ABC | Volume 114, Nº1, January 2019

Original Article Adar et al. Aortic calcification and non-dipper blood pressure Arq Bras Cardiol. 2020; 114(1):109-117 Figure 1 – Aortic arch calcification grading. Discussion NDBP pattern is one of the important causes of HT-related target organ damage and future cardiovascular events. 1,5,6 In this study, the presence of AAC on chest radiography was a strong and independent predictor of NDBP pattern. Diagnosis of HT is generally based on daytime office BP measurements, and nighttime BP and NDBP are usually overlooked in clinical practice. However, the association of nighttime and NDBP with HT-related target organ damage is more powerful than daytime BP. 17-19 Patients with NDBP pattern are at high risk for target organ damage including myocardial infarction, LVH, carotid artery disease, chronic kidney disease and stroke. 2-4,20 In the Ohasama study, impaired nocturnal BP decline was associated with cardiovascular mortality. 21 Each 5% decrease in the decline in nocturnal BP was associated with an approximately 20% greater risk of cardiovascular mortality. Importantly, this association was observed not only in hypertensive, but also in normotensive individuals. 21 Moreover, cardiovascular mortality and morbidity can be reduced by achieving a better nocturnal BP control. 22 Thus, effective treatment of HT should include nighttime BP control as well. Currently, ABPM remains the only method for the diagnosis of nocturnal BP variations. Unfortunately, it is relatively expensive, inconvenient for routine usage and not widely available tool. Yet, it may not be practical to perform ABPM in every hypertensive patient. A practical and inexpensive tool may help the filtration of the unselected population for ABPM. Here, in this study, we have shown that AAC on plain chest radiography, an inexpensive and widely available tool, has a strong predictive ability for NDBP pattern. There are several possible mechanisms that may explain the relationship between AAC and NDBP pattern. First, AAC was found to be strongly correlated with pineal gland calcification which may reduce melatonin secretion during sleep. 23 Melatonin plays a pivotal role in the regulation of nocturnal BP. 24-26 Autonomic nervous system activity is involved in the control of the circadian variation of BP 27,28 and impaired sympathovagal balance with increased sympathetic nervous activity and/or decreased vagal activity has been documented in non-dippers. 29,30 Melatonin shifts the balance between the sympathetic and parasympathetic system in favor of the parasympathetic system. It may also reduce nighttime BP by its direct arterial vasodilator effect. 25 Accordingly, exogenous melatonin has been shown to reduce nighttime BP. 31,32 Thus, a reduced melatonin secretion during nighttime may significantly impair nocturnal BP decline. Second, AAC is closely related with vascular stiffness and loss of arterial compliance 33 which in turn may impair arterial relaxation capacity. An impaired nocturnal decrease in BP was found to be independently associated with aortic stiffness in patients with nocturnal HT. 34 Moreover, it has been found that increased arterial stiffness is more associated with nighttime BP load than day time BP. 35 Third, the relationship between arterial BP and arterial calcifications is likely a bidirectional phenomenon. Increased arterial BP load may facilitate arterial calcification and vice versa. Non‑dippers are exposed to an abnormal the nocturnal BP load which may accelerate arterial calcification and stiffness. Fourth, the underlying clinical profile of the patients with impaired nocturnal BP decline and arterial calcification are similar. Both conditions are associated with age, renal diseases, diabetes, sleep apnea, autonomic dysfunction, malignant HT and coronary artery disease. 36,37 NDBP pattern is associated with disease severity and a higher risk of subsequent cardiovascular events. This risk can be reduced by achieving better dipping patterns and nocturnal BP levels. In clinical practice, many patients with controlled daytime BP levels are not evaluated for the nighttime BP levels. Our results may help to improve detection of NDBP pattern and nocturnal HT. Appropriate treatment of these patients by changing antihypertensive medications or administering the antihypertensive medications in the night may eventually help to improve dipping pattern and patient outcomes. 111