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Monday, 3 December 2012

#ECGclass Case 18

This ECG educational blog runs alongside Twitter.
A new ECG is launched most Monday nights, in term time. Cases are generally aimed at Primary Care. 
Please use the Hashtag #ECGclass if you want to ask the patient any questions, or request any further investigations. 

Remember there are no right or wrong answers, and everyone's opinion is valid. 
Do feel free to join in, but most important of all, have fun! :-)

Case 18

An 82yr old lady is brought to see you by her daughter.
She is complaining of intermittent dizzy spells.
On examination, the lady appears frail, but clinically well. Her BP is good and heart sounds are normal. Her pulse seems a bit irregular, but not fast.

You obtain the ECG below:

Q1 What's going on?
What is the rate?
What is the rhythm?
Can you see P-waves?
Anything else you want to know?

The ECG shows a Sinus bradycardia, with a variable rate of around 50 beats per minute.
(Remember how to calculate the rate of an irregular ECG?  Count the number of complexes in 6 seconds and multiple this by 10.  Assuming paper speed of 25mm/sec then 6 seconds = 30 large squares).

Now study the Lead II rhythm strip.
There are P waves in front of every QRS complex, and the P waves appear morphologically constant and normal; as do the QRS complexes. Every P wave is conducted.

The PR interval is constant, but slightly prolonged (at just over the max. of 5 small squares, or 0.20 secs).   So a First degree AV block is present.

But that's not all.

You also note a 'pause' on the long lead II.  No P wave (and no QRS complex) occurs when expected. 
If this pause was interrupted by an odd looking QRS complex, this would be called an "escape" beat originating from an abnormal site within the ventricular wall.  However, no escape beats are seen, and the pause is terminated by a sinus beat. 

You are concerned about the ECG and ask a bit more about her dizzy spells.
Her daughter is discloses that she is worried, that on at least one occasion, she thinks her mother may have transiently 'blacked' out.

Q2. What are you thinking now?
Would any other investigations be helpful here?

Update 2
You decide to get a long lead II rhythm strip to help you:

What do you think of the pauses now?

This looks a bit more sinister. Far more pauses can be seen.
The duration of each pause is double the basic R-R interval.

When you've had a go,  you'll find the full discussion on the next blog!

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