Quantification of glyceryl trinitrate effect through analysis of the synthesised ascending aortic pressure waveform

Objective: To establish through analysis of the radial pressure pulse waveform the dose dependent effects of glyceryl trinitrate (GTN) on properties of different blood vessels. Design: Radial pulse waveform was measured in randomised order before, during a five hour application of a GTN patch delivering 0.104-0.625 mg/h, and for two hours after patch removal. The radial pressure waveform (Millar applanation tonometer) was convolved into an ascending aortic wave using a generalised transfer function (SphygmoCor process) enabling measurement of aortic systolic, diastolic, pulse, mean, and augmented pressure and left ventricular ejection duration in addition to standard brachial cuff pressures. Setting: Fu Wai and Ren Ming hospitals in Beijing, China. Patients: 46 recumbent hospitalised patients aged 56 (9) years, awaiting electrophysiological or other diagnostic studies, fasting, and with other treatments suspended. Major outcome measures: Conventional brachial pressure measures and data from the synthesised aortic pulse. Results: There was no consistent change in heart rate or brachial pressures except for a decrease in systolic and pulse pressures (p < 0.01) at dose > 0.416 mg/h. In contrast, there were substantial and significant (p < 0.0001) decreases in aortic systolic, pulse, and augmented pressures at all doses, mean pressure (p < 0.001) at doses > 0.416 mg/h, and ejection duration (p < 0.001) at doses > 0.208 mg/h. Conclusions: Pulse waveform analysis exposes dose dependent effects of GTN on the aortic waveform, suggesting muscular conduit arterial dilatation with reduced wave reflection at the lowest dose, arteriolar dilatation and decreased peripheral resistance at the highest dose, and venous dilatation at the intermediate dose.