A nurse is providing teaching to a client who has atrial fibrillation and reports dizziness and palpitations. Which of the following should the nurse understand is the cause of these manifestations?

A. "Your heart condition is caused by excessive stretching of the ventricles": Dilated cardiomyopathy (DCM) is characterized by the dilation or enlargement of the heart's chambers, particularly the ventricles. This dilation results in weakened myocardial contraction and impaired systolic function. The primary cause of DCM is often idiopathic (unknown), but it can also be secondary to various factors such as genetics, infections, toxins, or systemic diseases. The statement correctly identifies the pathophysiological basis of DCM as excessive stretching or dilation of the ventricles, leading to impaired cardiac function.

B. "Your heart condition is caused when the ventricular tissue becomes fibrous and fatty": This statement is incorrect. Fibrous and fatty changes in ventricular tissue are characteristic of another type of cardiomyopathy known as hypertrophic cardiomyopathy (HCM), not dilated cardiomyopathy (DCM). In DCM, the primary abnormality is dilation of the heart chambers rather than fibrous and fatty changes in the myocardium.

C. "Your heart condition is caused from stiffening of the walls of the ventricles": This statement describes restrictive cardiomyopathy (RCM), not dilated cardiomyopathy (DCM). In restrictive cardiomyopathy, the ventricular walls become stiff and rigid, impairing diastolic filling and ventricular relaxation. However, in DCM, the primary abnormality is dilation or enlargement of the ventricles rather than stiffening of the ventricular walls.

D. "Your heart condition is caused by thickening of the ventricular walls and septum": This statement describes hypertrophic cardiomyopathy (HCM), not dilated cardiomyopathy (DCM). In HCM, there is abnormal thickening of the ventricular walls and septum, leading to reduced chamber size and impaired diastolic filling. However, in DCM, the primary abnormality is dilation or enlargement of the ventricles rather than thickening of the ventricular walls.

A. The aortic and mitral valves are the most commonly replaced valves: This statement is accurate. The aortic and mitral valves are indeed the most commonly replaced valves in cardiac valve replacement surgeries. Aortic valve replacement is commonly performed for conditions such as aortic stenosis or regurgitation, while mitral valve replacement is often indicated for mitral regurgitation or stenosis.

B. Mitral valve insufficiency occurs during the diastolic phase of the cardiac cycle: This statement is incorrect. Mitral valve insufficiency, also known as mitral regurgitation, occurs during the systolic phase of the cardiac cycle. It involves the backflow of blood from the left ventricle into the left atrium during ventricular systole, leading to volume overload of the left atrium and potentially causing symptoms such as dyspnea and fatigue.

C. Inadequate closure of the tricuspid valve causes overload in the left ventricle: This statement is incorrect. Inadequate closure of the tricuspid valve leads to regurgitation of blood from the right ventricle back into the right atrium during ventricular systole. This condition, known as tricuspid regurgitation, causes volume overload in the right atrium and ventricle, rather than overload in the left ventricle.

D. Aortic stenosis increases right ventricular systolic pressure and decreases afterload: This statement is partially correct. Aortic stenosis indeed increases left ventricular systolic pressure and decreases afterload, not right ventricular pressure. The increased afterload on the left ventricle can lead to left ventricular hypertrophy and eventually heart failure. However, aortic stenosis does not directly affect right ventricular systolic pressure.