低压缺氧时的QT离散度。

Oztürk Cengiz, Sen Ahmet, Açikel Cengiz Han, Ilgenli Tevfik Fikret, Onem Yalçin, Oztürk Ahmet, Akin Ahmet

Department of Cardiology, Military Hospital, Eskişehir, Turkey.

Anadolu Kardiyol Derg. 2008 Aug;8(4):266-70.

OBJECTIVE

Hypoxia is one of the major concerns in aviation. Clinical hypoxia has been shown to increase QT dispersion (QTd). We aimed to examine QTd during hypobaric chamber training to observe the effect of hypobaric hypoxia on QT dispersion.

METHODS

A total of 38 healthy male aviators volunteered to take part in this longitudinal study. Subjects' electrocardiograms were recorded by 12-lead digital Holter device before, during, and after hypobaric exposure at simulated altitude of 30,000 ft. Data from 23 of the subjects, aged 27.91+/-6.02 years (range 22-39) was used. QT intervals were measured manually. QT dispersion and heart rate adjusted QTd (QTcd) were calculated for each subject. Statistical significance of changes in parameters was analyzed using the Friedman test. Comparison of pre-post exposure clusters was made using Dunn's test.

RESULTS

QT dispersion values were as following: prehypoxic 64.09+/-8.39 ms, hypoxic 50.35+/-11.06 ms and posthypoxic 59.83+/-9.06 ms (Median: 64, 50, 60; Mean rank: 2.65, 1.28, 2.07) (p=0.0001 for prehypoxic-hypoxic, p=0.046-prehypoxic-posthypoxic, and p=0.002 for posthypoxic-hypoxic). Heart rate values were as following: prehypoxic 74.09+/-6.43 beats/min, hypoxic 127.1+/-17.39 beats/min, and posthypoxic 95.17+/-11.35 beats/min (Median: 75, 122, 92; Mean rank: 1, 3, 2) (p=0.0001 for prehypoxic-hypoxic, prehypoxic-posthypoxic, and posthypoxic-hypoxic). The change in QTd and HR during hypobaric chamber exposure was statistically significant but, the change in QTcd was not (p<0.001, p<0.001, p>0.1, respectively).

CONCLUSION

From the findings of present study, it is not possible to directly comment on the validity of QTd in revealing arrhythmogenic predisposition of healthy subjects exposed to hypobaric hypoxia. The relationship between QT dispersion and hypobaric hypoxic exposure is not clear, particularly when QTd is corrected for the increased heart rate. QT dispersion measurement has not been proven a reliable and practical method to show arrhythmia predisposition during a hypobaric hypoxic exposure in healthy individuals.

目的

缺氧是航空领域的主要关注点之一。临床研究表明，缺氧会增加QT离散度（QTd）。我们旨在通过低压舱训练来检测QTd，以观察低压缺氧对QT离散度的影响。

方法

共有38名健康男性飞行员自愿参与这项纵向研究。在模拟海拔30000英尺的低压暴露前、暴露期间和暴露后，使用12导联数字动态心电图仪记录受试者的心电图。使用了23名年龄在27.91±6.02岁（范围22 - 39岁）的受试者的数据。手动测量QT间期。计算每个受试者的QT离散度和心率校正QTd（QTcd）。使用Friedman检验分析参数变化的统计学意义。使用Dunn检验对暴露前后的数据组进行比较。

结果

QT离散度值如下：缺氧前64.09±8.39毫秒，缺氧时50.35±11.06毫秒，缺氧后59.83±9.06毫秒（中位数：64、50、60；平均秩次：2.65、1.28、2.07）（缺氧前与缺氧时比较p = 0.0001，缺氧前与缺氧后比较p = 0.046，缺氧后与缺氧时比较p = 0.002）。心率值如下：缺氧前74.09±6.43次/分钟，缺氧时127.1±17.39次/分钟，缺氧后95.17±11.35次/分钟（中位数：75、122、92；平均秩次：1、3、2）（缺氧前与缺氧时比较p = 0.0001，缺氧前与缺氧后比较p = 0.0001，缺氧后与缺氧时比较p = <0.001）。在低压舱暴露期间，QTd和心率的变化具有统计学意义，但QTcd的变化无统计学意义（分别为p < 0.001、p < 0.001、p > 0.1）。