Intra-atrial block after COVID-19 vaccination-induced fulminant myocarditis: a case report

Abstract

Background: Myocarditis is associated with an increased risk of conduction disturbances during the acute phase, which recovers in most cases but rarely recurs during the chronic phase.

Case summary: A 50-year-old man who developed fulminant myocarditis after COVID-19 mRNA vaccination was discharged 24 days after admission. He was readmitted for heart failure associated with two P waves: one P wave (P1) had a normal amplitude and was dissociated from the QRS, and the other (P2) had a very low amplitude and was associated with the QRS. The patient was referred for pacemaker implantation. Before implantation, an electrophysiological study was conducted using electro-anatomical mapping (EAM). During the P1 wave activation, the sinus rhythm spread to the right atrium but was blocked in the atrioventricular (AV) node area. During P2 activation, the activation originated from the right superior pulmonary vein (RSPV), spread to the left atrium and AV node area through the interatrial septum, and was conducted to the right ventricle, exhibiting a complete intra-atrial block with two discrete rhythms. An atrial lead was successfully placed in a narrow area in the right atrial septum where the pacing captured the left atrium and AV node area under the guidance of EAM findings.

Discussion: The EAM technology has demonstrated intra-atrial block and two types of atrial rhythms, sinus and RSPV. Electro-anatomical mapping findings were also useful for identifying the ideal pacemaker implantation site. Synchrony between the left atrium and ventricle via His-Purkinje conduction, which was achieved with EAM-guided atrial septal pacing, was prioritized.

Keywords: COVID-19 mRNA vaccine; Case report; Intra-atrial block; Myocarditis; Pacemaker; Two P waves.

Figure 1

Electrocardiogram findings. (A) Electrocardiogram findings on the second day of admission. The electrocardiogram showed two types of P waves: a P wave with a cycle length of 780 ms and normal amplitude (P1) that was dissociated from the QRS, mimicking a complete atrioventricular block with an atrioventricular junctional escape rhythm. The other type with a cycle length of 1140 ms and very low amplitude (P2) was associated with QRS. (B) Electrocardiogram findings obtained on the day after the second admission. Atrial fibrillation occurred, and in addition to the fibrillatory waves, a P wave with a cycle length of 640 ms, mimicking P1 morphology, was observed, especially in lead V1. (C) Electrocardiogram findings at discharge from the second admission. Complete atrioventricular block developed 11 months after the first admission. Again, two P waves were observed with dissociated QRS complexes.

Figure 2

Intracardiac electrocardiograms. The P1 wave, which was dissociated from the QRS, had a cycle length of 750 ms and showed the earliest activation in the high right atrium. The P2 wave, which was associated with the QRS with an atrio-His interval of 68 ms, had a cycle length of 1095 ms and exhibited the earliest activation at a distal site in the coronary sinus. The His-ventricular conduction interval following the P2 wave was within the normal range (48 ms). AH, atrio-His; CS, coronary sinus; HRA, high right atrium; HV, His-ventricular; LAO, left anterior oblique; RAO, right anterior oblique.

Figure 3

Activation map of the right atrium during sinus rhythm. During P2 wave activation, right atrial activation began in the sinus node area (A and B), spread to the right atrium (C and D), and was blocked around the atrioventricular node area (E and F), indicating entrance block to the atrioventricular node. PA, postero-anterior; SN, sinus node; RA, right atrium; RAO, right anterior oblique.

Figure 4

Activation map of the right atrial septum and left atrium during right superior pulmonary vein rhythm. During P1 wave activation, the atrial activation originated from the right superior pulmonary vein (A), spread to the left atrium and atrioventricular node area (B, C, and D) via the interatrial septum, and was conducted to the right ventricle (E and F). AV, atrioventricular; LA, left atrium; PA, postero-anterior; RA, right atrium; RSPV, right superior pulmonary vein.

Figure 5

Voltage map findings of both atria. A voltage map revealed large low-voltage areas (defined as ≤0.1 mV) in both atria. In a narrow area of the right atrial septum, the pacing captured the left atrium and atrioventricular node area at a threshold of 116 mA. AV, atrioventricular; IVC, inferior vena cava; LSPV, left superior pulmonary vein; PA, postero-anterior; RAO, right anterior oblique; RSPV, right superior pulmonary vein; SVC, superior vena cava; TA, tricuspid annulus.