Lab-and-imaging-cardio.pdf

Cardiac Diagnostic Evaluation Kristine A. Velasco, RN, UAE-RN, US- Diagnostic Evaluation A wide range of diagnostic studies may be performed in patients with cardiovascular conditions. The nurse should note trends in results because they provide information about diseases progr...

Cardiac Diagnostic Evaluation Kristine A. Velasco, RN, UAE-RN, US- Diagnostic Evaluation A wide range of diagnostic studies may be performed in patients with cardiovascular conditions. The nurse should note trends in results because they provide information about diseases progression as well as the patient’s response to therapy.  Laboratory Test To screen for risk factors associated with CAD To establish baseline values before initiating other diagnostic tests, procedures, or therapeutic interventions. Loading… To monitor response to therapeutic interventions To assess abnormalities in the blood that affect prognosis.  Cardiac Biomarker Analysis Diagnosis of MI is made by evaluating history and physical examination, 12 lead ECG and laboratory tests that measure serum cardiac biomarkers. Myocardial cells that becomes nevrotic from prolonged ischemia or trauma Release specific enzymes Creatinine Kinase (CK) CK isoenzymes (CK-MB) Proteins (myoglobin, troponin T and Troponin I)  Blood Chemistry, Hematology and Coagulation Studies Lipid Profile -cholesterol, triglycerides, and lipoproteins are measured to evaluate a person’s Risk of developing CAD, especially of there is a family history of premature heart Disease, or to diagnose a specific lipoprotein abnormality. Loading… Cholesterol Levels - is a lipid required for hormone synthesis and cell membrane formation. It is Found in large quantities in brain and nerve tissue. -total cholesterol level is calculated by adding the HDL, LDL and 20% of the Triglyceride level. Common Serum Laboratory Tests and Implications for Patients with Cardiovascular Disease Laboratory Tests Reference Implications Range Blood Chemistries Blood Urea Nitrogen (BUN) BUN and creatinine are end 8-20mg/dL products of protein metabolism excreted by the kidneys. Elevated BUN reflects reduced renal perfusion from decreased CO or intravascular fluid volume deficit as a result of diuretic therapy or dehydration. Laboratory Tests Implications Reference Range Calcium (Ca++) 8.8-10.4 Calcium is necessary for blood coagulability, mg/dL neuromuscular activity, and automaticity of the nodal cells (Sinus and atrioventricular nodes) Hypocalcemia : slows nodal function and impair myocardial contractility. The latter effect increases the risk for heart failure. Hypercalcemia: Increased calcium levels can occur with the administration of thiazide diuretics because these medications reduce renal excretion of calcium. Hypercalcemia potentiates digitalis toxicity, causes increased myocardial contractility, and increases the risk for varying degrees of heart block and sudden death from ventricular fibrillation. Laboratory Tests Implications Reference Range Creatinine Both BUN and creatinine are used to Male: 0.6-1.2mg/dL assess renal function, although Female: 0.4- creatinine is a more sensitive measure. 1.0mg/dL Renal impairment is detected by an increase in both BUN and creatinine. A normal creatinine level and an elevated BUN suggest an intravascular fluid volume deficit. Laboratory Tests Reference Implications Range Magnesium (Mg++): 1.8- Magnesium is necessary for the absorption of calcium, 2.6mg/dL maintenance of potassium stores, and metabolism of adenosine triphosphate. It plays a major role in protein and carbohydrate synthesis and muscular contraction. Hypomagnesemia: due to enhanced renal excretion of magnesium levels are due to enhanced renal excretion of magnesium from the use of diuretic or digitalis therapy. Low magnesium levels predispose patients to atrial or ventricular tachycardias. Hypermagnesemia: commonly caused by the use of cathartics or antacids containing magnesium. Increased magnesium levels depress contractility and excitability of the myocardium, causing heart block and if severe, asystole. Laboratory Tests Reference Range Implications Potassium (K+) : 3.5- Potassium has a major role in cardiac electrophysiologic 5mEq/L function. Hypokalemia: decreased potassium levels due to administration of potassium-excreting diuretics can cause many forms of arrythmias, including life-threatening ventricular tachycardia or ventricular fibrillation, and Loading… predispose patients taking digitalis preparations to digitalis toxicity. Hyperkalemia: increased potassium levels can result from an increased intake of potassium, decreased renal excretion of potassium, the use of potassium-sparing diuretics (e.g. spironolactone) or the use of angiotensin-converting enzyme inhibitors that inhibit aldosterone function. Serious consequences of hyperkalemia include heart block, asystole, and life-threatening ventricular arrhythmias. Laboratory Tests Reference Range Implications Sodium (Na+) 135-145mEq/L Low or high serum sodium levels do not directly affect cardiac function. Hyponatremia: decreased sodium levels indicate fluid excess and can be caused by heart failure or administration of thiazide diuretics. Hypernatremia: increased sodium levels indicate fluid deficits and can result from decreased water intake or loss of water through excessive sweating and diarrhea. Laboratory Tests Implications Reference Range Coagulation Studies Injury to a vessel wall or tissue initiates the formation of a thrombus. This injury activates the coagulation cascade, the complex interactions among phospholipids, calcium and clotting factors that convert prothrombin to thrombin. The coagulation cascade has two pathways: the intrinsic and extrinsic pathways. Coagulation studies are routinely performed before invasive procedures, such as cardiac catheterization, electrophysiology testing and cardiac surgery. Laboratory Tests Reference Range Implications Activated partial thromboplastin time aPTT measures the activity of the (aPTT) intrinsic pathway and is used to Lower limit of normal 21-35s assess the effects of unfractionated heparin. A therapeutic range is 1.5- 2.5 times baseline values. Adjusment of heparin dose is required for aPTT 100s (decrease dose) Lower limit of normal 11-13s PT measures the extrinsic pathway activity and is used to monitor the level of anticoagulation with warfarin. Laboratory Tests Implications Reference Range International Normalized Ratio The INR, reported with the PT, (INR) provides a standard method for 0.8-1.2 reporting PT levels and Therapeutic range INR 2-3.5, eliminates the variation of PT although specific ranges vary results from different based on diagnosis. laboratories. The INR, rather than the PT alone, is used to monitor the effectiveness of warfarin. Laboratory Tests Reference Implications Range Complete blood count (CBC) The CBC identifies the total number of white and red blood cells and platelets, and measures hemoglobin and hematocrit. The CBC is carefully monitored in patients with cardiovascular disease. Laboratory Tests Implications Reference Range Hematocrit The hematocrit represents the Male: 42-52% percentage of red blood cells Female: 36-48% found in 100mL of whole blood. The red blood cells contain hemoglobin, which transports oxygen to the cells. Laboratory Tests Implications Reference Range Hemoglobin Low hemoglobin and hematocrit Male: 14-17.4g/dL levels have serious consequences Female: 12-16 g/dL for patients with cardiovascular disease, such as more frequent angina episodes or acute myocardial infarction. Laboratory Tests Implications Reference Range Platelets : 140,000- Platelets are the first line of protection 400,000/mm3 against bleeding. Once activated by blood vessel wall injury or rupture of atherosclerotic plaque, platelets undergo chemical changes that form a thrombus. Several medications inhibit platelet functions, including aspirin, clopidogrel, and IV glycoprotein Iib/IIIa inhibitors (abciximab, eptifibatide and tirofiban). When these medications are given, it is essential to monitor from thrombocytopenia (low Laboratory Tests Reference Implications Range White Blood cell (WBC) count WBC Counts are monitored in 4500-11,000/mm3 patients who are immunocompromised, including patients with heart transplants or in situations where there is concern for infection (e. g. after invasive procedures or surgery) Triglycerides -composed of 3 fatty acids and glycerol, are stored in the adipose tissue and are source of energy. Triglyceride levels increase after meals and are affected by stress. Diabetes, alcohol use and obesity can elevate Triglyceride levels. These levels have a direct correlation with LDL and an inverse one with HDL. Brain (B-type) Natriuretic Peptide (BNP) - is a neurohormone that helps regulate BP and fluid volume. BNP levels are useful for prompt diagnosis Of heart failure. Elevations in BNP can occur from a number of other condition such as pulmonary embolus, MI, And ventricular hypertrophy.  C-Reactive Protein -produced by the liver in response to systemic inflammation. Homocysteine - An amino acid, linked to the development of atherosclerosis because it can damage the endothelial lining of Arteries and promote thrombus formation. Chest Xray and Fluoroscopy Chest X-ray – obtained to determine the size, contour and position of the heart. -reveals cardiac and pericardial calcifications and demonstrates physiologic alterations in the pulmonary circulation. Fluoroscopy – is an X-ray imaging technique that allows a visualization of the heart on the screen. Electrocardiography The ECG is a graphic representation of the electrical currents of the heart. Several different recordings can be obtained by using a variety of electrode combinations, Called Leads. The standard ECG is composed of 12 leads or 12 different views, although it is possible To record 15 to 18 leads. 12 leads ECG – diagnose arrhythmias, conduction abnormalities and chamber enlargement, as Well as myocardial ischemia, injury or infarction. 15 leads ECG – adds 3 additional chest leads across the right precordium and is used for early Diagnosis of right ventricular and left posterior (ventricular) infarction. 18 leads ECG – useful for early detection if myocardial ischemia and injury.  Continuous Electrocardiographic Monitoring Monitor more than one ECG lead simultaneously Monitor ST segment Provide graded visual and audible alarms Interpret and store alarms. Trend data over time. Print a copy of rhythms from one or more specific ECG leads over a set time Ambulatory ECG -continuous or intermittent ECG Home monitoring. RA –Right arm (White) LA – Left arm (Black) RL – Right leg (Green) LL – Left leg (red) V1 – chest or precordium (brown)  Holter Monitors -records all ECG activity using 2 or more leads onto a digital memory device. Patients usually wear it for 24 to 48 hours. Loading…  Cardiac Stress Testing - the coronary artery dilate to four times their usual diameter in response to increased metabolic demands for oxygen and nutrients. Therefore, abnormalities in cardiovascular function are more likely to be detected during times of increased oxygen demand or “stress” The Exercise test Pharmacologic stress test Radionucleotide Imaging Pharmacologic Stress Testing Patient who are cognitively impaired and unable to follow or physically disabled or deconditioned will not be able to achieve their target heart rate by exercising on a treadmill or bicycle. Nursing Interventions -instruct patient not to eat or drink anything atleast 3 hours before the test. -patient must be instructed to avoid stimulant foods, drinks and medications. -stress test may take about 1 hour or up to 3 hours if imaging is performed. Myocardial Perfusion Imaging Myocardial perfusion imaging is performed using two types of techniques: single photon emission computed tomography (SPECT) or positron emission tomography (PET). It is commonly performed after an acute MI to determine if arterial perfusion to the heart is compromised during activity and to evaluate the extent of myocardial damage. It is also used to evaluate if myocardial ischemia from CAD is the cause of chest pain or other CAD-related symptoms. These imaging techniques are performed in combination with stress testing to compare images obtained when the heart is resting to images of the heart in a stressed state resulting from exercise or medications. Single Photon Emission Computed Tomography SPECT is widely available and is the most common technique of myocardial perfusion imaging. In addition, the ability of SPECT to detect myocardial ischemia is between 80% and 90% (King, 2017). Procedure SPECT is a painless, noninvasive procedure that involves the injection of the nuclear medicine radionucleotide (technetium-99m [99mT]; rubidium-82) and imaging. During SPECT, patients are positioned supine on the table with their arms over their heads. Positron Emission Tomography PET is another noninvasive procedure in which a radioactive tracer chemical is administered to the patient and images are obtained. These images generally have a higher resolution compared to SPECT. Test of Ventricular Function and Wall Motion Equilibrium radionuclide angiocardiography (ERNA), also known as multiple-gated acquisition (MUGA) scanning, is a common noninvasive technique that uses a conventional scintillation camera interfaced with a computer to record images of the heart during several hundred heartbeats. The computer processes the data and allows for sequential viewing of the functioning heart. The sequential images are analyzed to evaluate left ventricular function, wall motion, and ejection fraction. Computed Tomography Procedure Cardiac CT scanning is a form of cardiac imaging that uses x-rays to provide accurate cross-sectional "virtual" slices of specific areas of the heart and surrounding structures. Two types of cardiac CT scanning include coronary CT angiography and electron beam CT (EBCT) (for coronary calcium scoring). Coronary CT angiography requires the use of an IV contrast agent to enhance the x-rays and improve visualization of cardiac structures. This test is used to evaluate coronary arteries for stenosis, the aorta for aneurysms or dissections, graft patency after coronary artery bypass grafting, pulmonary veins in patients with atrial fibrillation, and cardiac structures for congenital anomalies. Patients may receive beta-blockers prior to the scan to control heart rate and rhythm and reduce artifact. Another way to minimize artifact is to have patients hold their breath periodically throughout the scan. Coronary CT angiography is used with caution in patients with renal insufficiency. Magnetic Resonance Angiography Procedure MRA is a noninvasive, painless technique that is used to examine both the physiologic and anatomic properties of the heart. MRA uses a powerful magnetic field and computer-generated pictures to image the heart and great vessels. It is valuable in diagnosing diseases of the aorta, heart muscle, and pericardium, as well as congenital heart lesions. Echocardiography Transthoracic Echocardiography Echocardiography is a noninvasive ultrasound test that is used to measure the ejection fraction and examine the size, shape, and motion of cardiac structures. It is particularly useful for diagnosing pericardial effusions; determining chamber size and the etiology of heart murmurs; evaluating the function of heart valves, including prosthetic heart valves; and evaluating ventricular wall motion. Procedure Echocardiography involves transmission of high-frequency sound waves into the heart through the chest wall and the recording of the return signals. With the traditional transthoracic approach, the ultrasound is generated by a handheld transducer applied to the front of the chest. The transducer picks up the echoes and converts them to electrical impulses that are recorded and displayed on a monitor. It creates sophisticated, spatially correct images of the heart. Transesophageal Echocardiography Procedure A significant limitation of transthoracic echocardiography is the poor quality of the images produced. Ultrasound loses its clarity as it passes through tissue, lung, and bone. An alternative technique involves threading a small transducer through the mouth and into the esophagus. This technique, called transesophageal echocardiography (TEE), provides clearer images because ultrasound waves pass through less tissue. A topical anesthetic agent and sedation are used during TEE because of the discomfort associated with the positioning of the transducer in the esophagus Cardiac Catheterization Cardiac catheterization is a common invasive procedure used to diagnose structural and functional diseases of the heart and great vessels. This procedure involves the percutaneous insertion of radiopaque catheters into a large vein and an artery. Fluoroscopy is used to guide the advancement of the catheters through the right and left heart, referred to as right and left heart catheterizations, respectively In preparation for the procedure, patients have blood tests performed to evaluate metabolic function (electrolytes and glucose) and renal function (blood urea nitrogen and creatinine level). Baseline coagulation studies (activated partial thromboplastin time [aPTT], international normalized ratio [INR], and prothrombin time [PT]) are obtained to guide dosing of anticoagulation during the procedure. Electrophysiologic Testing The electrophysiology study (EPS) is an invasive procedure that plays a major role in the diagnosis and management of serious arrhythmias. EPS may be indicated for patients with syncope, palpitations, or both, and for survivors of cardiac arrest from ventricular fibrillation (sudden cardiac death) EPS is used to distinguish atrial from ventricular tachycardias when the determination cannot be made from the 12-lead ECG; to evaluate how readily a life-threatening arrhythmia (e.g., ventricular tachycardia, ventricular fibrillation) can be induced; to evaluate AV node function; to evaluate the effectiveness of antiarrhythmic medications in suppressing the arrhythmia; or to determine the need for other therapeutic interventions, such as a cardiac implantable electronic device, or radiofrequency ablation. Central Venous Pressure Monitoring CVP is a measurement of the pressure in the vena cava or right atrium. The pressure in the vena cava, right atrium, and right ventricle is equal at the end of diastole; thus, the CVP also reflects the filling pressure of the right ventricle (preload). The normal CVP is 2 to 6 mm Hg. It is measured by positioning a catheter in the vena cava or right atrium and connecting it to a pressure monitoring system. The CVP is most valuable when it is monitored over time and correlated with the patient's clinical status. A CVP greater than 6 mm Hg indicates an elevated right ventricular preload. Pulmonary Artery Pressure Monitoring Pulmonary artery pressure monitoring is used in critical care for assessing left ventricular function, diagnosing the etiology of shock, and evaluating the patient's response to medical interventions (e.g., fluid administration, vasoactive medications). A pulmonary artery catheter and a pressure monitoring system are used. A variety of catheters are available for cardiac pacing, oximetry, cardiac output measurement, or a combination of functions. Pulmonary artery catheters are balloon-tipped, flow-directed catheters that have distal and proximal lumens (Fig. 21-11). The distal lumen has a port that opens into the pulmonary artery. Once connected by its hub to the pressure monitoring system, it is used only to continuously measure pulmonary artery pressures. The proximal lumen has a port that opens into the right atrium. It is used to administer IV medications and fluids or to monitor right atrial pressures (i.e., CVP). Each catheter has a balloon inflation hub and valve. A syringe is connected to the hub, which is used to inflate or deflate the balloon. Intra-Arterial Blood Pressure Monitoring is used to obtain direct and continuous BP measurements in critically ill patients who have severe hypertension or hypotension. Arterial catheters are also useful when arterial blood gas measurements and blood samples need to be obtained frequently. The radial artery is the usual site selected. However, placement of a catheter into the radial artery can further impede perfusion to an area that has poor circulation. As a result, the tissue distal to the cannulated artery can become ischemic or necrotic. Patients with diabetes, peripheral vascular disease, or hypotension, receiving IV vasopressors, or having had previous surgery are at highest risk for this complication. Before arterial line insertion, two tests may be considered to assess circulation; namely, a Doppler ultrasound or a modified Allen's test. A Doppler ultrasound assesses blood flow of the artery. The modified Allen's test assesses collateral circulation. To perform the Allen's test, the patient's hand is elevated and the patient is asked to make a fist. The nurse compresses the radial and ulnar arteries simultaneously, causing the hand to blanch. After the patient opens the fist, the nurse releases the pressure on the ulnar artery. If blood flow is restored (hand turns pink) within 7 seconds, the circulation to the hand may be adequate enough to tolerate placement of a radial artery catheter.