1. Sick sinus syndrome  (Trust Mark: Doctor-Reviewed)
Sick sinus syndrome is a collection of heart rhythm disorders that include: Sinus bradycardia - slow heart rates from the natural pacemaker of the heart; Tachycardias - fast heart rates; Bradycardia-tachycardia - alternating slow and fast heart rhyt...• Reviewer: Larry A. Weinrauch, MD, Assistant Professor of Medicine, Harvard Medical School, and Private practice specializing in Cardiovascular Disease, Watertown, MA. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

2. Sick Sinus Syndrome  (Trust Mark: Doctor-Reviewed)
Sick sinus syndrome is a disorder of the sinus node of the heart, which regulates heartbeat. With sick sinus syndrome, the sinus node fails to signal properly, resulting in changes in the heart rate.• Author: Teresa Norris RN