Echocardiography has been the mainstay of imaging for initial assessment, diagnosis, and treatment of HF. Transthoracic echocardiogram is a key tool for establishment of diagnosis and tracking of function in HF. Transthoracic echocardiography is a class I diagnostic test for management of HF, as described by the American College of Cardiology/American Heart Association, and serves as a basis for comparison when there is a change in clinical status or to determine the impact of medical treatment. Underuse of transthoracic echocardiography is associated with reduced survival (Senni et al. 1999). Numerous important diagnostic measures obtained by echocardiography assist with treatment: left ventricular dimensions, left ventricular function, diastolic function, secondary valvular dysfunction, tissue characterization, pulmonary hypertension, as well as right ventricular dysfunction and dilation. This discussion focuses on left ventricular function.

Treatment of all dilated cardiomyopathies targets myocardial remodeling. Cardiomyopathy management is based on formal assessment that demonstrates systolic dysfunction and left ventricular dilation.

Initial single linear measurements of ventricular function and volume are measured along the minor axis of the heart using Teichholz M-mode echocardiography as shown by Fig. 11.1. Measurements are made during diastole and systole with further calculation of ventricular shortening to determine function. Single segment measurement leads to geometric assumptions that a single recording represents the ventricular function as a whole (Teichholz et al. 1976).

Two-dimensional echocardiography has largely replaced M-mode for evaluation of left ventricular volume and function. One common method for measurement of left ventricular volume is the Simpson biplane method, for which the transducer must be at true apex to obtain four- and/or ­two-chamber views. Simpson calculation is measured by dividing the ventricle into a series of equal disks per its long axis. Volume is then calculated from the total of all disk volumes. This method can underestimate left ventricular volume and overestimate ejection fraction if the transducer is positioned tangentially and not at the true apex. Additionally, the borders of the ventricle are outlined prior to calculation but can be difficult to determine due to the boundaries of the trabeculae.

Contrast echocardiography is routinely used and can further delineate endocardial borders and improve assessment of ventricular volume and wall motion abnormalities (Kasprzak et al. 1999; Konstam et al. 2011; Mulvagh et al. 2000). Expanding on this modality with harmonic enhanced contrast imaging with echocardiogram is an alternative for assessment of ventricular volumes (Kasprzak et al. 1999).

Tissue Doppler imaging assesses left ventricular function, by using the time velocity integral (TVI) of the left ventricular outflow tract, which is generally assessed via the apical view. The TVI is obtained by determining the cross-sectional area of flow multiplied by the mean velocity of flow. TVI then correlates to the volumetric flow for a single heart beat and corresponds to stroke volume. Limitations of this method include the use of only one beat for overall cardiac output, which may not be accurate. Additionally, the use of circular dimensions to calculate the area of the left ventricular outflow tract can lead to error because the outflow tract is not perfectly circular. Time velocity integral calculation can be used to assess flow across valves.

Three-dimensional echocardiogram gives a geometric assessment of left ventricular function and shape independent of plane (see Fig. 11.1c, d). It is more accurate in assessment of left ventricular volume, shape, and function than 2D echocardiography and comparable to cardiac MRI (Chuang et al. 2000). Three-dimensional echocardiography is rising in use and availability, but has not fully replaced 2D echocardiogram techniques.

Newer echocardiographic methods for evaluation of left ventricular function include the use of Doppler and speckle for assessment of strain. These imaging modalities are able to quantify ventricular shape, mechanics, and deformation using strain techniques (Helle-Valle et al. 2005; Urheim et al. 2000). Strain refers to myocardial stress and can be determined by the change in length between points. Strain rate refers to changes in flow velocities between points (Helle-Valle et al. 2005; Urheim et al. 2000). Strain and strain rate are used to formally calculate left ventricular function and tissue deformation, but are not used in routine management of HF.

Approximately 50 % of HF patients have HFnEF with diastolic dysfunction as the primary pathophysiology (Vasan et al. 1995). Several different pathological processes lead to diastolic dysfunction, defined as ventricular stiffness and impaired ventricular relaxation (Paulus et al. 2007). Most patients with LVSD have diastolic dysfunction. Older patients may have diastolic dysfunction or “age-related changes” identified on echocardiogram, without HF.

Diastolic function is evaluated with pressure gradients, velocities, and volumes using Doppler transthoracic echocardiogram. No single echocardiographic parameter defines the severity of diastolic dysfunction. Flow velocities are quantified from pulsed wave Doppler in an apical four-chamber view. Mitral inflow velocity in early diastolic filling, when most left ventricular filling is completed, is referred to as E velocity. The E velocity reflects pressure between the left atrium and left ventricle, compliance, and rate and level ventricular relaxation. As pressures equalize the filling slows in diastasis, the velocity of flow across the mitral valve decreases; the time over which this occurs is referred as deceleration time. Movement of the mitral valve annulus with left ventricular filling is characterized with Doppler echo with its velocity of movement E′ and ­considered a measurement of relaxation. Late filling flow velocity occurs with atrial systole and is referred to as A velocity. Normally, early mitral velocity (E) is greater than late mitral velocity (A) so the ratio E/A >1 (Kasner et al. 2007; Rokey et al. 1985). Left ventricular filling pressure can be predicted by using early mitral flow velocity and mitral annulus velocity as calculated by E/E′ which has been well correlated to measurements of mean capillary wedge pressures (PCWP) (Bruch et al. 2007; Nagueh et al. 2009). Additional common measurements that assist with characterization of diastolic function include the isovolumetric relaxation time (IVRT) and pulmonary venous flow patterns.

Diastolic dysfunction severity is characterized by stages (see Table 11.2 and Fig. 11.2). Stage I involves impaired relaxation, causing decreased early diastolic filling with subsequent lower E, increased filling with atrial contraction, and prolonged deceleration time (Nishimura and Tajik 1997). There is a reversal of E/A ratio, without an increase in filling pressures or left atrial pressure. This pattern is seen in many elderly patients. Stage I patients are not symptomatic at rest but may develop HF symptoms with exertion or stress.

Stage II diastolic dysfunction, called “pseudo normalization,” occurs with continued worsening in relaxation and increasing left ventricular stiffness that requires compensatory increase in left atrial pressure and increased pressure across the mitral valve. Early mitral velocity (E) and shortening of deceleration time leads to measurements of E/A ratio and deceleration times within normal ranges (Nishimura and Tajik 1997). The Valsalva maneuver will decrease preload so echocardiographic imaging shows a ≥50 % decrease in E velocity and unchanged A velocity with subsequent decrease in E/A ratio (Hurrell et al. 1997; Nagueh et al. 1997, 2009).

In grade III diastolic dysfunction, the primary deficit is restriction to filling as the ventricular becomes increasingly stiff. At this point it remains very difficult to maintain filling with rising atrial pressures. Flow velocities during this stage show a very high early mitral inflow velocity but concurrently a rapid equalization of atrial to ventricle pressures with shorter deceleration times. Flow continues during diastole with decreased mitral velocity with atrial contraction. The E/A ratio rises (Appleton et al. 1988). Filling pressures rise as documented by rising E/E′ and there is pulmonary flow reversal (Nagueh et al. 2009). Treatment of grade III diastolic function can improve filling pressures and some hemodynamic reversal is possible. However, this can progress to grade IV dysfunction when the hemodynamics associated with further restrictive filling cannot be improved upon.

At initial diagnosis of HF, further characterization of anatomic abnormalities and potential causes is imperative. Echocardiography identifies dilated cardiomyopathy, usually demonstrating biventricular dilation and dysfunction, atrial dilation, secondary valvular regurgitation, diastolic dysfunction, and pulmonary hypertension.

Medical management of HF can improve clinical symptoms. For patients with dyssynchronous contraction of the left and right ventricle, cardiac resynchronization therapy (CRT) may improve quality of life, ejection fraction, and survival and reduces hospitalization for HF (Cleland et al. 2005).

Echocardiographic measures of dyssynchrony may identify individuals who will respond to CRT. Small single center studies have shown connections between echocardiographic features of dyssynchrony and response to CRT (Hawkins et al. 2009). On the other hand, a multicenter study of 12 measures of dyssynchrony by echocardiogram did not successfully identify patients who would respond to CRT therapy (Chung et al. 2008). The use of echocardiography for cardiac resynchronization is a complex and controversial topic.

Transthoracic echocardiogram is widely available, affordable, and safe and can be performed at a patient’s bedside. Table 11.4 reviews the advantages and disadvantages of 2D and 3D echocardiography. Echocardiography requires experienced and expert sonographers as well as echocardiographers. The transducer itself is very sensitive and can easily generate artifacts, which can make interpretation difficult.