Estimation of pulmonary artery pressure and pulmonary vascular resistance from ultra low frequency precordial movements (kinetocardiograms) ∗

Abstract

TECHNICS Kinetocardiograms (low frequency precordial displacement movements) were recorded by the method previously presented.lp3 Right heart catheterization was performed by the usual procedure. A Statham P23A or D transducer was used in recording the pulmonary artery pressure. The mean pressure was usually obtained electrically; however, in a few instances it was calculated by adding 42 per cent of the pulse pressure to the diastolic pressure. In a large series in which the mean pressure was determined by planimetry this calculation was found sufficiently close to justify its use.4 Cardiac output was determined by the Fick principle. Total pulmonary vascular resistance was calculated by multiplying the mean artery pressure by 80 and dividing this by cardiac output (pulmonary blood flow in patients with left-toright ventricular shunts) in liters per minute. The resultant figure is expressed in dynes seconds centimeters-j. Correction for body size is achieved by dividing this by the surface area. It should be noted that the vascular resistance is different from pulmonary arteriolar resistance in that the mean capillary pressure (an estimation of left atria1 or pulmonary venous pressure) is not subtracted from the mean pulmonary artery pressure in the former. This type of calculation for vascular resistance was chosen, since this probably represents more closely the total load on the right ventricle. Pulmonary blood flow was used in the calculations for pulmonary resistance rather than systemic flow in patients with left-to-right intracardiac shunts. Pulmonary blood flow was estimated by the formula