Which of the following is NOT a complication of rheumatic heart disease?

Rheumatic heart disease is a condition that arises following rheumatic fever, which is a complication of untreated streptococcal throat infections. It primarily affects the heart valves and can lead to various complications as a result of inflammatory damage.

Cystic fibrosis, on the other hand, is a genetic disorder that affects the lungs and digestive system due to the malfunction of the CFTR gene. It is not related to rheumatic heart disease or its complications. The pathology of cystic fibrosis is distinct from the inflammatory processes seen in rheumatic heart disease, which primarily affects heart valves and can lead to conditions such as mitral valve stenosis and aortic regurgitation due to scarring and deformity of the valves after episodes of rheumatic fever.

The other options provided are, in fact, complications associated with rheumatic heart disease: myocardial fibrosis can develop due to chronic damage to the heart muscle, while mitral valve stenosis and aortic regurgitation are specific types of valve damage that may occur due to scarring and deformity from rheumatic fever. Therefore, identifying cystic fibrosis as the outlier emphasizes the need to differentiate between conditions that stem from autoimmune responses to infections and those resulting from genetic factors.