Carol D. Kraft

Recommendations for evaluation of the severity of native valvular regurgitation with two-dimensional and doppler echocardiography

A report from the American Society of Echocardiography’s Nomenclature and Standards Committee and The Task Force on Valvular Regurgitation, developed in conjunction with the American College of Cardiology Echocardiography Committee, The Cardiac Imaging Committee Council on Clinical Cardiology, the American Heart Association, and the European Society of Cardiology Working Group on Echocardiography, represented by:

Prospective Study of Asymptomatic Valvular Aortic Stenosis Clinical, Echocardiographic, and Exercise Predictors of Outcome

BACKGROUND Only limited data on the rate of hemodynamic progression and predictors of outcome in asymptomatic patients with valvular aortic stenosis (AS) are available. METHODS AND RESULTS In 123 adults (mean age, 63 +/- 16 years) with asymptomatic AS, annual clinical, echocardiographic, and exercise data were obtained prospectively (mean follow-up of 2.5 +/- 1.4 years). Aortic jet velocity increased by 0.32 +/- 0.34 m/s per year and mean gradient by 7 +/- 7 mm Hg per year; valve area decreased by 0.12 +/- 0.19 cm2 per year. Kaplan-Meier event-free survival, with end points defined as death (n = 8) or aortic valve surgery (n = 48), was 93 +/- 5% at 1 year, 62 +/- 8% at 3 years, and 26 +/- 10% at 5 years. Univariate predictors of outcome included baseline jet velocity, mean gradient, valve area, and the rate of increase in jet velocity (all P < or = .001) but not age, sex, or cause of AS. Those with an end point had a smaller exercise increase in valve area, blood pressure, and cardiac output and a greater exercise decrease in stroke volume. Multivariate predictors of outcome were jet velocity at baseline (P < .0001), the rate of change in jet velocity (P < .0001), and functional status score (P = .002). The likelihood of remaining alive without valve replacement at 2 years was only 21 +/- 18% for a jet velocity at entry > 4.0 m/s, compared with 66 +/- 13% for a velocity of 3.0 to 4.0 m/s and 84 +/- 16% for a jet velocity < 3.0 m/s (P < .0001). CONCLUSIONS In adults with asymptomatic AS, the rate of hemodynamic progression and clinical outcome are predicted by jet velocity, the rate of change in jet velocity, and functional status.

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

BackgroundValve 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 ResultsUsing 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). ConclusionsIn 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.

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.

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.

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.

Quantitative Three-Dimensional Echocardiography by Rapid Imaging from Multiple Transthoracic Windows: In Vitro Validation and Initial In Vivo Studies

Three-dimensional echocardiography has demonstrated superiority over two-dimensional techniques in the determination of left ventricular mass and volumes. We describe a technique based on a magnetic tracking system which provides rapid three-dimensional image acquisition from multiple acoustic windows. Interactive three-dimensional border tracking and reconstruction with a piecewise smooth subdivision model accurately reproduced phantom volume (calculated volume = 1.00 true volume - 0.6 ml, r = 1.000, standard error of the estimate = 1.3 ml), in vitro heart volume (calculated volume = 1.02 true volume - 1.3 ml, r = 1.000, standard error of the estimate = 0.4 ml), in vitro heart mass (calculated mass = 0.98 true mass + 1.4 gm, r = 0.998, standard error of the estimate = 2.5 gm), and in vivo stroke volume (calculated stroke volume = 1.18 Doppler stroke volume - 17.9 ml, r = 0.990, standard error of the estimate = 2.8 ml). The three-dimensional in vivo data sets, which include views from three acoustic windows, were acquired in less than 90 seconds. We conclude that this method of three-dimensional echocardiographic data acquisition and analysis overcomes limitations inherent in currently available systems.

Advancing Recognition of the Responsibilities of Cardiac Sonographers

For patients undergoing echocardiographic examinations, and for physicians responsible for interpreting echocardiograms and providers of health care who order echocardiograms, the importance of the cardiac sonographer cannot be overstated. A cardiac sonographer is an allied health professional with special education and training who is responsible for performing and recording diagnostic echocardiograms. The cardiac sonographer typically makes a number of measurements and calculations that are important considerations in the final diagnostic interpretation that is prepared and rendered by the physician responsible for the overall echocardiography service. Although on occasion the supervising physician will be present while the echocardiographic images and related data are being acquired and recorded, and although on some occasions the supervising physician will repeat a specific part of the examination, in the majority of echocardiographic studies, the cardiac sonographer is the person who bears responsibility for the appropriate technical conduct and diagnostic content of the echocardiographic study. This is a significant responsibility, and an important reason why the American Society of Echocardiography (ASE) considers that a cardiac sonographer with appropriate training, skills, and experience is a critical component of high-quality echocardiography. In this issue of the Journal of the American Society of Echocardiography, an ASE Task Force, commissioned several years ago by ASE leadership and chaired by Carol Mitchell, PhD, RDMS, RDCS, RVT, RT(R), FASE, describes the role of an Advanced Cardiovascular Sonographer (ACS). This document discusses the rationale for, educational background and training required to become, and responsibilities expected of a cardiovascular sonographer who practices at an advanced level. In general, by virtue of his or her training and experience, an ACS would be expected to fill a number of important roles: (1) instructing less experienced cardiac sonographers in the use of sophisticated echocardiographic technology; (2) reviewing both the study indications and the images acquired during echocardiography examinations, and assisting the performing sonographer if additional views or data were needed; (3) educating staff about new echocardiographic technologies and methods when these are ready for incorporation into clinical use; and (4) helping to implement measures designed to enhance quality. The authors of this editorial, all of whom are experienced educators and authors of prior publications on education and training of physician echocardiographers and

The Use of a Stand-of Device in High Pulse Repetition Frequeny Doppler Echocardiography

An interesting case of severe mitral stenosis in which Doppler echocardiographic evaluation was greatly enhanced by use of a stand-off pad is discussed. When employing high pulse repetition frequency (HPRF) Doppler, it may be difficult to place the sample volume at the area of interest while remaining in HPRF mode, because it is not always clear that there is a certain minimum sample volume depth below which a system will not operate in HPRF. This and other related technical constraints vary from machine to machine. This case illustrates that sample volumes can be manipulated by using a stand-off pad, thereby making use of HPRF possible. The specifications of the HPRF mode on the Acuson 128XP (Acuson, Mountain View, CA) are examined in detail, and possible applications of this technique in similar difficult situations that may arise in clinical practice are discussed.