Jump to content

If the QT Is prolonged wouldn't the QRS Always be widened?

CCU   (1,808 Views 9 Comments)
by BSN_Studnt BSN_Studnt (Member) Member

2,020 Profile Views; 49 Posts

So, I was thinking (random thought) if the QT interval is prolonged wouldn't that always mean there has to be some widening of the QRS ? 

Share this post


Link to post
Share on other sites

1 Follower; 1,319 Posts; 12,305 Profile Views

It measures the time interval of 2 events, ventricular depolarization and repolarization. So, depending on which one (or both) of those events are prolonged, that corresponding element of the ekg will be prolonged as well.

So the answer is "sometimes".

Share this post


Link to post
Share on other sites

/username is a BSN, RN and specializes in Critical Care.

504 Posts; 8,770 Profile Views

Not always.  You can have normal depolarization (QRS), which will be narrow, and delayed repolarization (QT).  

Share this post


Link to post
Share on other sites

Pheebz777 has 18 years experience as a BSN, RN and specializes in ICU, CVICU, E.R..

225 Posts; 4,518 Profile Views

The QRS complex will always be narrow in a heart with a normal functioning conduction system and a supraventricular pacemaker. The QRS will be prolonged in a BBB or from a ventricular source (PVC) since both signals will be conducted from muscle to muscle tissue in the myocardium outside of the normal conduction system pathways.

So to answer your question, a prolonged QT interval does not necessarily prolong the QRS. A prolonged QRS is always originating from a conduction issue. (BBB, Ventricular pacemaker, elevated K+)

Share this post


Link to post
Share on other sites

ambersky004 has 11 years experience as a BSN, RN and specializes in CardiacStep-down/Progressive Care Unit.

39 Posts; 1,361 Profile Views

The QT interval is the time from the start of the Q wave to the end of the T wave. From the time taken for ventricular contraction and relaxation. How fast the ventricles recharged for the next cycle.

While the QRS duration is how fast the ventricles contracts. 

It's not always that way. But both prolongation of these two will cause a lethal arrhythmias. 

Share this post


Link to post
Share on other sites

GSDlvrRN has 4 years experience as a BSN and specializes in Telemetry.

87 Posts; 1,495 Profile Views

Yass. Nerds 🙂 #telenerds

Share this post


Link to post
Share on other sites

1 Follower; 73 Posts; 1,047 Profile Views

On 3/2/2019 at 1:12 PM, Pheebz777 said:

The QRS complex will always be narrow in a heart with a normal functioning conduction system and a supraventricular pacemaker. The QRS will be prolonged in a BBB or from a ventricular source (PVC) since both signals will be conducted from muscle to muscle tissue in the myocardium outside of the normal conduction system pathways.

So to answer your question, a prolonged QT interval does not necessarily prolong the QRS. A prolonged QRS is always originating from a conduction issue. (BBB, Ventricular pacemaker, elevated K+)

Your reply "A prolonged QRS is always originating from a conduction issue. (BBB, Ventricular pacemaker, elevated K+)" is not complete.

Type 1C antiarrhythmic drugs can potentially cause prolonged QRS and QT.

Some patients at a cardiac ward are likely to have antiarrhythmic medications.

Share this post


Link to post
Share on other sites

Pheebz777 has 18 years experience as a BSN, RN and specializes in ICU, CVICU, E.R..

225 Posts; 4,518 Profile Views

On ‎4‎/‎19‎/‎2019 at 1:20 AM, Nursing Au said:

Your reply "A prolonged QRS is always originating from a conduction issue. (BBB, Ventricular pacemaker, elevated K+)" is not complete.

Type 1C antiarrhythmic drugs can potentially cause prolonged QRS and QT.

Some patients at a cardiac ward are likely to have antiarrhythmic medications.

Yes, they alter the action potential thus delaying conduction.  

Share this post


Link to post
Share on other sites
×