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J Am Coll Cardiol, 2007; 50:381-396, doi:10.1016/j.jacc.2007.03.048 (Published online 12 July 2007).
© 2007 by the American College of Cardiology Foundation
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STATE-OF-THE-ART PAPER

Echocardiography in Heart Failure

Applications, Utility, and New Horizons

James N. Kirkpatrick, MD*,*, Mani A. Vannan, MBBS, FACC{dagger},1, Jagat Narula, MBBS, PhD, FACC, FAHA{dagger},2 and Roberto M. Lang, MD, FACC, FAHA, FESC, FASE{ddagger},3

* Hospital of the University of Pennsylvania, Philadelphia, Pennsylvania
{dagger} University of California–Irvine, Orange, California
{ddagger} University of Chicago Hospitals, Chicago, Illinois.

Manuscript received January 16, 2007; revised manuscript received March 27, 2007, accepted March 29, 2007.

* Reprint requests and correspondence: Dr. James N. Kirkpatrick, Hospital of the University of Pennsylvania, 9 Gates, 3400 Spruce Street, Philadelphia, Pennsylvania 19104. (Email: James.Kirkpatrick{at}uphs.upenn.edu).


   Abstract
Top
 Abstract
Clinical Measurements and...
 Therapeutic Guidance
 New Horizons for Advanced...
 Conclusions
 References
 
Echocardiography is well qualified to meet the growing need for noninvasive imaging in the expanding heart failure (HF) population. The recently-released American College of Cardiology/American Heart Association guidelines for the diagnosis and management of HF labeled echocardiography "the single most useful diagnostic test in the evaluation of patients with HF...," because of its ability to accurately and noninvasively provide measures of ventricular function and assess causes of structural heart disease. It can also detect and define the hemodynamic and morphologic changes in HF over time and might be equivalent to invasive measures in guiding therapy. In this article we will discuss: 1) the clinical uses of echocardiography in HF and their prognostic value; 2) the use of echocardiography to guide treatment in HF patients; and 3) promising future techniques for echocardiographic-based imaging in HF. In addition, we will highlight some of the limitations of echocardiography.

Abbreviations and Acronyms
  CRT = cardiac resynchronization therapy
  EF = ejection fraction
  HF = heart failure
  ICD = implantable cardioverter-defibrillator
  LV = left ventricle/ventricular
  LVEDP = left ventricular end-diastolic pressure
  LVOT = left ventricular outflow tract
  TDI = tissue Doppler imaging
  SF = systolic fraction of pulmonary venous forward flow
  VAD = ventricular assist device
  Vp = flow propagation slope of early diastolic left ventricular filling

Echocardiography is, according to the recently released American College of Cardiology/American Heart Association (ACC/AHA) guidelines for the diagnosis and management of heart failure (HF), "the single most useful diagnostic test in the evaluation of patients with HF...," because of its ability to accurately and noninvasively provide measures of ventricular function and assess causes of structural heart disease (1). An estimated 5 million people have HF, and their ranks are increased by an estimated 550,000 each year (2). Heart failure hospital stays have increased 150% over the last 20 years (2). The lifetime risk of developing HF has been estimated at 20% for the U.S. population. And, although ischemic heart disease is the most common cause of HF, up to 11% of the population without evidence for coronary artery disease will also develop HF (3).

Heart failure is classically described as left ventricular (LV) dysfunction leading to congestion and reduced systemic perfusion, most often manifesting symptomatically as dyspnea and fatigue. After an insult to the myocardium, the LV progressively dilates or hypertrophies, a process followed by spherical remodeling. These morphologic changes cause further stress on the myocardium by increasing wall tension and cause or exacerbate mitral regurgitation, which, in turn, results in further dilatation and contractile dysfunction in a vicious cycle (1). Such remodeling is often the final common pathway for many although not all etiologies of HF.

Because this morphologic process begins before the onset of symptoms, the recent HF guidelines place special emphasis on detecting subclinical LV systolic and diastolic dysfunction (1,4). Several studies have emphasized that standard physical examination maneuvers are suboptimal in detecting either systolic or diastolic LV dysfunction, especially in the preclinical phase. Similarly, physical examination is limited in its ability to accurately characterize the volume and cardiac output status in patients with LV dysfunction (5,6). As a rapid and accurate modality, echocardiography can improve the noninvasive detection and definition of the hemodynamic and morphologic changes in HF. Echocardiography might also be equivalent to catheter-based techniques in guiding therapy and improving outcomes, without the risks and cost of invasive measures (5).

In this review we will discuss: 1) the clinical uses of echocardiography in HF and their prognostic value; 2) the use of echocardiography to guide treatment in HF patients; and 3) promising future echocardiographic techniques for cardiac imaging in HF. We will also highlight some of the limitations of echocardiography (outlined in Tables 1 and 2).Go We will use the term "echocardiography" in a general sense to refer to all cardiac ultrasound imaging techniques, including M-mode, 2- and 3-dimensional imaging, and spectral and color Doppler, which comprise the comprehensive sonographic assessment of cardiac structure and function.


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  		Table 1 Evaluation of Standard Doppler Echocardiographic Techniques in HF
 

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  		Table 2 Evaluation of Novel Doppler Echocardiographic Techniques in HF
 

   Clinical Measurements and Prognosis
Top
 Abstract
 Clinical Measurements and...
Therapeutic Guidance
 New Horizons for Advanced...
 Conclusions
 References
 
Used for many years to provide structural correlates to the clinical picture of HF, echocardiography can also measure multiple clinically important parameters of cardiac function, including hemodynamic status and LV ejection fraction (EF), volumes, and mass.

Hemodynamics.   Intracardiac pressure measurements have traditionally required invasive methods. This limitation, which also precludes serial measurements outside of the intensive care context, can often be circumvented with the use of echocardiographic techniques. In selected patients, echocardiography might be a noninvasive surrogate (Fig. 1). Stroke volume and cardiac output can be estimated from the velocity time integral obtained by pulse wave Doppler recordings in the left ventricular outflow tract (LVOT), multiplied by the LVOT area. Figure 1 illustrates the echocardiographic estimates of right atrial pressure, right ventricular systolic pressure/pulmonary artery systolic pressure, and pulmonary artery mean and diastolic pressures (7–9). All of these measurements require adequate imaging windows and parallel alignment of the Doppler cursor with blood flow to avoid underestimation of Doppler jet velocity and calculated pressure. Stroke volume as measured in the LVOT is overestimated in the presence of significant aortic insufficiency. Small errors in the measurement of LVOT diameter lead to large errors in the calculation of LVOT area. Pulmonary artery pressure estimates require the presence of tricuspid valve regurgitation for systolic pressure and pulmonic valve regurgitation for mean and diastolic pressures as well as an accurate estimate of right atrial pressure (10).


Figure 1
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  		Figure 1 Illustration of "Echo Right Heart Catheterization"

(A) Inferior vena caval (IVC) size and degree of collapse yields a range of right atrial pressure (RAP): <1.2 cm with full collapse = RAP 0 mm Hg; 1.2 to 1.7 cm with >50% collapse = RAP 0 to 5 mm Hg; >1.7 cm with >50% collapse = RAP 6 to 10 mm Hg; <50% collapse = RAP 10 to 15 mm Hg; and >1.7 cm with 0% collapse = RAP >15 mm Hg (51). (B) The tricuspid regurgitant velocity (TR Vel) is used to estimate the systolic right ventricle—right atrium gradient (and the pulmonary artery systolic pressure, in the absence of pulmonic stenosis). (C) The maximal pulmonic valve regurgitant velocity is used to estimate the mean pulmonary artery pressure (PAPm). The end diastolic pulmonic regurgitant velocity is used to estimate diastolic pulmonary artery pressure (PAPd). (D) The early mitral inflow (E-wave)/early diastolic mitral valve annular motion (E’-wave) ratio <8 or >15 is calculated to assess PCWP <15 mm Hg or >15 mm Hg, respectively. E/E’ = ratio of early diastolic mitral inflow velocity to early diastolic velocity of the mitral valve annulus; IVCCI = inferior vena cava collapsibility index; PCWP = pulmonary capillary wedge pressure; PR Vel. = pulmonic valve regurgitant velocity; RVSP = right ventricular systolic pressure.

 
A variety of echocardiographic techniques can determine abnormal diastolic function, increased left atrial pressure and left ventricular end-diastolic pressure (LVEDP). These measurements have demonstrated considerable prognostic value in symptomatic and asymptomatic patients with either preserved or abnormal LV systolic function (11). The adverse prognosis associated with systolic dysfunction is well described, but isolated diastolic HF also carries a poor prognosis, including future development of systolic HF (12).

Diastolic function can be characterized according to severity. Mild diastolic dysfunction—abnormal LV relaxation—can be detected via a decrease in early diastolic flow velocity (E-wave) and a greater reliance on atrial contraction (A-wave) to fill the LV (E/A <1). Moderate diastolic dysfunction—"pseudonormalization"—reflects increasing left atrial pressure at the onset of diastole and an increase in early diastolic flow velocity to a level near that of normal filling (E/A 1 to 1.5). Severe diastolic dysfunction—restrictive filling—occurs when left atrial pressure is further elevated such that early diastolic flow is extremely rapid and left atrial and LV pressures equalize quickly during early diastole (E/A >2, DT <115 to 150 ms). Reduction in preload with the Valsalva maneuver can unmask diastolic dysfunction by changing a pseudonormalized pattern to an abnormal relaxation pattern or a restrictive pattern to a pseudonormalized one (13,14). Persistence of a restrictive filling pattern during the Valsalva maneuver or on follow-up echocardiogram after HF therapy portends a particularly grim prognosis, as shown by Pinamonti et al. (15) and others. These traditional techniques, however, are dependent on heart rate and loading conditions and lack validity in patients with preserved EF.

Additional parameters such as: 1) an abnormal ratio of the systolic and diastolic velocities of pulmonary venous inflow (S/D <1); 2) a systolic fraction of pulmonary venous forward flow (SF) of <40%; and 3) an early LV filling flow propagation slope (Vp) of <45 cm/s are less dependent on loading conditions and heart rate and have been shown to be robust predictors of high LV filling pressures and cardiovascular mortality (16,17). These measures are limited by inability to adequately image the pulmonary veins in some patients and by the limited reproducibility of Vp. A ratio of peak early mitral inflow velocity (E) to peak early diastolic myocardial velocity (E’) of ≤8 predicts an LVEDP of <15 mm Hg, whereas a ratio of >15 predicts an elevated LVEDP (≥15 mm Hg) (Fig. 1D) (14). The ratio of peak early mitral inflow velocity to slope of the propagation velocity (E/Vp) of ≥1.5 predicts a LVEDP >15 mm Hg and has been shown to have prognostic value in post-myocardial infarction patients (18). Increased left atrial volumes (>32 ml/m2), which are usually larger in diastolic compared with systolic HF, have been shown to predict morbidity (19). Among multiple diastolic parameters in patients with a broad range of EF and degrees of mitral regurgitation, Rossi et al. (20) have demonstrated that a >30-ms difference between pulmonary vein atrial flow reversal and mitral A-wave durations was the most sensitive predictor of elevated LVEDP >18 mm Hg. Interestingly, E/E’ has proven superior to brain natriuretic peptide (BNP) levels in diagnosing volume overload, even in patients with preserved systolic function (21,22). Tables 3 and 4 Go list patient population, Doppler modality, cutoff values, and outcome measures used in a variety of prognostic studies of diastolic function and filling pressures (12,15–17,19,23–41). Figures 2A and 2B depict strategies for using Doppler techniques to noninvasively estimate filling pressures and characterize the severity of diastolic dysfunction in patients with reduced EF. The strategies reflect the fact that synthesis of multiple parameters is often required to give an assessment of filling dynamics, particularly when poor acoustic windows might limit the ability to make every measurement.


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  		Table 3 Prognostic Significance of Echocardiographic Diastolic Dysfunction Measures: Single Component Studies
 

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  		Table 4 Prognostic Significance of Echocardiographic Diastolic Dysfunction Measures: Composite Studies
 

Figure 2
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  		Figure 2 Diastolic Filling Parameters and the Prediction of Normal Versus Elevated Filling Pressure

(A) Prediction of normal versus elevated filling pressure. In patients with preserved and reduced left ventricular ejection fraction (LVEF), normal filling pressures are predicted by normal mitral inflow E-wave to tissue Doppler E’-wave ratio (E/E’) and mitral inflow E-wave to flow propagation ratio (E/Vp) values or intermediate values with normal left atrium (LA) size, normal pulmonary vein atrial reversal duration minus mitral inflow A-wave duration (ARdur – Adur), and a minimal change in the E/A wave ratio with Valsalva. Elevated filling pressures are predicted by elevated E/E’ and E/Vp values or intermediate values with elevated LA size, prolonged ARdur – Adur, a substantial change in the E to A valve with Valsalva, or a prolonged pulmonary vein D-wave deceleration time (DDT). (B) Degree of diastolic dysfunction. In patients with reduced LVEF, mitral inflow E/A, mitral inflow E-wave deceleration time (EDT), and isovolumic relaxation time (IVRT) parameters, confirmed by pulmonary vein S to D ratio (S/D), systolic fraction of pulmonary venous forward flow (SF), and DDT can further define filling dynamics by stratifying diastolic function into "abnormal relaxation" (normal filling pressures), "pseudonormal" (elevated filling pressures), and "restrictive" (very high filling pressures) categories. Valsalva {Delta}E/A = change in mitral inflow E to A-wave ratio with Valsalva maneuver. (Modified from Nagueh SF, Zoghbi WA. Clinical Assessment of LV Diastolic Filling by Doppler Echocardiography. ACC Current Journal Review. 2001; July/Aug: 49).

 
The myocardial performance index.   The myocardial performance index (better known as the Tei index) is a simple Doppler parameter that provides global assessment of systolic and diastolic function. The Tei index consists of the ratio of the isovolumic contraction + isovolumic relaxation times/the ejection time—all parameters that can be obtained from Doppler interrogation. The Tei index is independent of heart rate and blood pressure, applies to left and right ventricular systolic and diastolic dysfunction, does not rely on geometric assumptions, and is highly reproducible, although normal values vary with age (42,43). It has been correlated with invasively measured changes in LV dP/dt (44). The prognostic value of the Tei index was initially tested in patients with infiltrative cardiomyopathy and pulmonary hypertension (45). It has subsequently been validated in patients with dilated cardiomyopathy, with a value of >0.77 proving superior to EF in predicting cardiac death and disease severity (46). The Tei index also proved beneficial in predicting the development of HF in a cohort of elderly men without baseline LV dysfunction (47) and in predicting the lack of clinical response to medical treatment in a study including both patients with systolic HF and HF with preserved systolic function (48). Because adequate Doppler images can often be acquired when 2-dimensional (2D) image quality is suboptimal, the Tei index might be particularly useful when other measures of left and right ventricular function are obscured or indeterminate.

EF and dimensions.   Traditionally, EF measurements have been visually estimated with important limitations of subjectivity and dependence on highly trained expert interpretation for accuracy. Although symptoms guide the majority of HF management decisions, precise and reproducible EF measurements play an increasingly important role in guiding important interventions. Consequently, quantified, objective measurements of LV systolic function should become standard practice in echocardiography. Although fractional shortening measured from M-mode tracings can quantify LV function, it is valid only in a symmetrically contracting heart without regional variability and is therefore inappropriate for the remodeled ventricles of many HF patients. The new guidelines from the American Society of Echocardiography (ASE) advocate the biplane method of discs for EF quantification and discourage the use of M-mode measurements that rely on geometric assumptions to convert linear measurements to 3-dimensional (3D) volumes (49). An alternative method for volume calculation, useful when the endocardium is not well defined, is the area-length method. This method assumes a bullet-shaped ventricle and involves planimetry of the mid-ventricle short-axis area and the annulus-to-apex length in systole and diastole. With either 2D method, the new ASE guidelines define an abnormal EF as <55%, with the cutoffs for moderately abnormal and severely abnormal at 44% and 30%, respectively. The reference ranges for LV dimensions are best indexed to body surface area, with reference ranges 2.4 to 3.2 cm/m2 and cutoff values of 3.5 and 3.8 cm/m2 for moderate and severe dilation, respectively (49).

Image quality in patients with poor acoustic windows has traditionally played a major role in limiting the accuracy of quantification of LV volumes and EF. Tissue harmonic imaging with and without echocardiographic contrast for LV cavity opacification has improved the accuracy and reproducibility of EF measurements (50,51). This method has enabled the accurate assessment of LV function in nearly all patients, irrespective of body habitus, chest wall deformities, or pulmonary diseases (52–54) (Fig. 3). Two-dimensional echocardiography, even when employing these methods, lacks accuracy compared with the gold standards of magnetic resonance imaging (MRI) or radionuclide ventriculography for quantification of EF and volumes (55). The reasons for the consistent underestimation of LV volumes and EF involve reliance on geometric assumptions, combined with foreshortening of the LV from transducer positioning errors. This underestimation might be overcome with the use of 3D echocardiography (56).


Figure 3
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  		Figure 3 Contrast Opacification of the Left Ventricular Cavity

(A) Apical 4-chamber views with poor endocardial definition. (B) The same view with improved endocardial definition after echocardiographic contrast administration.

 
Although EF and LV dimensions do not correlate with HF symptoms, exercise capacity, or myocardial oxygen consumption (57,58), they do provide crucial prognostic information (59). Morbidity and mortality are closely linked to both EF and LV volumes in HF patients in multicenter trials (60,61). Although influenced by a myriad of demographic and clinical factors, post-myocardial infarction prognosis is most powerfully predicted by EF and LV size. Early studies of acute myocardial infarction survivors using cineangiography and radionuclide ventriculography demonstrated EF <40% and increased LV volumes to be predictors of subsequent cardiovascular mortality and sudden death (62–65). More recent studies using echocardiography have also found EF and LV volumes to be powerful prognosticators for major adverse cardiac events (66,67). The ability of echocardiography to assess global dysfunction and regional wall motion has aided in the assessment of the size of myocardial infarctions. This measurement predicts cardiogenic shock (if >40% of the myocardium is involved), development of chronic HF, and mortality, despite the fact that myocardial stunning and hibernation complicate the prediction of eventual infarct size (68,69).

LV mass.   Although LV mass has received less attention in clinical cardiology than EF, it is an important prognostic marker in HF in patients with and without coronary artery disease (70). This observation in smaller studies was confirmed in the echocardiographic substudy of the SOLVD registry and trials, in which investigators examined the effect of LV hypertrophy on clinical outcomes and found that increased LV mass was associated with high mortality and rate of cardiovascular hospital stays, independent of EF (71). Because population studies suggest that the etiology of HF in African-American patients is more likely to be hypertensive than ischemic (72), the routine and accurate measurement of LV mass and its prognostic significance might be even more salient in this population.

Left ventricular mass assessment is subject to the same limitations in reproducibility and accuracy as measurement of LV dimensions (73). The current ASE guidelines recommend mass calculation from linear dimensions with the cubed formula, modeling the LV as a prolated ellipse, because this method has been validated in multiple studies with pathologic correlation. The cubed formula lacks precision, however, when applied to many HF patients, because it involves geometric assumptions that are invalid in a nonsymmetrically contracting, remodeled ventricle. Two-dimensional methods, including the truncated ellipsoid and the area-length formula, might be more appropriate for distorted ventricles with regional wall motion abnormalities. These methods, however, rely heavily on geometric assumptions. Furthermore, as mentioned, these methods are subject to inaccuracies from foreshortening.

Unlike EF and LV dimensions, LV mass has different cutoff values for men and women and for linear and 2D methods. The reference ranges for women are 67 to 162 g and 66 to 150 g for the linear and 2D methods, respectively. Indexed to body surface area, these ranges are 43 to 95 g/m2 and 44 to 88 g/m2. For men the reference ranges are 88 to 224 g and 96 to 200 g, and 49 to 115 g/m2 and 50 to 102 g/m2 (49).

The LV mass increases in the remodeled, failing heart, either from increased volumes with myocardial thinning or from wall hypertrophy in patients with hypertensive cardiomyopathy (74). Despite its limitations, the assessment of LV mass provides not only an important research tool to evaluate remodeling but also a precise and prognostically powerful way to characterize clinical status.


   Therapeutic Guidance
Top
 Abstract
 Clinical Measurements and...
 Therapeutic Guidance
New Horizons for Advanced...
 Conclusions
 References
 
Echocardiography not only provides clinical measures and prognostic assessments in patients with HF but can also supply information to guide application of HF therapies.

Medications.   In addition to the demonstrated benefit of angiotensin-converting enzyme (ACE) inhibitors for patients with both symptomatic and asymptomatic LV dysfunction (75), beta-blocker drugs are beneficial for almost all well-compensated patients with LV systolic dysfunction (76,77), and aldosterone antagonists reduce mortality in New York Heart Association functional class III and IV patients hospitalized for HF with EF ≤35% and in post-myocardial infarction patients with EF <40 % (78,79). Not only does echocardiographic EF measurement commonly establish an indication for these medications but also improvements in EF and LV volumes by echocardiography are used as standard measures of therapeutic effect in many clinical trials of HF medications (80,81). Conversely, echocardiography also supplies an assessment tool for the detrimental effects on LV function of cardiotoxic medications, such as anthracycline chemotherapeutic agents. The EF decrements while taking these medications is often an indication for discontinuation (82,83).

The strategy of combining echocardiographic assessment of filling pressures with BNP measurement has definite prognostic value and might prove one of the most accurate ways to noninvasively guide fluid management. In a study by Dokainish et al. (31), an E/E’ value >15, combined with BNP ≥250 pg/ml, measured on the day before discharge, had incremental power in predicting readmission or cardiac death compared with traditional clinical risk factors. If proven to be cost-effective, echocardiography with BNP might become an important strategy for triaging HF patients in acute care settings, for assessing suitability for discharge, or for identifying patients who need more intensive outpatient management.

Implantable cardioverter-defibrillators (ICDs).   Recent studies have demonstrated the benefit of prophylactic ICD for the primary prevention of sudden death in patients with reduced EF (84,85). Reimbursement strategies for ICDs therefore rely on EF as a common parameter for placement of these devices in HF patients, and echocardiography is often employed to assess EF (1). Repeat EF assessment at 30 to 40 days after myocardial infarction and after initiation of optimal HF medical therapy is necessary to determine candidacy for ICD. Many patients’ EF rise above 30% to 35% cutoff after a month on an appropriate medical regimen, and premature ICD implantation has shown no benefit (86).

Cardiac resynchronization therapy (CRT).   Many HF patients lack coordinated contraction of the LV walls (intraventricular dyssynchrony) and between the right and left ventricles (interventricular dyssynchrony). Cardiac resynchronization therapy can restore coordinated contraction with demonstrated improvement in symptoms and survival (87). Current recommendations and reimbursement strategies advocate that only patients with EF ≤35%, moderate-to-severe HF symptoms, a widened QRS interval, and sinus rhythm should undergo CRT (1). Nevertheless, it is now clear that not all patients meeting these criteria will respond to CRT; furthermore, it has been recently shown that a subgroup of patients lacking these criteria could benefit from CRT (88). Echocardiographic measurement of dyssynchrony can accurately predict beneficial response in the form of reverse remodeling (reduction in LV volumes, improved EF, and reduced mitral regurgitation) (89), and echocardiographically demonstrated reverse remodeling predicts improved survival (90,91). Currently, different techniques are used to assess dyssynchrony, some of which are discussed in the following text (92). It remains to be seen which measurement or combination of measurements will prove most accurate in predicting beneficial response to CRT. This is an area of active investigation in the PROSPECT (Predictors of response to cardiac resynchronization therapy) trial and other studies (93).

Mitral valve surgery.   So-called "functional" mitral regurgitation in HF has traditionally been ascribed to stretching of the mitral annulus and malcoaptation of the mitral valve leaflets. More recent echocardiographic and pathologic investigations have described tethering of the mitral valve leaflets from remodeling-induced displacement of 1 or both papillary muscles and structural changes of the mitral valve itself. These mechanisms rather than annular dilatation might be the main determinants of functional mitral regurgitation (94,95).

The rationale behind repair or replacement of the mitral valve has been the traditional perspective on functional mitral regurgitation; nonetheless, surgery has demonstrated efficacy, even in advanced HF (96). But it is not always clear whether repair or replacement is indicated. Furthermore, the severity of functional mitral regurgitation can be reduced by CRT and by ACE inhibitor therapy without surgery, presumably owing to the effects of reverse remodeling (97).

Traditional echocardiographic evaluation of mitral regurgitation has significant limitations. The mitral valve annulus is saddle-shaped and cannot be fully visualized in 2D imaging planes (98). The mitral valve regurgitant jet, especially when eccentric, is also incompletely visualized in traditional imaging planes, leading to misclassification of mitral regurgitation severity. Similarly, the geometric assumptions involved in calculating mitral regurgitation severity with Doppler flow and color Doppler (e.g., calculations of effective regurgitant orifice area) lead to inaccuracies in non-central jets (99,100).

Ventricular reconstruction surgery.   A number of ventricular reconstruction surgeries have been proposed for patients with ischemic HF and apical dyskinesis or LV aneurysms (101,102). These surgical mechanical techniques reduce ventricular remodeling and have improved both morbidity and mortality in HF patients in small studies (103,104), but definitive conclusions await the results of ongoing trials (105). Decision-making for these surgical procedures relies heavily on accurate determination of dyskinesis or akinesis, thinning of the apical segment, depressed EF, coexistence of mitral regurgitation, and volumetric measurement (106,107). An elevated LV end systolic volume index >60 ml/m2, in particular, portends poor postoperative survival (108). Echocardiography provides accurate preoperative modeling to guide the amount of myocardium to be excluded or resected (109). And echocardiography provides an important way to judge the efficacy of these procedures in improving ventricular remodeling, hemodynamic status, and EF.

Ventricular assist devices.   Ventricular assist devices (left ventricular assist device = LVAD, bi-ventricular assist device = bi-VAD) are commonly used as bridges to heart transplantation or ventricular recovery and, more recently, have demonstrated both mortality and quality of life benefit as "destination therapy" in patients for whom heart transplantation is not an option (110). Candidates for VAD placement, however, require careful preoperative consideration. Significant intracardiac shunts, such as an atrial septal defect, will be exacerbated by LVAD placement, leading to significant hypoxia (111). Furthermore, significant valvular disease, especially significant aortic stenosis or aortic regurgitation, must be detected to allow valve repair or replacement before VAD implant. Decreased right ventricular function and high pulmonary pressures often necessitate placement of a bi-VAD. Preoperative echocardiography can detect all of these disorders. After implantation, echocardiography can detect thrombus formation within the VAD (112) or other causes of inflow cannula obstruction. (Fig. 4) Doppler and color Doppler imaging can also detect significant inflow and outflow cannulae regurgitation and also assess aortic valve opening and insufficiency (113).


Figure 4
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  		Figure 4 Left Ventricular Assist Device Cannula Obstruction From Trabeculation

(A) Transesophageal echocardiogram in the mid-esophageal 4-chamber view demonstrating inflow cannula of a left ventricular assist device (arrow). (B) Transgastric short-axis view demonstrates inflow cannula proximity to an area of hypertrabeculation that is consistent with non-compaction of the left ventricular myocardium (arrows). (C) Close-up view in the mid-esophageal 4-chamber view demonstrates an area of hypertrabeculation being pulled into the inflow cannula (arrow). (D) Continuous wave Doppler imaging demonstrates high velocities into the inflow cannula, consistent with partial obstruction.

 

   New Horizons for Advanced Echocardiographic Techniques in HF
Top
 Abstract
 Clinical Measurements and...
 Therapeutic Guidance
 New Horizons for Advanced...
Conclusions
 References
 
Echocardiographic techniques applicable to HF patients are advancing rapidly. New techniques have been developed to image myocardial mechanics and provide more precise measurements to guide therapeutic decisions. Although MRI is an established technique for measuring myocardial mechanics and obtaining highly accurate measurements of cardiac size and structures, the evaluation of these parameters by echocardiography is considerably more feasible for clinical use, because it is widely available and repeat assessment can be readily performed.

Myocardial motion, strain, and strain rate.   One of the most promising techniques, already used in daily clinical practice, is tissue Doppler imaging (TDI) (Fig. 5). Tissue Doppler imaging has been used with M-mode, 2D, and pulse wave Doppler (114). The peak systolic myocardial velocity, reflective of longitudinal myocardial fiber shortening, has been used to assess systolic function in HF. Yip et al. (115) and Yu et al. (116) noted systolic abnormalities (Sm <4.4 m/s) with TDI in 38% to 52% of HF patients with normal EFs. Their findings suggest that systolic myocardial velocity might provide a more accurate measure of systolic dysfunction than EF. Many HF patients with normal EF might have systolic as well as diastolic HF. In this setting, tissue velocity measures have demonstrated incremental (117,118) and, in a recent study, superior (119) prognostic ability compared with standard echocardiographic measures, including EF.


Figure 5
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  		Figure 5 Tissue Doppler Imaging and Assessment of Regional Function

Apical 4-chamber view with tissue Doppler imaging showing regional analysis of the contraction patterns of the septal and lateral walls in a patient with dilated cardiomyopathy. Regions of interest (ROI) are drawn at the mid portions of the septal and lateral walls, and the contraction velocities within each ROI in the vertical plane are graphically displayed over time.

 
Tissue velocity measurements are susceptible to artifact from tethering and translational motion (i.e., displacement of the entire heart is recorded as tissue motion of the specific segment being measured). Strain imaging, derived from tissue velocity measurements, overcomes this limitation by measuring actual deformation of the myocardium (expressed as a percentage) in systole and diastole. Strain rate is the inverse of the time to deformation. As measured in the longitudinal direction (base to apex in the apical views), the normal values for strain are 15% to 25% and for strain rate are 1 to 1.5 s–1 (120). Like tissue velocity measures, strain and strain rate imaging detect abnormalities of systolic and diastolic function in patients with infiltrative cardiomyopathies (121). In addition, Palka et al. (122) described the use of strain rate to differentiate restrictive cardiomyopathy (reduced early diastolic strain rate, compared with normal hearts) from constrictive physiology (increased early diastolic strain rate).

The identification and measurement of dyssynchrony is one of the most widely published uses of tissue velocity, strain, and strain rate imaging in HF. The TDI techniques predict echocardiographic and clinical response to bi-ventricular pacing with high sensitivity and specificity. Several parameters have been used, such as an intersegmental delay in peak systolic longitudinal motion between segments (abnormal >60 to 65 ms) and the SD of time to peak velocity of 12 segments (abnormal >30 to 31 ms) (123,124). Tissue Doppler imaging can identify the specific regions involved in dyssynchrony as well as the magnitude of dyssynchronous contraction. This information can be available to guide specific placement of bi-ventricular pacing leads and assess response during long-term follow-up. Furthermore, as bi-ventricular pacemakers can be set with a delay between right ventricular and LV activation, dyssynchrony measures can been used to optimize these settings, improving intraventricular and interventricular synchrony and hemodynamic status (125).

Tissue tracking.   The major limitation to TDI is Doppler angle dependency and problems in assessing regional LV torsional dynamics. In particular, the rotational component of cardiac contraction plays a significant role in LV ejection and relaxation and is poorly imaged by most TDI techniques.

Newer techniques such as "speckle tracking" algorithms involve identification of multiple unique patterns of echocardiographic pixel intensity that are automatically tracked throughout the cardiac cycle. The angular displacement of these pixels can be plotted over time for the apex, mid ventricle, and basal segments. Each pixel’s angular displacement is averaged to provide a measurement of both degree and direction of rotational motion for each segment (Fig. 6). This method is not limited by angle dependency and compares favorably with MRI (126,127).


Figure 6
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  		Figure 6 Velocity Vector Imaging

The upper panels display radial and rotational mechanics of the left ventricle (LV) by Velocity Vector Imaging (VVI). (A) Depiction of radial velocity vectors (yellow arrows) in end-systole with the direction of the arrows pointing to a counter-clockwise rotation of the apex. Velocities that are orthogonal to these radial velocities are rotational velocities (red arrows). These velocities are automatically calculated at each location of the arrows around the LV circumference. (B and C) Depiction of visual representation of the rotational motion at the base (B) of the LV and at the apex (C). The lower panels show the magnitude of the rotational motion at the apex and base (degrees of rotation). The apical rotation in this example is –7°, the minus sign depicting counterclockwise rotation. The basal rotation in the clockwise direction is 4°. Thus, the LV twist is 11°, and LV torsion is derived by dividing LV twist by the distance between the base and the apex in centimeters.

 
Although the prognostic significance of abnormal ventricular torsion has not been validated in large studies, measurement of rotational motion has shown promise as a sensitive marker for cardiac ischemia (128) and loading conditions (129) and might prove beneficial as a refined measure of LV dysfunction in HF and regional and global dyssynchrony (130). As such, it might become an important marker of the functional significance of remodeling and reverse remodeling in HF patients (131). It might also be able to detect early allograft rejection in transplant patients, potentially circumventing the need for frequent myocardial biopsies. In fact, when combined with 3D imaging techniques, it might prove to be a more sensitive marker for occult LV dysfunction.

3D echocardiography.   Previously hampered by the need for cumbersome off-line reconstruction of images, 3D echocardiography has benefited from the development of new matrix array transducers that acquire full volume data sets to allow real-time imaging (132). The ability to visualize all LV walls contemporaneously prevents foreshortening of the LV cavity and allows analysis of regional myocardial function (Fig. 7). No geometric assumptions are required in calculating volumes from a 3D image. In recent studies, 3D echocardiography demonstrated accurate global and regional assessments of LV size and function compared with the gold standard of MRI as well as lower intra- and inter-observer variability than traditional techniques (133). Sugeng et al. (134) showed 3D imaging to be superior to cardiac computed tomography in EF and volumes assessment. Application of new endocardial border detection techniques to 3D images might allow direct calculation of LV volumes and EF, leading to improved reproducibility (135). Mor-Avi et al. (136) demonstrated that, as in volumetric assessments, 3D echocardiography is more accurate and reproducible than methods for LV mass calculation, compared with the gold standard of MRI.


Figure 7
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  		Figure 7 Real Time 3-Dimensional Echocardiographic Volume Measurements

(A) A real time 3-dimensional full volume image is acquired in the apical 4-chamber view. (B) The image can be cropped and rotated along multiple planes (red, green, and blue lines) to isolate the left ventricle (LV) for analysis. (C) Application of an automated border detection algorithm yields a cast of the endocardium. (D) From the cast, LV cavity volumes can be calculated and tracked over the cardiac cycle. Stroke volume, end systolic and end diastolic volumes, ejection fraction, and filling dynamics can be measured. (E) The cast can also be automatically divided into wall segments. (F) Regional/segmental volume changes can be tracked over the cardiac cycle, enabling regional wall motion and dyssynchrony analyses.

 
The 3D imaging of global and regional function and LV volumes has not yet translated into clear improvements in or predictions of clinical outcomes. Three-dimensional echocardiography might, in the future, prove beneficial in several areas. The improved precision in measuring EF might guide more appropriate selection of patients for ICD and CRT therapy. Like TDI, 3D echocardiography can assess segmental myocardial motion over time, thereby detecting and characterizing dyssynchrony. Three-dimensional echocardiography has been used in the functional assessment of mitral annular size and tenting volume and improves the echocardiographic measurement of mitral regurgitation (137). A recent review discusses these and other applications of 3D echocardiography in imaging HF patients, such as assessments of atrial size and of right ventricular size and function (138).


   Conclusions
Top
 Abstract
 Clinical Measurements and...
 Therapeutic Guidance
 New Horizons for Advanced...
 Conclusions
References
 
Echocardiography is well qualified to meet the growing need for noninvasive imaging in the HF population. Because HF patients often have more than 1 structural and/or functional abnormality contributing to their disease state, echocardiography’s versatility in detecting valvular and pericardial pathology along with myocardial disorders yields obvious benefits. Doppler measurements provide important information to direct management of volume status, diagnose and characterize HF with preserved systolic function, and identify patients at high risk for cardiovascular morbidity and mortality. Not surprisingly, the underuse of echocardiography in populations at significant risk for HF is associated with adverse cardiovascular outcomes (139,140). Assessment of LVEF in clinical HF is one of the primary measures in a number of cardiovascular quality improvement initiatives, including the AHA’s "Get with the Guidelines" and the ACC’s "Guidelines Applied in Practice" (141,142). Echocardiography is well suited to repeated measurements of EF and LV mass in clinical trials and routine patient care. In fact, the new HF guidelines recommend repeat echocardiography for HF patients with changes in symptoms, a clinical event, or a treatment likely to affect cardiac function (1). Echocardiography provides important data for therapeutic decision-making, including defining candidacy for medications, implantable cardiac devices, and surgical procedures. New techniques for the characterization of ventricular mechanics and recent developments in 3D echocardiography hold great promise for improving the quality of care to the growing population of HF patients.


   Acknowledgments
 
The authors would like to thank Richard A. Kirkpatrick, MD, for editorial assistance.


   Footnotes
 
Alan Pearlman, MD, FACC, acted as the Guest Editor for this article.

1 Dr. Vannan has received honoraria and research support from Siemens. Back

2 Dr. Narula has served on the speakers’ bureau for GlaxoSmithKline and received honoraria from General Electric, Toshiba, and Bristol-Myers Squibb. Back

3 Dr. Lang has served on the speakers’ bureau for Philips and received an equipment grant from Philips. Back


   References
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