**2. Pathophysiology**

In 2006, American Heart Association (AHA) in their document entitled "Contemporary Definition and Classification of the Cardiomyopathies" defined cardiomyopathies as "a heterogeneous group of diseases of the myocardium associated with mechanical and/or electrical dysfunction that usually (but not invariably) exhibit inappropriate ventricular hypertrophy or dilation and are due to a variety of causes that frequently are genetic. Cardiomyopathies either are confined to the heart or are a part of generalised systemic disorders, often leading to cardiovascular death or progressive heart failure-related disability." According to the new AHA classification, cardiomyopathies are divided into two broad groups: primary cardiomyopathies and secondary cardiomyopathies. Primary cardiomyopathies encompass those that are exclusively or predominantly confined to the heart muscle and are acquired, genetic, or of mixed origin. Secondary cardiomyopathies include the subset of multiorgan involving diseases, which cause involvement of the heart as a part of their pathophysiology. In spite of this detailed classification, some confusion may arise because some primary cardiomyopathies may have associated extra cardiac components while as a few secondary cardiomyopathies can affect the heart exclusively.

**Classification of primary cardiomyopathies:**

Left ventricular noncompaction Glycogen storage disease

Arrhythmogenic right ventricular cardiomyopathy

Conduction system disease (Lenègre's disease)

Primary restrictive nonhypertrophied cardiomyopathy

Ion channelopathies: long QT syndrome, Brugada syndrome, short QT syndrome

Acquired Myocarditis (inflammatory cardiomyopathy): viral, bacterial, rickettsial, fungal, parasitic (Chagas

Genetic Hypertrophic cardiomyopathy

106 Current Topics in Intensive Care Medicine

Mixed Dilated cardiomyopathy

disease)

Infiltrative Amyloidosis

Storage Hemochromatosis

Stress cardiomyopathy Peripartum cardiomyopathy

**Classification of secondary cardiomyopathies:**

Gaucher's disease Hunter's syndrome

Glycogen storage disease Niemann-Pick disease

Cardiomyopathy itself can present as either systolic dysfunction or diastolic dysfunction, which in turn are both related to the ventricular dysfunction.

**Systolic dysfunction:** This type of dysfunction is mainly seen in dilated cardiomyopathy. The predominant pathophysiology is a global decrease in myocardial contractility, which in turn leads to reduction in left ventricular ejection fraction. In the initial phases, the heart tries to compensate this change by increasing the size of left ventricular cavity which allows for an improvement in stroke volume with an associated improved force of contraction. As the disease progresses, these compensatory mechanisms prove to be inadequate in maintaining the cardiac output, eventually leading to the failure of left heart.

**a.** Fractional myocardial shortening <25% and/or ejection fraction <45%.

Familial DCM contribute about 20–48% of all DCM and can defined by

disease.

tum cardiomyopathy.

**3.1. Pathophysiology**

cardiac output (CO).

marked.

**3.2. Signs and symptoms**

**b.** Left ventricular end-diastolic diameter > 117% excluding any known cause of myocardial

Current Perspectives on Cardiomyopathies http://dx.doi.org/10.5772/intechopen.79529 109

• the presence of two or more affected relatives with DCM meeting the above criteria or

The prevalence of DCM is 920/100,000 individuals and is common in Afro-Caribbean population. It is the commonest form of cardiomyopathy and is the third most common cause of congestive heart failure. DCM is the commonest indication for heart transplantation. In 30–40% patients, it is transmitted in an autosomal dominant fashion while in others it can be post viral or idiopathic. It can be of ischemic or nonischemic variety with ischemic type being related to atherosclerosis or CAD. The nonischemic variety may present itself secondary to the use of chemotherapeutic agents (doxorubicin and adriamycin), infections (Coxsackie virus, HIV, cytomegalovirus Chagas' disease, trichinosis, toxoplasmosis, Lyme disease, and leptospirosis), drug abuse (alcohol, heroin, cocaine, and methamphetamines), or as peripar-

Dilated cardiomyopathy presents with a decrease in LV ejection fraction (LVEF) as described earlier, congestive heart failure (CHF) or as ventricular arrhythmias. Initially, the ventricle dilates to increase the force of contraction and stroke volume in order to maintain the cardiac output (Frank-Starling law); however, as the disease progresses, these compensatory mechanisms gradually fail, leading to the ventricular failure and ultimately failure to maintain the

The patients of dilated cardiomyopathy present with symptoms like dyspnea, orthopnea, fatigue, weakness, and oedema in the lower extremities. Physical findings are similar to those seen in CHF. Some patients complain of dyspnea on exertion that may look like angina pectoris. Patients may have jugular venous distention, crepitation on auscultation, resting tachycardia, audible s3 and s4 heart sounds, pulmonary oedema, and cardiomegaly. Mitral and/or tricuspid regurgitation may be audible clinically if the ventricular dilation is

The ECG may show ST-T segment abnormalities, atrial fibrillation, intraventricular conduction defects, and PVCs. The echocardiography reveals dilated cardiac chambers, global hypokinesia, low EF/fractional shortening, raised LVEDP, mitral or tricuspid regurgitation and/or mural thrombi. Right-sided cardiac catheterisation using a Swan Ganz Catheter reveals a high

• a relative of a DCM patient with unexplained sudden death before the age of 35.

**Diastolic dysfunction:** This is the most common type of dysfunction associated with the cardiomyopathies, occurring in HCM, RCM, and other types of cardiomyopathies. The main pathophysiology is impairment of filling of blood in the left ventricle, which leads to increase in the left ventricular filling pressures. During the beginning of the diastolic phase of a normal cardiac cycle, left ventricle undergoes the phase of Isometric relaxation (which is an energy dependent process) just before the start of left ventricle filling phase. This relaxation continues in the early left ventricular filling phase. The later part of the left ventricular filling is a passive process and depends on the compliance of the left ventricle. Diastolic dysfunction can be because of the impairment of any of the two phases: active relaxation or left ventricular compliance or a combination of the two. Ischaemia mainly affects the phase of isometric relaxation, while intrinsic myocardial pathologies including fibrosis or external restriction due to pericardial diseases may lead to a reduction in left ventricular compliance.

The main types of cardiomyopathy that we come across clinically in our day-to-day practice are:


Some other types of cardiomyopathy are known as "unclassified cardiomyopathy." Another type of cardiomyopathy known as Takotsubo cardiomyopathy has been recently listed and is also known as "stress-induced cardiomyopathy," or broken heart syndrome.

Therefore, we focus our attention towards the commonest types of cardiomyopathies in this chapter.
