Stent thrombosis is one of the most serious complications of percutaneous coronary intervention (PCI). Even with the use of newer antiplatelet agents, such as P2Y12 receptor inhibitors (e.g., prasugrel and ticagrelor) in combination with aspirin, the incidence of early stent thrombosis (EST) after PCI has been reported to be 1.4%–1.7% [1]. Although this incidence seems relatively low, EST is a life-threatening complication, as it often leads to acute myocardial infarction or sudden death, and is associated with a mortality rate of up to 45% [2]. Therefore, the risk factors for EST should be identified, and high-risk patients should be carefully monitored.

Obstructive sleep apnea (OSA) is very common in patients with cardiovascular diseases. The prevalence of OSA in patients with cardiovascular diseases has been reported to be 46% [3], while in patients undergoing PCI or coronary artery bypass graft, the prevalence of moderate-to-severe OSA is as high as 63.7% [4]. OSA is an independent risk factor for coronary heart disease, hypertension, atrial fibrillation and other arrhythmias, and stroke.[5‐8] Moreover, it adversely affects patient prognosis. A recent prospective study [9] reported that OSA was associated with an increase in the rate of major adverse cardiac events (MACE) in patients who had undergone coronary stenting. The incidence of MACE after coronary stenting is much higher in patients with sleep apnea (25%) than in patients without sleep apnea (16%, P = 0.038, [10]. Additionally, most of the increase in the MACE rate was accounted for by an increase in the incidence of perioperative myocardial infarction. Considering the above reports, we hypothesized that OSA may be a risk factor for EST after PCI. We, therefore, conducted this case–control study to determine the association between OSA and EST in patients undergoing PCI.

The main findings of our study were that the prevalence of OSA was high in patients who developed EST after undergoing PCI and that OSA was an independent risk factor for EST. We found that 60.87% of patients with EST had OSA, which was significantly higher than the rate in the control group (23.09%) as well as that reported in the literature (48.3% or 57%) [19, 20]. Many studies have shown that patients with OSA are more likely to be male and have a high BMI [21]. A survey of adults aged 30–60 years from the general population found that the prevalence of OSA was 24% in men and 9% in women [3]. However, because of the relatively low number of female patients in the present study, the sex-specific difference in OSA prevalence was not analyzed.

The case and control groups had similar risks in terms of smoking, hypertension, diabetes, and hyperlipidemia, but operation type (emergency vs. non-emergency), tirofiban and statin usage, and stent length significantly differed between the two groups. These results are consistent with those of Jones et al. who found that hypertension, hypercholesterolemia, and diabetes were risk factors for stent thrombosis [22]. We therefore adjusted for obesity, smoking, hypertension, diabetes, hyperlipidemia, emergency operation, tirofiban use, statin use, and stent length in the conditional logistic regression models, and the analysis revealed that OSA was an independent risk factor for EST (Table 2). Further analysis of the relationship between OSA and EST based on the number of concomitant conventional risk factors showed a stronger relationship and a higher OR in patients with fewer conventional risk factors. This provides favorable evidence for OSA as a risk factor for EST.

The pathophysiology of stent thrombosis is multifactorial and depends on patient as well as treatment factors, such as vascular endothelial injury, excessive activation of platelets and the coagulation system, slow blood flow, systemic inflammatory response, type of operation, type of implant, and perioperative drug use [23]. Sleep apnea leads to recurrent, complete or partial obstruction of the upper airway, causing fluctuations in arterial blood oxygen saturation and arterial blood pressure [24]. Most of our patients were overweight, which is associated with excessive fat deposits around the upper airway, a smaller airway lumen, and increased collapsibility of the airway structures [25]. In obese patients, the root of the tongue can easily fall down and block the throat passage during sleep, leading to OSA. OSA can cause chronic intermittent hypoxia, and long-term hypoxia can damage multiple organs through oxidative stress and inflammation. Intermittent hypoxia and hypercapnia can also lead to considerable sympathetic nervous activation and vascular endothelial injury. This disrupts the balance between coagulation and fibrinolytic mechanisms, leading to further vascular endothelial injury and plaque formation. Thrombotic lesions and plaques in the coronary artery can become unstable and lead to emboli formation. Thus, OSA patients are in a hypercoagulable state [26], and have a high risk of stent thrombosis. In patients undergoing PCI, OSA has been associated with an increased 2-year composite MACE rate, mainly due to an increase in the periprocedural myocardial infarction rate [5]. Stent thrombosis is the main cause of postoperative acute myocardial infarction. Our study showed that OSA is an independent risk factor for stent thrombosis. This was further verified by the finding that in patients with few conventional cardiovascular risk factors, the contribution of OSA to stent thrombosis was more obvious. This discovery is worthy of clinical attention. The mechanism via which OSA increases the risk of stent thrombosis may be similar to that in chronic obstructive pulmonary disease (COPD)[27, 28]. Studies have shown that a screening test to identify those with negligible risk of undiagnosed COPD among patients with acute coronary syndrome is helpful to evaluate prognosis[29] and provide early treatment to reduce mortality risk[30]. These reports in combination with the results of our study suggest that early screening for OSA with the BQ may be necessary in patients with ischemic heart disease.

Stent size should be selected on the basis of lesion characteristics to ensure total attachment of the stent to the blood vessel wall and proper stent expansion. Techniques such as rotational atherectomy, cutting balloon angioplasty, intravenous ultrasonography, and optical coherence tomography can help ensure appropriate stent placement. Complete stent expansion and restoration of Thrombolysis in Myocardial Infarction grade-3 blood flow can reduce the risk of stent thrombosis. In addition to concerns about stent-implantation techniques and drug factors, identifying and closely monitoring patients who are at a high risk of stent thrombosis are of great importance.

OSA is an independent risk factor for EST in patients undergoing stent implantation. In addition, the effect of OSA on EST is more obvious in the presence of fewer conventional cardiovascular risk factors. Thus, it may be worthwhile to test for OSA in patients with few conventional cardiovascular risk factors.