Which is true about sinus tachycardia?

(D) All of the above > In the adult, sinus tachycardia is said to be present when the heart rate exceeds 100 beats/min. Sinus tachycardia rarely exceeds 200 beats/min and is not a primary arrhythmia; instead, it represents a physiologic response to a variety of stresses, such as fever, volume depletion, anxiety, exercise, thyrotoxicosis, hypoxemia, hypotension, or CHF. Sinus tachycardia has a gradual onset and offset. The ECG demonstrates P waves with sinus contour preceding each QRS complex. Carotid sinus pressure usually produces modest slowing with a gradual return to the previous rate upon cessation. This contrasts with the response of PSVTs, which may slow slightly and terminate abruptly. The PR interval and the presence of 1:1. AV conduction properties are AV nodal and His purkinje conduction and therefore PR interval is dramatically prolonged while sinus tachycardia remains the mechanism of Atrial activity,