Abstract
Background: Obstructive sleep apnea (OSA) is associated with an increased risk of cardiovascular events, including acute coronary syndrome (ACS). There is conflicting evidence that suggests OSA has a cardioprotective effect (ie, lower troponin), via ischemic preconditioning, in patients with ACS.
Purpose: This study had 2 aims: (1) compare peak troponin between non-ST elevation (NSTE) ACS patients with and without moderate OSA identified using a Holter-derived respiratory disturbance index (HDRDI) and (2) determine the frequency of transient myocardial ischemia (TMI) between NSTE-ACS patients with and without moderate HDRDI.
Method: This was a secondary analysis. Obstructive sleep apnea events were identified from 12-lead electrocardiogram Holter recordings using QRSs, R-R intervals, and the myogram. Moderate OSA was defined as an HDRDI of greater than or equal to 15 events per hour. Transient myocardial ischemia was defined as greater than or equal to 1 mm of ST-segment [up arrow] or [down arrow], in 1 or more electrocardiogram lead, lasting at least 1 minute.
Results: In 110 patients with NSTE-ACS, 39% (n = 43) had moderate HDRDI. Peak troponin was lower in patients with moderate HDRDI (6.8 ng/mL yes vs 10.2 ng/mL no; P = .037). There was a trend for fewer TMI events, but there were no differences (16% yes vs 30% no; P = .081).
Conclusions: Non-ST elevation ACS patients with moderate HDRDI have less cardiac injury than those without moderate HDRDI measured using a novel electrocardiogram-derived method. These findings corroborate previous studies suggesting a possible cardioprotective effect of OSA in patients with ACS via ischemic precondition. There was a trend for fewer TMI events in patients with moderate HDRDI, but there was no statistical difference. Future research should explore the underlying physiologic mechanisms of this finding.