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Hypertension, or high blood pressure, is a condition afflicting a large segment of the population. A common therapeutic strategy for the treatment of hypertension is administration of beta adrenergic receptor blocking agents (beta blockers), which induce vasodilation, or relaxation of the smooth muscle fibers in the walls of blood vessels. There are a number of subtypes of beta adrenergic receptors, and some drugs are more selective than others in the type of receptor with which they interact; some beta blockers also have mild stimulatory (sympathomimetic) actions on certain classes of beta receptors. It has been shown that nonselective beta blockers do not modify arterial compliance (the distensibility of the relatively rigid arterial wall); in other words, these drugs do not alter the rigidity of the arterial wall by causing it to expand and stretch. While it has been claimed that beta blockers with sympathomimetic actions induce a slight increase in arterial diameter, this effect has not been well studied. To further investigate the actions of bisoprolol, a beta blocker with both selective (beta-one) antagonist properties as well as sympathomimetic effects, a study was carried out with 14 patients suffering from sustained essential hypertension, or hypertension with no clearly defined cause. Patients were administered either an inactive placebo or bisoprolol for an eight-week period. At the end of the treatment period, hemodynamic (blood flow) characteristics were determined by Doppler flowmetry (a form of ultrasound measurement of blood flow dynamics). Bisoprolol administration caused a significant decrease in blood pressure and heart rate, with no change in the diameter, blood flow, or vascular resistance of several major arteries. Pulse wave velocity (the speed of a wave in arterial walls, initiated when the ventricle pumps blood into the aorta) was significantly decreased following bisoprolol treatment; this measurement is the inverse, or opposite, of arterial compliance. Hence, bisoprolol causes not only a sustained decrease in blood pressure (with no reflex increase in heart rate), but also an improvement in the mechanical properties of several major arteries. (Consumer Summary produced by Reliance Medical Information, Inc.)