narrow qrs wave and wide qrs wave

duration measurement ventricular excitation q-wave r-wave s-wave right bundle branch left ventricular interventricular septum depolarization cardiac waves purkinje fibers electrical activity cardiac cardiology diagnosis ecg ecg education monitoring ekg electrocardiogram heart heart disease heartbeat human medical qrs wave rhythm segment sudden death action potentials atrioventricular node electrocardiograph analysis diagnostic graph health pulse rate ventricle science wide narrow wave