A disproportionate thickening of the interventricular septum is the hallmark of which form of cardiomyopathy?

A. Fungus: While fungal infections can cause infective endocarditis, they are much less common compared to bacterial infections. Fungal endocarditis typically occurs in immunocompromised individuals or those with specific risk factors.

B. Virus: Viral infections can affect the heart, but they are not a common cause of infective endocarditis. Most cases of endocarditis are associated with bacterial infections rather than viral ones.

C. Bacterium: The most common cause of infective endocarditis is bacterial infection. Bacteria, particularly Staphylococcus aureus, Streptococcus viridans, and Enterococcus, are frequently implicated in this condition. These bacteria can enter the bloodstream and adhere to heart valves or damaged cardiac tissue, leading to infection and inflammation.

D. Rickettsiae: Rickettsial infections are caused by a specific type of bacteria that are typically transmitted through arthropod vectors, such as ticks. While they can cause various illnesses, they are not a common cause of infective endocarditis.

A. Septal: Septal cardiomyopathy typically refers to abnormalities in the interventricular septum and does not specifically address the rigidity and noncompliance of the myocardium that affects diastolic filling.

B. Restrictive: Restrictive cardiomyopathy is characterized by a rigid and noncompliant myocardium that impedes ventricular filling during diastole. This results in elevated pressures in the ventricles and may lead to heart failure symptoms due to poor filling capacity.

C. Infiltrative: Infiltrative cardiomyopathy involves the deposition of abnormal substances (such as amyloid or sarcoid) within the myocardial tissue, which can lead to stiffness. While this may contribute to restrictive physiology, "restrictive" is the more precise term for the condition described.

D. Hypertrophic: Hypertrophic cardiomyopathy is characterized by an abnormal thickening of the heart muscle, particularly the left ventricle. While this condition can affect diastolic filling, it is primarily due to muscle hypertrophy rather than rigidity and noncompliance of the myocardium.