USMLE (United States Medical Licensing Examination) Step 1 Practice Exam

Which type of heart failure is characterized by impaired contractility and increased afterload?

1. Diastolic heart failure

2. Coarctation of the aorta

3. Systolic heart failure

4. Mitral stenosis

The correct answer is: Systolic heart failure

Systolic heart failure is characterized by impaired contractility of the heart muscle, leading to a decreased ability to pump blood effectively. In this condition, the heart cannot generate enough force during contraction to maintain adequate cardiac output. This impairment can occur due to various factors, including damage to the myocardial tissue from ischemia or infarction, dilated cardiomyopathy, or volume overload resulting in muscle stretch. In addition to impaired contractility, systolic heart failure often involves increased afterload. Afterload refers to the resistance the heart must work against to eject blood during systole. Conditions that lead to increased vascular resistance, such as hypertension or aortic stenosis, contribute to this increased afterload. As the heart struggles to pump against this elevated resistance, it may become progressively weaker, exacerbating the heart failure condition. Understanding systolic heart failure in this context is crucial, as it differentiates it from other forms of heart failure, such as diastolic heart failure, which primarily involves impaired filling of the heart rather than contractility, and their respective hemodynamic profiles.