Overview.
Rickettsial myocarditis is myocarditis caused by rickettsial infection. Its pathologic changes are vasculitis with peri-arterial interstitial inflammatory infiltration, which may be followed by thrombosis, focal hemorrhage and myocardial necrosis. Patients mainly have fever, chest pain, dyspnea, rash and other typical clinical manifestations. Symptomatic and anti-infective treatment is mostly adopted, and the prognosis is generally good.
Causes
1. Biological factors
The pathogen is rickettsiae, which is a class of prokaryotic organisms parasitized in eukaryotic cells, and the vectors are mainly arthropods, such as ticks, lice, fleas and mites. The pathogen invades the human body from the bite of the vector, reproduces locally first, causing local skin lesions, and then enters the bloodstream directly or through the lymphatic system, grows and reproduces in vascular endothelial cells and monocytes-macrophages, producing toxins and causing systemic toxemia and inflammatory lesions in multiple organs. patients with Q-fever, Rocky Mountain spotted fever, typhus fever are often affected by rickettsial myocarditis.
2. Other
It can also occur as a result of scratching and biting by domestic animals such as cats and dogs.
Symptoms
1. Symptoms
Chills, high fever, severe headache, precordial pain, dyspnea, muscle and joint pain and other symptoms often appear, and heart failure can occur in severe cases.
2. Signs
Dark red congestive maculopapular rash on the skin, weakened pulse, weakened heart sounds on auscultation, murmur in the precordial region, and liver and spleen enlargement can be seen.
Examination
1. Laboratory examination
(1) Blood test: white blood cell count is often elevated.
(2) Serologic examination: positive reaction to exophthalmos, antibody potency＞1:160.
(3) Isolation of pathogens: pathogens can be isolated from blood specimens of patients with fever.
2. Imaging examination
(1) Echocardiography: Decreased ventricular systolic function can be seen.
(2) Electrocardiogram: the most common manifestations are transient ST-segment changes and T-wave flattening or inversion; conduction block may also occur.
Diagnosis
Ask for a detailed history of scratches and bites from pets, jungle excursions, or arthropod bites. If there is a history of suspicion, the disease should be suspected in conjunction with clinical manifestations such as fever, chest pain, dyspnea, and skin rash. Appropriate laboratory tests and auxiliary tests should be performed. The diagnosis can be made if the serologic antibody potency is 4 times higher than normal or if rickettsiae are isolated from the blood, and the diagnosis can be confirmed by combining with auxiliary tests such as imaging and electrocardiogram.
Complications
Toxic hepatitis, meningitis, gastrointestinal hemorrhage, acute renal failure are common.
Treatment
1. General treatment
Actively treat the primary disease, bed rest, strengthen nutrition.
2. Drug treatment
Tetracyclines, macrolide antibiotics, chloramphenicol and other drugs should be given for antibacterial treatment, and the application of adrenocorticotropic hormone can also be considered.
Prognosis
Cardiac lesions in patients are mostly temporary, and the prognosis is poor if serious myocardial infection is combined after the primary disease is cured.
Prevention
Arthropod bites should be prevented and pet management should be done.