Even in pacemaker patients, look for P-waves
An 11-year old female patient was admitted to the pediatric ER for syncope. She had a VVI pacemaker due to sinus node disease. Syncope happened 20 minutes prior to admission. Loss of consciousness lasted for some seconds. Patient was fully oriented afterwards, no history of seizures. The ECG at admission revealed the following:
Sometimes, in pacemaker patients, people tend to look for pacing spikes to confirm adequate pacemaker function and capture, and forget about other things. However, one should assess every ECG thoroughly and not get distracted by the presence of a pacemaker.
In this case, the patient was in atrial flutter (AFL). Flutter waves can be identified quite well due to alternating block (2:1 vs 3:1).
90% of AFL is typical tricuspid isthmus dependent flutter. About 90% typical counterclockwise flutter with negative P waves in leads II/III/aVF, 10% "reverse typical" clockwise flutter (P waves positive in leads II/III/aVF).
AFL represents a rather uncommon arrhythmia in pediatric patients. Hoever, there are two groups of patients in whom AFL appears more commonly: neonates and children who had cardiac surgery.
With regard to pacing, there is only one pacing spike atop the R wave of the second QRS complex in V2. This one shows functional non-capture. Intrinsic conduction during AFL exceeded the lower rate limit of 60 bpm. Therefore, adequate pacemaker function.