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Three Part Question

Is [troponin] level a good indicator of underlying [cardiac damage] after [blunt chest trauma]?

Clinical Scenario

A 45 year old man attends the emergency department after being involved in a road traffic accident. He has sustained a blunt chest injury during the impact and has bruising across his chest wall. His ECG shows non specific ST segment changes and the chest radiograph are normal. You wonder about the benefit of performing a troponin level to aid the diagnosis or exclusion of myocardial contusion.

Search Strategy

Medline 1966-11/04 using the Ovid interface.
[exp Troponin OR troponi$.mp] AND [exp Wounds, Nonpenetrating OR exp Thoracic Injuries OR blunt chest injury.mp OR blunt chest trauma.mp OR blunt thoracic injury.mp OR blunt thoracic trauma.mp] AND [exp Heart Injuries OR myocardial contusion.mp OR cardiac contusion.mp OR myocardial damage.mp OR myocardial injur$.mp OR cardiac damage.mp OR cardiac injur$.mp] LIMIT to human AND English language.

Search Outcome

Altogether 75 papers were found of which 20 were directly relevant to the three part question. Of these, 3 were literature reviews which covered 6 of the papers found, 5 were letters relating to other papers included, 3 were case reports and 3 were journal articles. The 3 review articles and the 3 journal articles (not included in the reviews) are shown in the table.

Relevant Paper(s)

Author, date and country	Patient group	Study type (level of evidence)	Outcomes	Key results	Study Weaknesses
Velmahos G et al, 2003, USA	333 consecutive patients with significant blunt thoracic trauma. TnI was performed on all patients at admission, 4 and 8 hours post admission. Significant blunt cardiac injury was determined by any of the following: hypotension in the absence of bleeding or a neurogenic cause, cardiac arrhythmia, echocardiagraphic abnormality, severe arrhythmia or shock of unexplained origin	Prospective observational study	Clinical diagnosis of significant blunt cardiac injury. Serial ECG and TnI analysis	None with normal ECG and TnI at 8 hours were felt to have significant blunt cardiac injury. TnI was considered abnormal if values were greater than 1.5 ng/mL	The diagnosis of significant blunt cardiac injury was made clinically High cut off for raised TnI (1.5ng/ml)
Mori F et al, 2001, Italy	32 patients with clinical or radiological signs of acute blunt chest trauma. All patients had cTnI measured at 6, 12, 24, 48 and 96 hours post injury. Cardiac contusion defined as abnormal trans-oesophageal echocardiography	Prospective observational study	Sensitivity of raised Troponin	All with normal or minimally raised TnI (<0.4ng/ml )had a normal echo (mean 0.6 +/-1.4)	Excluded patients with pre-existing cardiac disease Small numbers included in the study
			Specificity of raised Troponin	Mean TnI was higher in those with abnormal echo (mean 2.6 +/-1.6) p<0.0001
Ferjani M et al, 1997, France	128 consecutive patients who had suffered blunt chest trauma. All patients had TnT measured at admission, 4 and 24 hours after admission. Cardiac contusion defined as abnormal echocardiograpthy compatible with contusion, severe cardiac rhythm abnormality, severe cardiac conduction abnormality or haemopericardiumecutive patients who had suffered blunt chest trauma	Prospective observational study	Sensitivity and Specificity of Troponin T >0.5ug over 1st 24 hours	ROC curve analysis performed AROC=0.69 with 95% C.I. of 0.56 to 0.80. TnT of >0.5ug has specificity of 0.91 but sensitivity of 0.31 indicating that it is unreliable	Excludes patients with pre-existing coronary artery disease. Only measured TnT at admission, 4 and 24 hours Used TnT not TnI Trop of >0.5ug is a high level
			Troponin vs CKMB	Trop T had greater AROC than CKMB or CKMB/CK ration
Adams JE, 1997, USA	Patients with suspected cardiac trauma	Review article including 3 relevant papers	Serial TnT and total CK	Sensitivity 0.63 and specificity 0.71 for TnT	Excluded those with pre-exisiting cardiac disease Very small numbers involved
			CK and TnI over first 72hours and echo	Sensitivity 1 and specificity 0.68 for TnI
			TnI, CK and CK-MB at 12 and 24 hours and echo	Specificity 0.72 for TnI
			Trop T vs Trop I	TnI specificity better than TnT specificity
Kaye P et al, 2002, UK	Patients with suspected myocardial contusion. ECG and ECHO used to define significant blunt cardiac injury	Review article including 3 relevant papers	Utility of troponin to diagnose myocardial contusion	Animal studies suggest troponin may be useful. 2 Human studies show high sensitivity, 1 shows low spensitivity (but had questionable gold standard)	Papers used variable gold standards, abnormal ECG, clinically significant finding and/or ECHO 1 paper looked at ventilated trauma patients and none had an abnormal echo Small numbers involved in the trials
Sybrandy KC et al, 2003, Netherlands	Patients with suspected cardiac contusion	Review article including 2 further relevant papers	Utility of troponins to detect myocardial contusion	Sensitivity 100%, all with normal TnI had no problems. Specificity 83-87.5%	One paper excluded intubated and haemodynamically unstable patients Small numbers involved in the trials

Comment(s)

There is no gold standard as yet for the diagnosis of myocardial contusion which makes it difficult to assess the newer forms of detection of myocardial injury. Troponin T may be less sensitive than a Troponin I in the context of blunt chest trauma. The diagnostic window for myocardial contusion appears to be smaller and occur earlier after the injury than in the case of myocardial infarction in some studies. Other papers suggest levels should be taken at admission and at 4-6 hours.

Clinical Bottom Line

An abnormal troponin level seems to be a sensitive indicator of myocardial damage.

Level of Evidence

Level 3 - Small numbers of small studies or great heterogeneity or very different population.

References

1. Velmahos G, Karaiskakis M, Salim A, et al. Normal electrocardiography and serum troponin I levels preclude the presence of clinically significant blunt cardiac injury. J Trauma 2003;54:45-51.
2. Mori F, Zuppiroli A, Ognibene A, et al. Cardiac contusion in blunt chest trauma: a combind study of transoesophageal echocardiography and cardiac troponin I determination. Ital Heart J 2001;2(3):222-227.
3. Ferjani M, Droc G, Dreux S, et al. Circulating Cardiac Troponin T in Myocardial Contusion. Chest 1997;111:427-33.
4. Adams JE. Utility of Cardiac Troponins in Patients with Suspected Cardiac Trauma or after Cardiac Surgery Clin Lab Med 1997;17(4):613-623
5. Kaye P, O'Sullivan I. Myocardial contusion: emergency investigation and diagnosis. Emerg Med J 2002;19:8-10.
6. Sybrandy KC, Cramer MJ, Burgersdijk C. Diagnosing cardiac contusion: old wisdom and new insights. Heart 2003;89(5):485-489.