Question 15.3
15.3. A 75-year-old patient is admitted to the ICU with community acquired pneumonia suddenly develops tachycardia. The 12 lead ECG is shown below.
a. Explain the ECG and provide the diagnosis. (10% marks)
b. List two co-existing diseases in critically ill patients where this condition is commonly seen.
(10% marks)
College answer
Aim: To allow the candidate to demonstrate expertise in the analysis of ECGs.
Key sources include: This is a repeat question from paper 2014.1 Q18. CanMEDS Medical Expert.
Discussion:
15.3 - Recognition of multifocal atrial tachycardia was poor.
Discussion
a)
This SAQ was a repeat of Question 18.3 from the first paper of 2014, and so the image and interpretation were also a repeat. The last time, the college gave this as a model answer:
a)
- Multifocal atrial tachycardia
- Irregularly irregular rhythm rate > 100 bpm
- Multiple P wave morphologies
b)
- COPD
- Congestive cardiac failure
The above-displayed ECG comes from the LITFL page on multifocal atrial tachycardia.
The cardinal features are irregularity and a plethora of different P-wave morphologies.
You need to have
- Tachycardia (HR >100)
- Irregular rate
- Variability in P wave morphology
The same findings with a normal heart rate does not qualify for MAT, because it's not tachycardia; you have to call that a "wandering atrial pacemaker".
The CICM question also asked for associated diseases. In adults, MAT is almost uniformly associated with COPD. Not only are the atria stretched by pulmonary hypertension, but the proarrhythmic bronchodilators also make for an irritable myocardium. In the paediatric population the differentials are more broad, including bronchiolitis, croup, bronchomalacia, etc.
References
Bradley, David J. "Multifocal atrial tachycardia." DEVELOPMENTS IN CARDIOVASCULAR MEDICINE 257 (2006): 135.
LiPSON, MANUEL J., and SHAPUR NAIMI. "Multifocal Atrial Tachycardia (Chaotic Atrial Tachycardia) Clinical Associations and Significance." Circulation 42.3 (1970): 397-407.