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Old 08-14-2012
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Help Physiology--cardiology

A 67-year-old Caucasian male is brought to the emergency department after a syncopal episode. An ECG recording demonstrates bradycardia ith regular rhythm and normal QRS complexes but no P waves. Which of the following is the most likely cardiac pacemaker location in this patient?
A. SA node
B. AV node
C. AV bundle branch
D. Purkinje system
E. Left ventricular muscle

Anyone can help me clear the inquiry of how to rule out the possibility of the pacemakers originating from the ventricular system

Very appreciate your explanation!
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Old 08-14-2012
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The only way this question makes sense to me is if it's a-fib with complete heart block. Explains the lack of p wave and regular bradycardia.
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Old 08-14-2012
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I just did this question in uworld today!! Answer is B --AV node

It's because absence of P wave suggests absence of atrial depolarization, but normal QRS complex meaning normal ventricular depolarization; so it makes sense if the SA node isnt working, and the conduction begins from AV node in this patient. Hence only ventricular depolarization and bradycardia..

If there is still some confusion, look up the normal conduction pathway- it starts from SA node- atria- AV node- bundle of His- Purkinje- Ventricles.

Hope that cleared it up for you?
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The above post was thanked by:
belindalimm (08-14-2012), offpiste (08-14-2012)
  #4  
Old 08-14-2012
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Question

Quote:
Originally Posted by DrSK View Post
I just did this question in uworld today!! Answer is B --AV node

It's because absence of P wave suggests absence of atrial depolarization, but normal QRS complex meaning normal ventricular depolarization; so it makes sense if the SA node isnt working, and the conduction begins from AV node in this patient. Hence only ventricular depolarization and bradycardia..

If there is still some confusion, look up the normal conduction pathway- it starts from SA node- atria- AV node- bundle of His- Purkinje- Ventricles.

Hope that cleared it up for you?
nice explanation but can you please tell that how we can rule out option "C"?????????
as D & E always give wide QRS complex but ectopic pacemaker activity by bundle branch can give us narrow QRS complex provided there is no bundle branch block as evident in this question
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