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 ...

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 ...

Russians have blown up a satellite, sparking concerns about the safety of vital equipment in space. An SA manufacturing hub is working on a selfie stick that can check for damage. The research will ...

A premature atrial contraction (PAC) occurs when a focus in the atrium (not the SA node), generates an action potential before the next scheduled SA node action potential. When this occurs prior to ...

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 ...

In a normal heart rhythm, your heart beats in a steady, even way. The upper part of your heart (atria) squeezes and pushes blood to the lower part (ventricles), pumping blood and oxygen out to the ...