Acute rheumatic fever (ARF) is a multi-systemic inflammation as a consequence of group A streptococcal (GAS) infection. Several studies on the pathogenesis of ARF pointed to the molecular mimicry between GAS antigens called M-protein or carbohydrate antigen (N-acetyl-beta-D-glucosamine) that produce antibodies, and human protein, such as cardiac myosin or laminin. This mechanism results in humoral immune response injury and T-cell recruitment leading to granulomatous inflammation and Aschoff body formation, which are the hallmark of ARF[3, 4]. The organs mostly involve in ARF are the heart, joints and subcutaneous tissues.
Acute rheumatic fever (ARF) is diagnosed based on the Modified Jones' criteria, which classifies the clinical manifestations and laboratory results into major and minor criteria. Major characteristics of ARF include joints involvement (mono- or polyarthritis or polyarthralgia), chorea, skin manifestation (subcutaneous nodules or erythema marginatum) and carditis.
Carditis is a manifestation secondary to ARF, also considered to be pancarditis, which refers to the involvement of pericardium, myocardium and endocardium. The endocardium is the most common manifestation of carditis that results in chordal elongation with prolapse of the leaflet coaptation leading to permanent valvular damage. Myocardial involvement with conduction pathway abnormalities is considered a minimal myocardial dysfunction that may not be detected clinically . Several studies reported rhythm conduction defects in ARF for decades, and 40–60% of patients exhibit a prolonged PR interval (first-degree atrioventricular (AV) block [8–10]. Other rhythm disturbances included accelerated junctional tachycardia, premature contractions, ventricular tachycardia, Torsade de pointes due to prolonged QT interval, complete bundle branch block and rarely second or third-degree AV block[5, 10–12]. The incidence of second-degree AV block (Mobitz I) was reported as 1.5%-2.6% and third-degree or complete AV block as 0.6%-4.6% in different studies[7–8]. Mobitz II was reported in one patient on the 24-hour Holter monitoring but not on the standard 12-lead ECG. A presentation with supraventricular tachycardia (SVT) followed by complete AV block, the same as the second case in our study, has never been reported. Most of the conduction abnormalities are transient. Sevket B et al. reported some short-term conduction abnormalities do not appear on the standard 12-lead ECG but reported on 24-hour Holter monitoring, including premature contraction and complete heart block. The 24-hour rhythm Holter recording is suggested to be part of the routine ARF screening to detect rhythm abnormality and prevent bradyarrhythmia.
Rhythmic disturbances in ARF have no correlation with valvular involvement[13–17]. Several studies reported that the occurrence of conduction defect is not a specific sign of carditis[7, 8, 10, 12–14]. Although the exact mechanism of conduction defects in ARF is unknown, they were thought to be due to localized myocardial inflammation involving AV node or due to vasculitis involving the AV nodal arteries as the consequence of immune-mediated mechanism in ARF. As mentioned above, the molecular mimicry in ARF refers to a reaction between glycoprotein of GAS antigen and host tissue, especially the cardiac myosin in the heart valves resulting in valvulitis. The atrioventricular node has a very low content of glycoprotein but rich in glycogen, which is believed to be a substrate for the rheumatic process as it is implicated by the presence of short PR interval in patients with glycogen storage disease.
Most of the ARF rhythm conduction defects are transient, self-limiting with complete resolution at the end of the acute stage of the disease following anti-inflammatory medications. Some of the patients whose symptoms persisted or reported an Adams-Stokes attack may require a transient pacemaker. One patient reported a complete heart block presented with Adam-Stokes attack had temporary pacemaker for four days. The first patient in our study had a second-degree AV block that was resolved with anti-inflammatory drugs in the first week. In comparison, the second patient had a supraventricular tachycardia and a complete AV block that resulted in unstable bradycardia requiring a temporary pacemaker for five days along with anti-inflammatory drugs.