Is a first-degree heart block consistent with acute rheumatic fever?

First-Degree Heart Block in Acute Rheumatic Fever

Yes, first-degree heart block is consistent with acute rheumatic fever (ARF) and is recognized as a minor criterion in the Jones criteria for ARF diagnosis. 1

Cardiac Conduction Abnormalities in ARF

First-Degree Heart Block

• First-degree heart block (PR prolongation) is a well-established minor criterion in the Jones criteria for diagnosing ARF 1
• It is one of the most common ECG abnormalities seen in ARF patients, occurring in up to 72.3% of children with ARF 2
• First-degree heart block typically resolves with conventional anti-inflammatory treatment without requiring specific therapy beyond NSAIDs 2

Advanced Heart Block in ARF

• While first-degree heart block is more common, higher degrees of heart block can also occur in ARF, though they are rare 3, 4
• Second-degree AV block (reported in approximately 1.5% of ARF cases) and complete (third-degree) heart block (reported in about 4.6% of cases) have been documented 2, 5
• Advanced heart blocks in ARF are typically transient and resolve with anti-inflammatory treatment 2, 6
• In a study of 201 ARF patients, 8.5% had transient abnormalities of atrioventricular conduction beyond first-degree block 4

Cardiac Manifestations of ARF

Carditis in ARF

• Carditis is a major manifestation of ARF, occurring in 50-70% of patients during their first episode 1
• ARF causes a pancarditis involving the pericardium, myocardium, and endocardium 1
• Valvulitis is the most consistent feature of rheumatic carditis, with isolated pericarditis or myocarditis rarely considered rheumatic in origin 1
• Carditis can be diagnosed clinically (through auscultation of typical murmurs) or subclinically (through echocardiography/Doppler findings) 1

Conduction System Involvement

• Sinus tachycardia and PR prolongation (first-degree heart block) are common in ARF 1
• Bundle-branch block, nonspecific ST-T wave changes, and atrial and ventricular premature complexes may also occur 1
• Complete heart block and ventricular arrhythmias are rare but documented complications 1, 6
• ARF has been associated with prolonged QT interval and torsades de pointes in some cases 1

Diagnostic Considerations

Echocardiography in ARF

• Current guidelines recommend echocardiography with Doppler for all cases of confirmed and suspected ARF 1
• Echocardiography can detect subclinical carditis, which is now included as a major criterion in the Jones criteria 1
• Serial echocardiography is reasonable in any patient with diagnosed or suspected ARF, even if carditis is not present at diagnosis 1

Clinical Pitfalls and Caveats

• The presence of first-degree heart block alone is insufficient for ARF diagnosis; additional Jones criteria must be met 1
• Normal erythrocyte sedimentation rate and C-reactive protein levels should prompt reconsideration of ARF diagnosis (except in isolated chorea) 1
• Patients presenting with acquired heart block should be evaluated for ARF 3
• Serial ECG monitoring is important in ARF patients as conduction abnormalities can evolve during the course of the disease 3, 6
• Advanced heart blocks in ARF generally have a good prognosis without long-term sequelae, unlike rheumatic valvulitis which can cause permanent damage 5

In conclusion, first-degree heart block is not only consistent with ARF but is an established minor criterion for its diagnosis. While more advanced heart blocks are less common, they can occur in ARF and typically resolve with appropriate anti-inflammatory treatment.