A 72-year-old woman with a history of SVT and taking prophylactic metoprolol but no other cardiac history was brought to the ED by ambulance for chest palpitations. The paramedics stated that she had gone in and out of atrial fibrillation four or so times since they picked her up, and the rate averaged around 120 bpm. The patient had no shortness of breath, dizziness, chest pain, or other complaints. She said she felt a little pressure but no pain when asked if she felt any chest discomfort.
Her vital signs were normal except for a pulse of 105 bpm. Her exam was otherwise normal.
The initial differential diagnosis included tachydysrhythmia, electrolyte abnormality, pulmonary embolism, and ACS. This was the initial ECG.
The computer read the ECG as abnormal and as sinus tachycardia and an undetermined inferior infarct age. Do you agree with the computer?
The computer read was incorrect. The 12-lead shows atrial flutter with a ventricular rate of about 100 bpm, which would usually signify a 3:1 block because the typical atrial rate in flutter is about 300 bpm. This ECG, however, is actually a 2:1 block with slow flutter waves at an atrial rate of only 200 bpm. Flutter waves this slow are usually found in patients on certain medications, especially flecainide. In this case, it may have been due to the metoprolol she was taking. The patient was admitted for observation and ruled in for an NSTEMI.
The computer not infrequently gets the rhythm wrong and may say that atrial flutter is sinus tachycardia, and vice versa. Whenever you see a heart rate of about 150 bpm, look carefully for flutter waves because this is the classic rate for flutter with a 2:1 block. Other ventricular rates may occur with a 3:1 block or a variable block. The rate may be slower if the patient is on AV nodal blockers.
Palpitations alone are rarely a sign of cardiac ischemia, but it could be considered equivalent to failing a stress test if the patient feels pressure or there are significant ST changes with a rapid heart rate. Be sure to ask if there is chest discomfort if patients report no pain.
This post was peer-reviewed by Stephen W. Smith, MD, of Dr. Smith's ECG Blog (http://hqmeded-ecg.blogspot.com).
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Dr. Pregersonis an emergency physician at Cedars-Sinai Medical Center in Los Angeles and Tri-City Medical Center in Oceanside. He is the author of the EMN blog Bradycardia athttp://bit.ly/EMN-Bradycardia, and of Emergency Medicine 1-Minute Consult, Tarascon Emergency Department Quick Reference Guide, A to Z Emergency Pharmacopoeia & Antibiotic Guide, Don't Try This at Home, and Think Twice: More Lessons from the ER. Follow him on Twitter@EM1MinuteGuru, and visit his website atEMresource.org.