Resident's Corner

CASE OF THE MONTH - each month, a new interesting case; diagnosis, treatment ???

INTERESTING HALF-DAY DEBATES - follow up from great topics of discussion during half-day

THE WAITING ROOM- rounds, research and more ...

CASE OF THE MONTH:

Sooo, after our discussions about dysrrhythmias, here are some ECGs and a review of what we talked about ...

This is a 38 y/o M with a previous MI who presented with CP the EXACT same as his previous MI.

The ECG shows an irregular, narrow complex tachycardia = Rapid Atrial Fibrillation. It also shows ST depression in V1 ->V4 with tall R waves. This is the pattern (classically in V1 and V2) that suggests you may need to do a 15 lead ECG in order to look at the posterior leads.

As you can see in leads V8 and V9 on the next ECG, this patient does indeed have a STEMI in his posterior section of his Left Ventricle. Sorry about the quality of the image ! On the far Right of the ECG, the top lead is V4R, the next one down is V8 followed by V9 wth lead V1 as the rhythm strip across the bottom.

The other reason for doing a 15 lead ECG is in order to get Lead V4R which looks at the Right Ventricle. The indication for doing a 15 lead here would be in someone with a STEMI in the inferior distribution (leads II, III and aVF) as the inferior portion of the LV is supplied by the RCA which also gives blood flow to the RV. Giving nitrates to these patients (with a RV infarction) can be dangerous as they are very pre-load dependent and can drop their blood pressure. At least 55% of people also get blood supply to their SA node via the RCA and so these people can also come in bradycardic. Not great combos ...

So Review ...

V1 and V2 ST depression and large R waves --> mirror test to show Q waves and ST elevation ==> 15 lead ECG to show leads V8 and V9

Okay, so now onto HemiBlocks, on the ECG, you will see ...

Left Anterior HemiBlock (Fascicle) ==>

• Left Axis Deviation
• qR in lateral leads = small q wave with large R wave in leads I and aVL
• rS in inferior leads = small R wave with large S wave in leads II, III and aVF

Left Posterior HemiBlock ==>

• Right Axis Deviation
• rS in lateral leads
• qR in inferior leads

Trifasicular Block ==>

• prolonged PR interval
• Right Bundle Branch Block
• LAHB or LPHB

Here's an Example of a TriFasicular Block: This patient presented with syncope and so was admitted to Cardiology and had a pacemaker inserted

INTERESTING HALF-DAY DEBATES:

Soooooooo ... the dreaded Wolf-Parkinson-White Syndrome

accessory pathways are not rate-limiting the way the AV Node is and also are not affected by many drugs (Beta Blockers, Calcium Channel Blockers, Adenosine ...) and so are very dangerous as they can transmit very fast rates from the atria to the ventricles (Atrial fib becomes Ventricular Fibrillation)

Patient presents with tachycardia and known WPK:

1) Orthodromic Conduction ==>

• narrow complex regular tachycardia
• anterograde conduction thru AV Node
• retrograde conduction thru accessory pathway

Tx: as for any narrow complex tachycardia (Adenosine, CCB, BB)

2) Antidromic Conduction ==>

• wide complex regular tachycardia
• anterograde conduction thru accessory pathway
• retrograde conduction thru AV Node

Tx: all AV node blocking agents are contra-indicated, use only procainamide or CD cardioversion

THE WAITING ROOM:

• Warren and Suzanne will be heading off to Kingston for the review !
• The EMs are in St John, hopefully rolling up their pant legs after the flood !

Send comments/questions to: wfieldus@dal.ca or dlkeefe@dal.ca