Heart Rate Variability Correlates to Functional Aerobic Impairment in Hemodialysis Patients

Background

Autonomic dysfunction (AD) is highly prevalent in hemodialysis (HD) patients and has been implicated in their increased risk of cardiovascular mortality.

Objective

To correlate heart rate variability (HRV) during exercise treadmill test (ETT) with the values obtained when measuring functional aerobic impairment (FAI) in HD patients and controls.

Methods

Cross-sectional study involving HD patients and a control group. Clinical examination, blood sampling, transthoracic echocardiogram, 24-hour Holter, and ETT were performed. A symptom-limited ramp treadmill protocol with active recovery was employed. Heart rate variability was evaluated in time domain at exercise and recovery periods.

Results

Forty-one HD patients and 41 controls concluded the study. HD patients had higher FAI and lower HRV than controls (p<0.001 for both). A correlation was found between exercise HRV (SDNN) and FAI in both groups. This association was independent of age, sex, smoking, body mass index, diabetes, and clonidine or beta-blocker use, but not of hemoglobin levels.

Conclusion

No association was found between FAI and HRV on 24-hour Holter or at the recovery period of ETT. Of note, exercise HRV was inversely correlated with FAI in HD patients and controls.     

Effect of Aerobic and Resistance Exercise Training on Liver Enzymes and Hepatic Fat in Iranian Men With Nonalcoholic Fatty Liver Disease

Background:

Nonalcoholic fatty liver disease (NAFLD) has different prevalence rates in various parts of the world and is a risk factor for diabetes and cardiovascular disease that could progress to nonalcoholic steatohepatitis, cirrhosis, and liver failure.

Objectives:

The current study aimed to investigate the effect of Aerobic Training (AT) and resistance training (RT) on hepatic fat content and liver enzyme levels in Iranian men.

Patients and Methods:

In a randomized clinical trial study, 30 men with clinically defined NAFLD were allocated into three groups (aerobic, resistance and control). An aerobic group program consisted of 45 minutes of aerobic exercise at 60% - 75% maximum heart rate intensity, a resistance group performed seven resistance exercises at intensity of 50% - 70% of 1 repetition maximum (1RM ) and the control group had no exercise training program during the study. Before and after training, anthropometry, insulin sensitivity, liver enzymes and hepatic fat were elevated.

Results:

After training, hepatic fat content was markedly reduced, to a similar extent, in both the aerobic and resistance exercise training groups (P ≤ 0.05). In the two exercise training groups, alanine amino transferase and aspartate amino transferase serum levels were significantly decreased compared to the control group (P = 0.002) and (P = 0.02), respectively. Moreover, body fat (%), fat mass (kg), homeostasis model assessment insulin resistance (HOMI-IR) were all improved in the AT and RT. These changes in the AT group were independent of weight loss.

Conclusions:

This study demonstrated that RT and AT are equally effective in reducing hepatic fat content and liver enzyme levels among patients with NAFLD. However, aerobic exercise specifically improves NAFLD independent of any change in body weight.     

Exercise above the ischemic threshold and serum markers of myocardial injury

BACKGROUND:

Current guidelines for exercise training in coronary patients state that in the presence of exercise-induced ischemia, the heart rate during exercise should be at least 10 beats/min below the heart rate associated with an ST segment depression of 1 mm or greater. For patients with a relatively low ischemic threshold, this recommendation does not allow for a sufficient training stimulus.

OBJECTIVE:

To document the effects of a single session of exercise above the ischemic threshold on biochemical markers of myocardial injury in stable coronary patients with exercise-induced ischemia. Because creatine kinase (CK) and its MB isoenzyme (CK-MB) can both increase after exercise because of skeletal muscle injury, troponin T was also measured.

METHODS:

Twenty-one patients with documented coronary artery disease underwent two 20 min exercise sessions. The intensity of the first exercise training session was fixed at a heart rate below the ischemic threshold (ie, approximately 10 beats/min lower than the heart rate associated with the appearance of an ST segment depression of 1 mm or greater). The intensity of the second exercise session was fixed at a heart rate above the ischemic threshold.

RESULTS:

Blood test measurements at baseline, 6 h after and 24 h after the exercise sessions did not show any increase in total CK, CK-MB or troponin. The value of all measurements remained well below the lower limits associated with myocardial damage.

CONCLUSION:

A 20 min period of exercise above the ischemic threshold did not result in myocardial necrosis.     

Circulatory and Ventilatory Power: Characterization in Patients with Coronary Artery Disease

Background

Circulatory power (CP) and ventilatory power (VP) are indices that have been used for the clinical evaluation of patients with heart failure; however, no study has evaluated these indices in patients with coronary artery disease (CAD) without heart failure.

Objective

To characterize both indices in patients with CAD compared with healthy controls.

Methods

Eighty-seven men [CAD group = 42 subjects and healthy control group (CG) = 45 subjects] aged 40–65 years were included. Cardiopulmonary exercise testing was performed on a treadmill and the following parameters were measured: 1) peak oxygen consumption (VO₂), 2) peak heart rate (HR), 3) peak blood pressure (BP), 4) peak rate-pressure product (peak systolic HR x peak BP), 5) peak oxygen pulse (peak VO₂/peak HR), 6) oxygen uptake efficiency (OUES), 7) carbon dioxide production efficiency (minute ventilation/carbon dioxide production slope), 8) CP (peak VO₂ x peak systolic BP) and 9) VP (peak systolic BP/carbon dioxide production efficiency).

Results

The CAD group had significantly lower values for peak VO₂ (p < 0.001), peak HR (p < 0.001), peak systolic BP (p < 0.001), peak rate-pressure product (p < 0.001), peak oxygen pulse (p = 0.008), OUES (p < 0.001), CP (p < 0.001), and VP (p < 0.001) and significantly higher values for peak diastolic BP (p = 0.004) and carbon dioxide production efficiency (p < 0.001) compared with CG. Stepwise regression analysis showed that CP was influenced by group (R² = 0.44, p < 0.001) and VP was influenced by both group and number of vessels with stenosis after treatment (interaction effects: R² = 0.46, p < 0.001).

Conclusion

The indices CP and VP were lower in men with CAD than healthy controls.     

Prognostic value of treadmill exercise and dobutamine stress positron emission tomography

BACKGROUND:

Although positron emission tomography (PET) is routinely performed using vasodilator stress, exercise and dobutamine stress are available alternatives. Evidence suggests that vasodilator PET myocardial perfusion imaging (MPI) has prognostic value, but the prognostic value of treadmill exercise and dobutamine PET MPI is unknown.

OBJECTIVE:

To determine the potential prognostic value of nonvasodilator stress PET MPI.

METHODS:

Patients underwent treadmill exercise or dobutamine PET MPI. Images were assessed qualitatively and semiquantitatively. PET results were categorized as normal (summed stress score [SSS] of less than 4), abnormal (SSS of 4 or greater) or inconclusive (SSS of less than 4 and submaximal peak stress heart rate). Patient follow-up (cardiac death, nonfatal myocardial infarction [MI] and/or late revascularization) was performed.

RESULTS:

Of the 124 patients (mean follow-up period of 2.3±1.6 years), 46 patients (37%) had a normal study, 15 patients (12%) had an inconclusive study and 63 (51%) had an abnormal PET. Patients with a normal PET had no deaths or nonfatal MI. One patient with a normal PET underwent late revascularization (annual event rate of 1.7%). Patients with an abnormal PET had 15 cardiac events (one cardiac death, four nonfatal MIs and 10 late revascularizations), with an annual event rate of 13.0% (P=0.002).

CONCLUSIONS:

Although small, the present study suggests that defects seen on PET myocardial perfusion, resulting from stressors (treadmill exercise and dobutamine) that increase myocardial oxygen demand, may have prognostic value.     

Plasma homocysteine levels are independently associated with alterations of large artery stiffness in men but not in women

Objectives To investigate the associations of the plasma homocysteine (HCY) levels with the alterations in arterial stiffness in a community-based cohort. The gender differences in these associations were examined. Methods We evaluated the relationship between plasma HCY levels to three measures of vascular function [carotid-femoral pulse wave velocity (CF-PWV), carotid-ankle PWV (CA-PWV) and heart rate corrected augmentation index (AI)] in 1680 participants (mean age: 61.5 years; 709 men, 971 women) from communities of Beijing, China. Results In univariate analysis, plasma HCY levels was positively related to the CF-PWV (r = 0.211, P < 0.0001) and CA-PWV (r = 0.148, P < 0.0001), whereas inversely associated with AI (r = ?0.052, P = 0.016). In multiple linear regression models adjusting for covariants, plasma HCY remained positively related to the CF-PWV (standardized β = 0.065, P = 0.007) in total cases. When the groups of men and women were examined separately, plasma HCY remained positively associated with the CF-PWV (standardized β = 0.082, P = 0.023) in men, whereas the relations between HCY and any of the arterial stiffness indices were not further present in women. Conclusions In Chinese population, plasma HCY levels are independently associated with alterations of large artery stiffness in men but not in women.     

Hemoglobin in normal range,the lower the better?—Evidence from a study from Chinese community-dwelling participants

Objective

To examine the association between hemoglobin (Hb) levels and cardiovascular risk factors in a large community-dwelling cohort.

Methods

A total of 4,186 women and 4,851 men were enrolled in the study. Data on personal history, physical examination and biochemical parameters were collected. Subjects were categorized by gender and divided into different group according to the level of Hb or blood pressure, and the association between Hb levels and cardiovascular risk factors was examined using Pearson’s correlation analysis.

Results

In both men and women even with normal Hb level, tertiles of Hb levels were positively associated with body mass index (BMI), total-cholesterol (TC), triglyceride (TG), uric acid (UA), diastolic blood pressures (DBP) and fasting plasma glucose (FPG) (all P=0.000 in men and women). Furthermore, significantly increased incidence of hyperuricemia (P=0.000 both in men and women) and obesity (P=0.000 both in men and women) were observed with the gradually increased Hb level. In addition, Pearson’s correlation analysis revealed obvious correlation between Hb level and various cardiovascular risk factors including blood pressure and UA. Binary logistic regression analysis further demonstrated that the level of Hb was an important risk factor for elevated blood pressure (OR =1.216; 95% CI: 1.138-1.293, P=0.000 in men; OR =1.287; 95% CI: 1.229-1.363, P=0.000 in women).

Conclusions

Increasing Hb levels, even in subjects with normal level were associated with increasing prevalence of cardiovascular risk factors, suggesting that a slightly low Hb level might be beneficial to Chinese community-dwelling individuals.     

Effect of angiotensin-converting enzyme inhibition on C-reactive protein levels: The Ramipril C-Reactive pRotein Randomized evaluation (4R) trial results

BACKGROUND:

Plasma levels of the inflammatory biomarker C-reactive protein (CRP) predict cardiovascular risk and may represent a target for treating and/or monitoring risk-reduction strategies. The effect of angiotensin-converting enzyme inhibitors on CRP levels has not been adequately studied.

METHODS:

A total of 264 men and women, with CRP levels of 2 mg/L or greater and no history of cardiovascular disease, were enrolled in a 12-week randomized, double-blind, placebo-controlled study. Participants were randomly assigned to receive 10 mg/day of ramipril (n=132) or placebo (n=132) for 12 weeks. The main outcome measure was the change in CRP levels from baseline to 12 weeks in the ramipril- versus placebo-treated patients.

RESULTS:

The mean (± SD) age was 53±9 years (60% men). Baseline demographics were similar between the volunteers allocated to receive either placebo or ramipril. The geometric mean CRP at baseline was 3.84 mg/L (95% CI 3.62 mg/L to 4.06 mg/L). The percentage change in geometric mean CRP values over 12 weeks was −13.2% (95% CI −22.3% to −3.2%) in the placebo group compared with −21.1% (95% CI −29.9% to −11.2%) in the ramipril group (P nonsignificant), indicating no significant reduction in the primary end point of the trial.

CONCLUSIONS:

A 12-week ramipril treatment protocol for healthy middle-aged volunteers did not lower CRP levels compared with placebo. However, because of the inherent variability of CRP levels, a much larger study is required to exclude a small treatment effect.     

Effects of metoprolol and amiodarone combination on heart rate,myocardial contractility and coronary flow: Study in isolated perfused rat hearts

BACKGROUND:

Beta-blockers and amiodarone have been used concomitantly to treat arrhythmias associated with congestive heart failure. However, the combination of metoprolol and amiodarone has only been studied restrospectively, and its potential effects in congestive heart failure remain to be properly elucidated in prospective trials.

OBJECTIVE:

The present investigation focused on evaluating the pharmacological interaction between metoprolol and amiodarone in an isolated perfused rat heart preparation.

MATERIALS AND METHODS:

Adult male Wistar rats (n=24) were divided into four groups of six animals, and the effects of the metoprolol/amiodarone combination on systolic pressure, myocardial contractility (dP/dt), coronary flow (CF) and heart rate were analyzed, and the interdependent variables were compared.

RESULTS:

There was a negative chronotropic effect by both metoprolol and the metoprolol/amiodarone combination in isolated rat hearts. However, the acute effects of the metoprolol/amiodarone combination showed no myocardial contractility depression or bradycardia accentuation compared with metoprolol alone. CF increased by 9.2% at minute 1 through minute 5 (P=0.004) with the metoprolol/amiodarone combination. There was no difference in systolic pressure or myocardial contractility among the groups.

CONCLUSIONS:

The acute effects of the metoprolol/amiodarone combination in the isolated rat heart were an increase in CF, and no myocardial contractility depression or bradycardia accentuation.     

Incremental shuttle and six-minute walking tests in the assessment of functional capacity in chronic heart failure

BACKGROUND

The incremental shuttle test presents some theoretical advantages over the six-minute walk test in chronic heart failure (CHF), including better standardization and less dependency on collaboration.

OBJECTIVES

The present study evaluated test-retest repeatability, test accuracy in predicting a peak oxygen consumption (VO₂) of 14 mL/kg/min or less, as well as the prognostic value of both walking tests in stable CHF patients.

METHODS

Sixty-three patients (44 men; New York Heart Association functional class II to IV) underwent an incremental treadmill exercise test and, on another day, the walk test in duplicate.

RESULTS

Patients showed well-preserved functional capacity according to the distance walked in both tests (six-minute walk test 491±94 m versus incremental shuttle walk test 422±119 m; P<0.001). Interestingly, the six-minute and incremental shuttle walk test differences in distance walked were higher in more disabled patients. The mean bias ±95% CI of the within-test differences were similar (7±40 m and 8±45 m, respectively). Peak VO₂, but not distance walked in either test, was associated with survival (P<0.05).

CONCLUSIONS

The incremental shuttle walk test showed similar repeatability and accuracy in estimating peak VO₂ compared with the six-minute walk test in CHF patients. Direct measurement of peak VO₂, however, remains superior to either walking test in predicting survival – at least in patients with well-preserved functional capacity.     

Hepatoprotective Effect of 17β-Estradiol as Antioxidant Modulators Against Stress Damage

Background:

Liver is one of the most important organs affected by exercise. According to the literature a few study to date has investigated the effects of estrogen supplementation on exercise-induced oxidative stress in liver tissue of rats.

Objectives:

We aimed to investigate the effects of estrogen supplementation on oxidative stress markers in liver tissue of exercised rats.

Materials and Methods:

Male rats (n = 35) were divided as estrogen supplemented (n = 18) and non-supplemented groups (n = 17); these groups were further divided as rest and eccentric exercised groups. Eccentric exercise groups were further divided as rats killed after 1 hour and 48 hours of eccentric exercise. Estrogen (10 mg/kg) was administered subcutaneously for 30 days. Eccentric exercise was applied as treadmill run (15° downhill, 20 m/min) consisting of periods of "5 min" run and 2 min rest repeated 18 times. The rat liver was examined biochemically and histologically. Activities of GST, GSH-Px, CAT, SOD and MDA concentration were also measured spectrophotometrically.

Results:

Some disruptions were detected in experimental groups compared with the control group. Additionally, exercise training caused an increase in SOD and decrease in GSH-Px activities in some experimental groups. SOD activities increased significantly in group 3 (Estrogen (-), eccentric exercise (+) killed (after 1 h), compared with group 5 (Estrogen (-), eccentric exercise (+) killed (after 48 h). On the other hand, GSH-Px activities were also significantly decreased in groups 3, 4 and 5 compared with the control group. Leukocyte infiltration in liver increased after 48 hours compared with after 1 hour and estrogen supplementation was not able to prevent this infiltration.

Conclusions:

Estrogen seemed to be not very effective to prevent eccentric exercise-induced liver damage.     

Effects of aerobic exercise training and irbesartan on blood pressure and heart rate variability in patients with chronic obstructive pulmonary disease

BACKGROUND AND OBJECTIVES:

The present pilot study was undertaken to evaluate the efficacy of an aerobic exercise training (AET) program alone or combined with an antihypertensive agent (irbesartan) to reduce blood pressure (BP) and enhance heart rate variability (HRV) in chronic obstructive pulmonary disease patients.

METHODS:

Twenty-one patients were randomly assigned to a double-blind treatment with exercise and placebo (n=11) or exercise and irbesartan (n=10). Subjects underwent 24 h BP monitoring and 24 h electrocardiographic recording before and after the 12-week AET. HRV was investigated using three indexes from the power spectral analysis and three indexes calculated from the time domain. The AET program consisted of exercising on a calibrated ergocycle for 30 min three times per week. Five patients in the placebo group were excluded during follow-up because they were not compliant.

RESULTS:

There was no change in 24 h systolic and diastolic BP before (130±14 mmHg and 70±3 mmHg, respectively) and after (128±8 mmHg and 70±8 mmHg, respectively) exercise training in the placebo group, whereas in the irbesartan group systolic and diastolic BP decreased from 135±9 mmHg and 76±9 mmHg to 126±12 mmHg and 72±8 mmHg, respectively (P<0.02). There were no changes in HRV parameters in either group.

CONCLUSIONS:

The present study suggests that a 12-week AET program is not associated with a significant reduction in BP or enhancement in HRV, whereas an AET program combined with irbe-sartan is associated with a reduction in 24 h BP.     

New Exercise-Dipyridamole Combined Test for Nuclear Cardiology in Insufficient Effort: Appropriate Diagnostic Sensitivity Keeping Exercise Prognosis

Background

Myocardial perfusion scintigraphy (MPS) in patients not reaching 85% of the maximum predicted heart rate (MPHR) has reduced sensitivity.

Objectives

In an attempt to maintain diagnostic sensitivity without losing functional exercise data, a new exercise and dipyridamole combined protocol (EDCP) was developed. Our aim was to evaluate the feasibility and safety of this protocol and to compare its diagnostic sensitivity against standard exercise and dipyridamole protocols.

Methods

In patients not reaching a sufficient exercise (SE) test and with no contraindications, 0.56 mg/kg of dipyridamole were IV administered over 1 minute simultaneously with exercise, followed by 99mTc-MIBI injection.

Results

Of 155 patients, 41 had MPS with EDCP, 47 had a SE test (≥ 85% MPHR) and 67 underwent the dipyridamole alone test (DIP). They all underwent coronary angiography within 3 months. The three stress methods for diagnosis of coronary lesions had their sensitivity compared. For stenosis ≥ 70%, EDCP yielded 97% sensitivity, SE 90% and DIP 95% (p = 0.43). For lesions ≥ 50%, the sensitivities were 94%, 88% and 95%, respectively (p = 0.35). Side effects of EDCP were present in only 12% of the patients, significantly less than with DIP (p < 0.001).

Conclusions

The proposed combined protocol is a valid and safe method that yields adequate diagnostic sensitivity, keeping exercise prognostic information in patients unable to reach target heart rate, with fewer side effects than the DIP.     

Aerobic Interval Exercise Training Induces Greater Reduction in Cardiac Workload in the Recovery Period in Rats

Background

Aerobic interval exercise training has greater benefits on cardiovascular function as compared with aerobic continuous exercise training.

Objective

The present study aimed at analyzing the effects of both exercise modalities on acute and subacute hemodynamic responses of healthy rats.

Methods

Thirty male rats were randomly assigned into three groups as follows: continuous exercise (CE, n = 10); interval exercise (IE, n = 10); and control (C, n = 10). Both IE and CE groups performed a 30-minute exercise session. The IE group session consisted of three successive 4-minute periods at 60% of maximal velocity (Max Vel), with 4-minute recovery intervals at 40% of Max Vel. The CE group ran continuously at 50% of Max Vel. Heart rate (HR), blood pressure(BP), and rate pressure product (RPP) were measured before, during and after the exercise session.

Results

The CE and IE groups showed an increase in systolic BP and RPP during exercise as compared with the baseline values. After the end of exercise, the CE group showed a lower response of systolic BP and RPP as compared with the baseline values, while the IE group showed lower systolic BP and mean BP values. However, only the IE group had a lower response of HR and RPP during recovery.

Conclusion

In healthy rats, one interval exercise session, as compared with continuous exercise, induced similar hemodynamic responses during exercise. However, during recovery, the interval exercise caused greater reductions in cardiac workload than the continuous exercise.     

Noninvasive prediction of the exercise-induced elevation in left ventricular filling pressure in post-heart transplant patients with normal left ventricular ejection fraction

OBJECTIVES:

At present, there are conflicting data on the ability of echocardiographic parameters to predict the exercise-induced elevation of left ventricular (LV) filling pressure. The purpose of the present study was to validate the ratio of early diastolic transmitral (E) to mitral annular velocity (e′) obtained at peak exercise in its capacity to determine the exercise-induced elevation of pulmonary capillary wedge pressure (PCWP) and to reveal new noninvasive parameters with such capacity.

METHODS:

Sixty-one patients who had undergone heart transplantation with normal LV ejection fraction underwent simultaneous exercise echocardiography and right heart catheterization.

RESULTS:

In 50 patients with a normal PCWP at rest, exercise E/e′ ≥8.5 predicted exercise PCWP ≥25 mmHg with a sensitivity of 64.3% and a specificity of 84.2% (area under the curve [AUC]=0.74). A comparable or slightly better prediction was achieved by exercise E/peak systolic mitral annular velocity (s′) ≥11.0 (sensitivity 79.3%; specificity 57.9%; AUC=0.75) and exercise E/LV systolic longitudinal strain rate ≤−105 cm (sensitivity 78.9%; specificity 78.6%; AUC=0.87). Combined, exercise E/s′ and exercise E/e′ resulted in a trend toward a slightly more precise prediction (sensitivity 53.6%; specificity 89.5%; AUC=0.78) than did either variable alone.

CONCLUSIONS:

Exercise E/e′, used as a sole parameter, is not sufficiently precise to predict the exercise-induced elevation of PCWP. Exercise E/s′, E/LV systolic longitudinal strain rate or combinations of these parameters may represent further promising possibilities for predicting exercise PCWP elevation.     

Hypotensive Response Magnitude and Duration in Hypertensives: Continuous and Interval Exercise

Background

Although exercise training is known to promote post-exercise hypotension, there is currently no consistent argument about the effects of manipulating its various components (intensity, duration, rest periods, types of exercise, training methods) on the magnitude and duration of hypotensive response.

Objective

To compare the effect of continuous and interval exercises on hypotensive response magnitude and duration in hypertensive patients by using ambulatory blood pressure monitoring (ABPM).

Methods

The sample consisted of 20 elderly hypertensives. Each participant underwent three ABPM sessions: one control ABPM, without exercise; one ABPM after continuous exercise; and one ABPM after interval exercise. Systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP), heart rate (HR) and double product (DP) were monitored to check post-exercise hypotension and for comparison between each ABPM.

Results

ABPM after continuous exercise and after interval exercise showed post-exercise hypotension and a significant reduction (p < 0.05) in SBP, DBP, MAP and DP for 20 hours as compared with control ABPM. Comparing ABPM after continuous and ABPM after interval exercise, a significant reduction (p < 0.05) in SBP, DBP, MAP and DP was observed in the latter.

Conclusion

Continuous and interval exercise trainings promote post-exercise hypotension with reduction in SBP, DBP, MAP and DP in the 20 hours following exercise. Interval exercise training causes greater post-exercise hypotension and lower cardiovascular overload as compared with continuous exercise.     

4-Second Exercise Test: Reference Values for Ages 18–81 Years

Background

Physiological reflexes modulated primarily by the vagus nerve allow the heart to decelerate and accelerate rapidly after a deep inspiration followed by rapid movement of the limbs. This is the physiological and pharmacologically validated basis for the 4-s exercise test (4sET) used to assess the vagal modulation of cardiac chronotropism.

Objective

To present reference data for 4sET in healthy adults.

Methods

After applying strict clinical inclusion/exclusion criteria, 1,605 healthy adults (61% men) aged between 18 and 81 years subjected to 4sET were evaluated between 1994 and 2014. Using 4sET, the cardiac vagal index (CVI) was obtained by calculating the ratio between the duration of two RR intervals in the electrocardiogram: 1) after a 4-s rapid and deep breath and immediately before pedaling and 2) at the end of a rapid and resistance-free 4-s pedaling exercise.

Results

CVI varied inversely with age (r = -0.33, p < 0.01), and the intercepts and slopes of the linear regressions between CVI and age were similar for men and women (p > 0.05). Considering the heteroscedasticity and the asymmetry of the distribution of the CVI values according to age, we chose to express the reference values in percentiles for eight age groups (years): 18–30, 31–40, 41–45, 46–50, 51–55, 56–60, 61–65, and 66+, obtaining progressively lower median CVI values ranging from 1.63 to 1.24.

Conclusion

The availability of CVI percentiles for different age groups should promote the clinical use of 4sET, which is a simple and safe procedure for the evaluation of vagal modulation of cardiac chronotropism.     

Chronotropic Incompetence and its Relation to Exercise Intolerance in Chronic Obstructive Pulmonary Disease

Background

To study the relationship between chronotropic incompetence (CI) and disease severity and to assess the effect of CI on exercise capacity in patients with chronic obstructive pulmonary disease (COPD).

Heart Rate Recovery in the First Minute at the Six-Minute Walk Test in Patients with Heart Failure

Background

Heart rate recovery at one minute of rest (HRR₁) is a predictor of mortality in heart failure (HF), but its prognosis has not been assessed at six-minute walk test (6MWT) in these patients.

Objective

This study aimed to determine the HRR₁ at 6MWT in patients with HF and its correlation with six-minute walk distance (6MWD).

Methods

Cross-sectional, controlled protocol with 161 individuals, 126 patients with stable systolic HF, allocated into 2 groups (G1 and G2) receiving or not β-blocker and 35 volunteers in control group (G3) had HRR₁ recorded at the 6MWT.

Results

HRR₁ and 6MWD were significantly different in the 3 groups. Mean values of HRR₁ and 6MWD were: HRR₁ = 12 ± 14 beat/min G1; 18 ± 16 beat/min G2 and 21 ± 13 beat/min G3; 6MWD = 423 ± 102 m G1; 396 ± 101m G2 and 484 ± 96 m G3 (p < 0.05). Results showed a correlation between HRR₁ and 6MWD in G1(r = 0.3; p = 0.04) and in G3(r = 0.4; p= 0.03), but not in G2 (r= 0.12; p= 0.48).

Conclusion

HRR₁ response was attenuated in patients using βB and showed correlation with 6MWD, reflecting better exercise tolerance. HRR₁ after 6MWT seems to represent an alternative when treadmill tests could not be tolerated.     

Silent ischemia: Silent after all?

OBJECTIVE:

To examine the association of nonpain symptoms in men and women with exercise-related silent ischemia, as well as the independence of these findings from other clinical factors.

METHODS:

A prospective study of 482 women and 425 men (mean age 58 years) undergoing exercise stress testing with myocardial perfusion imaging. Analyses were performed on 60 women and 155 men with no angina but medical perfusion imaging evidence of ischemia during exercise.

MEASURES:

The presence of various non-pain-related symptoms. Ischemia is indicated by myocardial perfusion defects on exercise stress testing with single photon emission computed tomography.

RESULTS:

Women reported more nonangina symptoms than men (P<0.05). They experienced fatigue, hot flushes, tense muscles, shortness of breath and headaches more frequently (P<0.05). Symptoms relating to muscle tension and diaphoresis were associated with ischemia after controlling for pertinent clinical covariates. However, the direction of association differed according to sex and history of coronary artery disease events or procedures. Sensitivity of the detection models showed modest improvements with the addition of these symptoms.

CONCLUSIONS:

While patients who experience silent ischemia experience a number of nonpain symptoms, those symptoms may not be sufficiently specific to ischemia, nor sensitive in detecting ischemia, to be of particular help to physicians in the absence of other clinical information.