Modified orifice equation for the calculation of mitral valve area

Precision medicine in human heart modeling : Perspectives, challenges, and opportunities

Precision medicine is a new frontier in healthcare that uses scientific methods to customize medical treatment to the individual genes, anatomy, physiology, and lifestyle of each person. In cardiovascular health, precision medicine has emerged as a promising paradigm to enable cost-effective solutions that improve quality of life and reduce mortality rates. However, the exact role in precision medicine for human heart modeling has not yet been fully explored. Here, we discuss the challenges and opportunities for personalized human heart simulations, from diagnosis to device design, treatment planning, and prognosis. With a view toward personalization, we map out the history of anatomic, physical, and constitutive human heart models throughout the past three decades. We illustrate recent human heart modeling in electrophysiology, cardiac mechanics, and fluid dynamics and highlight clinically relevant applications of these models for drug development, pacing lead failure, heart failure, ventricular assist devices, edge-to-edge repair, and annuloplasty. With a view toward translational medicine, we provide a clinical perspective on virtual imaging trials and a regulatory perspective on medical device innovation. We show that precision medicine in human heart modeling does not necessarily require a fully personalized, high-resolution whole heart model with an entire personalized medical history. Instead, we advocate for creating personalized models out of population-based libraries with geometric, biological, physical, and clinical information by morphing between clinical data and medical histories from cohorts of patients using machine learning. We anticipate that this perspective will shape the path toward introducing human heart simulations into precision medicine with the ultimate goals to facilitate clinical decision making, guide treatment planning, and accelerate device design.

Percutaneous mitral commissurotomy in rheumatic mitral stenosis associated with cor triatriatum

Cor triatriatum is an uncommon congenital anomaly and its coexistence with rheumatic mitral stenosis is rare. We report two patients with rheumatic mitral stenosis with associated cor triatriatum. Percutaneous mitral valvuloplasty was successfully performed in both cases. We describe the clinical presentation and discuss the technical issues related to balloon mitral valvotomy in these cases.

Assessment of mitral valve area during percutaneous mitral valve repair using the MitraClip system: comparison of different echocardiographic methods

BACKGROUND

Quantification of the mitral valve area (MVA) is important to guide percutaneous mitral valve repair using the MitraClip system. However, little is known about how to best assess MVA in this specific situation.

METHODS AND RESULTS

Immediately before and after MitraClip implantation, comprehensive 3-dimensional (3D) transesophageal echocardiography data were acquired for MVA assessment by the pressure half-time method and by two 3D quantification methods (mitral valve quantification software and 3D quantification software). In addition, transmitral gradients by continuous-wave Doppler (dPmeanCW) were measured to indirectly assess MVA. Data are given as median (interquartile range). Thirty-three patients (39% women) with a median age of 77.1 years (12.4 years) were studied. Before intervention, the median MVAs by the pressure half-time method, mitral valve quantification software, and 3D quantification software were 4.4 cm(2) (2.0 cm(2)), 4.7 cm(2) (2.4 cm(2)), and 6.2 cm(2) (2.4 cm(2)), respectively (P<0.001). After intervention, MVA was reduced to 1.9 cm(2) (0.7 cm(2)), 2.1 cm(2) (1.1 cm(2)), and 2.8 cm(2) (1.1 cm(2)), respectively (P=0.001). The median values for dPmeanCW before and after intervention were 1.0 mm Hg (1.0 mm Hg) and 3.0 mm Hg (3.0 mm Hg; P<0.001), respectively. At discharge, the median dPmeanCW was 4.0 mm Hg (3.0 mm Hg). In multivariate regression analyses including body surface area, the 3 different MVA methods, and dPmeanCW, a post-dPmeanCW ≥5 mm Hg was the best independent predictor of an elevated transmitral gradient at discharge.

CONCLUSIONS

Transmitral gradients by continuous-wave Doppler are quick, feasible in all patients, and superior to direct peri-interventional assessment of MVA. A postinterventional transmitral gradient by continuous-wave Doppler of ≥5 mm Hg best predicted elevated transmitral gradients at discharge.

Prediction of atrial fibrillation in patients with severe mitral stenosis--role of atrial contribution to ventricular filling

OBJECTIVE

Atrial contribution to ventricular filling was studied to assess its role in predicting the future development of atrial fibrillation (AF) in patients with severe mitral stenosis (MS) and sinus rhythm.

DESIGN

Two hundred and eight patients with severe MS and sinus rhythm were followed up for 1 year. Baseline data were compared between group I (who developed AF at follow-up) and group II (who maintained sinus rhythm). Left atrial size, severity of MS, velocity time integral (VTI) of mitral valve flow and VTI due to atrial systole (A-VTI) were noted. Percentage contribution of A-VTI to the total VTI (A-%) was calculated. Sensitivity and specificity of A-% to predict the onset of AF was obtained.

RESULTS

Left atrial size, severity of MS and total VTI were similar in the two groups. Group I patients were older (31.1 +/- 9.1 and 18.4 +/- 6.5 years, respectively, p < 0.03) with smaller A-VTI (5.3 +/- 2.2 and 6.7 +/- 3.4 cm, respectively, p < 0.01) and A-% (8.9 +/- 1.8 and 11.2 +/- 2.7, respectively, p < 0.003). A-% of <9% (mean value of A-VTI in group I) had high sensitivity (84%, positive predictive value 76%) and specificity (80%, negative predictive value 87%) to predict the development of AF.

CONCLUSION

Atrial contribution to ventricular filling is reduced in patients prone to develop AF (due to inefficient left atrial contraction, much before its dilatation). It can be used for early identification of patients likely to develop AF with high sensitivity and specificity. It is simple, easily available, cost-effective and will guide earlier intervention and more frequent follow-up. There is a preclinical loss in atrial pump function much before the eventual onset of AF.

Effect of three-dimensional valve shape on the hemodynamics of aortic stenosis: three-dimensional echocardiographic stereolithography and patient studies

OBJECTIVES

This study tested the hypothesis that the impact of a stenotic aortic valve depends not only on the cross-sectional area of its limiting orifice but also on three-dimensional (3D) valve geometry.

BACKGROUND

Valve shape can potentially affect the hemodynamic impact of aortic stenosis by altering the ratio of effective to anatomic orifice area (the coefficient of orifice contraction [Cc]). For a given flow rate and anatomic area, a lower Cc increases velocity and pressure gradient. This effect has been recognized in mitral stenosis but assumed to be absent in aortic stenosis (constant Cc of 1 in the Gorlin equation).

METHODS

In order to study this effect with actual valve shapes in patients, 3D echocardiography was used to reconstruct a typical spectrum of stenotic aortic valve geometrics from doming to flat. Three different shapes were reproduced as actual models by stereolithography (computerized laser polymerization) with orifice areas of 0.5, 0.75, and 1.0 cm(2) (total of nine valves) and studied with physiologic flows. To determine whether valve shape actually influences hemodynamics in the clinical setting, we also related Cc (= continuity/planimeter areas) to stenotic aortic valve shape in 35 patients with high-quality echocardiograms.

RESULTS

In the patient-derived 3D models, Cc varied prominently with valve shape, and was largest for long, tapered domes that allow more gradual flow convergence compared with more steeply converging flat valves (0.85 to 0.90 vs. 0.71 to 0.76). These variations translated into differences of up to 40% in pressure drop for the same anatomic area and flow rate, with corresponding variations in Gorlin (effective) area relative to anatomic values. In patients, Cc was significantly lower for flat versus doming bicuspid valves (0.73 +/- 0.14 vs. 0.94 +/- 0.14, p < 0.0001) with 40 +/- 5% higher gradients (p < 0.0001).

CONCLUSIONS

Three-dimensional valve shape is an important determinant of pressure loss in patients with aortic stenosis, with smaller effective areas and higher pressure gradients for flatter valves. This effect can translate into clinically important differences between planimeter and effective valve areas (continuity or Gorlin). Therefore, valve shape provides additional information beyond the planimeter orifice area in determining the impact of valvular aortic stenosis on patient hemodynamics.

Percutaneous transluminal mitral valvuloplasty improves cardiopulmonary baroreflex sensitivity in patients with mitral stenosis

Patients with heart failure frequently have increased sympathetic tone, which could result in part from impairment of the inhibitory influence of cardiopulmonary baroreflexes. Percutaneous transluminal mitral valvuloplasty (PTMV) provides a unique model for evaluating functional changes in cardiopulmonary baroreflexes without open-heart surgical manipulation. We examined the effects of PTMV on cardiopulmonary baroreflexes and sympathetic nerve activity in 10 patients with mitral stenosis. We measured muscle sympathetic nerve activity using microneurography. Cardiopulmonary baroreflex provocation was performed by applying a lower body negative pressure of -10 mm Hg, and its sensitivity was determined by dividing the percent change in muscle sympathetic nerve activity by the change in central venous pressure. Response to isometric exercise was assessed by handgrip at 30% of maximal voluntary contraction for 3 min. PTMV significantly increased mitral valve area and cardiac index and decreased mean left atrial pressure. PTMV significantly decreased burst rate from 25.1+/-2.5 to 15.6+/-2.6 bursts/min (p < 0.01) and burst incidence from 37.1+/-3.7 to 23.6+/-3.3 bursts/100 heart beats (p < 0.01). After PTMV, cardiopulmonary baroreflex sensitivities measured using burst rate and burst incidence were -39.9+/-4.9%/mm Hg and -38.7+/-6.2%/mm Hg, respectively, which were significantly steeper than those before PTMV (-9.2+/-1.1%/mm Hg and -8.4+/-1.1%/mm Hg; p < 0.01). There were significant correlations between muscle sympathetic nerve activity at rest and cardiopulmonary baroreflex sensitivity. PTMV did not affect muscle sympathetic responses to handgrip exercise. These results suggest that patients with mitral stenosis have baseline sympathetic nerve activation, which could result in part from impaired cardiopulmonary baroreflexes.

In vivo hemodynamic, histologic, and antimineralization characteristics of the Mosaic bioprosthesis

BACKGROUND

Performance of bioprosthetic valves is limited by tissue degeneration due to calcification with reduced performance and longevity. The Mosaic bioprosthetic valve (Medtronic Heart Valves, Inc, Minneapolis, MN) combines zero pressure fixation, antimineralization properties of alpha-amino oleic acid (AOA), and a proven stent design. We tested the hypothesis that AOA treatment of Mosaic valves improves hemodynamics, antimineralization properties, and survival in a chronic ovine model.

METHODS

Mitral valves were implanted in juvenile sheep with Mosaic valves with AOA treatment (n = 8) or without AOA treatment (non-AOA, n = 8), or Hancock I (HAN, n = 4) tissue valves, and explanted at 20 postoperative weeks.

RESULTS

Survival was equivalent in AOA and non-AOA (140 +/- 0.4 and 129 +/- 30 days), but was significantly less in HAN (82 +/- 35). Leaflet calcium (microgCa/mg tissue) was less in AOA (9.6 +/- 13.9; p < 0.05 versus non-AOA and HAN) than non-AOA (96.3 +/- 63.8) and HAN (130.8 +/- 43.2). Explant valve orifice area (cm2) was significantly preserved in the AOA group compared with the non-AOA group (1.5 +/- 0.7 vs 0.8 +/- 0.3; p < 0.05 versus non-AOA and HAN).

CONCLUSIONS

We conclude that AOA treatment of Mosaic valves reduces leaflet calcification and valve gradient in juvenile sheep, and that the Mosaic design and fixation features may offer survival advantages that must be confirmed in extended trials.

Significance of commissural calcification on outcome of mitral balloon valvotomy

OBJECTIVE

To evaluate the significance of commissural calcification, identified by transthoracic echocardiography, on the haemodynamic and symptomatic outcome of mitral balloon valvotomy.

METHODS

Commissural calcification was graded from 0-4 using parasternal short axis transthoracic views. The morphology of the mitral valve was also assessed using the Massachusetts General Hospital echo score.

SETTING

A tertiary cardiac centre in Scotland.

PATIENTS

300 patients were studied, 85 retrospectively and 215 prospectively. Mean (SD) age was 59.8 (12.7) years, range 13 to 87; 30% had been judged unsuitable for surgery. Median echo score was 6.8 (3.0), range 2-16.

MAIN OUTCOME MEASURES

Immediate increase in mitral valve area and in New York Heart Association functional class 1-3 months after balloon valvotomy.

RESULTS

On univariate and multivariate analysis, commissural calcification grade was a significant predictor of achieving a mitral valve area of > 1.50 cm(2) without severe mitral reflux. Its influence was greatest in patients with an echo score </= 8: those with commissural calcification grade 0/1 had significantly greater improvement in valve area and symptom status than those with grade 2/3; the proportions of patients achieving a final valve area of > 1.50 cm(2) were 67% and 46%, respectively (p < 0.05). In patients with an echo score of > 8, the influence of commissural calcification was smaller and not significant.

CONCLUSIONS

Commissural calcification as assessed by transthoracic echocardiography is a useful predictor of outcome in patients with otherwise "good" valves (echo score </= 8). Calcification of one commissure or more predicts a less than 50% probability of achieving a valve area above 1.50 cm(2) and is an indication for valve replacement in those who are suitable for surgery.

Long term outcome of percutaneous mitral balloon valvotomy in patients aged 70 and over

OBJECTIVE

To assess the immediate haemodynamic improvement and long term symptomatic benefit of percutaneous mitral balloon valvotomy in patients aged over 70 years.

DESIGN

Pre- and postprocedure haemodynamic data and follow up for 1 to 10 years by clinic visit or telephone contact.

SETTING

Tertiary referral centre in Scotland.

SUBJECTS

80 patients age 70 and over who had mitral balloon dilatation: 55 were considered unsuitable for surgical treatment because of frailty or associated disease. In an additional four patients mitral dilatation was not achieved.

MAIN OUTCOME MEASURES

Increase in valve area after balloon dilatation and survival, freedom from valve replacement, and symptom class at follow up.

RESULTS

Mean (SD) valve area increased by 89% from 0.84 (0.28) to 1. 59 (0.67) cm(2). There was a low rate of serious complications, with only two patients having long term major sequelae. Of 55 patients unsuitable for surgical treatment, 28 (51%) were alive without valve replacement and with improvement by at least one symptom class at one year, and 14 (25%) at five years. In the 25 patients considered suitable for surgical treatment, 16 (64%) achieved this outcome at one year and nine (36%) at five years.

CONCLUSIONS

Percutaneous mitral balloon valvotomy is a safe and useful palliative procedure in elderly patients who are unsuitable for surgery. Balloon dilatation should also be used for elderly patients whose valve appears suitable for improvement by commissurotomy, but echo score is an imperfect predictor of haemodynamic improvement.

Is redo percutaneous mitral balloon valvuloplasty (PMV) indicated in patients with post-PMV mitral restenosis?

OBJECTIVES

The purpose of this study was to assess the immediate and long-term outcome of repeat percutaneous mitral balloon valvuloplasty (PMV) for post-PMV mitral restenosis.

BACKGROUND

Symptomatic mitral restenosis develop in 7% to 21% of patients after PMV. Currently, most of these patients are referred for mitral valve replacement. However, it is unknown if these patients may benefit from repeat PMV.

METHODS

We report the immediate outcome and long-term clinical follow-up results of 36 patients (mean age 58+/-13 years, 75% women) with symptomatic mitral restenosis after prior PMV, who were treated with a repeat PMV at 34.6+/-28 months after the initial PMV. The mean follow-up period was 30+/-33 months with a maximal follow-up of 10 years.

RESULTS

An immediate procedural success was obtained in 75% patients. The overall survival rate was 74%, 72% and 71% at one, two, and three years respectively. The event-free survival rate was 61%, 54% and 47% at one, two, and three years respectively. In the presence of comorbid diseases (cardiac and noncardiac) the two-year event-free survival was reduced to 29% as compared with 86% in patients without comorbid diseases. Cox regression analysis identified the echocardiographic score (p = 0.03), post-PMV mitral valve area (p = 0.003), post-PMV mitral regurgitation grade (p = 0.02) and post-PMV pulmonary artery pressure (p = 0.0001) as independent predictors of event-free survival after repeat PMV.

CONCLUSIONS

Repeat PMV for post-PMV mitral restenosis results in good immediate and long-term outcome in patients with low echocardiographic scores and absence of comorbid diseases. Although the results are less favorable in patients with suboptimal characteristics, repeat PMV has a palliative role if the patients are not surgical candidates.

Clinical assessment and management of mitral stenosis

There have been significant advances in the diagnosis and treatment of the patient with mitral stenosis over the past two decades. Two-dimensional and Doppler echocardiography have supplanted the cardiac catheterization laboratory in the diagnosis and determination of the hemodynamic severity of the stenotic mitral valve. The development of a catheter-based approach for splitting fused commissures has led to earlier indications for intervention. It is likely that with the resurgence of rheumatic fever as well as influx of immigrant populations, the incidence of mitral stenosis may increase in the twenty-first century. It is thus important for the clinician to have a complete understanding of the evaluation and treatment options for the patient with mitral stenosis in the modern-day era.

Plasma levels of adrenomedullin in patients with mitral stenosis

Although plasma levels of adrenomedullin are elevated in patients with heart failure, levels in patients with mitral stenosis are unknown. We determined plasma levels of adrenomedullin in specimens of blood obtained from the peripheral veins of 15 consecutively treated patients with mitral stenosis 1 week before and 1 week after percutaneous mitral valvuloplasty. We also measured adrenomedullin in blood obtained from the right and left atria of 13 of 15 patients immediately before valvuloplasty. Plasma adrenomedullin level in the peripheral vein was 27.3 +/- 3.2 pg/ml among healthy subjects (n = 15) and 59.8 +/- 2.7 pg/ml among patients with mitral stenosis (n = 15, p < 0.0001). Plasma adrenomedullin level in the peripheral veins of patients with mitral stenosis before valvuloplasty correlated significantly with mean pulmonary artery pressure, mean pulmonary arterial wedge pressure, and mean left atrial pressure. Plasma levels of adrenomedullin in the peripheral vein and the right atrium were significantly higher than those in the left atrium (59.5 +/- 3.0 and 55.8 +/- 2.4 versus 45.9 +/- 2.9 pg/ml, n = 13, p < 0.005). Percutaneous mitral valvuloplasty caused a significant decrease in plasma adrenomedullin levels in peripheral veins from 59.8 +/- 2.7 to 49.9 +/- 3.1 pg/ml (p < 0.02). Percentage decrease in plasma adrenomedullin levels in the peripheral vein correlated significantly with percentage decreases in mean pulmonary artery pressure and mean pulmonary arterial wedge pressure. This study demonstrated that plasma adrenomedullin levels of patients with mitral stenosis correlated positively with mean pulmonary artery pressure and pulmonary arterial wedge pressure. These findings suggested that adrenomedullin may play an important role in the pulmonary circulation of these patients.

Changing concepts in the determination of valvular stenosis

The cardiovascular system can be characterized as a series of chambers connected by tubes and orifices. The circulatory physiology of this system is governed by hydrodynamic laws. The first application of hydrodynamics to stenotic valve orifices was by Gorlin and Gorlin in 1951, with direct measurement of transvalvular pressure gradients in the catheterization laboratory. The relative imprecision of fluid-filled catheters was corrected by the introduction of high fidelity micromanometric catheters in 1978. Echocardiography, which directly measures blood velocity, currently provides an accurate and widely applied tool for hemodynamic evaluation. Measured changes in blood velocity can derive pressure gradients previously measured by cardiac catheterization. In the clinically important range of determinations, there is excellent correlation between echocardiographic methods and the Gorlin formula for calculating valvular stenosis. Although noninvasive evaluation of heart valve stenosis has become standard, the same physical laws apply as in the 1950s, and practitioners need to be aware of the limitations of the various methods of hemodynamic calculation.

Effect of mitral valvuloplasty in mitral stenosis on coagulation activity

We investigated the plasma levels of molecular markers for the status of thrombin generation and fibrinolysis in patients with mitral stenosis before and after percutaneous mitral valvuloplasty. Our results show that percutaneous mitral valvuloplasty results in decreased coagulation activity, suggesting that percutaneous mitral valvuloplasty is also useful for prevention of systemic embolism in patients with mitral stenosis.

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.

Actuarial outcome after catheter balloon commissurotomy in patients with mitral stenosis

BACKGROUND

The goal of the present study was to determine the intermediate-term survival and the independent predictors of survival and event-free survival for patients who undergo catheter balloon commissurotomy (CBC).

METHODS AND RESULTS

CBC for the treatment of mitral stenosis was performed in 132 patients from 1986 through 1994. The use of CBC increased the mitral valve area (MVA) from 1.0 +/- 0.3 to 1.9 +/- 0.6 cm2 (P < .001). There were six early deaths (4.5%) up to 1 month after CBC ("hospital" deaths). In the past 4.5 years, there have been no hospital deaths. Four late deaths occurred after elective mitral valve replacement (MVR). Actuarial 7-year survival was 95 +/- 1%; when mortality after MVR is included, 7-year survival was 83 +/- 6%. Actuarial 1-, 3-, 5-, and 7-year event-free survival (survival without MVR or repeat CBC) was 80 +/- 4%, 77 +/- 4%, 65 +/- 6%, and 65 +/- 6%. On multivariate analysis, the only two independent predictors (both after CBC) of 7-year event-free survival were MVA of > or = 1.5 versus < 1.5 cm2 (75 +/- 7% versus 32 +/- 12%) and mean pulmonary artery wedge pressure of < or = 18 versus > 18 mm Hg (84 +/- 6% versus 38 +/- 11%) (P < .001 for both). Patients with MVA of > or = 1.5 cm2 (n = 96) could be further subdivided into high- and low-risk subgroups for 7-year event-free survival by two post-CBC variables: mean pulmonary artery wedge pressure of < or = 18 versus > 18 mm Hg (90 +/- 6% versus 48 +/- 14%) (P = .0002) and cardiac index of > or = 2.5 versus < 2.5 L.min-1.m-2 (82 +/- 8% versus 61 +/- 13%) (P = .004). Patients with post-CBC MVA of < 1.5 cm2 (n = 24) had no additional predictors of event-free survival. Of patients who did not undergo MVR or repeat CBC, 8% were in New York Heart Association functional class III and 92% were in class I or early class II at the last follow-up.

CONCLUSIONS

The rates for intermediate-term survival and event-free survival after CBC are very encouraging. Most patients without events were asymptomatic or minimally symptomatic. Thus, in selected patients with mitral stenosis who require an interventional procedure, CBC is the procedure of choice at centers with physicians who have experience and skill in performing this procedure.

Quantification of mitral valve stenosis by three-dimensional transesophageal echocardiography

The aim of this study was the evaluation of the diagnostic potentials of transesophageal 3D- echocardiography in the determination of mitral valve stenosis. 54 patients were investigated by transthoracic and multiplane transesophageal echocardiography. In 41 patients cardiac catheterization was performed. 3D- echocardiographic data acquisition was performed by automatic transducer rotation at 2 degree increments over a span of 180 degrees. The transesophageal probe was linked to an ultrasound unit and to a 3D- workstation capable of ECG- and respiration gated data acquisition, postprocessing and 2D/3D image reconstruction. The mitral valve was visualized in sequential cross-sectional planes out of the 3D data set. The spatial position of the planes was indicated in a reference image. In the cross-sectional plane with the narrowest part of the leaflets the orifice area was measured by planimetry. For topographic information a 3D view down from the top of the left atrium was reconstructed. Measurements were compared to conventional transthoracic planimetry, to Doppler-echocardiographic pressure half time and to invasive data. The mean difference to transthoracic planimetry, pressure half time and to invasive measurements were 0.3 +/- 0.1 cm2, 0.2 +/- 0.1 cm2 and 0.1 +/- 0.1 cm2, respectively. Remarkable differences between the 3D- echocardiographic and the 2D- or Doppler- echocardiographic methods were observed in patients with severe calcification or aortic regurgitation. In 22% of the patients the 3D data set was not of diagnostic quality. New diagnostic information from a 3D view of the mitral valve could be obtained in 69% of the patients. Thus, although image quality is limited, 3D- echocardiography provides new topographic information in mitral valve stenosis. It allows the use of a new quantitative method, by which image plane positioning errors and flow-dependent calculation is avoided.

Correspondence of aortic valve area determination from transesophageal echocardiography, transthoracic echocardiography, and cardiac catheterization

The correspondence of aortic valve area measurements from transesophageal echocardiography, transthoracic echocardiography, and cardiac catheterization was determined in 100 patients with severe aortic stenosis (aortic valve area < or = 0.75 cm2), moderate aortic stenosis (aortic valve area > 0.75 to < or = 1.2 cm2), mild aortic stenosis (aortic valve area > 1.2 to < or = 2.0 cm2), and nonstenotic aortic valves (aortic valve area > 2.0 cm2). Because high correlation does not require high agreement, data were assessed by analysis of agreement. Aortic valve areas determined by transthoracic echocardiography (1.43 +/- 0.76 cm2), transesophageal echocardiography (1.40 +/- 0.79 cm2), and cardiac catheterization (1.47 +/- 0.82 cm2) were similar. Correlations between methods were excellent (r values = 0.96). "Limits of agreement" between the three comparisons did not differ significantly. Similar levels of agreement when comparing these independent methods for determining the aortic valve area indicate that direct planimetry by transesophageal echocardiography, the continuity equation with transthoracic echocardiography, and the Gorlin formula are equally accurate and may be used interchangeably. Clinically important discrepancies between methods are uncommon and are readily settled by adding a third method.

Measurement of mitral valve area in mitral stenosis: four echocardiographic methods compared with direct measurement of anatomic orifices

OBJECTIVES

This study sought to compare the mitral valve areas of patients with rheumatic mitral valve stenoses as determined by means of four echocardiographic and Doppler methods with those obtained by direct anatomic measurements.

BACKGROUND

There has been no systemic comparison between Doppler-determined valve areas and the true anatomic orifice in a single cohort.

METHODS

In 30 patients with mitral stenosis, the mitral valve areas determined by two-dimensional echocardiographic planimetry, pressure half-time, flow convergence region and flow area were compared with the values directly measured on the corresponding excised specimen by means of a custom-built sizer.

RESULTS

The correlation coefficient was r = 0.95 (SE 0.06, p < 0.0001) for two-dimensional planimetry; r = 0.80 (SE 0.09, p < 0.0001) for pressure half-time; r = 0.87 (SE 0.09, p < 0.0001) for flow convergence region; and r = 0.54 (SD 0.1, p < 0.002) for flow area. Two-dimensional echocardiographic planimetry, pressure half-time, flow convergence region and flow area overestimated the actual anatomic orifice by > 0.3 cm2 in 2, 1, 6 and 0 patients, respectively, and underestimated it by > 0.3 cm2 in 0, 4, 1 and 8 patients, respectively.

CONCLUSIONS

Mitral valve areas determined by two-dimensional planimetry, pressure half-time and proximal flow convergence region reliably correlated with size of the anatomic orifice. The flow area method provided a less reliable correlation.

Determination of mitral valve area in patients with mitral stenosis by the flow-convergence-region method during changing hemodynamic conditions

Twenty-eight patients with mitral stenosis underwent Doppler echocardiography at rest and during exercise to determine the accuracy of mitral valve area determination by the flow-convergence-region method during exercise-induced changing hemodynamic conditions. The mitral valve area calculated by using the flow-convergence-region method correlated strongly with that measured by the Gorlin formula both at rest (r = 0.85) and during exercise (r = 0.92) for all 28 patients studied. Although mitral valve area obtained by the flow-convergence-region method did not change (p = 0.1) in 16 patients with echocardiographic mitral scores > or = 12, it increased significantly during exercise (p = 0.0001) in 12 patients with echocardiographic mitral scores < 12. This study suggests that in mitral stenosis, the mitral valve area can be accurately estimated by the flow-convergence-region method both at rest and during changing hemodynamic conditions induced by supine bicycle exercise.

Insights from three-dimensional echocardiographic laser stereolithography. Effect of leaflet funnel geometry on the coefficient of orifice contraction, pressure loss, and the Gorlin formula in mitral stenosis

BACKGROUND

Three-dimensional echocardiography can allow us to address uniquely three-dimensional scientific questions, for example, the hypothesis that the impact of a stenotic valve depends not only on its limiting orifice area but also on its three-dimensional geometry proximal to the orifice. This can affect the coefficient of orifice contraction (Cc = effective/anatomic area), which is important because for a given flow rate and anatomic area, a lower Cc gives a higher velocity and pressure gradient, and Cc, routinely assumed constant in the Gorlin equation, may vary with valve shape (60% for a flat plate, 100% for a tube). To date, it has not been possible to study this with actual valve shapes in patients.

METHODS AND RESULTS

Three-dimensional echocardiography reconstructed valve geometries typical of the spectrum in patients with mitral stenosis: mobile doming, intermediate conical, and relatively flat immobile valves. Each geometry was constructed with orifice areas of 0.5, 1.0 and 1.5 cm2 by stereolithography (computerized laser polymerization) (total, nine valves) and studied at physiological flow rates. Cc varied prominently with shape and was larger for the longer, tapered dome (more gradual flow convergence proximal and distal to the limiting orifice): for an anatomic orifice of 1.5 cm2, Cc increased from 0.73 (flat) to 0.87 (dome), and for an area of 0.5 cm2, from 0.62 to 0.75. For each shape, Cc increased with increasing orifice size relative to the proximal funnel (more tubelike). These variations translated into important differences of up to 40% in pressure gradient for the same anatomic area and flow rate (greatest for the flattest valves), with a corresponding variation in calculated Gorlin area (an effective area) relative to anatomic values.

CONCLUSIONS

The coefficient of contraction and the related net pressure loss are importantly affected by the variations in leaflet geometry seen in patients with mitral stenosis. Three-dimensional echocardiography and stereolithography, with the use of actual information from patients, can address such uniquely three-dimensional questions to provide insight into the relations between cardiac structure, pressure, and flows.

Myocardial adrenergic nervous activity is intensified in patients with heart failure without left ventricular volume or pressure overload

OBJECTIVES

To clarify whether myocardial adrenergic activity is different in patients with heart failure without left ventricular volume or pressure overload, we used iodine-123 metaiodobenzylguanidine (MIBG) imaging to study patients with mitral stenosis.

BACKGROUND

In patients with heart failure due to cardiomyopathy or to valve diseases with volume or pressure overload, or both, myocardial adrenergic nerve activity is accelerated independent of underlying cause. However, it is not clear whether this change in myocardial adrenergic nerve activity is present in patients without left ventricular volume or pressure overload.

METHODS

The study patients were 20 men and women with normal left ventricular function and heart failure due to mitral stenosis. Planar MIBG images obtained from these patients were compared with images from nine age-matched healthy subjects (control group). Myocardial uptake of MIBG was calculated as the heart/mediastinal activity ratio. Storage and release of MIBG were calculated as percent myocardial MIBG washout from 15 min to 4 h after isotope injection. All 20 study patients underwent echocardiography, and 16 underwent right heart catheterization.

RESULTS

The heart/mediastinal activity ratio in the immediate images (15 min) did not show any significant difference between the patient and control groups. Myocardial washout was increased in patients with severe heart failure. The level of myocardial washout correlated with left atrial diameter (r = 0.51, p = 0.02) and mitral valve area calculated with Doppler echocardiography (r = -0.61, p < 0.01) and mitral valve area calculated with cardiac catheterization (r = -0.62, p = 0.02). The closest correlation existed between myocardial washout and cardiac output (r = -0.80, p < 0.01).

CONCLUSIONS

In heart failure due to mitral stenosis, myocardial adrenergic nerve activity is intensified. A decrease in cardiac output associated with mitral stenosis acts as a potent stimulus for this intensification.

Immediate and long-term results of balloon mitral commissurotomy for rheumatic mitral stenosis: comparison between Inoue and double-balloon techniques

We examined the immediate results and 2-year follow-up of percutaneous transvenous mitral commissurotomy (PTMC) using the Inoue balloon (IB) and double-balloon (DB) techniques. Short-term comparisons have been described, but long-term comparisons have not been available. PTMC was performed in 208 adult patients with symptomatic mitral stenosis (MS) and mitral valve area (MVA) of 0.94 +/- 0.2 cm2, by use of the IB in 157 (73.4%) and the DB technique in 56 (26.3%). Procedures were performed successfully and without complications in 198 (93%) cases. Adequate mitral dilatation (MVA = 1.6 cm2) without significant regurgitation was obtained in 179 (86%) of 192 patients. The final MVA was 2.0 +/- 0.43 cm2 after IB and 2.06 +/- 0.51 cm2 after DB (not significant). Technical difficulties and complications were more frequent with DB (16% vs 3.8%; p<0.001). Severe mitral regurgitation (grade III to IV) occurred in 4.6% of IB and 4.1% of DB (not significant), whereas grade 1 mitral regurgitation was greater with IB (21% vs 10.2%; p=0.01). A total of 172 patients were monitored an average of 23.8 +/- 10.6 months, with 83% in New York Heart Association functional class 1, echocardiographic MVA of 1.84 +/- 0.44 cm2, and restenosis rate of 22% at 36 months. PTMC is a safe, effective treatment for symptomatic MS. Results of both IB and DB techniques are similar, but the IB is simpler and safer, Long-term clinical improvement is maintained, although the restenosis rate seems to be progressive and related to inadequate immediate results.

Echocardiographic evaluation of congenital mitral valve anomalies in children

Congenital mitral valve anomalies were diagnosed in 65 children, whose ages ranged from newborn to 18 years, using 2-dimensional, color, pulsed-, and continuous-wave Doppler ultrasound. Data were collected over 7.5 years from 13,400 new studies. Data in these patients were compared with those obtained by cardiac catheterization, cardiac surgery, and autopsy. We detected 4 different lesions: (1) congenital mitral stenosis with 2 papillary muscles (n = 24); (2) parachute mitral valve, with a single papillary muscle (n = 24); (3) isolated cleft in the mitral valve (n = 10); and (4) double-orifice mitral valve (n = 7). A supravalvar mitral ring was detected in 21 patients with mitral stenosis; however, it never occurred as an isolated lesion and was invariably associated with some other left ventricular inflow or outflow obstruction. The supravalvar ring was associated with a parachute deformity of the mitral valve in 17 patients; in only 4 was this abnormality associated with mitral stenosis with 2 papillary muscles. In patients with congenital mitral stenosis, the peak and mean transmitral Doppler velocities were increased significantly compared with those in controls (peak velocity 1.53 +/- 0.74 vs 0.86 +/- 0.25 m/s, respectively, p < 0.01; mean velocity 1.13 +/- 0.61 vs 0.58 +/- 0.11 m/s, respectively, p < 0.01). The correlation between mean transmitral pressure gradient obtained by Doppler and cardiac catheterization was fair (r = 0.75). However, the correlation between the mitral valve areas calculated by the Doppler pressure half-time method and by the Gorlin formula was poor (r = 0.57).(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of proximal isovelocity surface area method with pressure half-time and planimetry in evaluation of mitral stenosis

OBJECTIVES

This study sought to 1) compare the accuracy of the proximal isovelocity surface area (PISA) and Doppler pressure half-time methods and planimetry for echocardiographic estimation of mitral valve area; 2) evaluate the effect of atrial fibrillation on the accuracy of the PISA method; and 3) assess factors used to correct PISA area estimates for leaflet angulation.

BACKGROUND

Despite recognized limitations of traditional echocardiographic methods for estimating mitral valve area, there has been no systematic comparison with the PISA method in a single cohort.

METHODS

Area estimates were obtained in patients with mitral stenosis by the Gorlin hydraulic formula, PISA and pressure half-time method in 48 patients and by planimetry in 36. Two different factors were used to correct PISA estimates for leaflet angle (theta): 1) plane-angle factor (theta/180 [theta in degrees]); and 2) solid-angle factor [1-cos(theta/2)].

RESULTS

After exclusion of patients with significant mitral regurgitation, the correlation between Gorlin and PISA areas (0.88) was significantly greater (p < 0.04) than that between Gorlin and pressure half-time (0.78) or Gorlin and planimetry (0.72). The correlation between Gorlin and PISA area estimates was lower in atrial fibrillation than sinus rhythm (0.69 vs. 0.93), but the standard error of the estimate was only slightly greater (0.24 vs. 0.19 cm2). The average ratio of the solid- to the plane-angle correction factors was approximately equal to previously reported values of the orifice contraction coefficient for tapering stenosis.

CONCLUSIONS

1) The accuracy of PISA area estimates in mitral stenosis is at least comparable to those of planimetry and pressure half-time. 2) Reasonable accuracy of the PISA method is possible in irregular rhythms. 3) A simple leaflet angle correction factor, theta/180 (theta in degrees), yields the physical orifice area because it overestimates the vena contracta area by a factor approximately equal to the contraction coefficient for a tapering stenosis.

Coagulation activity is increased in the left atrium of patients with mitral stenosis

OBJECTIVES

This study investigated the hemostatic status of the right and left atria in patients with mitral stenosis.

BACKGROUND

Systemic thromboembolism is a serious major complication in patients with mitral stenosis. However, the pathogenesis of thromboembolism in mitral stenosis is not fully understood.

METHODS

We determined the plasma levels of biochemical markers for platelet activity (platelet factor 4 and beta-thromboglobulin) and status of thrombin generation (fibrinopeptide A and thrombin-antithrombin III complex) and fibrinolysis (D-dimer and plasmin-alpha 2-plasmin inhibitor complex) in specimens of blood obtained from the peripheral vein and right and left atria of 12 consecutive patients with mitral stenosis who were undergoing percutaneous mitral valvuloplasty.

RESULTS

Plasma levels of platelet factor 4, beta-thromboglobulin, D-dimer and plasmin-alpha 2-plasmin inhibitor complex in the patients did not differ significantly between the right and left atria, whereas levels of fibrinopeptide A and thrombin-antithrombin III complex in the left atrium were significantly higher than those in the right atrium (fibrinopeptide A in the left and right atria 19.35 +/- 4.64 and 6.31 +/- 0.75 ng/ml [mean +/- SE], respectively, p < 0.02; thrombin-antithrombin III complex in the left and right atria 11.45 +/- 2.29 and 3.98 +/- 0.60 ng/ml, respectively, p < 0.01). Levels of fibrinopeptide A and thrombin-antithrombin III complex in the left atrium did not correlate with mean transmitral gradient, dimension of the left atrium or reciprocal of the mitral valve area. Peripheral blood plasma levels of von Willebrand factor antigen were significantly higher in the patients than in an age-matched control group of normal subjects (168 +/- 25% and 99 +/- 7%, respectively, p < 0.05) but showed no difference in the peripheral blood and right and left atria of the patients.

CONCLUSIONS

The coagulation system is activated in the left atrium of patients with mitral stenosis even during anticoagulation.

Color flow Doppler determination of transmitral flow and orifice area in mitral stenosis: experimental evaluation of the proximal flow-convergence method

To evaluate the in vivo accuracy of color Doppler flow-convergence methods for determining transmitral flow volumes and effective orifice areas in mitral stenosis, we studied two models for flow-convergence surface geometry, a hemispheric (HS) model and an oblate hemispheroid (OH) model in a chronic animal model with quantifiable mitral flows. Color Doppler flow mapping of the proximal flow-convergence region has been reported to be useful for evaluation of intracardiac flows. Flow-convergence methods in patients with mitral stenosis that use HS assumption for the isovelocity surface have resulted in underestimation of actual flows. Chronic mitral stenosis was created surgically in six sheep with annuloplasty rings (group 1) and 11 sheep with bioprosthetic porcine valves (group 2). Hemodynamic and echocardiographic/Doppler studies (n = 18 in group 1; n = 21 in group 2) were performed 20 to 34 weeks later. Left ventricular inflow obstruction was of varied severity, with mean transmitral valve gradients in group 1 ranging from 1.3 to 18 mm Hg and in group 2 ranging from 6.3 to 25.6 mm Hg. Although transmitral flows derived by both geometric flow convergence models showed significant correlations with reference cardiac outputs, the correlations for the OH model were better than those for the HS model (group 1, r = 0.86 for the OH model vs r = 0.72 for the HS model; group 2; r = 0.84 for the OH model vs r = 0.62 for the HS model). The OH model was also superior to the HS model in determining effective orifice areas compared to reference orifice areas determined by postmortem planimetry of anatomic orifices (group 1 only, r = 0.64 for OH vs 0.58 for HS), by the Gorlin and Gorlin formula (group 1, r = 0.63 for OH vs 0.72 for HS; group 2, r = 0.82 for OH vs 0.76 for HS), and by the Doppler pressure half-time method (group 1, r = 0.76 for OH vs 0.69 for HS; group 2, r = 0.84 for OH vs 0.62 for HS).(ABSTRACT TRUNCATED AT 400 WORDS)

A comparison of cylindrical and Inoue balloon techniques for mitral valvotomy in patients in the United Kingdom

OBJECTIVES

To compare the use of cylindrical balloons and the Inoue balloon for percutaneous mitral valvotomy in patients in the United Kingdom.

DESIGN

Comparison of the haemodynamic results, complications, and symptomatic outcome of balloon dilatation for mitral stenosis in consecutive patients treated by cylindrical balloons and a second consecutive series of patients treated by the Inoue balloon.

SETTING

A tertiary cardiac referral centre in Scotland.

PATIENTS

70 patients (mean age 60.6 years) treated by the single or double cylindrical balloon technique and 70 patients (mean age 58.9 years) treated with the Inoue balloon method.

MAIN OUTCOME MEASURES

Success in obtaining dilatation at the mitral orifice, procedure and screening times, increase in valve area, complications, and early symptomatic outcome.

RESULTS

Dilatation of the mitral valve was obtained in 91% of patients when cylindrical balloons were used and in 99% of patients treated with the Inoue balloon. Use of the Inoue balloon gave significantly shorter procedure and screening times. Technical problems in obtaining and maintaining the position at the mitral orifice were more common with cylindrical balloons. Improvements in valve area and symptoms were not significantly different with use of the two types of balloon. The Inoue balloon avoided cardiac tamponade and the creation of larger atrial septal defects, but had a higher incidence of increase in mitral reflux.

CONCLUSIONS

In these elderly patients, the Inoue balloon method was safer and faster for percutaneous mitral valvotomy, with a higher success rate for dilatation within the valve orifice. Haemodynamic and symptomatic improvement was similar with the two techniques.

Thermodilution left-sided cardiac output for valve area determination after balloon mitral valvotomy

This study was conducted to establish the validity of left-sided cardiac output measurement with a Swan-Ganz catheter and assess its accuracy in estimating mitral valve area (MVA) by the Gorlin formula. The use of right-sided cardiac output after balloon mitral valvotomy (BMV) can give inaccurate measurements for Gorlin-derived MVA because of the atrial septal defect (ASD) created during the procedure. The left-sided cardiac output was measured with a Swan-Ganz catheter (proximal port in the left atrium and then in the left ventricle, and distal port in the ascending aorta) in 10 consecutive patients before and after BMV. Gorlin-derived MVA cardiac output by this method was compared with (1) Gorlin-derived MVA by means of right-sided cardiac output with and without balloon occlusion of the ASD and (2) MVA measured by echocardiography. Before BMV, a close agreement with a good correlation between left-sided and right-sided cardiac output was found (r = 0.83, p = 0.006). Furthermore, Gorlin-derived MVA by cardiac output with either method was comparable with valve area by echo. After BMV, left-sided cardiac output correlated well (r = 0.92, p = 0.0002) and was comparable with right-sided cardiac output with occlusion of the ASD (mean difference 0.17 +/- 0.49 L/min, p = 0.3) but was significantly lower than the value obtained with open ASD (mean difference 0.93 +/- 0.77 L/min, p = 0.004). Comparison of the correspondent MVAs yielded similar results. Gorlin-derived MVA with left-sided cardiac output and MVA by echo were also similar.(ABSTRACT TRUNCATED AT 250 WORDS)

Value of exercise Doppler-echocardiography in patients with mitral stenosis

The value of exercise Doppler-echocardiography was studied in 60 patients with mitral valve stenosis. Patients were divided in three groups. In patients with a mitral valve area of more than 1.4 cm2, maximal and mean diastolic gradient over the mitral valve increased from 13.2 +/- 3.6 to 18.4 +/- 5.4 and from 5.2 +/- 1.9 to 8.8 +/- 3.0 mmHg, respectively. In patients with a mitral valve area in between 1.0 and 1.4 cm2, maximal and mean gradient increased from 19.0 +/- 8.0 to 28.1 +/- 8.9 and from 8.8 +/- 4.9 to 14.8 +/- 6.4 mmHg, respectively. In patients with a mitral valve area of less than 1 cm2, the maximal gradient increased from 21.5 +/- 5.8 to 34.2 +/- 8.7 and mean gradient increased from 11.8 +/- 4.1 to 20.3 +/- 5.8 mmHg. Mean tricuspid regurgitation velocity increased from 2.9 +/- 0.5 m/s to 3.6 +/- 0.5 m/s, indicating increase in right ventricular to right atrial pressure difference from 34 mmHg to 52 mmHg. We conclude that exercise during the Doppler-echocardiographic evaluation provides additional information about the hemodynamic significance of mitral stenosis and can therefore be of value in decision making.

Percutaneous transatrial mitral commissurotomy: immediate and intermediate results

OBJECTIVES

The purpose of this study was to evaluate the immediate and follow-up results of percutaneous transatrial mitral commissurotomy in 600 patients with rheumatic mitral stenosis.

BACKGROUND

Percutaneous transatrial mitral commissurotomy has emerged as an effective nonsurgical technique for patients with symptomatic mitral stenosis. Several studies have shown that the immediate results are comparable to closed and open mitral valvotomy.

METHODS

Percutaneous transatrial mitral commissurotomy was performed in 600 patients with rheumatic mitral stenosis by the double-balloon (290 patients [48.3%]) and flow-guided Inoue balloon (310 patients [51.7%]) techniques. There were 154 male (25.6%) and 446 female (77.4%) patients with a mean [+/- SD] age of 27 +/- 8 years (range 8 to 60). Atrial fibrillation was present in 26 patients (4.3%), mitral regurgitation < or = grade 2 in 62 (10.3%) and densely calcific valve in 12 (2%). All patients had clinical and echocardiographic (two-dimensional, continuous wave Doppler, color flow imaging) follow-up at 3-month intervals.

RESULTS

Percutaneous transatrial mitral commissurotomy was successful in 589 patients (98.1%), and optimal commissurotomy was achieved in 562 (93.6%), with an increase in mitral valve area from (mean +/- SD) 0.75 +/- 0.18 to 2.2 +/- 0.38 cm2 (p < 0.001) and a decrease in transmitral end-diastolic gradient from 27.3 +/- 6.1 to 3.8 +/- 4.2 mm Hg (p < 0.001). Mitral regurgitation developed or increased in 208 patients (34.6%). Six patients (1%) with mitral regurgitation required mitral valve replacement. Cardiac tamponade occurred in 8 patients (1.3%). Six patients (1%) died. Restenosis developed in 10 patients (1.7%) during a mean follow-up period of 37 +/- 8 months (range 6 to 66).

CONCLUSIONS

Percutaneous transatrial mitral commissurotomy is an effective, safe procedure with gratifying intermediate results. It should be considered the treatment of choice for rheumatic mitral stenosis.

Relation of pulmonary venous flow to mean left atrial pressure in mitral stenosis with sinus rhythm

To determine whether pulmonary venous flow measured by transesophageal Doppler echocardiography can be used to estimate mean left atrial pressure (LAP), we prospectively studied 12 consecutive patients with sinus rhythm undergoing percutaneous mitral balloon commissurotomy for their severe mitral stenosis (mitral valve area < 1.5 cm2). We correlated Doppler variables of pulmonary venous flow and the mean LAP measured by left atrial catheterization. Among the variables of the pulmonary venous flow, the systolic fraction (i.e., the systolic velocity-time integral expressed as a fraction of the sum of systolic and early diastolic velocity-time integral) correlated significantly with mean LAP (r = -0.71, p < 0.05) and mitral valve area (r = 0.64, p < 0.05). Peak velocity and velocity-time integral in systole also significantly correlated with mean LAP (r = -0.66, r = -0.67 respectively, p < 0.05). We conclude that the more severe the degree of mitral stenosis in patients with sinus rhythm, the less systolic pulmonary venous flow in severe mitral stenosis.

Exercise echocardiography in combined mild mitral valve stenosis and regurgitation

Dynamic mitral regurgitation (MR) is typically associated with either severe systolic left ventricular dysfunction or episodes of acute myocardial ischemia. We report three patients with mild combined mitral stenosis and regurgitation and normal global left ventricular systolic function who presented with severe exertional dyspnea. Upright bicycle exercise echocardiography revealed development of severe dynamic MR in all three cases with Doppler evidence of severe pulmonary hypertension. There was no echocardiographic or electrocardiographic evidence of ischemia. Exercise echocardiography is an established tool for assessing dynamic changes in transvalvar pressure gradients. These results suggest that exercise echocardiography may also be useful for evaluating changes in severity of MR and for the assessment of dynamic changes in pulmonary artery systolic pressures.

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.

Validation of the proximal flow convergence method. Calculation of orifice area in patients with mitral stenosis

BACKGROUND

It has been proposed recently that measuring the flow convergence region proximal to an orifice by Doppler flow mapping can provide a means of calculating regurgitant flow rate. Although verified in experimental models, this approach is difficult to validate clinically because there is no ideal gold standard for regurgitant flows in patients. However, this method also can be used to derive cardiac output or flow rate proximal to stenotic orifices and therefore to calculate their areas by the continuity equation (area = flow rate/velocity). Applying this method in mitral stenosis would provide a unique way of validating the underlying concept because the predicted areas could be compared with those measured directly by planimetry.

METHODS AND RESULTS

We studied 40 patients with mitral stenosis using imaging and Doppler echocardiography. Doppler color flow recordings of mitral inflow were obtained from the apex, and the radius of the proximal flow convergence region was measured at its peak diastolic value from the orifice to the first color alias along the axis of flow. Flow rate was calculated assuming uniform radial flow convergence toward the orifice, modified by a factor that accounted for the inflow funnel angle formed by the mitral leaflets. Mitral valve area was then calculated as peak flow rate divided by peak velocity by continuous-wave Doppler. The calculated areas agreed well with those from three comparative techniques over a range of 0.5 to 2.2 cm2: 1) cross-sectional area by planimetry (y = 1.08x-0.13, r = .91, SEE = 0.21 cm2); 2) area derived from the Doppler pressure half-time (y = 1.02x-0.14, r = .89, SEE = 0.24 cm2); and 3) area calculated by the Gorlin equation in the 26 patients who underwent catheterization (y = 0.89x + 0.08, r = .86, SEE = 0.24 cm2). Agreement with planimetry was similar for 22 patients with mitral regurgitation and 18 without it (P > .6), as well as for 6 in atrial fibrillation (P > .2).

CONCLUSIONS

These results validate the proximal flow convergence concept in the clinical setting and also demonstrate that it can be extended to orifice area calculation using the continuity equation.

Effects of mitral stenosis on pulmonary venous flow as measured by Doppler transesophageal echocardiography

Pulmonary venous flow as assessed by transesophageal echocardiography (TEE) is influenced by changes in left atrial pressure and function. In mitral stenosis (MS), normal left atrial hemodynamics are altered because there is a prolonged decay in diastolic pressure from the left atrium to the left ventricle and atrial function may be altered because of atrial fibrillation. To assess the effect of the prolonged atrial diastolic pressure decay caused by MS on pulmonary venous flow, we studied 27 patients with MS (mitral valve range 0.7 to 2.4 cm2) by pulsed-wave Doppler TEE of the left or right upper pulmonary vein, and compared results with those of 13 normal subjects. Of the 27 subjects with MS, 61% showed a blunted systolic flow pattern and 39% showed a normal flow pattern with greater systolic to diastolic flow ratio. Patients with atrial fibrillation had a predominantly blunted pattern, whereas patients with normal sinus rhythm exhibited both blunted and normal flow patterns. Patients with MS had a lower pulmonary venous peak systolic flow velocity and a longer diastolic pressure halftime than control subjects. Pulmonary venous peak systolic flow velocity was significantly decreased in the presence of atrial fibrillation (p = 0.004). The mitral valve pressure halftime significantly correlated with pulmonary venous diastolic pressure halftime (r = 0.54; p = 0.004) mitral valve area (r = -0.46; p = 0.02). In conclusion, it was found that MS alters pulmonary venous flow patterns, showing a decreased pulmonary venous systolic flow and a prolonged diastolic flow, which may be useful in assessing the hemodynamics of MS.

Cardiac compression with mitral stenosis: a haemodynamic challenge

The hemodynamics of pericardial restriction (diastolic equilibration of pressures in all the four chambers of heart) and that of mitral stenosis (presence of an end diastolic gradient between the left atrium and the left ventricle) appear mutually exclusive. We describe herein hemodynamic findings in two patients of rheumatic mitral stenosis associated with pericardial constriction in one patient and pericardial effusion with tamponade in the other. Disproportionate elevation of the pulmonary artery diastolic and wedge pressures as compared to the right atrial mean, and left and right ventricular end diastolic pressures was present in both patients. In constrictive pericarditis, the respiratory variation in pressure was reflected in the pulmonary artery wedge pressure but not in the left ventricular end diastolic pressure. The gradient between the pulmonary artery wedge pressure and the left ventricular end diastolic pressure was abolished completely during the inspiratory phase of respiration despite significant mitral stenosis. The difference in the pressure, however, was maintained throughout inspiration and expiration in pericardial effusion with tamponade. In patients with constrictive pericarditis and mitral stenosis, the pulmonary artery wedge pressure does not appear to be a true indicator of the left atrial pressure.

Comparison of results of percutaneous balloon valvuloplasty in patients with mild and moderate mitral stenosis to those with severe mitral stenosis. The North American Inoue Balloon Investigators

Most reported studies of percutaneous balloon valvuloplasty in adults with acquired mitral stenosis have used patients with severely stenosed valves. The risks and benefits of valvuloplasty were examined in a multicenter registry of patients to determine whether balloon valvuloplasty can effectively dilate less severely obstructed valves, and to clarify the role of this procedure in symptomatic patients with mild and moderate mitral stenosis. The study groups were derived from the North American Inoue Balloon Valvuloplasty Registry. Full hemodynamic data were available in 264 patients; 45 (17%) with mild or moderate mitral stenosis (mitral valve area > or = 1.3 cm2) were compared with the remaining 219 with severe mitral stenosis (valve area < 1.3 cm2). Percutaneous balloon valvuloplasty was performed using the anterograde transseptal technique with an Inoue balloon. The mean age of patients with mild and moderate mitral stenosis was 53 +/- 13 years, and all were symptomatic with a mean New York Heart Association functional class of 2.9 +/- 0.7. Balloon valvuloplasty resulted in an increase in calculated mitral valve area from 1.4 +/- 0.1 to 2.3 +/- 0.7 cm2 (p < 0.05), and a final valve area > or = 1.9 cm2 was achieved in 37 patients (82%). There were no procedural deaths, but complications included right atrial perforation, transient ischemic attack and emergency surgery for severe mitral regurgitation. One-year follow-up evaluation revealed symptomatic improvement in most patients (mean New York Heart Association class 1.4 +/- 0.6; p < 0.0001). However, 2 patients needed repeat valvuloplasty for restenosis, and 5 had mitral valve replacements.(ABSTRACT TRUNCATED AT 250 WORDS)

Factors determining late success after mitral balloon valvulotomy

Mitral balloon valvulotomy (MBV) has proved to be an effective method in the treatment of patients with mitral stenosis. Although several factors determining an optimal immediate result have been described, there is little information regarding long-term follow-up, as well as factors influencing late success after MBV. This study analyzes 350 patients (mean age 46 +/- 12 years) treated by MBV who were clinically followed up between 6 months and 6 years. At least 1 echo-Doppler follow-up study was obtained in 298 patients 28 +/- 14 months after MBV; hemodynamic reevaluations were performed in 66 patients after 23 +/- months. Late success was considered if the patient was in functional class I to II and free of major events (death, restenosis and valve surgery). Restenosis was defined as a 50% loss of initial gain with regard to valve area by echocardiography, which was confirmed hemodynamically. After a mean follow-up of 38 +/- 15 months, 296 patients (84%) remained in functional class I to II, without surgery or the need for an increase in medical treatment. The 5-year Kaplan-Meier survival rate was 94 +/- 1%, whereas restenosis, valve surgery and major event-free probability were 90 +/- 3%, 91 +/- 2% and 85 +/- 2%, respectively. Multivariate study (Cox regression model) identified the presence of sinus rhythm (p < 0.001) and the absence of calcium at fluoroscopy (p < 0.003) as the only independent factors of late success.(ABSTRACT TRUNCATED AT 250 WORDS)

Long-term echocardiographic evaluation of closed and open mitral valvulotomy

From 1968 to 1989, 280 patients with post-rheumatic pure mitral stenosis underwent surgical commissurotomy; 134 a closed and 146 an open technique. Follow-up exceeded 15 years in 56.7% of the patients. Echocardiographic analysis was performed in 120 patients and disclosed a larger mitral valve area in patients who underwent open valvulotomy (1.9 +/- 0.5 cm2 vs. 1.5 +/- 0.4 cm2 for the closed technique, P < 0.0002). On the other hand, considering the occurrence of post-surgical mitral regurgitation at a level greater than, or equal to moderate, open valvulotomy produced less favorable results (18.5% vs. 5% for the closed technique, P < 0.01).