What is ejection fraction?

Choice A reason: This is not the preferred agent for the initial treatment of heart failure. Vasodilators are a class of medications that lower the blood pressure by relaxing the blood vessels and reducing the resistance to blood flow. They can be used to treat hypertension, angina, and heart failure, but they are usually added to other medications, such as diuretics or beta blockers, to improve the symptoms and outcomes.

Choice B reason: This is the preferred agent for the initial treatment of heart failure. Diuretics are a class of medications that increase the urine output and reduce the fluid retention in the body. They can be used to treat hypertension, edema, and heart failure, as they reduce the preload and afterload on the heart, and decrease the pulmonary congestion and peripheral edema.

Choice C reason: This is not the preferred agent for the initial treatment of heart failure. Calcium channel blockers are a class of medications that lower the blood pressure and heart rate by blocking the calcium channels in the heart and blood vessels, which cause vasodilation and reduced cardiac contractility. They can be used to treat hypertension, angina, and arrhythmias, but they are not recommended for most patients with heart failure, as they may worsen the cardiac function and increase the mortality.

Choice D reason: This is not the preferred agent for the initial treatment of heart failure. Direct renin inhibitors are a class of medications that lower the blood pressure by inhibiting the enzyme renin, which initiates the renin-angiotensin-aldosterone system, a hormonal pathway that regulates the blood pressure and fluid balance. They can be used to treat hypertension, but they have not been proven to be effective or safe for patients with heart failure.

Choice A reason: This is not the cause of airway obstruction in asthma. Collapse of the cartilaginous rings in the bronchi is a feature of tracheobronchomalacia, a condition in which the airways are weak and floppy.

Choice B reason: This is not the cause of airway obstruction in asthma. Type II alveolar cell injury and decreased surfactant are associated with acute respiratory distress syndrome (ARDS), a condition in which the alveoli are damaged and filled with fluid.

Choice C reason: This is not the cause of airway obstruction in asthma. Alveolar changes and pulmonary congestion are seen in chronic obstructive pulmonary disease (COPD), a condition in which the alveoli are enlarged and lose their elasticity.

Choice D reason: This is the correct cause of airway obstruction in asthma. Asthma is a chronic inflammatory disorder of the airways, characterized by mucus secretion, bronchoconstriction, and airway edema. These factors reduce the diameter of the airways and increase the resistance to airflow.