Elevated levels of CK-MB reliably indicate acute MI.³ Generally, CK-MB levels rise about 3 to 6 hours after the onset of acute MI, peak after about 12 to 18 hours, and may remain elevated for up to 72 hours. Normal CK levels are 38 to 190 units/L for men and 10 to 150 units/L for women. Remember, CK normal values are always laboratory specific so there can be a slight deviation of the normal values provided here from the normal values of your laboratory.

Rising myoglobin levels may be the first marker of cardiac injury after acute MI. Levels may rise within 30 minutes to 4 hours, peak within 6 to 7 hours, and return to baseline by 24 hours. However, because skeletal muscle damage may also cause myoglobin levels to rise, other tests (such as CK-MB or troponin) may be required to determine myocardial injury.³

Troponin levels rise within 3 to 6 hours after myocardial damage. Troponin I peaks in 14 to 20 hours, with a return to baseline in 5 to 7 days, and troponin T peaks in 12 to 24 hours, with a return to baseline in 10 to 15 days. Because troponin levels stay elevated for a prolonged time, they can detect an infarction that occurred
several days earlier. Troponin T levels can be determined at the bedside in minutes, making them a useful tool for determining treatment in acute MI.

• Perform a venipuncture; collect the sample in a 5-ml tube containing EDTA.

• Send the sample to the laboratory immediately to be frozen in a plastic vial on dry ice.

• If a hematoma develops at the venipuncture site, apply warm soaks to help ease discomfort.

• Perform a venipuncture and collect the sample in a 5-ml nonanticoagulated tube.

• If a hematoma develops at the venipuncture site, apply warm soaks to help ease discomfort.

A BNP test helps accurately diagnose and grade the severity of heart failure. A quick diagnosis of heart failure in patients who present with dyspnea is important in order to begin appropriate treatment early.

A result greater than 100 pg/ml is abnormal. The higher the number, the more likely heart failure is present and the more severe it is. Patients in renal failure, on dialysis, or waiting for dialysis may have elevated levels whether or not heart failure is present. As a result, the BNP assay is not useful in renal failure patients. Patients with right-sided heart failure (due to pulmonary hypertension, cor pulmonale, or pulmonary emboli) also have elevated levels (usually 300 to 400 pg/ml).¹,⁶

Triglyceride values less than 150 mg/dl are widely accepted as normal.

Triglyceride levels between 150 and 199 mg/dl are considered borderline high. Levels between 200 and 499 mg/dl are considered high. Levels greater than 500 mg/dl are very high.

Measuring cholesterol may also be necessary, because cholesterol and triglyceride levels vary independently. If both triglyceride and cholesterol levels are high, the patient is at risk for CAD.

For adults, a desirable cholesterol level is less than 200 mg/dl. Levels are considered borderline high if they’re between 200 and 240 mg/dl and high if they’re greater than 240 mg/dl.⁷

For children ages 12 to 18, desirable levels are less than 170 mg/dl. Levels are considered high if they’re greater than 200 mg/dl.

HDL level is inversely related to the risk of CAD—that is, the higher the HDL level, the lower the incidence of CAD. For males, normal HDL values range from 37 to 70 mg/dl; in females, from 40 to 85 mg/dl.

Conversely, the higher the LDL level, the higher the incidence of CAD. For individuals who don’t have CAD, desirable LDL levels are less than 130 mg/dl, borderline high levels are in the range of 130 to 159 mg/dl, and high levels are more than 160 mg/dl. For individuals who have CAD, optimal levels are less than 100 mg/dl, and higher than optimal levels are more than 100 mg/dl.

• Tell the patient receiving heparin therapy that this test may be repeated at regular intervals to assess response to treatment.

• Perform a venipuncture and collect the sample in a 7-ml tube containing sodium citrate.

• Completely fill the collection tube, invert it gently several times, and send it to the laboratory on ice.

• For a patient on anticoagulant therapy, additional pressure may be needed at the venipuncture site to control bleeding.

The PT test is an excellent screening procedure for overall evaluation of extrinsic coagulation factors V, VII, and X and of prothrombin and fibrinogen. It’s also the test of choice for monitoring oral anticoagulant therapy.

Normally, PT ranges from 10 to 14 seconds. In a patient receiving warfarin (Coumadin) therapy, the goal of treatment is to attain
a PT level 1.5 to 2 times the normal control value—for example, a level of 15 to 20 seconds. (See Understanding the INR.)

Foods rich in vitamin K include beef liver, broccoli, Brussels sprouts, cabbage, collard greens, endive, kale, lettuce, mustard greens, parsley, soy beans, spinach, Swiss chard, turnip greens, watercress, and other green leafy vegetables. Moderate to high levels of vitamin K are also found in other foods such as asparagus, avocados, dill pickles, green peas, green tea, canola oil, margarine, mayonnaise, olive oil, and soybean oil. The diet in general should remain consistent, as other foods containing little or no vitamin K such as mangos and soy milk have been reported to interact with warfarin. Patients should also consider avoiding or limiting the consumption of cranberry juice, pomegranate juice, black currant juice, and black currant seed oil.

This test is commonly performed during procedures that require extracorporeal (occurring outside the body) circulation, such as cardiopulmonary bypass, ultrafiltration, hemodialysis, and extracorporeal membrane oxygenation. It is also commonly used in cardiac and radiological invasive procedures such as stent angioplasty or ablations.

The standard 12-lead ECG uses a series of electrodes placed on the patient’s extremities and chest wall to assess the heart from 12 different views (leads). The 12 leads include three bipolar limb leads (I, II, and III), three unipolar augmented limb leads (aV_R, aV_L, and aV_F), and six unipolar precordial limb leads (V₁ to V₆). The limb leads and augmented leads show the heart from the frontal plane. The precordial leads show the heart from the horizontal plane.

ECG can be used to identify myocardial ischemia and infarction, rhythm and conduction disturbances, chamber enlargement, electrolyte imbalances, and drug toxicity.

• P waves should be upright; however, they may be inverted in lead aV_R or biphasic or inverted in leads III, aV_L, and V₁.

• PR intervals should always be constant, like QRS-complex durations.

• QRS-complex deflections vary in different leads. Observe for pathologic Q waves, which are defined as one-third the height of the R wave and must be present in contiguous or groups of leads representing the different walls of the heart.

• ST segments should be isoelectric or have minimal deviation.

• ST-segment elevation greater than 1 mm above the baseline and ST-segment depression greater than 0.5 mm below the baseline are considered abnormal and must be present in contiguous leads. Leads facing toward an injured area have ST-segment elevations, and leads facing away show ST-segment depressions.

• The T wave normally deflects upward in leads I, II, and V₃ through V₆. It’s inverted in lead aV_R and variable in the other leads. T-wave changes have many causes and aren’t always a reason for alarm. Excessively tall, flat, or inverted T waves occurring with such symptoms as chest pain may indicate ischemia.

• A normal Q wave generally has a duration less than 0.04 second. An abnormal Q wave has a duration of 0.04 second or more, a depth greater than 4 mm, or a height one-fourth of the R wave.



Abnormal Q waves indicate myocardial necrosis, developing when depolarization can’t follow its normal path because of damaged tissue in the area.

• Remember that aV_R normally has a large Q wave, so disregard this lead when searching for abnormal Q waves.