Infective endocarditis is caused by infection and damage to the endocardium of the heart and carries a high morbidity and mortality. This condition is more common in patients with prosthetic heart valves, congenital or acquired structural abnormalities of the heart or valves, or risk factors such as injection drug use, implanted intravascular devices, poor dental hygiene, HIV, or chronic hemodialysis.
Staphylococcus species are the most common cause of infective endocarditis in patients with either native or prosthetic heart valves. Streptococcus and Enterococcus species are other common infections associated with this condition. Endocarditis with negative blood cultures and no identified causative organism occurs in about 5% of patients. The mitral valve is the most commonly affected valve, followed by aortic, tricuspid, and pulmonic in order of decreasing frequency. Infective endocarditis associated with injection drug use has a predilection for right-sided valvular lesions.
Patients present with symptoms along a continuum, from the fulminant and acute onset of disease associated with fever, a new heart murmur, and acute heart failure, to insidious and indolent symptoms such as malaise and fatigue in a patient with a prosthetic valve. Fever is the most common symptom (80%) followed by chills, weakness, and dyspnea (40%). Other nonspecific symptoms include anorexia, cough, and malaise. The most common findings on physical examination include fever and a heart murmur. Classic skin findings such as tender nodules on pads of fingers and toes (Osler's nodes), painless hemorrhagic plaques on fingers and toes (Janeway lesions), petechiae, and splinter hemorrhages occur in less than 50% of cases.
Patients often present with cardiac, neurologic, and embolic complications. Acute heart failure occurs in approximately 70% of patients due to distortion or perforation of valves or cardiac chambers, or rupture of chordae tendinae. Other less frequent cardiac manifestations include heart blocks and dysrhythmias. Neurologic complications occur in 20% to 40% of patients, including ischemic stroke, brain abscess, cerebral hemorrhage, mycotic aneurysm, or seizure. Other embolic events may occur in the lungs, spleen, intestines, kidneys, and can cause acute limb ischemia.
DIAGNOSIS AND DIFFERENTIAL
Infective endocarditis is difficult to definitively diagnose in the emergency department, given the necessary components for diagnosis are blood culture results, echocardiography, and clinical observation. Consider the diagnosis in patients with unexplained fever and risk factors for the disease, such as injection drug users, patients with prosthetic valves, and those with new or changing murmurs or evidence of arterial emboli. The Duke criteria have long been used to make the diagnosis as detailed in Tables 93-1 and 93-2.
Duke Criteria* for Infective Endocarditis