Chapter 1. Chronic Heart Failure
MM is a 58-year-old woman with cardiomyopathy (left ventricular ejection fraction [LVEF] 25%) following an acute MI. Immediately following her MI, she developed signs and symptoms of HF including shortness of breath (SOB) at rest. Which of the following best characterizes MM’s current ACC/AHA HF stage and NYHA class?
a. Stage A, NYHA class not applicable
c. Stage C, NYHA class II
d. Stage C, NYHA class IV
Answer d is correct. MM meets the criteria for Stage C. Patients such as MM who are Stage C have developed signs and/or symptoms of HF. Additionally, MM has symptoms at rest; therefore, she is NYHA class IV.
Answers a, b, and c are incorrect. Answers a to c are incorrect because MM has symptoms at rest and is post-MI. Patients who are Stage A are at risk for developing left ventricular dysfunction and HF (eg, due to hypertension, coronary artery disease). Patients who are Stage B have developed structural heart disease but have not developed signs and symptoms of HF. The NYHA classification system categorizes patients as class I if they are relatively asymptomatic and physical activity is not limited by the HF disease process. Patients who are NYHA class II and III are symptomatic with minimal and moderate physical activity, respectively.
Which of the following therapies decreases HR via inhibition of the If current in the sinoatrial node?
Answer d is correct. Ivabradine inhibits If current in the sinoatrial node, leading to reductions in HR without affecting myocardial contractility.
Answers a and b are incorrect. Metoprolol succinate and carvedilol are β-blockers, and decrease HR by inhibiting the effects of adrenergic neurotransmitters (eg, epinephrine) on β1 receptors in myocardial tissue. Consequently, transient reductions in myocardial contractility may also occur.
Answer c is incorrect. Although a precise mechanism of action for digoxin has not been well-elucidated, it is thought to lower HR via parasympathetic (ie, vagal) activation.
Which of the following laboratory values may be helpful in differentiating HF from other disease states that cause similar symptoms?