Demonstration of postvalvuloplasty hemodynamic improvement in aortic stenosis based on Doppler measurement of valvular resistance

Impact of valvular resistance on aortic regurgitation after transcatheter aortic valve replacement according to the type of prosthesis

BACKGROUND

The impact of aortic valvular resistance (VR) on the degree of post-transcatheter aortic valve replacement (TAVR) aortic regurgitation (AR) remains unclear. The objective of the study was to investigate the relationship between VR and paravalvular AR after TAVR.

METHODS

Between August 2007 and December 2015, 708 TAVR patients had sufficient data to calculate VR before the intervention and were eligible for the present analysis. The patient population was dichotomized according to VR. The association between VR and post-TAVR AR was separately assessed by prosthesis type.

RESULTS

Among patients with low VR (LVR; < 238 dynes/cm⁵), 176 (49.7%) patients were treated with balloon-expandable (BE) valves and 178 (51.3%) patients with self-expandable (SE) transcatheter valves. Among patients with high VR (HVR ≥ 238), 147 (41.5%) and 207 (68.5%) patients received BE and SE, respectively. Baseline characteristics were similar in both groups irrespective of the type of valve. Patients with HVR had a 2.5-fold risk of ≥ moderate post-TAVR AR compared to patients with LVR. Both, HVR (HR_adj 2.45, 95% CI 1.33-4.51) and the use of SE (HR_adj 3.11, 95% CI 1.66-5.82), emerged as independent predictors of ≥ moderate post-TAVR AR. Moderate or greater post-AR was consistently predicted in patients treated with SE (HR_adj 2.42, 95% CI 1.22-4.80) irrespective of the level of VR.

CONCLUSIONS

HVR is associated with a nearly 2.5-fold increased risk of moderate or greater post-TAVR AR and is an independent predictor of post-TAVR AR.

Mitral valve resistance determines hemodynamic consequences of severe rheumatic mitral stenosis and immediate outcomes of percutaneous valvuloplasty

INTRODUCTION

The mitral valve area (MVA) poorly reflects the hemodynamic status of (MS). In this study, we compared the MVA with mitral valve resistance (MVR) with regard to the determination of hemodynamic consequences of MS and the immediate outcomes of percutaneous balloon mitral valvuloplasty (PBMV).

METHODS

In a prospective study, 36 patients with severe rheumatic MS with left ventricular ejection fraction (LVEF) >50% were evaluated. They underwent transthoracic echocardiography (TTE) and catheterization. The MVA was measured by two-dimensional planimetry and pressure half-time (PHT), and the MVR was calculated using the equation: 1333 × transmitral pressure gradient mean transmitral diastolic flow rate.

RESULTS

The patients' mean age was 47.8±10.5 years. MVR ≥140.6 dynes·s/cm⁵ detected systolic pulmonary arterial pressure (sPAP) >55 mm Hg with a sensitivity of 100% and a specificity of 74%. The sensitivity and specificity of MVA<0.75 cm² to discriminate elevated sPAP were 81% and 89%, respectively. PHT ≥323.5 mseconds had a sensitivity of 78% and a specificity of 96% to detect an elevated sPAP. To predict a successful PBMV, preprocedural MVR ≥106.1 dynes·s/cm⁵ had a sensitivity of 100% and a specificity of 67% (area under the curve [AUC]=0.763; 95% confidence interval [CI]=0.520-1.006; P=.034); preprocedural MVA <0.95 cm² had a sensitivity of 78% and a specificity of 73% (AUC=0.730; 95% CI=0.503-0.956; P=.065); and preprocedural PHT ≥210.5 mseconds had a sensitivity of 73% and a specificity of 78% (AUC=0.707; 95% CI=0.474-0.941; P=.095).

CONCLUSIONS

MVR seems to be more accurate than MVA in determining the hemodynamic consequences of severe MS as determined by sPAP. In addition, preprocedural MVR detected successful PBMVs.

Mitral Valve Resistance as a Determinant of Resting and Stress Pulmonary Artery Pressure in Patients with Mitral Stenosis: A Dobutamine Stress Study

BACKGROUND

Severity of mitral stenosis (MS) is assessed by means of mitral valve area and mean transmitral gradient. However, these conventional stenosis indexes poorly reflect the major hemodynamic consequence of MS, which is increase in pulmonary artery pressure (PAP). Valve resistance (VR) is a physiologic expression of stenosis because it incorporates both the pressure gradient and flow data. Previously, in patients with aortic stenosis, hemodynamic burden on the left ventricle has been shown to be closely related to aortic VR but not to aortic valve area. Accordingly, we hypothesized that mitral VR may also better reflect the hemodynamic burden of MS and, hence, be an important determinant of PAP in patients with MS. This study sought to evaluate the relation between several echocardiographic parameters of MS severity, in particular mitral VR and the resting and stress PAP in patients with MS. Determinants of exercise capacity were also assessed.

METHODS

Twenty patients with pure MS were studied by Doppler echocardiography. Mitral valve area, mean transmitral gradient, mitral VR, net atrioventricular compliance, and left atrial diameter were derived from resting Doppler echocardiographic examination as possible determinants of resting and stress PAP. PAP was measured by Doppler echocardiography at rest and during dobutamine-induced stress. Patients completed a symptom-limited exercise test to determine exercise capacity. Determinants of resting and stress PAP and exercise capacity were analyzed.

RESULTS

Systolic PAP increased significantly from 39.2 +/- 9.4 mm Hg at rest to 59.5 +/- 18.4 mm Hg during dobutamine-induced stress. Mitral VR was the most closely correlated stenosis index with the resting and stress PAP (r = 0.80, P < .001 and r = 0.93, P < .001, respectively) and it was an independent predictor for both with multivariate analysis. Exercise capacity was mostly and equally correlated with stress PAP (r = -0.62, P = .004) and mitral VR (r = -0.62, P = .004). Multivariate analysis revealed stress PAP as the only significant independent predictor of exercise capacity.

CONCLUSION

Mitral VR is the strongest and the independent predictor of both resting and stress PAP in patients with MS and by this aspect it is superior to mitral valve area and mean transmitral gradient in the expression of stenosis severity. These results underline the importance of mitral VR as a severity index in patients with MS.

Echocardiographic and hemodynamic characteristics of reconstructed bicuspid aortic valves at rest and exercise

Repair of diseased bicuspid aortic valves has gained increasing interest as an alternative to conventional valve replacement. Hemodynamic data at exercise have not been reported before. The aim of this study was to investigate the clinical and echocardiographic status of patients after bicuspid aortic valve repair at rest and exercise. Between 03/94 and 09/02 a reconstruction of an incompetent bicuspid aortic valve was performed in 25 patients (mean age 35+/-12.1 years, group A, mean insufficiency 2.8 preoperatively). Patients were investigated clinically and echocardiographically after 2.1+/-2.4 (0.1-8.9) years at rest and exercise and compared to 20 controls (group B). Clinical followup was complete. There were no deaths, reoperations, thromboembolic or bleeding complications. At last examination 21 patients were in NYHA class I, n=4 in NYHA class II and mean aortic valve insufficiency (AI) was 1.0 with one patient having an AI>II degrees. Maximum and mean pressure gradient (dPmax/mean) across the aortic valve at rest were 14+/-5.5/7+/-2.6 mmHg for patients of group A and 7+/-2.5/3.6+/-1.1 mmHg in group B. Mean AVA at rest was 2.6+/-0.8 (group A) vs 2.9+/-0.6 cm(2) (group B, p=0.025), valvular resistance 13.4+/-4.8 (group A) vs 13.6+/-2.9 dyn x s x cm(-5) (group B, p>0.05). All individuals were stressed up to 100 W (dPmax/mean 21+/-6.8/11+/-3.6, group A vs 11+/-2.9/6+/-1.3 mmHg, group B). 56% of group A and 85% of group B could be stressed up to 175 W with dPmax/mean 24.5+/-8.3/12+/-4.2 and 16+/-3.6/8+/-1.4 mmHg, respectively (p<0. 01). Heart rate and blood pressure behavior were comparable. Left ventricular mass regression (preoperatively 369.3+/-76.4 vs 277.3+/-80.7 g at last examination, p<0.01) was significant in group A but did not reach normal values (group B, 227.8+/-71.1; p<0.01). Bicuspid aortic valve reconstruction reduces left ventricular volume load significantly. Although residual mild subclinical obstruction and incompetence were observed, the behavior of hemodynamics at exercise was comparable to controls. The clinical relevance of these findings in long term follow-up has to be evaluated.

Noninvasive quantitation of blood flow turbulence in patients with aortic valve disease using online digital computer analysis of Doppler velocity data

Previous experimental studies have demonstrated that aortic valve disease is associated with significant downstream turbulence (T). In this study, we developed a noninvasive method on the basis of Doppler velocity recording for quantitating aortic blood flow T in patients with aortic valve disease. The instantaneous blood velocity at a point in the aorta is equal to the sum of a mean periodic velocity component with a random or turbulent velocity component. According to the ensemble average method, time mean absolute T intensity is the root-mean-square value of turbulent velocity averaged over time and T is better quantitated by the relative T intensity (TIr), which is the ratio of absolute T intensity to the ensemble average velocity averaged over time. We computed TIr in 18 patients with mild to severe aortic stenosis and in 13 healthy volunteers from instantaneous modal velocities of 70 cycle length-matched heart beats recorded in the proximal part of the descending aorta by pulsed Doppler using an ultrasound system with an output port for online digital data transfer into a microcomputer. TIr was greater in patients with aortic valve disease (18.4 +/- 5.1%, range 11.2%-28.9%) than in control patients (7.9 +/- 1.9%, range 4.8%-9.8%; P =.0001). In patients with aortic valve disease, TIr was better linearly related to the ratio of postvalvular aorta to valvular orifice cross-sectional areas (r = 0.89, P =.0001) than to other parameters of valve restriction: transvalvular pressure gradient (r = 0.78, P =.0001); valve area (r = -0.56, P =.01); and valve resistance (r = 0.72, P =.0002). Thus, T that can be computed noninvasively from direct digital transfer of Doppler velocity data appears to be linearly related to indices of aortic valve restriction. Our data support the concept of the postvalvular aorta to valvular orifice cross-sectional areas ratio as a new important hemodynamic parameter in patients with aortic valve disease.

Dobutamine echocardiography in patients with aortic stenosis and left ventricular dysfunction: predicting outcome as a function of management strategy

STUDY OBJECTIVE

To prospectively address the question whether the assessment of valvular hemodynamics and myocardial function during low-dose dobutamine infusion can guide decision making in patients with aortic stenosis and left ventricular (LV) dysfunction.

PATIENTS AND MEASUREMENTS

Twenty-four patients with aortic stenosis and LV dysfunction (mean ejection fraction, 28%; New York Heart Association class, II to IV) were studied by dobutamine echocardiography assessing mean pressure gradient, aortic valve area, and aortic valve resistance. Patients were prospectively divided into severe and nonsevere aortic stenosis groups according to the response of the valve area to the augmentation of systolic flow. The clinical decision was considered to be concordant with the results of dobutamine echocardiography, when patients with severe aortic stenosis and preserved contractile function were referred by a specialist for aortic valve replacement and when patients with nonsevere aortic stenosis were not. Patients were observed for up to 3 years.

RESULTS

All eight patients with severe aortic stenosis who were referred for surgery survived and had good cardiovascular outcomes, and six of eight patients who were not initially referred for surgery had poor outcomes, including heart failure and sudden cardiac death. The eight patients with nonsevere aortic stenosis did comparatively well without valve replacement. Cardiac death or pulmonary edema occurred in 4 of 16 patients (25%) when the clinical decision was concordant with the results of the dobutamine echocardiogram and occurred in 6 of 8 patients (75%) when the clinical decision was discordant (p = 0.019 [chi(2) test]).

CONCLUSION

Patients with aortic stenosis, LV dysfunction, and relatively low gradients have better outcomes when management decisions are based on the results of dobutamine echocardiograms. Those patients identified as having severe aortic stenosis and preserved contractile reserve by dobutamine echocardiography should undergo surgery, while patients identified as having nonsevere aortic stenosis can be managed conservatively.

Stress Echocardiography in Aortic Stenosis: Insights into Valve Mechanics and Hemodynamics

Stress interventions have been classically combined with cardiac catheterization recordings to understand the hemodynamic principles of valvular stenosis. Indices of aortic stenosis such as pressure gradient and valve area were based on simple hydraulic principles and have proved to be clinically useful for patient management during a number of decades. With the advent of Doppler echocardiography, these hemodynamic indices can be readily obtained noninvasively. Abundant evidence obtained using exercise and pharmacological stress echocardiography has demonstrated that the assumptions of classic hemodynamic models of aortic stenosis were wrong. Consequently, it is recognized that conventional indices may be misleading indicators of aortic stenosis significance in particular clinical situations. To improve diagnostic accuracy, several alternative hemodynamic models have been developed in the past few years, including valve resistance and left ventricular stroke work loss, among others. Nevertheless, these more-accurate indices should be obtainable noninvasively and need to demonstrate greater diagnostic and prognostic power than conventional indices; preliminary data suggest such superiority. Stress echocardiography is well established as the tool of choice for testing hypothesis and physical models of cardiac valve function. Although the final role of alternative indices is not yet well established, the new insights into valvular hemodynamics provided by this technique may change the clinical assessment of aortic stenosis.

The relation between transaortic pressure difference and flow during dobutamine stress echocardiography in patients with aortic stenosis

OBJECTIVE

To investigate the relation between transaortic pressure difference and flow in patients with aortic stenosis.

METHODS

50 asymptomatic patients with all grades of aortic stenosis were studied using dobutamine stress echocardiography. Individual plots of mean pressure drop against flow were drawn. Comparisons were made between grades of aortic stenosis as defined by the continuity equation.

RESULTS

A significant linear relation between pressure difference and flow was found in 34 patients (68%). There was a significant curvilinear relation in four (8%), while no significant regression line could be fitted in 12 (24%). In the 34 patients with linear fits, the slopes (mean (SD)) were 0.08 (0.07) in mild, 0.10 (0.04) in moderate, and 0.22 (0.16) in severe aortic stenosis (p = 0. 0055).

CONCLUSIONS

Transaortic pressure difference can be related directly to flow in many patients with all grades of aortic stenosis. However, there are individual differences in slope and intercept suggesting that resistance calculated at rest may not always be representative. Raw pressure drop/flow plots may be an alternative method of describing valve function.

Aortic stenosis. Clinical evaluation and optimal timing of surgery

Aortic valve disease is common in the elderly with recent data suggesting that aortic sclerosis and stenosis are the end-stage of an active disease process. Aortic atenosis may be diagnosed at symptom onset (angina, heart failure or syncope) but often the diagnosis is suspected in an asymptomatic patient with a systolic murmur. The diagnosis can be confirmed and disease severity evaluated reliably using Doppler echocardiography. Symptomatic severe aortic stenosis is treated with valve replacement, even in the elderly, due to the extremely poor prognosis without relief of outflow obstruction. Management is controversial when there is coexisting moderate aortic stenosis and left ventricular systolic dysfunction.

Valve Resistance in Mitral Stenosis: Its Determinants and its Role in the Evaluation of the Disease

To evaluate the value and the determinants of valve resistance in mitral stenosis, 95 patients with pure mitral stenosis were examined by Doppler echocardiography during their clinical follow-up, measuring cavity dimensions, left ventricular function, mitral area (by planimetry and pressure half time), mean transmitral pressure gradient, aortic flow, and pulmonary artery systolic pressure. The mitral resistance was calculated as mean transmitral pressure gradient/aortic flow ratio. To graduate the severity of the morphological abnormalities in valvular structure, we used a point score system with evaluation of leaflet and subvalvular thickness, calcification, and valvular mobility. The functional class was determined according to NYHA classification. In this study, both mitral area (r = -0.79, P < 0.001 and r(p) = -0.60, P < 0.001) and mitral score (r = 0.68, P < 0.001 and r(p) = 0.25, P = 0.013) were independent determinants of mitral resistance. In multivariate analysis, mitral resistance and female gender were selected by multiple linear regression analysis as determinants of pulmonary artery systolic pressure, and mitral area and pulmonary artery systolic pressure were selected by logistic linear regression analysis as determinants of NYHA functional class. In patients with moderate or severe mitral stenosis, the estimated probability for III and IV NYHA functional class considering mitral area 1 cm(2) or below went from 51.1-86.4% when mitral resistance below or above 130 dynes.sec.cm(-5), respectively, was considered together. Thus, mitral valve resistance should be used as a complement to the mitral area method in assessment of mitral stenosis, adding the effects of the reduction in mitral area and the damage in mitral valve apparatus.

Aortic valve resistance in aortic stenosis: Doppler echocardiographic study and surgical correlation

Four hundred seven patients with aortic stenosis who had Doppler echocardiography before surgery were studied to determine the feasibility of Doppler-derived valve resistance calculation and its clinical value. Patients with milder aortic stenosis had lower mean gradient, larger valve area, and lower maximal resistance than those with severe stenosis. Maximal resistance was related strongly to aortic stenosis severity but did not add any information after valve area and gradient were known and was not related to surgical mortality.

Comparison of valvular resistance, stroke work loss, and Gorlin valve area for quantification of aortic stenosis. An in vitro study in a pulsatile aortic flow model

BACKGROUND

Valvular resistance and stroke work loss have been proposed as alternative measures of stenotic valvular lesions that may be less flow dependent and, thus, superior over valve area calculations for the quantification of aortic stenosis. The present in vitro study was designed to compare the impacts of valvular resistance, stroke work loss, and Gorlin valve area as hemodynamic indexes of aortic stenosis.

METHODS AND RESULTS

In a pulsatile aortic flow model, rigid stenotic orifices in varying sizes (0.5, 1.0, 1.5 and 2.0 cm2) and geometry were studied under different hemodynamic conditions. Ventricular and aortic pressures were measured to determine the mean systolic ventricular pressure (LVSPm) and the transstenotic pressure gradient (delta Pm). Transvalvular flow (Fm) was assessed with an electromagnetic flowmeter. Valvular resistance [VR = 1333.(delta Pm/Fm)] and stroke work loss [SWL = 100.(delta Pm/LVSPm)] were calculated and compared with aortic valve area [AVA = Fm/(50 square root of delta Pm)]. The measurements were performed for a large range of transvalvular flows. At low-flow states, flow augmentation (100-->200 mL/s) increased calculated valvular resistance between 21% (2.0 cm2 orifice) and 66% (0.5-cm2 orifice). Stroke work loss demonstrated an increase from 43% (2.0 cm2) to 100% (1.0 cm2). In contrast, Gorlin valve area revealed only a moderate change from 29% (2.0 cm2) to 5% (0.5 cm2). At physiological flow rates, increase in transvalvular flow (200-->300 mL/s) did not alter calculated Gorlin valve area, whereas valvular resistance and stroke work loss demonstrated a continuing increase. Our experimental results were adopted to interpret the results of three clinical studies in aortic stenosis. The flow-dependent increase of Gorlin valve area, which was found in the cited clinical studies, can be elucidated as true further opening of the stenotic valve but not as a calculation error due to the Gorlin formula.

CONCLUSIONS

Within the physiological range of flow, calculated aortic valve area was less dependent on hemodynamic conditions than were valvular resistance and stroke work loss, which varied as a function of flow. Thus, for the assessment of the severity of aortic stenosis, the Gorlin valve area is superior over valvular resistance and stroke work loss, which must be indexed for flow to adequately quantify the hemodynamic severity of the obstruction.

The role of percutaneous aortic balloon valvuloplasty in patients with cardiogenic shock and critical aortic stenosis

OBJECTIVES

The goal of this study was to evaluate the role of percutaneous aortic valvuloplasty in patients with cardiogenic shock due to severe aortic stenosis and associated major comorbid conditions and to establish predictors of survival.

BACKGROUND

The prognosis for patients in cardiogenic shock with severe aortic stenosis is poor. Aortic valve replacement can be lifesaving, but the presence of multiorgan failure precludes these patients from operation. Percutaneous aortic balloon valvuloplasty has been used in these patients with short-term improvement and could be an alternative therapeutic option.

METHODS

Of 310 patients undergoing percutaneous aortic balloon valvuloplasty, 21 were in cardiogenic shock and were included in this study. All 21 patients had associated major comorbid conditions at the time of presentation.

RESULTS

After percutaneous aortic balloon valvuloplasty, systolic aortic pressure increased from 77 +/- 3 (mean +/- SEM) to 116 +/- 8 mm Hg (p = 0.0001); aortic valve area increased from 0.48 +/- 0.04 to 0.84 +/- 0.06 cm2 (p = 0.0001); and cardiac index increased from 1.84 +/- 0.13 to 2.24 +/- 0.15 liters/min per m2 (p = 0.06). Nine patients died in the hospital, two during the procedure and seven after successful percutaneous aortic balloon valvuloplasty (five from multiorgan failure). Five patients had vascular complications. Stroke, cholesterol emboli and aortic regurgitation requiring aortic valve replacement occurred in one patient each. Twelve patients (57%) survived and were followed up for 15 +/- 6 months; five patients subsequently died. The Kaplan-Meier survival curve showed a 38 +/- 11% survival rate at 27 months. The only predictor for longer survival rate was the postprocedure cardiac index.

CONCLUSIONS

1) Emergency percutaneous aortic balloon valvuloplasty can be performed successfully as a lifesaving procedure. 2) Morbidity and mortality remain high despite successful percutaneous aortic balloon valvuloplasty. 3) For nonsurgical candidates, percutaneous aortic balloon valvuloplasty may be the only therapeutic alternative.

A new Doppler imaging measurement in aortic stenosis: the contour length of the jet origin flow area. Relationships between both, with usual Doppler data and left ventricular hypertrophy

Planimetry of stenotic aortic jet origin flow areas was performed using transthoracic Doppler imaging, with measurement of the contour length of flow areas and calculation of a contour/area (C/A) Doppler ratio on a group of 75 patients with aortic stenosis ranging from 0.27 to 2.44 cm2. The purpose was to study correlations of these data with the usual Doppler data and with left ventricular hypertrophy. The "r" coefficient between planimetered flow areas and those calculated by the continuity equation method was 0.89. Mean values (SD) of data were: areas: (planimetry) 1.00 +/- 0.53 cm2, (continuity equation) 0.91 +/- 0.42 cm2, contours: 5.6 +/- 1.6 cm, C/A: 0.66 +/- 0.25, maximal and mean pressure gradients: 68 +/- 34 and 37 +/- 21 mmHg, left ventricular hypertrophy: 138 +/- 30 g/m2 BSA (vs. 100 +/- 18 in normals). All values except age, gender and BSA, differed significantly (p < 0.001) between areas below or over 0.85 cm2. Other correlations between parameters were significant (p < 0.01 to 0.001), but with lower "r" coefficients due to widely scattered individual values. Contours increased much less rapidly than areas did, and were correlated with left ventricular hypertrophy only when coupled in the C/A ratio, with a higher "r" coefficient (0.62) than areas alone (0.52). Study of both areas and contours helps to approach the geometry of the orifice. This suggests that the individual geometry of the stenosis might weigh on the left ventricular mass growth, as an associated factor for a given decrease in stenotic area.

Effect of exercise on valvular resistance in patients with mitral stenosis

OBJECTIVES

This exercise study assessed the relation between valvular resistance and flow in patients with mitral stenosis.

BACKGROUND

Valvular resistance has been proposed as an alternative measure of stenotic valvular lesions, which is speculated to remain stable under changing hemodynamic conditions.

METHODS

In 35 of 40 patients with pure or predominant mitral stenosis, continuous wave Doppler measurements of the mitral stenotic jet were possible at rest and during supine bicycle ergometry. Simultaneously, transvalvular flow was assessed by thermodilution technique. For calculation of valvular resistance, the mean mitral valve pressure gradient was determined according to the simplified Bernoulli equation and divided by transvalvular flow. Additionally, effective mitral valve area was calculated according to the continuity equation method, dividing flow by the mean diastolic flow velocity.

RESULTS

Valvular resistance was 65 +/- 32 dynes.s.cm-5 at rest and increased to 82 +/- 43 dynes.s.cm-5 at 25 W (p < 0.001). The most prominent increase in valvular resistance (rest to 25 W 63 +/- 28 to 95 +/- 48 dynes.s.cm-5, p < 0.001) was found in those patients who had no or only a moderate (< 20%) change in effective mitral valve area. In contrast, valvular resistance remained constant (67 +/- 36 vs. 70 +/- 32 dynes.s.cm-5) in patients with a significant (> or = 20%) increase in mitral valve area with exercise.

CONCLUSIONS

In patients with mitral stenosis, the exercise-induced changes in valvular resistance are heterogeneous. This is the result of the variable response of mitral valve area to an increase in flow. In the individual patient, mitral valve area can significantly increase, a factor that has to be taken into account when interpreting the hemodynamic relevance of the obstruction. Calculated valvular resistance is flow dependent and has no advantage over valve area calculations for quantifying mitral stenosis.

Simplified method for calculating aortic valve resistance: correlation with valve area and standard formula

Aortic valve resistance (AVR) is a useful index to assess the severity of aortic stenosis. This study compared the standard method to calculate AVR with a simplified method based on the conventional approach for measuring vascular resistance: AVR = (peak-to-peak transaortic pressure gradient/(cardiac output*2.5))*80, where 80 is a conversion factor and 2.5 assumes that the systolic ejection period comprises 40% of the R-R cycle. We compared the standard AVR, the simplified AVR, and the Gorlin-derived value area in 118 patients with pure or dominant aortic stenosis. There was a strong linear correlation between the standard and simplified AVR (r = 0.96, p < .0001). There was a curvilinear relation between the aortic valve area and AVR (r = 0.92, p < .001). In 48 patients with aortic valve area > or = 0.7 cm2, the AVR was < 300 dynes-sec-cm-5 in 45 patients (94%) by the standard method and in 42 patients (88%) by the simplified method (p = NS). In conclusion, our method for measuring AVR is accurate and simpler than the standard method.

Effects of dobutamine on Gorlin and continuity equation valve areas and valve resistance in valvular aortic stenosis

Previous studies demonstrated changes in aortic valve area calculated by the Gorlin equation under conditions of varying transvalvular flow in patients with valvular aortic stenosis (AS). To distinguish between flow-dependence of the Gorlin formula and changes in actual orifice area, the Gorlin valve area and 2 other measures of severity of AS, continuity equation valve area and valve resistance, were calculated under 2 flow conditions in 12 patients with AS. Transvalvular flow rate was varied by administration of dobutamine. During dobutamine infusion, right atrial and left ventricular end-diastolic pressures decreased, left ventricular peak systolic pressure and stroke volume increased, and systolic arterial pressure did not change. Heart rate increased by 19%, cardiac output by 38% and mean aortic valve gradient by 25%. The Gorlin valve area increased in all 12 patients by 0.03 to 0.30 cm2. The average Gorlin valve area increased from 0.67 +/- 0.05 to 0.79 +/- 0.06 cm2 (p < 0.001). In contrast, the continuity equation valve area (calculated in a subset of 6 patients) and valve resistance did not change with dobutamine. The data support the conclusion that flow-dependence of the Gorlin aortic valve area, rather than an increase in actual orifice area, is responsible for the finding that greater valve areas are calculated at greater transvalvular flow rates. Valve resistance is a less flow-dependent means of assessing severity of AS.