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Predicting Heart Failure. Группа авторов
Читать онлайн.Название Predicting Heart Failure
Год выпуска 0
isbn 9781119813033
Автор произведения Группа авторов
Жанр Медицина
Издательство John Wiley & Sons Limited
2.2.3 Auscultation Examination
Auscultation means listening carefully to the heart sounds or murmurs through a stethoscope. The stethoscope tool consists of two parts: the bell and the diaphragm. Each part has its particular features, with the bell focusing on low-pitched sounds and detecting murmurs of aortic valve stenosis or carotid bruits, and the diaphragm focusing on high-pitched sounds that can detect valve closures or systolic clicks. During auscultation examination, the physician makes the patient lie in four different positions (shown in Figure 2.1): supine, upright, left lateral decubitus, and upright leaning forward [2]. The physician should be looking for irregular murmurs or heart sounds and identifying their location, duration, intensity, and pitch. This will all help in diagnosing heart conditions. Although irregular murmurs or heart sounds are not always linked with underlying heart conditions, they can, however, in certain conditions be an early warning of heart diseases.
Figure 2.1 Supine, left lateral decubitus, upright, and upright leaning forward positions.
2.2.4 Electrocardiogram (ECG)
This ECG is generated by a method called electrocardiography, where several electrodes are placed on the patient’s heart, legs, and arms and monitor the pulses for around 10 minutes. The technique measures the electrical activity of each heartbeat resulting in an electrocardiogram that shows the heart’s functionality. The electrocardiogram generated during the electrocardiography technique is a graph that depicts the characteristic of voltage versus time of the heart’s electrical activity. During each cardiac cycle, these electrodes detect the minor electrical changes that occur as a result of cardiac muscle depolarization and repolarization. Several cardiac anomalies, such as cardiac rhythm disruptions (e.g. atrial fibrillation and ventricular tachycardia), insufficient coronary artery blood flow (e.g. myocardial ischemia and myocardial infarction), and electrolyte disturbances (e.g. hypokalemia and hyperkalemia) cause changes in the usual ECG pattern. An illustration of the ECG test is shown in Figure 2.2. An ECG test is required only if the patient has any risk factors, such as hypertension, or physical discomforts, such as angina or palpitations including irregular heartbeats or rapid heartbeats. Patients with an existing history of heart disease are required to do the ECG test. Moreover, healthy individuals with a family history of heart disease are advised to do the ECG test if they are going to begin any heavy exercise routine or heavy labor routine.
Figure 2.2 ECG. E denotes electrodes placed for detecting the small electrical changes induced by cardiac muscle depolarization. The graph of voltage versus time of the heart’s electrical activity is showing in the ECG monitor. A physician/nurse is assigned to supervise the ECG test.
The major waves of a single ECG pattern and the normal values of ECG signals for normal heart rate are given in Figure 2.3. Arrhythmia is detected by verifying against the intervals shown in the table.
Figure 2.3 Major waves of a single ECG signal and the normal values of ECG signals.
2.2.5 Treadmill Test
The treadmill test is done by making patients walk briskly on a treadmill, which makes their hearts pump fast. The treadmill test is conducted to identify how well the heart of a patient handles their work and exercise capacity. During the test session, the heart rhythm, breathing, and blood pressure of the patient are monitored to detect abnormalities. The test is normally done after detecting signs or symptoms of coronary heart disease. It can assist the physician in understanding the severity of heart disease. Generally, the treadmill test is safe and devoid of any risks. However, patients suffering from low blood pressure can feel dizzy or faint due to the impact of the exercise. Figure 2.4 shows a patient running on a treadmill under the supervision of a nurse; their blood pressure is being monitored as is their heart rate via ECG electrodes placed on their chest.
Figure 2.4 Treadmill assessment.
A treadmill test is required for individuals who have been experiencing angina or other heart disease symptoms. Specifically, the treadmill test is preferred for patients with symptoms of myocardial ischemia, acute chest pain, valvular heart disease, etc. Moreover, the treadmill test is preferred for patients with cardiac arrhythmias to evaluate the chronotropic competence.
Chronotropic competence is the capability of the heart to raise its rate when the body demands or during increased activity. The purpose of the test is to determine whether the patient’s heart is receiving enough oxygen as well as proper blood flow under stressed conditions, such as exercise or vigorous activities.
The target heart rate is calculated by the equation: target heart rate = 0.85 ×(220-Age). If the patients feel chest pain or severe arrhythmia the test result is considered positive. Furthermore, ECG recorded during the treadmill test is analyzed to evaluate the condition of the patient. If the ST-segment changes are greater or equal to 1 mm then the test is considered positive. In addition, changes in T-wave and a prolonged QT interval indicate abnormalities with the heart. These abnormalities are not usually found in resting ECG.
2.2.6 Cardiac Biomarker Examination
Cardiac biomarkers are the enzymes released into the blood when the heart experiences any discomfort or defects, such as stress or impairments. The quantity of cardio enzymes in the blood can be utilized to detect heart diseases, especially acute coronary syndrome (ACS) and cardiac ischemia. The test is done by taking a sample of the patient’s blood and analyzing it to measure the level of cardiac biomarkers in their blood. It can detect low oxygen intake conditions or injuries in the heart. Myoglobin, troponin, and creatine kinase are the three cardiac biomarkers or enzymes. Among these, the most commonly used cardiac biomarker is troponin due to its highest sensitivity [3]. Usually, the quantity of cardiac markers in the blood is measured in nanogram/milliliter (ng/ml) units. The normal measure of troponin in the blood ranges from 0 to 0.4 ng/ml. The high-sensitivity troponin test can detect a very small level of troponin. The normal range value is 14 ng/l for troponin during cardiac biomarker examination (high-sensitivy troponin test). Anything above 14 ng/l is considered abnormal.
2.2.7 Chest Roentgenography
Despite the increasing number of modern diagnostic imaging techniques accessible to clinicians, chest roentgenography remains a straightforward, low-cost, and highly insightful examination. A roentgenogram, also known as an x-ray image is a photograph of internal structures made by moving x-rays through the body and forming a shadow image on specially sensitized film. Roentgenography was named after Wilhelm Conrad Röntgen, a German physicist who invented it in 1895. The chest x-ray is a reliable method for predicting