Revision of Gorlin constant for calculation of mitral valve area from left heart pressures

Real-time 3D transoesophageal measurement of the mitral valve area in patients with mitral stenosis

AIMS

Planimetry measured by two-dimensional transthoracic echocardiography (TTE, MVA2D) is the reference method for the evaluation of the severity of mitral stenosis (MS) but requires experienced operators and good echocardiographic windows. Real-time three-dimensional transoesophageal echocardiography (3D-TEE, MVA3D) may overcome these limitations but its accuracy has never been evaluated.

METHODS AND RESULTS

We prospectively enrolled 80 patients (58±15 years, 86% female) referred for MS evaluation who underwent, within 1 week, a clinically indicated TTE and TEE. MVA2D was measured by experienced operators (Level III), MVA3D by one experienced and one non-experienced (Level I) operators blinded of any clinical or TTE information. MVA3D measured by the experienced operator [1.11±0.32 cm2; median, 1.1 cm2; range (0.45-2.20)] did not differ from and correlated well with MVA2D [1.10±0.34 cm2; median, 1.05 cm2; range (0.45-2.30)], P=0.87; r=0.79, P<0.0001; ICC=0.79) and mean difference between methods was small (+0.004±0.21 cm2). MVA3D measured by the non-experienced operator [1.08±0.34 cm2; median 1.02 cm2; range (0.45-2.23)] also did not differ from and correlated well with MVA2D measured by experienced operators (P=0.25; r=0.86, P<0.0001; mean difference -0.02±0.18 cm2; ICC=0.86). Intra and interobserver variability were 0.02±0.25 and 0.01±0.33 cm2.

CONCLUSION

3D-TEE provides accurate and reproducible MVA measurements similar to 2D planimetry performed by experienced operators. Thus, 3D-TEE could be considered as a second-line alternative tool for the evaluation of MS severity in patients with poor echocardiographic windows or for team less accustomed to evaluate MS patients.

Left ventricular response to isometric exercise in aortic valve diseases and its value in the optimal timing of aortic valve replacement

In order to evaluate the left ventricular response to isometric exercise in different types of aortic valve disease, isometric exercise tests were performed during cardiac catheterization in 14 patients with pure aortic stenosis, 20 with combined aortic stenosis and regurgitation, and 18 with pure aortic regurgitation. Patients with angina pectoris in whom coronary angiography had not been performed were excluded. Thirty-seven patients were recatheterized 12 months after aortic valve replacement, and the ventricular response to exercise was re-evaluated. Preoperatively, the ejection fraction did not change significantly during exercise in patients with aortic stenosis, tended to decrease in patients with combined valve lesion, and decreased significantly in patients with aortic regurgitation (p less than 0.001). In the three patients whose ejection fraction during preoperative exercise decreased to below 0.40, it remained below 0.50 after successful aortic valve replacement. It appears possible to reveal left ventricular dysfunction in many patients with aortic regurgitation and in some with combined aortic valve disease by means of isometric exercise. The severely depressed ventricular dysfunction during exercise does not appear to correct totally after surgery.

Determination of pressure gradient in mitral stenosis with a non-invasive ultrasound Doppler technique

A 2 MHz continuous waveform non-invasive ultrasound doppler system has been used in the present investigation. With the aid of the audio signals of the frequency shifts, the ultrasound probe was positioned on the external chest so that the axis of the incident ultrasonic beam coincided with the direction of the maximum velocity vectors of the mitral jet. The frequency shifts due to the mitral jet were frequency analyzed and the time course of the maximum frequency shift was determined. The time course of the maximum mitral jet velocity was then determined from the doppler equation and the time course of the mitral pressure gradient from an orifice equation. The usefulness of the technique was evaluated by studying 25 patients with mitral stenosis and 10 without heart disease. The patients with mitral stenosis were studied during cardiac catheterization and the ultrasound data, the pulmonary artery wedge pressure, and the left ventricular pressure were recorded simultaneously. A table is presented where the gradient determined with the ultrasound technique, deltaPU, is compared with the gradient determined from the pressure tracing, deltaPM. Averaged over the 25 patients studied, deltaPU was 1.7 mmHg smaller than deltaPM at 0.08 sec diastolic time and 1.8 mmHg smaller at 0.25 sec diastolic time. The findings in the patients without heart disease differed distinctly from those in the patients with mitral stenosis. The investigation demonstrated that the non-invasive ultrasound technique can be used with confidence to gain an impression of the magnitude of the mitral pressure gradient. The findings also suggest that deltaPU represents the actual pressure gradient more accurately than deltaPM. Another investigation is proposed to assess the accuracy of the technique more completely.

Real-time three-dimensional echocardiography for rheumatic mitral valve stenosis evaluation

OBJECTIVES

Our aim was to assess which echo-Doppler method has the best agreement with the mitral valve area (MVA) invasively evaluated by the Gorlin's formula. We also evaluated the feasibility and reproducibility of real-time three-dimensional echocardiography (RT3D) for the estimation of MVA and the Wilkins score in patients with rheumatic mitral stenosis (RMVS).

BACKGROUND

Real-time three-dimensional echocardiography is a novel technique that allows us to visualize the mitral valvular anatomy in any desired plane orientation. The usefulness and accuracy of this technique for evaluating RMVS has not been established.

METHODS

We studied a series of consecutive patients with RMVS from two tertiary care hospitals. Mitral valvular area was determined by conventional echo-Doppler methods and by RT3D, and their results were compared with those obtained invasively. Real-time three-dimensional echocardiography planimetry and mitral score were measured by two independent observers and then repeated by one of them.

RESULTS

Eighty patients with RMVS comprised our study group (76 women; 50.6 +/- 13.9 years). Compared with all other echo-Doppler methods, RT3D had the best agreement with the invasively determined MVA (average difference between both methods and limits of agreement: 0.08 cm(2) [-0.48 to 0.6]). Interobserver variability was as good for RT3D (intraclass correlation coefficient [ICC] = 0.90) as for pressure half-time (PHT) (ICC = 0.95). For PHT and RT3D, the intraobserver variability was similar (ICC 0.92 and 0.96, respectively). Real-time three-dimensional echocardiography valvular score evaluation showed a better interobserver agreement with RT3D than with 2D echocardiography.

CONCLUSIONS

Real-time three-dimensional echocardiography is a feasible, accurate, and highly reproducible technique for assessing MVA in patients with RMVS. Real-time three-dimensional echocardiography has the best agreement with invasive methods.

Improved assessment of mitral valve stenosis by volumetric real-time three-dimensional echocardiography

OBJECTIVES

This study was performed to determine the feasibility, accuracy and reproducibility of real-time volumetric three-dimensional echocardiography (3-D echo) for the estimation of mitral valve area in patients with mitral valve stenosis.

BACKGROUND

Planimetry of the mitral valve area (MVA) by two-dimensional echocardiography (2-D echo) requires a favorable parasternal acoustic window and depends on operator skill. Transthoracic volumetric 3-D echo allows reconstruction of multiple 2-D planes in any desired orientation and is not limited to parasternal acquisition, and could thus enhance the accuracy and feasibility of calculating MVA.

METHODS

In 48 patients with mitral stenosis (40 women; mean age 61 +/- 13 years) MVA was determined by planimetry using volumetric 3-D echo and compared with measurements obtained by 2-D echo and Doppler pressure half-time (PHT). All measurements were performed by two independent observers. Volumetric data were acquired from an apical view.

RESULTS

Although 2-D echo allowed planimetry of the mitral valve in 43 of 48 patients (89%), calculation of the MVA was possible in all patients when 3-D echo was used. Mitral valve area by 3-D echo correlated well with MVA by 2-D echo (r = 0.93, mean difference, 0.09 +/- 0.14 cm2) and by PHT (r = 0.87, mean difference, 0.16 +/- 0.19 cm2). Interobserver variability was significantly less for 3-D echo than for 2-D echo (SD 0.08cm2 versus SD 0.23cm2, p < 0.001). Furthermore, it was much easier and faster to define the image plane with the smallest orifice area when 3-D echo was used.

CONCLUSIONS

Transthoracic real-time volumetric 3-D echo provides accurate and highly reproducible measurements of mitral valve area and can easily be performed from an apical approach.

Assessing the severity of mitral stenosis: variability between noninvasive and invasive measurements in patients with symptomatic mitral valve stenosis

BACKGROUND

This study evaluated the correlation and variability between noninvasive and invasive measures of mitral stenosis severity before and after balloon mitral commissurotomy (BMC) in a large group of patients with symptomatic mitral stenosis. Factors related to variability between measurements were determined.

METHODS

The Doppler transmitral gradient, Doppler half-time valve area, and 2-dimensional echocardiographic (2D) mitral valve area (MVA) were measured immediately before and 1 day after BMC in 272 consecutive patients with mitral stenosis and compared with their respective measures during cardiac catheterization.

RESULTS

The correlation coefficient for the comparison of noninvasive and invasive measurements of the transmitral gradient was 0.63 before BMC and 0.60 after the procedure; for 2D versus Gorlin-derived MVA, 0.39 and 0.57, respectively; and for Doppler half-time versus Gorlin-derived MVA, 0.31 and 0.18, respectively. A large degree of variability in the measurement of MVA was present among the 3 techniques before BMC and increased after BMC. Before BMC, for the comparison of 2D and Gorlin-derived MVA, variables predictive of the discrepancy were age, echocardiographic score, transmitral gradient during catheterization, and cardiac index. For the comparison of Doppler half-time versus Gorlin-derived MVA, age, heart rate during cardiac catheterization and echocardiography, cardiac output and left ventricular end-diastolic pressure predicted the difference between the 2 measures.

CONCLUSIONS

In symptomatic patients with mitral stenosis, there is significant variability between noninvasive and invasive measures of mitral stenosis severity despite careful, reproducible measurements. The difference between noninvasive and invasive measures of MVA before BMC is strongly related to cardiac output.

Predictors and significance of atrial rhythm before and six months after percutaneous balloon mitral commissurotomy

Clinical, echocardiographic, and cardiac catheterization data were evaluated in 263 patients with mitral stenosis who were undergoing balloon commissurotomy to determine the predictors of atrial rhythm and its effect on functional status. Conversion from atrial fibrillation to sinus rhythm at 6 months after the procedure occurred in 16 of 86 patients (19%) and was predicted by the duration of atrial fibrillation, baseline functional class, and antiarrhythmic therapy; patients who remained in atrial fibrillation had a poorer functional status compared with those in sinus rhythm despite similar procedural results.

What does the left atrial v wave signify during balloon commissurotomy of mitral stenosis?

Left atrial v-wave amplitude has been associated with the presence and severity of chronic mitral regurgitation (MR) but it has not been evaluated for the detection of acute MR. We evaluated the left atrial v-wave amplitude of 205 consecutive patients with mitral stenosis immediately before and after stepwise, incremental balloon mitral commissurotomy to determine predictors of large v waves at baseline and an increase in v-wave amplitude after balloon commissurotomy. The sensitivity and specificity of an increase in v-wave amplitude for detecting worsening and severe MR were determined. A large v wave was present in 44% of patients before balloon commissurotomy and was predicted by age, mean left atrial pressure, mean transmitral gradient, mean pulmonary artery pressure, and angiographic severity of MR. There was a strong inverse correlation between v-wave amplitude and calculated left atrial compliance (r = -0.92). An increase in v-wave amplitude after balloon commissurotomy was associated with an increasing probability of worsening or severe MR. This indicator had a sensitivity, specificity, and positive and negative predictive values of 35%, 91%, 64%, 75%, respectively, for detecting any increase in MR. For the detection of severe MR, the sensitivity was 79%, specificity 89%, positive predictive value 42%, and negative predictive value 98%. Thus, left atrial v-wave amplitude reflects left atrial compliance and severity of mitral stenosis before balloon commissurotomy. An increase in v-wave amplitude is an insensitive but very specific indicator of worsening or severe MR during stepwise, incremental balloon mitral commissurotomy.

Accurate assessment of mitral valve area in patients with mitral stenosis by three-dimensional echocardiography

The accuracy of measurements of mitral valve orifice area (MVA) from three-dimensional echocardiographic (3DE) image data sets obtained by a transthoracic or transesophageal rotational imaging probe was studied in 15 patients with native mitral stenosis. The smallest MVA was identified from a set of eight parallel short-axis cut planes of the mitral valve between the anulus and the tips of leaflets (paraplane echocardiography) and measured by planimetry. In addition, MVA was measured from the two-dimensional short-axis view (2DE). Values of MVA measured by 3DE and 2DE were compared with those calculated from Doppler pressure half-time (PHT) as a gold standard. Observer variabilities were studied for 3DE. MVA measured from PHT ranged between 0.55 and 3.19 cm2 (mean +/- SD 1.57 +/- 0.73 cm2), from 3DE between 0.83 and 3.23 cm2 (mean +/- SD 1.55 +/- 0.67 cm2), and from 2DE between 1.27 and 4.08 cm2 (mean +/- SD 1.9 +/- 0.7 cm2). The variability of intraobserver and interobserver measurements for 3DE measurements was not significantly different (p = 0.79 and p = 0.68, respectively); for interobserver variability, standard error of the estimate = 0.25. There was excellent correlation, close limits of agreement (mean difference +/- 2 SD), and nonsignificant differences between 3DE and PHT for MVA measurements (r = 0.98 [0.02 +/- 0.3] and p = 0.6), respectively. There was moderate correlation, wider limits of agreement, and significant difference between 2DE and PHT for MVA measurements (r = 0.89 [0.32 +/- 0.66] and p = 0.002), respectively. This may be related to the difficulties in visualization of the smallest orifice in precordial short-axis views. This study suggests that three-dimensional image data sets, by providing the possibility of "computer slicing" to generate equidistant parallel cross sections of the mitral valve independently from physically dictated ultrasonic windows, allow accurate and reproducible measurement of the MVA.

Methodologic issues in clinical evaluation of stenosis severity in adults undergoing aortic or mitral balloon valvuloplasty. The NHLBI Balloon Valvuloplasty Registry

Although both catheterization and Doppler measures of valvular stenosis severity have been validated, each has specific advantages and limitations, particularly in the setting of balloon valvuloplasty. Invasive valve area and mean pressure gradient recorded immediately before and after aortic (n = 589) or mitral (n = 608) catheter balloon valvuloplasty were compared with Doppler valve area and mean pressure gradient recorded less than 30 days before and 24 to 72 hours after the procedure. For aortic stenosis, Doppler valve area ranged from 0.1 to 1.4 cm2 before and 0.2 to 2.3 cm2 after catheter balloon valvuloplasty. Doppler and invasive aortic valve areas differed by less than or equal to 0.5 cm2 in 99% and by less than 0.2 cm2 in 92% of patients. Linear correlation was higher before versus after catheter balloon valvuloplasty, for both valve area (r = 0.49 vs r = 0.35, p = 0.01) and mean pressure gradient (r = 0.64 vs r = 0.50, p = 0.01). Group mean invasive valve area was slightly smaller before (0.50 vs 0.59 cm2, p less than 0.0001) but was not different after (0.80 vs 0.78 cm2, p = 0.16) catheter balloon valvuloplasty. Variables affecting the valve area differences were cardiac output, aortic regurgitation, heart rate and blood pressure. Mean pressure gradient differences were related to echo quality, blood pressure and mitral regurgitation. For mitral stenosis, 2-dimensional echocardiographic valve area ranged from 0.4 to 2.8 cm2 before and 0.7 to 3.8 cm2 after catheter balloon valvuloplasty. Two-dimensional echocardiography and invasive mitral valve areas differed by less than or equal to 0.5 cm2 in 96% and by less than 0.2 cm2 in 81% of cases. Linear correlation was not different before versus after catheter balloon valvuloplasty for two-dimensional echocardiographic valve area (r = 0.40 vs 0.36), pressure halftime valve area (r = 0.31 vs 0.32) or mean pressure gradient (r = 0.55 vs r = 0.46). Group mean 2-dimensional echocardiography and pressure halftime valve areas were larger than invasive valve areas before (1.09 vs 1.02 cm2, p = 0.001) and smaller after (1.71 vs 2.02 cm2, p less than 0.0001) catheter balloon valvuloplasty. Important variables affecting the differences were mitral regurgitation, interatrial shunt, cardiac output and heart rate. Nonsimultaneous studies, differing volume flow measurements, and the underlying accuracy of each technique largely account for discrepancies between these methods. The clinical use of each will depend on its ability to predict long-term patient outcome.

Mitral valve resistance as a hemodynamic indicator in mitral stenosis

Variability of the valve area calculated by the Gorlin formula has been noted in bioprosthetic and aortic valves, but few data are available for native stenotic mitral valves. Valve resistance has been proposed as an alternative hemodynamic indicator; however, its value in mitral stenosis has not been assessed. Thirty-four patients had simultaneous recordings of left atrial and ventricular pressures, 26 after percutaneous balloon mitral dilatation (PBMD). Patients with shunt or mitral regurgitation were excluded. Mitral valve resistance correlated exponentially with Gorlin mitral area (y = 133*[area]-1.5; p less than 0.0001). Both Gorlin mitral area and mitral resistance improved after PBMD (0.89 +/- 0.07 cm2 to 2.22 +/- 0.15 cm2; p less than 0.001; and 166 +/- 20 to 40 +/- 8 dynes.s.cm-5; p less than 0.001). Gorlin area and mitral resistance correlated with New York Heart Association functional class. After infusion of isoproterenol in 17 patients, there was an increase in Gorlin area (baseline 1.77 +/- 0.22 cm2, change 0.23 +/- 0.10; p less than 0.03), whereas mitral resistance did not change (baseline 96 +/- 16 dynes.s.cm-5, change 2 +/- 5; p = not significant). Mitral resistance is valuable in the assessment of mitral stenosis. It varies less than Gorlin mitral area under changing hemodynamic conditions.

A new method of haemodynamic assessment of mitral stenosis in atrial fibrillation: construction of a nomogram

Accurate haemodynamic assessment of mitral stenosis by hydraulic formulas requires measurement of the mean valve gradient and the cardiac output. The calculation is laborious, particularly in the presence of atrial fibrillation when averaged values obtained from multiple beat-to-beat determinations must be used. The relations between valve area, end diastolic gradient, and heart rate in 20 patients with mitral stenosis and atrial fibrillation were examined. In each patient the end diastolic pressure gradient for each cardiac cycle was related linearly to the RR interval of that cycle, and this relation was unchanged on exercise. The slope (S) and intercept (I) of this relation correlated with the degree of mitral stenosis as measured by the Gorlin valve area. The regression equations describing these relations were then used to construct a nomogram relating end diastolic pressure gradient to mitral valve area at different heart rates. When the nomogram was applied to catheterisation data from a further 30 patients the results correlated well with direct calculation of valve area by the Gorlin formula. The nomogram is simple to use, does not require measurement of cardiac output, and is independent of heart rate so that it is unnecessary for the patient to exercise during catheterisation.

When should Doppler-determined valve area be better than the Gorlin formula?: Variation in hydraulic constants in low flow states

In low flow states, underestimation errors occur when the Gorlin formula is used to calculate valve area. A model of valvular stenosis designed to examine changes in the hydraulic discharge coefficient (Cd) and coefficient of orifice contraction (Cc) may explain these errors. Unsteady flow was examined in a pulsatile pump model and in a dog model. Valve areas were calculated from pressure and flow data using: a modified form of the Gorlin formula (assuming constant values for Cd and Cc) and a corrected formula (with values of Cd and Cc obtained from steady state data). Valve area was also calculated using the continuity equation with velocity and flow data (constant Cc). Flow velocities were measured using a newly designed ultrasound Doppler catheter capable of resolving flow velocities of up to 5.5 m/s. Both the corrected formula and continuity equation were highly predictive of actual valve area (r = 0.99, slope or M = 0.96 and r = 0.99, M = 1.06, respectively). The modified Gorlin equation was less accurate and tended to underestimate valve areas (r = 0.87, M = 0.83). This underestimation was most notable at low rates of flow (Gorlin: r = 0.94, M = 0.53; continuity: r = 0.93, M = 0.81 and r = 0.94, M = 0.89, respectively) more accurately than the modified Gorlin formula (r = 0.69, M = 0.49). In patients with low cardiac output, hemodynamic formulas, such as the Gorlin formula, which assume a constant value for the hydraulic discharge coefficient (Cd), may be less accurate than formulas using either a corrected value of Cd or Doppler-determined flow velocity and mean systolic flow.

Detection of coronary artery disease by thallium scintigraphy in patients with valvar heart disease

In patients with valvar heart disease detection of coronary artery disease by conventional non-invasive methods may be difficult. The usefulness of thallium-201 exercise scintigraphy for detecting coronary artery disease was evaluated in 16 patients with aortic stenosis, 17 with aortic regurgitation, nine with mitral stenosis, and six with mitral regurgitation who were investigated by coronary angiography. Only two of 21 patients with greater than or equal to 50% coronary artery obstruction had normal thallium images. Three patients without angiographic evidence of coronary artery stenoses had perfusion defects demonstrated by thallium scintigraphy. Only one patient with greater than or equal to 75% coronary stenosis had a normal thallium scan. Angina pectoris or ST segment depression evoked by exercise test were not useful in distinguishing patients with coronary artery disease from those with normal coronary vessels. These data suggest that thallium exercise scintigraphy may be a useful non-invasive test for detecting coronary artery disease in patients with valvar heart disease.

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 less than 0.05). Doppler echocardiography can estimate valve area in patients with MS regardless of the presence of MR or AF.

In vitro verification of Doppler prediction of transvalve pressure gradient and orifice area in stenosis

This study was designed to analyze the validity of application of the modified Bernoulli equation (pressure gradient = 4.0 X velocity2) for estimating the pressure drop and valve orifice area from the jet velocity measured by Doppler ultrasound. We used an in vitro model which permitted interchangeable orifices, accurate measurement of the valve area and pressure drop across the valve. An in-line Doppler ultrasound transducer measured jet velocity (VEL D) at various water flow rates at an incident angle of 180 degrees beyond the various tested orifices. Jet velocity was also determined independently by application of a modified Bernoulli equation using the experimentally measured pressure drop (VEL P) and by a standard continuity equation (VEL Q). VEL P correlated very closely with VEL D (r = 0.981, standard error of the estimate [SEE] = 17.0 and slope of the regression = 0.988). VEL Q, corrected for vena contracta effects, correlated with VEL P (r = 0.986, SEE = 21.6), but had a slope of 0.673. To experimentally determine the exponent of velocity in the Bernoulli equation, we plotted pressure drop against VEL D and found a value of 2.11; theory predicts 2.0. Experimental coefficient of velocity was 3.36 torr/m (standard deviation = 0.52), whereas theory predicts 3.75 for water. Orifice area, calculated using VEL D and the continuity equation, was consistently overestimated by 3 to 12% for flows that produced laminar jets. The pressure gradient and orifice areas calculated from Doppler-derived data accurately predict actual pressure gradients and orifice areas.

Value of isometric exercise testing during cardiac catheterization in mitral stenosis

To examine the value of preoperative isometric exercise testing during cardiac catheterization in patients with mitral stenosis, the isometric handgrip exercise test was performed on 28 patients during preoperative diagnostic catheterization. Eighteen patients who subsequently underwent mitral valve surgery were recatheterized and reevaluated clinically 12 months after operation. Preoperatively, the patients were divided into 2 groups: 16 whose mean mitral valve pressure gradient increased greater than 4 mm Hg during isometric exercise (group A) and 12 whose pressure gradient decreased or increased less than 4 mm Hg (group B). The ejection fraction remained unchanged and the peak systolic pressure/end-systolic volume ratio increased during isometric exercise in group A (p less than 0.001). In group B, the ejection fraction decreased (p less than 0.001) and the peak systolic pressure/end-systolic volume ratio remained unchanged. In the total group, a positive correlation existed between the change in mean mitral valve pressure gradient during isometric exercise and the changes in measures of left ventricular function during exercise. The patients in group A had a significant improvement in both symptoms and in exercise tolerance as determined by symptom-limited bicycle ergometry after surgery. The patients in group B showed minimal or no symptomatic improvement and their exercise tolerance did not improve. The change in mitral valve pressure gradient during isometric exercise appears to reflect the left ventricular response to exercise.

Effect of mitral valve replacement on left ventricular function in mitral regurgitation

To evaluate the effect of mitral valve replacement on left ventricular function in mitral regurgitation, we measured (1) the end-systolic stress/volume ratio, which is practically independent of changes in loading conditions, and (2) the left ventricular contractile reserves upon isometric exercise, both before and one year after mitral valve replacement in 11 patients with mitral regurgitation. The end-systolic stress/volume ratio increased, though the ejection fraction decreased after mitral valve replacement. The ejection fraction decreased and the end-systolic stress/volume ratio remained unchanged during isometric exercise before operation, whereas afterwards the ejection fraction remained unchanged and the end-systolic stress/volume ratio increased during exercise. Ventricular function improves after mitral valve replacement in patients with mitral regurgitation, though the ejection fraction, which is affected by altered loading conditions, deteriorates. The left ventricular response to stress caused by isometric exercise is also improved after surgery.

Left ventricular response to isometric exercise and its value in predicting the change in ventricular function after mitral valve replacement for mitral regurgitation

Reduced left ventricular (LV) afterload and its effect on the resting ejection fraction may lead to overestimation of LV function in mitral regurgitation (MR). To evaluate LV function during increased afterload of the heart, an isometric handgrip test was performed during cardiac catheterization in 15 patients with mitral regurgitation (MR group) and in 9 normal subjects (normal group). Twelve months after successful mitral valve replacement (MVR) the patients were recatheterized, and the value of preoperative stress testing in predicting the change in resting ventricular function after surgery was estimated. Isometric exercise caused an increase in endsystolic wall stress, a measure of ventricular afterload, in both the MR group and the control group (p less than 0.001). The ejection fraction remained unchanged in the control group, but decreased from 0.58 +/- 0.08 to 0.53 +/- 0.08 in the MR group (p less than 0.001). After MVR, end-systolic wall stress increased significant (p less than 0.001) and the ejection fraction decreased from 0.58 +/- 0.05 to 0.51 +/- 0.1 (p less than 0.05). A positive correlation existed between the change in the ejection fraction during preoperative stress testing and the change in the resting ejection fraction after MVR (r = 0.65, p less than 0.01). In 8 patients whose resting ejection fraction was within normal limits (greater than 0.55) preoperatively, the ejection fraction was depressed (less than 0.55) 1 year after surgery. In all but 1 of these patients the isometric exercise revealed the reduced ventricular response to afterload stress preoperatively (decrease of the ejection fraction greater than 0.03 during exercise). Therefore, the isometric exercise-induced change in LV function appears to predict the influence of MVR on LV function.

Hemodynamic factors that affect calculated orifice areas in the mitral hancock xenograft valve

From June 1974 to December 1978, 714 Hancock valves have been placed in 605 patients. One hundred seventy-five patients with a mitral xenograft have been restudied. The results were questionable due to the wide scatter and disparity between the calculated and the theoretical orifice of each valve size. To elucidate these differences, the hemodynamic data of 40 isolated, normal functioning mitral Hancock valves were reviewed. Early, middle and late diastolic mitral valve gradients were measured by planimetry and their corresponding flows were estimated by angiography. The paired data were fitted to exponential functions and specific lines for each Hancock valve size were obtained. By superimposing Gorlin's pressure and flow curves on these lines, the instantaneous effective orifice for each Hancock valve can be determined. We concluded that 1) the Hancock valve effective orifice is flow related and always lower than its theoretical opening; 2) normal function frequently cannot be firmly established by the mean effective area; and 3) the nomogram described may help in determining the time-related variations of a particular valve.

Determination of pre- and postoperative flow obstruction in patients undergoing closed mitral commissurotomy from non-invasive ultrasound Doppler data and cardiac output

A non-invasive ultrasound Doppler system and indwelling thermodilution catheter system were used to determine the pre- and postoperative mitral flow obstruction in eight adults undergoing closed mitral commissurotomy. The effective valve area (Ae) was used as a measure of the obstruction. In the eight patients Ae was 1.08 +/- 0.34(SD) cm. 2 preoperatively and increased to 1.71 +/- 0.43(SD) cm. 2 postoperatively. The technique used in the investigation appears useful for the evaluation of surgical procedures designed to reduce the mitral flow obstruction.

Hemodynamic evaluation of Lillehei-Kaiser and Starr-Edwards prosthesis

The central-flow low profile disc-valve prosthesis has been offered as an alternative to ball- and tissue-valve prostheses. Extensive laboratory investigation with both pulse duplicator and experimental animals has been reported for the Lillehei-Kaster prosthesis. A series of patients receiving this prosthesis underwent postoperative cardiac catheterization to better define the hemodynamic function of this prosthesis in vivo. Because of the variations in reports of hemodynamic data from various institutions, the results of post-operative studies in an earlier group of patients with Starr-Edwards prostheses were used as a standard for comparison. Good hemodynamic function was found with the pivoting-disc prosthesis in all but the smallest valve sizes. Lillehei-Kaster and early model Starr-Edwards prostheses with equivalent tissue annulus dimensions were found to have nearly equal valve areas in vivo in the aortic position. The Lillehei-Kaster mitral valves provided larger areas than Starr-Edwards prostheses in large tissue annulus sizes.

Determination of effective orifice area in mitral stenosis from non-invasive ultrasound Doppler data and mitral flow rate

Ten patients with mitral stenosis, but without mitral insufficiency, have been studied during cardiac catheterization. The mitral orifice blood velocities, the mitral pressure gradient, and the mitral flow rate were determined with ultrasound, manometry, and the direct Fick method, respectively. The effective orifice area was calculated from the ultrasound data and the mitral flow rate. The geometric orifice area was calculated from the pressure gradient and the mitral flow rate, using a revised Gorlin formula. A comparison of the two methods showed a correlation coefficient of 0.975. The investigation demonstrated that the ultrasound method represents an alternative to the conventional catheterization methods used for the quantification of mitral flow obstruction.

Hemodynamic changes during ventricular pacing in patients with complete heart block and aortic and mitral valvular heart disease

Increasing the heart rate to near normal in patients with complete heart block (CHB) and slow ventricular rates may lead to greater improvement in ventricular function than when the heart rate is increased from normal to more rapid heart rates. Improvement in ventricular function is usually manifested by a decrease in left ventricular end-diastolic pressure (LVEDP) and volume and by an increase in contractility. In patients with both CHB and valvular heart disease improvement in ventricular function during pacing may be modified by the nature of the valvular disease. Hemodynamic data from six patients with both valvular heart disease and CHB were compared with those from ten patients with CHB and normal cardiac valves. Hemodynamic studies were performed at slow or idioventricular rates and again after increasing the heart rate to more nearly normal levels by ventricular pacing. When obstruction to left ventricular inflow (mitral stenosis) co-existed with CHB, increasing the heart rate resulted in a reduction of an elevated LVEDP to normal. This resulted in only a small increase in left atrial pressure in spite of a striking increase in the mean left atrial-ventricular gradient. When obstruction to left ventricular outflow prevailed (aortic stenosis), improvement in cardiac function was manifested mainly by a decrease in LVEDP and was accompanied by a decrease in left ventricular stroke work. When a large regurgitant volume (aortic insufficiency) was added to a ventricle which has enlarged subsequent to CHB, there was striking elevation in ventricular filling pressures which returned to more nearly normal levels when the heart rate was increased. This was accompanied by a reduction in regurgitant stroke volume in the patient in whom it was measured. Thus, an increase in heart rate may be especially beneficial to those patients with CHB who also have valvular lesions which contribute to an increase in LVEDP and end-diastolic volume. Careful hemodynamic evaluation is helpful in determining appropriate therapy in these patients.