Atrial fibrillation

Complete heart block

• atrioventricular dissociation where no P wave produces a QRS complex
• complain of symptoms resembling profound bradycardia (loss of atrial kick) and reduced cardiac output (syncope, angina, presyncope)

Left atrial enlargement

• increase in the terminal portion of the P wave
• best seen in lead II, this terminal deflection is often demonstrated as a distinct second peak within the P wave (arrow below)

Left ventricular hypertrophy

• increased R wave voltage and duration in leads over the right ventricle (V5 and V6 )
• delayed repolarization produces ST depression and T wave inversion in the same leads

Left bundle branch block

• activation of the intraventricular septum is reversed and electrical impulses to the left ventricle are delayed
• produce a wide QRS complex with an abnormal morphology.

Right atrial enlargement

• P wave duration is unaffected, but its shape is peaked and its amplitude is increased to greater than 2.5 mm in leads II, III, aVF (arrows below) and sometimes V1.

Right bundle branch block

• delayed activation of the right ventricle, leading to a wide QRS complex
• "m-shaped" RSR' complex in lead V1
• "w-shaped" qRS complex in lead V6

Ventricular tachycardia

• three or more ventricular complexes in succession at a rate greater than 100 bpm
• heart rate between 100 and 250 bpm
• QRS morphology is constant and abnormally wide
• can demonstrate AV dissociation in which the ventricular rate > rate
• P waves are frequently hidden, can sometimes be identified as bumps or notches in the ventricular cycles