What is heart failure?

Heart failure is a condition characterized by the heart's inability to pump blood to the rest of the body. As a result, it can no longer meet the body’s metabolic demands, including the supply of sufficient oxygen.^1,2 Heart failure, which is often the end stage of many common cardiac conditions, is prevalent in the United States, affecting between 8% and 10% of all people over the age of 60.³ Diagnosis of new cases of heart failure increases with age and lifetime risk of heart failure increases with other cardiovascular risk factors, such as hypertension.⁴ Despite many evidence-based therapies, heart failure has a high mortality rate.⁵

Types of Heart Failure

Heart failure is often divided into two main sub-types based on ejection fraction, which is a measurement of the amount of blood pumped out of the heart with each contraction. The first subtype is Heart Failure with Reduced Ejection Fraction (HFrEF), which is generally associated with etiologies that cause systolic dysfunction from either an increase in afterload or a decrease in contractility of the heart.¹ Common causes include myocardial infarction, mitral regurgitation, aortic regurgitation, and dilated cardiomyopathies. Diagnosis requires an ejection fraction of less than or equal to 40% by transthoracic echocardiogram. The second subtype is Heart Failure with Preserved Ejection Fraction (HFpEF), which is generally associated with etiologies that cause diastolic dysfunction and is typically characterized by increased left ventricular filling pressures and impaired ventricular relaxation. Recent studies have shown that HFpEF, which may account for about 50% of HF cases⁶, has more complex and heterogeneous pathophysiology than HFrEF.^7,8 Some causes include left ventricular hypertrophy, restrictive cardiomyopathy from illnesses such as amyloidosis or sarcoidosis and myocardial fibrosis.¹ Diagnosis requires relatively normal left ventricular function signified by a left ventricular ejection fraction of over 50% and evidence of left ventricular diastolic dysfunction.⁹ The HFrEF and HFpEF patient populations differ in terms of characteristics and comorbid conditions, with HFpEF patients more likely to be diagnosed with obesity, hypertension, and atrial fibrillation.¹⁶ Data from the Organized Program to Initiate Lifesaving Treatment in Hospitalized Patients With Heart Failure (OPTIMIZE-HF) registry, which compared over 40,000 patients diagnosed with either HFpEF and HFrEF, found that patients with HFpEF were more likely to be Caucasian, female, older and have a history of hypertension, however both groups had similar rehospitalization rates and mortality risk.¹⁰

As explained above, HFpEF diagnosis requires an ejection fraction of 50% or more and HFrEF diagnosis requires an ejection fraction of 40% or less, this leaves patients with an ejection fraction between 41% and 49% without a clear subtype. These patients are often referred to as having heart failure with borderline ejection fraction (or mid-range EF) and are thought to be similar in characteristics and outcomes to those with HFpEF.^11,12 

Heart failure may initially (or primarily) affect the right or left ventricle and can be further categorized as right-sided heart failure or left-sided heart failure. Right-sided heart failure is most commonly caused by left-sided heart failure or other conditions that increase right ventricular afterload, such as pulmonary hypertension or pulmonary embolism.¹³

Symptoms

Symptoms may vary depending on whether the heart failure is right or left-sided. The symptoms associated with right-sided heart failure are due to the physiologic effects of transmission of the increased right ventricular pressure throughout the veins of the body, such as jugular venous distension, peripheral edema, or hepatomegaly.¹ Left-sided heart failure can cause insufficient cardiac output to the body as well as increased pressure in the lung vasculature, both are implicated in dyspnea which is one of the most common symptoms associated with this disease.

Diagnosis

Although ejection fraction is necessary to determine a patient’s heart failure subtype, the general diagnosis of heart failure relies on clinical signs and symptoms and there is no single diagnostic test.¹¹ The American College of Cardiology Foundation and American Heart Association Task Force recommend physicians utilize history and physical exam to identify patients with heart failure. Once heart failure is suspected there are tests and imaging that can help make the diagnosis. Echocardiography is considered the most useful diagnostic test for heart failure. Echocardiograms can determine ejection fraction as well as identify causes for heart failure such as heart valve abnormalities, increased left ventricular wall thickness, or increased pulmonary artery pressures.¹¹ Chest radiography is another form of imaging that can be useful in diagnosing heart failure. On chest radiography physicians should look for signs of cardiomegaly or pulmonary congestion which are both associated with heart failure.¹⁵ Another useful test is serum levels of B-type natriuretic peptide (BNP) which is a hormone secreted in response to increased intracardiac pressure.¹ High levels of BNP are associated with heart failure and levels below 80pg/ml have been found to have a strong negative predictive value.¹⁴ Additional tests, such as a cardiac catheterization, or serum laboratory tests (e.g. thyroid hormone, amyloid, iron levels), may be done to investigate the HF sub-type.

^References

1. Lilly LS. Pathophysiology of Heart Disease: A Collaborative Project of Medical Students and Faculty, Sixth Edition. Wolters Kluwer; 2016.
2. Braunwald E, Ross J, Jr., Sonnenblick EH. Mechanisms of contraction of the normal and failing heart. N Engl J Med 1967; 277 (19): 1012-1022 concl.
3. Roger VL, Go AS, Lloyd-Jones DM, et al. Heart disease and stroke statistics--2012 update: a report from the American Heart Association. Circulation 2012; 125 (1): e2-e220.
4. Huffman MD, Berry JD, Ning H, et al. Lifetime risk for heart failure among white and black Americans: cardiovascular lifetime risk pooling project. J Am Coll Cardiol 2013; 61 (14): 1510-1517.
5. Stewart S, MacIntyre K, Hole DJ, Capewell S, McMurray JJ. More 'malignant' than cancer? Five-year survival following a first admission for heart failure. Eur J Heart Fail 2001; 3 (3): 315-322.
6. Owan TE, Redfield MM. Epidemiology of diastolic heart failure. Prog Cardiovasc Dis. 2005;47(5):320-332.
7. Westphal JG, Bekfani T, Schulze PC. What's new in heart failure therapy 2018? Interact Cardiovasc Thorac Surg 2018; 27 (6): 921-930.
8. van Heerebeek L, Paulus WJ. Understanding heart failure with preserved ejection fraction: where are we today? Neth Heart J 2016; 24 (4): 227-236.
9. Paulus WJ, Tschope C, Sanderson JE, et al. How to diagnose diastolic heart failure: a consensus statement on the diagnosis of heart failure with normal left ventricular ejection fraction by the Heart Failure and Echocardiography Associations of the European Society of Cardiology. Eur Heart J 2007; 28 (20): 2539-2550.
10. Fonarow GC, Stough WG, Abraham WT, et al. Characteristics, treatments, and outcomes of patients with preserved systolic function hospitalized for heart failure: a report from the OPTIMIZE-HF Registry. J Am Coll Cardiol 2007; 50 (8): 768-777.
11. Yancy CW, Jessup M, Bozkurt B, et al. 2013 ACCF/AHA guideline for the management of heart failure: a report of the American College of Cardiology Foundation/American Heart Association Task Force on practice guidelines. Circulation 2013; 128 (16): e240-327.
12. Butler J, Anker SD, Packer M. Redefining Heart Failure With a Reduced Ejection Fraction [published online ahead of print, 2019 Sep 13]. JAMA. 2019;10.1001/jama.2019.15600.
13. Konstam MA, Kiernan MS, Bernstein D, et al. Evaluation and Management of Right-Sided Heart Failure: A Scientific Statement From the American Heart Association. Circulation 2018; 137 (20): e578-e622.
14. Maisel A. B-type natriuretic peptide levels: diagnostic and prognostic in congestive heart failure: what's next? Circulation 2002; 105 (20): 2328-2331.
15. Badgett RG, Mulrow CD, Otto PM, Ramirez G. How well can the chest radiograph diagnose left ventricular dysfunction? J Gen Intern Med 1996; 11 (10): 625-634.
16. Owan TE, Hodge DO, Herges RM, Jacobsen SJ, Roger VL, Redfield MM. Trends in prevalence and outcome of heart failure with preserved ejection fraction. N Engl J Med. 2006;355(3):251-259.