MECHANISMS OF ADAPTATION OF THE LEFT VENTRICLE TO MUSCULAR EXERCISE

PEDIATRICS ◽  
1963 ◽  
Vol 32 (4) ◽  
pp. 660-670
Author(s):  
Jere H. Mitchell
Keyword(s):  
Cardiac Output ◽  
Left Ventricle ◽  
Stroke Volume ◽  
Pulse Rate ◽  
Individual Factors ◽  
Normal Male ◽  
Oxygen Intake ◽  
Mechanisms Of Adaptation ◽  
Male Subjects ◽  
Oxygen Difference

THE mechanisms of adaptation of the left ventricle to the demands of muscular exercise have intrigued cardiovascular physiologists for many years. Although highly complex, these adaptive mechanisms are more and more susceptible to analysis and quantification. In this presentation I will attempt to identify some of the individual factors which appear to be important in the response of the left ventricle to exercise, beginning with data obtained from experiments on conscious normal male subjects and proceeding to experiments performed on dog preparations in which individual factors were controlled and analyzed. The changes in oxygen intake, cardiac output, estimated arteriovenous oxygen difference, pulse rate and estimated mean stroke volume were determined in 15 normal male subjects during rest in the standing position and during treadmill exercise at the maximal oxygen intake level. Oxygen intake was obtained from the volume and composition of expired air, cardiac output by the dye dilution technique, and pulse rate from the electrocardiogram. Estimated arteriovenous oxygen difference was obtained by dividing the oxygen intake by the cardiac output (Fick principle) and estimated mean stroke volume by dividing the cardiac output by the heart rate. The data are shown in Figure 1. Oxygen intake increased from a mean value of 0.34 at rest to a maximal value of 3.22 L./min. The corresponding mean values for cardiac output were 5.4 and 23.4 L./min. and for arteriovenous oxygen difference were 6.5 and 14.3 ml./100 ml. Thus, as oxygen intake increased 9.5 times, the cardiac output increased 4.3 times and the arterio venous oxygen difference 2.2 times.

Biplane ventriculography in the rat

1986 ◽  
Vol 250 (1) ◽  
pp. H131-H136
Author(s):  
J. L. Heckman ◽  
L. Garvin ◽  
T. Brown ◽  
W. Stevenson-Smith ◽  
W. P. Santamore ◽  
...  
Keyword(s):  
Cardiac Output ◽  
Left Ventricle ◽  
Ejection Fraction ◽  
Stroke Volume ◽  
Methyl Methacrylate ◽  
High Speed ◽  
Water Displacement ◽  
Systolic Volume ◽  
End Diastolic Volume ◽  
End Systolic Volume

Biplane ventriculography was performed on nine intact anesthetized rats. Images of the left ventricle large enough for analysis were obtained by placing the rats close to the radiographic tubes (direct enlargement). Sampling rates, adequate for heart rates of 500 beats/min, were obtained by filming at 500 frames/s. From the digitized silhouettes of the left ventricle the following information was obtained (means +/- SE): end-diastolic volume 0.60 +/- 0.03 ml, end-systolic volume 0.22 +/- 0.02 ml, stroke volume 0.38 +/- 0.02 ml, ejection fraction 0.63 +/- 0.02, cardiac output 118 +/- 7 ml/min, diastolic septolateral dimension 0.41 +/- 0.01 mm, diastolic anteroposterior dimension 0.40 +/- 0.01 mm, diastolic base-to-apex dimension 1.58 +/- 0.04 mm. To determine the accuracy with which the volume of the ventricle could be measured, 11 methyl methacrylate casts of the left ventricle were made. The correlation was high (r = 0.99 +/- 0.02 ml E) between the cast volumes determined by water displacement and by use of two monoplane methods (Simpson's rule of integration and the area-length method applied to the analysis of the anteroposterior films) and a biplane method (area-length). These results demonstrate that it is possible to obtain accurate dimensions and volumes of the rat left ventricle by use of high-speed ventriculography.

In the Loop—Left Ventricular Pressures

2011 ◽  
pp. 42-47
Author(s):  
James R. Munis
Keyword(s):  
Heart Rate ◽  
Cardiac Output ◽  
Aortic Valve ◽  
Left Ventricle ◽  
Stroke Volume ◽  
Cardiovascular System ◽  
Aortic Root ◽  
Left Ventricular ◽  
Root Pressure ◽  
The Third

We've already looked at 2 types of pressure that affect physiology (atmospheric and hydrostatic pressure). Now let's consider the third: vascular pressures that result from mechanical events in the cardiovascular system. As you already know, cardiac output can be defined as the product of heart rate times stroke volume. Heart rate is self-explanatory. Stroke volume is determined by 3 factors—preload, afterload, and inotropy—and these determinants are in turn dependent on how the left ventricle handles pressure. In a pressure-volume loop, ‘afterload’ is represented by the pressure at the end of isovolumic contraction—just when the aortic valve opens (because the ventricular pressure is now higher than aortic root pressure). These loops not only are straightforward but are easier to construct just by thinking them through, rather than by memorization.

Circulatory and metabolic reactions to work in heat

1962 ◽  
Vol 17 (4) ◽  
pp. 625-638 ◽  
Author(s):  
C. G. Williams ◽  
G. A. G. Bredell ◽  
C. H. Wyndham ◽  
N. B. Strydom ◽  
J. F. Morrison ◽  
...  
Keyword(s):  
Heart Rate ◽  
Cardiac Output ◽  
Stroke Volume ◽  
Major Change ◽  
Oxygen Intake ◽  
Lower Oxygen ◽  
Submaximal Work ◽  
Metabolic Reactions ◽  
Work Up ◽  
Arteriovenous Difference

Oxygen consumptions were measured at various levels of work up to the individual's maximum. At submaximal work they were significantly lower in heat than in comfortable temperatures, but maximum oxygen intakes were not significantly different. In comfortable conditions cardiac output and A-V difference both contributed to rise in oxygen intake during submaximal work. At maximal effort increase in arteriovenous difference accounted for the ultimate rise in oxygen intake. Both heart rate and stroke volume contributed to increase in cardiac output up to 1.0 liters/min oxygen intake; above this heart rate was the sole factor. In heat the major change in hemodynamics was an increase in heart rate with an associated fall in stroke volume. Neither cardiac output nor arteriovenous difference was significantly altered from comfortable conditions. “Excess” lactate occurred at significantly lower levels of work in heat than in comfortable conditions. Working muscles were therefore relatively more anoxic in heat at submaximal work, and this accounted for lower oxygen intakes. At maximal work the degree of anoxia was the same in both temperature conditions. Submitted on August 22, 1961

Haemodynamics in Patients with Phaeochromocytoma

1980 ◽  
Vol 58 (5) ◽  
pp. 349-356 ◽  
Author(s):  
J. A. Levenson ◽  
M. E. Safar ◽  
G. M. London ◽  
A. CH. Simon
Keyword(s):  
Cardiac Output ◽  
Essential Hypertension ◽  
Blood Volume ◽  
Total Peripheral Resistance ◽  
Peripheral Resistance ◽  
Normal Male ◽  
Hypertensive Patients ◽  
Normal Limits ◽  
Male Patients ◽  
Male Subjects

1. Cardiac haemodynamics were studied in 14 male patients with phaeochromocytoma, in comparison with 33 normal male subjects and 65 males with essential hypertension. 2. At the time of the investigation, seven patients with phaeochromocytoma were hypertensive and seven were normotensive. Cardiac output was within normal limits. Total peripheral resistance was elevated in the hypertensive patients. Heart rate was elevated both in the normotensive and in the hypertensive patients, but decreased after surgical treatment. 3. The relationships between blood volume and blood pressure and between blood volume and cardiac output were the same as those observed in the control groups. 4. During tilt, a predominant systolic orthostatic hypotension was observed and was associated with decreased stroke volume and impaired adaptation of total peripheral resistance during tilt, indicating inadequate arteriolar and venous reflexes. 5. The study suggested that, except for tachycardia, the haemodynamic pattern of patients with phaeochromocytoma and with essential hypertension was nearly the same.

Relative effects of fat-, carbohydrate- and protein-containing liquid diets on cardiac output in healthy adult subjects

1992 ◽  
Vol 83 (4) ◽  
pp. 483-487 ◽  
Author(s):  
Susan K. Hawley ◽  
Kevin S. Channer
Keyword(s):  
Blood Pressure ◽  
Cardiac Output ◽  
Stroke Volume ◽  
Pulse Rate ◽  
Healthy Adult ◽  
Nutritional Composition ◽  
Significant Rise ◽  
Mean Blood Pressure ◽  
Carbohydrate Diet ◽  
Liquid Meal

1. Nine healthy adult subjects consumed four types of proprietary liquid diet of similar volume and calorific value but of different nutritional composition. The effects on resting cardiac output, mean blood pressure and pulse rate were measured. 2. A significant rise in cardiac output occurred with the balanced, protein and carbohydrate diets but not with the fat diet. The greatest rise was seen with the balanced diet. Water alone had no effect on cardiac output. 3. The average time taken to reach peak cardiac output was shortest with the carbohydrate diet and longest with the fat diet. 4. The increases in cardiac output resulted from a rise in both pulse rate and stroke volume. The carbohydrate diet produced the most sustained rise in pulse rate but the least sustained elevation in stroke volume. 5. No significant changes were seen in mean blood pressure when each liquid meal was compared with water. 6. Our data show that the increase in cardiac output with liquid ingestion is related to the dietary components. These effects are additive.

The Blood Pressure of Giraffes

2021 ◽  
pp. 187-215
Author(s):  
Graham Mitchell
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Blood Flow ◽  
Cardiac Output ◽  
Hydrostatic Pressure ◽  
Left Ventricle ◽  
Stroke Volume ◽  
Body Mass ◽  
The Brain ◽  
Very High

As discussed in this chapter, giraffes have, compared with any other mammal, a very high mean blood pressure of ~250 mmHg. Human blood pressure is ~90 mmHg. Its size is determined by the length of the neck, the height of the head above the heart, by hydrostatic pressure generated by gravity acting on the column of blood in the carotid artery, and contractions of the heart muscles: blood pressure must be high enough to ensure that blood reaches the brain. Uniquely in giraffes blood pressure is regulated by receptors that are located in both the carotid and occipital arteries. Once thought to be ~2.5% of body mass the heart is smaller (~0.5% of body mass) but its muscle walls, especially of the interventricular wall and left ventricle wall, are exceptionally thick (up to 8 cm). The relative cardiac output is the same as in other mammals (~5 L 100 kg–1 of body mass) through a combination of a higher than predicted heart rate (70 b min–1 vs 50 b min–1) and smaller than predicted stroke volume (~0.7 ml kg–1 body mass vs 1.2 ml kg–1). Stroke volume is small because the left ventricle muscle wall is thick. The origin of high blood pressure is the resistance to blood flow, which is about twice what it is in other mammals. The higher resistance results from a combination of the thick muscular walls and narrow lumens of a giraffe’s blood vessels and unique mechanisms that regulate blood flow to the brain.

Influence of age and sex on exercise cardiac output

1965 ◽  
Vol 20 (5) ◽  
pp. 938-947 ◽  
Author(s):  
Margaret R. Becklake ◽  
H. Frank ◽  
G. R. Dagenais ◽  
G. L. Ostiguy ◽  
Carole A. Guzman
Keyword(s):  
Heart Rate ◽  
Sex Differences ◽  
Cardiac Output ◽  
Stroke Volume ◽  
Age Differences ◽  
Normal Subjects ◽  
Age Effect ◽  
Oxygen Pulse ◽  
Oxygen Difference ◽  
Age And Sex

Exercise cardiac output has been measured by an indirect Fick technique in 94 normal subjects (48 men and 46 women) whose ages ranged from 20 to 85 years. With increasing age, exercise cardiac output was found to be greater despite no such trend in oxygen uptake; in consequence, exercise arteriovenous oxygen difference decreased with age. These trends were seen in both sexes, though the age effects were apparent a decade earlier in men. In addition, in men the heart rate was lower and stroke volume higher with increasing age. By contrast, no age effect on exercise pulse rate was noted in women. When the sexes were compared, exercise cardiac output was higher in women of the younger two decades (20 to 39 years), a difference which was not apparent in subsequent decades. sex differences in exercise cardiac output; age differences in exercise cardiac output; stroke volume during exercise; oxygen pulse during exercise Submitted on January 13, 1965

Cardiac function and morphology with aging in the spontaneously hypertensive rat

1979 ◽  
Vol 237 (4) ◽  
pp. H461-H468 ◽  
Author(s):  
J. M. Pfeffer ◽  
M. A. Pfeffer ◽  
M. C. Fishbein ◽  
E. D. Frohlich
Keyword(s):  
Cardiac Output ◽  
Left Ventricle ◽  
Stroke Volume ◽  
Right Ventricle ◽  
Cardiac Function ◽  
Spontaneously Hypertensive Rat ◽  
Left Ventricular ◽  
Ether Anesthesia ◽  
Spontaneously Hypertensive ◽  
The Right

To determine the effects of a chronic pressure load on cardiac function and morphology, spontaneously hypertensive rats (SHR) and two normotensive strains of Wistar rats (WKY and NWR) were studied under ether anesthesia at 13, 25, 52, and 90 wk of age. Although resting cardiac index of the SHR was comparable to that of WKY and NWR at all ages, the peak cardiac output and peak stroke volume per gram of left ventricle determined during a rapid intravenous infusion of Tyrode solution was markedly reduced in the SHR only at 90 wk of age. Autonomic inhibition did not alter the peak stroke volume attained, but reduced peak cardiac output at all ages in each of the strains. Absolute left ventricular dimensions in the SHR increased out of proportion to body growth, consistent with concentric hypertrophy. As peak pumping ability markedly declined from 52 to 90 wk of age in the SHR, the free wall of the left ventricle greatly thickened whereas the septum remained unchanged. At this time the right ventricle also hypertrophied. This disproportionate thickening of the walls of the left ventricle and the hypertrophy of the right ventricle were reflected in measurements of their fiber diameters. These alterations in ventricular architecture may contribute to the decrease in pumping ability observed in long-standing hypertension.

Cardiovascular response to graded exercise in the sympathectomized-vagotomized dog

1963 ◽  
Vol 204 (2) ◽  
pp. 291-296 ◽  
Author(s):  
Edmundo Ashkar ◽  
William F. Hamilton
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Cardiac Output ◽  
Oxygen Consumption ◽  
Mean Arterial Pressure ◽  
Stroke Volume ◽  
Cardiovascular Response ◽  
Peripheral Resistance ◽  
Graded Exercise ◽  
Oxygen Difference

Seven dogs who ran well on a motor-driven treadmill were completely sympathectomized (including adrenal denervation) and subjected to unilateral vagotomy below the recurrent laryngeal branch. After recovery and retraining, a terminal experiment was performed in which, after completing the vagotomy, direct Fick determinations of cardiac output and continuous recordings of mean arterial pressure, heart rate, and oxygen consumption were made at rest and during increasing exercise The results were compared with those described by Barger et al. ( Am. J. Physiol. 184: 613, 1956) for normal dogs running at smaller speeds and grades. The heart rate of the operated dogs increased from 117 to 134. Barger's normal dogs doubled their heart rate. The A-V oxygen difference increased with work slightly less than Barger's normal dogs but the scatter in both groups was wide, as was the case with the stroke volume. The resting cardiac output was nearly normal in the operated dogs but increased only 34% with exercise, as against 200–300% in Barger's normals. Oxygen consumption increased about twofold as against the expected normal of three- to sevenfold. Peripheral resistance in both groups went down about 40%. The blood pressure in the normal increased substantially while that in the operated dogs fell about 20% to an average of 60 mm Hg.

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