Response of blood pressure and plasma norepinephrine to propranolol, metoprolol and clonidine during isometric and dynamic exercise in hypertensive patients

Exercise and Physical Activity for the Post-Aortic Dissection Patient: The Clinician's Conundrum

Despite the paucity of evidence, it is often presumed, and is physiologically plausible, that sudden, acute elevations in blood pressure may transiently increase the risk of recurrent aortic dissection (AD) or rupture in patients with a prior AD, because a post-dissection aorta is almost invariably dilated and may thus experience greater associated wall stress as compared with a nondilated aorta. Few data are available regarding the specific types and intensities of exercise that may be both safe and beneficial for this escalating patient population. The purpose of this editorial/commentary is to further explore this conundrum for clinicians caring for and counseling AD survivors. Moderate-intensity cardiovascular activity may be cardioprotective in this patient cohort. It is likely that severe physical activity restrictions may reduce functional capacity and quality of life in post-AD patients and thus be harmful, underscoring the importance of further exploring the role of physical activity and/or structured exercise in this at-risk patient population.

Do β-blockers prolong survival in heart failure only by inhibiting the β1-receptor? A perspective on the results of the COMET trial

Experimental and clinical studies indicate that carvedilol exerts multiple antiadrenergic effects in addition to beta(1)-receptor blockade, but the prognostic importance of these actions has long been debated. This controversy has now been substantially advanced by the results of the recently completed Carvedilol Or Metoprolol European Trial (COMET), which showed that carvedilol (25 mg twice daily) reduced mortality by 17% when compared with metoprolol (50 mg twice daily), P=.0017--a result that was consistent with the differences seen across earlier controlled trials with beta-blockers in survivors of an acute myocardial infarction and in patients with chronic heart failure. Questions have been raised about the interpretation of these findings in view of the fact that the trial did not use the dose or formulation of metoprolol that was shown to prolong life in a placebo-controlled trial (ie, Metoprolol CR/XL [Controlled Release] Randomized Intervention Trial in Heart Failure). Pharmacokinetic and pharmacodynamic analyses, however, indicate that the dosing regimen of metoprolol selected for use in the COMET trial produces a magnitude and time course of beta(1)-blockade during a 24-hour period that is similar to the dose of carvedilol targeted for use in the trial. These analyses suggest that the observed difference in the mortality effects of metoprolol and carvedilol is not related to a difference in the magnitude or time course of their beta(1)-blocking effects but instead reflect antiadrenergic effects of carvedilol in addition to beta(1)-blockade.

Evaluation and treatment of hypertension in active individuals

Hypertension is a very common vascular disease. It is seen in adolescents, obese persons, postmenopausal women, and the elderly. A nonpharmacologic approach to treatment is a critical first step in management. The modalities include a diet low in salt and saturated fat, exercise, less than 2 ounces of alcohol daily, and abstinence from smoking. Dynamic (aerobic) exercise is effective in lowering blood pressure (BP) only if performed regularly. Weight reduction by diet must be combined with exercise if there is to be a reduction in BP. Strength training is not to be considered as an alternative to aerobic training for reducing BP. Antihypertensive mediation can be added to nonpharmacologic interventions for additional BP reduction. Beta-blockade is not a contraindication to exercise training.

Comparison of the effects of terazosin and enalapril on laboratory stress testing blood pressure in patients with essential hypertension

It is the current opinion that an ideal antihypertensive drug should reduce blood pressure (BP) not only at rest but also during stressful situations. The current study was aimed to compare the effects of the selective alpha 1-adrenergic blocker terazosin (5 mg once daily) and of the angiotensin-converting enzyme inhibitor enalapril (20 mg once daily) on cardiovascular response to a set of standardized laboratory stressors, such as mental arithmetic, handgrip test and cycle ergometry, in a group of 16 essential hypertensive patients. The study was a randomized, double-blind, cross-over trial preceded by a placebo run-in period. Terazosin and enalapril had a comparable effect on resting BP, reducing systolic (SBP) and diastolic (DBP) blood pressure from 159.5 +/- 13.9/101.6 +/- 8.8 mm Hg during placebo by 7.8%/6.7% and by 11.3%/10.2%, respectively. The "response" rate to the two treatments was approximately the same, being 69% and 75% after terazosin and enalapril, respectively. During mental arithmetic, from an average of 181.6 +/- 17.8/118.6 +/- 11.5 mm Hg during placebo, BP was reduced by 11.5%/7.9% after terazosin and by 13.6%/8.5% after enalapril; during handgrip test, BP decreased from 207.2 +/- 22.2/142.2 +/- 13.6 mm Hg by 7.3%/8.4% after terazosin and by 7.7%/7.1% after enalapril; finally, during cycle ergometry, terazosin and enalapril lowered BP by 5.4%/6.7% and 7%/3.1%, respectively, from a placebo value of 215.5 +/- 17.3/127.6 +/- 11.2. No significant difference in antihypertensive efficacy was observed between the two drugs, either at rest and during stress testing.(ABSTRACT TRUNCATED AT 250 WORDS)

A pressor effect of noncardioselective beta-blockers in mildly hypertensive patients during acute hospitalization

Pressor effects of noncardioselective beta-blockers have been demonstrated in situations of increased sympathetic activity; however, data are limited and the clinical significance of this finding is in doubt. The present study was performed to supply data about the effect of noncardioselective beta-blockers on the stress of acute hospitalization. Of 2,989 patients acutely admitted to a 50-bed unit of general internal medicine in a 647-bed teaching hospital, 234 had used beta-blockers without intrinsic sympathicomimetic activity (ISA) for at least six weeks because of mild hypertension; 199 were evaluable, 56 using nonselective, 143 using selective beta-blockers. The authors found a marked pressor effect of noncardioselective beta-blockers as compared with selective (mean arterial pressure 125 versus 102 mm Hg, p less than 0.001). In the patients who could continue their outpatient medication this effect could be attributed to an overall increase of total peripheral resistance and disappeared within five days of admission. In the patients admitted because of unstable angina pectoris (nonselective n = 15, selective n = 48) myocardial oxygen demand as estimated by the double product (systolic blood pressure heart rate) was significantly higher in the nonselective group (12.926 versus 9.581 mmHg.beats/min, p less than 0.01). The present study supports the need for more controlled data to determine the ultimate place of noncardioselective beta-blockers in situations of increased sympathetic activity.

Pressor responses from noncardioselective beta-blockers

This study reviews more than fifty papers dealing with pressor responses from noncardioselective beta-blockers. It is concluded that the responses are usually mild. They occur mainly in situations of increased sympathetic activity. Therefore some patients seem to be at risk, eg, patients with unstable diabetes type 1, sportsmen performing isometric exercise, and heavy smokers. In orthostatic hypotension, noncardioselective beta-blockers may be beneficial. Cardiac output tends, however, to decrease, and patients with orthostatic hypotension will probably not benefit from this effect.

The hypertensive patient with concomitant cardiovascular disease

Many drugs for the treatment of hypertension are available in the United States today. Of the various factors that determine the appropriate treatment for a particular patient, the presence of concomitant heart disease requires specific tailoring of the antihypertensive therapy. Coronary artery disease, aortic insufficiency, congestive heart failure, left ventricular hypertrophy, premature ventricular contractions, supraventricular arrhythmias, mitral valve prolapse, orthostatic hypotension, and aortic dissection are some of the conditions that influence the choice of treatment. Diabetes places hypertensive patients at increased risk of heart disease, and exercise and sexual function are other considerations that govern the selection of treatment for the hypertensive person. For all of these conditions, more than one drug choice is often possible, but usually hypertensive patients can be treated with a beta-blocker or a calcium channel blocker in these special circumstances.

Exercise and antihypertensive therapy

The effects of exercise on central hemodynamic mechanisms and the changes induced by treatment have been studied invasively in approximately 500 men with essential hypertension. In patients with mild hypertension, the increase in blood pressure (BP) during dynamic exercise is similar to that seen in normal subjects, but in patients with severe hypertension it is steeper. During dynamic exercise total peripheral resistance is increased in all categories of hypertensive patients, including young subjects with apparently "normal" resistance at rest. The increase in stroke volume in transition from rest to exercise is subnormal, probably reflecting increased stiffness in the left ventricle. Static exercise causes dramatic increase in systolic as well as diastolic BP. Most antihypertensive agents control BP similarly during exercise and at rest. The hemodynamic mechanisms, however, differ greatly. The beta blockers induce a long-term reduction in cardiac output, muscle blood flow and, frequently, endurance capacity. In contrast, alpha-receptor blockers, calcium antagonists and angiotensin converting enzyme inhibitors all reduce total peripheral resistance and do not decrease blood flow. Increase in endurance time has been reported with long-term calcium antagonist treatment. It would seem logical to select an antihypertensive drug that does not reduce exercise capacity when treating physically active patients with mild and moderate hypertension.

Cardioselective and nonselective beta-adrenoceptor blocking drugs in hypertension: a comparison of their effect on blood pressure during mental and physical activity

The ability of cardioselective and nonselective beta-adrenoceptor blocking drugs, with and without partial agonist activity, to control increases in blood pressure associated with mental and physical activity was compared in 35 subjects with hypertension. Direct measurements of blood pressure and radioenzymatic determinations of plasma norepinephrine were obtained before, during and after four activities, and were repeated after random allocation to treatment with atenolol, metoprolol, pindolol or propranolol. Cardioselective and nonselective drugs modestly reduced the pressor response to reaction time testing, but not to mental arithmetic or isometric exercise. The increase in systolic blood pressure during bicycling was attenuated significantly by the cardioselective drugs atenolol (by 23 mm Hg, or 38%) and metoprolol (21 mm Hg, or 41%), but not by the nonselective agents pindolol (with partial agonist activity) (13 mm Hg, or 20%) and propranolol (10 mm Hg, or 17%) (p less than 0.02 cardioselective versus nonselective; p = NS pindolol versus propranolol). Only bicycle exercise increased plasma norepinephrine concentrations (by 80%). These results suggest that beta-adrenoceptor blocking drugs will not attenuate increases in blood pressure during mental or physical activities unless intense sympathoadrenal activation also occurs. Marked elevations in circulating epinephrine, with or without norepinephrine, and peripheral beta 2-blockade appear necessary for alpha-mediated vasoconstriction to predominate and for the contrasting effects of cardioselective and nonselective drugs to be appreciated.

The cyclic-AMP concentration in plasma and in muscle in response to exercise and beta-blockade in man

At rest the cAMP concentration in (muscle samples of) the quadriceps femoris ranged from 1.55 to 3.00 mumol per kg dry muscle and in plasma from 15.3 to 32.3 nmol per 1. Blockade of the beta adrenoreceptors with propranolol resulted in a significant decrease in the concentration in muscle at rest, the magnitude of the fall being related to the initial level. Similarly in plasma there was a trend towards lower levels of cAMP in those with the highest pretreatment levels, but the overall change was not statistically significant. There was no relation between the concentrations in muscle and plasma, before or after beta-blockade. Maximum dynamic exercise for 4-8 min resulted in an approximate doubling in the cAMP concentration in both muscle and blood. The increase in plasma was closely related to that in muscle. Beta-blockade inhibited totally the rise in cAMP in muscle during exercise but was marginally less effective in preventing the increase in blood. No increase in plasma or muscle cAMP levels during 40-70 s isometric contraction were observed.

Systolic time intervals as possible predictors of pressure response to sustained beta-adrenergic blockade in arterial hypertension. A within-patient, placebo-controlled study

Systolic time intervals (STI) were recorded at rest and during isometric exercise (IHG) in 20 hypertensive outpatients, WHO Stage 1 or 2. In a double-blind crossover study, slow-release metoprolol 200 mg once daily and matched placebo were given for 4 weeks each, at the end of a 2-week placebo washout. Blood pressure and STI were taken in the last day of washout and of either crossover period. Treatment decreased blood pressure and heart rate values at rest and on peak IHG; it didn't modify preejection period index (PEPI), left ventricular ejection time index (LVETI), and their ratio at rest, but decreased the ratio between diastolic blood pressure and PEPI (DBP/PEPI ratio) at rest and on peak IHG and lengthened the PEPI at peak IHG. Resting PEPI values on placebo treatment showed a negative correlation with systolic (r = -0.72) as well as diastolic (r = -0.80) pressure reduction on slow-release metoprolol as compared with placebo treatment. The PEP/LVET ratio at rest on placebo treatment showed a negative correlation with systolic (r = -0.78) as well as diastolic (r = -0.82) pressure reduction at rest on metoprolol compared with placebo treatment. Patients with a resting PEP/LVET ratio less than 0.43 showed a reduction in both systolic and diastolic pressure approximating or exceeding 20 mm Hg, whereas patients with a PEP/LVET ratio greater than 0.47 showed a decrease in systolic and diastolic blood pressure of less than 10 mm Hg. In patients with a PEP/LVET ratio of 0.43 to 0.47 (50% of the trial population), STI didn't show any correlation with the pressure response to beta-blockade. A positive correlation was found between the DBP/PEPI ratio at rest on placebo treatment and systolic (r = 0.56) as well as diastolic (r = 0.76) pressure reduction at rest on slow-release metoprolol compared with placebo treatment. Thus, STI appeared as promising predictors of the magnitude of blood pressure response to sustained beta-blocking therapy in mild-to-moderate essential hypertension, mostly in patients with a resting PEP/LVET ratio less then 0.43 or greater then 0.47.