Ingle Lee, Goode Kevin, Carroll Sean, Sloan Rebecca, Boyes Carrie, Cleland John G F, Clark Andrew L
Department of Academic Cardiology, University of Hull, Castle Hill Hospital, Cottingham, Kingston-upon-Hull, United Kingdom.
Int J Cardiol. 2007 Jun 12;118(3):350-5. doi: 10.1016/j.ijcard.2006.07.105. Epub 2006 Oct 25.
Maximal exercises testing, whether involving cycling- or walking-based protocols, are often not well tolerated in patients with chronic heart failure (CHF). The peak oxygen consumption and the slope of the relation between ventilation (V(E)) and carbon dioxide production (V(CO(2))) are independent predictors of outcome and help risk stratification. The prognostic usefulness of submaximal exercise testing is not clear. The aim of the present study was to assess the prognostic value of the V(E)/V(CO(2)) slope when derived from data acquired from submaximal exercise.
394 patients referred with breathlessness and suspected heart failure (74% male) (mean+/-S.D.) age 60+/-12 years; BMI 27+/-5 performed a CPET to determine peak V(O(2)) and the V(E)/V(CO(2)) slope. The V(E)/V(CO(2)) slope was calculated using least squares regression from data acquired from the first 25% of exercise (mean V(E)/V(CO(2)) slope+/-SD; 30.6+/-5.7), 50% (29.6+/-6.9), below the ventilatory compensation point (sub-VCP) (29.9+/-6.8), and all data points (full slope) (32.1+/-7.8). For each measure, patients were divided into quartiles and Kaplan-Meier curves were constructed to determine probability of death after 24 months. The prognostic value of the different classifications was assessed using the chi(2) statistic from the Mantel-Cox log-rank test.
During a mean follow-up period of 41+/-19 months, 48 patients died. For the V(E)/V(CO(2)) slope, the log-rank statistic was greatest for the full slope (chi(2)=53.7; P=0.0001), followed by the sub-VCP (chi(2)=45.5; P=0.0001), 50% (chi(2)=41.9; P=0.0001), and 25% (chi(2)= 26.0; P=0.01). The pair-wise log-rank statistic between the fourth and third quartiles was also greatest using the full slope (chi(2)=25.4; P=0.001) followed in order by the sub-VCP (chi(2)=20.1; P=0.001), 50% (chi(2)=19.7; P=0.001), and 25% (chi(2)=14.2; P=0.05). Using the stratified slope measurements entered into a Cox regression analysis using a forward LR stepwise elimination procedure; only the full slope remained significant (P=0.0001).
The V(E)/V(CO(2)) slope should be calculated from all data points to optimise prognostic sensitivity. Data acquired from the first 50% of exercise and below the VCP provide adequate prognostic surrogates in patients who may not be able to perform maximal exercise testing (i.e. in patients with a respiratory exchange ratio<1.10).
最大运动测试，无论采用基于骑行还是步行的方案，慢性心力衰竭（CHF）患者往往耐受性不佳。峰值耗氧量以及通气量（V(E)）与二氧化碳产生量（V(CO₂)）之间关系的斜率是预后的独立预测指标，有助于进行风险分层。次最大运动测试的预后价值尚不清楚。本研究的目的是评估从次最大运动获取的数据得出的V(E)/V(CO₂)斜率的预后价值。
394例因呼吸困难就诊且疑似心力衰竭的患者（74%为男性），年龄60±12岁；体重指数27±5，进行心肺运动试验（CPET）以确定峰值V(O₂)和V(E)/V(CO₂)斜率。V(E)/V(CO₂)斜率通过对运动最初25%的数据（平均V(E)/V(CO₂)斜率±标准差；30.6±5.7）、50%的数据（29.6±6.9）、低于通气补偿点（亚VCP）的数据（29.9±6.8）以及所有数据点（全斜率）（32.1±7.8）进行最小二乘法回归计算得出。对于每种测量方法，将患者分为四分位数，并构建Kaplan-Meier曲线以确定24个月后的死亡概率。使用Mantel-Cox对数秩检验的卡方统计量评估不同分类的预后价值。
在平均41±19个月的随访期内，48例患者死亡。对于V(E)/V(CO₂)斜率，对数秩统计量在全斜率时最大（卡方=53.7；P=0.0001），其次是亚VCP（卡方=45.5；P=0.0001）、50%（卡方=41.9；P=0.0001）和25%（卡方=26.0；P=0.01）。使用全斜率时，第四和第三四分位数之间的两两对数秩统计量也最大（卡方=25.4；P=0.001），其次依次是亚VCP（卡方=20.1；P=0.001）、50%（卡方=19.7；P=0.001）和25%（卡方=14.2；P=0.05）。将分层斜率测量值纳入Cox回归分析，采用向前似然比逐步消除程序；只有全斜率仍然显著（P=0.0001）。
应从所有数据点计算V(E)/V(CO₂)斜率以优化预后敏感性。对于可能无法进行最大运动测试的患者（即呼吸交换率<1.10的患者），从运动最初50%的数据以及低于通气补偿点的数据得出的结果可提供足够的预后替代指标。
