Heart Attack Blood Tests: Creatine Phosphokinase (CPK) and Troponin

In the United States each year approximately 1.1 million people have a heart attack (myocardial infarction 3) and almost half die. Unfortunately, many people who die of a heart attack ignore the symptoms and fail to seek medical attention within the first hour. 1 In a hospital diagnostic tests confirm or rule-out a heart attack. Symptoms of a heart attack confirmed by specific bloods tests (After a heart attack, abnormally high protein enzymes are detected in the blood) and electrocardiogram. 2

Sudden clot in a coronary artery results in the stoppage of blood and oxygen, causing death of the heart muscle. 3 Most common cause of a heart attack is coronary artery disease: Accumulation of plaque (cholesterol) over a period of time (years) inside the walls of the coronary arteries result in a blood clot. 1 "If blood flow is not restored to the heart muscle within 20 to 40 minutes, irreversible death of the heart muscle will begin to occur." 3 Symptoms of a heart attack include: Shortness of breath, sweating, squeezing / fullness or pain sensation of the chest, nausea, vomiting, heartburn, upper back pain, arm pain (more likely left arm), and general feeling if illness. These symptoms can be attributed to stress or result of a heart attack but can only be conclusively confirmed undergoing specific blood tests in a hospital and electrocardiogram (Monitoring electrical activity of the heart for abnormal heart rhythm 15), sooner than later. 4

During a heart attack, outer coat of the heart muscle cell membrane rupture slowly muscle protein enzymes: Abnormally high cardiac enzymes in the blood is evidence of a heart attack 2 "One of the most reliable and commonly tested cardiac enzymes (blood test) is creatinine phosphokinase (CPK isoenzymes test 7)." 5 However, creatinine phophokinase is present in heart, brain, and skeletal muscle. 6 Three types of blood tests (categories) distinguish where CPK isoenzymes is concentrated: CPK-BB (CPK-1) - concentration in the brain and lungs (caused by stroke, or lung injury), CPK-MB (CPK-2) - found mostly in the heart and CPK-MM (CPK-3) - found mostly in the skeletal muscle. CPK-2 level increases after three to six hours following a heart attack, peak within 12- 24 hours (or longer depending on the severity of the heart attack) and return to normal level 12 - 48 hours after tissue death. 8 Confirmation of heart attack when CK-MB is elevated and the ratio of CK-MB to total CK (relative index) greater than 2.5 - 3. 9 A hospital patient can be diagnosed with a normal electrocardiogram but have elevated creatinine phosphokinase (CPK-MB) elevation indicating a heart attack. 5

Chest pain (symptom) a sign of a heart attack, but attributed to congestive heart failure, angina or pulmonary embolism (blood clot in the lung.) does not usually cause CPK-2 level to increase. Certain drugs (Ampicillin, some anesthetics, aspirin, Clofibrate, Dexamethasone, Furosemide, and Morphine), illegal substances and alcohol could increase the level of CPK (creatinine phophokinase). 8 Also, kidney failure can elevate CPK-MB levels without having a heart attack. 9

Detection of a cardiac injury or heart attack is measured by the blood level bio-marker troponin (TNI - protein in the blood 11). 10 "Depending on the hospital, either troponin I or troponin T is measured, in general, both work equally well." 17 When more troponin is released into the blood correlates to a greater degree of damage to the heart muscle. 16 "Troponin values can remain high for 1 - 2 weeks after a heart attack." 14 According to American Heart Association recommends doctors focus on troponin test results more than test results of creatine-kinase-MB (CK-MB), as a "gold standard'' for blood tests measuring heart damage and prognosing long-term care. 19 Also, the American College of Cardiology and the European Society of Cardiology preference troponin over CK-MB (reported in 2001). 20 However, a study of 30,000 patients suspected of a heart attack and tested at hospital emergency room for both troponin and CK-MB. Eighteen percent of these patient tested high for troponin and low for CK-MB tended to get less aggressive treatment according to their physicians, who emphasized the CK-MB tests result more significantly. Lead researcher of the study Dr. Kristin Newby (cardiologist at Duke University Medical Center) says "are under treated patients at higher risk for a second heart attack." Dr. Niece Goldberg, a New York City cardiologist and an American Heart Association spokeswoman, suggests patients who are informed they have positive troponin or proteins in their blood should ask: "Am I getting an aspirin? Should I take a statin? Should I be on a beta-blocker?" Dr. Kristin Newby said regarding troponin blood test: "We know it does a better job at predicting who's going to have another heart attack or who's going to die after they have a heart attack." 19

During long term chemotherapy, troponin level increase as indication of heart damage, requiring medical attention.11 Forty percent of patients who have critical hilliness such as sepsis (Included among the symptoms of sepsis faster than normal heart rate attributed to body's response to an infection that causes symptoms to occur throughout the body 12).have increase level of troponin. Also, cardiotoxic affects from venomous snakes / scorpions and carbon monoxide poisoning (one third of the time) or cyanide poisoning increase the level of troponins due to cardiac injury. 13 However, troponin level can increase as result of strenuous exercise absent of any signs or symptoms of a heart attack, not requiring any medical attention most of the time. 14

In the United States more than nine million people have Angina Pectoris: Insufficient supply of blood and oxygen to the heart. Troponin test is recommended when symptoms of angina included chest pains get worse. Elevated level of Troponin indicates risk of heart attack or serious heart problems in the near future. 14

Drugs that are harmful to muscle, injections and accidents do not affect troponin levels. 14 However, heparin drug to treat angina or heart attack can interfere with Troponin tests, indicating a falsely high level. 18

"Some people who have a heart attack will have normal troponin concentrations, and some people with increased troponin concentrations have no apparent heart injury." 14 Also, when troponin is not detected does not conjecture no heart disease, only the non-existence of heart damage. 17

References:

1.) What is a Heart Attack? - http://www.nhlbi.nih.gov/health/dci/Diseases/HeartAttack/HeartAttack_WhatIs.html

2.) Question Regarding Cardiac enzymes in the diagnosis of heart attack - http://www.medicinenet.com/script/main/ques.asp?qakey=11823

3.) Heart Attack - http://www.medicinenet.com/heart_attack/article.htm

4.) What are the symptoms of a heart attack? - http://www.medicinenet.com/heart_attack/page2.htm

5.) Cardiac Enzymes - http://www.saheart.net/library/encyclo/enzyme.asp

6.) CPK - definition - http://adam.about.com/encyclopedia/CPK.htm

7.) CPK isoenzymes test - http://adam.about.com/encyclopedia/CPK-isoenzymes-test.htm

8.) CPK isoenzymes test - http://www.nlm.nih.gov/medlineplus/ency/article/003504.htm

9.) CK-MB - http://www.labtestsonline.org/understanding/analytes/ckmb/test.html

10.) Troponin: the biomaker of choice for the detection of cardiac injury - http://www.cmaj.ca/cgi/content/full/173/10/1191

11.) Protein marker troponin I predicts possible heart damage after chemotherapy - http://www.laleva.org/eng/2004/05/protein_marker_troponin_i_predicts_possible_heart_damage_after_chemotherapy.html

12.) Understanding sepsis - http://www.sepsis.com/family_friends/understanding.jsp?reqNavId=5.2

13.) Troponin Test - http://en.wikipedia.org/wiki/Troponin_test

14.) Troponins - http://www.labtestsonline.org/understanding/analytes/troponin/test.html

15.) Electrocardiogram - http://en.wikipedia.org/wiki/Electrocardiogram

16.) Blood - http://texasheart.org/HIC/Anatomy/blood.cfm

17.) New Blood Tests for Detecting Heart Disease - http://circ.ahajournals.org/cgi/content/full/109/3/e12

18.) Troponin Test - http://www.health.am/cardio/more/troponin_test/

19.) Heart Patients Undertreated in ER, Despite New Tests - http://www.statesman.com/health/content/shared-auto/healthnews/hatt/517849.html

20.) Revising the Definition of Heart Attack: Troponin New Leading Diagnostic- http://www.labtestsonline.org/news/troponin011221.html