Noninvasive Ambulatory 24-Hour Blood Pressure in Patients With High Normal Blood Pressure and Exaggerated Systolic Pressure Response to Exercise
Abstract Few studies have investigated the significance of abnormal increases in systolic pressure during exercise in patients with high normal blood pressure and its correlation with 24-hour ambulatory blood pressure monitoring and left ventricular structure. This study was performed in 30 sedentary subjects (42±4 years old) with high normal blood pressure. Fifteen subjects presenting <220 mm Hg systolic pressure during ergometric exercise were compared with 15 others with systolic pressure ≥220 mm Hg. Average 24-hour (systolic, 127±5 versus 142±4 mm Hg, P<.01; diastolic, 82±4 versus 92±3 mm Hg, P<.01), daytime (systolic, 130±6 versus 144±4 mm Hg, P<.01; diastolic, 84±4 versus 92±4 mm Hg, P<.01), and nighttime (systolic, 116±7 versus 132±6 mm Hg, P<.01; diastolic, 72±6 versus 85±6 mm Hg, P<.01) ambulatory blood pressure monitoring values were significantly higher in subjects with an exaggerated blood pressure response to exercise. No significant differences were observed in left ventricular morphology. These findings indicate that subjects presenting high normal blood pressure and exaggerated systolic pressure during exercise show significantly high ambulatory blood pressure monitoring values that are not associated with left ventricular hypertrophy.
Subjects with SBP and/or DBP levels designated as high normal in the classification of hypertension are at higher risk of developing systemic hypertension and nonfatal and fatal cardiovascular events compared with subjects with normal BP.1 The results of the Trials of Hypertension Prevention2 suggest that subjects with HNBP should be more frequently evaluated and advised to change their lifestyle with the aim of reducing their arterial pressure levels. Moreover, therapeutic procedures are not suitable at this stage. In the longitudinal Framingham Heart Study, Leitschuh et al3 found that from a total of 5209 examinations, more than 50% presented initial levels of arterial BP that could be classified as HNBP. After a follow-up of 30 years these subjects displayed a risk two or three times higher than the control group of developing hypertension.
Those studies were based on BP measurement at rest. However, the use of casual recording methods is not appropriate for diagnosis because the subject could experience changes in the regulation of the circulatory system during daily physical and psychological activities. Nowadays, the important trend is the early identification of those subjects who are at risk of developing sustained arterial hypertension. The ergometric test has been shown to be one of the most important noninvasive tests for early diagnosis of hypertension.4 5 6 In addition, various studies in normotensive subjects have shown a positive correlation between BP levels during exercise and the future development of arterial hypertension7 8 9 and increased LV mass measured by echocardiography.10 11 12 13
Higher BP levels during daily 24-hour activities also were registered in those subjects during ABPM.10 However, few studies have been done on the behavior of SBP during exercise in subjects with HNBP.
We designed the present study to evaluate the behavior of SBP of HNBP subjects when submitted to an ergometric test followed by 24-hour ABPM and to correlate the pressure levels during exercise with LV structure as determined by echocardiography.
We studied 30 sedentary men between 30 and 50 years of age (mean, 42±4 years) with HNBP at rest (SBP, ≥130 and <139 mm Hg; DBP, ≥85 and <89 mm Hg). Baseline BP was considered to be the average of those taken during three medical visits after the participant had been resting for at least 5 minutes in a seated position. Casual BP was based on the average of three readings with the patient in a seated position before installation of the ABPM device. The two groups consisted of 30 subjects who had HNBP at rest. Fifteen subjects presenting SBP <220 mm Hg during ergometric exercise (group 1) were compared with 15 others with SBP ≥220 mm Hg during exercise testing (group 2).
Subjects were excluded if they (1) had a history of coronary, valvular, cerebrovascular, or peripheral vascular diseases; (2) had electrocardiographic evidence of coronary disease or cardiac arrhythmia; or (3) were taking any medication known to affect BP.
Written consent was obtained from subjects after they had received a detailed explanation of the purpose of the study and procedures. The protocol was approved by the Ethics Committee of the Cardiovascular Investigation Clinics at the Biomedical Center.
All subjects were submitted to continuous and maximal exercise testing conducted according to the adapted protocol of Astrand and Rodahl.14 The test consisted of a starting workload of 50 W, which was progressively increased in steps of 25 W every 3 minutes. Arterial BP was recorded by the cuff method before and during the last minute of each 3 minutes of exercise.
Ambulatory Blood Pressure Monitoring
Ambulatory BP averages were obtained with the SpaceLabs 90207 monitor (SpaceLabs, Inc). BP readings were obtained automatically at 15-minute intervals from 9 am to 10 pm, every 60 minutes between 10 pm and 6 am, and every 15 minutes from 7 to 9 am.
The subjects were instructed not to restrict their usual daily activities during the registration period and to keep a diary of any changes in their daily routine. Recordings were accepted only if more than 80% of the raw data were valid.
All subjects studied presented suitable acoustic windows. The echocardiographic studies were always made and read by the same trained observer, who did not know the BP levels of the examined subjects, using M-mode and two-dimensional echocardiograms by standard techniques in all subjects.
The following parameters were recorded: LV internal end-diastolic dimension, interventricular septal thickness, posterior wall thickness, LV fractional shortening, LV ejection fraction, isovolumic relaxation time, and the ratio of rapid filling phase/late diastolic filling phase (E/A) peak flow velocity.
Data are expressed as mean±SD. Unpaired Student’s t test for independent samples was used for comparison of mean values. For correlation, regression analyses were applied using computerized programs. Probability values less than .05 were considered statistically significant.
We studied 30 subjects with similar anthropometric characteristics (Table 1⇓). These individuals were divided into two groups: subjects who had HNBP at rest and SBP of 220 mm Hg or less during the exercise testing (group 1) and another 15 subjects with HNBP and SBP greater than 220 mm Hg during an ergometric test (group 2). Both groups had similar baseline SBP and DBP values (Table 1⇓). At maximal exercise SBP but not DBP was significantly higher in group 2 than in group 1 (Figure⇓). Maximal heart rate was similar in both groups during the ergometric test (172±10 versus 172±8 beats per minute). Mean casual BP values for the subjects from each group are shown in Table 2⇓. Casual, average 24-hour, daytime, and nighttime BP values were significantly higher in group 2 than in group 1. Subjects with an exaggerated BP response during dynamic exercise (group 2) presented an LV echocardiographic profile similar to that of the control group (Table 3⇓).
No correlations were observed between resting SBP or maximal SBP with ABPM or echocardiography, as shown in Table 4⇓.
Numerous studies have shown that subjects with initial normal resting BP when submitted to an ergometric test present an exaggerated SBP elevation.4 5 6 7 10 It is claimed that an exaggerated BP response to exercise predicts future hypertension. The exaggerated SBP was due to higher cardiac output accompanied by a similar total vascular resistance in these subjects.15 Although there are few data related to the mechanism responsible for the exaggerated BP response to exercise, it is reasonable to speculate that a neurohumoral mechanism might be involved. The role of the sympathetic nervous system and other vasoactive substances has been previously reviewed.16
Longitudinal studies have shown that subjects with normal resting BP but high values during exercise have a high risk of developing sustained hypertension.7 8 9 However, exercise testing as a predictor of hypertension is still a controversial issue. The protocols must be rigidly standardized, and the cutoff point separating a normal from an abnormal response should be defined according to age, sex, and physical fitness.17 Studies have reported that individuals with HNBP progress to hypertension more frequently than those with normal BP3 and have a twofold to threefold higher probability of developing hypertension.
Results of the Trials of Hypertension Prevention2 concluded that nonpharmacological interventions, such as weight reduction and sodium and stress management, are effective for BP reduction in people with HNBP. In our study exaggerated pressor responses were characterized by a greater systolic component and similar DBP and heart rate. All subjects underwent 24-hour ABPM, and the mean casual, 24-hour, daytime, and nighttime BP values were significantly higher in group 2 (Table 2⇑). The relative BP elevation during the day (BP load) was higher than 50% in those subjects. Since all subjects were sedentary, it is unlikely that higher physical activity levels were responsible for this BP increase during the day. Moreover, an increase in sympathetic activity, which may or may not depend on increased mental stress, might be a good stimulus for the BP rises. Urinary concentrations of vanylmandelic acid and metanephrine were reported to be significantly higher in individuals with such a behavior profile.10
When subjects with higher initial basal resting BP were submitted to ABPM,12 their 24-hour mean BP was observed to be high, and after 1 year a follow-up showed that 14.7% had developed established hypertension. Recently, Bergbrant et al18 showed a significantly higher SBP by ABPM in subjects with borderline hypertension compared with normotensive individuals during both the daytime and nighttime. It was suggested that borderline hypertension was not due to a measuring artifact but probably to anxiety, indicating that the elevated BP was an entity characterized by mild but persistent elevation of BP.
Recent studies have suggested that SBP during exercise is superior to resting SBP in predicting LV mass.11 Polónia et al10 studied a sedentary cohort (50±8 years old) using a partition BP value of 210 mm Hg during exercise and found that individuals with an exaggerated BP response during bicycle exercise presented LV hypertrophy. The hyperreactivity to physical exercise was also associated with higher ambulatory BP. Michelsen et al13 observed that apparently healthy men with normal resting supine BP showed a positive correlation between LV mass and maximal SBP during an exercise test. Contrary to previous reports, Bendersky et al19 made an echocardiographic study of heart structure comparing individuals with exaggerated and normal BP responses during an ergometric test and did not find significant differences between the groups regarding heart structure.
Recently, Smith et al20 investigated normotensive and moderately hypertensive cohort patients and did not find an association between LV hypertrophy and exaggerated BP during exercise. In the present study we did not find a positive correlation between LV structure or ABPM values and maximal SBP at rest or during exercise testing in both normotensive and HNBP subjects (Table 4⇑). The subjects included in our study underwent an annual medical checkup in our service, and no high BP values had been previously detected through medical examination, which could explain the lack of correlation between LV hypertrophy and high BP in these individuals.
In a parallel study21 sedentary individuals with an exaggerated BP response to bicycle exercise test (SBP >220 and ΔDBP >15 mm Hg) who were submitted to stress tests (isometric handgrip, cold pressor, mathematical calculation, and word/color conflict) presented a pressor response significantly higher than that of normotensive individuals with a normal response during the exercise test (SBP <220 and ΔDBP <15 mm Hg). The authors suggested that hyperreactive individuals presented higher levels of sympathetic drive and/or an increased response of the cardiovascular system to adrenergic stimulation.
The findings of the present study support the concept that subjects with HNBP at rest but an elevated arterial pressor response during both an ergometric test and ABPM may be more likely to develop hypertension compared with individuals with a normal BP response, which could indicate a higher cardiovascular risk. An increase in sympathetic activity could explain the transitory BP rise in these subjects.
Selected Abbreviations and Acronyms
|ABPM||=||ambulatory blood pressure monitoring|
|DBP||=||diastolic blood pressure|
|HNBP||=||high normal blood pressure|
|SBP||=||systolic blood pressure|
Financial support for this research is from the National Institute for Studies and Projects, the Brazilian Council for Scientific and Technological Development, and the Abel Almeida Foundation.
- Received June 18, 1995.
- Revision received September 16, 1995.
- Accepted October 3, 1995.
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