A nurse is teaching a client who has restrictive cardiomyopathy (RCM). Which of the following statements should the nurse include in the client teaching to explain the cause of RCM?

A. Atrial fibrillation: Atrial fibrillation is characterized by an irregularly irregular rhythm, absence of identifiable P waves, and irregular ventricular response. The heart rate in atrial fibrillation can be variable, and the absence of identifiable P waves indicates disorganized atrial electrical activity.

B. Sinus bradycardia: Sinus bradycardia is characterized by a regular rhythm with a heart rate less than 60 beats per minute (bpm) and normal P waves preceding each QRS complex. In sinus bradycardia, the PR interval and QRS duration are typically within normal limits.

C. Supraventricular tachycardia: Supraventricular tachycardia (SVT) is characterized by a regular rhythm with a heart rate greater than 100 bpm. SVT typically presents with narrow QRS complexes and may or may not have discernible P waves.

D. First-degree heart block: First-degree heart block is characterized by a prolonged PR interval (>0.20 seconds) but maintains a regular rhythm with normal QRS duration. In first-degree heart block, P waves are typically identifiable, and the rhythm is not irregular.

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.