Congenital increase in cardiac outflow tract resistance would lead to chronic ventricular pressure overloading, and eventually ventricular hypertrophy and dysfunction. Conventional echocardiographic assessment of global ventricular systolic and diastolic function is far from ideal because of the lack of sensitivity. There is a pressing need in developing a clinical tool to unveil the degree of myocardial dysfunction as well as to monitor the treatment effect in these patients. M-mode and tissue Doppler recordings of the left and right atrioventricular rings' motion in a longitudinal cardiac axis allowed us to assess segmental ventricular function in a more sensitive and specific way. This thesis aimed to assess ventricular long axis function in patients with congenital outflow tract obstructions. It is based on the anatomical observation that a major part of long axis function is subtended by subendocardial fibers, and the hypothesis that the function of these fibers might be more sensitive to effect of pressure overload than circumferential ones. / Normal values for left and right ventricular (RV) long axis function (in left, septal and tricuspid sites of atrioventricular rings) were first established by studying normal healthy volunteers without cardiovascular diseases with M-mode and pulse wave (PW) tissue Doppler Imaging (TDI). These values included: / 1) M-mode derived systolic amplitude of motion (displacement) / 2) Any long axis incoordination (long axis shortening after end of ejection which was reported as a sign of coronary ischemia after excluding interventricular conduction abnormalities) / 3) TDI-derived peak systolic and diastolic velocities. / The following groups of patients with congenital outflow tract obstructions were therefore studied: / 1) Congenital aortic valve stenosis and subaortic stenosis (21 patients, study 1). / 2) Congenital coarctation of aorta (23 patients, study 2). / 3) Congenital pulmonary valve stenosis (43 patients, study 3). / Study 1 investigated the presence of "isolated" diastolic disease, defined as reduced long axis early diastolic velocity with normal systolic velocity in 21 young patients with congenital aortic valve stenosis (AVS). Most patients with normal left ventricular (LV) ejection fractions in fact had depressed long axis systolic velocities. This work demonstrated the selective sensitivity of long axis function in unveiling myocardial dysfunction in AVS patients. Moreover, good correlation was found between long axis systolic and diastolic velocities which suggested isolated diastolic disease is unlikely. / Patients with coarctation of aorta (CoA) are often less symptomatic (fewer reported chest pain or heart failure) that AVS patients despite having similar degree of outflow resistance. Study 2 addressed such phenomenon by studying the long axis function in 23 CoA patients and the results were compared to 23 AVS patients and normal controls. This work again confirmed the presence of LV long axis impairment in patients with chronic increase in LV afterload. Moreover, a worse deterioration of LV long axis function and a higher prevalence of long axis incoordination independent of LV outflow resistance is seen in patients with proximally increased LV afterload (AVS) compared with distal disease (CoA) that might account for their difference in clinical behavior. / Data are scant to address the impact of chronic increase in RV outflow resistance on RV diastolic performance. Study 3 evaluated the relationship of restrictive RV physiology (defined as the presence of antegrade pulmonary arterial flow in late diastole measured by conventional PW Doppler echocardiography) to RV long axis function and patients' symptoms in 43 patients with pulmonary valve stenosis (PVS). Restrictive RV physiology was found in 42% studied patients who were more symptomatic and had more severe RV long axis dysfunction. This work implied regular follow-up of adult PVS patients using simple qualitative RV Doppler echocardiographic measurements should guide toward early identification of myocardial dysfunction and the need for removal of outflow tract obstruction before irreversible damage occurs. / Given the selective sensitivity of long axis function in assessing myocardial damage In patients with pressure overloaded ventricle, I further studied the effect of interventions on change of long axis behavior in patients with CoA: / 1) Before and 14 month after successful endovascular stenting (21 patients, study 4). / 2) Long term follow up after surgical correction, by either angioplasty or endovascular stenting (80 patients, study 5). / Study 4 prospectively evaluated the effect of endovascular stenting on intermediate-term biventricular function in 21 adults with CoA and the results were compared with surgically repaired patients and normal controls. LV long axis disturbances were improved with sparing of RV long axis function after intervention. Subclinical myocardial dysfunction was observed in both stented and repaired patients compared with normal controls. This work supported aortic stenting in patients with anatomically suitable lesions. It also prompted further studies on the clinical significance of persistent myocardial dysfunction in "corrected" CoA patients. / In study 5, I went on to examine the prevalence of LV long axis diastole dysfunction (defined as septal PW TDI early diastolic velocity 8cm/s) in a relatively large cohort of CoA patients (n=80) and its relationships to patient demo graphics and aortic elastic properties. Forty-seven patients (59%) were found to have LV long axis dysfunction. As a group, they were older when received treatment and had higher ascending aortic stiffness indices despite similar systemic blood pressure, prevalence of anti-hypertensive use and associated bicuspid aortic valve as compared to other CoA patients. This work addressed the age at intervention and increased aortic stiffness are important determinants of persistent myocardial dysfunction after intervention. Intervention at an early age before structural damage to proximal aorta and appropriate medications to reduce central aortic stiffness might preserve LV long axis function in "corrected" CoA patients and further improve their long term prognosis. / CONCLUSIONS: / In conclusion, conventional global echocardiographic assessment is inadequate for assessing patients with congenital outflow tract obstructions. Segmental ventricular long axis function is frequently abnormal at rest in these patients. The site of these disturbances corresponds to the ventricle that is subjected to pressure overloading. Assessment of long axis function is simple and sensitive. It has considerable potential in investigating the natural course of myocardial damage, to clarify the basis of abnormal ventricular function, particularly during diastole and to evaluate treatment effect on myocardial recovery in patients with congenital outflow tract obstructions. Further studies should focus on the role of long axis function in determining prognosis for these patients. / Lam, Yat Yin. / "November 2011." / Thesis (M.D.)--Chinese University of Hong Kong, 2012. / Includes bibliographical references (leaves 134-160). / ABSTRACT --- p.1 / Chapter PART1 --- HISTORIC REVIEW --- p.5 / Chapter Chapter1 --- VENTRICULAR OUTFLOW TRACT OBSTRUCTION SYNDROME --- p. 6 / Chapter 1.1 --- BACKGROUND --- p.7 / Chapter 1.2 --- AORTIC VALVULAR STENOSIS --- p.8 / Chapter 1.2.1 --- Anatomy pathophysiology and clinical features --- p.8 / Chapter 1.2.2 --- Investigations --- p.9 / Chapter 1.2.3 --- Treatment --- p.9 / Chapter 1.3 --- COARCTATION OF AORTA --- p.9 / Chapter 1.3.1 --- Anatomy pathophysiology and clinical features --- p.9 / Chapter 1.3.2 --- Investigations --- p.11 / Chapter 1.3.3 --- Treatment --- p.11 / Chapter 1.4 --- PULMONARY VALVULAR STENOSIS --- p.12 / Chapter 1.4.1 --- Anatomy pathophysiology and clinical features --- p.12 / Chapter 1.4.2 --- Investigations --- p.13 / Chapter 1.4.3 --- Treatment --- p.13 / Chapter Chapter2 --- VENTRICULAR RESPONSE TO HIGH AFTERLOAD --- p.14 / Chapter 2.1 --- VENTRICULAR ADAPTATION IN AORTIC VALVULAR STENOSIS --- p.15 / Chapter 2.2 --- VASCULAR STIFFENING AORTIC COARCTATION --- p.17 / Chapter 2.3 --- VENTRICULAR ADAPTATION IN PULMONARY VALVULAR STENOSIS --- p.18 / Chapter 2.4 --- LIMITATIONS OF CONVENTIONAL ECHOCARDIOGRAPHY --- p.19 / Chapter Chapter3 --- MYOCARDIAL FIBER ARCHITECTURE AND LONG AXIS FUNCTION --- p.21 / Chapter 3.1 --- MYOCARDIAL FIBER STRUCTURE AND LONG AXIS FUNCTION --- p.22 / Chapter 3.2 --- NOMRAL LONG AXIS EXCURSION AND TIMING --- p.25 / Chapter 3.3 --- QUANTIFICATION OF LONG AXIS MOTIONS --- p.26 / Chapter 3.3.1 --- M-mode --- p.26 / Chapter 3.3.2 --- Clinical applications of atrio-ventricular plane displacement --- p.27 / Chapter 3.3.3 --- Tissue Doppler Imaging --- p.28 / Chapter 3.3.4 --- Clinical application of tissue Doppler imaging --- p.30 / Chapter 3.3.5 --- Limitations of M-mode and TDI in the assessment of long axis function --- p.31 / Chapter Chapter4 --- HYPOTHESIS AND SPECIFIC OBJECTIVES OF THE THESIS --- p.32 / Chapter 4.1 --- INTRODUCTION --- p.33 / Chapter 4.2 --- HYPOTHESIS --- p.34 / Chapter Chapter5 --- METHODOLOGY --- p.35 / Chapter 5.1 --- STUDY PATIENTS --- p.36 / Chapter 5.1.1 --- Patients with ventricular outflow tract obstruction --- p.36 / Chapter 5.1.2 --- Normal controls --- p.36 / Chapter 5.2 --- CLINICAL ASSESSMENT --- p.37 / Chapter 5.3 --- ECHO CARDIOGRAPHIC ASSESSMENT --- p.37 / Chapter 5.3.1 --- Imaging acquisition protocol --- p.37 / Chapter 5.3.2 --- Assessment of severity of outflow tract obstruction --- p.38 / Chapter 5.3.3 --- Assessment of global ventricular structure and function --- p.40 / Chapter 5.3.4 --- Assessment of long axis function --- p.42 / Chapter 5.3.5 --- Evaluation of restrictive RV physiology in PVS patients --- p.42 / Chapter 5.3.6 --- Determination of aortic elastic properties in CoA patients --- p.43 / Chapter 5.3.7 --- Reproducibility --- p.45 / Chapter 5.4 --- CARDIAC CATHETERIZATON AND ENDOVASCULAR STENTING FOR COARCTATION OF AORTA --- p.45 / Chapter 5.5 --- STATISTICS --- p.46 / Chapter PART 2 --- CLINICAL STUDIES --- p.48 / Chapter Chapter6 --- "ISOLATED" DIASTOLIC DYSFUNCTION IN LEFT VENTRICULAR OUTFLOW TRACT OBSTRUCTION --- p.49 / Chapter 6.1 --- INTRODUCTION --- p.50 / Chapter 6.2 --- METHODS --- p.50 / Chapter 6.2.1 --- Study population --- p.50 / Chapter 6.2.2 --- Echocardiographic examination --- p.51 / Chapter 6.2.3 --- Reproducibility --- p.51 / Chapter 6.2.4 --- Statistics --- p.51 / Chapter 6.3 --- RESULTS --- p.52 / Chapter 6.3.1 --- Baseline characteristics --- p.52 / Chapter 6.3.2 --- Echocardiographic measurements --- p.52 / Chapter 6.3.3 --- Correlation analysis between long axis variables --- p.55 / Chapter 6.3.4 --- Reproduci bility --- p.58 / Chapter 6.4 --- DISCUSSION --- p.58 / Chapter 6.4.1 --- Selective sensitivity oflong axis function --- p.58 / Chapter 6.4.2 --- Close coupling of long axis systolic and diastolic function --- p.59 / Chapter 6.4.3 --- Limitations --- p.60 / Chapter 6.5 --- CONCLUSIONS --- p.61 / Chapter Chapter7 --- EFFECT OF CHRONIC AFTERLOAD INCREASE ON LEFT VENTRICULAR MYOCARDIAL FUNCTION IN PATIENTS WITH CONGENITAL LEFT-SIDED OBSTRUCTIVE LESIONS --- p.62 / Chapter 7.1 --- INTRODUCTION --- p.63 / Chapter 7.2 --- METHODS --- p.63 / Chapter 7.2.1 --- Study population --- p.63 / Chapter 7.2.2 --- Echocardiographic examination --- p.64 / Chapter 7.2.3 --- Reproducibility --- p.65 / Chapter 7.2.4 --- Statistics --- p.65 / Chapter 7.3 --- RESULTS --- p.66 / Chapter 7.3.1 --- Baseline characteristics --- p.66 / Chapter 7.3.2 --- Patients versus controls --- p.66 / Chapter 7.3.3 --- Aortic valvular stenosis versus coarctation patients --- p.70 / Chapter 7.3.4 --- Reproducibility --- p.70 / Chapter 7.4 --- DISCUSSION --- p.72 / Chapter 7.4.1 --- Long axis function in patients with increased LV afterload --- p.72 / Chapter 7.4.2 --- Difference between aortic valvular stenosis and coarctation patients --- p.72 / Chapter 7.4.3 --- Limitations --- p.74 / Chapter 7.5 --- CONCLUSIONS --- p.74 / Chapter Chapter8 --- RESTRICTIVE RIGHT VENTRICULAR PHYSIOLOGY: ITS PRESENCE AND SYMPTOMATIC CONTRIBUTION IN PATIENTS WITH PULMONARY STENOSIS --- p.75 / Chapter 8.1 --- INTRODUCTION --- p.76 / Chapter 8.2 --- METHODS --- p.77 / Chapter 8.2.1 --- Study population --- p.77 / Chapter 8.2.2 --- Echocardiographic examination --- p.77 / Chapter 8.2.3 --- Reproducibility --- p.78 / Chapter 8.2.4 --- Statistics --- p.78 / Chapter 8.3 --- RESULTS --- p.79 / Chapter 8.3.1 --- Baseline characteristics --- p.79 / Chapter 8.3.2 --- Patients versus controls --- p.81 / Chapter 8.3.3 --- Comparison between patient groups --- p.81 / Chapter 8.3.4 --- Predictors for symptoms --- p.84 / Chapter 8.3.5 --- Reproducibility --- p.85 / Chapter 8.4 --- DISCUSSION --- p.85 / Chapter 8.4.1 --- Main findings --- p.85 / Chapter 8.4.2 --- Characterization of diastolic performance in pulmonary valvuar stenosis patients --- p.85 / Chapter 8.4.3 --- Mechanism for restrictive RV physiology in PVS patients --- p.87 / Chapter 8.4.4 --- Study inlplications --- p.89 / Chapter 8.4.5 --- Limitations --- p.90 / Chapter 8.5 --- CONCLUSIONS --- p.90 / Chapter Chapter9 --- EFFECT OF ENDOVASCULAR STENTING OF AORTIC COARCTATION ON BIVENTRlCULAR FUNCTION IN ADULTS --- p.91 / Chapter 9.1 --- INTRODUCTION --- p.92 / Chapter 9.2 --- METHODS --- p.92 / Chapter 9.2.1 --- Study population --- p.92 / Chapter 9.2.2 --- Implantation procedure --- p.93 / Chapter 9.2.3 --- Echocardiographic examination --- p.94 / Chapter 9.2.4 --- Reproducibility --- p.94 / Chapter 9.2.5 --- Statistics --- p.95 / Chapter 9.3 --- RESULTS --- p.95 / Chapter 9.3.1 --- Baseline characteristics --- p.95 / Chapter 9.3.2 --- Blood pressure data --- p.96 / Chapter 9.3.3 --- Echocardiographic measurements --- p.97 / Chapter 9.3.3.1 --- Pre-stenting versus post-stenting (group 1) --- p.97 / Chapter 9.3.3.2 --- Stenting (group 1) versus post-surgical repair (group 2) --- p.101 / Chapter 9.3.3.3 --- Coarctation patients (group 1 post-stenting and group 2) versus control (group 3) --- p.101 / Chapter 9.3.4 --- Reproducibility --- p.101 / Chapter 9.4 --- DISCUSSION --- p.103 / Chapter 9.4.1 --- Main findings --- p.103 / Chapter 9.4.2 --- Potential impact of stenting on cardiovascular outcome --- p.103 / Chapter 9.4.2.1 --- BP control --- p.103 / Chapter 9.4.2.2 --- LV mass and long axis function --- p.104 / Chapter 9.4.3 --- RV function after stenting --- p.105 / Chapter 9.4.4 --- Subclinical LV myocardial function in coarctation patients --- p.105 / Chapter 9.4.5 --- Limitations --- p.106 / Chapter 9.5 --- CONCLUSIONS --- p.107 / Chapter Chapter10 --- LEFT VENTRICULAR LONG AXIS DYSFUNCTION IN ADULTS WITH "CORRECTED" AORTIC COARCTATION IS RELATED TO AN OLDER AGE AT INTERVENTION AND INCREASED AORTIC STIFFNESS --- p.108 / Chapter 10.1 --- INTRODUCTION --- p.109 / Chapter 10.2 --- METHODS --- p.110 / Chapter 10.2.1 --- Study population --- p.110 / Chapter 10.2.2 --- Echocardiographic examination --- p.111 / Chapter 10.2.3 --- Reproducibility --- p.111 / Chapter 10.2.4 --- Statistics --- p.112 / Chapter 10.3 --- RESULTS --- p.112 / Chapter 10.3.1 --- Patients versus controls --- p.112 / Chapter 10.3.2 --- Patients with long axis dysfunction (LAD) versus without LAD --- p.113 / Chapter 10.3.3 --- Predictors of LAD --- p.117 / Chapter 10.3.4 --- Reproducibility --- p.120 / Chapter 10.4 --- DISCUSSION --- p.120 / Chapter 10.4.1 --- Main findings --- p.120 / Chapter 10.4.2 --- LV dysfunction and adverse remodeling in "corrected" aortic coarctation --- p.120 / Chapter 10.4.3 --- Mechanism behind LV dysfunction in "corrected" aortic coarctation --- p.121 / Chapter 10.4.4 --- Study implications --- p.124 / Chapter 10.4.5 --- Limitations --- p.124 / Chapter 10.5 --- CONCLUSIONS --- p.125 / Chapter Chapter 11 --- DISCUSSION --- p.126 / Chapter 11.1 --- DISCUSSION --- p.127 / Chapter 11.2 --- LIMITATIONS --- p.129 / Chapter 11.3 --- THE FUTURE --- p.129 / Chapter Chapter12 --- CONCLUSIONS --- p.131 / APPENDIX --- p.133 / BIBLIOGRAPHY --- p.134
| Identifer | oai:union.ndltd.org:cuhk.edu.hk/oai:cuhk-dr:cuhk_328781 |
| Date | January 2012 |
| Contributors | Lam, Yat Yin., Chinese University of Hong Kong Graduate School. Division of Medicine. |
| Source Sets | The Chinese University of Hong Kong |
| Language | English |
| Detected Language | English |
| Type | Text, bibliography |
| Format | electronic resource, electronic resource, remote, 1 online resource (160 leaves) : ill. |
| Rights | Use of this resource is governed by the terms and conditions of the Creative Commons “Attribution-NonCommercial-NoDerivatives 4.0 International” License (http://creativecommons.org/licenses/by-nc-nd/4.0/) |
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