Myocardial Diseases (Cardiomyopathies) PDF

Myocardial diseases (Cardiomyopathies) Definition: 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 abn...

Myocardial diseases (Cardiomyopathies) Definition: 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 Cardiomyopathies are divided into 2 major groups based on predominant organ involvement. -Primary cardiomyopathies (genetic, nongenetic, and acquired) are those solely or predominantly confined to heart muscle and are relatively few in number (Figure 1). - Secondary cardiomyopathies show pathological myocardial involvement as part of a large number and variety of generalized systemic (multiorgan) disorders. Figure (1): AHA classification of primary cardiomyopathies Pathophysiology of cardiomyopathies Genetic mutation + Exogenous insult Contraction and relaxation disorder Ineffective energy utilization Altered Ca ions handling Activation of compensatory neurohumoral mechanisms Apoptosis Fibrosis Hypertrophy Heart failure Arrhythmia, sudden death Hypertrophic Cardiomyopathy (HCM) Clinically heterogeneous but relatively common autosomal dominant (AD) genetic heart disease. HCM is the most common cause of sudden cardiac death in the young (including trained athletes) and is an important substrate for heart failure disability at any age. Morphologically: hypertrophied, nondilated LV in the absence of another systemic or cardiac disease that is capable of producing the magnitude of wall thickening evident (eg, systemic hypertension, aortic valve stenosis). Figure 2: The morphology of normal heart (a) and hypertrophic cardiomyopathy (b). As noted, there is hypertrophy of the myocardium with relatively small chamber dimensions relative to the normal heart. Diagnosis: 2-dimensional echocardiography (or alternatively with cardiac magnetic resonance imaging) by detection of otherwise unexplained LV wall thickening, usually in the presence of a small LV cavity, after suspicion is raised by the clinical profile or as part of family screening. Individuals harboring a genetic defect for HCM do not necessarily express clinical markers of their disease such as LV hypertrophy on echocardiogram, ECG abnormalities, or symptoms at all times during life. Most HCM patients have the propensity to develop dynamic obstruction to LV outflow under resting or physiologically provocable conditions, produced by systolic anterior motion of the mitral valve with ventricular septal contact. Figure 3: The mechanism of systolic anterior motion (SAM) and left ventricular outflow tract - ECG alterations can precede the appearance of hypertrophy. - Laboratory DNA analysis; 11 mutant genes are associated with HCM, most commonly ß-myosin heavy chain (the first identified) and myosin-binding protein C. TREATMENT: - if symptomatic: B-blockers or calcium channel blockers. - if still symptomatic: septal myomectomy or alcoholic septal ablation. Dilated Cardiomyopathy Definition: Dilated LV + systolic dysfunction in the absence of coronary ischemia or loading conditions capable of causing such dysfunction (CAD, HTN, valvular disease, congenital heart disease). Figure 4: The morphology of normal heart and dilated cardiomyopathy DCM is the 3rd most common cause of HF & the most frequent indication of heart transplantation. Causes of DCM Primary: aggregate in families (20-35% of the DCM cases are reported as familial), or remain designated as idiopathic. Secondary including: ▪ Infectious agents, particularly viruses, often producing myocarditis (cardiotropic virus-like coxsackie, adenovirus, parvovirus, HIV); but also bacterial, fungal, parasitic (Chagas disease due to trypanosome infection). ▪ Toxins. ▪ Chronic excessive consumption of alcohol.  ▪ Chemotherapeutic agents (anthracyclines such as doxorubicin and daunorubicin). ▪ Metals and other compounds (cobalt, lead, mercury, and arsenic); ▪ Autoimmune and systemic disorders (including collagen vascular disorders); pheochromocytoma. ▪ Neuromuscular disorders such as Duchenne/Becker and Emery- Dreifuss muscular dystrophies; mitochondrial, metabolic, endocrine, and nutritional disorders (e.g. carnitine, selenium deficiencies). Subtypes of dilated cardiomyopathies: Tako-Tsubo Tachycardic mediated Peri-partum cardiomyopathy Stress ("Tako-Tsubo") Cardiomyopathy Definition: Acute but rapidly reversible LV systolic dysfunction in the absence of atherosclerotic coronary artery disease, triggered by profound psychological stress. This distinctive form of ventricular stunning typically affects older women and preferentially involves the distal portion of the LV chamber ("apical ballooning"), with the basal LV hypercontractile. Although presentation often mimics ST-segment-elevation myocardial infarction, outcome is favorable with appropriate medical therapy. Peripartum (postpartum) cardiomyopathy Definition: a rare and dilated form associated with LV systolic dysfunction and heart failure of unknown cause that manifests clinically in the third trimester of pregnancy or the first 5 months postpartum and requires a high index of suspicion for diagnosis. "It is regarded as a clinical entity distinct from preexisting cardiomyopathies that may be adversely affected by the stress of pregnancy". Peripartum cardiomyopathy most frequently occurs in obese, multiparous women >30 years of age with preeclampsia. Prognosis: complete or nearly complete recovery within 6 months in ≥50% of cases but may result in progressive clinical deterioration, heart failure, death, or transplantation.  Tachycardia-mediated cardiomyopathy Definition: An underrecognized and reversible dilated cardiomyopathy with LV contractile dysfunction occurs secondary to prolonged periods of supraventricular or ventricular tachycardia. Prognosis: Systolic function normalizes without residual impairment on cessation of the tachycardia. Primary Restrictive Cardiomyopathy A disease characterized by: Normal or decreased volume of both ventricles. Biatrial enlargement. Normal LV wall thickness and atrioventricular valves. Impaired ventricular filling with restrictive physiology, normal (or near normal) systolic function. The etiologies of RCM may be grouped into broad categories as follows: Primary/idiopathic: Endomyocardial fibrosis (EMF), Loeffler eosinophilic endomyocardial disease. Secondary: Infiltrative, amyloidosis (the most common cause of RCM in the United States), sarcoidosis, hemochromatosis, progressive systemic sclerosis (scleroderma, carcinoid heart disease, glycogen storage disease of the heart, radiation/treatment induced, metastatic malignancy, anthracycline toxicity. Myocarditis (inflammatory cardiomyopathy) Definition: inflammation of the myocardium Causes 1) infection: viral = most common cause (enteroviruses (coxsackieviruses, echoviruses), herpesviruses (EBV, CMV, HHV-6), adenoviruses, parvovirus B19, HIV, SARS-CoV-2) 2) immune-mediated: rheumatic fever giant cell myocarditis systemic immune-mediated diseases: Systemic lupus, scleroderma, Rheumatoid arthritis, systemic vasculitis, eosinophilic myocarditis, sarcoidosis 3)toxic Myocarditis usually manifests in an otherwise healthy person and can result in rapidly progressive (and often fatal) heart failure and arrhythmia. Clinical presentation Mild symptoms of chest pain (in concurrent pericarditis), fever, sweats, chills, dyspnea. In viral myocarditis: Recent history (≤1-2 week) of flulike symptoms of fevers, arthralgias, and malaise or pharyngitis, tonsillitis, or upper respiratory tract infection Heart failure Palpitations, syncope, or sudden cardiac death due to underlying ventricular arrhythmias or atrioventricular block (especially in giant cell myocarditis); Myocarditis creates an electrically unstable substrate predisposing to the development of ventricular tachyarrhythmias. Investigation: routine, ESR, CRP: raised troponin: positive ECG Echocardiography CMR: myocardial edema ± hyperemia ± necrosis Endomyocardial biopsy (EMB): if rapidly deteriorating and not responding to medical treatment. Course either: Spontaneous recovery progression to DCM Fulminant myocarditis - severe cardiovascular compromise with ventricular dysfunction and multiple foci of active myocarditis; either resolves spontaneously or results in death. Treatment: HF therapy exercise restriction R of cause in case of syst immune disease