547 Point-of-care cardiac assessment using machine learning to guide image acquisition

Funding Acknowledgements

Bay Labs, Inc; San Francisco, CA

Background/Introduction: When used by experienced examiners, the utility of point-of-care (POC) ultrasound for assessing cardiac anatomy and function has been well established. However, in some clinical circumstances (Primary Care offices, Intensive Care Unit, some Emergency Rooms, or in remote settings) in which a rapid assessment of cardiac anatomy and dynamics can facilitate patient care, an examiner experienced at POC scanning may not be immediately available.

Purpose

To help novice users acquire clinically useful standard cardiac views using novel machine learning (ML) software.

Methods

We used an investigational device that employs ML software to provide real-time adaptive guidance of transducer position and orientation to help novice users acquire tomographic views of the heart. We tested the utility of this approach when 4 nurses with no prior training in sonography performed POC studies on 16 subjects (10 healthy, 6 with cardiac abnormalities; 9 men; body mass index normal in 6, overweight in 6, and obese in 4 subjects). Each nurse underwent didactic training and 4 hours of supervised practice using the ML program. Each nurse scanned each study subject using a scanner equipped with ML software to acquire 10 digital two-dimensional image clips, including: parasternal long axis, short axis at the aortic valve, mitral valve, and mid-left ventricle (LV), apical 2-, 4-, and 5-chamber, subcostal 4-chamber, and longitudinal views of the inferior vena cava (IVC). All video clips (n = 640) were later reviewed independently by 5 level 3-trained cardiologists who were blinded to subject, scanner, and each other"s assessments. The expert readers reviewed each set of 10 clips to determine if the following variables could be assessed qualitatively: LV size and function; right ventricular (RV) size and function; aortic, mitral and tricuspid valves; pericardial effusion; left atrial size; IVC size.

Results

The majority of expert readers concurred, independently, that the sets of images acquired by nurses using ML guidance allowed qualitative assessment of LV size and function in 98%, pericardial effusion in 98%, RV size and function in 92%, and aortic and mitral valve anatomy and dynamics in 94-97% of cases. Qualitative assessment of LA size was feasible in 95%. Images of the IVC were judged as adequate for assessment in 58%.

Conclusion

This preliminary study suggests the potential value of novel ML software by demonstrating that nurses with limited training can acquire tomographic images useful for qualitative assessment of the cardiac chambers and valves in more than 90% of the subjects examined. This approach might be useful when timely POC cardiac assessment is indicated in settings where an experienced examiner is not available. Further refinements in the guiding software are needed to improve the success rate of IVC imaging, since IVC size can be a useful indicator of volume status.

The growing use of echocardiography--a double-edged sword?

I believe that the growing volume of echocardiographic services is indeed a double-edge sword. On the one hand, it provides eloquent testimony to the versatility and perceived value of echocardiography to patient care. On the other hand, it underlines the significant resources consumed by providing these services. In these times of "do more with less," doing more can have some negative consequences. I believe that we must each act in a responsible manner, doing our part to be sure that the services we provide are truly needed. We must ask ourselves, and discuss with our referring physicians, "How will the results of this study alter patient care?" On occasion, we may find that a requested study really does not need to be performed. At the very least, this dialogue should allow us to refine the focus of the study and provide the most useful information to the treating physician. We must collect good outcomes data documenting those circumstances in which echocardiography improves outcomes and those clinical settings in which echocardiography is not helpful. We must continue to improve our skills to provide the best services to our patients. And we must also continue to adapt to changes in the health care environment. At the same time, I do not think that we can or should sacrifice quality in an effort to control costs. Clearly, incorrect or misleading information cannot be either cost-effective or good for patient care. We must therefore continue to uphold high professional standards and to work with regulatory agencies ensure that the resources allocated to echocardiographic services are adequate to do them well. ASE's mission statement, which emphasizes that we are "...dedicated to excellence in the development and application of cardiovascular ultrasound to patient care," demands no less.

Transesophageal echocardiographic assessment of embolic sources: intracardiac and extracardiac masses and aortic degenerative disease

The increased sensitivity of transesophageal echocardiography (TEE) makes it complementary and, in many cases, superior to transthoracic echocardiography in the detection of various sources of embolism. These sources include intracardiac thrombus, tumors, spontaneous echocardiographic contrast, and others. TEE is also helpful as an adjunctive test for the diagnosis of pulmonary embolisms.

Flow dependence of measures of aortic stenosis severity during exercise

OBJECTIVES

This study was designed to investigate the effect of altering transvalvular volume flow rate on indexes of aortic stenosis severity (valve area, valve resistance, percent left ventricular stroke work loss) derived by using Doppler echocardiography.

BACKGROUND

Assessment of hemodynamic severity in aortic stenosis has been limited by the absence of an index that is independent of transvalvular flow rate. The traditional measurement of valve area by the Gorlin equation has been shown to vary with alterations in transvalvular flow. Recently, valve resistance and percent stroke work loss have been proposed as indexes that are relatively independent of flow. Although typically derived with invasive measurements, valve resistance and percent stroke work loss (in addition to continuity equation valve area) can be determined noninvasively with Doppler echocardiography.

METHODS

We performed 110 symptom-limited exercise studies in 66 asymptomatic patients with valvular aortic stenosis. Continuity equation valve area, valve resistance (the ratio between mean transvalvular pressure gradient and mean flow rate) and the steady component of percent stroke work loss (the ratio between mean transvalvular pressure gradient and left ventricular systolic pressure) were assessed by Doppler echocardiography at rest and immediately after exercise.

RESULTS

Mean transvalvular volume flow rate increased 24% (from [mean +/- SD] 319 +/- 80 to 400 +/- 140 ml/s, p < 0.0001); mean pressure gradient increased 36% (from 30 +/- 14 to 41 +/- 18 mm Hg, p < 0.0001); continuity equation aortic valve area increased 14% (from 1.38 +/- 0.50 to 1.58 +/- 0.69 cm2, p < 0.0001); valve resistance increased 13% (from 137 +/- 81 to 155 +/- 97 dynes.s.cm-5, p < 0.0001); and percent stroke work loss increased 17% (from 17.4 +/- 6.9% to 20.3 +/- 8.5%, p < 0.0001). The effects of flow on valve area, valve resistance and percent stroke work loss were independent of the presence of an aortic valve area < or = or > 1.0 cm2 or reduced transvalvular flow rate (rest cardiac output < 4.5 liters/min).

CONCLUSIONS

In patients with asymptomatic aortic stenosis, Doppler echocardiographic measures of valve area, valve resistance and percent stroke work loss are flow dependent. Flow dependence is observed with valve area < or = or > 1.0 cm2 and in the presence of both normal and low transvalvular flow states. The potential effects of transvalvular flow should be considered when interpreting Doppler measures of aortic stenosis severity.

Dependence of Gorlin formula and continuity equation valve areas on transvalvular volume flow rate in valvular aortic stenosis

BACKGROUND

Valve areas derived by the Gorlin formula have been observed to vary with transvalvular volume flow rate. Continuity equation valve areas calculated from Doppler-echo data have become a widely used alternate index of stenosis severity, but it is unclear whether continuity equation valve areas also vary with volume flow rate. This study was designed to investigate the effects of changing transvalvular volume flow rate on aortic valve areas calculated using both the Gorlin formula and the continuity equation in a model of chronic valvular aortic stenosis.

METHODS AND RESULTS

Using a canine model of chronic valvular aortic stenosis in which anatomy and hemodynamics are similar to those of degenerative aortic stenosis, each subject (n = 8) underwent three studies at 2-week intervals. In each study, transvalvular volume flow rates were altered with saline or dobutamine infusion (mean, 10.3 +/- 5.1 flow rates per study). Simultaneous measurements were made of hemodynamics using micromanometer-tipped catheters, of ascending aortic instantaneous volume flow rate using a transit-time flowmeter, and of left ventricular outflow and aortic jet velocity curves using Doppler echocardiography. Valve areas were calculated from the invasive data by the Gorlin equation and from the Doppler-echo data by the continuity equation. In the 24 studies, mean transit-time transvalvular volume flow rate ranged from 80 +/- 33 to 153 +/- 49 mL/min (P < .0001). Comparing minimum to maximum mean volume flow rates, the Gorlin valve area changed from 0.54 +/- 0.22 cm2 to 0.68 +/- 0.21 cm2 (P < .0001), and the continuity equation valve area changed from 0.57 +/- 0.18 cm2 to 0.70 +/- 0.20 cm2 (P < .0001). A strong linear relation was observed between Gorlin valve area and mean transit-time volume flow rate for each study (median, r = .88), but the slope of this relation varied between studies. The Doppler-echo continuity equation valve area had a weaker linear relation with transit-time volume flow rate for each study (median, r = .51).

CONCLUSIONS

In this model of chronic valvular aortic stenosis, both Gorlin and continuity equation valve areas were flow-dependent indices of stenosis severity and demonstrated linear relations with transvalvular volume flow rate. The changes in calculated valve area that occur with changes in transvalvular volume flow should be considered when measures of valve area are used to assess the hemodynamic severity of valvular aortic stenosis.

Echocardiographic volume flow and stenosis severity measures with changing flow rate in aortic stenosis

The anatomy of degenerative valvular aortic stenosis has been poorly represented in animal models, limiting the evaluation of noninvasive echo-Doppler measures of transvalvular volume flow rate and stenosis severity during progressive disease evolution or under conditions of changing volume flow rates. To study these issues, chronic valvular aortic stenosis, characterized by stiff leaflets without commissural fusion, was created in nine adult mongrel dogs by suturing pericardial covered Teflon-felt pads into the sinuses of Valsalva below the coronary ostia during hypothermic cardiac arrest. In the eight surviving dogs, echo-Doppler examinations were performed weekly for up to 8 wk postoperatively. Simultaneous invasive micromanometer pressure data were collected at 2-wk intervals in all subjects, with simultaneous ascending aortic transit time-volume flow measurement in four subjects. Volume flow rates were altered with saline and dobutamine infusions during invasive studies for comparison of echo-Doppler and invasive pressure gradients, volume flow, and valve areas. Serial echo-Doppler follow-up (39 +/- 11 days) demonstrated that, from baseline to final study, mean transvalvular pressure gradient increased (4 +/- 1 to 38 +/- 7 mmHg, P = 0.001), continuity equation aortic valve area decreased (2.06 +/- 0.18 to 0.54 +/- 0.04 cm2, P < 0.0001), and progressive left ventricular hypertrophy developed (62 +/- 6 to 114 +/- 9 g, P = 0.0003). Echo-Doppler and invasive data correlated well for measures of transvalvular pressure gradients (n = 98, maximum instantaneous gradient r = 0.95, mean gradient r = 0.91), volume flow (n = 75, stroke volume r = 0.86, cardiac output r = 0.86), and valve area (n = 73, r = 0.73) despite acute alterations in volume flow and progressive disease evolution. This chronic canine model, with anatomy and hemodynamics similar to clinical degenerative valvular aortic stenosis, should provide a valuable tool for investigating clinically relevant new measures of stenosis severity with use of invasive or noninvasive techniques.

Development of an aortic valve mass after radiofrequency catheter ablation

A 49-year-old woman underwent a successful radiofrequency catheter ablation of a left-sided accessory pathway using a retrograde approach across the aortic valve. Routine echocardiography performed 20 hours after the procedure revealed a new aortic valve mass. Five blood cultures were negative. An echocardiogram after 2 days of heparin therapy showed complete resolution of the mass. There was no clinical evidence of embolization. Echocardiography may need to be performed routinely after catheter ablations performed retrograde across the aortic valve so that this potentially devastating complication can be diagnosed and treated early in its course.

Subacute ventricular free wall rupture complicating myocardial infarction

Myocardial free wall rupture accounts for between 8% and 17% of mortality after myocardial infarction. In up to 40% of cases death occurs subacutely over a matter of hours, not minutes. Illustrative clinical cases and data suggest that a high degree of clinical suspicion, along with the early use of echocardiography, could significantly reduce mortality resulting from myocardial free wall rupture complicating myocardial infarction. Myocardial free wall rupture should be suspected in patients with recent myocardial infarction who have recurrent or persistent chest pain, hemodynamic instability, syncope, pericardial tamponade, or transient electromechanical dissociation. In this clinical situation, emergent echocardiography showing a pericardial effusion or pericardial thrombus is highly suggestive of free wall rupture. Surgical exploration and rupture repair is the definitive diagnostic and therapeutic procedure.

Physiologic changes with maximal exercise in asymptomatic valvular aortic stenosis assessed by Doppler echocardiography

OBJECTIVES

We hypothesized that the physiologic response to exercise in valvular aortic stenosis could be measured by Doppler echocardiography.

BACKGROUND

Data on exercise hemodynamics in patients with aortic stenosis are limited, yet Doppler echocardiography provides accurate, noninvasive measures of stenosis severity.

METHODS

In 28 asymptomatic subjects with aortic stenosis maximal treadmill exercise testing was performed with Doppler recordings of left ventricular outflow tract and aortic jet velocities immediately before and after exercise. Maximal and mean volume flow rate (Qmax and Qmean), stroke volume, cardiac output, maximal and mean aortic jet velocity (Vmax, Vmean), mean pressure gradient (delta P) and continuity equation aortic valve area were calculated at rest and after exercise. The actual change from rest to exercise in Qmax and Vmax was compared with the predicted relation between these variables for a given orifice area. Subjects were classified into two groups: Group I (rest-exercise Vmax/Qmax slope > 0, n = 19) and Group II (slope < or = 0, n = 9).

RESULTS

Mean exercise duration was 6.7 +/- 4.3 min. With exercise, Vmax increased from 3.99 +/- 0.93 to 4.61 +/- 1.12 m/s (p < 0.0001) and mean delta P increased from 39 +/- 20 to 52 +/- 26 mm Hg (p < 0.0001). Qmax rose with exercise (422 +/- 117 to 523 +/- 209 ml/s, p < 0.0001), but the systolic ejection period decreased (0.33 +/- 0.04 to 0.24 +/- 0.04, p < 0.0001), so that stroke volume decreased slightly (98 +/- 29 to 89 +/- 32 ml, p = 0.01). The increase in cardiac output with exercise (6.5 +/- 1.7 to 10.2 +/- 4.4 liters/min, p < 0.0001) was mediated by increased heart rate (71 +/- 17 to 147 +/- 28 beats/min, p < 0.0001). There was no significant change in the mean aortic valve area with exercise (1.17 +/- 0.45 to 1.28 +/- 0.65, p = 0.06). Compared with Group I patients, patients with a rest-exercise slope < or = 0 (Group II) tended to be older (69 +/- 12 vs. 58 +/- 19 years, p = 0.07) and had a trend toward a shorter exercise duration (5.3 +/- 2.9 vs. 7.3 +/- 4.9 min, p = 0.20). There was no difference between groups for heart rate at rest, blood pressure, stroke volume, cardiac output, Vmax, mean delta P or aortic valve area. With exercise, Group II subjects had a lower cardiac output (7.4 +/- 2.4 vs. 11.5 +/- 4.6 liters/min, p = 0.005) and a smaller percent increase in Vmax (3 +/- 9% vs. 22 +/- 14%, p < 0.0001).

CONCLUSIONS

Doppler echocardiography allows assessment of physiologic changes with exercise in adults with asymptomatic aortic stenosis. A majority of subjects show a rest-exercise response that closely parallels the predicted relation between Vmax and Qmax for a given orifice area. The potential utility of this approach for elucidating the relation between hemodynamic severity and clinical symptoms deserves further study.

Value of transesophageal color Doppler echocardiography for detection of different types of atrial septal defect in adults

In 121 adults, the value of transthoracic and transesophageal color Doppler echocardiography for detection of different types of atrial septal defect (ASD) or of partial anomalous pulmonary venous return was analyzed. The 121 patients had a total of 129 defects with left-to-right atrial shunting (including eight patients with two types of defects). All of six cases with primum-type ASD were diagnosed correctly by both echocardiographic methods. Ninety-seven patients showed a secundum-type ASD during transesophageal echocardiography: by transthoracic echocardiography, only eight (20%) of the 40 small defects (diameter < 5 mm) were detected as compared with 15 (83%) of the 18 defects with a diameter of 5 to 10 mm and all 39 defects with a diameter > 10 mm. A sinus venosus--type ASD was evident by transesophageal echocardiography in 11 patients, of which only one (9%) was demonstrated by the transthoracic approach. Partial anomalous pulmonary venous return was seen by transesophageal echocardiography in 13 patients but missed in two other patients in whom anomalous pulmonary venous return was subsequently identified by surgery (both with anomalous return of the upper right pulmonary vein into the superior vena cava). By use of the transthoracic technique, partial anomalous venous return was detected in only two cases, both of which had "scimitar syndrome." Compared with transthoracic echocardiography, the transesophageal approach is clearly superior in the detection of small secundum-type ASD, sinus venosus--type ASD, and partial anomalous pulmonary venous return.

Subclavian artery stenosis masquerading as prosthetic aortic stenosis: a potential source of confusion in Doppler evaluation of aortic valve disease

In this case report we describe a patient with a prosthetic aortic valve in whom a high-velocity signal from a right subclavian artery stenosis initially was mistaken for the aortic jet signal. Differences in the shapes of the jets obtained from an apical and right supraclavicular position suggested different origins of these two high-velocity systolic signals. Correct identification of the origin of each signal was possible with pulsed Doppler recordings of the subclavian artery and high pulse-repetition-frequency pulsed Doppler interrogation of the aortic valve.

Role of echocardiography in the diagnosis and evaluation of severity of mitral and tricuspid stenosis

The presence, severity, and hemodynamic consequences of mitral and tricuspid stenosis can be determined by echocardiographic techniques. In mitral stenosis two-dimensional echocardiographic imaging allows definition of leaflet anatomy and dynamics, subvalvular disease, ventricular function, and involvement of other valves. Spectral and color Doppler echocardiographic techniques permit accurate measurement of transvalvular gradient, determination of functional orifice area, evaluation of associated valvular regurgitation, and assessment of pulmonary artery pressures. These approaches are of recognized clinical value, and they provide additional diagnostic information that is unavailable from clinical assessment alone in a significant number of patients. Compared with available invasive diagnostic standards of reference, echocardiographic data have been found to be comparable in accuracy. In tricuspid stenosis echocardiographic imaging and Doppler techniques provide an assessment of valve morphology and function that should be similarly useful in clinical management decisions, although rigorous comparative studies have not been performed. Currently, carefully done echocardiographic studies are a definitive means of establishing the presence and significance of mitral stenosis and tricuspid stenosis, thereby obviating the need for invasive evaluation in many patients, reducing risk, and potentially decreasing the cost of diagnostic assessment.

Tricuspid valve repair for tricuspid valve endocarditis: tricuspid valve "recycling"

Tricuspid valve endocarditis traditionally has been treated with either valve excision or valve replacement. To avoid implantation of foreign material in an infected field, we have applied the principles of mitral valve repair to 4 patients with tricuspid valve endocarditis. On preoperative echocardiography, all patients had 3 to 4+ tricuspid regurgitation, evidence of progressive right ventricular enlargement, and mobile vegetations. In each case, up to three quarters of the anterior leaflet was excised en bloc with infected chordae and papillary muscle heads. Surgical procedures included standard quadrangular resection, conversion to a bicuspid valve, and pericardial patch replacement of the anterior leaflet with mobilization of basal chordae to replace resected marginal chordae. On postoperative echocardiography, tricuspid regurgitation and right ventricular dimensions were reduced in 2 of 4 patients in spite of loss of leaflet tissue. All excised valve tissue demonstrated bacteria on Gram stain or culture. Nonetheless, all repaired valves were successfully sterilized without recurrent infections. Tricuspid valve repair can allow eradication of infection with potential for improving valve competency in complicated tricuspid valve endocarditis.

Infective endocarditis, 1983-1988: echocardiographic findings and factors influencing morbidity and mortality

The echocardiograms and clinical records of 70 patients with infective endocarditis seen between 1983 and 1988 were examined to evaluate the role of two-dimensional and Doppler echocardiography in the diagnosis of infective endocarditis and identify risk factors for morbidity and mortality. A blinded observer reviewed the echocardiograms for the presence and size of vegetations and the severity of the valvular regurgitation. Vegetations were identified in 54 (78%) of 69 technically satisfactory echocardiograms. In 38 patients whose heart was examined at surgery or autopsy, all vegetations diagnosed by echocardiography were confirmed, but six additional vegetations were found. Abnormal (greater than or equal to 2+) valvular regurgitation was present in 88% of patients. No patient with less than or equal to 1+ regurgitation (n = 8) died or required valve surgery for heart failure, but three of the eight patients did undergo surgery for mycotic aneurysm, recurrent embolism or paravalvular abscess. In patients without embolism before echocardiography, there was a trend toward a greater incidence of subsequent embolism in those with vegetations greater than 10 mm in size (26% [8 of 31] compared with 11% [2 of 18] with vegetations less than or equal to 10 mm) (p = 0.19). By multivariate analysis, risk factors for in-hospital death (n = 7) were an infected prosthetic valve (p less than 0.007), systemic embolism (p less than 0.02) and infection with Staphylococcus aureus (p = 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

A case of delayed postoperative cardiac tamponade with unusual echocardiographic findings

Postoperative cardiac tamponade due to localized compression of the atria occurred in a 64-year-old man after aortic valve replacement and repair of an ascending aortic dissection. The clinical findings were subtle and the echocardiographic findings were unusual. Color Doppler flow imaging assisted in making the diagnosis of localized atrial compression.

[Development of echocardiographic diagnosis of congenital cardiopathies: from M-mode to color Doppler]

The general aspects and newer applications of two-dimensional, contrast, and doppler echocardiography in the assessment of congenital heart diseases are reviewed. The M-mode techniques are presently of limited value as diagnostic tool and are confined to few detailed findings which are often missed at standard examination: particularly the M-mode is useful in the visualization of pulmonic valve which shows characteristic abnormalities in pulmonary hypertension. Two-dimensional echocardiography has opened a new era of investigation in the evaluation of congenital heart diseases. It has enhanced the ultrasonic resolution in the delineation and connection of intracardiac structures, providing a systematic approach to the diagnosis of complex cardiac abnormalities. The left and right ventricular chambers can be identified through the position and morphology of their atrioventricular valves and papillary muscles, and by evaluation of the mitral-semilunar valve continuity. The newest utilization of standard echocardiography involves the prenatal diagnosis of congenital heart diseases by way of intrauterine echocardiography: the fetal heart can be visualized in several planes by transabdominal approach in the mother. With careful attention, a complete examination including four and five chambers view of the ventricle and short axis view of the great arteries, can be accomplished in almost all cases, allowing an accurate determination of many congenital defects. The contrast technique was originally used for identifying right cardiac chambers on M-mode echocardiograms: it provides excellent times resolutions and an accurate analysis of flow related events across the cardiac structures.(ABSTRACT TRUNCATED AT 250 WORDS)

Hemodynamic progression of aortic stenosis in adults assessed by Doppler echocardiography

Doppler echocardiography was used to follow the hemodynamic severity of aortic stenosis. First, the reproducibility of repeat recordings (mean interval 28 +/- 36 days) of aortic jet velocity, made by two independent observers, was tested in 38 adults with aortic stenosis and unchanged clinical status. The two recordings of maximal velocity correlated well (r = 0.96, y = 0.88x + 0.46m/s, SEE = 0.21 m/s) with a mean coefficient of variation of 3.2%. Repeat recording of left ventricular outflow tract velocity by two independent observers in 10 other patients with aortic stenosis also correlated well (r = 0.94, y = 1.06x + 0.0 m/s, SEE = 0.06 m/s) with a mean coefficient of variation of 4.6%. Next, Doppler echocardiography was used to study 42 patients with aortic stenosis (mean age 66 years) over a follow-up interval of 6 to 43 months (mean 20). Maximal aortic jet velocity increased by 0.36 m/s per year (range -0.3 to +1.0 m/s per year). Mean transaortic pressure gradient changed by -7 to +23 (mean 8) mm Hg/year. Aortic valve area by the continuity equation (n = 25) decreased by 0 to 0.5 cm2/year (mean decrease 0.1 cm2/year). Some patients had a worsening of stenosis (decrease in valve area) even though they had no change or a decrease in pressure gradient, because of concurrent decreases in transaortic volume flow. Twenty-one patients (50%) developed new or progressive symptoms of aortic stenosis necessitating valve replacement.(ABSTRACT TRUNCATED AT 250 WORDS)

Doppler echocardiographic evaluation of left ventricular diastolic filling in isolated valvular aortic stenosis

Doppler echocardiography was used to study left ventricular (LV) diastolic filling in 49 adults with isolated aortic stenosis (AS), selected from 155 consecutive patients with AS by excluding coexisting mitral disease (n = 41) and/or significant aortic regurgitation (n = 80). There were no differences between patients with AS and age-matched normal subjects for early diastolic filling (E) velocity (68 +/- 17 vs 67 +/- 13 cm/s), late diastolic filling (A) velocity (79 +/- 25 vs 67 +/- 21 cm/s), E/A ratio (1.00 +/- 0.78 vs 1.06 +/- 0.32) or early diastolic deceleration slope (264 +/- 151 vs 319 +/- 137 cm/s2, differences not significant for all). There was no correlation between any LV filling parameter and AS severity, but late diastolic filling velocity was higher in patients with AS who had LV hypertrophy (n = 33) vs those who did not (n = 16) (86 +/- 23 vs 65 +/- 26 cm/s, p less than 0.01). In the patients with AS and systolic dysfunction (LV ejection fraction less than 50%) (n = 6), early diastolic filling velocity was higher (88 +/- 20 vs 65 +/- 15 cm/s, p less than 0.01), late diastolic filling velocity lower (53 +/- 23 vs 83 +/- 23 cm/s, p less than 0.01), E/A ratio higher (2.20 +/- 1.80 vs 0.84 +/- 0.28, p less than 0.01), deceleration slope steeper (439 +/- 230 vs 240 +/- 121 cm/s2, p = 0.02) and LV end-diastolic pressure higher (23 +/- 9 vs 10 +/- 6 mm Hg, p less than 0.01) than in patients with AS and normal systolic function.(ABSTRACT TRUNCATED AT 250 WORDS)

Doppler echocardiography in adults with symptomatic aortic stenosis. Diagnostic utility and cost-effectiveness

To evaluate the diagnostic utility and cost-effectiveness of Doppler echocardiography in adults with symptomatic aortic stenosis, we performed a prospective study in which the need for aortic valve replacement (AVR) was the outcome event. The total sample consisted of 103 adults (mean age, 69 years) undergoing cardiac catheterization for suspected aortic stenosis. Twenty-six patients (25%) were used as a training set to develop a clinical prediction rule. (1) If maximum aortic jet velocity (Vmax) was more than 4.0 m/s, AVR was recommended. (2) If Vmax was less than 3.0 m/s, AVR was not needed. (3) If Vmax was 3.0 to 4.0 m/s and (a) Doppler aortic valve area (AVA) was 1.0 cm2 or less, AVR was recommended, while (b) if Doppler AVA was 1.7 cm2 or greater, AVR was not needed, and (c) if Doppler AVA was 1.1 to 1.6 cm2, consideration of the degree of coexisting aortic insufficiency was necessary. When this rule was applied to the test set (n = 77), the sensitivity was 98%, with a specificity of 89% and a total error rate of 3.9%. The approach could have resulted in cost savings between 24% and 34% compared with an invasive diagnostic approach.

Experimental validation of Doppler echocardiographic measurement of volume flow through the stenotic aortic valve

In aortic stenosis, evaluation of aortic valve area by the continuity equation assumes that the volume of flow through the stenotic valve can be measured accurately in the left ventricular outflow tract. To test the accuracy of Doppler volume-flow measurement proximal to a stenotic valve, we developed an open-chest canine model in which the native leaflets were sutured together to create variable degrees of acute aortic stenosis. Left ventricular and aortic pressures were measured with micromanometer-tipped catheters. Volume flow was controlled and varied by directing systemic venous return through a calibrated roller pump and back to the right atrium. Because transaortic volume flow will not equal roller pump output when there is coexisting aortic insufficiency (present in 67% of studies), transaortic flow was measured by electromagnetic flowmeter with the flow probe placed around the proximal descending thoracic aorta, just beyond the ligated arch vessels. In 12 adult, mongrel dogs (mean weight, 25 kg), the mean transaortic pressure gradient ranged from 2 to 74 mm Hg, and transaortic volume flow ranged from 0.9 to 3.2 l/min. In four dogs, electromagnetic flow that was measured distal to the valve was accurate compared with volume flow determined by timed collection of total aortic flow into a graduated cylinder (n = 24, r = 0.97, electromagnetic flow = 0.87 Direct +0.13 l/min). In eight subsequent dogs, electromagnetic flow was compared with transaortic cardiac output measured by Doppler echocardiography in the left ventricular outflow tract as circular cross-sectional area [pi(D/2)2] x left ventricular outflow tract velocity-time integral x heart rate.(ABSTRACT TRUNCATED AT 250 WORDS)

Simplification of the Doppler continuity equation for calculating stenotic aortic valve area

Determination of aortic valve area by the continuity equation is feasible and accurate but requires planimetry. Because the ratio of maximum velocities in the left ventricular outflow tract (LVOT) to aortic jet is quite similar to the ratio of velocity-time integrals at these sites, the continuity equation can be simplified by substituting maximum velocities for velocity-time integrals. Agreement with invasively determined aortic valve areas is similar with the conventional and simplified forms of the continuity equation. However, substitution of the average or sex-specific LVOT diameter for measured LVOT diameter in individual patients leads to less accurate aortic valve area determination. We conclude that simplification of the continuity equation, with measured LVOT diameter and maximum velocity and aortic jet maximum velocity, allows noninvasive calculation of the aortic valve area in a way that is simple and accurate.

Guidelines for optimal physician training in echocardiography. Recommendations of the American Society of Echocardiography Committee for Physician Training in Echocardiography

Over the past few years, the clinical use of echocardiography has continued to expand. Echocardiographic techniques are used widely to define normal and abnormal cardiac anatomy, evaluate cardiac chamber sizes and dynamics, assess valvular and pericardial diseases, detect intracavitary masses, measure pressure gradients across discrete stenoses, determine flow volumes, detect and assess the severity of valvular regurgitation, demonstrate and quantitate intracardiac shunts, and measure the timing of cardiac events. These and related applications have led to the increasing use of echocardiography in the diagnostic evaluation of many cardiac disorders. Echocardiography requires considerable theoretical knowledge, technical skill and practical experience to be used in an optimal manner. Previous publications have suggested guidelines for physician training in the techniques of M-mode and 2-dimensional echocardiography. The clinical applications of echocardiography continue to grow, however, and Doppler techniques for evaluating blood flow have become an established component of the echocardiographic evaluation of many disorders. This article presents the current recommendations of the American Society of Echocardiography as to the background knowledge, the nature and amount of practical experience, and the type of training site that are optimal for the training of physicians who take responsibility for the conduct and interpretation of echocardiographic studies.

A new three-dimensional echocardiographic method of right ventricular volume measurement: in vitro validation

Right ventricular volume is difficult to measure accurately from one or two views because the complexity of right ventricular shape invalidates simplifying geometric assumptions. This article describes a new three-dimensional echocardiographic reconstruction method of right ventricular volume calculation, and reports the results of testing this method in vitro using normal animal hearts and pathologic specimens from infants and children who died with aortic stenosis or hypoplastic left heart. The correlation with reference volumes was excellent for both groups (r = 0.98, n = 25 for the animal data; r = 0.97, n = 15 for the human data). Given the calculated echocardiographic volume (Vc), the reference volume (Vr) was best estimated by the equation Vr = 1.16 Vc for the animal data and Vr = 0.92 Vc for the human data. Three-dimensional echocardiographic measurement of right ventricular volume is an accurate method that deserves further study and application in a clinical setting.

Determination of the stenotic aortic valve area in adults using Doppler echocardiography

The severity of aortic stenosis was evaluated by Doppler echocardiography in 48 adults (mean age 67 years) undergoing cardiac catheterization. Maximal Doppler systolic gradient correlated with peak to peak pressure gradient (r = 0.79, y = 0.63x + 25.2 mm Hg) and mean Doppler gradient correlated with mean pressure gradient (r = 0.77, y = 0.59x + 10.0 mm Hg) by manometry. The transvalvular pressure gradient is flow dependent, however, and associated left ventricular dysfunction was common in our patients (33%). Thus, of the 32 patients with an aortic valve area less than or equal to 1.0 cm2 at catheterization, 6 (19%) had a peak Doppler gradient less than 50 mm Hg. To take into account the influence of volume flow, aortic valve area was calculated as stroke volume, measured simultaneously by thermodilution, divided by the Doppler systolic velocity integral in the aortic jet. Aortic valve areas calculated by this method were compared with results at catheterization in the total group (r = 0.71). Significant aortic insufficiency was present in 71% of the population. In the subgroup without significant coexisting aortic insufficiency, closer agreement of valve area with catheterization was noted (n = 14, r = 0.91, y = 0.83x + 0.24 cm2). Transaortic stroke volume can be determined noninvasively by Doppler echocardiographic measures in the left ventricular outflow tract, just proximal to the stenotic valve. Aortic valve area can then be calculated as left ventricular outflow tract cross-sectional area times the systolic velocity integral of outflow tract flow, divided by the systolic velocity integral in the aortic jet.(ABSTRACT TRUNCATED AT 250 WORDS)

Noninvasive detection of aortic insufficiency in patients with mitral stenosis by pulsed Doppler echocardiography

In patients with mitral stenosis, routine noninvasive techniques are insensitive for the detection of coexistent aortic insufficiency. The ability of pulsed Doppler echocardiography to detect the presence or absence of angiographically demonstrated aortic insufficiency was evaluated in 45 patients with rheumatic mitral stenosis. Pulsed Doppler echocardiography correctly identified the presence of aortic insufficiency in 97% of the 35 patients with documented aortic regurgitation. More important, pulsed Doppler echocardiography disclosed aortic insufficiency in all 7 patients in whom it was not suspected on physical examination and in 28 of the 29 patients in whom it was not suspected by M-mode echocardiography. Pulsed Doppler echocardiography also demonstrated excellent specificity, correctly detecting the absence of aortic insufficiency in 9 of the 10 patients who had no angiographic evidence of aortic insufficiency. It is concluded that in patients with mitral stenosis, pulsed Doppler echocardiography is a useful noninvasive diagnostic test for evaluating the presence of aortic insufficiency, even when this lesion is not detectable by physical examination or M-mode echocardiography.

Assessment of valvular heart disease by Doppler echocardiography

Doppler echocardiography provides direct hemodynamic data that are often complementary to those demonstrated by M-mode and two-dimensional echocardiographic imaging. This relatively new noninvasive technique has a number of important uses in patients with valvular heart disease. In both adults and children, Doppler measures of peak flow velocity through a stenotic valve allow accurate prediction of the pressure gradient across the valve, and the technique has particular promise for screening patients with suspected aortic or pulmonic stenosis. In patients with mitral stenosis but parasternal short-axis images of limited quality, Doppler velocity measures can provide novel data about the pressure gradient and mitral orifice area. Doppler techniques can also provide direct evidence for or against the presence of valvular regurgitation, and several approaches allow clinically useful estimation of the extent of aortic, mitral, or tricuspid regurgitation. In patients with known disease of one cardiac valve, Doppler is accurate for evaluating the integrity of a second valve. Finally, Doppler techniques have great promise for defining the nature, and perhaps the severity, of suspected prosthetic valve malfunction. Hence, we believe that Doppler echocardiography should become a routine part of the noninvasive evaluation of patients with known or suspected valvular heart disease.

Detection of left ventricular thrombus by two-dimensional echocardiography: sensitivity, specificity, and causes of uncertainty

To define the sensitivity, specificity and predictive accuracy of two-dimensional echocardiographic detection of left ventricular thrombus, the echocardiograms of 78 patients who had independent proof of the presence or absence of a left ventricular thrombus were interpreted without knowledge of any clinical data. The presence of thrombus was established by autopsy in four patients, by aneurysmectomy in three, and by indium-111 platelet imaging in 15; the absence of thrombus was proved by autopsy in 55 patients and by aneurysmectomy in one patient. The characteristics of true-positive and false-positive echocardiograms, interobserver variability, and clinical features associated with proved thrombus were also defined. The echocardiogram was positive for thrombus in 22 patients, equivocal in seven and negative in 49. For detection of thrombus, a positive or equivocal echocardiogram had a sensitivity of 95% (21 of 22), a specificity of 86% (48 of 56), and a predictive value of 72% (21 of 29); the predictive value of a negative study was 98% (48 of 49). Considering positive and equivocal studies separately, the predictive value of a positive study was 86% (19 of 22), while that of an equivocal study was only 29% (two of seven). Compared with patients who had no thrombus, patients with proved thrombus had a higher prevalence of electrocardiographic transmural anterior infarction (86% vs 13%), left ventricular aneurysm (73% vs 5%), and clinical systemic emboli (36% vs 7%) (all p less than 0.05). These clinical features help to identify a subset of patients most likely to have left ventricular thrombi who may benefit from echocardiography. Two-dimensional echocardiography is highly sensitive in detecting left ventricular thrombus, but false-positive studies are relatively common. Several echocardiographic criteria derived from analysis of the true and false positives in this study may help minimize diagnostic errors.

Evaluation of ventricular function using Doppler echocardiography

Doppler echocardiography is closely related to M mode and two dimensional echocardiography, although it uses reflected ultrasonic signals to examine blood flow rather than to image cardiac anatomy. It is a useful adjunct to standard echocardiographic methods when one wishes to evaluate ventricular function, but at present it plays a supporting role. In theory, Doppler techniques can be used to assess global ventricular function directly and without regard to ventricular geometry, to calculate volume flow from both the right and left ventricles, and to follow changes in ventricular stroke volume induced by interventions. In practice, various technical limitations restrict the routine clinical application of Doppler echocardiography, but solutions to several of these problems should be forthcoming. Doppler echocardiography can properly be viewed as a useful method for evaluating mechanical lesions that may mimic ventricular dysfunction, and as a promising future method for analyzing ventricular function directly.