What occurs to PR Interval in Sinus bradycardia?

What occurs to PR Interval in Sinus bradycardia?

September 1, 2024 by dr s venkatesan

This ECG can assist you discover a solution .HR is 50/mt. Discover the PR interval .It’s also printed proper there.

What occurs to PR Interval in sinus Bradycardia ?

A. Stays regular

B. Extended however inside regular

C. Extended past regular

D. Relies on the reason for Sinus bradycardia

Reply

When cardiac cycle slows down, each interval should get extended. PR interval is not any exception. For those who apply that rule the reply could be easy (Its B ).However this query has way more points hidden into it. On this ECG it touches on the doorways of first diploma AV blcok. Usually PR doesn,t stretch that far in remoted benign sinus bradycardia.

Sinus fee is decided by SA nodal, humorous pacemaker present(if) .The speed of which is decided by the fragile stability between sympathetic and para-sympathetic sign flux. The dynamicity of the slope of section 4 , ie spontaneous resting membrane is one other key determinant aside from sift within the density of imply P cell firing focus .(see under)

The sinus fee relies upon upon the cranio- caudal shift that happen inside specialised tissue .(10-15mm slender the basmati rice formed SA node)

When do PR interval lengthen in sinus bradycardia ?

The most typical explanation for sinus bradycardia is because of elevated vagal tone . It’s no secret , vagal tone do Affect AV node as a lot because it does the SA node . So, what can we count on ? Logically .the AV node should additionally decelerate . However does it occur actually ?

No, more often than not the AV nodal delay doesn’t not happen in sinus bradycardia . Does that imply the vagal spill over don’t attain the AV node ? It does, however the reality is, the decreased coronary heart fee attenuates the usually prevalent decremental conduction property of AV node. So we don’t count on a chronic PR in sinus bradycardia.

Nevertheless, if PR interval is extended in sinus bradycardia , we will besides silent pathological states like , sinus node dysfunction the place AV node may also be affected. Additionally, prolongation of PR is quite common in ACS conditions in Infero- posterior (RCA/LCX) territory the place each SA and AV nodes are concurrently focused.

Extended PR in bradycardia some instances is a hemodynamic necessity as ventricular filling time is extended.

Medical Implication

It’s a good behavior to have speedy look at PR interval in each affected person with sinus bradycardia. It will guarantee a uncommon miss of AV nodal dysfunction .

Remaining message

PR interval is regular or present little prolongation in most of sinus bradycardia. Whether it is extended, with none circumstantial proof for enhanced vagotonia , then, it might point out some factor fallacious within the conduction system. Atropine take a look at may assist us out in differentiating true vagotonia from intrinsic delay.