Helmut Baumgartner

Natriuretic Peptides Predict Symptom-Free Survival and Postoperative Outcome in Severe Aortic Stenosis

Background—The prognostic value of natriuretic peptides in aortic stenosis (AS) remains unknown. Methods and Results—B-type natriuretic peptide (BNP), N-terminal BNP (NtBNP), and N-terminal atrial natriuretic peptide (NtANP) were determined in 130 patients with severe AS (mean age, 70±12 years; mean gradient, 64±21 mm Hg; valve area, 0.64±0.15 cm2) who were followed up for 377±150 days. Natriuretic peptides increased with NYHA class and with decreasing ejection fraction (EF). Even asymptomatic patients frequently had elevated neurohormones. Asymptomatic patients who developed symptoms during follow-up had higher BNP and NtBNP levels at entry compared with those remaining asymptomatic (median for NtBNP, 131 pmol/L [interquartile range, 50 to 202 pmol/L] versus 31 pmol/L [range, 19 to 56 pmol/L]; P <0.001). Symptom-free survival at 3, 6, 9, and 12 months for patients with NtBNP <80 versus ≥80 pmol/L was 100%, 88±7%, 88±7%, and 69±13% compared with 92±8%, 58±14%, 35±15%, and 18±15%, respectively (P <0.001). Seventy-nine patients eventually underwent surgery because of symptoms. Considering preoperative neurohormone levels, age, NYHA class, aortic valve area, EF, and presence of coronary artery disease, we found that neurohormones, EF, and NYHA class predicted survival; neurohormones predicted postoperative symptomatic status; and neurohormones and preoperative EF predicted postoperative EF. However, by multivariate analysis, NtBNP was the only independent predictor of outcome. Conclusions—In severe AS, natriuretic peptides provide important prognostic information beyond clinical and echocardiographic evaluation. NtBNP independently predicts symptom-free survival, and preoperative NtBNP independently predicts postoperative outcome with regard to survival, symptomatic status, and left ventricular function. Thus, neurohormones may gain particular importance for timing of surgery in asymptomatic severe AS.

Normal values for Doppler echocardiographic assessment of heart valve prostheses

Assessment of normal and abnormal function of heart valve prostheses remains challenging. Doppler echocardiography has been shown to allow hemodynamic evaluation in various clinical settings and has become the most widely used tool to assess prosthetic valve function. Prosthetic valves, even when they function normally, are to some degree obstructive to the blood flow. The normal values of gradients, pressure half-time, and effective orifice area depend on valve type and valve size. Doppler assessment of prosthetic valve function, thus, requires specification of valve type and valve size, and knowledge of the normal values. This study provides an updated overview on the available data of normal values to facilitate adequate interpretation of Doppler data.

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

OBJECTIVESnThis study was performed to determine the feasibility, accuracy and reproducibility of real-time volumetric three-dimensional echocardiography (3-D echo) for the estimation of mitral valve area in patients with mitral valve stenosis.nnnBACKGROUNDnPlanimetry of the mitral valve area (MVA) by two-dimensional echocardiography (2-D echo) requires a favorable parasternal acoustic window and depends on operator skill. Transthoracic volumetric 3-D echo allows reconstruction of multiple 2-D planes in any desired orientation and is not limited to parasternal acquisition, and could thus enhance the accuracy and feasibility of calculating MVA.nnnMETHODSnIn 48 patients with mitral stenosis (40 women; mean age 61 +/- 13 years) MVA was determined by planimetry using volumetric 3-D echo and compared with measurements obtained by 2-D echo and Doppler pressure half-time (PHT). All measurements were performed by two independent observers. Volumetric data were acquired from an apical view.nnnRESULTSnAlthough 2-D echo allowed planimetry of the mitral valve in 43 of 48 patients (89%), calculation of the MVA was possible in all patients when 3-D echo was used. Mitral valve area by 3-D echo correlated well with MVA by 2-D echo (r = 0.93, mean difference, 0.09 +/- 0.14 cm2) and by PHT (r = 0.87, mean difference, 0.16 +/- 0.19 cm2). Interobserver variability was significantly less for 3-D echo than for 2-D echo (SD 0.08cm2 versus SD 0.23cm2, p < 0.001). Furthermore, it was much easier and faster to define the image plane with the smallest orifice area when 3-D echo was used.nnnCONCLUSIONSnTransthoracic real-time volumetric 3-D echo provides accurate and highly reproducible measurements of mitral valve area and can easily be performed from an apical approach.

Long-term outcome of patients with ventricular septal defect considered not to require surgical closure during childhood ☆

OBJECTIVESnThe purpose of the study was to assess the long-term outcome of patients with small ventricular septal defects (VSDs) considered not to require surgical closure during childhood.nnnBACKGROUNDnAlthough patients with small VSDs have generally been considered not to require surgery, more recent data suggest that a significant percentage of these patients develop serious problems during adult life.nnnMETHODSnA total of 229 consecutive patients (115 females) with a VSD considered too small to require surgery during childhood as defined by normal pulmonary artery pressure, less than 50% shunt, pulmonary vascular resistance < or =200 dynes x s cm(-5), no VSD-related aortic regurgitation (AR), and no symptoms and who had no additional hemodynamically relevant heart defect were followed in an adult congenital heart disease program. Physical examination, electrocardiography, and echocardiography were performed in all patients in one- to three-year intervals; exercise tests and Holter monitoring were performed in 140 and 127 patients, respectively.nnnRESULTSnFollow-up was completed in 222 patients (97%). Mean age at last visit was 30 +/- 10 years. Spontaneous VSD closure was observed in 14 patients (6%). No patients died, four patients (1.8%) had an episode of endocarditis, of whom two required aortic valve replacement, and one additional patient (0.4%) had surgical closure for hemodynamic reasons. For 118 patients who entered the study between 1993 and 1996 and were prospectively followed for 7.4 +/- 1.2 years, event-free survival with end points defined as death, endocarditis or heart surgery was 99.1 +/- 0.8% at three years, 96.5 +/- 1.7% at six years and 95.5 +/- 1.9% at eight years. At last visit, 94.6% of all patients studied were symptom free. Left ventricular (LV) size by echocardiography was normal in 198 (89%) patients, borderline in 23 patients and definitely enlarged in only one patient. None had systolic LV dysfunction, and pulmonary artery pressure (PAP) was normal in all patients. Mean exercise capacity was 92 +/- 21% of expected, and 87% of patients had no arrhythmias on Holter monitoring, with the remainder showing benign rhythm disorders.nnnCONCLUSIONSnOutcome in well-selected patients with a small VSD is good. Surgical closure does not appear to be required during childhood as long as left-to-right shunt is <50% and signs of LV volume overload are absent, when PAP is not elevated, and no VSD-related AR or symptoms are present.

Value and Limitations of Proximal Jet Dimensions for the Quantitation of Valvular Regurgitation: An In Vitro Study Using Doppler Flow Imaging

To evaluate usefulness and limitations of proximal jet dimensions for the quantitation of valvular regurgitation, fluid jets were created in a pulsatile flow model, and proximal jet width and cross-sectional area were measured by means of color Doppler flow imaging. When circular orifices with diameters from 1 to 6 mm were studied, jet width and cross-sectional jet area measured as close as possible to the orifice were directly related to the orifice diameter (r = 0.97; standard error of the estimate, 0.4 mm; y = 0.5 + 0.97x) and the orifice area (r = 0.97; standard error of the estimate, 5.7 mm2; y = 0.22 + 2.47x), respectively. No significant dependence on flow rate or pressure gradient was found for these measurements. Jet width was measured with color M-mode Doppler by use of the smallest sample volume size (1 mm) and was slightly greater than the orifice diameter (4.2 +/- 1.7 mm versus 3.8 +/- 1.7 mm). However, cross-sectional areas were approximately fourfold the orifice areas, on average (52.5 +/- 24.6 mm2 versus 12.3 +/- 9.7 mm2), with a range of twelvefold (smallest orifice) to threefold (largest orifice). When the sample volume size was reduced from 2.4 to 1.0 mm, color areas decreased by 25.6 +/- 6.0%. Slit-shaped orifices were studied with two different orientations of the slit-parallel and perpendicular to the ultrasound beam: Color M-mode measurements were again slightly greater than length and width of the slit, but cross-sectional areas were substantially larger than the orifice areas and increased between 44% and 115% when changing the orientation of the slit from perpendicular to parallel. This, again, reflected problems with lateral resolution. When cross-sectional areas were measured at increasing distances from the orifice, the cross-sectional jet area increased significantly within a few millimeters. This increase was greater with higher gradients and smaller orifice sizes. In case of a small orifice (2 mm) and a high gradient (130 to 160 mm Hg), increase in area was as great as 122% within a distance of only 5 mm. Thus, proximal jet width and cross-sectional area were directly related to the orifice size, which could be a valuable parameter for the evaluation of valvular regurgitation. Measurements of jet width by color M-mode seemed to be most accurate but are limited by the fact that in vivo valvular defects may be irregular rather than of circular shape.(ABSTRACT TRUNCATED AT 400 WORDS)

Stereolithographic biomodeling to create tangible hard copies of cardiac structures from echocardiographic data: in vitro and in vivo validation.

OBJECTIVESnThis study investigated the feasibility, accuracy and clinical potential of creating polymer hard copies of echocardiographic data using stereolithography.nnnBACKGROUNDnThree-dimensional (3D) echocardiography has so far been limited by the need to display reconstructed 3D objects on a two-dimensional screen. Thus, tangible stereolithographic polymer models created from echocardiographic data could enhance our spatial perception of cardiac anatomy and pathology.nnnMETHODSnHard-copy replicas of water-filled latex balloon phantoms (n = 7) and porcine liver specimens (n = 12) were generated from echocardiographic images using stereolithography (computerized laser polymerization). In addition, we created 24 models of the mitral valve from 12 transesophageal studies (normal = 6, mitral stenosis n = 4, prolapse/flail leaflet n = 8, annular dilation n = 2, leaflet restriction n = 2 and following mitral valve repair n = 2).nnnRESULTSnExcellent agreement was found for comparison of volumes (r = 0.98, SEE = 3.46 mm3, mean difference = 0.25 +/- 3.33 mm3) and maximal dimensions (r = 0.99, SEE = 0.16 cm, mean difference = 0.03 +/- 0.16 cm) between phantoms and their corresponding replicas. Visual and tactile examination of mitral valve models by two blinded observers allowed correct depiction of mitral valve anatomy and pathology in all cases.nnnCONCLUSIONSnStereolithographic modeling of echocardiographic images is feasible and provides tangible polyacrylic models that are true to scale, shape and volume. Such models offer accurate depiction of mitral valve anatomy and pathology in patients studied with transesophageal echocardiography. This technique could have substantial impact on diagnosis, management and preoperative planning in complex cardiovascular disorders.

Artificial neural networks and spatial temporal contour linking for automated endocardial contour detection on echocardiograms: a novel approach to determine left ventricular contractile function

This study investigated the use of artificial neural networks (ANN) for image segmentation and spatial temporal contour linking for the detection of endocardial contours on echocardiographic images. Using a backpropagation network, the system was trained with 279 sample regions obtained from eight training images to segment images into either tissue or blood pool region. The ANN system was then applied to parasternal short axis images of 38 patients. Spatial temporal contour linking was performed on the segmented images to extract endocardial boarders. Left ventricular areas (end-systolic and end-diastolic) determined with the automated system were calculated and compared to results obtained by manual contour tracing performed by two independent investigators. In addition, ejection fractions (EF) were derived using the area-length method and compared with radionuclide ventriculography. Image quality was classified as good in 12 (32%), moderate in 13 (34%) and poor in 13 (34%) patients. The ANN system provided estimates of end-diastolic and end-systolic areas in 36 (89%) of echocardiograms, which correlated well with those obtained by manual tracing (R = 0.99, SEE = 1.44). A good agreement was also found for the comparison of EF between the ANN system and Tc-radionuclide ventriculography (RNV, R = 0.93, SEE = 6.36). The ANN system also performed well in the subset of patients with poor image quality. Endocardial contour detection using artificial neural networks and spatial temporal contour linking allows accurate calculations of ventricular areas from transthoracic echocardiograms and performs well even in images with poor quality. This system could greatly enhance the feasibility, accuracy and reproducibility of calculating cardiac areas to derive left ventricular volumes and ejection fractions.

Estimation of coronary flow reserve by transesophageal coronary sinus Doppler measurements in patients with syndrome X and patients with significant left coronary artery disease

OBJECTIVESnThis study sought to determine the feasibility of coronary sinus flow velocity analysis by transesophageal Doppler echocardiography for estimation of coronary flow reserve in patients with syndrome X and patients with coronary artery disease.nnnBACKGROUNDnCoronary flow reserve provides useful information in patients with coronary artery disease and patients with syndrome X. Current methods of measuring coronary flow reserve are invasive or require extensive laboratory equipment, or both. Transesophageal Doppler recordings of coronary sinus flow velocity before and after vasodilator application may allow noninvasive determination of coronary flow reserve.nnnMETHODSnWe obtained coronary sinus flow velocity recordings before and after dipyridamole administration (0.6 mg/kg body weight per 5 min) in 9 patients with syndrome X, 14 with significant left coronary artery disease and 22 age-matched control patients. We used the formula anterograde minus retrograde flow velocity time integral times heart rate as an index of coronary sinus flow. Coronary flow reserve was calculated by dividing coronary sinus flow variables after dipyridamole administration by the respective baseline values.nnnRESULTSnTechnically adequate recordings were obtained in 44 (98%) of 45 patients. Compared with that in the control group (2.78 +/- 0.95 [mean +/- SD]), coronary flow reserve was significantly lower in patients with syndrome X (1.21 +/- 0.23, p < or = 0.001) as well as in those with coronary artery disease (1.47 +/- 0.7, p < or = 0.001). Using a cutoff coronary flow reserve value of 1.8, sensitivity, specificity and overall predictive value of coronary flow reserve determinations were, respectively, 100%, 91% and 94% for syndrome X and 86%, 91% and 89% for coronary artery disease.nnnCONCLUSIONSnCoronary flow reserve calculation by transesophageal coronary sinus flow velocity recordings is feasible in a large proportion of patients and might be useful for the noninvasive evaluation of patients with syndrome X and patients with severe left coronary artery disease.

Assessment of coronary stenoses by Doppler wires: a validation study using in vitro modeling and computer simulations

The present study evaluates the use of intracoronary velocity measurements by Doppler guidewires for assessing coronary obstructions. In vitro experiments were performed in a flow model using acrylic phantoms of coronary stenoses with different configurations (stenosis area: 56%, 75% and 89%; stenosis length: 1 and 5 mm; stenosis border: tapering or abrupt). Nonpulsatile laminar flow conditions of a test fluid were established at flow rates ranging from 0.5 to 2.0 mL/s to simulate baseline flow and flow after vasodilation. Peak Doppler velocity was measured proximal to, within and distal to the model stenoses. Computer simulations were employed to calculate radial flow profiles with and without a Doppler wire aligned with the vessel center. In 84 in vitro flow experiments, peak Doppler velocity correlated well with the average flow velocity as calculated from the actual flow rate and the vessels cross-sectional area proximal to (r = 0.98, SEE = 1.4, p < 0.001) and within (r = 0.97, SEE = 16.4, p < 0.001) the stenosis. However, the ratio of calculated average velocity to Doppler-measured peak velocity was significantly different from 0.5, the expected value for a parabolic flow profile (0.76+/-0.08, 0.81+/-0.14; p < 0.001). Acceptable accuracy was found for the Doppler estimation of stenosis severity using the continuity equation (error: 0.9+/-1.2% and -4.6+/-3.5% for stenosis with a length of 5 mm and 1 mm, respectively). Doppler velocity reserve significantly underestimated the true flow reserve for the 56% and 75% stenoses (p < 0.01). Computer simulations demonstrated significant alterations of flow profiles by the wire, which explained the observed underestimation of the true flow reserve by the Doppler velocity reserve. Thus, Doppler guidewire measurements of intracoronary flow velocities are useful to assess the severity of coronary stenoses. However, the in vitro results and computer simulations indicate that guidewires alter the flow profile, so that Doppler velocity reserve may underestimate the true flow reserve.

Relation Between Left Atrial Size and Secondary Atrial Arrhythmias After Successful Catheter Ablation of Common Atrial Flutter

Catheter ablation ptovides an effective cure for patients with typical atrial flutter. However, these patients may have the potential to develop atrial tachyarrhythmias other than common atrial flutter. This study examines clinical and echocardiographic predictors for the occurrence of uncommon atrial flutter or atrial fibrillation after abolition of common atrial flutter. The study population comprised 17 patients (12 men, 5 women, age 32–74 years) who underwent successful radiofrequency catheter ablation of common atrial flutter. Common atrial flutter did not recur in any patient during a median follow‐up time of 8 (range 1–25) months. Within a median of 7 (range 1–223) days, however, symptomatic atrial tachyarrhythmias occurred in 8 of 17 patients (47%): uncommon atrial flutter (n = 4); atrial fibrillation (n = 3); and both uncommon atrial flutter and atrial fibrillation in one patient. Preablation left atrial volume was significantly larger in patients who developed secondary arrhythmias compared with patients who remained in sinus rhythm (57.9 ± 15.6 vs 43.7 ± 16.4 cm3, P < 0.05). Enlarged left atrial volume dichotomized at 51 cm3 independently predicted postablation atrial arrhythmias (x2=5.11, rel. risk = 5.3, P < 0.05). On Kaplan‐Meier analysis, time to occurrence of postablation atrial arrhythmias was significantly shorter in patietits with enlarged left atrium (P < 0.02). In conclusion, symptomatic uncommon atrial flutter and atrial fibrillation develops in a substantial proportion of patients after successful ablation of common atrial flutter. Out of a series of clinical and echocardiographic parameters, preablation left atrial size is the best predictor for the occurrence of these postablation atrial arrhythmias.