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E Schwammenthal

Publications and source records attributed to E Schwammenthal.

At least 37 records · Page 2Linked to original sources
PubMed1997

Insights from three-dimensional echocardiography into the mechanism of functional mitral regurgitation: direct in vivo demonstration of altered leaflet tethering geometry.

BACKGROUND: Recent advances in three-dimensional (3D) echocardiography allow us to address uniquely 3D scientific questions, such as the mechanism of functional mitral regurgitation (MR) in patients with left ventricular (LV) dysfunction and its relation to the 3D geometry of mitral leaflet attachments. Competing hypotheses include global LV dysfunction with inadequate leaflet closing force versus geometric distortion of the mitral apparatus by LV dilatation, which increases leaflet tethering and restricts closure. Because geometric changes generally accompany dysfunction, these possibilities have been difficult to separate. METHODS AND RESULTS: We created a model of global LV dysfunction by esmolol and phenylephrine infusion in six dogs. initially with LV expansion limited by increasing pericardial restraint and then with the pericardium opened. The mid-systolic 3D relations of the papillary muscle (PM) tips and mitral valve were reconstructed. Despite severe LV dysfunction (ejection fraction, 18+/-6%), only trace MR developed when pericardial restraint limited LV dilatation; with the pericardium opened, moderate MR accompanied LV dilatation (end-systolic volume, 44+/-5 mL versus 12+/-5 mL control, P<.001). Mitral regurgitant volume and orifice area did not correlate with LV ejection fraction and dP/dt (global function) but did correlate with changes in the tethering distance from the PMs to the anterior annulus derived from the 3D reconstructions, especially PM shifts in the posterior and mediolateral directions, as well as with annular area (P<.0005). By multiple regression, only changes in the PM-to-annulus distance independently predicted MR volume and orifice area (R2=.82 to .85, P=2x10(-7) to 6x10(-8)). CONCLUSIONS: LV dysfunction without dilatation fails to produce important MR. Functional MR relates strongly to changes in the 3D geometry of the mitral valve attachments at the PM and annular levels, with practical implications for approaches that would restore a more favorable configuration.

Animals↗
PubMed1997

Patients with valvular heart disease presenting with sustained ventricular tachyarrhythmias or syncope: results of programmed ventricular stimulation and long-term follow-up.

BACKGROUND: Programmed ventricular stimulation is commonly used to guide therapy in post-myocardial infarction patients with sustained monomorphic ventricular tachycardia (VT) or ventricular fibrillation (VF). In patients with valvular heart disease presenting with spontaneous VT, VF, or syncope, the usefulness of this technique is still unclear. The aim of the study was to analyze whether programmed ventricular stimulation was helpful in guiding therapy and determining prognosis in 97 patients with valvular heart disease presenting with VT (60%), VF (18%), or syncope (22%). METHODS AND RESULTS: Patients were classified as having either predominant ventricular pressure or volume overload or no significant pressure or volume overload. Overall, sustained VT or VF was inducible in 38 (39%) and 19 (20%) patients, respectively. Forty-six (47%) patients were discharged on antiarrhythmic drugs, 29 (30%) received an implantable cardioverter-defibrillator, and 22 (23%) remained without therapy. With serial drug testing, inducibility was completely or partially suppressed in 18 (19%) and 9 (9%) patients, respectively. During a mean follow-up of 51 months (n=97), 17 patients (18%) died (sudden death, n=7; heart failure, n=4; noncardiac causes, n=6). One-, 2- and 3-year event-free survival for sudden death, sustained VT, or VF was 77%, 68%, and 61%, respectively. Only inducibility of VT during baseline study (P<.0003) and left ventricular volume overload (P<.008) were significant predictors of arrhythmic events. Recurrence of arrhythmic events occurred in 56% and 56% of patients with complete or partial suppression of inducibility during serial drug testing as well as in 10 of 19 (53%) patients without a change in inducibility. CONCLUSIONS: Although programmed ventricular stimulation seems to predict adverse outcome, serial drug testing is unreliable in guiding therapy. The type of workload imposed on the ventricles influences outcome, being worse in patients with left ventricular volume overload. Therefore, implantation of a cardioverter-defibrillator should be considered early for the management of these patients.

Adolescent↗
PubMed1997

Stress echocardiography beyond coronary artery disease.

Doppler echocardiography has become the major diagnostic tool of evaluation of valvular heart disease and the cardiomyopathies because of its ability to provide valuable haemodynamic information accurately and non-invasively. It is therefore ideally suited for haemodynamic stress testing in these patients. In aortic stenosis, dobutamine echocardiography can distinguish severe from non-severe stenosis in patients with depressed left ventricular function, low transvalvular gradients, and a relatively small (flow-related) valve area at baseline. Patients with non-severe aortic stenosis increase cardiac output and valve area with dobutamine infusion while the transvalvular gradient does not change significantly. In severe aortic stenosis, the pressure gradient increases significantly with stroke volume, but valve area does not. In patients who fail to increase stroke volume (absent contractile reserve) and therefore do not show a change in haemodynamics, the severity of the lesion is 'indeterminate'; these patients are characterized by a very poor prognosis. In mitral stenosis, patients can be identified who increase valve area during exercise, which is the fundamental mechanism by which stroke volume can be increased in mitral stenosis. The increase in pulmonary artery pressure during exercise (assessed from tricuspid regurgitant signal) can be dramatically different in patients with comparable resting haemodynamics; therefore exercise echocardiography provides information which cannot be obtained from resting measurements alone and can help to guide medical and surgical therapy. Whether stress echocardiography may be similarly helpful in patients with regurgitant lesions is still a subject of investigation. Exercise Doppler echocardiographic studies following aortic valve replacement (small valves) can identify impairment of systolic and diastolic function indicative of 'valve prosthesis-patient mismatch'. In hypertrophic cardiomyopathy the dynamics of outflow obstruction can be assessed following exercise or pharmacological intervention. In dilative cardiomyopathy, contractile reserve can be assessed by dobutamine echocardiography which may help in evaluating prognosis, guiding heart failure therapy, and monitoring therapy with cardiotoxic chemotherapeutic agents.

Aortic Valve Insufficiency↗
PubMed1997

Importance of leaflet elongation in causing systolic anterior motion of the mitral valve.

BACKGROUND AND AIMS OF THE STUDY: There is growing evidence for mitral leaflet elongation in patients with hypertrophic cardiomyopathy. Such elongation could predispose to systolic anterior motion (SAM) of the mitral valve by increasing leaflet mobility and providing a geometry that promotes this condition. METHODS: To test this postulate, five porcine mitral valves were studied in a physiologic left heart pulsatile flow duplicator. They were elongated with patches sutured to the basal posterior leaflet (three sizes per valve) or anterior leaflet (basal, middle, or distal). Each geometry was studied with normal papillary muscle position and with anterior and inward displacement, as seen in hypertrophic cardiomyopathy, to shift the leaflets into the outflow stream. RESULTS: Four points became clear. 1) Leaflet elongation promoted the development of SAM in response to papillary muscle displacement by creating long overlapping residual leaflets capable of moving anteriorly. 2) Posterior leaflet elongation also promoted SAM by shifting leaflet coaptation anteriorly, with progressive increases in SAM. 3) Basal and mid-anterior leaflet elongation caused SAM with prolapse; distal anterior leaflet elongation created SAM with a mobile flap (leaflet elongation without papillary muscle displacement created prolapse). 4) Residual leaflet length correlated well with total leaflet length (r = 0.87-0.98 for each valve), and the degree of SAM in turn correlated well with residual leaflet length (r = 0.62-0.98 for individual valves). CONCLUSIONS: Mitral leaflet elongation, by increasing the residual leaflet length and leaflet mobility, can play an important role in promoting SAM in response to outflow forces, as demonstrated by prospectively altering leaflet length. These findings are consistent with recent observations that reducing leaflet redundancy and posterior leaflet height can reduce obstructive SAM following mitral valve repair in patients with mitral valve prolapse and help relieve obstruction in patients with hypertrophic cardiomyopathy and enlarged leaflets.

Cardiomegaly↗
PubMed1996

New method for accurate calculation of regurgitant flow rate based on analysis of Doppler color flow maps of the proximal flow field. Validation in a canine model of mitral regurgitation with initial application in patients.

OBJECTIVES: The purpose of this study was to develop a rational and objective method for selecting a region in the proximal flow field where the hemispheric formula for calculating regurgitant flow rates by the flow convergence technique is most accurate. BACKGROUND: A major obstacle to clinical implementation of the proximal flow convergence method is that it assumes hemispheric isovelocity contours throughout the Doppler color flow map, whereas contour shape depends critically on location in the flow field. METHODS: Twenty mitral regurgitant flow rate stages were produced in six dogs by implanting grommet orifices into the anterior mitral leaflet and varying driving pressures so that actual peak flow rate could be determined from the known effective regurgitant orifice times the orifice velocity. Because plotting flow rate calculated by using a hemispheric formula versus alias velocities produces underestimation near the orifice and overestimation far from it, this plot was fitted to a polynomial function to allow identification of an inflection point within a relatively flat intermediate zone, where factors causing overestimation and underestimation are expected to be unimportant or balanced. The accuracy of flow rate calculation by the inflection point was compared with unselective and selective averaging techniques. Clinical relevance, initial feasibility and correlation with an independent measure were tested in 13 consecutive patients with mitral regurgitation who underwent cardiac catheterization. RESULTS: 1) The accuracy of single-point calculations was improved by selecting points in the flat portion of the curve (y = 1.15x - 3.34, r = 0.87, SEE = 22.1 ml/s vs. y = 1.34x - 1.99, r = 0.71, SEE = 45.6 ml/s, p < 0.01). 2) Selective averaging of points in the flat portion of the curve further improved accuracy and decreased scatter compared with unselective averaging (y = 1.08x + 4.8, r = 0.96, SEE = 11.6 ml/s vs. y = 1.30x + 0.6, r = 0.90, SEE = 20.9 ml/s, p < 0.01). 3) The proposed algorithm for mathematically identifying the inflection point provided the best results (y = 0.96x + 4.5, r = 0.96, SEE = 9.9 ml/s), with a mean error of 1.6 +/- 9.7 ml/s vs. 11.4 +/- 11.7 ml/s for selective averaging (p < 0.01). In patients, the proposed algorithm identified an inflection point at which calculated regurgitant volume agreed best with invasive measurements (y = 1.1x - 0.61, r = 0.93, SEE = 17 ml). CONCLUSIONS: The accuracy of the proximal flow convergence method can be significantly improved by analyzing the flow field mathematically to identify the optimal isovelocity zone before using the hemispheric formula to calculate regurgitant flow rates. Because the proposed algorithm is objective, operator independent and, thus, suitable for automatization, it could provide the clinician with a powerful quantitative tool to assess valvular regurgitation.

Adult↗
PubMed1996

New insights into the reduction of mitral valve systolic anterior motion after ventricular septal myectomy in hypertrophic obstructive cardiomyopathy.

To determine the mechanism of reduction of mitral valve systolic anterior motion by myectomy, we examined 33 patients with hypertrophic obstructive cardiomyopathy echocardiographically before and after myectomy. Measurements included outflow tract diameter, the direction of ejection streamline (the angle between the ejection flow and the mitral valve), midventricular fractional area change, and papillary muscle inward excursion in the short-axis image. After myectomy, the outflow tract was enlarged (from 1.2 +/- 0.3 cm to 2.1 +/- 0.4 cm; p < 0.001), and the ejection flow became more parallel to mitral leaflets (from 51 +/- 10 degrees to 28 +/- 8 degrees; p < 0.001), whereas hyperdynamic midventricular fractional area change was reduced (81% +/- 14% to 62% +/- 14%; p < 0.001), and papillary muscle excursion decreased (1.3 +/- 0.3 cm to 0.8 +/- 0.3 cm; p < 0.001). Outflow enlargement and reduced ventricular contraction would decrease the Venturi force. Change of ejection streamline and reduced contraction would decrease the drag force onto the mitral leaflets. Blunted papillary motion would increase the mitral leaflet tension and decrease the effect of drag force on both leaflets. Thus myectomy decreases Venturi and drag forces and appears to reduce systolic anterior motion of the mitral valve.

Cardiomyopathy, Hypertrophic↗
PubMed1996

Intracardiac echocardiography: in vitro and in vivo validation for right ventricular volume and function.

To determine the feasibility and accuracy of intracardiac ultrasonography (ICUS) for the measurement of right ventricular (RV) volumes and function, a 10 MHz ICUS catheter was used in an in vitro and in vivo model. In the in vitro study, 16 sheep hearts were imaged. Sequential cross-sectional images from RV apex to base were recorded during a calibrated pullback. Volumes were calculated by applying Simpson's algorithm. ICUS-obtained volumes correlated well with actual volumes (standard error of estimate [SEE] = 2.3 ml, r = 0.98). For the in vivo study, a beating-heart canine model was used (31 hemodynamic stages in six dogs). Actual volumes were measured by an intracavitary balloon connected to an external column. Sequential cross-sectional images were recorded during the ICUS catheter pullback from apex to base of the RV, and volumes calculated by Simpson's algorithm. Good correlations were observed between ICUS and actual values for diastolic (SEE = 4.1 ml, r = 0.97), systolic (SEE = 3.4 ml, r = 0.96), and ejection fraction (SEE = 3.1%, r = 0.87) values. This new technique can accurately quantitate RV volumes, can function both in vitro and in vivo, and has the potential for increasing applications to questions of clinical and research interest.

Algorithms↗
PubMed1995

Proximal jet size by Doppler color flow mapping predicts severity of mitral regurgitation. Clinical studies.

BACKGROUND: Recent studies have shown that many instrument and physiological factors limit the ability of color Doppler total jet area within the receiving chamber to predict the severity of valvular regurgitation. In contrast, the proximal or initial dimensions of the jet as it emerges from the orifice have been shown to increase directly with orifice size and to correlate well with the severity of aortic insufficiency. Only limited data, however, are available regarding the value of proximal jet size in mitral regurgitation, and it has not been examined in short-axis or transthoracic views. The purpose of the present study, therefore, was to evaluate the relation between proximal jet size and other measures of the severity of mitral regurgitation. METHODS AND RESULTS: In 49 patients, the anteroposterior height of the proximal jet as it emerges from the mitral valve was measured in the parasternal long-axis view; proximal jet width and area were measured in the short-axis view at the same level. Results were compared with regurgitant volume and fraction by pulsed Doppler subtraction of aortic and mitral flows in 47 patients without more than trace aortic insufficiency; with angiographic grade determined within 24 hours in 33 catheterized patients; and with angiographic regurgitant fraction in 13 patients who were in normal sinus rhythm and had no significant aortic and tricuspid insufficiency. Proximal jet height, width, and area correlated well with Doppler regurgitant volume and fraction (r = .86 to .95; SEE = 7.7 to 9.0 mL; 5.9% to 7.3%). Proximal jet size could also be used to distinguish angiographic grades of mitral regurgitation with minimal overlap (P < .0001) and correlated well with angiographic regurgitant fraction (r = .85 to .91; SEE = 4.1% to 5.1%). CONCLUSIONS: Proximal jet size correlates well with established measures of the severity of mitral regurgitation. It is conveniently available with transthoracic clinical scanning and should be useful in the routine evaluation of patients with mitral regurgitation.

Adult↗
PubMed1995

Intracardiac ultrasonographic assessment of atrial septal defect area: in vitro validation and technical considerations.

Assessment of atrial septal defect (ASD) size and shape is important for planning and guiding its transcatheter occlusion and can potentially be achieved by intracardiac ultrasonography (ICUS). ICUS accuracy, however, must first be established against stable standards and technical imaging requirements defined. We therefore used 10, 20, and 30 MHz ICUS catheters to examine 17 ASDs that were 0.16 to 6.7 cm2 in area and were surgically created in excised ovine hearts with 10, 20, and 30 MHz ICUS catheters. ASD shape and area by ICUS were compared with direct video images of the actual ASD. In all instances minimal area by ICUS pullback agreed well with actual values (y = 1.04x + 0.2, SEE = 0.23 cm2, r = 0.99) and corresponded well with defect shapes. The maximum angle between ultrasonography beam and septal plane allowing for complete ASD visualization was 20 degrees. The angle depended on transducer frequency and septal thickness. This new technique has potential value for the accurate assessment of ASD shape and size and may be especially useful in the setting of transcatheter occlusion.

Animals↗
PubMed1995

[Initial experiences with dobutamine stress echocardiography in heart transplant patients].

UNLABELLED: Cardiac allograft vasculopathy (CAV) has become one of the primary obstacles to long-term survival of patients after heart transplantation. The low sensitivity of currently available noninvasive tests still remains a problem in the early diagnosis of the disease. To assess the feasibility, safety, and usefulness of dobutamine stress echocardiography as a noninvasive predictor of cardiac allograft vasculopathy, we examined 20 patients (3 female) 3-35 months after orthotopic heart transplantation. All patients underwent coronary angiography within 2 weeks of dobutamine stress echocardiography. RESULTS: 89% of the segments examined could be evaluated for wall motion abnormalities. Under increasing doses of dobutamine (5 to max. 30 micrograms/kg/min), heart rate increased from 88 +/- 13 bpm to 141 +/- 16 bpm. and systolic blood pressure from 139 +2- 14 mm Hg to 154 +/- 28 mm Hg. Two of 4 patients with angiographically detected CAV developed new wall motion abnormalities under dobutamine; their wall motion score increased from 1.23 +/- 0.22 to 1.31 +/- 0.24. In the other patients without CAV, the wall motion score remained almost unchanged (1.01 +/- 0.3 to 1.02 +/- 0.4). Dobutamine was well tolerated, and there were no serious complications. Thus, dobutamine stress echocardiography seems to be feasible and safe in patients after heart transplantation. Our results suggest that it might be useful for the detection of cardiac allograft vasculopathy. The final determination of its clinical usefulness in the diagnosis of cardiac allograft vasculopathy needs further extensive investigations.

Adult↗
PubMed1994

Detection of regional left ventricular asynchrony in obstructive hypertrophic cardiomyopathy by magnetic resonance imaging.

Cine magnetic resonance imaging was used to analyze global and regional left ventricular function in seven patients with obstructive hypertrophic cardiomyopathy (HC) and 10 normal subjects. In patients with HC a 38% higher left ventricular mass index (106.4 +/- 20.2 gm/m2 vs 77.0 +/- 16.1 gm/m2, p < 0.005) associated with a lower end-diastolic volume index (44.9 +/- 8.9 ml/m2 vs 58.3 +/- 9.0 ml/m2, p < 0.005) resulted in an 85% higher mass-to-volume ratio (2.4 +/- 0.52 vs 1.3 +/- 0.57, p < 0.0005). Stroke volume did not differ significantly, whereas ejection fraction was higher (80.4% +/- 6.5% vs 65.4% +/- 7.2%, p < 0.0005) in patients with HC. Although early diastolic filling fraction was smaller in patients with HC (61.0% +/- 22.8% vs 68.4% +/- 14.6%), the difference did not reach significance because of substantial variability. In patients with HC (in contrast to normal subjects) the time to maximal wall thickening was shorter (p < 0.025) in the hypertrophied basal region of the ventricle (223 +/- 42 msec) than in the apical region (267 +/- 35 msec), reflecting asynchrony between these regions. Additionally, in patients with HC the standard deviation of the time to maximal wall thickening in the basal region was significantly higher when compared with that of normal subjects (40.0 +/- 24 msec vs 16.9 +/- 17 msec, p < 0.0005), reflecting asynchrony even within one region. Thus magnetic resonance imaging can detect regional left ventricular asynchrony, an important cause of impaired diastolic function, in patients with HC and normal global systolic function.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Significant tricuspid regurgitation is a marker for adverse outcome in patients undergoing percutaneous balloon mitral valvuloplasty.

OBJECTIVES: This study examined the association between the presence of tricuspid regurgitation and immediate and late adverse outcomes in patients undergoing balloon mitral valvuloplasty. BACKGROUND: Significant tricuspid regurgitation has an adverse impact on morbidity and mortality in patients undergoing mitral valve surgery for mitral stenosis. METHODS: We studied 318 consecutive patients (mean [+/- SD] age 54 +/- 15 years) who underwent balloon mitral valvuloplasty and had color Doppler echocardiographic studies before the procedure. Patients were classified into three groups: 221 with no or mild (69%), 60 with moderate (19%) and 37 with severe (12%) tricuspid regurgitation. Clinical follow-up ranged from 6 to 62 months. RESULTS: Before mitral valvuloplasty, increasing degrees of tricuspid regurgitation were associated with a smaller initial mitral valve area (p < 0.05), higher echocardiographic score (p < 0.05), lower cardiac output (p < 0.01) and higher pulmonary vascular resistance (p < 0.01). Although the initial success rate did not differ significantly between groups, patients with a higher degree of tricuspid regurgitation had less optimal results, as reflected by a smaller absolute increase in mitral valve area (1.02 vs. 0.9 vs. 0.7 cm2, p < 0.01). The estimated 4-year event-free survival rate (freedom from death, mitral valve surgery, repeat valvuloplasty and heart failure) was lower for the group with severe tricuspid regurgitation (68% vs. 58% vs. 35%, p < 0.0001). At 4 years, 94% of patients with mild tricuspid regurgitation were alive compared with 90% and 69%, respectively, of patients with moderate or severe tricuspid regurgitation (p < 0.0001). Cox proportional analysis identified tricuspid regurgitation as an independent predictor of late outcome (p < 0.001). CONCLUSIONS: Patients with mitral stenosis and severe tricuspid regurgitation undergoing mitral valvuloplasty have advanced mitral valve and pulmonary vascular disease, suboptimal immediate results and poor late outcome.

Adult↗
PubMed1994

Determinants of functional tricuspid regurgitation in incomplete tricuspid valve closure: Doppler color flow study of 109 patients.

OBJECTIVES: The aim of this study was to investigate the association between the pattern of incomplete tricuspid valve closure and the presence of tricuspid regurgitation and to identify factors that determine the severity of regurgitation associated with this pattern. BACKGROUND: The incomplete tricuspid valve closure pattern (defined as apical displacement of the leaflets) has been described by two-dimensional echocardiography. However, whether this pattern is universally associated with tricuspid regurgitation and the determinants of severity of regurgitation in its presence have not been studied by Doppler color flow mapping. METHODS: We identified 109 consecutive patients (mean age 62 +/- 17 years) with incomplete tricuspid valve closure who were studied by Doppler color flow mapping. We measured the linear apical displacement of the coaptation point from the tricuspid annulus and the area of displacement between the leaflets and annulus. Right atrial, ventricular and annular dimensions were measured and compared with those in a group of normal subjects. RESULTS: Tricuspid regurgitation was present in all patients with the incomplete closure pattern; it was mild in 14%, moderate in 19% and severe in 67%. Apical displacement was significantly greater (p < 0.02) in those with severe regurgitation than in those with mild regurgitation or in normal subjects. Tricuspid annulus dilation was the only independent predictor of severity of regurgitation. The right ventricle was not significantly dilated in 32% of patients, and right ventricular systolic pressure was not correlated with the severity of regurgitation and was < 30 mm Hg in 11% of patients. CONCLUSIONS: Tricuspid regurgitation was associated with incomplete tricuspid valve closure in all patients studied and was moderate to severe in 86%. Impaired coaptation is best reflected by the displacement area between the leaflets and the annulus. High pulmonary pressure and significant right ventricular dilation are not prerequisites for functional tricuspid regurgitation. Annular dilation is the most consistent and important determinant of this lesion.

Adult↗
PubMed1994

Quantification of pericardial effusions by three-dimensional echocardiography.

OBJECTIVES: The purpose of this study was to examine the accuracy of three-dimensional echocardiography for the quantification of asymmetric pericardial effusion volume and to compare this new technique with two-dimensional echocardiography. BACKGROUND: Quantification of pericardial effusion by two-dimensional echocardiography relies on a symmetric distribution of the fluid. Three-dimensional echocardiography can quantitate volume without these limitations, but its accuracy for pericardial effusion volume has not yet been assessed. METHODS: In six open chest dogs, 41 different asymmetrically distributed pericardial effusions of known volume were created by serial infusions of fluid through a pericardial catheter. The hearts were imaged using an automated echocardiographic method that integrates three-dimensional spatial and imaging data. The surfaces of the pericardial sac and heart were then reconstructed, and the volumes of pericardial effusions were calculated. Two-dimensional echocardiography was performed simultaneously, and volumes were calculated using the prolate ellipsoid method. Asymmetric distribution of the fluid was obtained by applying localized hydrostatic pressure to the pericardium. RESULTS: The volumes of pericardial effusion quantified using three-dimensional echocardiography correlated well with actual volumes (y = 1.0x - 1.4, SEE = 7.7 ml, r = 0.98). Two-dimensional echocardiography had an acceptable correlation (y = 1.0x + 2.3, SEE = 23 ml, r = 0.84), but a marked degree of variation from the true value was observed for any individual measurement. CONCLUSIONS: Three-dimensional echocardiography accurately quantifies pericardial effusion volume in vivo, even when the fluid is distributed asymmetrically, whereas two-dimensional echocardiography is less reliable. This new technique may be of clinical value in quantitating pericardial effusion, especially in the serial evaluation of asymmetric or loculated effusions.

Algorithms↗
PubMed1994

Dynamics of mitral regurgitant flow and orifice area. Physiologic application of the proximal flow convergence method: clinical data and experimental testing.

BACKGROUND: The proximal flow convergence method, a quantitative color Doppler flow technique, has been validated recently for calculating regurgitant flow and orifice area. We investigated the potential of the method as a tool to study different pathophysiological mechanisms of mitral valve incompetence by assessing the time course of regurgitant flow and orifice area and analyzed the implications for quantification of mitral regurgitation. METHODS AND RESULTS: Fifty-six consecutive patients with mitral regurgitation of different etiologies were studied. The instantaneous regurgitant flow rate Q(t) was computed from color M-mode recordings of the proximal flow convergence region and divided by the corresponding orifice velocity V(t) to obtain the instantaneous orifice area A(t). Regurgitant stroke volume (RSV) was obtained by integrating Q(t). Mean regurgitant flow rate Qm was calculated by RSV divided by regurgitation time. Peak-to-mean regurgitant flow rates Qp/Qm and orifice areas Ap/Am were calculated to assess the phasic character of Q(t) and A(t). In the first 24 patients (group 1), computation of Qm and RSV from the color Doppler recordings was compared with the conventional pulsed Doppler method (r = .94, SEE = 29.4 mL/s and r = .95, SEE = 9.7 mL) as well as with angiography (rs = .93 and rs = .94, P < .001). The temporal variation of Q(t) and A(t) was studied in the next 32 patients (group 2): In functional regurgitation in dilated cardiomyopathy (n = 12), there was a constant decrease in A(t) throughout systole with an increase during left ventricular relaxation; Ap/Am was 5.49 +/- 3.17. In mitral valve prolapse (n = 6), A(t) was small in early systole, increasing substantially in midsystole, and decreasing mildly during left ventricular relaxation; Ap/Am was 2.48 +/- 0.26. In rheumatic mitral regurgitation (n = 14), a roughly constant regurgitant orifice area during most of systole was found in 4 patients. In the other patients there was significant variation of A (t) and the time of its maximum; Ap/Am was 1.81 +/- 0.56. ANOVA demonstrated that the differences in Ap/Am were related to the etiology of mitral regurgitation (P < .0001). To verify that the calculated variation in regurgitant orifice area during the cardiac cycle reflects an actual variation, the ability of the method to predict a constant orifice area throughout systole was tested experimentally in a canine model of mitral regurgitation. Five flow stages were produced by implanting fixed grommet orifices of different sizes into the anterior mitral leaflet. A constant regurgitant orifice area was correctly predicted throughout systole with a mean percent error of -1.8 +/- 4% (from -6.9% to +5.8%); the standard deviation of the individual curves calculated at 10% intervals during systole averaged 13.3% (from 3.6% to 19.6%). In addition, functional mitral regurgitation caused by ventricular dysfunction was produced pharmacologically in five dogs, and the color M-mode recordings of the proximal flow convergence region were obtained with the transducer placed directly on the heart instead of the chest, thus ruling out a significant effect of translational motion on the observed flow pattern. The pattern of regurgitant flow variation was identical to that observed in patients. CONCLUSIONS: The proximal flow convergence method demonstrates that regurgitant flow and orifice area vary throughout systole in distinct patterns characteristic of the underlying mechanism of mitral incompetence. Therefore, in addition to the potential of the method as a tool to quantify mitral regurgitation, it allows analysis of the pathophysiology of regurgitation in the individual patient, which may be helpful in clinical decision making. Calculating mitral regurgitant flow rate and volume from the time-varying proximal flow field (ie, without assuming a constant orifice area that would produce overestimation in individual patients) provides excellent agreement with independent te

Adult↗
PubMed1994

Intracardiac ultrasound measurement of volumes and ejection fraction in normal, infarcted, and aneurysmal left ventricles using a 10-MHz ultrasound catheter.

BACKGROUND: Our objective was to examine the accuracy of intracardiac ultrasound (ICUS) measurement of left ventricular (LV) volumes and ejection fraction (EF) using a 10-MHz ultrasound catheter. ICUS can image the LV in cross sections at all levels along the long axis with a transducer mounted on the tip of a catheter. Sequential serial LV cross-sectional images can be obtained during cardiac catheterization and used to calculate LV volumes by Simpson's rule. This technique may be an alternative to contrast LV angiography. METHODS AND RESULTS: A beating-heart in vivo model was created to measure LV volume directly and continuously with an intracavity high-compliance latex balloon connected to a calibrated extracardiac reservoir in eight dogs in 35 experimental stages. A 10F ICUS catheter with a 10-MHz single-element transducer was introduced retrogradely via the aortic valve to the apex. Series of sequential LV cross-sectional images were recorded from the apex to the base during a calibrated pullback of the catheter. At each 5-mm interval, the LV cross section was traced at end diastole and end systole. LV volume was calculated by Simpson's rule by integrating all segmental areas multiplied by segmental height. The effect on accuracy of selecting 5-, 10-, or 15-mm heights or a single section at the midventricular level for measurement was assessed. The influence of distorted ventricular shape on the accuracy of ICUS measurements of LV volume was evaluated. This method was applied in 19 experimental stages in 10 intact dogs and pigs catheterized via the femoral artery. In the in vivo canine model, LV end-diastolic volume, end-systolic volume, and EF determined by ICUS using 5-, 10-, or 15-mm segments were not different from the actual measurements. But correlation and agreement between ICUS end-diastolic volume and direct measurements for 5- and 10-mm segments were significantly better than for 15-mm segments or a single section. Similar excellent correlations and agreement were observed for actual and ICUS-derived end-systolic volumes using 5-, 10-, or 15-mm segments. The ICUS-derived EF correlated very well with actual EF with a small measurement error of 3.91 +/- 2.59% for 5-mm or 4.13 +/- 2.79% for 10-mm segments but a significantly greater measurement error for 15-mm segments (5.35 +/- 3.76%) or single sections (14.8 +/- 12.2%). The presence of LV infarction or aneurysm did not significantly influence the accuracy of ICUS calculations for segmental heights < or = 10 mm. Application in intact animals demonstrated a good correlation between stroke volume measured by ICUS and by thermodilution or flowmeter. ICUS-derived LV volumes correlated well with biplane angiographic volumes, with a tendency toward underestimation. There was no significant difference between ICUS-determined LV EF and EF determined by angiography. CONCLUSIONS: Intracardiac echocardiography accurately measures LV volumes and global systolic function in both regularly shaped and distorted left ventricles. This technique directly and continuously visualizes circumferential LV endocardium and wall thickness without contrast agents or geometric assumptions for calculation of LV volume. Thus, it should be particularly useful in patients at high risk for contrast-related complications or distorted LV shapes in which geometric assumptions may not be valid.

Animals↗