HEART DISEASE
CARDIAC ANATOMY AND PHYSIOLOGY OF HEART
HEART TISSUE ;
The heart wall is made up of three tissue layers.The outermost layer of the heart is a doublewalled sac termed the pericardium. he two layers of the pericardium include an outer tough fibrous layer of dense irregular connective tissue termed the parietal pericardium and an inner thin visceral pericardium.5 Between these two layers is a closed space filled with pericardial fluid, which serves as a lubricant allowing the two surfaces to slide past one another. Clinically, patients may develop an infection with resultant inflammation of the pericardium termed pericarditis. he clinical signs that accompany this pathology and used to differentially diagnose pericarditis include a pericardial friction rub (an audible grating sound suggesting irritation of the pericardium) that can be auscultated with each heartbeat accompanied by constant chest pain.In some patients excessive fluid accumulation within the closed pericardial space may lead to a secondary condition known as cardiac tamponade. Tamponade involves compression of the heart caused by fluid buildup in the space between the myocardium and pericardium. In this state, patients will demonstrate compromised cardiac function and contractility due to the excess fluid within the closed space pushing against the heart.7,8 he muscular middle layer of the heart is termed the myocardium. It is the layer that facilitates the pumping action of the heart to move blood to the entire body.
Alterations in the muscular wall of the heart are termed cardiomyopathies. here are three common classifications of cardiomyopathies: dilated, hypertrophic, and restrictive. Dilated cardiomyopathy is evidenced by ventricular dilation and altered cardiac muscle contractile function. CAD is the prime cause of dilated cardiomyopathy, causing mitochondrial dysfunction and resultant myocardial damage. Myocarditis (inflammation of the heart muscle) and alcohol abuse are additional causes of dilated cardiomyopathy. Hypertrophic cardiomyopathy presents as diastolic dysfunction with an increased ventricular mass. Chronic HTN and aortic stenosis are examples of hypertrophic cardiomyopathy. Restrictive cardiomyopathy also presents as diastolic dysfunction owing to the presence of excessively rigid ventricular walls, resulting in a decrease in compliance. he connective tissue changes of the heart associated with diabetes are an example of a restrictive cardiomyopathy. Damage to myocardial cells from cardiomyopathies and various other etiologies lead to cardiac muscle dysfunction and resultant heart failure, which will be comprehensively discussed later in this chapter. he innermost layer of the heart is termed the endocardium.
The tissue of the endocardium forms the inner lining of the chambers of the heart and is continuous with the tissue of the valves and the endothelium of the blood vessel. Because the endocardium and valves share similar tissue, patients with infections of the endocardium are at risk for developing valvular dysfunction. Endocardial infections can spread into valvular tissue developing vegetations (a mixture of bacteria and blood clots) on the valve.9 In patients with newly developed vegetations, bronchopulmonary hygiene procedures including percussions and vibrations are contraindicated because they may dislodge, move as emboli, and cause an embolic stroke.
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