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A simplified method for calculating the pulmonary valvular area
A simplified calculating
method for the pulmonary
valvular
area
James H. Moller, M.D. Paul Adams, Jr., M.D. Minneapolis, M&n.
T
he selection of patients with isolated pulmonary valvular stenosis for operation is commonly made on the basis of the level of right ventricular systolic pressure. The severity of the pulmonary stenosis can be more accurately assessed when both the right ventricular pressure and the cardiac output are considered. In 1951, Gorlin and co-workers’J presented formulae for pulmonary valvular area and pulmonary valvular resistance. These formulae consider various relationships between the right ventricular pressure and the cardiac output. The determination of the pulmonary valvular area yields information which is easily understood by the clinician and surgeon evaluating a patient with pulmonary stenosis. The formula for pulmonary valvular area is probably not more widely applied because of several time-consuming steps necessary in performing the calculation from the pressure tracings recorded at catheterization. The purpose of this communication is to present a simplified method of determining the pulmonary valvular area which eliminates the necessity of measuring various factors of the pressure contour. This method is based on data obtained at cardiac catheterization in children with isolated pulmonary valvular stenosis and by the
application of the formulae the analysis of this data. Source of data
In 108 children with isolated pulmonary valvular stenosis studied in the cardiovascular laboratory at the University of Minnesota Hospitals, pressure tracings recorded at cardiac catheterization were adequate for this analysis. In 40 of the 108 cases, oxygen consumption was determined by the Tissot-Scholander method, so that by applying the Fick principle the cardiac output could be calculated, utilizing the simultaneously measured arteriovenous difference in oxygen content. Pulmonary valvular area and the pulmonary valvular resistance were calculated in each of these 40 cases utilizing the following formulae of Gorlin1~2: PVA
(cm.“)
PVA
= __ velocity
PVR
=
(dynes-sec.-cm. PVR
systolic flow through valve
cox SEPX 44.5
From the Department of Pediatrics. University of Minnesota, This study was supported by Public Health Service Fellowship National Heart Institute, and the Dwan Family Fund. Received for publication Jan. 3. 1966.
463
of Gorlin1s2 to
1,000 HR
4RV.m -6)
= “Vmn;
-
PA,,,
pressure = __
PAta
X
gradient flow
1,3f~,x,60
. . Minneapolis, HE19,
Minn. 867 and
Research
Grant
HE-5694
from
the
I’C’A = pulmonary valvular area, I’\:K = pulmonary valvular resistance, C’.(.). = cardiac output, RI,‘, 11,= mean right ventricular systolic ejection pressure, PA,,, = mean pulmonary arterial pressure, SEI’ = s),stolic ejection period, and HR = heart rate. To determine the mean right ventricular systolic ejection pressure, the right ventricular pressure contour was analyzed and perpendiculars were dropped to the zero line of the recording from the point in systole at which the right ventricular pressure first exceeded the pulmonary arterial pressure and from the dicrotic notch. The interval between these two perpendiculars is the systolic ejection period, i.e., the period when the pulmonary valve is open. The area under the right ventricular pressure curve ljetween the perpendiculars was measured by a planimeter and divided by the distance between the perpendiculars to find the mean right ventricular systolic ejection pressure. In each instance, duplicate or triplicate measurements lvere made of each of four ventricular complexes. The mean pulmonary arterial pressure was used instead of the mean pulmonary arterial systolic ejection pressure. This assumption introduced only a small error in the calculations, since the values are nearly identical. Observations
Of the formulae for pulmonary valvular area and for pulmonary val+ular resistance, the latter requires the least number of steps in its calculation. If a constant relationship existed between these formulae, by calculating the pulmonary valvular resistance, one could determine pulmonar> valvular area. In the formula for pulmonar)’ valvular resistance, hokvever, the value for the mean right ventricular systolic ejection pressure is required in the calculation. Our initial step was to determine whether a direct relationship existed between the right ventricular systolic pressure and the mean right ventricular systolic ejection pressure. In 108 cases the values for the right ventricular systolic pressure, measured at the time of catheterization, were compared to the values of the mean right ventricular systolic ejection pressure dc-
Fig. I. Relationship between systolic pressure and mean right ejection pressure in 108 children.
IO@0 Pulmonary
Fig. 2. Relationship and a& (13n.~) (dynes-sec.-rnl.-5) cardiac output.
2000
right ventricular ventricular systolic
3000
Volvular Restonce ei ., .,‘I
hetweeu pulmonary pulmonary \-alvular in 40 rhildrcn with
valvular resistance measured
termined by the method outlined above. There is a linear relationship between these two measurements of pressure (Fig. 1). The mean right ventricular systolic ejection pressure is equal to 0.66 peak right ventricular systolic pressure (y = 3.16 + .63 x, r = .97). This ratio of 0.66 is similar to that found by other workers.3-5 Since a linear relationship exists between these two factors, one can estimate the mean right ventricular systolic ejection pressure by knowing the peak right ventricular systolic pressure. The necessity of making measurements from the right ventricular pressure contours is thereby eliminated and this factor may be used to calculate the pulmonary valvular resistance.
Simplijied
method for ctrlculnfing
In Fig. 2 the pulmonary valvular area calculated by Gorlin’s method has been related to the pulmonary valvular resistance in the 40 patients in whom the cardiac output was measured. The values are clustered along the curve (y = 74e-. 76Zl~g~.~). By knowing the pulmonary valvular resistance, therefore, one can estimate a corresponding pulmonary valvular area. Conclusions
_ KV,,,
- PA, C.O.
x
1,332 x 60 1,000
A substitution of 0.66 peak right ventricular systolic pressure is made for the mean right ventricular systolic ejection pressure and the pulmonary valvular resistance is calculated : PVR=
vulvz~lnr cweu
465
consider both the right ventricular systolic pressure and the cardiac output. The calculation for the pulmonary valvular area utilizes both of these factors, but has been time consuming to perform. A simplified method is presented for determining the pulmonary valvular area by calculating the pulmonary valvular resistance and relating this value to the pulmonary valvular area. REFERENCES
To determine the pulmonary valvular area the formula for pulmonary valvular resistance is utilized : pvIi
pubnoncrry
0.66RV -
P-LX
80.
C.O.
This value for resistance is located on the abscissa of Fig. 2, and the corresponding pulmonary valvular area is found on the ordinate. Summary
In order to accurately assessthe severity of pulmonary valvular stenosis, one must
1. Gorlin, R., and Gorlin, S. G.: Hydraulic formula for calculation of the area of the stenotic mitral valve, other cardiac valves, and central circulatory shunts. I, AX HEAKT J. 41:1, 1951. 2. Gorlin, R., Haynes, F. W., Goodale, W. T., Sawyer, C. G., Dow, J. W., and Dexter, L.: Studies of circulatory dynamics in mitral stenosis. I I. Altered dynamics at rest, AM. HEAKT J. 41:30, 1951. 3. Bassingthwaighte, J. B., Parkin, R. LI;., DuShane, J. IV., \Vood, E. H., and Burchell, H. B.: The electrocardiographic and hemodynamic findings in pulmonary stenosis with intact ventricular septum, Circulation 28:893, 1963. 4. Furies, J. C., Labourt, F. E., Pietrafesa, E. R., and Bidoggia, H. J.: Tables for calculating the potency and work of the right ventricle and the right ventricular strain index in pulmonary stenosis with intact ventricular septum. II, AM. HEAIIT J. 52:819, 1956. 5I Campbell, M.: Relationship of pressure and valve area in pulmonary stenosis, Brit. Heart J. 22:101, 1960.
method for the pulmonary
valvular
area
James H. Moller, M.D. Paul Adams, Jr., M.D. Minneapolis, M&n.
T
he selection of patients with isolated pulmonary valvular stenosis for operation is commonly made on the basis of the level of right ventricular systolic pressure. The severity of the pulmonary stenosis can be more accurately assessed when both the right ventricular pressure and the cardiac output are considered. In 1951, Gorlin and co-workers’J presented formulae for pulmonary valvular area and pulmonary valvular resistance. These formulae consider various relationships between the right ventricular pressure and the cardiac output. The determination of the pulmonary valvular area yields information which is easily understood by the clinician and surgeon evaluating a patient with pulmonary stenosis. The formula for pulmonary valvular area is probably not more widely applied because of several time-consuming steps necessary in performing the calculation from the pressure tracings recorded at catheterization. The purpose of this communication is to present a simplified method of determining the pulmonary valvular area which eliminates the necessity of measuring various factors of the pressure contour. This method is based on data obtained at cardiac catheterization in children with isolated pulmonary valvular stenosis and by the
application of the formulae the analysis of this data. Source of data
In 108 children with isolated pulmonary valvular stenosis studied in the cardiovascular laboratory at the University of Minnesota Hospitals, pressure tracings recorded at cardiac catheterization were adequate for this analysis. In 40 of the 108 cases, oxygen consumption was determined by the Tissot-Scholander method, so that by applying the Fick principle the cardiac output could be calculated, utilizing the simultaneously measured arteriovenous difference in oxygen content. Pulmonary valvular area and the pulmonary valvular resistance were calculated in each of these 40 cases utilizing the following formulae of Gorlin1~2: PVA
(cm.“)
PVA
= __ velocity
PVR
=
(dynes-sec.-cm. PVR
systolic flow through valve
cox SEPX 44.5
From the Department of Pediatrics. University of Minnesota, This study was supported by Public Health Service Fellowship National Heart Institute, and the Dwan Family Fund. Received for publication Jan. 3. 1966.
463
of Gorlin1s2 to
1,000 HR
4RV.m -6)
= “Vmn;
-
PA,,,
pressure = __
PAta
X
gradient flow
1,3f~,x,60
. . Minneapolis, HE19,
Minn. 867 and
Research
Grant
HE-5694
from
the
I’C’A = pulmonary valvular area, I’\:K = pulmonary valvular resistance, C’.(.). = cardiac output, RI,‘, 11,= mean right ventricular systolic ejection pressure, PA,,, = mean pulmonary arterial pressure, SEI’ = s),stolic ejection period, and HR = heart rate. To determine the mean right ventricular systolic ejection pressure, the right ventricular pressure contour was analyzed and perpendiculars were dropped to the zero line of the recording from the point in systole at which the right ventricular pressure first exceeded the pulmonary arterial pressure and from the dicrotic notch. The interval between these two perpendiculars is the systolic ejection period, i.e., the period when the pulmonary valve is open. The area under the right ventricular pressure curve ljetween the perpendiculars was measured by a planimeter and divided by the distance between the perpendiculars to find the mean right ventricular systolic ejection pressure. In each instance, duplicate or triplicate measurements lvere made of each of four ventricular complexes. The mean pulmonary arterial pressure was used instead of the mean pulmonary arterial systolic ejection pressure. This assumption introduced only a small error in the calculations, since the values are nearly identical. Observations
Of the formulae for pulmonary valvular area and for pulmonary val+ular resistance, the latter requires the least number of steps in its calculation. If a constant relationship existed between these formulae, by calculating the pulmonary valvular resistance, one could determine pulmonar> valvular area. In the formula for pulmonar)’ valvular resistance, hokvever, the value for the mean right ventricular systolic ejection pressure is required in the calculation. Our initial step was to determine whether a direct relationship existed between the right ventricular systolic pressure and the mean right ventricular systolic ejection pressure. In 108 cases the values for the right ventricular systolic pressure, measured at the time of catheterization, were compared to the values of the mean right ventricular systolic ejection pressure dc-
Fig. I. Relationship between systolic pressure and mean right ejection pressure in 108 children.
IO@0 Pulmonary
Fig. 2. Relationship and a& (13n.~) (dynes-sec.-rnl.-5) cardiac output.
2000
right ventricular ventricular systolic
3000
Volvular Restonce ei ., .,‘I
hetweeu pulmonary pulmonary \-alvular in 40 rhildrcn with
valvular resistance measured
termined by the method outlined above. There is a linear relationship between these two measurements of pressure (Fig. 1). The mean right ventricular systolic ejection pressure is equal to 0.66 peak right ventricular systolic pressure (y = 3.16 + .63 x, r = .97). This ratio of 0.66 is similar to that found by other workers.3-5 Since a linear relationship exists between these two factors, one can estimate the mean right ventricular systolic ejection pressure by knowing the peak right ventricular systolic pressure. The necessity of making measurements from the right ventricular pressure contours is thereby eliminated and this factor may be used to calculate the pulmonary valvular resistance.
Simplijied
method for ctrlculnfing
In Fig. 2 the pulmonary valvular area calculated by Gorlin’s method has been related to the pulmonary valvular resistance in the 40 patients in whom the cardiac output was measured. The values are clustered along the curve (y = 74e-. 76Zl~g~.~). By knowing the pulmonary valvular resistance, therefore, one can estimate a corresponding pulmonary valvular area. Conclusions
_ KV,,,
- PA, C.O.
x
1,332 x 60 1,000
A substitution of 0.66 peak right ventricular systolic pressure is made for the mean right ventricular systolic ejection pressure and the pulmonary valvular resistance is calculated : PVR=
vulvz~lnr cweu
465
consider both the right ventricular systolic pressure and the cardiac output. The calculation for the pulmonary valvular area utilizes both of these factors, but has been time consuming to perform. A simplified method is presented for determining the pulmonary valvular area by calculating the pulmonary valvular resistance and relating this value to the pulmonary valvular area. REFERENCES
To determine the pulmonary valvular area the formula for pulmonary valvular resistance is utilized : pvIi
pubnoncrry
0.66RV -
P-LX
80.
C.O.
This value for resistance is located on the abscissa of Fig. 2, and the corresponding pulmonary valvular area is found on the ordinate. Summary
In order to accurately assessthe severity of pulmonary valvular stenosis, one must
1. Gorlin, R., and Gorlin, S. G.: Hydraulic formula for calculation of the area of the stenotic mitral valve, other cardiac valves, and central circulatory shunts. I, AX HEAKT J. 41:1, 1951. 2. Gorlin, R., Haynes, F. W., Goodale, W. T., Sawyer, C. G., Dow, J. W., and Dexter, L.: Studies of circulatory dynamics in mitral stenosis. I I. Altered dynamics at rest, AM. HEAKT J. 41:30, 1951. 3. Bassingthwaighte, J. B., Parkin, R. LI;., DuShane, J. IV., \Vood, E. H., and Burchell, H. B.: The electrocardiographic and hemodynamic findings in pulmonary stenosis with intact ventricular septum, Circulation 28:893, 1963. 4. Furies, J. C., Labourt, F. E., Pietrafesa, E. R., and Bidoggia, H. J.: Tables for calculating the potency and work of the right ventricle and the right ventricular strain index in pulmonary stenosis with intact ventricular septum. II, AM. HEAIIT J. 52:819, 1956. 5I Campbell, M.: Relationship of pressure and valve area in pulmonary stenosis, Brit. Heart J. 22:101, 1960.