Goldman's Cecil Medicine || Echocardiography

CHAPTER  55  ECHOCARDIOGRAPHY 278

quantitative measurements, and clinical indications. The specific use of echo-cardiography and additional images is shown in other chapters on individual types of cardiovascular diseases.

ECHOCARDIOGRAPHIC IMAGINGPrinciplesEchocardiography is based on the use of a piezoelectric crystal that converts electrical to mechanical energy, and vice versa, allowing both transmission and reception of an ultrasound signal. The frequency of ultrasound waves used for diagnostic imaging ranges from 2 to 10 MHz, with lower frequencies having greater tissue penetration and higher frequencies providing better image resolution. Each transducer consists of a complex array of piezoelectric crystals arranged to provide images in a fanlike two-dimensional image, with the narrow top of this sector scan indicating the origin of the ultrasound signal. Transducers also include an acoustic lens that determines the focal depth, height, and width of the ultrasound beam.

Images are generated based on the reflection of ultrasound from acoustic interfaces: for example, the boundary between the blood in the left ventricle and the myocardium. The time delay between transmission and reception is used to determine the depth of origin of the ultrasound reflection. The depths of the reflected signals from multiple ultrasound beams are combined to generate a two-dimensional image. The speed of signal analysis allows acqui-sition of two-dimensional ultrasound images at frame rates of 30 to 60 per second. Ultrasound is strongly attenuated by bone and air, so echocardiogra-phy relies on acoustic “windows” where, for example, ultrasound can pene-trate to the heart while avoiding the ribs and lungs. With transthoracic imaging, the patient is positioned to bring the cardiac structures close to the chest wall, usually in a left lateral decubitus position, and the transducer is placed on the chest, using gel to provide acoustic coupling between the trans-ducer and skin. Standard acoustic windows are parasternal, apical, subcostal, and suprasternal notch.

Standard Image PlanesFrom the parasternal window, the image plane is adjusted manually by an experienced physician or sonographer to provide long and short axis views. Standard cardiac imaging planes are aligned relative to the axis of the heart, with the long axis defined as the plane that intersects the cardiac apex and the middle of the aortic valve. Short axis views are perpendicular to this long axis, with standard image planes at the cardiac base (aortic valve level), mitral valve, and midventricular levels. From the apical window, the transducer is rotated to provide three views oriented 60 degrees from each other, producing a four-chamber, a two-chamber, and a long axis view (Fig. 55-1).

55 ECHOCARDIOGRAPHY CATHERINE M. OTTO

Echocardiography is the clinical standard for evaluating cardiac function in patients with known or suspected heart disease. This chapter reviews the basic principles of echocardiography, echocardiographic approaches,

Rightventricular

outflow tract

Leftventricle

Left ventricle

Left ventricleRight

ventricle

Rightventricle

Right atriumLeft atrium

Descendingaorta

Left atrium

Left atriumauricle

Left ventricle

Aorta

Left atrium

FIGURE 55-1.  The  four  basic  image  planes  used  in  trans-thoracic echocardiography. A parasternal transducer position or “window”  is  used  to  obtain  long  and  short  axis  views. The long axis view (purple outline) extends from the left ventricular apex  through  the  aortic  valve  plane.  The  short  axis  view  is perpendicular to the long axis view, resulting in a circular view of the left ventricle (red outline). The transducer is placed at the ventricular apex to obtain the two-chamber (blue outline) and four-chamber  (green outline)  views,  each  of  which  is  about a 60-degree rotation from the long axis view and perpendicu-lar  to  the  short  axis  view.  The  four-chamber  view  includes  both ventricles and both atria. The two-chamber view includes the left ventricle and left atrium; sometimes the atrial append-age  is visualized.  (From Otto CM. Textbook of Clinical Echocar-diography,  4th  ed.  Philadelphia:  Elsevier  Saunders;  2009:32, Fig. 2-1.)

CHAPTER  55  ECHOCARDIOGRAPHY  279

MeasurementsEchocardiography provides accurate cardiac dimensions from two-dimen-sional or two-dimensional-guided linear depth (M-mode) recordings. The measurements typically provided include left ventricular (LV) end-diastolic and end-systolic internal dimensions, LV wall thickness, left atrial anterior-posterior diameter, and aortic sinus dimension. LV ejection fraction (EF) is determined by visual estimation or, more accurately, by tracing the endocar-dial borders at end diastole and end systole in two orthogonal views. End-diastolic and end-systolic ventricular volumes (EDV and ESV, respectively) are calculated using validated formulas, and the EF is determined as follows:

EF EDV ESV EDV= −( )

LimitationsEchocardiography is a very accurate, widely available, and widely used imaging approach. However, the quality of images can be suboptimal because of poor tissue penetration (e.g., excessive adipose tissue, position of the lungs relative to the heart), although images are nondiagnostic in fewer than 5% of patients with current instrumentation. Reflections are stronger when the interface is perpendicular to the ultrasound beam, so structures that are paral-lel to the beam may not be visible, an artifact called echo dropout. This poten-tial limitation may be avoided by the use of appropriate imaging planes and the integration of data from multiple transducer positions. Ultrasound arti-facts, such as beam width, shadowing, and reverberations, may be misinter-preted by inexperienced observers.

DOPPLER ECHOCARDIOGRAPHYPrinciplesUltrasound energy that is backscattered from moving red blood cells is shifted to a higher frequency when the blood is moving toward the transducer and a lower frequency when it is moving away. The magnitude of this Doppler shift corresponds to the velocity of blood flow.

ModalitiesPulsed Doppler allows measurement of flow velocity at a specific intracardiac site with the advantages of high spatial and temporal resolution. However, spatial localization is based on intermittent sampling at a time interval cor-responding to the depth of interest. The sampling frequency, which is depth dependent, limits the maximum detectable velocity because of a phenome-non called signal aliasing. Normal intracardiac flow velocities are about 1 m/second, which can usually be recorded with pulsed Doppler.

Continuous-wave Doppler allows measurement of high velocities along the entire length of the ultrasound beam, but the origin of the high-velocity signal must be inferred from the two-dimensional images. With stenotic and regur-gitant valves, blood flow velocities may be as high as 5 to 6 m/second, requir-ing the use of the continuous-wave Doppler mode. Both pulsed and continuous-wave Doppler velocities are displayed as a graph of velocity versus time, with the density of the spectral display corresponding to signal strength.

Color flow Doppler imaging is a modification of pulsed Doppler in which the flow velocity is displayed across a two-dimensional image using a color scale to indicate direction and velocity. The advantage is a visually appealing display of intracardiac flow patterns. Disadvantages are low temporal

resolution (frame rates of 10 to 30 per second) and poor velocity resolution due to signal aliasing.

Tissue Doppler uses the Doppler principle to record the velocity of motion of the myocardial wall. Tissue Doppler recordings of the myocardium adja-cent to the mitral annulus are used to evaluate diastolic ventricular function.

MeasurementsA standard echocardiographic study includes pulsed Doppler measurement of antegrade flow velocities (transmitral and transaortic) and evaluation for valve regurgitation using continuous-wave and color Doppler modalities. Other Doppler measurements depend on the specific clinical indication.

Quantitative measurements using Doppler data are derived from two basic concepts: volume flow rate and the pressure-velocity relationship. Stroke volume (in cubic centimeters) can be calculated as the volume of a cylinder, where the base is the spatial cross-sectional area (CSA, in square centimeters) of flow, determined as the area of a circle from a two-dimensional diameter measurement. The height of the cylinder is the distance the average blood cell travels in one cardiac cycle, which is the velocity time integral (VTI, in centimeters) of flow. Therefore,

SV cm CSA cm VTI cm3 2( ) = ( )× ( )

This approach has been validated for measurement of transaortic, transmitral, and transpulmonic flow. Measurement of volume flow rate at two different intracardiac sites allows quantitation of intracardiac shunts and valvular regurgitation.

The relationship between the pressure gradient (ΔP) across a narrowing and the velocity (v) of blood flow is described by the simplified Bernoulli equation:

∆P v= 4 2

This equation allows calculation of maximum and mean gradients across stenotic valves, estimation of pulmonary systolic pressure, and detailed evalu-ation of intracardiac hemodynamics with regurgitant valves.

ECHOCARDIOGRAPHIC APPROACHESSeveral echocardiographic modalities are in clinical use. If it is unclear which modality is optimum in a specific clinical setting, consultation with the echo-cardiographer is appropriate.

Transthoracic echocardiography (TTE) is the standard clinical approach in most patients with suspected or known cardiac disease. Advantages are that it is noninvasive, has no known adverse effects, and provides detailed data on cardiac anatomy and physiology. Limitations include poor image quality in some patients, limited visualization of structures distant from the transducer (e.g., atrial septum, left atrial appendage), and the inability to visualize struc-tures immediately distal to prosthetic heart valves (acoustic shadowing).

Transesophageal echocardiography (TEE) offers superior image quality because of a shorter distance between the transducer and the heart, the absence of interposed bone or lung, and the use of a higher-frequency trans-ducer. TEE usually is well tolerated, but intubation of the esophagus entails some risk, and most clinicians do this procedure with the patient under conscious sedation. TEE is much more sensitive than TTE for detection of left atrial thrombus (95% vs. 50%), valvular vegetations (99% vs. 60%), and prosthetic mitral valve regurgitation (Fig. 55-2).

TTE TEE

Aorta Left atrium

Acousticshadow

MVR

Aorta Left atrium

Acousticshadow

MVR

Left ventricleLeft ventricle

FIGURE 55-2.  The  problem  of  acoustic  shadowing  from  a  prosthetic mitral valve replacement (MVR). On the left, with transthoracic echocardiog-raphy  (TTE),  the  acoustic  shadow  distal  to  the  prosthetic  valve  obscures  the left atrium, limiting assessment of valve regurgitation by Doppler techniques. On  the  right,  with  transesophageal  echocardiography  (TEE),  the  left  atrium now can be evaluated for valvular regurgitation. However, the acoustic shadow now  obscures  the  left  ventricle.  (From  Otto  CM.  Textbook of Clinical Echocar-diography, 4th ed. Philadelphia: Elsevier Saunders; 2009:117, Fig. 5-9.)

CHAPTER  55  ECHOCARDIOGRAPHY 280

A B

FIGURE 55-3.  Poor-quality  apical  view  (A)  with  marked  improvement  in definition of the left ventricular cavity after opacification using contrast echo-cardiography (B). The dots  indicate the left ventricular endocardial tracing for calculation of ejection fraction. 

Bileaflet AVR

FIGURE 55-4.  Real-time  three-dimensional  transesophageal  echocardiographic imaging  of  a  bileaflet  aortic  valve  replacement  (AVR)  with  the  leaflets  open  during systole. The three-dimensional data set was cropped and rotated so that the viewer is looking at the valve from the aortic side.  (From Otto CM. Textbook of Clinical Echocardiog-raphy, 4th ed. Philadelphia: Elsevier Saunders; 2009:91, Fig. 4-3.)

Handheld echocardiography refers to the use of smaller, less expensive ultra-sound systems that can be carried by the physician, who can perform quick, limited examinations in the office or at the bedside. These laptop-sized echo-cardiography units range from the very simple, with only two-dimensional imaging and limited controls, to systems with high-quality imaging and all Doppler modalities. Handheld echocardiography does not replace a complete imaging study but can serve as an adjunct to the physical examination, par-ticularly in the acute care setting, such as to distinguish ventricular dilation from a pericardial effusion or to estimate ventricular systolic performance.

Contrast echocardiography may be performed using intravenous injection of agitated saline to opacify the right-sided heart chambers. These micro-bubbles are relatively large and do not pass through pulmonary capillaries. Therefore, appearance of contrast in the left side of the heart within one or two beats after right heart opacification is consistent with an intracardiac shunt. Although most atrial-level shunts are predominantly left-to-right shunts, a small amount of right-to-left shunting occurs, which is the basis of this approach.

Contrast echocardiography also may be performed with commercially available microbubbles in the range of 1 to 5 µm. Because these microbubbles are smaller than the pulmonary capillaries, right heart opacification is fol-lowed by left heart opacification, which can enhance the evaluation of systolic function when image quality is suboptimal, especially during stress echocar-diography (Fig. 55-3).

Three-dimensional echocardiography is increasingly available and is useful in some clinical settings, particularly for the evaluation of complex structural heart disease and for transcatheter interventions (Fig. 55-4).

Stress echocardiography is a standard approach for evaluating patients with known or suspected coronary artery disease; it has a sensitivity (85 to 95%) and a specificity (80 to 90%) similar to those of radionuclide stress imaging (Chapters 56 and 71). Myocardial infarction results in thinning and akinesis of the affected wall. However, in the absence of infarction, resting myocardial function is normal, even when severe epicardial coronary disease is present. The increased myocardial demand associated with exercise or pharmacologic stress leads to myocardial ischemia, which results in a regional wall motion abnormality, often before the onset of chest pain or electrocardiographic changes (Fig. 55-5).

In patients who can exercise, standard views of the left ventricle are recorded at baseline and immediately after maximal treadmill or bicycle exercise. If endocardial definition is suboptimal, left-sided contrast is used. The rest and exercise images are compared in a side-by-side cine loop format. Myocardial ischemia is present if resting wall motion is normal but hypokinesis or akinesis is seen after exercise. The pattern of regional wall motion accurately identifies the area of myocardium at risk and is reasonably reliable for identification of the affected coronary artery. With three-vessel coronary disease, rather than a regional wall motion abnormality, the only clue on imaging may be an absence of the expected decrease in chamber size at peak exercise, caused by diffuse ischemia. Interpretation of an exercise echocardiogram includes exer-cise duration, hemodynamic response, symptoms, and electrocardiographic changes, in addition to the echocardiographic images (see Fig. 55-5).

In patients who are unable to exercise, stress testing is performed using a graded intravenous infusion of dobutamine, beginning at 5 to 10 µg/kg/

minute and increasing every 3 minutes to a maximum dose of 40 µg/kg/minute. If needed, atropine is used to achieve 85% of the maximum predicted heart rate. In addition to evaluation for myocardial ischemia, dobutamine stress echocardiography can assess myocardial viability in areas of stunning or hibernation, based on an improvement in endocardial motion from base-line to low-dose dobutamine, with subsequent worsening of function at higher doses—the “biphasic” response.

Intracardiac echocardiography (ICE) is performed using an ultrasound probe on a catheter that is inserted into the right side of the heart through the femoral vein. ICE is used in the cardiac catheterization laboratory to guide percutaneous closure of a patent foramen ovale (PFO) and other pro-cedures. In the electrophysiology laboratory, ICE helps guide catheter posi-tioning and identify complications.

CARDIAC FUNCTION MEASUREMENTSIn addition to qualitative descriptions of cardiac anatomy and physiology, echocardiography provides precise and accurate quantitation of cardiac func-tion, including ventricular systolic and diastolic function, an estimate of the severity of valve stenosis and regurgitation, and a noninvasive estimate of pulmonary pressures.

Systolic Ventricular FunctionOverall LV systolic function is graded by visual estimation, with an approxi-mate correspondence to EF as follows: normal (EF > 55%), mildly reduced (EF, 40 to 55%), moderately reduced (EF, 20 to 40%), severely reduced (EF < 20%). More precise quantitation is performed when clinically indicated by calculation of a biplane ejection fraction. Cardiac output calculations are not routine but may be helpful for noninvasive monitoring of therapy in patients with heart failure. Because EF measurements are affected by preload and afterload, measures that are less dependent on loading conditions, including

CHAPTER  55  ECHOCARDIOGRAPHY  281

Resting Stress

AortaLeft atrium Left atrium

Leftventricle

Leftventricle

Aorta

FIGURE 55-5.  The concept of stress echocardiogra-phy  in  a  patient  with  70%  stenosis  in  the  proximal third of  the  left anterior descending  (LAD) coronary artery. At rest (left), endocardial motion and wall thick-ening are normal. After stress (right), either exercise or pharmacologic, the middle and apical segments of the anterior wall become ischemic, showing reduced endo-cardial  wall  motion  and  wall  thickening.  If  the  LAD extends  around  the  apex,  the  apical  segment  of  the posterior  wall  also  will  be  affected,  as  shown  here.  The normal segment of the posterior wall shows com-pensatory  hyperkinesis.  (From  Otto  CM.  Textbook of Clinical Echocardiography, 4th ed. Philadelphia: Elsevier Saunders; 2009:191, Fig. 8-9.)

the end-systolic dimension or volume, are generally preferred for clinical decision making in situations such as the timing of surgery for chronic valvu-lar regurgitation.

Diastolic Ventricular FunctionEvaluation of diastolic ventricular function is challenging because the pat-terns of ventricular filling are affected by preload, heart rate, and coexisting valvular regurgitation in addition to the diastolic properties of the ventricle. However, echocardiography can classify diastolic function based on the com-bination of LV inflow, pulmonary vein flow, tissue Doppler velocities, and the isovolumic relaxation time. An estimate of LV filling pressure (e.g., LV end-diastolic pressure) also can be inferred using these approaches.

Valvular StenosisEchocardiography is the clinical standard for evaluation of aortic valvular heart disease (see Fig. 75-1). Cardiac catheterization can be reserved for cases in which echocardiography is nondiagnostic, clinical data are discrepant with echocardiographic findings, or coronary anatomy needs to be assessed (Chapter 75).

In patients with aortic stenosis, the most direct measure of stenosis severity is the antegrade velocity across the valve, indicating mild (<3 m/second), moderate (3 to 4 m/second), or severe (>4 m/second) valve obstruction. The maximum and mean transaortic pressure gradients also can be calculated using the Bernoulli equation. Accurate evaluation depends on a careful exam-ination by an experienced echocardiographer.

Aortic valve area (AVA) is calculated using the continuity equation, based on the concept that volume flow rates proximal to and within the narrowed orifice are equal:

AVA VTI CSA VTIAS LVOT LVOT× = ×

or

AVA CSA VTI VTILVOT LVOT AS= ×( )

where LVOT = left ventricular outflow tract, VTI = velocity time integral, CSA = cross-sectional area, and AS = aortic stenosis (Fig. 55-6). It is especially important to calculate the AVA when LV systolic dysfunction accompanies aortic valve disease. In some patients, dobutamine stress echo-cardiography is helpful in distinguishing ventricular dysfunction caused by severe aortic stenosis from primary myocardial disease with concurrent mod-erate stenosis.

The evaluation of mitral stenosis (see Fig. 75-3) includes measurement of the mean transmitral gradient from the velocity curve and calculation of the valve area, both from two-dimensional planimetry of a short-axis image of the orifice and from the deceleration slope of the Doppler curve (pressure half-time method).

Valvular RegurgitationThe current approach to evaluating valvular regurgitation is based on the proximal geometry of the regurgitant jet, with measurement of the narrowest jet width (vena contracta; see Fig. 75-5). When further quantitation is

FIGURE 55-6.  In a patient with aortic stenosis, the aortic jet velocity is recorded with continuous  wave  Doppler  from  the  window  that  yields  the  highest  velocity  signal. Maximum velocity (Vmax)  is used to calculate the maximum systolic gradient. The Doppler curve is traced, as shown, to calculate the mean systolic gradient, using the Bernoulli equa-tion, by which the pressure gradient (ΔP) equals four times the square of the velocity. 

needed, regurgitant volume (RV), regurgitant fraction (RF), and regurgitant orifice area (ROA) are calculated. Although color flow visualization of the flow disturbance may be helpful for detection of regurgitation and for under-standing the mechanism of valve dysfunction, this approach should no longer be used to evaluate severity.

For aortic regurgitation, a narrow vena contracta (<3 mm) indicates mild regurgitation, whereas a wide vena contracta (>6 mm) indicates severe regur-gitation. Additional evaluation of the severity of aortic regurgitation is based on the presence of holodiastolic flow reversal in the abdominal aorta and the density and slope of the continuous wave Doppler velocity curve. The approach to evaluating mitral regurgitation (see Fig. 75-5) is similar, begin-ning with measurement of the vena contracta. In addition to calculation based on transmitral versus transaortic volume flow rates, the proximal accel-eration of flow into the regurgitant orifice allows evaluation with central regurgitant jets. Color flow shows a proximal isovelocity surface area (PISA).

Pulmonary PressuresEstimation of pulmonary artery systolic pressure (PAP) is a standard com-ponent of a complete examination. The systolic pressure difference between the right ventricle and right atrium is calculated from the peak velocity in the tricuspid regurgitant (VTR) jet, using the Bernoulli equation. Then, the right atrial pressure (RAP) is estimated from the size and appearance of the inferior vena cava. Because right ventricular and pulmonary artery systolic pressures are equal (in the absence of pulmonic stenosis),

PAP V RAPTR= ( ) +4 2

A small amount of tricuspid regurgitation is present in most patients, so pulmonary pressures can be estimated with this approach in more than 90%

CHAPTER  55  ECHOCARDIOGRAPHY 282

of patients. Because this approach measures only pulmonary systolic pres-sure, not pulmonary vascular resistance, invasive evaluation may still be needed in some clinical situations (Chapter 68).

THE ECHOCARDIOGRAPHIC EXAMINATIONClinical IndicationsEchocardiography is an effective approach to the initial evaluation of many cardiac signs and symptoms (Table 55-1). Even when transesophageal imaging might be helpful, most clinicians begin with a transthoracic

examination; exceptions are for the patient with a possible acute aortic dis-section (Chapter 78), in whom TEE should be performed as quickly as possible, and in the evaluation of possible left atrial thrombosis before car-dioversion without anticoagulation (Chapter 64). It is important to remem-ber that resting echocardiography is not helpful for diagnosis of coronary artery disease; stress imaging is needed if this diagnosis is suspected (Chapter 71). In patients with known cardiac disease, echocardiography is used to evaluate severity, assess the results of medical and surgical interven-tions, and guide procedures (Table 55-2).

TABLE 55-1  COMMON SYMPTOMS AND SIGNS EVALUATED BY ECHOCARDIOGRAPHYREASON FOR ECHOCARDIOGRAPHY

POSSIBLE ECHOCARDIOGRAPHIC FINDINGS OR DIAGNOSIS

Chest pain Coronary artery disease Acute myocardial infarction on resting

echocardiography Stress echocardiography needed to detect coronary

diseaseAortic dissectionPericarditisValvular aortic stenosisHypertrophic cardiomyopathy

Heart failure Left ventricular systolic dysfunction (global or segmental)

Valvular heart diseaseLeft ventricular diastolic dysfunctionPericardial diseaseRight ventricular dysfunction

Palpitations Left ventricular systolic dysfunctionMitral valve diseaseCongenital heart disease (e.g., ASD, Ebstein’s anomaly)PericarditisNo structural cardiac disease

REASON FOR ECHOCARDIOGRAPHY

POSSIBLE ECHOCARDIOGRAPHIC FINDINGS OR DIAGNOSIS

Cardiac murmur Flow murmur (no valve abnormality) Systolic Aortic stenosis—valvular or subaortic

Hypertrophic cardiomyopathyMitral regurgitationVentricular septal defectPulmonic stenosisTricuspid regurgitation

Diastolic Mitral stenosisAortic regurgitationPulmonic regurgitationTricuspid stenosis

Cardiomegaly on chest radiography

Pericardial effusionDilated cardiomyopathySpecific chamber enlargement (e.g., left ventricle in

chronic aortic regurgitation)

Systemic embolic event Left ventricular systolic function and segmental wall motion abnormalities (aneurysms)

Left ventricular thrombusAortic valve diseaseMitral valve diseaseLeft atrial thrombus (TTE has low sensitivity, TEE

required)Atrial septal defect or patent foramen ovale

ASD = atrial septal defect; TEE = transesophageal echocardiography; TTE = transthoracic echocardiography.From Otto CM. Textbook of Clinical Echocardiography, 4th ed. Philadelphia: Elsevier Saunders; 2009:114-115, Tables 5-1 and 5-2.

TABLE 55-2  INDICATIONS FOR ECHOCARDIOGRAPHY BY KNOWN DIAGNOSISCLINICAL DIAGNOSIS KEY ECHOCARDIOGRAPHIC FINDINGS LIMITATIONS OF ECHOCARDIOGRAPHY ALTERNATIVE APPROACHESVALVULAR HEART DISEASE (CHAPTER 75)

Valve stenosis Etiology of stenosis, valve anatomy Possible underestimation of the severity of stenosis Cardiac catheterization; MRITransvalvular ΔP, valve area Possible coexisting coronary artery diseaseChamber enlargement and hypertrophyLV and RV systolic functionAssociated valvular regurgitation

Valve regurgitation Mechanism and etiology of regurgitation TEE may be needed to evaluate mitral regurgitant severity and valve anatomy (especially before MV repair)

Cardiac catheterization; MRISeverity of regurgitationChamber enlargementLV and RV systolic functionPA pressure estimate

Prosthetic valve function Evidence for stenosisDetection of regurgitationChamber enlargementVentricular functionPA pressure estimate

Imaging of prosthetic valves is limited by shadowing and reverberations

Cardiac catheterization

TEE is needed for suspected prosthetic MR due to “masking” of the LA on TTE

Endocarditis (Chapter 76) Detection of vegetations (TTE sensitivity 70-85%)

Presence and degree of valve dysfunctionChamber enlargement and functionDetection of abscessPossible prognostic implications

TEE more sensitive for detection of vegetations (>90%)

A definite diagnosis of endocarditis also depends on bacteriologic criteria

TEE more sensitive for detecting an abscess

Blood cultures and clinical findings also are diagnostic criteria for endocarditis

CHAPTER  55  ECHOCARDIOGRAPHY  283

TABLE 55-2  INDICATIONS FOR ECHOCARDIOGRAPHY BY KNOWN DIAGNOSIS—cont’dCLINICAL DIAGNOSIS KEY ECHOCARDIOGRAPHIC FINDINGS LIMITATIONS OF ECHOCARDIOGRAPHY ALTERNATIVE APPROACHESCORONARY ARTERY DISEASEAcute myocardial infarction

(Chapters 72 and 73)Segmental wall motion abnormality reflects

“myocardium at risk”Coronary artery anatomy itself is not directly

visualizedCoronary angiographyRadionuclide LV angiographyCardiac catheterizationGlobal LV function (EF)

Complications: Acute MR vs. VSD Pericarditis LV thrombus, aneurysm RV infarct

Angina (Chapter 71) Global and segmental LV systolic function Resting wall motion may be normal despite significant CAD

Coronary angiographyExclude other causes of angina (e.g., AS,

HOCM)Stress thallium ETT

Stress echocardiography is needed to induce ischemia and wall motion abnormality

Pre-revascularization/post-revascularization

Assess wall thickening and endocardial motion at baseline

Improvement in segmental function after procedure

Dobutamine stress and/or contrast echocardiography is needed to detect viable but nonfunctioning myocardium

MRIPETThallium ETTContrast echocardiography

End-stage ischemic disease Overall LV systolic function (EF) — Coronary angiographyPA pressures Radionuclide EFAssociated MRLV thrombusRV systolic function

CARDIOMYOPATHY (CHAPTERS 58-60)

Dilated Chamber dilation (all four) Indirect measures of LVEDP Radionuclide EFLV and RV systolic function (qualitative and

EF)Accurate EF may be difficult if image quality is poor LV and RV angiography

Coexisting atrioventricular valve regurgitationPA systolic pressureLV thrombus

Restrictive LV wall thickness Must be distinguished from constrictive pericarditis Cardiac catheterization with direct, simultaneous RV and LV pressure measurement after volume loading

LV systolic functionLV diastolic functionPA systolic pressure

Hypertrophic Pattern and extent of LV hypertrophy — —Dynamic LVOT obstruction (imaging and

Doppler)Coexisting MRDiastolic LV dysfunction

Hypertension (Chapter 67) LV wall thickness and chamber dimensions — —LV massLV systolic functionAortic root dilation

PERICARDIAL DISEASE (CHAPTER 77)

Pericardial thickening Diagnosis of tamponade is a hemodynamic and clinical diagnosis

Intracardiac pressure measurements for tamponade or constrictionDetection, size, and location of PE

2D signs of tamponade physiologyDoppler signs of tamponade physiology

Constrictive pericarditis is a difficult diagnosisNot all patients with pericarditis have an effusion

MRI or CT to detect pericardial thickening

DISEASES OF THE AORTA (CHAPTER 78)

Aortic root dilation Etiology of aortic dilation — CT, MRI, aortographyAccurate aortic root diameter measurementsAnatomy of sinuses of Valsalva (especially

Marfan syndrome)Associated aortic regurgitation

Aortic dissection 2D images of ascending aorta, aortic arch, descending thoracic and proximal abdominal aorta

TEE more sensitive (97%) and more specific (100%)Cannot assess distal vascular beds

AortographyCTMRITEEImaging of dissection “flap”

Associated aortic regurgitationVentricular function

CARDIAC MASSES (CHAPTER 60)

LV thrombus High sensitivity and specificity for diagnosis of LV thrombus

Technical artifacts can be misleading5-MHz or higher frequency transducer and angulated

apical views neededTEE is needed to detect LA thrombus reliably

LV thrombus may not be recognized on radionuclide or contrast angiography

Suspect with apical wall motion abnormality or diffuse LV systolic dysfunction

LA thrombus Low sensitivity for detection of LA thrombus, although specificity is high

— TEE

Suspect with LA enlargement, MV disease

TABLE 55-2  INDICATIONS FOR ECHOCARDIOGRAPHY BY KNOWN DIAGNOSIS—cont’dCLINICAL DIAGNOSIS KEY ECHOCARDIOGRAPHIC FINDINGS LIMITATIONS OF ECHOCARDIOGRAPHY ALTERNATIVE APPROACHESCardiac tumors Size, location, and physiologic consequences of

tumor massExtracardiac involvement is not well seenCannot distinguish benign from malignant tumor or

tumor from thrombus

TEECTMRI (with cardiac gating)Intracardiac echocardiography

PULMONARY HYPERTENSION (CHAPTER 68)

Estimate of PA pressure Indirect PA pressure measurement Cardiac catheterizationEvidence of left-sided heart disease to account

for increased PA pressuresCannot determine pulmonary vascular resistance

accuratelyRV size and systolic function (cor pulmonale)Associated TR

 CONGENITAL HEART DISEASE (CHAPTER 69)

Detection and assessment of anatomic abnormalities

Quantitation of physiologic abnormalitiesChamber enlargementVentricular function

No direct intracardiac pressure measurementsComplicated anatomy may be difficult to evaluate if

image quality is poor (TEE is helpful)

MRI with 3D reconstructionCardiac catheterizationTEE

2D = two-dimensional; 3D = three-dimensional; AS = aortic stenosis; CAD = coronary artery disease; CT = computed tomography; EF = ejection fraction; ETT = exercise treadmill test; HCM = hypertrophic cardiomyopathy; LA = left atrial; LV = left ventricular; LVEDP = left ventricular end-diastolic pressure; LVOT = left ventricular outflow tract; MR = mitral regurgitation; MRI = magnetic resonance imaging; MV = mitral valve; ΔP = pressure gradient; PA = pulmonary artery; PE = pericardial effusion; PET = positron emission tomography; RV = right ventricular; TEE = transesophageal echocardiography; TR = tricuspid regurgitation; TTE = transthoracic echocardiography; VSD = ventricular septal defect.From Otto CM. Textbook of Clinical Echocardiography, 4th ed. Philadelphia: Elsevier Saunders; 2009:475-478.

Normal FindingsTrace to mild regurgitation is considered “physiologic” and is seen with 70 to 80% of mitral valves, 80 to 90% of tricuspid valves, and 70 to 80% of pul-monic valves in normal individuals. The prevalence of aortic regurgitation increases with age, but it is found in only 5% of young normal adults; the presence of aortic regurgitation raises the possibility of subtle aortic valve or root abnormalities.

A PFO (Chapter 69) is present in 25 to 35% of normal individuals and may be identified by color Doppler or by contrast echocardiography. Use of the Valsalva maneuver enhances identification of a PFO because the slight eleva-tion in right atrial pressure may lead to a brief right-to-left shunt. The signifi-cance of a PFO in patients without clinical events is unclear. Other common anatomic variants seen on echocardiography include aberrant chords (or “webs”) in the left ventricle; small, linear, mobile echoes associated with the valves (Lambl’s excrescences); and normal ridges in the left and right atrium.

Unexpected abnormal findings also may be found on studies requested for other indications. A bicuspid aortic valve is present in 1 to 2% of the popula-tion; most of these patients are asymptomatic until late in life, so many cases are diagnosed “incidentally” by echocardiography. Aortic valve sclerosis, which is a frequent unexpected echocardiographic diagnosis, is a marker of cardiovascular disease and an increased risk of myocardial infarction even if valve function is normal.

INTEGRATING THE ECHOCARDIOGRAPHIC AND CLINICAL FINDINGS

The echocardiographic request should indicate the specific reason for the study and any relevant symptoms or signs. The echocardiographic examina-tion then can be tailored to answer the clinical question. The echocardio-graphic results should be interpreted in conjunction with other clinical data. If the echocardiographic data seem discrepant with the clinical data, the requesting physician should review the images with the echocardiographer to identify areas of uncertainty and to determine the next best diagnostic step.

SUGGESTED READINGS

Melamed R, Sprenkle MD, Ulstad VK, et al. Assessment of left ventricular function by intensivists using hand-held echocardiography. Chest. 2009;135:1416-1420. A small bedside diagnostic ultrasound imaging system can allow intensivists, after a short training period, to estimate left ventricular systolic function.

Mitiku TY, Heidenreich PA. A small pericardial effusion is a marker of increased mortality. Am Heart J. 2011;161:152-157. Even a small asymptomatic pericardial effusion is associated with a 17% increased mortality after adjustment for other clinical factors.

Pepi M, Evangelista A, Nihoyannopoulos P, et al. Recommendations for echocardiography use in the diagnosis and management of cardiac sources of embolism: European Association of Echocardiog-raphy (EAE) (a registered branch of the ESC). Eur J Echocardiogr. 2010;11:461-476. Consensus guidelines.