Aminophylline and isoprenaline, two drugs widely used in the managem2nt of asthma, have a pulmonary vasodilator action as well as a bronchodilator action. If regional pulmonary vasoconstriction in poorly ventilated parts of the lungs is a significant compensatory phenomenon in asthma, the effects of administration of these agents on gas exchange would depend on the relative magnitudes of bronch...

Epoxyeicosatrienoic acids (EETs) are cytochrome P450-derived metabolites of arachidonic acid that elicit vasodilation via activation of K(+) channels. They have been implicated as endothelium-derived hyperpolarizing factors (EDHFs), mediating the effect of some endothelium-dependent vasodilator agents such as bradykinin in some vascular tissues. We reasoned that an agent that increases the avai...

Shifting legs to a gravity-dependent position provokes a physiological vasoconstrictive response that forms the basis of several diagnostic tests based on initial (< 5 min) blood perfusion decreases. However, it is not known if responses are maintained over longer duration and if they depend on the volume shifted to the limb during the manoeuvre. These issues were investigated by measurements o...

To assess factors responsible for phasic behavior of renal blood flow in essential hypertension, we applied an analytic method based on the estimation of power spectral density to xenon transit through the kidney and examined the renal vasodilator response to a range of agents in 53 normal subjects and 53 patients with essential hypertension. The renal vasodilator response to the calcium channe...

Spasm of arterial and venous graft conduits can occur both during harvesting and after the graft is connected. Attempts to overcome spasm during harvesting by probing or hydraulic distension can cause structural damage to the graft, which may impair short- and long-term patency. After a coronary artery bypass graft is connected, spasm can cause major problems with myocardial perfusion. To selec...

Background Patients referred to cardiac MRI (CMR) for suspicion of obstructive coronary artery disease typically undergo vasodilator stress testing using either adenosine or regadenoson. Both of these agents are effective and have been evaluated for stress testing in both the CMR and nuclear medicine setting but the cardiovascular physiologic effects of each of these agents have not been well s...