The effect of different extrinsic and intrinsic factors on the cardiovascular system

Abstract

Introduction: Being responsible for 37% of all deaths and representing an economic burden of 210 billion Euros in the European Union, cardiovascular diseases are the leading cause of mortality. Therefore, the thorough understanding of cardiovascular risk factors is essential to reduce this health impact. Aims: My thesis aimed to evaluate the effects of short-term (24-h) smoking cessation and circadian rhythm on hemodynamic and arterial stiffness parameters, as well as the influence of AB0 blood groups on the cardiovascular risk. Materials and methods: A 24-hour database was created for the first and second study consisting of peripheral systolic and diastolic blood pressure, heart rate, mean arterial pressure, pulse pressure, central systolic blood pressure, central and peripheral augmentation index and pulse wave velocity values of 10 healthy light-smokers and 10 age- and BMI matched, healthy control persons. For the analysis of circadian changes, daytime period was divided into four closely equal sections. In the third study, study population consisted of 63 men and 112 women undergoing surgical intervention or heart surgery after an acute cardiovascular event, whereas control population consisted of 30 men and 54 women without acute cardiovascular event in their history. Results: In the first study, daytime systolic blood pressure and mean arterial pressure were significantly higher among smokers on the smoking day than among smokers on the non-smoking day (p=0.02, p=0.02, respectively) and non-smokers (p=0.005, p=0.01, respectively), the night-time systolic blood pressure was significantly higher among smokers on both non-smoking (p=0.004) and smoking days (p=0.03) than among non-smokers. Daytime diastolic blood pressure was significantly higher among smokers on the smoking day than among smokers on the non-smoking day (p=0.02) and non-smokers (p=0.04). Daytime heart rate was significantly lower among smokers on the non-smoking day than among both smokers on the smoking day (p= 0.001) and non-smokers (p=0.03). Night-time pulse pressure was significantly higher among smokers on the non-smoking day than among non-smokers (p=0.046). Daytime pulse wave velocity was significantly higher among smokers on the smoking day than among smokers on the non-smoking day (p=0.03). In the second study, brachial systolic (p=0.003) and diastolic blood pressure (p=0.035), mean arterial pressure (p=0.008) and central systolic blood pressure (p=0.033) were significantly higher in non-smokers during period 3 than the daily average, whereas heart rate (p=0.032) and pulse wave velocity (p=0.022) were significantly higher in non-smokers during period 2 and 3 than the daytime average. Central (p=0.002) and peripheral augmentation indices (p=0.002) were significantly lower in smokers during period 3 than the daytime average. Apart from augmentation index values, no significant differences were identified in smokers between any time periods and the daily average. In the third study, blood group A occurred significantly more frequently in the patient group than in the control group (p=0.007), whereas blood group AB (p<0.001) and allele B (p=0.002) occurred significantly less frequently in the patient group than in the control group. Discussion: Beside confirming our presumptions based on the results of previous studies, the first study revealed that the heart rate of smokers on the non-smoking day was lower with 9.41 ± 8.10 bpm than that of non-smokers possibly explained with an improper heart rate adaptation to ordinary physical activity or a secondary decrease of heart rate resulting from the decreased vascular resistance causing an increased cardiac output. Arterial stiffness results represented that pulse wave velocity appears to be the most sensitive parameter to smoking. In non-smokers, the second study demonstrated a significant daily peak of brachial systolic and diastolic blood pressure, mean arterial pressure and central systolic blood pressure, as well as a double daily peak of heart rate and pulse wave velocity. The negative peak of central and peripheral augmentation indices could be explained with the opposite change of augmentation index values to pulse wave pressure values. The effect of diminished/disappeared daily peak in most hemodynamic and arterial stiffness parameters on cardiovascular morbidity and the timing of cardiovascular examinations is yet to be determined. The results of the third study demonstrate that blood group A can be considered as an independent cardiovascular risk factor, whereas allele B can be considered as an independent cardiovascular protective factor.