Dissertation committee:
Απόστολος Αχείμαστος, Ομότιμος Καθηγητής, Ιατρική Σχολή, ΕΚΠΑ
Γεώργιος Στεργίου, Καθηγητής, Ιατρική Σχολή, ΕΚΠΑ, Επιβλέπων
Χαράλαμπος Βλαχόπουλος, Καθηγητής, Ιατρική Σχολή, ΕΚΠΑ
Θεόδωρος Παπαϊωάννου, Αναπληρωτής Καθηγητής, Ιατρική Σχολή, ΕΚΠΑ
Αθανάσιος Πρωτογέρου, Αναπληρωτής Καθηγητής, Ιατρική Σχολή, ΕΚΠΑ
Αλεξάνδρα Σολδάτου, Επίκουρη Καθηγήτρια, Ιατρική Σχολή, ΕΚΠΑ
Ευστάθιος Μανιός, Επίκουρος Καθηγητής, Ιατρική Σχολή, ΕΚΠΑ
Summary:
Introduction: The systolic blood pressure (BP) varies along the arterial tree due to amplification of the forward-travelling pulse wave by the reflected waves. This knowledge, together with the evidence that the central (aortic) pressure may be more strongly associated with target-organ damage and cardiovascular events than brachial BP, have rendered its non-invasive assessment attractive in clinical research and practice, particularly when there is the possibility of 24-hour ambulatory BP (ABP) monitoring. The consideration of central BP appears to be crucial in the case of the isolated systolic hypertension (ISH) in the youth. The latter is the most common hypertension phenotype in the young individuals and associated with different pathophysiological background than in the elderly.
Objectives: To investigate the diurnal variation of central versus peripheral ambulatory systolic blood pressure, and its relationship with preclinical target-organ damage in adolescents and young adults.
Methods: Individuals aged 10-25 years referred for elevated blood pressure (BP) and healthy volunteers had: (i) conventional office BP measurements (2-3 visits, triplicate measurements, standard mercury sphygmomanometer), (ii) home BP measurements (duplicate morning and evening measurements for 7 days, validated oscillometric device) and (iii) simultaneous 24-hour peripheral (brachial) and central (aortic) ABP monitoring, using the same automated upper-arm cuff device (Mobil-O-Graph 24h PWA). Central BP was calculated by the device using two different calibration methods (C1 SBP using pSBP and diastolic BP, and C2 SBP using mean arterial and diastolic BP). Their association with preclinical organ damage (left ventricular mass index [LVMI], common carotid intima-media thickness [IMT], 24-hour pulse wave velocity [PWV]) was investigated. Systolic BP amplification was calculated as the difference between peripheral and central C1 SBP (or their ratio). The nighttime SBP change was calculated as percentage ([nighttime SBP-daytime SBP]x100/daytime SBP). The variability of 24-hour central SBP was quantified using the 24-hour weighted standard deviation and the average real variability.
Results: A total of 136 participants (age 17.9±4.7 years, 54% adolescents, 77% males, 25% volunteers, 54% with elevated body mass index [BMI], 34% with elevated peripheral ABP) were analyzed. Twenty-four-hour peripheral systolic ABP (pSBP) was higher than C1 systolic ABP (C1 SBP) by 14.1±3.7 mmHg, but lower than C2 SBP by 6.5±7.6 mmHg (all p<0.01). The difference was more pronounced during daytime than nighttime (16.3±4.5 and 10.5±3.2 mmHg respectively, p<0.001). Younger age, higher body height and male gender were associated with greater SBP amplification (p<0.05). C1 SBP followed the variation pattern of pSBP, yet with smaller nighttime dip (8.4±6.0% versus 11.9±4.6%, p<0.001), whereas C2 SBP exhibited a rise during nighttime sleep (2.4±7.2%, p<0.001 for comparison with pSBP change). Older age remained independent determinant of larger nighttime fall for pSBP and C1SBP, whereas male gender predicted a larger nighttime C2 SBP rise. C2 SBP quartiles provided better stratification of preclinical organ damage than pSBP. C2SBP exhibited stronger correlations than pSBP with LVMI (r=0.35/0.17, p<0.05) and IMT (0.39/0.17, p=0.01) in adolescents, but not in adults. Peripheral SBP was more strongly associated than central SBP with PWV in adolescents (r=0.98/0.76) and adults (0.97/0.85; all p<0.01). LVMI variation was best determined by C2 SBP in adolescents and by pSBP in adults; IMT by C2 SBP and PWV by pSBP in both age subgroups. The variability of 24-hour central SBP was determined by gender, age, BMI and 24-hour mean, and exhibited a statistically significant association with all the indices of preclinical target-organ damage. The frequency of ISH ranged from 17 to 26% depending on the BP monitoring method, with the agreement among them being fair (71-82%). Individuals with ISH exhibited higher central BP and BP amplification than normotensives (p<0.01), but lower vascular resistance than those with diastolic hypertension (p<0.01). Furthermore, they had higher PWV than normotensives (p<0.01), and there was a similar trend for the IMT (p=0.09).
Conclusions: These data suggest that the calibration method of the BP monitor considerably influences the results about the diurnal variation of central BP, leading to lesser nocturnal dip than pSBP, or even nocturnal BP rise, which are determined by the individual’s age and gender. In addition, the calibration method for 24-hour central ABP plays a major role in determining its association with preclinical organ damage. In adolescents, 24-hour central ABP appears to be more strongly associated with early cardiac and carotid damage than peripheral BP. The diagnostic agreement among office, home and 24-hour ABP monitoring for the detection of ISH was fair. The latter in the young individuals appears to be associated with excessive amplification of an already increased central BP, together with increased arterial stiffness and hyperkinetic circulation.
Keywords:
Central blood pressure, Aortic blood pressure, Ambulatory monitoring, Diurnal variation, Target-organ damage, Adolescents, Young adults
