الفهرس 
IntroductionOnly 14 pages are availabe for public view
 |  | from | 72 |  |  |
| | | from | 72 | | |
Abstract
T2DM, a chronic metabolic disease, is a major health concern, as it affects >382 million individuals worldwide. CAD is the major cause of death among patients with T2DM. Population-based studies have reported a 2- to 4-fold frequency in the number of cardiovascular events experienced by patients with T2DM. The diagnosis of CAD is commonly missed or delayed, since the symptoms of CAD are usually absent in patients with T2DM, which in turn enhances the risk for cardiovascular events. (133)
Invasive coronary angiography (ICA) is considered the gold standard for detecting the presence, localization and severity of CAD. However, it is an invasive method associated with complications. Furthermore, the procedural cost is substantial. Coronary CTA is an alternative to ICA for the detection of CAD, and 64-slice multidetector CT has been found highly effective in the diagnosis of significant coronary stenosis. (134).
Coronary CTA has proved to provide comprehensive information on CAD, including lesion location, disease severity, and plaque characteristics. On the basis of the diagnostic accuracy of coronary CTA for CAD, the long-term prognostic value of coronary CTA for predicting cardiac events has been demonstrated in diabetic patients (135).
Glycosylated hemoglobin A1c (HbA1c) is a marker of long-term glycemic control and elevated HbA1c was associated with an increased risk of cardiovascular diseases in patients with diabetes, moreover elevated HbA1c is also associated with all-cause of death and cardiovascular disease even in absence of diabetes. (136) In present study, we found that a significant positive correlation between HbA1C with number and severity of affected coronary arteries, these results are consistent with the study done by Tomizawa et al. who noted that diabetic patients with (HbA1c > 6.5%) were related with extensive disease (137) and also concordant with the study done by Ayhan et al. who found that HbA1c levels correlated with the severity of coronary atherosclerosis in both diabetic and non-diabetic patients (138).
In current study we found that no significant correlation between coronary artery disease incidence with gender and age in asymptomatic diabetic patient these results were concordant with study done by Gillian L. et al who found that diabetes greatly attenuates the usual protective effect afforded by female sex, thereby narrowing the relative gap in cardiovascular risk between the sexes, the Disease duration is a potent risk factor for coronary events in patients with type 2 diabetes rather than age of patient. (139)
A family history of early heart disease in 1st degree family member is also a known risk factor of CAD, (before age 55 years in males and before age 65 years in females). (120), premature coronary artery disease (P-CAD) has a multifactorial etiology and is most likely a mixture of genetic and environmental factors. The relationship between family history of P-CAD in first-degree relatives and increased risk of atherosclerosis-based diseases is well described (140). In present study we found that family history of P-CAD was significantly associated with significant CAD and with higher severity of stenosis, and this finding is in concordant with the results of the study done by Ciampi A. et al. who found that family history of CHD is often considered in clinical practice a positive risk marker and may be more helpful for detecting increased CVD risk when present. (141)
Discussion
39
Dyslipidemia is one of the risk factors for vascular complications and adverse cardiovascular events in diabetic patients. The disorder is characterized by an abnormal lipid profile, which can include elevated levels of plasma cholesterol, triglycerides, or both, or reduced levels of high-density lipoprotein cholesterol (HDL-C) (142). In the current study, we found a significant positive correlation between extent and severity of diseased vessels by CCT with total cholesterol, triglycerides, LDL-cholesterol. These results were concordant with Conkbayir et al. who revealed a significant relationship between lipid quartiles with the extent and severity of CAD (143) and also concordant with the study done by Wallace et al. who had demonstrated a direct relationship between serum LDL-C and CVD incidence (144).
Hypertension and T2DM seem to be two aspects of common pathophysiological pathways, especially in people who suffer from metabolic syndrome. It is estimated that almost two thirds of the population with T2DM is also affected by hypertension Elevated arterial blood pressure (BP) contributes to increased incidence of both micro and macro-vascular complications in patients with T2DM (145). Besides that, co- existence of these two major risk factors, leads to a four-fold increased risk for cardiovascular disease (CVD) as compared to normotensive non-diabetic controls. (146) In our study number of hypertensive patient 67 (67.67%) and we find that, there is non-significant relation between coronary artery disease incidence in asymptomatic diabetic patient and hypertension and there is may be due to that most patient enrolled in study had short duration of hypertension (less than three years), small sample size. Smoking is one of the key risk factors for cardiovascular disease, which contributes substantially to the overall cardiovascular burden. Consequently, smoking increases the risk of macrovascular complications in patients with type 2 DM (T2DM) (1). in current study we found that smoking is positive significantly correlates with coronary heart disease in patients with type 2 diabetes and there is significant correlation between smoking and significant coronary stenosis and revascularization and this results concordant with study done by Barengo et al in a large prospective cohort study assessed the risk of CHD incidence and mortality, and all-cause mortality in Finnish people with and without T2DM according to smoking status and study showed that smoking men and women with T2D had a higher risk of CHD incidence, and CHD and all-cause mortality compared with non-smoking people free of diabetes. (147)
The amount of coronary artery calcium reflects the total atherosclerotic burden, in present study we found that a zero CACS warrantied very good prognosis in a one-year follow-up duration but does not exclude obstructive CAD in a substantial proportion of patients and These results are in concordant with Plank F. et al. who Reported that high prevalence of CAD in a high-risk asymptomatic population and CACS = 0 did not exclude significant non-calcified coronary atherosclerosis. (148). Also, we found that patients with CAC score ≥ 100 associated with significant coronary stenosis and increase number of affected vessels, these results are in concordant with study done by Van den Hoogen et al. who demonstrated CAC-score ≥ 100 as independent predictor of number and severity of CAD and coronary revascularization. (149)
Not surprisingly, we found that CCTA provided additional value over CACS, CCTA improved discrimination by maximal stenosis, number of obstructive vessels and the coronary segment stenosis, and these results are in
Discussion
40
concordant with CONFIRM registry for 27,125 asymptomatic individuals with diabetes were assessed the prognostic value of stenosis degree on CTA beyond CACS and concluded that CTA provided additional value over CACS. (150) we found that 10 patients 10.1% with zero calcium score have coronary lesions (6 patient had obstructive coronary lesions and 4 patients with non-obstructive coronary lesions).
Screening for CAD in patients with diabetes could enable the identification of high-risk patients in whom event-free survival may be improved through risk factor modification, medical surveillance, or elective revascularization (151).
In the present study, 99 patients with asymptomatic T2DM were enrolled, and CTA was performed to detect coronary stenosis. Based on the coronary CTA results, we classified the patients into 3 groups, Normal coronary artery group, obstructive CAD group (≥50% stenosis) and non‐obstructive CAD group (<50% stenosis). We found a high prevalence (15%) of non-obstructive CAD in asymptomatic patients with diabetes. Theoretically, non-obstructive CAD cannot be detected by other noninvasive modalities used to identify ischemia (e.g., single-photon emission computed tomography, exercise tolerance test, or stress echocardiography). Moreover, in our study we found absence of CAD in most patients with a prevalence of 58%, which is associated with one year free event period, These results are in concordant with Csilla et al. who found that the absence of CAD is a common diagnosis in patients with diabetes, which is associated with a very low event rate (0.1%). (151). And this finding also demonstrates the role of coronary CTA in safely ruling out future events in patients with diabetes and yielding a similar event rate for absence of CAD as a general patient population referred for CTA (152)
In present study, despite the absence of symptoms, approximately 26.3% of patients with type 2 diabetes mellitus had significant coronary stenosis and these results are in concordant with Lim S. et al who found that the prevalence of significant stenosis of asymptomatic patients ranged from 15.2 to 29% (153).
Multiple studies assessed plaque composition on coronary CTA in diabetic patients without chest pain syndrome, current classification of plaque on CT images is often based on the presence of calcification, such as calcified plaque, noncalcified plaque and mixed plaque (154). Comparable to the present study, the majority of these studies described an increased prevalence of mixed lesions in asymptomatic diabetic patients. (155) and these results are in concordant with the result of present study, as we found that increased prevalence of mixed lesions in asymptomatic diabetic patients with prevalence 18.2% (18 patients), Non calcific plaques 7 patients (7.1%) and calcific plaques in one patient (1.0%).
The main findings of this study were asymptomatic patients with type 2 diabetes mellitus and normal coronary arteries or non-obstructive CAD on coronary CTA showed excellent prognosis with no cardiac event rates during one year follow up period. This result was consistent with the study by Kang et al, who found that asymptomatic patients with T2DM and normal coronary arteries or non-obstructive CAD on coronary CTA exhibit excellent clinical outcomes over a follow-up period of >5 years (156). As diabetes is associated with a poorer outcome especially in-hospital mortality rates in patients undergoing urgent versus elective revascularization (12.7% vs. 1.4%). And in patients with high-risk CAD noted on coronary CTA, coronary revascularization provided a survival benefit over medical
Discussion
41
treatment (157), therefore, in present study to prevent future cardiac events and improve prognosis in asymptomatic patients with type 2 diabetes mellitus, patient subgroups with sever stenosis (23.2%) underwent elective invasive interventions in form of PCI with stent implantation or CABG.