Torsades de pointes cause?

Ans. is 'c' i.e., Wide QT Torsades - de pointes is a cardiac arrhythmia, which may cause blackouts or even sudden death Q (d/t ventricular fibrillation).The phrase "Torsades de pointes" literally means "Twisting of the point referring to the characteristic appearance of the electrocardiogram during the rhythm abnormality.Torsade is defined as polymorphous VT in which the morphology of the QRS complexes varies from beat to beat.The ventricular rate can change from 150 beats per minute to 250 bpm.The regular variation of the morphology of the QRS vector changes from positive to net negative and back again.Thus the QRS complexes tend to be bizarre and multiform, and to have sharply pointed apices or nadirs.Both, the QRS form and axis undulate.Thus, the sharp points of the QRS complex may, for a short period of a few seconds, be directed upwards, to be followed, for a short period of few seconds by a change in the QRS contour where the sharp points are directed downwards.This was symbolically termed "Torsades - de pointes" or "twisting of the point" about the isoelectric axis because it is reminiscent of the Torsades - de pointes movement in the ballet.Most cases exhibit polymorphism, but the axis changes may not have regularity.The definition also requires that the OT interval be increased markedly (usually to 600msec or greater).Cases of polymorphous VT, which are not associated with a prolonged QT interval, are treated as generic VT. Torsades usually occurs in bursts that are not sustained; thus, the rhythm strip usually shows the patient's baseline QT prolongation.The underlying basic for rhythm disturbance is delay in the phase 3 of action potential.The delay is mediated by sodium or potassium channels.The prolonged period of repolarization and the inhomogeneity of repolarization times among myocardial fibres allow dysrhythmia to emerge.