This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Cardiovascular system, Subject name: Pharmacology
Vagal stimulation of hea causes? (irrelevant to pharmacology) 
Select and explain. 
A. Increased hea rate, B. Increased RR interval in ECG, C. Increased cardiac output, D. Increased force of contraction
B: Increased RR interval in ECG
Answer: B: Increased RR interval in ECG 
Explanation: Increased RR interval is seen in ECG on vagal stimulation. Normal values for waves and intervals are as follows: RR interval: 0.6-1.2 seconds. P wave: 80 milliseconds. ... QT interval: 420 milliseconds or less if the hea rate is 60 beats per minute (bpm) Ref: KD Tripathi 8th ed.