Effects Of Enhanced External Counterpulsation On Pulsatility Of Blood Flow And Dilatory Function Of Resistance Vessels

BackgroundsVascular endothelial dysfunction plays a key role to reduce vascular dilatory capacity and accelerate atherosclerosis. Impaired function of the vascular endothelium has been well documented in coronary heart disease (CHD). Researchers are exploring ways to improve endothelial function, which will likely benefit the patients of CHD. It has been proved that enhanced external counterpulsation (EECP) can increase myocardial blood supply in diastolic period. However, it is not proved if EECP can improve endothelial function. Researchers have found that pulsatile blood flow and shear stress is helpful to maintain normal endothelial function. It is clear that EECP can elevate shear stress of blood flow to endothelium. Effect of EECP on the pulsatility of blood flow is still unknown.ObjectivesQuantitative measurement of pulsatility of arterial blood pressure and blood flow is going to be established and effects of EECP on blood pulsatility and vascular resistance will be investigated in the study. We are also going to establish the iontophoresis technique to observe effects of EECP on endomelium-dependent andendothelium-independent vasodilatation in the skin of patients with CHD. MethodsMeasurement of Pulsatility of Blood Pressure and Blood Flow in Dogs and Effect of Enhanced External Counterpulsation on PulsatilityCommon carotid artery blood pressure and blood flow was measured in6 beagle dogs those had an acute myocardial infarction 6 weeks ago. A 6F tip-transducer catheter was inserted into right common carotid artery to measure blood pressure, and blood flow was measured in the left common carotid artery by an electromagnetic blood flow probe while the dog was under anaesthesia before and during EECP. Blood pressure pulsation, pulsatility index (ratio of peak pressure to trough pressure) and standard deviation of blood pressure was calculated to evaluate the pulsatility of arterial blood pressure. Blood flow pulsation, pulsatility index (ratio of peak flow to trough flow) and standard deviation of blood flow was calculated to evaluate the pulsatility of blood flow. Mean vascular resistance (MVR) was calculated as MVR = mean blood pressure / mean blood flow. The experiment was repeated in another7 healthy mongrel dogs with pretreatment of N(G) -nitro-L-arginine methyl ester (L-NAiME) 25mg/kg intravenously, a nitric oxide synthase competitive inhibitor.Measurement of Pulsatility of Arterial Blood Pressure in Healthy Young Men and Effect of Enhanced External Counterpulsation on PulsatilityEight healthy young men volunteers aged 22 to 35 were included. A 4F tip-transducer catheter of 50cm in length was inserted from radial artery under local anaesthesia. Arterial blood pressure was recorded before and during EECP. Blood pressure pulsation, pulsatility index(ratio of peak pressure to trough pressure) and standard deviation of blood pressure was calculated to evaluate the pulsatility of arterial blood pressure. Establishment of Laser Doppter-Iontophoresis SystemIn 40 healthy volunteers aged 28 to 45 years old, we delivered acetylcholine (ACh), an endothelium-dependent vasodilator, and sodium nitroprusside, an endothelium-independent vasodilator ^(SNP), to dermal vessels of the forearm using iontophoresis, and measured vasodilatation (laser Doppler blood flow, LDF) using laser Doppler fluximetry. ACh was diluted in 5% NaH2P04 and sodium nitroprusside was diluted in nature saline. We performed the measurement twice to investigate the reproducibility of the results measured by the laser Doppler-inotophoresis system. We also delivered 5% NaH2P04 and nature saline without ACh or NSP iontophoretically to investigate electric current induced nonspecific vasodilatation in 12 healthy volunteers. Effect of Enhanced External Counterpulsation on Cutaneous Microvascular Dilatory Function of Patients with Coronary Heart DiseaseLaser Doppler-iontophoresis system was used to measure cutaneous vascular conductance (CVC) in response to iontophoresis of SNP and ACh in forearms an...