Epidemiology of Heart Failure: Heart Failure With Preserved Ejection Fraction and Heart Failure With Reduced Ejection Fraction

Definitions

The American Heart Association/American College of Cardiology Foundation (AHA/ACCF) define HF as a “complex clinical syndrome that results from any structural or functional impairment of ventricular filling or ejection of blood,” with a variety of symptoms, including dyspnea, edema, malaise, and decreased exercise tolerance. Cardiomyopathies are a group of diseases that affect the myocardium and frequently lead to HF, but should not be used interchangeably with the term HF. The term congestive heart failure is no longer preferred because patients may present with a variety of symptoms and not strictly volume overload.

HF can be divided into two broad categories: HF with reduced ejection fraction (HFrEF) and HF with preserved ejection fraction (HFpEF). This terminology supplants the terms systolic HF and diastolic HF, respectively. In the past, there have been multiple different definitions and variable left ventricular ejection fraction (LVEF) cutoffs used in clinical trials and guidelines for HFrEF (≤35%, <40%, and ≤40%) and HFpEF (>40%, >45%, >50%, and ≥55%). The most recent consensus guidelines from the ACC, AHA, Heart Failure Society of America (HFSA), and separate guidelines from the European Society of Cardiology (ESC) have attempted to provide some uniformity. Both groups define HFrEF as a LVEF of ≤40% and HFpEF as a LVEF of ≥50%. Per the ACC/AHA/HFSA guidelines, a LVEF of 41% to 49% is borderline HFpEF, considered similar in many respects to patients with HFpEF. Patients with previously diagnosed HFrEF who have recovered to a LVEF of >40% are categorized as improved HFpEF and represent a group that has not been well studied.

According to nomenclature from the ESC, HF with a LVEF of 40% to 49% is termed HF with mid-range EF (HFmrEF). To meet the ESC definitions of the HFpEF or HFmrEF, patients must have elevated natriuretic peptide levels in addition to HF symptoms and either relevant structural heart disease or diastolic dysfunction.

HF is further classified based on either symptoms or stages ( Table 27.1 ). The frequently used New York Heart Association functional classification system divides HF into four classes based on symptoms. The ACC/AHA system has four distinct stages that incorporate risk factors, structural heart disease, and symptoms. The ACC/AHA stages were devised to identify patients at risk for HF to help guide preventative measures. To prevent progression of HF, interventions are aimed at modifying risk factors for stage A and treating structural heart disease for stage B. Once the patient becomes symptomatic and progresses to stages C and/or D, therapies are aimed at reducing morbidity and mortality.

Causes of Heart Failure

There are multiple etiologies for HF, but a large proportion is secondary to ischemic heart disease. The prevalence of coronary artery disease (CAD) in new HF cases has been estimated to be as high as 68%. HF secondary to CAD is frequently referred to as ischemic cardiomyopathy, which results from compromised circulation of approximately two-thirds of the coronary blood supply. The nonischemic cardiomyopathy label represents all the other diverse etiologies of HF ( Box 27.1 ).

Prevalence

The prevalence of HF in the United States is estimated at 6.5 million American adults based on National Health and Nutrition Examination Survey (NHANES) data from 2011 to 2014. Despite many advances in the care of patients with cardiovascular disease and increased awareness of risk factors, it is estimated that HF prevalence will increase by 46% from 2012 to 2030, to >8 million Americans with HF. This prediction is largely due to an aging population and the increased burden of HF in older adults because HF prevalence increases with age. For example, between 2011 and 2014, the prevalence of HF in men was 0.3%, 1.4%, 6.2%, and 14.1% at ages 20 to 39, 40 to 59, 60 to 79, and 80+ years, respectively. Prevalence rates were similar in woman, increasing from 0.5% at age 20 to 39 years to 13.4% for age 80+ years. Overall, HF prevalence is similar between the sexes, affecting 2.3% of men and 2.6% of women in 2012. Over the past decade in the United States, prevalence continues to rise despite the incidence of HF leveling off ( Fig. 27.1 ).

The prevalence of HFpEF is also increasing. Among the Get With the Guidelines-Heart Failure Registry patients, 49.8% had HFrEF, 13.7% had borderline HFpEF, and 36.5% had HFpEF between 2005 and 2010. The proportion of patients hospitalized for HFpEF exacerbations increased from 33% to 39% over this time, whereas the proportion of HFrEF hospitalizations decreased.