How to deal with ECGs in your OSCE

Intro

The most daunting exam that any medical student will undertake during their university career is without a doubt "the OSCE".

Whilst written exams may present their own unique challenges, all students that we come across live in fear of their practical exams. There's likely several reasons for this.

1. It feels closer to real life: Students think that if they can't handle simulations, they won't be able to handle real life problems in the medical workplace

2. They are more time pressured: Most OSCE stations only last for 5-10 minutes, and if you haven't gotten the marks by that point, they're lost for good

3. They are observed directly by your tutors: When you're sitting a written exam, no one can see you hum and haw over questions that you know should be easy. No one can see you drop your syringe or fumble over a sexual health history. OSCEs are very different. They highlight your every flaw directly to your tutors and often to your future bosses, making you feel awkwardly judged

That said, one of the most dreaded stations in the OSCE is the ECG station.

So what can we do to help you get through this?

Well, first of all, sometimes fear of the unknown can be the worst thing. There are so many different pathologies that ECGs can highlight that it's easy to feel overwhelmed.

Let's start by making a list of all the possible ECGs that could possibly come up. This helps you track your learning progress, and tick off each pathology once you're comfortable identifying it. Some of these traces will be rhythm based and some will be morphological. By your final year OSCE you should have a full ticked off spreadsheet.

EXG ecg exam guide

You can download the above checklist and tick them off as you go. If you're a site member, head to our ECG library to see our collection of ECGs for your reference as well. All of the above traces can be found there, with explanations of their characteristic findings.

Interpreting the features of the ECG

ECGs can be split into those with morphological problems (e.g. bundle branch blocks, myocardial infarctions etc) and those with rhythm problems (e.g. heart blocks, ventricular tachycardia, SVT etc). For rhythm problems we recommend using the 6 step interpretation guide that we teach on our platform. Click here to be directed to our beginner's tutorial, and select lesson 5.

For morphological problems, you should look at each setion of the ECG in turn (the P-wave, PR interval, QRS complex, ST segment and T-wave). Knowing the normal durations for each of these ECG sections is really important here. As well as this, you can comment on the cardiac axis, and the R-wave progression in the chest leads. If these terms sound unfamilliar to you, then you can join our website and go through the intermediate tutorial, which coveres morphological problems.

Some common things to look out for are:

• P-waves: bifid or peaked P-waves can signal atrial enlargement, absent P-waves may suggest AF

• PR Interval: prolonged PR interval is present in 1st degree heart block, short PR interval is present in WPW syndrome

• QRS complex: a wide QRS complex means that the electrical impulses are not following the His-purkinje system, and instead are spreading across the myocytes. If the rate is rapid, consider VT, if the rate is normal or slow consider a bundle branch block or complete heart block. Deep Q-waves in concomitant leads suggest an established transmural infarct.

• ST segment: if this is elevated in concomitant leads then this could suggest a STEMI, if it is depressed in multiple leads then this could represent an NSTEMI or unstable angina, or it may be reciprocal change. Remember also that the ST segments can't be reliably analysied in the presence of bundle branch blocks.

• T-waves: look for T-wave inversions. Whilst they are non-specific they may suggest underlying ischaemia or strain

These are not exhaustive lists, but they may help you if you are in a tight spot in the exam.

Reporting Your Findings

Now that you feel confident with the above tracings, its time to work on how you report them to your examiner. Simply put there are 2 different ways you can go about structuring your answers

1. Start with the diagnosis, then describe the ECG features that lead you to this - Recommended way to report

2. Talk through each of the ECG findings in turn, and then suggest a diagnosis - This is better if you are not sure what the diagnosis is

You should aim to keep your summaries short and succinct. Try to aim for 3 sentences in total, and no more than 5 at a maximum. Examiners tune out very easily.

Here's an example ECG with an example report:

"This patient's ECG is consistent with a diagnosis of atrial fibrillation with a normal ventricular rate. Electrical activity is present and the rate is 60bpm in an irregular rhythm. The QRS complexes are narrow and there is a distinct lack of P-waves, with the presence of a fibrillating baseline. All of these features are characteristic of atrial fibrillation."

This is a nice 3 sentence summary which encompasses all the points of the 6 step rhythm approach. Even if you have a 12 lead ECG with morphological problems present, you can still report it in the same way. In these cases, it is important to put any key morphological findings first in your report, and then follow with the rhythm interpretation.

Like in this next example:

"This patient presents with an ECG consistent with an anterio-septal STEMI and Q-wave formation in V2 and aVL. There are large tombstone ST-elevations present in leads V1-V4 with associated reciprocal ST-depression in leads III and aVF. In terms of rhythm, this patient's heart rhythm is sinus tachycardia as evidenced by a regular rhythm at 100bpm with narrow QRS completes and a 1:1 P:QRS ratio."

Top Tips

1. Don't panic: ECG interpretation will likley only account for a small proportion of your OSCE station (unless it's a written station). There will probably only be a few marks for getting the diagnosis

2. When in doubt ask to see any previous ECGs. ECGs are dynamic, and just like for imaging studies, it's very important to ask for previous ECGs

3. Always check the patient details match! Everything in an OSCE is done on purpose. If the names or CHIs are slightly wrong on the trace you MUST mention this.

4. Join EXG: If there is one skill in medicine that it is worth nailing, it's ECG interpretation. Every single sick patient gets an ECG and it will be the first thing handed to you in a clinical emergency. You need to know what to do with them and not just pass them off to a colleague. We also recommend undergoing advanced life support training at the earliest notice. This course is put on by the resuscitation council and every person who completes the course will feel like a much better clinician.

Keep practising :)

Dr Ali James