STENOSIS AND INSUFFICIENCY 



651 



("■pulmonary capillary venous" pressure). It has 

 since been agreed to call the tracing, obtained in this 

 way, pulmonary arterial wedge pressure. 



In dog experiments the pulmonary arterial wedge 

 pressure has been recorded simultaneously with the 

 pressure in a pulmonary vein or the left atrium, 

 reached either by arterial catheterization or by punc- 

 ture at thoracotomy (3, 4, 51). In these experiments 

 the two pressures have usually been found to be 

 reasonably in accord. Following such experimental 

 changes as rapid intravenous infusions, positive- 

 pressure respiration, severe anoxia, constriction or 

 embolization of the pulmonary artery, induced mitral 

 stenosis or incompetence, and artificial septal defect, 

 the wedge pressure has also been in close accord with 

 the changes in pressure in the left atrium, but it has 

 usually remained uninfluenced by changes in the pul- 

 monary arterial pressure. Horvath & MacCanon (105) 

 observed no pulsations in the wedge pressure when 

 the tip of the catheter was situated near the surface of 

 the lung, and suspected that the intrapleural pressure 

 was dominating the measurements in such ca.ses. 

 Ankeney (3, 4) could in no case find convincing 

 accord between the shape of the wedge pressure 

 curve and tiiat of the left atrial cur\-e. On this basis — 

 and from the (wrong) assumption that the higher 

 pressure in the pulmonary artery than in the left 

 atrium should prexent retrograde transmission of the 

 atrial pulse wave — this author maintained that all 

 possible pulsations in the wedge curve must be trans- 

 mitted from the pulmonary artery, and that only 

 cur\es without such pulsations could be considered a 

 definite indication of the pulmonary capillary pres- 

 sure. VVerko et a/. (201 ) in 1953 reported some investi- 

 gations in two patients with pulmonary hypertension, 

 showing that the pulmonary artery wedge pressure 

 remained uninfluenced by obstruction of the pulmo- 

 nary artery proximal to the tip of the catheter, whereas 

 positive-pres,sure respiration in another patient 

 diminished or suspended the pulsations in the wedge 

 pressure curve. 



In patients with interatrial septal defect (or dis- 

 placed pulmonary veins) direct catheterization 

 affords an opportunity for recording the pressure in 

 the left atrium or in a pulmonary vein. Comparisons 

 between such measurements and the wedge pressure 

 in sinole cases or in small series of up to six patients 

 have been published (200). In these measurements, 

 performed at minimal time intervals with few excep- 

 tions, the mean pressure was almost always in accord 

 within limits of a few mm Hg; and in most cases with 

 a slight positive difference between the wedge pressure 



and the left atrial pressure. Distinct accord in the 

 shapes of the curves, with a delay slightly under o. i 

 sec as compared to the left atrium, was found in most 

 instances. 



Allison & Linden (i), who punctured the left 

 atrium from the right main bronchus and registered 

 wedge and left atrial pressure simultaneously, state 

 that the two curves are identical oni\- under certain 

 circumstances; they could, however, give an example 

 in which the wedge pressure curve reproduced all 

 main features of the left atrial pressure curve with a 

 delay of about 0.09 sec. Epps & Adler (66) traced the 

 two curves in immediate continuation, connecting 

 by means of a three-way cock the same manometer 

 with both the wedged catheter and the left atrial 

 needle. In seven patients with mitral disease, in both 

 sinus rhythm and auricular fibrillation, and at both 

 high and low values of pressure and pulmonary resist- 

 ance, the authors always found a close accord in the 

 shape of the wedge and the left atrial pressure curves. 

 No difference could be .seen in the time relation to the 

 electrocardiogram in these examples. Bjork and co- 

 workers (21) punctured the left atrium from the back, 

 and in seven cases generally found good accord with 

 the shape of the wedge pressure curve, which was 

 delayed for about 0.10 sec; the mean pressure, how- 

 ever, showed differences from —1.5 to -I-10.9 mm 

 Hg. This comparatively great \ariation could be 

 partly explained by hydrostatic differences, as the 

 measurements were performed with the patients in a 

 lateral recumbent position. In a subsequent study 

 complete parallelism was found between the varia- 

 tions in pressure levels and shapes of the two curves 

 during X'alsalva's experiment in nine patients with 

 mitral disease. Using the same technique, Werko, 

 et a/. (200) also found identity between the two pres- 

 sure curves, except for a time difference of about 0.08 

 sec, in one patient with mitral disease. 



At thoracotomy, too, the wedge pressure has been 

 recorded simultaneously with the left atrial pressure. 

 Connolly et al. (37) examined patients with mitral 

 disease and found good accord between the two pres- 

 sure curves, with regard to both level and configura- 

 tion. In ten patients with mitral or pulmonary disease, 

 Wilson et al. (205) also found fairly good accord be- 

 tween the pressure levels in the left atrium and the 

 wedge curve (the maximal difference on either side 

 being from 5 to 6 mm Hg), but in no case did they 

 find distinct pulsations. 



Much discussion has thus been conducted both in 

 clinical and physiological literature as to whether the 

 tracing obtained in this manner reallv reflects the 



