Usefulness of carotid sinus pressure in detecting thesick sinus syndrome

Electrophysiological studies are often normal in the sick sinus syndrome (SSS). His bundle electrograms (HBE), with right atrial pacing and sinus node recovery times (SNRT) were obtained in 30 patients with the SSS and in 20 patients without the SSS. Carotid sinus pressure was also applied to all patients during the HBE studies. Corrected SNRT, which is the observed SNRT minus the unpaced cycle length, was calculated as well as the corrected carotid sinus recovery time, which is the observed carotid sinus recovery time (SSRT) minus the unpaced cycle length. In the 30 patients with the SSS, the SNRT was greater than 1680 msec in five patients, with a sensitivity of 17%. The CSRT was greater than 2000 msec in 16 patients, with a sensivity of 53%. The corrected SNRT was greater than 450 msec in eight patients, with a sensitivity of 27%. The corrected CSRT was greater than 450 msec in 22 patients, with a sensitivity of 73%. Thus, the corrected CSRT is a major provocative test for the SSS. In the 20 patients without the SSS, the SNRT and CSRT were normal in every patient, with a specificity of 100%. The corrected SNRT was less than 450 msec in 19 of 20 patients. The average SNRT was 997 msec, while the average CSRT was 1054 msec (r=0.71, p<0.001). Therefore, the carotid sinus recovery time is a non-invasive estimate of the sinus node recovery time in patients without the SSS.