MedGen

Sick sinus syndrome-4 (SSS4) is characterized by early and progressive sinus node and atrioventricular conduction dysfunction. Patients show bradycardia and chronotropic incompetence, and may experience syncope. Atrioventricular conduction block ranges from mild to severe, and some patients also have intermittent atrial fibrillation. Many require implantation of a pacemaker, but sudden cardiac death has not been reported (Stallmeyer et al., 2017). For a general phenotypic description and discussion of genetic heterogeneity of sick sinus syndrome, see SSS1 (608567). [from OMIM]

An anomaly of the PR interval, which is the portion of the ECG from the onset of the P wave to the beginning of the QRS complex. A normal PR interval in adults is 0.12-0.2 seconds. [from HPO]