AJP - Heart and Circulatory Physiology, Vol 265, Issue 6 1996-H2008, Copyright © 1993 by American Physiological Society
Physiology of cardiac tamponade and paradoxical pulse in conscious dogs
M. A. Savitt, G. S. Tyson, J. R. Elbeery, C. H. Owen, J. W. Davis, M. P. Feneley, D. D. Glower and J. S. Rankin
Department of Cardiothoracic Surgery, Vanderbilt University Medical Center, Nashville, Tennessee 37232.
The physiological mechanism of paradoxical pulse in cardiac tamponade
remains controversial. In eight conscious dogs with intact pericardia,
ultrasonic dimension transducers assessed biventricular geometry and
volumes, while micromanometers measured right ventricular (RV), left
ventricular (LV), pleural, and pericardial pressures. With normal
inspiration, peak LV pressure fell by 7.7 +/- 1.3 mmHg at control and by
20.3 +/- 3.7 mmHg during tamponade (P < 0.001), consistent with the
development of paradoxical pulse. At peak inspiration during tamponade, RV
filling increased, the interventricular septum shifted leftward, transeptal
pressure became negative, and LV septal arc length (l theta) became smaller
than its respective unpreloaded value at maximal vena caval occlusion
(l(o)). Analysis of stroke work (SW)-end-diastolic volume (EDV) and
end-systolic pressure-volume coordinates at peak inspiration during
tamponade revealed that end-systolic pressure was 19.1 +/- 10.2 mmHg below
the baseline end-systolic pressure-volume curve (P < 0.01), and SW was
24.2 +/- 8.8% below the baseline SW-EDV curve (P < 0.01), indicating
transient inspiratory LV dysfunction. It is proposed that inspiratory
leftward interventricular septal shifting at low LV EDV during tamponade
completely unloads the septum (l theta < l o), eliminates the septal
contribution to global LV SW, results in transient inspiratory LV
dysfunction, and contributes to the phenomenon of paradoxical pulse.
