Heart rate recovery after constant-load exercise tests is decreased in proportion to the importance (severity and diffusion) of exercise-induced lower-limb ischaemia

BACKGROUND: Conditions that may influence heart rate recovery at 1 min of recovery from exercise (HRR1: end-exercise heart rate minus heart rate 1 min after exercise) are not fully understood. We hypothesized that the \u27importance\u27 (both local severity and regional diffusion) of peripheral skeletal muscle ischaemia is associated with low HRR1. DESIGN AND METHODS: In 529 patients with suspected or confirmed peripheral vascular disease not receiving beta-blockers (61.4 +/- 11.3 years old), we retrospectively studied the relationship of HRR1 to exercise-induced changes in transcutaneous oxygen DROP index (limb changes minus chest changes from rest). The sum of DROP indices observed on both calves and both buttocks (DROPtot) provides the unique opportunity to estimate both the severity and the diffusion of exercise-induced ischaemia on the right and left side simultaneously. It was used during a constant-load treadmill test (3.2 km h(-1) ; 10% grade) to classify patients in quartiles, the fourth quartile representing the more \u27important\u27 ischaemias.RESULTS: There was an inverse relationship between quartiles of DROPtot and HRR1, even after adjustment for heart rate reserve (Delta HR: end-exercise minus resting heart rate), age (60 years), gender, body mass index, treadmill maximal walking distance and ankle brachial index: adjusted R = 0.629; P<0.0001. CONCLUSIONS: During constant-load treadmill testing, DROPtot, an index of the \u27importance\u27 of exercise-induced lower-limb ischaemia, correlates with HRR1. Whether HRR1 is improved in proportion of DROPtot improvement in patients undergoing surgery or rehabilitation for peripheral artery disease is a fascinating issue for future studies

Objective determination of the predefined duration of a constant-load diagnostic tests in arterial claudication

OBJECTIVE: The predefined duration to arbitrarily stop the tests during constant-load treadmill exercise is a subject of debate and widely variable in the literature. We hypothesized that the upper and lower limits for predefined durations of constant-load 3.2 km/hour 10% grade tests could be derived from the distribution of walking distances observed on a treadmill in a population of subjects referred for claudication or from the optimal cutoff point distance on a treadmill to confirm a limitation self-reported by history.METHODS: We conducted a retrospective analysis using a referral center, institutional practice, and ambulatory patients. We studied 1290 patients (86% male), 62.1 +/- 11.2 years of age, 169 +/- 8 cm height, 75.7 +/- 14.2 kg weight. Patients performed a standard constant-load treadmill test: 3.2 km hour(-1), 10% slope, maximized to 1000 meters (approximately 20 minutes). We analyzed the maximal walking distance self-reported (MWD(SR)) by history and the maximal walking distance measured on the treadmill (MWD(TT)). Patients reporting MWD(SR) >or=1000 meters were considered unlimited by history. RESULTS: Only 197 patients (15.3%) completed the 20-minute treadmill test. Among the 504 patients who did not stop before 250 meters, 47.8% stopped within the next 250 meters (were unable to walk 500 meters). This proportion falls to 7.5% among the 213 patients who did not stop before 750 meters. When the final goal was to estimate whether the treadmill test can discriminate patients with or without limitation by history, area under the receiver operating characteristic (ROC) curve was 0.809 +/- 0.016 (95% confidence interval [CI], 0.778-0.841; P < .0001), the best diagnostic performance was attained for an MWD(TT) of 299 meters (approximately 6.15 minutes). CONCLUSION: In patients undergoing constant-load treadmill exercise with a protocol of 3.2 km hour(-1) and 10% slope: a predefined duration of 7 minutes could be proposed as a lower limit for the predefined duration of the tests specifically if one aims at confirming the limitation by history with treadmill testing. Owing to the low risk that patients that could walk 750 meters (approximately 15 minutes) will have to stop in the next 250 meters, 15 minutes seems a reasonable upper limit for the predefined test duration in clinical routine

Axon-reflex cutaneous vasodilatation is impaired in type 2 diabetic patients receiving chronic low-dose aspirin

Low-dose aspirin is largely but non-homogeneously used in primary prevention of cardiovascular complication in type-2 diabetic patients. We hypothesised that low-dose aspirin could interfere with the cutaneous neurovascular responses in type-2 diabetic patients. Galvanic current-induced vasodilatation (CIV) is an original non-noxious integrative model of neurovascular interaction and is impaired under low-dose aspirin in healthy subjects. Twenty type-2 diabetic patients (ten not receiving aspirin: D-NA and ten regularly receiving ≤ 150 mg/day aspirin: D-A), and ten age-, BMI-, and gender-matched non-diabetic control volunteers (MC), underwent macro- and microvascular investigations, including: CIV, acetylcholine (ACh) and sodium nitroprusside (SNP) iontophoresis, post-occlusive hyperemia (POH), neuropathy symptom (NSS) and disability (NDS) scores, and thermal and vibration sensory thresholds. Results are presented as median [25–75 centile] and microvascular results are expressed in multiple from baseline conductance (%Cb). CIV was 554 [349–769] %Cb in MC, 251 [190–355] %Cb in D-NA and 159 [136–202] %Cb in D-A (p < 0.05). No differences were observed between the three groups except for CIV, which is impaired in diabetic patients and further impaired in those regularly receiving low-dose aspirin, while other macrovascular, microvascular and clinical-sensitivity investigations show no significant difference. Potential clinical markers for the impairment of the neurovascular interaction are still required in diabetes. Correlation of the CIV response with the risk of cutaneous complications in diabetic patients remains to be tested

Multifractal analysis of heart rate variability and laser Doppler flowmetry fluctuations:comparison of results from different numerical methods

To contribute to the understanding of the complex dynamics in the cardiovascular system (CVS), the central CVS has previously been analyzed through multifractal analyses of heart rate variability (HRV) signals that were shown to bring useful contributions. Similar approaches for the peripheral CVS through the analysis of laser Doppler flowmetry (LDF) signals are comparatively very recent. In this direction, we propose here a study of the peripheral CVS through a multifractal analysis of LDF fluctuations, together with a comparison of the results with those obtained on HRV fluctuations simultaneously recorded. To perform these investigations concerning the biophysics of the CVS, first we have to address the problem of selecting a suitable methodology for multifractal analysis, allowing us to extract meaningful interpretations on biophysical signals. For this purpose, we test four existing methodologies of multifractal analysis. We also present a comparison of their applicability and interpretability when implemented on both simulated multifractal signals of reference and on experimental signals from the CVS. One essential outcome of the study is that the multifractal properties observed from both the LDF fluctuations (peripheral CVS) and the HRV fluctuations (central CVS) appear very close and similar over the studied range of scales relevant to physiology

Self-reported estimation of usual walking speed improves the performance of questionnaires estimating walking capacity in patients with vascular-type claudication

OBJECTIVE: Most questionnaires do not estimate the usual walking speed of the patient, although it is well known that patients may experience apparently different walking capacities if walking slow or fast. We hypothesized that correcting the self-reported estimated walking capacity by a coefficient issued from the self-reported estimation of usual walking speed would significantly improve the correlation between questionnaire-estimated and treadmill-measured walking capacity. METHODS: Three hundred ten consecutive patients complaining of vascular-type claudication were asked to estimate their usual walking speed in comparison to people of their age (or friends or relatives) with ratings ranging from much slower (1 pt) to much faster (5 pts), in addition to the filling out of the walking impairment questionnaire (WIQ) and the estimated ambulatory capacity by history questionnaire (EACH-Q). Corrected WIQ (WIQc) and corrected EACH-Q (EACH-Qc) scores were obtained by multiplying the scores of each questionnaire by the "usual-speed" coefficient and dividing by 5. Results for questionnaire scores were compared to maximal walking time (MWT) on a treadmill. RESULTS: All but four patients self-completed the usual-speed question. Median scores (25-75 centiles) were 41% (26-59) for the WIQ and 24% (11-41) for the EACH-Q. Coefficients of correlation of the three WIQ subscales and of the EACH-Q with treadmill results were significantly improved after correction by the "usual-speed" question. Overall, WIQ (mean of the three WIQ subscales) tended to improve but did not reach significance. CONCLUSION: Correcting the self-reported estimation of walking capacity by a self-reported estimation of usual walking pace significantly improves the correlation of all WIQ subscale scores and of the EACH-Q score with treadmill measurements of capacity. This confirms the interest of speed estimation in patients with peripheral arterial occlusive disease and claudication

Multifractal analysis of central (electrocardiography) and peripheral (laser Doppler flowmetry) cardiovascular time series from healthy human subjects

Analysis of the cardiovascular system (CVS) activity is important for several purposes, including better understanding of heart physiology, diagnosis and forecast of cardiac events. The central CVS, through the study of heart rate variability (HRV), has been shown to exhibit multifractal properties, possibly evolving with physiologic or pathologic states of the organism. An additional viewpoint on the CVS is provided at the peripheral level by laser Doppler flowmetry (LDF), which enables local blood perfusion monitoring. We report here for the first time a multifractal analysis of LDF signals through the computation of their multifractal spectra. The method for estimation of the multifractal spectra, based on the box method, is first described and tested on a priori known synthetic multifractal signals, before application to LDF data. Moreover, simultaneous recordings of both central HRV and peripheral LDF signals, and corresponding multifractal analyses, are performed to confront their properties. With the scales chosen on the partition functions to compute Renyi exponents, LDF signals appear to have broader multifractal spectra compared to HRV. Various conditions for LDF acquisitions are tested showing larger multifractal spectra for signals recorded on fingers than on forearms. The results uncover complex interactions at central and peripheral CVS levels