EKG

What is an EKG Electrocardiogram ~it is also called an ECG (the name comes from the German Elektrokardiogramm) - this is a graph produced by measuring the magnetic field produced by the electric current causing the contraction of the heart muscles.

History All muscles, including the heart, contract from electrical impulses. The first to look at the heart from an electrical point-of-view was Augustus Waller. Willem Einthoven contiuned this work and used the string galvanometer that he invented. Einthoven assigned the letters P, Q, R, S and T to the various deflections on the graph. He was awarded the 1924 Nobel Prize for Physiology or Medicine for his discovery.

Einthoven’s EKG

Einthoven’s Letters

Normal EKG A typical ECG tracing of a normal heartbeat consists of a P wave, a QRS complex and a T wave.

Human Heart

Human Heart

P-Wave The P wave is caused atrial contraction. The relationship of the P Wave to QRS complex may indicate presence of a heart block. Irregular or absent P waves could be arrhythmia.

QRS complex The QRS complex is caused by the contraction ventricles, which are much bigger than the atria. Therefore, this is much larger than the other waves.

T-Wave The T wave represents the repolarization of the ventricles muscles. This is the muscles getting ready to contract again. The QRS complex hides the atrial repolarization.