Outcomes of transcatheter aortic valve implantation in high surgical risk and inoperable patients with aortic stenosis: a single Australian Centre experience.

BACKGROUND: Degenerative aortic stenosis is the most common valvular heart disease in the elderly, and many patients are not suitable for aortic valve replacement surgery. Transcatheter aortic valve implantation (TAVI) is a new therapeutic option for selected patients at high risk for surgery. AIM: To evaluate the safety and efficacy of TAVI in Australian patients. METHODS: This is a prospective study of patients undergoing TAVI for severe symptomatic aortic stenosis at The Prince Charles Hospital, Brisbane, Australia between August 2008 and July 2013. Patients were at high risk of surgical aortic valve replacement, or inoperable, as deemed by a multidisciplinary 'heart team'. Outcomes include procedural success and complications, 30-day and 1-year mortality and stroke, combined end-points as outlined by the Valve Academic Research Consortium 2 consensus document. RESULTS: Two hundred and nine patients underwent TAVI during the study period. The mean age was 83.7 ± 6.7 years, and 101 (48%) were men. The valve systems utilised were as follows: Edwards-SAPIEN valve in 104 (49.5%), Medtronic CoreValve in 86 (41.2%) and Boston Scientific Lotus valve in 19 (9.3%) patients. Thirty-day and 1-year mortality rates were 5.7% and 11.5% respectively. Thirty-day and 1-year stroke rates were 4.3% and 6.2% respectively. The composite end-points of device success, early safety and clinical efficacy occurred in 80.4%, 27.3% and 68.4%. CONCLUSIONS: TAVI with various valve systems, delivered through several approaches, is feasible in high surgical risk and inoperable patients with severe aortic stenosis, with acceptable outcomes at short-term and intermediate-term follow up.

Unusual case of acute posteromedial papillary muscle rupture after acute anterior myocardial infarction.

Papillary muscle rupture is now a rare complication of acute myocardial infarction. Posteromedial papillary muscle rupture is more common than anterolateral papillary muscle rupture. The posteromedial papillary muscle is usually supplied from a branch of the right coronary artery. We present a case of posteromedial papillary muscle rupture due to an isolated left anterior descending artery lesion. This was diagnosed on the fifth day post infarction. The patient progressed to mitral valve replacement and coronary artery bypass grafting to the left anterior descending artery. We believe this unusual arterial supply to the posteromedial papillary muscle is due to an apex forming left anterior descending artery coupled with an apically located posteromedial papillary muscle.

Echocardiography for the clinician: a practical update.

Echocardiography is the mainstay of cardiovascular diagnostics, and is the most performed test for the evaluation of cardiac function. Critical and costly management decisions are based on quantification of left ventricular volumes and ejection fraction. Recent advances in echocardiography, such as microsphere contrast echocardiography for left ventricular opacification and perfusion imaging, three-dimensional transthoracic and trans-oesophageal imaging, strain and tissue Doppler imaging, all contribute to improving accuracy and reproducibility of these important measurements. Such techniques are now routinely available on standard echocardiography equipment in Australian centres for daily use. Hand-carried ultrasound devices have been developed, which are portable, are affordable and offer increased availability of echocardiography to the wider community. Clinicians should be actively encouraged to adopt these technologies to improve the diagnostic quality and reproducability of echocardiography for our patients. This article provides an overview of important recent advances in echocardiographic imaging with an emphasis on their role in clinical practice today.

Lack of effect of coenzyme Q on left ventricular function in patients with congestive heart failure.

OBJECTIVES: This study evaluated the effects of oral therapy with coenzyme Q on echocardiographic and hemodynamic indexes of left ventricular function and on quality of life in patients with chronic left ventricular dysfunction. BACKGROUND: Coenzyme Q is a coenzyme for oxidative phosphorylation and an antioxidant and free radical scavenger. It has been claimed to improve symptoms, quality of life, left ventricular ejection fraction and prognosis in patients with cardiac failure. METHODS: Thirty patients with ischemic or idiopathic dilated cardiomyopathy and chronic left ventricular dysfunction (ejection fraction 26 +/- 6%) were randomized to a double-blind crossover trial of oral coenzyme Q versus placebo, each for 3 months. Right heart pressures, cardiac output and echocardiographic left ventricular volumes were measured at baseline and after each treatment phase, and quality of life was assessed using the Minnesota "Living With Heart Failure" questionnaire. It was calculated that to demonstrate an increase in left ventricular ejection fraction from 25% to 30% with a standard deviation of 5% using 95% confidence intervals with a power of 80% we would require 17 patients. RESULTS: Twenty-seven completed both treatment phases. There was no significant difference in left ventricular ejection fraction, cardiac volumes or hemodynamic and quality of life indices after treatment with coenzyme Q or placebo, although plasma coenzyme Q levels increased from 903 +/- 345 nmol/l(-1) to 2,029 +/- 856 nmol/l(-1). CONCLUSIONS: In patients with left ventricular dysfunction, treatment for three months with oral coenzyme Q failed to improve resting left ventricular systolic function or quality of life despite an increase in plasma levels of coenzyme Q to more than twice basal values.

Doppler characterization of left ventricular diastolic function in cardiac amyloidosis.

Sixty-four patients with primary systemic amyloidosis-53 with two-dimensional echocardiographic features of cardiac involvement (Group I) and 11 without cardiac involvement (Group II)--underwent Doppler echocardiographic assessment of left ventricular diastolic function. Pulsed wave Doppler recordings of left ventricular inflow velocities and pulmonary vein flow velocities with respiratory monitoring in these patients were compared with findings in a normal group. Patients in Group I showed striking abnormalities of left ventricular diastolic filling when classified into subgroups by mean left ventricular wall thickness: early greater than 12 but less than 15 mm; advanced greater than or equal to 15 mm. In early amyloidosis, relaxation was abnormal, with decreased peak early velocity (75 +/- 20 versus 86 +/- 16 cm/s; p less than 0.01), increased late velocity (71 +/- 22 versus 56 +/- 13 cm/s; p less than 0.01), decreased early to late velocity ratio (1.2 +/- 0.6 versus 1.6 +/- 0.5; p less than 0.01) and prolonged isovolumic relaxation time (87 +/- 15 versus 73 +/- 13 ms; p less than 0.01) compared with normal values. In advanced amyloidosis, there was a restrictive filling pattern with a markedly shortened deceleration time (148 +/- 50 versus 199 +/- 32 ms; p less than 0.001), decreased pulmonary vein peak systolic flow velocity (34 +/- 16 versus 54 +/- 12 cm/s; p less than 0.01) and increased diastolic flow velocity (55 +/- 20 versus 44 +/- 12 cm/s; p less than 0.01) compared with normal values. Group and the subgroup with early amyloidosis had similar flow velocity patterns. Thus, this study documents that in cardiac amyloidosis, a spectrum of diastolic filling abnormalities exists; the restrictive filling pattern is seen only in the advanced stages.

Comprehensive Doppler assessment of right ventricular diastolic function in cardiac amyloidosis.

To assess right ventricular diastolic function in cardiac amyloidosis, pulsed wave Doppler ultrasound measurements of right ventricular inflow velocities and superior vena cava and hepatic vein flow velocities with respiratory monitoring were performed in 41 patients with primary systemic amyloidosis and two-dimensional echocardiographic features of cardiac involvement. Right ventricular diastolic function was abnormal in 31 (76%) of these patients, the major abnormality being a short deceleration time (less than 150 ms) in 21 (68%), suggesting restriction. In contrast, 7 (23%) of the 31 patients had a decreased ratio of early (E) and late (A) diastolic peak flow velocities and a prolonged deceleration time (greater than 240 ms), suggesting abnormal relaxation. The patients were classified into two groups on the basis of right ventricular free wall thickness: group 1, less than 7 mm and group 2, greater than or equal to 7 mm. Compared with normal values, group 1 showed an increased peak late flow velocity (44 +/- 19 versus 39 +/- 6 cm/s; p less than 0.01) and a decreased E/A velocity ratio (1.1 +/- 0.4 versus 1.5 +/- 0.3; p less than 0.01). Group 2 showed a markedly shortened deceleration time (151 +/- 37 versus 225 +/- 28 ms; p less than 0.01), characteristic of restriction. In the overall group, superior vena cava peak flow velocity was decreased in systole and increased in diastole and flow reversals during inspiration were increased compared with normal values. Hepatic venous flow velocities were similar to those in the superior vena cava except for larger flow reversals in the hepatic vein. Thus, in cardiac amyloidosis, right ventricular diastolic function is abnormal. There is a spectrum of right ventricular filling abnormalities and the restrictive filling pattern is seen only in the advanced stages of the disease.

Two-dimensional echocardiographic findings in systemic sarcoidosis.

The records of 88 patients with systemic sarcoidosis who underwent 2-dimensional echocardiography were reviewed to define the typical echocardiographic abnormalities in patients with clinical evidence of cardiac involvement. Twelve patients (14%) had echocardiographic evidence of left ventricular systolic dysfunction attributed to cardiac sarcoidosis (segmental hypokinesis in 8 patients and global hypokinesis in 4 patients). A high incidence of congestive heart failure (9 of 12) and conduction system disease (7 of 12) was characteristic of these patients. The remaining 76 patients had normal echocardiograms or abnormalities attributed to nonsarcoid sources. In 8 (11%) of these 76 patients, there were significant clinically unexplained conduction abnormalities likely related to sarcoidosis.

Cardiac tamponade: characteristic Doppler observations.

Abnormal respiratory variation in diastolic filling has been reported in patients with cardiac tamponade. To determine the characteristic diastolic filling abnormalities in this disorder, we recorded left ventricular isovolumic relaxation time and transvalvular and hepatic venous flow velocities by pulsed-wave Doppler echocardiography in 28 patients with pericardial effusion (16 with and 12 without cardiac tamponade) and 20 normal control subjects. The phase of respiration was recorded simultaneously with all profiles. In 13 of the 16 patients with cardiac tamponade, Doppler examination was repeated after pericardiocentesis. In patients with cardiac tamponade, respiratory variations in transvalvular flow velocities and isovolumic relaxation time were substantially increased in comparison with values in normal subjects, patients without tamponade, and those who had undergone pericardiocentesis. An exaggerated expiratory decrease in diastolic forward flow and increase in reverse flow in the hepatic vein also were characteristic of patients with cardiac tamponade. Thus, Doppler echocardiography is an additional noninvasive means of detecting hemodynamic compromise in patients with pericardial effusion.

Effects of age on left ventricular dimensions and filling dynamics in 117 normal persons.

OBJECTIVE: To determine standard left ventricular Doppler measurements in a large reference group of various ages to reflect the senescence process. DESIGN: We prospectively studied the influence of aging on left ventricular diastolic filling by performing Doppler echocardiography in 117 normal healthy volunteers. MATERIAL AND METHODS: Transthoracic pulsed-wave Doppler echocardiographic studies of pulmonary venous flow and left ventricular inflow were done in the 53 male and 64 female study subjects. For analysis, the study subjects were arbitrarily classified into two groups: those younger than 50 years of age (group 1; N = 61) and those 50 years old or older (group 2; N = 56). RESULTS: A striking difference was found in pulmonary venous flow and left ventricular inflow between group 1 and group 2 subjects. Group 2 had increased pulmonary venous peak systolic flow velocity (71 +/- 9 versus 48 +/- 9 cm/s), decreased peak diastolic flow velocity (38 +/- 9 versus 50 +/- 10 cm/s), increased peak atrial reversal flow velocity (23 +/- 4 versus 19 +/- 4 cm/s), and increased percentage of forward flow in systole (65 +/- 7 versus 55 +/- 8%) in comparison with group 1. In group 2, peak early filling velocity (62 +/- 14 versus 72 +/- 14 cm/s) and ratio of early filling to atrial filling (1.1 +/- 0.3 versus 1.9 +/- 0.6) were lower and peak atrial filling velocity (59 +/- 14 versus 40 +/- 10 cm/s) was higher than in group 1. Deceleration time (210 +/- 36 versus 179 +/- 20 ms) and isovolumic relaxation time (90 +/- 17 versus 76 +/- 11 ms) were prolonged in group 2 in comparison with group 1. CONCLUSION: This study confirms the major influence of the aging process on left ventricular diastolic function in a large series of normal subjects. This physiologic factor should be considered in Doppler assessment of left ventricular diastolic filling in future studies.

Transesophageal echocardiography in an operation for pulmonary arteriovenous malformation.

Transesophageal echocardiography has been described as a useful tool in the diagnosis of pulmonary arteriovenous malformations. We describe a case in which intraoperative transesophageal echocardiography was used to aid localization and ensure complete surgical ligation.

Fenestrated atrial septal aneurysm: diagnosis by transesophageal echocardiography.

The diagnosis of atrial septal defect by transthoracic echocardiography remains difficult in a small subset of patients because of either suboptimal acoustic windows or unusual anatomy, for example, fenestrated defects. We report the case of a 55-year-old woman with a fenestrated atrial septal aneurysm that was incompletely visualized by transthoracic echocardiography. Subsequent transesophageal echocardiography demonstrated three defects within the atrial septal aneurysm with left-to-right shunting across each defect. Normal pulmonary venous connections were also defined. All echocardiographic findings were confirmed at surgery. This case demonstrates the additional diagnostic accuracy of transesophageal echocardiography for detecting disease of the atrial septum.

Three-dimensional echocardiography: historical development and current applications.

Three-dimensional (3D) echocardiography facilitates spatial recognition of intracardiac structures, potentially enhancing diagnostic confidence of conventional echocardiography. The accuracy of 3D images has been validated in vitro and in vivo. In vitro, a detail 1.0 mm in dimension and 2 details separated by 1.0 mm can be identified from a volume-rendered 3D image. In vitro 3D volume measurements are underestimated by approximately 4.0 mL. In vivo, left ventricular volume measurements correlate highly with both cineventriculography (limits of agreement +/-18 mL for end diastole and +/-10 mL for end systole) and magnetic resonance imaging, including measurements for patients with functionally single ventricles. Studies on congenital heart lesions have shown good accuracy and good reproducibility of dynamic "surgical" reconstructions of septal defects, aortoseptal continuity, atrioventricular junction, and both left and right ventricular outflow tract morphology. Transthoracic 3D echocardiography was shown feasible in 81% to 96% of patients with congenital heart defects and provided additional information to that available from conventional echocardiography in 36% of patients, mainly in more detailed description of mitral valve morphology, aortoseptal continuity, and atrial septum. In patients with mitral valve insufficiency, 3D echocardiography was shown to be accurate in the quantification of the dynamic mechanism of mitral regurgitation and in the assessment of mitral commissures in patients with mitral stenosis. This includes not only valve tissue reconstruction but also color flow intracardiac jets. Three-dimensional reconstructions of the aortic valve were achieved in 77% of patients, with an accuracy of 90%. In conclusion, the role of 3D echocardiography, which continues to evolve, shows promise in the assessment of congenital and acquired heart disease.

Transesophageal echocardiographic abnormalities in a case of cardiac sarcoidosis.

Sarcoidosis is a granulomatous disease that may involve multiple organ systems, including the heart. Manifestations include atrial and ventricular arrhythmias, conduction abnormalities, congestive cardiac failure, pericarditis, and sudden death. Whereas cardiac involvement is a relatively common finding at autopsy, antemortem diagnosis is often missed because the clinical manifestations are nonspecific, and the sensitivity and specificity of investigations are low. We report a case of a 62-year-old woman who had clinically significant cardiac sarcoidosis associated with echocardiographic abnormalities that had not been reported previously in association with this condition.

Age-related prevalence of valvular regurgitation in normal subjects: a comprehensive color flow examination of 118 volunteers.

We prospectively assessed the influence of aging on the prevalence of valvular regurgitation by using color flow imaging. One hundred eighteen healthy volunteers (21 to 82 years old) had a two-dimensional Doppler echocardiographic study that included color flow imaging to assess valvular regurgitation and that was semiquantitated by mapping the dimensions of the color flow regurgitant jet in orthogonal views. The subjects were divided into two groups: group 1 consisted of subjects who were younger than 50 years old (n = 61), and group 2 consisted of subjects who were at least 50 years old (n = 57). Mitral regurgitation was detected in 57 (48%) of the 118 subjects: 24 subjects (39%) in group 1 and 33 subjects (58%) in group 2. The severity of mitral regurgitation was trivial to mild. Aortic regurgitation was detected in 13 (11%) of the 118 subjects, all in group 2. The severity was trivial to mild. Tricuspid regurgitation was detected in 77 (65%) of the 118 subjects: 35 (57%) in group 1 and 42 (74%) in group 2. The severity was trivial to mild. Pulmonary regurgitation was detected in 24 (31%) of 78 subjects: nine (22%) in group 1 and 15 (41%) in group 2. The severity was trivial. These findings suggest that valvular regurgitation of a trivial or mild degree is a frequent finding in normal subjects and that it increases with age.

Haemodynamics and left ventricular mass regression: a comparison of the stentless, stented and mechanical aortic valve replacement.

OBJECTIVE: Our objective was to compare the degree of change in hemodynamics and left ventricular mass (LVM) regression after aortic valve replacement (AVR) with stentless, stented and mechanical valves. METHODS: Patients greater than 59 years of age had AVR for aortic stenosis with the stentless xenograft (Cryolife-O'Brien, CLOB), stented xenograft (Carpentier-Edwards, C-E) or mechanical valve (ATS). One-hundred and forty-two patients received stentless, 40 stented, and 69 mechanical valves (mean age 74 +/- 6 vs. 72 +/- 7 and 67 +/- 6 years, respectively). Serial echocardiography was performed. RESULTS: The left ventricular outflow tract diameter was similar pre-operatively in the stentless versus the stented versus the mechanical groups (2.2 +/- 0.4 vs. 2.3 +/- 0.2 vs. 2.2 +/- 0.3 cm; P, n.s). The effective orifice area was larger immediately post-operatively in the stentless versus the stented or the mechanical group (2.4 +/- 0.4 vs. 2.0 +/- 0.6 vs. 2.0 +/- 0.7 cm2, P = 0.0001 for both comparisons). The peak aortic gradient at 6 months was significantly less in the stentless versus the stented and mechanical groups (15 +/- 7 vs. 25 +/- 9 vs. 22 +/- 9 mmHg, P < 0.0001). LVM regressed over 6 months in all subgroups: stentless 272 +/- 64 g vs. 220 +/- 72 g, P = 0.0001, stented 257 +/- 58 vs. 230 +/- 74 g, P = 0.02, and mechanical 267 +/- 95 vs. 204 +/- 54 g, P = 0.003. The reduction in LVM was greater in the stentless versus the stented (P = 0.05) but similar to the mechanical group. CONCLUSIONS: AVR with the stentless xenograft results in superior hemodynamics compared to the stented and mechanical valve replacements. AVR in all three groups leads to a significant regression of left ventricular hypertrophy within 6 months. However the reduction in LVM is greater in subjects with stentless and mechanical valves, which may have prognostic significance.

Renin-angiotensin system gene polymorphisms and left ventricular hypertrophy. The case against an association.

There is accumulating evidence for association between genetic polymorphisms of components of the renin angiotensin system (RAS), especially angiotensin-converting enzyme (ACE), and cardiovascular disease. However, there is lack of agreement that the ACE polymorphism is associated with left ventricular hypertrophy (LVH) in hypertension. A possible paradigm for the development of LVH involves the ACE gene polymorphism influencing cardiac mass by an action on plasma and/or tissue levels of angiotensin II. Such a model has experimental support and provides the basis for examining the lack of agreement between studies. The finding of lack of association between RAS gene polymorphism and LVH may be due to methodological problems, differences in genetic background between populations, interactions between genetic variants of RAS components or to the model being inappropriate. Low predictability of ACE genotype markers for LVH together with conflicting reports on the influence of RAS genetic variants on angiotensin II production suggests that the simple RAS paradigm may not apply for hypertension. Further information on the nature of the link between the ACE polymorphism and ACE regulation as well as the relation between the RAS and pathophysiology of LVH is needed. At present there is insufficient evidence to accept ACE gene polymorphism as a susceptibility marker for LVH.

Angiotensin-converting enzyme and angiotensinogen genes in patterns of left ventricular hypertrophy and in diastolic dysfunction.

1. The association of different patterns of left ventricular hypertrophy and diastolic dysfunction with angiotensin converting enzyme (ACE) genotypes or angiotensinogen dinucleotide repeat alleles were studied in human subjects. 2. Three abnormal patterns of hypertrophy (remodelled, eccentric and concentric) were associated with a history of hypertension. The presence of remodelled or concentric hypertrophy was associated with diastolic dysfunction. 3. There was no difference between the frequencies of the ACE genotypes in normotensive and hypertensive subjects, in subjects with normal ventricles and those with different patterns of left ventricular hypertrophy, nor in subjects with normal and abnormal diastolic function. Similarly, there was no difference between the relative frequencies of AGT alleles in the same clinical subgroups. 4. We conclude that in this population of hospital patients, variants of the ACE and AGT genes do not contribute to the presence of different patterns of hypertrophy or to diastolic dysfunction.

Genetic variants of proteins from the renin angiotensin system are associated with pressure load cardiac hypertrophy.

1. The relationship between the angiotensinogen (AGT) T174M, angiotensin converting enzyme (ACE) insertion/deletion (I/D) and the angiotensin II type 1 receptor (AT1) genetic markers and left ventricular hypertrophy was examined in normal subjects and those with aortic stenosis. 2. Subjects with aortic stenosis had higher left ventricular systolic pressure and relative wall thickness (RWT) compared with normal. However, within aortic stenosis subjects, left ventricular RWT did not correlate with left ventricular systolic pressure or with aortic valve area. 3. In subjects with aortic stenosis, left ventricular RWT was higher in those with ACE DD (P < 0.05) or AGT T174M (P < 0.06) compared with those with the ACE II or ID genotype or AGT TT174 genotype. No relationship was observed with any of the AT1 alleles. The ACE and AGT genetic markers independently predicted left ventricular RWT in aortic stenosis. No association was observed between these genotypes and left ventricular RWT in normal subjects. 4. The data suggest that the AGT T174M and ACE I/D genotypes may act together to influence the degree of hypertrophy in subjects with aortic stenosis. 5. In patients with aortic stenosis, genetic variants of proteins from the renin angiotensin system may be at least as important as left ventricular systolic pressure in determining the degree of left ventricular hypertrophy and could therefore explain the clinical variation observed in the progression to cardiac dysfunction.

Renin and angiotensin-converting enzyme genotypes in patients with essential hypertension and left ventricular hypertrophy.

1. The associations between left ventricular hypertrophy (LVH) and specific alleles of the renin and angiotensin-converting enzyme (ACE) genes were studied in patients with essential hypertension and normal blood pressure. 2. LVH was present in 42% of those with essential hypertension (n = 72) and 17% of those with normal blood pressure (n = 44). 3. The frequency of each renin allele was the same in hypertensive and in normotensive patients. Renin allele frequencies were also the same for those with LVH and those with normal cardiac mass. When only hypertensives were considered, renin alleles were in the same proportion for the groups with and without LVH. Similarly, ACE alleles were not associated with essential hypertension nor with elevated cardiac mass. 4. We conclude that, in this population, variations in the renin or ACE genes do not contribute significantly to the development of LVH or to essential hypertension.

Continuous wave Doppler echocardiographic measurement of prosthetic valve gradients. A simultaneous Doppler-catheter correlative study.

Studies correlating prosthetic valve gradients determined by continuous wave Doppler echocardiography with gradients obtained by cardiac catheterization have, to date, been limited to patients with mitral and tricuspid prostheses or have compared nonsimultaneous measurements. Simultaneous Doppler and catheter pressure gradients in 36 patients (mean age, 63 +/- 13 years) with 42 prosthetic valves (20 aortic, 20 mitral, one tricuspid, and one pulmonary) were studied. Catheter gradients were obtained using a dual-catheter technique. The simultaneous pressure tracings and Doppler flow velocity profiles were digitized at 10-msec intervals to derive the corresponding maximal and mean gradients. The correlation between the maximal Doppler gradient and the simultaneously measured maximal catheter gradient was 0.94 (SEE = 6), and that between the Doppler gradient and the simultaneously measured mean catheter gradient was 0.96 (SEE = 3). There were no significant differences in correlation between gradients for the 32 mechanical valves (maximal gradients: r = 0.95, SEE = 6; mean gradients: r = 0.96, SEE = 3) and the 10 bioprosthetic valves (maximal gradients: r = 0.89, SEE = 6; mean gradients: r = 0.93, SEE = 3). In patients with mitral prostheses, Doppler gradients correlated well with the corresponding catheter gradients obtained with direct measurement of left atrial pressure (maximal gradients: r = 0.96, SEE = 2; mean gradients: r = 0.97, SEE = 1.2). A close correlation between corresponding Doppler and catheter gradients also was found in patients with aortic prostheses (maximal gradients: r = 0.94, SEE = 6; mean gradients: r = 0.94, SEE = 3). Thus, continuous wave Doppler echocardiography can accurately predict the pressure gradient across prosthetic valves.