CPAP May Prevent CV Events in Patients With OSA, ACS, and High Hypoxia Burden

Among patients with acute coronary syndrome (ACS), obstructive sleep apnea (OSA) treatment with continuous positive airway pressure (CPAP) prevented cardiovascular disease (CVD)-related events in those with high baseline hypoxic burden (HB), according to study findings published in the European Respiratory Journal.

Previous research indicates hypoxic burden is a strong predictor of CVD-related morbidity and mortality. Investigators therefore sought to assess whether hypoxic burden could serve as a predictor for determining the cardiovascular benefit of treating OSA with CPAP.

The investigators conducted a post-hoc analysis of the ISAACC study (ClinicalTrials.gov Identifier: NCT01335087), which assessed the effect of OSA and its treatment on the clinical course of patients with ACS. From 2011 to 2018, ISAACC study researchers recruited 727 patients (mean age, 59.7 years; 84.5% male) with OSA (apnea-hypopnea [AHI] index ≥15 events/hour) who were not sleepy (Epworth Sleepiness Scale score ≤10) and had ACS. To assess the effectiveness of CPAP, participants were randomly assigned to receive CPAP (n=362) or usual care (n=365) and were categorized as having high or low baseline HB (based on the median baseline value of 73.1% min/h).

The primary endpoints of ISAACC were a composite of death from any cardiovascular cause or nonfatal events such as acute myocardial infarction, nonfatal stroke, hospital admission for heart failure, and new hospitalizations for unstable angina or transient ischemic attack.

In the current study, the researchers sought to use patient HB level data to identify a subgroup of patients receiving cardiovascular benefit from CPAP therapy. In the CPAP-treated group of the ISAACC trial, 32.0% of participants had been in the low HB group, and 44.1% had been in the high HB group (P =.025).

The mean (SD) follow-up was 32.31 (22.46) months and 117 patients with OSA had a major adverse cardiovascular event. A significant interaction was observed between CPAP treatment and HB categories (P =.023), suggesting a differential effect of the treatment according to baseline HB level. The findings remained after adjustment for confounding factors (P =.035).

No association of CPAP therapy with cardiovascular prevention was observed in the full cohort. However, in the high HB group, a significant CPAP-related decrease in the incidence of adverse cardiovascular events occurred during the follow-up (hazard ratio [HR], 0.57; 95% CI, 0.34-0.96; P =.035).

For the low HB group, CPAP-treated patients had a trend for an increased risk for adverse cardiovascular outcomes during follow-up compared with those who had usual care (HR, 1.33; 95% CI, 0.79-2.25; P =.281). The magnitude of the effect size remained after adjustment for confounders.

Participants who had CPAP had a lower cardiovascular risk as the HB level increased. In the usual care group, the risk for cardiovascular events increased as the HB levels increased.

In analyses of the effect of CPAP on the cardiac components of the primary endpoint, CPAP had a stronger protective effect against cardiac events only in patients with high HB (HR 0.52; 95% CI, 0.29-0.92; P =.025).

The researchers noted that cause-effect relationships remain unproven and that the unavailability of raw respiratory polygraphy data for all patients with OSA may be a potential limitation. Also, patients with excessive daytime sleepiness were excluded from the ISAACC trial, and the population was limited to patients admitted to the hospital for ACS.

“Our exploratory findings highlight the potential for this oximetry-based metric to identify OSA patients without excessive daytime somnolence who are more likely to respond to CPAP therapy in the long term,” the study authors stated. “The HB represents a simple, inexpensive, and easily accessible metric that could feasibly be translated into routine clinical practice to guide CPAP treatment allocation for cardiovascular prevention in asymptomatic OSA.”

This article originally appeared on Pulmonology Advisor