Research in Cardiovascular Medicine

ORIGINAL ARTICLE
Year
: 2019  |  Volume : 8  |  Issue : 1  |  Page : 19--22

Walking performance in the 6-min walk test and gait speed in patients undergoing open heart surgery: A preliminary cohort study


Kornanong Yuenyongchaiwat1, Sasipa Buranapuntalug1, Khajonsak Pongpanit1, Chitima Kulchanarat2,  
1 Department of Physiotherapy, Faculty of Allied Health Sciences, Thammasat University, Pathum Thani, Thailand
2 Physical Therapy Center, Thammasat University Hospital, Pathum Thani, Thailand

Correspondence Address:
Dr. Kornanong Yuenyongchaiwat
Department of Physiotherapy, Faculty of Allied Health Sciences, Thammasat University, 99 Moo 18, Paholyothin Road, Klong Luang, Rangsit, Prathum Thani, 12120
Thailand

Abstract

Context: The 6-minute walk test (6-MWT) has been commonly used to assess patients after open heart surgery. However, due to some situations, where patients could not perform the test for the duration of 6-minutes, a short walking distance test has been utilized to test the patients (i.e., 5-meter walk distance: 5-MWD). However, little is known whether fixed duration walking test, or fixed-distance walking test, regarding to the prediction of duration of hospital admission. Aims: The aim of the study was to evaluate the 6-MWT and 5-MWD in patients who had undergone open heart surgery, in order to predict hospital admission. Settings and Design: A prospective cohort study was designed at Thammasat University Hospital, Thailand. Methods and Material: Fifty-seven participants, who had open heart surgery were recruited and were asked to perform 6-MWT and 5-MWD pre and post-operative heart operation. Statistical Analysis Used: Regression analysis was used to test the prediction of the length of hospital admission and the walking performance.Results: A regression analyses indicated that after adjustment for age and gender, baseline 5-MWD and 6-MWT were associated with increased the hospital admission (ΔR2 = 0.112 and ΔR2 = 0.068, respectively). Conclusions: The 5-MWD might be an alternative to predict the length of hospital admission in patients who had undergone open heart surgery.



How to cite this article:
Yuenyongchaiwat K, Buranapuntalug S, Pongpanit K, Kulchanarat C. Walking performance in the 6-min walk test and gait speed in patients undergoing open heart surgery: A preliminary cohort study.Res Cardiovasc Med 2019;8:19-22


How to cite this URL:
Yuenyongchaiwat K, Buranapuntalug S, Pongpanit K, Kulchanarat C. Walking performance in the 6-min walk test and gait speed in patients undergoing open heart surgery: A preliminary cohort study. Res Cardiovasc Med [serial online] 2019 [cited 2019 Aug 23 ];8:19-22
Available from: http://www.rcvmonline.com/text.asp?2019/8/1/19/256877


Full Text



 Introduction



The evaluation of physical capacity is an important part of cardiopulmonary assessment. The 6-min walk test (6-MWT) has been recommended for the evaluation of submaximal exercise testing in patients with chronic respiratory and heart diseases, including assessing the performance of the patients who had been through open heart surgery.[1],[2],[3],[4] The 6-MWT is performed on a long corridor of 30 m for a duration of 6 min.[5] However, one limitation is that a walking track which might be short and requires the participant has to turn back and forth.[6] Therefore, short walking distance tests are suggested and these distance tests vary from 2 to 15 m.[6],[7],[8],[9],[10],[11] In addition, these have been related to the 6-MWT whether in participants with cardiopulmonary impairment[10],[11],[12],[13] or neurological disorders.[14],[15] Recently, gait speed has been recommended as a predictor of mortality and morbidity in patients who had cardiac surgery.[16],[17],[18],[19],[20] In addition, Karpman et al.[13] recommended that gait speed might be an easy-to-use assessment of the clinical condition for chronic lung disease and postsurgical cardiac.[13],[20],[21],[22] However, few studies have been directly compared between gait speed and 6-MWT in patients who had undergone open heart surgery, particularly in Thailand.

Therefore, the study will try to determine the relationship between the gait speed and 6-MWT among individuals who have undergone open heart surgery and the prediction of hospital admission.

 Materials and Methods



Fifty-seven participants undergoing cardiac surgery were recruited from the Thammasat Chalermprakiat Medical Hospital aged 35–70 years, with both male and female individuals. All participants had no known, high resting blood pressure (BP) >180/100 mmHg or uncontrollable BP, high resting heart rate (more than 100 beat per minute). Participants who had a current congestive heart failure, unstable angina, uncontrolled cardiac arrhythmia, chronic cough or had a high temperature within 48 h before the test and had other operative treatment such as thoracotomy were excluded. The participants who had been reported with left ventricular ejection fraction less than 30% were also excluded. Further, the participants who had the rate perceived exertion more than 13 from 20, chest pain, and dyspnea during and after test were terminated from the study. Furthermore, participants who were unable to walk independently were excluded from the study. The ethics and protocol were approved by the Ethics Committee of Thammasat University, Thailand (066/2558). All participants were given their written and informed consent. In addition, the prospective cohort study was designed to determine the correlation of walking performance and the duration of hospital admission.

Participates who had operative open heart surgery were asked to perform the 6-MWT and 5-m walk distance (5-MWD) before the heart operation. The protocols were obtained according to the American Thoracic Society.[5] Individuals performed 5-MWD, which was repeated for three measures, and the average values were calculated.[16] All volunteers received the standard cardiac rehabilitation program for pre- and post-operative open heart surgery (i.e., cardiac rehabilitation program phase I). The duration of admission was then recorded from the date of an operation to the date of patients discharge from the hospital.

Descriptive data were presented as a percentage (%), mean, and standard deviation (SD). Data were verified for normality of distribution (Kolmogorov–Smirnov Goodness-of-Fitness test). A paired t-test was used to determine whether the effect of open heart surgery decreased significant changes in walking performance. The relationship between walking performance and duration of admission was used by the Pearson correlation, and then, the partial correlation was then calculated after adjusted for gender and age. To evaluate the walking performance for predicting duration of admission, a hierarchical regression analysis was performed.

 Results



Of 57 participants who performed the walking tests (i.e., 6-MWT and gait speed) and had open heart surgery, 26 were females and 31 were males. The characteristics of the study are presented in [Table 1]. An average of walking distance was 335.58 ± 124.07 m in 6-MWT and gait speed was 1.15 ± 0.37 m/s for 5-MWD [Table 1]. Further, significant decreased 6-min walking distance (6-MWD) and gait speed were evidenced after the open heart surgery [p < 0.001 in all cases; [Table 2].{Table 1}{Table 2}

Next, the relationships between duration of hospital admission and walking performance were examined; these are shown in [Table 3]. The significant associations were noted in 5-MWD and 6-MWT and the length of hospital admission (r = −0.411, p = 0.001 and r = − 0.374, p = 0.004, respectively). In addition, partial correlation coefficients with adjustment for age and gender revealed that these relationships remained statistically significant (r = -0.352, p = 0.008; r = -0.274, p = 0.043, respectively).{Table 3}

The study then focused on whether walking performance could predict duration of admission. A multiple hierarchical regression analysis was performed to determine the contribution of walking performance to the prediction of the length of hospital admission. As can be seen in [Table 4], gait speed accounted for 11.2% of the variance (β = −0.350, standard error [SE] = 2.323; p = 0.008), with all predictors together accounting for 21.1% of the variance in the length of hospital admission. By comparison, the 6-MWT to the predictor model resulted in smaller increases in R2 with values equivalent to 6.8% of the variance of the duration of stay in the hospital (β = −0.299, SE = 0.008; p = 0.043).{Table 4}

In sum, these results suggest that decreasing walking performance (i.e., gait speed and 6-MWT) relates to a longer to stay in hospital, after postoperative open heart surgery. In fact, the total regression model explained 16.7%–21.1% of the variance of the duration of stay in the hospital.

 Discussion



The present study evaluated the 6-MWT and 5-MWD in patients undergoing open heart surgery. All participants were requested to perform a walking test (i.e., 5-MWD and 6-MWT). The results of the present study revealed that a reduced walking performance is evident in patients underwent open heart surgery. In addition, the efficacy of walking performance could predict the duration of stay in hospital in person undergoing open heart surgery. However, the gait speed test, which is a fixed distance walking test, appears to be a more modest, independent predictor of length of stay in the hospital, than the 6-MWT. In addition, the duration of stay in hospital was negatively associated with gait speed and 6-MWT, even after accounting for age and gender.

Kamiya et al.[23] examined the relationship between gait speed and 6-MWD and the prognosis of mortality in individuals with cardiovascular disease (CVD). They found that both walking tests had a strong positive correlation (r = 0.80, p < 0.001) in older participants with CVD and the walking performance was a predictor of mortality. In the present study, gait speed has a strong positive association with 6-MWT (r = 0.63, p < 0.001) which has been consistent with Kamiya et al.[23] They also showed that low 6-MWD and slow gait speed were related to all causes of mortality and significant predictors of mortality in cardiovascular disease (e.g., cardiac surgery, heart failure). In addition, several studies have been reported that walking performance has been promoted as a vital sign in clinical outcome measurement.[12],[24],[25],[26] DePew et al.[12] reported that gait speed is significantly and independently correlated to 6-MWT and they suggested that gait speed may be useful measure for morbidity and mortality.

The 5-MWD, a short walking duration test, has also been correlated to the length of hospital stay.[27] Similarly, the present study shows a modest correlation between gait speed and the length of stay in hospitals. Therefore, gait speed (i. e., 5-m walking test) was successfully implemented in patients who had undergone open heart surgery and it was independently predictive of duration of stay in hospital. By comparison, the 6-MWT was also an independently predictive value of operative mortality. It could be said that the present findings of an association between the 5-m walk test and the 6-MWT have relevance and these could be a predictor for morbidity in patients undergone open heart surgery. Further, a short distance measurement (e.g., 5-m walking test) is an easy assessment for participants, and it is simple, rapid and only requires a little space,[23] whereas the 6-MWT requires a long corridor (i.e., 30-m walk distance) and requires 6 min to administer the test.

The present study is the first study in Thailand; however, there are a number of limitations with the present study. The number of the participants was a relatively small sample size. Several studies have been reported that risk factors of prolonged length of stay in the hospital such as duration of open heart surgery, type of surgery (i.e., on pump or off pump), cardiopulmonary bypass time, and allogeneic blood transfusions had a significant association. However, these clinical data were not recorded in the study. In addition, the duration of weaning off an invasive mechanical ventilation tube was not noted in the present study. Therefore, these factors should be considered in future studies. The clinical factors such as echocardiographic alterations and clinical laboratory values should be a consideration that may, in part, account for the duration of stay in hospital.

 Conclusion



Waking performance (i.e., 5-MWD and 6-MWT) could be an independent predictor of duration of stay in hospital among patients undergoing cardiac surgery.

Acknowledgment

We acknowledge the help of Physical Therapy Center, the Traumatic Ward II, the Surgical Outpatient Department at Thammasat University Hospital and the staff for their kindly support. In addition, we would also like to thank all participants who had open heart surgery in the hospital to participate the study. Finally, we would like to thank Asst. Prof. Opas Satdhabudha, MD., for his invaluable help. This study was partially supported from the Foundation for Thammasart Chalerm Prakiat Hospital in 2015.

Conflicts of interest

There are no conflicts of interest.

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