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Hemodynamics at rest and during supine and sitting bicycle exercise in normal subjects
Hemodynamics at Rest and During Supine and Sitting Bicycle Exercise in Normal Subjects
UDHO THADANI, MBBS, MRCP, FRCP (C)l JOHN 0. PARKER, MD, FRCP (C), FACC Kingston, Ontario, Canada
From the Depertment of Medicine, Queen’s Uni-
versity,Kingston, Ontario, Canada. This work was supported by &&s-in-Aid from the Ontario Heat-I Foundation (Toronto), and the Medical Research Council of &da (Ottawa). Manuscript received April 18.1977; revised manuscript received June 9, 1977, accepted June 14, 1977. Address for reprints: John 0. Parker, MD, Etherington Hall, Queen’s Unfversity, Kingston, Ontarlo, Canada. Research Fellow of the Ontario Heart Founl
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To assess left ventricular function and to compare mean pulmonary wedge pressure and left ventricular end-diastolic pressure In the supine and sitting positions, 10 patients without demonstrable cardiovascular disease underwent hemodynamic studies at rest and during exercise In the two positions. At rest the values for heart rate were higher and the values for cardiac index, stroke index, left ventricular stroke work index, mean pulmonary capillary wedge pressure and lefl ventricular end-diastolic pressure were lower in the sitting pobitlon. Durlng both supine and sitting exercise left ventricular end-diastolic pressure, cardiac index, stroke index and left ventricular stroke work index increased significantly from the resting values. Comparison of data durlng exercise revealed higher values for heart rate and rate-pressure product and lower values for pulmonary capillary wedge pressure, left ventricular end-diastolic pressure and stroke index in the sitting position; systolic and mean systemic pressure, cardiac index and left ventrkular stroke work index were similar during the two exercise periods. When absolute changes from rest to exercise were compared, the increase in heart rate, systolic blood pressure, pulmonary capillary wedge pressure, lefl ventricular end-dlastollc pressure, cardiac index, stroke index, and left ventricular stroke work index were similar In the two positions. There was a good correlation between lefl ventricular end-diastolic pressure and pulmonary capillary wedge pressure at rest and during exercise in the two postures.
Recent studies in patients with coronary artery disease’ have shown marked differences in the hemodynamic patterns in the supine and upright positions both at rest and during exercise. In these patients, left ventricular filling pressures were substantially lower during upright exercise than during exercise in the supine position. Comparative hemodynamic data are available in normal subjects at rest and during exercise in supine and upright postures,2-13 and the normal values for left ventricular filling pressure during supine exercise have been defined.14J5 However, no information is available regarding left ventricular filling pressure either at rest or during exercise in the upright posture. This communication presents hemodynamic data including left ventricular end-diastolic pressure and pulmonary capillary wedge pressure measurements obtained at rest and during supine and upright exercise in patients without demonstrable cardiovascular disease. Methods Subjects: Hemodynamic investigations with subsequent selective coronary cinearteriography and left ventriculography were performed in 10 men aged 32 to 58 years (average 46 years). All were leading a sedentary life and were referred for investigation of chest pain. The majority of of these patients had been considered to be suffering from coronary artery disease and had been advised by their family physicians to restrict their level of activity. All had sinus rhythm and were normotensive. Cardiac examination was normal and no subject had
The American Journal of CARDIOLOGY
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EXERCISE AND HEMODYNAMICS
clinical or radiologic evidence of cardiomegaly or cardiac failure. None manifested chest pain or S-T segment depression during treadmill exercise testing. Despite the atypical nature of symptoms in many patients and the negative stress test it was felt advisable to perform angiographic studies to determine whether coronary artery disease was present. None had been taking medications for at least 7 days before the investigation. Protocol: On the day before the investigation, the patients were taken to the laboratory, the study explained and informed consent obtained. Each patient then exercised on a bicycle ergometer in both the supine and sitting positions. During the supine exercise, the ergometer was positioned over the catheterization table, the axle being 12 inches (30.5 cm) above the table level. The work load that would induce mild fatigue while permitting exercise to be continued for 4 to 6 minutes was determined for each subject. These work loads (range 300 to 1250 kilopond-meters per minute) were recorded and were subsequently utilized in the definitive studies. Patients were studied in the fasting state 2 hours after receiving an oral dose of 10 mg of diazepam. Under local anesthesia, the brachial artery and a vein were isolated in the right antecubital fossa. A no. 7 Swan-Ganz catheter was passed to one of the branches of the pulmonary artery supplying the right lower lobe. The position of the catheter was considered satisfactory only if good quality pulmonary capillary wedge pressure measurements were obtained after balloon inflation. A no. 8 Lehman ventriculographie catheter was inserted into the left ventricle from the right brachial artery, and the left brachial artery was cannulated with a Teflon@ needle using the Seldinger technique. Each patient was studied in both the supine and sitting positions at rest and during bicycle exercise at the predetermined work loads. A rest period of 15 minutes followed the instrumentation and a 30 minute rest period was interspaced between the two periods of exercise. The order of exercise was randomized; five patients exercised first in the upright position and five patients first in the supine position. Great care was taken in moving patients from the supine to sitting positions with continuous electrocardiographic and left ventricular pressure monitoring. The electrocardiogram (modified lead V,) and intracardiac
TABLE
IN NORMAL SUBJECTS-THADANI
AND PARKER
and intravascular pressures were recorded at 5 minute intervals during a 10 minute control period at rest in both the supine and sitting postures, and during the final 2 minutes cardiac output was measured in duplicate with the dye-dilution technique using indocyanine green. During exercise, the electrocardiogram and pressures were monitored continually and recorded at 1 minute intervals. Cardiac output was measured in duplicate between 3 and 5 minutes of exercise and then the final pressure measurements were made and exercise discontinued. Measurements and recordings: Pressures were measured with P23 DB Statham strain gauges from a zero reference level 5 cm below the level of the angle of Louis in the studies in the supine position, and from the fourth intercostal space at the sternal border in the sitting position. Pressures were measured over at least two respiratory cycles, and the mean pressures in the brachial artery, pulmonary artery and pulmonary capillary wedge positions were obtained electronically. Recordings were made on a photographic recorder at a paper speed of 25 mm/set; however, for determination of left ventricular end-diastolic pressure and pulmonary capillary wedge pressure, a speed of 100 mm/set was employed and these pressures were measured at a high level of sensitivity. Left ventricular stroke work index (g-m/m2) was calculated using the formula LVSWI = SI X (BAm - LVEDP) X 13.6/1000, where SI = stroke index (ml/beat per m2), BAm = brachial arterial mean pressure (mm Hg) and LVEDP = left ventricular end-diastolic pressure (mm Hg). Systo&c ejection rate index (ml/set per m2) ‘was calculated using the formula SI/SEP where SEP = systolic ejection period in seconds obtained from the brachial arterial tracings at a speed of 100 mm/set. In two patients, left ventricular end-diastolic pressure was not measured in the sitting position because of ventricular irritability, and in these patients values of pulmonary capillary wedge pressure were substituted for left ventricular enddiastolic pressure in the calculations for both the supine and sitting position. The rate-pressure product (mm Hg/min X 10p2) was calculated as the product of systolic arterial pressure and heart rate X 10e2. The first derivative of the left ventricular pressure curve (dP/dt [mm Hg/sec]) was obtained using an electronic differentiator. After completion of these hemodynamic studies, selective
I
Summary of Hemodynamic Data and Statistical Analysis (mean 4~ standard error of the mean)
1. Supine Rest HR Pressures (mm Hg) Brachial artery Diastolic Systolic Mean KW LVED Cl &RI LVSWI HR X SBP dP/dt
73 f 4
76 f 3 130 5
6fl 8fl 3.5 f 0.3 161 50 f 514
1601 f
125
State 2. Supine Exercise
3. Sit;tng
128 f 6
a4 f 4
84 f 178f 119f4 24 f 13f 16 f 7.7 f 61 f6
3 6 2 1 2 0.5
228 f 15 3278 f 215
82 i 132f
3 5
4fl 4fl 2.8 f 0.2 134 35 f 3 9 44 f 3 111 f 8 1658 f 188
4. Sitting
Exercise
1 vs. 2
P Values 3 vs. 4 1 vs. 3
2 vs. 4
146f7
<0.005
1 0.5 518
<0.05
80 f 7 264 f 21 3777 f 210
<0.05 <0.05 NS
89 f 184f 121 f 22f 8fl 11 f 7.3 f 228 52 f
4 7 5 1
1: NS
K <0.05 NS
Cl = cardiac index (liters/min per m2); dP/dt = first derivative of left ventricular pressure (mm Hglsec); HR = heart rate (beats/min); HR X SBP = rate pressure product (heart rate X systolic blood pressure (mm Hg/min X lo-*); LVED = left ventricular end-diastolic; LVSWI = left ventricular stroke work index (g-m/beat per m*); NS = not significant: P = probability: PA = mean pulmonary arterial; PCW = pulmonary capillary wedge; SERI = systolic ejection rate index (mllsec per m ); SI = stroke Index (ml/beat per m*).
January 1978
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EXERCISE
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30-
REST
IN NORMAL
EXERCISE
SUBJECTS-THADANI
REST
AND PARKER
EXERCISE
EXERCISE
REST o SUPINE 0 SITTING Meant SEM n=IO
20-
PCWP mm Hg
FIQURE 1. Individual and group mean values for mean pulmonary capillary wedge pressure (PCWP) in the supine and sitting positions at rest and during exercise. n = number of subjects; P = probability; SEM = standard error of the mean.
OI
SUPINE
30
REST
EXERCISE
SITTING
REST
EXERCISE
0
SUPINE SITTING Mean*_ SEM n=8 l
20
LVEDP mmHg IO
-0.005
SITTING
SUPINE
coronary cineangiography and left ventriculography were carried out in all patients. For the statistical analysis of data, Student’s paired t test was used. Results
The hemodynamic and angiographic studies were completed without complications. None of the patients experienced chest pain or manifested S-T segment depression during exercise. Two subjects performed greater work loads in the sitting position and another performed a greater work load in the supine position. The remaining seven subjects performed similar work loads during the two exercise periods. The work loads required to induce fatigue during upright exercise (590 f 289 kilopond-meters per minute) (mean f standard deviation) and during supine exercise (589 f 211 kilopond-meters per minute) were similar. Left ventriculography and selective coronary angiography revealed normal findings in all subjects. Studies in the Supine Position (Table I)
Resting hemodynamics: In the supine studies, mean pulmonary capillary wedge pressure averaged 6 mm Hg (range 3 to 8), and left ventricular end-diastolic pressure averaged 8 mm Hg (range 4 to 11) (Fig. 1 and 2). These differences were significant (P
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1978
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FlOURE 2. lndhrkfual and group mean values of left ventricular end-diastolic pressure (LVEDP) in the supine and sitting positions at rest and during exercise. Left ventricular end-diastolic pressure in the sitting position was recorded in only eight subjects.
index averaged 50 ml/m2 (range 32 to 84) and left ventricular stroke work index averaged 61 g-m/m2 (range 47 to 108). Exercise hemodynamics: During exercise there were significant increases from resting values in heart rate; systolic, diastolic and mean systemic arterial pressure; rate-pressure product; mean pulmonary arterial pressure and pulmonary capillary wedge and left ventricular end-diastolic pressures (Fig. 1,2,4 and 5). The group mean values were heart rate 128 f 6 beats/ min (mean f standard error of the mean), systolic blood pressure 178 f 6 mm Hg and mean pulmonary arterial pressure 24 f 2 mm Hg. The mean pulmonary capillary wedge pressure, 13 f 1 mm Hg, was less than the left ventricular end-diastolic pressure, 16 f 2 mm Hg (P
Resting hemodynamics: In the sitting position, mean pulmonary capillary wedge pressure averaged 4 mm Hg (range 1 to 6) and left ventricular end-diastolic pressure, recorded in eight patients, averaged 4 mm Hg (range 3 to 7); the correlation coefficient between the
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EXERCISE AND HEMODYNAMICS IN NORMAL SUBJECTS-THADANI AND PARKER
HEART
Soo
RATE
BLOOD PRESSUREmm Hs
beatrhin
0 SUPINE 0 SITTING Mean, SEM
rgo
n=lO 160 20-
LVEDP mmHg
160
IS-
IO-
0
SUPINE
REST
.
SUPINE
EXERCISE
n
SITTING
REST
.
SITTING
EXERCISE
,; 120-I
5-
NS
NS
( 0.05
NS
II0
I 6
I IO
I 15
1 20
I 25
100
1 30
i
94
Meon PCWP mm Hg
80
FIGURE 3. Relation between mean pulmonary capillary wedge pressure (PCWP) and left ventricular end-diastolic pressure (LVEDP) at rest and during exercise. There is a good correlation between the two pressures at rest (r = 0.94 supine and 0.92 sitting) and during exercise (r = 0.96 supine and 0.91 sitting).
-1 REST
EXERCISE
REST
EXERCISE
FIGURE 4. Group mean values for heart rate and systemic arterial blood pressure at rest and during exercise. NS = not significant.
REST
EXERCISE
REST
REST
EXERCISE
EXERCISE
400-
o
SUPINE
.
SITTING Meant SEM
300-
HR x SBP mmtigknin
x KSL
2oo-
looFIGURE 5. Individual and group mean changes in ratepressure product from rest to exercise. Both at rest and during exercise, group mean values of rate-pressure product were significantly higher in the sitting position. HR X SBP = rate-pressure product (heart rate X systolic blood pressure [mm Hg/min X lo-*]).
p*o.os
0 SUPINE
January
1975
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SITTING
Journal of CARDIOLOGY
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EXERCISE AND HEMODYNAMICS
REST
IN NORMAL SUBJECTS-THADANI
EXERCISE
REST
EXERCISE
AND PARKER
REST
EXERCISE
, SUPINE , SITTING kant SEY
7
CI L/minh’ 6
L
/
P< 0.005
SUPINE
FIGURE 6. Individual and group mean values for cardiac Index (Cl) at rest and during exericse. At rest, cardiac index is significantly lower in the sitting position.
SITTING
two pressures was r = 0.92 (Fig. 3). The cardiac index averaged 2.8 liters/min per m2 (range 2.4 to 3.7), stroke index averaged 35 ml/m2 (range 24 to 52) and left ventricular stroke work index averaged 44 g-m/m2 (range 32 to 57). In comparison with the resting values in the supine position, the values for heart rate and diastolic arterial pressure were higher and those for mean pulmonary capillary wedge pressure and left ventricular end-diastolic pressure were lower in the sitting posture (Fig. 1, 2 and 4). In the sitting position, mean cardiac index was 2.8 f 0.2 liters/min per m2 and was significantly lower than in the supine position (3.5 f 0.3 liters/min per m2) (P
January 1978
NS
The American Journal of CARDIDLDGY
between the two pressures was r = 0.91 (Fig. 3). During exercise, increases in cardiac index, stroke index, left ventricular stroke work index and systolic ejection rate index were observed in all subjects (Fig. 6 to 8). Comparison of values obtained during supine exercise showed that in the sitting position there were significantly higher values for heart rate and rate pressure product (Fig. 4 and 5), similar values for systolic and mean systemic arterial pressures, mean pulmonary arterial pressure, cardiac index, left ventricular stroke work index and systolic ejection rate index (Fig. 4,6 and 8) and lower values for mean pulmonary capillary wedge pressure, left ventricular end-diastolic pressure and stroke index (Fig. 1,2 and 7). However, when changes from rest to exercise in the sitting and supine postures were compared, it was observed that the increases in the variables measured were similar in the two positions: heart rate (59 versus 55 beats/min), systolic blood pressure (52 versus 47 mm Hg), mean systemic arterial pressure (22 versus 23 mm Hg), rate-pressure product (145 versus 134 mm Hg/min X 10m2), mean pulmonary arterial pressure (9 versus 11 mm Hg), mean pulmonary capillary wedge pressure (4 versus 7 mm Hg), left ventricular end-diastolic pressure (7 versus 8 mm Hg), cardiac index (4.5 versus 4.2 liters/min per m2), stroke index (17 versus 1 l’ml/beat per m2) and left ventricular stroke work index (36 versus 26 g-m/beat per m2). On the other hand, increases in systolic ejection rate index were greater in the sitting position than during supine exercise (94 versus 66 ml/set per m2) (P <0.05).
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IOO-
SO-
i/ 80-
SI
70-
ml/beat/m’ 80-
50-
l SlTTlNG bank SEM n=IO
I
40-
I _t 30 1 20
SITTING
SUPINE I I 20 IO
I 30
LEFT
I IO
’
VENTRICULAR
1 20
FILLING
1 30
I
1 IO
PRESSURE
I 20
r 30
mmHg
FIGURE 7. Relation between left ventricular filling pressure and stroke index (3) at rest and during exercise in the two positions. The lines joining the points in the left and middle columns represent individual values at rest and during exercise, respectively. The group mean values for stroke index and left ventricular filling pressure were significantly lower both at rest and during exercise in the sitting position.
120.
LVSWI
EO
Gm-m/beat/m’ FIGURE 8. Relation between left ventricular filling pressure and left ventricular stroke work index (LVSWI) (g-m/beat per m*) at rest and during exercise in the two positions. The lines joining the points in the left and middle columns represent individual values at rest and during’ exercise, respectively. At rest, the group mean values for left ventricular stroke index and left ventricular end-diastolic pressure were significantly lower in the sitting position. However, during exercise, the group values for left ventricular stroke index were similar in the two postures.
70
60
50
o SUPINE 0 SITTING Moon t SEY n * IO
40
I
IO
SITTINQ
I
SUPlNE SC
I
20
30
ICI
I
20
I
LEFT VENTRICULAR FILLING PRESSURE
January 1978
I
1
IO
30
20
30
mmHg
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Discussion Hemodynamics at Rest in Supine Versus Sitting Posture
This study has shown that in normal untrained subjects, the hemodynamic profile in the supine and sitting postures is different both at rest and during exercise. At rest in the supine position the left ventricular filling pressure was normal in all subjects. In normal subjects, no information is available regarding left ventricular end-diastolic pressure or pulmonary capillary wedge pressure in the upright position. Mean pulmonary capillary wedge pressure and left ventricular end-diastolic pressure averaged 4 mm Hg in the upright posture; these values were significantly lower than those obtained in the supine posture. It should be pointed out that the zero reference levels for pressure measurement were different in the two positions. The standard technique for measuring pressures in the supine position in our laboratory is from a zero reference level 5 cm below the level of the angle of Louis, whereas for studies in the sitting position we chose a reference level at the fourth intercostal space at the border of the sternum. In the sitting position, it was not possible to define exactly the location of the catheter in the ventricular chamber. The mid portion of the left ventricle in the sitting posture often lies in the fifth or sixth intercostal space and it is possible that the pressures recorded from this chamber in the sitting position were somewhat underestimated. The resting values for cardiac index, stroke index and left ventricular stroke work index were significantly lower in the sitting position and these observations are in keeping with previous reports in normal human subjects and in patients with coronary artery disease.‘-I3 In the present study, the heart rate in the sitting position was higher than in the supine posture and it would appear that the lower cardiac index and stroke index in this position were due primarily to diminished venous return. Hemodynamics During Exercise in Supine Versus Sitting Posture
Left ventrictilar pressure: During supine exercise, both the mean pulmonary capillary wedge pressure and left ventricular end-diastolic pressure increased significantly. The increase in left ventricular filling pressure during supine leg exercise observed in our study and in previous reports14J5 is at variance with some published data in normal subjects.m-1s In the latter reports, left ventricular filling pressure and volumes during supine exercise either did not change or actually decreased from the resting values. These differences may well be due to varying methods of carrying out exercise in the supine posture. In our studies, the bicycle ergometer was placed so that the legs were elevated above the chest during supine exercise. Thus, increased venous return might have been responsible for the increased left ventricular filling pressures. This seems unlikely, however, because the left ventricular enddiastolic pressure in the same patient increased by a similar amount during upright bicycle exercise. 58
January 1978
The American Journal of CARDIOLOGY
There are no previous data relating to left ventricular end-diastolic pressure or pulmonary capillary wedge pressure during exercise in the sitting position in normal subjects. In our study during exercise in the sitting position, both the mean pulmonary capillary wedge and left ventricular end-diastolic pressures increased. Although the absolute values for these pressures during exercise were lower in the sitting than in the supine posture, the increases in these pressures from rest to exercise in the two postures were similar. In contrast, previous studies in patients with coronary artery diseasel demonstrated significantly smaller increases in left ventricular filling pressure during sitting than during supine bicycle exercise. Cardiac output: In normal human subjects, the cardiac output during supine leg exercise increases as a linear function of oxygen consumption.l’ However, the changes reported in stroke volume during exercise have been variable. A review of published findings by Rushmerlg in 1959 showed that in normal subjects the stroke volume changed only slightly over a wide range of exercise. Ten healthy men studied by Beveg&rd et a1.5 more than doubled their cardiac output during supine leg exercise with increases in stroke volume averaging less than 5 percent. Ross and co-worker@ studied patients with no evidence of impaired cardiac reserve. During supine exercise, these subjects attained a cardiac index of up to 10 liters/min per m2, whereas the stroke volume was unchanged in four and increased in two subjects and decreased in one subject. In our study, cardiac output during supine leg exercise increased significantly in all subjects; stroke volume increased in nine and was unchanged in the remaining subject. Cardiac output increased an average of 120 percent during supine exercise and stroke volume an average of 22 percent. These observations are in agreement with previous reports in normal subjects from this laboratory.14 Thus, it would appear that in normal subjects there is a wide individual variation in the changes in stroke volume during supine leg exercise. It is difficult to reconcile the differences in results from different laboratories, but these may well be clue to differences in the study population or the leg position during exercise. In our study, an increase in left ventricular stroke work index was observed during supine exercise in all subjects. These observations are in accord with previous reports in normal subjects,14 but are different from those reported in patients with coronary artery disease.‘J4 In the latter group, the cardiac index increased but there was no significant increase in stroke index or left ventricular stroke work index during exercise in the supine posture.‘J4 During exercise performed in the sitting position, the cardiac output also increases linearly with oxygen consumption.ll In our study, the cardiac output during bicycle exercise in the sitting position increased by 160 percent from the resting values in this position. However, the values obtained during supine and sitting exercise were similar despite significantly lower resting values in the sitting position. Stroke volume: When a person sits or stands, the stroke volume and heart volume consistently dimin-
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EXERCISE AND HEMODYNAMICS IN NORMAL SUBJECTS-THADANI
ish.QOJl Beginning at this lower baseline, the stroke volume increases promptly at smaller work loads and approaches the values obtained during supine rest.4s,7r22-24In our study, during exercise in the sitting position, stroke index increased by 71 percent from the resting values in this posture. However, this value during upright exercise was similar to the resting stroke index in the supine posture but was significantly lower than the stroke index during exercise in the supine posture. Left ventricular stroke work index during sitting bicycle exercise increased in all subjects and both the absolute values of this variable during supine and sitting exercise and the increase from rest to exercise were similar in the two postures. Pulmonary capillary wedge pressure as an index of left ventricular diastolic pressure: Numerous studies in the supine position have confirmed that in the absence of severe pulmonary hypertension or obstruc-
AND PARKER
tion at the level of the pulmonary veins or left atrium, the mean pulmonary capillary wedge pressure corresponds approximately to the left atria1 pressure, which itself is approximately equal to the diastolic pressure in the left ventricle.1,25T26 Our study shows that the wedge pressure provides a good index of left ventricular end-diastolic pressure at rest and during exercise in both the supine and upright postures. Thus, it should be possible to explore left ventricular hemodynamics in the upright posture using the flotation catheter technique, which is safer than obtaining direct left ventricular pressures. Acknowledgment For their helpful cooperation throughout the study, we thank Mr. F. Bradley and Mr. G. Ewart and the nursing staff of the Cardio-Pulmonary Laboratory. The secretarial assistance of Miss G. Whiteside is gratefully acknowledged.
References 1. Thadanl U, West RO, Mathew TM, et al: Hemodynamics at rest and during supine and sitting bicycle exercise in patients with coronary artery disease. Am J Cardiol 39:776-783, 1977 2. McMichael J, Sharpey-Schafer EP: Cardiac output in man by a direct Fick method. Effect of posture, venous pressure changes, atropine, and adrenaline. Br Heart J 6:33-40, 1944 3. Stead EA Jr, Warren Jy, Merrill AJ, et al: The cardiac output in male subjects as measured by the technique of right atrial catheterization. Normal values with observations on the effects of anxiety and tilting. J Clin Invest 24:326-331, 1945 4. Weissler AM, Leonard JJ, Warren JV: Effects of posture and atropine on the cardiac output. J Clin Invest 36:1656-1662, 1957 5. Betregard BS, Holmgren A, Jonsson B: The effect of body position on the circulation at rest and during exercise with special reference to the influence on the stroke volume. Acta Physiot Stand 49: 279-298, 1960 6. Chapman CB, Fisher JM, Sproule BJ: Behaviour of stroke volume at rest and during exercise in human beings. J Clin Invest 39: 1208-1213.1960 7. Wang Y, Marshall RJ, Shepherd JT: The effect of changes of posture and of graded exercise on stroke volume in man. J Clin Invest 39:1051-1061, 1960 8. Reeves Jr, Grover RL, Blount SG, et al: Cardiac output response to standing and treadmill walking. J Appl Physiol 16:283-288, 1961 9. McGregor M, Adam W, Skoljl P: Influence of posture on cardiac output and minute ventillation during exercise. Circ Res 9: 10891092, 1961 10. Beveg&d BB, Hokngren A, Jonsson B: Circulatory studies in well trained athletes at rest and during heavy exercise with special reference to stroke volume and influence of body position. Acta Physiol Stand 57:26-50, 1963 11. Beveghd S: Studies on the regulation of the circulation in man with special reference to the stroke volume and the effects of muscular work, body position, and artificially induced variations of heart rate. Acta Physiol Stand 57:Suppl 200:1-36, 1963 12. Granath A, Jonssom B, StrandelI T: Circulation in healthy old men studied by right heart catheterization at rest and during exercise in the supine and sitting position. Acta Med Stand 176:425-446. 1964 13. Tuckman J, Shillingford J: Effect of different degrees of tilts on
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26.
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cardiac output, heart rate, and blood pressure in normal man. Br Heart J 28:32-39, 1966 Parker JO, Diglorgi S, West RO: A hemodynamic study of acute coronary insufficiency precipitated by exercise. Am J Cardiol 171470-483, 1966 McCallfster BD, Yipintson T, Hallermann FJ, et al: Left ventricular performance during mild supine leg exercise in coronary artery disease. Circulation 37:922-931. 1968 Braunwald E, Gofdblatl A, Harrlson DC, et al: Studies on cardiac dimensions in intact, unanesthetized man. Ill. Effects of muscular exercise. Circ Res 13:448-467, 1963 Gorlln R, Cohen LS, Elliott WC, et al: Effect of supine exercise on left ventricular volume and oxygen consumption in man. Circulation 32:361-371, 1965 Ross J, Llnhart JW, Braunwald E: Effects of changing heart rate in man by electrical stimulation of the right atrium. Studies at rest, during exercise, and with isoproterenol. Circulation 32:549-558, 1965 Rushmer RF: Postural effects on the baseline of ventricular performances. Circulation 20:897-905, 1959 Holmgren A, Ovenfors CO: Heart volume at rest and during muscular work in the supine and in the sitting position. Acta Med Stand 167:267-277,196O Wang Y, Blomquisf A, Rowell LB, et al: Central blood volume during upright exercise in normal subjects (abstr). Fed Proc 21:124, 1964 Astrand PO, Cuddy TE, Saltfn B, et al: Cardiac output during submaximal and maximal work. J Appl Physiol 19:268-274, 1964 Damato AN, Galante JG, Smith WH: Hemodynamic response to treadmill exercise in normal subjects. J Appl Physiol 21:959-966, 1966 Epstein SE, Belser GD, Stamper M, et al: Characterization of the circulatory response to maximal uprightexercise in normal subjects and patients with heart disease. Circulation 35:1049-1062, 1967 Luchsenger PC, Selpp HW, Pate1 DJ: Relationship of pulmonary artery wedge pressure to left atrial pressure in man. Circ Res 11:315-318. 1962 Forrester J, Diamond G, Ganz W, et al: Right and left heart pressures in the acutely ill patient (abstr). Clin Res 18:306. 1970
The American Journal of CARDIOLOGY
volume 41
59
UDHO THADANI, MBBS, MRCP, FRCP (C)l JOHN 0. PARKER, MD, FRCP (C), FACC Kingston, Ontario, Canada
From the Depertment of Medicine, Queen’s Uni-
versity,Kingston, Ontario, Canada. This work was supported by &&s-in-Aid from the Ontario Heat-I Foundation (Toronto), and the Medical Research Council of &da (Ottawa). Manuscript received April 18.1977; revised manuscript received June 9, 1977, accepted June 14, 1977. Address for reprints: John 0. Parker, MD, Etherington Hall, Queen’s Unfversity, Kingston, Ontarlo, Canada. Research Fellow of the Ontario Heart Founl
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January 1978
To assess left ventricular function and to compare mean pulmonary wedge pressure and left ventricular end-diastolic pressure In the supine and sitting positions, 10 patients without demonstrable cardiovascular disease underwent hemodynamic studies at rest and during exercise In the two positions. At rest the values for heart rate were higher and the values for cardiac index, stroke index, left ventricular stroke work index, mean pulmonary capillary wedge pressure and lefl ventricular end-diastolic pressure were lower in the sitting pobitlon. Durlng both supine and sitting exercise left ventricular end-diastolic pressure, cardiac index, stroke index and left ventricular stroke work index increased significantly from the resting values. Comparison of data durlng exercise revealed higher values for heart rate and rate-pressure product and lower values for pulmonary capillary wedge pressure, left ventricular end-diastolic pressure and stroke index in the sitting position; systolic and mean systemic pressure, cardiac index and left ventrkular stroke work index were similar during the two exercise periods. When absolute changes from rest to exercise were compared, the increase in heart rate, systolic blood pressure, pulmonary capillary wedge pressure, lefl ventricular end-dlastollc pressure, cardiac index, stroke index, and left ventricular stroke work index were similar In the two positions. There was a good correlation between lefl ventricular end-diastolic pressure and pulmonary capillary wedge pressure at rest and during exercise in the two postures.
Recent studies in patients with coronary artery disease’ have shown marked differences in the hemodynamic patterns in the supine and upright positions both at rest and during exercise. In these patients, left ventricular filling pressures were substantially lower during upright exercise than during exercise in the supine position. Comparative hemodynamic data are available in normal subjects at rest and during exercise in supine and upright postures,2-13 and the normal values for left ventricular filling pressure during supine exercise have been defined.14J5 However, no information is available regarding left ventricular filling pressure either at rest or during exercise in the upright posture. This communication presents hemodynamic data including left ventricular end-diastolic pressure and pulmonary capillary wedge pressure measurements obtained at rest and during supine and upright exercise in patients without demonstrable cardiovascular disease. Methods Subjects: Hemodynamic investigations with subsequent selective coronary cinearteriography and left ventriculography were performed in 10 men aged 32 to 58 years (average 46 years). All were leading a sedentary life and were referred for investigation of chest pain. The majority of of these patients had been considered to be suffering from coronary artery disease and had been advised by their family physicians to restrict their level of activity. All had sinus rhythm and were normotensive. Cardiac examination was normal and no subject had
The American Journal of CARDIOLOGY
Volume 41
EXERCISE AND HEMODYNAMICS
clinical or radiologic evidence of cardiomegaly or cardiac failure. None manifested chest pain or S-T segment depression during treadmill exercise testing. Despite the atypical nature of symptoms in many patients and the negative stress test it was felt advisable to perform angiographic studies to determine whether coronary artery disease was present. None had been taking medications for at least 7 days before the investigation. Protocol: On the day before the investigation, the patients were taken to the laboratory, the study explained and informed consent obtained. Each patient then exercised on a bicycle ergometer in both the supine and sitting positions. During the supine exercise, the ergometer was positioned over the catheterization table, the axle being 12 inches (30.5 cm) above the table level. The work load that would induce mild fatigue while permitting exercise to be continued for 4 to 6 minutes was determined for each subject. These work loads (range 300 to 1250 kilopond-meters per minute) were recorded and were subsequently utilized in the definitive studies. Patients were studied in the fasting state 2 hours after receiving an oral dose of 10 mg of diazepam. Under local anesthesia, the brachial artery and a vein were isolated in the right antecubital fossa. A no. 7 Swan-Ganz catheter was passed to one of the branches of the pulmonary artery supplying the right lower lobe. The position of the catheter was considered satisfactory only if good quality pulmonary capillary wedge pressure measurements were obtained after balloon inflation. A no. 8 Lehman ventriculographie catheter was inserted into the left ventricle from the right brachial artery, and the left brachial artery was cannulated with a Teflon@ needle using the Seldinger technique. Each patient was studied in both the supine and sitting positions at rest and during bicycle exercise at the predetermined work loads. A rest period of 15 minutes followed the instrumentation and a 30 minute rest period was interspaced between the two periods of exercise. The order of exercise was randomized; five patients exercised first in the upright position and five patients first in the supine position. Great care was taken in moving patients from the supine to sitting positions with continuous electrocardiographic and left ventricular pressure monitoring. The electrocardiogram (modified lead V,) and intracardiac
TABLE
IN NORMAL SUBJECTS-THADANI
AND PARKER
and intravascular pressures were recorded at 5 minute intervals during a 10 minute control period at rest in both the supine and sitting postures, and during the final 2 minutes cardiac output was measured in duplicate with the dye-dilution technique using indocyanine green. During exercise, the electrocardiogram and pressures were monitored continually and recorded at 1 minute intervals. Cardiac output was measured in duplicate between 3 and 5 minutes of exercise and then the final pressure measurements were made and exercise discontinued. Measurements and recordings: Pressures were measured with P23 DB Statham strain gauges from a zero reference level 5 cm below the level of the angle of Louis in the studies in the supine position, and from the fourth intercostal space at the sternal border in the sitting position. Pressures were measured over at least two respiratory cycles, and the mean pressures in the brachial artery, pulmonary artery and pulmonary capillary wedge positions were obtained electronically. Recordings were made on a photographic recorder at a paper speed of 25 mm/set; however, for determination of left ventricular end-diastolic pressure and pulmonary capillary wedge pressure, a speed of 100 mm/set was employed and these pressures were measured at a high level of sensitivity. Left ventricular stroke work index (g-m/m2) was calculated using the formula LVSWI = SI X (BAm - LVEDP) X 13.6/1000, where SI = stroke index (ml/beat per m2), BAm = brachial arterial mean pressure (mm Hg) and LVEDP = left ventricular end-diastolic pressure (mm Hg). Systo&c ejection rate index (ml/set per m2) ‘was calculated using the formula SI/SEP where SEP = systolic ejection period in seconds obtained from the brachial arterial tracings at a speed of 100 mm/set. In two patients, left ventricular end-diastolic pressure was not measured in the sitting position because of ventricular irritability, and in these patients values of pulmonary capillary wedge pressure were substituted for left ventricular enddiastolic pressure in the calculations for both the supine and sitting position. The rate-pressure product (mm Hg/min X 10p2) was calculated as the product of systolic arterial pressure and heart rate X 10e2. The first derivative of the left ventricular pressure curve (dP/dt [mm Hg/sec]) was obtained using an electronic differentiator. After completion of these hemodynamic studies, selective
I
Summary of Hemodynamic Data and Statistical Analysis (mean 4~ standard error of the mean)
1. Supine Rest HR Pressures (mm Hg) Brachial artery Diastolic Systolic Mean KW LVED Cl &RI LVSWI HR X SBP dP/dt
73 f 4
76 f 3 130 5
6fl 8fl 3.5 f 0.3 161 50 f 514
1601 f
125
State 2. Supine Exercise
3. Sit;tng
128 f 6
a4 f 4
84 f 178f 119f4 24 f 13f 16 f 7.7 f 61 f6
3 6 2 1 2 0.5
228 f 15 3278 f 215
82 i 132f
3 5
4fl 4fl 2.8 f 0.2 134 35 f 3 9 44 f 3 111 f 8 1658 f 188
4. Sitting
Exercise
1 vs. 2
P Values 3 vs. 4 1 vs. 3
2 vs. 4
146f7
<0.005
1 0.5 518
<0.05
80 f 7 264 f 21 3777 f 210
<0.05 <0.05 NS
89 f 184f 121 f 22f 8fl 11 f 7.3 f 228 52 f
4 7 5 1
1: NS
K <0.05 NS
Cl = cardiac index (liters/min per m2); dP/dt = first derivative of left ventricular pressure (mm Hglsec); HR = heart rate (beats/min); HR X SBP = rate pressure product (heart rate X systolic blood pressure (mm Hg/min X lo-*); LVED = left ventricular end-diastolic; LVSWI = left ventricular stroke work index (g-m/beat per m*); NS = not significant: P = probability: PA = mean pulmonary arterial; PCW = pulmonary capillary wedge; SERI = systolic ejection rate index (mllsec per m ); SI = stroke Index (ml/beat per m*).
January 1978
The American Journal of CARDIOLOGY
Volume 41
53
EXERCISE
AND HEMODYNAMICS
30-
REST
IN NORMAL
EXERCISE
SUBJECTS-THADANI
REST
AND PARKER
EXERCISE
EXERCISE
REST o SUPINE 0 SITTING Meant SEM n=IO
20-
PCWP mm Hg
FIQURE 1. Individual and group mean values for mean pulmonary capillary wedge pressure (PCWP) in the supine and sitting positions at rest and during exercise. n = number of subjects; P = probability; SEM = standard error of the mean.
OI
SUPINE
30
REST
EXERCISE
SITTING
REST
EXERCISE
0
SUPINE SITTING Mean*_ SEM n=8 l
20
LVEDP mmHg IO
-0.005
SITTING
SUPINE
coronary cineangiography and left ventriculography were carried out in all patients. For the statistical analysis of data, Student’s paired t test was used. Results
The hemodynamic and angiographic studies were completed without complications. None of the patients experienced chest pain or manifested S-T segment depression during exercise. Two subjects performed greater work loads in the sitting position and another performed a greater work load in the supine position. The remaining seven subjects performed similar work loads during the two exercise periods. The work loads required to induce fatigue during upright exercise (590 f 289 kilopond-meters per minute) (mean f standard deviation) and during supine exercise (589 f 211 kilopond-meters per minute) were similar. Left ventriculography and selective coronary angiography revealed normal findings in all subjects. Studies in the Supine Position (Table I)
Resting hemodynamics: In the supine studies, mean pulmonary capillary wedge pressure averaged 6 mm Hg (range 3 to 8), and left ventricular end-diastolic pressure averaged 8 mm Hg (range 4 to 11) (Fig. 1 and 2). These differences were significant (P
54
January
1978
7he Arnerlcan
Journal
ef CARDlOLOaY
Volume
FlOURE 2. lndhrkfual and group mean values of left ventricular end-diastolic pressure (LVEDP) in the supine and sitting positions at rest and during exercise. Left ventricular end-diastolic pressure in the sitting position was recorded in only eight subjects.
index averaged 50 ml/m2 (range 32 to 84) and left ventricular stroke work index averaged 61 g-m/m2 (range 47 to 108). Exercise hemodynamics: During exercise there were significant increases from resting values in heart rate; systolic, diastolic and mean systemic arterial pressure; rate-pressure product; mean pulmonary arterial pressure and pulmonary capillary wedge and left ventricular end-diastolic pressures (Fig. 1,2,4 and 5). The group mean values were heart rate 128 f 6 beats/ min (mean f standard error of the mean), systolic blood pressure 178 f 6 mm Hg and mean pulmonary arterial pressure 24 f 2 mm Hg. The mean pulmonary capillary wedge pressure, 13 f 1 mm Hg, was less than the left ventricular end-diastolic pressure, 16 f 2 mm Hg (P
Resting hemodynamics: In the sitting position, mean pulmonary capillary wedge pressure averaged 4 mm Hg (range 1 to 6) and left ventricular end-diastolic pressure, recorded in eight patients, averaged 4 mm Hg (range 3 to 7); the correlation coefficient between the
41
EXERCISE AND HEMODYNAMICS IN NORMAL SUBJECTS-THADANI AND PARKER
HEART
Soo
RATE
BLOOD PRESSUREmm Hs
beatrhin
0 SUPINE 0 SITTING Mean, SEM
rgo
n=lO 160 20-
LVEDP mmHg
160
IS-
IO-
0
SUPINE
REST
.
SUPINE
EXERCISE
n
SITTING
REST
.
SITTING
EXERCISE
,; 120-I
5-
NS
NS
( 0.05
NS
II0
I 6
I IO
I 15
1 20
I 25
100
1 30
i
94
Meon PCWP mm Hg
80
FIGURE 3. Relation between mean pulmonary capillary wedge pressure (PCWP) and left ventricular end-diastolic pressure (LVEDP) at rest and during exercise. There is a good correlation between the two pressures at rest (r = 0.94 supine and 0.92 sitting) and during exercise (r = 0.96 supine and 0.91 sitting).
-1 REST
EXERCISE
REST
EXERCISE
FIGURE 4. Group mean values for heart rate and systemic arterial blood pressure at rest and during exercise. NS = not significant.
REST
EXERCISE
REST
REST
EXERCISE
EXERCISE
400-
o
SUPINE
.
SITTING Meant SEM
300-
HR x SBP mmtigknin
x KSL
2oo-
looFIGURE 5. Individual and group mean changes in ratepressure product from rest to exercise. Both at rest and during exercise, group mean values of rate-pressure product were significantly higher in the sitting position. HR X SBP = rate-pressure product (heart rate X systolic blood pressure [mm Hg/min X lo-*]).
p*o.os
0 SUPINE
January
1975
The American
SITTING
Journal of CARDIOLOGY
Volume 41
55
EXERCISE AND HEMODYNAMICS
REST
IN NORMAL SUBJECTS-THADANI
EXERCISE
REST
EXERCISE
AND PARKER
REST
EXERCISE
, SUPINE , SITTING kant SEY
7
CI L/minh’ 6
L
/
P< 0.005
SUPINE
FIGURE 6. Individual and group mean values for cardiac Index (Cl) at rest and during exericse. At rest, cardiac index is significantly lower in the sitting position.
SITTING
two pressures was r = 0.92 (Fig. 3). The cardiac index averaged 2.8 liters/min per m2 (range 2.4 to 3.7), stroke index averaged 35 ml/m2 (range 24 to 52) and left ventricular stroke work index averaged 44 g-m/m2 (range 32 to 57). In comparison with the resting values in the supine position, the values for heart rate and diastolic arterial pressure were higher and those for mean pulmonary capillary wedge pressure and left ventricular end-diastolic pressure were lower in the sitting posture (Fig. 1, 2 and 4). In the sitting position, mean cardiac index was 2.8 f 0.2 liters/min per m2 and was significantly lower than in the supine position (3.5 f 0.3 liters/min per m2) (P
January 1978
NS
The American Journal of CARDIDLDGY
between the two pressures was r = 0.91 (Fig. 3). During exercise, increases in cardiac index, stroke index, left ventricular stroke work index and systolic ejection rate index were observed in all subjects (Fig. 6 to 8). Comparison of values obtained during supine exercise showed that in the sitting position there were significantly higher values for heart rate and rate pressure product (Fig. 4 and 5), similar values for systolic and mean systemic arterial pressures, mean pulmonary arterial pressure, cardiac index, left ventricular stroke work index and systolic ejection rate index (Fig. 4,6 and 8) and lower values for mean pulmonary capillary wedge pressure, left ventricular end-diastolic pressure and stroke index (Fig. 1,2 and 7). However, when changes from rest to exercise in the sitting and supine postures were compared, it was observed that the increases in the variables measured were similar in the two positions: heart rate (59 versus 55 beats/min), systolic blood pressure (52 versus 47 mm Hg), mean systemic arterial pressure (22 versus 23 mm Hg), rate-pressure product (145 versus 134 mm Hg/min X 10m2), mean pulmonary arterial pressure (9 versus 11 mm Hg), mean pulmonary capillary wedge pressure (4 versus 7 mm Hg), left ventricular end-diastolic pressure (7 versus 8 mm Hg), cardiac index (4.5 versus 4.2 liters/min per m2), stroke index (17 versus 1 l’ml/beat per m2) and left ventricular stroke work index (36 versus 26 g-m/beat per m2). On the other hand, increases in systolic ejection rate index were greater in the sitting position than during supine exercise (94 versus 66 ml/set per m2) (P <0.05).
Volume 41
EXERCISE AND HEMODYNAMICS IN NORMAL SUBJECTS-THADANI
AND PARKER
IOO-
SO-
i/ 80-
SI
70-
ml/beat/m’ 80-
50-
l SlTTlNG bank SEM n=IO
I
40-
I _t 30 1 20
SITTING
SUPINE I I 20 IO
I 30
LEFT
I IO
’
VENTRICULAR
1 20
FILLING
1 30
I
1 IO
PRESSURE
I 20
r 30
mmHg
FIGURE 7. Relation between left ventricular filling pressure and stroke index (3) at rest and during exercise in the two positions. The lines joining the points in the left and middle columns represent individual values at rest and during exercise, respectively. The group mean values for stroke index and left ventricular filling pressure were significantly lower both at rest and during exercise in the sitting position.
120.
LVSWI
EO
Gm-m/beat/m’ FIGURE 8. Relation between left ventricular filling pressure and left ventricular stroke work index (LVSWI) (g-m/beat per m*) at rest and during exercise in the two positions. The lines joining the points in the left and middle columns represent individual values at rest and during’ exercise, respectively. At rest, the group mean values for left ventricular stroke index and left ventricular end-diastolic pressure were significantly lower in the sitting position. However, during exercise, the group values for left ventricular stroke index were similar in the two postures.
70
60
50
o SUPINE 0 SITTING Moon t SEY n * IO
40
I
IO
SITTINQ
I
SUPlNE SC
I
20
30
ICI
I
20
I
LEFT VENTRICULAR FILLING PRESSURE
January 1978
I
1
IO
30
20
30
mmHg
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EXERCISE AND HEMODYNAMICS
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AND PARKER
Discussion Hemodynamics at Rest in Supine Versus Sitting Posture
This study has shown that in normal untrained subjects, the hemodynamic profile in the supine and sitting postures is different both at rest and during exercise. At rest in the supine position the left ventricular filling pressure was normal in all subjects. In normal subjects, no information is available regarding left ventricular end-diastolic pressure or pulmonary capillary wedge pressure in the upright position. Mean pulmonary capillary wedge pressure and left ventricular end-diastolic pressure averaged 4 mm Hg in the upright posture; these values were significantly lower than those obtained in the supine posture. It should be pointed out that the zero reference levels for pressure measurement were different in the two positions. The standard technique for measuring pressures in the supine position in our laboratory is from a zero reference level 5 cm below the level of the angle of Louis, whereas for studies in the sitting position we chose a reference level at the fourth intercostal space at the border of the sternum. In the sitting position, it was not possible to define exactly the location of the catheter in the ventricular chamber. The mid portion of the left ventricle in the sitting posture often lies in the fifth or sixth intercostal space and it is possible that the pressures recorded from this chamber in the sitting position were somewhat underestimated. The resting values for cardiac index, stroke index and left ventricular stroke work index were significantly lower in the sitting position and these observations are in keeping with previous reports in normal human subjects and in patients with coronary artery disease.‘-I3 In the present study, the heart rate in the sitting position was higher than in the supine posture and it would appear that the lower cardiac index and stroke index in this position were due primarily to diminished venous return. Hemodynamics During Exercise in Supine Versus Sitting Posture
Left ventrictilar pressure: During supine exercise, both the mean pulmonary capillary wedge pressure and left ventricular end-diastolic pressure increased significantly. The increase in left ventricular filling pressure during supine leg exercise observed in our study and in previous reports14J5 is at variance with some published data in normal subjects.m-1s In the latter reports, left ventricular filling pressure and volumes during supine exercise either did not change or actually decreased from the resting values. These differences may well be due to varying methods of carrying out exercise in the supine posture. In our studies, the bicycle ergometer was placed so that the legs were elevated above the chest during supine exercise. Thus, increased venous return might have been responsible for the increased left ventricular filling pressures. This seems unlikely, however, because the left ventricular enddiastolic pressure in the same patient increased by a similar amount during upright bicycle exercise. 58
January 1978
The American Journal of CARDIOLOGY
There are no previous data relating to left ventricular end-diastolic pressure or pulmonary capillary wedge pressure during exercise in the sitting position in normal subjects. In our study during exercise in the sitting position, both the mean pulmonary capillary wedge and left ventricular end-diastolic pressures increased. Although the absolute values for these pressures during exercise were lower in the sitting than in the supine posture, the increases in these pressures from rest to exercise in the two postures were similar. In contrast, previous studies in patients with coronary artery diseasel demonstrated significantly smaller increases in left ventricular filling pressure during sitting than during supine bicycle exercise. Cardiac output: In normal human subjects, the cardiac output during supine leg exercise increases as a linear function of oxygen consumption.l’ However, the changes reported in stroke volume during exercise have been variable. A review of published findings by Rushmerlg in 1959 showed that in normal subjects the stroke volume changed only slightly over a wide range of exercise. Ten healthy men studied by Beveg&rd et a1.5 more than doubled their cardiac output during supine leg exercise with increases in stroke volume averaging less than 5 percent. Ross and co-worker@ studied patients with no evidence of impaired cardiac reserve. During supine exercise, these subjects attained a cardiac index of up to 10 liters/min per m2, whereas the stroke volume was unchanged in four and increased in two subjects and decreased in one subject. In our study, cardiac output during supine leg exercise increased significantly in all subjects; stroke volume increased in nine and was unchanged in the remaining subject. Cardiac output increased an average of 120 percent during supine exercise and stroke volume an average of 22 percent. These observations are in agreement with previous reports in normal subjects from this laboratory.14 Thus, it would appear that in normal subjects there is a wide individual variation in the changes in stroke volume during supine leg exercise. It is difficult to reconcile the differences in results from different laboratories, but these may well be clue to differences in the study population or the leg position during exercise. In our study, an increase in left ventricular stroke work index was observed during supine exercise in all subjects. These observations are in accord with previous reports in normal subjects,14 but are different from those reported in patients with coronary artery disease.‘J4 In the latter group, the cardiac index increased but there was no significant increase in stroke index or left ventricular stroke work index during exercise in the supine posture.‘J4 During exercise performed in the sitting position, the cardiac output also increases linearly with oxygen consumption.ll In our study, the cardiac output during bicycle exercise in the sitting position increased by 160 percent from the resting values in this position. However, the values obtained during supine and sitting exercise were similar despite significantly lower resting values in the sitting position. Stroke volume: When a person sits or stands, the stroke volume and heart volume consistently dimin-
Volume 41
EXERCISE AND HEMODYNAMICS IN NORMAL SUBJECTS-THADANI
ish.QOJl Beginning at this lower baseline, the stroke volume increases promptly at smaller work loads and approaches the values obtained during supine rest.4s,7r22-24In our study, during exercise in the sitting position, stroke index increased by 71 percent from the resting values in this posture. However, this value during upright exercise was similar to the resting stroke index in the supine posture but was significantly lower than the stroke index during exercise in the supine posture. Left ventricular stroke work index during sitting bicycle exercise increased in all subjects and both the absolute values of this variable during supine and sitting exercise and the increase from rest to exercise were similar in the two postures. Pulmonary capillary wedge pressure as an index of left ventricular diastolic pressure: Numerous studies in the supine position have confirmed that in the absence of severe pulmonary hypertension or obstruc-
AND PARKER
tion at the level of the pulmonary veins or left atrium, the mean pulmonary capillary wedge pressure corresponds approximately to the left atria1 pressure, which itself is approximately equal to the diastolic pressure in the left ventricle.1,25T26 Our study shows that the wedge pressure provides a good index of left ventricular end-diastolic pressure at rest and during exercise in both the supine and upright postures. Thus, it should be possible to explore left ventricular hemodynamics in the upright posture using the flotation catheter technique, which is safer than obtaining direct left ventricular pressures. Acknowledgment For their helpful cooperation throughout the study, we thank Mr. F. Bradley and Mr. G. Ewart and the nursing staff of the Cardio-Pulmonary Laboratory. The secretarial assistance of Miss G. Whiteside is gratefully acknowledged.
References 1. Thadanl U, West RO, Mathew TM, et al: Hemodynamics at rest and during supine and sitting bicycle exercise in patients with coronary artery disease. Am J Cardiol 39:776-783, 1977 2. McMichael J, Sharpey-Schafer EP: Cardiac output in man by a direct Fick method. Effect of posture, venous pressure changes, atropine, and adrenaline. Br Heart J 6:33-40, 1944 3. Stead EA Jr, Warren Jy, Merrill AJ, et al: The cardiac output in male subjects as measured by the technique of right atrial catheterization. Normal values with observations on the effects of anxiety and tilting. J Clin Invest 24:326-331, 1945 4. Weissler AM, Leonard JJ, Warren JV: Effects of posture and atropine on the cardiac output. J Clin Invest 36:1656-1662, 1957 5. Betregard BS, Holmgren A, Jonsson B: The effect of body position on the circulation at rest and during exercise with special reference to the influence on the stroke volume. Acta Physiot Stand 49: 279-298, 1960 6. Chapman CB, Fisher JM, Sproule BJ: Behaviour of stroke volume at rest and during exercise in human beings. J Clin Invest 39: 1208-1213.1960 7. Wang Y, Marshall RJ, Shepherd JT: The effect of changes of posture and of graded exercise on stroke volume in man. J Clin Invest 39:1051-1061, 1960 8. Reeves Jr, Grover RL, Blount SG, et al: Cardiac output response to standing and treadmill walking. J Appl Physiol 16:283-288, 1961 9. McGregor M, Adam W, Skoljl P: Influence of posture on cardiac output and minute ventillation during exercise. Circ Res 9: 10891092, 1961 10. Beveg&d BB, Hokngren A, Jonsson B: Circulatory studies in well trained athletes at rest and during heavy exercise with special reference to stroke volume and influence of body position. Acta Physiol Stand 57:26-50, 1963 11. Beveghd S: Studies on the regulation of the circulation in man with special reference to the stroke volume and the effects of muscular work, body position, and artificially induced variations of heart rate. Acta Physiol Stand 57:Suppl 200:1-36, 1963 12. Granath A, Jonssom B, StrandelI T: Circulation in healthy old men studied by right heart catheterization at rest and during exercise in the supine and sitting position. Acta Med Stand 176:425-446. 1964 13. Tuckman J, Shillingford J: Effect of different degrees of tilts on
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cardiac output, heart rate, and blood pressure in normal man. Br Heart J 28:32-39, 1966 Parker JO, Diglorgi S, West RO: A hemodynamic study of acute coronary insufficiency precipitated by exercise. Am J Cardiol 171470-483, 1966 McCallfster BD, Yipintson T, Hallermann FJ, et al: Left ventricular performance during mild supine leg exercise in coronary artery disease. Circulation 37:922-931. 1968 Braunwald E, Gofdblatl A, Harrlson DC, et al: Studies on cardiac dimensions in intact, unanesthetized man. Ill. Effects of muscular exercise. Circ Res 13:448-467, 1963 Gorlln R, Cohen LS, Elliott WC, et al: Effect of supine exercise on left ventricular volume and oxygen consumption in man. Circulation 32:361-371, 1965 Ross J, Llnhart JW, Braunwald E: Effects of changing heart rate in man by electrical stimulation of the right atrium. Studies at rest, during exercise, and with isoproterenol. Circulation 32:549-558, 1965 Rushmer RF: Postural effects on the baseline of ventricular performances. Circulation 20:897-905, 1959 Holmgren A, Ovenfors CO: Heart volume at rest and during muscular work in the supine and in the sitting position. Acta Med Stand 167:267-277,196O Wang Y, Blomquisf A, Rowell LB, et al: Central blood volume during upright exercise in normal subjects (abstr). Fed Proc 21:124, 1964 Astrand PO, Cuddy TE, Saltfn B, et al: Cardiac output during submaximal and maximal work. J Appl Physiol 19:268-274, 1964 Damato AN, Galante JG, Smith WH: Hemodynamic response to treadmill exercise in normal subjects. J Appl Physiol 21:959-966, 1966 Epstein SE, Belser GD, Stamper M, et al: Characterization of the circulatory response to maximal uprightexercise in normal subjects and patients with heart disease. Circulation 35:1049-1062, 1967 Luchsenger PC, Selpp HW, Pate1 DJ: Relationship of pulmonary artery wedge pressure to left atrial pressure in man. Circ Res 11:315-318. 1962 Forrester J, Diamond G, Ganz W, et al: Right and left heart pressures in the acutely ill patient (abstr). Clin Res 18:306. 1970
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