Diagnostic Accuracy

Diagnostic Accuracy

Diagnosis and management of cardiac disease represents most important challenges to the present health care system, influencing a great number of patients every year. However, the accurate diagnosis of cardiac disease has been possible now by means of several important tests, including Exercise test, Routine Echo study, Coronary CT study, Stress Echo and Cardiac Catheterization. Additionally, early diagnosis of chest pain and assessment of risk for heart attacks can help prevent complications in the long run.

Exercise or stress testing is one of the simple yet well-established tests that have been in common clinical use for several decades. Exercise stress testing offers a less expensive, non-invasive technique of risk stratification before coronary angiography, and if it comes to be negative, then it may actually suggest avoiding angiography (Ellestad, 2003). Exercise testing has a specificity of 70% and a sensitivity of 78% for identifying any disease in the coronary artery. Therefore, it cannot be employed to diagnose ischaemic heart disease unless the chance of coronary artery disease is taken into consideration (Whaley, Brubaker, Otto and Armstrong, 2006).

Stress testing is often performed for an early assessment of patients with suspected heart disease, particularly coronary heart disease. Stress testing has been in use since the late 1920s as a suitable, non-invasive way to evaluate exercise induced myocardial ischemia (Master and Oppenheimer, 1929).  The myocardial oxygen demand is increased by the exercise increases and it may not be met when a stenosis of a coronary artery is present, leading to ischemia of the heart muscles. This is presented as a change in ST segment on the ECG, in addition to symptoms. ST segment depression is the most consistent indicator of ischaemia induced by exercise.  

Echocardiography, on the other hand, has raised the diagnostic precision of non-invasive cardiac assessment. It helps to monitor cardiac functions. By the help of sound waves Echocardiography differentiates body tissues of dissimilar density.  This test is required where there is complaint of heart murmur, heart attack, unexplained chest pains, congenital heart defect and rheumatic fever. It determines the shape and size of the heart along with how well it is working (Yong, Wu, Fernandes, Kopelen, Shimoni, Nagueh et al., 2002). It also helps to identify the problems with the heart’s valves and thrombosis formation within the vessels. A number of different types of echocardiography are performed nowadays, including Doppler echocardiography, M-mode echocardiography, Stress echocardiography, etc. The sensitivity and specificity of echocardiography are 80% and 100% with regard to ventricular dysfunction and heart failure respectively (Yong, Wu, Fernandes, Kopelen, Shimoni, Nagueh et al., 2002).

Stress echo usually involves the utilisation of Doppler and 2-D echocardiography to verify the doubt of coronary artery disease, and in case the disease is present, it helps to find out its severity (Elhendy, Windle and Porter, 2001). This test is carried out at rest and following pharmacological or physical stress and the images obtained are then compared with each other. It is performed as soon as the patient is asked to stop exercising in order take images of the heart functioning under stress. This test is harmless non-invasive and has rare complications. The results from echocardiography stress test are quite reliable.

Coronary computed tomography is a cardiac imaging test that assists in determining if thrombosis formed has constricted the coronary arteries of a patient (Hoffmann, Shi and Schmitz, 2005). Coronary arteries are the main blood vessels that supply blood to the heart. Thrombosis or plaque is composed of different substances present in the blood, for example calcium, cholesterol, and fat that deposit inside the arteries.

Computed tomography, also known as a CT scan, is a similar diagnostic test to conventional x-rays, but it generates numerous images of the inside of the body.  Coronary CT angiogram procedure utilizes intravenous dye containing iodine (Kuettner, Beck, Drosch, et al., 2005). Coronary CT serves as a major new test in the diagnosis of coronary artery disease. This test plays a great role in the diagnosing of diseases in patients with high risk of developing coronary disease, and in those patients who have undecided findings with treadmill or other medical testing (Achenbach, Giesler, Ropers,et al., 2001). The patients at high risk are usually cigarette smokers, diabetics, patients with high levels of cholesterol and hypertensive patients.

In case the CT scan comes out normal or shows only mildly abnormality, the chances of a severe obstruction of the coronary arteries decrease. On the other hand, if the CT scan is considerably abnormal, then the need of cardiac catheterization may occur, in order to see if stenting, angioplasty, or coronary bypass surgery is required.

A cardiac catheterization, also known as angiogram, is a procedure that helps to get the direct information of the patterns of blood flow and blood pressures within the heart. The catheterization is basically placing of small intravenous tubes in the artery and vein of a leg, neck or the arm (Leopold and Faxon, 2015). Via these intravenous tubes the thinner tubes, known as catheters, are passed into the circulation. This catheter is then moved slowly via the circulation so that it reaches the heart. From the heart it is then passed to certain chambers of the heart and to the arteries and veins joined to the heart. The pressures in the cardiac chambers can be measured.   Most of the time during this process of catheterization an angiogram is also carried out. This is performed by injecting a dye or contrast via the catheter into a chamber or a blood vessel of the heart.  As the dye is perceptible by X-ray, the blood flow through the heart is noted. Valves and blood vessels also become visible and evaluated for abnormalities. An angiogram needs much more X-rays compared to a simple chest X-ray’s need (Leopold and Faxon, 2015). Hence, the test is done only when there is an absolute indication. Nevertheless, a number of studies have been established no long-term adverse effects of angiography and cardiac catheterization in people who had undergone such tests.

Thus, a prompt and precise assessment of acute chest pain has enormous implications for morbidity and mortality of the patient as well as health care economics (Schillinger, Sodeck, Meron, Janata et al., 2004).  The majority of patients with chest pain in the emergency department have no bothersome electrocardiographic abnormalities, in addition to any history of coronary artery disease. Same is the case with Fed and this presents a little challenge to physicians. In this regard, for this particular patient, the most appropriate tests would be Echocardiography and Coronary CT. These tests are chosen because via echo the structure and function of heart of the patient can be evaluated and through Coronary CT the coronary arteries can be assessed. In this way, several causes of chest pain pertaining to heart can be indentified and excluded.

The principal goal of the assessment of patients with sudden chest pain in the emergency department is precise risk stratification and detection or exclusion of acute coronary syndromes, rather than the identification of coronary artery disease (Sun, Lin, Davidson, Dong et al., 2008). According to a research by Tong, Kaul, Wang et al (2005) echocardiography not only provides information regarding the shape and size of the heart but also reveals areas of scanty blood flow to the heart, regions of cardiac heart muscle not contracting normally, and preceding injury to the cardiac muscle as a result of poor blood flow. Overall, it gives a complete picture and is simple to detect the causes of chest pain by detecting poor flow of blood to the cardiac muscles.

Likewise, coronary CT approach helps established the immediate cause of chest pain i.e. acute coronary syndrome and also reveals cardiac problems in high risk patients as mentioned above.  A study by Laudon et al (2010) found cardiac coronary CT approach specific for the evaluation of possible acute coronary syndrome; the quantification of coronary artery calcium. The elevated the coronary artery calcium score, the greater the likelihood of an unstable plaque present in the coronary artery tree that may associate with a patient's chest pain. A studies by Chang, Choi, Choi, et al. (2008) and Goldstein, Gallagher, O'Neill, et al. (2007) stated that cardiac CT angiography facilitate early discharge of patients and also lower the cost than common standard assessment algorithms. Hoffmann U, Nagurney, Moselewski, et al. (2006) studied coronary CT angiography and found the 100% sensitivity for distinguishing acute coronary syndrome while the specificity found was 54%.

Conversely, other tests like Stress echo and stress testing require patient being stable and capable of undergoing a physical activity. Since Fred is in pain and has an arthritis and walk with the support of a cane, therefore he cannot undergo such testings. No doubt, stress testing is the first line diagnostic test, yet considering the condition of the patient, this test cannot be advised here.  It is his right to be comfortable while undergoing cardiac evaluation. Cardiac catheterization is little invasive and is not needed for now when non-invasive can help established the diagnosis. Furthermore, it is done when other factors or tests suggest that a person has chronic heart disease (Maron, Stone, Berman, Mancini, et al., 2011).

In Fred, the test will carried out with the following order. At First, the routine Echo study will be carried out in order to check the function and structure of the heart. It is better to go with the non-invasive first considering the condition of this patient (Sharples, Hughes, Crean, Dyer et al., 2007).  Following this coronary CT study will be conducted to determine the cause within the coronary arteries since the use of coronary calcium scoring via coronary CT is a first line testing approach for lower risk groups, as it is expected to be cost-effective.

The probable outcomes from echocardiography and coronary CT scan would be helpful for the detection of cause of chest pain associated with the heart. Patients with chest pain of sudden origin may have vague results from tests like ECG and thus needs not only functional imaging but further testing. Also, early testing has been shown to improve the health outcomes of the patients.  The most probable outcomes in Fred would be the detection of presence of areas of heart where blood supply is poor or presence of plaque or thrombosis in the coronary artery causing obstruction to blood flow and a chest pain. These tests will help in either detecting or excluding possible cause of chest pain related to heart. If the cause is linked to the problems in the heart, it can be easily detected via both of the selected tests. Since, the frequency of non-cardiac causes of chest pain is common too, these test will help to find whether the cause of chest pain is cardiac or non-cardiac.

References

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Chang SA, Choi SI, Choi EK, et al. Usefulness of 64-slice multidetector computed tomography as an initial diagnostic approach in patients with acute chest pain. Am Heart J. 2008;156:375-383 

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Goldstein JA, Gallagher MJ, O'Neill WW, et al. A randomized controlled trial of multi-slice coronary computed tomography for evaluation of acute chest pain. J Am Coll Cardiol. 2007;49:863-871 

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