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.
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.
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).
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.
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. http://www.heartonline.org.au/media/DRL/6MWT_standardised_instructions.pdf Also there are instructional videos on YouTube such as this one about how to carry out the 6MWT. https://www.youtube.com/watch?v=6EXNes7mO1o.