michael s
(Michael S)
#1
20 What is the role of troponin T in the diagnosis
and risk stratification of acute coronary
syndromes?
David J Brull
A significant proportion of patients presenting to accident and
emergency departments complain of chest pain. Early risk
stratification is vital with the primary aim being to identify life-
threatening conditions such as acute coronary syndromes (ACS)
and ensure their appropriate management, especially since the
majority of patients have either non-cardiac chest pain or stable
angina and are at low risk.
Standard diagnostic approach
The standard approach to the diagnosis of acute chest pain is to
combine features of the clinical history, including cardiac risk
factor profile, with electrocardiogaphic features and biochemical
markers. The Braunwald classification was initially introduced to
allow the identification of patients with unstable angina at
different levels of risk. It correlates well with in-hospital event
rate and prognosis. Unfortunately symptoms may be difficult to
interpret and clinical assessment alone is insufficient for risk
stratification. Many studies have shown that admission 12-lead
ECG provides direct prognostic information in patients with
ACS. However, as many as 50% of patients ultimately diagnosed
as having either unstable angina or myocardial infarction present
with either a normal ECG or with minor or non-specific ECG
changes only.
Traditionally the biochemical diagnosis of myocardial injury
was confirmed by measurements of non-specific enzymes such as
CK-MB mass or myoglobin, whose levels may also be elevated
after non-cardiac injury. The availability of rapid and accurate
bedside assays of cardiac troponin T has transformed the
diagnostic process. Troponin T is an essential structural protein of
the myocardial sarcomere. It is a highly sensitive and specific
marker of myocardial damage that is not detectable in the healthy
state. Troponin T is released within 4–6 hours of injury peaking
after 12 to 24 hours. Elevated levels of troponin T reflect even
minor myocardial damage and remain detectable for up to 14
