Redefining Acute MI: The Potential Impact on Rehabilitation
Due to the new definition of acute myocardial infarction (AMI) based on the chemical marker troponin, it is predicted that more patients will be defined as having AMIs, some of whom would have been previously labelled 'unstable angina' using the World Health Organization (WHO) criteria. A prospective study was undertaken in order to assess the increase in demand on coronary rehabilitation services. The study looked at patients admitted to Ninewells, Dundee (currently using the WHO definition) with ischaemic symptoms.

Patients' ECG findings, chemical markers creatine kinase (CK), and cardiac troponin-T statistics were documented in order to compare the number of patients having had MI defined by the WHO definition with those having MI under the new ESC/ACC definition.

Included were patients admitted acutely with troponin T data and those referred as in-patients to cardiac rehabilitation.

From all 152 patients admitted to rehabilitation, 39 came from the admissions ward. Nineteen of those were defined as having had an acute MI using the new definition but not with the old WHO definition. The demand for cardiac rehabilitation services would increase by approximately 80% if the new definition were put in place.

The European Society of Cardiology (ESC)/American College of Cardiology (ACC) joint committee has redefined myocardial infarction (MI). The World Health Organisation (WHO) previously defined a patient with MI as having two out of chest discomfort, enzyme change or ECG changes. Using more sensitive techniques such as troponin level it is thought that an individual formerly diagnosed with severe, stable or unstable angina pectoris might now be diagnosed 'acute coronary syndrome (ACS) with MI'. Troponin's value in predicting risk, thrombus formation and optimum management, (heparin, fragmin or glycoprotein IIb/IIIa inhibitors) has been well documented. McKenna and Forfar appreciate the value of more precise risk stratification and more targeted patient management but are concerned about how the patient will feel if diagnosed with a 'heart attack' with the new inclusive definition unexplained. With greater numbers of MIs diagnosed, it is hypothesised that there will be a greater demand on cardiac rehabilitation services.