Correlation between Blood Pressure and Severity of Atherosclerosis in The Left Main Coronary Artery with CT Coronary Angiography Examination

Background: Cardiovascular disease, especially hypertension, is the main cause of death in both developed and developing countries. Hypertensioncan lead to atherosclerosis, which is the most common cause of ischemic and coronary heart disease. Some countries have used Computed Tomography Coronary Angiography (CTCA), which is a noninvasive test, to observe the anatomy of coronary artery. Nevertheless, invasive angiography isstill the gold standard for coronary artery visualization. Atherosclerotic plaques cancause left main coronary artery stenosis. Purpose: The purpose of this research is to analyze the correlation between blood pressure and severity of the atherosclerosis in the left main coronary artery. With CTCA examination, the presence of plaque, severity of stenosis and type of plaques were assessed. Methods: The study design was analytic observational with cross sectional design. Data was drawn from medical records. The sample included a total of 29 patients which were suspected of having coronary heart disease and examined with CTCA who meet inclusion and exclusion criteria in Dr. Kariadi Hospital, Semarang, Indonesia. Result: The correlation between systolic blood pressure and left main coronary artery stenosis was obtained by Spearman’s rho r = 0.0429, p-value of with of 0.020 (2-tailed). The correlation between diastolic blood pressure and left main coronary artery stenosis was obtained by Spearman’s rho r = 0.354 with p-value of 0.060(2 -tailed). Some types of plaques were found in left main coronary artery, and systolic blood pressure are significantly different analysed using Anova (analysis of variance) which probability was significant with p value 0.041. Conclusion: There was a significant correlation between systolic blood pressure and left main coronary artery stenosis. Therewas no correlation between diastolic blood pressure and left main coronary artery stenosis. Furthermore, there was a significant difference between systolic blood pressure and the type of plaques in the left main coronary artery.


INTRODUCTION
Cardiovascular disease is the main cause of death in both developed and developing countries.By 2020 it is estimated that there will be 25 million deaths each year from cardiovascular disease, almost half caused by coronary heart disease.Coronary heart disease is a cardiovascular disease that has high morbidity and mortality. 1,2,3e risk factors for cardiovascular disease are smoking, hypertension, diabetes, obesity, and dyslipidemia. 2According to WHO, nearly one billion people has hypertension, two thirds of them were found in developing countries and as one of the leading cause of death in the world, the number was expected to increase.By 2025 it is estimated that 1.56 billion people will suffer from hypertension.Hypertension is the most cause of coronary heart disease, patients with hypertension will also lead to complications such as diabetes mellitus. 1,2,3herosclerosis is the leading cause for ischemic heart disease and coronary heart disease.If there is more atherosclerotic plaque were found, the greater possibility of obstruction found.Blood pressure is closely related with atherosclerotic plaque formation in coronary artery.In a study by Tae Soeng, patients with stage 2 hypertension may have coronary heart disease by 9,4% and may develop atherosclerotic plaque by 40%.
Even in patients with normal blood pressure, atherosclerotic plaque could be found in around 16,5% and have the possibility of getting coronary heart disease by 2,2%.
Hypertension is also related with the type of atherosclerotic plaque.In study by Tae Seong, patients with stage 2 hypertension were found to have about 13,6% with non calcified plaques, 21,7% with mixed plaques, and 12,8% with calcified plaques. 1,5,6,7veral countries have used Computed  11,12,13 According to a study by Gamal et al., in 40 patients suspected with coronary heart disease, 26 patients had coronary artery stenosis with 58.4% in left main coronary artery and its branches and 30% in right coronary artery.If there were about 70% stenosis on the left main coronary artery, patient's three years survival rate would be just 41%. 14,15,16,17,18sed on this background, the authors aim to examine the correlation between blood  As continuation from analysis of variance hypothetical test, a multiple comparison test were performed because there was significant difference between systolic blood pressure and type of plaque in left main coronary artery.To see which group were different, significance value was set as < 0.05.From multiple comparisons result, it was concluded that there were differences between mean systolic blood pressure with no plaque and calcified plaque, with significance value of 0.018.There were no differences between no plaque and soft plaque, no plaque and mixed plaque, soft plaque and calcified plaque, and soft plaque and mixed plaque because of the significance value of > 0.05 (figure 3).
From the correlation test between diastolic blood pressure and plaque type in left main coronary artery using Chi Square test, it was obtained the significance value of 0.212, which indicated there was no significant correlation between diastolic blood pressure and plaque type in left main coronary artery (figure 3).

DISCUSSION
In this study, significant stenosis in left main coronary artery (> 50%) occurred in patients with average systolic and diastolic blood pressure of 170/85 mmHg (stage 2 hypertension).In Tae Seong's study, patients with stage 2 hypertension have coronary heart disease (obstructive CAD/significant stenosis).
The difference between this study and previous study was that this study focused only on left main coronary artery, whereas in previous study, all segments of coronary artery were taken into account. 18 this study correlation between systolic blood pressure and stenosis of left main coronary artery were concluded from Spearman's value rho r of 0.429 with sig.
(2-tailed) of 0.020 which means there were significant correlation between systolic blood pressure with stenosis of left main coronary artery.Correlation between diastolic blood pressure and left main coronary artery were concluded from Spearman's value rho r of 0,354 with sig.(2-tailed) of 0.060 which means there were no correlation between diastolic blood pressure with stenosis of left main coronary artery.According to Borghi's study, there was also significant correlation between systolic blood pressure (p = 0.003) with myocardial infarction, on the other hand, there was no significant correlation between diastolic blood pressure with myocardial infarction. 7e difference between this study and Borghi's study is that this study focused only on stenosis of left main coronary artery, whereas previous study look at the correlation between blood pressure and risk of myocardial infarction like acute coronary syndrome, but still has the same result which is systolic blood pressure has big impact to stenosis occurence in left main coronary artery which leads to myocardial infarction. 7cause there were several types of plaque in left main coronary artery, hypothetical test was performed using variance analysis or ANOVA and obtained significance probability value of 0.041, which means there were significant difference between systolic blood pressure and plaque type in left main coronary artery.
From the result of multiple comparisons, it is concluded that there were differences between mean systolic blood pressure of no plaque and calcified plaque with significance value of 0.018.
There were no differences between no plaque and soft plaque, no plaque and mixed plaque, This study result shows that blood pressure is related with occurance of left main coronary artery disease, but the weakness of this study is that blood pressure data was taken secondarily from patients' medical record, without considering the anti-hypertension medicine consumed by the patients, variants of the tools used as well as the officer performing the blood pressure measurement.
It is suggested that for the next research blood pressure data could be taken in better an more accurate manner.

CONCLUSION
From the study of the correlation between blood pressure and severity of atherosclerosis in left main coronary artery on CTCA, it was concluded that there are significant correlation between systolic blood pressure with stenosis of left main coronary artery, there is no correlation between diastolic blood pressure with stenosis of left main coronary artery, there is significant difference between mean systolic blood pressure and plaque type in left main coronary artery, there are difference in mean systolic blood pressure between no plaque and calcified plaque and there is no correlation between mean diastolic blood pressure and type of plaque in left main coronary artery.
Our suggestion for the next study are the consideration for more samples, the consideration of factors like blood glucose level, lipid profile, age, smoking history, and body weight which are not evaluated in this study.

Figure 3 .
Figure 3.The boxplotof mean systolic blood pressure (TD Sistol) and diastolic blood pressure (TD Diastol) in mmHg based on type of left main coronary artery plaques

Table 1 .
Characteristics of subjects plaque and calcified plaque, and soft plaque and mixed plaque because of its significance