This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Medicine
All of the following features can differentiate between ventricular tachycardia and supraventricular tachycardia except: 
Select and explain. 
A. QRs < 0.14 seconds, B. Ventricular rate > 160/min, C. Variable first hea sound, D. Relieved by carotid sinus massage
B: Ventricular rate > 160/min
Answer: B: Ventricular rate > 160/min 
Explanation: Answer is B (Ventricular rate > 160/min) In both ventricular and supraventricular tachycardia the ventricular rate is greater than 100/min, therefore ventricular rate > 160/min cannot be used to differentiate between ventricular & supraventricular tachycardia. Ventricular tachycardia (Broad complex tachycardia) Ventricular rate > 100 bpm QRS duration > 0.12 sec. (>.14 sec.- Harrison)Q Cannot be relieved by carotid sinus massage. Q Supraventricular tachycardia (Narrow complex tachycardia) Ventricular rates > 100 bpm QRS duration < 0.12 sec. Can be relieved by carotid sinus message Q 100 bpm * QRS duration > 0.12 sec. (>.14 sec.- Harrison)Q * Cannot be relieved by carotid sinus massage. Q " align="left" height="74" width="277"> 100 bpm * QRS duration < 0.12 sec. * Can be relieved by carotid sinus message Q " align="left" height="74" width="314"> Other features can be used to distinguish ventricular and supraventricular tachycardia. Variable First hea sound is a features of ventricular tachycardia only. In ventricular tachycardia QRS duration is greater then 0.14 Sec, while in supra ventricular tachycardia it is less than 0.14 Sec. Supraventricular tachycardia can be relieved by carotid sinus massage while ventricular tachycardia cannot.