The Value Of 6-minute Walk Test(6-MWT)in Heart Failure Patients And The Effects Of 6-MWT On Cytokines And OT Dispersion

Background: Exercise testing and exercise training have been accepted and developed for more than 20 years. 6-minute walk test (6-MWT) is studied and used relatively widely overseas, but there are only a few studies about 6-MWT in our country. The mortality of heart failure is very high and sudden death is an important reason; QT dispersion (QTd) has been shown to be a marker of myocardial electrical instability and may predict sudden death; So studying QTd in congestive heart failure (CHF) is very significant. Scholars have been realizing that cytokines play critical roles in pathophysiology in CHF, but works about the effects of exercise on the expression of cytokines in CHF is few. Objective: To study the feasibility and the potential usefulness of the 6- minute walk test (6-MWT) in CHF patients of Chinese; To study the effects of 6-MWT on QTd by measuring QTd in congestive heart failure patients at rest and after exercise; To study cytokines mechanisms of TNF- a in CLLF by assessing the five cytokines at rest and after exercise; To investigate the effects of exercise on the expression of cytokines in CHF. Methods: 22 normal subjects and 49 CHF patients underwent 6-MWT, 12 patients of which repeated the exercise the next day. Before and after 6-MWT, standardized 12-lead surface ECGs were obtained to measure QTd and heart rate-corrected QTd (QTcd). The blood samples were taken before and after 6- MWT immediately from all subjects, and more blood samples were taken from 15 patients at 3Ominutes, 60minutes and 120 minutes after exercise. Blood samples were taken only in bed from the 7 patients in NYHA IV that couldn抰 -5- tolerate 6-MWT. The plasma TNF- a sFas and sICAM- 1 levels were assessed with a sandwich ELISA and the plasma MDA and NO levels were measured by colorimetric analysis. Results: 1. 6-MWT is safe and well repeated. The distances ambulated during 6 minutes can represent the function of the failing heart. During follow-up, the hospitalization percentage and time were significantly correlated with the distance level. 2. Both before and after 6-MWT, the QTd and QTcd in CHF patients were longer than those in the controls. What抯 more, QTd and QTcd after 6-MWT were significantly shorter than before 6-MWT in CHF patients, but there is no significant change in QTd and QTcd in controls. 3. In basic state, the levels of plasma TNF- a sFas~. ICAM-1~ NO and MDA were all significantly higher in patients with CHF than those in controls; What抯 more, the levels were related to severity of heart failure. There was positive correlation between plasma TNF- a concentration and the other four factors concentrations in CHF patients. There was also positive correlation between MDA value and sFas value. 4. After 6-MWT, the levels of plasma TNF- a~ sFas~ ICAM-1~ NO and MDA were still significantly higher in patients with CHF than those in controls. And the five factors were all higher after 6-MWT than at rest in CHF patients. The time-value curves of NO and MDA showed that the increased concentrations come back to the basic level in two hours after 6-MWT. After 6- MWT, the levels of plasma TNF- a sFas~. ICAM-l.. NO and MDA had no significant change in controls. Conclusions: 1. 6-MWT is a simple~. safe., cheap and well-repeated exercise testing. Its virtue is good feasibili...