Check out the comments on our original post here.
|Click to enlarge|
- 102 bpm
- Sinus Rhythm
- Alternating QRS Morphologies
- See annotated ECG below
|Annotated ECG showing two distinct QRS morphologies in an alternating pattern|
Click to enlarge
- All complexes
Intervals - QRS Complexes Labelled in Red
- PR - Short at ~110ms
- QRS - Normal at 100ms
- QT - 340ms
Intervals - QRS Complexes Labelled in Green
- PR - Normal at ~140ms
- QRS - Normal at 80ms
- QT - 320ms
- Alternating variation in QRS voltages
- Alternating variation in T wave voltages in right precordial leads
- Subtle delta waves seen in the complexes labelled red in the right precordial and inferior leads
- Alternating pre-excitation / accessory pathway conduction with sinus conduction
The EP members of our team agree this is likely a weak left sided pathway with classical intermittent pre-excitation which usually confers a benign prognosis in the setting of atrial fibrillation.
For a great overview article on pre-excitation and paroxysmal SVT check out:
Almendrala J, Castellanosa E, Ortiza M. Paroxysmal Supraventricular Tachycardias and Preexcitation Syndromes. Rev Esp Cardiol. 2012;65:456-69. Full text here.
Thanks to Dr S Razak for recommending this article.
References / Further Reading
Life in the Fast Lane
- Chan TC, Brady WJ, Harrigan RA, Ornato JP, Rosen P. ECG in Emergency Medicine and Acute Care. Elsevier Mosby 2005.