Isorhythmic atrioventricular dissociation

At an increased ECG gain setting of 16 mm/mV (instead of the standard setting of 10 mm/mV), P waves are more visible, making the arrhythmia more clearly evident. The atrial rate (48 beats/minute) is slightly slower than the ventricular rate (50 beats/minute). Consequently the P waves appear before the R waves at the beginning of the tracing and progressively "march through" the QRS complex, indicating dissociation of atrial and ventricular beats. Note that the P waves are hidden in the QRS complex in the 8^th through 11^th beats.