Prognostic Value of a 6-Minute Walk Test in Patients Undergoing Percutaneous Coronary Intervention: A Prospective Study

6 Minute Walk Distance (6MWD) is a well-validated prognostic tool in heart failure. However its utility in post percutaneous coronary intervention (PCI) patients remains unknown. We conducted a prospective study (N=212) from July 2010-October 2011 wherein patients underwent a 6-minute walk test (N=176) within 2 weeks of PCI (for acute coronary syndrome (ACS), stable angina and abnormal non-invasive stress test). The primary endpoint was major adverse cardiac events (MACE)-death, ACS and HF admission, within one year post PCI. ROC curves were used to determine the predictability of 6MWD on MACE. Youden Index was applied on the ROC curve to measure the effectiveness of 6MWD to classify patients with MACE. 98% of the subjects were male. Mean age was 64.9± 8.8 yrs. and major co-morbidities were hypertension (88%), diabetes (45%) and dyslipidemia (88%). 176 (83%) patients had 6MWD and clinical follow up data available. In the overall population one year adverse event rates were: MACE (22%), ACS (18%), HF admission (4%), and death (3%). 6MWD had an AUC of 0.58, indicating that 6MWD may be a poor predictor of MACE. However the 6MWD was shorter for patients who had MACE (293 vs 326 meters, p=0.038). Among patients with previous history of HF (N=50): 8(21%) had MACE. 6MWD in this group had an AUC of 0.64. For the end-point of HF admission during the follow up, the AUC was 0.78, suggestive of good predictive power (Figure 1, panel A&B). Using this curve for HF admissions, a cut off of 335 m was derived. Patients who achieved < 335m(6MWD) had a greater probability of having HF admission although this did not reach statistical significance (Odds ratio (0.44; 95% CI 0.037-5.38). 6MWD could be a simple and reliable tool to identify a high-risk group of patients post PCI, especially those with previous HF. However, larger adequately powered studies are needed to confirm these findings.