Elsevier

Sleep Medicine

Volume 15, Issue 8, August 2014, Pages 880-886
Sleep Medicine

Original Article
Elimination of central sleep apnea by cardiac valve replacement: a continuous follow-up study in patients with rheumatic valvular heart disease

https://doi.org/10.1016/j.sleep.2014.02.007Get rights and content

Abstract

Background

Recent studies have suggested that cardiac surgery may affect sleep-disordered breathing (SDB) in chronic heart failure patients. However, the dynamic changes in sleep apnea and heart function after cardiac surgery and the mechanisms responsible for these changes remain unknown.

Methods

Patients with rheumatic valvular heart disease (RVHD) and SDB were enrolled and followed up at three, six and 12 months after cardiac valve replacement (CVR). Baseline and follow-up clinical data consisting of NYHA classification, 6 min 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 BNP, 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

CSA patients with RVHD had a worse baseline cardiac function, enhanced chemosensitivity and disordered hemodynamic as compared with OSA patients with RVHD. CSA were eliminated after CVR; however, there were no changes in OSA. The elimination of CSA, post CVR, is associated with the combined efficacies of improvement of cardiac function, normalized chemosensitivity, and stabilized hemodynamic.

Introduction

Sleep-disordered breathing (SDB) may be classified into central sleep apnea (CSA) and obstructive sleep apnea (OSA). SDB, especially CSA, occurs frequently in patients with chronic heart failure (CHF). One large-scale study showed that SDB was present in 76% (40% CSA, 36% OSA) of patients with symptomatic CHF [1]. Of the two types of sleep apnea, studies have shown that OSA is implicated as a cardiovascular risk factor, and that CSA is an end-result of deteriorating cardiac function [2], [3], [4], [5].

Several case reports strongly suggest that heart valve repair or replacement may lead to improvements in SDB [6], [7], [8], [9]. Tomcsanyi and Yasuma reported that CSA events were substantially reduced after successful cardiac valve replacement (CVR) [7], [9], and Collop and Mansfield found an improvement in CSA after successful heart transplant [10], [11]. Abe [12] investigated 74 patients with valvular heart disease and reported significant improvements in CSA index (CSAI), pulmonary capillary wedge pressure (PCWP), and mean pulmonary artery pressure (PAP), and no changes in OSA index (OSAI) 14 days post heart-valve repair.

Although heart valve treatment has been reported to eliminate CSA or cause a shift from CSA to OSA, the mechanisms responsible for these effects are not fully understood. Some researchers [8], [13], [14], [15], [16], [17] have suggested that the decrease in CSA may be related to enhanced lower partial pressure of arterial CO2 (PaCO2) and reduced lung-to-ear circulation time, whereas others [12] have considered that the improvements in CSA or shift from CSA to OSA may be the result of improved cardiac function.

In our previous study, we demonstrated that 38.8% of patients with rheumatic valvular heart disease (RVHD) also suffered from SDB [18]. We hypothesized that CVR surgery may affect CSA and OSA in patients with RVHD and SDB, and that the changes in SDB may be due to an improvement of heart function, chemosensitivity and hemodynamic circulation. In the current prospective study, we therefore investigated the dynamic changes in the various parameters at three, six, and 12 months after heart valve surgery in patients with RVHD and SDB.

Section snippets

Subjects and study design

Data were collected from 262 patients with RVHD who were admitted to the Cardiothoracic Surgery Department for CVR. The inclusion criteria were: (i) age 18–70 years; (ii) symptomatic stable heart failure, New York Heart Association (NYHA) class ⩾II despite optimal drug therapy; (iii) diagnosis of RVHD based on the 2004 World Health Organization (WHO) criteria for the diagnosis of rheumatic fever and rheumatic heart disease [19]; (iv) indications for valvular replacement surgery met the American

Results

Of 39 patients who completed follow-up assessments, there were 24 with CSA and 15 with OSA. The comparison of clinical and sleep parameters baselines is shown in Table 1. There were no significant differences in age, LVEF, ESS score, AHI, mean SpO2, minimum SpO2, sleep efficiency, or PaO2 between the CSA and OSA patients. Compared with the OSA patients, CSA patients experienced a higher prevalence of atrial fibrillation, higher NYHA class, lower BMI, shorter 6-MWD, larger left atrial diameter

Discussion

There were no differences in the severity of SDB between CSA and OSA patients. However, compared with OSA patients, CSA patients had worse baseline heart function (represented by NYHA class, plasma BNP, 6-MWD and LAD), as well as enhanced chemosensitivity (represented by blood gas) and disordered hemodynamics (represented by LFCT). In addition, there was also a higher prevalence of atrial fibrillation in CSA patients. These findings were in accordance with the results of previous studies [1],

Conclusions

The results of the present study demonstrate 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

Funding sources

This study was supported by the Priority Academic Program of Jiangsu Higher Education Institutions (Grants JX10231801) and Jiangsu Provincial Department of Education (Grants CXLX12_0557).

Conflict of interest

The ICMJE Uniform Disclosure Form for Potential Conflicts of Interest associated with this article can be viewed by clicking on the following link: http://dx.doi.org/10.1016/j.sleep.2014.02.007.

. ICMJE Form for Disclosure of Potential Conflicts of Interest form.

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