Heart failure
Overview
What is heart failure?
Heart failure is a pathophysiological state in which an abnormality in cardiac function results in the failure of the heart to pump blood under normal cardiac pressures at a rate that meets the requirements of metabolizing tissues1. Heart failure is a leading and increasing cause of morbidity and mortality worldwide2.
The pathophysiology of heart failure
Heart failure can be divided into heart failure with reduced ejection fraction (HFrEF) and heart failure with preserved ejection fraction (HFpEF)1. In both HFrEF and HFpEF, the amount of blood that is pumped out with each heart beat is reduced, but the mechanisms underlying these conditions are different. In patients with HFrEF, the ejection fraction is usually defined as ≤40%. The ventricular myocardium can no longer contract with a force that is sufficient to adequately pump the blood either because it has weakened or impaired contractility or because it cannot overcome an increased afterload1.
Conversely, HFpEF is a clinical syndrome of heart failure in the presence of preserved or normal left ventricular ejection fraction, with evidence of diastolic dysfunction by non-invasive or invasive hemodynamic measurement. The ventricular myocardium fails to relax during diastole1 (Figure 1).
Figure 1. Subtypes of heart failure. (a) HFrEF (b) HFpEF1
The pathophysiology of HFrEF is a progressive condition; risk factors lead to cardiac injury and then the development of myocardial dysfunction (initially asymptomatic), and then to worsening symptoms until the patient develops end-stage heart failure2. At the genetic and molecular levels, changes in cell structure occur. In the failing myocardium, pathological alterations in contractile, regulatory and cytoskeletal proteins that lead to myofibril dysfunction can be found (including dephosphorylation and altered expression, activity and localization of proteins). At the cellular level, the prolongation of action potentials is present in both patients and animal models due to abnormalities in sodium and potassium channels on the myocardial membrane, which leads to arrhythmias1. The pathophysiology of HFpEF remains highly debated and incompletely studied2.
Facts about heart failure
Symptoms2
Many patients experience symptoms for weeks or months before receiving a diagnosis of heart failure. The symptoms and signs of heart failure are necessary but not sufficient for its diagnosis2, which including:
Symptom2:
- Breathlessness
- Orthopnea
- Paroxysmal nocturnal dyspnea
- Fatigue
- Palpitations
- Ankle swelling
- Early satiety; abdominal bloating
- Anorexia, depression, confusion
- Cachexia
Sign2:
- Elevated jugular venous pressure
- Displaced apex beat
- Cardiac holosystolic murmur
- Third heart sound, gallop rhythm
- Pulmonary crackles
- Pleural effusion
- Hepatomegaly
- Hepatojugular reflux
- Ascites
- Peripheral oedema
Risk factors and causes1,3
Epidemiological studies have observed pathophysiological differences between patients with HFrEF and patients with HFpEF1. Data from a cohort study revealed the different of risk factors between HFrEF and HFpEF3:
Risk factors were associated with HFpEF and HFrEF:
- Baseline age
- Amino-terminal pro-B-type natriuretic peptide levels
- Pulse pressure
- Ischemic heart disease
- Waist circumference
- Obstructive sleep apnea
- Pacemaker
Risk factors were associated with HFpEF:
- Atrial fibrillation
- Warfarin therapy
- Body mass index (BMI)
- Hypertension
- Diabetes
- Renal dysfunction
- Low hemoglobin
- White cell count
- Β-blocker, statin, loop diuretic, non-steroidal anti-inflammatory and clopidogrel therapies
Risk factors were associated with HFrEF:
- Peripheral vascular disease
- Low platelet count
- Male gender
- Cigarette smoking
In validated models, male sex, left ventricular hypertrophy, bundle branch block, previous myocardial infarction and smoking were more strongly associated with HFrEF than with HFpEF, and age was more strongly correlated with HFpEF than with HFrEF. Other risk factors for heart failure include atherosclerosis, obesity and metabolic syndrome1.
Incidence, mortality and prevalence
The 2021 American Heart Association Statistical Update estimates the prevalence of HF to be 6 million which ~1.8% of the total US population. Other estimates indicate that the prevalence of HF in the United States and Canada is 1.5% to 1.9% of the population and in Europe 1% to 2%.4
The incidence of HF differed across studies due to differences in definitions and analysis. Importantly, however, temporal trends were congruent across reports and indicated that the incidence of HF was stable or perhaps even decreasing. Available data indicate that lifetime risks are very high regardless of sex, race, and geography, underscoring the importance of population-wide efforts to contain the burden of heart failure.4
Several analyses of National Statistics have convincingly shown that HF death rates have recently begun to increase. Recent increases broadly affect counties in the United States and racial and sex disparities persisted as mortality trends changed.4
Trends in incidence and mortality in hospitalized heart failure patients in Taiwan5
- According to Taiwan’s National Health Insurance Research Database, the age-stratified heart failure incidences were declined by 10–20% in people aged 55 years or older, but increased by ~4% among people younger than 44 years old between 2010 and 2015.5
- The all-cause mortality rate during index hospitalization was 8.5%, whereas the mortality rates at 30 days, 90 days, 180 days, 1 year, 2 years, and 3 years following discharge were 3.5%, 8.9%, 14.4%, 22.5%, 33.9%, and 42.8%, respectively, for those surviving index heart failure hospitalization.5
Footnotes:
-
HF, heart failure; HFrEF, heart failure with reduced ejection fraction; HFpEF, heart failure with preserved ejection fraction; LA, left atrium; LV, left ventricle; RA, right atrium;
RV, right ventricle; US, United States. -
References:
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Bloom MW, et al. Nat Rev Dis Primers. 2017;3:17058.
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Metra M, Teerlink JR. Lancet. 2017;390(10106):1981-1995.
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Gong FF, et al. Open Heart. 2018;5(2):e000782.
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Roger VL. Circ Res. 2021;128(10):1421-1434.
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Wang TD, et al. ESC Heart Fail. 2020;7(6):3653-3666.