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Effect of Plethora and Hemorrhage on Left Ventricular Volume and Pressure By J. P. HOLT, M.D., PH.D. With the collaboration of J. Allensworth, J. Diana, David Collins and Jfelga Kines By combining conventional methods for recording pressures from the left ventricle and pleural cavity with a new procedure for estimating end-diastolic volume (EDV) and end-systolic volume (ESV) of the left ventricle it was found in the closed-chest dog that plethora increased EDV, ESV and stroke volume while hemorrhage had the opposite effect. There were linear relationships between EDV and ESV, and between EDV and stroke volume. There was little change in left ventricular "effective" end-diastolic pressure when the EDV changed over a wide range, beginning with the smallest EDV consistent with life; but after a certain large EDV had been reached, large increases in effective end-diastolic pressure were associated with little or no further increase in EDV. Downloaded from http://circres.ahajournals.org/ by guest on May 8, 2017 mental conditions.5 It was hoped that the studies described here would bring evidence to bear on these points. W ITH the development of the electric conductivity method for estimating enddiastolic volume (EDV), end-systolic volume (ESV), and stroke volume of the left ventricle,1 it became of interest to determine the relationship between these factors and other circulatory factors in dogs subjected to a wide variation of EDV, ESV, and stroke volume such as occurs following plethora and hemorrhage. Since the applicability of Starling's law2 has never been studied in the intact, closedchest animal by measuring the volume of an individual ventricle, it was desirable that these studies be carried out. Although it is generally agreed that Starling's law of the heart is an important concept describing one of the basic properties of heart muscle, evidence has been presented in recent years that under certain circumstances other factors may at times play an important role in the regulation of the heart's contraction.3 Kor instance the tone of the heart muscle may change,4 and the heart may operate at one energy level at one time and at another level under different environ- METHODS hi the anesthetized closed-chest dog (morphine, dial urethane,* phenobarbital), a large radio-opaque ureteral catheter was passed through the carotid artery and the ascending aorta into the left ventricle in such a manner that the tip of the catheter lay approximately in the middle of the ventricular chamber. A single lumen electric conductivitycatheter,1 containing the electric conductivity cell at the end of the catheter, was passed through the other common carotid artery into the ascending aorta within a few millimeters of the aortic valve. In some cases a double lumen electric conductivity catheter,1 was similarity introduced so that one of the catheter tips lay in the ventricular cavity and the other in the ascending aorta near the aortic valve. Their location was judged by the form of pressure tracings obtained with a Statham strain gage, and were verified at autopsy. Use of a fluoroscope was not found necessary. The EDV, ESV, and stroke volume of the left ventricle were determined as previously described. Approximately 1.5 ml. of 4 per cent NaCI solution were injected "instantaneously" into the left ventricle and the electric conductivity of the blood in the archof the aorta was measured. A continuous record of the pressure within the left ventricle was recorded by means of either a Brush electromagnetic ink-writing oscillograph or a Hathaway photographic oscillograph using a Brush amplifier. While ventricular pressure recording was discontinued for approximately 1 sec. the 4 per cent NaCI solution was injected "instantaneously" into From the Institute for Medical Research, University of Louisville, Louisville, Ky. This work was supported in part by grants from the National Heart Institute, USPHS, and the American, Kentucky and Louisville Heart Associations. A preliminary report of this work was presented at the meeting of the American Heart Association in Cincinnati, Ohio, on October 29, 1956. Received for publication January 29, 1957. * Kindly supplied by Ciba Pharmaceutical Products, Inc. 2/3 Circulation ifrsroyrh, I'olutne V. Mar/ /fl.i~ 274 PLETHORA AXD HEMORRHAGE ON LEFT VENTRICULAR VOLUME ANO PRESSURE Downloaded from http://circres.ahajournals.org/ by guest on May 8, 2017 the left ventricle. Immediately following this injection the pressure within the ventricle was recorded for several seconds. In this way a record of intraventricular pressure was obtained at the time of the measurement of the EDV. Intrapleural pressure was usually measured by means of a metal cannula inserted between the ribs over the left side of the heart and connected to a Statham strain gage and recorded as described. In some cases a small polyethylene tube was passed into the pleural space through the lumen of a blunt 15-gage needle. "Effective" pressure within the left ventricle was calculated by subtracting the intrapleural pressure from the intraventricular pressure. Femoral arterial pressure was measured with a strain gage and recorded as described above. The areas of pressure curves were obtained by means of a planimeter. Stroke work was calculated in the usual manner using the average of left ventricular systolic pressure and femoral diastolic pressure. In some experiments, several determinations of effective intraventricular pressure and EDV were made at 5 or 10 min. intervals. Following this, plethora was induced by means of rapidly infusing into the femoral vein, in a period of approximately 5 min., a large volume of blood from a donor dog. Immediately following this, several determinations of effective ventricular pressure and EDV were made at approximately 5 min. intervals. In another series of experiments a state of plethora was induced by infusing a mixture of the dog's blood with 5 per cent dextran*-saline solution in an amount equal to 8 per cent of the dog's body weight. This blooddextran mixture was prepared by infusing a 5 per cent dextran-saline solution into the dog in an amount equal to 2?s per cent of the dog's body weight and allowing the dextran solution to mix with the. clog's blood in vivo. A few minutes later the dog was bled an amount equal to the injected solution. This procedure was carried out three times until all of the dextran solution had been mixed with the dog's blood in vivo. This gave a total amount of withdrawn blood-dextran mixture equal to S per cent of the dog's body weight. Plethora was then induced by infusing all of this blood-dextran mixture into the animal at one time. It was desirable to induce plethora in this manner, because a change in the per cent of plasma in the blood produces a change in the calibration factor of the electric conductivity measurement used in determining the EDV. Because of the. large volume of dextran solution infused, the average per cent concentration of plasma in the blood was quite high in all experiments, the average being 78.5 per cent plasma. Before and immediately following the infusion of the blood-dextran solution the EDV, ESV, stroke volume and pressure determinations were repeated several times; the animal * Kindly supplied by the Commercial Solvents Corporation. was then bled approximately 250 ml. and the determinations repeated several times. The bleedings were repeated, carrying out two or more determinations of EDV, and effective intraventricular pressure after each determination, until the animal was bled to death. RESULTS Relationship Between EDV and End-Diastolic Ventricular Pressure. We have carried out 154 simultaneous determinations of "effective" end-diastolic pressure (EEDP) or intraventricular end-diastolic pressure (EDP) and EDV in 12 dogs. In 3 dogs left ventricular EDV determinations were made in the control state and after infusing several hundred milliliters of blood from a donor dog. In 9 dogs the studies were carried out in the control state, after infusing a dextran-blood mixture in an amount equal to 8 per cent of the body weight, and after each of several hemorrhages until the animal was bled to death. Examples of the results in individual animals are given in figures \A, B, C. Each figure gives the results of all the determinations on an individual animal. In figure 1/1, it is seen that although the EDV changed greatly there was no consistent change in EDP; there were random variations but it remained constant, or increased slightly, even though the EDV changed several fold. In figure IB, it is seen that with the smallest EDV consistent with life, EEDP was the same or slightly less than it was when the EDV was several times larger. After a certain large EDV was reached EEDP increased greatly with no consistent change in EDV. In figure \C, it will be noted that as the EDV increased several fold from its lowest value up to a certain point, there was some increase in EEDP; beyond this point there was no consistent change in EDV although EEDP increased greatly. In all animals studied, beginning with the smallest EDV consistent with life, there was either no change or a slight increase in EEDP or EDP while the EDV increased several fold; in 8 of 12 animals studied, after a certain large value of EDV was reached, a further small increase in EDV was associated with a very large increase in EEDP or EDP. It will be noted in figure \C, that immedi- 275 HOLT One Dog 60 H One Dog 1 1 H- X E 40 Q. Q 20 Downloaded from http://circres.ahajournals.org/ by guest on May 8, 2017 0 I OneDog 40 E a. 20 Q H.O t-0.5 N -0.5 -1.0'0 20 40 60 80 100 120 140 EDV(ml.) 160 10 20 30 40 50 60 70 EDV(ml.) FIG. 1. /I, B, C, D. Relationships between end-diastolic (EDP) effective end-diastolic (EEDP) pressures and blood volume as ordinates to end-diastolic volume (EDV) as abscissa under conditions described. E, F, G, H. Relationships of end-systolic volume (ESV), stroke volume, pressure and stroke work as ordinates to end-diastolic volume (EDV) as abscissa under conditions described. ately following the infusion (point 1) the EEDP was at its highest value (41 mm. Hg) and this was associated with an EDV of 79 ml., while 20 min. later and after bleeding 300 ml. of blood (point 4) the EEDP was lower (16 mm. Hg) but the EDV was larger, namely 112 ml. Results similar to this were obtained in 10 of 12 dogs. Although the reason is not well understood a possible explanation is that, immediately following the infusion into the venous system, the right ventricle is greatly distended under a high pressure and because of the relatively inelastic pericardium the right ventricle imposes on the left and prevents the left ventricle from increasing further in volume; after .15 or 20 min., or after hemorrhage, a redistribution of blood takes place with the right ventricle decreasing in volume, thus allowing the left ventricle to increase its EDV. Relationship Between EDV and Blood Volume. Although the blood volume was not measured in these experiments the relative blood volume was estimated to be the control blood volume plus the amount of fluid infused or minus the amount hemorrhaged. Results similar to those shown in figure ID, were obtained in 8 of 9 experiments. It is seen that as the estimated blood volume decreased the end-diastolic volume decreased. Relationship Between EDV and ESV. The results of a typical experiment are shown in figure IE. As the EDV increased the ESV 27G PLETHORA AND HEMORRHAGE OX LEFT VENTRICULAR VOLUME AX I) PRESSURE Relationship Between EDV and Systolic Pressure, Diastolic Pressure, and. Pulse Pressure. The results of a typical experiment showing ESV = 0.V2EDV - 0.43 the relationship between left ventricular systolic pressure and EDV in one animal are The standard deviation of ESV from the shown in figure .1(7. It will be noted that as regression of ESV on EDV in this experiment the EDV increased from a minimal value there was ±2.5 ml. The equations of the lines, in was an increase in systolic pressure; after a the 12 dogs studied, calculated by the method certain large value of EDV was reached of least squares with the standard deviation of further increase in EDV was associated with no ESV from the regression of ESV on EDV are consistent change in systolic pressure. Results given in table 1. similar to these were obtained in all 12 dogs. Relationship Between ED V and Stroke Volume Similar results were obtained for femoral (S). The results of a typical experiment are diastolic pressure and femoral pulse pressure, shown in figure l/<\ As the EDV increased the as well as for total femoral arterial pressure stroke volume increased in a linear fashion area per heart beat. having the equation: Relationship Between EDV and, Stroke Work. S = 0.38 EDV + 0.38 The results of a typical experiment are shown The standard deviation of the stroke, <S, from in figure Iff. As the EDV increased the stroke the regression of the stroke on EDV in this work increased until a certain large value for experiment was ±2.4 ml. The equation of the stroke work was reached, beyond this point lines, in all dogs studied is given in table 1. further increase in EDV was associated with little or no increase in stroke work. Results similar to this were obtained in all but a few TABLE 1.—Results of Experiments Shoxoinij a Linear Relationship Between ESV and EDV, and Stroke dogs, and in these dogs the stroke work conVolume and EDV tinued to increase over the entire range of the end-diastolic volumes and the point was not Equation Equation DOR ESV --= m(EDV) + b S = m(EDV) + b reached where stroke work remained constant but the end-diastolic volume continued to in b s b m 5" * (K-K.) (±) (±) increase. Relationship Between ES\' and, "Effective" 4.5 0.50 -15.2 2 10.9 0.50 16.0 4.5 3.7 0.29 20.0 0.73 - 5 . 9 5.1 3.S 3 End-Diastolic Pressure. There was no con4 27.1 0.S4 - 9 . 5 4.3 0.15 10.1 4.3 sistent relationship between "effective" end 16.7 0.62 1.5 10.5 0.36 - 0 . 3 9.4 0 diastolic pressure and ESV, there being con6.2 10 15.5 0.51 3.9 0.49 - 6 . 2 2.9 siderable scatter of the data. 11 5.1 0.67 -10.2 5.4 16.5 0.32 10.0 16.3 0.64 12 4.5 0.37 -6.S Relationship Between Ventricular Residual 5.5 5.0 - 0 . 2 5.7 5.7 0.42 .18.7 0.57 13 1.5 Fraction and Blood, Volume. The results ob18.0 0.71 - 3 . 3 3.0 5.7 0.30 14 5.7 tained in one dog are shown in figure 2/1. 13.2 0.47 2.1 2.9 0.52 -2.S 2.S 15 As the blood volume increased the fraction of 2.2 2.2 0.35 6.9 20.9 0.64 -2.4 16 the EDV retained at the end of each beat 0.4 2.4 17 14.8 0.62 -0.4 2.5 0.38 (Cn/C-i) decreased. Results similar to this were Avgs. 18.2 0.60 + 1.0 +5.0 0.40 -1.7 ±4.5 obtained in 10 of 12 dogs. Relationship Between Ventricular Residual Under the equation of the line relating ESV and Fraction and Systolic Pressure, Diastolic PresEDV are listed for each experiment the values of the sure, and Pulse Pressure. The results of a typical slope of the line, m, the intercept of the line, b, on the ESV axis and the standard deviation, s, of ESV experiment on one animal are shown in figure from the regression of ESV on EDV. The data relatIB. It will be noted that as the ventricular ing stroke volume, S, to EDV is treated in a similar systolic pressure increased the fraction of the manner. In all of the above equations EDV, ESV, EDV retained at the end of each beat decreased. and stroke volume are expressed in ml. See text for further discussion. Results similar to this were obtained in 11 of increased in a linear fashion having the equation : Downloaded from http://circres.ahajournals.org/ by guest on May 8, 2017 HOLT 277 + 2.0 One Dog a> +1.0 E Blood Voh 3 N -1.0 -2.0 -+• One Dog X E 150 Downloaded from http://circres.ahajournals.org/ by guest on May 8, 2017 100 50 0.2 0.4 0.6 0.8 1.0 Residual Fraction FIG. 2. A . Relationship between estimated blood volume and loft ventricular residual fraction. The residual fraction, average value of C,,/Cn-t, obtained in each electric conductivity determination. A', Control animal. H. Relationship between left ventricular peak systolic pressure and residual fraction. 12 dogs. Similar results were obtained when 0,,/C-i was plotted against femoral diastolic pressure and femoral pulse pressure in most of the animals studied. Relationship Between Ventricular Residual Fraction and Stroke Work. As the stroke work increased the residual fraction decreased. Jn G of 12 experiments the relationship appeared to be linear while in the remaining half of the experiments there was considerable scatter of the data. Relationship Between Stroke Work and "Effective" I'Jnd-Diastolic Pressure. The results of a typical experiment are shown in figure 3/1. It will be noted that as the stroke work increased several fold from a low value there was a small increase in the EED.P; after a certain value of EKJDP was reached further increase of EISDP was associated with a small increase or no change in stroke work. Results similar to this were obtained in 4 of 7 dogs; in the remaining 3 of the 7 dogs a small increase in EEDP was associated with a large increase in stroke work, and the point was not reached where a further increase in EEDP 0 20 40 60 80 100 Stroke Work (gram.) FJG. 3. A. Relationship between stroke work and left ventricular "effective" end-diastolic pressure, li. Relationship between loft ventricular peak systolic pressure and stroke work. C. Relationship between planimetered femoral arterial pulse pressure area and stroke work. Xote the approximately linear relationship. Equation of the line is shown in the figure. W, Stroke work. was associated with little or no change in stroke work. Relationship Between Stroke Work and Systolic Pressure, Diastolic Pressure, and Mean Arterial Pressure. As the stroke work increased the systolic pressure increased as shown in figure 3B. Results similar to this were obtained in all 12 experiments. A similar relationship 278 PLETHORA AND HEMORRHAGE OX LEFT VENTRICULAR VOLUME AND PRESSURE 250 Downloaded from http://circres.ahajournals.org/ by guest on May 8, 2017 20 30 Stroke (ml.) FIG. 4. Relationship between left ventricular peak systolic pressure and stroke volume. Note that as the stroke volume increases the pressure increases but after a certain large pressure is reached further increase in stroke volume is associated with little or no increase in pressure. was found between stroke work and mean arterial pressure and diastolic pressure. When the data in figure 3B was plotted on semi-log paper, with the stroke work plotted on the logarithmic scale and the systolic pressure plotted on the linear scale, there appeared to be a linear relationship between the log of the stroke work and the systolic pressure. Relationship Between Stroke Work and Planimetered Pulse Pressure Area -per Beat. As the stroke work increased the pulse area per beat increased in a linear fashion, as shown in figure 3C. Results similar to this were obtained in 11 of 12 experiments. Relationship Between Stroke Volume and Systolic Pressure, Diastolic Pressure, and Pulse Pressure. The results of a typical experiment in one dog are shown in figure 4. It will be noted that as the stroke volume increased the left ventricular systolic pressure increased markedly; after a certain large value for stroke volume was reached further increase in stroke volume was associated with little or no increase in systolic pressure. Results similar to this were obtained in all 12 dogs. Similar results were obtained in most experiments when stroke volume was plotted against femoral diastolic pressure and femoral pulse pressure. DISCUSSION It is clear, I believe, from the results obtained when the EDV and the EEDP or EDP were measured simultaneously in an animal subjected to plethora and hemorrhage, that the EDV may vary over a wide range with either no change or a slight increase in the EEDP distending the ventricle. It would appear from these results that up to a point the left ventricle behaves as a flaccid bag and that its volume may change with little or no change in its distending pressure. This view is supported to some degree by the results obtained by Rushmer and Thai6 which show no consistent relationship between effective filling pressure and cross section of the left ventricle in diastole. After a certain large volume is reached the ventricle appears no longer to behave as a flaccid bag, but behaves as if its walls were more or less rigid; and therefore the EDV remains constant even though the distending pressure increases greatly. Under these circumstances one or more of the following may have occurred: (1) The tone of the left ventricular muscle may have increased; (2) the ventricular muscle may have been stretched to its elastic limit; (3) the ventricle and other chambers of the heart may have increased to the point where the inelastic pericardial membrane supported the ventricular walls in such a manner that they behaved as if they were rigid; (4) the right ventricle may in some way have affected the volume of the left ventricle. That the ventricle was not stretched to its elastic limit is suggested by the earlier work of Evans and Matsuoka7 and Kunos on the heart-lung preparation. The view that the pericardium may restrict the ventricles from expanding beyond a certain point is supported by the recent work of Berglund and co-workers9 who have presented evidence that in the openchest dog when the left ventricle was stressed and caused to dilate, the right, ventricle function curve was lowered. Removal of the pericardium abolished this effect of the left ventricle on the right ventricle. The fact that immediately following infusion the EEDP was high but the EDV was small compared to the EDV a short time later (or after a small 279 HOLT Downloaded from http://circres.ahajournals.org/ by guest on May 8, 2017 hemorrhage) when it was lower, suggests that either the tone of the left ventricle changed or the right ventricle in some way affected the EDV of the left ventricle. Further experiments are necessary to clarify this matter. In particular, it is desirable to cany out similar studies on animals before and after removal of the pericardium, in order to ascertain the role played by the pericardium; and to carry out studies similar to those described here on the right ventricle and simultaneously on both ventricles. Since the right and left atria, as well as the right and left ventricles, are contained within the pericardium, consideration must be given to what effect the atria have on the ventricular volumes and pressures. The data on estimated blood volume, EDV, ESV, and stroke volume indicate that as blood volume increases the EDV, ESV, and stroke volume increase, and as blood volume decreases these factors decrease. It is desirable that studies be carried out in which blood volume is accurately measured simultaneously with the determination of EDV, ESV, and stroke volume. The fact that the EDV, stroke volume, and stroke work may vary over a wide range with either no increase or a slight increase in EEDP and that after a certain large EDV, stroke volume or stroke work is reached there may be large variations in EEDP with little change in EDV, stroke volume or stroke work indicates that in the closed-chest dog neither the useful work nor the energy of myocardial contraction are related to the EEDP. This view is given further support by the fact that in 10 out of 12 experiments immediately following the development of plethora the EEDP or EDP was higher than it was 15 or 20 min. later, but the EDV immediately following the development of plethora was smaller than it was 15 or 20 min. later when the EEDP was lower. Our results which show that the stroke work may vary over a wide range with only a small increase in EEDP and that after a certain large stroke work is reached there may be large variations in EEDP with little change in stroke work are in general agreement with the results obtained by Sarnoff and Berglund6 in (he open-chest dog, except that in their experiments the increase in stroke work, beginning with the smallest stroke work, was at times associated with a greater increase in left ventricular distending pressure; and our data differs to some degree from the data of Ullrich and Kramer10 on the pressure-volume curves of the left ventricle in the open-chest dog which show that for a given increase in EDV, beginning with the smallest EDV, there is generally a considerable increase in left intraventricular pressure. The reason for the small difference between our data and that of the above workers is not perfectly clear, but it may well be that the difference is due to the fact that our experiments were carried out in the closed-chest dog, while theirs were carried out in the open-chest dog. This view is given support by the fact that in the studies of Berglund,11 relating stroke work to "effective" mean left atrial pressure in the dog after closure of the chest and with the pericardium intact, the results obtained were similar to those of our experiments. It may well be that the functioning of the left ventricle differs in the openchest animal from that of the closed-chest animal. The fact that there is a decrease in the fraction of the EDV that is retained by the ventricle with each stroke as the blood volume, systolic pressure, diastolic pressure, pulse pressure, stroke work, stroke volume, and ESV increase is explained by the fact that the ventricle is never able to completely empty itself, and the fact that as the EDV increases the ESV increases. For after a severe hemorrhage the EDV and stroke volume are small, and since a certain minimum ESV is always retained by the ventricle, the fraction of the EDV retained by the ventricle at the end of systole is large after hemorrhage; while when the EDV is large, the ESV and stroke volume are large and the fraction of the EDV retained after each stroke is small. SUMMARY In the anesthetized closed-chest animal the effects of plethora and hemorrhage on the end-diastolic volume (EDV), end systolic volume (ESV), stroke volume and other circulatory factors were studied. Increase in 280 'LKTHORA AND HKMORRHAGE OX LEFT VENTRICULAR VOLUME AND PRESSURE Downloaded from http://circres.ahajournals.org/ by guest on May 8, 2017 blood volume resulted in an increase in enddiastolie volume, end-systolic volume, stroke volume, stroke work, and arterial pressure, and a decrease in the traction of the end-diastolic volume retained at the end of systole. A decrease in blood volume had the opposite effect. It was shown that there was little change, or a slight increase, in "effective" end-diastolic pressure when the end-diastolic volume increased several fold, beginning with the smallest end-diastolie volume consistent with life. After a certain large value of enddiastolic volume was reached the "effective" end-diastolic pressure increased greatly with little or no change in end-diastolic volume. Equations showing the linear relationship between end-diastolic volume and end-systolic volume and between end-diastolic volume and stroke volume are given. vite e que, post ciue un certe alte valor del volumine termino-diastolic esseva attingite, le "effective" pression termino-diastolic se augmentava grandemente con pane o nulle alteration in le volumine termino-diastolic. Es presentate equationes que demonstra le relation linear inter le volumine termino-diastolic e le volumine termino-systolic e inter le volumine termino-diastolic e le volumine per pulso. 1 2 I am indebted to Dr. 0. \V. Shadle for his participation in the measurement of the pressure in many of these experiments. SUMMAUK) IX IXTEHLINGUA in anesthesiate animates a thorace clauditc, le elTectos esseva studiate c[lie plethora e hemorrhagia exerce super le volumine terminodiastolie, le volumine termino-systolic, le volumine pulsatile, e altere factores circulatori. Augmento de volumine sanguinee resultava in un augmento del volumine termino-diastolic, del volumine termino-systolic, del volumine per pulso, del labor pulsatile, e del pression arterial e in un reduction del fraction del volumine termino-diastolic que es retenite al tin del systole. Un reduction del volumine de sanguine habeva le effecto contrari. Esseva monstrate que il occurreva pane alteration o leve grados de augmento in le "effective" pression terminodiastolic quando le volumine termino-diastolic esseva augmentate per plure vices le plus basse valor initial sufh'cientc pro le mantenentia de PATTERSON, S. \V., PIPER, If., AND STARLING, I'J. H.: The regulation of the heart beat. .1. Physiol. 48: 465, 1914. 3 HAMILTON, W. F.: The Lewis A. Connor Memorial Lecture: The physiology of the cardiac output. Circulation 8: 527, 1953. 4 ACKNOWLEDGMENT REFERKXCI'K HOLT, .1. P.: Estimation of the residual volume of the venti'icle of the dog's heart by two indicator dilution technics. Circulation Research 4: IS7, 1956. KATZ, A. M., KATZ, L. X., AND WILLIAMS, F. L.: Registration of left ventricular volume curves in the dog with the systemic circulation intact. Circulation Research 3: 5SS, 1955. 5 SAHNOKF, S. J. ANC BERGLUND, E.: Ventricular function, Starling's law of the heart studied by means of simultaneous right and left ventricular function curves in the dog. Circulation 9: 706, 1954. c RUSIIMEK, R. F. AND TIIAL, X.: Factors influencing stroke volume: A cinefluorographic study of angiocardiography. Am. .1. Physiol. 168: 509, 1952. 7 EVANS, C. L. AND -MATSUOKA, Y.: The effect of various mechanical conditions on the gaseous metabolism and efficiency of the mammalian heart. .1. Physiol. 49: 378, 1915. s KUNO, Y.: The significance of the pericardium. 9 BERGLUND, E., SARNOFK, S. .)., AND ISAACS, J. P.: .1. Physiol. 50: 1, 1915-16. Ventricular function, role of the pericardium in regulation of cardiovascular hemodynamics. Circulation Research 3: 133, 1955. 10 ULLRICH, K. ,!., RIECKER, O., AND KRAMER, K.: Das Druckvolumdiagramm des Warmblueterhcrzens. Arch. ges. Physiol. 259: 4S1, 1954. 11 BERGLUND, E.: The function of the ventricles of the heart. Actn physiol. scandinav. 33: Supp. 119, 1955. Effect of Plethora and Hemorrhage on Left Ventricular Volume and Pressure J. P. HOLT, J. Allensworth, J. Diana, David Collins and Helga Kines Downloaded from http://circres.ahajournals.org/ by guest on May 8, 2017 Circ Res. 1957;5:273-280 doi: 10.1161/01.RES.5.3.273 Circulation Research is published by the American Heart Association, 7272 Greenville Avenue, Dallas, TX 75231 Copyright © 1957 American Heart Association, Inc. All rights reserved. Print ISSN: 0009-7330. 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