Decreased left ventricular (LV) function, often manifested as reduced ejection fraction (EF), is a hallmark of heart failure with reduced ejection fraction (HFrEF), also known as systolic heart failure. This condition signifies a significant impairment in the heart's ability to pump blood effectively to the body, leading to a cascade of debilitating symptoms and potentially life-threatening complications. Understanding the mechanisms, symptoms, diagnosis, and management of decreased LV function is crucial for effective patient care.
Ejection Fraction (EF) and its Significance:
Ejection fraction is a crucial indicator of LV function. It represents the percentage of blood ejected from the left ventricle with each contraction. A normal EF generally ranges from 55% to 70%. An EF below 40% is indicative of reduced LV function and often signifies HFrEF. However, it's important to note that EF is not the sole determinant of heart failure; some individuals can experience heart failure with preserved ejection fraction (HFpEF), where the EF remains within the normal range, but diastolic dysfunction impairs the heart's ability to fill properly. This article focuses primarily on HFrEF, where decreased LV function is directly linked to a reduced EF.
Mechanisms Leading to Decreased LV Function:
Several factors can contribute to the decline in LV function, resulting in HFrEF. These include:
* Coronary Artery Disease (CAD): The most common cause, CAD reduces blood flow to the heart muscle, leading to ischemia and subsequent damage to the myocardium. This damage weakens the heart muscle, impairing its contractile ability and reducing EF.
* Myocardial Infarction (MI): A heart attack, or MI, causes significant damage to the heart muscle, often resulting in a large scar tissue area that reduces the heart's pumping capacity. The extent of the damage directly correlates with the severity of LV dysfunction.
* Dilated Cardiomyopathy (DCM): This condition involves the enlargement and weakening of the heart muscle. The dilated ventricle struggles to contract efficiently, leading to a significant reduction in EF. Causes of DCM can be diverse, including genetic factors, infections, toxins, and certain medications.
* Hypertensive Heart Disease: Chronic high blood pressure places excessive strain on the heart muscle, leading to thickening and eventual weakening of the LV. Over time, this can result in decreased LV function and HFrEF.
* Valvular Heart Disease: Conditions affecting the heart valves, such as aortic stenosis or mitral regurgitation, can impair the heart's ability to pump blood effectively, leading to LV dysfunction.
* Cardiomyopathies of other causes: Various other conditions, including infiltrative cardiomyopathies (e.g., amyloidosis), inflammatory cardiomyopathies (e.g., myocarditis), and arrhythmogenic right ventricular cardiomyopathy (ARVC), can all contribute to decreased LV function.
Symptoms of Left-Sided Heart Failure (Related to Decreased LV Function):
The symptoms of left-sided heart failure, stemming from decreased LV function, are often related to the body's inadequate perfusion due to the reduced cardiac output. These can include:
* Shortness of breath (dyspnea): This is a cardinal symptom, often occurring initially during exertion but progressing to rest. It may manifest as breathlessness on lying down (orthopnea) or the need to sit up to breathe (paroxysmal nocturnal dyspnea).
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