Critically evaluate the use of plasma troponin in the critically ill patient.
Greater specificity to cardiac damage than CK-MB / AST which can also be found in skeletal muscle
• Useful marker in acute coronary syndromes, where a higher level is indicative of a greater mortality and morbidity
• There has been recent discussion regarding the use of troponin and the diagnosis of myocardial infarction, and the definition has been standardised by the ECS / AHA. Myocardial infarction is defined as demonstration of myocardial ischaemia plus the addition of a significant plasma troponin rise (Circulation 2007)
• Numerous studies that show plasma troponin can be raised in other cardiac conditions, e.g. pericarditis, atrial fibrillation cardioversion, and non cardiac conditions e.g. renal failure, PE, sepsis.
• Plasma troponin levels should be used as a risk stratification tool in conjunction with other tests e.g. ecg and echo, depending on the presenting medical condition
• This has significance in critically ill patients in the non ACS-AMI setting. Medications used for a troponin rise in the setting of ACS / AMI, e.g. anti-coagulants and anti-platelet therapy are not benign, and can have detrimental effects in critically ill patients who have troponin rises due to non ACS / AMI
• Monitoring for ischaemia in the ICU patient
Though the college answer is different, this question closely resembles Question 8 from the second paper of 2006. One is tempted to point out that these questions do not ask specifically about troponin use in the acute coronary syndromes.
In general, the college seems to have wanted to observe several key points in the answer:
Rationale for the use of troponin in the critically ill:
Advantages of using troponin in critically ill patients
Advantages of using troponin in acute coronary syndromes
Disadvantages for the use of troponin in critical illness
This article has a nice graph of cardiac biomarker concentrations over time after an infarct:
Wu et al; National Academy of Clinical Biochemistry Standards of Laboratory Practice: Recommendations for the Use of Cardiac Markers in Coronary Artery Diseases. Clinical Chemistry 45:7 1104 –1121 (1999)
There is a CICM fellowship question regarding the critical appraisal of troponin in the ICU population.
The ECS and AHA statement referred to in the college answer is this article published in Circulation in 2007:
(Kristian Thygesen et al; Universal Definition of Myocardial Infarction. Circulation 2007, 116:2634-2653
This article from Current Opinion in Critical care (2004) discusses the various causes of raised troponin among ICU patients:
Ammann et al,Troponin as a risk factor for mortality in critically ill patients without acute coronary syndromes. Journal of the American College of Cardiology Volume 41, Issue 11, 4 June 2003, Pages 2004–2009
The fact that troponin rise among the critically ill population is associated with a poorer prognosis is supported by this study:
Gunnewiek et al. Cardiac troponin elevations among critically ill patients. Current Opinion in Critical Care: October 2004 - Volume 10 - Issue 5 - pp 342-346
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Ammann, P., et al. "Elevation of troponin I in sepsis and septic shock." Intensive care medicine 27.6 (2001): 965-969.
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Wens, Stephan CA, et al. "Elevated Plasma Cardiac Troponin T Levels due to Skeletal Muscle Damage in Pompe Disease." Circulation: Genomic and Precision Medicine (2016): CIRCGENETICS-115.
Sribhen, Kosit, Rewat Phankingthongkum, and Nilrat Wannasilp. "Skeletal muscle disease as noncardiac cause of cardiac troponin T elevation." Journal of the American College of Cardiology 59.14 (2012): 1334-1335.