Title : The 6-minute walk test modifies the New York heart association classification of hypertrophic obstructive cardiomyopathy and congestive heart failure patients
Abstract:
Background: The New York Heart Association (NYHA) classification system is a subjective assessment tool used by physicians to evaluate the functional status of patients. In the era of novel pharmacologic treatments for hypertrophic obstructive cardiomyopathy (HOCM), it is commonly used to aid treatment decision-making. However, the NYHA scale has known limitations in discerning functional impairment due to its subjective nature, lack of standardized methodology in assigning NYHA classes, and consequently poor performance in clinical settings. The objective of this study was to determine whether the addition of an objective measurement, the 6-minute walk test (6MWT), reclassified the NYHA category of patients with HOCM and congestive heart failure (CHF) to improve the accuracy of NYHA classification as a marker of functional status.
Methods: This was a pilot cross-sectional analysis of 17 adult (≥18 years old) patients diagnosed with HOCM and CHF based on genetic or echocardiographic findings. Patients completed a brief demographic survey followed by a 6MWT. Their NYHA classification pre-6MWT was based on the cardiologist assessment. The 6-minute walk distance (6MWD) of all patients was recorded, and this information was provided to the cardiologist who was subsequently asked whether the achieved 6MWD changed their assessment of the patient’s NYHA class, given that these two variables are inversely correlated. The proportion of patients reclassified from one NYHA class to another between their pre- and post-test assessments was calculated, and the relationship between 6MWD and the NYHA classification was evaluated.
Results: A total of 17 patients were enrolled and completed the 6MWT. Prior to the 6MWT, 8 patients were classified as NYHA Class 1 (47%), with walking distances ranging from 283 to 605 metres. Five patients were classified as NYHA Class 2 (29%), with walking distances between 234 and 465 metres, whereas 3 patients were classified as NYHA Class 3 (18%), with walking distances between 195 and 500 metres, and 1 patient was classified as NYHA Class 4 (6%), with a walking distance of 360 metres. A scatter plot of the 6MWD according to pre-6MWT NYHA Class is shown in Figure 1. Substantial variability in 6MWD was observed across pre-6MWT NYHA Classes 1, 2 and 3. When the NYHA classification of patients pre-6MWT was compared with their NYHA classification post-6MWT, the vast majority of patients (14/17; 82%) had either the same or worse functional status (Figure 2). Most patients (9/17; 53%) were re-classified to a higher NYHA Class following the 6MWT. Furthermore, patients who were re-classified were mainly those with NYHA Class 1 pre-6MWT (5/8; 63%) and Class 2 pre-6MWT (4/5; 80%).
Conclusion: The results from this pilot study confirm that the NYHA is a poor marker of functional status, represented by high variability in the corresponding 6MWD achieved. The addition of a 6MWT to the NYHA assessment of cardiomyopathy patients modified their NYHA classification.
Audience Take Away Notes:
- Variability in the 6MWD was high among patients with NYHA Classes 1 and 2
- Distinguishing between mildly presenting patients with NYHA Classes 1 and 2 may be more challenging and subjective than higher NYHA classes
- Following the 6MWT, the majority of patients were re-classified and had either the same or worse functional status
- Patients who were re-classified post-6MWT were mainly those with NYHA Classes 1 and 2
- Addition of a 6MWT as an objective measure to the NYHA classification enhanced functional status assessment of HOCM and CHF patients
