Fatal Cardiac Arrhyhmia
The heart is a muscle that is the only organ in the body with a single function: to pump. In order to perform this function, the cardiac muscle fibers must first be stimulated to beat by an electrical impulse. This stimulus is provided by a series of specialized electrical tissue known as the conduction system.
In order for the heart muscle to pump effectively, the individual muscle fibers must contract sequentially. This sequential activation of muscle fibers is achieved by serial contraction of the fibers originating at the superior aspect of the heart -the atria, and terminating in the lower chambers – the ventricles.
The electrical conduction system originates in a small area of specialized tissue in the superior aspect of the heart – the sinoatrial node, and conducts the electrical impulse across the right and left before being filtered at the atrioventricular node, which is between the ventricles. Eventually, the impulse is conducted to the muscular pumping chamber (the ventricles) and blood is pumped to the vital organs in a rhythmic fashion.
A cardiac arrhythmia refers to an irregular heartbeat that may or may not reduce pump function and reduce flow of blood to vital organs. Such an arrhythmia may have several causes, such as myocardial infarction (heart attack), blood clot (pulmonary embolism), and abnormal blood sugar.
Common cardiac arrhythmias, such as atrial fibrillation, premature ventricular contractions (PVCs), and sinus tachycardia, generally do not reduce cardiac output. However, an arrhythmia that reduces pump function will also reduce blood flow to the heart, further increasing electrical instability and creating a downward spiral of cardiac function. Low blood pressure leads to reduced blood flow to vital organs (including the heart), which eventually ceases to function. This sequence leads to a series of events that we refer to as irreversible organ dysfunction- or death.
© James Lineback, MD, August 2015.