Myocardial Infarction Algorithm Strategy 77% Effective In One Hour

More than 2,500 Americans die from myocardial infarction (heart attack) every day. Early treatment in the case of heart disease can usually extend a heart attack victim’s quality of life. In the past symptom recognition was not easy, other than a few overt indicators, such as high blood pressure, chest pain, shortness of breath, weakness and irregular heartbeat, the medical field lacked an operative tool for effective evaluation and treatment.   Once a patient began to exhibit symptoms, hospitals used an electrocardiogram, or EKG test, and a check of blood sugar and cholesterol levels, blood pressure, and body mass index. Patients would receive a comprehensive report, including an analysis of their cardiac risk factors. Last year two new tests, “artery age” and “ankle brachial index” were added to determine myocardial infarction risk for young and thin patients. “Ankle brachial index” or (ABI) tests help gauge a person’s circulation, which is crucial in preventing strokes and heart attacks. These available diagnostic tools, though encumbered by long process times, gave doctors a significant advantage to combat heart disease; however, recent research reveals that an additional tool may soon be available for use.

A new strategy using an algorithm that incorporates high-sensitivity cardiac troponin T (hs-cTnT) values appears to be associated with ruling-out or ruling-in myocardial infarction within one hour in 77 percent of patients with acute chest pain who presented to an emergency department, according to a report published Online First by Archives of Internal Medicine, a JAMA Network publication.

Patients with symptoms that suggest an acute myocardial infarction (AMI) account for about 10 percent of all emergency department consultations. Along with clinical assessment, electrocardiography and measurement of cardiac troponin (cTn) levels are the diagnostic cornerstones. The development of sensitive and high-sensitivity cardiac troponin (hs-cTn) tests appears to have improved the early diagnosis of AMI, but how best to use these assays in clinical practice is not clear because the more sensitive tests have increased the number of positive results in conditions other than AMI, according to the study background.

Tobias Reichlin, M.D., of University Hospital Basel, Switzerland, and colleagues sought to develop and validate an algorithm to rapidly rule-in or rule-out an AMI. The prospective multicenter study enrolled 872 patients with acute chest pain presenting to the emergency department and AMI was the final diagnosis in 147 patients (17 percent). The algorithm incorporated hs-cTnT baseline values and absolute changes within the first hour.

The algorithm was developed in a sample of 436 patients and validated in the remaining 436 patients. Applying the algorithm to the validation cohort, 259 patients (60 percent) could be classified as rule-out, 76 patients (17 percent) as rule-in and 101 patients (23 percent) as being in the observational zone within one hour. Cumulative 30-day survival was 99.8 percent, 98.6 percent and 95.3 percent in patients classified as rule-out, observational zone and rule-in, respectively, according to the study results.

“The use of this algorithm seems to be safe, significantly shortens the time needed for rule-out and rule-in of AMI, and may obviate the need for prolonged monitoring and serial blood sampling in 3 of 4 patients with chest pain,” the authors conclude.

“With this study, Reichlin et al provide an important step forward in application of hsTn [high-sensitivity troponin] as a tool for triage of ED patients with possible MI. However much work remains to develop the evidence to bring hsTn testing and the algorithms they have developed to use in clinical practice,” Newby continues.

“Finally, although touted as ‘simple’ by the authors, the need for multicomponent algorithms that are different for rule-in and rule-out and that vary by age group or other parameters will challenge application by busy clinicians unlikely to remember or accurately process the proposed algorithm. As such, it will imperative that hsTn algorithms, if validated, are built into clinical decision support layered onto electronic health records so that testing results are provided electronically to physicians along with the algorithmic interpretation to allow systematic application in triage and treatment,” Newby concludes.

What this all means is that more than three-quarters of people with chest pain can be triaged within an hour of arrival at the emergency department with a novel strategy utilizing high-sensitivity cardiac troponin (hs-cTnT), according to a study from Switzerland.

The strategy is promising, according to the accompanying editorial, but much work remains before it can be implemented in clinical practice.

Tobias Reichlin and colleagues first studied 436 patients and developed a treatment algorithm utilizing hs-cTnT baseline changes and absolute changes over the initial hour. The algorithm was then tested in a second validation cohort of 436 patients, with the following results:

  • 60% were classified as “rule-out”
  • 17% were classified as “rule-in”
  • 23% required further observation
  • Overall sensitivity and negative predictive value: 100% for rule-out
  • Specificity for rule-in: 97%
  • Positive predictive value for rule-in: 84%
  • Prevalence of MI in the observational group:  8%
  • 30-day survival: 99.8% in the rule-out group, 98.6% in the observational group, and 95.3% in the rule-in group

The authors claim that their strategy “may obviate the need for prolonged monitoring and serial blood sampling in 3 of 4 patients.”

L. Kristin Newby writes that the Swiss study “is a major advance in understanding the application of hsTn testing that with continued development could substantially improve evaluation of ED patients with suspected MI.” However, she notes that the excellent results obtained in this initial study will probably not be equaled in the real world. In addition, she writes, “although touted as ‘simple’ by the authors, the need for multicomponent algorithms that are different for rule-in and rule-out and that vary by age group or other parameters will challenge application by busy clinicians unlikely to remember or accurately process the proposed algorithm. As such, it will be imperative that hsTn algorithms, if validated, are built into clinical decision support layered onto electronic health records so that testing results are provided electronically to physicians along with the algorithmic interpretation to allow systematic application in triage and treatment.”

There is great need to expedite final test in order to produce multicomponent algorithms and bring this new myocardial infarction tool to the market, especially during a time of what appears to be increased information about the lives this preventable disease has devastated.

 

Contributor D. Chandler

Leave a Reply

Your email address will not be published.