Causes and consequences of blood pressure alterations in obstructive sleep apnea

The obstructive sleep apnea (OSA) syndrome has been considered to be a cause of both transient blood pressure elevations during sleep and sustained hypertension during the awake state. The purpose of this review was to examine critically the existing literature regarding (1) the blood pressure alterations associated with OSA, (2) causal mechanisms relating specific blood pressure alterations to OSA, and (3) potential consequences of the systemic circulatory abnormalities associated with OSA. Particular attention was directed at studies that assessed the prevalence of OSA in patients with hypertension and that examined the effects on blood pressure of treatment of OSA. We conclude that patients with OSA have abnormal sleep blood pressure patterns, manifested most frequently by apnea-associated blood pressure elevations. Confounding factors such as obesity and antihypertensive drug therapy, and conflicting evidence regarding changes in daytime blood pressure after therapy for OSA, make it premature to conclude that OSA and daytime hypertension are directly associated. Circumstantial evidence suggests that the blood pressure alterations that occur during sleep could contribute to the high cardiovascular morbidity in patients with OSA. Further research into the relationship between OSA and hypertension should improve the future care of patients with these conditions and enhance our understanding of cardiopulmonary pathophysiology.     

缬沙坦对非勺型高血压患者血压昼夜节律的影响

目的观察缬沙坦对非勺型高血压患者血压昼夜节律的影响。方法选择经24h动态血压监测且诊断为非勺型2级高血压的患者60例为研究对象,将其按电脑数字表法随机均分为治疗组30例：上午7：00和晚上7：00各服缬沙坦80mg;对照组30例：上午7：00服缬沙坦160mg,两组用药8周后复测24h动态血压。比较两组血压昼夜节律的变化。结果两组治疗后24h、白昼、夜间收缩压及舒张压均较治疗前显著下降,差异有统计学意义（P〈0．05）。治疗组的夜间收缩压、舒张压及白昼、夜间血压负荷较对照组显著下降,差异有统计学意义（P〈0．05）。治疗组血压昼夜节律改变有效率明显高于对照组,差异有统计学意义（收缩压：73．33％抵46．67％,P〈0．05;舒张压：76．67％眠43．33％,P〈0．01）。结论应用缬沙坦治疗非勺型高血压,可以很好地控制2级高血压,并改变血压昼夜节律,早晚两次服用,效果更好。     

Altered circadian blood pressure profile and prognosis

BACKGROUND: In a previous analysis of the Progetto Ipertensione Umbria Monitoraggio Ambulatoriale we found a higher rate of cardiovascular morbid events among hypertensive nondippers than we did among dippers (5.86 versus 1.18 events per 100 person-years, P = 0.0002) for women, whereas the difference between the two groups was smaller and not statistically significant for men (4.15 versus 2.48 events per 100 person-years). These differences held in a multivariate analysis after adjustment for several confounders including average 24 h ambulatory blood pressure. In another analysis, the rate of occurrence of cardiovascular end-points was higher among nondippers than it was among dippers regardless of the definition of day and night (0600-2200 h and 2200-0600 h, awake and asleep, and 1000-2000 h and 2400-0600 h) and of the dividing line between dippers and nondippers (10 versus 0% day-night difference in blood pressure). OBJECTIVE: To test in a subsequent analysis based on a larger sample and a longer follow-up period, for both sexes, the prognostic value of a blunted diurnal rhythm of blood pressure. METHOD: We used the night: day ratio of ambulatory blood pressure, a continuous and normally distributed variable. RESULTS: A night: day systolic blood pressure ratio > 0.899 for men and > 0.909 for women (upper tertiles of distributions) identified a subset of subjects with greater than normal cardiovascular risk for any level of concomitant risk factors, wherease the hight:day diastolic blood pressure ratio was not statistically significant as an independent predictor. The excess risk for subjects in the upper tertile of the night: day systolic blood pressure ratio held after adjustment for several risk markers, including average 24 h ambulatory blood pressure. CONCLUSION: These data suggest that a blunted reduction in blood pressure from day to night predicts an increased cardiovascular morbidity at any level of concomitant risk factors including average 24 h ambulatory blood pressure. Nondippers can be defined in terms of a night: day ambulatory systolic blood pressure ratio > 0.899 for men and > 0.909 for women, regardless of the diastolic blood pressure profile.     

Alterations of sleep and circadian blood pressure profile

The organization of sleep activity in stages of different depth is reflected by consistent changes in blood pressure that account for the major part of the day-night blood pressure difference. On the other hand, different mechanisms may underlie dysregulation of nocturnal blood pressure. Cyclic variations in autonomic nervous system activity play an important role in the mediation of the influences of sleep and wakefulness on blood pressure. In addition, several physiologic substances that are knoiwn to induce sleep or arousal are knoiwn to exert actions on blood pressure. Hence, derangements in autonomic nervous system activity, either primitive or secondary to alterations in the circadian rhythm of a variety of neurohumoral factors, are reflected in changes of the circadian blood pressure profile. Important additional influences of sleep on blood pressure may be exerted through respiratory variations, so that sleep-disordered breathing is bound to alter nocturnal blood pressure. Finally, insomnia has to be taken into account as a major cause of sleep-related alteration of the circadian blood pressure profile. The number of medical disorders that can cause insomnia is huge, and includes many if not all of the conditions in which a loss or reversal of the physiologic blood pressure fall at night is found to be prevalent. Unfortunately, objective sleep studies have been performed only in studies of a minority of these disorders, and further studies to assess the pathophysiologic mechanisms actually involved in causing sleep disturbances in each pathologic condition are necessary.     

Diabetes and hypertension: blood pressure control and consequences

Diabetes and hypertension are the leading causes of end-stage renal disease in the Western world. Inadequate control of both systemic and glomerular capillary pressure in diabetics results in increasing hydraulic force and mechanical stretch on the glomeruli, with a subsequent increase in proteinuria and ultimately glomerulosclerosis. Therapeutic strategies that combine systemic and glomerular capillary pressure reduction result in reduced proteinuria and are ideal for preventing renal injury. Both experimental and clinical studies have demonstrated the importance of intensive control of blood pressure, preferably to systolic blood pressure (SBP) < or =130 mm Hg to delay progression of renal disease. In particular, drugs that block the renin-angiotensin system (RAS) offer the advantage of consistently reducing glomerular capillary pressure and proteinuria relative to changes in systemic blood pressure. This combination of events is ideal for delaying progression of renal disease. However, the use of drugs that block the RAS is not a surrogate for maintaining tight control of blood pressure.     

Diabetes and hypertension: blood pressure control and consequences

Diabetes and hypertension are the leading causes of end-stage renal disease in the Western world. Inadequate control of both systemic and glomerular capillary pressure in diabetics results in increasing hydraulic force and mechanical stretch on the glomeruli, with a subsequent increase in proteinuria and ultimately glomerulosclerosis. Therapeutic strategies that combine systemic and glomerular capillary pressure reduction result in reduced proteinuria and are ideal for preventing renal injury. Both experimental and clinical studies have demonstrated the importance of intensive control of blood pressure, preferably to systolic blood pressure (SBP) ≤ 130 mm Hg to delay progression of renal disease. In particular, drugs that block the renin-angiotensin system (RAS) offer the advantage of consistently reducing glomerular capillary pressure and proteinuria relative to changes in systemic blood pressure. This combination of events is ideal for delaying progression of renal disease. However, the use of drugs that block the RAS is not a surrogate for maintaining tight control of blood pressure.     

Altered circadian blood pressure profile and renal damage

Introduction. The relationship between arterial hypertension and renal damage has long been recognized. In 1836, Bright reported an association between cardiac hypertrophy and contraction of the kidney [1] and 40 years later Gull and Sutton [2] suggested that the renal damage in patients with arterial hypertension could be the consequence of vascular hypertensive alterations.     

24-hour blood pressure profile in centenarians

OBJECTIVE: Ambulatory blood pressure in the elderly has been studied in the past, the age range most frequently examined being 65 to 80 years. The present study was aimed at determining 24-h blood pressure means and profile in centennial human beings. PATIENTS AND METHODS: Sphygmomanometric blood pressure (average of three values) and 24-h ambulatory blood pressure measurements were performed in 16 centennial subjects (age 101.7 0.4 years, mean SEM) and in 20 healthy normotensives aged 80.7 1.1 years. All subjects were in good clinical and mental conditions for their age. They had no history, signs or symptoms of cardiovascular or non-cardiovascular diseases and were under no drug treatment. RESULTS: In the centennial group sphygmomanometric blood pressure amounted to 131.2 3.0/70.7 2.2 mmHg (systolic/diastolic) and 24-h blood pressure and heart rate average values to 125.6 +/- 3.4/64.8 2.0 mmHg and 77.5 4.3 bpm, respectively. Blood pressure and heart rate showed no difference between daytime and night-time values, i.e. night-time was accompanied by no blood pressure and heart rate fall. In contrast, in all subjects, a significant reduction in blood pressure was observed during the post-prandial period, with no significant heart rate changes. In the octogenarian group, sphygmomanometric and 24-h blood pressure averages were 146.6 4.4/82.8 2.2 and 131.8 2.5/75.3 1.6 mmHg, respectively, with a clearcut reduction in night-time as well as in post-prandial values. CONCLUSIONS: In centenarians 24-h blood pressure values are: (1) lower than sphygmomanometric blood pressures and (2) slightly less than in subjects aged 80 years. At variance with these subjects, however, in centenarians nocturnal hypotension and bradycardia are abolished, presumably because of a derangement in the central sleep influences on the cardiovascular system.     

In newly diagnosed hypertensive children,increased arterial stiffness and reduced heart rate variability were associated with a non-dipping blood pressure pattern

ObjectivesThis study was designed to investigate the differences in pulsatile hemodynamics, echocardiographic findings, 24-h Holter monitoring and heart rate variability parameters of dipper patterns in children with newly diagnosed essential hypertension.MethodsThis study included 30 children with newly diagnosed essential hypertension and 30 healthy controls. The essential hypertension cohort was divided into dippers and non-dippers. Physical examinations, 24-hour ambulatory blood pressure monitoring, 24-h Holter monitoring, 24-h heart rate variability, conventional 2-dimensional and Doppler echocardiography, and tissue Doppler imaging were performed. Pulse wave analysis using an oscillometric monitor was conducted to measure augmentation index (AIx) and pulse wave velocity (PWV).ResultsIn patients with essential hypertension, left ventricular (LV) wall thickness and LV mass index were increased. There were no significant differences in LV mass index and LV wall thickness based on the dipping patterns. Time domain values and the standard deviation of all RR intervals (SDNN) were substantially lower in the essential hypertension group. SDNN values were considerably lower in the non-dipper group compared with the dipper group. In terms of frequency domain measures, low frequency measured in daytime values was much lower in the essential hypertension group compared with the control. The dipper patterns revealed that low frequency measured in nighttime values was also substantially lower in the non-dipper group. Pulse wave analysis and AIx values were notably higher in the essential hypertension patient group and those with non-dipper status.ConclusionSDNN values, which reflect parasympathetic activity, were markedly lower in children with hypertension and the non-dipper group than healthy controls and the dipper group, respectively. Also, parameters related to arterial stiffness, such as PWV and AIx values were significantly higher in children with hypertension and the non-dipper group.     

Even mild depression is associated with among-day blood pressure variability,including masked non-dipping assessed by 7-d/24-h ambulatory blood pressure monitoring

Abstract

The effect of mild depression on blood pressure (BP) was assessed in 116 Japanese (32–79 years). As compared to non-depressive (Geriatric Depression Scale, GDS-15 score <5) subjects, mild depressives (GDS-15 score: 1–15) had shorter sleep duration (p?=?0.021), lower subjective quality of life (health: p?=?0.016; life satisfaction: p?<?0.001; and happiness: p?<?0.001), and higher 7-d systolic BP (p?<?0.05). “Masked non-dipping” (dipping on day 1, but non-dipping on at least 1 of the following 6?d) was more frequent among depressive than non-depressive normotensives (p?=?0.008). Among-day BP variability may underlie cardiovascular disease accompanying a key component of psychological depression.     

Twenty-four-hour blood pressure monitoring, diurnal blood pressure profile and drug therapy under hospital care conditions

OBJECTIVES: To elucidate the prevalence of nondipping in 24 h blood pressure monitoring (BPM) during hospital care with respect to antihypertensive drug therapy, diabetes, renal artery stenosis, and inverse diurnal blood pressure profiles. METHODS: Prospective, consecutive categorization of routine 24 h BPM was performed according to nondipping, drug therapy, normotension, severity of hypertension, diabetes, and inverse diurnal profile for 2 years. Retrospective analysis of patients examined by intraarterial renal artery angiography were performed. Nondipping was defined as a drop in night-time blood pressure (2200-0600 h) by less than 10% of the daytime values. Normotension was considered a daytime 24 h BPM value below 135/85 mmHg without antihypertensive therapy. RESULTS: We categorized 2105 24 h BPM protocols for patients of mean age 59 years. Nondipping was found for 26% of the normotensives, 38% of hypertensive patients not being administered medication, and 48% of drug-treated hypertensives. The significant increase in nondipping among patients under drug therapy applied for patients with daytime blood pressures below and above 135/85 mmHg and was thus independent of the severity of hypertension. Among the subgroup of 561 predominantly type 2 diabetic patients the prevalence of nondipping was increased significantly only for those patients who were hypertensive and being administered antihypertensive drugs. Subgroup analysis of patients using intraarterial angiography did not find different prevalences of nondipping for patients with and without renal artery stenosis. Patients with an inverse diurnal blood pressure profile and an increase in night-time blood pressure by more than 5% of the daytime values presented as a high-risk group because of morbidity associated with renal, cardiac, and cerebral disease. CONCLUSION: Nondipping is a common phenomenon among hospital patients. Drug therapy of hypertension should be directed not only towards the daytime blood pressure, but also toward alleviation of night-time hypertension.     

Influence of different supine body positions on blood pressure: consequences for night blood pressure/dipper-status

OBJECTIVES: To investigate the influence of different supine body positions on blood pressure measured by an ambulatory device. DESIGN AND METHODS: Twenty hypertensive and 20 normotensive subjects of a tertiary hospital outpatient clinic participated. Blood pressure was measured with an ambulatory blood pressure device while lying in the back, left side, right side and abdominal positions. The distance between the antecubital fossa and sternum was measured in all four body positions. An expected blood pressure difference between the arm of measurement and the right atrium (i.e. the midsternum) was calculated for the different body positions. RESULTS: When blood pressure was measured in side position at the left arm in hypertensive subjects, the mean systolic and diastolic blood pressure differences (+/- SD) between the left arm in the lower position and in back position at the same arm were +5/+4 (8/6) mmHg. These differences were -14/-17 (6/4) mmHg for the left arm lying above heart level in side position. Values of the right arm in hypertensives and the measurement at both arms in normotensive subjects yielded similar differences. CONCLUSIONS: Body and arm position can both significantly influence the ambulatory blood pressure and therefore the day-night difference. This comprises one of the main reasons for the moderate individual reproducibility of the blood pressure fall at night.     

Target organ damage and non-dipping pattern defined by two sessions of ambulatory blood pressure monitoring in recently diagnosed essential hypertensive patients

OBJECTIVE : To evaluate in a selected population of patients with a recent diagnosis of hypertension whether a reduced nocturnal fall in blood pressure, confirmed by two 24 h ambulatory blood pressure monitoring (ABPM) sessions is associated with more prominent target organ damage (TOD). METHODS : The study was structured in two phases: in the first, 141 consecutive, recently diagnosed, never-treated essential hypertensives underwent 24 h ABPM twice within 3 weeks; in the second phase, 118 of these patients showing reproducible dipping or non-dipping patterns underwent the following procedures: (1) routine blood chemistry, (2) 24 h urinary collection for microalbuminuria, (3) amydriatic photography of ocular fundi, (4) echocardiography and (5) carotid ultrasonography. RESULTS : The 92 patients with (>10%) night-time fall in systolic blood pressure (SBP) and diastolic blood pressure (DBP) (dippers) in both monitoring sessions were similar for age, gender, body surface area, smoking habit, clinic BP, 24 h and 48 h BP to the 26 patients with a < or = 10% nocturnal fall (non-dippers) in both sessions. The prevalence of left ventricular hypertrophy (LVH) (defined by two criteria: (1) LV mass index > or = 125 g/m2 in both genders; (2) LV mass index > or = 120 and 100 g/m2 in men and women, respectively) and that of carotid intima-media (IM) thickening (IM thickness > or = 0.8 mm) were significantly higher in non-dippers than in dippers (23 versus 5%, P < 0.01; 50 versus 22%, P < 0.05; and 38 versus 18%, P < 0.05, respectively). There were no differences among the two groups in the prevalence of retinal changes and microalbuminuria. The strength of the association of LV mass index with night-time BP was slightly but significantly greater than that with daytime BP. CONCLUSIONS : This study suggests that a blunted reduction in nocturnal BP, persisting over time, may play a pivotal role in the development of some expressions of TOD, such as LVH and IM thickening, during the early phase of essential hypertension, despite similar clinic BP, 24 h and 48 h BP levels observed in non-dippers and dippers.     

Long-term development of blood pressure profile in hypertensive hemodialysis patients

OBJECTIVE: The prognostic value of nocturnal blood pressure (BP) in hemodialysis patients has been well established. The aim of this study was to evaluate the long-term outcome of ambulatory BP in hypertensive hemodialysis patients. DESIGN AND METHODS: Medical records of all hemodialysis patients seen for uncontrolled hypertension between 1993 and 1999 and who underwent an ambulatory blood pressure measurements (ABPM) were retrospectively studied. Uncontrolled hypertension was defined as office BP = 140/90 mmHg and 24 h ABP = 125/80 mmHg. Patients who underwent a second ABPM after an interval of at least 1 year were included in the study. Demographic characteristics, medical history, cardiovascular risk factors and treatments were recorded for each patient. A t-test (bilateral) was used to compare BP. RESULTS: 26 patients were included (545 +/- 18.9 years; 14 men). 7 had previous history of cardiovascular disease and 2 were diabetic. At the end of the follow-up (29 +/- 12.8 months), 9 patients (36%) had 24 h BP < 125/80 mmHg. A significant decrease in diurnal and nocturnal BP was observed (p < 0.05). No significant change was observed for office systolic BP and predialytic BP. CONCLUSION: Our data show that a long-term decrease in nocturnal BP can be obtained in hypertensive patients on hemodialysis. With respect to the prognostic value of this criteria, randomised trials could be carried out to determine whether nocturnal BP is superior to office BP as a target for antihypertensive therapy in this population.