The 6-min walking test early after cardiac surgery. Reference values and the effects of rehabilitation programme

The 6-min walking test (6MWT) is a simple test, which does not require expensive equipment or advanced training. It has been used in heart failure patients to assess exercise tolerance, the effects of therapy and prognosis. Accordingly, post-surgical cardiac rehabilitation may be a potential field of application of this test.

One thousand three hundred seventy patients (70% males, mean age 64+/-10 years), consecutively admitted for intensive cardiac rehabilitation, underwent 6MWT within 15 days after different types of cardiac surgery (67% coronary artery bypass graft (CABG), 25% valve replacement, 4% both, 4% other). The 6MWT was repeated in a subgroup of 348 patients after 15+/-3 days of an in-hospital cardiac rehabilitation programme.

6MWT (expressed as absolute value in metres and as a percentage of the predicted value) was well tolerated in all patients. The mean distance walked in 1370 patients was 304+/-89 m (corresponding to 58+/-15% of the predicted value). Distances walked were significantly shorter in older patients than younger (p<0.05) and in women compared to men (251+/-78 m, 53+/-15%, vs 328+/-34 m, 60+/-14%, p<0.001). Furthermore, the absolute distance walked in 6 min was significantly shorter in diabetics compared to non-diabetics (283+/-85 m vs 302+/-87 m, p=0.001) and in no CABG compared to CABG patients (285+/-91 m vs 303+/-84 m, p<0.001); no relation was found between distance walked and left ventricular ejection fraction (p=0.5). Gender, age, comorbidities and type of surgery were independently associated with 6MWT in the multivariate model. In the subgroup of patients repeating the 6MWT after the rehabilitation programme, the distance walked significantly increased (from 281+/-90 m, 51+/-76%, to 411+/-107 m, 77+/-81%, p<0.001). The extent of improvement observed was similar according to sex, age, presence/absence of diabetes and type of surgery.

Our data suggest that 6MWT is feasible and well tolerated in adult and older patients shortly after uncomplicated cardiac surgery and provides reference values for distance walked after cardiac surgery in this population.