Effects of nicorandil on aortic input impedance: a comparative study with nitroglycerin

Relationship between radial and central arterial pulse wave and evaluation of central aortic pressure using the radial arterial pulse wave

Since a decrease of central aortic pressure contributes to the prevention of cardiovascular events, simple measurement of not only brachial blood pressure but also central aortic pressure may be useful in the prevention and treatment of cardiovascular diseases. In this study, we simultaneously measured radial artery pulse waves non-invasively and ascending aortic pressure invasively, before and after the administration of nicorandil. We then compared changes in central aortic pressure and radial arterial blood pressure calibrated with brachial blood pressure in addition to calculating the augmentation index (AI) at the aorta and radial artery. After nicorandil administration, the reduction in maximal systolic blood pressure in the aorta (Deltaa-SBP) was -14+/-15 mmHg, significantly larger than that in early systolic pressure in the radial artery (Deltar-SBP) (-9+/-12 mmHg). The reduction in late systolic blood pressure in the radial artery (Deltar-SBP2) was -15+/-14 mmHg, significantly larger than Deltar-SBP, but not significantly different from Deltaa-SBP. There were significant relationships between Deltaa-SBP and Deltar-SBP (r=0.81, p<0.001), and between Deltaa-SBP and Deltar-SBP2 (r=0.91, p<0.001). The slope of the correlation regression line with Deltar-SBP2 (0.83) was larger and closer to 1 than that with Deltar-SBP (0.63), showing that the relationship was close to 1:1. Significant correlations were obtained between aortic AI (a-AI) and radial AI (r-AI) (before nicorandil administration: r=0.91, p<0.001; after administration: r=0.70, p<0.001). These data suggest that the measurement of radial artery pulse wave and observation of changes in the late systolic blood pressure in the radial artery (r-SBP2) in addition to the ordinary measurement of brachial blood pressure may enable a more accurate evaluation of changes in maximal systolic blood pressure in the aorta (a-SBP).

Effects of Nifedipine on Systemic and Pulmonary Vascular Impedance in Subjects Undergoing Cardiac Catheterization

Nifedipine 10 mg, administered sublingually to 12 patients following diagnostic cardiac catheterization, caused reduction in systemic resistance, and change of impedance together with alteration in contour of the ascending aortic and left ventricular pressure waves. The substantial reduction in ascending aortic and left ventricular systolic pressure with nifedipine occurred despite an increase in stroke volume and cardiac output, and was associated with similar reductions in mean pressure and indices of wave reflection. In the same patients, there were no significant changes in pulmonary vascular resistance or impedance, nor in pulmonary artery or right ventricular pressure pulse contour. For the systemic circulation, as with nitroglycerin and nitroprusside, reduction in wave reflection appears to be an important factor in the drug's action and for its beneficial effects on cardiac load in the treatment of angina pectoris, systemic hypertension and left ventricular failure. Thus the observed effects of nifedipine were attributed to vasodilatation of the systemic arteries and arterioles.