Association between Radiation Exposure and Endothelium-Dependent Vasodilation: Results from Clinical and Experimental Studies.

PURPOSE: The association between occupational radiation exposure and endothelium-dependent vasodilation (EDV) remains unclear. This study evaluated the association between radiation exposure and EDV among fluoroscopy-guided interventional procedure specialists and explored the possible mechanisms. MATERIALS AND METHODS: Brachial flow-mediated dilation was compared in 21 interventional cardiologists (the radiation group) and 15 noninterventional cardiologists (the nonradiation group). Animal radiation experiments were also performed to observe the impact of radiation on EDV. RESULTS: Flow-mediated dilation in both the left (radiation group, 3.63% vs. nonradiation group, 6.77%; P < .001) and right brachial arteries (5.36% vs. 7.33%, respectively; P = .04) and serum nitric oxide (NO) level (343.69 vs. 427.09 µmol/L, respectively; P = .02) were significantly reduced in the radiation group compared to those in the nonradiation group. EDV was significantly impaired in acetylcholine concentrations of 3 × 10-6 mol/L and 10-5 mol/L (60.09% vs.74.79%, respectively; P = .03; and 62.73% vs. 80.56%, respectively; P = .002), and reactive oxygen species levels in the aorta intima and media layers were significantly increased in mice after a single x-ray exposure, which could be partly rescued by pretreatment with folic acid (P < .05). CONCLUSIONS: Radiation exposure can lead to impairment of flow-mediated vasodilation in human or EDV in mice. In mice acutely exposed to radiation, folic acid alleviated radiation-induced EDV impairment by possible reduction of reactive oxidative species.

Effects of Different Therapeutic Ultrasound Waveforms on Endothelial Function in Healthy Volunteers: A Randomized Clinical Trial.

The purpose of this study was to determine the effects of different therapeutic 1-MHz ultrasound waveforms on endothelial function before and after cyclooxygenase (COX) inhibition. Forty-two healthy volunteers aged 27.2 ± 3.8 y underwent interventions and an evaluation for endothelial function (n = 15; with COX inhibition, n = 15; duration of the vasodilator effect, n = 12) by technique flow-mediated dilation. Continuous ultrasound therapy (0.4 W/cm(2 SATA)), pulsed ultrasound therapy (20% duty cycle, 0.08 W/cm(2 SATA)) or placebo (equipment power off) was randomly applied over the brachial artery for 5 min. COX inhibition (aspirin) was carried out 30 min before treatments. In relation to the placebo, flow-mediated dilation increased by 4.8% using continuous ultrasound and by 3.4% using pulsed ultrasound. After COX, flow-mediated dilation was enhanced by 2.1% by continuous ultrasound and 2.6% by pulsed ultrasound. This vasodilation persisted for 20 min. Continuous and pulsed therapeutic 1-MHz ultrasound waveforms improved endothelial function in humans, which provided them with anti-inflammatory vascular effects.

[Solar phase effect on elasticity of the brachial artery and blood flow in humans].

Single and double examinations of normal males and females in the course of 11-year solar cycle with the use of oscillovasometry and occlusive plethysmography established a direct correlation between the effective diastolic radius of the brachial artery and solar activity characteristics on the day of examination, i.e. number of solar spots and intensity of radiation with the 10.7 cm wavelength. Other blood flow parameters demonstrated opposite correlations with the factors in males and females. As solar activity increased, females displayed linear decrements of arterial elasticity and regional peripheral resistance and growth of the volumetric blood flow velocity equally at rest and at the peak of post-occlusion reactive hyperemia. In males, the correlations had the reversed sign. Besides, males were noted to reduce venous reserve and venous outflow from antebrachial muscles proportionally to the increase of Wolf number. It is inferred that elevated solar activity may be responsible for impairment of the feeling of well-being of people with reduced cardiovascular reserve, particularly in space tight or at high altitudes in the absence of or under weak protection of the geomagnetic field and ozone layer.

Correlation of flicker-induced and flow-mediated vasodilatation in patients with endothelial dysfunction and healthy volunteers.

OBJECTIVE Flicker-induced vasodilatation is reduced in patients with vascular-related diseases, which has at least partially been attributed to endothelial dysfunction of retinal vessels. Currently, the standard method to assess endothelial function in vivo is flow-mediated vasodilatation (FMD). Thus, the present study was performed to investigate whether a correlation exists between flicker-induced vasodilatation and FMD in patients with known endothelial dysfunction and healthy subjects. RESEARCH DESIGN AND METHODS In the present study, 20 patients with type 1 diabetes, 40 patients with systemic hypertension (systolic blood pressure 140-159 mmHg; diastolic blood pressure 90-99 mmHg) and/or serum cholesterol levels > or =0.65 mmol/l, and 20 healthy control subjects were included. The flicker response was measured using the Dynamic Retinal Vessel Analyzer. FMD was determined using a high-resolution ultrasound system, measuring brachial artery diameter reactivity during reperfusion after arterial occlusion. RESULTS The flicker response of both retinal arteries and veins was significantly reduced in the two patients groups. Likewise, FMD was significantly reduced in patients compared with healthy control subjects. However, only a weak correlation between flicker-induced vasodilatation and FMD was observed. CONCLUSIONS The study confirms that flicker responses and FMD are reduced in the selected patient groups. Whether the weak correlation between FMD and flicker is due to the different stimulation type, the different vascular beds measured, or other mechanisms has yet to be investigated.

[Evaluation of coronary bed function by positron emission tomography using 13N-ammonium during cold stimulation].

The present investigation was to study the time course of changes in myocardial blood flow (MBF) in response to cold stimulation. Thirty-eight patients having risk factors of cardiovascular complications were examined. The time course of MBF changes was estimated by positron emission tomography (PET) using 13N-ammonium at rest and during a cold test (CT). Endothelium-dependent vasodilation of the brachial artery was determined from the results of a reactive hyperemia test, by applying ultrasonic duplex scanning. No significant MBF increase in response to the cold test was an indicator of coronary arterial endothelial dysfunction at cardiac 13N-ammonium PET. Agreement of the results of brachial arterial ultrasonography during reactive hyperemia and cardiac 13N-ammonium PET in the presence of the cold test suggests that endothelial dysfunction is generalized. Cardiovascular risk factors, such as left ventricular hypertrophy, smoking, dyslipidemia, and diabetes mellitus, substantially affect coronary arterial function. Left ventricular hypertrophy is an independent factor that influences the size of the coronary reserve and, in combination with endothelial dysfunction, worsens coronary microcirculation.

External beam radiation therapy to prevent anastomotic intimal hyperplasia in prosthetic arteriovenous fistulas: results of a randomized trial.

External beam irradiation has a documented effect on intimal hyperplasia reduction. However, it did not result in less reinterventions or stenoses after radiation treatment of the venous anastomosis in polytetrafluoroethylene dialysis access.

Arteritis and brachial plexus neuropathy as delayed complications of radiation therapy.

Radiation-induced arteritis of large vessels and brachial plexus neuropathy are uncommon delayed complications of local radiation therapy. We describe a 66-year-old woman with right arm discomfort, weakness, and acrocyanosis that developed 21 years after local radiation for breast adenocarcinoma. Arteriography revealed arteritis, with ulcerated plaque formation at the subclavian-axillary artery junction, consistent with radiation-induced disease, and diffuse irregularity of the axillary artery. Electromyography showed a chronic brachial plexopathy. The patient's acrocyanosis, thought to be due to digital embolization from her vascular disease, improved with antiplatelet therapy. The concurrent combination of radiation-induced arteritis and brachial plexopathy is uncommon but should be considered in patients presenting with upper extremity pain or weakness after radiation therapy.

Upper extremity occlusive arterial disease after radiotherapy for breast cancer.

Upper extremity arterial occlusive disease is a rare complication of radiation therapy for breast cancer. We present the case of a 74 year old woman who developed upper extremity ischemia 32 years after mastectomy and radiation therapy. Arteriography identified a stenotic proximal brachial artery lesion within the previous radiation field. Balloon angioplasty was unsuccessful. An axillo-brachial bypass relieved the ischemia and is still patent after 24 months. The previous literature shows that arterial bypass procedures have been uniformly successful in this circumstance. Little experience has been reported with balloon angioplasty for these lesions.