All of the following features can differentiate between ventricular tachycardia and supraventricular tachycardia EXCEPT :
Ans. is 'b' Ventricular rate > 160/min In ventricular and supraventricular tachycardia the ventricular rate is greater than 160/min, therefore it cannot be used to differentiate between ventricular & supraventricular tachycardia.Variable 1st heart sound is a features of ventricular tachycardia only.In ventricular tachycardia QRS duration is greater than 0.14 Sec. While in supra ventricular tachycardia it is less than 0.14 Sec.Only supraventricular tachycardia can be relieved by carotid sinus massage because ventricle is not innervated by vagus.Ventricular tachycardia Supraventricular tachycardiaUsual rate 160-240/min * Ventricular rates greater than 170/m (Page 423, 2002/e C.M.D.T.)QRS duration >.14 Sec. * QRS >.12 Sec. but no longer than. 14 Sec.Cannot be relieved by carotid * Can be relieved by carotid sinus message sinus massage.Monophasic (R) or biphasic * Triphasic QRS complexes (qR, QR or RS) complexesCapture or fusion beats * Presence of Preexcitation syndrome.AV dissociation reflected by canon a waves and variable 1st heart sound.
QRs < 0.14 seconds
Ventricular rate > 160/min
Variable first heart sound
Relieved by carotid sinus massage
Arrhythmias