(1) Background: Early treatment of sleep-disordered breathing (SDB) with adaptive servo-ventilation (ASV) after acute myocardial infarction (AMI) has been shown to improve myocardial salvage. This analysis evaluates nocturnal electrocardiogram (ECG) Holter data, derived from polygraphy in a randomised clinical trial (NCT02093377), to assess the occurrence of nocturnal cardiac arrhythmias in patients with SDB and to explore the effect of ASV therapy. (2) Methods: In the TEAM-ASV I trial, patients were stratified by the presence/absence of SDB, defined by an apnoea–hypopnoea index (AHI) ≥15 events/h assessed with polygraphy. Those with SDB were subsequently randomised to receive ASV in addition to standard AMI care. Guideline-conforming semi-automated ECG analysis of nocturnal cardiac arrhythmias was conducted via Holter–ECG software (custo diagnostic, version 5.4). (3) Results: Patients with SDB had an increased incidence of non-sustained ventricular tachycardia (NSVT) (SDB: n = 8 (16%) vs. no SDB: n = 1 (2%); p = 0.024) and premature atrial contractions (PAC) (SDB: 1.2/h [0.3, 3.4] vs. no SDB: 0.3/h [0.1, 1.2]; p = 0.017). In patients with SDB who were randomised to ASV treatment early after AMI, we found no reduction in cardiac arrhythmias when ASV was added to standard care. (4) Conclusions: After AMI, SDB was linked to increased NSVT and PAC. ASV treatment demonstrated neither a harmful nor a beneficial effect on the occurrence of nocturnal cardiac arrhythmias. Further trials are warranted to confirm these findings.