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Troponin Test Information

The troponin test can be used as a test of several different heart disorders, including myocardial infarction.

Contents

Conditions

Cardiac conditions

Certain subtypes of troponin (cardiac troponin I and T) are very sensitive and specific indicators of damage to the heart muscle (myocardium). They are measured in the blood to differentiate between unstable angina and myocardial infarction (heart attack) in patients with chest pain or acute coronary syndrome. A patient who had suffered from a myocardial infarction would have an area of damaged heart muscle and so would have elevated cardiac troponin levels in the blood.[1] This can also occur in patients with coronary vasospasm.

It is important to note that cardiac troponins are a marker of all heart muscle damage, not just myocardial infarction. Other conditions that directly or indirectly lead to heart muscle damage can also increase troponin levels.[2][3] Severe tachycardia (for example due to supraventricular tachycardia) in an individual with normal coronary arteries can also lead to increased troponins for example, presumably due to increased oxygen demand and inadequate supply to the heart muscle.

Troponins are also increased in patients with heart failure, where they also predict mortality and ventricular rhythm abnormalities. They can rise in inflammatory conditions such as myocarditis and pericarditis with heart muscle involvement (which is then termed myopericarditis). Troponins can also indicate several forms of cardiomyopathy, such as dilated cardiomyopathy, hypertrophic cardiomyopathy or (left) ventricular hypertrophy, peripartum cardiomyopathy, Takotsubo cardiomyopathy or infiltrative disorders such as cardiac amyloidosis.

Heart injury with increased troponins also occurs in cardiac contusion, defibrillation and internal or external cardioversion. Increased troponins are commonly increased in several procedures such as cardiac surgery and heart transplantation, closure of atrial septal defects, percutaneous coronary intervention or radiofrequency ablation.

Non-cardiac conditions

The distinction between cardiac and non-cardiac conditions is somewhat artificial; the conditions listed below are not primary heart diseases, but they exert indirect effects on the heart muscle.

Troponins are increased in around 40% of patients with critical illnesses such as sepsis. There is an increased risk of mortality and length of stay in the intensive care unit in these patients.[4] In severe gastrointestinal bleeding there can also be a mismatch between oxygen demand and supply of the myocardium.

Chemotherapy agents can exert toxic effects on the heart (examples include anthracycline, cyclophosphamide, 5-fluorouracil and cisplatin). Several toxins and venoms can also lead to heart muscle injury (scorpion venom, snake venom, venom from jellyfish or centipedes). Carbon monoxide poisoning or cyanide poisoning can also be accompanied by release of troponins due to hypoxic cardiotoxic effects. Cardiac injury occurs in about one third of severe CO poisoning cases, and troponin screening is appropriate in these patients.[5][6]

Some patients with dissection of the ascending aorta have elevated troponins, and increased hemodynamic stress has been suggested as a mechanism.[7]

In both primary pulmonary hypertension, pulmonary embolism and acute exacerbations of chronic obstructive pulmonary disease (COPD), right ventricular strain with increased wall tension and ischemia. Of course, patients with COPD exacerbations might also have concurrent myocardial infarction or pulmonary embolism, so care has to be taken to attribute increased troponin levels to COPD.

Central nervous system disorders can lead to increased sympathetic tone and/or catecholamine release which lead to cardiac overstimulation. This is seen in subarachnoid hemorrhage, stroke, intracranial hemorrhage and (generalized) seizures (in patients with epilepsy or eclampsia, for example).

Patients with end-stage renal disease can have chronically elevated troponin T levels, which are linked to a poorer prognosis.[8][9] Troponin I is less likely to be falsely elevated.[8]

Strenuous endurance exercise such as marathons or triathlons can lead to increased troponin levels in up to one third of subjects, but it is not linked to adverse health effects in these competitors.[10][11][12] High troponin T levels have also been reported in patients with inflammatory muscle diseases such as polymyositis or dermatomyositis.[13][14] Troponins are also increased in rhabdomyolysis.

In hypertensive disorders of pregnancy such as preeclampsia, elevated troponin levels indicate some degree of myofibrillary damage.[15][16]

Cardiac troponin T and I can be used to monitor drug and toxin induced cardiomyocyte toxicity. .[17]

Detection of cardiac troponin

Cardiac troponin T and I are measured by immunoassay methods.[18].[19]

Reference ranges for blood tests, showing troponin in yellow at left, that is, among the compounds of lowest concentration in the blood, normally.

Prognostic use

Raised troponin levels are prognostically important in many of the conditions in which they are used for diagnosis.

In a community-based cohort study indicating the importance of silent cardiac damage, troponin I has been shown to predict mortality and first coronary heart disease event in men free from cardiovascular disease at baseline.[20]

References

  1. ^ Antman EM, Tanasijevic MJ, Thompson B, Schactman M, McCabe CH, Cannon CP, Fischer GA, Fung AY, Thompson C, Wybenga D, Braunwald E. Cardiac-specific troponin I levels to predict the risk of mortality in patients with acute coronary syndromes. N Engl J Med 1996;335:1342-9. PMID 8857017.
  2. ^ Ammann P, Pfisterer M, Fehr T, Rickli H. Raised cardiac troponins. BMJ 2004;328:1028-9. PMID 15117768.
  3. ^ Tsai SH, Chu SJ, Hsu CW, Cheng SM, Yang SP (March 2008). "Use and interpretation of cardiac troponins in the ED". Am J Emerg Med 26 (3): 331–41. doi:10.1016/j.ajem.2007.05.031. PMID 18358946.
  4. ^ Lim W, Qushmaq I, Devereaux PJ, et al. (2006). "Elevated cardiac troponin measurements in critically ill patients". Arch. Intern. Med. 166 (22): 2446–54. doi:10.1001/archinte.166.22.2446. PMID 17159009. http://archinte.ama-assn.org/cgi/pmidlookup?view=long&pmid=17159009.
  5. ^ Henry CR, Satran D, Lindgren B, Adkinson C, Nicholson CI, Henry TD (January 2006). "Myocardial injury and long-term mortality following moderate to severe carbon monoxide poisoning". JAMA 295 (4): 398–402. doi:10.1001/jama.295.4.398. PMID 16434630.
  6. ^ Satran D, Henry CR, Adkinson C, Nicholson CI, Bracha Y, Henry TD (May 2005). "Cardiovascular manifestations of moderate to severe carbon monoxide poisoning". J. Am. Coll. Cardiol. 45 (9): 1513–6. doi:10.1016/j.jacc.2005.01.044. PMID 15862427.
  7. ^ Bonnefoy E, Godon P, Kirkorian G, Chabaud S, Touboul P (April 2005). "Significance of serum troponin I elevation in patients with acute aortic dissection of the ascending aorta". Acta Cardiol 60 (2): 165–70. doi:10.2143/AC.60.2.2005027. PMID 15887472.
  8. ^ a b Needham DM, Shufelt KA, Tomlinson G, Scholey JW, Newton GE (October 2004). "Troponin I and T levels in renal failure patients without acute coronary syndrome: a systematic review of the literature". Can J Cardiol 20 (12): 1212–8. PMID 15494773.
  9. ^ Khan NA, Hemmelgarn BR, Tonelli M, Thompson CR, Levin A (November 2005). "Prognostic value of troponin T and I among asymptomatic patients with end-stage renal disease: a meta-analysis". Circulation 112 (20): 3088–96. doi:10.1161/CIRCULATIONAHA.105.560128. PMID 16286604.
  10. ^ Rifai N, Douglas PS, O'Toole M, Rimm E, Ginsburg GS (April 1999). "Cardiac troponin T and I, echocardiographic [correction of electrocardiographic wall motion analyses, and ejection fractions in athletes participating in the Hawaii Ironman Triathlon"]. Am. J. Cardiol. 83 (7): 1085–9. doi:10.1016/S0002-9149(99)00020-X. PMID 10190525. http://linkinghub.elsevier.com/retrieve/pii/S000291499900020X.
  11. ^ Neumayr G, Gaenzer H, Pfister R, et al. (February 2001). "Plasma levels of cardiac troponin I after prolonged strenuous endurance exercise". Am. J. Cardiol. 87 (3): 369–71, A10. doi:10.1016/S0002-9149(00)01382-5. PMID 11165984. http://linkinghub.elsevier.com/retrieve/pii/S0002-9149(00)01382-5.
  12. ^ Urhausen A, Scharhag J, Herrmann M, Kindermann W (September 2004). "Clinical significance of increased cardiac troponins T and I in participants of ultra-endurance events". Am. J. Cardiol. 94 (5): 696–8. doi:10.1016/j.amjcard.2004.05.050. PMID 15342317.
  13. ^ Kobayashi S, Tanaka M, Tamura N, Hashimoto H, Hirose S (September 1992). "Serum cardiac troponin T in polymyositis/dermatomyositis". Lancet 340 (8821): 726. doi:10.1016/0140-6736(92)92262-E. PMID 1355820.
  14. ^ Erlacher P, Lercher A, Falkensammer J, et al. (April 2001). "Cardiac troponin and beta-type myosin heavy chain concentrations in patients with polymyositis or dermatomyositis". Clin. Chim. Acta 306 (1-2): 27–33. doi:10.1016/S0009-8981(01)00392-8. PMID 11282091. http://linkinghub.elsevier.com/retrieve/pii/S0009898101003928.
  15. ^ Fleming SM, O'Gorman T, Finn J, Grimes H, Daly K, Morrison JJ (November 2000). "Cardiac troponin I in pre-eclampsia and gestational hypertension". BJOG 107 (11): 1417–20. doi:10.1111/j.1471-0528.2000.tb11658.x. PMID 11117772. http://www.blackwell-synergy.com/openurl?genre=article&sid=nlm:pubmed&issn=1470-0328&date=2000&volume=107&issue=11&spage=1417.
  16. ^ Morton A (July 2004). "Raised cardiac troponins: troponin is raised in pre-eclampsia". BMJ 329 (7457): 111. doi:10.1136/bmj.329.7457.111-a. PMC 449874. PMID 15242925. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=449874.
  17. ^ Gaze DC,Collinson PO; Collinson, PO (December 2005). "Cardiac troponins as biomarkers of drug- and toxin-induced cardiac toxicity and cardioprotection.". Expert Opin Drug Metab Toxicol. 1 (4): 715–25. doi:10.1517/17425255.1.4.715. PMID 16863435.
  18. ^ Melanson SEF, Tanasijevic MJ, Jarolim P. Cardiac Troponin Assays Circulation. 2007;116:e501-e504.
  19. ^ a b Collinson PO, Boa FG, Gaze DC. Measurement of cardiac troponin. Ann Clin Biochem 2001;38:423-449. PMID 11587122.
  20. ^ Zethelius B, Johnston N, Venge P (February 2006). "Troponin I as a predictor of coronary heart disease and mortality in 70-year-old men: a community-based cohort study". Circulation 113 (8): 1071–8. doi:10.1161/CIRCULATIONAHA.105.570762. PMID 16490824.
· · Medical test: Serology, reference range: Clinical biochemistry blood tests (including BMP, CMP)
Fluid/electrolytes

electrolytes (Na+/K+, Cl-/HCO3-) · renal function, BUN-to-creatinine ratio (BUN/Creatinine) · Ca

derived values: Plasma osmolality · Serum osmolal gap
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Blood sugar: Glucose test · C-peptide · Fructosamine · Glycated hemoglobin
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