Background: There is conflicting information with regard to the effect of beta-blockers on arterial stiffness and wave reflection. We compared a vasodilating beta-blocker, nebivolol, with atenolol.
Methods: We randomized 40 subjects with untreated hypertension (mean +/- s.e.m. systolic/diastolic blood pressure (BP) of 160 +/- 3/98 +/- 1 mm Hg, age 49 +/- 1 years) 16 of whom were women, to atenolol 50 mg or nebivolol 5 mg daily for 4 weeks. Arterial stiffness was assessed in terms of carotid-femoral pulse wave velocity (PWV, Complior) and arterial wave reflection (augmentation index (AIx) by applanation tonometry, Sphygmocor).
Results: Both beta-blockers produced an equal reduction in brachial BP but aortic pulse pressure (PP) was reduced to a greater extent by nebivolol (P < 0.05). PWV was decreased significantly by both therapies (nebivolol: from 11.5 +/- 0.5 to 9.9 +/- 0.5 m/s; atenolol: from 11.1 +/- 0.4 to 9.8 +/- 0.4 m/s; P < 0.01) but only nebivolol significantly reduced AIx (from 35 +/- 5 to 28 +/- 2%, P < 0.05). In addition, whereas PP amplification (PP, mm Hg) decreased with atenolol therapy (from 10 +/- 1 to 7 +/- 1, P < 0.01), it increased with nebivolol therapy (from 8 +/- 1 to 14 +/- 3, P < 0.01). Atenolol reduced heart rate to a greater extent than nebivolol did (14 +/- 3/min reduction by atenolol vs. 8 +/- 2/min reduction by nebivolol, P < 0.05). There was no difference between the two treatments in respect of the effect on transit time.
Conclusion: The beta-blockers, atenolol and nebivolol, have a similar effect in reducing arterial stiffness in the large elastic aorta, largely secondary to BP reduction. Nebivolol, in contrast to atenolol, has an effect on small muscular arteries, increasing PP amplification and reducing wave reflection, possibly because of increased levels of nitric oxide (NO). Such ancillary properties may impart important distinct hemodynamic effects, and therefore beta-blockers cannot be regarded as a homogeneous group.