During nightshift at the PICU you encounter the following ECG in a patient suffering from spinal muscle atrophy who was recently extubated following several days of mechanical ventilation.
As you enter the room the patient looses consciousness.
This is a 25mm/s monitoring ECG strip showing lead II. The first beats are low atrial rhythm (negative P wave) at a HR of 60 bpm. In line 3 the heart rate gets lower and the 3rd beat in this row is a junctional escape beat (narrow complex, no preceding P wave). Subsequently, as SpO2 dropped to <30%, asystoly appears, interrupted only by scarce escape beats.
As the PICU team started resuscitation, the following could be noted on the ECG:
Rhythmic wide complexes at a heart rate of 100 bpm. These are CPR artifacts (rounded wide complexes). In line 2 CPR was shortly stopped for rhythm assessment, still showing asystoly. Afterwards CPR was continued. Intermittent escape beats can be noticed.
On next cessation of CPR intrinsic rhythm returned, accompanied by palpable pulses. Rhythm restored.
This event of asystoly necessitating CPR resulted from mucus aspiration and prompt desaturation. Initial low atrial rhythm may be associated with enhanced vagal tone.
CPR produces ECG alterations that must not be confused with regular ventricular rhythm.