| ObjectiveIn cardiac magnetic resonance(CMR) imaging, the T1 relaxation time for the 1H magnetization in myocardial tissue may represent a valuable biomarker for a variety of pathological conditions. This possibility has driven the growing interest in quantifying T1. The techniques have advanced to where pixellevel myocardial T1 mapping has become a routine component of CMR examinations. Combined with the use of contrast agents, T1 mapping has led an expansive investigation of interstitial remodeling in ischemic and nonischemic heart disease. Cardiac magnetic resonance(CMR) measurements of myocardium and blood before and after contrast allow quantification of the myocardial extracellular volume fraction(ECV), a tissue parameter that has been shown to change in proportion to the connective tissue fraction. The work first established to investigate the characteristics of myocardial extracellular volume fraction(ECV) derived from pre- and post-contrast T1 measurements among healthy volunteers. A second investigation of this study was to assess the relationship among ECV in hypertensive patients with left ventricular hypertrophy(HTN-LVH), hypertensive patients without LVH(HTN no-LVH),and normotensive controls. Next study was to investigate diffuse myocardial fibrosis in hypertensive patients with Diastolic heart failure symptoms from those with LVH, but without Diastolic heart failure symptoms using T1 mapping. A final study investigated myocardial extracellular volume(ECV) is increased in patients with hypertension and whether there is an association between ECV and post-procedural occurrence of Atrial Fibrillation, Diastolic heart failure and Death events. MethodsA total of 57 healthy volunteers underwent standard CMR imaging with administration of gadolinium. T1 measurements were performed with a Look-Locker sequence followed by gradient-echo acquisition(GRE). We tested the segmental, interslice,inter-, intra-, and test-retest characteristics of the ECV,as well as the association of the ECV with other variables. Secondly retrospectively selected 54 cases,T1 mapping was performed in 18 HTN-LVH, 20 HTN non-LVH, and 16 control subjects. We selected 98 patients with hypertensive heart disease(HTN 35 cases, 30 HTN-LVH without diastolic heart failure, 33 HTN-LVH with diastolic heart failure)was used to study the relationship between the degree of diffuse myocardial fibrosis and diastolic heart failure. Consecutive patients with hypertension underwent a contrast CMR study with measurement of ECV and were followed up 24 months, The first endpoint of interest was late occurrence Atrial Fibrillation, the second endpoint of interest was late Diastolic heart failure and Death events. ResultsFifty-seven healthy volunteers were recruited and were included in the analysis. There were 26 men(46%) and 31 women,The mean age of volunteers was 47±17 years(range 21 to 78 years). The average body mass index was 27±4kg/m2,systolic blood pressure(SBP) was 119±11mm Hg,diastolic blood pressure(DBP) was 74±4mm Hg,heart rate was 67±6 beats/min, and hematocrit was 43±2%. The ECV averaged 0.27±0.04(range 0.21 to 0.34). The intraclass coefficients for the intraobserver, interobserver and test-retest absolute agreements of the ECV were 0.95(95% confidence interval: 0.85 to 0.98), 0.87(95% confidence interval: 0.64 to 0.96), and 0.97(95% confidence interval: 0.84 to 0.99), respectively. In volunteers, the ECV was associate with age(r=0.81, P<0.001), maximal left atrial volume index(r=0.38, P=0.00036(P<0.01)), and indexed left ventricular mass. There were no differences in the ECV between segments in a slice or between slices. In the Second part of this study, the ECV in HTN-LVH was significantly higher than the control group(0.30 + 0.02 vs. 0.26 + 0.01, P < 0.001), HTN-LVH was higher than that of HTN(0.30 + 0.02 vs. 0.27 + 0.02, P < 0.001), ECV in HTN group were similar to the control group(0.27 + 0.02 vs. 0.26 + 0.01. P=0.136). ECV value had positive correlation with left ventricular mass index.(Speaman rho=0.524, 95% CI: 0.298, to 0.694, P=0.0002). In the third part ECV was from high to low were HTN-LVH-HF(0.33 + 0.03), HTN-LVH(0.30 + 0.02), HTN(0.27 + 0.02), there were significant differences between three groups(P < 0.001). ROC curve to establish myocardial ECV, the area under the curve for 0.844,95%CI was 0.757 to 0.910, myocardial ECV > 0.3, occurrence of diastolic heart failure. The sensitivity was 78.79%, specificity was 73.85%. Ninety-six cases of hypertensive heart disease patients after a follow-up found that the secondary endpoints of hypertensive heart disease population average myocardial ECV was 0.34 + 0.03, hypertensive heart disease without secondary endpoint of mean population of myocardial ECV was 0.32 + 0.03, ECV value of composite event within 2 years of patients with hypertensive heart disease(atrial fibrillation, diastolic heart failure and death has independent predictive value(HR2.946), 95%CI 1.159-7.488, chi square = 5.155, P=0.023). Different myocardial ECV values during follow-up in patients with atrial fibrillation by Kaplan-Meier method, diastolic heart failure or death analysis of incidence curve, with ECV value of 0.34 for the risk stratification of patients with hypertensive heart disease, myocardial ECV. The incidence of risk in 0.34 patients during the follow-up period of Atrial Fibrillation,Diastolic heart failure and death is 2.7471 times less than 0.34 of patients with myocardial ECV, 95% confidence interval 1.5574-4.8457(P < 0.001).ConclusionsIn summary, the ECV is a novel and potentially useful index for quantification of the myocardial extracellular volume fraction. The findings suggest that in healthy volunteers, the myocardial ECV ranges from 0.21 to 0.34, In humans, the myocardial ECV increases with age, is associated with left ventricular mass and left atrial volume, and has reliable test characteristics. T1 mapping can be used in the quantitative evaluation of hypertensive heart disease with diffuse myocardial fibrosis, especially in the Native T1 value, the distribution coefficient of Gd and ECV value can be used as reference for the quantitative evaluation of myocardial fibrosis in hypertensive heart disease. The left ventricular hypertrophy in patients with diffuse myocardial fibrosis compared with hypertensive heart disease group and control group patients with heart disease. Hypertension with left ventricular hypertrophy ECV parameters can be used as a new indicator of subtle differences in assessment of myocardial fibrosis and myocyte hypertrophy. Hypertensive heart disease patients with left ventricular hypertrophy of cardiac diastolic dysfunction in patients with Native T1 and ECV values compared with patients with hypertensive heart disease and hypertensive left ventricular hypertrophy without heart dysfunction, suggesting that the myocardial diffuse interstitial fibrosis with severe.T1 mapping fibrosis quantitative measurement indexes and hypertension heart disease Dirty systolic function and cardiac diastolic dysfunction index between the relationship and show that myocardial structure and cardiac function between there is a mechanical connection. ECV value can early identification of hypertensive heart disease myocardial fibrosis, myocardial ECV is hypertensive heart disease patients with arrhythmia(Atrial Fibrillation), diastolic heart failure and death were independent predictors. Clinical application can be determined by T1 mapping technique of ECV value changes of early evaluation of therapeutic effect and improve the prognosis in patients with hypertensive heart disease, further works need multi center, large sample size studies to test. |
PDF Full Text Request