Tests and diagnosis of Ischaemic Heart Disease
Medical history. The first step in diagnosing Ischaemic Heart Disease derives from an interview with your doctor. Your doctor will first evaluate the presence of any cardiovascular risk factors: family history, whether you smoke, the presence of diseases associated with ischaemic cardiomyopathy, such as diabetes, high blood pressure or high cholesterol levels.
Secondly, your doctor will identify the characteristics of any pain by determining whether it is a restrictive or a stabbing feeling, is associated with physical effort or a certain position, is associated with nausea or a shortness of breath, or it radiates towards the shoulders, jaw or back. The combined information taken from both sections of the interview is used to determine whether the patient has Ischaemic Heart Disease and to select the most suitable tests to confirm the diagnosis.
Electrocardiogram. An electrocardiogram employs some conductive patches (electrodes) stuck to the skin to record the heart’s electrical activity. The cells in a diseased heart do not conduct electricity normally; patients with an infarction tend to produce an atypical electrocardiogram tracing. Electrocardiograms also reveal any scar tissue from previous infarctions or the presence of an arrhythmia. Nevertheless, it is important to realise that not all heart problems are reflected in an electrocardiogram. Angina can only be detected if the test is performed while the patient experiences the chest pain. Nor does an electrocardiogram provide any information about the state of the valves or the size of the heart.
Blood analysis. A heart attack causes certain proteins (troponins) to be released from the heart and into the blood stream. It sometimes takes several hours before these proteins can be detected in a blood sample so the analysis must be repeated after six hours.
Chest X-ray. Chest X-rays help estimate the size of the heart and the great vessels, as well as the condition of the lungs. They can provide guidance regarding the presence of fluid in the lungs and help rule out other causes of chest pain, such as pneumonia.
Echocardiography or echocardiogram. Doctors use ultrasound to visualise the heart’s size, shape and movement on a screen. The technique does not provide a view of the arteries, so we cannot tell whether or not they are obstructed, but it does provide very important information regarding heart function. If the patient has suffered a large infarction the damaged area of the heart will move abnormally. Hence ultrasound can be used to estimate the size of an infarction and its repercussions on the heart muscle. It also helps us determine whether the valves are working correctly or if there are any other complications secondary to the heart attack.
Cardiac stress test or ergometry. If there are doubts as to whether or not the patient’s chest pain is due to a lack of blood supply reaching an area of the heart, then the best option is to carry out a stress test. It consists of recording an electrocardiogram while the patient reaches ever-increasing levels of physical strain at programmed intensities. The test can be conducted on a treadmill (the speed and slope are both increased progressively) or a stationary exercise bike (in which case the resistance increases gradually). Patients who cannot exert themselves physically can be administered medicines that exercise the heart without having to move the rest of the body.
The patient’s response to this stress is observed throughout the test: do they experience any pain, what are the effects on blood pressure and pulse, or are there any alterations on the electrocardiogram indicating a lack of coronary blood supply? The stress electrocardiogram trace can be combined with imaging studies in order to increase the test’s diagnostic accuracy.
Some of the stress tests performed in combination with imaging studies are: Myocardial perfusion single-photon emission computed tomography (SPECT) or a heart scan, Stress echocardiogram, Echocardiogram with dobutamine or Cardiac magnetic resonance with adenosine or dobutamine.
Coronary computed tomography (coronary CT). To carry out a coronary CT, the patient lies on a table that enters into a tomography machine or scanner. The machine uses X-rays to collect images of the heart, these can subsequently be used to determine the degree of obstruction in the coronary arteries. To produce reliable images, the patient must not have a lot of calcium in their arteries. Furthermore, the heart needs to be beating slowly in order to gather the images, so patients are sometimes administered a medicine to decrease their heart rate before undergoing the scan.
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