The association of tachycardia with obesity and elevated blood pressure
2002; Elsevier BV; Volume: 140; Issue: 6 Linguagem: Inglês
10.1067/mpd.2002.125519
ISSN1097-6833
Autores Tópico(s)Blood Pressure and Hypertension Studies
ResumoSee related article, page 660. The importance of tachycardia as a marker of underlying pathophysiologic features in hypertension is not widely recognized. In clinical practice, the presence of tachycardia is often viewed as a sign of benign “nervousness.” This view, probably rooted in the belief that only sustained hypertension causes damage, has no support. To the contrary, tachycardia is a strong predictor of excessive coronary morbidity and of cardiovascular mortality.1Palatini P Julius S Heart rate and the cardiovascular risk.J Hypertens. 1997; 15: 1-15Crossref PubMed Scopus (424) Google Scholar In this issue of The Journal, Sorof et al2Sorof JM Poffenbarger T Franco K Bernard L Portman RJ Isolated systolic hypertension, obesity, and hyperkinetic hemodynamic states in children.J Pediatr. 2002; 140: 660-666Abstract Full Text Full Text PDF PubMed Scopus (263) Google Scholar provide important and very well documented new data about the early association of faster heart rate, higher blood pressure, and overweight in a group of school-age children. They view tachycardia as a sign of enhanced sympathetic tone and speculate about the mechanism by which sympathetic overactivity could eventually lead to sustained hypertension. Whereas children with higher blood pressure are at risk of adult-sustained hypertension, this tracking is by no means 100%. Thus, the first question is whether “nervous” subjects with tachycardia are at risk of having hypertension. The answer is unequivocally “yes.”1Palatini P Julius S Heart rate and the cardiovascular risk.J Hypertens. 1997; 15: 1-15Crossref PubMed Scopus (424) Google Scholar There is also little doubt that tachycardia reflects an increased sympathetic tone in the early phases of hypertension.3Goldstein DS Plasma catecholamines and essential hypertension: an analytical review.Hypertension. 1983; 5: 86-99Crossref PubMed Scopus (616) Google Scholar Masuo4Masuo K Obesity-related hypertension: role of the sympathetic nervous system, insulin, and leptin.Curr Hypertens Rep. 2002; 4: 112-118Crossref PubMed Scopus (40) Google Scholar documented that an early elevation of plasma norepinephrine predicts which individuals will develop higher blood pressure readings after 10 years of observation. Akin to the data by Sorof et al,2Sorof JM Poffenbarger T Franco K Bernard L Portman RJ Isolated systolic hypertension, obesity, and hyperkinetic hemodynamic states in children.J Pediatr. 2002; 140: 660-666Abstract Full Text Full Text PDF PubMed Scopus (263) Google Scholar Masuo et al5Masuo K Mikami H Ogihara T Tuck ML Sympathetic nerve hyperactivity precedes hyperinsulinema and blood pressure elevation in a young, nonobese Japanese population.Am J Hypertens. 1997; 10: 77-83Crossref PubMed Scopus (172) Google Scholar found a very strong intertwining of elevated blood pressure, elevated plasma norepinephrine, and overweight in young Japanese men. They documented that elevation of plasma norepinephrine preceded the development of elements of the metabolic syndrome associated with hypertension.4Masuo K Obesity-related hypertension: role of the sympathetic nervous system, insulin, and leptin.Curr Hypertens Rep. 2002; 4: 112-118Crossref PubMed Scopus (40) Google Scholar Records of young adults with hyperkinetic borderline hypertension (with tachycardia and elevated cardiac output) in the Tecumseh study showed that they had higher blood pressure levels at 5, 8, 21, and 23 years of age.6Julius S Krause L Schork NJ Mejia AD Jones KA van de Ven C et al.Hyperkinetic borderline hypertension in Tecumseh, Michigan.J Hypertens. 1991; 9: 77-84Crossref PubMed Scopus (220) Google Scholar At 32 years of age, when they underwent hemodynamic measurements, they had elevated plasma norepinephrine values and were overweight. It is safe to assume that the overweight children in the study by Sorof et al2Sorof JM Poffenbarger T Franco K Bernard L Portman RJ Isolated systolic hypertension, obesity, and hyperkinetic hemodynamic states in children.J Pediatr. 2002; 140: 660-666Abstract Full Text Full Text PDF PubMed Scopus (263) Google Scholar also had, or were on the way to having, the full metabolic syndrome characterized by overweight, insulin resistance, and hypertension. The close and early association of sympathetic overactivity, overweight, insulin resistance, and hypertension is so strong that it can be called a clinical syndrome. It is reasonable to assume that a common pathophysiologic feature might mediate the various signs of this syndrome. Two theories to explain the relationship between sympathetic overactivity, overweight, insulin, and hypertension have been proposed.7Landsberg L Saville ME Young JB Sympathoadrenal system and regulation of thermogenesis.Am J Physiol. 1984; 247: E181-E189PubMed Google Scholar, 8Julius S Valentini M Palatini P Overweight and hypertension: a 2-way street?.Hypertension. 2000; 35: 807-813Crossref PubMed Scopus (203) Google Scholar In a series of animal experiments, Landsberg et al7Landsberg L Saville ME Young JB Sympathoadrenal system and regulation of thermogenesis.Am J Physiol. 1984; 247: E181-E189PubMed Google Scholar demonstrated that excessive food intake results in higher plasma insulin levels and that high insulin levels in the presence of glucose act on the central nervous system to increase the sympathetic outflow. Whereas the experiments7Landsberg L Saville ME Young JB Sympathoadrenal system and regulation of thermogenesis.Am J Physiol. 1984; 247: E181-E189PubMed Google Scholar proved beyond doubt that excessive feeding can start the chain of insulin resistance, enhanced sympathetic tone, increased blood pressure, and overweight, it is very likely that other mechanisms might be involved under other circumstances. A sequence of events in which sympathetic overactivity occurred first, followed by high plasma insulin (a sign of insulin resistance) and higher blood pressure levels among subjects who did not become overweight, has been also been described.4Masuo K Obesity-related hypertension: role of the sympathetic nervous system, insulin, and leptin.Curr Hypertens Rep. 2002; 4: 112-118Crossref PubMed Scopus (40) Google Scholar This suggests that, under certain conditions, sympathetic overactivity might trigger higher insulin levels through mechanisms other than increase of weight. Mechanisms by which sympathetic overactivity might lead to high insulin/insulin resistance have been described.9Julius S Gudbrandsson T Jamerson K Shahab ST Andersson O Hypothesis: the hemodynamic link between insulin resistance and hypertension.J Hypertens. 1991; 9: 983-986Crossref PubMed Scopus (242) Google Scholar The facts that in the Tecumseh study a faster heart rate is seen early6Julius S Krause L Schork NJ Mejia AD Jones KA van de Ven C et al.Hyperkinetic borderline hypertension in Tecumseh, Michigan.J Hypertens. 1991; 9: 77-84Crossref PubMed Scopus (220) Google Scholar and that a higher blood pressure preceded the development of overweight10Julius S Jamerson K Mejia A Krause L Schork N Jones K The association of borderline hypertension with target organ changes and higher coronary risk.JAMA. 1990; 264: 354-358Crossref PubMed Scopus (259) Google Scholar suggest that a primary sympathetic activity might lead to overweight. Landsberg et al7Landsberg L Saville ME Young JB Sympathoadrenal system and regulation of thermogenesis.Am J Physiol. 1984; 247: E181-E189PubMed Google Scholar postulated that an increased facultative thermogenesis is an important compensatory mechanism by which an individual dissipates excess calories to prevent weight gain. Ample literature exists to show that β-adrenergic receptors are involved in facultative and obligatory thermogenesis and that β-adrenergic responses are consistently decreased in patients with hypertension.8Julius S Valentini M Palatini P Overweight and hypertension: a 2-way street?.Hypertension. 2000; 35: 807-813Crossref PubMed Scopus (203) Google Scholar There is also evidence that, among weight-matched subjects, the presence of higher blood pressure levels predicts a larger future gain of weight. We therefore proposed that the increased sympathetic tone in hypertension causes a down regulation of β-adrenergic responses, thereby decreasing the thermogenic capacity and rendering such subjects vulnerable to excessive weight gain.8Julius S Valentini M Palatini P Overweight and hypertension: a 2-way street?.Hypertension. 2000; 35: 807-813Crossref PubMed Scopus (203) Google Scholar The study by Sorof et al2Sorof JM Poffenbarger T Franco K Bernard L Portman RJ Isolated systolic hypertension, obesity, and hyperkinetic hemodynamic states in children.J Pediatr. 2002; 140: 660-666Abstract Full Text Full Text PDF PubMed Scopus (263) Google Scholar raises the difficult question of the mechanism of transition from childhood blood pressure elevation to an adult-established hypertension. Lund-Johansen and Omvik11Lund-Johansen P Omvik P Hemodynamic patterns of untreated hypertensive disease.in: Hypertension: pathophysiology, diagnosis, and management. : Ravel Press, Ltd, New York1990: 305-327Google Scholar demonstrated how a cohort of subjects that initially had high cardiac output eventually developed classical high-resistance hypertension. Their main observations were a steady decrease in stroke volume coupled with an increase in vascular resistance. The mechanism of this transition has not been fully explicated. Whereas Sorof et al find some support in the literature for the intellectually appealing concept that hypertension undergoes a phase of increased blood pressure variability, which (presumably through summation of frequent pressor episodes) leads to established hypertension, there are also strong arguments to the contrary. Transition from repeated pressor episodes to self-accelerating sustained hypertension has never been demonstrated in experimental animals, and longitudinal observations do not support a phase of increased blood pressure variability before established hypertension. Blood pressure variability tends to increase with increasing blood pressure levels, excessive reactivity to mental and physical stress could not be confirmed in 289 subjects in the Tecumseh study, and there is no evidence that hyperresponsiveness to mental stress translates into a generalized excessive blood pressure variability.12Weder AB Julius S Behavior, blood pressure variability, and hypertension.Psychosom Med. 1985; 47: 406-414Crossref PubMed Scopus (47) Google Scholar, 13Julius S Jones K Schork N Johnson E Krause L Nazzaro P et al.Independence of pressure reactivity from pressure levels in Tecumseh, Michigan.Hypertension. 1991; 17: 12-21Google Scholar There is, however, credible evidence, as quoted by the authors, that enhanced blood pressure variability might be a predictor of cardiovascular damage. Whether this is mediated by increased oscillatory wall stress or through transition to higher blood pressure levels has not been resolved. Another possibility is that in the course of hypertension the β-adrenergic responsiveness decreases,14Bertel O Buhler FR Kiowski W Lutold BE Decreased β-adrenoreceptor responsiveness as related to age, blood pressure, and plasma catecholamines in patients with essential hypertension.Hypertension. 1980; 2: 130-138Crossref PubMed Scopus (261) Google Scholar, 15Egan B Panis R Hinderliter A Schork N Julius S Mechanism of increased α-adrenergic vasoconstriction in human essential hypertension.J Clin Invest. 1987; 80: 812-817Crossref PubMed Scopus (178) Google Scholar which, combined with the evolving cardiac restructuring, tends to limit the stroke volume and bring the cardiac output into a normal range. In parallel, probably because of endothelial damage and a hypertrophy of the vascular wall, the vascular α-adrenergic responsiveness increases.16Mokdad AH Serdula MK Dietz WH Bowman BA Marks JS Koplan JP The spread of the obesity epidemic in the United States, 1991-1998.JAMA. 1999; 282: 1519-1522Crossref PubMed Scopus (1920) Google Scholar Differences in opinion about the pathophysiologic features of the association of tachycardia (sympathetic tone), higher blood pressure, and obesity do not detract from the importance of the findings of Sorof et al.2Sorof JM Poffenbarger T Franco K Bernard L Portman RJ Isolated systolic hypertension, obesity, and hyperkinetic hemodynamic states in children.J Pediatr. 2002; 140: 660-666Abstract Full Text Full Text PDF PubMed Scopus (263) Google Scholar They have provided excellent evidence that sympathetic overactivity and overweight play an important role in early childhood hypertension. We hope that pediatricians will find the evidence sufficiently convincing to include evaluation of the heart rate in their physical examination. A young person whose heart paces at a faster rate than those of average age-matched peers deserves attention. Such a child is very likely obese, is more likely to develop sustained hypertension, and has a poorer long-term cardiovascular prognosis. The literature lacks longitudinal data to support a therapeutic approach to such children. There is no doubt, however, that the blood pressure trends in children with systolic hypertension, tachycardia, and obesity must be followed more closely than among other healthy children. It stands to reason that lifestyle modification might be useful in these children. Promoting exercise training appears eminently sensible: the heart rate, the blood pressure, and the sympathetic tone decrease, and the insulin sensitivity increases with cardiovascular conditioning. Exercise training might also be a good adjunct against overweight, a battle that in spite of pleas about dieting, we as a nation are losing.16Mokdad AH Serdula MK Dietz WH Bowman BA Marks JS Koplan JP The spread of the obesity epidemic in the United States, 1991-1998.JAMA. 1999; 282: 1519-1522Crossref PubMed Scopus (1920) Google Scholar Isolated systolic hypertension, obesity, and hyperkinetic hemodynamic states in childrenThe Journal of PediatricsVol. 140Issue 6PreviewObjective: To determine the factors that contribute to the pathogenesis of isolated systolic hypertension in children. Methods: School-based measurement was performed of blood pressure (BP), heart rate, weight, and height in 2460 students (49% Hispanic, 31% black, 13% white) 12 to 16 years of age in 8 urban public schools. An independent group of 71 untreated children underwent 24-hour ambulatory BP monitoring (ABPM) to confirm clinic hypertension and assess circadian BP patterns. Results: Hypertension and obesity were found in 17% and 23% of students, respectively. Full-Text PDF
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