ED Misdiagnosis Case Alleged Failure to Use Decision Tool
Failure to obtain an ordered ECG, failure to use a decision tool, and anchoring bias were factors in a recent ED malpractice claim alleging missed pulmonary embolism (PE). Ken Zafren, MD, FAAEM, FACEP, clinical professor of emergency medicine at Stanford University Medical Center, reviewed the case as an expert witness.
The plaintiff was an otherwise healthy 30-year-old male who had been ill with cough and shortness of breath for several weeks. He had been diagnosed with bronchitis at a clinic, for which he was prescribed azithromycin.
The following day he was seen in the ED, where he was found to be tachycardic with an oxygen saturation of 94%. A chest X-ray was read as normal. An ECG was ordered but never obtained.
The oxygen saturation improved to 98% without treatment, but the tachycardia did not resolve. The patient was given a dose of azithromycin and told to fill the prescription from the day before.
The next day, the patient experienced sudden shortness of breath. Someone called 911. The paramedics found the patient hyperventilating with a heart rate of 130 beats per minute, a blood pressure reading of 110/76, a respiratory rate of 48, and oxygen saturation at 93%. The paramedics helped the patient slow his breathing and transported him to the same ED in which he had been treated the previous day.
Initial vital signs in the ED were: Heart rate of 125, respiratory rate of 28, blood pressure of 116/97, and oxygen saturation at 95%. The lungs were clear. Lower extremities were neither swollen nor tender. The ECG showed tachycardia, inverted T waves in leads V1-3, and a biphasic T wave in V4, with an S1Q3T3 pattern. The machine reading gave the axis as indeterminate, although visual inspection showed a rightward axis. “The patient’s mother asked if her son could have a blood clot, and mentioned that she had a history of a blood clot,” Zafren notes.
The patient was sent home with diagnoses of cough and shortness of breath and with instructions to continue azithromycin. “Unfortunately, he was found dead the next morning on his bathroom floor,” Zafren says. The autopsy showed a saddle pulmonary embolus and a lower extremity deep venous thrombosis (DVT).
At the first ED visit, the physician misdiagnosed the patient with bronchitis despite abnormal vital signs that suggested PE. “A normal chest X-ray in a patient without underlying disease who is short of breath and hypoxemic is virtually diagnostic of PE,” Zafren says.
The EP likely demonstrated anchoring bias stemming from the initial misdiagnosis of bronchitis at the clinic, Zafren adds. The EP also failed to follow up on the ECG that was not performed. Zafren says that errors at the second ED visit included:
• Failure to interpret abnormal vital signs. In a healthy patient with clear lungs, hyperventilation should result in an oxygen saturation of 99-100%. “The oxygen saturation of 93% strongly suggested PE, especially when associated with sudden onset of shortness of breath,” Zafren explains. Persistent tachypnea and tachycardia also should have raised concern for PE.
• Failure to interpret diagnostic tests correctly. A normal chest X-ray in a patient with shortness of breath and hypoxemia should have led to the diagnosis of PE, Zafren says. Additionally, the ECG, which strongly suggested PE, was read as “nonspecific.”
• Premature elimination of the correct diagnosis from the list of differential diagnoses. The EP at the second ED documented, “Although patient is tachycardic with a family [h/o] DVT, low suspicion of PE given that his legs are nontender, symmetric, no chest pain, not hypoxic, and no recent travel or immobilization. VS otherwise stable and his tachycardia and RR improved somewhat after he rested here in the ED.”
• Failure to consider all pertinent elements of the history. Although the EP’s note stated that the patient’s mother mentioned her own history of DVT, she actually had a history of PE for which she was treated at the same hospital many years previously.
“The misdiagnosis could have been avoided had the physicians correctly interpreted the vital signs and diagnostic testing been carefully interpreted,” Zafren concludes.
At trial, it was clear that the second EP had misread the abnormal ECG as nonspecific. Consultation with a cardiologist, another physician, or a web resource regarding the ECG likely would have led to the correct diagnosis.
“Failure to obtain expert consultation is a common failing in malpractice cases, including those involving misdiagnosis,” Zafren notes. The patient’s presenting complaint also strongly suggested the correct diagnosis of PE. “Pulmonary embolus without the classic findings of chest pain or leg swelling is common,” Zafren notes.
The patient was hypoxic, but the physician testified at trial that 93% and 95% were normal oxygen saturations for this patient. “An SpO2 of 93% or even 94% is not normal for a healthy 30-year-old patient with clear lungs. It screams PE,” Zafren says.
Zafren notes that premature closure of the diagnostic process was caused by:
- anchoring on the previous diagnosis of bronchitis;
- deciding that the diagnosis was hyperventilation despite evidence to the contrary;
- dismissing findings that did not support the diagnoses of bronchitis and hyperventilation.
“The process of documentation might have helped in this case by clarifying the thought process, leading the physicians to the correct diagnosis,” Zafren says.
Although the claim was defended successfully, the fatal outcome and great personal cost to the defendant ED could have been avoided if either EP had made the correct diagnosis.
“The successful defense hinged on the fact that the EP at the first visit and the emergency medicine resident at the second visit, who were not named in the lawsuit, had also missed the diagnosis,” Zafren says. Investigators recently studied whether the Pulmonary Embolism Rule-out Criteria (PERC) in ED patients with low clinical probability of PE safely exclude the diagnosis of PE.1 PERC criteria are safe for very low-risk ED patients, the researchers concluded.
“Although you could theorize that the findings support EPs if a bad outcome occurs despite the use of PERC, the fact is that patients with a negative PERC will always have a very low risk,” Zafren says. The components of PERC are very similar to the components of PE risk scores. “It is very unlikely that a patient with a low risk of PE and a negative PERC score will have a bad outcome,” Zafren adds.
In the above case, there was no evidence that the EP used a decision tool in her decision-making. “Instead of clearly imperfect clinical gestalt, the second physician could have chosen to use a decision tool such as the Wells or Geneva PE score,” Zafren offers. In either case, the patient would have had moderate risk. Even if the Wells score had been applied improperly, by failing to award points for the fact that there was no more likely diagnosis, the patient still would have been classified as low probability.
“The next step in both cases would have been to order a D-dimer, which would almost certainly have been positive, leading to the diagnosis of PE,” Zafren says.
REFERENCE
- Freund Y, Cachanado M, Aubry A, et al. Effect of the pulmonary embolism rule-out criteria on subsequent thromboembolic events among low-risk emergency department patients: The PROPER randomized clinical trial. JAMA 2018;319:559-566.
SOURCE
- Ken Zafren, MD, FAAEM, FACEP, Alaska Native Medical Center, Anchorage, AK; Stanford University Medical Center, Stanford, CA. Phone: (907) 346-2333. Email: [email protected].
Failure to obtain an ordered ECG, failure to use a decision tool, and anchoring bias were factors in a recent ED malpractice claim alleging missed pulmonary embolism.
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