The New York Heart Association (NYHA) classification sorts patients with heart failure into four classes, I to IV, by how much their symptoms limit physical activity. Class I has no limitation, Class II slight limitation, Class III marked limitation and Class IV symptoms at rest. A clinician assigns the class from the patient's symptoms, and it can move up or down as treatment works or the disease progresses.
The system is named after the New York Heart Association, which first published it in 1928, and it is still the most widely used way to describe heart failure symptoms in clinics and clinical trials. It matters to device clinics because NYHA class is written into the eligibility criteria for ICDs, cardiac resynchronization therapy and pulmonary artery pressure sensors, and it is the shorthand that referrals and implant notes use to describe how a patient is doing.
You may also see it written as NYHA functional class (NYHA FC), the NYHA scale or the NYHA score. All of these refer to the same four-class system.
Key Takeaways
- NYHA class describes symptoms and functional limitations today. ACC/AHA stages describe how far the disease has progressed, and a patient never moves back to an earlier stage.
- Class II and Class III are the most searched and the most common in practice. The difference is whether ordinary activity (Class II) or less than ordinary activity (Class III) brings on symptoms.
- NYHA class is part of the eligibility criteria for implantable cardioverter-defibrillators (ICDs), cardiac resynchronization therapy (CRT) and implantable pulmonary artery pressure monitoring such as CardioMEMS.
- The class is a clinician's judgement from the patient's account, so it varies between visits and between clinicians. Objective measures such as a 6-minute walk test or natriuretic peptide levels are often used alongside it.
- Patients in Class II to IV with a CRT device, ICD or pulmonary artery pressure sensor generate heart failure data that the device clinic reviews remotely.
What Are NYHA Classes I, II, III and IV?
The American Heart Association describes the four classes as follows.
| NYHA class | Limitation of physical activity | Symptoms | Everyday example |
|---|---|---|---|
| Class I | None | Ordinary physical activity does not cause undue fatigue, palpitations or shortness of breath | Climbs stairs and walks briskly without symptoms |
| Class II | Slight | Comfortable at rest; ordinary physical activity causes fatigue, palpitations or shortness of breath | Short of breath after two flights of stairs or a long walk |
| Class III | Marked | Comfortable at rest; less than ordinary activity causes fatigue, palpitations or shortness of breath | Short of breath walking one block or getting dressed |
| Class IV | Unable to carry on any physical activity without discomfort | Symptoms at rest; any activity increases discomfort | Short of breath sitting still or lying flat |
What is NYHA Class I heart failure?
NYHA Class I means the patient has heart failure but no limitation of physical activity. Ordinary activity does not cause undue fatigue, palpitations or shortness of breath.
What is the difference between NYHA Class II and Class III?
NYHA Class II indicates slight limitation of physical activity, with symptoms during ordinary activity. NYHA Class III indicates marked limitation, with symptoms during less than ordinary activity. Patients in both classes are generally comfortable at rest.
What is NYHA Class IV heart failure?
NYHA Class IV means the patient cannot carry on any physical activity without discomfort and has symptoms even at rest, such as shortness of breath while sitting or lying flat. Class IV patients are often evaluated for advanced heart failure therapies.
What does an NYHA class mean for a patient?
If your care team has told you your NYHA class, it describes how your heart failure symptoms affect your daily activities right now. It is not a fixed label. Many people move to a lower class as their medicines and treatment take effect. Your class also helps your care team decide on treatments, including whether a device such as an ICD, a CRT device or a pressure sensor could help. Ask your cardiology team what your class means for your own treatment plan.
How Is NYHA Class Different From ACC/AHA Heart Failure Stages?
The two systems answer different questions and are used together. The 2022 AHA/ACC/HFSA heart failure guideline defines four stages, A to D, that track the disease itself. NYHA class rates the symptoms of patients who are already in Stage C or D.
| ACC/AHA stage | What it means | NYHA class |
|---|---|---|
| Stage A: at risk | Risk factors such as hypertension or diabetes, no structural heart disease, no symptoms | Not applicable |
| Stage B: pre-heart failure | Structural heart disease or abnormal cardiac function, no symptoms | Not applicable (no symptoms) |
| Stage C: symptomatic heart failure | Current or previous heart failure symptoms | Class I to IV, depending on current symptoms |
| Stage D: advanced heart failure | Marked symptoms that interfere with daily life despite treatment | Usually Class IV |
A patient in Stage C stays in Stage C even when treatment controls their symptoms, while their NYHA class can improve from III to I. That is why NYHA class is the measure clinicians track from visit to visit.
How Do Clinicians Assign an NYHA Class?
There is no test that produces an NYHA class. The clinician asks what activities bring on symptoms and assigns the class that best fits the answer. That makes it quick and familiar, and also subjective. A 2019 analysis in the Journal of the American Heart Association, using data from four National Institutes of Health heart failure trials, found that patients classed as NYHA II and III overlapped considerably on objective measures, including NT-proBNP levels, Kansas City Cardiomyopathy Questionnaire (KCCQ) scores and 6-minute walk distance.
Clinicians therefore often record objective measures alongside the class:
- 6-minute walk distance
- KCCQ or another patient-reported symptom score. Patient-reported outcomes such as the KCCQ also feature in Medicare's new heart failure payment model.
- Natriuretic peptides (BNP or NT-proBNP)
- Peak oxygen uptake on cardiopulmonary exercise testing
- Left ventricular ejection fraction (LVEF) on echocardiography
Why Does NYHA Class Matter for Device Therapy?
NYHA class appears in the eligibility criteria for most heart failure devices, which is why device clinics see it on referrals and in implant documentation.
| Therapy | Where NYHA class fits in eligibility | Source |
|---|---|---|
| Primary prevention ICD | LVEF 35% or less with NYHA Class II or III symptoms despite guideline-directed medical therapy | 2022 AHA/ACC/HFSA guideline |
| Cardiac resynchronization therapy (CRT) | LVEF 35% or less, sinus rhythm, left bundle branch block with QRS of 150 ms or more, and NYHA Class II to ambulatory Class IV symptoms on guideline-directed therapy | 2022 AHA/ACC/HFSA guideline |
| Implantable pulmonary artery pressure sensor (CardioMEMS) | NYHA Class II or III with a heart failure hospitalization in the past year or raised natriuretic peptides | FDA-approved indication (expanded 2022) |
| Advanced therapies (mechanical circulatory support, transplant) | Considered for Stage D, usually NYHA Class IV | 2022 AHA/ACC/HFSA guideline |
How Does NYHA Classification Affect Remote Heart Failure Monitoring?
NYHA classification provides clinical context for remote heart failure monitoring but does not independently determine monitoring frequency or device alerts. Remote cardiac devices provide diagnostic trends that help clinicians identify potential worsening heart failure between visits.
Patients in Class II to IV are the ones most likely to have a device that sends heart failure data to the clinic:
- CRT-D and ICD diagnostics. Many devices record trends linked to fluid build-up and worsening heart failure, such as thoracic impedance, heart rate variability, activity levels and night-time heart rate. Some combine them into a single heart failure alert.
- Pulmonary artery pressure sensors. CardioMEMS patients take a daily pressure reading at home, and the heart failure team adjusts treatment based on the trend. Remote monitoring of the sensor is billed with CPT 93264; our cardiac remote monitoring CPT codes guide covers the related codes.
- Arrhythmia data. New or rising atrial fibrillation burden often accompanies worsening heart failure and shows up in the same transmissions.
For the clinic, the practical point is that a patient's NYHA class and their device data should tell the same story. A Class II patient whose heart failure diagnostic alert is rising, or whose atrial fibrillation burden has jumped, may be heading toward Class III before the next office visit. Our guide to pacemaker and ICD remote monitoring explains how those transmissions reach the clinic and how alerts are triaged.
How Octagos Supports Heart Failure Monitoring
Octagos brings heart failure diagnostics from every major device manufacturer, and pulmonary artery pressure data from CardioMEMS, into one vendor-neutral queue. Atlas AI™ triages each transmission, and in the Two-Brain Approach™ an IBHRE-certified cardiac device specialist reviews it before it reaches the heart failure team, with the report filed in the clinic's EHR.
At Penn Presbyterian Medical Center, the heart failure program grew from 18 to 154 actively monitored patients, and 92% of HeartLogic alerts were addressed within three days. Learn more about heart failure monitoring with Octagos.
See how Octagos supports heart failure monitoring. Book a demo.
Frequently Asked Questions
What are the four NYHA classes?
Class I: no limitation of physical activity. Class II: slight limitation, with symptoms during ordinary activity. Class III: marked limitation, with symptoms during less than ordinary activity. Class IV: symptoms at rest and discomfort with any activity.
Is NYHA class the same as heart failure stage?
No. ACC/AHA stages A to D track how far heart failure has progressed and only move forward. NYHA classes I to IV describe current symptoms in patients who have heart failure, and they can improve with treatment.
Can NYHA class improve?
Yes. A patient can move from Class III to Class II or Class I as guideline-directed medical therapy or device therapy such as CRT takes effect. The class also worsens if the heart failure progresses.
Who assigns the NYHA class?
The treating clinician, usually a cardiologist, heart failure specialist or advanced practice provider, assigns it from the patient's description of what activities bring on symptoms.
Is the NYHA classification used for angina?
No. NYHA classes describe heart failure symptoms. Angina is usually graded with a separate scale, the Canadian Cardiovascular Society (CCS) angina classification, which also has four classes. The two are easy to confuse because both use Roman numerals I to IV.
Which NYHA classes qualify for CardioMEMS?
The FDA-approved indication covers patients in NYHA Class II or III who have had a heart failure hospitalization in the past year or have raised natriuretic peptide levels.
Sources: American Heart Association, Classes and Stages of Heart Failure; 2022 AHA/ACC/HFSA Guideline for the Management of Heart Failure (Circulation); 2019 analysis of NYHA class and objective measures in NIH heart failure trials (Journal of the American Heart Association). This article is general information and is not medical advice.