Is the Ability index superior to the NYHA classification for assessing heart failure?

Background Heart failure (HF) is a major problem in the long-term follow-up of adolescents and adults with congenital heart disease (ACHD) after cardiac surgery. The functional status of ACHD may be assessed in terms of the NYHA classification or the Ability index (ABILITY). Objective The purpose of our study was to examine which of the two classification systems is more closely related to objectively defined HF. Methods NT-pro brain natriuretic peptide (N-BNP) and maximal oxygen uptake (VO2max) were measured in 360 consecutive ACHD patients. HF was defined as an elevated N-BNP level >= 100 pg/ml combined with a reduced VO2max <= 25 ml/kg/min. Results There were no significant differences between the NYHA and ABILITY in grading HF in these patients. In both classifications, the risk of HF increases continuously over the classes and grades from odds ratio (OR) 1 in NYHA I/ABILITY 1 to an OR = 3.4 in NYHA II/ABILITY 2 up to 11.6 or 5.4 (ns) in NYHA III/ABILITY 3. Thus in the highest scores HF is found in 70-77 % of the patients. The fact that in NYHA class I and ABILITY grade 1, 15 % and 19 % of the patients exhibited HF according to the measured indices underscores the discrepancy between subjective and objective assessment of the individual patients condition. Conclusion The NYHA classification and the Ability index take different approaches to the patients with congenital heart defects but are equally suitable for the judgement of HF in post surgical ACHD.