New York Heart Association (NYHA) Functional Classification


The original NYHA Functional Classification was published in 1928. This was a time before important diagnostic modalities like the portable ECG, echocardiogram, exercise stress test and the cardiovascular disease biomarker B-type natriuretic peptide (BNP) assay.

McDonald and Wilkinson (2017) and other researchers are advocating for the increased use of natriuretic peptides as part of the strategies for heart failure diagnosis and prevention. The use of these biomarkers has been shown to improve diagnostic accuracy for HF and provide prognostic information for more than a decade of use with recommendations by national and international cardiovascular organizations.

The NYHA classification has been updated many times. Today's version includes two sections; 1) a subjective description of functional capacity and 2) an objective diagnostic assessment of cardiovascular disease. While subjective inconsistencies may result when classifying patients in class II or III, functional capacity remains a powerful prognostic indicator and is routinely used for clinical staging of heart failure today.

New York Heart Association (NYHA) Functional Classification
Class Patient Symptoms
I No limitation of physical activity. Ordinary physical activity does not cause undue fatigue, palpitation, dyspnea (shortness of breath).
II Slight limitation of physical activity. Comfortable at rest. Ordinary physical activity results in fatigue, palpitation, dyspnea (shortness of breath).
III Marked limitation of physical activity. Comfortable at rest. Less than ordinary activity causes fatigue, palpitation, or dyspnea.
IV Unable to carry on any physical activity without discomfort. Symptoms of heart failure at rest. If any physical activity is undertaken, discomfort increases.

Source: https://www.heart.org/en/health-topics/heart-failure/what-is-heart-failure/classes-of-heart-failure

One commonly used technique to assess the functional capacity of patients is the Six-minute walk test (6MWT). The 6MWT has been shown to be a reliable, inexpensive, safe and easy to administer test that correlates with health outcomes (Rostagno, C. Gensini, 2008). (https://www.lung.org/lung-health-and-diseases/lung-procedures-and-tests/six-minute-walk-test.html, updated 2018).

Casanova et al (2011) studied 444 healthy subjects from seven countries to determine standard performance on the 6MWT. The 6MWT measures meters (m) walked as quickly as possible by the individual in six minutes.

The mean meters walked by all subjects was 571+ or – 90 m with male subjects walking 30m more than females. This is consistent with other similar studies. Older subjects walked shorter distances than younger subjects.

Rasekaba, Lee, Naughton, Williams & Holland (2009) determined a distance less than 350 m on the 6MWT to be associated with an increased mortality in chronic HF patients. A lowering of the walking distance of 50 m or more is considered clinically significant. Ferreira, et al. (2019) concluded in their research the 6-minute walk test distance at baseline and a decline in walking distance were both associated with worse prognosis.

Bittner et al (1993) studied 898 patients with left ventricular dysfunction with either radiological evidence of HF and/or an ejection fraction of 0.45 or lower. During the 242 days of follow up 114 patients either died or were hospitalized for CHF. The lowest performance group on the 6MWT had a statistically greater chance of dying or being hospitalized than the higher performing group. See detailed instruction about the 6MWT at the Heart Foundation website.

In an updated study by Wegrzynowska-Teodorczyk (2013), the researchers also found the distance covered during the 6MWT predicted the risk of death or hospitalization. Distance covered during a six-minute walk test predicts long-term cardiovascular mortality and hospitalization rates in men with systolic heart failure: an observational study. They studied 243 men with stable systolic heart failure.

69% of the participants died or required hospitalization during the following 3 years. The statistical analysis showed the shorter the distance walked in the 6MWT, the greater the 1-year and 3-year mortality risk.
Du, et al., (2017) reviewed research on the 6MWT in chronic heart failure published from 2012 to 2017. The researchers found the 6MWT not to be as accurate as possible in determining peak VO2. They suggest using mobile apps to better assess actual distance walked and heart rate.


References

American Heart Association. Professional Heart Daily. Accessed 8/2/16
http://professional.heart.org/professional/General/UCM_423811_Classification-of-Functional-Capacity-and-Objective-Assessment.jsp

Bittner et al. (1993). Prediction of mortality and morbidity with a 6-minute walk test in patients with left ventricular dysfunction. SOLVD Investigators. JAMA, 270(14), 1702-7.

Casanova, C. et al. (2011). The 6-min walk distance in healthy subjects: reference standards from seven countries. European Respiratory Journal, 37, 150-156.

Du, H., Wonggom, P., Tongpeth, J. & Clark, R.A. (2017). Six-Minute Walk Test for Assessing Physical Functional Capacity in Chronic Heart Failure. Curr Heart Fail Rep. 14(3),158-166.

Ferreira, J.P., Metra, M., Anker, S.D., Dickstein, K., Lang, C.C.. & Ng, L. (2019). Clinical correlates and outcome associated with changes in 6-minute walking distance in patients with heart failure: findings from the BIOSTAT-CHF study. Eur J Heart Fail. 21(2), 218-226.

McDonald, K., Wilkinson, M. (2017). Evolving Use of Natriuretic Peptides as Part of Strategies for Heart Failure Prevention. Clin Chem. 63(1), 66-72.

Rasekaba, T., Lee, A. L., Naughton, M. T. ,Williams, T. J. & Holland, A. E. (2009). The six-minute walk test: a useful metric for the cardiopulmonary patient. Intern Med J., 39(8),495-501.

Rostagno C., Gensini G.F. (2008). Six minute walk test: a simple and useful test to evaluate functional capacity in patients with heart failure. Intern Emerg Med. 3(3):205-12.

The Criteria Committee of the New York Heart Association. (1994). Nomenclature and Criteria for Diagnosis of Diseases of the Heart and Great Vessels. (9th ed.). Boston: Little, Brown & Co. pp. 253–256.

Wegrzynowska-Teodorczyk, K., Rudzinska, E., Lazorczyk, M., Nowakowska, K., Banasiak, W. Ponikowski, P et al. (2013). Distance covered during a six-minute walk test predicts long-term cardiovascular mortality and hospitalization rates in men with systolic heart failure: an observational study. J Physiother. 59(3), 177-87.


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