以三分鐘登階測試結合心率變異預測心臟病患之尖峰攝氧量

Prediction of Peak Oxygen Consumption in Patients with Cardiac Disease using a 3 Minutes' Step Test Combined with Heart Rate Variability.

劉家豪(Chia-Hao Liu) ； 黃書群(Shu-Chun Huang) ； 王鐘賢(Jong-Shyan Wang)

《台灣復健醫學雜誌》 45卷2期 (2017/12) Pp. 75-87

https://doi.org/10.6315/2017.45(2)04

摘要

目的：尖峰攝氧量(Peak VO_2)是目前被認定測試心血管系統整體功能的重要因子，它是預測心血管退化或評估心肺耐力的重要指標。要量測尖峰攝氧量的黃金測量方式是使用心肺運動測試(Cardiopulmonary exercise test, CPET)。然而要施行心肺運動測試可能會有諸多限制，例如冗長的測試時間、繁雜的儀器設備，此外病人在做測試時所產生的不適感，可能會影響病人接受測試的動機。因此如果要讓心臟疾患的病人能普遍接受測試，那麼次強度功能性運動測試(Sub-maximal functional exercise testing)可以是測試心血管適能的替代性方案，其中著名的例子即為登階測試(Step test)，然而過去研究曾建議次強度功能測試應依照受試者生理參數的反應為依據較為準確。另一方面，心率變異(Heart rate variability, HRV)則是近年來廣泛運用在臨床醫學上的生理參考值，心臟除了本身的節律性放電引發的跳動之外，也受到自律神經系統(Autonomic nervous system，ANS)所調控。過去研究顯示自律神經調控可能因為運動訓練而改變，因此自律神經活性指標，包含心率變異值(HRV)及血管硬度指標(Arterial stiffness)，可能可以做為運動測試或是運動訓練效果的重要檢測參數。因此，本實驗目的為結合三分鐘登階測試與心率變異值，分析自律神經活性和運動耐受度的相關性，進而預測心臟疾患病人之心肺適能，希冀能幫助臨床工作者制定適當的心肺運動計畫與做出臨床決策。設計：橫斷式研究方法：於醫學中心之心臟復健中心收取罹患心臟相關疾病的病患，接受心肺運動測試(漸進式阻力法，10W/min)，並以測試結果依美國紐約心臟協會(NYHA)訂定之心臟疾患嚴重度分為NYHA 功能分級第三級(Fc III)及功能分級第二級(Fc II)兩組。經過至少一日的休息後，接下來兩組皆接受特別設定的三分鐘登階測試(5 分鐘休息期、3 分鐘登階期、10 分鐘運動恢復期。階梯高度為15 公分，登階速度為96 拍/每分鐘)，並同時在測試中結合自律神經活性的分析(含心率變異值及血管硬度指標)。完成兩個測試後，將以Independent T-test 法比較組間差異，並以Pearson correlation coefficient 法檢視心肺運動測試結果與三分鐘登階結果的相關性，以及使用Multiple regression analysis 法進一步分析計算預測尖峰攝氧量的最佳公式。結果：本實驗共納入23 位病患，所有受試者皆完成心肺運動測試並且依測試結果被分為兩組，分別為NYHA class III (Fc III, n= 11)及NYHA class II (Fc II, n=12)，兩組在充分休息後即接受三分鐘登階測試。其中Fc II 組有一人因故離開，故最後完成三分鐘登階測試為11 人；Fc III 組則是6 人完成登階測試，其中5 個未完成測試的人中包含兩位於登階過程中產生心律不整、兩位有頭暈及過度換氣的現象以及一位抱怨膝蓋疼痛而自行中止測試。三分鐘登階測試的組間差異方面，在「休息狀態」及「運動狀態」兩組的自律神經調控(含心率變異及血管硬度指標)並無顯著差異。不過在「運動恢復期」的前五分鐘，心率變異值在SDNN、SD2、LF、lnLF、lnHF、TP、lnTP 及血管硬度RI 值有顯著組間差異，至於運動恢復期的後五分鐘則是沒有組間差異。若評估整體18 分鐘測試過程中的自律神經活性平均值，可以發現在平均SDNN 還有平均SD2 都有顯著的組間差異。心肺測試結果與自律神經調控數值的相關性方面，整體心跳間期標準偏差值(SDNN avg)與尖峰攝氧量(VO_(2peak))之間有顯著的正相關性(r=0.88，p＜0.01)。此外以Poincaré Plots 非線性動態的心率變異分析所得的整體平均SD2 值 (SD2 avg)也和尖峰攝氧量有很高的正相關(r=0.89，p＜0.01)。而在運動恢復期前5分鐘，時域分析的SDNN recovery (r=0.67，p=0.02)，Poincaré Plots 的SD2 recovery 值(r=0.69，p=0.01)，頻域分析的lnLF recovery (r=0.83，p＜0.01)、lnHF recovery (r=0.72，p＜0.01)及lnTP recovery (r=0.76，p＜0.01)方面和最大攝氧量間皆有顯著的中高強度相關性。至於尖峰心跳與心率變異值的相關性方面，平均心率變異值SDNN avg (r=0.59，p=0.05)、lnHFavg (r=0.6，p=0.04)、lnTPavg (r=0.63，p=0.03)，以及在運動恢復期前五分鐘的SDNN recovery (r=0.63，p=0.01)、pNN50 recovery (r=0.57，p=0.03) 、SD1 recovery(r=0.54，p=0.04)、lnHF recovery (r=0.65，p＜0.01)與lnTP recovery (r=0.63，p=0.03) 和心肺運動測試所得的尖峰心跳值皆有中度以上的正相關。結論：本實驗顯示心臟病患之自律神經活性、特別是心率變異值，和尖峰攝氧量、尖峰心跳之間存在很高的相關性，因此以固定強度的三分鐘登階測試結合心率變異值預測病患之心肺適能是可行的。尖峰攝氧量的最佳預測公式為:「Peak VO_2 predict = 9.684 + 0.062 x avg SD2」其解釋力達78.8% (R^2 =0.788)，或是以「Peak VO_2 predict = 9.8293 + 0.0853 xavg SDNN」其解釋力亦高達76.9% (R^2 = 0.769)。未來臨床工作者將能夠以此簡單、易施行的運動測試來得知並且監測病患的心肺適能，進而制定合適的運動處方。

關鍵字

尖峰攝氧量(peak oxygen consumption) ； 心率變異(heart rate variability) ； 自律神經活性(autonomic nervous activity) ； 登階測試(step tests) ； 心臟病(cardiac diseases)

並列摘要

Background: Peak oxygen consumption (Peak VO_2) is a recognized indicator of overall functions of the cardiac-vascular system, and the cardiopulmonary exercise test (CPET) is considered the golden standard for determining peak VO_2. However, there are limitations to performing CPET, including high cost, long testing time, staff risks and participant’s discomfort during the test. In contrast, Submaximal exercise testing can be an alternative for assessing cardiovascular fitness with minimal risk and lower cost. The step test, one of the submaximal exercise tests, was the first to be described as a method for assessing exercise capacity in the early 20th century. Various protocols have been developed since then, all of them have been proved by previous studies to be useful in different needs and all have shown good reliability and validity. However, to date, clinical evidence on cardiac disease population is sparse, and scientists have pointed out that it is necessary to estimate the participants' physiological parameters during submaximal exercise to reveal their real capacity. Heart rate variability (HRV) is the physiological phenomenon of variation in the time interval between heartbeats and it is influenced by the autonomic nervous system (ANS). The ANS has been proved to be an important role for cardiac-autonomic modulation and arterial stiffness control. Therefore, analysis of HRV and arterial stiffness may provide us with useful information about autonomic control of the cardiovascular system, and furthermore, it may be an effective tool for assessing one's cardiopulmonary fitness and predicting the prognosis for patients with cardiac diseases. Taking into account the above factors, the aim of this study was to develop a unique, tailored 3- minute step test that combined ANS modulation to predict peak VO_2 in patients with cardiac diseases. Methods: Twenty-three subjects with cardiac-vascular disease history were recruited. All subjects received CPET (Grading protocol, 10W/min) and were further divided into the NYHA class III group (FcIII) and the class II (FcII) group according to their performance. Then, all subjects took the 3-minute step test with ANS activity evaluation. HRV parameters and arterial stiffness indexes were recorded and analyzed in the ＂pre-exercise＂, ＂in-motion＂ and ＂recovery＂ phases of the step test. Minute ventilation (VE), oxygen consumption (VO_2) and carbonic dioxide production (VCO_2) were measured breath by breath using a gas analyzing system in the CPET test. Correlations between 3-minute step test and the CPET parameters were assessed using the Pearson's correlation coefficient method. Results: All patients completed the CPET and were divided into 2 groups (Fc II: n=12, Fc III: n=11) according to their peak VO_2 performance. Five of the eleven patients in the Fc III group did not complete the 3-minute step test (two with atrial arrhythmia, two with head dizziness plus dyspnea and one complained of knee pain during test), and eleven of the twelve patients in the Fc II group completed the test. There were no differences between the groups at baseline, including age, BMI, cardiac output, cardiac index and cardiac medications. In the recovery phase, the Fc II group had higher HRV parameters (SDNN, SD2, lnLF, lnHF, lnTP and arterial reflex indexes) than the Fc III group. In the entire step test process, the Fc II group still had higher average SDNN and SD2. There were strong positive correlations among average SDNN (r=0.88, p=0.001), average SD2 (r=0.89, p=0.001) and the peak VO_2. Also, SDNN (r=0.67, p=0.02), SD2 (r=0.691, p=0.01), lnLF (r=0.83, p=0.01), lnHF (r=0.72, p=0.01) and lnTP (r=0.76, p=0.004) showed significant correlations with the peak VO_2 in the recovery phase. Arterial stiffness indexes were not significantly correlated with the peak VO_2,but positively correlated with nHF (r= 0.68, p= 0.01) and negatively correlated with LF/HF(r= -0.66, p=0.02). Conclusions: This study showed that peak VO_2 has high correlation with the activity of ANS, especially the HRV. Therefore, it may be feasible and reliable to use a step test combined with heart rate variability parameters to predict the cardiopulmonary fitness in patients with heart disease. The best prediction formula could be: ＂Peak VO_2 predict = 9.684 + 0.062 x avg SD2＂ with 78.8% statistical explanatory power (R^2 = 0.788) or ＂Peak VO_2 predict = 9.8293 + 0.0853 x avg SDNN＂ with 76.9% power (R^2 = 0.769). In the future, clinical physiotherapists may use this safe and feasible method to predict and monitor patients' cardiopulmonary fitness condition and establish proper prescriptions in cardiac rehabilitation. Acknowledgement：The authors wish to thank the support of the Center for Big Data Analytics and Statistics (Grant CLRP3D0043) at Chang Gung Memorial Hospital.

並列關鍵字

Peak oxygen consumption ； heart rate variability ； autonomic nervous activity ； step test ； cardiac diseases

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