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Elimination of Central Sleep Apnea by Cardiac Valve Replacement: A Continuous Follow-Up Study in Patients With Rheumatic Valvular Heart Disease
Study Questions:
What are the dynamic changes in the various parameters at 3, 6, and 12 months after heart valve surgery in patients with rheumatic valvular heart disease (RVHD) and sleep-disordered breathing (SDB)?
Methods:
Patients with rheumatic valvular heart disease (RVHD) and SDB were enrolled and followed up at 3, 6, and 12 months after cardiac valve replacement (CVR). Baseline and follow-up clinical data consisting of New York Heart Association (NYHA) classification, 6-minute walk distance (6-MWD), medications, echocardiography, electrocardiography, chest X-ray, arterial blood gas, lung-to-finger circulation time (LFCT), and sleep data were collected and evaluated.
Results:
Twenty-four central sleep apnea (CSA) patients and 15 obstructive sleep apnea (OSA) patients completed three follow-up assessments. Comparison of the baseline parameters between OSA patients and CSA patients showed that CSA patients had a worse baseline cardiac function assessed by higher NYHA class, shorter 6-MWD, larger left atrial diameter, longer LFCT, and enhanced chemosensitivity (higher pH and lower arterial carbon dioxide tension [PaCO2]). A continuous significant elevation in 6-MWD and left ventricular ejection fraction and decrease in NYHA class, plasma B-type natriuretic peptide, and left atrial diameter were found in both CSA and OSA patients. When comparing CSA and OSA patients, the CSA indices were remarkably reduced at month 3 post-CVR and sustained throughout the trial, whereas there were no significant decreases in OSA index and hypopnea index. pH values and LFCT were markedly decreased and PaCO2 markedly increased in patients with CSA at the end of the third months following CVR. These changes were sustained until the end of the trial.
Conclusions:
The authors concluded that the elimination of CSA, post-CVR, is associated with the combined efficacies of improvement of cardiac function, normalized chemosensitivity, and stabilized hemodynamics.
Perspective:
This study reports that CSA patients with RVHD had a worse baseline cardiac function, enhanced chemosensitivity, and disordered hemodynamic circulation compared with OSA patients with RVHD. CSA was eliminated after CVR; however, there were no post-CVR changes noted in OSA. The elimination of CSA is thought to be associated with the combined effects of improvement of overall cardiac function (fundamental factor), normalized chemosensitivity, and hemodynamics (direct factors). These results would support the viewpoint that CSA is a consequence of heart failure, since improvement of heart failure following CVR surgery almost eliminated CSA.
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