2.3. Outcomes
The primary outcome was SSS. SSS was defined from any discharge
diagnoses or two outpatients visits (ICD-10 codes for SSS and
tachybradycardia syndrome [I495]). The secondary outcomes were
pacemaker implantation or atrioventricular (AV) block. AV block was
defined from any discharge diagnoses or two outpatient visits [I441
(Second-degree AV block, Mobitz type Ⅰ and Ⅱ), I442 (Complete AV block),
I443 (AV block NOS), I453 (Trifascicular block), I458 (AV dissociation),
I459 (Stokes-Adams syndrome, Heart block NOS)] (eTable 1 in the
Supplement). To evaluate the accuracy of the outcome definitions, we
conducted a validation study using hospital administrative data from two
hospitals. The positive predictive values were found to be 91.1%
(307/337) and 95.7% (264/276) for SSS and AV block, respectively.