Diagnosis of Heart Failure
When there is a suspicion that a patient might have heart failure, a number of tests can be performed to verify the diagnosis and determine the cause.
Blood tests sometimes help identify the underlying cause of the heart failure. For example:
- High levels of blood sugar and/or glycated hemoglobin can suggest that the person has diabetes.
- Low red blood cell count is not a cause but a sign of congestive heart failure. It results from chronic renal ischemia which reduces the production of erythropoietin (which stimulates the production of erythrocytes).
- Liver function tests – are made to identify the damage done to the liver by the congestion of blood.
- Levels of natriuretic peptide (BNP). When the heart is under stress, it releases natriuretic peptidase. Identifying the levels of this factor can also reveal the severity of the heart failure (higher levels of BNP signify that the patient has a more severe heart failure).
Echocardiogram uses high-frequency sound waves to produce a detailed image of the structure of the heart. It can provide the doctor with the following information:
- Evaluate the function and structure of the heart valves. The Doppler echocardiogram can be used to detect the direction of the blood flow. Thus, it can register the backward flow of the blood caused by valve insufficiency.
- Evaluate the systolic function of the heart (how well can the heart contract). Probably, the most important finding is to determine the systolic function of the left ventricle, since it is responsible for pumping the blood throughout the body. In order to evaluate its function, the left ventricular ejection fraction (LVEF) is measured. LVEF is an estimate of how much blood that enters the left ventricle is ejected after the heart muscle contract. Normal LVEF is between 50% and 70%. While LVEF of 40% and below can signify heart failure.
- Determine how well can the heart relax after each systole. This is known as diastolic function.
- Notice any abnormal connections between the heart chambers (intracardiac shunts).
- Determine the type of treatment that is best for the patient, which can include medication, or implantation of cardioverter-defibrillator or other devices.
Aside from regular echocardiogram, special types of echocardiogram can be performed to provide the doctor with more data:
- Stress echocardiogram. As the name suggests, this echocardiogram is taken when heart is put under stress. This is done by asking the patient to use a treadmill or an exercise bike. If the patient is unable to do so, a special drug can be used to increase the heart rate. Aside from regular echocardiogram, special types of echocardiogram can be performed to provide the doctor with more data:
- Transesophageal echocardiography. Since ultrasound cannot travel through the lungs, imaging the heart through the chest wall is rather difficult. However, since the esophagus lies right behind the heart, a special thin tube carrying a small ultrasound probe can be used to examine the heart in much greater detail. A mild sedative is usually given to the patient before this procedure and an anesthetic will be applied to the back of the patient’s throat.
During heart failure, the heart chambers usually become dilated which can be clearly seen on an X-ray (this condition is known as cardiomegaly). As well, X-ray can detect any fluid in the lungs which signifies left-sided heart failure. It can also detect other conditions in the region such as pericarditis, pleurisy, etc.
Electrocardiogram can be used to identify ischemic heart disease, arrhythmias, left and right ventricular hypertrophy and damage to the electrical conduct system of the heart. Even though these conditions do not point directly at heart failure, a normal ECG can completely exclude left ventricular systolic dysfunction.
The main cause of heart failure is ischemic heart disease, which is why it is essential to find out how well the coronary arteries can supply the blood to the myocardium. Coronary catheterization can be used to evaluate the state of coronary arteries and identify the options for revascularization through bypass surgery or percutaneous coronary intervention.
Next Chapter: Treatment of Heart failure