How is infective endocarditis diagnosed?
The diagnosis of endocarditis may be suggested by the patient's symptoms and by physical examination. Unfortunately, the symptoms are often nonspecific and may only suggest the condition. In most cases, patients with endocarditis experience fever. During physical examination, the physician often discovers a new heart murmur. Heart murmurs are sounds heard
with a stethoscope that occur when there is abnormal, turbulent blood flow in the heart. The development of a leaky heart valve caused by infection-induced damage to the heart valve can result in this turbulent blood flow.
Bacteria in the bloodstream are highly suggestive of endocarditis and if endocarditis is suspected, multiple sets of blood cultures usually are obtained. Approximately a tablespoon of blood is withdrawn from a vein and mixed with a special nutrient-containing solution. This mixture is then observed to determine if any bacteria grow in it. If bacteria are present in the sampled blood, growth is usually observed within 1 or 2 days.
Additional evidence for the diagnosis will come from your physical examination, when your doctor checks for fever, skin symptoms of endocarditis (tiny hemorrhages in the skin, tender nodules on finger and toes) and a heart murmur, which indicates possible heart valve damage. Additional testing includes:
Blood cultures - In these tests, several blood samples will be drawn over a 24-hour period. These blood samples will be added to culture bottles that contain special nutrients to aid bacterial growth. If bacteria are living in your bloodstream, they will grow inside the culture bottles in the laboratory. Once bacteria grow, the specific species can be identified, and it can be tested for its sensitivity to various types of antibiotics. Results of this sensitivity testing will guide the doctor in selecting the specific antibiotic that will be most effective in treating the endocarditis.
Echocardiography - In this test, sound waves are used to outline the structure of the heart, the heart chambers and heart valves. By using echocardiography, your doctor can check for vegetations (abnormal growths that contain infecting organisms) on the heart valves or elsewhere inside the heart. He or she also can look for abscesses inside the heart and for signs of damage to natural or artificial heart valves. The best type of echocardiography for evaluating heart valves is transesophageal echocardiography, in which a tube is inserted through your mouth, allowing images of the heart to be obtained from just behind it. This test may be recommended if the diagnosis remains uncertain after conventional echocardiography. Transesophageal echocardiography is also a much better test for evaluating artificial heart valves.
Serological tests - These are blood tests that look for evidence of icreased immune system activity, which is a sign of infection. Serological tests may be helpful in the small percentage of patients with endocarditis whose blood cultures do not show bacterial growth. |
