Sleep apnoea may occur, evolve following AMI
Obstructive sleep apnoea (OSA) and central sleep apnoea (CSA) appear to occur in nearly half and one-tenth of patients with acute myocardial infarction (AMI), respectively, and may resolve or change from one type to another in the 6 months following AMI, according to results of a Singaporean study presented at the American College of Cardiology’s 66th Annual Scientific Session in Washington, D.C.
“In view of the strong association between sleep disordered breathing and heart attack and the established negative prognostic implications of untreated sleep apnoea in these patients, cardiologists are becoming increasingly aware of the importance of screening for sleep disorders in their daily practice,” said lead author Dr Jeanette Ting from the National University Heart Centre in Singapore.
The prospective study, which aimed to determine the prevalence and evolution of sleep-disordered breathing after AMI, involved a total of 397 patients with AMI who underwent a sleep test within 5 days of admission. A repeat study was done in a subgroup of patients (n=102) at 6 months to check for the evolution of OSA or CSA.
Of the 397 patients, 166 (42 percent) had OSA and 39 (10 percent) had CSA. Compared with those who did not have sleep apnoea (n=192), patients with OSA and CSA tended to be older and hypertensive with a higher body mass index (BMI), and were more likely to receive discharge medications such as beta blockers and angiotensin converting enzyme inhibitors (p<0.05 for all). Patients with CSA were also noted to have a lower left ventricular ejection fraction (45±13 percent) compared with the OSA and nonsleep apnoea groups (p=0.004). [Ting J, et al, ACC 2017]
At the 6-month follow-up, 21 (46 percent) patients with OSA no longer had sleep apnoea, 10 (83 percent) CSA cases had evolved to OSA, and 93 percent of those with no sleep apnoea remained apnoea-free. No significant changes in BMI were reported between initial and repeat sleep studies.
Often undiagnosed and untreated, sleep apnoea is common in individuals with cardiovascular disease and may even increase the risk for disease progression. Usually seen in patients with hypertension and stroke, OSA is characterised by repetitive interruptions in breathing due to a collapsed pharyngeal airway. On the other hand, CSA is due to loss of ventilatory drive and mainly affects patients with heart failure. [Circulation 2008;118:1080-1111]
Apart from demonstrating that post-AMI sleep apnoea may eventually resolve on its own, findings of the current study suggest that it may be more effective to repeat or delay sleep studies after initial hospitalisation because of the observed evolution of the apnoea types over time.
“It is important to determine if the patient truly has underlying sleep-disordered breathing,” said Dr Ting, who recommended doing a repeat sleep study after 6 months in post-AMI patients with OSA or CSA before starting therapy.
“Alternatively, deferring the sleep study to 6 months’ follow-up may be considered,” added Dr Ting. Further investigation in the form of larger studies may be needed.