Risk Factors Evaluation for Changes of Cardiac Structure and QT Dispersion in Ageing Heart

• Main Authors: Tsung-Hsien Lin, 林宗憲
• Other Authors: Sheng-Hsiung Sheu
• Format: Others
• Language: zh-TW
• Published: 2007
• Online Access: http://ndltd.ncl.edu.tw/handle/32753787406062526370

博士 === 高雄醫學大學 === 醫學研究所博士班 === 95 === Because of low birth rate and relatively increased ageing population, the percentage of Taiwan people aged 65 years old rises up to 7.1% in 1993, which had achieved the World Health Organization so-called "the advanced age society". Therefore, our society should pay more attention to the health problems on the elders. According to the national health survey, the cardiovascular problem is the leading chronic disease in the people aged 50 years and older. Ageing-related structure changes, including vlave, cardiac chambers and QT parameter, may predispose to future development of cardiovascular events. Clinical physcians should have knowledge about the risk factors aggravating the heart problems. Mitral regurgitation from chordae tendinae rupture (CTR) may cause severe clinical symptoms and is a progressive disease eventually resulting in the need for mitral valve surgery. Early recognition of CTR and identification of risk factors are important because early intervention increases the chances of survival. Ageing is associated valvular degeneration and hypertension may increase mitral valve complex mechanical strain and cause the chordae tendinae to rupture. Using a cross-sectional study of medical files in one medical center in Taiwan, we enrolled 98 patients with mitral CTR and classified them into two groups: 68 (69%) without obvious predisposing factors (primary group) and 30 (31%) with known predisposing causes (secondary group). Sixty-three (64%) of the patients were men with a mean age of 57.5?b1.5 years old. The posterior mitral leaflet was most commonly involved (64%). The known predisposing factors in secondary group include mitral valve prolapse, infective endocarditis, and rheumatic heart disease. The patients who had primary CTR were older (59.9?b1.6 vs. 52.1?b3.1 years, p = 0.029), had a higher prevalence of hypertension (56% vs. 30%, p = 0.018) and complained more often of dyspnea (82% vs. 53%, p = 0.003) than the patients in the secondary group. Using binary logistic regression analyses, the variation in primary group was found to be independently explained by age (P = 0.039, OR = 1.039, 95% CI = 1.002 to 1.077) and hypertension (P = 0.048, OR = 2.717, 95% CI = 1.008 to 7.326). Therefore, we conclude that age and hypertension were independent predictors for primary CTR in this study. Left ventricular hypertrophy (LVH), as measured by M-mode echocardiography, is a potent, independent predictor of cardiovascular events. Trophic effect of insulin is believed to stimulate myocardial cell growth, and thus take part in the development of LVH. Non-insulin-dependent diabetes mellitus, which is related to hyperinsulinemia, has been shown to be a risk factor for left ventricular hypertrophy. Therefore fasting glucose, which is closely related with insulin level and diabetes, may be associated with the left ventricular mass (LVM) and LVH. To test the association between fasting glucose level and LVM and LVH in people aged 60 and older. We conducted a population-based prospective study with 4-year follow-up from the department of internal medicine and family medicine, Kaohsiung medical university Hospital and graduate institute of public health. Of 1500 people screened, 105 participants without symptoms or signs of diabetes, hypertension or cardiovascular disease were recruited from senior activity centers in the Kaohsiung city. All received two-dimensional echocardiography and fasting glucose examination at baseline, the second and fourth year follow-up. LVH was defined as a LVM index (LVMI) greater than 122.4 g/m2 or 51 g/height2.7. Age ranged from 60 to 81 (mean 71.7?b3.9) years old. Baseline glucose ranged from 83 to 118 mg/dl (mean 99.7?b7.9 mg/dl). LVMI was significantly increased at the 4-year follow-up (97.5?b24.9 to 104.5?b27.5 g/m2 and 44.2?b12.1 to 47.2?b13.4 g/m2.7, both p < 0.01) as well as the occurrence of LVH (16 to 32% and 25 to 39 %, both p < 0.01). Baseline glucose correlates with 4-year change of LVMI (both p < 0.02). In the fourth year, baseline glucose was a significant predictor of LVMI (both p < 0.01) and LVH (p = 0.034 in g/m2 definition) using logistic regression analysis. Because fasting glucose is an independent predictor for increased LVM and for development of LVH, it should be considered in assessment of cardiac disease and LVM in non-diabetic healthy elders. Cross-sectional studies investigated the impact of renin-angiotensin system (RAS) gene polymorphism on left ventricular mass index (LVMI) with conflict results. We conduct a longitudinal study to investigate the influence of the angiotensin converting enzyme (ACE) insertion/deletion (I/D), angiotensinogen (AGT) M235T and angiotensin II type 1 receptor (AT1R) A1166C gene polymorphisms on the LVMI and geometry. Of 1500 people screened, 110 non-diabetic normotensive elderly Chinese were recruited and received echocardiography at the baseline, at the second and fourth year follow-up. No subjects had history of organic heart disease or chronic medication. The gene polymorphisms were analyzed by the polymerase chain reaction. Age was 71.9?b3.9 years old (ranges 60-81). The prevalence of concentric remodeling, eccentric hypertrophy and concentric hypertrophy was significantly increased as well as LVMI after 4 years (all p < 0.05). These changes and the magnitude of LVMI increase were significantly higher in subjects carrying the ACE D allele than non-D-allele carriers (all p < 0.05). This association was still significant in multivariate analyses (p ≦ 0.02). The similar analysis showed a borderline significance in the AT1R but not in the AGT gene polymorphism. This longitudinal study showed aging process was associated with increase of LVMI and changes of geometry. The RAS system gene polymorphism, especially the ACE D-allele, might modulate these changes in the Chinese. This provides further knowledge essential in the assessment of cardiac disease and determination of the left ventricular structure in the older subjects. There was no longitudinal investigation of the influence of angiotensin converting enzyme (ACE) insertion/deletion (I/D) and angiotensinogen (AGT) M235T gene polymorphisms on repolarization parameters, such as QT dispersion (QTd) and the peak and the end of the T wave interval (Tpe). ECGs were recorded from 106 elderly Chinese at baseline, second and fourth year follow-ups. The QTc (corrected QT), QTd, QTc dispersion (QTcd) and Tpe were manually calculated. Age was 72.7?b4.1 years old (ranges 62-81). QTd, QTcd and Tpe were significantly prolonged (all p < 0.001 at the 2nd and 4th year). At the 4th year the magnitude of QTd prolongation but not Tpe was significantly higher in subjects carrying the ACE D allele than non-D-allele carriers (p = 0.001) as well as QTcd (p = 0.002). This association was still significant in multivariate analyses (p < 0.001 and p = 0.001 for QTc and QTcd, respectively). No significant correlation was found between repolarization parameters and AGT genotype. This longitudinal study showed ageing process was associated with prolongation of QTd, QTcd and Tpe after 4 years follow-up. These subjects with ACE D-allele have higher magnitude of QTd and QTcd prolongation in elderly Chinese. Accoding the above four studies, we found ageing is associated with significant cardiovascular modification and changes. Ageing may predispose to the development of chordae tendinae rupture and is associated with increased LVM, geometry changes and QT dispersion prolongation. Furthermore, fasting glucose is an independent predicotor for future LVM increase and occurrence of LVH. The RAS system gene polymorphism, especially the ACE D-allele, might modulate LVM, geometry and QT parameters changes in the Chinese. In the future, we hope that our study findings may help doctor to stratify the high-risk population and prevent the disease progression.