Six-minute walk test among heart transplant recipients

Six-minute walk test (6MWT) is an important measure to assess the exercise capacity of cardiac patients. This study aimed to evaluate the correlations of 6MWT with findings of cardiopulmonary exercise testing (CPET), health-related quality of life (HRQoL), and obesity among heart transplantation recipients (HTR) at least 1 year after transplantation.

Clinically stable HTR were recruited for this study from the National Taiwan University Hospital, Taipei, Taiwan. The 6MWT was performed by a physical therapist following the American Thoracic Society standard. Each subject underwent a symptom-limited CPET to evaluate cardiorespiratory fitness and bioelectrical impendence analysis for determination of body composition. The HRQoL of study subjects was evaluated by the Medical Outcomes Trust 36-item health survey (SF-36).

The study subjects included 43 HTR (age: 47.8±11.1 years; 37 men, 6 women) at 4.8±3.2 years after transplantation. The 6MWT distance was 539±108 m (89.9±18.2% of the predicted value). The peak oxygen uptake was 19.3±4.7 mL/kg/min. The body composition analysis showed body fat percentage 25.2±7.9%, body mass index 26.5±4.8, and waist circumference 94.8±13.3 cm. The 6MWT distance was significantly positively correlated with peak oxygen uptake, peak heart rate, peak work rate, and peak systolic blood pressure during CPET, and significantly negatively correlated with body fat percentage, body mass index, and waist circumference. The 6MWT distance was also significantly positively correlated with SF-36 HRQoL parameters including general health perception and standardized physical component scale. The peak HR during CPET and standardized physical component scale was significantly correlated with 6MWT distance in multivariate analysis.

Our findings indicate that 6MWT is a simple and useful measure to assess the exercise capacity of clinically stable HTR. The 6MWT distance is positively correlated with HRQoL and negatively correlated with obesity among HTR. The prognostic significance of 6MWT for HTR requires further investigation.