Critical illness heart attack definitions are under scrutiny as medical advances redefine the condition, as Joan Coverson explains the main conditions covered under CI policies in the UK have been subject to standardised definitions, determined by the Association of British Insurers (ABI), since 1999.
The main conditions covered under CI policies in the UK have been subject to standardised definitions, determined by the Association of British Insurers (ABI), since 1999.
The latest set of ABI definitions was developed in 2006, with the definition of Myocardial Infarction (MI) being worded as follows.
One of the features of this definition, which was not present in previous versions, is the specification of defined levels of troponin.
Troponin is found in muscle cells, where it plays an important part in regulating the contraction of muscle. The cardiac troponins, labelled T and I, are structural proteins unique to heart cells that, when released into the bloodstream during an MI, serve as sensitive and specific biochemical markers of cardiac cell (myocyte) death.
Definition questioned
This explains why troponin measurement is prominent in the current ABI definition. However, since 2006, medical diagnostic techniques, practices and tools have developed such that the applicability of the current definition is now being questioned.
It is interesting to consider the diagnostic processes now being used when a patient presents with a suspected MI. Patients with chest pain and other typical signs are routinely tested for troponin.
Almost everyone who has an MI will have increased troponin levels within 6 to 12 hours of experiencing symptoms but there is no necessity for doctors to wait to take blood before initiating treatment.
Typically, an MI results from a fully or partially blocked artery and both the diagnosis and treatment may differ depending on the extent of the blockage.
Events are categorised on the basis of changes in the "ST segment" of the ECG tracing as either ST elevation myocardial infarction (STEMI) associated with complete artery blockage, or non-ST elevation myocardial infarction (NSTEMI) associated with partial blockage.
STEMI usually means that the coronary artery is completely occluded whereas in NSTEMI there is usually less than total occlusion. In the case of STEMI, intervention to reopen the artery is of the utmost urgency, usually with immediate or emergency angioplasty, while in the case of NSTEMI more time is available before any intervention is necessary.
In cases where an artery is only partially blocked, troponin is often measured as part of the diagnostic procedure.
However, the measurement may be taken relatively quickly after the patient presents with a suspected MI, and often well before troponin has reached its peak, which could take up to 12 hours.
In either scenario, the troponin measurements made by cardiologists for clinical purposes may not be optimal in the context of CI claims assessment.
