"Body positioning of ECG placement can have a large impact on ECG tracings and their interpretation," Dr. Henry D. Huang of Rush University Medical Center, in Chicago, told Reuters Health by email. "12-leads obtained in the prone position should be clearly annotated to avoid confusion when possible."
Mechanical ventilation in a prone position is increasingly used to treat acute respiratory distress syndrome (ARDS), particularly during the COVID-19 pandemic. ECG recorded through leads placed in analogous positions on the back avoids the necessity of placing the patient in a potentially harmful supine position.
Dr. Huang and colleagues describe the case of a morbidly obese woman in her 50s with obstructive sleep apnea who was admitted to the intensive care unit for management of COVID-19-related ARDS. She was ultimately treated with mechanical ventilation in the prone position and, because of treatment with hydroxychloroquine and azithromycin, underwent serial ECGs to monitor QT intervals.
The ECG on day 3 of hospitalization showed low amplitudes in the "anterior" precordial leads and Q waves in leads V1 to V3 and was interpreted as an anteroseptal infarct.
Subsequent ECGs recorded when the patient was supine remained completely normal, the researchers report in JAMA Internal Medicine.
To confirm whether these findings apply to other patients, the team reviewed prone and traditional supine ECGs from 20 randomly selected patients with COVID-19 who had both performed during their hospitalization.
This comparison found no significant differences in limb-lead waveform characteristics, except for lower overall Q/S-wave amplitude in lead aVR. In addition, there were significant decreases in mean QRS amplitude in leads V1 to V5 and reduced R-wave amplitude in leads V1 to V4 on prone ECGs (compared with standard supine ECGs).
ECGs obtained in the prone position often demonstrated minuscule P waves and prominent Q waves in leads V1 to V3 that consistently led to interpretation as an anteroseptal infarct.
"Given recognition of some pathologic conditions on ECG is pattern based, it was interesting for us to learn that ECG tracings obtained in the prone position often mimic a pattern suggestive of anterior myocardial infarction," Dr. Huang said. "However, vector loop tracings, which reflect a global activation pattern of the heart, explain why these differences occur with ECG leads obtained on the back."
"Given the possibility that cardiac complications secondary to COVID-19 are sometimes a concern, recognition of non-pathologic loss of R-wave forces in the anterior precordial leads on the prone ECG is clinically important in order to avoid unnecessary workup and minimize excess staff exposure," he said.
"If a pathologic ECG pattern in a COVID-19 suggestive of acute coronary syndrome does not fit the patient's clinical presentation, ECG lead positioning should be retrospectively verified, as a false 'anterior-infarct' pattern may be evident on most ECGs obtained from the prone position," Dr. Huang said.
By Will Boggs MD
SOURCE: https://bit.ly/3mSpEq2 JAMA Internal Medicine, online September 28, 2020.
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