Summary
Highlights
A 23-year-old woman presents to the ED with a pounding heart, pale appearance, and weakness. Her symptoms started 20 minutes prior. Initial vital signs are taken, and she is hooked up to a cardiac monitor.
The rhythm is identified as Supraventricular Tachycardia (SVT) due to its rapid, regular nature and narrow QRS complexes, indicating an origin above the AV node. An IV is inserted, and a 12-lead ECG is requested.
Vagal maneuvers, specifically carotid massage, are considered. Contraindications include carotid bruits, history of stroke/TIA/MI, cardiac stenosis (>50%), or a history of ventricular or symptomatic bradyarrhythmias. No contraindications are found.
Carotid massage is performed for five seconds on both sides with a 30-second break, but the heart rate only transiently decreases before returning to 180 BPM. The next step is to administer adenosine.
The recommended initial dose of adenosine is 6 milligrams. After administration, the patient's rhythm slows, with a brief period of asystole. The patient experiences shortness of breath, chest discomfort, and flushing. It is important to warn the patient about these unpleasant, but transient, side effects.
The brief asystole following adenosine does not require treatment due to its short half-life; simply observe. If the rhythm doesn't convert, the next intervention is to give a second dose of adenosine, doubled to 12 milligrams.
Following the second dose of adenosine, the cardiac monitor shows conversion to a normal sinus rhythm. The patient's vital signs are stable, and all symptoms have resolved.