All of the following are seen in digitalis toxicity except (All India 2011)
|B||Paroxysmal atrial tachycardia with fast ventricular rate|
|C||Regularization of atrial fibrillation|
|D||Bidirectional ventricular tachycardia|
· Digitalis characteristically cause Atrial tachycardia (paroxysmal or non-paroxysmal) with A-V block, it does not cause tachycardia with fast ventricular rate.
· Ventricular premature beats and bigeminy are the most common arrhythmias caused by digitalis.
· In a patient having atrial fibrillation (AF), P waves are completely absent when no organized atrial activity is present
· Uncontrolled AF result in irregular tachycardia with ventricular rate of 80 to 140 beats per min. This is clinically demonstrated by irregularly irregular pulse seen in AF. However, regularization of atrial fibrillation means that complete heart block (block in conduction from atrium to ventricle) is present and thus no atrial impulse is conducted. Ventricles start to beat according to their intrinsic rate (i.e. ventricles take over the function of pacemaker). There is regular heart rate of 40 to 60 beats per minute is seen. This regularization of atrial fibrillation is highly suggestive of digitalis toxicity.
· Bidirectional ventricular tachycardia is an unusual tachyarrhythmia that usually resolves spontaneously after a seconds to a few minutes. It is often associated with severe structural heart disease or digoxin toxicity. It is also known as biventricular tachycardia.
· Arrhythmias characteristically pointing towards the diagnosis of digitalis toxicity are non-paroxysmal atrial tachycardia with atrio-ventricular block (most characteristic), paroxysmal atrial tachycardia with atrio-ventricular block, bidirectional ventricular tachycardia and regularization of atrial fibrillation.