Year: 1978
Type: review
Abstract: THE PRIMARY purpose of this review is to take the reader back to the classical pressure-volume plane on which a beating ventricle draws a variety of trajectories under conditions of different preload and afterload. In this return visit I hope to show that the contractile state of the ventricle can be traced by focusing attention on the relation of the blood volume remaining in this ventricle at the end of systole to the ventricular pressure at that time, just as the passive property of the relaxed ventricle is implied uniquely by the end-diastolic pressure-volume data plotted in the same plane. A somewhat similar contention was expressed earlier by Holt1. However, I would also indicate that the instanta-neous pressure-volume relationship throughout sys-tole provides a simple way to describe the mechan-ical process of ventricular contraction. Early Studies on Active Pressure-Volume Relationships Nearly a century ago, Frank2 represented the cycle of ventricular contraction as a loop in a plan defined by pressure (P) in the vertical direction and volume (V) in the horizontal direction (Fig. 1). In the case of in vivo contractions, the loop would consist of a vertical ascending segment for the iso-volumic contraction phase (ao to ai in Fig. 1), a curved horizontal segment for the ejection phase during which the pressure may be increasing, un-changing, or decreasing toward the end (ai to a2), a vertical descending segment for the isovolumic re-laxation phase (a2 to as), and a horizontal curved segment which represents the filling phase (a3 to ao). This loop (ao — * ai — * a2 — * a3 — » ao) has been called the pressure-volume diagram of the cardiac cycle. Its major use in today's textbooks of physi-ology is to illustrate the external stroke work that the ventricle does to the loading system represented by the area circumscribed by the loop. Frank, how-
Source: Circulation Research
Author: K Sagawa
Language: English
Subfield: Cardiology and Cardiovascular Medicine
Field: Medicine
Domain: Health Sciences
Open Access status: bronze
OpenAlex ID: W2121560256