**2.1 Cardiomyopathies**

Definitions of cardiomyopathies differ over time and between clinical traditions. While in the future cardiomyopathies might be classified after causative mutations, they have traditionally been classified by phenotype and cardiac morphology, e.g. DCM or hypertrophic cardiomyopathy (HCM). This system of classification has the advantage that the phenotype is most often known prior to the genotype.

Originally, cardiomyopathies were considered distinct primary myocardial disorders of unknown etiology, whereas heart muscle disorders of known etiology or caused by systemic disease were classified as secondary or specific heart muscle disease. In 2006 the American Heart Association proposed a classification that defined cardiomyopathies either as primary or secondary, referring either to a disease were the heart is the sole or primarily affected organ, alternatively where myocardial involvement is part of a systemic disease [7]. However, in 2008, the European Society of Cardiology (ESC) proposed an alternate classification in which a cardiomyopathy is defined as "a myocardial disorder in which the heart muscle is structurally and functionally abnormal in the absence of coronary artery disease, hypertension, valvular disease and congenital heart disease sufficient to cause the observed myocardial abnormality". Furthermore, the ESC subdivides cardiomyopathies depending on morphology and function as well as based upon inheritance pattern; distinguishing between familial or genetic forms versus non-familial or non-genetic forms of cardiomyopathy (**Figure 1**) [2].

## **2.2 Dilated cardiomyopathy**

DCM is a distinct cardiomyopathy and a common cause of heart failure defined by dilatation of the left ventricle and reduced ejection fraction [2]. In later phases dilation of the right ventricle and the atria is often seen, however this is not required for diagnosis. For the diagnosis of DCM, the reduction in global systolic function should not solely be attributable to coronary artery disease or abnormal loading conditions (hypertension, valve disease) [2].

#### **Figure 1.**

*Classification of cardiomyopathies proposed by the European Society of Cardiology [2]. Cardiomyopathies are primarily classified according to morphology and function, then based on whether the disease is familial or non-familial, and lastly depending on either known disease causing mutation or pathophysiological mechanism.*

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**Figure 2.**

*Familial Dilated Cardiomyopathy: Risk Stratification for Sudden Cardiac Death*

Familial DCM is diagnosed when at least two relatives (first-degree or second-

Diagnostic evaluation for suspected heart failure should be managed in accordance with guidelines, such as those of the ESC [1]. Echocardiography constitutes a cornerstone of the evaluation and is readily available. For the diagnosis of DCM both left ventricular systolic dysfunction, as well as dilatation of the left ventricle, needs to be present and not explained by coronary artery disease or abnormal loading conditions (hypertension, valve disease) [9]. Left ventricular systolic dysfunction is defined as abnormal left ventricular systolic ejection fraction measured with any modality, preferentially echocardiography or cardiac magnet resonance tomography. Left ventricular dilatation (**Figure 2**) is defined as left ventricular end-diastolic volumes or diameters >2 standard deviations according to nomograms (Z > 2 standard deviations) after correction for body surface area and age, or body surface area and sex [9].

Cardiac magnetic resonance tomography is valuable as a complement to echocardiography. It allows for a better evaluation of the whole myocardium including the right ventricle and septum which provides aid in ruling out other cardiomyopathies such as arrhythmogenic right ventricular cardiomyopathy (ARVC) and HCM. Myocarditis has been identified as a cause of acquired forms of DCM [10]. Cardiac magnetic resonance can be used to assess the presence of active myocarditis as well as scar tissue that could indicate previous episodes of myocarditis. Cardiac magnetic resonance imaging is, according to the ESC, indicative of active myocarditis if it, in the setting of clinically suspected myocarditis, fulfills 2 out of 3 Lake Louise criteria [11]. These criteria include; high signaling on T2-weighted images (indicative of edema), early gadolinium enhancement (indicative of increased blood flow), and

*Echocardiography with apical four chamber view showing spherical dilatation of the left ventricle. Image adapted from Jamil et al. [12]. Published by IntechOpen under open access https://creativecommons.org/licenses/by/3.0/.*

*DOI: http://dx.doi.org/10.5772/intechopen.94437*

degree) meet the diagnostic criteria for DCM [8].

**3.2 Cardiac magnetic resonance tomography**

late gadolinium enhancement (indicative of scar tissue) [11].

**3. Diagnostic evaluation of dilated cardiomyopathy**

**2.3 Familial dilated cardiomyopathy**

**3.1 Echocardiography**

*Familial Dilated Cardiomyopathy: Risk Stratification for Sudden Cardiac Death DOI: http://dx.doi.org/10.5772/intechopen.94437*
