Normal Heart Rhythm & Arrhythmias

The heart is a remarkable muscle that beats by way of an electrical conduction system. Disease abnormalities in the electrical pathways may cause the normal rhythm (called sinus rhythm) to be disrupted, prompting an arrhythmia.

More specifically, an arrhythmia is the result of one of three electrical mishaps:

• The sinoatrial (SA) node (the heart's natural pacemaker) becomes diseased (sick sinus syndrome).
• The atrioventricular (AV) node that sits at the base of the heart's upper chambers fails to pass an impulse along the heart's electrical pathway.
• There is blockage in the heart's conduction system.

An arrhythmia affects the heart's pumping ability by either speeding up or slowing down the electrical impulses responsible for each heartbeat. If the heart beats too slowly (bradyarrhythmia), it will not pump enough blood to meet the body's demands. If the heart beats too quickly (tachyarrhythmia), it will not have enough time between contractions to fill completely and will fail to pump enough blood to the body. Sometimes a tachycardia will progress into fibrillation, which is a quivering of either the heart's atria (atrial fibrillation) or ventricles (ventricular fibrillation) and an inability to pump at all.