Most ED patients’ chest pain is not cardiac-related. “But it requires that we do our due diligence and be somewhat conservative in our management,” says Robert B. Takla, MD, MBA, FACEP, medical director and chief of the Emergency Center at Ascension St. John Hospital in Detroit.
The ED recently trialed magnetocardiography, a noninvasive diagnostic tool that measures the heart’s magnetic activity, to determine if it could identify which patients can be discharged safely more quickly and accurately than current practice.
“We were able to get some pretty good preliminary data on negative predictive value and also on specificity,” Takla reports.
Early data on 101 patients of low-to-intermediate risk between August 2017 and February 2018 showed a negative predictive value of 95.5% and a specificity of 94.4%.1 “This is way better than you would find with the current standard of care, which is a noninvasive stress test, and even a nuclear stress test, which maybe gets into the low 90s,” Takla explains.
A diagnostic test with higher specificity and negative predictive value than usual care means EDs are less likely to discharge STEMI patients. “Using magnetocardiography in this case will increase our confidence in being able to discharge patients home safely and further decrease our potential liability,” Takla says.
For EPs making a decision about whether it is safe to discharge a chest pain patient, specificity in negative predictive value, if sufficiently high, is “extremely valuable,” Takla says. Positive predictive value and sensitivity are important from a different perspective. “Many patients have to go to the cardiac cath lab not because they have a STEMI but because they have acute coronary syndrome, or the cardiologist feels that the patient is at high risk for disease,” Takla explains.
Some chest pain patients produce a normal ECG reading but still require repeat cardiac troponin levels. Even if these are negative, acute coronary syndrome cannot always be ruled out with an intermediate HEART score. Currently, these patients are placed in the hospital’s 31-bed observation unit and a stress test is ordered. This takes hours to complete. If ordered after 5:00 p.m., the test is not performed until the following day.
In contrast, the new device tells ED providers more quickly and accurately if the chest pain is cardiac-related. “We can now get two sets of enzymes and do this 90-second scan and may have a better negative predictive value and better overall specificity than with the current standard of care. I don’t have to keep them overnight,” Takla reports. Currently, the ED is involved in a multicenter trial to determine the tool’s accuracy with high-risk patients — those more likely to have coronary artery disease.
“If this is truly as good as the preliminary data suggest, we have not only saved time and money but also unnecessary waits and radiation,” Takla says.
If the patient receives an intervention such as a stent, ED providers also scan him or her afterward to compare the magnetic scan with the gold standard of cardiac catheterization. “We are going to see how well it correlates with patients that have a high likelihood of disease prevalence,” Takla notes.
Even if subsequent research confirms the preliminary findings, it will take time for the test to become common practice in EDs.
“Unfortunately, there is always a lag time between evidence-based medicine and adoption of standard of care,” Takla laments.
- Pena M, Goulet M, Pearson C, et al. Magnetocardiography using a novel analysis system (Cardioflux) in the evaluation of emergency department observation unit chest pain. Ann Emerg Med 2018;72:S2.