Pathology USMLE Step 1 Volume 2 Systemic Pathology PDF Free Download
Heart failure is any cause of heart dysfunction that keeps the heart from pumping enough blood to meet the metabolic needs of tissues in the body. Commonly in heart failure, the left ventricle is unable to eject volume of blood into the aorta, resulting in increased left ventricular end-diastolic volume and pressure (LVEDV and LVEDP, respectively). Heart failure is a common end point of many different cardiac diseases. Heart fa ilure can be divided into left- and right-sided heart failure. 1.1 Left-Sided Heart Failure Left-sided heart failure has a variety of causes, but usually can be broken into five categories. 1.1.1 Etiology of Congestive Heart Failure (CHF) • Cardiac Muscle Loss (Ischemia/Infarction): • Most common cause of CHF. • Lack of blood supply (ischemia) to cardiomyocytes secondary to myocardial infarction may result in coagulative necrosis. • Pressure Overload: The cardiomyocyte consistently functions at a higher level of contractility to achieve the same amount of cardiac output (CO) as prior, resulting in eventual heart failure. • Hypertension: Pressure overload can be caused by hypertension because it forces the heart to pump against high arterial pressures.
• Aortic Stenosis: Ventricular pressure must increase dramatically to overcome the increased afterload that is created by aortic stenosis, resulting in pressure overload. • Volume Overload: Volume overload can cause left-sided heart failure if an abundance of blood on the left side of the heart overloads the left atrium and ventricle. • Mitral Regurgitation: One cause of volume overload is mitral regurgitation because this causes blood to f low back into the left atrium during systole. • High Output: The other main cause of volume overload is high output failure, which can be seen in patients with severe anemia or thyrotoxicosis. • Loss of Contractility: Impaired muscle contractility may result in congestive heart failure. • Toxicity: Alcohol and chemotherapeutic drugs, such as doxorubicin, may be toxic to cardiomyocytes. • Infectious Myocarditis: Adenovirus, amastigotes phase in Chagas, diphtheria, and rheumatic fever; nnay cause cardiac injury.
