Mechanisms Underlying Very-Low-Frequency RR-Interval Oscillations in Humans

• DOI: 10.1161/01.cir.98.6.547
• Publication Date: 2012-06-12T00:41:02Z
• Authors: J. Andrew Taylor; Deborah L. Carr; Christopher W. Myers; Dwain L. Eckberg
• Keywords: Atenolol; Supine position; Vagal Tone

Background —Survival of post–myocardial infarction patients is related inversely to their levels very-low-frequency (0.003 0.03 Hz) RR-interval variability. The physiological basis for such oscillations unclear. In our study, we used blocking drugs evaluate potential contributions sympathetic and vagal mechanisms the renin-angiotensin-aldosterone system variability in 10 young healthy subjects. Methods Results —We recorded RR intervals arterial pressures during three separate sessions, with patient supine 40 degree upright tilt positions, 20-minute frequency (0.25 tidal volume–controlled breathing after intravenous injections: saline (control), atenolol (0.2 mg/kg, β-adrenergic blockade), atropine sulfate (0.04 parasympathetic (complete autonomic enalaprilat (0.02 ACE blockade). We integrated fast Fourier transform spectral power at very low Hz), (0.05 0.15 respiratory 0.3 frequencies. β-Adrenergic blockade had no significant effect on very-low- or low-frequency but increased 2-fold. modestly (≈21%) (but not tilt) position ( P <0.05). most profound effects were exerted by blockade: Atropine, given alone atenolol, abolished nearly all decreased 92%. Conclusions —Although heart period rhythms are influenced system, as rhythms, they depend primarily presence outflow. Therefore prognostic value may derive from fundamental importance cardiovascular health.