Overview of diphtheria
Diphtheria is an acute respiratory infectious disease caused by Corynebacterium diphtheriae, clinically characterized by pharyngeal tonsillitis and/or laryngitis, typical grayish-white pseudomembrane formation of the pharynx, and symptoms of intoxication caused by its exotoxin, which can be combined with myocarditis in severe cases, known as diphtheria cardiomyopathy, which is the most serious comorbidities of diphtheria and the main cause of death. It is the most serious complication of diphtheria and the main cause of death. The disease is most common in children and occurs more often in winter and spring. It is mainly transmitted by droplet infection, and can also be transmitted indirectly through toys, clothes and utensils.
Causes
Myocardial damage in diphtheria myocarditis is caused by the release of toxins by Corynebacterium diphtheriae, which inhibit protein synthesis by interfering with the conversion of amino acids from soluble ribonucleic acid to polypeptide structures.
Corynebacterium diphtheriae is weakly invasive, growing and multiplying only locally on the skin and mucous membranes at the site of its injury. However, the exotoxin produced is extremely toxic, which can produce toxemia after absorption and lead to systemic pathological changes, mainly in the myocardium, adrenal glands and peripheral nerves. Diphtheria myocarditis mainly involves cardiomyocytes and cardiac conduction system, its pathological changes can be seen in the early stage of the heart is obviously enlarged, cardiomyocytes are turbid swelling and fatty degeneration, followed by the emergence of multiple focal vitreous degeneration, granulomatous degeneration and necrosis of cardiomyocytes, accompanied by polymorphonuclear leukocyte infiltration; late stage can have connective tissue hyperplasia, the cardiac conduction system can occur in the denaturation, necrosis, and scar formation, resulting in abnormal function of the conduction system. The cardiac conduction system may undergo degeneration, necrosis and scarring, resulting in abnormal conduction system function.
The exotoxin of Corynebacterium diphtheriae causes degeneration, necrosis and scarring of the myocardium and cardiac conduction system, which is common at the end of the first week and at the beginning of the second week of diphtheria. Restorative changes, including granulation tissue formation, recovery of myocardial lesions, and proliferation of collagenous tissue and fibroblasts, may occur by the end of week 2. Scar tissue may form in the myocardium by weeks 3 and 4 of the disease.
Symptoms
Diphtheria-induced circulatory dysfunction may manifest as peripheral circulatory failure and myocardial injury. Peripheral circulatory failure often occurs at the end of the first week of the disease. The sudden onset of pale skin, cold extremities, rapid and weak pulse, and drop in blood pressure may be due to the action of Corynebacterium diphtheriae exotoxin on the vasomotor center or peripheral blood vessels.
Myocardial injury often occurs at the end of the 2nd week or the beginning of the 3rd week of the disease. Patients are mostly in the recovery period, sudden arrhythmia or congestive heart failure, pale or blue skin, tachycardia, shortness of breath, inability to lie down, facial edema, rales in the lungs, liver enlargement, low heart sound, may occur in prancing heart rhythm or arrhythmia, may show serious arrhythmia such as complete atrioventricular block, complete bundle branch block, ventricular tachycardia, or ventricular fibrillation, etc., which may lead to aa -s syndrome.
Tests
1. Blood tests
There may be increased white blood cell count and neutrophil ratio, and in severe cases, toxic particles can be seen in white blood cells and neutrophils.
2. Bacteriologic examination
Smear on the junction of pseudomembrane and mucous membrane, smear examination and culture can often find gram-positive bacilli or Corynebacterium diphtheriae. Bacterial culture can also be positive. Bacterial toxin test and virulence test can be done if necessary.
3. Electrocardiogram
ST-segment depression, T-wave flattening or inversion, sinus tachycardia are common, followed by atrioventricular block of varying degrees, and those with complete block have a dangerous prognosis and mostly die in the acute stage. Other ECG abnormalities may include bundle branch block, sinus bradycardia, ventricular pre-systole, paroxysmal tachycardia, atrial flutter or atrial fibrillation.
4. X-ray and echocardiographic examination
The heart is mildly to moderately enlarged, the heart beat is generally weakened, and cardiac function measurements often show changes in cardiac output and reduced ejection fraction.
5. Others
When the collected pseudomembrane is smeared with 2% potassium antimonite solution, the pseudomembrane can be seen to turn black or dark gray.
Diagnosis
In children with clinical symptoms of infection and pseudomembrane formation in the throat, if there are various manifestations of myocardial involvement, including electrocardiographic abnormalities, circulatory failure or congestive heart failure, the presence of diphtheria myocarditis can be considered, and a positive bacteriological examination can help to confirm the diagnosis.
Treatment
1. Actively treat the primary disease.
2. Absolute bed rest
Generally, bed rest should not be less than 2 months until the heart disease recovers. Because sometimes very mild physical activities, such as sitting up in bed, going to the toilet to urinate and defecate, may cause sudden death.
3. Appropriate application of drugs to nourish the heart muscle
Such as ARP, CTP, coenzyme A, pan-decanolone (coenzyme Ql0), vitamin B1, vitamin C, inosine and 1,6-diphosphate fructose.
4.Correcting heart failure and peripheral circulatory failure
Heart failure patients should be given a low-sodium diet and limit water intake, careful use of digitalis preparations, generally can be given to poisonous trichothecenes K (poisonous trichothecenes K), depending on the condition of the application of diuretics and vasodilators. Digitalis dosage should be controlled in the conventional dose of 1/2 ~ 2/3, in order to avoid poisoning (at this time, the patient is sensitive to digitalis drugs, easy to cause overdose poisoning, the application of the dose should be small, but the effect is not obvious). If the complication of peripheral circulatory failure can be used dopamine, dobutamine and meso hydroxylamine and so on.
5.Correcting arrhythmia
For bradycardia, atrioventricular block caused by decreased cardiac output, atropine, scopolamine or isoproterenol can be applied, and if necessary, a temporary cardiac pacemaker can be placed. If tachycardia occurs, especially ventricular tachycardia, it should be treated with lidocaine, benzethonium bromide, or procainamide, but the dosage should be smaller than the regular dosage so as not to excessively inhibit the myocardium. In addition, attention to water and electrolyte balance, intensive nursing care and supportive therapy should not be neglected.
Prognosis
Before the application of antitoxin, the morbidity and mortality rate of diphtheria myocarditis was high, especially in children, which could be more than 50%, and in adults, which was about 25%. In recent years, with the widespread use of antibiotics, the disease is rarely seen. The prognosis of diphtheria myocarditis is severe, and the mortality rate is high when complicated by severe conduction block, but recovery is usually complete with few sequelae.
Prevention
1. Protect susceptible people and control the source of infection. Isolate and treat patients until 2 negative nasopharyngeal cultures are obtained after symptoms disappear.
2. Cut off the way of transmission.
3. Improve immunity. Use white, hundred, broken mixed bacterial vaccine or adsorption of refined diphtheria toxoid injection.