Editing Heart failure (section)

==Diagnosis==
No diagnostic criteria have been agreed on as the [[Gold standard (test)|gold standard]] for heart failure, especially [[heart failure with preserved ejection fraction]] (HFpEF).

In the [[UK]], the [[National Institute for Health and Care Excellence]] recommends measuring [[N-terminal prohormone of brain natriuretic peptide|N-terminal pro-BNP (NT-proBNP)]] followed by an [[echocardiography|ultrasound of the heart]] if positive.<ref name="NICE2018ch1"/> In [[Europe]], the [[European Society of Cardiology]], and in the United States, the [[American Heart Association|AHA]]/[[American College of Cardiology|ACC]]/[[Heart Failure Society of America|HFSA]], recommend measuring NT-proBNP or BNP followed by an [[echocardiography|ultrasound of the heart]] if positive.<ref name="ESC2021"/><ref name="AHA2022"/> This is recommended in those with symptoms consistent with heart failure such as [[shortness of breath]].<ref name="AHA2022"/>

The [[European Society of Cardiology]] defines the diagnosis of heart failure as symptoms and signs consistent with heart failure in combination with "objective evidence of cardiac structural or functional abnormalities".<ref name="ESC2021"/> This definition is consistent with an international 2021 report termed "Universal Definition of Heart Failure".<ref name="ESC2021"/>{{rp|p=3613}} Score-based algorithms have been developed to help in the diagnosis of [[heart failure with preserved ejection fraction|HFpEF]], which can be challenging for physicians to diagnose.<ref name="ESC2021"/>{{rp|p=3630}} The [[American Heart Association|AHA]]/[[American College of Cardiology|ACC]]/[[Heart Failure Society of America|HFSA]] defines heart failure as symptoms and signs consistent with heart failure in combination with shown "structural and functional alterations of the heart as the underlying cause for the clinical presentation", for HFmrEF and HFpEF specifically requiring "evidence of spontaneous or provokable increased left ventricle filling pressures".<ref name="AHA2022"/>{{rp|pages=e276–e277}}

=== Algorithms ===
The [[European Society of Cardiology]] has developed a diagnostic algorithm for [[heart failure with preserved ejection fraction|HFpEF]], named HFA-PEFF.<ref name="ESC2021"/>{{rp|p=3630}}<ref name="HFA2019">{{cite journal | vauthors = Pieske B, Tschöpe C, de Boer RA, Fraser AG, Anker SD, Donal E, Edelmann F, Fu M, Guazzi M, Lam CS, Lancellotti P, Melenovsky V, Morris DA, Nagel E, Pieske-Kraigher E, Ponikowski P, Solomon SD, Vasan RS, Rutten FH, Voors AA, Ruschitzka F, Paulus WJ, Seferovic P, Filippatos G | title = How to diagnose heart failure with preserved ejection fraction: the HFA-PEFF diagnostic algorithm: a consensus recommendation from the Heart Failure Association (HFA) of the European Society of Cardiology (ESC) | journal = European Heart Journal | volume = 40 | issue = 40 | pages = 3297–3317 | date = October 2019 | pmid = 31504452 | doi = 10.1093/eurheartj/ehz641 | url = https://academic.oup.com/eurheartj/article/40/40/3297/5557740 | access-date = 20 February 2023 | url-status = live | doi-access = free | archive-url = https://web.archive.org/web/20230220182959/https://academic.oup.com/eurheartj/article/40/40/3297/5557740 | archive-date = 20 February 2023 }}</ref> HFA-PEFF considers symptoms and signs, typical clinical demographics (obesity, hypertension, diabetes, elderly, atrial fibrillation), and diagnostic laboratory tests, ECG, and echocardiography.<ref name="AHA2022"/>{{rp|p=e277}}<ref name="HFA2019"/>

=== Classification ===
==== "Left", "right" and mixed heart failure ====
One historical method of categorizing heart failure is by the side of the heart involved (left heart failure versus right heart failure). Right heart failure was thought to compromise blood flow to the lungs compared to left heart failure compromising blood flow to the [[aorta]] and consequently to the brain and the remainder of the body's systemic circulation. However, mixed presentations are common, and left heart failure is a common cause of right heart failure.<ref>{{cite web|url=http://www.ucsfhealth.org/conditions/heart_failure/signs_and_symptoms.html|title=Heart Failure: Signs and Symptoms|publisher=UCSF Medical Center|url-status=live|archive-url=https://web.archive.org/web/20140407080141/http://www.ucsfhealth.org/conditions/heart_failure/signs_and_symptoms.html|archive-date=7 April 2014|df=dmy-all}}</ref>

==== By ejection fraction ====
A more accurate classification of heart failure type is made by measuring [[ejection fraction]], or the proportion of blood pumped out of the heart during a single contraction.<ref name="HRS2014">{{cite web|url=http://www.hrsonline.org/Patient-Resources/The-Normal-Heart/Ejection-Fraction#axzz31jSSC7Uo|title=Ejection Fraction|website=Heart Rhythm Society|url-status=live|archive-url=https://web.archive.org/web/20140502123346/http://www.hrsonline.org/Patient-Resources/The-Normal-Heart/Ejection-Fraction#axzz31jSSC7Uo|archive-date=2 May 2014|access-date=7 June 2014|df=dmy-all}}</ref> Ejection fraction is given as a percentage with the normal range being between 50 and 75%.<ref name="HRS2014" /> The types are:
# [[Heart failure with reduced ejection fraction]] (HFrEF): Synonyms no longer recommended are "heart failure due to left ventricular systolic dysfunction" and "systolic heart failure".<ref name="pmid35460242">{{cite journal |vauthors=Santulli G, Wang X, Mone P |title=Updated ACC/AHA/HFSA 2022 guidelines on heart failure: what is new? From epidemiology to clinical management |journal=Eur Heart J Cardiovasc Pharmacother |volume=8 |issue=5 |pages=e23–e24 |date=August 2022 |pmid=35460242 |doi=10.1093/ehjcvp/pvac029 |pmc=9366633 |url=|doi-access=free }}</ref> HFrEF is associated with an ejection fraction less than 40%.<ref>{{cite web|url=http://www.heart.org/HEARTORG/Conditions/HeartFailure/SymptomsDiagnosisofHeartFailure/Ejection-Fraction-Heart-Failure-Measurement_UCM_306339_Article.jsp|title=Ejection Fraction Heart Failure Measurement|date=Feb 11, 2014|website=American Heart Association|url-status=live|archive-url=https://web.archive.org/web/20140714140152/http://www.heart.org/HEARTORG/Conditions/HeartFailure/SymptomsDiagnosisofHeartFailure/Ejection-Fraction-Heart-Failure-Measurement_UCM_306339_Article.jsp|archive-date=14 July 2014|access-date=7 June 2014|df=dmy-all}}</ref>
# Heart failure with mildly reduced ejection fraction (HFmrEF), previously called "heart failure with mid-range ejection fraction",<ref name="HFmrEF_ESC2021">{{Cite journal |title=2021 ESC Clinical Practice Guidelines for the diagnosis and treatment of acute and chronic heart failure |url=https://www.escardio.org/Congresses-Events/ESC-Congress/Congress-resources/Congress-news/2021-esc-clinical-practice-guidelines-for-the-diagnosis-and-treatment-of-acute-a |date=2021-08-27 |access-date=2023-02-06 |website=European Society of Cardiology |language=en |archive-date=6 February 2023 |archive-url=https://web.archive.org/web/20230206211913/https://www.escardio.org/Congresses-Events/ESC-Congress/Congress-resources/Congress-news/2021-esc-clinical-practice-guidelines-for-the-diagnosis-and-treatment-of-acute-a |url-status=live }}</ref> is defined by an ejection fraction of 41–49%.<ref name="HFmrEF_ESC2021"/>
# [[Heart failure with preserved ejection fraction]] (HFpEF): Synonyms no longer recommended include "diastolic heart failure" and "heart failure with normal ejection fraction."<ref name="NICE2010chp1" /><ref name=":0" /> HFpEF occurs when the left ventricle contracts normally during systole, but the ventricle is stiff and does not relax normally during diastole, which impairs filling.<ref name="NICE2010chp1" />
# Heart failure with recovered ejection fraction (HFrecovEF or HFrecEF): patients previously with HFrEF with complete normalization of left ventricular ejection (≥50%).<ref>{{cite journal | vauthors = Bozkurt B, Hershberger RE, Butler J, Grady KL, Heidenreich PA, Isler ML, Kirklin JK, Weintraub WS | title = 2021 ACC/AHA Key Data Elements and Definitions for Heart Failure: A Report of the American College of Cardiology/American Heart Association Task Force on Clinical Data Standards (Writing Committee to Develop Clinical Data Standards for Heart Failure) | journal = Circulation: Cardiovascular Quality and Outcomes | volume = 14 | issue = 4 | pages = e000102 | date = April 2021 | pmid = 33755495 | pmc = 8059763 | doi = 10.1161/HCQ.0000000000000102 }}</ref><ref>{{cite journal | vauthors = Devgun JK, Kennedy S, Slivnick J, Garrett Z, Dodd K, Derbala MH, Ortiz C, Smith SA | title = Heart failure with recovered ejection fraction and the utility of defibrillator therapy: a review | journal = ESC Heart Failure | volume = 9 | issue = 1 | pages = 1–10 | date = February 2022 | pmid = 34953039 | pmc = 8787956 | doi = 10.1002/ehf2.13729 }}</ref>

Heart failure may also be classified as acute or chronic. Chronic heart failure is a long-term condition, usually kept stable by the treatment of symptoms. [[Acute decompensated heart failure]] is a worsening of chronic heart failure symptoms, which can result in [[acute respiratory distress]].<ref name="Jessup2009">{{cite journal | vauthors = Jessup M, Abraham WT, Casey DE, Feldman AM, Francis GS, Ganiats TG, Konstam MA, Mancini DM, Rahko PS, Silver MA, Stevenson LW, Yancy CW | title = 2009 focused update: ACCF/AHA Guidelines for the Diagnosis and Management of Heart Failure in Adults: a report of the American College of Cardiology Foundation/American Heart Association Task Force on Practice Guidelines: developed in collaboration with the International Society for Heart and Lung Transplantation | journal = Circulation | volume = 119 | issue = 14 | pages = 1977–2016 | date = April 2009 | pmid = 19324967 | doi = 10.1161/CIRCULATIONAHA.109.192064 | doi-access =  }}</ref> [[High-output heart failure]] can occur when there is increased cardiac demand that results in increased left ventricular diastolic pressure which can develop into pulmonary congestion (pulmonary edema).<ref name="ReferenceA">{{DorlandsDict|nine/000953450|high-output heart failure}}</ref>

Several terms are closely related to heart failure and may be the cause of heart failure, but should not be confused with it. [[Cardiac arrest]] and [[asystole]] refer to situations in which no cardiac output occurs at all. Without urgent treatment, these events result in sudden death. Myocardial infarction ("Heart attack") refers to heart muscle damage due to insufficient blood supply, usually as a result of a blocked [[coronary artery]]. Cardiomyopathy refers specifically to problems within the heart muscle, and these problems can result in heart failure.<ref name="pmid36356656">{{cite journal |vauthors=Somma V, Ha FJ, Palmer S, Mohamed U, Agarwal S |title=Pacing-induced cardiomyopathy: A systematic review and meta-analysis of definition, prevalence, risk factors, and management |journal=Heart Rhythm |volume= 20|issue= 2|pages= 282–290|date=October 2022 |pmid=36356656 |doi=10.1016/j.hrthm.2022.09.019 |s2cid=253409509 |url=}}</ref> Ischemic cardiomyopathy implies that the cause of muscle damage is coronary artery disease. [[Dilated cardiomyopathy]] implies that the muscle damage has resulted in enlargement of the heart.<ref name="pmid34685747">{{cite journal |vauthors=Mages C, Gampp H, Syren P, Rahm AK, André F, Frey N, Lugenbiel P, Thomas D |title=Electrical Ventricular Remodeling in Dilated Cardiomyopathy |journal=Cells |volume=10 |issue=10 |date=October 2021 |page=2767 |pmid=34685747 |pmc=8534398 |doi=10.3390/cells10102767 |url=|doi-access=free }}</ref> [[Hypertrophic cardiomyopathy]] involves enlargement and ''thickening'' of the heart muscle.<ref name="pmid30219395">{{cite journal |vauthors=Tower-Rader A, Mohananey D, To A, Lever HM, Popovic ZB, Desai MY |title=Prognostic Value of Global Longitudinal Strain in Hypertrophic Cardiomyopathy: A Systematic Review of Existing Literature |journal=JACC Cardiovasc Imaging |volume=12 |issue=10 |pages=1930–1942 |date=October 2019 |pmid=30219395 |doi=10.1016/j.jcmg.2018.07.016 |url=|doi-access= |s2cid=52280408 }}</ref>

===Ultrasound===
An [[echocardiogram]] ([[ultrasound]] of the heart) is commonly used to support a clinical diagnosis of heart failure. This can determine the [[stroke volume]] (SV, the amount of blood in the heart that exits the ventricles with each beat), the [[end-diastolic volume]] (EDV, the total amount of blood at the end of diastole), and the SV in proportion to the EDV, a value known as the [[ejection fraction]] (EF). In pediatrics, the [[shortening fraction]] is the preferred measure of systolic function. Normally, the EF should be between 50 and 70%; in systolic heart failure, it drops below 40%. Echocardiography can also identify valvular heart disease and assess the state of the [[pericardium]] (the connective tissue sac surrounding the heart). Echocardiography may also aid in deciding specific treatments, such as medication, insertion of an [[implantable cardioverter-defibrillator]], or [[cardiac resynchronization therapy]]. Echocardiography can also help determine if acute myocardial ischemia is the precipitating cause, and may manifest as regional wall motion abnormalities on echo.<ref>{{cite journal | vauthors = Sirajuddin A, Mirmomen SM, Kligerman SJ, Groves DW, Burke AP, Kureshi F, White CS, Arai AE | title = Ischemic Heart Disease: Noninvasive Imaging Techniques and Findings | journal = Radiographics | volume = 41 | issue = 4 | pages = 990–1021 | date = 2021-07-01 | pmid = 34019437 | pmc = 8262179 | doi = 10.1148/rg.2021200125 }}</ref>

<gallery>
File:UOTW 48 - Ultrasound of the Week 1.webm|Ultrasound showing severe systolic heart failure<ref name=UOTW48>{{cite web |title=UOTW #48 – Ultrasound of the Week |url=https://www.ultrasoundoftheweek.com/uotw-48/ |website=Ultrasound of the Week |access-date=27 May 2017 |date=23 May 2015 |url-status=live |archive-url=https://web.archive.org/web/20170509130822/https://www.ultrasoundoftheweek.com/uotw-48/ |archive-date=9 May 2017 |df=dmy-all}}</ref>
File:UOTW 48 - Ultrasound of the Week 2.webm|Ultrasound showing severe systolic heart failure<ref name=UOTW48/>
File:UOTW 48 - Ultrasound of the Week 3.webm|Ultrasound of the lungs showing edema due to severe systolic heart failure<ref name=UOTW48/>
File:UOTW 48 - Ultrasound of the Week 4.webm|Ultrasound showing severe systolic heart failure<ref name=UOTW48/>
File:UOTW 48 - Ultrasound of the Week 5.jpg|Ultrasound showing severe systolic heart failure<ref name=UOTW48/>
</gallery>

===Chest X-ray===
[[File:Chest radiograph with signs of congestive heart failure - annotated.jpg|thumb|upright=1.3|[[Chest radiograph]] of a lung with distinct [[Kerley lines|Kerley B lines]], as well as an [[Cardiomegaly|enlarged heart]] (as shown by an increased [[cardiothoracic ratio]], cephalization of pulmonary veins, and minor [[pleural effusion]] as seen for example in the right [[Horizontal fissure of right lung|horizontal fissure]]. Yet, no obvious lung edema is seen. Overall, this indicates intermediate severity (stage II) heart failure.]]
[[Chest X-ray]]s are frequently used to aid in the diagnosis of CHF. In a person who is compensated, this may show [[cardiomegaly]] (visible enlargement of the heart), quantified as the [[cardiothoracic ratio]] (proportion of the heart size to the chest). In left ventricular failure, evidence may exist of vascular redistribution (upper lobe blood diversion or cephalization), [[Kerley lines]], [[peribronchial cuffing|cuffing of the areas around]] the [[bronchi]], and interstitial edema. Ultrasound of the lung may also detect Kerley lines.<ref>{{cite journal | vauthors = Al Deeb M, Barbic S, Featherstone R, Dankoff J, Barbic D | title = Point-of-care ultrasonography for the diagnosis of acute cardiogenic pulmonary edema in patients presenting with acute dyspnea: a systematic review and meta-analysis | journal = Academic Emergency Medicine | volume = 21 | issue = 8 | pages = 843–52 | date = August 2014 | pmid = 25176151 | doi = 10.1111/acem.12435 | doi-access = free }}</ref>
<gallery>
File:CHF2016.png|Congestive heart failure with small bilateral effusions
File:Kerley b lines.jpg|Kerley B lines
</gallery>

===Electrophysiology===
An [[electrocardiogram]] (ECG or EKG) may be used to identify [[arrhythmia]]s, [[ischemic heart disease]], [[right ventricular hypertrophy|right]] and [[left ventricular hypertrophy]], and presence of conduction delay or abnormalities (e.g. [[left bundle branch block]]). Although these findings are not specific to the diagnosis of heart failure, a normal ECG virtually excludes left ventricular systolic dysfunction.<ref>{{cite book | vauthors = Loscalzo J, Fauci AS, Braunwald E, Kasper DL, Hauser SL, Longo DL |title=Harrison's Principles of Internal Medicine |edition=17 |publisher=McGraw-Hill Medical |year=2008 |page=1447 |isbn=978-0-07-147693-5 }}</ref>

===Blood tests===
[[N-terminal prohormone of brain natriuretic peptide|N-terminal pro-BNP (NT-proBNP)]] is the favored biomarker for the diagnosis of heart failure, according to guidelines published 2018 by [[National Institute for Health and Care Excellence|NICE]] in the [[United Kingdom|UK]].<ref name="NICE2018ch2"/> [[Brain natriuretic peptide 32]] (BNP) is another biomarker commonly tested for heart failure.<ref name="NICE2018ch5">{{Cite book |last=National Guideline Centre (UK) |url=http://www.ncbi.nlm.nih.gov/books/NBK536086/ |title=Chronic Heart Failure in Adults: Diagnosis and Management |chapter=5. Diagnosing heart failure |date=September 2018 |publisher=National Institute for Health and Care Excellence (NICE) |isbn=978-1-4731-3093-7 |series=National Institute for Health and Care Excellence: Guidelines |location=London |pmid=30645061 |access-date=12 February 2023 |archive-date=20 March 2023 |archive-url=https://web.archive.org/web/20230320112711/http://www.ncbi.nlm.nih.gov/books/NBK536086/ |url-status=live }}</ref><ref name="ESC2021"/><ref name="pmid18290826">{{cite journal | vauthors = Ewald B, Ewald D, Thakkinstian A, Attia J | title = Meta-analysis of B type natriuretic peptide and N-terminal pro B natriuretic peptide in the diagnosis of clinical heart failure and population screening for left ventricular systolic dysfunction | journal = Internal Medicine Journal | volume = 38 | issue = 2 | pages = 101–13 | date = February 2008 | pmid = 18290826 | doi = 10.1111/j.1445-5994.2007.01454.x | s2cid = 35294486 }}</ref> An elevated NT-proBNP or BNP is a specific test indicative of heart failure. Additionally, NT-proBNP or BNP can be used to differentiate between causes of dyspnea due to heart failure from other causes of dyspnea. If a myocardial infarction is suspected, various [[cardiac marker]]s may be used.

[[Blood test]]s routinely performed include [[electrolyte]]s ([[sodium]], [[potassium]]), measures of [[kidney function]], [[liver function tests]], [[thyroid function test]]s, a [[complete blood count]], and often [[C-reactive protein]] if infection is suspected.

[[Hyponatremia]] (low serum sodium concentration) is common in heart failure. [[Vasopressin]] levels are usually increased, along with renin, angiotensin II, and catecholamines to compensate for reduced circulating volume due to inadequate cardiac output. This leads to increased fluid and sodium retention in the body; the rate of fluid retention is higher than the rate of sodium retention in the body, this phenomenon causes hypervolemic hyponatremia (low sodium concentration due to high body fluid retention). This phenomenon is more common in older women with low body mass. Severe hyponatremia can result in accumulation of fluid in the brain, causing [[cerebral edema]] and [[intracranial hemorrhage]].<ref name="US cardiology 2008">{{cite journal |vauthors=Abraham WT |title=Managing hyponatremia in heart failure |journal=US Cardiology Review |date=2008 |volume=5 |issue=1 |pages=57–60 |doi=10.15420/usc.2008.5.1.57 |url=https://www.uscjournal.com/articles/managing-hyponatremia-heart-failure |access-date=16 January 2018 |doi-access=free |archive-date=16 November 2021 |archive-url=https://web.archive.org/web/20211116040441/https://www.uscjournal.com/articles/managing-hyponatremia-heart-failure |url-status=live |url-access=subscription }}</ref>

===Angiography===
[[Angiography]] is the [[X-ray]] imaging of [[blood vessel]]s, which is done by injecting contrast agents into the [[Circulatory system|bloodstream]] through a thin plastic tube ([[catheter]]), which is placed directly in the blood vessel. X-ray images are called angiograms.<ref>{{Cite news|url=https://www.insideradiology.com.au/angiography/|title=Angiography – Consumer Information – InsideRadiology|date=2016-09-23|work=InsideRadiology|access-date=2017-08-22|language=en-US|url-status=live|archive-url=https://web.archive.org/web/20170822134640/https://www.insideradiology.com.au/angiography/|archive-date=22 August 2017|df=dmy-all}}</ref> Heart failure may be the result of coronary artery disease, and its prognosis depends in part on the ability of the [[coronary artery|coronary arteries]] to supply blood to the [[myocardium]] (heart muscle). As a result, [[coronary catheterization]] may be used to identify possibilities for revascularisation through [[percutaneous coronary intervention]] or [[Coronary artery bypass surgery|bypass surgery]].

===Staging===
Heart failure is commonly stratified by the degree of functional impairment conferred by the severity of the heart failure, as reflected in the [[New York Heart Association Functional Classification|New York Heart Association (NYHA) functional classification]].<ref>{{cite book |author=Criteria Committee, New York Heart Association |title=Diseases of the heart and blood vessels. Nomenclature and criteria for diagnosis |publisher=Little, Brown |location=Boston |year=1964 |page=114 |edition=6th}}</ref> The NYHA functional classes (I–IV) begin with class I, which is defined as a person who experiences no limitation in any activities and has no symptoms from ordinary activities. People with NYHA class II heart failure have slight, mild limitations with everyday activities; the person is comfortable at rest or with mild exertion. With NYHA class III heart failure, a marked limitation occurs with any activity; the person is comfortable only at rest. A person with NYHA class IV heart failure is symptomatic at rest and becomes quite uncomfortable with any physical activity. This score documents the severity of symptoms and can be used to assess response to treatment. While its use is widespread, the NYHA score is not very reproducible and does not reliably predict walking distance or exercise tolerance on formal testing.<ref>{{cite journal | vauthors = Raphael C, Briscoe C, Davies J, Ian Whinnett Z, Manisty C, Sutton R, Mayet J, Francis DP | title = Limitations of the New York Heart Association functional classification system and self-reported walking distances in chronic heart failure | journal = Heart | volume = 93 | issue = 4 | pages = 476–82 | date = April 2007 | pmid = 17005715 | pmc = 1861501 | doi = 10.1136/hrt.2006.089656 }}</ref>

In its 2001 guidelines, the [[American College of Cardiology]]/[[American Heart Association]] working group introduced four stages of heart failure:<ref name="Hunt-2005">{{cite journal | vauthors = Hunt SA, Abraham WT, Chin MH, Feldman AM, Francis GS, Ganiats TG, Jessup M, Konstam MA, Mancini DM, Michl K, Oates JA, Rahko PS, Silver MA, Stevenson LW, Yancy CW, Antman EM, Smith SC, Adams CD, Anderson JL, Faxon DP, Fuster V, Halperin JL, Hiratzka LF, Jacobs AK, Nishimura R, Ornato JP, Page RL, Riegel B | title = ACC/AHA 2005 Guideline Update for the Diagnosis and Management of Chronic Heart Failure in the Adult: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Writing Committee to Update the 2001 Guidelines for the Evaluation and Management of Heart Failure): developed in collaboration with the American College of Chest Physicians and the International Society for Heart and Lung Transplantation: endorsed by the Heart Rhythm Society | journal = Circulation | volume = 112 | issue = 12 | pages = e154–235 | date = September 2005 | pmid = 16160202 | doi = 10.1161/CIRCULATIONAHA.105.167586 | doi-access = free }}</ref>
* Stage A: People at high risk for developing HF in the future, but no functional or structural heart disorder
* Stage B: A structural heart disorder, but no symptoms at any stage
* Stage C: Previous or current symptoms of heart failure in the context of an underlying structural heart problem, but managed with medical treatment
* Stage D: Advanced disease requiring hospital-based support, a heart transplant, or [[palliative care]]

The ACC staging system is useful since stage A encompasses "pre-heart failure" – a stage where intervention with treatment can presumably prevent progression to overt symptoms. ACC stage A does not have a corresponding NYHA class. ACC stage B would correspond to NYHA class I. ACC stage C corresponds to NYHA class II and III, while ACC stage D overlaps with NYHA class IV.
* The degree of coexisting illness: i.e. heart failure/systemic hypertension, heart failure/pulmonary hypertension, heart failure/diabetes, heart failure/kidney failure, etc.
* Whether the problem is primarily increased venous back pressure ([[Preload (cardiology)|preload]]), or failure to supply adequate arterial perfusion ([[afterload]])
* Whether the abnormality is due to low cardiac output with high [[systemic vascular resistance]] or high cardiac output with low vascular resistance (low-output heart failure vs. high-output heart failure)

===Histopathology===
[[File:Histopathology of pulmonary congestion and siderophages.jpg|thumb|Siderophages (one indicated by white arrow) and pulmonary congestion, indicating left [[congestive heart failure]]]]
[[Histopathology]] can diagnose heart failure in [[autopsy|autopsies]]. The presence of [[siderophage]]s indicates chronic left-sided heart failure, but is not [[sensitivity and specificity|specific]] for it.<ref>{{cite book| vauthors = Majno G, Joris I |title=Cells, Tissues, and Disease: Principles of General Pathology|url=https://books.google.com/books?id=8yAf6U7njlcC&pg=PA620|access-date=19 March 2013|date=12 August 2004|publisher=Oxford University Press|isbn=978-0-19-974892-1|page=620}}</ref> It is also indicated by congestion of the pulmonary circulation.