The effect of withdrawal of beta-adrenergic blockade on intermittent claudication

The effects of acebutolol and metoprolol on walking distances and distal blood pressure in hypertensive patients with intermittent claudication

The effects of acebutolol (with intrinsic sympathomimetic activity (ISA] and metoprolol (without ISA) on arm blood pressure, ankle systolic blood pressure, claudication distances (CD) and maximal walking distances (MWD) were compared in patients with essential hypertension and intermittent claudication. Fourteen patients participated in a long-term, open, randomized cross-over study. After randomization the patients received either acebutolol, 200 mg b.i.d., or metoprolol, 100 mg b.i.d. After eight weeks the drugs were shifted and after another eight weeks they were withdrawn. Arm and ankle blood pressure, CD and MWD were determined before randomization and after 4, 8, 12 and 16 weeks, and again 4-6 weeks after withdrawal of the drugs. The arm blood pressure was reduced by 20/13 mmHg after acebutolol and by 22/21 mmHg after metoprolol. In spite of a significant decrease in arm blood pressure there were no significant changes in ankle blood pressure, CD or MWD after the two drugs. After withdrawal of the drugs and after the arm blood pressure had returned to the control value no significant changes were seen in CD, MWD or ankle blood pressure. It is concluded that beta-blockers have no deleterious effect on CD, MWD or ankle blood pressure in patients with hypertension and intermittent claudication. No effect of ISA was demonstrated.

Peripheral arterial disease--natural outcome

Three hundred and twelve patients with peripheral arterial disease were followed up for 8 3/4 years or more (maximum 11 3/4 years) to assess the natural history of the disease and factors determining its outcome. Of the 312 patients, 188 (69%) died during the follow-up, 68% of the deaths having cardiovascular causes. The 10-year relative cumulative survival rate was 0.61 for males and 0.48 for females. The role of smoking as a risk factor could not be analysed without bias. In addition to known risk factors diabetes mellitus, cerebrovascular disease and coronary heart disease, the degree of peripheral arterial disease itself also proved to be a risk factor among men. The expected life lost for men with intermittent claudication was 20%, but 44.3% for men with advanced lower limb ischaemia (p less than 0.01). This difference could not be explained by the well-known association of advanced ischaemia and diabetes mellitus. The present results therefore suggest that the state of advanced ischaemia indicates larger involvement of the whole of the arterial tree and predicts fatal cardiovascular events among these patients.

Beta-blocker underuse in secondary prevention of myocardial infarction

OBJECTIVE

To review the clinical benefits of beta-blockers as secondary prevention following a myocardial infarction (MI) and to address the reasons that clinicians are reluctant to use beta-blockers in specific patient populations.

DATA SOURCES

MEDLINE was searched for articles published from January 1966 to October 2002. Relevant studies were identified by systematic searches of the literature for all reported studies of associations between beta-blocker underuse and secondary prevention of MI. Additional studies were identified by a hand search of references of original or review articles.

STUDY SELECTION AND DATA EXTRACTION

English-language human studies were selected and analyzed.

DATA SYNTHESIS

Associations were observed in studies of beta-blocker use as secondary prevention of MI. A lower rate of beta-blocker treatment occurred in older patients and in patients with comorbid conditions such as diabetes, heart failure, chronic obstructive pulmonary disease, asthma, and peripheral arterial disease. In addition, underuse was attributed to the perception of high rates of adverse events associated with beta-blockers. beta-Blocker use as secondary prevention of an MI can lead to a 19-48% decrease in mortality and up to a 28% decrease in reinfarction rates. Nonetheless, beta-blockers are significantly underused in many patient populations due to concomitant disease states. Due to their normal physiologic deterioration, the elderly are at an increased risk of low cardiac output and bradycardia when given a beta-blocker; therefore, they should be started on a low dose that is then slowly titrated. In diabetic patients, beta-blockers can impair glucose control leading to hypoglycemia; therefore, post-MI diabetic patients must routinely monitor their blood glucose levels. In patients with decompensated heart failure, beta-blocker use can lead to further cardiac depression, but lower oral starting doses with slow titration can reduce this risk. beta-Blockers can induce bronchospasm in patients with chronic obstructive pulmonary disease or asthma, but cardioselective beta-blockers and appropriate use of medications such as albuterol can minimize these effects. Finally, in patients with peripheral arterial disease, with the exception of hypertensive patients with Reynaud's phenomenon, beta-blockers can be used safely. The only absolute contraindications to beta-blockers are severe bradycardia, preexisting sick sinus syndrome, second- and third-degree atrioventricular block, severe left ventricular dysfunction, active peripheral vascular disease with rest ischemia, or reactive airway disease so severe that airway support is required.

CONCLUSIONS

Overall, the cardiovascular benefits of beta-blockers as secondary prevention of MI significantly outweigh the risks associated with their use.

Effect of beta-blockers on peripheral skin microcirculation in hypertension and peripheral vascular disease

OBJECTIVE

This study was undertaken to investigate the possible negative effect of beta-blockers on skin microcirculation in patients with intermittent claudication and hypertension. Methods and materials In this clinical crossover study, 20 patients with mild to moderate hypertension, treated with long-term beta-blockade, and intermittent claudication or ischemic rest pain, underwent assessment of peripheral circulation before and after 2-week withdrawal of beta-blocking therapy and again 2 weeks after restarting therapy. Replacement therapy (calcium antagonist) was given if considered necessary to control hypertension. Skin microcirculation was assessed with three noninvasive techniques: capillary microscopy of the hallux nailfold, transcutaneous oximetry of the forefoot, and laser Doppler fluxmetry of the great toe.

RESULTS

Mean initial blood pressure was 163/81 mm Hg. Mean heart rate significantly increased with withdrawal of beta-blocker, from 65 bpm to 85 bpm. No significant differences in skin microcirculation and blood pressure were found between measurements obtained before, during, and after withdrawal of beta-blocking therapy. Patients experienced no change in symptoms during the study.

CONCLUSION

beta-Blockers do not appear to have a negative effect on peripheral skin microcirculation and are therefore not contraindicated to treat hypertension when intermittent claudication or ischemic rest pain is also present.

beta blockade and intermittent claudication: placebo controlled trial of atenolol and nifedipine and their combination

OBJECTIVE

To determine the effects of the beta 1 selective adrenoceptor blocker atenolol, the dihydropyridine calcium antagonist nifedipine, and the combination of atenolol plus nifedipine on objective and subjective measures of walking performance and foot temperature in patients with intermittent claudication.

DESIGN

Randomised controlled double blind four way crossover trial.

SETTING

Royal Hallamshire Hospital, Sheffield.

SUBJECTS

49 patients (40 men) aged 39-70 with chronic stable intermittent claudication.

INTERVENTIONS

Atenolol 50 mg twice daily; slow release nifedipine 20 mg twice daily; atenolol 50 mg plus slow release nifedipine 20 mg twice daily; placebo. Each treatment was given for four weeks with no washout interval between treatments.

MAIN OUTCOME MEASURES

Claudication and walking distances on treadmill; skin temperature of feet as measured by thermistor and probe; blood pressure before and after exercise; subjective assessments of walking difficulty and foot coldness with visual analogue scales.

RESULTS

Atenolol did not significantly alter claudication distance (mean change -6%; 95% confidence interval 1% to -13%), walking distance (-2%; 4% to -8%), or foot temperature. Nifedipine did not alter claudication distance (-4%; 3% to -11%), walking distance (-4%; 3% to -10%), or foot temperature. Atenolol plus nifedipine did not alter claudication distance but significantly reduced walking distance (-9%; -3% to -15% (p less than 0.003)) and skin temperature of the more affected foot (-1.1 degrees C; 0 to -2.2 degrees C (p = 0.05)). These effects on walking distance and foot temperature seemed unrelated to blood pressure changes.

CONCLUSIONS

There was no evidence of adverse or beneficial effects of atenolol or nifedipine, when given singly, on peripheral vascular disease. The combined treatment, however, affected walking ability and foot temperature adversely. This may have been due to beta blockade plus reduced vascular resistance, which might also explain the reported adverse effects of pindolol and labetalol on claudication.

A multicenter study of doxazosin in the treatment of patients with mild or moderate essential hypertension and concomitant intermittent claudication

This study assessed the efficacy and safety of once-daily doxazosin in the treatment of patients (n = 19) with mild or moderate essential hypertension (sitting diastolic blood pressure [DBP] 95 to 114 mm Hg) and concomitant intermittent claudication (Doppler ankle/arm ratio of less than 0.80 and walking tolerance of less than 700 m on the treadmill). After 14 weeks of treatment with doxazosin, a significant (p less than 0.05) reduction in systolic blood pressure and DBP was observed. Mean blood pressures were reduced from 170/100 mm Hg at baseline to 161/93 mm Hg at the end of treatment. Minor changes in heart rate occurred, which with continued treatment were not statistically significant from baseline. In 12 of 16 (75.0%) efficacy-evaluable patients blood pressure was normalized (DBP to less than or equal to 90 mm Hg with an greater than or equal to 5 mm Hg reduction from baseline) with a mean daily dose of 7.6 mg/day. Doxazosin improved the hypertension severity category in 13 of 16 (81.3%) patients. The blood pressure ratios between both the thighs and arms and ankles and arms showed no statistically significant changes after treatment with doxazosin. Thigh blood flow at rest and the reactive hyperemia after 3 minutes of arterial occlusion did not change statistically. There was a tendency for pain-free distance to improve. Laboratory data were not significantly changed after treatment with doxazosin. Of the 19 patients studied, 5 reported mild or moderate side effects that were either tolerated or disappeared with continued treatment. No patient had therapy withdrawn and no patient required a dose reduction.(ABSTRACT TRUNCATED AT 250 WORDS)

Placebo-controlled comparison of captopril, atenolol, labetalol, and pindolol in hypertension complicated by intermittent claudication

In a six month placebo-controlled cross-over trial twenty patients with hypertension and peripheral arterial disease were randomised to captopril 25 mg twice daily, atenolol 100 mg once daily, labetalol 200 mg twice daily, or pindolol 10 mg twice daily for one month. Although all treatments were equally effective at lowering blood pressure, pain-free and maximum walking distances on a treadmill were decreased by atenolol, labetalol, and pindolol, but not by captopril. Post-exercise calf blood flow availability was impaired by atenolol, labetalol, and pindolol, but not by captopril. Despite ancillary characteristics of cardioselectivity, intrinsic sympathomimetic activity, or combination with alpha-blockade, beta-blockers seem to impair the lower limb circulation in such patients, whereas captopril seems to preserve it, possibly by maintaining the collateral blood supply.

Walking capacity of patients with intermittent claudication during chronic antihypertensive treatment with metoprolol and methyldopa

In a placebo-controlled double-blind crossover trial, the effect of a 3-week course of treatment with metoprolol (100-200 mg daily) and methyldopa (500-1000 mg daily) on walking capacity on a treadmill with increasing work load was studied in 14 hypertensive patients with intermittent claudication. The walking capacity was not affected by the antihypertensive treatment.