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Heart failure is a long-term condition wherein the heart fails to pump blood as efficiently as it should [1]. Various factors cause this condition, one of the most common being hypertension [2]. As a result, blood gets backed up in the body, and pressure builds up in the lungs and the digestive system, causing chest pain and shortness of breath [3]. Ejection Fraction measures the efficiency and strength of the heart's performance. It determines how well the left ventricle, the heart's main pumping chamber, pumps blood and oxygen with each beat [4]. Heart failure with a low ejection fraction occurs when the left ventricular muscle does not pump as efficiently as normal [4]. An Ejection Fraction of less than 40% indicates that the heart is not pumping enough blood and may fail [4,5]. The most common cause of ejection fraction, being less than 45%, is a blockage or narrowing in one or more of the heart's four main arteries, which supply blood to the entire body [6]. Half of all heart failure patients have a reduced ejection fraction of 40% or below and are classified as heart failure with reduced ejection fraction. The other half may be grouped as heart failure with midrange ejection fraction (40–50%) or preserved ejection fraction (HFpEF), where the ejection fraction is greater than or equal to 50% [7].

Keywords: Heart Failure, Etiology, Reduced Ejection Fraction, Preserved Ejection fraction, Revascularization, CABG, Ventricular remodeling

Introduction

Over time, heart failure can damage the kidneys and other organs and lead to anemia, fluid retention, and fatigue, among other symptoms [8]. Several medications and procedures exist to help heart failure sufferers manage their symptoms and live longer healthier lives [9]. HFpEF is a rising problem in cardiac health, associated with getting older, being overweight, and having high blood pressure or even metabolic disorders [10]. Unfortunately, no available treatment is effective against this cardiac ailment [10]. It can be marked by an excessive amount of left ventricular pressure building up due to diastolic dysfunction, and there will be a hike in pressure can be observed both at rest and during exercise, ultimately can result in pulmonary hypertension [10]. Although the ejection fraction looks normal, people with HFpEF still experience mild deficiencies in systolic functioning and cannot take advantage of their systolic reserve capacity under stress. This results in a lesser degree of ejection fraction increase when compared to healthy subjects [10]. In this case, heart failure is due to left ventricular hypertrophy, or an enlargement of the left ventricle, which is often a result of the extra strain put on the heart by high blood pressure [11]. Heart failure with reduced ejection fraction is a complex, progressive medical condition associated with shortness of breath and impaired physical function. With its high mortality rate and risk of readmission, it has become one of the biggest public health challenges [12,13]. A person with high blood pressure will develop heart volume overload, leading to left ventricular hypertrophy. Thus, a person with high blood pressure and HFpEF will have signs and symptoms of both conditions [14].

One of the main challenges in treating heart failure with reduced ejection fraction is the highly individualized nature of the disease, in which age, comorbidities, and patient-specific factors can influence [15]. As a result, no single treatment approach is effective in all cases of heart failure with reduced ejection fraction. However, interventions such as exercise regimens and lifestyle modifications may help reduce heart failure symptoms with reduced ejection fraction [5]. Additionally, certain medications, such as angiotensin-converting enzyme inhibitors and beta blockers, may help slow the disease's progression and improve the quality of life for patients suffering from heart failure with reduced ejection fraction [7]. Statins have been shown to reduce left ventricular hypertrophy and fibrosis under laboratory conditions. A small study indicated that taking statins could decrease the risk of death among patients with HFpEF [7]. It is now understood that the most significant predictor of long-term survival following a heart attack is the capability of the left ventricle. This function has conventionally been described regarding ejection fraction, yet it remains unclear if this metric holds much value in a post-heart attack context [6]. Hence, the relevance of discussing this topic is proven. A low ejection fraction may be caused by a lack of contractility from severe cardiac damage or ongoing ischemia and could also arise from the dilation of the left ventricle due to infarct expansion. Therefore, end-systolic volume (ESV) or end-diastolic volume (EDV) might provide better indicators of prognoses than an ejection fraction alone [6].

Pathophysiology of Heart Failure

Cardiac failure can result from either systolic or diastolic dysfunction or both [16]. The etiological factors behind heart failure can be attributed to myocardial cell damage and decreased functional cells [17]. The three main culprits of this condition are ischemic heart disease, hypertension, and diabetes, doubling the risk of developing heart failure compared to those with normal blood pressure [17, 7].

Excessive alcohol consumption, exposure to toxic drugs, valvular disease, and prolonged arrhythmias can all cause heart failure. However, these are much less common when compared to the primary three factors [17].

Physiological processes in Heart failure with preserved ejection fraction (HFpEF) can be explained as a condition that happens more and more in people when they get older, or for those who are obese, those who have diabetes, and those who have high blood pressure. One of the other main characteristics of heart failure with preserved ejection fraction is the reduced ability or capacity for physical activity [18]. In any such case, the left ventricular filling pressure gets affected, resulting in pressure overload [10]. This extra pressure can lead to other consequences, such as secondary pulmonary hypertension [10]. In addition, this has become the most common type of heart failure, and its rate of occurrence compared to heart failure with reduced ejection fraction is still hiking [29].

Heart failure with reduced ejection fraction is when the left ventricle of the heart cannot pump adequate blood to the rest of the body [18]. This results in symptoms such as shortness of breath and fatigue caused by weakened, ineffective, or decreased heart pumping [5]. Based on epidemiological research, around half of heart failure (HF) patients have either normal or preserved ejection fraction [5]. Therefore, heart failure patients are classified into two groups:

1) Those with reduced or decreased ejection fraction, known as systolic failure [5].

2) Those with a preserved ejection fraction are usually referred to as diastolic failure [5].

Signs and Symptoms

As the heart weakens, patients experience shortness of breath due to lung buildup and swelling of their extremities and stomach area from their blood not circulating correctly [20]. Other symptoms such as nausea, lack of appetite, exercise intolerance, heart palpitations, rapid or irregular heartbeat, chest discomfort, weakness, and dizziness also become apparent [20]. Patients may also experience clammy or sweaty skin. Often cardiac disorders may have signs such as swelling or edema, abnormal heart rhythm, abnormal lung sounds, and symptoms like dyspnea, fatigue, and inability to perform physical functions [21]. The signs and symptoms associated with reduced ejection fraction are almost the same as in any heart disease; sometimes, it may be asymptomatic. Similarly, heart failure with preserved ejection fraction presents similar signs and symptoms [20].

Risk Factors

The elderly population is more prone to develop cardiovascular disease when compared to the younger generation [22]. Risk factors associated with any chronic heart disease, including the reduced ejection fraction and preserved ejection fraction, apart from aging, are hypertension, obesity, diabetes, high cholesterol, sedentary lifestyle [10]. Hypertension is a major factor causing diastolic heart failure or HFpEF. Although, many patients with systolic heart failure or heart failure with reduced ejection fraction may have a history of hypertension. The most common etiology of heart failure with reduced ejection fraction is ischemic heart disease, found to be a contributor in more than 60% of diagnoses. Patients with heart problems caused by lack of blood flow to the left ventricle have a much higher mortality rate than those with non-ischemic conditions [23]. Patients with diastolic heart failure may have coronary artery disease [23,22]. As a preventive measure, the same risk factors should be modified in both cases [22]. Also, sodium intake and other dietary features may influence the risk of heart failure in obese individuals and those over a certain age [24] .Above all, social or behavioral factors can harm heart health, such as smoking and drinking too much alcohol [25]. These social or behavioral factors can be considered as modifiable risk factors [25].