Assessment Of Right Heart Dysfunction In Patients With Obstructive Sleep Apnea Syndrome Using Velocity Vector Imaging

Obstructive sleep apnea syndrome(OSAS)is the most common type of sleep disorder caused by repetitive partial or complete upper airway collapse during sleep.Patients with OSAS always complain of snoring,sleep fragmentation,waking up with a choking sensation,excessive sleepiness,unrefreshing sleep,fatigue or tiredness,and morning headache.The prevalence of OSAS is high of about 4%.Just because of its high prevalence and negative effect on the quality of life,OSAS is considered as a global health problem.OSAS may lead to pulmonary hypertension and systemic hypertension and associates with a series of cardiovascular disorders,including right ventricular(RV)and right atrium(RA)dysfunction,arrhythmia,hypertrophy,coronary artery disease,and even heart failure.Episodes of obstructive hypopneas or apneas result in intermittent hypoxia,autonomic nervous dysfunction,and consequently may have a direct or an indirect adverse effect on RV myocardial function even in patients without cardiac or obstructive pulmonary diseases.The right ventricle plays an important role in the morbidity and mortality of patients presenting with signs and symptoms of cardiopulmonary disease.However,the right ventricle has a more complex geometrical shape and is wrapped around the left ventricle.Therefore,it is difficult to assess the RV function systematically using a conventional two-dimensional echocardiography(2DE).The tissue Doppler echocardiography method is also used for evaluating RV dysfunction,but it has high interobservational variability and is susceptible to the cardiac translational motion.The 2D speckle tracking echocardiography(2D-STE)method is a more sensitive method for assessing myocardial deformation characteristics.However,studies showed that the 2D-STE method underestimates the longitudinal strain of septum and global RV strain when compared with cardiac magnetic resonance,which is a "gold standard" in patients with ischemic heart disease.As an important part of the heart,the importance of the function of the RA has been paid more and more attention.RA plays an important role in maintaining RV filling.The basic functions of the RA include:1.Reservoir function,the function of storing blood at the time of RV contraction.2.Conduit function,acting as a conduit of blood from the vein to RV in the early ventricular diastolic time.3.Contraction function,contracting actively to increase RV filling in the late ventricular diastolic time.The volume produced by the RA contraction account for about 15-25%of the whole RV filling volume,and increase along with age and heart rate.Magnetic resonance imaging(MRI)can be used to assess the RA function,but it is impossible to assess the RA regional function using MRI.Two-dimensional echocardiography(2DE),pulsed Doppler and tissue Doppler echocardiography also can be used to assess the RA function.However,these parameters are less reliable because of the influence of loading conditions and the angle of examination.Therefore,accurate assessment of RA function remains a challenge.Two-dimensional strain has been applied to the evaluation of cardiac function.The RA function has been evaluated by 2D-STE in patients with pulmonary artery hypertension,RV myocardial infarction and healthy subjects.But there is no reports about studies of the RA function in patients with OS AS.The velocity vector imaging(VVI)method is a unique technology that assesses myocardial movement and deformation by detecting and tracking speckles in the myocardium on grayscale(B-mode)images.VVI is independent of inspection Doppler beam angle.The offline analysis of VVI quantify global and regional ventricular functions with several parameters,including tissue velocities(V),strain(S),and strain rate(SR).The purpose of this study was to investigate RA and RV dysfunction in patients with OS AS and evaluate the application of VVI technology.PART 1 Assessment of right ventricular dysfunction in patients with obstructive sleep apnea syndrome using velocity vector imagingObjective:This study aimed to assess the regional right ventricular potential dysfunction in patients with obstructive sleep apnea syndrome(OSAS)using velocity vector imaging(VVI)and to evaluate the application of VVI technology.Methods:According to the apnea-hypopnea index(AHI),69 patients with OSAS were divided into three groups:mild,moderate,and severe.A total of 30 cases of healthy subjects were enrolled as the control group.Digital images of apex four-chamber views were acquired to measure RV peak systolic velocity(V),RV global systolic strain(RV-GLSs)and strain rate(RV-GLSRs),as well as V(V-B?V-M?V-A),strain(S-B?S-M?S-A)and strain rate(SR-B?SR-M?SR-A)of each segment of right ventricular free wall(RVFW)using VVI.Results:1.Right ventricle RV-GLSs and RV-GLSRs were decreasing along with the disease severity and began to decrease from the moderate OSAS group(t=3.80,P=0.003;t=4.41,P=0.003)The peak systolic velocity of RVFW basal segments in the mild OSAS group increased(t = 2.216,P = 0.049),and gradually reduced in the moderate and severe groups(P<0.05).The values of systolic strain and strain rate of apical segments(S-A,SR-A)decreased in the mild OSAS group compared with the normal control group(t=3.30,P=0.02;t=3.75,P=0.01,respectively),and decreased furthermore in segments of moderate and severe OSAS groups(P<0.05).Multiple linear regression analysis showed that RV-GLSs(t=-2.011,P=0.032),RV-GLSRs(t=-2.173,P=0.006),S-A(t=-2.495,P=0.025)and SR-A(t=-2.391,P=0.004)were associated with OSAS severity(AHI)?2.Right ventricle RV-SRe,RV-SRa and RV-SRe/RV-SRa were decreasing a along with the disease severity.RV-SRa showed lower than control in severe group(t=3.83,P=0.01).RV-SRe,RV-SRe/RV-SRa showed lower than the control from the moderate OSAS group(t=3.152,P=0.025;t=2.86,P=0.035)and reduced more obviously in severe group(P<0.05).Multiple linear regression analysis showed that RV-SRe(t=-2.495,P=0.026)was associated with OSAS severity(AHI)?Conclusions:1.The right ventricular systolic and diastolic dysfunction starts before the development of heart dysfunction and pulmonary hypertension.2.At the early stage of OSAS,decreased regional deformation in the RVFW apical segment can be checked earlier than RV-GLSs and RV-GLSRs perhaps because of the compensatory of other segments.3.S-A and SR-A may be the early detector for RV systolic dysfunction of OSAS patients.RV-GLSs,RV-GLSRs,S-A,SR-A were correlate with the OSAS severity(AHI)and may be the detectors of OSAS severity for RV systolic dysfunction.4.RV-SRe was associated with the OSAS severity(AHI)and may be a detector of OSAS severity for RV diastolic dysfunction.5.The VVI is a sensitive method which is expected to be a worthy technique for early clinical therapy in patients with OSAS.PART 2 Assessment of right atrium dysfunction in patients with obstructive sleep apnea syndrome using velocity vector imagingObjective:This study aimed to assess the right atrium dysfunction in patients with OSAS using VVI and to evaluate the application of VVI technology.Methods:According to the apnea-hypopnea index(AHI),69 patients with OSAS were divided into three groups:mild,moderate,and severe.A total of 30 cases of healthy subjects were enrolled as the control group.Digital images of apex four-chamber viewswere acquired to measure the right atrium diameter(RAL,RAT).Manual tracings of right atrial endocardium trajectory,to obtained the RA maximum volume(1)(Vmax);(2)RA minimum volume(Vmin);(3)right atrial volume before contraction(Vpre);(4)the total right atrial emptying fraction(RATEF),RATEF=(Vmax-Vmin/Vmax),(5)right atrial passive emptying fraction(RAPEF),RAPEF=(Vmax-Vpre/Vmax),(6)right atrial active contraction emptying fraction(RAAEF),RAAEV=(Vpre-Vmin/Vpre).Right atrial volume parameters were corrected by body surface area(VImax,VImin).The VVI data measuring right atrial global strain(RA-GLS),right atrial strain rate in ventricular systolic phase(RA-SRs),right atrial strain rate in ventricular early diastolic phase(RA-SRe),right atrial strain rate in ventricular late diastolic phase(RA-SRa).Results 1.The values of right atrial diameters and volumes of OSAS patients increased.The RAL,RAT in severe OSAS group were higher than the control group(t=2.498,P=0.022;t=2.245,P=0.033;respectively).The VImax in the severe OSAS group is higher than that of control group(t=2.237,P=0.047;t=2.469,P=0.031;respectively).The VImin and VIpre in severe OSAS is higher than that of control group(t=2.326,P=0.044;t=2.405,P=0.035;respectively).RAPEF in the severe group was lower than the control group and mild OSAS group(t=2.681,P=0.021;t=2.985,P=0.011;respectively).RAAEF in OSAS medium group is higher than that of control group(t=3.006.P=0.02),and without statistical difference(P>0.05)in the severe OSAS group and the control group.2.RA-GLS in moderate OSAS group was significantly lower than that of the control group(t=2.333,P=0.040)and reduced more obvious in the severe OSAS group(vs control,t=3.25,P=0.008,vs mild;t=3.011,P=0.012;respectively).RA-SRe in the moderate and severe OSAS groups were lower than that of the control group(t=2.466,P=0.031;t=3.547,P=0.005;respectively).RA-SRs of OSAS in severe group was lower than that of control group and mild group(t=3.665,P=0.004;t=3.204,P=0.008;respectively).RA-SRa in severe OSAS group was lower than that in control group(t=2.425,P=0.034).3.Multivariate regression analysis showed RA-GLS and RA-SRe directly affect the AHI(t=-2.738,P=0.010;t=-2.A91,t=-0.036;respectively).RA-GLS and RA-SRe were associated with RV-GLSs and RV-SRe.Conclusion 1.With RV systolic and diastolic function decreased,there will be varying degrees of impairment of atrial function in OSAS patients,which occurred before the beginning of pulmonary hypertension and heart failure.2.On hemodynamics,the change of right atrial function performed increased of reserve function,reduced pipeline function and increased of auxiliary pump(contraction)function.However,the strain and strain rate reduced in different degree.RA-GLS and RA-SRe decreased the earliest,which suggested that strain and strain rate were the parameters which can reflect myocardial function damage earliest.3.RA-GLS and RA-SRe were directly correlated with AHI,suggesting that it was one of the independent predictors of disease severity.4.RA-GLS and RA-SRe were associated with RV-GLSs and RV-SRe,suggesting that the reduced RA function is due to the reduced RV diastolic and systolic function.At the same time,it also suggested that RA-GLS and RA-SRe can reflect the function of right ventricle indirectly.5.VVI can more earlierly and accurately detect myocardial dysfunction of right atrium in patients with OSAS,which is expected to be a worthy technique for early clinical therapy in patients with OSAS.