Читать книгу Predicting Heart Failure - Группа авторов - Страница 54

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.