In a school‑aged child with suspected rheumatic fever and no prior heart disease, what ECG changes are expected and how should they be managed?

ECG Changes in Rheumatic Fever

In school-aged children with suspected rheumatic fever, ECG changes are common but nonspecific, with PR interval prolongation being the most characteristic finding; however, these ECG abnormalities alone do not establish the diagnosis and should prompt echocardiographic evaluation for carditis, as echo is far more sensitive than clinical examination or ECG for detecting cardiac involvement.

Expected ECG Findings

First-Degree AV Block (PR Prolongation)

• PR interval prolongation is the most common ECG finding in acute rheumatic fever, occurring as a minor criterion in the 2015 modified Jones criteria 1
• This represents inflammation of the AV node and conduction system but does not correlate with disease severity or prognosis 2
• PR prolongation can occur even without clinically evident carditis 3

Other ECG Abnormalities

• ST-segment and T-wave changes may be present, particularly in patients with myocarditis or pericarditis 4
• Tachycardia disproportionate to fever is frequently observed 5
• Arrhythmias including atrial fibrillation may develop in severe cases with significant cardiac involvement 1

Critical Diagnostic Considerations

ECG Limitations

• ECG changes are nonspecific and cannot diagnose or exclude carditis - echocardiography is essential 1
• Auscultation has very low sensitivity for diagnosing carditis in children with suspected acute rheumatic fever, missing significant cardiac involvement 1
• Silent carditis (valvular lesions on echo without auscultatory findings) occurs in 18.3% of cases, emphasizing the need for echocardiographic evaluation regardless of ECG or examination findings 3

Echocardiography is Mandatory

• The 2015 modified Jones criteria include echocardiography to assess for cardiac involvement 1
• Echocardiography is more sensitive and specific than auscultation or ECG for identifying cardiac involvement 1
• Even handheld echocardiography shows excellent discrimination for rheumatic heart disease cases when standard echo is unavailable 1

Management Approach

Immediate Actions

• Administer a full 10-day course of penicillin to eradicate Group A Streptococcus, even if throat culture is negative at diagnosis 6, 4
• Oral penicillin V 250 mg twice daily for children or 500 mg 2-3 times daily for adolescents is the standard regimen 4
• For penicillin-allergic patients, use erythromycin or first-generation cephalosporins (if no immediate-type hypersensitivity) 4

Secondary Prophylaxis (Most Critical for Outcomes)

• Initiate benzathine penicillin G 1.2 million units intramuscularly every 4 weeks immediately upon diagnosis - this is the gold standard providing approximately 10 times greater protection than oral antibiotics (0.1% vs 1% recurrence rate) 6, 4
• In high-risk populations or with recurrence despite adherence, administer every 3 weeks 6, 4

Duration of Prophylaxis Based on Cardiac Involvement

• With carditis and residual heart disease: 10 years after last episode OR until age 40 (whichever is longer), sometimes lifelong 6, 4
• With carditis but no residual heart disease: 10 years OR until age 21 (whichever is longer) 6, 4
• Without carditis: 5 years OR until age 21 (whichever is longer) 6, 4

Anti-inflammatory Therapy

• For severe inflammation or cardiac involvement, consider prednisone 1-2 mg/kg/day for 1-2 weeks 4
• In severe cases with significant cardiac involvement, intravenous methylprednisolone (1000 mg/day initially) may be considered 4

Common Pitfalls to Avoid

Never Rely on ECG Alone

• Do not assume absence of carditis based on normal ECG - proceed with echocardiography in all suspected cases 1
• Normal ESR and CRP should prompt serious reconsideration of ARF diagnosis, except in patients with isolated chorea 5
• In typical ARF, CRP should always be elevated above normal and commonly >7.0 mg/dL 5

Prophylaxis Errors

• Never discontinue prophylaxis prematurely based on normal echocardiographic findings - patients remain susceptible to recurrent GAS infection 6
• Prophylaxis must continue even after valve surgery, including prosthetic valve replacement 6, 4
• Recurrent attacks cause progressively worse cardiac damage, making continuous (not episodic) prophylaxis essential 6, 4

Diagnostic Delays

• At least one-third of rheumatic fever cases result from asymptomatic GAS infections, making prevention challenging 6, 4
• Antibiotics must be started within 9 days of symptom onset to effectively prevent acute rheumatic fever 6
• In high-risk populations, fever may be absent in 25% of ARF cases - don't exclude the diagnosis based on lack of fever 5