You are able to finally explain to Hazel (you politely and finally got a word in

Question

You are able to finally explain to Hazel (you politely and finally got a word in edgewise) what the

cardiologist who wrote the report described, that she saw waves of varying height, length, and shape instead

of normal P waves.

Hazel’s arrhythmia is

A) sinus tachycardia (or tachycardia with the SA node as pacemaker)

B) atrial fibrillation

C) both of the above make sense and could be Hazel’s arrhythmia

D) neither of the above makes sense and neither could be Hazel’s arrhythmia

Instead of using the apical pulse (the pulse felt over the apex of the heart) or listening to the heart with a

stethoscope to determine heart rate, would it be possible to use an electrocardiogram? That is, can you

determine heart rate using an EKG? (Hint: think of what the waves in the EKG represent) (Another hint:

ASSUME THAT EACH VENTRICULAR MUSCLE DEPOLARIZATION CAUSES CONTRACTION)

A. no

B. yes

Explanation / Answer

a)Sinus tachycardia is recognized on an ECG with a normal upright P wave in lead II preceding every QRS complex.In this P wave and QRS complex follows the normal morphology whereas the PR interval shortens with increasing heart rate. Atrial fibrillation is an abnormal heart rhythm characterized by the rapid and irregular beating of the atria and will have no visible P waves and an irregularly irregular QRS complex because of irregular conduction of the impulse through ventricles.

So, waves of varying height, length, and shape instead of normal P waves are pointing towards Atrial fibrillation arrhythmia in case of Hazel

b)Yes, one can measure the heart rate using EKG.

The RR interval is the time measurement between the R wave of one heartbeat and the R wave of the preceding heartbeat.

Heart rate = 300/ no of the large square box between R-R interval

                   = 1500/ no of the small square box between R-R interval

Normally, there are 4 large square/20 small square box, therefore on an average normal H.R= 300/4=75

OR 1500/20=75 beats per min.

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