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Pediatric Viral Myocarditis

                                                               
 

VIRAL MYOCARDITIS

               Dr.M.Zulfikar Ahamed, Professor of Pediatric Cardiology,SAT Hospital, Govt Medical College ,Thiruvananthapuram

 

                 

Myocarditis, according to Dallas criteria, 1984 is defined as a condition in which an inflammatory infiltrate of the myocardium exists with or without death or degeneration of adjacent myocytes, not typical of ischemic damage associated with coronary artery disease (CAD). It is most often caused by virus especially Coxsackie virus, more particularly type B, but could be caused by other virus like Adenovirus ,other enterovirus, salmonella, Weil’s disease and diphtheria.

            Myocarditis can present as

 

1.                  Recent onset congestive heart failure (CHF)

2.                  Shock

3.                  CHF and shock coexisting

4.                  Arrhythmia – Tachy or Brady arrhythmia

5.                  Acute myocardial infarction (in ECG)

6.                  Inappropriate tachycardia

7.                  Sudden cardiac death (SCD)

8.                  Systemic or pulmonary embolism

9.                  Cardiomegaly in X-ray

10.             Dilated Cardiomyopathy (DCM)

There may be a prodroma with a flue like illness. There is Cardiomegaly, S1 is soft, S3 gallop is present with variable S2. Faint apical murmur of Mitral regurgitation (MR) is common. Tricuspid regurgitation (TR) murmur may be found. There is often evidence of CHF. When a child presents with shock it is called a fulminant form.

 

INVESTIGATIONS

A.        Blood Counts:

 

            Hemoglobin is often normal or mildly reduced. Total leukocyte count is raised in 25%. In more than 50%, ESR and CRP are elevated.

  

B.        Blood Enzymes:

 

            CPK-MB is elevated in 25%. SGOT and LDH may be elevated. Trop-T and Trop-I tests have been used in the diagnosis with moderate yield. Serum BNP may be elevated in the presence of CHF.

 

C.        X-ray:

            It shows Cardiomegaly invariably, except in situations where child presents in a fulminant form. A viral Myocarditis of 2-3 days duration presenting without Cardiomegaly in X-ray is very unusual. There can be left atrial enlargement and pulmonary venous congestion (PVH).

 

D.        14 lead ECG with Rhythm strip:

 

The classical triad are sinus tachycardia (>100 in a child; >120 in an infant; >150 in a neonate), low voltage complexes and ST segment and T wave changes. However these changes are fund in 50% only. Global T inversion in precordial leads is a useful finding. There can be other abnormalities like, varying AV blocks, bundle branch blocks, both supraventricular and ventricular arrhythmias and an even an anterior wall myocardial infarction pattern.

 

E.        SEROLOGY:

4 four fold rise in IgG for a particular virus over 4 weeks is useful in deciding the etiology.

 

F.         ECHOCARDIOGRAPHY:

            In clinical practice, along with the characteristic clinical presentation, echocardiography is virtually diagnostic. M-mode will show enlarged Left Ventricular (LV) dimensions, left atrial enlargement and impaired ejection fraction (EF) and shortening fraction (WF). Normal EF in children is 64+4%.  Any value below 60% is suspicious and value below 55% is clearly abnormal. 2D echo reveals a large, hypo contractile LV which is globular, with thin walls, mild pericardial effusion and occasional regional wall motion abnormalities (RWMA). In severely impaired LV function there can be either a ‘smoke’ or clot in LV or left atrium. Doppler and CFM will reveal MR and TR and will help in calculating PA pressure. Echocardiographically derived MR is often out of proportion to clinical MR.

            In infants it is always essential to exclude

1.                  ALCAPA (Anomalous origin of Left Coronary Artery from Pulmonary Artery)

2.                  Coarctation of Aorta

before concluding it is Myocarditis. Recently Kawasaki Disease has been found to be cause of Myocarditis and hence coronary artery anatomy and size has to be assessed. It is to be noted that most of the findings in echo in Myocarditis may be common to DCM also

 

G.        Newer Modalities are:

i.                    Radionuclide imaging with Indium labeled Antimyosin antibody.

ii.                  Endomyocardial biopsy (EMB) – available only in research centers.

iii.                MRI – said to pick up earliest abnormality in Myocarditis.

NOTE:    DALLAS Criteria 1984

                   Active Myocarditis – see definition above.

i.                    Ongoing Myocarditis – both inflammation and necrosis present.

ii.                  Resolving Myocarditis – inflammation may be present; cell necrosis not

iii.                Resolved Myocarditis – No inflammation / cell necrosis.

 

TREATMENT

1.         FULMINANT MYOCARDITIS (in Shock):

            Steps are

a.                  Admit into PICU

b.                  Start an IV Line and infuse

                  Ringer lactate 5 ml/kg/hour

c.                  Start Dopamine 5-10 mcgm / kg/mt IV infusion; can go up to 15 mcg/1kg.

d.                  Oxygen administration by mask/ canula and monitor hypoxia by pulse Oxymetry.

e.                  Sodium bicarbonate 0.5 ml/kg/IV slowly if there is metabolic acidosis.

f.                    Once BP has improved with improved perfusion we can switch over to Dobutamine as inotrope.

g.                  Ventilation if required

h.          In refractory cases.

i.          Intra Aortic Balloon Pump (IABP) can be attempted in   older children.

ii.         Extra Corporeal Membrane Oxygenator (ECMO) can be used in infants and children.

            iii.        May need heart transplantation in a few.

            Mortality rate is very high; as high as 80%.

 

NON FULMINANT TYPE:

            This is the more common presentation. Child is immediately admitted into PICU.

1.                  Start an IV Line or Two.

2.                  Dobutamine infusion 5-12 mcg/kg/mt IV infusion .Start with 5 mcg/kg and slowly titrate up to 10-12 mcgm/kg/mt. The infusion may have to be continued for at least 48 hours. Beyond that period, tolerance may develop.

3.                  Oxygen by mask or canula.

4.                  Start (ACE inhibitor) Captopril 0.5 mgm / kg stat dose and slowly build up to 3-4 mgm / kg / day in 3 divided doses over a period of 3-4 days. Captopril is beneficial in viral Myocarditis in more ways than one as a vasodilator, antioxidant and as an agent which reduces viral multiplication in myocytes. Unless complicated by hypotension, all children with Myocarditis should receive Captopril.

5.                  Digoxin can be started. If oral rapid digitalization is planned TDD is 0.03 mgm / kg. Generally it would be safer to start a reduced dose (75%) as maintenance ie 7.5 mcg/kg/day.

6.                  Diuretics – IV Frusemide is routinely used to reduce pulmonary congestion and edema. Dose is 1 mgm/kg/dose up to a maximum of 3 mgm / kg/ day.

7.                  Other supportive measures like rest, positioning, nutrition etc has to be taken care of.

8.                  Once the Dobutamine has been weaned off, child should be on Digoxin, Captopril and diuretic – oral.

9.                  Special situations

a.      Anticoagulants – Warfarin is indicated if there is a

    i.            LA or LV clot

   ii.            Ejection fraction less than 25%

iii.  h/o embolism

b.      Antiarrhythmics – Amiodarone is probably useful in treating ventricular tachycardia (VT) or even supraventricular tachycardia (SVT). Drugs causing myocardial suppression should be avoided.

c.      Heart blocks – If profound Brady arrhythmia develops, isoprenaline infusion may be used; occasionally may require temporary pacing of the heart.

d.      In refractory failure – Milrinone may be given a trial – Dose is IV  0.375 mgm/kg/bolus followed by infusion for  24 to 48 hours.

 

NEWER MODALITIES

1.         Antriviral agents

            Theoretically useful in the initial phase virus replication stage. Drugs are  interferon and ribavirin. Not very popular.

 

2.         Immuno suppressants

            Not routinely used. Agents which have been used are steroids, cyclosporine and azathioprine, either alone or in combination eg.

                                    Steroids + azathioprine

                                    Steroids + cyclosporine

            It would be useful in viral myocarditis once virus multiplication phase is over.

 

Note: Major randomized controlled trails have not shown genuine benefit with immuno suppressants in viral Myocarditis and it can’t be routinely recommended.

 

3.         Immuno modulation

            Immuno modulation with IVIG is an attractive proposition.

 

            Dose   2 gm / kg / total dose given in 2 doses (2 days)

            ie         I gm/kg/dose on day  I

                        I gm / kg dose on day II

 

Many small studies have shown benefit with IVIG. However the major randomized trial (IMAC) did not show any benefit. So it is not routinely recommended. However IVIG could be probably used in selected cases with benefit and  no risk of harm. It may be noted that many children may have immune inflammation and probably better candidates for IVIG than adults.

 

4.         Newer regimens

            Anti cytokines, Anti endothelin agents are all in trial stage. L-carnitine is probably not useful.

Note:

            b-blockers are now regularly used in post viral Myocarditis DCM. However it has been our policy not to start Carvedilol in the acute stage. The children are recalled for initiation of Carvedilol later.

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