EMERGENCY MEDICAL SERVICES-ECG September EDITION

The ECG shows a normal sinus rhythm at 72 bpm, with a prolonged QT interval (QT 508). The QT interval is measured in milliseconds (ms) from the start of the QRS complex to the return to baseline at the end of the T wave. The QT interval lengthens as the heart rate slows and shortens with faster heart rate. Thus, a corrected QT (QTc) is calculated on ECG printouts to “standardize” the interval to what it would be if the heart rate was 60 bpm. This table shows normal and prolonged QT ranges for adults.

Note that a QTc >500 is associated with an increased risk of Torsades de Pointes, a type of ventricular tachycardia (VT). In this patient the QTc is 527.

While prolonged QT can be an inherited syndrome; more commonly, it results from electrolyte abnormalities (i.e. low potassium, low magnesium, or low calcium) and/or medications that may prolong the QT. Whether inherited or acquired, long QT syndrome is a cause of sudden cardiac death (much less commonly, an inherited short QT syndrome with a QTc <340 is also associated with sudden cardiac arrest in young people). A rule of thumb is that if the T waves extend past the halfway point between two QRS complexes, you should presume a long QT unless the “patient information” section of your ECG print-out reports a QTc < 460. A QTc >500 may lead to intermittent or persisting VT, demonstrated through syncope, chest pain, shortness of breath, or sudden cardiac arrest.

Image Source: CardioNetworks: Drj, CC BY-SA 3.0 <https://creativecommons.org/licenses/by-sa/3.0>, via Wikimedia Commons

The patient is demonstrating evidence of a behavioral emergency – the primary reason for the call – and is also complaining of chest pain and nausea. In considering treatments that may be indicated for this patient, you are likely to follow protocols per Ref. No. 1209, Behavioral/Psychiatric Crisis, as well as Ref. No. 1211, Cardiac Chest Pain.

While your suspicion for acute cardiac syndrome or STEMI/NSTEMI is normally low in a young woman, the risks of aspirin are low and the potential benefit of aspirin is high. Thus, given the larger than normal T waves and complaint of chest pain, it would be reasonable to administer Aspirin 325mg chewable tablets per Ref. No. 1211, Cardiac Chest Pain if the patient has no contraindications (no aspirin allergy or signs/symptoms of GI bleeding).

In this patient you may consider administering Ondansetron 4mg ODT/IV/IM for nausea and vomiting. You may also consider Olanzapine 10mg Oral Disintegrating Tablet for this agitated but cooperative patient. However, the ECG demonstrates QT prolongation, and both Ondansetron and Olanzapine are known to further prolong the QT interval. Per Medical Control Guideline Ref. No. 1317.32, these drugs should not be co-administered due to the risk of inducing Torsades de Pointes (polymorphic VT). Base Contact could be made to discuss options including transporting without medications, or using midazolam if her agitation continues or worsens, since midazolam does not prolong the QT interval.

With the complaint of chest pain and report of possible syncope, the patient should be transported with monitoring, regardless of the ECG findings. The patient is not a candidate for triage to a Psychiatric Urgent Care Center (PUCC) per Ref 526, Behavioral/Psychiatric Crisis Patient Destination.

The patient was transferred by ambulance to the most accessible receiving center (MAR) for psychiatric and medical evaluation. Her ECG on arrival to the ED continued to show a prolonged QT. Labs demonstrated low potassium and magnesium. In addition, her urine was positive for opiates and on specific questioning she acknowledged daily methadone use (methadone is a known QT prolonging medication) as well as a history of Bipolar Disorder, for which she had stopped taking medications two weeks earlier. She received both intravenous magnesium and potassium supplementation and was observed in the Emergency Department for 8 hours until her QT normalized, at which point she was medically cleared and voluntarily transferred to an inpatient psychiatric facility for treatment of this manic crisis related to her bipolar disorder.