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Effect of severe pulmonary hypertension on the calculation of mitral valve area in patients with mitral stenosis
Volume
121
Number
2.
Part
1
Fiu. 1. Continuous-wave Donnler velocitv recording of,387 msec and a valve area ‘02 0.717 crn2:
mitral valve area by the pressure half-time and by the Gorlin formula.
method
METHODS Patients. Fifty-four consecutive patients with mitral stenosis who underwent both cardiac catheterization and adequate Doppler echocardiography were initially included in the study. Four patients were subsequently excluded because of the presence of moderately severe to severe mitral regurgitation, as determined by catheterization.sO Both tests were performed during the same hospital admission in the majority of patients. Cardiac catheterization. Right- and left-sided cardiac catheterization was performed in all patients according to standard techniques through the brachial or femoral approach. Right-sided heart pressures and pulmonary artery wedge pressure were measured by a No. 7 or 7.5 Swan-Ganz thermodilution catheter (Baxter Healthcare Corp., Edwards Division, Santa Ana, Calif.). A true wedge position was confirmed by demonstrating a change in mean and phasic pressure configuration and in value from that recorded in the pulmonary artery on pullback. Oximetry in the wedge position was not performed. Left ventricular pressures were recorded using pigtail (19 patients), Sones (24 patients), King (one patient), or Multipurpose catheters (six patients) (all catheters manufactured by USC1 Angiographic Systems Division, C. R. Bard, Inc., Tewksbury, Mass.). Intracardiac pressures were measured using equisensitive paired transducers. The mean pulmonary artery wedge and left ventricular pressures were simultaneously recorded and the mean diastolic mitral gradient was calculated by planimetry of the diastolic area between the left ventricular and mean pulmonary wedge pressure tracings of at least three cardiac cycles after correction for time delay. Cardiac output was measured
Mitral
valve
of a stenotic
mitral
area
in pulmonaq
hypertension
valve with a pressure
489
half-time
by the thermodilution technique before contrast injection. Mitral valve area was calculated using the modified Gorlin formula.” When mitral regurgitation was present, its severity was assessed using accepted criteria.“” Doppler echocardiography. All patients underwent complete evaluation by two-dimensional echocardiography and cardiac Doppler using a Hewlett Packard 77020A machine (Hewlett-Packard Co., Medical Products Group, Andover, Mass.). Continuous wave Doppler recording of mitral diastolic flow was obtained from the apical fourchamber and apical long-axis views. All studies were recorded on magnetic tape for later review. Calculation of mitral valve area by pressure half-time method was performed on on-screen still frames of the recorded continuous-wave Doppler spectral display of mitral diastolic flow using a built-in computer program (Fig. 1). Area was then determined from at least 10 calculations. The mid-diastolic line drawing method, as described by Gonzalez et a1.,2’ was used when the recorded velocities were nonlinear. The measurements and calculations were performed independently by both authors on two separate occasions to ensure reproducibility and consistency of the findings. Two-dimensional echocardiography. Direct measurement of mitral valve area by two-dimensional echocardiography was not routinely performed, as previous studies have confirmed the excellent correlation between twodimensional echocardiographic-derived area and that derived by Doppler.3-5 After the analysis of data showed the discrepancy between Doppler-derived and catheterizationderived mitral valve area calculation in the 17 patients with pulmonary artery systolic pressure of 70 mm Hg or more, an attempt was made to measure the valve area by two-dimensional echocardiography in these patients. The smallest orifice of the mitral valve in early diastole in the
490
Tabbalat
and Haft
1
1.5
2
2.5
Catheterization Fig. 2. Comparison between catheterization and Doppler estimates of mitral valve area in patients pulmonary artery systolic pressure (PAS) <70 mm Hg (n = 33). Line of identity is shown. Table
1. Characteristics
Sex Mean age Rhythm Hx of commissurotomy Hx of rheumatic fever Severity of MR Absent Mild Moderate Mean interval between cath & Doppler Mean valve area Cath Doppler Mean PAS MR, Mitral normal tory.
sinus
regurgitation; PAS, rhythm; AF, atria1
of the 50 patients 35 women 15 men 59 + 13 years 23 NSR 27 AF 6 patients 27 patients 27 17 6 5.7 -t 15 days
(range
31-87)
(range
O-90)
1.05 k 0.38 cm2 1.12 k 0.37 cm2 61 -+ 12 mm Hg (range pulmonary fibrillation
32-128)
artery systolic pressure; NSR, Cath, catheterization; Hx, his-
parasternal short-axis view was planimetered. Adequate planimetry was possible in 12 of the 17 patients (71% ). All calculations were performed in a blinded fashion. Statistical analysis. Least-squares linear regression analysis was used to compare catheterization and Doppler estimates of mitral valve area and to compare two-dimensional echocardiography and Doppler estimates in the 12 patients with pulmonary artery systolic pressure (PAS) ~70 mm Hg. Results are reported plus or minus standard deviation. A p valve less than 0.05 was considered statistically significant. RESULTS
Fifty patients were studied (Table I), including 35 women and 15 men, with a mean age of 59 -t 13 years
with
(range 31 to 87). Twenty-three patients were in sinus rhythm and 27 were in atria1 fibrillation. Twentyseven patients had pure mitral stenosis, 17 had mild mitral regurgitation, and the remaining six patients had moderate mitral regurgitation. A history of mitral commissurotomy was present in only six patients and a history of rheumatic fever was present in 27 (56%). The mean interval between the two tests was 5.7 f 15 days (range 0 to 90). The mean mitral valve area for all 50 patients as measured by cardiac catheterization was 1.05 2 0.38 cm2, and from Doppler ultrasound it was 1.12 +- 0.37 cm2. The mean PAS pressure for the entire group was 61 r 12 mm Hg (range 32 to 128 mm Hg). The correlation between catheterization and Doppler was r = 0.68 (p < .OOl). In the 33 patients with PAS <70 mm Hg, mean mitral valve area by catheterization was 1.16 k 0.32 cm2, and by Doppler it was 1.16 -+ 0.33 cm2. The correlation between catheterization and Doppler was r = 0.85 (p < 0.001); standard error of the estimate (SEE) was 0.27 cm2 (Fig. 2). In this group the mean PAS pressure was 47 + 9 mm Hg (range 32 to 60). Eighteen patients (55 % ) had pure mitral stenosis, 12 (36 % ) had mild mitral regurgitation, and three (9 % ) had moderate mitral regurgitation. In the 17 patients with PAS ~70 mm Hg, mean mitral valve area by catheterization was 0.85 f 0.49 cm2, and by Doppler it was 1.06 i 0.53 cm2 (p = NS). The correlation between catheterization and Doppler was r = 0.57 (p < 0.05) (SEE = 0.52 cm2) (Fig. 3). In this group the mean PAS pressure was 88 f 16 mm Hg (range 70 to 128 mm Hg). Mitral regurgitation was absent in nine patients (53 % ), was mild in five (29%), and was moderate in three (18%). Di-
Volume
121
Number
2,
Part
Mitral
1
ualue area in pulmonary
hypertension
491
r = 0.57 y = 0.80x + 0.38 SEE = 0.52 cm’
0
0.5
Fig. 3. Comparison between catheterization PAS ~70 mm Hg (n = 17). Line of identity
2 and Doppler is shown.
rect measurement of mitral valve area by twodimensional echocardiography was possible in 12 of the 17 patients with PAS pressure 270 mm Hg. Mean mitral valve area by Doppler in these 12 patients was 1.08 -+ 0.37 cm2, and by twodimensional echocardiography it was 1.02 k 0.24 cm2. The correlation between Doppler and twodimensional echocardiography was r = 0.91 (SEE = 0.12 cm’) (Fig. 4). DISCUSSION
The clinical manifestations associated with mitral valve stenosis do not always reflect the severity of narrowing of the mitral valve orifice. Therefore the optimal timing of surgical intervention has been based on the accurate estimation of the mitral valve orifice area.23 The valve area can be calculated at cardiac catheterization by the application of the Gorlin formula.“4 Estimation of the valve area can also be achieved noninvasively by two-dimensional echocardiography or by the Doppler pressure halftime method. Direct measurement of mitral valve orifice by twodimensional echocardiography has been shown to accurately correlate with measurements obtained at catheterization.3-5x ‘L2,“% 26 However, accurate measurement of the mitral valve area by two-dimensional echocardiography may not be possible in severely calcific or distorted valves,25, 27 in the presence of previous commissurotomy,4 in patients with prosthetic valves, and when technically adequate echocardiograms cannot be obtained. An alternative noninvasive method based on Dop-
estimates
of mitral
2.5 valve area in patients
with
pler echocardiographic measurements of transmitral flow velocity was initially described by Hatle et a1.l in 1979. They proposed that dividing the empiric constant 220 by the Doppler-derived pressure halftime accurately estimated the mitral valve area.2x This method has rapidly gained acceptance as an accurate estimate of mitral valve area in both native,“-“< 2Zand prosthetic69 7, 2g valves, in the presence of mitral regurgitation and atria1 fibrillation3 and in aortic regurgitation.5 It has also been shown to be superior to two-dimensional echocardiography in patients who have undergone commissurotomy.4 In contrast to the Gorlin formula, the pressure half-time has been shown to be relatively independent of flow, heart rate, cardiac output, and left atria1 and ventricular pressures.’ Calculation of mitral valve area by the Gorlin equation requires an accurate estimation of the transmitral pressure gradient. This is best accomplished by simultaneously recording left atria1 and left ventricular pressures. However, significant morbidity is associated with transseptal left heart catheterization.30p”’ Therefore the pulmonary capillary wedge pressure is generally used in place of the left atria1 pressure to calculate mitral valve area.i4-16 In our patients, the pulmonary wedge pressure was used to calculate the mitral valve area. Although the same catheterization protocol was used in all patients, we noted that when the pulmonary artery pressure was normal or moderately elevated (i.e., PAS <70 mm Hg), the valve area calculated by the Gorlin formula showed excellent correlation with
492
Tabhalat
and
American
Haft
February ,991 Heart Journal
2-D Echocardiography
r = 0.91 y 0.59x + 0.39 SEE 0.12 cm’ n
n
0
1.5
0.5
Fig. 4. Comparison between Doppler and two-dimensional echocardiographic arca in patients with PAS ~70 mm Hg (n = 12). Line of identity is shown.
obtained by Doppler. However, at higher pulmonary pressures (PAS 270 mm Hg), the correlation was less accurate, with a mean valve area at catheterization smaller than that at Doppler. Although several studies have shown excellent correlation between pulmonary wedge and left atria1 pressures,“‘-16, lx some investigators have indicated that the former may not always accurately represent the latter, 11,I:?.:<“-:jsand therefore inaccurate estimation of the mitral valve area may result. Waltson et al.“’ have noted that when the wedge pressure was below 25 mm Hg, no significant difference existed between mean wedge and mean left atria1 pressure, but that they were significantly different at higher wedge pressures. They also noted that the degree of scatter increased as the wedge and left atria1 pressure rose. Schoenfeld et al. ‘I demonstrated that in patients with prosthetic mitral valve stenosis, the transvalvular gradient was greater (and therefore the estimated prosthetic valve area was smaller) when wedge pressure rather than direct left atria1 pressure was used. Similar results were reported by Hosenpud et al.“” In an elegant study, Halperin et al.‘” concluded that in patients with long-standing mitral valve disease and pulmonary hypertension, the pulmonary wedge pressure was consistently higher than the left atria1 pressure. They attributed the discrepancy to reversible pulmonary vasoconstriction. Mammana et al.,3’ in a study of 20 patients immediately after cardiopulmonary bypass, found that the mean pulmonary wedge pressure significantly exceeded the mean left atria1 pressure in the early postbypass period. They speculated that the discrepancy may be due to an increase in lung interstitial water as a rethat
2
estimates
of mitral
valve
sult of hemodilution or to the effects of afterload reducing agents on the pulmonary circulation. The unreliability of the pulmonary wedge pressure in the presence of elevated pulmonary arterial resistance was confirmed by other investigators.161 “‘, X7 To confirm our postulate that the discrepancy was due to underestimation of the valve area by the Gorlin equation, we measured the valve area in the 17 patients with PAS ~70 mm Hg by two-dimensional echocardiography. The excellent correlation between two-dimensional echocardiography and Doppler-derived valve areas was evident. We believe that the failure of the Gorlin equation to accurately estimate the mitral valve area in our patients in the presence of severe pulmonary hypertension may have been due to overestimation of the transvalvular gradient when the wedge, rather than the left atrial, pressure was used to calculate the valve area. Clinical implications. In patients with mitral stenosis and severe pulmonary hypertension, the mitral valve area calculated by direct two-dimensional echocardiography or by the Doppler-derived pressure half-time method may be more accurate than that obtained by using the Gorlin formula at cardiac catheterization when the capillary wedge pressure is used as an index of left atria1 pressure. REFERENCES
Hatle L, Angelsen B, Tromsdal A. Noninvasive assessment of atrioventricular pressure half-time by Doppler ultrasound. Circulation 1979;60:1096-104, 2. Stamm RB, Martin RP. Quantification of pressure gradient across stenotic valves by Doppler ultrasound. .J Am Co11Cardiol 1983;2:707-18. 1.
Volume
121
Number
2,
Part
1
3. Bryg RJ, Williams GA, Labovitz AJ, Aker U, Kennedy HL. Effect of atria1 fibrillation and mitral regurgitation on calculated mitral valve area in mitral stenosis. Am J Cardiol 1986;57:634-8. 4. Smith MD, Handshoe R, Handshoe S, Kwan OL, DeMaria AN. Comparative accuracy of two-dimensional echocardiography and Doppler pressure half-time methods in assessing severity of mitral stenosis in patients with and without prior commissurotomy. Circulation 1986;73:100-7. 5. Grayburn PA, Smith MD, Gurley JC, Booth DC, DeMaria AN. Effects of aortic regurgitation on the assessment of mitral valve orifice area by Doppler pressure half-time in mitral stenosis. Am J Cardiol 1987;60:322-6. 6. Williams GA, Labovitz AJ. Doppler hemodynamic evaluation of prosthetic (Starr-Edwards and Bjork-Shiley) and bioprosthetic (Hancock and Carpentier) cardiac valves. Am J Cardiol 1985;56:325-32. 7. Sagar KB, Wann LS, Paulsen WHJ, Romhilt DW. Doppler echocardiographic evaluation of Hancock and Bjork-Shiley prosthetic valves. J Am Co11 Cardiol 1986;7:681-7. 8. Thomas JD, Wilkins GT, Choong CYP, Abascal VM, Palacios IF, Block PC, Weyman AE. Inaccuracy of mitral pressure half-time immediately after percutaneous mitral valvotomy. Circulation 1988;78:980-93. 9. Karp K, Teien D, Bjerle P, Eriksson P. Reassessment of valve area determinations in mitral stenosis by the pressure halftime method:impact of left ventricular stiffness and peak diastolic pressure-difference. J Am Co11 Cardiol 1989;<3:594-9. of the Donnler 10. Chen C. Wann Y. Guo B. Lin Y. Reliabilitv _. pressure half-time method for assessing effects of percutaneous mitral balloon valvuloplasty. J Am Co11 Cardiol 1989; 13:1309-13. MH, Palacios IF, Hutter AM, Jacoby SS, Block 11. Schoenfeld PC. Underestimation of prosthetic mitral valve areas:role of transseptal catheterization in avoiding unnecessary repeat mitral valve suraerv. J Am Co11 Cardiol 1985:5:1387-92. JL, Brooks KM, Rothlauf EB, Mind&h BP, Ambrose 12. Halperin JA, Teichholz LE. Effect of nitroglycerin on the pulmonary venous gradient in patients after mitral valve replacement. J Am Co11 Cardiol 1985;5:34-9. of pulmonary wedge and 13. Waltson A, Kendall ME. Comparison left atria1 pressure in man. AM HEART J 1973;86:159-64. L, Varnauskas E, Eliasch H, Lagerlof H, Senning A, 14. Werko Thommasson B. Further evidence that the pulmonary capillary venous pressure pulse in man reflects cyclic pressure changes in the left atrium. Circ Res 1953;1:337-9. DC, Kirklin JW, Wood EH. The relationship be15. Conn\lly tween pulmonary artery wedge pressure and left atria1 pressure in man. Circ Res 1954;2:434-40. PC, Seipp HW, Pate1 DJ. Relationship of pulmo16. Luchsinger nary artery wedge pressure to left atria1 pressure in man. Circ Res 1962;11:315-8. 17. Levin RI, Glassman E. Left atrial-pulmonary artery wedge pressure relation:effect of elevated pulmonary vascular resistance. Am J Cardiol 1985;55:856-7. 18. Lange RA, Moore DM Jr, Cigarroa RG, Hillis LD. Use of pulmonary capillary wedge pressure to assess severity of mitral stenosis:is left atria1 pressure needed in this condition? J Am Co11 Cardiol 1989;13:825-9.
Mitral
valve area in pulmonary
hypertension
493
19. Hatle L, Brubakk A, Tromsdal A, Angelsen B. Noninvasive assessment of pressure drop in mitral stenosis by Doppler ultrasound. Br Heart J 1978;40:131-40. W. Profiles in valvular heart disease. In: Grossman 20. Grossman W, ed. Cardiac catheterization and angiography. 3rd. ed. Philadelphia: Lea & Febiger, 1986:360. 21. Cohen MV, Gorlin R. Modified orifice equation for the calculation of mitral valve area. AM HEART J 1972;84:839-40. 22. Gonzalez MA, Child JS, Krivokapich J. Comparison of twodimensional and Doppler echocardiography and intracardiac hemodynamics for quantification of mitral stenosis. Am J Cardiol 1987;60:327-32. 23. Hugenholtz PG, Ryan TJ, Stein SW, Abelmann WH. The spectrum of pure mitral stenosis: hemodynamic studies in relation to clinical disability. Am J Cardiol 1962;10:773-84. 24. Gorlin R, Gorlin SG. Hydraulic formula for calculation of the area of the stenotic mitral valve, other cardiac valves, and central circulatory shunts. AM HEART J 1951;41:1-29. 25. Nichol PM, Gilbert BW, Kisslo JA. Two-dimensional echocardiographic assessment of mitral stenosis. Circulation 1977; 55:120-g. 26. Wann LS, Weyman AE, Feigenbaum H, Dillon JC, Johnston KW, Eggleton RC. Determination of mitral valve area by cross-sectional echocardiography. Ann Intern Med 1978; 88337-41. 27. Martin RP, Rakowski H, Kleiman JH, Beaver W, London E, Popp RL. Reliability and reproducibility of two-dimensional echocardiographic measurement of the stenotic mitral valve orifice area. Am J Cardiol 1979;43:560-8. 28. Hatle L, Angelson B. Doppler ultrasound in cardiologyphysical principles and clinical applications. Trondheim, Norway: SINTEF Report, 1981:lOO. 29. Ryan T, Armstrong WF, Dillon JC, Feigenbaum H. Doppler echocardiographic evaluation of patients with porcine mitral valves. AM HEART J 1986;111:237-44. 30. Brockenbrough EC, Braunwald E. A new technic for left ventricular angiography and transseptal left heart catheterization. Am J Cardiol 1960;6:1062-4. 31. Ross J Jr. Considerations regarding the technique dor transseptal left heart catheterization. Circulation 1966;34:391-9. JP. Inaccuracy of wedge pressure as an index of pul32. Murphy monary capillary pressure. Circulation 1958;17:199-203. RB, Hiro S, Levitsky S, Thomas PA, Plachetka J. 33. Mammana Inaccuracy of pulmonary wedge pressure when compared to left atria1 pressure in the early postsurgical period. J Thorac Cardiovasc Surg 1982;84:420-5. 34. Verel D, Stentiford NH. Comparison of left atria1 pressure and wedge pulmonary capillary pressure. Pressure gradients between left atrium and left ventricle. Br Heart J 1970;32:99-102. 35. Hosenpud JD, McAnulty JH, Morton MJ. Overestimation of mitral valve gradients obtained by phasic pulmonary capillary wedge pressure. Cathet Cardiovasc Diagn 1983;9:283-90. WH, Fierer EM, Laszlo MH, Samet P, Litwak RS. 36. Bernstein The interpretation of pulmonary artery wedge (pulmonary capillary) pressures. Br Heart J 1960;22:37-44. the character of the 37. Shaffer AB, Silber EN. Factors influencing pulmonary arterial wedge pressure. AM HEART J 1956;51:52232.
121
Number
2.
Part
1
Fiu. 1. Continuous-wave Donnler velocitv recording of,387 msec and a valve area ‘02 0.717 crn2:
mitral valve area by the pressure half-time and by the Gorlin formula.
method
METHODS Patients. Fifty-four consecutive patients with mitral stenosis who underwent both cardiac catheterization and adequate Doppler echocardiography were initially included in the study. Four patients were subsequently excluded because of the presence of moderately severe to severe mitral regurgitation, as determined by catheterization.sO Both tests were performed during the same hospital admission in the majority of patients. Cardiac catheterization. Right- and left-sided cardiac catheterization was performed in all patients according to standard techniques through the brachial or femoral approach. Right-sided heart pressures and pulmonary artery wedge pressure were measured by a No. 7 or 7.5 Swan-Ganz thermodilution catheter (Baxter Healthcare Corp., Edwards Division, Santa Ana, Calif.). A true wedge position was confirmed by demonstrating a change in mean and phasic pressure configuration and in value from that recorded in the pulmonary artery on pullback. Oximetry in the wedge position was not performed. Left ventricular pressures were recorded using pigtail (19 patients), Sones (24 patients), King (one patient), or Multipurpose catheters (six patients) (all catheters manufactured by USC1 Angiographic Systems Division, C. R. Bard, Inc., Tewksbury, Mass.). Intracardiac pressures were measured using equisensitive paired transducers. The mean pulmonary artery wedge and left ventricular pressures were simultaneously recorded and the mean diastolic mitral gradient was calculated by planimetry of the diastolic area between the left ventricular and mean pulmonary wedge pressure tracings of at least three cardiac cycles after correction for time delay. Cardiac output was measured
Mitral
valve
of a stenotic
mitral
area
in pulmonaq
hypertension
valve with a pressure
489
half-time
by the thermodilution technique before contrast injection. Mitral valve area was calculated using the modified Gorlin formula.” When mitral regurgitation was present, its severity was assessed using accepted criteria.“” Doppler echocardiography. All patients underwent complete evaluation by two-dimensional echocardiography and cardiac Doppler using a Hewlett Packard 77020A machine (Hewlett-Packard Co., Medical Products Group, Andover, Mass.). Continuous wave Doppler recording of mitral diastolic flow was obtained from the apical fourchamber and apical long-axis views. All studies were recorded on magnetic tape for later review. Calculation of mitral valve area by pressure half-time method was performed on on-screen still frames of the recorded continuous-wave Doppler spectral display of mitral diastolic flow using a built-in computer program (Fig. 1). Area was then determined from at least 10 calculations. The mid-diastolic line drawing method, as described by Gonzalez et a1.,2’ was used when the recorded velocities were nonlinear. The measurements and calculations were performed independently by both authors on two separate occasions to ensure reproducibility and consistency of the findings. Two-dimensional echocardiography. Direct measurement of mitral valve area by two-dimensional echocardiography was not routinely performed, as previous studies have confirmed the excellent correlation between twodimensional echocardiographic-derived area and that derived by Doppler.3-5 After the analysis of data showed the discrepancy between Doppler-derived and catheterizationderived mitral valve area calculation in the 17 patients with pulmonary artery systolic pressure of 70 mm Hg or more, an attempt was made to measure the valve area by two-dimensional echocardiography in these patients. The smallest orifice of the mitral valve in early diastole in the
490
Tabbalat
and Haft
1
1.5
2
2.5
Catheterization Fig. 2. Comparison between catheterization and Doppler estimates of mitral valve area in patients pulmonary artery systolic pressure (PAS) <70 mm Hg (n = 33). Line of identity is shown. Table
1. Characteristics
Sex Mean age Rhythm Hx of commissurotomy Hx of rheumatic fever Severity of MR Absent Mild Moderate Mean interval between cath & Doppler Mean valve area Cath Doppler Mean PAS MR, Mitral normal tory.
sinus
regurgitation; PAS, rhythm; AF, atria1
of the 50 patients 35 women 15 men 59 + 13 years 23 NSR 27 AF 6 patients 27 patients 27 17 6 5.7 -t 15 days
(range
31-87)
(range
O-90)
1.05 k 0.38 cm2 1.12 k 0.37 cm2 61 -+ 12 mm Hg (range pulmonary fibrillation
32-128)
artery systolic pressure; NSR, Cath, catheterization; Hx, his-
parasternal short-axis view was planimetered. Adequate planimetry was possible in 12 of the 17 patients (71% ). All calculations were performed in a blinded fashion. Statistical analysis. Least-squares linear regression analysis was used to compare catheterization and Doppler estimates of mitral valve area and to compare two-dimensional echocardiography and Doppler estimates in the 12 patients with pulmonary artery systolic pressure (PAS) ~70 mm Hg. Results are reported plus or minus standard deviation. A p valve less than 0.05 was considered statistically significant. RESULTS
Fifty patients were studied (Table I), including 35 women and 15 men, with a mean age of 59 -t 13 years
with
(range 31 to 87). Twenty-three patients were in sinus rhythm and 27 were in atria1 fibrillation. Twentyseven patients had pure mitral stenosis, 17 had mild mitral regurgitation, and the remaining six patients had moderate mitral regurgitation. A history of mitral commissurotomy was present in only six patients and a history of rheumatic fever was present in 27 (56%). The mean interval between the two tests was 5.7 f 15 days (range 0 to 90). The mean mitral valve area for all 50 patients as measured by cardiac catheterization was 1.05 2 0.38 cm2, and from Doppler ultrasound it was 1.12 +- 0.37 cm2. The mean PAS pressure for the entire group was 61 r 12 mm Hg (range 32 to 128 mm Hg). The correlation between catheterization and Doppler was r = 0.68 (p < .OOl). In the 33 patients with PAS <70 mm Hg, mean mitral valve area by catheterization was 1.16 k 0.32 cm2, and by Doppler it was 1.16 -+ 0.33 cm2. The correlation between catheterization and Doppler was r = 0.85 (p < 0.001); standard error of the estimate (SEE) was 0.27 cm2 (Fig. 2). In this group the mean PAS pressure was 47 + 9 mm Hg (range 32 to 60). Eighteen patients (55 % ) had pure mitral stenosis, 12 (36 % ) had mild mitral regurgitation, and three (9 % ) had moderate mitral regurgitation. In the 17 patients with PAS ~70 mm Hg, mean mitral valve area by catheterization was 0.85 f 0.49 cm2, and by Doppler it was 1.06 i 0.53 cm2 (p = NS). The correlation between catheterization and Doppler was r = 0.57 (p < 0.05) (SEE = 0.52 cm2) (Fig. 3). In this group the mean PAS pressure was 88 f 16 mm Hg (range 70 to 128 mm Hg). Mitral regurgitation was absent in nine patients (53 % ), was mild in five (29%), and was moderate in three (18%). Di-
Volume
121
Number
2,
Part
Mitral
1
ualue area in pulmonary
hypertension
491
r = 0.57 y = 0.80x + 0.38 SEE = 0.52 cm’
0
0.5
Fig. 3. Comparison between catheterization PAS ~70 mm Hg (n = 17). Line of identity
2 and Doppler is shown.
rect measurement of mitral valve area by twodimensional echocardiography was possible in 12 of the 17 patients with PAS pressure 270 mm Hg. Mean mitral valve area by Doppler in these 12 patients was 1.08 -+ 0.37 cm2, and by twodimensional echocardiography it was 1.02 k 0.24 cm2. The correlation between Doppler and twodimensional echocardiography was r = 0.91 (SEE = 0.12 cm’) (Fig. 4). DISCUSSION
The clinical manifestations associated with mitral valve stenosis do not always reflect the severity of narrowing of the mitral valve orifice. Therefore the optimal timing of surgical intervention has been based on the accurate estimation of the mitral valve orifice area.23 The valve area can be calculated at cardiac catheterization by the application of the Gorlin formula.“4 Estimation of the valve area can also be achieved noninvasively by two-dimensional echocardiography or by the Doppler pressure halftime method. Direct measurement of mitral valve orifice by twodimensional echocardiography has been shown to accurately correlate with measurements obtained at catheterization.3-5x ‘L2,“% 26 However, accurate measurement of the mitral valve area by two-dimensional echocardiography may not be possible in severely calcific or distorted valves,25, 27 in the presence of previous commissurotomy,4 in patients with prosthetic valves, and when technically adequate echocardiograms cannot be obtained. An alternative noninvasive method based on Dop-
estimates
of mitral
2.5 valve area in patients
with
pler echocardiographic measurements of transmitral flow velocity was initially described by Hatle et a1.l in 1979. They proposed that dividing the empiric constant 220 by the Doppler-derived pressure halftime accurately estimated the mitral valve area.2x This method has rapidly gained acceptance as an accurate estimate of mitral valve area in both native,“-“< 2Zand prosthetic69 7, 2g valves, in the presence of mitral regurgitation and atria1 fibrillation3 and in aortic regurgitation.5 It has also been shown to be superior to two-dimensional echocardiography in patients who have undergone commissurotomy.4 In contrast to the Gorlin formula, the pressure half-time has been shown to be relatively independent of flow, heart rate, cardiac output, and left atria1 and ventricular pressures.’ Calculation of mitral valve area by the Gorlin equation requires an accurate estimation of the transmitral pressure gradient. This is best accomplished by simultaneously recording left atria1 and left ventricular pressures. However, significant morbidity is associated with transseptal left heart catheterization.30p”’ Therefore the pulmonary capillary wedge pressure is generally used in place of the left atria1 pressure to calculate mitral valve area.i4-16 In our patients, the pulmonary wedge pressure was used to calculate the mitral valve area. Although the same catheterization protocol was used in all patients, we noted that when the pulmonary artery pressure was normal or moderately elevated (i.e., PAS <70 mm Hg), the valve area calculated by the Gorlin formula showed excellent correlation with
492
Tabhalat
and
American
Haft
February ,991 Heart Journal
2-D Echocardiography
r = 0.91 y 0.59x + 0.39 SEE 0.12 cm’ n
n
0
1.5
0.5
Fig. 4. Comparison between Doppler and two-dimensional echocardiographic arca in patients with PAS ~70 mm Hg (n = 12). Line of identity is shown.
obtained by Doppler. However, at higher pulmonary pressures (PAS 270 mm Hg), the correlation was less accurate, with a mean valve area at catheterization smaller than that at Doppler. Although several studies have shown excellent correlation between pulmonary wedge and left atria1 pressures,“‘-16, lx some investigators have indicated that the former may not always accurately represent the latter, 11,I:?.:<“-:jsand therefore inaccurate estimation of the mitral valve area may result. Waltson et al.“’ have noted that when the wedge pressure was below 25 mm Hg, no significant difference existed between mean wedge and mean left atria1 pressure, but that they were significantly different at higher wedge pressures. They also noted that the degree of scatter increased as the wedge and left atria1 pressure rose. Schoenfeld et al. ‘I demonstrated that in patients with prosthetic mitral valve stenosis, the transvalvular gradient was greater (and therefore the estimated prosthetic valve area was smaller) when wedge pressure rather than direct left atria1 pressure was used. Similar results were reported by Hosenpud et al.“” In an elegant study, Halperin et al.‘” concluded that in patients with long-standing mitral valve disease and pulmonary hypertension, the pulmonary wedge pressure was consistently higher than the left atria1 pressure. They attributed the discrepancy to reversible pulmonary vasoconstriction. Mammana et al.,3’ in a study of 20 patients immediately after cardiopulmonary bypass, found that the mean pulmonary wedge pressure significantly exceeded the mean left atria1 pressure in the early postbypass period. They speculated that the discrepancy may be due to an increase in lung interstitial water as a rethat
2
estimates
of mitral
valve
sult of hemodilution or to the effects of afterload reducing agents on the pulmonary circulation. The unreliability of the pulmonary wedge pressure in the presence of elevated pulmonary arterial resistance was confirmed by other investigators.161 “‘, X7 To confirm our postulate that the discrepancy was due to underestimation of the valve area by the Gorlin equation, we measured the valve area in the 17 patients with PAS ~70 mm Hg by two-dimensional echocardiography. The excellent correlation between two-dimensional echocardiography and Doppler-derived valve areas was evident. We believe that the failure of the Gorlin equation to accurately estimate the mitral valve area in our patients in the presence of severe pulmonary hypertension may have been due to overestimation of the transvalvular gradient when the wedge, rather than the left atrial, pressure was used to calculate the valve area. Clinical implications. In patients with mitral stenosis and severe pulmonary hypertension, the mitral valve area calculated by direct two-dimensional echocardiography or by the Doppler-derived pressure half-time method may be more accurate than that obtained by using the Gorlin formula at cardiac catheterization when the capillary wedge pressure is used as an index of left atria1 pressure. REFERENCES
Hatle L, Angelsen B, Tromsdal A. Noninvasive assessment of atrioventricular pressure half-time by Doppler ultrasound. Circulation 1979;60:1096-104, 2. Stamm RB, Martin RP. Quantification of pressure gradient across stenotic valves by Doppler ultrasound. .J Am Co11Cardiol 1983;2:707-18. 1.
Volume
121
Number
2,
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3. Bryg RJ, Williams GA, Labovitz AJ, Aker U, Kennedy HL. Effect of atria1 fibrillation and mitral regurgitation on calculated mitral valve area in mitral stenosis. Am J Cardiol 1986;57:634-8. 4. Smith MD, Handshoe R, Handshoe S, Kwan OL, DeMaria AN. Comparative accuracy of two-dimensional echocardiography and Doppler pressure half-time methods in assessing severity of mitral stenosis in patients with and without prior commissurotomy. Circulation 1986;73:100-7. 5. Grayburn PA, Smith MD, Gurley JC, Booth DC, DeMaria AN. Effects of aortic regurgitation on the assessment of mitral valve orifice area by Doppler pressure half-time in mitral stenosis. Am J Cardiol 1987;60:322-6. 6. Williams GA, Labovitz AJ. Doppler hemodynamic evaluation of prosthetic (Starr-Edwards and Bjork-Shiley) and bioprosthetic (Hancock and Carpentier) cardiac valves. Am J Cardiol 1985;56:325-32. 7. Sagar KB, Wann LS, Paulsen WHJ, Romhilt DW. Doppler echocardiographic evaluation of Hancock and Bjork-Shiley prosthetic valves. J Am Co11 Cardiol 1986;7:681-7. 8. Thomas JD, Wilkins GT, Choong CYP, Abascal VM, Palacios IF, Block PC, Weyman AE. Inaccuracy of mitral pressure half-time immediately after percutaneous mitral valvotomy. Circulation 1988;78:980-93. 9. Karp K, Teien D, Bjerle P, Eriksson P. Reassessment of valve area determinations in mitral stenosis by the pressure halftime method:impact of left ventricular stiffness and peak diastolic pressure-difference. J Am Co11 Cardiol 1989;<3:594-9. of the Donnler 10. Chen C. Wann Y. Guo B. Lin Y. Reliabilitv _. pressure half-time method for assessing effects of percutaneous mitral balloon valvuloplasty. J Am Co11 Cardiol 1989; 13:1309-13. MH, Palacios IF, Hutter AM, Jacoby SS, Block 11. Schoenfeld PC. Underestimation of prosthetic mitral valve areas:role of transseptal catheterization in avoiding unnecessary repeat mitral valve suraerv. J Am Co11 Cardiol 1985:5:1387-92. JL, Brooks KM, Rothlauf EB, Mind&h BP, Ambrose 12. Halperin JA, Teichholz LE. Effect of nitroglycerin on the pulmonary venous gradient in patients after mitral valve replacement. J Am Co11 Cardiol 1985;5:34-9. of pulmonary wedge and 13. Waltson A, Kendall ME. Comparison left atria1 pressure in man. AM HEART J 1973;86:159-64. L, Varnauskas E, Eliasch H, Lagerlof H, Senning A, 14. Werko Thommasson B. Further evidence that the pulmonary capillary venous pressure pulse in man reflects cyclic pressure changes in the left atrium. Circ Res 1953;1:337-9. DC, Kirklin JW, Wood EH. The relationship be15. Conn\lly tween pulmonary artery wedge pressure and left atria1 pressure in man. Circ Res 1954;2:434-40. PC, Seipp HW, Pate1 DJ. Relationship of pulmo16. Luchsinger nary artery wedge pressure to left atria1 pressure in man. Circ Res 1962;11:315-8. 17. Levin RI, Glassman E. Left atrial-pulmonary artery wedge pressure relation:effect of elevated pulmonary vascular resistance. Am J Cardiol 1985;55:856-7. 18. Lange RA, Moore DM Jr, Cigarroa RG, Hillis LD. Use of pulmonary capillary wedge pressure to assess severity of mitral stenosis:is left atria1 pressure needed in this condition? J Am Co11 Cardiol 1989;13:825-9.
Mitral
valve area in pulmonary
hypertension
493
19. Hatle L, Brubakk A, Tromsdal A, Angelsen B. Noninvasive assessment of pressure drop in mitral stenosis by Doppler ultrasound. Br Heart J 1978;40:131-40. W. Profiles in valvular heart disease. In: Grossman 20. Grossman W, ed. Cardiac catheterization and angiography. 3rd. ed. Philadelphia: Lea & Febiger, 1986:360. 21. Cohen MV, Gorlin R. Modified orifice equation for the calculation of mitral valve area. AM HEART J 1972;84:839-40. 22. Gonzalez MA, Child JS, Krivokapich J. Comparison of twodimensional and Doppler echocardiography and intracardiac hemodynamics for quantification of mitral stenosis. Am J Cardiol 1987;60:327-32. 23. Hugenholtz PG, Ryan TJ, Stein SW, Abelmann WH. The spectrum of pure mitral stenosis: hemodynamic studies in relation to clinical disability. Am J Cardiol 1962;10:773-84. 24. Gorlin R, Gorlin SG. Hydraulic formula for calculation of the area of the stenotic mitral valve, other cardiac valves, and central circulatory shunts. AM HEART J 1951;41:1-29. 25. Nichol PM, Gilbert BW, Kisslo JA. Two-dimensional echocardiographic assessment of mitral stenosis. Circulation 1977; 55:120-g. 26. Wann LS, Weyman AE, Feigenbaum H, Dillon JC, Johnston KW, Eggleton RC. Determination of mitral valve area by cross-sectional echocardiography. Ann Intern Med 1978; 88337-41. 27. Martin RP, Rakowski H, Kleiman JH, Beaver W, London E, Popp RL. Reliability and reproducibility of two-dimensional echocardiographic measurement of the stenotic mitral valve orifice area. Am J Cardiol 1979;43:560-8. 28. Hatle L, Angelson B. Doppler ultrasound in cardiologyphysical principles and clinical applications. Trondheim, Norway: SINTEF Report, 1981:lOO. 29. Ryan T, Armstrong WF, Dillon JC, Feigenbaum H. Doppler echocardiographic evaluation of patients with porcine mitral valves. AM HEART J 1986;111:237-44. 30. Brockenbrough EC, Braunwald E. A new technic for left ventricular angiography and transseptal left heart catheterization. Am J Cardiol 1960;6:1062-4. 31. Ross J Jr. Considerations regarding the technique dor transseptal left heart catheterization. Circulation 1966;34:391-9. JP. Inaccuracy of wedge pressure as an index of pul32. Murphy monary capillary pressure. Circulation 1958;17:199-203. RB, Hiro S, Levitsky S, Thomas PA, Plachetka J. 33. Mammana Inaccuracy of pulmonary wedge pressure when compared to left atria1 pressure in the early postsurgical period. J Thorac Cardiovasc Surg 1982;84:420-5. 34. Verel D, Stentiford NH. Comparison of left atria1 pressure and wedge pulmonary capillary pressure. Pressure gradients between left atrium and left ventricle. Br Heart J 1970;32:99-102. 35. Hosenpud JD, McAnulty JH, Morton MJ. Overestimation of mitral valve gradients obtained by phasic pulmonary capillary wedge pressure. Cathet Cardiovasc Diagn 1983;9:283-90. WH, Fierer EM, Laszlo MH, Samet P, Litwak RS. 36. Bernstein The interpretation of pulmonary artery wedge (pulmonary capillary) pressures. Br Heart J 1960;22:37-44. the character of the 37. Shaffer AB, Silber EN. Factors influencing pulmonary arterial wedge pressure. AM HEART J 1956;51:52232.