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Myocarditis in children : summarized


Myocarditis

Dr Anum Arif

Acute or chronic inflammation of myocardium characterized by inflammatory cell infiltrates, myocyte necrosis or degeneration.
Causes:
i.                    Infections:
Viral infections
Bacterial
Fungal
Protozoal
Parasitic
Adenovirus
Parvovirus
Ebstein barr virus
Parechovirus
Influenza virus
Cytomegalovirus
Hepatitis c virus

Diphtheria
Mycoplasma pneumonia
Mycobacteria
Streptococcus species

Aspergillus
Candida
Histoplasma

Toxoplasma gondi
Trypanosoma cruzi
Babesia

Schistosomiasis


ii.                   Immune mediated:
Ø  Churg strauss syndrome
Ø  Ibd
Ø  Sle
Ø  Kawasaki disease
Ø  Takayasu arteritis
Ø  Celiac
iii.                 Drugs:
Ø  Sulphonamides
Ø  Cephalosporin
Ø  Diuretics
Ø  Dobutamine
Ø  Tricyclic antidepressants
iv.                 Toxic:
Ø  Snake bite
Ø  Scorpion bite
Ø  Spider bite
Ø  Ethanol
PATHOPHYSIOLOGY;
Ø  Acute deterioration: myocardial inflammation, injury, necrosis leading to cardiac enlargement systolic dysfunction and ccf ( shock, atrial / ventricular arrhythmia)
Ø  Chronic: myocarditis may become chronic with persistence of viral nucleic acid in myocardium.
CLINICAL FEATUES:
Severe respiratory distress, central/peripheral cyanosis may be there ,
cold peripheries , pallor due to circulatory failure, dehydration due to reduced intake , grunting, head nodding, nasal flaring, suprasternal,intercostal,subcostal,substernal recessions may be there.
Pulses may be good volume but later low volume or absent pulses.
Capillary refill time may be prolonged(>3 Sec)
B.P may be recordable initially but later hypotension or BP not recordable.
Altered Sensorium, or irritability due to decreased cerebral perfusion.
tachypnea,tachycardia, hyperdynamic precordium, muffled heart sounds , gallop rhythm, apical systolic murmur. Hepatomegaly due to congestive cardiac failure, peripheral edema and rales or basal crepitation may occur due to cardiac  failure.
Differential Diagnosis:
Carnitine deficiency
DCM
Hereditary mitochondrial defects
Anomalies of coronary arteries.
Diagnosis:
Ø  Ecg: lOW VOLTAGE ECG  i-e QRS complexes (QRS  amplitude of less then 5 mm in 3 consecutive limb leads and/or less then 10 mm in precordial leads.
Ø  nonspecific st and t wave changes.
Ø  Chest xray: cardiomegaly (ratio of maximum horizontal thoracic diameter and maximum cardiac diameter more then 0.5., pulmonary vascular markings, pleural effusion.
Ø  Cardiac MRI: standard imaging modality.
Treatment:
            Admit the patient.
o   Keep Cleared Airway,
               Prop up to 45 degrees
               Oxygen inhalation via NG in nostril with continuous sp02 monitoring
                Check for adequate/B/L comparable chest rise
o   Maintain I/V line
Monitor :
PR, RR, BP, CRT, Temp, BSL, Urine Output,
Attach spO2 monitor,
Attach Chest electrodes for continuous ECG monitoring.

Restricted maintenance fluids 70%  ( 5%DW + N/2 e 2ccKCl/100ml)
For inotropic support: dobutamine, dopamine, adrenaline infusion or  milrinone(50mcg/kg iv over 10-60 min followed by 0.25-0.75mcg/kg per min iv  can be used) . Consult seniors regarding choice of inotropic support .
Milrinone has the same effects as that of dobutamine , but since it acts through inhibition of Phosphodiesterase, it reduces the myocardial oxygen demand and hence reduces the mortality as compared to dobutamine.

Ø  Diuretics to reduce cardiac pre load.
                Frusemide 1mg per kg per dose X BD (after recording BP)
Ø  Immunomodulation : Intravenous immunoglobins may be given
Inflammatory dose Dexamethasone(steroids) : 1mg/kg/day has a controversial role in acute phase.
Antivirals do not have any proven role.
Ø  If arrhythmias occur, patient may need Pharmacologic or Electric cardioversion.
Ø  Mechanical ventilation may be indicated during the course of disease.

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