| Hypertrophic cardiomyopathy (HCM) is a euchromosome-dominant hereditary disease due to fault mutation in spectrin gene of myocomma.The exact cause of this disease is not very clear yet. However,sudden death in youth and euchromosome-dominant heritage result in attentions of people. At present, echocardiography remains the primary examination method in HCM clinical diagnoses.Conventional two-dimensional echocardiography and M-mode echocardiography can make a comparatively accurate diagnose in HCM with asymmetric septal hypertrophy. But for some cases with substandard hypertrophy, they can not make an early diagnosis. Moreover, myocardiac mechanical parameters of denatured myocardium can not be described quantificationally. The objective of this study is to quantify the myocardiac mechanical characters in patients with HCM by strain imaging ( SI ) and strain rate imaging ( SRI ) ,and to find a kind of myocardiac mechanical parameter, which can evaluate regional myocardial pathologic changes in the early stage of HCM, so that an effective tool can be provided to serve clinical early diagnosis and treatment of HCM. This thesis is composed of two parts:Part I. Assessment of Regional Myocardial Systolic Function of Left Ventricle in Patients with Hypertrophic Cardiomyopathy by Tissue Strain and Strain Rate ImagingForty patients were categorized into two groups according to pressure gradient difference at the left ventricle outflow tract(LVOT), which were obstruction HCM group (LVOT PG≥20mmHg) and non-obstruction HCM group (LVOT PG<20mmHg). Twenty-five age-matched healthy persons were used as control group. Systolic peak strain (εet),Systolic peak strain rate (SRs)of different left ventricular segments have been measured along left ventricle longitudinal axis both in patients with HCM and healthy subjects. Results:①In normal group, SRs andεet showed a decreasing trend from base segment to apical segment in the same left ventricular wall .There were no differences between parameters from every segment (P>0.05). Regional SRs andεet were homogeneous in all normal subjects.②In HCM group, above trend was unavailable. SRs andεet of hypertrophic segments were significantly less (P<0.05) than those from mild-thickening and non-thickening segments, and the lowest value was found in the midseptum segment (P<0.001).In addition, reversedεet (positiveεet, namely paradoxical longitudinal expansion in systole) had been revealed in 40% hypertrophic segments in systolic period. In combined HCM and normal group, there was a significant negative correlations between longitudinalεet (absolute value) and thickness in midseptum segment (r=0.83), which revealed that systolic strain and strain rate had the ability to reflect pathologic characters in different ventricular wall thickness.③As for strain, strain rate of regional segment, no significant differences were found between obstruction HCM group and non-obstruction HCM group(P>0.05). It suggested that tissue strain and strain rate imaging are independent of obstruction status of ventricle. This viewpoint could be further verified in the later part, where no statistically significant correlation were found between systolic peak strain of midseptum and left ventricle outflow pressure gradient in HCM group.④SRs andεet in both hypertrophic and non-hypertrophic segments in patients with HCM were all notably lower than those of normal group(P<0.05), which revealed that global systolic functions decreased in patients with HCM.Part II.Assessment of Regional Myocardial Diastolic Function of Left Ventricle in Patients with Hypertrophic Cardiomyopathy by Tissue Strain and Strain Rate ImagingThe study subjects were divided into two groups: 40 cases with asymmetric septal hypertrophy as HCM group and 25 aged-matched healthy persons as control group. Diastolic peak SRe and SRa, isovolumic relaxation peak SR(SRIVR), systolic maximaum strain(εmax) of different left ventricular segments have been measured along left ventricle longitudinal axis both in patients with HCM and healthy subjects,and SRIVR/SRs andεpss (εpss=εmax-εet)were calculated. Results:①In normal group, diastolic peak strain rate of left ventricle showed a decreasing trend from base segment to apical segment, which was the same as systolic SR. There were no differences between parameters from every segment. However, this trend was unavailable in patients with HCM. SRe and SRe/SRa in hypertrophic segment were notably lower than those from mild-thickening and non-thickening segments, and the lowest value was found in the midseptum segment (P<0.001). It could indicate that there was a close relationship between diastolic peak strain rate and ventricular thickness. SRe,SRa and SRe/SRa in patients with HCM were significantly less than those in normal subjects (P<0.05), which revealed that diastolic dysfunction of regional myocardial existed in both hypertophic and non-hypertrophic myocardium. Among these parameters, SRe and SRe/SRa decreased more remarkably than SRa in HCM group, which demonstrated that SRe and SRe/SRa were more sensitive indexes in evaluating diastolic dysfunction. In normal group, mean SRe/SRa of differet segments was larger than 1, while that in HCM group was smaller than 1.②In normal group, there were no notably differences between absolute value of SRIVR of every segments. with the values ranged from -0.08±0.26cm/s to 0.26±0.25cm/s. Statistical results from 40 patients with HCM showed that the absolute values of negative SRIVR in hypertrophic segments was significantly larger than those in mild-thickening and non-thickening segments. SRIVR/SRs was smaller than 0.25 in the normal subjects and this was larger than 0.60 in hypertrophic segments of HCM group, The absolute values of SRIVR and SRIVR/SRs of mild-thickening and non-thickening segments showed no notable difference compared with those of normal subjects. Post systolic-shortening (PSS) existed in 22% segments in the normal subjects andεpss ranged from -2.8% to-2.4%. While PSS existed in 62% segments in the patients with HCM, and 83% of hypertrophic segments occurred PSS. Moreover, Theεpss of hypertrophic segments were notably larger than those of non-hypertrophic segments and those of normal group. SRIVR,SRIVR/SRs and PSS are sensitive indexes for detecting ischemic myocardium , and above-mentioned results indicated that hypertrophic myocardium has presented evident blood supply shortage.Conclusion:①SI and SRI can sensitively detect systolic and diastolic dysfunction of different segments along left ventricle longitudinal axis in patients with HCM. This technology are recommended to assess early pathologic abnormality and dysfunction of regional myocardium.②SI and SRI are independent of LVOT obstruction. They are relatively less influenced global cardiac movement and traction from nearby regions. And it can more actually reflect myocardiac mechanical characters than TVI. This technology has wide clinical applicant perspective in evaluating regional myocardial function.
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