Infectious Causes Of Myocarditis

1.    Viral: Coxsackievirus, adenovirus, HIV, CMV, Parvovirus, EBV, hepatitis C, HSV, influenza A and B, echovirus, RSV, measles, rubella, rabies 

2.    Bacterial: Corynebacterium diphtheriae, H. flu, Gonococcus, mycoplasma pneumoniae, Mycobacterium, Salmonella, Staph. aureus, Strep. pyogenes, Treponema pallidum 

3.    Fungal: Actinomyces, aspergillus, candida, coccidioides, blastomyces, cryptococcus, histoplasma, mucormycoses, nocardia

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Management of Pediatric Cardiac Tachyarrhythmias

Treatment:

All patients presenting to the ED with tachyarrhythmias should have an immediate hemodynamic assessment, a 12-lead ECG, and continuous cardiac monitoring initiated. The initial treatment strategy depends on the patient’s presentation and clinical status (hemodynamically stable or unstable).

SVT, Hemodynamically Unstable:  

Altered mental status or signs of shock and severe heart failure may be present. Perform immediate synchronized cardioversion with 0.5 to 1 J/kg. Cardioversion in a synchronous mode will not allow a shock to be delivered during a vulnerable repolarization period. Perform cardioversion in children over 10 kg using adult electrode paddles, which results in lower thransthoracic impedance and higher current flow. If time permits, give the patient adequate sedation before the procedure. Sedation for cardioversion may be provided by 0.1 mg/kg midazolam and/or 1 to 2 mg/kgpropofolintravenous.
 

Ventricular Tachycardia: Hemodynamically Unstable:  

Acute management of ventricular tachycardia requires a full evaluation of the ABCs of resuscitation. Management of VT with a pulse in an unstable patient requires immediate synchronized cardioversion at 0.5 to 1 J/kg. Medications may include amiodarone, lidocaine, or procainamide. Amiodarone and procainamide should not be used together. Treat pulseless VT or VF with defibrillation at 2 J/kg and re-start CPR immediately after defibrillation. If the defibrillation is unsuccessful, epinephrine should be given, and repeated every three to five minutes as necessary. If shockable rhythm is present after five rounds of CPR, additional defibrillation attempts with 4 J/kg are indicated (PALS 2005). Seek and treat any acute and reversible causes, such as electrolyte abnormalities, acidosis, or drug toxicity. Intravenous administration of magnesium sulfate (MgSo4) was found to be a very effective and safe treatment for torsades de pointes in pediatric patients with LQTS.67 Bolus injection is given at 3 to 9 mg/kg initially up to 12 mg/kg over one to two minutes until the torsades de pointes is completely abolished. A second bolus can be given under the same protocol within 5 to 15 minutes. It should be followed by a continuous infusion at a rate of 0.5 to 1.0 mg/kg/hr. When the total bolus dose of MgSo4 exceeds 24 mg/kg in a pediatric patient and 400 mg in adults, measurement of serum Mg concentration and careful monitoring is mandatory. Optimal serum Mg concentration is 3 to 5 mg/dL.

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Pediatric Acute Infectious Myocarditis Risk Management Pitfalls and Key Points

Risk Management Pitfalls:

1. Failure to identify myocarditis in a patient presenting with respiratory distress and cardiomegaly on chest radiograph. 

2. Failure to identify myocarditis in a patient presenting with new onset recalcitrant arrhythmias. 

3. Failure to have resuscitative equipment available.

Key Points:

1. Patients with acute myocarditis often present with vague symptoms not clearly referable to the cardiovascular system. Therefore, one must keep a high index of suspicion when caring for patients with viral symptomatology. 

2. The true incidence of acute myocarditis is unknown. For this reason, definitive determination of outcome is not possible. 

3. The pathobiology of acute myocarditis is complex and not completely understood. There are ill-defined virus and host factors that determine the severity of the disease course. 

4. The development of chronic, dilated cardiomyopathy is a common sequela of the acute infectious process. 

5. An elevated troponin level may support the diagnosis of myocarditis, but a normal troponin level does not exclude the diagnosis.

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Pediatric Acute Infectious Myocarditis Case Study

Case Study: 

During a rare slow evening shift, the triage nurse notifies you that he has just put a sick infant into the resuscitation bay. The parents of the 2-month-old baby boy brought him to the emergency department because he “didn’t look right.” His father reports that for the past 24 hours, his son has been fussy and felt hot to the touch. The family initially attributed the boy’s condition to the recent hot weather, especially because their air conditioner is broken. However, for the past 8 hours, the boy has refused formula, and has started “breathing funny.”

As you enter the room, the nurse reports that the patient has a rectal temperature of 38.5°C (101.3°F), that he is unable to obtain a cuff blood pressure, and that the pulse oximeter will not pick-up. You look up at the cardiac monitor to see a heart rate of 205 bpm. The infant is listless and grunting. His extremities are mottled and cold with weakly palpable pulses. Cardiac auscultation is confounded by the baby’s grunting and tachycardia, but there seems to be a systolic murmur. His liver edge is palpable below his umbilicus. What is the etiology of this infant’s shock state? Is he septic? Does he have a ductal dependent congenital heart lesion? Is this a primary dysrhythmia? Does he need a fluid bolus? Should you start a prostaglandin infusion? an inotropic infusion? Does he need to be intubated? What drugs should you use for the intubation? 

You make the decision to intubate him. With judicious use of fentanyl and rocuronium, and with the code cart open and nearby, you successfully intubate him. Despite his poor perfusion, one of the nurses is able to get enough blood for an arterial blood gas and lactate level which reveal a pH of 7.0, PaCO2-50, PaO2-60, and a base deficit of -20, with a lactate level of 15 mmol/L. You alert the on-call cardiologist and the cardiac intensive care service, and suggest that they mobilize the Extracorporeal Life Support (ECLS) team. The patient’s chest radiograph demonstrates cardiomegaly and pulmonary edema. The electrocardiogram (ECG) demonstrates sinus tachycardia. The echocardiogram demonstrates severe globally depressed biventricular function with moderate mitral regurgitation. Should the patient be placed on extracorporeal membranous oxygenation (ECMO) immediately? Which inotropic infusion should you start in the mean time? dopamine? Dobutamine? milrinone? You decide to start him on a dobutamine infusion.

Conclusion to the above case study…
Your patient is transferred to the Cardiac Intensive Care unit. He fails initial attempts at medical management and is placed on ECMO. The following day, the service is notified that blood, rectal, and nasopharyngeal specimens are all positive for enteroviral ribonucleic acid (RNA) as determined by polymerase chain reaction (PCR).

The patient remains on ECMO for 5 days, is successfully weaned and decannulated on day 6, and is ultimately discharged from the hospital after a few weeks. He has regular cardiologic follow-up for mild residual left ventricular dysfunction, though he remains asymptomatic and is growing well.

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