Electrocardiogram (ECG)

Electrocardiogram (ECG) refers to the heart in every cardiac cycle, the point, atrial pacing, ventricular have excited, along with the change of bioelectricity electrocardiogram, through the body was drawn from ECG DuoZhong form of potential changes graphics (hereinafter referred to as ECG). Electrocardiogram (ecg) is the heart of the occurrence of excitement and restoration of the objective process spread index.

Generation principle

The heart of the tissues surrounding and body fluid can conduct electricity, so it can be read to become a human body will have the length, width and thickness of the three dimensional volume conductor. The heart is like power, countless myocardial cell action potential changes can reflect the sum total of the transmission and to surface. Many points on the body potential difference exists between ecg

, also have a lot of points between each other without such as the electric potential difference is.

According to the principle of mechanics heart electrical activity can be summed up as a series of instant comprehensive vector ecg. In each of the cardiac cycle, make space of a three-dimensional track ring movement ecg vector loop. Application of cathode rays oscilloscope on the screen of the EMian, specific see face and lateral electrocardiogram vector loop, is stereo vector loop in the corresponding plane projection. The potential of electrocardiogram record change is a series of instant ecg in different guide comprehensive vector coupling in response, also is the plane vector loop in the coupling of the projection on again. The size of the potential projection income depends on the comprehensive vector of ecg moment itself and its size and guide the coupling relationship between Angle. Projection direction and the coupling direction was potential when, on the contrary, as negative potential. Use certain transitional record to speed paper these projection for them was got is electrocardiogram, of the wave. Electrocardiogram (ecg) waveform in baseline (potential) the rise and fall of up and down the line, the direction of the operation with vector loop relevant. And the coupling direction, electrocardiogram (ecg) in the rise of teams, contrary to the projection, a decline. Vector ring zero is the projection of electrocardiogram potential line, line of extension cord will vector loop is divided into two parts, they respectively projection for is wave and the negative waves. Therefore, electrocardiogram and heart vector graph has a very close relationship. Electrocardiogram strengths are different from different points of view of the plane, the use of comparative simple waveform, line of complex three-dimensional ecg vector loop, the projection to quantitative and schedule of the analysis. Ecg vector graphics and the development of the theory and further enrich the content of study and electrocardiogram (ecg) the easier to understand.

Electrocardiogram (ecg) represent the entire heart electricity exciting comprehensive process, to a myocardial cell electric excited as the foundation, myocardial cells excited happening in the telex changes. Myocardial cells in the resting state cell membrane and a positive charge and the film inside take the same amount of negative charge, myocardial cells in the resting state kept inside and outside the cell membrane potential difference, this is called the polarization state. If the microelectrode insert within cells, can record a negative potential, called the transmembrane resting potential, resting potential formation is mainly due to ionic membrane permeability is different, the film inside and outside all sorts of ion is mainly K + + the concentration of making, there was a big difference in cells, K + cells to the high level than about 20 to 30 times, and making the cells within the cell levels higher than + 10 to 20 times. Cell membrane to the permeability of high K +, K +, and part of the outflow concentration gradient to film along the membrane, increase the positive charge in the negative ion membrane organic (mainly protein molecules) have with the tendency of the outflow of K +, but by molecular big, not through the membrane and stuck in the inner surface of the film. The role of the positively charged membrane rejection within the attract negatively and membrane effect, make K + to drain the balance by, in both sides of the film they form polarization state. Different types of myocardial fibers, resting potential different; Fast reaction, such as ventricle muscle fiber for 80 ~ 90 mV, slow reaction fiber, if antrum room knot, only to 40 ~ 70 mV. When myocardial cells stimulated (or spontaneously) and excitement, inside and outside the cell membrane potential rapid change. Inside and outside the cell membrane potential difference in the instant disappeared, the potential in cells by 90 mV quickly to 0, and even the mV + 20 ~ + 30 mV. That is the polarization state disappeared, the process is called in addition to a process. For example, in ventricular muscle membrane potential from the static breath-80 ~ 90 mV down to-60 ~ 70 mV threshold potential level, that is, except for very quickly began. Then cells and recover gradually its negative potential, the process is called bipolar. Except by extreme bipolar, membrane potential from negative change is within and again returned to the resting potential to a series of potential changes called transmembrane action potential. But as a curve, divided into 5 is for. Figure 1 and table 1 and ventricular muscle action potential and the membrane surface and the relationship between the ion flow electrocardiogram.

1, 2 and 3 a photograph is metabolic process, this stage in the membrane potential return to 90 mV, the process called bipolar, but at the moment, film distribution has not yet returned to internal and external ion the resting state level, finally potassium sodium-the transfer of pump action to make inside and outside all sorts of ion and back to the resting state. In four times the self-discipline cells in the resting state level in stable, its action potential is horizontal line; And the autonomic Ca2 + myocardial cells slowly open channel Ca2 + steadily, in the flow, make the membrane potential gradually move to potential level, its are in action potential up, it also called slash four phase, when achieved very spontaneous except threshold potential, they inspire Ca2 + Ca2 + open, slow channel in the flow and the rapid XiangChu a 0 bit. This is the heart of self-discipline mechanism, because antrum room knot of four phase XiangChu very fastest, so normal antrum room knot issue impulse exciting heart.

According to the shape of the action potential and the physiological characteristics, myocardial cells can be divided into two categories: fast response cells and slow response cells. The resting state in the cell membrane between any two points potentials, not equal potential difference, when myocardial cell a side the stimulation except when the film began a negative charge not adjacent to go in the section is a positively charged, the former, the latter is called hole called electric power supply, called the electric dipole. Electric acupuncture point and power supply voltage, shielding is formed between an electric current, current constantly by power supply electricity to flow to point, then the power supply part also began in addition to become it has not been a part of the very front in electric acupuncture point; The program is so expand, until the whole cell and heart completely in addition to extremely. In addition to a process can be thought of as a group of electric dipole keep moving along the cell membrane, its power source (+) before, electric acupuncture point (), except in the extremely finished, the cells are reversed polarization state, film inside take a positive charge and the membrane to go negative charges, followed by polarization. Bipolar process from the very first part, in addition to start first bipolar membrane for the part, which made the place cationic potential higher than not bipolar front part of the form, and a group of electric acupuncture point before, the power of electric dipole, this group of electric dipole progress continuously, and until the whole myocardial cell bipolar finished.

The human body body fluids containing electrolytes, has the conductivity, so the human body is also a kind of volume conductor, so in the human body and all the body of the current ecg accidentally positive into negative, forming a heart electric field. But through the ecg accidentally center in vertical shaft of electric dipole of zero potential heart is divided into the surface electric field, negative potential area. The heart of the distribution of the electric field in the human body surface potential body surface is potential. The electrocardiogram machine body surface potential electrical signal amplifier and according to the time sequence of the heart is excited to record, namely for ecg. In addition to a face detection electrode electric dipole, the positive recorded a wave, in the face of negative record is a negative waves (figure 3). The closer the electrode ecg accidentally shaft, then the absolute value of the potential is high, the greater the waveform. Every heart throb field including contraction and relaxation, called a cardiac cycle, the corresponding ecg activities including except extremely and bipolar, become a ecg cycle.

Ecg vector and normal ecg heart is excited originated in the upper right atrium, the superior vena cava entrance antrum room knot, excited by the conduction system transferred in turn to atrium, ministries, the addition to ventricular extremely and bipolar. The heart is a solid device, the brain the various parts of the electricity transmission of excited direction, and the amount of different size, this is called the vector. At the same moment, there were many myocardial every direction to electric dipole, the comprehensive method of vector with parallelogram diagonal represents a moment of ecg vector, comprehensive in a remote ecg cycle, the instant comprehensive ecg in changing vector, so to form a vector loop: atrial except extremely and ventricular except a Mosaic P vector loop respectively and QRS vector loop; Ventricular bipolar constitute T vector loop. This stereo vector map (VCG) called space vector, the EMian in ecg, sagittal and the horizontal plane projection, a plane ecg vector diagram, clinical application for less. Plane vector diagram in the electrocardiogram ecg guide on the coupling projection constitute an ecg in clinical widely used the latter.