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How to cite: Grunkemeier, G. L., & Starr, A. (1993). Reply to correspondence on randomization in surgical studies. The Journal of heart valve disease, 2(3), 359–361.

A 60-year-old woman underwent mitral and aortic valve replacement with Carpentier-Edwards supra-annular bioprosthesis in 1986. Six years later rapidly progressing exercise dyspnea and orthopnea made hospital admission necessary. At chest x-ray and cardiac catheter examination one of the wire struts of the mitral bioprosthesis was found completely broken causing cusp prolapse. Surgical findings at reoperation confirmed the diagnosis. No apparent cause of the stent fracture was found.

How to cite: Griffin, S., Bouboulis, N., & Holden, M. P. (1993). Fracture of the wire stent in a Carpentier-Edwards porcine bioprosthesis. The Journal of heart valve disease, 2(3), 357–358.

Previous studies have shown that in vitro endothelialization of synthetic vascular prostheses with cultured autologous cells leads to a reduction in their thrombogenicity. It is possible that pre-endothelialization of mechanical heart valve prostheses would have a similarly advantageous effect. In this study we have therefore investigated the possibility of creating an endothelium layer on mechanical heart valve prostheses by seeding in vitro with cultured adult human endothelial cells. After harvest, endothelial cells were cultured for two to three weeks before seeding of six valves (three Monostrut, three CarboMedics bileaflet) with 1.5-2 x 10(5) cells/cm2. The valves were then kept under culture conditions for seven days. A confluent lining of cultured endothelial cells was observed in the scanning electron microscope on the parts covered with pyrolitic carbon, e.g. disc, leaflet, flange, and on carbon coated sewing rings. Untreated sewing rings showed a discontinuous endothelial lining. On the metallic surface only a few scattered cells were observed. Two endothelialized bileaflet valves were implanted in the mitral position in pig and permitted to perform physiologic work for one hour. A mainly continuous endothelium remained on the carbon covered sewing rings but the endothelium detached from the leaflets and flanges. This study demonstrates that mechanical heart valves do not contain cytotoxic compounds. It also demonstrates that cultured adult human endothelial cells are able to form a monolayer when seeded on monostrut and bileaflet valve prostheses. A significant number of cells remain on the sewing ring after pulsatile flow in the mitral position but not on the polished pyrolitic carbon surfaces.(ABSTRACT TRUNCATED AT 250 WORDS)

How to cite: Bengtsson, L. A., & Haegerstrand, A. N. (1993). Endothelialization of mechanical heart valves in vitro with cultured adult human cells. The Journal of heart valve disease, 2(3), 352–356.

An experimental protocol was developed and a series of laboratory experiments started to assess the function and behaviour of replacement valves under simulated low cardiac output, that is low flow and low pressure conditions. The Helmholtz Institute's pulse duplicator (1) and instrumentation were carefully tuned in order to achieve accurate and reproducible delivery of the required extremely small stroke volumes. A pilot study was completed with 27 mm St. Jude Medical and CarboMedics bileaflet valves and Wessex porcine bioprostheses, three each, in the simulated aortic position. The results of these experiments suggest that the performances of the two bileaflet prostheses are inadequate if the flow is less than 2.0 l/min; the porcine bioprosthesis needs relatively low flow to start proper function, but its stenotic nature soon becomes apparent; increase in pressure without a corresponding increase in flow has a deleterious effect on valve performances by increasing regurgitation; increasing pulse rate is inversely correlated with valve efficiency; and there is no "all-or-none" cut off point between functional and non-functional situation for the tested devices; there is a semilogarithmic relation between increasing flow and valve performance. The clinical consequences are manifold and may be related both to the stabilization of circulation and to the increased thromboembolic risk during the early postoperative period.

How to cite: Bodnar, E., Reul, H., & Schmitz, B. (1993). Prosthetic valve function under simulated low cardiac output conditions: preliminary observations. The Journal of heart valve disease, 2(3), 348–351.

Dysfunction of prosthetic heart valves is a common complication after heart valve replacement, affecting both biologic and mechanical prostheses. A preoperative, non-destructive test of each individual valve may help to prevent the implantation of a valve which has material weaknesses. To this end we developed a technique for testing heart valve prostheses by holographic interferometry. The advantage of this technique is that it provides a non-contact, non-destructive, highly sensitive three dimensional analysis of the valve under loading. Samples of several mechanical and biologic valve substitutes were investigated. Deformations of the valve, due to small pressure differences applied to the samples in a specially developed test chamber, were recorded by double exposure holography. A fringe pattern superimposed on the image of the valve reconstructed from the hologram clearly indicates the presence of even the slightest defect in the valve material. Our experimental results demonstrate the ability of non-destructive holographic screening testing to detect defects or weaknesses which may potentially lead to dysfunction in replacement valves.

How to cite: Geiger, A. W., Zarubin, A., Fahrenkamp, A., Hertel, M., von Bally, G., & Scheld, H. H. (1993). Non-destructive evaluation of prosthetic heart valves by holographic interferometry. The Journal of heart valve disease, 2(3), 343–347.

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How to cite: Bokros J. C. (1993). Comments on "Non-destructive evaluation of prosthetic heart valves by holographic interferometry". The Journal of heart valve disease, 2(3), 341–342.

A finite element model was developed to examine deformation and stress patterns in the mitral valve under systolic loading conditions. This is the first three-dimensional finite element model of the mitral valve, incorporating all essential anatomic components, regional tissue thickness, collagen fiber orientation and related anisotropic material properties. A non-linear, transient, dynamic analysis was performed which included time-dependent loading, leaflet and chordal mass inertial effects and chordal element bi-linearity. The model was first analyzed without either annular or papillary muscle contraction and then with either or both. The hypothesis was that the combination of annular and papillary muscle contraction would have a beneficial effect on valve function. In all models, the computed anterior leaflet principal stresses were tensile and of greater magnitude than those in the posterior leaflet. The principal stress directions were observed to correlate well with collagen fiber orientation. Earlier leaflet coaptation was demonstrated with annular contraction, promoting valve closure, while papillary muscle contraction increased the stress on the chordae tendineae and both leaflets, tending to pull the latter apart. The combination of the two combined these effects, and showed the most even stress distribution. The effects of annular and papillary muscle contraction on valve function were shown to be beneficial by this model, and they can be further elucidated by varying the extent and timing of the individual contractions. This model can be used to examine the effects of pathologic changes, surgical manipulations and proposed material replacements. It can thus aid both the surgeon and the biomedical engineer in improving the materials and techniques available for the repair and/or replacement of mitral valve system components.

How to cite: Kunzelman, K. S., Cochran, R. P., Chuong, C., Ring, W. S., Verrier, E. D., & Eberhart, R. D. (1993). Finite element analysis of the mitral valve. The Journal of heart valve disease, 2(3), 326–340.

Balloon valvuloplasty is currently the preferred therapeutic alternative to surgical valvotomy in selected patients with isolated congenital pulmonary stenosis. Not only does pulmonary valvuloplasty consistently afford safe and dramatic reduction of the valvular obstruction, it also produces less trauma and an equivalent sustained gradient relief when compared to surgical intervention. However, despite its established role, controversies persist in certain aspects of balloon pulmonary valvuloplasty (BPV). They include the timing of intervention, the suitability of certain valve morphologies and the choice of balloon techniques. Based on clinical experience, the following recommendations can be made: 1. BPV is currently recommended for moderate to severe pulmonary stenosis. Patients with mild stenosis are better served by conservative management and serial echocardiographic assessments. 2. Classic pulmonary stenosis is most suitable for BPV. However, patients with milder forms of dysplastic valves are still potential candidates for BPV. 3. Adequate dilatation with optimal relief of obstruction can be achieved with either the single or double balloon technique. Whether the Inoue or fixed-balloon system is used is a personal preference. Equally good results can potentially be obtained by either balloon design.

How to cite: Lau, K. W., & Hung, J. S. (1993). Controversies in percutaneous balloon pulmonary valvuloplasty: timing, patient selection and technique. The Journal of heart valve disease, 2(3), 321–325.

The Bioflo pericardial bioprosthesis was introduced to improve the durability of previous pericardial bioprostheses by means of a protective sheath of bovine pericardium around the stent. It has since been withdrawn from the market. Before its withdrawal, we studied 19 patients with mitral Bioflo valves (three of 25 mm, seven of 27 mm, eight of 29 mm, one of 31 mm) and 21 patients with aortic Bioflo valves (eight of 19 mm, nine of 21 mm, four of 23 mm) between two weeks and six months postoperatively, at which time all were in NYHA functional classes I or II. Standard Doppler echocardiographic measurements were taken to determine the effective orifice area of all valves, the peak and mean diastolic gradients across the mitral valves, and the peak and mean systolic gradients across the aortic valves. The smaller Bioflo valves performed poorly both in absolute terms and in comparison with other valves, presumably due to a reduction in the effective orifice area by the protective sheath. This finding should be borne in mind by the designers of future pericardial bioprostheses.

How to cite: Gonzalez-Juanatey, J. R., Garcia-Bengoechea, J. B., Vega, M., Garcia-Acuna, J. M., Rubio, J., Duran, D., Sierra, J., & Gil, M. (1993). Doppler echocardiographic evaluation of the Bioflo pericardial bioprosthesis. The Journal of heart valve disease, 2(3), 315–320.

Of 94 patients who underwent intravalvular mitral valve replacement with CarboMedics bileaflet mechanical prosthesis, 10 presented with heavily calcified stenotic valves. After total excision of the mitral valve in these patients, both papillary muscles were reconnected to the annulus with Goretex sutures. Repeat cardiac catheterization was completed in six of these 10 patients two to 24 months after surgery. Global and segmental left ventricular function was estimated using the MEDIS program (Thorax Centrum, Rotterdam) for analysis of left ventricular function. In five of the six patients re-examined, the ejection fraction was improved, the global ejection fraction increasing from 54% +/- 6% to 63% +/- 10%. We conclude, even though the number of followed patients is extremely small, that mitral valve replacement with suspension of the papillary muscles is surgically feasible and has beneficial effects on the contractility of the left ventricle in patients with mitral stenosis.

How to cite:  Vucinic M. (1993). Suspension of the papillary muscles during valve replacement for mitral stenosis. The Journal of heart valve disease, 2(3), 311–314.

A successful operation for acute and severe aortic regurgitation after balloon valvuloplasty together with mitral regurgitation is described in a 9-month-old infant. Aortic root replacement was performed using a pulmonary autograft, while the right ventricular outflow tract was reconstructed with an interposed left atrial appendage posteriorly and a heterologous pericardial patch anteriorly. Mitral valve reconstruction was also effectively accomplished. This combination of right and left ventricular outflow tract reconstruction has a good potential for growth and may provide a solution for the future in infants.

How to cite: Matsuki, O., Yagihara, T., Yamamoto, F., Nishigaki, K., Uemura, H., Kagisaki, K., & Kawashima, Y. (1993). Growth potential after root replacement of the right and left ventricular outflow tracts. The Journal of heart valve disease, 2(3), 308–310.

A selected group of patients who underwent valve replacement were analyzed to evaluate the feasibility, effectiveness and safety of combined treatment with moderate intensity anticoagulation plus aspirin. One hundred ninety-six patients who received a total of 204 mechanical valve prostheses between 1985 and 1991 were selected according to rigid criteria. The prostheses included 124 valves of caged ball design, 62 St. Jude valves and 18 others. The follow up of the whole population was 581.8 patient years, with an average of 2.97 patient years, and was complete by the definition criteria. All patients received moderate intensity anticoagulation with acenocoumarol (target International Normalized Ratio 2.5 to 3.5) and daily aspirin (100 mg or 325 mg). The incidence of thromboembolic events for the whole group was 3.26% per patient year, but only 1.6% in patients "compliant" with treatment. Preoperative embolism and non-compliance with treatment had a strong correlation with postoperative thromboembolism. The INR values had a strong correlation with both thromboembolic and hemorrhagic events. The incidence of serious hemorrhagic events was 4.12% patient years although only two cases (0.34%/pty) were fatal (cerebral hemorrhages). There was no difference in hemorrhagic incidence between patients receiving either 325 mg or 100 mg daily. A low incidence of thromboembolic complications was attained with the use of combined antithrombotic and antiplatelet therapy, even in the first generation caged ball type prostheses. However, the combination of moderate intensity anticoagulation with either 325 mg or 100 mg aspirin was associated with a risk of bleeding similar to high intensity anticoagulation alone. The risk of bleeding appeared to be greater in the presence of gastric pathology, and the combination of anticoagulants and aspirin should be avoided in patients with these conditions.

How to cite: Albertal, J., Sutton, M., Pereyra, D., Segura, E. V., Aramburu, D. F., Lardani, H., & Diaz, R. (1993). Experience with moderate intensity anticoagulation and aspirin after mechanical valve replacement. A retrospective, non-randomized study. The Journal of heart valve disease, 2(3), 302–307.

Five hundred and four St. Jude Medical valves (SJM) were implanted in 435 patients between September 1978 and March 1982. There were 234 females and 201 males with a mean age of 52.8 +/- 10.1 years (range 12-83 years), who underwent 204 aortic, 163 mitral, 67 mitral plus aortic and one triple valve replacements. All patients were followed prospectively. Follow up was 100% complete and averaged 122.2 +/- 1.1 months for operative survivors. The total follow up for aortic patients was 1968.5, for mitral patients 1520.4, and for double valve replacement 573.9 pty. For the entire patient population the total follow up was 4080.8 pty. Early mortality was 2% after aortic, 4.3% after mitral and 5.9% after mitral plus aortic valve replacement. There were 68 late deaths representing a linearized incidence of 1.37%/pty in the aortic, 1.71%/pty in the mitral and 2.61%/pty in the double valve replacement groups. The corresponding cumulative survival after ten years at risk was 85% in the aortic, 78% in the mitral and 72% in the double valve replacement groups. The ten year event-free survival was 64% in the aortic, 57% in the mitral and 47% in the double valve replacement groups. The linearized incidence for thromboembolic events was 3.71%/pty taking all events into account, and 2.67%/pty taking only the first or most severe of several events into account for aortic, 5.1%/pty and 4.08%/pty for mitral, and 6.62%/pty and 5.40%/pty for double replacements, respectively. There were two cases of valve thrombosis, both with proven inadequate anticoagulation. When the prothrombin times measured with the different thromboplastize used in this patient group were converted to INR, the so far homogeneous values could be separated into three groups: INR = 3.0 to 4.5, 2.5 to 3.2 and 1.8 to 2.7. Low INR values caused only a marginal increase in the rate of embolism but a highly significant decrease in the rate of bleeding. These results suggest that the generally recommended INR of 3.0 to 4.5 is too high for the SJM. A large, multicenter, prospective randomized study is therefore proposed to establish the safe INR levels with low intensity anticoagulation after SJM implantation.

How to cite: Horstkotte, D., Schulte, H., Bircks, W., & Strauer, B. (1993). Unexpected findings concerning thromboembolic complications and anticoagulation after complete 10 year follow up of patients with St. Jude Medical prostheses. The Journal of heart valve disease, 2(3), 291–301.

The specificity and sensitivity of the questionnaire method, whether through direct contact or via mail, in collecting information on thrombosis, embolism and bleeding after heart valve replacement were assessed by a critical analysis of methods currently in clinical use. The 16 questions contained in the standard questionnaire of the Albert Einstein College of Medicine searching for transient events were put to 1000 apparently healthy individuals. Additional questions related to risk factors such as previous heart valve replacement, any existing heart disease, hypertension, diabetes or current anticoagulant treatment for any reason were also asked. The male/female ratio was 54.9/45.1, and the mean age was 36.3 years with a range of 14-97 years. Eighty-five persons had one or more risk factors, 915 had none. A positive answer to at least one of the questions searching for TIA (transient ischemic attack) was given by 69.4% (n = 59) of those with, and by 54.8% (n = 501) without any risk factors. The total number of reported 'events' was 164 (1.93/person) for those with, and 1331 (1.45/person) for those without any risk factors. Four different follow up methods were applied to each of 123 patients after heart valve replacement: (a) regular follow up at an out-patient clinic, questionnaires sent at (b) six, (c) 18 and (d) 36 months after the start of the study. 57% of the transient and reversible events reported at the out-patient clinic were forgotten and not mentioned by the same patients in the 36 month questionnaire. One of the three permanent disabilities was also 'forgotten'.(ABSTRACT TRUNCATED AT 250 WORDS)

How to come: Bodnar, E., & Horstkotte, D. (1993). Potential flaws in the assessment of minor cerebrovascular events after heart valve replacement. The Journal of heart valve disease, 2(3), 287–290.

Sixteen of 20 patients who underwent tricuspid valve replacement with a St. Jude Medical valve at our hospital were followed for three to 164 months. Doppler echocardiographic and cineradiographic examinations of the replacement device were performed in 13 patients. There were six males and seven females in the study, with a mean age of 41.9 years. A St. Jude Medical prosthesis had also been implanted in the mitral or mitral and aortic positions of eight of these thirteen patients. Ten patients had normally functioning valves in the tricuspid position and three were diagnosed as malfunctioning. The peak velocity in those patients with normally functioning tricuspid valves was 1.3 +/- 0.2 m/sec. The calculated peak and mean pressure gradients were 6.7 +/- 1.9 mmHg and 2.6 +/- 1.1 mmHg, respectively, and the mean pressure half-time was 120 +/- 22 msec. All normally functioning valves in the tricuspid position had peak velocities of less than 1.55 m/sec, and peak and mean pressure gradients of less than 9.6 mmHg and 5 mmHg, respectively, with the pressure half-time being less than 140 msec in all cases, except for one of the three Doppler studies performed in one patient. However, three Doppler studies performed in two patients with a malfunctioning tricuspid valve revealed peak velocities, peak and mean pressure gradients and pressure half-times which were above these values. After replacement of the malfunctioning valve, or thrombolysis, all of the Doppler-derived values returned to the range found in normally functioning valves.(ABSTRACT TRUNCATED AT 250 WORDS)

How to cite: Aoyagi, S., Nishi, Y., Kawara, T., Oryoji, A., Kosuga, K., & Ohishi, K. (1993). Doppler echocardiographic evaluation of St. Jude Medical valves in the tricuspid position. The Journal of heart valve disease, 2(3), 279–286.

The development of late tricuspid regurgitation following mitral valve replacement is accompanied by a severe reduction in exercise capacity and a poor functional outcome. In this study, we compared the clinical and echocardiographic characteristics of two matched groups with (n = 13) and without (n = 13) clinically significant tricuspid regurgitation. The preoperative pulmonary artery pressures and symptom durations were similar, but tricuspid regurgitation at palpation was detected only in patients who later developed severe tricuspid regurgitation (5/13 vs. 0/13; p < 0.02). None of the patients had echocardiographic evidence of rheumatic tricuspid valve disease at the time of the study, but the tricuspid annular diameter (3.7 +/- 0.5 cm vs. 3.2 +/- 0.4 cm; p < 0.05) and right ventricular diameter (4.9 +/- 0.4 cm vs. 4.0 +/- 0.8 cm; p < 0.01) were greater in patients who had developed severe late tricuspid regurgitation. Echocardiographic parameters of left ventricular function and Doppler estimated pulmonary artery systolic pressures were similar in the two groups, and no evidence of prosthetic dysfunction or aortic valve disease was found. These results imply that late tricuspid regurgitation following mitral valve replacement develops as a result of dilation of the tricuspid annulus associated with right ventricular decompensation. The persistence of uncorrected tricuspid incompetence would seem to be an important contributory factor, and its accurate detection and correction at the time of initial surgery may prove to be the most effective means of preventing the development of this important complication of mitral valve replacement.

How to cite: Groves, P. H., Ikram, S., Ingold, U., & Hall, R. J. (1993). Tricuspid regurgitation following mitral valve replacement: an echocardiographic study. The Journal of heart valve disease, 2(3), 273–278.

The aim of this study was to investigate the factors related to the presence of left atrial spontaneous echo contrast in mitral valve disease, and to ascertain whether it is a predictor of thromboembolism. One hundred and one patients (47 men, 54 women) with a mean age of 57.04 +/- 10.6 years who underwent transthoracic and transesophageal echocardiography were included in the study. Forty-five (44.5%) had isolated or predominant mitral valve stenosis, 12 (11.9%) predominant mitral insufficiency and 44 (43.6%) had had previous mitral valve replacement. Left atrial spontaneous echo contrast was detected by transesophageal echocardiography in 58 patients, while the transthoracic approach detected it in only 15 (14.9%) (P < 0.0001). An atrial thrombus was found in six cases, with a history of recent systemic embolism in three of them. There was no thrombus in the left atria of a further nine patients, despite definitive histories of recent systemic embolism. The finding of left atrial spontaneous echo contrast was related to the presence of atrial fibrillation or enlarged left atrium, the severity of mitral stenosis and the absence of significant mitral insufficiency. Anticoagulant therapy was not significantly associated with spontaneous left atrial echo contrast, but a stepwise linear regression analysis showed that its presence was the only independent predictor of thromboembolism (p < 0.0001). We conclude that left atrial spontaneous echo contrast in mitral valve disease can be discovered mainly by transesophageal echocardiography, and is correlated with factors which are associated with low left atrial blood flow velocity such as atrial fibrillation, enlarged left atrium, mitral stenosis of increased severity and the absence of significant mitral insufficiency.(ABSTRACT TRUNCATED AT 250 WORDS)

How to cite: Kranidis, A., Koulouris, S., & Anthopoulos, L. (1993). Clinical implications of left atrial spontaneous echo contrast in mitral valve disease. The Journal of heart valve disease, 2(3), 267–272.

Early transesophageal echocardiography (TEE) after mitral valve replacement can detect symptomless, non-obstructive thrombus on prosthetic valves and also small filamentous abnormal echoes (SAE). The object of this study is to evaluate their respective frequency and predisposing factors. Between October 1988 and June 1992, 129 consecutive patients underwent mitral valve replacement with a bileaflet prosthesis and had transesophageal echocardiography at an average of 15 +/- 7 days (range: 6-35 days) after surgery. Details of postoperative anticoagulation were analyzed in 99 patients from five surgical centers having comparable postoperative anticoagulation protocols. Among those patients presenting with SAE, 76% had a second transesophageal echocardiography at an average of 145 +/- 166 days after the first examination. Mean age was 56 +/- 13 years. Small filamentous echoes were found in 55 patients (43%). In univariate analysis, independent predictors were age, absence of systolic regurgitation across the mitral prosthesis as observed with continuous Doppler, and the presence of spontaneous echo contrast (SC) in the left atrium: 54 +/- 14 years in the absence vs. 59 +/- 10 in the presence of SAE (p < 0.05); 54% of systolic leak vs. 36% (p < 0.05); 43% of SC vs. 75% (p < 0.00001). In multivariate analysis, spontaneous echo contrast was the only independent predictor for SAE (p < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

How to cite: Iung, B., Cormier, B., Dadez, E., Drissi, M. F., Tsezana, R., Viguier, E., Caviezel, B., Michel, P. L., Samama, M., & Vahanian, A. (1993). Small abnormal echos after mitral valve replacement with bileaflet mechanical prostheses: predisposing factors and effect on thromboembolism. The Journal of heart valve disease, 2(3), 259–266.

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How to cite: Shah P. M. (1993). Significance of spontaneous echo contrast, or, does "smoke" indicate "fire"?. The Journal of heart valve disease, 2(3), 257–258.

Background: Quantitative Doppler echocardiography has become an established method for estimating aortic valve area in aortic stenosis, replacing cardiac catheterization as the confirmatory study. The technique is time consuming, especially when measuring the transaortic velocity, which is performed by convention. This is accomplished by interrogating multiple windows with a non-imaging probe to record the maximal velocity. To determine how the examination could be expedited, we prospectively compared aortic valve gradients measured by Pedof and duplex transducers.

Methods: One hundred eighty-two consecutive patients with native aortic valve disease, mechanical or bioprosthetic aortic valves were studied. Two technicians measured maximal transaortic valve velocities from apical, subcostal, right parasternal and suprasternal notch windows with a 2 MHz Pedof probe and from the apical window with a 3-3.5 MHz duplex probe using color flow to orient the continuous wave beam. Angle-corrected and non-angle-corrected signals were recorded. There were 109 comparisons read by two observers; intra- and inter-reader variations were 0.4% and 2.0%, respectively.

Results: Duplex imaging velocity gradients were consistently smaller than Pedof non-imaging measurements with a mean +/- 1 standard deviation difference between peak velocities of 0.40 +/- 0.71 meters per second (m/s) for angle-corrected, and 0.76 +/- 0.68 for non-angle-corrected signals (both p < 0.001). Technician variability accounted for some of the difference (p < 0.02).

Conclusion: Although non-imaging and imaging methods share the apical window, the Pedof probe scans unlimited planes to locate the maximal aortic valve gradient, whereas the duplex probe is confined to the plane providing the optimal two-dimensional image. Therefore, Doppler echocardiographic estimations of aortic valve areas still require careful, time-intensive non-imaging recordings of transaortic velocities.

How to cite: Tavli, T., Ammar, A., & Wong, M. (1993). Doppler-derived aortic valve gradients: imaging versus non-imaging techniques. The Journal of heart valve disease, 2(3), 253–256.

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How to cite: Carabello B. A. (1993). The mitral valve apparatus: is there still room to doubt the importance of its preservation?. The Journal of heart valve disease, 2(3), 250–252.