| Reference |
Preload Definition |
Afterload Definition |
|
| Textbook of Medical Physiology (9) |
". . . the degree of tension on the muscle when it begins to contract . . . is the preload . . ." (p. 115) |
". . . the load against which the muscle exerts its contractile force . . . is called the afterload." (p. 115) |
|
"For cardiac contraction, the preload is usually considered to be the end-diastolic pressure when the ventricle has become filled." (p. 115) |
"The afterload of the ventricle is the pressure in the artery leading from the ventricle." (p. 115) |
| Physiology (2) |
". . . the resting muscle is stretched by a preload, which in the intact heart represents the end of filling of the left ventricle during diastole (in other words, it represents the end diastolic volume)." (p. 366) |
"During ejection, the afterload is represented by aortic and intraventricular pressures, which are virtually equal to each other." (p. 366) |
| Best and Taylor’s Physiological Basis of Medical Practice (31) |
"The end-diastolic pressure in the ventricle can also be equated to the preload." (p. 220) |
"Afterload = wall tension (stress). Diagram showing how the systolic wall tension or wall stress (which represents the afterload in the myocardial fibers during left ventricular ejection) is affected by the geometry of the left ventricle (LV)." (p. 220, legend of Figure 2.111) |
|
"In the whole heart the preload should constitute the tension in the wall at the end of diastole (which determines the resting fiber length), but for practical purposes the ventricular end-diastolic volume of the ventricular end-diastolic pressure is used to indicate the preload." (p. 227) |
| Review of Medical Physiology (6) |
"In vivo, the preload is the degree to which the myocardium is stretched before it contracts . . ." (p. 546) |
". . . and the afterload is the resistance against which blood is expelled." (p. 546) |
| Essential Medical Physiology (14) |
"The filling pressure is often termed the preload because this is the load on the muscle fibers before contraction." (p. 192) |
"The afterload for the contraction is the aortic pressure . . ." (p. 192) |
| Medical Physiology (23) |
"At the end of diastole the intraventricular pressure is analogous to the ‘preload’ in a simple muscle strip preparation (i.e., the weight that is suspended from such a strip to stretch it to the desired initial length)." (p. 994) |
"During ejection the aortic pressure is related to the ‘afterload,’ or weight that the muscle [strip] is required to lift." (p. 994) |
| Human Physiology (26) |
"The preload is given by the end-diastolic pressure . . ." (p. 387) |
". . . and the afterload by the diastolic arterial pressure." (p. 387) |
| Human Physiology: Foundations and Frontiers (21) |
"In the case of the heart, the preload is the right atrial pressure . . ." (p. 376) |
"In the case of the heart, . . . the afterload is the aortic pressure." (p. 376) |
| Textbook of Physiology: Circulation, Respiration, Body Fluids, Metabolism, and Endocrinology (24) |
"The end-diastolic filling pressure or maximal diastolic volume (preload) is the most important determinant of stroke volume." (p. 973) |
"The second intrinsic factor that determines the stroke volume is the aortic pressure or afterload." (p. 974) |
| Physiology (3) |
"The force required to stretch the muscle . . . is called the preload. The term preload is also used to indicate the length of the sarcomere or muscle before contraction." (p. 43) |
"The afterload represents an impediment to the shortening of muscle fibers or to ejection in the heart. The afterload for the ventricles is the arterial pressure . . ." (p. 163) |
| Circulatory Physiology (28) |
". . . during diastole a greater influx of blood into the ventricle will cause the ensuing contraction to be more forceful. This may be thought of as a ‘preload’ stimulus since it was applied before contraction began." (p. 76) |
"He [Starling] also controlled the aortic pressure (or afterload) by means of an artificial aortic resistance." (p. 76) |
|
". . . he [Starling] controlled the right atrial pressure (and thereby the right ventricular diastolic pressure or preload) . . ." (p. 76) |
| Cardiovascular Physiology (22) |
"During diastolic ventricular filling, for example, the progressive increases in ventricular pressure and volume combine to increase muscle tension (T = P · r) . . ." (p. 55) |
"Systemic arterial pressure is often referred to as the ventricular afterload because it determines the tension which must be developed by cardiac muscle fibers before they can shorten." (p. 56) |
|
"End-diastolic pressure is referred to as ventricular preload because it sets the resting tension of the cardiac muscle fibers at the end of diastole." (p. 55) |
| Cardiovascular Physiology (1) |
". . . the preload refers to the stretch of the left ventricle just before the onset of contraction (the so-called end-diastolic volume) . . ." (p. 65) |
". . . and the afterload refers to the aortic pressure during the period when the aortic valve is open." (p. 65) |
| Physiology of the Heart and Circulation (18) |
"It is customary to refer to this length [just before contraction] in terms of the force or preload required to stretch the muscle to its precontraction length." (p. 77) |
"In summary, cardiac afterload . . . is the left ventricular myocardial force necessary to overcome opposition to ventricular ejection. In the clinical setting, as a rough index, it is frequently related to aortic pressure." (p. 177) |
| An Introduction to Cardiovascular Physiology (15) |
"To study the effect of stretch, the relaxed muscle is stretched to a known length by means of a small weight or preload . . ." (p. 78) |
"The afterload is the stress, S [force per unit cross-sectional area of wall], during systole, and from the statement S = Pr/2w we see that it depends not only on the arterial pressure but also on chamber radius and wall thickness." (p. 89) |
| Modern Cardiovascular Physiology (11) |
"This volume [end-diastolic volume] is often termed preload because it is a load applied to the muscle fibers before they contract." (p. 9) |
"This resistance [to outflow] is termed the afterload, since it is applied after contraction is initiated." (p. 11) |
| Cardiovascular Physiology (20) |
". . . the upper end of the muscle is anchored, and a weight (preload) is suspended from the lower end. The resting force is equal to the weight attached . . ." (p. 94) |
"The afterload on an intact ventricle is consequently not a simple quantity, and authorities do not agree on how it should be measured or expressed." (p. 118) |
|
"Preload, the force just prior to contraction (Chapter 3), is related in the ventricle to end-diastolic pressure." (p. 118) |
"The input impedance of the systemic or pulmonary arteries is the most appropriate measure of ventricular afterload, but it is complicated to analyze and takes the form of a frequency-dependent spectrum (Chapter 6). The choice is thus between a simple variable like mean aortic pressure, which is an indirect, partial representation of the real afterload, and the more complete but complicated analysis involving in computing impedance." (p. 118) |
| Clinical Cardiology (4) |
n/a |
"The Frank-Starling Law was established in animal studies in which a constant aortic pressure (afterload) and a constant contractility were maintained." (p. 23) |
| Fundamental Cardiovascular and Pulmonary Physiology (7) |
"The ventricle begins to contract . . . at a measurable end-diastolic pressure that represents the initial load of the ventricle or preload." (p. 73) |
"Ejection begins . . . and the ventricular pressure at this point (equal to aortic pressure) represents ventricular afterload." (p. 73) |
| Pathophysiology of Heart Disease (16) |
". . . the preload can be thought of as the amount of myocardial stretch at the end of diastole, just prior to contraction." (p. 195) |
"afterload: the ventricular wall tension during contraction; the resistance that must be over come in order for the ventricle to eject its contents. It is often approximated by the systolic ventricular (or arterial) pressure." (p. 196, Table 9.1)
"It [afterload] is more formally defined as the ventricular wall stress that develops during systolic ejection." (p. 196) |
|
"preload: the ventricular wall tension at the end of diastole. In clinical terms, it is the stretch on the ventricular fibers just prior to contraction, often approximated by the end-diastolic volume or end-diastolic pressure" (p. 196, Table 9.1) |
| Pathophysiology of Disease: An Introduction to Clinical Medicine (19) |
" ‘Preload’ is the amount of filling of the ventricle at end-diastole." (p. 227–229) |
"The impedance against which the heart must work is termed ‘afterload;’ increased afterload (aortic pressure for the left ventricle) will cause a decrease in stroke volume." (p. 227) |
| Cardiopulmonary System (25) |
"In terms of muscle performance, the preload is the stretch on a muscle fiber prior to contraction." (p. 39) |
"Aortic pressure (PAo, the afterload) . . ." (p. 39) |
| Harrison’s Online (10) |
"In the heart-lung preparation the stroke volume within limits correlates directly with the diastolic fiber length (preload) . . ." (Chap. 232) |
"In the intact heart the afterload may be defined as the tension or stress developed in the ventricular wall during ejection. Therefore, the afterload is determined by the aortic pressure as well as the volume and thickness of the ventricular cavity." (Chap. 232) |
|
". . . the stroke volume of the intact ventricle [is] determined by three influences: (1) the length of the muscle at the onset of contraction, i.e., the preload; . . ." (Chap. 232) |
|
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" . . . the tension that the muscle is called upon to develop during contraction, i.e., the afterload." (Chap. 232) |
| Integrated Medical Curriculum Online (13) |
"Preload is end diastolic volume (EDV)." |
"Afterload . . . can be defined as ‘the force the heart has to overcome to eject blood.’ " |
| Physiological Medicine: a clinical approach to basic medical physiology (17) |
"Preload is the venous pressure that results in filling of the heart in diastole." (p. 322) |
"Afterload is the pressure against which the heart must work to pump blood." (p. 322) |
| Human Physiology: From Cells to Systems (27) |
"The extent of filling is referred to as the preload, because it is the workload imposed on the heart before contraction begins." (p. 292) |
"The arterial pressure is referred to as the afterload because it is the workload imposed on the heart after the contraction has begun." (p. 294) |
| Physiology: A Review with Questions and Explanations (12) |
"The preload is the ventricular end-diastolic volume or pressure." (p. 83) |
"The third factor that determines stroke volume is the afterload, or pressure load, i.e., the total peripheral resistance. This is the load which the heart must pump against in order to eject blood, and its magnitude is best represented by the [arterial] diastolic pressure." (pp. 84–85) |
| Physiology (5) |
"The preload for the left ventricle is left ventricular end-diastolic volume, or end-diastolic fiber length; that is, the resting length from which the muscle contracts." (p. 127) |
"The afterload for the left ventricle is aortic pressure." (p. 127) |
| Physiology: An Illustrated Review with Questions and Answers (29) |
"Preload, the ventricular end-diastolic volume (or pressure), reflects how much the heart is stretched before contraction." (p. 45) |
"Afterload, the pressure against which the heart must pump to eject blood, is a function of the total peripheral resistance." (p. 45) |
| Blond’s Medical Guides: Physiology (8) |
EDV (or preload) is directly affected by the amount of blood that enters the ventricle while the heart is in diastole." (p. 156) |
"While afterload relates mainly to the blood pressures in the arteries . . ." (p. 157) |
| Taber’s Cyclopedic Medical Dictionary (30) |
preload. In cardiac physiology, the end-diastolic stretch of the muscle fiber. In the intact ventricle, this is approximately equal to the end-diastolic volume or pressure. (p. 1585) |
afterload. In cardiac physiology, the stress or tension that develops in the ventricular wall during systole. (p. 51) |
