New research helps explain how the body's "flight-or-fight" response is mediated. The study may provide new answers to the question of how the heart pacemaker -- the sinoatrial node -- is regulated.

The term bradycardia refers to an abnormally slow heart rate, of under 60 beats per minute (bpm). The heart has a complex system of nerves that conduct the electrical impulses fired by the sino-atrial ...

Genetically-engineered heart cells may be able to replace the electronic pacemakers that hundreds of thousands of cardiac patients have transplanted each year, suggests a new study in guinea-pigs. In ...

Dear Doctor: What is sick sinus syndrome? Is a pacemaker the only cure? My grandmother was just diagnosed with it but, at age 94, has refused to even consider a pacemaker. Dear Reader: Sick sinus ...