The aim of this randomized controlled trial to investigate the effects of CPAP treatment on myocardial salvage index and clinical outcomes at 3 months in patients with OSA and ST-Segment Elevation Myocardial Infarction (STEMI) after primary percutaneous coronary intervention (PPCI).

Inclusion Criteria:

1. 18 to 80 years old
2. First-time STEMI
3. Successful PPCI (≥1 coronary artery) within 24h after symptom onset
4. Moderate to severe OSA (AHI≥15)
5. Written informed consent

Exclusion Criteria:

1. Prior myocardial infarction
2. Prior myocardial revascularization (PCI or CABG)
3. Cardiogenic shock (mean arterial pressure <60mmHg), severe heart failure (Killip≥3)
4. LM or multivessel disease indicated for CABG
5. History of stroke
6. Severe insomnia, chronic sleep deprivation, abnormal circadian rhythm (sleep <4h/night)
7. Severe COPD: FEV1/FVC <70% or FEV1 <50% predicted value (within 4 weeks)
8. Predominantly central sleep apnea (≥25% central events or central AHI ≥10/h)
9. Previous or current use of CPAP
10. Severe comorbidities: eg. malignancy (life expectancy <2 years)
11. Known or planned pregnancy
12. Known contraindication to CMR
13. Patients with contraindication to CPAP or who cannot tolerate it
14. Participation in other clinical trial in recent 3 months
15. Any condition that in the opinion of investigator that may jeopardize patient compliance, eg. significant memory, perceptual, or behavioral disorder, depression, severe alcohol consumption, or a history of noncompliance