35: Dilated Cardiomyopathy, Myocarditis, and Heart Transplantation

Dilated Cardiomyopathy, Myocarditis, and Heart Transplantation

Renee Margossian

Harvard Medical School; Boston Children’s Hospital, Boston, MA, USA


Echocardiography is the primary diagnostic tool in the initial evaluation of children with suspected dilated cardiomyopathy (DCM), and long‐term management decisions rely in part on serial echocardiographic assessment. The echocardiographic evaluation of patients with myocarditis is similar to that performed in DCM since the clinical course of myocarditis and DCM overlap. Echocardiography also plays an instrumental role in the evaluation of patients who undergo cardiac transplantation, from initial pre‐transplant evaluation, to the perioperative period, through long‐term follow‐up. Patients with DCM or myocarditis or who have undergone heart transplantation may also require interventions such as mechanical ventricular support or resynchronization therapy. In each of these situations, the clinical focus is on myocardial performance, and the echocardiographic approach is similar under each of these circumstances, with a focus on systolic and diastolic function.

Dilated cardiomyopathy


In 1995, the World Health Organization defined cardiomyopathies as “diseases of the myocardium associated with cardiac dysfunction,” and classified them according to morphology into four distinct types: dilated cardiomyopathy, hypertrophic cardiomyopathy, restrictive cardiomyopathy, and arrhythmogenic right ventricular cardiomyopathy [1]. Specifically, DCM was defined as “dilation and impaired contraction of the left ventricle or both ventricles” [1]. The weakness of this approach has become more apparent as diagnostic advances in fields such as molecular genetics have broadened the understanding of cardiomyopathies in general. More than 30 genes have been associated with the DCM phenotype, expressed through mitochondrial (e.g., Barth syndrome), X‐linked (e.g., Duchenne and Becker muscular dystrophies), dominant (e.g., LMNA mutations), and recessive (e.g., TNNI3 mutations) inheritance patterns [24]. Current debate continues as to the method of classification of cardiomyopathies, with a newer proposed classification recommending a cause‐based approach (genetic, acquired, or mixed) [5]. This classification system carries its own limitations, however. The same mutations in cTnT, α‐tropomycin and β‐myosin heavy chain, among others, have been found in patients with hypertrophic cardiomyopathy (HCM) and in patients with primary DCM [6,7]. Additionally, phenotype can change over time within the same individual, as in the case of end‐stage HCM, with a change from a hypertrophied left ventricle with normal systolic function to one of dilated left ventricle with systolic dysfunction, sometimes referred to as “burned‐out HCM” [8]. Registries of large populations have typically described cardiomyopathies by morphologic phenotype, with a modifier for cause when known [9].

Regardless of the nomenclature difficulties faced by the field, echocardiographic establishment of the predominant phenotype (dilated, hypertrophic, or restrictive) is relatively straightforward, even in patients with mixed phenotypes. This has allowed large multicenter registries to evaluate the epidemiology and outcomes of cardiomyopathies in children [911].


The true incidence of DCM has been difficult to ascertain, and may vary by geography, race/ethnicity, and socioeconomic status. Data from the US Pediatric Cardiomyopathy Registry (PCMR) and Australia estimate the annual incidence of all forms of primary pediatric cardiomyopathy to be 1.13–1.24 cases per 100,000, with DCM accounting for approximately 50–60% of these cases [911]. These reports exclude patients with DCM due to congenital heart disease, arrhythmia, and/or chemotherapy exposure. This contrasts with an annual incidence of nonischemic DCM in the adult population in the USA of 6–7 cases per 100,000 [12,13]. Presentation with DCM is most common in children under 1 year of age. PCMR data indicate that in children with primary DCM, 66% of cases are idiopathic in nature, with myocarditis and neuromuscular diseases predominating among those with known causal etiology [14].


As noted above, most cases of pediatric DCM are idiopathic in nature, with known causes identified 32–44% of the time [11,14,15]. Specific etiologies include genetic, metabolic, infectious, immune‐mediated, mitochondrial, and environmental toxins (Table 35.1) [5]. In the PCMR group, myocarditis was the largest single cause of DCM in those under 18 years of age, accounting for 16–18% of all cases and 50% of cases with a known etiology [14,15]. Other causes of DCM in the pediatric or adolescent population include neuromuscular disorders, familial DCM, and inborn errors of metabolism, accounting for 9%, 5%, and 4% of cases, respectively [14]. Additional etiologies include congenital heart disease, valvular heart disease, postpartum cardiomyopathy, pacemaker‐induced DCM, arrhythmia‐induced DCM, and coronary artery/ischemic disease; these will not be addressed in this chapter.

In familial DCM, most of the known mutations are associated with autosomal dominant inheritance, with 35–40% of those associated with sarcomeric mutations. Familial cases of DCM are probably underestimated, as not all families undergo mutation analysis and some mutations may manifest incomplete penetrance. Mutations associated with autosomal dominant inheritance include those involving cytoskeletal proteins such as β‐ and δ‐sarcoglycan, and sarcomere proteins such as titin (responsible for 25% of genetic DCM cases), actin, and cardiac troponin T. More than 50 single genes have been linked to DCM, with many of the same genes also linked to other forms of cardiomyopathy, particularly HCM [5,9,16,17]. In addition, several genetic forms of DCM are associated with skeletal myopathy, including Duchenne and Becker muscular dystrophy, Barth syndrome, Emery–Dreifuss muscular dystrophy, and limb–girdle muscular dystrophy.

An emerging subspecialty in pediatric cardiology is the field of cardio‐oncology. As survival rates for childhood cancers have improved, so has the risk for long‐term chronic health conditions. Cardiovascular disease is the third most common cause of morbidity and mortality among survivors, after recurrence of primary malignancy and occurrence of secondary malignancies. In fact, the relative risk for development of heart failure is 15 compared with healthy siblings [18]. Multiple classes of chemotherapeutic agents are known to affect the cardiovascular system including anthracyclines (e.g., doxorubicin), alkylating agents (e.g., busulfan), antimetabolites (e.g., cytarabine), and radiation. Each of these classes affect the myocardium through varying mechanisms and to varying degrees, with late effects that include cardiac dysfunction, arrhythmias, and pericardial effusions. Although left ventricular dilation is often minimal in the most common form of cardiotoxic late effects related to anthracycline therapy, identifying left ventricular (LV) dysfunction with or without overlapping features of restrictive cardiomyopathy are the target of long‐term surveillance.


Myocardial damage and reduced cardiac function lead to decreased cardiac output; this results in a complex cascade of neurohormonal and vascular changes that increase preload and afterload, triggering a cycle of continued myocardial damage and remodeling. Stimulation of the sympathetic and renin–angiotensin systems leads to vasoconstriction, increased circulating catecholamines, stimulation of aldosterone secretion, and salt and water retention. Both the primary myocardial insult and the secondary effects of vascular and neurohormonal alterations result in myocardial cellular changes, including necrosis, apoptosis, and fibrosis. These changes lead to myocardial remodeling, with alterations in LV geometry and compliance. A comprehensive review of these events is beyond the scope of this chapter, but can be found elsewhere [19,20].

Treatment and outcome

Current therapeutic strategies for treatment of cardiomyopathy are aimed at improving symptoms as well as reversing the negative effects of maladaptive ventricular remodeling (e.g., LV dilation and myocyte hypertrophy). This phenomenon of improving cardiac geometry and function with various therapies is known as “reverse remodeling” and occurs at the molecular, cellular, tissue, and chamber levels. These therapies may be aimed at decreasing afterload (angiotensin converting enzyme inhibitors or receptor blockers), decreasing preload (diuretics), and altering the neurohormonal profile (β‐blockers). Intravenous therapy with agents such as milrinone and dobutamine further decreases afterload and increases myocardial contractility. Additional interventions may include anticoagulation, nutritional support, and use of antiarrhythmic medication when necessary.

A recent addition to the therapeutic armamentarium is the new class of agents referred to as angiotensin receptor–neprilysin inhibitors which combine a neprilysin inhibitor and an angiotensin receptor inhibitor [21]. Both of these classes of medication inhibit the renin–angiotensin–aldosterone system, by different methods. The combination of sacubitril and valsartan was approved by the US Food and Drug Administration in 2019 for use in children over 1 year of age.

Failure of maximal medical therapies indicates the need for other forms of support, including biventricular pacing (cardiac resynchronization therapy (CRT)), mechanical support (ventricular assist device (VAD) or extracorporeal membrane oxygenation (ECMO)), or cardiac transplantation.

The clinical course of DCM in the pediatric population is highly variable, and a comprehensive risk stratification algorithm does not exist. Recent data suggest that the 1‐ and 5‐year risks of death or transplantation in pediatric DCM are 28–31% and 37–46%, respectively [14,22], with most events occurring within the first 2 years after initial presentation. On the other end of the spectrum, approximately 20–45% of patients ultimately recover normal cardiac function [23]. In a systematic review of outcome predictors in pediatric DCM [24], younger age at diagnosis, higher LV shortening fraction (SF) and ejection fraction (EF), and the presence of myocarditis have been associated with better prognosis. Poor prognostic factors inconsistently identified in smaller studies have included the presence of a more spherically shaped LV (higher sphericity index (SI)), presence of endocardial fibroelastosis, lack of improvement in cardiac function over time, arrhythmia, presence of intracardiac thrombus, thinning of the posterior wall, and significant mitral regurgitation [14,22,2528]. Data also suggest that measures of myocardial velocities and right ventricular (RV) function may be predictive [29]. A word of caution is warranted regarding patients who do recover function: the PCMR experience showed that 9% of those who had normal LV function and size within 2 years of diagnosis later died or required heart transplantation [23]. Thus, long‐term follow‐up is necessary, even for those whose function returns to normal limits.

Table 35.1 Classification of the dilated cardiomyopathies (modified phenotype‐based classification)

Source: Colan SD. Classification of the cardiomyopathies. Prog Pediatr Cardiol 2007;23:5–15. © 2007, Elsevier.

Peripartum cardiomyopathy
Primary familial dilated cardiomyopathy
Stress cardiomyopathy (“tako‐tsubo”)
X‐linked cardiomyopathy (dystrophinopathy)

Fatty acid oxidation

Congenital heart disease
Valvar heart disease

Cytochrome C oxidase deficiency
Kearns–Sayre syndrome
Mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke (MELAS)
Myoclonic epilepsy associated with ragged‐red fibers (MERRF)
NADH–coenzyme Q reductase deficiency

Connective tissue disorders
Juvenile rheumatoid arthritis
Lupus erythematosus
Osteogenesis imperfect
Polyarteritis nodosa
Reye syndrome
Systemic sclerosis

Selenium deficiency (Keshan disease)
Thiamine deficiency (beri‐beri)

Inflammatory (myocarditis)
Infectious: viral, bacterial, fungal parasitic, protozoal, rickettsial, spirochetal

Dystrophinopathies (Duchenne and Becker dystrophies)
Emery–Dreifuss muscular dystrophy
Myotonic dystrophy
Roussy–Lévy polyneuropathy
Scapulohumeral muscular dystrophy
Spinal muscular atrophy

Iron (hemochromatosis)

Congenital coronary artery malformation
Acquired coronary artery disease

Fetal dilated cardiomyopathy

Fetal DCM is rare and accounts for a very small portion of heart disease discovered during fetal ultrasonography; it accounted for 0.2% of all fetal echocardiograms over a 20‐year period in one large tertiary center [30]. Etiologies of DCM in the fetus are typically the same as in the neonate and include metabolic disease, myocarditis, tachycardia, familial/genetic, and idiopathic causes. Other causes that may be seen predominantly in fetal life include anemia, premature closure of the ductus arteriosus, and endocardial fibroelastosis. Cardiac dysfunction secondary to structural heart disease (such as LV outflow tract obstruction) must be excluded. Fetal cardiac function may appear normal early in pregnancy, with evidence of DCM developing after 23 weeks [31]. Overall prognosis of DCM diagnosed in fetal life is poor, although fetuses with DCM secondary to treatable causes (such as arrhythmia) may have a better outcome [31]. Survival is less than 20% in fetuses with DCM and hydrops, and approximately 50% in nonhydropic fetuses with DCM [30].



Myocarditis is defined as an inflammatory disease of the myocardium diagnosed by established histologic, immunologic, and immunohistochemical criteria. Idiopathic, autoimmune, and infectious forms of inflammatory cardiomyopathy are recognized [1]. These inflammatory forms of cardiomyopathy are typically acquired, although some people may be genetically predisposed to these diseases. The Dallas criteria [32], which require histopathologic evidence of inflammatory infiltrate and myocardial cell damage, have been used to diagnose myocarditis. However, these criteria underestimate the incidence because of issues with sampling error, variation in interpretation, immune modulation in the heart, variable host immunologic response, and differences in patient selection for cardiac biopsy. Identification of viral DNA or evidence of systemic immune activation can aid in the diagnosis of myocarditis in the appropriate clinical setting. Clinical pathologic classification of myocarditis includes fulminant, chronic persistent, giant cell, and eosinophilic types [33]. In myocarditis, diagnostic echocardiographic findings are nonspecific; the distinction between DCM and myocarditis is often not possible. Cardiac magnetic resonance (CMR) imaging is more sensitive and specific than echocardiography [34,35] in confirming the inflammatory nature of the disease, particularly in the acute setting [36]. Its role in the diagnosis of myocarditis has evolved such that adult criteria specify that endomyocardial biopsy be reserved for small subsets of patients: those who have heart failure with rapid disease onset (<2 weeks), LV dilation of less than 3 months’ duration, or in other specific instances [37].


Myocarditis as a separate entity is typically sporadic and its incidence has been even more difficult to ascertain than DCM. Clinical manifestations are variable, the ability to confirm active or preceding viral infection is limited, and the initial presentation may be clinically silent. In one retrospective study, biopsy‐proven myocarditis in children occurred at a rate of 2.5 cases per year in a population of 3 million people [38].


The primary etiology of myocarditis in the pediatric population is viral or post‐viral. Viruses implicated include coxsackie B, adenovirus, cytomegalovirus, enterovirus, influenza A and B, varicella, picornavirus, parvovirus, HIV, and Epstein–Barr virus [13,39], with far fewer cases associated with bacterial, rickettsial, fungal, and parasitic infections. Giant cell myocarditis is an aggressive inflammatory myocarditis that is rare in children and associated with severe ventricular arrhythmia. Eosinophilic myocarditis is also rare and associated with hypersensitivity reactions. Chronic myocarditis may be due to chronic viral infection and autoimmune conditions.


The immunopathogenesis of inflammatory cardiomyopathy has been primarily studied in mice [40]. Host factors that play a role in susceptibility to infection and the development of myocarditis include genetic factors (i.e., major histocompatibility complex), age, gender, and nutritional state [40]. Myocardial damage can result directly from infection or through immune‐modulated mechanisms. Evidence indicates that the development and severity of myocarditis is related to cellular‐mediated immune function, primarily associated with T‐cell lymphocyte activity [40], with cytokine activation probably playing a major role in the inflammatory response [40,41]. Viral RNA can be detected using molecular techniques and viral persistence in the myocardium may play a role in chronic myocarditis [42]. There is also evidence that viral myocarditis could be a trigger for apoptotic cell death [40].

Treatment and outcome

Supportive treatment similar to that discussed for DCM is utilized for acute myocarditis as well. There is no consistent approach or recommendation for immune‐modulated therapy for myocarditis. Some pediatric centers use intravenous γ‐globulin and/or steroids in the clinical setting of myocarditis; some patients with fulminant myocarditis require mechanical support with ECMO or VAD. There are some data to suggest that those with biopsy‐proven myocarditis may have a better outcome than those with idiopathic disease [14,22,24].

Heart transplantation

The first successful pediatric heart transplant occurred in 1984; since then, more than 14,000 transplants in children have been reported to the International Society for Heart and Lung Transplantation (ISHLT) [43]. Survival of pediatric post‐transplant patients over this time period has increased steadily with an overall median survival of more than 18 years. The highest risk time period for death post‐transplant is within the first year. Over 60% of patients who were transplanted in infancy and survived the first year are alive at 25 years [43]. The most common causes of death early after transplant are infection and rejection. By 3 years, coronary artery vasculopathy and graft failure predominate [43].

The leading indication for heart transplantation in children over 1 year of age is DCM with end‐stage heart failure. The PCMR data indicate that 40–45% of children with DCM died or were transplanted within 5 years of diagnosis [14], and there was no difference in survival between the idiopathic group of DCM patients and those with familial DCM in the PCMR cohorts [44]. While timing and indications for transplant vary somewhat among centers, in general, patients are listed for transplant if they cannot be separated from inotropic and/or mechanical support. Outpatients with severely impaired quality of life or intractable growth failure may also be considered.

Myocarditis can present with acute, fulminant heart failure, and marked hemodynamic compromise; however, many of these patients normalize systolic function over time, with relatively fewer deaths/transplants when compared with DCM groups. The PCMR reported a death or transplant rate of 24% in patients with myocarditis compared with 47% in the DCM group [45]. In a registry report of ECMO centers, 7/255 patients with myocarditis underwent heart transplantation [46].

Even though allograft rejection is common following transplant, the incidence has been decreasing over time. In the two most recent time periods reported by the ISHLT, the percentage of patients treated for rejection between hospital discharge after transplantation and 1 year post‐transplantation fell from 24% (January 2005 to December 2009) to 13% (January 2010 to June 2018) [43]. The diagnosis of rejection is typically made by endomyocardial biopsy. Early signs and symptoms of acute rejection are often absent, necessitating frequent surveillance biopsies. Rejection can be classified as cellular or antibody‐mediated. Acute cellular rejection is graded according to well‐established histologic criteria, is treated with increased immunosuppression, and, in the current era, is infrequent beyond the first month post‐transplant. The diagnosis of antibody‐mediated rejection has evolved from inclusion of both pathologic and clinical criteria to a pathology schema that is guideline‐based from the ISHLT [47]. Antibody‐mediated rejection is the result of activation of the complement system by antibodies against the donor human leukocyte antigens present on the endothelium. Treatment is focused on removal and blockade of circulating antibodies, depletion of B‐lymphocytes and plasma cells, and inhibition of the complement cascade. Although some pediatric studies have shown an association among antibody‐mediated rejection, coronary vasculopathy, and graft failure [48], large‐scale analysis of their impact on patient survival is lacking.

In long‐term follow‐up, the most common causes of death in the child who has undergone cardiac transplantation are coronary artery vasculopathy and graft failure [49]. Clinical manifestations and symptoms of coronary vasculopathy may be subtle due to the diffuse, multifocal nature of the vascular changes and denervation of the heart. Current methods used to detect graft vascular disease include angiography, often in combination with other modalities such as exercise or dobutamine stress echocardiography (DSE) [50,51], or intravascular ultrasound [52].


Echocardiography is instrumental in the diagnosis, management, and follow‐up of myocarditis and DCM. However, it is usually not helpful in determining the etiology of these disease processes. The key elements of the echocardiographic examination are summarized in the following.

The presence of a dilated, poorly contractile ventricle is easily recognized with transthoracic imaging (Videos 35.1 and 35.2). Because afterload, preload, and contractility affect overall cardiac performance, volume‐ and/or pressure‐loading lesions (e.g., aortic stenosis or regurgitation, coarctation, mitral regurgitation) must be excluded at the time of initial presentation. It is also critically important to exclude other surgically correctable lesions, particularly anomalous origin of the left coronary artery from the pulmonary artery (ALCAPA) (Figure 35.1, Videos 35.3–35.5). In any patient presenting with features of DCM, the origin of the coronary arteries should be demonstrated by 2D imaging and confirmed by color Doppler in multiple views. Dilation of the right coronary artery in this setting also suggests that ALCAPA may be present. If the coronary artery origins are not demonstrated conclusively by color Doppler, then alternative imaging (i.e., angiography or cardiac computed tomography) is necessary.

Useful echocardiographic assessment in the patient with DCM or myocarditis includes data regarding flow, pressures, volumes, and fiber shortening. LV dimensions, wall thickness, volumes, mass, SF, and EF are the echocardiographic cornerstones of DCM evaluation. Myocardial strain, wall stress, rate‐corrected velocity of circumferential fiber shortening (VCFc), and sphericity are also utilized in many institutions. Other parameters may add information, including assessment of diastolic function, myocardial performance index (MPI, or Tei index), and 3D imaging. Other findings associated with DCM and/or myocarditis should be evaluated (see Key elements box).

Photos depict anomalous origin of the left coronary artery from the posterior aspect of the pulmonary artery; retrograde diastolic flow from the left coronary artery can be seen entering the pulmonary root.

Figure 35.1 Anomalous origin of the left coronary artery from the posterior aspect of the pulmonary artery; retrograde diastolic flow from the left coronary artery can be seen entering the pulmonary root.

Most measures of LV size and function in the pediatric population are based on normal values derived from age‐ and body surface area‐adjusted variables. Reporting these data as z‐scores (number of standard deviations from the mean value) allows standardization of variables that change with age and growth [53]. Additional information on this topic can be found in Chapter 5.

Left ventricular size and geometry

Left ventricular size

Measures of LV size typically include LV end‐diastolic and systolic dimensions from M‐mode or 2D imaging, and LV end‐diastolic and systolic volumes from 2D or 3D imaging. Often in DCM the heart is so large that the LV apex is difficult to image. Care must be taken not to foreshorten the ventricle and to understand the limitations of the measurements under these conditions. Not infrequently, the heart with dilated cardiomyopathy does not fit entirely in the imaging sector, which is particularly important when obtaining 3D volume sets for size and systolic function (Video 35.6). From 2D imaging, common algorithms of determining LV volume include both the Simpson biplane method (Figure 35.2a and b) and the 5/6 area–length method (Figure 35.2c and d) [54]. It is critical that the same method of determining ventricular volumes be used across serial examinations in a given patient. It should also be the same method as that used in the z‐score database, as these algorithms yield different values.

Photos depict common methods of calculating LV volume require images in two planes. (a, b) The biplane Simpson method requires LV areas in apical four-chamber (a) and two-chamber (b) views. (c, d) The 5/6 × area × length (5/6AL) method.

Figure 35.2 Common methods of calculating LV volume require images in two planes. (a, b) The biplane Simpson method requires LV areas in apical four‐chamber (a) and two‐chamber (b) views. (c, d) The 5/6 × area × length (5/6AL) method requires an apical four‐chamber view LV length (c) and a short‐axis LV area (d).

Left ventricular geometry

The alteration in LV geometry in the setting of LV dysfunction is characterized by change from an ellipsoid shape to a spherical shape. This process is associated with increased thinning of the ventricular wall, increased end‐systolic wall stress, decreased contractility, and increased mitral regurgitation [55,56]. The SI is a measure of the LV geometry and is calculated as the LV diastolic short‐axis dimension divided by the LV diastolic long‐axis dimension; the SI approaches unity as the LV becomes more spherical (Figure 35.3). It is useful only in structurally normal hearts. In a small group of children and adolescents, the mean SI has been reported as 0.66 ± 0.07 in healthy patients and 0.89 ± 0.10 in those with LV dysfunction [55]. This same study demonstrated a significant negative correlation between SI and measures of LV systolic function (SF and EF).

Left ventricular systolic function

Shortening fraction and ejection fraction

The measures of ventricular systolic function that are most commonly used in clinical practice include the SF and EF. M‐mode or 2D‐derived LV dimensions are used to determine SF, as well as the VCFc. 2D or 3D imaging and determination of ventricular volumes provides values for the EF. The VCFc, SF, and EF are sensitive to loading conditions and may not be true reflections of underlying myocardial contractility. Despite these limitations, SF and EF are relatively easy to measure and are useful for comparing systolic function in the same patient over time.

Wall stress and measurement of afterload

Left ventricular wall stress can be calculated as a measure of afterload. Afterload is an important determinant of overall cardiac performance; end‐systolic stress is the most relevant measurement with regard to systolic function [57]. The stress‐adjusted shortening (relationship of wall stress to SF, dependent on preload) and stress‐adjusted velocity (relationship of wall stress to VCFc, not dependent on preload) can then be used to adjust for preload and afterload, thus isolating true contractility. The method of measuring end‐systolic wall stress is discussed in Chapter 7. LV end‐systolic wall stress is predictive of outcome in adult patients with DCM [58].

Photos depict apical four-chamber view and parasternal short-axis views demonstrating the sphericity index in a normal patient (a, b) and in a patient with dilated cardiomyopathy (c, d). The sphericity indexes are 0.63 for the healthy patient and 0.91 for the patient with dilated cardiomyopathy.

Figure 35.3 Apical four‐chamber view and parasternal short‐axis views demonstrating the sphericity index in a normal patient (a, b) and in a patient with dilated cardiomyopathy (c, d). The sphericity indexes are 0.63 for the healthy patient and 0.91 for the patient with dilated cardiomyopathy.

Left ventricular diastolic function

Assessment algorithms

Multiple comprehensive and complex algorithms have been proposed for complete evaluation of LV diastolic function [59,60], although many of the guideline recommendations may not be applicable to children. In a recent update, the American Society of Echocardiography has revised its guidelines and standards for LV diastolic function assessment, simplifying the overall approach [61]. Nonetheless, much of the study of diastolic function in DCM focuses more on individual parameters than on the results of complete algorithms.

Left atrial size

During diastole, the left atrium is exposed to the loading pressure within the left ventricle, resulting in remodeling of the left atrium over time. Thus, left atrial size becomes a marker of the chronicity of LV diastolic dysfunction [59]. Robust normal adult data are available, and some pediatric normal data have also been published [62], including data obtained by 3D volume sets [63]. The presence and degree of mitral regurgitation should be taken into account when evaluating left atrial size.

Mitral inflow velocity profile

The mitral inflow Doppler pattern contains several items for examination including the E‐ and A‐wave velocities and the deceleration time of the E wave. The load dependence of these measures limits their utility somewhat, but they are particularly useful when combined with TDI.

Tissue Doppler imaging

Direct myocardial velocities can be measured using TDI. This technique allows quantitative evaluation of regional myocardial function and is considered less load dependent than spectral Doppler of the mitral valve. Myocardial velocities at the level of the mitral or tricuspid valve annulus are indicative of longitudinal LV or RV function, respectively (Figure 35.4). Systolic myocardial peak (s´), early diastolic velocity (e´) and late diastolic velocity (a´) are typically measured. Normal values for children have been published [6466]. Mitral annular velocities are decreased in adult [67] and pediatric [29,68] patients with DCM compared with healthy subjects (Table 35.2). Additional findings in DCM include increased mitrral valve pulsed‐wave E‐to‐TDI e´ ratio (E/e´) compared with controls [68], and lower mitral and tricuspid annular e´ velocities may be predictive of worse outcome in pediatric DCM [29].

Isovolumic contraction time and relaxation time

The time required for the ventricle to achieve enough pressure to open the aortic valve (isovolumic contraction time (ICT)) becomes longer as afterload increases or as contractility is impaired, common events in DCM. The ICT is measured as the time from the Q wave onset of the electrocardiogram QRS complex to the onset of aortic Doppler flow from an LV inflow–outflow Doppler tracing (Figure 35.5a) or from a TDI tracing (Figure 35.5b). The ventricular recoil and relaxation in diastole determine the isovolumic relaxation time (IRT). It is the interval between aortic valve closure and mitral valve opening, and can also be measured from the same tracings as the ICT. Both the ICT and IRT vary with heart rate, thus values may not always be able to be dichotomized into normal and abnormal [59]. In addition, the IRT decreases with higher filling pressures, but prolongs with impaired relaxation. Therefore, a measured IRT may be in the normal range, but in fact be the product of delayed relaxation and higher filling pressures [69].

Photos depict tissue Doppler imaging with myocardial velocities from the lateral mitral annulus. (a) In a normal subject with normal myocardial velocities. (b) In a patient with severe DCM, demonstrating significantly lower myocardial velocities.

Figure 35.4 Tissue Doppler imaging with myocardial velocities from the lateral mitral annulus. (a) In a normal subject with normal myocardial velocities. (b) In a patient with severe DCM, demonstrating significantly lower myocardial velocities.

Table 35.2 Myocardial performance index (MPI) and Doppler tissue imaging (DTI) data in patients with dilated cardiomyopathy and in control subjects (data expressed as mean ± SD)

Source: Eidem BW, McMahon CJ, Ayres NA, et al. Impact of chronic left ventricular preload and afterload on Doppler tissue imaging velocities: a study in congenital heart disease. J Am Soc Echocardiogr 2005;18:830–8. © 2005, Elsevier.

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Oct 30, 2022 | Posted by in EQUINE MEDICINE | Comments Off on 35: Dilated Cardiomyopathy, Myocarditis, and Heart Transplantation

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Dilated cardiomyopathy Control subjects
N 80 80
Age (years) 7.2 ± 6.1 7.1 ± 5.7
LV SF (%) 21.6 ± 6.6** 38.1 ± 4.0
LV MPI 0.67 ± 0.20** 0.33 ± 0.06
Mitral DTI
MV‐e´ 11.8 ± 4.8*** 16.8 ± 4.7
MV‐a´ 5.6 ± 3.0* 6.4 ± 1.9
MV‐s´ 6.5 ± 2.2*** 9.1 ± 3.0
Septal DTI