Is Right Ventricular Dysfunction in Obstructive Sleep Apnea a Potential Screening Tool?

Abstract

Circulation Journal Official Journal of the Japanese Circulation Society http://www. j-circ.or.jp n this issue of the Journal, Tugcu et al 1 report that by using velocity vector imaging (VVI), as well as tissue Doppler imaging (TDI), subclinical regional right ventricular (RV) dysfunction is diagnosed in patients with obstructive sleep apnea (OSA) who do not have systemic or pulmonary arterial hypertension. They found that the VVIderived RV peak systolic myocardial velocity, strain/strain rate, and the TDI-derived RV isovolumic acceleration were significantly impaired in those with OSA, and that the RV mid free wall stain and strain rate were best correlated with the apnea hypopnea index. Article p 312Quantification of regional myocardial function is crucially important in the diagnosis of various heart diseases. M-mode echocardiography is a good old standard that has survived over the decades in daily clinical practice for cases of nonischemic heart disease. M-mode, however, quantifies the left ventricular (LV) short-axis diameter, and therefore the results are not reliable in ischemic heart disease when regional wall motion abnormalities are present. 2 Two-dimensional echocardiography has emerged, but quantification of wall motion remains even more problematic than in M-mode. 3,4 Two-dimensional TDI was developed as a promising quantification technique in the early 1990s, 5,6 but because TDI measures tissue velocity in the direction of the ultrasound beam, Doppler angle dependency, as well as the translational motion, inherently affects the measurements. At the dawn of the TDI era, Uematsu et al developed the concept of a myocardial velocity gradient (MVG), which was the inclination of the velocity profile across the myocardial wall, to quantify regional myocardial thickening. 7 Here, the angle dependency is corrected, and the effects of translation are cancelled. The MVG was originally intended to be assessed only in the direction of myocardial thickening and thinning across the endocardium and the epicardium, the measurement of which was limited to the LV short-axis view. Urheim et al expanded the concept and introduced strain and strain rate, measured in the apical views of the LV. 8 Application of TDI in the apical views is theoretically sound because the ultrasound is transmitted almost parallel to the LV long-axis motion, thereby making angle correction unnecessary.Strain and strain rate measurements by TDI, however, have not yet become popular among practitioners. Reproducibility issues inherently arising from the lack of tracking capability have to be overcome because TDI still has fixed sample points in most TDI machines. Displacement calculations should first be done. Speckle or pixel tracking has emerged as an alternative method in which ultrasound speckles within the image are tracked and strain is determined from the displacement of speckles in relation to each other, thereby providing an angle-independent parameter of myocardial function. 9 VVI is an additional feature-tracking echocardiographic ...

Obstructive Sleep Apnea and Sleep Structure Assessed in Polysomnography and Right Ventricular Strain Parameters

“…Echocardiography is a suitable, non-invasive method for structural and functional assessment of the heart. A few studies concerning echocardiographic changes in the right ventricular of patients with OSA were published in recent years [16][17][18].…”