Diagnosis of Congestive Heart Failure
When symptoms suggest congestive heart failure, the diagnosis usually is confirmed by physical examination, patient history, and various tests to detect abnormal function of the left ventricle and/or heart valves.
During physical examination, the physician looks for an underlying cause and assesses heart function. A stethoscope is used to detect abnormal heart sounds (murmurs) that may indicate a leaky or narrowed (stenotic) valve, and to detect fluid accumulation in the lungs. The physician also looks for enlarged (distended) veins in the neck and for swelling (edema) in the legs (particularly the ankles and feet) and/or the abdomen.
A patient history may include gathering information about the following:
- Alcohol and drug use
- History of hypertension, including treatment
- Prior chest pains or heart attack
- Recent viral illness
- Recent pregnancy
Diagnostic tests may include an electrocardiogram (ECG or EKG), an echocardiogram (cardiac echo), and cardiac catheterization. The purpose of these tests is to evaluate heart function (e.g., assess ejection fraction), and to detect coronary artery disease, heart attack, and valve dysfunction.
An electrocardiogram (ECG or EKG) is a noninvasive test used to measure electrical activity in the heart. Electrical sensors called leads are attached to predetermined positions on the arms, legs, and chest to record electrical activity and help assess heart function.
Echocardiogram (cardiac echo) is an ultrasound examination of the heart that produces detailed images of the organ. It can be used to detect abnormalities in the structure of the heart and to measure the ejection fraction.
Normally, approximately 60% of the blood in the left ventricle is ejected each time the heart beats (contracts). Patients with ejection fractions of approximately 40–45% have mildly depressed ejection fractions; patients with ejection fractions of about 30–40% have moderately depressed ejection fractions; and patients with ejection fractions in the 10–25% range have severely depressed ejection fractions.
During an echocardiogram, a microphone-like device (transducer) is used to transmit and receive ultrasonic waves that travel through the chest wall to the heart and are reflected back to the transducer. The reflected sound waves are translated into images of the heart, including the valves, chambers, and walls.
Echocardiogram also is used to measure the pressure change (gradient) between the left ventricle and the aorta, to assess thickening of the walls of the heart, to evaluate pumping function, and to measure the amount of dilation (increased diameter) of the left ventricle.
Cardiac catheterization may be performed in patients with angina and patients with a history of heart attack to determine if coronary heart disease (CHD) is causing heart failure. This procedure produces angiograms (i.e., x-ray images) of the coronary arteries and the left ventricle, and can be used to monitor heart function.
Cardiac catheterization involves injecting a small amount of radioactive dye (contrast agent) into the left ventricle through a catheter (i.e., a thin flexible tube). A special camera is then used to determine how much of the dye is ejected from the heart with each beat. The infusion of dye typically produces a characteristic "hot flash" sensation throughout the body that lasts 10 to 15 seconds.
In some cases, a less invasive procedure (e.g., stress test) is used to assess the possibility of coronary heart disease. If the results of this procedure suggest the presence of coronary artery disease, a subsequent referral for cardiac catheterization is likely.
Several types of stress tests may be used. In some cases, a patient simply walks on a treadmill while connected to an electrocardiogram. In other cases, a drug is infused into the bloodstream to increase the heart rate or to affect the flow of blood within the heart and an echocardiogram is used to obtain images of the heart.
Nuclear stress test involves injecting a radioactive substance into a vein and using a special camera to obtain images of the heart during rest and immediately following exercise on a treadmill.