Any abnormality of conduction takes longer and causes "widened"<unk> es. In bundle branch block, there can be an abnormal second upward deflection within the<unk> . In this case, such a second upward deflection is referred to as R′ (pronounced "R prime"). This would be described as an RSR′ pattern. Ventricles contain more muscle mass than the atria. Therefore, the<unk>  is considerably larger than the P wave. The<unk>  is often used to determine the axis of the electrocardiogram, although it is also possible to determine a separate P wave axis. The duration, amplitude, and morphology of the<unk>  are useful in diagnosing cardiac arrhythmias, conduction abnormalities, ventricular hypertrophy, myocardial infarction, electrolyte derangements, and other disease states. High frequency analysis of the<unk>  may be useful for detection of coronary artery disease during an exercise stress test.
QRS complex
J wave
U wave
P wave 
Delta wave
T wave
ST segment
Plateau potentials