Kevin S. Heffernan

Impact of Excess Body Weight on Arterial Structure, Function, and Blood Pressure in Firefighters

Cardiovascular disease is the leading cause of death among firefighters. The purpose of the present study was to examine the effect of excess body weight on arterial structure and function and blood pressure (BP) in relatively young, apparently healthy, firefighters. The body mass index, brachial BP, carotid BP, aortic BP, radial augmentation index, central pulse wave velocity, forearm blood flow, forearm vasodilatory capacity, carotid arterial compliance, carotid intima-media thickness, and brachial flow-mediated dilation were assessed in 110 firefighters (aged 29.7 +/- 8.0 years). The group was divided into equal tertiles according to the body mass index (<25.9, 25.9 to 29.4, and >or=29.5 kg/m(2)). Group differences in hemodynamics, anthropometrics, microvascular function, and macrovascular structure and function were tested using multivariate analysis of variance. The obese group was older, heavier, and had a larger waist circumference compared to the lean and overweight groups (p <0.05). The overweight group was also older, heavier, and had a larger waist circumference than the lean group (p <0.05). Compared to the lean group, the overweight and obese groups had a greater systolic BP (p <0.05). The obese group also had a significantly greater mean arterial BP and carotid systolic BP than the lean group (p <0.05). The obese group had greater beta stiffness and elastic modulus compared to the lean and overweight groups (p <0.05), but no group differences were found in endothelial function. In conclusion, in a population of relatively young firefighters, an increased body mass index was associated with elevated peripheral BP and arterial stiffness, with no apparent decrements in endothelial function.

Augmentation Index Derived from Peripheral Arterial Tonometry Correlates with Cardiovascular Risk Factors

Background. Augmentation index (AIx) is traditionally obtained from pressure waveforms via arterial applanation tonometry. We sought to evaluate the association between AIx obtained from peripheral arterial tonometry (PAT) with cardiovascular risk factors (CRF) and coronary artery disease (CAD). Methods. 186 patients were enrolled in the study. The presence or absence of CRFs and CAD was assessed in each subject. AIx was calculated by an automated algorithm averaging pulse wave amplitude data obtained via PAT. Central blood pressures were assessed in a subset of patients undergoing clinically indicated cardiac catheterization. Results. An association was observed between AIx and age, heart rate, systolic blood pressure, mean arterial pressure, pulse pressure, body weight and body mass index. AIx was significantly lower in patients with <3 CRFs compared to those with >5 CRFs ( P = .02). CAD+ patients had significantly higher AIx compared to CAD− patients ( P = .008). Area under the ROC curve was 0.604 (P < .01). In patients undergoing cardiac catheterization, after adjusting for age, height and heart rate, AIx was a significant predictor of aortic systolic and pulse pressures (P < .05) Conclusion. AIx derived from PAT correlates with cardiac risk factors and CAD. It may be a useful measure of assessing overall risk for coronary artery disease.

Assessment of vascular endothelial function with peripheral arterial tonometry: information at your fingertips?

Endothelial dysfunction is an important component in the pathogenesis of atherosclerosis. The ability to assess the endothelium in a meaningful manner has been the subject of intense investigation over decades. Since the function of endothelial cells is a gauge of vascular health, assessment of vascular function is emerging as a useful tool for predicting cardiovascular risk and as a surrogate outcome measure for cardiovascular reduction intervention studies. This review highlights techniques for assessing endothelial function, focusing on a novel method of determining peripheral vascular reactivity via arterial tonometry.

The pulmonary artery pulsatility index identifies severe right ventricular dysfunction in acute inferior myocardial infarction.

Background: Right ventricular dysfunction (RVD) is a major cause of morbidity and mortality in the setting of acute inferior wall myocardial infarction (IWMI), and early detection may improve clinical outcomes. We defined a novel hemodynamic index, the pulmonary artery pulsatility index (PAPi), and explored whether the PAPi correlates with severe RVD in acute IWMI.

Muscular strength is inversely associated with aortic stiffness in young men.

UNLABELLEDnMuscular strength is associated with reduced mortality. Paradoxically, strength training may increase central artery stiffness, a predictor of cardiovascular morbidity and mortality. However, the relationship between muscular strength and central arterial stiffness has yet to be defined.nnnPURPOSEnThe purpose of this study was to determine the relationship between muscular strength and central arterial stiffness in young men.nnnMETHODSnCentral and peripheral pulse wave velocity (PWV), augmentation index, muscular strength, and aerobic capacity (V O2peak) were measured in 79 young men (mean +/- SD, age = 23 +/- 4 yr). Height, weight, and brachial blood pressure were also recorded. Muscular strength was determined using a one-repetition maximum bench press and normalized to bodyweight. Spearman correlations were used to determine the relationships between relative strength, aerobic fitness, and hemodynamic/vascular measures.nnnRESULTSnThere was a significant negative correlation between central PWV and strength (r = -0.222, P < 0.05). The relationship remained significant when controlling for aerobic fitness (r = -0.189, P < 0.05). Muscular strength was significantly higher (P < 0.05) in men with low central PWV (5.2 +/- 0.4 m.s) compared with men with high central PWV (6.6 +/- 0.4 m.s).nnnCONCLUSIONnThese results show that there is a significant inverse association between muscular strength and aortic stiffness independent of aerobic fitness.

Review Article: L-Arginine as a Nutritional Prophylaxis Against Vascular Endothelial Dysfunction With Aging

With advancing age, peripheral conduit and resistance arteries lose the ability to effectively dilate owing to endothelial dysfunction. This vascular senescence contributes to increased risk of cardiovascular disease (CVD) with aging. L-arginine plays a role in numerous physiological processes including nitrogen detoxification, immunocompetence, growth hormone (GH) secretion, and insulin secretion. Recently, a considerable amount of attention has been placed on the ability of this amino acid to affect vascular endothelial function. The purpose of this review will be to examine the use of L-arginine as a novel nutritional strategy to potentially stave progression of vascular dysfunction with aging and CVD. Emphasis will be placed on the ability of L-arginine to modulate the vascular inflammatory and systemic hormonal milieu, which in turn may have a positive effect on vascular endothelial function.

Spectral methods of heart rate variability analysis during dynamic exercise

ObjectivesTo apply both autoregressive (AR) and fast Fourier transform (FFT) spectral analysis at rest, during two different dynamic exercise intensities and in recovery from maximal exercise and to compare raw and normalized powers obtained with both methods.MethodsSixteen participants (age 22.3xa0±xa04.3xa0year) performed resting, submaximal and maximal protocols. The submaximal protocol consisted of two 5-min walks at 4xa0kmxa0h−1 at treadmill grades of 0 and 7.5%. Beat-to-beat R-R series were recorded. FFT and AR analyses were preformed on the same R-R series.ResultsCompared to AR, FFT provided higher total power (TP) and raw high-frequency (HF) power at rest and exercise. Furthermore, FFT LF/HF ratio was lower than with the AR, except under resting conditions. Both methods showed reductions in TP, raw HF and LF powers during exercise and recovery. Only the AR revealed a significant reduction for normalized HF power and increase for normalized LF power in transition from rest to exercise conditions.InterpretationAR and FFT methods are not interchangeable at rest or during dynamic exercise conditions. The AR method is more sensitive to the effects of exercise on the normalized power spectra of heart rate variability (HRV) than FFT. Finally, as both approaches are equally insensitive to the increase of exercise relative intensity, there is no practical advantage of performing HRV spectral analyses by the AR or FFT at higher workloads.

Transient suppression of heart rate complexity in concussed athletes

Heart rate variability (HRV) and complexity (HRC) were calculated at rest and during an isometric hand grip test (IHGT) within 48-hours (48 h) and two weeks (Week Two) of a concussion in athletes (CG) and control subjects. No differences were present at rest or in HRV during IGHT. HRC was significantly lower in the CG compared to controls at 48 h during IHGT. In CG at Week Two during IHGT, HRC was significantly greater than 48 h observations and not significantly different than controls. The findings suggest that HRC may have utility in detecting efferent cardiac autonomic anomalies within two weeks of concussion.

Association between cardiorespiratory fitness and arterial stiffness in men with the metabolic syndrome

AIMSnWe tested the hypothesis that high cardiorespiratory fitness (fitness) is associated with lower levels of arterial stiffness in 1035 (age 52 ± 6 years) men with and without the metabolic syndrome.nnnMETHODSnArterial stiffness was derived from brachial-ankle pulse wave velocity (baPWV). Fitness was directly measured by peak oxygen uptake during a standard treadmill test.nnnRESULTSnMen with the metabolic syndrome (n = 168) had significantly higher baPWV than men without the metabolic syndrome (1424 ± 175 cm/s vs. 1333 ± 150 cm/s, p < 0.05). When separated according to quartiles of fitness, men with and without the metabolic syndrome in the highest quartile of fitness had significantly lower baPWV compared to men in the lowest quartile of fitness (p < 0.05). Fitness was inversely correlated with baPWV in men with (p = -0.29, p < 0.05) and without the metabolic syndrome (p = -0.22, p < 0.05). There was no differences in baPWV levels between fit men with the metabolic syndrome and unfit men without the metabolic syndrome (fit/MetS; 1366 ± 140 vs. unfit/no MetS; 1401 ± 194 cm/s, p = 0.81).nnnCONCLUSIONSnThese results demonstrate that high fitness is inversely associated with arterial stiffness in men with and without the metabolic syndrome. Increased arterial stiffness in the metabolic syndrome is attenuated by high fitness.

Sex differences in linear and nonlinear heart rate variability during early recovery from supramaximal exercise.

Women demonstrate greater RR interval variability than men of similar age. Enhanced parasympathetic input into cardiac regulation appears to be not only greater in women, but also protective during periods of cardiac stress. Even though women may have a more favorable autonomic profile after exercise, little research has been conducted on this issue. This study was designed to examine the cardiac autonomic response, in both male and female participants, during the early recovery from supramaximal exercise. Twenty-five individuals, aged 20 to 33 years (13 males and 12 females), performed a 30-s Wingate test. Beat-to-beat RR series were recorded before and 5 min after exercise, with the participants in the supine position and under paced breathing. Linear (spectral analysis) and nonlinear analyses (detrended fluctuation analysis (DFA)) were performed on the same RR series. At rest, women presented lower raw low frequency (LF) power and higher normalized high frequency (HF) power. Under these conditions, the LF/HF ratio of women was also lower than that of men (p<0.05), but there were no differences in the short-term scaling exponent (α1). Even though both sexes showed a significant modification in linear and nonlinear measures of heart rate variability (HRV) (p<0.05), women had a greater change in LF/HF ratio and α1 than men from rest to recovery. This study demonstrates that the cardiac autonomic function of women is more affected by supramaximal exercise than that of men. Additionally, DFA did not provide additional information about sexual dimorphisms, compared with conventional spectral HRV techniques.