Key result
Propranolol increased high-frequency heart rate variability (7.4 vs placebo 6.9; P=0.003), whereas pindolol with intrinsic sympathomimetic activity did not improve autonomic balance.
Why the study?
Does beta blockade with and without intrinsic sympathomimetic activity affect heart rate variability and baroreflex sensitivity in healthy subjects?
RCT (n=30)
Does beta blockade with and without intrinsic sympathomimetic activity affect heart rate variability and baroreflex sensitivity in healthy subjects?
Absolute Event Rate: 7.4% vs 6.9%
p-value: p=0.003
Beta-blockers without intrinsic sympathomimetic activity (propranolol) improve autonomic balance and baroreflex sensitivity, whereas those with potent ISA (pindolol) do not, providing a physiological rationale for their differing clinical benefits.
Non-ISA beta-blockers may be prioritized for autonomic effects; confirms ISA attenuates HRV benefits in RCTs.
Beta blockers increase heart rate variability (HRV) and improve survival in coronary artery disease (CAD). The benefit of beta blockers with intrinsic sympathomimetic activity (ISA) in CAD still remains a matter of debate, and their effect on HRV has not yet been investigated. Therefore, we measured HRV, systolic blood pressure variability (BPV) and baroreflex sensitivity (BRS) under propranolol (PROP, without ISA, 160 mg q.d.), pindolol (PIN, with potent ISA, 15 mg q.d.) and placebo (PLA, q.d.) in 30 healthy subjects, aged 21-39 years, during controlled frequency breathing (0.30 Hz) in supine and tilt positions. PROP increased HRV in the high-frequency (0.15-0.40 Hz) band (PROP 7.4 +/- 1.0; PLA 6.9 +/- 1.4; PIN 6.8 +/- 1.0 ln MI2; P = 0.003), decreased BPV in the low-frequency band (at 0.1 Hz, Mayer waves) (PROP 0.6 +/- 0.7; PLA 1.3 +/- 1.1; PIN 1.2 +/- 1.2 ln mmHg2; P = 0.001) and enhanced BRS (PROP 14.6 +/- 9.5; PLA 8.0 +/- 6.8; PIN 8.7 +/- 6.8 ms mmHg-1; P = 0.001) in the supine position. After passive tilt, PROP decreased HRV in the low-frequency band (PROP 6.1 +/- 0.9; PLA 6.5 +/- 1.1; PIN 6.9 +/- 0.7 ln MI2; P < 0.001) and decreased Mayer waves (PROP 1.8 +/- 0.8; PLA 2.4 +/- 1.0; PIN 2.7 +/- 0.8 ln mm Hg2; P < 0.001). PIN increased the low-frequency HRV response, which is induced by passive tilt (PIN + 0.9 +/- 1.0; PLA + 0.3 +/- 1.3, PROP + 0.3 +/- 1.0 ln MI2; P = 0.026). Our results prove that beta-adrenergic blockade with potent ISA does not increase HRV, has no beneficial effect on autonomic balance and even exaggerates sympathetic responses to passive tilt.
No takes yet. Share an insight, caveat, or question.
Haberthür et al. (1999) conducted an RCT in Healthy subjects (n=30). Propranolol and Pindolol vs. Placebo was evaluated on Heart rate variability (HRV) in the high-frequency band (p=0.003). Propranolol increased high-frequency heart rate variability (7.4 vs placebo 6.9; P=0.003), whereas pindolol with intrinsic sympathomimetic activity did not improve autonomic balance.
Synapse has enriched 5 closely related papers on similar clinical questions. Consider them for comparative context: