Introduction: Congenital heart diseases present with an impressive spectre of atypical clinical and imaging features. Even more so do the arrhythmologic manifestations of patients with corrected congenital heart disease. We often reply to their pathology with answers derived from individual case-reports or from Guideline general recommendations extrapolation. Our case paints the abstract picture of a patient known with episodic tachyarrhythmia who is suprinsingly diagnosed with severe episodic bradiarrhythmia, thus raising the problem of quasiasymptomatic sinus arrest episodes in other patients with corrected congenital heart diseases.

Case report: 52-yo female known with corrected atrio-ventricular canal defect (1996, OP type ASD and ante-rior mitral leaflet, AML cleft closure), incomplete right bundle branch block (RBBB), intermittent 1 st degree AV block, describes palpitations the past 2 months ha-ving a suspicion of atrial flutter (undocumented). A 24h ECG showed episodes of ectopic atrial tachycardia and very frequent but isolated monomorphic prema-ture ventricular complexes (PVC), with indication of verapamil which she had stopped 48h before presenta-tion. She associates mild iatrogenic hyperthiroid status as recommended by the oncoendocrinologist. She has no signs of HF, but has grade 2/6 systolic murmur in the mitral and tricuspid area, normal BNP. ECG shows sinus rhythm, 86 bpm, PRi 200 ms, incomplete RBBB. Echo shows grade II mitral regurgitation originating in the sutured AML, grade II tricuspid regurgitation, biatrial dilatation, no apparent residual ASD shunt, no PH signs. Surprisingly, 24h ECG shows episodes of atrial bradicardia and 8 sinus pauses up to 2674 ms, followed by ectopic atrial and/or junctional rhythm. At this U-turn we performed a repeat 24h ECG which showed episodes of atrial tachicardia up to 175 bpm and frequent monomorphic PVC with 2 couplets. After diagnosing tachy-brady syndrome and the Heart Team discussion with the electrophysiologist multiple aspects were raised, which also represent the case’s highlights:

Discussion:

1.Aethiology? It appears to be a case of sick sinus syndrome (SSS) late after a surgical procedure that could have directly caused the arrhythmia, possibly because of scar tissue and atrial  dilatation, less possible due to verapamil which had already been voluntarily stopped. Vagal influence may also play a part because of the presence of intermittent 1 st degree AV block.

2. Manifestations? The surprising discovery was the quasiasymptomatic full spectre of SSS: sinus tachybrady, ectopic atrial tachy-brady, sinus pauses. The escape rhythm was inconstant, sometimes via ectopic atrial rhythm, other times late junctional rhythm. Sinus pau-ses are also inconstant, with paroxysmal status, always sudden (without previous tachyarrhythmia) and acting as sinus arrest more than sinoatrial exit block. Could this be a proper SSS or more likely a general atrial arrhythmic disease?

3.Management? On one hand, Guidelines ask for symptoms before invasive intervention and the patient is asymptomatic for syncope or dizziness despite severe bradiarrythmia episodes. On the other hand, medication for tachyarrhythmia asks for underlying pacing. Could the ablation of atrial tachycardia in the setting of scar tissue and atrial dilatation provide the answer? Facing a patient with all previous data suggestive for tachyarrhythmia and not the surprising discovery of SSS, we stopped the calcium channel blocker and recommended cardiac pacing, which is to be performed.