Clinical Study Of Right Ventricular Regional Myocardium And Global Function In Preoperative And Postoperative Patients With Tetralogy Of Fallot By Ultrasound Speckle Tracking Imaging

Tetralogy of Fallot (TOF) is the most common cyanotic congenital heart disease with a prevalence of 0.5 per 1000 live births, and represents approximately 9% of all congenital heart diseases. The natural prognosis of this disease is poor, and heart failure is the main cause of death in patients with TOF. Early repair of tetralogy of Fallot is generally advised to minimize the effects of chronic hypoxia and to reduce long-standing pressure overload to the right ventricle (RV) and its consequences. The surgical repair currently is achieved in children aged less than 1 year. With the improvement of intracardiac surgery, most people with postoperative TOF have a good long-term prognosis. However, it is well known that some patients can experience a prolonged, troublesome postoperative recovery, associated with severe postoperative complication. Therefore, assessment of complicated impact of the hemodynamic changes after the surgery, the change of RV load and the damage of cardiac surgery on RV function is of great importance. The ability to measure RV function before and after cardiac surgery would not only increase our knowledge of postoperative changes in myocardial contractility but also potentially guide modification of ventricular function by therapeutic changes in inotropic support in the early and mid-term postoperative period.Patients with repaired TOF have commonly associated with different degree of pulmonary regurgiatation. Long-term pulmonary regurgiatation leads to RV dilation and dysfunction, right heart failure, arrhythmias or sudden cardiac death. Postoperative RV dysfunction in patient with TOF is the determinant of the long-term survive and the independent predictor of poor clinical cardiac function status. Therefore, evavulation of RV function in patients with late repaired TOF is important. Most of patients with late repaired TOF have no clinical symptom, though, RV function of these patients have changed. Consequently, early detection of RV dysfunction in asymptomatic patients with late repaired TOF has great clinical value.Several histopathology of the myocardium in hearts with TOF have confirmed that patient with TOF exist myocyte hypertrophy and fiber disarray, different degree and form of fibrosis, which become more pronounced in older patients. These changes may result in ventricular dysfunction and arrhythmias in the long term.Accurate quantification of RV function remains a challenge due to complex geometry, affluent muscular trabeculations interrelationship with the left ventricle, and sensitivity to alterations in pulmonary pressure. Various techniques for RV assessment have been employed, including radioactive nuclide, ventriculography, magnetic resonance imaging (MRI), CT, cardiac catheter and echocardiography, all of which have their particular benefits and disadvantages. Ventriculography and cardiac catheter is invasive. Radioactive nuclide and CT expose to radioactive ray. Magnetic resonance imaging is the gold standard for evaluating the RV volume and ejection fraction, however, it is not suit for some patients (i.e. patient with pacemaker implantation),and time consuming and expensive, which limits its wide clinical application. Echocardiography is so simple, low-cost, noninvasive and reproducible that it appears to be widely clinical application. Recently, two-dimensional ultrasound speckle tracking imaging (STI) is a novel technique for obtaining strain and strain rate measurements. It quantitatively analyzes the displacement and velocity of the myocardium by tracking myocardial motion from frame to frame throughout the cardiac cycle. It is independent of geometric assumpation and affords a new method to assess ventricular global and regional function. The angle- independent method is more accurate and objective quantification of ventricular function than other techniques.This study included four parts as follow: Part 1 Assessment of right ventricular regional and global function in patients with tetralogy of Fallot by ultrasound speckle tracking imagingThe aim of this part was to assess RV global and regional function in patients with TOF by ultrasound speckle tracking imaging (STI), and to explore the main factors affecting the RV functional parameters.38 patients with TOF were enrolled in this study and divided into children group (25) and adult group (13) according to age. Longitudinal peak systolic velocity(V), strain (ε), strain rate(SRs) were measured in RV free wall and interventricular septum(IVS) for basal, mid and apical segment by STI from the apical 4-chamber view. RV global longitudinal peak systolic strain (GLS), strain rate (GLSRS), early diastolic strain rate (GLSRe) and late diastolic strain rate (GLSRa) were measured from the above view. Results①Compared with controls,εand SRs of RV free wall and IVS for all segments were significantly impaired in patients with TOF(P<0.05 for all). Whereas, V of RV each segment were normal (P>0.05 for all). In patients with TOF and controls. V,εand SRs of RV free wall for all segments were higher than those of IVS except SRs of RV apical segment.②Compared with controls, right ventricular GLS, GLSRS and GLSRe were significantly reduced in patients with TOF(P<0.05 for all). Right ventricular GLSRs significantly decreased in adult patients with TOF compared with children patients(P<0.05). Right ventricular GLS, GLSRe and GLSRa showed no significant difference between children and adult TOF groups(P>0.05).③The diameter of right ventricle, main pulmonary artery and ventricular septum defect had correlations with right ventricular GLSRS (r1=00.490, r2=-0.580, r3=-0.528, respectively, P<0.05 for all). Tricuspid valvular annular systolic peak velocity (Sm) was the independent predictor of RV global strain and strain rate (β1=0.355, P1,=0.031,β2=0.307,P2=0.021) Part 2 The impact of right ventricular myocardial remodeling on ventricular function in patients with tetralogy of FallotThe purpose of this part was to assess the impact of RV myocardial histopathologic changes on ventricular function in patients with TOF. Operatively resected crista supraventricularis muscle from 30 patients undergoing intracardiac repair of TOF were obtained for histopathologic evaluation. RV global longitudinal peak systolic strain (GLS), strain rate (GLSRs), early diastolic strain rate (GLSRe) and late diastolic strain rate (GLSRa) were measured by STI from the apical 4-chamber view. Results①Histopathologic data revealed hypertrophy of the cardiomyocytes, thickening endocardial, and increased interstitial and perivascular collagen in right ventricle.②Cardiomyocyte diameter, interstitial collagen volume fraction(CVF) and endocardial thickness were correlated with age (r,=0.703, P1=0.000; r2=0.593, P2=0.001; r2=0.549, P2=0.002).③RV cardiomyocyte diameter and CVF had correlation with GLSRs (r1=-0.614, P1=0.000; r2=-0.517,P2=0.003). Endocardial thickness was correlated with GLS(r=-0.432,P=0.017). CVF corresponded with GLSRe (r=-0.669, P=0.000).④RV cardiomyocyte diameter was the independent predictor of GLSRs (β=-0.596,P=0.002), endocardial thickness and CVF were the independent predictor of GLS (β1=-0.918,P1=0.001,β2=-0.690, P2=0.008), CVF was the independent predictor of GLSRe (β=-0.618, P=0.001). Part 3 Assessment of right ventricular regional and global function in preoperative and postoperative patients with tetralogy of Fallot by ultrasound speckle tracking imagingThe purpose of this part is to assess RV regional and global function in patients with TOF before and after operation by STI, and to explore the factors affecting RV preoperative and postoperative systolic function.36 patients with TOF before,1 week after,3 months after, and 6 months after operation were studied. RV longitudinal peak systolic strain (S) strain rate(SRs) were measured in RV free wall and interventricular septum(IVS) for basal, mid and apical segment by STI from the apical 4-chamber view, RV global longitudinal peak systolic strain (GLS) and strain rate (GLSRs) were measured from the above view.. Results①Compared with controls,RV GLS andεof RV free wall for basal,mid and apical segments were significantly reduced in preoperative patients with TOF(P<0.05 for all),these parameters further decreased at 1 week after operation, and increased to preoperative level at 3 months and 6 months after operation,and but lower than those of controls. Whileεof IVS for all segments did not decrease further at 1 week after operation, and increased to normal level at 3 months and 6 months after operation.②In comparison with controls, RV GLSRs and SRs of RV free wall for basal,mid and apical segments were significantly reduced in preoperative patients with TOF(P<0.05 for all),these parameters did not decrease further at 1 week after operation, and increased to normal level at 3 months and 6 months after operation. SRs of IVS for all segments did not decrease in preoperative patients with TOF, these indices increased at 1 week after operation, followed by toward normal level at 3 months and 6 months after operation.③GLS and GLSRs of RV was correlated inversely with the diameter of RV, QRS duration and age, and positively with tricuspid valvular annular peak systolic velocity (Sm). RV GLS and GLSRs had no correlation with the mode of operation. Age was the independent predictor of RV global strain and strain rate (β1=-0.212,P1=0.012,β2=-0.180, P2=0.033). Part 4 Assessment of right ventricular regional and global function in patients with late repaired tetralogy of Fallot by ultrasound speckle tracking imagingThe aim of this part was to assess RV regional and global function in asymptomatic patients with repaired TOF by STI. 36 asymptomatic patients with repaired TOF whose postoperative period is more than one year and 35 healthy controls were studied. RV longitudinal peak systolic strain (ε), strain rate(SRs) were measured in RV free wall and interventricular septum(IVS) for basal, mid and apical segment by STI from the apical 4-chamber view, RV global longitudinal peak systolic strain (GLS), strain rate (GLSRs), early diastolic strain rate (GLSRe) and late diastolic strain rate (GLSRa) were measured from the above view. The correlations between RV systolic functional parameters and the postoperative period, degree of pulmonary regurgitation (PR) and QRS duration were explored. Results①Compared with controls,εand SRs of RV free wall and IVS for all segments, GLS, GLSRs, GLSRe, and GLSRa were significantly impaired in patients with repaired TOF(P<0.05 for all). Both GLS and GLSRs were lower in postoperative patients with transannular patch than in those with RV out tract patch.②In comparison with controls, GLS, GLSRs,GLSRe and GLSRa were decreased in postoperative patients with mild, mid and severe PR, Whereas, there was no difference in RV global function among the patients with varying degree of PR.③GLSRs of RV was correlated inversely with postoperative period and QRS duration (r1=-0.431, P1=0.009; r2=-0.469, P2=0.004), RV GLS and GLSRs had no correlation with PR. Conclusions1. RV regional and global function in patients with TOF were decreased, especially in adult patients.2. Pulmonary arterial development and ventricular septum defect are the main factors affecting RV function in patients with TOF, the change in RV function highly correlates with altered RV morph.3. Myocardial tissues in TOF indicates hypertrophic cardiomyocytes, thickening endocardial, and interstitial and perivascular fibrosis. The changes are more pronounced in older patients subjected to long-standing hypoxia and pressure overload. RV myocardial remodeling impacts inversely on ventricular systolic and diastolic function in patients with TOF.4. RV regional and global function in patients with TOF can be improved after operation. The mode of operation has no influence on early postoperative RV function. Course of disease inversely impacts on postoperative RV function.5. RV regional and global function in patients with late repaired TOF are decreased, STI can early detect right ventricular dysfunction in asymptomatic patients with repaired TOF. The type of operation impacts on late prognosis, RV abnormal deformations are associated with electrical depolarization abnormalities.6. STI appear to be a potentially useful quantitative tool for follow-up evaluation of RV function after cardiac surgery.