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.

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.

Three-dimensional echocardiography improves noninvasive assessment of left ventricular volume and performance

To calculate left ventricular (LV) volume by two-dimensional echocardiography (2DE), assumptions must be made about ventricular symmetry and geometry. Three-dimensional echocardiography (3DE) can quantitate LV volume without these limitations, yet its incremental value over 2DE is unknown. The purpose of this study was to compare the accuracy of LV volume determination by 3DE to standard 2DE methods. To compare the accuracy of 3DE with standard 2DE algorithms for quantitating LV volume, 28 excised canine ventricles of known volume and varying shapes (15 symmetric and 13 aneurysmal) and 10 instrumented dogs prepared so that instantaneous ventricular volume could be measured were examined by 2DE (bullet and biplane Simpson's formulas) and again by 3DE. In both excised and beating hearts, 3DE was more accurate in quantitating volume than either 2DE method (excised: error = 0.6 +/- 3.2, 2.5 +/- 10.7, and 4.0 +/- 8.5 ml by 3D, bullet, and Simpson's, respectively; beating: error = -0.5 +/- 3.5, -0.3 +/- 9.6, and -7.6 +/- 8.0 ml by 3DE, bullet, and Simpson's, respectively). This difference in accuracy between 3DE and 2DE methods was especially apparent in asymmetric ventricles distorted by ischemia or right ventricular volume overload. Stroke volume and ejection fraction calculated by 3DE also demonstrated better agreement with actual values than the bullet or Simpson methods with less variability (ejection fraction: error = -2.0% +/- 5.1%, 7.7% +/- 8.5%, and 6.8% +/- 12.3% by 3DE, bullet, and Simpson's, respectively). In both in vitro and in vivo settings, 3DE provides improved accuracy for LV volume and performance than current 2DE algorithms.

Three-dimensional intravascular ultrasound assessment of plaque volume after successful atherectomy

The primary purpose of directional coronary atherectomy is the removal of intraluminal plaque. Angiography allows assessment of residual lumen narrowing but is limited in the assessment of residual plaque burden. Intravascular ultrasound has proven useful in assessing plaque size, but current use has been limited to a single, representative cross-sectional image rather than an evaluation of the entire plaque volume. To determine the volume of residual plaque after angiographically successful directional coronary atherectomy ( < or = 20% residual stenosis), we performed intravascular ultrasound in 19 patients before and after atherectomy. Only coronary lesions optimal for three-dimensional analysis (a single, discrete stenosis in a nontortuous, noncalcified native coronary artery) were selected. A 2.9F sheath-design intravascular ultrasound catheter with a motorized pullback device was used in all patients. The cross-sectional area of the artery (defined by the medial-adventitia border), the lumen, and the plaque were measured at 1 mm intervals over a 15 to 20 mm segment, which included the target lesion and a proximal reference segment (n = 362 cross-sections), before and after atherectomy. The volumes of the artery, vessel lumen, or plaque were calculated with a modified Simpson's equation and compared with standard area measurements at the point of maximal stenosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Three-dimensional surface geometry correction is required for calculating flow by the proximal isovelocity surface area technique

This study addressed the hypothesis that surface geometry must be taken into account in proximal convergence calculations of regurgitant flow rate. In vitro models allowed flow to converge within models designed to test derived angle correction equations. Flow was overestimated by the uncorrected equation for surfaces allowing flow to converge over less than a hemisphere and underestimated if flow converged over more than a hemisphere. The extent of deviation depended on the two-dimensional versus three-dimensional nature of the surface (angled flat surfaces versus conical surfaces). Correcting these estimates according to the derived equation produced good agreement for all geometries.

Incremental doses of dobutamine induce a biphasic response in dysfunctional left ventricular regions subtending coronary stenoses

BACKGROUND

Dobutamine stress echocardiography has been proposed as a diagnostic tool to identify viable myocardium. How regional wall thickening responds to dobutamine in the ischemic or short-term hibernating myocardium has not been adequately defined. We hypothesized that regional wall thickening would improve initially and subsequently deteriorate with incremental doses of dobutamine in viable myocardial regions supplied by a stenotic coronary artery. This study was undertaken to determine whether this biphasic pattern of regional function characterizes the response of ischemic or hibernating myocardium to dobutamine and to explore the factors and mechanisms that determine this response.

METHODS AND RESULTS

Twenty-six pigs in four groups were studied: a control group (n = 5) to assess the response of myocardium perfused by nonstenotic coronary artery to incremental doses of dobutamine, and three experimental groups with a left anterior descending coronary artery stenosis producing acute myocardial ischemia (n = 7), short-term myocardial hibernation for 90 minutes (n = 7), and short-term hibernation for 24 hours (n = 7) to determine the functional and metabolic response to dobutamine under these conditions. Regional coronary flow was reduced to 40% to 60% of baseline, with significant reductions of regional wall thickening as measured by two-dimensional echocardiography and sonomicrometers. An incremental dobutamine infusion from 2.5 to 25 micrograms.kg-1.min-1 increased wall thickening and coronary flow without lactate production in the control group. In the other three groups, during the incremental dobutamine infusion, regional wall thickening improved initially, from 11.4 +/- 7.5% to 19.8 +/- 11.4%, P < .01, at dobutamine doses of 2.5 to 10 (4.5 +/- 2.2) micrograms.min-1.kg-1 but deteriorated subsequently to 5.0 +/- 5.8% at the maximal dose of dobutamine of 12.6 +/- 4.1 micrograms.min-1.kg-1. The initial improvement of regional wall thickening was associated with a small increase in regional coronary flow (from 0.53 +/- 0.18 to 0.68 +/- 0.25 mL.min-1.g-1 myocardium, P < .05) and with regional lactate production. High doses of dobutamine did not further increase regional coronary flow but markedly increased lactate production and induced regional myocardial acidosis (pH 7.26 +/- 0.07). The biphasic pattern of response to dobutamine was observed in each of the three experimental groups. Both peak improvement and peak deterioration occurred earlier and at lower dobutamine dose levels in the group with acute ischemia compared with the group with short-term hibernation for 24 hours (P < .05).

CONCLUSIONS

A biphasic response of wall thickening to incremental dobutamine with initial improvement and subsequent deterioration is characteristic of ischemic or short-term hibernating myocardium. The initial low-dose dobutamine infusion improved wall thickening in the ischemic or hibernating myocardial region to a modest level. This initial modest improvement was transient and at the expense of metabolic deterioration of myocardial ischemia, so that at higher doses during prolonged dobutamine infusion, wall thickening deteriorated, lactate accumulated, and myocardial acidosis developed.

Effect of beta-adrenergic receptor blockade on the physiologic response to dobutamine stress echocardiography

Dobutamine is an effective pharmacologic stress agent because of its beta-adrenergic receptor agonist properties. Theoretically, concurrent beta-adrenergic receptor blockade might alter this effectiveness, but clinical experience has been variable. Before assessing the relative effectiveness and implications of dobutamine stress echocardiography (DSE) to detect myocardial ischemia in the presence of beta-blockade the physiologic and hemodynamic effects of dobutamine with simultaneous beta-blockade must be understood in a controlled setting. Therefore the purpose of this study was to determine if beta-blocking agents alter the timing and magnitude of the physiologic response to graded doses of dobutamine during a standard DSE. Paired DSEs were performed in seven instrumented open-chest dogs with and without beta-blockade (esmolol 500 micrograms/kg initial bolus and 100 micrograms/kg/min infusion). Heart rate, systolic pressure, proximal left anterior descending coronary artery flow, myocardial thickening, and percentage left ventricular area change (% AC) were monitored. The data for each parameter were fit to linear or exponential functions. With graded doses of dobutamine, the rate of increase in coronary flow was greater than that in %AC, which in turn was greater than that in heart rate (p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

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.

Dynamic expansion of the coronary arteries: implications for intravascular ultrasound measurements

The majority of coronary artery blood flow occurs in diastole; however, systolic epicardial coronary artery expansion has been described. With the advent of intravascular ultrasound, precise measurements of arterial structures with excellent spacial and temporal resolution are now readily available. However, the effect of dynamic expansion of the coronary arteries on routine intravascular ultrasound measurements has not been assessed. The purpose of this study was to determine in vivo the presence, timing, and extent of dynamic changes in the coronary arteries and saphenous vein grafts and to assess their implications for intravascular ultrasound measurements. Intravascular ultrasound images were obtained with simultaneous electrocardiographic monitoring in 202 coronary artery and 50 saphenous vein graft sites in 32 patients with varying plaque burden and morphologic features. Arterial, luminal, and plaque area were measured at end-diastole and early, mid-, and end-systole. Coronary luminal diameter increased 2.1%; luminal area increased 8.1%; arterial area increased 3.7%; and plaque area decreased 4.9% during mid and late systole (p < 0.01). There was no detectable cyclic change in saphenous vein graft dimensions. In coronary arteries there was significant systolic expansion of the artery and lumen and systolic thinning of the plaque. The magnitude of dynamic luminal area change was greater than the variability in measurement and thus warrants gating to the cardiac cycle. The lack of dynamic change in saphenous vein grafts and the relatively small dynamic change in luminal diameter and arterial and plaque areas suggest nominal utility in gating these measurements to the cardiac cycle.

Pulsatile pressure affects the disappearance of echocardiographic contrast agents

The purpose of this study was to determine in an in vitro model the effect of pulsatile pressure on the decay of echocardiographic contrast agents. Use of contrast agents for quantitative assessment of perfusion requires understanding of the factors controlling their rates of disappearance. Prior studies have shown that constant pressure affects the rate of disappearance of these agents. It is not known whether pulsatile pressure influences the rate of decay of contrast agents. In an in vitro chamber, three contrast agents (Albunex, hand-agitated saline solution, and hand-agitated Angiovist) were exposed to pulses of pressure at three rates (30, 60, and 120 pulsations/min), keeping pressure characteristics (peak, nadir, and mean) within a narrow range. Five injections were performed for each agent at each rate. Two-dimensional echocardiographic images of the effects of contrast material were recorded from injection until total disappearance. Videointensity was measured and time-intensity curves were generated. These curves of intensity decay were fitted to an exponential decay function (I = Ae-lambda t) and the velocity of decay (lambda) was used for comparisons. For all agents, intensity of contrast decreased over time. Saline solution and Angiovist, but not Albunex, showed pulsatile decreases in intensity of contrast with each peak pressure and partial recovery of contrast intensity with each nadir pressure. (ABSTRACT TRUNCATED AT 250 WORDS)

Optimal stage duration in dobutamine stress echocardiography

OBJECTIVES

This study attempted to determine the benefit of a 5-min dobutamine stress echocardiographic stage versus a 3-min stage in a canine model.

BACKGROUND

Dobutamine stress echocardiography, as currently performed, uses a variety of different protocols. Among the many aspects of dobutamine stress echocardiographic protocols that vary is stage duration. Because dobutamine has specific pharmacodynamics, it is possible that stages of different durations may have different cardiovascular effects.

METHODS

Paired dobutamine stress echocardiograms were obtained in 10 open chest instrumented dogs. The stage duration for the initial dobutamine stress echocardiogram was randomly allocated to either 3 or 5 min, and all hemodynamic and echocardiographic variables were allowed to return to baseline before the second dobutamine stress echocardiogram was obtained using the alternative stage duration. At each stage, heart rate, systolic blood pressure, coronary flow, myocardial wall thickness and left ventricular cavity area were recorded. Cavity obliteration, hypotension, ventricular tachycardia or a maximal dose of 40 micrograms/kg body weight per min served as the dobutamine stress echocardiographic end point.

RESULTS

At baseline, no difference was detected between the 3- or 5-min protocols for heart rate, systolic blood pressure, rate-pressure product, coronary blood flow, wall thickness or percent area change. Heart rate, systolic blood pressure and coronary flow increased more by the 10-micrograms/kg per min dose with the 5-min protocol than with the 3-min protocol. The dobutamine stress echocardiographic end points were achieved at a lower dobutamine dose (15.0 +/- 4.1 vs. 11.0 +/- 2.1 micrograms/kg per min [mean +/- SD], p = 0.01) with the longer stage duration.

CONCLUSIONS

In this canine model, a longer stage produced a greater hemodynamic effect at a lower peak dose. Thus, extending stage duration in clinical dobutamine stress echocardiography may achieve equivalent physiologic stress at lower doses and contribute to the optimization of dobutamine stress echocardiographic protocols.

Papillary muscle displacement causes systolic anterior motion of the mitral valve. Experimental validation and insights into the mechanism of subaortic obstruction

BACKGROUND

Systolic anterior motion (SAM) of the mitral valve in hypertrophic cardiomyopathy (HCM) has generally been explained by a Venturi effect related to septal hypertrophy, causing outflow tract narrowing and high velocities. Patients with HCM, however, also have primary abnormalities of the mitral apparatus, including anterior and inward or central displacement of the papillary muscles, and leaflet elongation. These findings have led to the hypothesis that changes in the mitral apparatus can be a primary cause of SAM by altering the forces acting on the mitral valve and its ability to move in response to them. Despite suggestive observations, however, it has never been prospectively demonstrated that such changes can actually cause SAM.

METHODS AND RESULTS

To test this hypothesis in vivo, anterior papillary muscle displacement was created in 7 dogs studied by echocardiography, with controlled cardiac output and heart rate. In all 7 dogs, papillary muscle displacement caused SAM, with an outflow tract gradient (33 +/- 19 mm Hg) and mitral regurgitation in 6. As in patients with HCM, the mitral valve was displaced anteriorly and the coaptation point shifted toward the insertion of the leaflets, creating longer distal residual leaflets that moved anteriorly.

CONCLUSIONS

Primary changes in the mitral apparatus can cause SAM without septal hypertrophy. In this model, SAM appears to be determined by the ability of the leaflets to move anteriorly (papillary muscle displacement causing slack and increased residual leaflet length) and their interposition into the outflow stream by anterior displacement, determining the direction of this motion. Geometric factors observed in HCM and in patients with SAM without HCM can therefore play a primary role in causing SAM.

Clinical follow-up of patients undergoing percutaneous mitral balloon valvotomy

BACKGROUND

This study is the clinical follow-up (20 +/- 12 months; range, 6 to 49 months) of 327 patients who had percutaneous mitral balloon valvotomy (PMV) at the Massachusetts General Hospital.

METHODS AND RESULTS

There were seven in-hospital deaths. Patients were divided into two groups according to their echocardiographic score; 211 patients had echocardiographic scores < or = 8 and 116, echocardiographic scores > 8. Patients with echocardiographic scores > 8 were older (64 +/- 11 versus 48 +/- 14 years, P < .01), and more had atrial fibrillation (65% versus 40%, P < .01), calcium under fluoroscopy (81% versus 29%, P < .01), and previous surgical commissurotomy (30% versus 16%, P < .01) than patients with echocardiographic scores < or = 8. With PMV, mitral valve area increased from 1.0 +/- 0.3 to 2.2 +/- 0.8 cm2 in patients with echocardiographic scores < or = 8 and from 0.8 +/- 1 to 1.7 +/- 0.7 cm2 in those with echocardiographic scores > 8. Rates of survival (98 +/- 2% versus 72 +/- 11%), survival with freedom from mitral valve replacement (91 +/- 4% versus 55 +/- 13%), and survival with freedom from combined events (79 +/- 10% versus 39 +/- 18%) at follow-up were greater in patients with echocardiographic scores < or = 8 (P < .00005). Cox regression analysis identified the echocardiographic score as the most important unfavorable intermediate long-term follow-up prediction factor after PMV.

CONCLUSIONS

The excellent intermediate long-term clinical follow-up of patients with echocardiographic score < or = 8 and no calcified mitral valves suggests that PMV may be the treatment of choice in this group of patients.

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.

Effect of hydration on cavity obliteration during dobutamine stress echocardiography

The purpose of this study was to determine whether it is possible to prevent or delay the onset of midventricular cavity obliteration during a dobutamine stress test with standard hydration. Left ventricular (LV) intracavitary obstruction has been reported as the mechanism for hypotension seen in approximately 20% of patients undergoing dobutamine stress echocardiography. In addition, it has been proposed that administration of a normal saline bolus prior to dobutamine infusion may avert the dynamic ventricular obstruction. We performed a standard graded dobutamine stress echocardiogram before and after fluid loading with 10 ml/kg of normal saline in 10 mongrel dogs. Measurements were made of left atrial pressure, aortic pressure, and the area of the LV cavity at the papillary muscle level throughout each infusion. Although hydration produced an increase in baseline left atrial pressure (5.7 +/- 3.2 to 8.1 +/- 2.7 mmHg, p < 0.01) and systolic blood pressure (128 +/- 18 to 139 +/- 22 mmHg, p = 0.03), there was no significant change in pre-dobutamine heart rate or systolic area. With dobutamine infusion, there was a similar change in heart rate, systolic blood pressure, diastolic area, and systolic area (SA) at each dose of dobutamine regardless of hydration status. In addition, the dose at which cavity obliteration occurred was not altered by hydration (p = NS). Although all dogs developed cavity obliteration (SA < 1.0 cm2) with dobutamine infusion, none experienced hypotension. In this canine model, cavity obliteration does not lead to systemic hypotension and cannot be prevented or delayed by volume loading.

Quantitative three-dimensional reconstruction of aneurysmal left ventricles. In vitro and in vivo validation

BACKGROUND

Current two-dimensional (2D) echocardiographic measures of left ventricular (LV) volume are most limited by aneurysmal distortion, which restricts application of simple geometric models that assume symmetrical shape. 2D methods also fail to provide separate volumes of the aneurysm and nonaneurysmal residual LV cavity, which could help assess the stroke volume wasted by dyskinesis and the potential residual LV body to guide surgical approaches and predict their outcome. Three-dimensional (3D) echocardiographic reconstruction has potential advantages for assessing aneurysmal left ventricles because it is not dependent on geometric assumptions, does not require standardized views that may exclude portions of the aneurysm, and can potentially measure separate aneurysm and nonaneurysm cavity volumes of any shape. The purpose of this study was first, to validate the accuracy of 3D echocardiographic reconstruction for quantifying total LV and separate LV body and aneurysm volumes in vitro so as to provide direct standards for the separate volumes; and second, to determine the feasibility and accuracy of 3D echocardiographic reconstruction for quantifying the total volume and function of aneurysmal left ventricles in an animal model, providing a reference standard for instantaneous LV volume.

METHODS AND RESULTS

A recently developed 3D system that automatically combines 2D images and their locations was applied (1) to reconstruct 10 aneurysmal ventricular phantoms and 12 gel-filled autopsied human hearts with aneurysms, comparing cavity volumes (total and aneurysm) to those measured by fluid displacement; and (2) to reconstruct the left ventricle during 19 hemodynamic stages in four dogs with surgically created LV aneurysms, comparing total volumes with actual instantaneous values measured by an intracavitary balloon attached to an external column for validation and also calculating the stroke volume wasted by aneurysmal dyskinesis. 3D reconstruction reproduced the distorted aneurysmal LV shapes. In vitro, calculated volumes (aneurysm, nonaneurysm, and total) agreed well with actual values, with correlation coefficients of .99 and SEEs of 3.2 to 6.1 cm3 for phantoms and 3.4 to 4.2 cm3 for autopsied hearts (mean error, < 4% for both). In vivo, LV end-diastolic, end-systolic, and stroke volumes as well as ejection fraction calculated by 3D echocardiography correlated well with actual values (r = .99, .99, .95, and .99, respectively) and agreed closely with them (SEE = 4.3 cm3, 3.5 cm3, 1.7 cm3, and 2%, respectively). The stroke volumes wasted by the aneurysm were -20.1 +/- 19.3% of LV body (nonaneurysm) stroke volume.

CONCLUSIONS

Despite distorted ventricular shapes, a recently developed 3D echocardiographic system and surfacing algorithm can accurately reconstruct aneurysmal left ventricles and quantify total LV volume (validated in vivo and in vitro) as well as the separate volumes of the aneurysm and residual LV body (validated in vitro). This should improve our ability to evaluate such ventricles and guide surgical approaches.

Natural history of vegetations during successful medical treatment of endocarditis

Although initial morphologic features of vegetations have been related to the risk of early complications, there is little information about the natural history of the vegetations during medical treatment or the relation of morphologic changes in vegetation to late complications. To assess the evolution of valvular vegetations by echocardiography during treatment of infective endocarditis and to relate the morphologic changes in vegetation to late prognosis, serial echocardiograms of patients with successful medical treatment for native valve infective endocarditis were reviewed to assess the presence and morphologic features of valvular vegetations at the onset and at the end of therapy. The evolution of vegetation size, mobility, consistency, the extent of the disease, and the severity of valvular regurgitation were related to late complications such as embolism, valve replacement, or death occurring after the end of therapy. Forty-one vegetations were identified in 32 patients on initial echocardiograms. At the end of treatment, 29 vegetations were still present; 59% had no significant change in size and 52% appeared to be denser in consistency. Morphologic changes did not relate to late complications, but the presence of severe valvular regurgitations was associated with late valve replacement. The echocardiographic persistence of vegetations is common after successful medical treatment of infective endocarditis. In the absence of severe valvular dysfunction, however, persistent vegetations are not independently associated with late complications.

Effective regurgitant orifice area in tricuspid regurgitation: clinical implementation and follow-up study

Analysis of the flow-convergence zone proximal to a regurgitant orifice permits the noninvasive, quantitative measurement of clinically useful parameters of valvular insufficiency. However, many indexes such as flow rate reflect not only the size of the regurgitant lesion but are also highly dependent on the hemodynamic loading conditions. The effective regurgitant orifice area (ROA) in contrast is a more fundamental parameter, less dependent on hemodynamics and more reflective of real changes in the geometry of the valve, making it a promising index for serial assessment of patients. In this study, the measurement of regurgitant orifice area by the flow-convergence method was tested in tricuspid regurgitation and then used to monitor patients noninvasively over time. The effective ROA was calculated in 45 patients with tricuspid regurgitation by means of the flow-convergence method and compared with the ROA obtained with pulsed Doppler echocardiographic methods. An excellent correlation was obtained between the two assessments of ROA (r = 0.96, delta ROA = -0.09 +/- 6.5 mm2). ROA also showed an excellent correlation with other indexes of valvular insufficiency such as regurgitant stroke volume (r = 0.89) and regurgitant fraction (r = 0.88). In a subgroup of 22 patients thought to be clinically stable, ROA was calculated serially over a mean follow-up period of 2 months and its variability compared with that of other flow-based parameters obtainable from proximal acceleration. The variation between the two studies in regurgitant stroke volume and regurgitant flow rate was 5% +/- 20.6% and 5.2% +/- 35.7%, respectively. The effective ROA showed significantly less variability at 1.8% +/- 15%.(ABSTRACT TRUNCATED AT 250 WORDS)

Significant tricuspid regurgitation does not resolve after percutaneous balloon mitral valvotomy

A total of 318 consecutive patients with mitral stenosis underwent percutaneous mitral valvotomy at our institution from 1987 to 1993. Of those, 98 patients had color Doppler echocardiographic studies performed before, 24 hours after, and late after the intervention. On the basis of color Doppler echocardiographic grading of tricuspid regurgitation, 32 patients (32%; mean age 57 +/- 15 years) had significant (moderate or severe) tricuspid regurgitation before the intervention and were the subject of this study. The follow-up study was performed 18.4 +/- 13 months after the procedure. Successful percutaneous mitral valvotomy (> or = 1.5 cm2 valve area or > or = 50% increase after valvotomy) with no restenosis at follow-up was achieved in 20 patients. Tricuspid regurgitation decreased by one grade (from severe to moderate) in only four subjects in this group and in none of the 12 patients who did not meet the criteria for successful percutaneous mitral valvotomy or who had restenosis. Thus tricuspid regurgitation did not improve in 88% of all patients studied. On average, no significant change was observed in the ratio of maximal tricuspid regurgitant jet area to right atrial area 24 hours after percutaneous mitral valvotomy and at late follow-up (37% vs .33% vs 34%, respectively) or in any of the right heart dimensions, even in patients who underwent successful percutaneous mitral valvotomy. Right ventricular systolic pressure also did not change significantly on average in those patients (46 +/- 15 versus 42 +/- 14 versus 48 +/- 18 mm Hg, respectively). However, right ventricular dimensions did not decrease and tricuspid regurgitation did not resolve even in a subgroup of patients in whom right ventricular systolic pressure fell by more than 10 mm Hg (up to 41 mm Hg).

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.

[The use of the proximal acceleration method in cases of incompetence of the right atrioventricular valve]

BACKGROUND

Quantitation of valvular regurgitation remains an important goal in cardiology. It has been described previously that using color Doppler flow mapping, measurements of apparent jet size do not correlate always closely with quantitative regurgitant indexes. Recently the proximal flow convergence method has been proposed to quantify valvular regurgitation by analysis of the converging flow field proximal to a regurgitant lesion. Assuming hemispherical convergence, peak flow rate Qp can be calculated as Qp = 2 pi r2Va, where Va is the aliasing velocity at a distance r from the orifice. For maximal accuracy, previously validated correction factors must be used to account for the flattening effect of the isovelocity contours close to the orifice and for the actual sector angle subtended by the valve leaflets (alpha) to yield a flow rate formula Qp = 2 pi r2Va (Vp/Vp-Va) (alpha/180), where Vp is the orifice velocity obtained by continuous wave Doppler.

METHODS

In 45 patients (35 in sinus rhythm, 10 with atrial fibrillation) with tricuspid regurgitation, regurgitant stroke volume, regurgitant flow rate were calculated using the proximal flow convergence method and compared with values obtained by the Doppler two-dimensional echocardiographic method.

RESULTS

Regurgitant stroke volumes (SV) calculated by the proximal flow convergence method correlated very closely with values obtained by the Doppler two-dimensional method with r = 0.95 (y = 0.94x + 0.99) and delta SV = -0.3 +/- 5.2 cm3. Regurgitant flow rates (Q) calculated by both methods showed a similar correlation: r = 0.96 (y = 0.97x + 45) and delta Q = 1.6 +/- 4.29 cm3/min. All correlations were slightly better for the group of patients in sinus rhythm.

CONCLUSION

This study demonstrates that the proximal flow convergence method is an accurate and reproducible technique for quantifying tricuspid regurgitation. While improvements of this method are to be expected, flow calculations based on the proximal flow field show excellent results and appear appropriate for clinical use.

Visual assessment of valvular regurgitation: comparison with quantitative Doppler measurements

To investigate which factors influence visual evaluation and how accurate it is in patients with valvular insufficiency, 83 patients were studied. All were in sinus rhythm, 43 with mitral and 40 with tricuspid regurgitation. Categoric visual grading (mild, moderate, and severe) was compared with jet area method and regurgitant fraction and the factors that influenced the assigned rank were identified. With jet area method (mean of areas in three planes), the correlation with regurgitant fraction was r = 0.61 for free jets and r = 0.32 for wall jets (overall r = 0.47) in patients with mitral regurgitation, and r = 0.81 and r = 0.46 for free and wall jets, respectively, in patients with tricuspid regurgitation (overall, r = 0.65). With visual grading, the correlation was for free and wall jets, respectively, rho = 0.80 and rho = 0.74 (overall rho = 0.76) in patients with mitral regurgitation, and rho = 0.79 and rho = 0.49 for free and wall jets, respectively (overall rho = 0.62), in patients with tricuspid regurgitation. The jet area parameter found to have the most influence on visual grading was the average area in three planes divided by atrial area, with rho = 0.80 and rho = 0.51 in patients with mitral regurgitation (free and impinging jets respectively) and rho = 0.60 and rho = 0.46 in tricuspid regurgitation. We conclude that visual grading of valvular regurgitant jets correlates well with quantitative measures of valvular incompetence and better than any simple jet area method.(ABSTRACT TRUNCATED AT 250 WORDS)