6.5 ACUTE β-ADRENERGIC BLOCKADE INCREASES AORTIC WAVE REFLECTION IN YOUNG MEN AND WOMEN: DIFFERING MECHANISMS BETWEEN SEXES
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Acute β-adrenergic blockade increases aortic wave reflection, however, the mechanisms remain unclear. Evidence suggests that β-adrenergic receptor sensitivity in the peripheral vasculature differs between sexes. Therefore, the goal of this study was to examine whether β-adrenergic blockade alters aortic wave reflection and forearm vasoconstrictor responsiveness to a similar extent in young men and women. In thirty-one subjects (16M/15F; 26±1 years) non-invasive aortic pressure waveforms were synthesized from high-fidelity radial pressure waveforms via applanation tonometry before and during systemic β-blockade (0.25 mg/kg bolus, followed by 0.004 mg/kg/min continuous infusion of propranolol). Forearm vasoconstrictor responses to exogenous intra-arterial norepinephrine (NE) were also assessed in a subset of subjects (13M/9F). Wave reflection characteristics are summarized in Table 1. β-blockade increased aortic augmentation index (AIx) and wave reflection amplitude (aortic augmented pressure (AG)) in both sexes. However, the increase in wave reflection tended to be greater (P<0.05 and P=0.07 for AG and AIx, respectively) in women following β-blockade. AIx adjusted for HR (AIx@75bpm) increased in women following β-blockade, whereas it was unchanged in men. Moreover, the change (Δ) in AIx was inversely associated to ΔHR only in men (r=−0.54, P<0.05). Finally, β-blockade caused an enhanced forearm vasoconstrictor response to exogenous NE in women (Figure 2). Our data suggest that: 1) aortic wave reflection is increased to a greater extent in women following systemic β-blockade; and 2) the mechanism for enhanced aortic wave reflection appears to be mediated by a reduced HR in men, whereas less peripheral β-mediated vasodilation likely contributes in women.
| Men | Women | |||
|---|---|---|---|---|
| Control | β-Blockade | Control | β-Blockade | |
| Heart Rate (bpm) | 58 ± 2 | 50 ± 1† | 62 ± 2 | 55 ± 2† |
| PSBP (mmHg) | 123 ± 3 | 119 ± 3† | 125 ± 3 | 121 ± 3† |
| PDBP (mmHg) | 69 ± 3 | 70 ± 2 | 70 ± 2 | 70 ± 2 |
| PPP (mmHg) | 53 ± 2 | 48 ± 2† | 55 ± 2 | 51 ± 1† |
| ASBP (mmHg) | 102 ± 2 | 101 ± 2 | 107 ± 3 | 107 ± 3 |
| ADBP (mmHg) | 70 ± 2 | 71 ± 2 | 71 ± 2 | 71 ± 2 |
| APP (mmHg) | 32± 2 | 30 ± 0† | 37 ± 2* | 37 ± 2* |
| MAP (mmHg) | 85 ± 2 | 85 ± 2 | 88 ± 2 | 88 ± 3 |
| PPA | 1.69 ± 0.03 | 1.62 ± 0.03† | 1.54 ± 0.05* | 1.44 ± 0.05*† |
| AIx (%) | −2 ± 3 | 2 ± 3† | 10 ± 3* | 17 ± 3*† |
| AIx@75bpm (%) | −10 ± 3 | −10 ± 3 | 4 ± 3* | 8 ± 3*†‡ |
| AG (mmHg) | −0.5 ± 0.8 | 0.9 ± 0.8† | 4.3 ± 1.5* | 7.1 ± 1.6*†‡ |
| Δtp (msec) | 159 ± 4 | 163 ± 3 | 153 ± 4 | 153 ± 3 |
| Ew (dyne· cm2 · s) | −74 ± 152 | 233 ± 154† | 864 ± 305* | 1408 ± 345*†‡ |
PSBP, peripheral systolic blood pressure; PDBP, peripheral diastolic blood pressure; PPP, peripheral pulse pressure; ASBP, aortic systolic blood pressure; ADBP, aortic diastolic blood pressure; APP, aortic pulse pressure; MAP, mean arterial pressure; PPA, pulse pressure amplification, AIx, aortic augmentation index; AG, augmented pressure; Δtp, round trip time of pressure wave to the peripheral reflecting sites and back to heart; Ew, wasted left ventricular pressure energy.
P < 0.05 vs. men;
P < 0.05 vs. control;
P < 0.05 Magnitude of change vs. men
Hemodynamic variables before (control) and during systemic β-adrenergic blockade
Forearm vasoconstrictor responses to exogenous norepinephrine (2, 4, and 8 ng/100 ml/min) in men and women before (control) and during systemic β-adrenergic blockade. * P< 0.05 vs. Control
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TY - JOUR AU - D.P. Casey AU - T.B. Curry AU - M.J. Joyner AU - N. Charkoudian AU - J.N. Barnes AU - E.C. Hart PY - 2011 DA - 2011/11/29 TI - 6.5 ACUTE β-ADRENERGIC BLOCKADE INCREASES AORTIC WAVE REFLECTION IN YOUNG MEN AND WOMEN: DIFFERING MECHANISMS BETWEEN SEXES JO - Artery Research SP - 145 EP - 146 VL - 5 IS - 4 SN - 1876-4401 UR - https://doi.org/10.1016/j.artres.2011.10.229 DO - 10.1016/j.artres.2011.10.229 ID - Casey2011 ER -