There are two different rates that can be determined on an ECG. The atrial rate is indicated by the frequency of the P waves. The ventricular rate is indicated by the frequency of the QRS complexes.
The axis of the ECG is the major direction of the overall electrical activity of the heart. It can be normal, leftward (left axis deviation, or LAD), rightward (right axis deviation, or RAD) or indeterminate (northwest axis).
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Mitral regurgitation is the abnormal backward flow of blood from the left ventricle (LV) to the left atrium (LA) due to disease of the mitral valve apparatus (primary MR) or due to dilation of the MV annulus from LA or LV disease (secondary MR).
Atrial fibrillation is the most common chronic arrhythmia, characterized by erratic atrial electrical activity with atrial rates of 400 to 600 beats per minute.