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Increased heart rate is a predictor of cardiovascular disease, heart failure, and all‐cause mortality. In those with high heart rates, interventions for heart rate reduction have been associated with reductions in coronary events. Asia is a diverse continent, and the prevalences of hypertension and cardiovascular disease differ among its countries. The present analysis of AsiaBP@Home study data investigated differences among resting heart rates (RHRs) in 1443 hypertensive patients from three Asian regions: East Asia (N = 595), Southeast Asia (N = 680), and South Asia (N = 168). This is the first study to investigate self‐measured RHR values in different Asian countries/regions using the same validated home BP monitoring device (Omron HEM‐7130‐AP/HEM‐7131‐E). Subjects in South Asia had higher RHR values compared with the other two regions, and the regional tendency found in RHR values was different from that found in BP values. Even after adjusting for age, sex, BMI, habitual alcohol consumption, current smoking habit, shift worker, hyperlipidemia, diabetes, chronic kidney disease, history of heart failure, and beta‐blocker use, both office and home RHR values in South Asia were the highest among Asia (mean values ± SE of office: East Asia [E] 75.2 ± 1.5 bpm, Southeast Asia [Se] 76.7 ± 1.5 bpm, South Asia [S] 81.9 ± 1.4 bpm; home morning: [E] 69.0 ± 1.2 bpm, [Se] 72.9 ± 1.2 bpm, [S] 74.9 ± 1.1 bpm; home evening: [E] 74.6 ± 1.2 bpm, [Se] 78.3 ± 1.2 bpm, [S] 83.8 ± 1.1 bpm). Given what is known about the impact of RHR on heart disease, our findings suggest the possible benefit of regionally tailored clinical strategies for cardiovascular disease prevention.

Aims Cancer patients suffer from impaired cardiovascular function. Elevated resting heart rate (RHR) has been identified as a marker for increased long‐term mortality in cancer patients prior to the receipt of anticancer treatment. We aimed to establish whether RHR is associated with survival in treatment‐naïve cancer patients. Methods and results This prospective study enrolled 548 unselected treatment‐naïve cancer patients between 2011 and 2013. The median age of the cohort was 62 years; 40.9% were male and 32.7% had metastatic disease. Median RHR was 72 b.p.m. Most patients were in sinus rhythm (n = 507, 92.5%). Clinical heart failure was noted in 37 (6.8%) patients. RHR was not related to cancer stage (P = 0.504). Patients in the highest RHR tertile had higher levels of high‐sensitivity troponin (P = 0.003) and N‐terminal pro‐B‐type natriuretic peptide (P = 0.039). During a median follow‐up of 25 months (interquartile range: 16–32 months; range: 0–40 months), 185 (33.8%) patients died from any cause [1‐year‐mortality: 17%, 95% confidence interval (CI) 13–20%]. In univariate survival analysis, RHR predicted all‐cause mortality [crude hazard ratio (HR) for a 5 b.p.m. increase in RHR: 1.09, 95% CI 1.04–1.15; P

Although resting heart rate is thought to be a generalizable risk factor for aggression, very little research has examined whether this relationship varies by race. We addressed this limitation using longitudinal data from the Pittsburgh Youth Study. Current data are from 197 men who participated in a teenage biosocial study (mean age = 15.7 years) and adult follow-up study (mean age = 32.1 years). Teenage resting heart rate interacted with race to predict teenage and adult aggression. The relationship between heart rate and aggression was significant in White, but not in Black males. To our knowledge, this is the first study to find that the relationship between resting heart rate and aggression is racially variant, suggesting that resting heart rate may not be a generalizable biomarker for conduct problems. At an intervention-level, findings could contribute to the development of more accurate risk assessment tools that take into account racial variance in risk factors.

The aim of our study was to determine how being overweight (OW) affects measures of ejection duration (ED), subendocardial viability ratio (SEVR), and central arterial health in a sample of adolescent children. Thirty‐four sex and age‐matched adolescent children (n = 34, 17 OW, age = 14 ± 2 years) participated in one laboratory visit. Anthropometric measures, body composition, and cardiovascular measures including resting heart rate, aortic systolic blood pressure (ASBP), carotid‐femoral pulse wave velocity (cf‐PWV), ED (EDms absolute vs. relative ED%), and the SEVR were ascertained. Transfer functions were applied to obtain ASBP. ED was measured as the time from the beginning of the upstroke of the pulse wave and the dicrotic notch, SEVR as the quotient of the diastolic pressure‐time area to the systolic pressure‐time area, and cf‐PWV as the quotient of distance between carotid‐femoral measurement sites and the transit time of the pulse wave. cf‐PWV was significantly higher in OW compared to normal weight participants (5.13 ± 0.85 vs. 4.53 ± 0.46 m/s respectively; p = 0.015, d = 0.51). OW adolescents also reported significantly higher values for ASBP (103.1 ± 11.8 vs. 95.7 ± 8.2 mmHg respectively; p = 0.043, d = 0.72) and significantly lower values of SEVR (114.4 ± 25.9% vs. 132.2 ± 22.0% respectively; p = 0.038; d = 0.33). Overweight adolescents demonstrated higher cf‐PWV, ASBP, and SEVR then normal weight peers., Employing non‐invasive measures of cardiac function to identify detrimental changes in cardiovascular health shows promising value in pediatric populations. This study investigated how being overweight affects measures of ejection duration, subendocardial viability ratio, and central arterial health in a sample of adolescent children. Overweight adolescents demonstrate higher cf‐PWV, ASBP, and SEVR then normal weight peers.

Background Little is known about the associations of resting heart rate (RHR) and heart rate reserve (HRR) with metabolic syndrome (MetS) in firefighters. Methods For each of 288 professional firefighters, HRR was calculated as the difference between measured RHR and estimated maximum HR. For comparison, VO2 max based on a treadmill test was included. MetS was defined according to the NCEP/ATP III criteria. Results The prevalence of MetS was 14.2%. The average of RHR was 61.5 beat/min. Only 5.8% of the firefighters had RHR of ≥80 beat/min. Between the firefighters in the lowest and highest quintiles, the prevalence ratios (95% confidence intervals) for MetS were 1.88 (0.71-4.94), 5.90 (1.74-20.02), and 8.03 (1.86-34.75) for RHR, HRR, and VO2 max, respectively. Both HRR and VO2 max, but not RHR, were significantly associated with MetS and its most component risk factors in middle-aged firefighters. Conclusions HRR, a simple cardiovascular fitness measure, was inversely associated with MetS among middle-aged professional firefighters.

Although low resting heart rate has been linked to frequent aggressive conduct in childhood, little is known about the interaction of this biological risk with social emotions that protect against aggression across development. With a sample of 5-, 8-, and 12-year-olds (N = 110), we tested whether the negative link between resting heart rate and physical aggression was offset by high guilt and sympathy. Caregivers reported their children's physical aggression and sympathy. Children's electrocardiogram data were collected while they viewed a nondescript video, after which they reported their guilt-or lack thereof-in response to vignettes depicting social transgressions. Lower resting heart rate was significantly associated with higher physical aggression in 5-year-olds who reported low-but not medium and high-levels of guilt, and in 8-year-olds with low-but not medium and high-ratings of sympathy. Neither guilt nor sympathy moderated the resting heart rate-physical aggression link in 12-year-olds. We discuss how social emotions may help children with low resting heart rates navigate social conflicts and avoid aggressive physical confrontations.

Chronic hypoxia increases resting heart rate (HR), but the underlying mechanism remains incompletely understood. We investigated the relative contributions of the sympathetic and parasympathetic ne ...

Objectives To examine whether the association between resting heart rate (RHR) and all-cause mortality and cardiovascular events differs according to age. Design Prospective cohort. Setting Community in Beijing, China. Participants Individuals aged 40 and older without cardiovascular disease at baseline (N = 6,209). Measurements Trained investigators interviewed participants using a standard questionnaire to obtain information on demographic characteristics, medical history and lifestyle risk factors in 1991. RHR was evaluated according to quartiles (

Even though sleep has been shown to be influenced by athletes’ training status, the association with resting heart rate and heart rate variability remains unclear. The purpose of this study was to compare the changes in and relationships between resting heart rate, heart rate variability and sleep characteristics across a female collegiate cross-country season. Ten NCAA Division I collegiate female cross-country athletes (mean ± SD; age, 19 ± 1 year; height, 167.6 ± 7.6 cm; body mass, 57.7 ± 10.2 kg; VO2max, 53.3 ± 5.9 ml kg-1 min-1) participated in this study. Resting heart rate, heart rate variability and the percentage of time in slow wave sleep were captured using a wrist-worn multisensor sleep device throughout the 2016 competitive cross-country season (12 weeks). Linear mixed-effects models and magnitude-based inferences were used to assess differences between each week. Pearson product moment correlations were used to investigate relationships between variables. Resting heart rate at the end of the season, specifically during weeks 10–12 (mean ± SE; week 10, 48 ± 2; week 11, 48 ± 3; week 12, 48 ± 3), showed a practically meaningful increase compared to the beginning of the season, weeks 2–4 (week 2, 44 ± 2; week 3, 45 ± 2; week 4, 44 ± 2). Higher resting heart rate (r = 0.55) and lower heart rate variability (r = -0.62) were largely associated with an increase in percentage of time spent in slow wave sleep. These data suggest that when physiological state was impaired, meaning the physiological restorative demand was higher, the percentage of time in slow wave sleep was increased to ensure recovery. Thus, it is important to implement sleep hygiene strategies to promote adequate slow wave sleep when the body needs physiological restoration.

Vagally mediated heart rate variability (vmHRV) is a measure of cardiac vagal tone, and is widely viewed as a physiological index of the capacity to regulate emotions. However, studies have not directly tested whether vmHRV is associated with the ability to facially express emotions. In extending prior work, the current report tested links between resting vmHRV and the objectively assessed ability to facially express emotions, hypothesizing that higher vmHRV would predict greater expressive skill. Eighty healthy women completed self-reported measures, before attending a laboratory session in which vmHRV and the ability to express six emotions in the face were assessed. A repeated measures analysis of variance revealed a marginal main effect for vmHRV on skill overall; individuals with higher resting vmHRV were only better able to deliberately facially express anger and interest. Findings suggest that differences in resting vmHRV are associated with the objectively assessed ability to facially express some, but not all, emotions, with potential implications for health and well-being.

Inappropriate sinus tachycardia (IST) is a rare cardiac disturbance documented in humans in which the sinus heart rate is inappropriately elevated without an obvious cause or trigger. It is characterised by a rhythm originating in the sinus node with a heart rate above normal at rest without the influence of drugs, pain, cardiac or extracardiac disease. IST may be caused by abnormal structure or function of the sinus node or abnormal function of the autonomous nervous system. This report describes the case of a young dog with a resting heart rate of 140 bpm with electrocardiographic characteristics consistent with sinus tachycardia. Additional cardiac or extracardiac disorders were not identified and the dog was otherwise healthy and not receiving any medication. These findings were suggestive of IST.

New Findings What is the central question of this study? The aim was to explore the relationships among resting heart rate, shear and endothelial function in humans. What is the main finding and its importance? The main finding is that resting heart rate is associated with shear and endothelial function in humans. This finding could have implications when studying endothelial function in humans with varying heart rates. Preclinical data have demonstrated that heart rate (HR) can directly impact vascular endothelial function, in part, through a shear-stress mechanism. This study sought to explore, in humans, the associations between resting heart rate and both shear and endothelial function assessed by flow-mediated dilation (FMD). The brachial artery FMD test was performed in 31 apparently healthy volunteers. Basal (B) and hyperaemic (H) shear were quantified in the following two ways using data from the FMD test: the traditional cumulative shear area under the curve up to peak dilation (Shearcum) method; and our novel method of shear summation (Shearsum), which accounts for HR by summing each individual cardiac cycle shear up to peak dilation. Data were grouped by tertiles based on resting HR as follows: low (LHR = 43–56 beats min−1; n = 10); middle (MHR = 58–68 beats min−1; n = 11); and high (HHR = 69–77 beats min−1; n = 10). Within the LHR group, both B-Shearcum and H-Shearcum were significantly higher (P

Heart rate variability (HRV) is a noninvasive indicator of autonomic control. This study examines HRV changes across a normal menstrual cycle and proposes a novel piecewise function controlling for the effects of breathing on HRV spectral parameters. A resting ECG was collected from 13 women at five points in their menstrual cycle. Both heart rate and breathing rate increased across the cycle (p < .01) while time-domain variability decreased (p = .04). Use of the piecewise function for breathing rate in HRV spectral analysis was confirmed by a substantial increase in model goodness-of-fit. HRV spectral parameters, controlled for breathing with the piecewise function, confirm that the decrease in variability is likely due to a parasympathetic withdrawal, since high frequency HRV decreases (p = .02). Descriptors: Heart rate variability, Autonomic nervous system, Menstrual cycle, Estrogen, Progesterone

Purpose This study examined relationships between cumulative trauma (CT) and urban African American (AA) adolescents' blood pressure (BP), heart rate (HR), and perceptions of health. Design and Method A correlational design using secondary data analysis studied effects of CT, health outcomes, and perceptions of health. Participants were 175 urban AA youth (11–16 years) who completed structured surveys and physiological measures of HR and BP before and after exercise. Results AA youth were experiencing high levels of CT. Negative correlations were obtained between AA females' perceptions of their health and systolic BP with levels of trauma. No gender differences were found in HR or BP. Practice Implications AA females with high CT may perceive themselves as less healthy and can be at risk for health problems.

Stair-climbing serves as a feasible opportunity to remain physically active within everyday-life. Data on neuromuscular and cardiorespiratory performance after regular stair-climbing in seniors are scarce. Forty-eight seniors were stratified to a one- (taking every step, INT1) or two-step strategy (every second step, INT2) or a control group (CON). Thirty-nine seniors [females: n = 22, males: n = 17; age: 70.5 (SD 5.1) years; BMI: 25.8 (3.1) kg/m(2)] completed the 8-week intervention (three weekly sessions). Before and after the intervention, balance, gait, strength, and submaximal endurance (at different intensities) were assessed. Maximal strength and explosive power did not improve significantly (0.10 < P < 0.78). Resting heart rate was significantly reduced in INT2 (-8/min) compared with INT1 (0/min, P = 0.02) and CON (0/min, P = 0.03). Compared with CON, perceived exertion for all intensities (0.007 < P < 0.03) and submaximal exercise heart rate during moderate uphill walking significantly decreased (-11/min; P < 0.05) in INT2. Step counts for forward beam balancing (4.5 cm width) increased in INT2 (P = 0.007) compared with CON. With more pronounced effects in INT2, stair-climbing significantly improved resting and exercise heart rates, perceived exertion, and dynamic balance performance in healthy seniors and may contribute to better overall fitness, reduced fall risk, and less perceived strain during daily life activities.

Background: High values of resting heart rate were found to be correlated with adverse outcomes in various patient groups. Heart rate variability (HRV) is a reliable technique in determining autonomic nervous system function. Our aim was to evaluate whether a 10-second resting heart rate obtained from a resting electrocardiogram (ECG), could be used as a reliable evaluation of short-term HRV. Methods: Seventy-nine healthy volunteers were included in the study. All participants underwent a 10-second ECG, and 5-minute HRV measurement under strict criteria. Results: A significantly negative correlation was found between resting heart rate and 5-minute max-RR, min-RR, standard deviation of normal RR intervals (SDNN), root mean square of successive differences of RR intervals (RMSSD), HRV triangular index, number of intervals differing by 50 milliseconds from the preceding interval (NN50), pNN50, standard deviation of the points perpendicular to the line of identity (SD1), standard deviation along the line of identity (SD2), and high frequency spectral component (HF). A significant positive correlation was found between resting heart rate and a 5-minute low frequency spectral component (LF) and LF/HF ratio. Specifically, max-RR and min-RR were found to have the best correlation with resting heart rate. Conclusions: Resting heart rate obtained from a 10-second ECG can be used for crude estimation of all HRV results in healthy individuals who do not take medications, with variable efficacy depending on the measured parameter. Resting heart rate was especially efficient in predicting max-RR and min-RR. Further research should focus on assessing the reliability of a resting heart rate for HRV evaluation, in patients with autonomic dysfunction and high-risk cardiac patients. (PACE 2011; 34:1498–1502)

The present study investigated whether football has favorable effects in the treatment of mild-to-moderate arterial hypertension in untrained middle-aged men. Twenty-five untrained males aged 31-54 year with mild-to-moderate hypertension were randomized to a football training group (FTG, two 1-h sessions per week) and a control group receiving physician-guided traditional recommendations on cardiovascular risk factor modification (doctoral advice group, DAG). After 3 months, systolic blood pressure (SBP) and diastolic blood pressure (DBP) were lowered (P

Heritability of QT Interval. Introduction: Objective of this study was to determine the optimal (most heritable) phenotype for gene finding studies of QT interval in the general population. We also studied the extent to which heritability of QT interval can be explained by genes that also influence resting heart rate. Methods and Results: Subjects in this classic twin study were 105 monozygotic and 256 dizygotic female twin pairs (mean age: 49.9 ± 11.5). ECG parameters were measured electronically using the Cardiofax ECG9020. Quantitative genetic modeling was performed with Mx software. Best-fitting univariate models showed significant heritabilities for resting heart rate (0.55, 95% CI: 0.44‐0.65), uncorrected QT interval (0.60, 95% CI: 0.49‐0.69), and the Framingham QTc interval (0.50, 95% CI: 0.39‐0.60). Familial resemblance of Bazett’s QTc was best explained by shared environmental factors (0.34, 95% CI: 0.24‐0.43) rather than genes. Simultaneously modeling heart rate and the uncorrected QT interval confirmed considerable heritabilities of 56% and 60%, respectively. Forty-four percent of the variance in QT interval was due to genes in common with heart rate, whereas 16% was due to genes specific to QT interval. The heritability of QT interval after the removal of effects shared with heart rate within the bivariate model (cf. QTc) was 51%. Conclusion: About a quarter of the QT interval heritability is due to genes specific for QT interval, while the majority is shared with genes for heart rate. Differences in QTc heritability estimates indicate that use of correction formulae is best avoided in gene finding studies to avoid erroneous results. (J Cardiovasc

Early-life experiences can have long-term effects on cardiovascular function and are likely mediated by a host of factors, such as inborn stress sensitivity and epigenetic alterations. To begin addressing this issue we exposed Wistar-Kyoto (WKY) rats to 180 min. maternal separation (MS) from postnatal day (P)1 to P14, while control rats experienced neonatal handling (NH; 15 min separation). Animals were weaned at P21, developed to adulthood undisturbed, assessed depressive- and anxiety- like behaviors followed by continuous blood pressure monitoring using radiotelemetry. Upon completion of cardiovascular recordings, whole genome methylation was quantified within select brain regions. Results of our behavioral analyses showed that MS-exposed rats exhibited decreased depression- and anxiety- like behaviors along with augmented social behaviors in adulthood. Cardiovascular recordings revealed that MS resulted in the decrease of resting heart rate throughout life, which was accompanied by an increase in baror...

The association between polymorphisms in the beta1, beta2 and alpha2B adrenergic receptor (ADR) genes (ADRB1, ADRB2 and ADRA2B) and resting heart rate was examined in white and African-American participants of the HyperGEN Study. All analyses were adjusted for age, sex, body mass index, alcohol use, smoking status and daily exercise within strata of race, hypertension status and beta-blocker use. The Ser49Gly polymorphism of the beta1 ADR was associated with resting heart rate in hypertensive African-Americans and hypertensive whites taking beta-blockers, with carriers of the Gly allele having a higher mean resting heart rate by 2.7 and 4.4 beats per minute (bpm), respectively. The Arg389Gly polymorphism of the beta1 ADR was associated with lower heart rate in the normotensive African-American sample. A beta1 haplotype (Ser49Gly-Arg389Gly) was modestly associated with resting heart rate in the hypertensive African-Americans. The alpha2B C/A polymorphism was associated with heart rate in hypertensive whites, and both whites and African-Americans taking beta-blockers, with carriers of the A allele having a higher mean resting heart rate. In summary, each of the ADR gene polymorphisms was associated with heart rate in at least one stratum studied, but there was no consistent association from which one would infer a large genetic contribution to heart rate.

Little is known about physiological parameters of free-ranging walruses (Odobenus rosmarus). The heart rate has been measured electronically during anesthesia (e.g., Born and Knutsen 1990a, Lanthier et al. 1999), but to allow interpretation of such results, and for meaningful monitoring of anesthesia, baseline heart and respiratory rates are essential. Furthermore, such data may contribute to estimation of energy consumption (e.g., McPhee et al. 2003). The heart rate in unrestrained walruses has been estimated based on inspection of movement of the thoracic region as part of pre-anaesthetic assessments (Born and Knutsen 1990a, Griffiths et al. 1993), but to the authors’ knowledge no exact data have been published. In this paper we describe a method for recording resting heart rate in unrestrained wild walruses and present data on respiratory rate and electronically recorded heart rate. The experiment was conducted during 12–16 August 2004 on the terrestrial haulout Sandoen in Young Sound in Northeast Greenland (74◦18′N, 20◦15′W). During summer, this haul-out is used by a group of approximately 60 Atlantic walruses, predominantly adult males (Born et al. 1995, Acquarone 2004). The feeding grounds are accessible from the ice break up in July until the formation of new fast-ice in October (Born et al. 1995, Rysgaard et al. 2003). Ten adult males (estimated body weight >1,000 kg) that had been out of the water for at least 1 h, and were resting at the perimeter of the hauled-out group were studied. Photo-identification was employed to avoid repeated measurements of the same individual. During the experiments, air temperature ranged between 3◦C and 12◦C and wind speed was between 3 m/s and 10 m/s. A battery-operated portable electrocardiograph (Cardiovit AT-4 vet, Schiller AG, Baar CH-6341, Switzerland) was equipped with two custom made cords for unipolar recording. These cords were made from 10 m screened cables ending in an insulated

BACKGROUND AND OBJECTIVES GH administration results in increased lean body mass (LBM), decreased fat mass (FM) and increased energy expenditure (EE). GH therapy may therefore have potential benefits, especially in the elderly, who are known to have decreased function of the GH/IGF-I axis. Several studies have focused on effects of GH administration in the elderly in the last decade. However, very limited information is available regarding changes in body composition and EE upon GH discontinuation in the elderly. The present study therefore investigated the effects of 12 weeks of GH administration and subsequent discontinuation on body composition, resting oxygen uptake (VO2), resting heart rate (HR) and GH related serum markers in healthy elderly men. SUBJECTS AND METHODS Sixteen healthy men [age 74 +/- 1 years (mean +/- SEM), height 174.2 +/- 1.6 cm, body weight 80.7 +/- 2.6 kg, body fat 27.5 +/- 1.1%] completed the study protocol. Recombinant human GH (1.80 +/- 0.24 IU/day) was administered for 12 weeks in a single-blinded, placebo-controlled design. Body composition (dual energy X-ray absorptiometry), resting VO2 (indirect calorimetry), resting HR (telemetry) and serum IGF-I, IGF-II, IGFBP-3 and acid labile subunit (ALS) were measured at baseline, after 12 weeks of GH administration and, additionally in the GH group, 1, 2, 3, 4, 5 and 9 days after GH discontinuation. RESULTS Body weight was unchanged from baseline to 12 weeks in both groups. However, GH administration caused a decrease in FM (3.4 +/- 1.0 kg, P < 0.012), paralleled by a similar increase in LBM (3.2 +/- 0.4 kg, P < 0.0002). Resting VO2 and resting HR increased by 31 +/- 3.6% and 7.3 +/- 1.9 per minute, respectively, in the GH-group, where significant increases in serum IGF-I, IGFBP-3 and ALS also were noted. None of the above parameters changed in the placebo group. Within 2-3 days after GH discontinuation, the GH related serum markers and resting HR returned to baseline levels, whereas resting VO2 remained elevated even 9 days after GH discontinuation. In addition, GH discontinuation caused a significant decrease in body weight (1.86 +/- 0.35 kg), derived exclusively from a decrease in LBM (1.63 +/- 0.43 kg), while the decreased FM was maintained (12 weeks: 17.93 +/- 1.65 kg, +9 days: 17.74 +/- 1.62 kg). CONCLUSIONS The increases in serum IGF-I, IGFBP-3, ALS and resting heart rate induced by 12 weeks of GH administration in elderly men returned to baseline levels within 2-3 days after GH discontinuation. However, resting VO2 remained elevated for a longer period. GH administration reduced fat mass but maintained body weight by increasing lean body mass. In contrast, 9 days of GH discontinuation reduced body weight exclusively by reducing lean body mass.

Background: Minute volume is a truly physiological sensor for rate adaptive pacing that correlates with metabolic expenditure throughout the range of physical activity. Criticism has centered on the slow initial response compared to less physiological sensors. A new algorithm, consisting of rate augmentation factor and programmable speed of response, has been incorporated in the 1206 META III pacemaker generator and was designed to improve the rate response at lower levels of exertions. Rate augmentation factor increases the programmed rate response factor by 3, 6, or 10 when set to low, medium, or high, respectively; this augmentation lasting to 50% of the maximum programmed rate. Response time can be programmed to medium or fast. Methods: Nine patients were studied during the first 3 minutes of an exercise test (Bruce protocol) in a single blind manner. The pacemaker generator was randomly programmed with rate augmentation factor at off, low, or high and speed of response to medium or fast, giving six possible combinations. Heart rates were recorded continuously for the duration of the test and until resting heart rate was achieved during recovery. The test was repeated until all six combinations had been tested. Results: During exercise significant differences appeared in response time from 30 seconds onward. Fast response and rate augmentation factor contributed to an improved rate response with greatest speed of response seen with fast response time and high rate augmentation factor. During recovery decreases in recovery time were seen with fast response time but rate augmentation factor prolonged recovery. Conclusions: Rate augmentation factor improves initial rate response in the early stages of exercise. Fast response gives an improved time to initial rate increase and shortens the duration of inappropriate postexercise tachycardia. These features improve the pattern of response of the minute ventilation sensor.

Heart rate reactivity to a brief psychological stressor (mental arithmetic or puzzle solving) administered under timed and competitive conditions was assessed for children from two age groups (5-year-old preschoolers and 10-year-old primary school children) and their parents. Although there were significant differences in resting heart rate and heart rate reactivity between the two groups of children according to age, these differences were not consistent for their parents. When examined within each age group, there were no significant correlations between parents' and children's heart reactivity to the stressor they received. Implications for some previously suggested familial effects regarding cardiac reactivity are discussed.

Blood pressure and resting heart rate were examined by standardized procedures in 33 air traffic controllers during a period of occupational conflict in 1981, followed by a reexamination of 27 of them in 1982 when the conflict was resolved, and again in 23 of them in 1988 when there was no conflict. The mean systolic blood pressure in the 27 air traffic controllers in 1982 was 116 mmHg as against 136 in 1981, a highly significant difference (p < 0.001). In 1988 the mean blood pressure was 121 mmHg in the 23 air traffic controllers examined on all three occasions, i.e. still significantly lower than in 1981 and only 5 mmHg higher than in 1982, roughly equivalent to the expected increase due to increase in age. The mean diastolic pressure was significantly higher (p < 0.001) in 1981 (90–87) than in 1982 (75–73) and 1988 (81–78), and thus slightly higher in 1988 than in 1982 as expected, due to age. The resting heart rates were essentially unaffected. The effect of occupational conflict on the blood pressures reported here should be kept in mind when considering blood pressure levels in occupational groups. It may in fact explain some of the conflicting results reported in the literature concerning the blood pressure of air traffic controllers.

Possible effects of environmental stress-induced elevation of the heart rate on the magnitude of cardiovascular autonomic responses were studied in 123 healthy subjects. The nocturnal heart rate was evaluated using ambulatory 24-h ECG monitoring. Some of the cardiovascular responses were found to be significantly weaker in those subjects whose resting heart rate during testing was greater than 10 beats min-1 higher than the resting nocturnal heart rate. It is thus highly important to minimize the environmental disturbances during autonomic testing.

This study was undertaken to assess a clinical measurement (leg squats) in order to determine the adequacy of beta-adrenergic blockade (AdBB) utilizing the symptom-limited exercise test heart rate of less than 120 beats/min as the standard. Seventy subjects were tested, 35 receiving beta-adrenergic-blocking drugs in clinically determined maximal doses, and 35 subjects not receiving these agents. Sensitivity (Se), specificity (Sp), and positive (Pv+) and negative (Pv-) predictive values were calculated for post-leg squat heart rates of less than or equal to 100, less than or equal to 110 and less than or equal to 120 beats/min. Other variables analyzed for AdBB were resting heart rates and post-leg squat heart rate increase greater than 50% over baseline. A cost-benefit analysis was also performed. It was concluded that: (1) Neither the resting heart rate or percent increase in heart rate compared to baseline reliably predicted AdBB. (2) In patients receiving beta-blocking drugs, a post-squat heart rate of less than or equal to 100 beats/min had a Se = .82, Sp = .67, Pv+ .70, and Pv- .80, values not high enough to be reliably used in many clinical situations. (3) If the post-squat heart rate was greater than 110 beats/min, however, AdBB is probably absent, since no subjects on beta blockers with maximum exercise test heart rate less than or equal to 120 beats/min had a post-leg squat heart rate greater than 110 beats/min. (4) For a reasonable range of cost and test performance estimates, utilization of the leg squat test as described here is favored on the basis of cost-benefit analysis.

1 ST-91, 2-(2,6-diethylphenylamino)-2-imidazoline hydrochloride produces in animal experiments bradycardia, and in larger doses, also hypertension, due to α-sympathomimetic activity and probable central sympathetic inhibition. 2 The effects of ST-91, after oral administration, were studied in 10 healthy volunteers. A dose-dependent, significant decrease of the heart rate was observed. On average the resting heart rate was reduced by 11-19 beats/min (15-29%). During exercise the decrease of the heart rate was less pronounced. After the largest dose there was a fall of the systolic blood pressure during exercise averaging at 14-15 mmHg (11-12%). Otherwise the blood pressure remained unchanged. 3 Eight out of the 10 test-subjects complained of hair-raising and goose-flesh after all doses, due to the α-sympathomimetic effect of the drug. No toxic effects were observed.

Autonomic control of resting heart rate was assessed using atropine and propranolol in 20 neonatal (2 to 3 weeks old) male Rhesus monkeys. After release from restraint for placement of a venous catheter, the average heart rate significantly decreased from 220 +/- 7 beats/min to 181 +/- 6 beats/min within 15 minutes and remained stable for the 2 hours. Autonomic control of resting heart rate is mediated through both divisions of the autonomic nervous system with the sympathetic system having a dominant influence. This is in contrast to the adult Rhesus, where the parasympathetic nervous system controls resting heart rate.

Summary. 1 Valsalva's experiment was carried out on 25 healthy subjects of whom 13 were smokers and 12 non-smokers before and after smoking of 1–3 cigarettes. In twelve of these subjects control experiments without smoking between two successive Valsalva experiments were carried out. 2 Smoking did not as a rule alter the resting heart rate in non-smokers, but increased it on an average for 16 beats/min. in smokers. 3 The total increase or decrease in heart rate during and after the strain was used as a measure of reactivity. It varied in different subjects, some showing no increase in heart rate at all. Occasionally the type of response obtained in a certain subject could be altered. The smoking tends to decrease the reactivity when effective. A significant correlation between heart rate response and alteration in the height of the P and T waves was found. No correlation between P-Q time and reactivity seemed to exist. 4 The mean electrical axis (and changes caused by strain and by smoking) was calculated with the help of the Dieuaide's chart. The strain tends to deflect the axis rightwards. Smoking did not as a rule affect the mean direction of the electrical field. In 5 instances, however, a leftward shift in the axis was noted. There was no correlation between the size of the heart rate reaction and the rightward deflection of the axis during the strain. 5 Certain special electrocardiogratphic findings will be treated in a separate paper.

The small bioelectrical signals of the heart detected at the body surface of animals are usually relayed to the initial amplifier stage of the electrocardiograph by the use of plate, needle or clip electrodes (Clark, Szabuniewicz & McCrady, 1966). In a series of experiments in which rapid and repeated measurements of the electrocardiogram (e.c.g.) and resting heart rate from conscious, unrestrained guinea-pigs were required none of the standard methods proved suitable and a modification was therefore developed in which the animals stand on plate electrodes. This method has been used to obtain recordings from conscious mice, rats, cats and dogs, and some applications of the method are illustrated in the experiments described in this article.