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QRS complex
a group of waves seen on an electrocardiogram, representing ventricular depolarization. It actually consists of three distinct waves created by the passage of the cardiac electrical impulse through the ventricles and occurs at the beginning of each ventricular contraction. In a normal surface electrocardiogram the R wave is the upward deflection; the first downward deflection represents a Q wave, and the final downward deflection is the S wave. One abnormality of the QRS complex is increased voltage resulting from enlargement of heart muscle and increased dlow of
electric current. Another is abnormally low-voltage QRS complexes, which may result from a toxic heart condition such as fluid
in the pericardium, or from pleural effusion or emphysema. Called also QRS wave.
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