Biomedical subjects

Kevin S Heffernan

Publications and source records attributed to Kevin S Heffernan.

9 recordsLinked to original sources

PubMed2006

Slow heart rate recovery after exercise is associated with carotid atherosclerosis.

OBJECTIVE: Slow heart rate recovery (HRR) after exercise is an estimate of impaired parasympathetic tone and predictor of all-cause and cardiovascular mortality. Carotid atherosclerosis is associated with high risk of developing coronary heart disease (CHD) and stroke. We tested the hypothesis that slow HRR is associated with carotid atherosclerosis in a cross-sectional study of 12,712 middle-aged men (age 49.1+/-8.9 years). METHODS: Carotid atherosclerosis was measured using B-mode ultrasonography and defined as stenosis >25% and/or intima-media thickness >1.2mm. HRR was calculated as the difference between peak heart rate during a graded exercise treadmill test and heart rate 2 min after cessation of exercise. RESULTS: The prevalence of carotid atherosclerosis was 8.4%. The prevalence of atherosclerosis was significantly higher among subjects in the lowest (<44 bpm) versus the highest (>61 bpm) quartile of HRR (14.4% versus 4.1%, p<0.001). In multivariable logistic regression models adjusted for established CHD risk factors, inflammatory markers, and exercise capacity, subjects in the lowest quartile of HRR (<44 bpm) were 1.50 times (95% CI: 1.13-2.00) more likely to have carotid atherosclerosis than subjects in the highest quartile (HRR>61 bpm). CONCLUSIONS: Slow heart rate recovery after exercise, an index of decreased parasympathetic activity, is associated with carotid atherosclerosis independent of established risk factors in middle-age men.

Adult↗

PubMed2006

Effect of single-leg resistance exercise on regional arterial stiffness.

To examine the effects of lower-limb unilateral resistance exercise on central and peripheral arterial stiffness, thirteen participants (7 male and 6 female, mean age = 21.5 +/- 0.7 years) performed leg press exercise using their dominant leg. Pulse wave velocity (PWV) was used to measure central (carotid to femoral) and peripheral (femoral to dorsalis pedis of both legs) arterial stiffness before, 5 min post, and 25 min post exercise. No change was found in central PWV. A leg-by-time interaction was found as peripheral PWV in the non-exercised leg did not change (7.9 +/- 0.3 m/s to 7.9 +/- 0.3 m/s to 8.0 +/- 0.3 m/s, P = 0.907) while peripheral PWV in the exercised leg significantly decreased from pre (8.7 +/- 0.4 m/s) to 5 min post exercise (7.5 +/- 0.3 m/s, P = 0.008) and 25 min post exercise (7.8 +/- 0.3 m/s, P = 0.031). Systolic blood pressure (BP) increased significantly from pre (126.9 +/- 3.4 mmHg) to 5 min post exercise (133.7 +/- 4.3 mmHg, P = 0.023) and was not different than resting values 25 min post exercise (123.2 +/- 3.1 mmHg). There was no change in diastolic BP. Compared to heart rate (HR) pre-exercise (55.4 +/- 1.4 bpm), HR was significantly increased 5 min post exercise (70.7 +/- 3.0 bpm, P = 0.001) and 25 min post exercise (69.1 +/- 2.0, P = 0.001). Acute resistance exercise appears to decrease arterial stiffness in the exercised leg while having no effect on central arterial stiffness or arterial stiffness of the non-exercised leg. These findings suggest that regional changes rather than systemic alterations may influence arterial stiffness following acute resistance exercise.

Adult↗

PubMed2006

Chronotropic response to exercise testing is associated with carotid atherosclerosis in healthy middle-aged men.

AIMS: Chronotropic incompetence, an attenuated heart rate (HR) response to exercise, is an independent predictor of cardiovascular mortality, but it is not known whether chronotropic incompetence is related to carotid atherosclerosis. The association between chronotropic incompetence and carotid atherosclerosis in 8567 (age 47.6+/-8.8 years) healthy men was examined. METHODS AND RESULTS: Chronotropic incompetence was defined as the failure to achieve 85% of the age-predicted maximal HR (APMHR), <80% HR reserve (HRR), and chronotropic response index (CRI). Carotid atherosclerosis was defined, using B-mode ultrasonography, as stenosis >25% and/or intima-media thickness (IMT) of >1.2 mm. In multivariable adjusted logistic regression models, the subjects who achieved less than 85% of APMHR exhibited an odds ratio (OR) of 1.72 [95% confidence intervals (CI): 1.32-2.22] for carotid atherosclerosis. Subjects with <80% of HRR were 1.45 (95% CI: 1.14-1.84) times more likely to have carotid atherosclerosis after multivariate adjustment. Also, the OR of carotid atherosclerosis across quartiles of CRI (highest to lowest) was 1.51 (95% CI: 1.10-2.09) after multivariate adjustment. CONCLUSION: These results suggest that the chronotropic response to exercise is associated with carotid atherosclerosis, independent of the established risk factors in healthy men, which could contribute to high incidence of cardiovascular diseases in subjects with chronotropic incompetence.

Arrhythmias, Cardiac↗

PubMed2006

Effects of lifestyle modifications on C-reactive protein: contribution of weight loss and improved aerobic capacity.

High-sensitivity C-reactive protein (hs-CRP) is associated with an increased risk of cardiovascular disease and the development of type 2 diabetes mellitus. We analyzed the effects of lifestyle modifications including exercise training on hs-CRP in 47 overweight and obese adults. Subjects were divided into a lifestyle modification group (n=23) (exercise and diet instruction) and a control group (n=24) who did not participate in any lifestyle modification. After 3 months, body weight (80.8+/-11.5 to 73.5+/-10.7 kg, P<.01), total cholesterol (217+/-38.4 to 178.0+/-25.6 mg/dL, P<.01), low-density lipoprotein cholesterol (151.3+/-34.9 to 116.7+/-27.8 mg/dL, P<.01), Vo(2)peak (30.3+/-5.1 to 37.1+/-6.9 mL/[kg . min], P<.01), and log hs-CRP (0.75+/-0.4 to 0.56+/-0.3 mg/dL, P=.01) were significantly improved in the lifestyle modification group, but there was no significant improvement in the control group. Changes in log hs-CRP were associated with changes in Vo(2)peak (r=-0.41, P=.004) and changes in weight loss (r=0.42, P=.004). In stepwise multiple regression analysis, weight loss (P=.034) and improved Vo(2)peak (P=.039) were independent predictors of the changes in hs-CRP. When grouped into quartiles according to decreasing weight and increasing Vo(2)peak, levels of changes in log hs-CRP improved across quartiles of weight loss (P<.05) and improved Vo(2)peak (P<.01). Thus, lifestyle changes including regular exercise training in overweight and obese adults decreased hs-CRP, and this was associated with weight loss and improved Vo(2)peak.

Adult↗

PubMed2006

Exaggerated blood pressure response to exercise is associated with carotid atherosclerosis in apparently healthy men.

OBJECTIVE: Although an exaggerated systolic blood pressure (SBP) response to exercise is a predictor of future hypertension and cardiovascular mortality, the underlying mechanisms are not fully understood. We tested the hypothesis that an exaggerated SBP response is associated with carotid atherosclerosis in a cross-sectional study of 9073 healthy men (aged 47.8 +/- 8.8 years). METHODS: Exaggerated SBP response was defined as an SBP of 210 mmHg or greater during a maximal treadmill test. Carotid atherosclerosis was defined as stenosis greater than 25% or intima-media thickness greater than 1.2 mm using B-mode ultrasonography. RESULTS: An exaggerated SBP response was present in 375 men (4.1%). The proportion of individuals with carotid atherosclerosis in the group with an exaggerated SBP response to exercise was higher than in the group with a normal SBP response (14.4 versus 5.3%, P < 0.001). In a multivariable logistic regression model, individuals with an exaggerated SBP (>or= 210 mmHg) response to exercise had a 2.02 times [95% confidence interval (CI) 1.33-3.05] increased risk of carotid atherosclerosis compared with individuals with an SBP response of less than 210 mmHg. The highest quartile (> 61 mmHg) group of relative exercise-induced increases in SBP showed a 1.57 (95% CI 1.18-2.08) greater risk of carotid atherosclerosis compared with individuals in the lowest quartile (< 38 mmHg) in the adjusted model. CONCLUSIONS: These results suggest that an exaggerated SBP response to exercise is strongly associated with carotid atherosclerosis, independent of established risk factors in healthy men. It may be an important factor in evaluating hypertension related to target-organ damage.

Adult↗

PubMed2006

Cardiac autonomic modulation during recovery from acute endurance versus resistance exercise.

BACKGROUND: The kinetics of parasympathetic reactivation after dynamic endurance exercise have been well elucidated. However, autonomic recovery of cardiac function after resistance exercise is not known. PURPOSE: The purpose of this study was to assess cardiac autonomic modulations during recovery from acute resistance exercise versus acute endurance exercise. METHODS: Electrocardiogram readings were collected before and 30 min after a single bout of endurance or resistance exercise in 14 male participants (aged 25.3+/-2.5 years). Heart rate (HR) variability was spectrally decomposed using an autoregressive approach. High frequency (HF) power was considered representative of vagal modulation. All values were expressed in both absolute and normalized units (normalized for change in total power). RESULTS: A mode-by-time interaction (P<0.05) was detected for HR, which remained elevated to a greater extent after resistance exercise. Total power was significantly reduced after resistance exercise (P<0.05) but not endurance exercise. An interaction (P<0.05) was also detected for both a change in absolute natural log function HF power and natural log function low frequency (LF) power (P<0.05), as both variables decreased more after resistance exercise. When normalized for changes in total power, interactions in LF and HF power were lost. The LF/HF ratio was significantly increased after both resistance and endurance exercise (P<0.05). CONCLUSION: Greater elevations in HR after acute resistance exercise versus acute endurance exercise may be related to greater reductions in cardiac parasympathetic tone.

Adult↗

PubMed2006

Heart rate variability during recovery from a Wingate test in adolescent males.

PURPOSE: To evaluate the effect of maturity status on the autonomic nervous system at rest and recovery after short-term, high-intensity exercise in adolescents. METHODS: A biological maturity age was estimated in 27 males by calculating the years from peak height velocity (PHV) using a multiple regression equation. Subjects were divided into two groups: pre-PHV (years from PHV < 0.49), N = 14, mean age = 12.29 +/- 0.91 yr; post-PHV (years from PHV > 0.5, N = 13, mean age = 15.12 +/-0.76 yr). HR variability was used to evaluate autonomic function. ECG tracings were collected during 5 min at rest and recovery after a Wingate test and were analyzed in the frequency domain (low-frequency (LF), high-frequency (HF), LF/HF, total power (TP)). Data are presented as natural logarithms (LN). RESULTS: Changes in HR from HR(peak) during exercise to HR measured at minute 4 after exercise ([DELTA]HR4) were significantly greater in the pre-PHV group (84.31 +/-17.58 bpm) compared with the post-PHV group (69.42 +/-17.63 bpm). There were no significant differences in resting HR variability between pre- and post-PHV groups (P > 0.05). Significant group x time interactions were found for LF(LN) (ms(2)) and TP(LN) (ms(2)) measured during recovery (P < 0.05). Post hoc tests showed that the pre-PHV group had significantly higher postexercise LF(LN) (5.02 +/- 0.97 vs 4.19 +/- 0.79) and TP(LN) (6.36 +/- 1.02 vs 5.62 +/- 0.65) compared with the post-PHV group. When postexercise LF(LN) (ms(2)) was normalized for TP(LN) (ms(2)), there were no significant differences between groups (P > 0.05). CONCLUSION: The pre-PHV group had higher total HR variability than the post-PHV group after a Wingate test, suggesting that maturity status significantly affects total HR variability during recovery after high-intensity exercise.

Adolescent↗

PubMed2005

Baroreflex sensitivity during static exercise in individuals with Down Syndrome.

INTRODUCTION: Individuals with Down syndrome (DS) have altered heart rate (HR) and blood pressure (BP) responses to orthostatic challenges and isometric handgrip (IHG) exercise, suggesting possible alteration in baroreflex sensitivity. PURPOSE: This study investigated baroreflex sensitivity (BRS) as a potential mechanism contributing to chronotropic incompetence during IHG in persons with DS. METHODS: Heart rate and BP were continually recorded in 12 individuals with DS and 10 controls, at rest and during 2 min of IHG, at 30% of maximal voluntary contraction (MVC). Spontaneous BRS was derived via the sequence method. RESULTS: No differences were seen in HR at rest between groups. Systolic BP (SBP) was significantly lower in the DS group at rest (106.1+/- 2.9 vs 116.5+/- 3.9 mm Hg, P < 0.05) and during IHG (123.9+/- 4.6 vs 150.1+/- 5.3 mm Hg, P<0.001). A significant group-by-task interaction was found for both change in HR and change in SBP with IHG, because of an attenuated HR and SBP response to IHG in participants with DS (P<0.05). When controlling for resting SBP, the DS group had a lower BRS at rest (16.0+/-1.7 vs 21.2+/-4.2 ms.mm Hg, P< 0.05) and during IHG (7.8 +/-1.0 vs 12.1+/- 2.6 ms.mm Hg, P< 0.05). CONCLUSIONS: Individuals with DS have lower BRS at rest and during IHG than controls and this may be related to their attenuated HR response during perturbation.

Adult↗

PubMedDate not supplied

Exaggerated blood pressure response to exercise is associated with inflammatory markers.

PURPOSE: An exaggerated blood pressure (EBP) response to exercise has been shown to be a predictor of future hypertension and risk of cardiovascular mortality. Although EBP is associated with endothelial dysfunction and increased left ventricular hypertrophy, the underlying mechanisms are not fully understood. Inflammatory markers, C-reactive protein (CRP) and white blood cells (WBCs), were predictive of future hypertension. The objective of this study was to examine the hypothesis that increasing levels of CRP and WBCs would be related to an EBP response during exercise. METHODS: Inflammatory markers were compared in 43 males with an EBP (systolic blood pressure [SBP] >or=210 mm Hg) response during maximal treadmill testing to an age and resting SBP-matched group of 42 males with a normal blood pressure response to exercise. RESULTS: There were significant group differences in maximal SBP and diastolic blood pressure (DBP), exercise induced increases in SBP and DBP (P <.01), and WBCs (P <.01), but CRP did not differ between groups (P =.39). White blood cells were significantly associated with maximal SBP (r = 0.31), and the exercise-induced increase in SBP (r = 0.34). However, CRP did not correlate with the maximal blood pressure response to exercise (r = 0.11, P =.33). In a stepwise multiple regression analysis, WBC was independently associated with the exercise-induced increase in SBP (beta = 0.256, P =.011). CONCLUSIONS: These results suggest that inflammation may be associated with an EBP response during exercise testing.

Biomarkers↗