AJP - Heart and Circulatory Physiology, Vol 246, Issue 2 245-H249, Copyright © 1984 by American Physiological Society
Postextrasystolic pulsus alternans and heart rate
C. J. Carlson and E. Rapaport
Postextrasystolic (PES) pulsus alternans, an alternation in systolic blood
pressure above and then below base line for several beats after a premature
ventricular depolarization was noted many years ago in patients with heart
failure. We noted in acute animals studies that the occurrence of PES
alternans was related to heart rate. We studied five open-chest dogs
suppressing intrinsic heart rate by vagal stimulation and pacing the right
ventricle over a range of 100-200 beats/min introducing an extrastimulus at
50% of the paced rate. We found that the pressure of the second PES beat
was augmented up to 120 beats/min and then began to decrease approximately
10 Torr for each 10-beats/min increase in rate. The physiological variables
most closely related to the occurrence of PES alternans were the duration
of systole of the first PES (strong) beat and the rate of rapid diastolic
filling of the second PES (weak) beat. Postextrasystolic and possibly
sustained pulsus alternans is an inevitable consequence of heart rate and
of the relationship between ejection and diastolic filling. The details of
that relationship and the effects of various diseases determine whether
alternans is observed or not.
