cardiac troponin I


cardiac troponin I

A regulatory protein that has been found to be a sensitive marker for heart damage from heart attack (myocardial infarction) occurring during surgery, a time when the detection of a heart attack may be clinically difficult. Blood levels of this protein are measured prior to surgery and at intervals of a few hours afterwards. A rise is strongly suggestive of a myocardial infarction. The method does not replace the conventional procedures of creatine kinase measurement, ELECTROCARDIOGRAPHY and ECHOCARDIOGRAPHY.

Troponins I and T

Synonym/acronym: Cardiac troponin, cardiac troponin I (cTnI), cardiac troponin T (cTnT).

Common use

To assist in evaluating myocardial muscle damage related to disorders such as myocardial infarction.

Specimen

Serum (1 mL) collected in a gold-, red-, or red/gray-top tube. Plasma (1 mL) collected in a green-top (heparin) tube is also acceptable. Serial sampling is highly recommended. Care must be taken to use the same type of collection container if serial measurements are to be taken.

Normal findings

(Method: Enzyme immunoassay)
Troponin I
 0–30 dLess than 4.8 ng/mL
 1–3 moLess than 0.4 ng/mL
 3–6 moLess than 0.3 ng/mL
 7–12 moLess than 0.2 ng/mL
 1–18 yrLess than 0.1 ng/mL
 AdultLess than 0.05 ng/mL
Troponin TLess than 0.2 ng/mL
Normal values can vary significantly due to differences in test kit reagents and instrumentation. The testing laboratory should be consulted for comparison of results to the corresponding reference range.

Description

Troponin is a complex of three contractile proteins that regulate the interaction of actin and myosin. Troponin C is the calcium-binding subunit; it does not have a cardiac muscle–specific subunit. Troponin I and troponin T, however, do have cardiac muscle–specific subunits. They are detectable a few hours to 7 days after the onset of symptoms of myocardial damage. Troponin I is thought to be a more specific marker of cardiac damage than troponin T. Cardiac troponin I begins to rise 2 to 6 hr after myocardial infarction (MI). It has a biphasic peak: It initially peaks at 15 to 24 hr after MI and then exhibits a lower peak after 60 to 80 hr. Cardiac troponin T levels rise 2 to 6 hr after MI and remain elevated. Both proteins return to the reference range 7 days after MI.
Timing for Appearance and Resolution of Serum/Plasma Cardiac Markers in Acute MI
Cardiac MarkerAppearance (hr)Peak (hr)Resolution (days)
AST6–824–483–4
CK (total)4–6242–3
Cardiac MarkerAppearance (hr)Peak (hr)Resolution (days)
CK-MB4–615–202–3
LDH1224–4810–14
Myoglobin1–34–121
Troponin I2–615–205–7
AST = aspartate aminotransferase; CK = creatine kinase; CK-MB = creatine kinase MB fraction; LDH = lactate dehydrogenase.

This procedure is contraindicated for

    N/A

Indications

  • Assist in establishing a diagnosis of MI
  • Evaluate myocardial cell damage

Potential diagnosis

Increased in

  • Conditions that result in cardiac tissue damage; troponin is released from damaged tissue into the circulation.

  • Acute MI
  • Minor myocardial damage
  • Myocardial damage after coronary artery bypass graft surgery or percutaneous transluminal coronary angioplasty
  • Unstable angina pectoris

Decreased in

    N/A

Critical findings

    N/A

Interfering factors

    N/A

Nursing Implications and Procedure

Potential nursing problems

ProblemSigns & SymptomsInterventions
Cardiac output (Prolonged myocardial ischemia; acute myocardial infarction; reduced cardiac muscle contractility; rupture papillary muscle; mitral insufficiency)Weak peripheral pulses; slow capillary refill; decreased urinary output; cool, clammy skin; tachypnea; dyspnea; altered level of consciousness; abnormal heart sounds; fatigue; hypoxia; loud holosystolic murmur; EKG changes; increased JVDAssess peripheral pulses and capillary refill; monitor blood pressure and check for orthostatic changes; assess respiratory rate, breath sounds, and orthopnea; assess skin color and temperature; assess level of consciousness; monitor urinary output; use pulse oximetry to monitor oxygenation; monitor EKG; administer ordered inotropic and peripheral vasodilator medications, nitrates; provide oxygen administration
Pain (Related to myocardial ischemia; myocardial infarction)Reports of chest pain; new onset of angina; shortness of breath; pallor; weakness; diaphoresis; palpitations; nausea; vomiting; epigastric pain or discomfort; increased blood pressure; increased heart rateAssess pain characteristics, squeezing pressure, location in substernal back neck or jaw; assess pain duration and onset (minimal exertion, sleep, or rest); identify pain modalities that have relieved pain in the past; monitor cardiac biomarkers (CK-MB, troponin, myoglobin); collaborate with ancillary departments to complete ordered echocardiography, exercise stress testing, pharmacological stress testing; administer prescribed pain medication; monitor and trend vital signs; administer prescribed oxygen; administer prescribed anticoagulants, anti-platelets, beta-blockers, calcium channel blockers, ACE inhibitors, ARBs, thrombolytic agents
Health management (Related to failure to regulate diet; lack of exercise; alcohol use; smoking)Inability or failure to recognize or process information toward improving health and preventing illness with associated mental and physical effectsCollaborate with health-care provider (HCP) to develop a plan of care that supports cardiac health; assist patient to adhere to recommended medication regime; ensure patient attends a smoking cessation program; encourage patient to comply with health-care follow-up appointments; assess diet and lifestyle choices
Fear (Related to threat of MI, possible death; recurrent pain)Verbalization of fear; restlessness; increased tension; continuous questioning; increased blood pressure, heart rate, respiratory rateEvaluate verbal and nonverbal indicators of fear; assess for the cause of fear; acknowledge the patient’s awareness of his or her fear; explain all procedures with simple age-appropriate and culturally appropriate language; administer proscribed mild tranquilizer; maintain a confident, assured professional manner in all patient interactions

Pretest

  • Positively identify the patient using at least two unique identifiers before providing care, treatment, or services.
  • Patient Teaching: Inform the patientthis test can assist in evaluating heart damage.
  • Obtain a history of the patient’s complaints, including a list of known allergens, especially allergies or sensitivities to latex.
  • Obtain a history of the patient’s cardiovascular system, symptoms, and results of previously performed laboratory tests and diagnostic and surgical procedures.
  • Obtain a list of the patient’s current medications, including herbs, nutritional supplements, and nutraceuticals (see Effects of Natural Products on Laboratory Values online at DavisPlus).
  • Review the procedure with the patient. Inform the patient that a number of samples will be collected. Collection at time of admission, 2 to 4 hr, 6 to 8 hr, and 12 hr after admission are the minimal recommendations. Additional samples may be requested. Inform the patient that specimen collection takes approximately 5 to 10 min. Address concerns about pain and explain that there may be some discomfort during the venipuncture.
  • Sensitivity to social and cultural issues, as well as concern for modesty, is important in providing psychological support before, during, and after the procedure.
  • Note that there are no food, fluid, or medication restrictions unless by medical direction.

Intratest

  • Potential complications: N/A
  • Avoid the use of equipment containing latex if the patient has a history of allergic reaction to latex.
  • Instruct the patient to cooperate fully and to follow directions. Direct the patient to breathe normally and to avoid unnecessary movement.
  • Observe standard precautions, and follow the general guidelines in Patient Preparation and Specimen Collection. Positively identify the patient, and label the appropriate specimen container with the corresponding patient demographics, initials of the person collecting the specimen, date, and time of collection. Perform a venipuncture.
  • Remove the needle and apply direct pressure with dry gauze to stop bleeding. Observe/assess venipuncture site for bleeding or hematoma formation and secure gauze with adhesive bandage.
  • Promptly transport the specimen to the laboratory for processing and analysis.

Post-Test

  • Inform the patient that a report of the results will be made available to the requesting HCP, who will discuss the results with the patient.
  • Nutritional Considerations: Increased troponin levels are associated with coronary artery disease (CAD). Nutritional therapy is recommended for the patient identified to be at risk for developing CAD or for individuals who have specific risk factors and/or existing medical conditions (e.g., elevated LDL cholesterol levels, other lipid disorders, insulin-dependent diabetes, insulin resistance, or metabolic syndrome). Other changeable risk factors warranting patient education include strategies to encourage patients, especially those who are overweight and with high blood pressure, to safely decrease sodium intake, achieve a normal weight, ensure regular participation in moderate aerobic physical activity three to four times per week, eliminate tobacco use, and adhere to a heart-healthy diet. If triglycerides also are elevated, the patient should be advised to eliminate or reduce alcohol. The 2013 Guideline on Lifestyle Management to Reduce Cardiovascular Risk published by the American College of Cardiology (ACC) and the American Heart Association (AHA) in conjunction with the National Heart, Lung, and Blood Institute (NHLBI) recommends a “Mediterranean”-style diet rather than a low-fat diet. The new guideline emphasizes inclusion of vegetables, whole grains, fruits, low-fat dairy, nuts, legumes, and nontropical vegetable oils (e.g., olive, canola, peanut, sunflower, flaxseed) along with fish and lean poultry. A similar dietary pattern known as the Dietary Approaches to Stop Hypertension (DASH) diet makes additional recommendations for the reduction of dietary sodium. Both dietary styles emphasize a reduction in consumption of red meats, which are high in saturated fats and cholesterol, and other foods containing sugar, saturated fats, trans fats, and sodium.
  • Social and Cultural Considerations: Numerous studies point to the prevalence of excess body weight in American children and adolescents. Experts estimate that obesity is present in 25% of the population ages 6 to 11 yr. The medical, social, and emotional consequences of excess body weight are significant. Special attention should be given to instructing the child and caregiver regarding health risks and weight-control education.
  • Recognize anxiety related to test results, and be supportive of fear of shortened life expectancy.
  • Depending on the results of this procedure, additional testing may be performed to evaluate or monitor progression of the disease process and determine the need for a change in therapy. Evaluate test results in relation to the patient’s symptoms and other tests performed.

  • Patient Education

    • Discuss the implications of abnormal test results on the patient’s lifestyle.
    • Provide teaching and information regarding the clinical implications of the test results, as appropriate.
    • Educate the patient regarding access to counseling services.
    • Provide contact information, if desired, for the AHA (www.americanheart.org) or the NHLBI (www.nhlbi.nih.gov).
    • Reinforce information given by the patient’s HCP regarding further testing, treatment, or referral to another HCP.
    • Answer any questions or address any concerns voiced by the patient or family.
    • Teach the patient and family to report chest pain as soon as it starts.
    • Teach the patient about the disease progression and pathophysiology.

  • Expected Patient Outcomes

    • Knowledge
    • States understanding of the signs and symptoms of heart attack
    • States the purpose of prescribed medications to treat medical condition
    • Skills
    • Identifies actions that can be taken to improve cardiac health, e.g., maintain a healthy diet, participate in regular physical activities, eliminate the use of tobacco products, and limit the use of alcohol, as appropriate.
    • Identifies positive coping strategies that can be used to reduce fear.
    • Attitude
    • Complies with the recommendation to undergo smoking cessation
    • Complies with recommendations for lifestyle improvements to decrease the risk of future cardiac injury

Related Monographs

  • Related tests include antiarrhythmic drugs, apolipoprotein A and B, AST, ANP, blood gases, blood pool imaging, BNP, calcium, ionized calcium, cholesterol (total, HDL, and LDL), CRP, CT cardiac scoring, CK and isoenzymes, culture viral, echocardiography, echocardiography transesophageal, ECG, exercise stress test, glucose, glycated hemoglobin, Holter monitor, homocysteine, ketones, LDH and isoenzymes, lipoprotein electrophoresis, magnesium, MRI chest, MI infarct scan, myocardial perfusion heart scan, myoglobin, pericardial fluid analysis, PET heart, potassium, and triglycerides.
  • Refer to the Cardiovascular System table at the end of the book for related tests by body system.