Valve Orifice Area Research Articles

Doppler ultrasound of normally functioning mechanical mitral and aortic valve prostheses

Doppler ultrasound flow velocities across clinically normally functioning mitral (Bjork-Shiley, Medtronic Hall, Lillehei-Kaster, Duromedic and Starr-Edwards) and aortic (Bjork-Shiley, Medtronic Hall, Lillehei-Kaster and Duromedic) valve prostheses are described. To enable ease of reference for the echocardiographer and to avoid the need for time-consuming calculations of pressure drops and effective valve orifice areas, peak flow velocities and, where relevant, pressure half times across valves of different types and sizes are tabulated. In the mitral position, there was significant negative correlation between peak velocity and valve size and between pressure half time and valve size only when a large number and a wide range of sizes of a given type of mitral prosthesis was studied. Similarly, there was significant negative correlation between peak velocity and aortic valve size for Bjork-Shiley and Duromedic valves. Regurgitant jets were detected across 18.4% of mitral and 42% of aortic prostheses.

Effect of Aortic Regurgitation on the Assessment of Mitral Valve Orifice Area by Doppler Pressure Half-Time in Mitral Stenosis

Effect of Aortic Regurgitation on the Assessment of Mitral Valve Orifice Area by Doppler Pressure Half-Time in Mitral Stenosis

Effect of nitroglycerin during hemodynamic estimation of valve orifice in patients with mitral stenosis

In patients with mitral stenosis, valve orifice calculations using pulmonary capillary wedge pressure as a substitute for left atrial pressure may overestimate the severity of disease. Previous studies have shown that mitral valve area determined from transseptal left atrial pressure measurements exceeds that area derived from pulmonary wedge pressure measurements. This is probably due to pulmonary venoconstriction, which is reversed by nitroglycerin. Nitroglycerin, 0.4 mg, was administered sublingually to 20 patients with mitral valve disease during preoperative cardiac catheterization using the pulmonary capillary wedge pressure as the proximal hydraulic variable. At the time of a peak hypotensive effect, 3 to 5 minutes after nitroglycerin administration, the mean pulmonary capillary wedge pressure decreased from 23 +/- 2 (mean +/- SEM) to 19 +/- 2 mm Hg (p less than 0.005). The mean diastolic transmitral pressure gradient (12.6 +/- 1.2 mm Hg before and 11.5 +/- 1.0 mm Hg after nitroglycerin; p = NS) and cardiac output (4.0 +/- 0.3 to 4.1 +/- 0.3 liters/min; p = NS) did not change significantly. Nevertheless, the hemodynamic mitral orifice area, calculated using the Gorlin formula, increased from 0.8 +/- 0.1 to 1.1 +/- 0.2 cm2 (p less than 0.05). In 12 patients with isolated mitral stenosis, without regurgitation, the mitral valve orifice area after nitroglycerin was 0.4 +/- 0.2 cm2 larger than it was before drug administration (p less than 0.05). Administration of nitroglycerin during evaluation of mitral stenosis eliminates pulmonary venoconstriction, which raises the pulmonary capillary wedge pressure above the left atrial pressure in some patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of aortic regurgitation on the assessment of mitral valve orifice area by Doppler pressure half-time in mitral stenosis

Evaluation of the severity of mitral stenosis by continuous-wave Doppler pressure half-time measurement is now well established. However, few data exist regarding the effect of aortic regurgitation (AR) on the validity of this method. Therefore, 73 patients were studied in whom cardiac catheterization and Doppler echocardiographic examinations were performed. Mitral valve orifice area was determined by the Gorlin equation, 2-dimensional echocardiography and Doppler pressure half-time. Doppler pressure half-time and catheterization estimates of mitral valve area correlated well (r = 0.85) in patients without significant mitral regurgitation. This correlation was maintained in patient subgroups with and without significant (at least 2+) AR (r = 0.86 and 0.83, respectively), Similarly, Doppler and 2-dimensional echocardiographic assessment of mitral valve area showed a strong correlation (r = 0.84). Again, the correlation between the 2 methods was similar in patients with and without significant AR (r = 0.86 and 0.82, respectively). Thus, Doppler pressure half-time estimates of mitral valve orifice area are accurate even in patients with AR.

Balloon dilation of mitral stenosis in adult patients: Postmortem and percutaneous mitral valvuloplasty studies

Preliminary reports have documented the utility of percutaneous balloon valvuloplasty of the mitral valve in adult patients with mitral stenosis, but the mechanism of successful valve dilation and the effect of mitral valvuloplasty on cardiac performance have not been studied in detail. Accordingly, mitral valvuloplasty was performed in five postmortem specimens and in 18 adult patients with rheumatic mitral stenosis, using either one (25 mm) or two (18 and 20 mm) dilation balloons. Postmortem balloon dilation resulted in increased valve orifice area in all five postmortem specimens, secondary to separation of fused commissures and fracture of nodular calcium within the mitral leaflets. In no case did balloon dilation result in tearing of valve leaflets, disruption of the mitral ring or liberation of potentially embolic debris. Percutaneous mitral valvuloplasty in 18 patients with severe mitral stenosis (including 9 with a heavily calcified valve) resulted in an increase in cardiac output (4.3 +/- 1.1 to 5.1 +/- 1.5 liters/min, p less than 0.01) and mitral valve area (0.9 +/- 0.2 to 1.6 +/- 0.4 cm2, p less than 0.0001), and a decrease in mean mitral pressure gradient (15 +/- 5 to 9 +/- 4 mm Hg, p less than 0.0001), pulmonary capillary wedge pressure (23 +/- 7 to 18 +/- 7 mm Hg, p less than 0.0001) and mean pulmonary artery pressure (36 +/- 12 to 33 +/- 12 mm Hg, p less than 0.01). Left ventriculography before and after valvuloplasty in 14 of the 18 patients showed a mild (less than or equal to 1+) increase in mitral regurgitation in five patients and no change in the remainder.(ABSTRACT TRUNCATED AT 250 WORDS)

In vitro analysis of mechanisms of balloon valvuloplasty of stenotic mitral valves

Preliminary reports indicate that percutaneous balloon valvuloplasty is efficacious for treatment of mitral stenosis. The present study was designed to evaluate whether anatomic features of stenotic mitral valves in older adults affect the efficacy of balloon valvuloplasty and to determine the mechanism by which increased orifice area is accomplished. Fifteen mitral valves excised intact at the time of mitral valve replacement from patients with no more than 2 +/ 4 + mitral regurgitation were selected for study. Balloon valvuloplasty was performed using a sequence of dilation catheters with balloons 18 to 25 mm in inflated diameter. Mitral valve area, measured with a conical valve sizer, increased from 0.71 ± 0.06 cm 2 (mean ± standard error of the mean) to 1.77 ± 0.19 cm 2 (p < 0.0001) after valvuloplasty, resulting in an increase in calculated orifice area of 185 ± 27% (range 34 to 407%). The increase in calculated orifice area correlated inversely with orifice area before valvuloplasty (r = −0.57; p = 0.026), but was unrelated to extent of calcific deposits on the prevalvuloplasty x-ray of the excised mitral valve. Gross examination together with x-ray analysis after valvuloplasty revealed that the mechanism of balloon valvuloplasty in each case involved commissural splitting, including splits through heavily calcified commissures, without grossly apparent detachment of tissue fragments. These findings suggest that balloon valvuloplasty augments the functional mitral valve orifice area in a manner analogous to standard surgical commissurotomy, and balloon valvuloplastv is likely to be efficacious for a wide spectrum of adult mitral valvular stenosis, including severe stenosis with extensive calcific deposits.

Determination of aortic valve orifice area in aortic valve stenosis by two-dimensional transesophageal echocardiography

Two-dimensional transesophageal echocardiography was used to measure aortic valve orifice area in 24 patients with aortic valve stenosis (AS) and 15 patients without aortic valve disease. Using transesophageal echocardiography, orifice area could be measured in 20 of 24 patients with AS. With transthoracic echocardiography, orifice area could be determined in only 2 of 24 patients. In patients with AS, orifice area determined by transesophageal echocardiography was 0.75 ± 0.34 cm 2 and that calculated with Gorlin's formula was 0.75 ± 0.32 cm 2. In normal aortic valves, orifice area was 3.9 ± 1.2 cm 2 by transesophageal echocardiography. A good correlation was demonstrated between aortic valve orifice area determined using transesophageal echocardiography and calculated orifice area using Gorlin's formula in patients with AS: r = 0.92, standard error of estimate = 0.14 cm 2. The absolute difference between orifice area measured with both methods ranged from 0.0 to 0.4 cm 2 (mean 0.09 ± 0.1). In 4 patients orifice area could not be determined with transesophageal echocardiography. The orifice could not be identified in 2 patients because an appropriate cross-sectional view of the aortic valve could not be achieved and in 2 patients with pinhole stenosis (aortic valve orifice area 0.3 cm 2). These data show that aortic valve orifice area can be measured reliably using 2-dimensional transesophageal echocardiography.

Percutaneous balloon valvotomy of congenital pulmonary stenosis using oversized balloons

Percutaneous balloon valvotomy was attempted in 27 patients (aged 6 days to 19 years, median 2 years, 11 months) with unoperated typical valvular pulmonary stenosis using a balloon 7 to 60% (mean 30%) larger than the valve anulus. One patient had undergone a previous balloon valvotomy elsewhere. To achieve an oversized dilation diameter in three larger patients, two balloons were inflated side by side. Their "effective dilation diameter" was determined by the diameter of the circle with the same area as that of the oval enveloping the two balloons. A significant reduction of the transvalvular gradient occurred in all patients (mean +/- SD = 74.3 +/- 14.7%, range 33 to 100%). The average gradient of 65.0 +/- 19.0 mm Hg (mean +/- SD) fell to 15.9 +/- 7.6 mm Hg (0 to 30 mm Hg). Twenty-five of 27 patients had a residual transvalvular gradient of less than 25 mm Hg. The calculated valve orifice area increased by an average of 183 +/- 80%. No significant complications occurred. It is concluded that percutaneous balloon valvotomy with a balloon 20 to 40% larger than the valve anulus is the treatment of choice for typical congenital valvular pulmonary stenosis.

Effect of atrial fibrillation and mitral regurgitation on calculated mitral valve area in mitral stenosis

Forty-nine patients with mitral stenosis (MS) were studied by Doppler echocardiography and 2-dimensional (2-D) echocardiography to assess the ability of Doppler ultrasound to accurately measure mitral valve orifice area and to assess whether atrial fibrillation (AF) or mitral regurgitation (MR) affected the calculation. Twenty-four patients underwent cardiac catheterization. Mitral valve area by Doppler was determined by the pressure half-time method. Mean mitral valve area of all 49 patients by Doppler and 2-D echocardiography correlated well (r = 0.90). There was good correlation between Doppler and 2-D echocardiography in patients with pure MS in sinus rhythm (r = 0.88), in patients with MR (r = 0.93) and in patients with AF (r = 0.96). In the 7 patients with pure MS in sinus rhythm, there was good correlation between Doppler, 2-D echocardiography and cardiac catheterization (r = 0.95). In patients with either MR or AF, cardiac catheterization appeared to underestimate mitral valve orifice compared with both Doppler and 2-D echocardiography (p < 0.05). Doppler echocardiography can estimate valve area in patients with MS regardless of the presence of MR or AF.

Importance of the “atrial kick” in determining the effective mitral valve orifice area in mitral stenosis

Atrial fibrillation with a rapid ventricular response in patients with mitral stenosis (MS) is often accompanied by pulmonary congestion and reduced cardiac output owing to a diminished diastolic filling period and the loss of the end-diastolic left ventricular (LV) pressure increment. To test the hypothesis that loss of atrial contraction (atrial kick) also results in a decrease in effective mitral valve orifice area, 6 patients with pure, isolated MS were studied in sinus rhythm during atrial pacing and simultaneous atrioventricular pacing. Atrial pacing at 140 beats/min caused no significant change from baseline in cardiac output or mitral valve area, but there was a decrease in LV end-diastolic volume and ejection fraction as well as an increase in left atrial pressure and mean diastolic gradient. Simultaneous atrioventricular pacing (to eliminate atrial kick) induced a decrease in cardiac output (4.4 ± 0.9 vs 5.2 ± 0.8 liters/min at 110 beats/min, 4.2 ± 0.9 vs 5.1 ± 0.9 liters/min at 140 beats/min; p < 0.05) and LV end-diastolic volume (77 ± 27 vs 93 ± 29 ml at 110 beats/min, 54 ± 17 vs 65 ± 19 ml at 140 beats/min; p < 0.05), an increase in left atrial pressure (28 ± 3 vs 20 ± 5 mm Hg at 110 beats/min, 30 ± 4 vs 25 ± 5 mm Hg at 140 beats/min; p < 0.05), and a decrease in mitral valve area (1.2 ± 0.4 vs 1.4 ± 0.5 cm 2 at 110 beats/min, 1.2 ± 0.4 vs 1.4 ± 0.4 cm 2 at 140 beats/min; p < 0.05). Thus, loss of atrial kick may cause pulmonary congestion and reduced cardiac output in patients with MS, partly because of a decrease in effective mitral valve area.

Early Clinical Results with the Xenomedica Porcine Bioprosthesis

All patients undergoing heart valve replacement with a glutaraldehyde-preserved Xenomedica xenograft from June 1983 through November 1983, were reviewed. This analysis included 75 patients: 37 having undergone aortic valve replacement, 23 mitral valve replacement, and 15 mitral and aortic valve replacement. Of 70 patients discharged from the hospital, there were 5 late deaths, which represents an incidence of 1.06% per patient-year. Twenty-six patients were recatheterized between 3 and 6 months postoperatively. The mean mitral valve orifice area was 1.57 +/- 0.37 cm2. The average mitral valve gradient was 9.8 +/- 2.9 mmHg. No differences in hemodynamic behavior were found between standard and composite mitral prostheses. The average aortic valve peak systolic gradient was 11 +/- 6 mmHg. Fourteen out of the 34 mitral (41%) and 5 out of 52 aortic (9.6%) prostheses have some degree of incompetence. We have discontinued the use of this cardiac bioprosthesis due to the frequent appearance of incompetence in mitral valves, and high transvalvular gradients in mitral prostheses.

Prognosis in valvular heart disease: I. Description of Purpose, Organization, Data Collection Techniques, Estimates of Statistical Power, and Criteria for Termination of Patient Entry

This report describes the design of a multicenter study with two major goals: (1) the identification of valvular heart disease patients at risk for death or a serious complication, and (2) the comparison of hemodynamic function and late outcome of a mechanical prosthetic valve (Björk-Shiley) with a bioprosthesis (Hancock porcine heterograft valve). Strengths of the study design are quantitative assessment of valvular and left ventricular function before and 6 months after valve replacement, measurement in a central laboratory of critical data items such as valve orifice area and left ventricular volumes, and assignment of cause of death and valve-related complications by a committee blinded to valve type. Statistical power calculated by a simulation technique shows only modest loss of power with frequent examination of outcome compared to infrequent examination. Guidelines for premature termination of the study because of superiority of one valve type are described; this includes a critical region with a sloping boundary, which allows for greater chance variation early in the study when the number of patients and events is small, gives the greatest statistical power, and yet appears to provide adequate protection for the subjects in the study.

In vivo hemodynamic comparison of porcine and pericardial valves

The bovine pericardial valve and the SupraAnnular valve have been developed to improve the hemodynamic function of tissue valves. Hemodynamic performances of the standard Carpentier-Edwards porcine valve, the Carpentier-Edwards SupraAnnular valve, and the Carpentier-Edwards bovine pericardial valve were compared in the aortic position. One hundred patients undergoing aortic valve replacement were studied intraoperatively. Mean gradient across the valve decreased for standard and pericardial valves as valve size increased. At the same flow rate, the 23 mm pericardial valve had larger valve orifice areas, higher performance indices, and lower gradients than the 23 mm SupraAnnular valve. The SupraAnnular valve is hemodynamically superior to the standard Carpentier-Edwards porcine bioprosthesis. The Carpentier-Edwards pericardial valve, however, is less obstructive in the aortic position than either of the porcine valves.

Left atrial size, pressure, and V wave height in patients with isolated, severe, pure mitral regurgitation.

In recent years, some concepts regarding the etiology and hemodynamics present in the syndrome of mitral regurgitation have changed. Coronary artery disease and mitral valve prolapse have replaced rheumatic heart disease as the most frequent cause of mitral regurgitation. Hemodynamic studies have shown that tall V waves in the pulmonary capillary wedge tracings are neither specific nor sensitive in detecting the presence of mitral regurgitation. In this study, we evaluated the role of various clinical, echocardiographic, and hemodynamic findings with regard to left atrial (LA) size, pressure, and V wave height. We found that the mean pulmonary capillary wedge pressure (PCW) and V wave height for the subset of patients with acute mitral regurgitation (PCW = 24.1 +/- 10.9; V = 41.2 +/- 20.7 mm Hg) was similar to the subset with chronic mitral regurgitation (PCW = 17.9 +/- 7.5; V = 32.0 +/- 18.2 mm Hg). In addition, we found that there was a significant logarithmic relationship between the LA size and the duration of the mitral regurgitation (y = 1.404 [log X] + 3.948; R = 0.678; p less than 0.0005). Lastly, we found that LA size, compliance, regurgitant volume, and regurgitant valve orifice area all increase with time.

Hemodynamic response and valve performance during graded physical exercise in patients with Medtronic-Hall aortic valve prosthesis.

The Medtronic-Hall aortic valve prosthesis has been studied in order to evaluate its efficacy to respond to moderate (50 Watts) and heavy (100 Watts) physical exercise. A marked increase in cardiac index from 2.86 +/- 0.45 l/min/m2 BSA at rest to 6.80 +/- 0.51 l/min/m2 BSA at the heaviest work load was well-tolerated. Peak pressure gradient rose from 7.9 +/- 8.7 mmHg at rest to 23.0 +/- 16.3 mmHg during the heaviest physical exercise. Utilization of the available valve orifice area was acceptably good. The discharge coefficient, which is the ratio between the effective orifice area and the internal stent orifice area, was 0.69 +/- 0.17 at rest. The performance index, which is the ratio between the effective orifice area and the annulus area, was 0.44 +/- 0.11 at rest. Both indices tended to increase during maximal exercise, possibly due to a more favorable position of the valve in relation to flow pattern.

The mitral valve orifice method for noninvasive two-dimensional echo Doppler determinations of cardiac output.

We developed and validated a mitral valve orifice method for Doppler cardiac output determination. In 15 open-chest dogs, cardiac output was controlled and measured by a roller pump interposed between the right atrium and pulmonary artery as a right-heart bypass. Left heart flows were measured in the open-chest dog model by Doppler measurements at the mitral valve orifice and compared not only to volume flow measured by the roller pump, but to electromagnetic flow meters as well. The maximum mitral valve orifice area was measured off short-axis two-dimensional echocardiographic views by planimetry. The maximal orifice was then adjusted for its diastolic variation in size by calculating a ratio of mean-to-maximal mitral valve separation on a derived M-mode echocardiogram. Flow was sampled parallel to mitral valve inflow in a four-chamber plane. The multiplication of mean flow throughout the cardiac cycle by the mean mitral valve area after correction for diastolic size variation yielded a cardiac output determination that could be compared to the roller pump measurement. Fifty-two cardiac output determinations over roller pump values of 1-5 l/min yielded a high correlation between roller pump flows and Doppler (r = 0.97 +/- 0.23 l/min). Our study shows that the mitral valve orifice provides an accurate site for Doppler cardiac output measurements.

Measurement of mitral valve orifice area in infants and children by two-dimensional echocardiography

Two-dimensional echocardiograms of the mitral valve orifice area were obtained in 50 normal pediatric subjects, 15 patients with congenital mitral stenosis and 7 patients with tricuspid atresia. The mitral area was measured near the tips of the mitral valve leaflets from a diastolic cross-sectional image of the left ventricle. The cardiac images were recorded on videotape and later transferred to video disc for high resolution contour tracing. Contour analysis was performed by a special purpose microcomputer system for calculation of the enclosed calibrated area. In normal patients, there was an excellent correlation (r = 0.95) between mitral valve area (MVA) (in cm2) and body surface area (BSA) (in m2) described by MVA = 4.83 X BSA - 0.07. Each patient with mitral stenosis had a mitral valve area that measured less than the third percentile predicted from the normal regression formula. In eight patients in whom the Gorlin formula could be applied, there was excellent correlation (r = 0.95) between echocardiographic and hemodynamic measurements of mitral valve area. Each patient with tricuspid atresia had a very large mitral valve area (greater than 99th percentile of normal). It is concluded that noninvasive measurement of mitral valve orifice area can be accurately achieved by two-dimensional echocardiography in pediatric patients with congenital mitral stenosis, allowing serial measurement of their mitral valve area.

Quantitative contrast angiography for assessment of ventricular performance in heart disease

Contrast angiography provides much information about ventricular and valvular size and function. This review describes the calculation of left ventricular chamber volume and wall thickness and the derivation of ejection fraction, cardiac output, mass and wall tension and stress. In patients with valvular regurgitation, valve orifice area can be calculated by using the angiographic output and regurgitant flow determined by comparing the angiographic output with the cardiac output measured using Fick or indicator-dilution techniques. By analyzing ventricular volume in conjunction with pressure, it is possible to assess pressure-volume work, compliance and contractility. Regional wall motion can be measured from the change in ventricular contour with time. When applied clinically, these methods and measurements have been used to determine the hemodynamic characteristics of the compensated and decompensated left ventricle in valvular and coronary heart disease. The information derived from quantifying information in angiographic images contributes to patient diagnosis, assessment of prognosis and evaluation of therapy, and has added to our knowledge concerning the pathophysiology of heart disease.

A new formula for the measurement of diastolic mitral valve orifice area.

This study evaluated the accuracy of a new formula for the calculation of mitral valve area. Fifty-two patients with mitral stenosis who underwent cardiac catheterization were evaluated by the standard Gorlin and the new formulas. The correlation between the two formulas was excellent (r = 0.89) for valve areas of 0-1.5 cm2. When the new valve area formula yielded an area greater than 1.5 cm2, there was no correlation with the Gorlin formula. However, the likelihood of the Gorlin mitral valve area being less than 1.0 cm2 was low (10%). The results of the new formula do not appear to be affected by atrial fibrillation and are probably subject to the same limitations when used in the presence of a regurgitant lesion. Therefore, with moderate to severe mitral stenosis, this new formula shows a good correlation. However, with mild stenosis, further work is needed to determine the accuracy and limitations of the new formula.

Mitral and aortic valve orifice area in normal subjects and in patients with congestive cardiomyopathy: Determination by two dimensional echocardiography

Previous determinations of normal valve orifice areas have been mainly from postmortem studies. In this study mitral and aortic valve orifice area were determined from two dimensional echocardiograms in 20 normal subjects and 20 patients with congestive cardiomyopathy. Mitral valve orifice area was larger than quoted in standard textbooks. Both mitral and aortic valve orifice area were reduced in patients with cardiomyopathy. Valve opening was assessed relative to left ventricular and aortic root size. The ratio of mitral valve orifice area to left ventricular cross-sectional area was markedly reduced in patients with cardiomyopathy compared with normal subjects. The ratio of aortic valve orifice area to aortic root size also was reduced in patients with cardiomyopathy. Anterior mitral leaflet E point-septal separation was similar to that in previous reports contrasting normal subjects with patients with myopathy. Among patients with cardiomyopathy, mitral E point-septal separation was primarily a function of left ventricular size and was not significantly correlated with fractional shortening or ejection fraction within this group having uniformly poor systolic function.