1、大鼠心電圖為什么沒有ST段？
從動作電位的角度來解釋。
以人的心電圖為例：靜息狀態(tài)下細胞內(nèi)電位約為-90mv，也就是說細胞內(nèi)電位比細胞外電位低90mv，細胞膜內(nèi)帶負電荷，膜外有同等數(shù)量的正電荷，稱為極化狀態(tài)。心肌細胞激動后，細胞發(fā)生除極，細胞膜內(nèi)變成正電荷，膜外變成負電荷，跨膜電位驟升到+30mv，這一過程稱為動作電位0相。復(fù)極時，細胞內(nèi)正電位下降，復(fù)極過程分為1、2、3相。復(fù)極過程中的2相很特殊，是一條相對平坦的曲線，接近零電位，對應(yīng)心電圖上的ST段。

那么動物的心電圖又如何呢？

比如狗的心室復(fù)極過程存在平坦的2相，在心電圖上就體現(xiàn)在明顯的ST段上，而大鼠的心室復(fù)極過程沒有2相，在心電圖上就沒有明顯的ST段。

（PS：心房也有復(fù)極波，但是很小，通常消失在QRS綜合波里，一般看不到）

2、如何計算大鼠的“ST段”？

對于存在ST段的動物心電圖（狗、猴子），可以按照常規(guī)ST段計算方法來計算：以線為基線，選擇ST段上某一個點作為取值點，比如J點，取值點到基線的距離就是ST段的數(shù)值，取值點在基線以上，ST段即為正值，取值點在基線以下，ST段即為負值。

盡管大鼠心電圖沒有常規(guī)的ST段，但是ST段是心電圖上極為重要的一個參數(shù)，不能輕易放棄，還是要解析的。在Rat心電圖里，我們用另一種方法來代替。
如果您使用的是北京軟隆公司的心電圖采集與解析系統(tǒng)SP2006，做大鼠的ST段解析時，推薦您使用公式S ST-index，延遲0，范圍10。代表的是從S波頂點開始，往后取10個點（10ms），以線為基線，計算10個點到基線距離的平均值。上圖的10個取值點均在基線以下，ST段數(shù)值為負值-41。下圖中的10個取值點一部分在基線以下，一部分在基線以上，10個點的平均值為0，所以ST段=0。（延遲和范圍的數(shù)值可以根據(jù)需要自行設(shè)定）

上圖中，橫坐標每個小格代表2.5ms，縱坐標每個小格代表5×1/100mV.
3、這些情況大鼠的心電圖上會出現(xiàn)ST段

①在大鼠成熟初期有可辨認清晰的ST段，但是伴隨著成長會*消失，已經(jīng)成熟的大鼠，就看不到ST段了。

②在低溫、缺氧時，或注射利血平等藥物時，作用于心室復(fù)極的2相離子活動，同時導(dǎo)致心率過緩，可能會在心電圖上出現(xiàn)明顯的ST段。如果在大鼠中采集到明顯的ST段，應(yīng)該考慮是否有低溫、缺氧或藥物的因素。采集心電圖時，要給麻醉的動物保溫也是極其有必要的。

4、正常大鼠ST段值應(yīng)該是多少？

與人的心電圖解析不同，目前尚無*的動物心電圖背景數(shù)據(jù)，在一些心電圖書籍或者文獻里能找到一些參考數(shù)值，但是，這些數(shù)值與動物種屬、周齡、使用哪款心電圖設(shè)備、采樣頻率、導(dǎo)聯(lián)方式、大鼠體位、解析公式等密切相關(guān)，而這些可能影響心電圖的因素并沒有統(tǒng)一的*規(guī)定，所以，還沒有*的背景數(shù)據(jù)，文獻里的數(shù)值也不能直接拿來使用。那么拿什么做正常參考值呢？答案是自己做空白對照組，你的空白對照組采集到的數(shù)值，就是你這個實驗的參考值。

1. Why does the electrocardiogram of rats have no ST segment?
It is explained from the angle of action potential.
Take human electrocardiogram as an example: resting state cell potential is about -90mv, that is to say, intracellular potential is 90mV lower than extracellular potential, cell membrane has negative charge, and the same number of positive charges outside the membrane is called polarization state. The myocardial cells excited after cell depolarization, the cell membrane becomes positively charged, the outer membrane becomes negatively charged, the transmembrane potential soared to +30mv, a process called phase 0 of the action potential. At the repolarization, the positive potential of the cells decreased and the repolarization process was divided into 1, 2, and 3 phases. The 2 phase in the repolarization process is very special. It is a relatively flat curve, close to the zero potential, and corresponds to the ST segment on the electrocardiogram.

So what about the animal's electrocardiogram?

For example, there is a flat 2 phase in the ventricular repolarization process of the dog, which is manifested in the obvious ST segment on the electrocardiogram, but there is no 2 phase in the ventricular repolarization process in the rat, and there is no obvious ST segment on the ECG.

(PS: have atrial repolarization wave, but very small, usually disappeared in the QRS wave, generally do not see)

2. How to calculate the "ST segment" of the rat?

For the existence of ST segment of ECG animal (dog, monkey), according to the conventional ST segment calculation method: using the line as the baseline, select the ST section of a point as a value, such as J, numerical value to the baseline distance is ST, above the baseline value, ST the positive value below the baseline, ST is negative.

Although the rat electrocardiogram has no regular ST segment, the ST segment is a very important parameter on the electrocardiogram. It is not easy to give up or to be parsed. In the Rat electrocardiogram, we replace it in another way.
If you are using the ECG acquisition and analysis system SP2006 of Beijing soft long company, when making the ST segment resolution of the rat, you are recommended to use the formula S ST-index, which is delayed by 0, and the range is 10. The representative is starting from the S wave vertex, taking 10 points (10ms) back, taking the line as the baseline, and calculating the average of the 10 points to the baseline distance. The 10 values of the above figure are below the baseline, and the ST segment is -41. The 10 value points in the following figure are below the baseline, one part above the baseline, and the average of the 10 points is 0, so the ST segment =0. (the value of the delay and range can be set according to the need)

In the above picture, each small lattice of the abscissa stands for 2.5ms, and each small lattice of the ordinate represents 5 * 1/100mV.
3. In these cases, the ST segment of the rat's electrocardiogram

(1) there is a clear ST segment in the early maturing of the rat, but as the growth will disappear compley, the mature rat can not see the ST segment.

(2) at low temperature, hypoxia, or injecting equal blood drug, the action of 2 phase ion acting on ventricular repolarization, at the same time, leads to slow heart rate, which may lead to obvious ST segment on ECG. If a clear ST segment is collected in the rat, it should be considered if there are factors of hypothermia, hypoxia or drug. When collecting the electrocardiogram, it is also extremely necessary to keep the heat of the anaesthetized animal.

4. What should the ST segment of normal rats be?

The ECG analysis and people are different, there is no animal ECG background of official data, in some books or documents in ECG can find some reference values, but these values and animal species, weeks, which lead ECG device, sampling frequency, mode, rat body, analytical formula closely related. These factors may affect the ECG and there is no uniform official, so no official background data, numerical literature cannot be directly used to use. So what do you do with the normal reference value? The answer is to make a blank control group. The value of your blank control group is the reference value of your experiment.

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