Time	Event
Day 1	Presentation to the emergency department due to recurrent syncope. Third-degree atrioventricular (AV) block with a ventricular escape rhythm (33 b.p.m.) was identified in the presenting electrocardiogram (ECG). Positive borrelia IgG/IgM titres were found. Begin of antibiotic treatment with ceftriaxone. Transfer to intensive care unit.
Day 2	Intermittent reversal of third-degree AV block with appearance of first- and second-degree AV block. Low-dose isoprenaline therapy (1–1.5 µg/min). Cardiac magnetic resonance imaging shows normal finding.
Day 3–4	Mainly first- and second-degree AV block with short periods of third-degree atrioventricular block. The patient is continuously haemodynamically stable.
Day 5	Cessation of isoprenaline therapy. There is mainly first-degree AV block (PQ interval 309 ms) with the last observed short appearance of complete heart block 9 h after cessation of isoprenaline therapy.
Day 6	Stable first-degree AV block with no observed PQ interval above 300 ms during 24 h. Antibiotic therapy is changed to an oral therapy with doxycycline.
Day 12	Discharge from the hospital. AV block I with PQ interval of 244 ms. Antibiotic therapy is prescribed for a total duration of 21 days.
Follow-up 3 months after the hospitalization	PQ interval is normalized (185 ms). Holter-ECG shows no higher-degree AV block. Patient is completely asymptomatic.