Further Observations on Experimental Aortic Insufficiency. III. Factors Accountable for the Systolic Collapse of the Central Pressure Pulse.

The arterial pressure pulse during aortic insufficiency is described as having both a “water hammer” and “collapsing” characteristic, the former term referring to the impression given by the abrupt and great systolic rise, the latter, to the tactile and graphic effects of the steep gradient of its decline. Stewart 1 first directed attention to the fact that the chief decline of pressure precedes the dicrotic wave in the peripheral pulse and from this drew the conclusion that it must be systolic in time rather than diastolic, as is commonly taught. Subsequent improvements in methods of graphic registration, together with a clearer understanding of the physical changes involved in pulse transmission, have shown that this inference was not justifiable. The writer 2 found that the diastolic gradient of the central arterial pulse is predominately affected and chiefly concerned in the collapse and lower diastolic pressure. The analyses of Frank 3 have shown that the end of systole does not correspond to the rise of the dicrotic wave of the peripheral pulse but coincides with an uncertain and not easily determinable point on that part of the descending slope which precedes the dicrotic wave. Nevertheless, careful inspection of optical records obtained from experimental and clinical valvular insufficiency reveals the fact that the decline of pressure previous to the apex of the V-shaped incisura is also greater (Cf. Figs. 1-2). Though not strictly correct, we may refer to this as the “systolic collapse”.

The cause of this phenomenon has not been analyzed. Obviously it can be due to either or both of 2 possible alterations: the systolic pressure maximum may be higher or the incisural apex may occupy a lower position on the pressure curve. A determination of the factor actually concerned is of importance in completing our conceptions of the dynamics of aortic insufficiency; for if the greater systolic pressure drop be due solely to the former it would be adequately accounted for by the increased force of ventricular contraction, but if it be due to an absolute decrease in the position of the incisura a late systolic or very early diastolic loss of pressure must be concerned.