Background: The systolic blood pressure lowering effect of sublingual nitroglycerin (NTG) administration is thought to primarily arise from its action on wave reflection, although recent invasive data indicate that at least part of the blood pressure reduction can be ascribed to an effect on left ventricular dynamics.

Methods: Carotid and radial pressure waveforms and aortic, carotid and radial flow were measured in 19 HFpEF patients using applanation tonometry and pulsed Doppler ultrasound, respectively. Signals were time-aligned and global systemic as well as regional impedance and wave reflection analysis was applied.

Results: NTG lowered carotid systolic (130.8±26 at baseline vs. 110.4±18.4mmHg after NTG, P<0.01) and mean (92.5±18.4 vs.85.4±14.3) blood pressure. Global systemic effects included a decrease in systemic vascular resistance (1.00±0.32 vs. 0.88±0.28 mmHg.ml⁻¹.s, P<0.05), characteristic impedance (0.133±0.089 vs. 0.089±0.034 mmHg.ml⁻¹.s, P<0.05) and an increase in total arterial compliance (1.20±0.58 vs. 1.52±0.53 ml.mmHg⁻¹, P<0.01). NTG had a major impact on the amplitude of the forward pressure wave (58±24.3 vs. 40.6±13.3 mmHg, P<0.01), with no significant change in reflection magnitude. Regional analysis demonstrated a large effect of NTG on carotid input impedance, lowering impedance over the entire frequency spectrum, with radial artery input impedance did not demonstrate any significant changes (despite large effects on pressure and flow waveform morphology).

Conclusions: Our data in patients with HFpEF confirm the absence of impact of NTG on reflection magnitude, and demonstrate large effects of NTG on the input impedance of the cerebral vascular district, with little effect on the distal forearm circulation.