Cardiac diagnostics demystified
The nurse is involved in the patient’s care before, during, and after many diagnostic studies. So guess what that means...yep, it is going to be on your exams! In addition to ensuring patient safety during these studies, it’s also important to be able to accurately interpret the results of certain diagnostic tests. In this post, we learn about some of the most commonly ordered cardiac diagnostic tests including their purposes, nursing care, and interpretation of critical results. For a complete EKG review, visit the resources section and scroll down to Med-Surg...We're going to kick this post off by talking about echocardiograms.
Echocardiogram (Echo)
Echocardiograms use ultrasound technology to evaluate cardiac structure and mobility, in particular the cardiac valves. An echo may be ordered to aid in the diagnosis of cardiomyopathy, valve disorders, pericardial effusion, left ventricular dysfunction, aneurysms, and cardiac tumors. Echos will also estimate ejection fraction (left ventricular function), which is the percentage of blood that leaves the left ventricle with each beat. Ejection fraction normally falls between 55-75%; an ejection fraction less than 40% indicates a degree of heart failure.
There are basically two types of echocardiograms: transthoracic and trans-esophageal (TEE). A transthoracic echo is non-invasive and is performed by an ultrasound technician. During a transthoracic echo, measurements are taken of heart chamber size and flow across the valves. While there is no specific nursing care involved with this type of echo, TEEs are invasive and require extensive nursing assessment and intervention. Informed consent is required prior to the procedure. For this test, the transducer is at the end of a probe that the provider will insert through the mouth down into the esophagus to get clear pictures of the heart. TEEs provide much more accurate and detailed information about the chambers and valves, and are very useful in the diagnosis of endocarditis, aortic aneurysms, and cardiac tumors. A TEE will also be ordered if a provider suspects the presence of a blood clot in the atria due to atrial fibrillation. Treatment for atrial fibrillation may include synchronized cardioversion, but cardioversion cannot be performed if there is a clot present. Nursing care prior to a TEE includes screening the patient for a history of drug allergies, problems related to conscious sedation, esophageal disease or surgery, or difficulty swallowing. Evaluate labs including coagulation studies such as PT, aPTT, and INR. Ensure that the patient has been NPO and that the patient has adequate IV access that will be required for sedation. The nurse will assist the provider by administering sedation as ordered, keeping the patient calm, and suctioning as needed. Vital signs including O2 saturation are monitored closely during the procedure. Following a TEE, it is essential that the patient’s ability to swallow is assessed before the patient is allowed to eat or drink.
Stress Test
The provider will order a stress test when a patient is suspected to have coronary artery disease as evidenced by reports of chest pain, dyspnea, positive cardiac enzymes, and/or dysrhythmias. There are various forms of stress tests, including exercise stress tests, pharmacologic stress tests, stress echocardiograms, and nuclear stress tests. An exercise stress test involves the patient using a treadmill or stationary bike at increasing levels of difficulty while the heart’s response is monitored via ECG, heart rate, and blood pressure. Intense activity causes the release of epinephrine and norepinephrine, which is a powerful vasoconstrictor. If coronary artery disease is present, ischemia will manifest on the ECG tracing. If a patient is unable to exercise, dobutamine or adenosine may be used as an alternative because these medications mimic the heart’s response to exercise. Dobutamine increases heart rate, stroke volume, and cardiac output just as intense exercise does. Adenosine is a powerful vasodilator that will increase blood flow in normal coronary arteries but would reveal no change in flow in clogged arteries. Echocardiography may be used in addition to exercise or pharmacologic stress testing for patients who have abnormal ECG findings at rest. If an echo is used during stress testing, it is performed before exercise begins and then again immediately after exercise is complete. Both exercise and pharmacologic stress testing can be used in conjunction with intravenous injection of a radiopharmaceutical medication, which is referred to as a nuclear stress test. Nuclear imaging studies involve the injection of a radiopharmaceutical agent first and a scan of the heart is taken while the patient is at rest. After the at rest scan, the heart is stressed and a second injection is given. After about 30 minutes, another scan is taken and compared with the at rest scan. Normal vessels will vasodilate and take up a large amount of the radiopharmaceutical. Vessels that do not accept the agent are considered stenotic and this is referred to as a perfusion defect which indicates ischemia. Nursing considerations before stress tests include ensuring that ACLS equipment is available and obtaining a baseline history and physical assessment including medications. Baseline vital signs are also obtained. Nurses should educate patients to stop any medications that could prevent them from reaching the target heart rate. These medications include beta blockers, calcium channel blockers, and digoxin and should be held for at least 24 hours prior to testing. Patients should be NPO for at least 4 hours prior to testing. In general, caffeine should also be avoided for at least 12 hours prior to testing.
I hope you all have found this post helpful and would love to hear your thoughts or answer any questions you may have! Thanks so much for reading!
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