Relationship of tachycardia with high blood pressure and metabolic abnormalities: a study with mixture analysis in three populations

Heart rate as a risk factor for cardiovascular disease

Almost all the epidemiological studies that aimed to answer the question of the relationship between heart rate and all-cause or cardiovascular morbidity and mortality reported that a high heart rate was associated with a higher risk of all-cause mortality and cardiovascular events. This relationship has been found to be generally stronger in men than among women. The increase in the cardiovascular risk, associated with the acceleration of heart rate, was comparable to the increase in risk observed with high blood pressure. It has been shown that an increase in heart rate by 10 beats per minute was associated with an increase in the risk of cardiac death by at least 20%, and this increase in the risk is similar to the one observed with an increase in systolic blood pressure by 10 mm Hg. It has also been shown that heart rate recorded in elderly men has a strong predictive value in survival to a very old age. Taken together, these results indicate that the risk associated with accelerated heart rate is not only statistical significant but also clinically relevant and that it should be taken into account in the evaluation of the patients. Although the association between elevated heart rate and cardiovascular morbidity and mortality has been demonstrated in a large number of epidemiological studies, tachycardia has remained a neglected cardiovascular risk factor until very recently. For the first time, the recent guidelines of the European Society of Cardiology and the European Society of Hypertension indicate than an accelerated heart rate is considered as an independent risk factor and potentially as a target for pharmacologic therapies, especially in high-risk patients.

Elevated heart rate: a "new" cardiovascular risk factor?

A number of epidemiologic studies and several experimental lines of research point to high heart rate as a main risk factor for cardiovascular disease. However, translating research into clinical practice has been a challenge throughout medical history. From the present symposium, it appears clear that this is particularly the case for heart rate. The complex nature of atherogenesis makes it difficult to establish the role of a putative risk factor because of the correlations and complex interactions among factors. The pathogenetic mechanisms for the connection of resting heart rate with atherosclerosis and cardiovascular morbidity have been elaborated extensively in the chapter papers of this symposium, suggesting that there is a causal relationship between heart rate and cardiovascular mortality. The benefit of heart rate reduction has been proved in patients with coronary artery disease or congestive heart failure. Until now it has been difficult to determine whether modulation of heart rate is beneficial also in patients free of cardiac diseases. This concern, however, does not in any fashion suggest that health care professionals should pay less attention to this clinical variable. The impressive amount of available epidemiologic data show support for the continued effort to raise awareness of the clinical importance of resting heart rate among health care professionals.

Variables influencing heart rate

In both physiologic and pathological conditions, instantaneous heart rate value is the result of a rather complex interplay. It constantly varies under the influence of a number of factors: nonmodifiable and modifiable ones. Pharmacologic blockade with beta-adrenergic antagonists and/or with parasympathetic antagonists such as atropine have permitted the identification of the mechanisms of autonomic nervous regulation of heart rate in a variety of physiologic and pathological conditions. The analysis of heart rate and blood pressure variability has yielded additional information on the autonomic control of the circulation, which has proven to have diagnostic and prognostic implications in a number of clinically relevant conditions such as hypertension, acute myocardial infarction, heart failure, and predisposition to sudden cardiac death. This article will summarize, based on available epidemiologic and clinical studies, the key variables influencing heart rate and heart rate variability in view of the known association between heart rate and cardiovascular disease.

Heart rate and cardiovascular disease: an alternative to Beta blockers

Ivabradine, an I_f inhibitor, acts primarily on the sinoatrial node and is used to reduce the heart rate with minimal effect on myocardial contractility, blood pressure, and intracardiac conduction. Heart rate reduction is an important aspect of care in patients with chronic stable angina and heart failure. Many patients with coronary artery disease have coexisting asthma or chronic obstructive airway disease, and most of them are unable to tolerate beta blockers. Ivabradine may thus be a useful medicine in therapeutic heart rate management especially in patients who are intolerant of beta-blockers.

Significance of heart rate in the prevalence of metabolic syndrome and its related risk factors in Japanese

BACKGROUND

Autonomic dysfunction is thought to be an important mechanism of metabolic syndrome (MetS), but there has not been a study on the direct association between MetS and heart rate (HR) in Japanese.

METHODS AND RESULTS

The association between MetS and HR was examined using medical check-up data from 1,880 men and 1,079 women. HR was significantly higher in MetS subjects than in non-MetS subjects in both men and women (P<0.0001 in men, P<0.001 in women). The prevalence of MetS increased linearly through the quartiles of HR in both men and women. HR was significantly correlated with MetS-related risk factors other than uric acid in men and other than uric acid, body mass index, waist circumference, and high-density lipoprotein cholesterol in women.

CONCLUSIONS

The prevalence of MetS increased linearly with the increase in HR among Japanese men and women, and HR was significantly correlated with MetS-related risk factors.

Heart rate as a risk factor for developing chronic kidney disease: longitudinal analysis of a screened cohort

BACKGROUND

High heart rate and chronic kidney disease (CKD) are both risk factors for cardiovascular morbidity and mortality. The relationship between heart rate and the risk of developing CKD, however, has not been studied in a large screened cohort.

METHODS AND RESULTS

We examined the relationship between heart rate and the risk of developing CKD in participants in a health evaluation program. CKD was diagnosed as glomerular filtration rate of less than 60 mL/min/1.73 m(2), calculated using the Modification of Diet in Renal Disease (MDRD) study equation or dipstick proteinuria. Among 7,958 subjects, 1,199 subjects diagnosed with CKD or with arrhythmia at baseline examination were excluded. A total of 6,759 subjects (4,268 men, 2,491 women, 20-84 years of age) were evaluated. The subjects were quadrisected according to baseline heart rate. The subjects were followed up for a mean of 47 +/- 16 months (range 7-71 months). Seven hundred and thirty-four subjects developed CKD over the 5-year follow-up period. Subjects with a high heart rate had greater magnitude of decreasing glomerular filtration rate (eGFR) and higher odds ratio of developing proteinuria. Cox analysis indicated that each heart rate category increment led to approximately 1.1 times increase in the risk of developing CKD, eGFR less than 60 mL/min/1.73 m(2), and 1.2 times increase of the risk of developing proteinuria in middle-aged or older subjects.

CONCLUSIONS

High heart rate is a risk factor for developing CKD in middle-aged or older subjects.

Higher heart rate may predispose to obesity and diabetes mellitus: 20-year prospective study in a general population

BACKGROUND

Emerging evidence indicates an association between sympathetic activation and metabolic syndrome. However, sympathetic activation in metabolic syndrome may be a cause, consequence, or just epiphenomenon. To elucidate this issue, the predictive power of resting heart rate for the development of abnormal glucose and lipid metabolisms after 20 years was evaluated in a general population.

METHODS

A total of 637 participants (>20 years old) underwent a health examination in 1979 including measurements of blood chemistries. Resting heart rate (bpm) was measured by an electrocardiogram. In 1999, all of the study participants again underwent a health examination, including electrocardiogram and blood chemistries. Because four of them had atrial fibrillation, and 19 subjects were taking antihypertensive medication in 1979, they were excluded from analysis. Therefore, a complete dataset of 614 subjects was available.

RESULTS

As was reported in our previous article, in 1999 we found a linear and significant (P < 0.05) cross-sectional relationship between resting heart rate and a cluster of cardiometabolic risk factors (blood pressure (BP), free fatty acid (FFA), plasma glucose, and homeostasis model assessment (HOMA) index). Baseline higher heart rate (heart rate >or=80 bpm in 1979) predicted the development of obesity, diabetes mellitus (DM), and insulin resistance in 1999 after adjustments for age, sex, and other confounders.

CONCLUSION

This is one of the first prospective reports demonstrating that higher heart rate may predispose to the development of obesity and DM, suggesting that the sympathetic nerve system may play a role in the development of obesity and DM.

Cardiovascular autonomic function tests in an African population

BACKGROUND

Diabetes mellitus is becoming increasingly common in sub-Saharan Africa. Autonomic dysfunction contributes to morbidity and mortality in diabetic patients. Data on autonomic dysfunction in the African population is scarce, and no reference values for standardized autonomic function tests are available. The aim of this study was to establish cut off values for five easy-to-use cardiovascular autonomic function tests that may be suitable for resource-poor settings.

METHODS

We recruited 276 healthy African individuals, 156 men and 120 women, aged > 20 years. Participants were tested for (1) resting heart rate (HR), (2) HR variation in response to deep breathing, (3) HR response to standing, and (4) postural changes in systolic and diastolic blood pressure (SBP and DBP). Respective cut-off values were calculated according to the 95th or 5th percentile.

RESULTS

Taking an association of the autonomic test results with gender and age into consideration, we defined the following cut-off values: resting HR (bpm) >or= 89 for men and >or= 97 for women; HR (bpm) in response to deep breathing <or= 13, <or= 11, <or= 9, <or= 8, and <or= 7 for age groups 20-29, 30-39, 40-49, 50-59, and 60+ years, respectively; HR (bpm) in response to standing <or= 14 for 20-29 years, and <or= 11 for 30+ years; postural decreases in SBP >or= 17 mmHg for all age groups; and postural decreases in DBP (mmHg) >or= 2 for men and >or= 5 for women.

CONCLUSION

The test battery revealed cut-off values different from those measured in Caucasians. Further studies are recommended a) to assess whether these cut off values are generally applicable, and b) to establish population specific reference values for Africans.

Prevalence of diabetes mellitus and the performance of a risk score among Hindustani Surinamese, African Surinamese and ethnic Dutch: a cross-sectional population-based study

Background

While the prevalence of type 2 diabetes mellitus (DM) is high, tailored risk scores for screening among South Asian and African origin populations are lacking. The aim of this study was, first, to compare the prevalence of (known and newly detected) DM among Hindustani Surinamese, African Surinamese and ethnic Dutch (Dutch). Second, to develop a new risk score for DM. Third, to evaluate the performance of the risk score and to compare it to criteria derived from current guidelines.

Methods

We conducted a cross-sectional population based study among 336 Hindustani Surinamese, 593 African Surinamese and 486 Dutch, aged 35–60 years, in Amsterdam. Logistic regressing analyses were used to derive a risk score based on non-invasively determined characteristics. The diagnostic accuracy was assessed by the area under the Receiver-Operator Characteristic curve (AUC).

Results

Hindustani Surinamese had the highest prevalence of DM, followed by African Surinamese and Dutch: 16.7, 8.1, 4.2% (age 35–44) and 35.0, 19.0, 8.2% (age 45–60), respectively. The risk score included ethnicity, body mass index, waist circumference, resting heart rate, first-degree relative with DM, hypertension and history of cardiovascular disease. Selection based on age alone showed the lowest AUC: between 0.57–0.62. The AUC of our score (0.74–0.80) was higher than that of criteria from guidelines based solely on age and BMI and as high as criteria that required invasive specimen collection.

Conclusion

In Hindustani Surinamese and African Surinamese populations, screening for DM should not be limited to those over 45 years, as is advocated in several guidelines. If selective screening is indicated, our ethnicity based risk score performs well as a screening test for DM among these groups, particularly compared to the criteria based on age and/or body mass index derived from current guidelines.

Association between heart rate and multiple risk factor syndrome: cross-sectional analysis of a screened cohort in Okinawa, Japan

BACKGROUND

Increased heart rate (HR) and metabolic syndrome are risk factors for cardiovascular morbidity and mortality, but their relationship has not been studied in a large, screened cohort.

METHODS AND RESULTS

The association between HR and multiple risk factor syndrome, resembling metabolic syndrome, was examined in participants of a health evaluation program in 1997. Of the 8,432 subjects (5,223 males, 3,209 females, 18-89 years of age), 1,502 (1,185 males, 317 females) were diagnosed with multiple risk factor syndrome and these subjects had higher HR than those without the syndrome (p<0.0001); subjects with a higher number of risk factors had higher HR than those with fewer risk factors (males, p<0.0001; females, p<0.0001). After adjusting for age, sex, and lifestyle factors, subjects within the highest HR quartile had a 2.5-fold higher risk for multiple risk factor syndrome than those in the lowest quartile (p<0.0001). An increase of 10 beats/min was associated with an approximately 30% increase in the risk for multiple risk factor syndrome.

CONCLUSIONS

A higher HR is closely associated with multiple risk factor syndrome.

Lower birth weight is associated with higher resting heart rate during boyhood

There is substantial evidence that low birth weight is associated with the development of cardiovascular disease in adult life. Moreover, resting heart rate is a prognostic factor of cardiovascular morbidity and mortality. However, there are scarce data regarding the association between birth weight and resting heart rate in later life. Therefore, we investigated the association of anthropometric data at birth and hemodynamic indices including resting heart rate in Japanese boys. The data of 1,107 male students of a junior high school in Tokyo, Japan, who underwent a medical check-up in the year of admission to the school (12 or 13 years old) were used. Information on anthropometric data at birth based on "The Maternal and Child Health Handbook" was obtained from 573 students. From a standard 12-channel resting electrocardiogram, 8 cardiac cycles were used to estimate heart rate. Resting heart rate correlated positively with body mass index at the same age (r=0.100, p=0.017) and correlated negatively with birth weight (r=-0.102, p=0.015), height at birth (r=-0.125, p=0.003), and head circumference at birth (r=-0.095, p=0.025). The negative correlation of anthropometric data at birth with heart rate at the age of 12 or 13 was independent of body mass index at the same age. The mean value of resting heart rate at the age of 12 or 13 adjusted for body mass index at the same age was significantly higher in the lower tertile of birth weight than in the higher tertile of birth weight (81.7 vs. 78.5 beats/min, p=0.028). In conclusion, lower birth weight is associated with higher resting heart rate during boyhood, suggesting that elevated heart rate may be one mechanism linking small size at birth with the development of cardiovascular disease in future life.

The role of heart rate reduction in angina management and beyond

This article highlights the significance of heart rate as an independent risk factor and prognostic marker for cardiovascular disease and examines the pharmacological measures available that lead to effective heart rate reduction.

Impact of resting heart rate on outcomes in hypertensive patients with coronary artery disease: findings from the INternational VErapamil-SR/trandolapril STudy (INVEST)

AIM

To determine the relationship between resting heart rate (RHR) and adverse outcomes in coronary artery disease (CAD) patients treated for hypertension with different RHR-lowering strategies.

METHODS AND RESULTS

Time to adverse outcomes (death, non-fatal myocardial infarction, or non-fatal-stroke) and predictive values of baseline and follow-up RHR were assessed in INternational VErapamil-SR/trandolapril STudy (INVEST) patients randomized to either a verapamil-SR (Ve) or atenolol (At)-based strategy. Higher baseline and follow-up RHR were associated with increased adverse outcome risks, with a linear relationship for baseline RHR and J-shaped relationship for follow-up RHR. Although follow-up RHR was independently associated with adverse outcomes, it added less excess risk than baseline conditions such as heart failure and diabetes. The At strategy reduced RHR more than Ve (at 24 months, 69.2 vs. 72.8 beats/min; P < 0.001), yet adverse outcomes were similar [Ve 9.67% (rate 35/1000 patient-years) vs. At 9.88% (rate 36/1000 patient-years, confidence interval 0.90-1.06, P = 0.62)]. For the same RHR, men had a higher risk than women.

CONCLUSION

Among CAD patients with hypertension, RHR predicts adverse outcomes, and on-treatment RHR is more predictive than baseline RHR. A Ve strategy is less effective than an At strategy for lowering RHR but has a similar effect on adverse outcomes.

Resting heart rate in cardiovascular disease

The importance of resting heart rate (HR) as a prognostic factor and potential therapeutic target is not yet generally accepted. Recent large epidemiologic studies have confirmed earlier studies that showed resting HR to be an independent predictor of cardiovascular and all-cause mortality in men and women with and without diagnosed cardiovascular disease. Clinical trial data suggest that HR reduction itself is an important mechanism of benefit of beta-blockers and other heart-rate lowering drugs used after acute myocardial infarction, in chronic heart failure, and in stable angina pectoris. Pathophysiological studies indicate that a relatively high HR has direct detrimental effects on the progression of coronary atherosclerosis, on the occurrence of myocardial ischemia and ventricular arrhythmias, and on left ventricular function. Studies have found a continuous increase in risk with HR above 60 beats/min. Although it may be difficult to define an optimal HR for a given individual, it seems desirable to maintain resting HR substantially below the traditionally defined tachycardia threshold of 90 or 100 beats/min. These findings suggest that the potential role of HR and its modulation should be considered in future cardiovascular guidance documents.

Prevalence of metabolic syndrome in young men in Japan

AIM

The prevalence of metabolic syndrome, as defined by the Third Report of the National Cholesterol Education Program Expert Panel on Detection, Evaluation and Treatment of High Blood Cholesterol in Adults (ATPIII) modified for age (>or=3 of the following abnormalities): waist circumference of at least 80 cm; serum glucose level of at least 110 mg/dL; triglyceride level of at least 110 mg/dL; high density lipoprotein (HDL) cholesterol level of 40 mg/dL or less; and blood pressure (BP) of at least 130/75 mmHg, was estimated in male high school students who attended an annual school health examination.

METHODS

The subjects were divided into three body mass index (BMI) categories (obese: >or=25; mildly obese: 23-24.9: and normal weight: <23 kg/m2). Of the 1446 students (mean age 15 years), 96 (6.6%) were obese and 158 (10.9%) were mildly obese.

RESULTS

The overall prevalence of metabolic syndrome was 1.4%, being present in; 15.6% of obese subjects. Overall, elevated systolic BP was most common (19.9%). In obese subjects, 51% had an elevated systolic BP.

CONCLUSION

Our study suggests that metabolic syndrome is present in more than 1% of male adolescents and 15% of obese male adolescents in Japan.

Heart Rate Elevation Precedes the Development of Metabolic Syndrome in Japanese Men: A Prospective Study

This observational study of Japanese men without metabolic syndrome (MetS) (age: 41+/-8 years) was conducted to clarify whether or not heart rate elevation precedes the development of full-blown MetS. MetS was defined based on two modifications of the criteria of the Japanese Expert Committee on the Diagnosis and Classification of Metabolic Syndrome. Premetabolic syndrome subjects were defined as those having one component of MetS with increased body mass index (BMI). Among the subjects without MetS (n=1,859 when the BMI criterion was >or=25 and n=2,020 when the BMI criterion was >or=27.5), the incidence of progression to full-blown MetS by the time of the second examination at the end of the 3-year study period was higher in the subjects with premetabolic syndrome than in those without it. The receiver-operator characteristic curve analysis and binary logistic regression analysis revealed that the odds ratio (OR) of a heart rate >or=69 beats/min at the first examination for progression to full-blown MetS by the time of the second examination was significant in subjects with premetabolic syndrome (BMI>or=25: OR=3.64 [1.22-10.88]; BMI>or=27.5: OR=3.67 [1.28-10.55]; p<0.05). Thus, heart rate elevation appears to precede the development of full-blown MetS in subjects with premetabolic syndrome. Heart rate seems to be a simple and useful marker for predicting the progression to full-blown MetS of middle-aged Japanese men with premetabolic syndrome.

Comparative effects of ivabradine, a selective heart rate-lowering agent, and propranolol on systemic and cardiac haemodynamics at rest and during exercise

AIM

To compare in humans the effects of ivabradine and propranolol on cardiac and systemic haemodynamics at rest, during tilt and exercise.

METHODS

Nine healthy volunteers randomly received single oral doses of ivabradine (Iva, 30 mg), propranolol (Propra, 40 mg) or placebo (Plac) during a double-blind cross-over study. Doses were selected to be equipotent in heart rate (HR) reduction. HR, systolic and diastolic blood pressure (SBP, DBP), cardiac index (CI, bioimpedance), rate pressure product (RPP), plasma epinephrine (E) and norepinephrine (NE), were measured at rest at baseline, before and after two tilt and exercise tests, started 2 and 5 h after drug intake. Heart rate variability (low to high frequency ratio LF/HF) was evaluated at rest and at 5 th minute of tilt.

RESULTS

At rest, HR and RPP decreased similarly with Iva and Propra (both P < 0.01). During tilt, HR increased less with Iva than Propra (P < 0.01), LF/HF decreased after Iva (P < 0.03), SBP and mean blood pressure decreased after Propra (both P < 0.01), RPP decreased similarly after Iva and Propra (both P < 0.01) and CI decreased to a greater extent with Propra than with Iva or Plac (both P < 0.04). During exercise, Iva and Propra similarly decreased HR (both P < 0.01) and RPP (P < 0.01).

CONCLUSIONS

These results demonstrate that for a similar decrease in HR at rest and during sympathetic stimulation, acute administration of ivabradine, a selective heart rate-lowering agent, decreased myocardial oxygen demand to the same extent as a reference beta-blocker, propranolol, but without evidence of depressant effect on cardiac function.

Progression to hypertension in the non-hypertensive participants in the Flemish Study on Environment, Genes and Health Outcomes

OBJECTIVE

To evaluate the consistency between a randomly recruited Western European population and the participants of the Framingham Heart Study, with respect to the rates and determinants of progression to hypertension.

METHODS

Among the non-hypertensive individuals enrolled in the Flemish Study on Environment, Genes and Health Outcomes, we assessed progression from optimal (< 120/80 mmHg), normal (120-129/80-84 mmHg) and high-normal (130-139/85-89 mmHg) blood pressure to hypertension (> or = 140/90 mmHg). Our analysis included 781 women and 675 men (age range 10-77 years) who were followed up for a median of 4.6 years (interquartile range 2.4-8.1 years). Our statistical methods included Kaplan-Meier survival function estimates, the log-rank test and multiple Cox regression.

RESULTS

In individuals younger than 50 years, 4-year progression rates associated with optimal, normal and high-normal blood pressure were 7.4% [95% confidence interval (CI) 5.5-9.3], 17.9% (95% CI 14.3-21.6) and 24.5% (95% CI 18.7-30.2), respectively. Corresponding 4-year rates of progression for individuals aged 50 years or older were 16.4% (95% CI 11.2-22.5), 26.3% (95% CI 19.8-32.9) and 54.0% (95% CI 45.7-62.3), respectively. In multivariate Cox regression, blood pressure category and body mass index at baseline were strong predictors of hypertension. Before the age of 50 years, male sex and a fast heart rate were also forerunners of hypertension.

CONCLUSIONS

The stepwise increase in incidence of hypertension across the three non-hypertensive blood pressure categories in our cohort was similar to that observed in the Framingham Heart Study. The Framingham findings, which have informed several guidelines, can be extrapolated to a Western European population.

Metabolic syndrome is associated with delayed heart rate recovery after exercise

Heart rate (HR) recovery after exercise is a function of vagal reactivation, and its impairment is a predictor of overall mortality and adverse cardiovascular events. While metabolic syndrome is associated with sympathetic overactivity, little is known about the relationship between metabolic syndrome and HR recovery. A symptom-limited exercise stress test in healthy subjects (n=1, 434) was used to evaluate HR recovery. Metabolic syndrome was defined according to the National Cholesterol Education Program's Adult Treatment Panel III (NCEP ATP-III) criteria. Seventeen percent of subjects had > or =3 criteria for metabolic syndrome. HR recovery was lower in men than women and in smokers than nonsmokers. The subject with metabolic syndrome (vs. without) showed lower HR recovery (10.3+/-11.6 vs. 13.6+/-9.7 per minute) and higher resting HR (64.3+/-10.3 vs. 61.6+/-9.1 per minute). HR recovery correlated inversely to age (r=-0.25, p<0.0001), but not to resting HR or maximal oxygen uptake. Delayed HR recovery was associated with metabolic syndrome after an adjustment for age, sex, resting HR and smoking (p<0.01). Metabolic syn-drome is associated with impaired vagal reactivation. Adverse cardiovascular out-comes associated with metabolic syndrome may be mediated by the failure of vagal reactivation in addition to sympathetic overactivity.

Can we improve cardiovascular risk prediction beyond risk equations in the physician's office?

BACKGROUND AND OBJECTIVES

Beyond a global estimation of the cardiovascular risk through the assessment of major risk factors and their integration in dedicated risk scales or equations, the use of specific markers provides additive prognostic information at an individual level, including predisposing factors, which are not included in the risk equations as well as the individual susceptibility to their long-term exposure. However, the majority of these markers require specific devices and skills, which are not widely available in primary care.

METHODS

Some clinical and/or "low-cost" parameters are shown to be valuable risk markers, and their use could refine the risk estimation in a physician's office. Several epidemiologic studies suggest the heart rate, the pulse pressure and the ankle-brachial index are effective cardiovascular risk markers. The arms systolic pressure asymmetry could also be a useful marker of risk.

RESULTS AND CONCLUSIONS

Through a general review, the authors evaluate the potential of these clinical markers, including their use in combination for more accurate risk determination.

Differentials and Determinants of Syndrome 'X' and its Role as Coronary Risk among Healthy Middle Aged Indian Army Personnel

BACKGROUND

Syndrome 'X', a clustering of impaired glucose tolerance (IGT), raised blood pressure, raised serum triglycerides and low HDL-cholesterol, occurring under the influence of insulin resistance and resultant hyperinsulinaemia, has been hypothesised to be a major risk factor for ischaemic heart disease (IHD). However, there is a lack of research based evidence in this field, in our country.

METHODS

The study was a cross-sectional analytical epidemiological design of 614 healthy Indian Army personnel, aged 35 years and above, selected by random sampling.

RESULTS

The study indicated that there is a statistically significant (p < 0.001) clustering between fasting hyperinsulinaemia, raised blood pressure, IGT, raised triglycerides and low HDL. The prevalence of syndrome 'X' was 8.47% (95% CI 6.27% to 10.47%). Initial univariate and subsequent multivariate analysis using multiple logistic regression method, indicated that predictors of syndrome 'X' were increasing age, overweight, increasing central (abdominal) obesity, lack of adequate physical exercise and low level of physical fitness. Presence of syndrome 'X' increased the risk of resting ECG changes suggestive of coronary insufficiency (OR = 6.29, p < 0.001).

CONCLUSION

Based on the findings, recommendations for prevention of this syndrome have been submitted.

Baroreceptor sensitivity is impaired in elderly subjects with metabolic syndrome and insulin resistance

OBJECTIVE

Metabolic syndrome consists of a collection of cardiovascular risk factors and is considered to increase the risk of cardiovascular morbidity and mortality. This study aimed to investigate whether altered baroreflex sensitivity (BRS), a measure of cardiovascular autonomic control, is related to metabolic syndrome and insulin resistance.

DESIGN AND METHODS

Spontaneously occurring fluctuations in blood pressure and heart rate were recorded during 5 min of controlled breathing in a population sample of 1016 subjects aged 70 (the Prospective Investigation of the Vasculature in Uppsala Seniors study). BRS was calculated through both sequence and frequency domain analysis in 77% of the sample.

RESULTS

BRS was reduced in those with metabolic syndrome (n = 172, median 4.3 versus 5.7; P < 0.0001 after correction for heart rate, cardiovascular diagnosis and medication) and was reduced in proportion to the number of fulfilled National Cholesterol Education Program/Adult Treatment Panel III metabolic syndrome criteria (P < 0.0001). BRS was inversely related to insulin resistance, calculated by homeostatic model assessment (HOMA index; r = -0.18, P < 0.0001).

CONCLUSIONS

Cardiovascular autonomic imbalance, measured as a reduced BRS, is present in metabolic syndrome and in subjects with insulin resistance. As BRS mainly reflects vagal activity, future prospective studies will address the possibility of vagal impairment in the pathogenesis of metabolic syndrome.

Evidence for a gene influencing heart rate on chromosome 5p13-14 in a meta-analysis of genome-wide scans from the NHLBI Family Blood Pressure Program

Background

Elevated resting heart rate has been shown in multiple studies to be a strong predictor of cardiovascular disease. Previous family studies have shown a significant heritable component to heart rate with several groups conducting genomic linkage scans to identify quantitative trait loci.

Methods

We performed a genome-wide linkage scan to identify quantitative trait loci influencing resting heart rate among 3,282 Caucasians and 3,989 African-Americans in three independent networks comprising the Family Blood Pressure Program (FBPP) using 368 microsatellite markers. Mean heart rate measurements were used in a regression model including covariates for age, body mass index, pack-years, currently drinking alcohol (yes/no), hypertension status and medication usage to create a standardized residual for each gender/ethnic group within each study network. This residual was used in a nonparametric variance component model to generate a LOD score and a corresponding P value for each ethnic group within each study network. P values from each ethnic group and study network were merged using an adjusted Fisher's combining P values method and the resulting P values were converted to LOD scores. The entire analysis was redone after individuals currently taking beta-blocker medication were removed.

Results

We identified significant evidence of linkage (LOD = 4.62) to chromosome 10 near 142.78 cM in the Caucasian group of HyperGEN. Between race and network groups we identified a LOD score of 1.86 on chromosome 5 (between 39.99 and 45.34 cM) in African-Americans in the GENOA network and the same region produced a LOD score of 1.12 among Caucasians within a different network (HyperGEN). Combining all network and race groups we identified a LOD score of 1.92 (P = 0.0013) on chromosome 5p13-14. We assessed heterogeneity for this locus between networks and ethnic groups and found significant evidence for low heterogeneity (P ≤ 0.05).

Conclusion

We found replication (LOD > 1) between ethnic groups and between study networks with low heterogeneity on chromosome 5p13-14 suggesting that a gene in this region influences resting heart rate.

Impact of Increased Heart Rate on Clinical Outcomes in Hypertension

Thirty-eight studies have been published to date on the association between elevated heart rate and mortality. After adjustment for other risk factors, only two studies for all-cause mortality and four studies for cardiovascular mortality reported an absence of association between heart rate and mortality in male populations. This relationship has been found to be generally weaker among females. Most of these studies investigated samples of general populations. The four studies performed in hypertensive men found a positive association between heart rate and all-cause mortality (hazard ratios ranging from 1.9 to 2.0) or cardiovascular mortality (hazard ratios ranging from 1.3 to 1.7). In spite of this evidence, elevated heart rate remains a neglected cardiovascular risk factor in both genders. The pathogenetic mechanisms connecting high heart rate, hypertension, atherosclerosis and cardiovascular events have also been explicated in many studies. Elevated heart rate is due to an increased sympathetic and decreased parasympathetic tone. This altered balance of the autonomic nervous system tone could explain the increase in events with the increased heart rate. However, it has also been proved that blood flow changes associated with high heart rate favour both the formation of the atherosclerotic lesion and the occurrence of the cardiovascular event. Reduction of heart rate in hypertensive patients with increased heart rate could be an additional goal of antihypertensive therapy. Several trials retrospectively showed the beneficial effect of cardiac-slowing drugs, such as beta-adrenoceptor antagonists (beta-blockers) and non-dihydropyridine calcium channel antagonists, on mortality, notably in patients with coronary heart disease, but no published data are available in patients with hypertension free of coronary heart disease. Other antihypertensive drugs that have been shown to reduce the heart rate are centrally acting drugs and angiotensin II receptor antagonists, but their bradycardic effect is rather weak. The f-channel antagonist ivabradine is a selective heart rate-lowering agent with no effect on blood pressure. Although it has not been proven in existing trials, it would seem reasonable to recommend antihypertensive agents that decrease the heart rate in hypertensive patients with a heart rate higher than 80-85 beats per minute. Since the fast heart rate per se causes cardiovascular damage, all drugs that lower the heart rate have the potential of further reducing cardiovascular events in patients with elevated heart rate. Unfortunately, lowering of the heart rate is not a clinically recognised goal. Prospective trials investigating whether treatment of high heart rate can prevent cardiovascular events, notably in hypertensive patients, are warranted.

Systolic and pulse hypertension

Epidemiology, genetic analysis and clinical studies are of help in understanding how, to what extent and why systolic blood pressure increases with age (at least in Western societies), while diastolic blood pressure increases only until the age of 60–65 years. Systolic blood pressure is a predictor of outcome in humans, but pulse pressure (systolic minus diastolic) is a better predictor, particularly in the elderly. Although the cardiovascular risk pattern is different in older patients, antihypertensive treatment remains useful in the elderly and even in the very old. Nevertheless, excessive reduction of diastolic blood pressure should be avoided in order to prevent increasing pulse pressure. Although all therapeutic regimens tend to reduce systolic more than diastolic blood pressure (reducing pulse pressure), the need for antihypertensive drugs acting selectively on systolic values remains very strong.

Elevated heart rate: a major risk factor for cardiovascular disease

Mounting evidence shows that elevated heart rate is associated with a greater risk of developing hypertension and atherosclerosis and that it is a potent predictor of cardiovascular morbidity and mortality. These relationships have been shown not only in general populations but also among hypertensive individuals, with important implications for the treatment of hypertension. In spite of this evidence heart rate has been overlooked as a risk factor, but the fact that in most studies the risk related to fast heart rate remained highly significant after controlling for major risk factors for atherosclerosis suggests that it plays a direct role in the induction of the risk. The clustering of several risk factors for coronary artery disease in subjects with fast heart rate suggests that sympathetic overactivity accounts for the increased cardiovascular morbidity in subjects with tachycardia. In fact, experimental studies have shown that a heightened sympathetic tone can cause obesity, hyperinsulinemia, and insulin resistance which in the long run can promote the development of atherosclerosis. Moreover, experimental studies in the animal suggest that the heamodynamic disturbances related to high heart rate have a direct impact on the arterial wall promoting the development of atherosclerotic plaques. Preliminary results in the experimental animal and pooled data from intervention studies in patients with myocardial infarction or congestive heart failure suggest that drug-induced reduction of heart rate may be beneficial in several clinical conditions.

Long-term prognostic value of resting heart rate in patients with suspected or proven coronary artery disease

AIMS

Heart rate reduction is the cornerstone of the treatment of angina. The purpose of this study was to explore the prognostic value of heart rate in patients with stable coronary artery disease (CAD).

METHODS AND RESULTS

We assessed the relationship between resting heart rate at baseline and cardiovascular mortality/morbidity, while adjusting for risk factors. A total of 24 913 patients with suspected or proven CAD from the Coronary Artery Surgery Study registry were studied for a median follow-up of 14.7 years. All-cause and cardiovascular mortality and cardiovascular rehospitalizations were increased with increasing heart rate (P<0.0001). Patients with resting heart rate > or =83 bpm at baseline had a significantly higher risk for total mortality [hazard ratio (HR)=1.32, CI 1.19-1.47, P<0.0001] and cardiovascular mortality (HR=1.31, CI 1.15-1.48, P<0.0001) after adjustment for multiple clinical variables when compared with the reference group. When comparing patients with heart rates between 77-82 and > or =83 bpm with patients with a heart rate < or =62 bpm, the HR values for time to first cardiovascular rehospitalization were 1.11 and 1.14, respectively (P<0.001 for both).

CONCLUSION

Resting heart rate is a simple measurement with prognostic implications. High resting heart rate is a predictor for total and cardiovascular mortality independent of other risk factors in patients with CAD.

Incidence of diabetes in middle-aged men is related to sleep disturbances

OBJECTIVE

Sleep deprivation in healthy men has been experimentally found to result in disturbances in glucose metabolism and in sympathovagal imbalance. The aim of the present study was to investigate whether sleep disturbances and elevated resting heart rate are associated with increased risk of developing diabetes.

RESEARCH DESIGN AND METHODS

A group of 6,599 initially healthy, nondiabetic men aged 44.5 +/- 4.0 years took part in a prospective, population-based study in Malmö, Sweden. The incidence of diabetes during a mean follow-up of 14.8 +/- 2.4 years was examined in relation to self-reported difficulties in falling asleep and resting heart rate at baseline. Diabetes was assessed at follow-up in all subjects by questionnaire and in a subgroup of 1,551 men by blood glucose measurement.

RESULTS

A total of 615 (9.3%) subjects reported either difficulties in falling asleep or regular use of hypnotics (seen as markers of sleep disturbances), and 158 (2.4%) subjects reported both of these. Altogether, 281 (4.3%) of the men developed diabetes during the follow-up period. Logistic regression models showed difficulties in falling asleep or regular use of hypnotics (odds ratio [OR] 1.52 [95% CI 1.05-2.20]) and resting heart rate (OR per 10 bpm 1.13 [0.99-1.30]) to be associated with development of diabetes when full adjustments were made for baseline age, biological risk factors, lifestyle, family history of diabetes, and social class.

CONCLUSIONS

The results suggest that sleep disturbances and, possibly, elevated resting heart rate, in middle-aged men, are associated with an increased risk of diabetes.

Administration of tibolone decreases 24h heart rate but not blood pressure of post-menopausal women

OBJECTIVE

Elevation of blood pressure and heart rate increase the risk of cardiovascular disease. Administration of estrogens does not affect heart rate but may decrease 24 h blood pressure. In this study, we tested the effect of the estro-progestogenic compound tibolone.

METHODS

Thirty healthy, post-menopausal women were randomized to receive placebo (n = 15) or tibolone, at the commonly prescribed dose of 2.5 mg per day (n = 15). Before and after 6 months of treatment, in each woman blood pressure and heart rate were monitored every 30 min for 41 h by an ambulatory device. Valuable readings were those collected from 8:00 a.m. of the second day to 8:00 a.m. of third day. Analyses were performed of 24 h, day-time (7:00 a.m.-11:00 p.m.) and night-time (11:00 p.m.-7:00 a.m.) values. Day to night difference was also calculated.

RESULTS

Placebo did not modify 24h, day-time, and night-time blood pressure or heart rate values. Day-night differences were also not affected by placebo. Similarly to placebo, tibolone administration did not modify any of the blood pressure parameters taken into consideration. By contrast, a significant decline of 24 h heart rate (73.2 +/- 2.3 beats/min versus 69.3 +/- 1.7 beats/min; P < 0.0008) was observed. The effect was significant both at day (76.6 +/- 2.4 beats/min versus 72.1 +/- 1.9 beats/min; P < 0.0001) and night (65.8 +/ 2.6 beats/min versus 62.4 +/- 1.9 beats/min; P < 0.05). Day-night blood pressure and heart rate differences were not affected by tibolone.

CONCLUSIONS

In post-menopausal women, administration of tibolone does not influence 24 h blood pressure but reduces heart rate.

Electrophysiological effects of a single intravenous administration of ivabradine (S 16257) in adult patients with normal baseline electrophysiology

INTRODUCTION

Ivabradine is a heart rate-lowering agent that selectively inhibits the pacemaker current, I(f), in the sinoatrial node. The objective of this study was to evaluate the effects of a single intravenous administration of ivabradine on cardiac electrophysiological parameters in patients with normal baseline electrophysiology. The safety profile of ivabradine was also investigated.

STUDY DESIGN

This was an open-label, single-dose, non-controlled study conducted at one centre. Patients received a single dose of ivabradine (0.2 mg/kg) intravenously as a slow bolus over 15 seconds. Electrophysiological investigations, after catheter ablation for cardiac dysrhythmia, were performed at baseline and 30 minutes and 1 hour after drug administration. Electrode catheters were introduced and advanced to the right atrium, the bundle of His and the right ventricular apex of the heart. Electrophysiological parameters assessed included heart rate, QT interval, corrected QT interval (QTc), PR interval, sinoatrial conduction time, sinus node recovery time, and right atrial and ventricle refractory periods. Changes in electrophysiological parameters over time were assessed using one-way analysis of variance. In the case of a significant time effect, the Newman-Keuls procedure was used for comparison.

PATIENTS

A total of 14 patients, 12 male and 2 female, aged 18-75 years were included in the study. The arrhythmia requiring catheter ablation was atrioventricular (AV) excitation in seven patients, paroxysmal supraventricular tachycardia in five patients, atrial fibrillation and flutter in one patient, and cardiac dysrhythmia in one patient. All patients had normal electrophysiology at baseline.

RESULTS

Mean heart rate decreased significantly with ivabradine by 12.9 beats/min at 30 minutes and 14.1 beats/min at 1 hour. The mean QT interval increased but QTc showed no significant change from baseline. The PR and QRS intervals were unchanged. The right atrial and right ventricle refractory periods showed no significant change from baseline. The measured QT interval and the sinus node recovery time were increased. There were no clinically relevant changes in any other major electrophysiological parameters. Ivabradine was well tolerated and no serious adverse events occurred.

CONCLUSION

A single intravenous dose of ivabradine had a significant heart rate-lowering effect, observed at 30 minutes and 1 hour after administration. Ivabradine did not prolong QTc or modify conductivity and refractoriness of the atrium, AV node, His-Purkinje system and ventricles, or repolarisation duration. These results confirm the action of ivabradine as a specific heart rate-lowering agent.

Pulse rate in childhood: reference limits

BACKGROUND AND AIM

Systematic quantitative resting pulse rate measurements may represent an additional parameter for the study of cardiovascular risk factors in youth as well as in adulthood. The aim of this study was to evaluate resting pulse rate and its distribution curve in order to define reference limits in a sample of adolescents from Turin, Italy.

METHODS AND RESULTS

The study population consisted of 2230 children aged 12-18 years, who were randomly enrolled from Turin Junior High Schools. All of the participants underwent pulse rate, blood pressure and height measurements. The 5th and 95th percentiles of the pulse rate in boys and girls are reported by age and height. The pulse rate was higher in the girls, but progressively decreased with age and somatic growth in both genders.

CONCLUSIONS

The present study provides reference blood pressure values by age, gender and height in a sample of male and female adolescents.

Fasting blood glucose is independently associated with resting and exercise blood pressures and development of elevated blood pressure

OBJECTIVE

To assess whether fasting blood glucose is independently related to blood pressure at rest and during exercise, and to development of elevated blood pressure.

DESIGN

Cross-sectional and prospective cohort study of 2014 apparently healthy middle-aged men.

METHODS

The baseline survey included carefully standardized blood pressure measurements at rest and during exercise testing, an intravenous glucose tolerance test and a panel of fasting blood tests, including fasting blood glucose. Results from 7-years follow-up provided data on development of elevated blood pressure.

RESULTS

Strong associations were found between quartiles of fasting blood glucose and baseline resting and/or exercise levels of blood pressure, and also development of elevated blood pressure over 7 years. Physical fitness, calculated from an exercise test, had a strong modulating effect on blood pressure at all levels of fasting blood glucose. In multivariate models - after adjusting for intravenous glucose tolerance, physical fitness, age, body mass index, triglycerides and cholesterol - fasting blood glucose was strongly associated with blood pressure at rest (coefficient = 2.83, P = 0.0004) and during exercise (coefficient = 6.57, P < 0.0001), and further to development of treated hypertension and/or elevated blood pressure [odds ratio (OR), 1.17; 95% confidence interval (CI), 1.05-1.31].

CONCLUSION

In healthy non-diabetic and non-hypertensive men, strong associations were found between fasting blood glucose and blood pressure at rest and during exercise and to development of elevated blood pressure after 7-years follow-up. Fasting glucose metabolism deserves scrutiny when studying the pathogenesis of hypertension.

Young men with high-normal blood pressure have lower serum adiponectin, smaller LDL size, and higher elevated heart rate than those with optimal blood pressure

OBJECTIVE

Three measures--heart rate, a global index of the influence of the autonomic nervous system on the heart; circulating concentrations of adiponectin, an adipose-specific protein; and C-reactive protein (CRP), a sensitive marker of inflammation--have been reported to be closely associated with insulin resistance. Patients with borderline hypertension are known to be more insulin resistant and dyslipidemic than those with normal blood pressure (BP). BP can be classified into three categories: optimal, normal, and high-normal. The present study examined whether those with high-normal BP have any of these three conditions as compared with those with optimal BP in young healthy men.

RESEARCH DESIGN AND METHODS

Anthropometric, blood pressure, heart rate, and blood tests, including tests for adiponectin and CRP, were conducted in 198 male students, ages 18-26 years, who had fasted overnight. Insulin resistance (IR) and insulin secretion (beta-cell levels) were calculated using the homeostasis model assessment (HOMA), and LDL size was measured by PAGE.

RESULTS

Compared with the 90 men who had optimal BP, the 46 men with high-normal BP had increased heart rate, BMI, percent body fat, and serum leptin levels. In addition, they had greater serum insulin, HOMA IR, and beta-cell levels, lower adiponectin levels, and comparable CRP levels. Furthermore, the 46 men with high-normal BP had higher serum triglyceride and apolipoprotein (apo) B levels, and smaller LDL size; however, there was no difference in LDL and HDL cholesterol and apoA-I between men with optimal and high-normal BP. After adjusting for BMI, differences were still significant in serum adiponectin, heart rate, and LDL particle size. As BP rose, there was an increase in heart rate (BMI-adjusted least square means were 63, 65, and 70 bpm in men with optimal, normal, and high-normal BP, respectively; P = 0.005), whereas serum adiponectin (7.5, 6.6, and 6.4 mg/l; P = 0.007) and LDL particle size (271, 269, and 269 A; P = 0.008) decreased.

CONCLUSIONS

Young men with high-normal BP have a faster heart rate, lower serum adiponectin levels, and smaller LDL size than men with optimal BP, even after adjustment for BMI. These results suggest the necessity of preventing further development of cardiac and metabolic diseases in young people who have high-normal BP.

Hormone replacement in postmenopausal women: impact of progestogens on autonomic tone and blood pressure regulation

OBJECTIVE

Depressed heart rate variability (HRV) reflects an imbalance of autonomic tone and independently predicts increased cardiovascular risk in patients with congestive heart failure or after acute myocardial infarction. While hormone replacement therapy (HRT) with estrogens beneficially modulates autonomic tone and blood pressure (BP) regulation in postmenopausal women, the impact of concomitant treatment with progestogens remains unclear.

DESIGN

In this cross-sectional study, HRV and BP were examined in 62 healthy women (ages 48-71 years) using digital beat-to-beat interval recordings of heart rate and 24-hour ambulatory BP measurements.

RESULTS

Demographic parameters did not differ among women without HRT (n = 23), on estrogen (n = 17; ERT), or on progestogen-estrogen containing HRT (n = 22; PERT). Total power of HRV was significantly lower, whereas mean heart rate (HR) was significantly higher among women on PERT group versus controls and ERT (total power: 1611 +/- 146 vs. 2497 +/- 308 and 2472 +/- 348 ms(2); heart rate: 80.7 +/- 1.2 vs. 75.0 +/- 1.4 and 74.0 +/- 2.2 bpm; p < 0.05). In addition, low-frequency power and time-dependent parameters of HRV were lower among women on PERT group versus controls and ERT (p < 0.05). ERT use was associated with reduced systolic and diastolic daytime BP, whereas no significant differences were evident PERT users compared with controls.

CONCLUSIONS

Progestogen-containing replacement therapy was associated with increased HR and an attenuation of HRV in postmenopausal women. BP was lower in women on ERT, whereas this effect was offset in the PERT group. These observations could at least partially explain the ambiguous results of progestogen-containing HRT on cardiovascular risk in the Heart and Estrogen/Progestin Replacement Study (HERS).

Sleep disturbance in association with elevated pulse rate for prediction of mortality--consequences of mental strain?

OBJECTIVES

Sleep deprivation has experimentally been shown to adversely influence glucose metabolism, endocrine function and sympathovagal balance in young men without known serious disease. We investigated the impact of sleep problems and resting heart rate in a large sample of self-reported, healthy middle-aged men and women on long-term mortality.

METHODS

In all 22,444 men and 10,902 women participated in a population-based health screening (71% mean attendance), including blood sampling and examination of blood pressure (BP) and pulse rate after 10 min supine rest, as well as a self-administered questionnaire on sleep problems. Mortality was assessed from national death registers.

RESULTS

Sleep disturbances were related to increased cardiovascular risk factor levels at baseline in both sexes, and predicted total and cause-specific mortality after a mean of 12 years (women) and 17 years (men) of follow-up. In men, self-reported healthy at baseline, total mortality during follow-up was independently predicted by both sleep problems and increased resting heart rate, also after adjustment for smoking, body mass index (BMI), systolic BP, cholesterol, smoking and problematic alcohol drinking habits. A step-wise increased total mortality was shown in men reporting successively worse sleep problems and higher heart rate, highest hazard ratio 2.7 [95% confidence interval (CI) = 2.1-3.4] after adjustments, compared with men free from sleep problems and with normal heart rate.

CONCLUSIONS

Sleep disturbance is a predictor of total and cause-specific mortality in both sexes, but only interacts with increased resting heart rate for this prediction in healthy men. Sleep problems correlated cross-sectional with disturbances in lipid and glucose metabolism, even after adjustment for degree of obesity and smoking. Sleep disturbance is a symptom for a biological pathway that is correlated to premature mortality. One possible explanation would be that it acts in concert with sympathetic nervous activation (SNA), both being consequences of chronic stress exposure.

Sympathetic overactivity in hypertension: a risk factor for cardiovascular disease

Numerous prospective studies have shown that high heart rate is related to the development of hypertension, atherosclerosis, and incidence of cardiovascular events. Experimental studies in monkeys have shown that high heart rate has direct atherogenic effects on the arteries as a result of increased wall stress. However, clustering of several risk factors for coronary artery disease in persons with high heart rate suggests that sympathetic overactivity also accounts for part of the increased cardiovascular morbidity that is observed in persons with tachycardia. Indeed, experimental studies have shown that heightened sympathetic tone can cause obesity, hyperinsulinemia, and insulin resistance, which in the long term can promote the development of atherosclerosis. Through its interaction with plasma insulin, sympathetic overactivity can promote the development of left ventricular hypertrophy. Sympathetic activation can also increase hematocrit and precipitate a procoagulant state. Angiotensin II has an effect both on the central nervous system, enhancing sympathetic outflow, and on the peripheral sympathetic nerves. Among the angiotensin II receptor antagonists, eprosartan showed a particular ability to block presynaptic angiotensin II receptor 1 (AT(1)) receptors at neuro-effector junctions in the sympathetic nervous system, as well as AT(1) receptors in blood vessels. This dual action may represent an important advance in treatment of elevated blood pressure.

Is the pulse rate useful in assessing risk of diabetic retinopathy and macular oedema? The Wisconsin Epidemiological Study of Diabetic Retinopathy

AIM

To describe the relation between pulse rate and incident diabetic retinopathy.

METHODS

Population based cohort study of people with diabetes. Resting pulse rate was measured in 30 second intervals. Diabetic retinopathy was evaluated from masked gradings of fundus photographs.

RESULTS

People with higher pulse rates were more likely to have 4 year progression of retinopathy, progression to proliferative retinopathy, and incident macular oedema than those with lower pulse rates. However, these associations were attenuated after controlling for blood pressure, glycosylated haemoglobin, and other risk factors.

CONCLUSION

Pulse rate may be a clinical indicator of overall risk of diabetic retinopathy, but is not independently associated with the condition.

Heart rate as a predictor of mortality: the MATISS project

OBJECTIVES

This study sought to verify the independent role of heart rate in the prediction of all-cause, cardiovascular, and noncardiovascular mortality in a low-risk male population.

METHODS

In an Italian population-based observational study, heart rate was measured in 2533 men, aged 40 to 69 years, between 1984 and 1993. Data on cardiovascular risk factors were collected according to standardized procedures. Vital status was updated to December 1997.

RESULTS

Of 2533 men followed up (representing 24,457 person-years), 393 men died. Age-adjusted death rates for 5 heart rate levels showed increasing trends. The adjusted hazard rate ratios for each heart rate increment were 1.52 (95% confidence interval [CI] = 1.29, 1.78) for all-cause mortality, 1.63 (95% CI = 1.26, 2.10) for cardiovascular mortality, and 1.47 (95% CI = 1.19, 1.80) for noncardiovascular mortality. Relative risks between extreme levels were more than 2-fold for all endpoints considered.

CONCLUSIONS

Heart rate is an independent predictor of cardiovascular, noncardiovascular, and total mortality in this Italian middle-aged male population.

Leptin interacts with heart rate but not sympathetic nerve traffic in healthy male subjects

OBJECTIVE

Administration of leptin to animals increases sympathetic nerve activity and heart rate. We therefore tested the hypothesis that plasma leptin is linked independently to muscle sympathetic nerve activity (MSNA) and heart rate in healthy humans.

METHODS

We measured plasma leptin, plasma insulin, body mass index (BMI), percent body fat, waist: hip ratio, MSNA, heart rate and blood pressure in 88 healthy individuals (50 men and 38 women).

RESULTS

In men, plasma leptin concentration correlated significantly with BMI (r = 0.75, P < 0.001), percent body fat (r = 0.70, P< 0.001), waist: hip ratio (r = 0.69, P < 0.001), insulin (r = 0.37, P = 0.009), and age (r = 0.38, P = 0.006). Only BMI and waist: hip ratio were linked independently to plasma leptin concentration (r = 0.78, P < 0.001). Plasma leptin concentrations also correlated with heart rate (r = 0.39, P = 0.006) and mean arterial pressure (MAP; r = 0.38, P = 0.007), but not with MSNA (r = 0.17, P = 0.24). After adjustment for BMI and waist: hip ratio, plasma leptin concentration correlated significantly only with heart rate (r = 0.29, P = 0.04), and not with MAP (r = 0.21, P = 0.14). Individuals were divided into high-leptin and low-leptin subgroups on the basis of plasma leptin concentrations adjusted for BMI and waist: hip ratio. Those with high leptin concentrations had significantly faster heart rates than those with low leptin. MAP and MSNA were similar in both subgroups. No relationship between leptin and either heart rate or MSNA was evident in women.

CONCLUSIONS

In normal men, heart rate, but not MSNA, is linked to plasma leptin concentration. This sex-specific relationship between heart rate and plasma leptin is independent of plasma insulin, BMI, waist:hip ratio and percentage body fat.

Heart rate as a cardiovascular risk factor: do women differ from men?

Considerable progress has been made in our understanding of the role of high heart rate in determining cardiovascular morbidity and mortality. However, whether the association between fast heart rate and cardiovascular disease is equally strong in males and females is still a matter for debate. In most studies, the predictive value of tachycardia for all-cause mortality has been found to be weaker in women than in men, and in some studies no association between heart rate and cardiovascular mortality was observed. In particular, high heart rate appeared to be a weak predictor of death from coronary heart disease in the female gender. Multiple mechanisms by which sympathetic overactivity could cause hypertension and the metabolic syndrome of insulin resistance have been documented. Recent results obtained at the Ann Arbor laboratory from the analysis of four populations indicate that these mechanisms are operative mostly in males in whom tachycardia reflects a heightened sympathetic tone. In women, fast heart rate would merely represent the extreme of a normal distribution. However, tachycardia can also have a direct impact on the arterial wall, as demonstrated in laboratory studies, and can favour the occurrence of cardiac arrhythmias. The impact of these mechanisms may be similar in men and women and could explain why a high heart rate has been found to have a detrimental effect also in the female gender. Pharmacological reduction of high heart rate is an additional desirable goal of therapy in several clinical conditions such as hypertension, myocardial infarction and congestive heart failure. Although a greater effect is expected in men, cardiac slowing could counteract the detrimental haemodynamic effect of tachycardia also in women.