630 



HANDBOOK OF PHYSIOLOGY ^^ CIRCULATION I 



FIG. 2. Left atrial and ventricular pressure pulses recorded through double lumen catheters in 

 normal subjects. Ordinate values in mm Hg. For labeled features, see text. [From Ankeney et al. 



(5)-] 



the atrial pressure, a prominent c wave appears. If, 

 however, at this moment the ventricular pressure is 

 higher than the atrial, no c wave is seen in the atrial 

 curve (5, 137, 184). 



During the ventricular contraction the pressure in 

 the atrium falls (the negative .v wave) and rises again 

 to the V wave, the peak of which corresponds to the 

 end of ventricular systole. When the ventricle rela.xes 

 and the mitral valve again opens, the period of rapid 

 filling starts. This period, i.e., the diastolic inflow 

 period, is marked by a continuous decline in the 

 atrial curve, the y descent. Diastasis, or the period of 

 slowed ventricular filling, starts when the atrial 

 pressure begins to rise during diastole. The onset of 

 the a wave produced by the next atrial contraction 

 marks the end of diastasis. The dynamic interval of 

 atrial systole lasts until the peak of the atrial contrac- 

 tion wave, whereas the inflow phase, which follows, 

 ends at the onset of ventricular isometric contraction 

 and completes the cardiac cycle. This point on the 

 atrial curve has also been referred to as the c point 

 (>57)- 



PULMONARY ARTERIAL WEDGE PRESSURE. Much of the 



experience gained regarding the pulmonary hemo- 

 dynamics in heart disease in man has been obtained 

 using the pulmonary arterial wedge pressure as an 

 index of left atrial pressure (7, 46, 48, 50, 51, 36, 38, 

 59, 78, 82, 85-87, 90, 108, 134, 136, 160, 184, 189, 



191, 199, 206, 208, 214, 213). Even now, when it is 

 possible to register directly the left atrial pressure in 

 man, many authors still use the pulmonary arterial 

 wedge pressure as an index of changes in the left atrial 

 pressure, because the procedure of left atrial puncture 

 is not without danger and has to be done under cir- 

 cumstances that more or less preclude any hemo- 

 dynamic studies. It thus seems appropriate to discuss 

 briefly the validity of the pulmonary arterial wedge 

 pressure. 



De.xter el a!. (47), in 1946, observed in man that 

 fully saturated blood was obtained through a heart 

 catheter introduced so far into one of the branches of 

 the pulmonary artery that its tip obstructed the lumen 

 completely. Some years later the same group pub- 

 lished pressure curves obtained through such an 

 impacted catheter in animals, followed by similar 

 studies conducted in man (102). The pressure pulses 

 recorded showed no oscillations due to the insensitiv- 

 ity of the manometers used ("pulmonary capillary" 

 pressures). Almost simultaneously, and independent 

 of the Boston group, Lagerlof & Werko (126) pub- 

 lished curves obtained in a similar manner in normal 

 man and in patients with various heart disea.ses. They 

 used the Tybjaerg-Hansen electrical capacitance 

 manometer and demonstrated the occurrence of a 

 \cnous pulse in most tracings. They also defined the 

 tracing tvpical for a series of heart disorders, for 

 exainplc mitral stenosis and mitral incompetence 



