Letter Regarding Article by Arias et al, “Obstructive Sleep Apnea Syndrome Affects Left Ventricular Diastolic Function: Effects of Nasal Continuous Positive Airway Pressure in Men”
To the Editor:
I read with great interest the article by Arias et al1 regarding effects of continuous positive airway pressure (CPAP) on diastolic function in patients with obstructive sleep apnea. Their study was meticulously done, and I applaud their effort in carrying out this project. Although they state that their data show an improvement in diastolic function after 12 weeks of CPAP, there are other possible interpretations to be considered. The group in whom changes in diastolic parameters were noted was older, with higher body mass index, blood pressure, and left ventricular mass. The vast majority had a pattern of impaired relaxation. Although there were statistically significant decreases in deceleration time and isovolumic relaxation time and a significant increase in E:A ratio, no patient changed to a different diastolic pattern, and there were no measurable changes in ventricular structure. The Doppler parameters that changed are sensitive to changes in diastolic function but also loading conditions, in particular left atrial pressure. In some of the patients, therefore, these changes might have been due to progression of diastolic dysfunction in the direction of a pseudonormal pattern.2
Given the careful study design, I do think the authors’ conclusion that diastolic function improved is quite possible. I also agree with them that tissue Doppler analysis would have been helpful. In light of reported improvement in systolic function after treatment of obstructive sleep apnea patients with a reduced ejection fraction,3 it would also be interesting to study the effects of CPAP on Doppler (including tissue Doppler) parameters of systolic function.
We thank Dr Pressman for his interest in our article on both the presence of diastolic dysfunction in obstructive sleep apnea (OSA) patients and the effects of continuous positive airway pressure (CPAP) on echocardiographic parameters of diastolic function.1 As we stated in the article, we share Dr Pressman’s view that tissue Doppler could have been helpful for assessing diastolic function in our selected group of OSA patients with normal systolic function. Certainly, the simplest approach to differentiate between normal and pseudonormal left ventricular filling patterns is the measurement of annular tissue velocity by tissue Doppler imaging. However, we sincerely believe our approach is valid to achieve the objectives of the study because the use of pulmonary venous flow by Doppler echocardiography is a widely accepted tool in both differentiating between normal and pseudonormal patterns in the presence of sinus rhythm and estimating left ventricular filling pressures.2,3
Although the mitral and pulmonary vein inflow pulsed-wave Doppler parameters are influenced by several factors such as heart rate, blood pressure, contractility, and loading conditions, the great majority of them were greatly controlled in our study. Our conclusion that diastolic dysfunction at baseline improved after CPAP treatment is based on the fact that significant changes obtained in the Doppler mitral flow parameters were not accompanied by significant changes in the direction of a pseudonormal pattern such as changes in the pulmonary venous flow variables (decrease in S/D and A/AR ratios) or increased values for left atrial diameter.3
Nevertheless, further investigations are warranted to determine the clinical benefits of long-term CPAP therapy in nonselected OSA patients with diastolic dysfunction and the real prevalence of isolated left ventricular diastolic dysfunction in OSA subjects based on large-scale epidemiological studies.
Arias MA, Garcia-Rio F, Alonso-Fernandez A, Mediano O, Martinez I, Villamor J. Obstructive sleep apnea syndrome affects left ventricular diastolic function: effects of nasal continuous positive airway pressure in men. Circulation. 2005; 112: 375–383.
Appleton CP, Galloway JM, Gonzalez MS, Gaballa M, Basnight MA. Estimation of left ventricular filling pressures using two-dimensional and Doppler echocardiography in adult patients with cardiac disease: additional value of analyzing left atrial size, left atrial ejection fraction and the difference in duration of pulmonary venous and mitral flow velocity at atrial contraction. J Am Coll Cardiol. 1993; 22: 1972–1982.