Sleep Apnea Is Underdiagnosed in Cardiovascular Disease

Several scientific studies have indicated a connection between obstructive sleep apnea and cardiovascular disease. According to Elizabeth Muxfeldt, MD, PhD, cardiologist and professor at the Federal University of Rio de Janeiro (UFRJ) and Estácio de Sá University, Rio de Janeiro, Brazil, the prevalence of obstructive sleep apnea among individuals with drug-resistant hypertension is around 80%. Leonardo Siqueira, MD, electrophysiologist at the UFRJ Clementino Fraga Filho Hospital, estimates that approximately half of patients with atrial fibrillation (AF) have some degree of obstructive sleep apnea.

Despite the prominence of the condition, obstructive sleep apnea remains underdiagnosed in the general population as well as among patients with cardiovascular diseases. In light of this fact, an alert was sounded during a virtual session of the 39th Congress of the State of Rio de Janeiro Society of Cardiology (SOCERJ), which took place in May.

At-Risk Populations

Many doctors still do not routinely assess the sleep quality of their patients. João Manoel Pedroso, MD, PhD, physician and professor at the UFRJ and moderator of the scientific session, believes that healthcare professionals need to ask patients about the quality of their sleep and provide guidance on sleep hygiene measures.

According to Luiz Lazzarini, MD, PhD, pulmonologist at the Pro-Cardiac Hospital and professor at the UFRJ, it is up to physicians, cardiologists, and clinicians in other specialties to increase research into snoring and daytime sleepiness — two symptoms often related to obstructive sleep apnea. “This investigation can be conducted using simple questions such as, ‘Do you snore and/or feel very sleepy during the day?’ If the answer is yes to one or, especially, both of these questions, we must at least consider the presence of sleep apnea,” Lazzarini emphasized during the debate.

It is essential to consider the diagnosis of obstructive sleep apnea, particularly for patients with risk factors for cardiovascular diseases. Although research into snoring and daytime sleepiness is relevant in the diagnosis of sleep apnea, some specific cases also call for investigation, regardless of the response to these questions. According to Muxfeldt, this applies, for example, to patients with drug-resistant hypertension, given the high prevalence of obstructive sleep apnea in this population.

Not only do most patients with drug-resistant hypertension have this sleep disorder as a comorbidity, but also more than half of these patients present with moderate to severe apnea, said Muxfeldt.

These days, it is well known that sleep apnea is the leading cause of secondary systemic hypertension, said Lazzarini. This means that, after genetic predisposition, obstructive sleep apnea is the main cause of hypertension.

Another group to which particular attention should be paid is patients with AF. According to Siqueira, it is crucial to study the occurrence of obstructive sleep apnea in this patient population, especially in cases of persistent AF or when other risk factors, such as hypertension and diabetes, are involved. Siqueira also noted that research is key for patients with bradyarrhythmia and sinus node dysfunction, particularly when pauses are noted on the Holter monitor throughout the night.

Moreover, Siqueira noted that the incidence of ventricular extrasystoles is significantly higher among patients with obstructive sleep apnea than among those without apnea. “We know that obstructive sleep apnea is related to increased risk of sudden death,” he added.

In contrast, central apnea is more prevalent in patients with congestive heart failure (HF), especially in patients with systolic HF. However, it also occurs in patients with diastolic HF, said Fernando Pacheco, MD, pulmonologist and chair of the Brazilian Association of Sleep – Rio de Janeiro Region. “Central apnea is a poor prognosis marker for HF, associated with higher mortality,” he pointed out.

Diagnosis and Treatment

The gold standard for diagnosing obstructive sleep apnea is polysomnography. Nevertheless, Lazzarini highlighted that improper practice is not uncommon. “Nowadays, we see patients with suspected apnea being referred for continuous positive airway pressure (CPAP) titration without even receiving the diagnosis,” he said. He also pointed out that polysomnography cannot be dismissed, as it provides extensive data and can confirm the presence or absence of obstructive sleep apnea.

“We will identify the degree and type of apnea, its duration, whether it is predominantly apnea or hypopnea, the degree of arterial hypoxemia, and whether it is most prevalent in one body position. The polysomnography provides a series of data. If we simply skip this stage of diagnosis, the patient would not be receiving the best care,” Lazzarini added.

Once the diagnosis is confirmed, the treatment will be based on symptom severity, which can be determined according to the apnea/hypopnea index.

The specialists stated that CPAP is currently considered the most effective therapy for obstructive sleep apnea, but it is not the only option. Options range from changing the body’s position during sleep to pushing the mandible forward using an intraoral device or by means of surgical intervention. In addition, lifestyle changes are essential, as there is a significant relationship between body weight and the severity of the condition.

It is important that patients remain in extended follow-up in all cases. Even with CPAP, it is important to follow up with the patient and monitor the long-term efficacy of the therapy, said Lazzarini.

Moreover, Pacheco emphasized the importance of referring patients with severe obstructive sleep apnea to a sleep medicine specialist. “This makes a great difference. It means that there is a personalized approach, the best mask, the search for the best device, the demystification that CPAP is not just an encumbrance at the patient’s bedside. It also reminds patients that there are other treatments if they are diagnosed with sleep apnea and struggle to adapt,” he explained.

Improvement of Cardiovascular Health?

Healthcare professionals often question the benefits of treating obstructive sleep apnea. This is because some studies, such as the SAVE study (Sleep Apnea Cardiovascular Endpoints), have shown that obstructive sleep apnea treatment did not change cardiovascular prognosis. However, Pacheco advised that, in these studies, poor adherence to CPAP treatment (mean of 3.5 hours per night) and the lack of patients with daytime sleepiness ― which is one of the phenotypes with higher mortality rates ― are some of the specific aspects of these studies that may have led to these findings.

For these reasons, the pulmonologist thinks that there is good reason to believe that it may be beneficial for those with severe obstructive sleep apnea to undergo extended treatment. Moreover, the physician added that it is likely that positive results are evident as soon as treatment is started. However, “long-term studies confirming this hypothesis are still needed.”

Muxfeldt mentioned that data from the HIPARCO study, which was published in 2021, revealed that treatment with CPAP for an average of approximately 5 years was associated with a significant drop in the number of cerebrovascular events. The approach “presented a threefold reduction in cerebrovascular events, but there was no change in the incidence of coronary events,” she pointed out.

Regarding blood pressure control, Muxfeldt commented that among patients with drug-resistant hypertension, those whose conditions are refractory to treatment seem to have a better response to CPAP.

In terms of sudden death, Siqueira explained there are still only a few relevant studies, with few patients, and that the results are unclear: some studies show that CPAP is beneficial, while others do not. “This is a question to which randomized studies may hold the answer,” he concluded.

This article was translated from the Medscape Portuguese edition.

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