients.
Results: SNRT was measured by pacing the high right atrium at rates ranging from 90 bpm to 170bpm with 10 bpm decrements for 30seconds periods. It was prolonged ( > 450ms ) in 10 patients. The EP study showed that AV conduction was abnormal in 5 patients. The indication for permanent pacemaker was based on clinical criteria only. Permanent pacing was indicated in 10 patients, 4 with prolonged SNRT and 6 with normal values. Among the 11 patients in whom we did not indicate permanent pacing, 4 had prolonged. A dual- chamber pacemaker was implanted in the 5 patients with compromised AV conduction and atrial pacemakers in the remaining 5 patients.
Conclusions: Rapid atrial pacing to measure SNRT was not consistent with the clinical and ECG findings of SSS. The indication of permanent pacing should be based on the clinical and evidence of SSS. However it may be of value for studying AV conduction and to select the type of pacing i.e. atrial vs. dual- chamber pacemaker in patients with suspected associated AV conduction disturbances. Further studies are required to confirm this assumption.