The sinoatrial (SA) node is the natural pacemaker of the heart. It generates electrical impulses that cause the heart’s chambers to contract, setting the heart rate. The SA node typically generates 60 ...

Sinoatrial exit block occurs when the action potential initiated by the sinoatrial node is inhibited or completely blocked before it is able to leave the SA node and reach the atrium, and thus no P ...

Junctional rhythm is an irregular heart rhythm that stems from a natural pacemaker in the heart known as the atrioventricular junction. The heart has several built-in pacemakers that help control its ...

Adam Taylor is affiliated with the Anatomical Society. Your heart beats around 60 times a minute, delivering nutrients and removing waste from every cell in your body. It has been doing this since you ...

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 ...

A premature atrial contraction occurs when a focus in the atrium (not the sinoatrial node) generates an action potential before the next scheduled SA node action potential. There are four main ...