Myocardial Pathology

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13 Myocardial Pathology

David S. Owens, Mariska Kemna

Hypertrophic Cardiomyopathy

Background

• Hypertrophic cardiomyopathy (HCM) is characterized by pathologic thickening of the left ventricle (LV) due to sarcomeric gene mutations.

• HCM commonly involves asymmetrical hypertrophy of the anterior septum, but can manifest as concentric hypertrophy or hypertrophy of other segments (Figs. 13-1 through 13-3).

• Resting left ventricular outflow tract obstruction (LVOTO) due to systolic anterior motion of the mitral apparatus is present in about one third of HCM patients; another one third has provocable obstruction.

• The presence of LVOTO is neither necessary nor sufficient to diagnose HCM.

• A diagnosis of HCM is suggested by wall thickness greater than 1.5 cm in adults or a Z score indexed to body surface area of more than 2 in children (in the absence of other causes for hypertrophy).

• Structural or valvular abnormalities that increase left ventricular afterload (e.g., aortic stenosis, coarctation of the aorta) need to be excluded before a diagnosis of HCM can be made.

• Other conditions that mimic HCM include hypertensive heart disease, infiltrative disorders (e.g., amyloidosis), and glycogen storage disorders (e.g., Fabry disease, Danon disease, PRKAG2 mutations).

• In infants, 30% to 50% of cases of an HCM-like phenotype can be attributed to metabolic or syndromal disorders (e.g., Noonan syndrome). Infants born to diabetic mothers can have transient biventricular hypertrophy.

• Physiologic adaptation to exercise can lead to mild to moderate ventricular hypertrophy, which can mimic HCM. Features distinguishing “athlete’s heart” from HCM are shown in Table 13-1.

• Massive left ventricular hypertrophy (LVH)—wall thickness greater than 30 mm in adults or a Z score for body surface area greater than +15 in children—is a risk factor for sudden death in HCM patients.

Figure 13-1 Parasternal long axis and short axis two-dimensional images of a patient with classic reverse curvature hypertrophic cardiomyopathy (HCM) and primary involvement of the basal anterior septum. Measurement of maximal wall thickness is performed at the greatest diameter, excluding right ventricular band insertion.

Figure 13-2 Apical four-chamber (4C) view of a patient with mid-ventricular HCM demonstrating mid-ventricular and papillary muscle hypertrophy and secondary apical aneurysm formation due to midventricular obstruction.

Figure 13-3 Apical 4C echocardiographic (left) and cardiac magnetic resonance imaging (MRI) (right) views of a patient with apical HCM. Cardiac MRI can provide a good depiction of apical thickness and function when echocardiographic imaging is inadequate.

TABLE 13-1 FEATURES DISTINGUISHING “ATHLETE’S HEART” FROM HCM IN ADULTS *

Feature	Athlete’s Heart	HCM
Maximal wall thickness	≤16 mm	≥13 mm
Pattern of LVH	Predominantly concentric	Concentric or asymmetrical
LV cavity dimension	Often > 55 mm (in endurance athletes)	Usually < 45 mm
Diastolic function	Normal	Normal or abnormal
Gender	Male > female	Male = female
Family history of HCM or SCD	No	Yes or no
Delayed enhancement (MRI)	No	Yes or no
Exercise capacity	Above normal	Normal to below normal
Response to deconditioning	LVH regression	No change in LVH

* Intended for adults or adult-sized teenagers. Corresponding Z scores can be calculated for children but have not been validated.

Echocardiographic Approach (Table 13-2)

Anatomic Imaging

• Step 1: Assess the magnitude and extent of LVH.

• Whenever possible, wall thickness measurements should be confirmed in more than one imaging plane (see Fig. 13-1).

• Short axis view imaging of the LV at multiple levels usually provides the best means of assessing wall thickness and overall hypertrophy.

• The right ventricular moderator band and papillary muscle insertions should not be included in wall thickness measurements. The parasternal long axis view is most susceptible to mismeasurement.

• Apical windows may be more suited to estimating LV wall thickness of the inferior septum and lateral wall, common regions of dropout on short axis view imaging.

• Use of contrast agents can improve endocardial border detection in patients with suspected midcavitary or apical hypertrophy.

• Step 2: Quantify systolic function.

• HCM patients often have an increase in circumferential shortening, but a decrease in longitudinal shortening.

• Hyperdynamic systolic function is also commonly seen in hypertensive heart disease or situations of decreased afterload.

• A small subset (∼5%) of HCM patients have declining LV systolic function due to progressive fibrosis.

• Step 3: Assess mitral leaflet motion for possible systolic anterior motion (SAM).

• SAM is best viewed in either the parasternal or apical long axis windows (Fig. 13-4).

• M-mode depiction of mitral leaflet motion is essential for determining the timing of SAM and the duration of mitral-septal contract (Fig. 13-5).

• The presence of LVOTO in the absence of SAM suggests fixed subaortic stenosis, and additional causes of obstruction should be sought.

• Early closure of the aortic valve (AV) on M-mode echocardiography (echo) is a nonspecific finding that may be present with either fixed or dynamic LVOTO.

• Step 4: If significant SAM is present, assess mitral leaflets and subvalvular anatomy.

• HCM can be associated with abnormalities in papillary muscle anatomy.

• Features that predispose to LVOTO include elongated mitral leaflets, chordal slack, direct insertion of the papillary muscle into the mitral leaflets, septal chordal attachments, and anteriorly or apically displaced papillary muscles.

TABLE 13-2 ECHOCARDIOGRAPHIC FEATURES OF CARDIOMYOPATHIES

Figure 13-4 Apical long axis view of a patient with outflow tract obstruction due to systolic anterior motion of the mitral valve (MV) leaflets.

Figure 13-5 M-mode at the level of the MV tips showing septal hypertrophy and systolic anterior motion of the mitral apparatus in a patient with HCM.

Physiologic Data

• Step 1: Assess the presence and severity of intracardiac obstruction.

• Obstruction can occur at either the midventricular or left ventricular outflow tract (LVOT) level.

• Midventricular obstruction predisposes to apical aneurysm formation and scarring; contrast agents should be considered if the apex is not well visualized.

• Changes in left ventricular geometry can alter intracardiac flow patterns, dragging the mitral leaflets anteriorly into the LVOT.

• Anterior movement of the tips of the mitral leaflets may result in a loss of coaptation and posteriorly directed mitral regurgitation (MR).

• This LVOTO is a complex, dynamic process that is affected by LV contractility, loading conditions, and both mitral leaflet and subvalvular anatomy.

• Step 2: Measure the velocity of blood flow down the length of the LV using pulsed wave (PW) Doppler.

• Marching the PW Doppler sample from apex to base allows localization of the site of obstruction.

• Anterior displacement of the mitral leaflets causes associated MR to originate more anteriorly, and thus care must be taken to differentiate LVOT flow from regurgitation flow.

• Resting LVOT velocities greater than 5 m/s are uncommon and should be confirmed by finding a separate, even higher velocity (>7 m/s) mitral regurgitant jet.

• Dynamic obstruction may produce a characteristic dagger-shaped, late-peaking Doppler waveform (Fig. 13-6A); however, complete LVOTO may produce a characteristic “lobster claw” appearance (Fig. 13-6B).

• Step 3: Assess changes in LVOT velocity with provocation in adults and older children.

• Perform in patients with known or suspected HCM without resting LVOTO.

• Provocation can unmask resting LVOT gradients; patients with provocable LVOTO are more likely to have exercise-induced obstruction.

• Common provocative factors include Valsalva maneuver, pharmacologic agents (amyl nitrate or isoproterenol), and exercise.

• Step 4: Assess MR.

• MR can be difficult to quantify because of its timing (originating in mid to late systole) and eccentricity, making proximal isovelocity surface area (PISA) calculations less reliable.

• If the mitral regurgitant jet is not posteriorly directed, other etiologies for the MR should be suspected.

• Step 5: Assess diastolic function.

• Assessment of diastolic function in HCM patients is challenging due to asymmetrical hypertrophy and changes in calcium kinetics.

• Because of the asymmetrical hypertrophy, mitral annular relaxation velocities should be sampled from the septal, lateral, anterior, and inferior aspects of the annulus, with an average velocity used to assess global diastolic function.

• The ratio of mitral inflow velocity deceleration (E wave) to early mitral annular relaxation (E′) velocity is not as robust a predictor of filling pressure as in other conditions.

• Abnormalities in diastolic relaxation can precede the development of hypertrophy in patients carrying otherwise subclinical sarcomeric gene mutations (Fig. 13-7).

• Step 6: Assess consequences of HCM.

• Assess left atrial enlargement.

• Assess pulmonary artery pressures (PAPs).

• Assess right ventricular function and hypertrophy.

Figure 13-6 Complete LVOTO may result in a “lobster claw” appearance of the pulsed wave (PW) Doppler (A); more commonly, a characteristic dagger-shaped, late-peaking continuous wave (CW) Doppler signal is seen (B).

Figure 13-7 Septal mitral annular tissue Doppler sample in a carrier of a known HCM gene mutation before the development of left ventricular hypertrophy (LVH). In this patient, the myocardial early relaxation velocity is markedly decreased.

Alternate Approaches

• Exercise echo is particularly useful in evaluating patients with suspected exercise-induced LVOTO.

• Cardiac magnetic resonance imaging (MRI) is useful for determining maximal wall thickness, and the use of delayed gadolinium enhancement can provide assessment of the extent of fibrosis.

• Consider the use of contrast agents for better visualization of the left ventricular apex in patients with midcavitary obstruction.

• 3D TEE can aid in the assessment of subvalvular architecture and the location of intracardiac obstruction.

Key Points

• HCM can present with asymmetric hypertrophy of any cardiac segment, and may also manifest as concentric hypertrophy.

• The presence of LVOTO is neither necessary nor sufficient to diagnose HCM.

• When LVOTO is present, care must be taken to differentiate the LVOT Doppler signal from MR.

• Abnormalities in mitral valve and papillary muscle anatomy are common in HCM and can predispose to LVOTO.

Dilated Cardiomyopathy

Background

• Dilated cardiomyopathy (DCM) is characterized by spherical enlargement of the LV with reduction in global systolic function. Four-chamber enlargement and dysfunction are often present (Fig. 13-8).

• Echo is an essential component of diagnosing and managing patients with DCM.

• DCM is often classified as ischemic (due to coronary artery disease) or nonischemic, based on the presence or absence of myocardial ischemia or infarction. Potential causes of DCM are listed in Table 13-3.

• Most cases of primary DCM in children are idiopathic, but a positive family history is present in 30% of cases, suggesting a genetic component.

• Anomalous origin of the left coronary artery from the pulmonary artery (ALCAPA) can present with DCM in the first weeks of life due to decreasing PAP and resultant myocardial ischemia.

• Chamber enlargement can lead to annular dilation and leaflet tethering of the semilunar valves, causing secondary (functional) valve regurgitation.

• In contrast, a primary valvular cardiomyopathy (CM) should be suspected when significant aortic regurgitation (AR) is present in the setting of DCM.

• Diastolic dysfunction is commonly present in patients with impaired systolic function, with increase in LV filling pressures.

• Important sequelae of DCM include atrial enlargement, pulmonary hypertension, ventricular aneurysm formation, and intracardiac thrombosis.

Figure 13-8 Apical 4C image of a dilated cardiomyopathy (DCM) showing globular 4C enlargement.

TABLE 13-3 CONGENITAL AND ACQUIRED CAUSES OF DCM PRESENTING IN CHILDREN AND ADULTS

Children	Adults
Congenital Familial/genetic Neuromuscular disorders Inborn errors of metabolism Left-sided stenotic lesions Coronary anomalies (e.g., ALCAPA) Malformation syndromes Acquired Myocarditis Infectious (viral, HIV) Medications (anthracyclines) Tachycardia mediated High output (chronic anemia, shunts) Idiopathic

Congenital

Familial/genetic

Neuromuscular

Idiopathic

Echocardiographic Approach (See Table 13-2)

Anatomic Imaging

• Step 1: Assess LV size and anatomy.

• A single left ventricular dimension, standardly taken from the parasternal long axis or short axis views at the level of the MV tips, using M-mode or 2D measurements, is a reasonable first estimate of left ventricular chamber size.

• Left ventricular volume measurements give more accurate assessments of cavity size and can be estimated using 2D formulae or 3D methods.

• Left ventricular dimensions and volumes should be indexed to body surface area in children and in adults when body size is particularly large or small.

• Stress-induced (takotsubo) CM demonstrates a characteristic pattern of apical ballooning.

• Step 2: Assess left ventricular systolic function.

• Assessment of left ventricular function should focus on both global and regional wall motion; regional wall motion abnormalities (RWMAs) suggest the presence of coronary artery disease (Fig. 13-9).

• Global systolic function is estimated using either fractional shortening or ejection fraction (EF) calculations.

• Volumetric methods for estimating EF are more robust than those based on 2D measures, which make assumptions of chamber geometry.

• The presence of RWMAs can suggest fibrosis, previous myocardial infarction, or regions of hibernating myocardium.

• Use of intravenous contrast agent can improve wall motion assessment through improved endocardial border definition.

• Patients with left ventricular dysfunction and alterations in ventricular conduction may demonstrate dyssynchronous ventricular contraction, wherein wall segments contact at slightly different times.

• Another good measure of global left ventricular contractility includes mitral regurgitant dP/dt (rate of change in pressure over time).

• Step 3: Evaluate the presence of aneurysms and intracardiac thrombi.

• In patients with previous transmural myocardial infarctions or fibrosis, aneurysms can develop, most commonly seen in the left ventricular apex.

• In patients with aneurysms or reduced systolic function, intracardiac thrombi can develop, especially in regions of aneurysm formation (Fig. 13-10).

• Scanning for apical aneurysms is best performed using a slow anterior-to-posterior sweep with 4- to 8-s digital capture.

• If aneurysms or thrombi are suspected but image quality is suboptimal, consider the use of intravenous contrast.

• Step 4: Evaluate valve anatomy.

• Ventricular chamber enlargement can distort the geometry of the MV and tricuspid valve (TV), resulting in annular dilation and leaflet tethering (Fig. 13-11).

• Severe annular dilation can result in failure of leaflet coaptation, which suggests the presence of severe regurgitation.

• AR is not an expected sequela of DCM, and a primary valvular CM should be suspected when significant AR is present.

• Step 5: Exclude anatomic causes for DCM.

• If intrinsic abnormalities of MV or TV anatomy are detected, a primary valvular etiology for the DCM should be considered.

• Severe left-sided obstructive lesions, including AV stenosis and coarctation (see Chapter 12), can occasionally result in DCM and should also be excluded.

• ALCAPA (see Chapter 12, Left Heart Anomalies) may present as DCM within the first few weeks of life. Retrograde flow within the left main coronary artery is best detected using PW Doppler from the parasternal long axis or short axis view.

Figure 13-9 Apical 4C images in diastole (left) and systole (right) of a patient with DCM and apical aneurysm secondary to Danon disease (i.e., LAMP2 gene mutation).

Figure 13-10 Contrast-enhanced apical 4C image showing a thrombus (arrow) within the left ventricular apex of a patient with apical akinesis.

Figure 13-11 Zoomed parasternal long axis view of a patient with DCM and severe functional mitral regurgitation (MR) due to mitral annular dilation and limited coaptation of the mitral leaflets.

Physiologic Data

• Step 1: Assess valvular function.

• Standard methods for assessing valvular function, using continuous wave (CW) Doppler, PW Doppler, and color Doppler, are appropriate.

• Quantification of valvular regurgitation, using the PISA or flow volume at two sites method, is particular useful in DCM.

• Functional MR or tricuspid regurgitation (TR) can improve or worsen with changes in patient’s volume status.

• Step 2: Assess left ventricular diastolic function (Fig. 13-12).

• Patients with significant systolic dysfunction will also have alterations in diastolic function. Estimation of left ventricular filling pressures is particularly useful in the management of patients with DCM.

• When RWMAs are present, mitral annular velocities should be sampled from the most unaffected regions.

• Parameters useful for assessment of diastolic function include transmitral flow velocities, the transmitral E/A ratio, the E-wave deceleration time, the isovolumic relaxation time (IVRT), tissue Doppler E′ velocities and the E/E′ ratio, and pulmonary vein flow patterns.

• Diastolic filling patterns may change with changes in the patient’s volume status.

Figure 13-12 Assessment of diastolic function. Diagram comparing typical Doppler findings in patients with normal, mild, moderate, and severe diastolic dysfunction. Top row: Left ventricular inflow with early (E) and atrial (A) phases of diastolic filling. Second row: Tissue Doppler recorded at the septal side of the mitral annulus with the myocardial early (E′) and atrial (A′) velocities and the expected ratio of E/E′. Third row: Isovolumic relaxation time (IVRT). Bottom row: Pulmonary venous inflow pattern with systolic (S) and diastolic (D) antegrade flow and the pulmonary vein atrial (PV_a) reversal of flow.

(From Otto C. Textbook of Clinical Echocardiography, 4th ed. Philadelphia: Saunders/Elsevier, 2009; Figure 7-28.)

Alternate Approaches

• Dobutamine stress echo can be useful for assessing myocardial viability in patients with RWMAs and reduced systolic function.

• Strain and strain rate echocardiographic imaging can be adjunctive in the assessment of global and regional systolic function.

• 3D transthoracic echo may provide more reliable volumetric assessments of the EF, but may be time-consuming for standard use.

• Several methods for quantifying left ventricular dyssynchrony using strain rate and 3D imaging are available, but the best predictors of a response to cardiac resynchronization therapy have not been established.

• Cardiac MRI can provide global and regional assessments of left ventricular function, and the use of delayed gadolinium enhancement can define the location and extent of scarring and viability.

Key Points

• DCM is characterized by spherical enlargement of the LV with reduction in global systolic function; causes of DCM are varied.

• Echocardiographic assessment of systolic and diastolic function plays a key role in the diagnosis and management of patients with DCM.

• When significant regurgitation of the semilunar valves is present, careful interrogation of the valves is required to distinguish a primary valvular etiology from secondary functional regurgitation.

• When systolic function is severely decreased or aneurysms are present, it is important to exclude thrombus formation within the ventricle.

Left Ventricular Noncompaction

Background

• Left ventricular noncompaction (LVN) is a rare disorder characterized by alteration in myocardial wall development, resulting in a thinned compact myocardial layer, prominent left ventricular trabeculations, and deep intertrabecular recesses (Fig. 13-13).

• Echo plays a critical role in identifying and diagnosing LVN.

• Several different sets of diagnostic criteria for LVN exist. Common echocardiographic findings include

• More than three prominent trabeculations protruding from the left ventricular apex or midcavity (distinct from papillary muscles).

• Greater than 2:1 ratio in thickness of noncompacted epicardial trabeculations to thickness of compact endocardium, measured at end-systole.

• Evidence of flow within the deep intertrabecular recesses.

• Although noncompaction can occur as an isolated finding (isolated LVN), it can also be seen in conjunction with other neuromuscular or congenital heart abnormalities.

• There is considerable genotypic and phenotypic overlap between LVN and dilated, hypertrophic (particularly the apical variant), and restrictive cardiomyopathies.

• Patients with LVN often have progressive left ventricular systolic dysfunction and dilation.

• Additional clinical complications of LVN include atrial and ventricular tachyarrhythmias, sudden cardiac death, and thromboembolic complications including strokes, with the intertrabecular spaces likely serving as a nidus of thrombus formation.

Figure 13-13 An apical 2C view showing left ventricular noncompaction characterized by prominent trabeculations along the inferior wall and apex. Color flow Doppler demonstrates flow within the intertrabecular recesses, differentiating this from HCM.

Echocardiographic Approach (See Table 13-2)

Anatomic Imaging

• Step 1: Assess left ventricular morphology and function.

• Trabeculations are often best visualized from the apical windows and should be distinguished from the hypertrophy of the apical compact myocardium seen in HCM.

• Use of intravenous contrast can help distinguish trabeculations (which are not generally visible with contrast) from compact myocardium.

• Because DCM is common in LVN, standard assessment of left ventricular size and function is appropriate.

• Trabecular microthrombosis is a common source of emboli in patients with LVN; screening for left ventricular thrombi, using contrast enhancement when appropriate, should be standard.

• Step 2: Screen for associated congenital abnormalities.

• An array of congenital heart abnormalities have been described as being coincident with LVN, including coronary anomalies and coronary-cameral fistulae, atrial septal defects (ASDs), ventricular septal defects (VSDs), bicuspid AVs, and Ebstein’s anomaly.

• Coronary ostia can usually be identified in young patients from the parasternal short axis view, although this is more challenging in older individuals.

• Screening for ASDs or VSDs is appropriate; consider use of saline solution contrast injections to screen for shunting.

Physiologic Imaging

• Step 1: Demonstration of flow in trabecular recesses.

• Color Doppler should be used to demonstrate flow within the trabecular recesses, confirming that this layer is loosely organized. Because flow in the recesses is slow, adjustments to the color scale and Nyquist limits may be required.

• If intertrabecular flow is not seen, alternative diagnoses should be considered.

• Step 2: Standard assessment of ventricular and valvular function (as described in the DCM section).

Alternate Approaches

• Cardiac MRI can be performed to help distinguish compact myocardium from trabeculation when the diagnosis of LVN is uncertain; separate MRI criteria for LVN have been proposed.

Key Points

• LVN is caused by alteration in myocardial wall development, and results in a thinned compact myocardial layer, prominent left ventricular trabeculations, and deep intertrabecular recesses.

• LVN can mimic DCM and apical HCM echocardiographically.

• Demonstration of flow within the intertrabecular recesses distinguishes LVN from apical HCM.

• Thrombi formation within the intertrabecular recesses can be a source of strokes and other embolic events in patients with LVN.

Restrictive Cardiomyopathy

Background

• Restrictive cardiomyopathy (RCM) is characterized by a nondilated LV with significant impairment in diastolic filling due primarily to abnormalities in myocardial compliance.

• Wall thickness in RCM can be normal or concentrically hypertrophied; left ventricular function is usually preserved but can be decreased in late-stage disease.

• Causes of RCM are varied and include infiltrative disorders (e.g., amyloidosis, sarcoidosis), storage disease (e.g., hemochromotosis, Fabry disease), endomyocardial fibrosis, hypereosinophilic syndrome, endomyocardial fibroelastosis, radiation exposure, or an underlying gene mutation. In children, RCM is most commonly idiopathic.

• RCM must be distinguished from constrictive pericarditis in which normal myocardium is constricted by a noncompliant pericardium, resulting in elevated filling pressures.

• Echo can suggest a diagnosis of RCM, but is not conclusive. RCM diagnosis is usually based on multimodality imaging, invasive hemodynamic testing, and possible pathologic examination of biopsy specimens.

• Myocardial tissue may appear echobright (e.g., a “starry sky” appearance with amyloidosis [Fig. 13-14]), or there may be a hyperechoic endocardial layer (e.g., in Fabry disease [Fig. 13-15]). These findings are suggestive, but not pathognomonic for RCM.

• Additional echocardiographic findings supporting a diagnosis of RCM include significant biatrial enlargement and elevated PAPs.

• Restrictive diastolic filling patterns can also be seen in patients with DCM and significant volume overload; these are not classified as RCM.

Figure 13-14 Apical 4C views of an adult with restrictive cardiomyopathy (RCM) (left) due to systemic amyloidosis demonstrating concentric LVH, a general increase in the echogenicity of the myocardium, severe biatrial enlargement, and mild thickening of the mitral leaflets. In children, RCM may give an “ice cream cone” appearance (right) with massive atrial enlargement with preserved ventricular size.

Figure 13-15 Apical 4C view of a patient with Fabry disease showing concentric LVH and increased echogenicity of the endocardium due to glycosphingolipid accumulation.

Echocardiographic Approach (See Table 13-2)

Anatomic Imaging

• Step 1: Assess chamber morphology and function.

• Standard assessment of left ventricular size and function is appropriate in patients with known or suspected RCM.

• Although echocardiographic findings may vary in each condition, common features of RCM include a small or nondilated LV with preserved systolic function but significant elevation in left ventricular filling pressures.

• Wall thickness is often concentrically hypertrophied but can be normal; when LVH is present, RCM must be distinguished from HCM.

• Endomyocardial fibrosis and secondary thrombus formation can result in apical obliteration and markedly reduced left ventricular chamber volumes.

• Standard harmonic imaging may cause normal myocardium to appear echobright or hyperechoic. When RCM is suspected, additional imaging without harmonics should be performed.

• Concurrent right ventricular dysfunction may be present, with elevated central venous pressure.

• Significant biatrial enlargement is a common feature of RCM due to chronic elevation in right and left ventricular filling pressures.

• In children, an “ice-cream cone” appearance can be seen, created by grossly enlarged atria resting on top of relatively small ventricles (see Fig. 13-14).

• If pericardial thickening or echogenicity is appreciated, constrictive pericarditis should be considered.

• Step 2: Assess valvular anatomy and function.

• Endomyocardial fibrosis can cause fibrosis of the atrioventricular subvalvular apparatuses, leading to leaflet tethering and regurgitation.

• Amyloidosis can result in diffuse leaflet thickening.

Physiologic Data

• Step 2: Differentiate RCM from constrictive pericarditis (Table 13-4).

• In clinical practice, differentiating RCM and constrictive pericarditis is often challenging because both demonstrate elevated filling pressures with normal chamber size and systolic function.

• Pericardial constriction may show signs of interventricular dependence, such as septal shifting with inspiration and discordant respiratory variation in tricuspid and mitral inflow.

• Using a respirometer, PW Doppler sampling of mitral and tricuspid inflow should be performed.

• An M-mode of the left ventricular septum, obtained from a parasternal window, may show abrupt posterior motion of the septum during early diastole, suggesting a constrictive process.

• Associated features that favor a diagnosis of RCM over constrictive pericarditis include

• PAPs greater than 60 mm Hg.

• Severe biatrial enlargement.

Figure 13-16 Left ventricular diastolic filling in a patient with RCM, with PW Doppler signal of transmitral inflow (top) and tissue Doppler imaging of the sepal mitral annulus (bottom). The mitral inflow E velocity is increased with a short deceleration time, whereas the aseptal annular E′ velocity is reduced, yielding a significantly elevated E/E′ ratio (>20).

TABLE 13-4 ECHOCARDIOGRAPHIC PARAMETERS IN RCM AND CONSTRICTIVE PERICARDITIS

	RCM	Constrictive Pericarditis
LV size	Normal	Normal
LV systolic function	Normal	Normal
LV wall thickness	Normal to increased	Normal
LV filling pressures	Markedly increased	Increased
LA size	Markedly increased	Increased
PA pressures	Markedly increased	Increased
Pericardium	Normal	Echobright
Septal shifting with respiration	Absent	Present
Variability in MV inflow	Absent	Present
MV-TV inflow velocities	Concordant	Discordant