Moderate dose of dietary nitrate improves skeletal muscle microvascular function in patients with peripheral artery disease

Peripheral artery disease (PAD) is an atherosclerotic disease characterized by compromised lower-extremity blood flow that impairs walking ability. We showed that a moderate dose of dietary nitrate in the form of beetroot juice (BRJ, 0.11 mmol/kg) can improve macrovascular function and maximal walking distance in patients with PAD. However, its impacts on the microcirculation and autonomic nervous system have not been examined. Therefore, we investigated the impacts of this dose of dietary nitrate on skeletal muscle microvascular function and autonomic nervous system function and further related these measurements to 6-min walking distance, pain-free walking distance, and exercise recovery in patients with PAD. Patients with PAD (n = 10) ingested either BRJ or placebo in a randomized crossover design. Heart rate variability, skeletal muscle microvascular function, and 6-min walking distance were performed pre- and post-BRJ and placebo. There were significant group × time interactions (P < 0.05) for skeletal muscle microvascular function, 6-min walking distance, and exercise recovery, but no changes (P > 0.05) in heart rate variability or pain-free walking distance were noted. The BRJ group demonstrated improved skeletal muscle microvascular function (∆ 22.1 ± 7.5 %·min-1), longer 6-min walking distance (Δ 37.5 ± 9.1 m), and faster recovery post-exercise (Δ -15.3 ± 4.2 s). Furthermore, changes in skeletal muscle microvascular function were positively associated with changes in 6-min walking distance (r = 0.5) and pain-free walking distance (r = 0.6). These results suggest that a moderate dose of dietary nitrate may support microvascular function, which is related to improvements in walking distance and claudication in patients with PAD.

Do Patients With Arterial Occlusive Disease of Different Etiologies Benefit Equally From Cilostazol?

BACKGROUND

Cilostazol is a guideline-recommended drug that improves intermittent claudication and quality of life in patients with chronic atherosclerotic peripheral arterial disease. The drug is used for most etiologies of arterial occlusive diseases in clinical practice. This study aimed to evaluate whether patients benefit equally from cilostazol regardless of etiology.

METHODS

Patients on cilostazol were divided into 4 groups according to arterial occlusive disease etiology: (1) atherosclerosis, (2) diabetic angiopathy, (3) embolism/thrombosis, and (4) Buerger disease. Patients' maximum walking distance, ankle-brachial index score and distal tissue oxygen saturation (Sto2), clinical improvement onset time, ability to reach maximum benefit time, vascular surgeries, and wounds were compared before they started cilostazol and after 12 months. Results were evaluated at a statistical significance of P < .05.

RESULTS

In 194 patients, 307 target extremities were evaluated in the 4 disease groups. After cilostazol use, maximum walking distance, ankle-brachial index score, and distal Sto2 increased significantly in all groups (P < .001), but distal Sto2 in the diabetic angiopathy and Buerger disease groups was significantly lower than in the atherosclerosis group (P < .001). Ankle-brachial index and distal Sto2 differences in the Buerger disease group were significantly lower (both P < .001). The vascular surgery counts decreased significantly in the atherosclerosis and embolism/thrombosis groups (P = .019 and P = .004, respectively).

CONCLUSION

Patients with nonatherosclerotic arterial occlusive disease also benefit from cilostazol, but patients with Buerger disease or diabetic angiopathy seem to benefit less. Combining cilostazol with anticoagulant or antiaggregant agents and closer monitoring of these patients may produce better results.

Post-Exertion Rate of Reperfusion vs Point-by-Point analysis of skeletal tissue near-infrared spectroscopy during repeated fatigue recovery under normoxia and hypoxemia

OBJECTIVE

Near-Infrared Spectroscopy (NIRS) analysis techniques can often be complex to perform and interpret resulting in a barrier for wide-spread clinical use. The traditional Point-by-Point analysis methodology and our Post-Exertion Rate of Reperfusion method were examined during the recovery phases following repeated bouts of physical exertion to determine the physiological processes and information captured by each methodology under normal exertion conditions (FiO₂: 0.210) and when in hypoxic conditions (FiO₂: 0.129).

METHODS

To achieve this, a total of n = 15 participants performed 3 sets of leg extensions to failure at 70 % their maximal effort. A 1-min rest was performed following each set where the Point-by-Point analysis means were calculated at every 6-s time to recovery for a total of 10 mean values. The Post-Exertion Rate of Reperfusion examined the linear slopes for the entire 60-s. The near-infrared spectroscopy device was placed over the vastus lateralis and measure for muscle tissue oxygen saturation, oxygenated hemoglobin, deoxygenated hemoglobin, and total hemoglobin were obtained for both the Point-by-Point and Post-Exertion Rate of Reperfusion analysis.

RESULTS

Post-Exertion Rate of Reperfusion slopes were significantly different between normoxia and hypoxia for muscle tissue oxygen saturation (Normoxia: 0.151-0.171; Hypoxia: 0.068-0.116), oxygenated hemoglobin (Normoxia: 0.127 - 0.134; Hypoxia: 0.045 - 0.076), deoxygenated hemoglobin (Normoxia: -0.142 to -0.152; Hypoxia: -0.054 to -0.100), and total hemoglobin (Normoxia: -0.011 to 0.0250; Hypoxia: -0.009 to 0.024). Point-by-Point analysis identified significant differences between muscle tissue oxygen saturation and oxygenated hemoglobin, but not deoxygenated hemoglobin and total hemoglobin.

CONCLUSION

Point-by-Point analysis and Post-Exertion Rate of Reperfusion can each provide distinctly unique information during exertional recovery. Point-by-Point analysis was ideal for detecting the onset of change in muscle oxygen status. Post-Exertion Rate of Reperfusion identified overall rates of change and was shown to be more sensitive at identifying changes in overall recovery of skeletal tissue reperfusion rates. Point-by-Point analysis and Post-Exertion Rate of Reperfusions may be utilized individually or separately to improve the interpretability of skeletal NIRS metrics within research or clinical settings.

Calf and non-calf hemodynamic recovery in patients with arterial claudication: Implication for exercise training

BACKGROUND

Previous studies in patients with arterial claudication have focused on calf hemodynamic recovery. We hypothesized that the duration of hemodynamic recovery with TcpO2 at calf and non-calf levels would be shorter than 10 min. We analyzed the factors that influence the recovery time.

METHODS

We monitored limb changes minus chest changes from rest (DROP) of transcutaneous oximetry on buttocks, thighs and calves, during and following a treadmill test (3.2 km/h; 10% grade). We calculated the time required to reach 50% (50%RT) and 10% (90%RT) of minimal DROP value (DROPm) from walking cessation. Regression analyses were used to determine the factors associated to 50%RT and 90%RT.

RESULTS

Of the 132 patients studied, 18.2% reported isolated non-calf pain by history. Of the 792 recovery time values, only 3 (0.4%) and 23 (2.9%) were in excess of 10 min for 50%RT and for 90%RT, respectively. A weak correlation was found between each of the 792 DROPm and 50%RT (r = -0.270, p < 0.001) as well as for 90%RT (r = -0.311 p < 0.001). Lowest DROPm and BMI (but not age, sex, the use of beta-blockers, the duration of the walking period) were associated to both 50%RT and 90%RT.

CONCLUSION

Although recovery duration correlates significantly with the severity of ischemia of the same location, a wide discrepancy exists and the longest recovery time does not always correlate to the localization of the most severe ischemia. Non-calf ischemia should be measured when one aims at objectifying the biological effects of exercise or the effects of treatments on recovery from exercise.

Patients With Peripheral Arterial Disease With Exaggerated Pressor Response Have Greater Ambulatory Dysfunction Than Patients With Lower Pressor Response

We determined whether patients with peripheral arterial disease (PAD) who have either an exaggerated or a negative pressor response during treadmill walking have shorter peak walking time (PWT) and claudication onset time (COT) than patients with a normal pressor response, independent of comorbid conditions. A total of 249 patients were categorized to 1 of 3 groups based on systolic blood pressure (SBP) responses at 2 minutes of treadmill walking (speed = 2 mph, grade = 0%): group 1 (negative pressor response, SBP < 0 mm Hg), group 2 (normal pressor response, SBP 18 mm Hg), and group 3 (exaggerated pressor response, SBP > 18 mm Hg). After adjusting for comorbid conditions, group 3 (exaggerated) had significantly reduced COT (P = .011) and PWT (P = .002) compared to group 2 (normal), while group 1 (negative) and group 2 (normal) were not different. Patients with symptomatic PAD with an increase in SBP > 18 mm Hg after 2 minutes of treadmill walking experience claudication earlier and thus have greater ambulatory dysfunction, compared to patients with PAD with a normal pressor response, whereas patients with PAD with negative pressor response had a similar walking performance. The implication is that the magnitude of pressor response to only 2 minutes of treadmill walking can partially explain the degree of ambulatory dysfunction in patients with PAD.