ECG

Resting membrane potential of a cell is Negative -70 mV.  Membrane potential is the difference between interior charged and exterior charged of a cell, at rest, it is -70 mV. So, inside of cell is negative charged. Sodium and potassium both are positive charged. During depolarization in order to function as contraction of cell, positive charged sodium enter into cell and cell become more positive inside until a level is called depolarization then it starts to be lost positivity through potassium out of the cell is called repolarization until reached -70 mV and if, further repolarization occurs is called hyper polarization. Cycle repeated in order to function of cell. This depolarization and repolarization work as electrical impulse is recorded on ECG Strip show it as waves named P, QRS, T and U as a result contraction and relaxation of muscle cells, specially cardiac muscles. Cardiac cells are specialized due to presence of SA node, AV node, and purkinje fibers have extra power to contract the cell, that is why short event than other cells to be contracted or to be function.

There are 6 chest leads, each of them record the P, QRS, and T waves. Chest leads are V1, V2, V3, V4, V5, and V6. Leads are placed from right side of chest wall to the left side of the chest wall (shown on picture). 

V1 and V2 record the right atrial and right ventricular contraction as waves due to anatomical location of the heart and placement of V1 and V2 on the right side of the chest wall. V5 and V6 record the left ventricular contraction as waves due to anatomical location of heart and placement of V5 and V6.

P, QRST and T have their own normal fixed length, duration, and width on normal healthy heart muscles. Remember , one complete contraction is shown by P, QRS and T on ECG Strip that come out from ECG machine , speed of Strip is about 25 mm/ second, in this period, many complete contractions may occurs, depends on  presence of  diseased cells and  presence of other factors.

Normal length, duration, and width of the P, QRS complex and T has been shown on ECG strip.

Remember, one large box contain 5 small squire boxes to pass one large box take 0.2 second.

One large box = 5mm, so 5 large box= 5*5=25mm = 5 *0.2 = 1.0 second so, waves pass the 25mm within 1 second  in normal healthy heart cells. Also look at R wave length as upward deflection, deep S wave as downward deflection, T wave and Q wave very precisely because these information need to identify the abnormality of the heart, you can imagine!!!!!?. Either Right Ventricular Hypertrophy, Left Ventricular Hypertrophy with or without strain, Right or left BBB and Myocardial Infarction. These are the main topics in this article.

Patient R, complaining of cardiac problem, on her or his ECG show, Tall R wave on V1, more than 5 small squires and R/S ratio is < 1 with inverted T wave, all findings are due to Right ventricular Hypertrophy with strain of the patient. There is no abnormality on V5 and V6 because of V5 and V6 are placed on left Ventricle as left side of the chest wall.

 

Patient S, complaining of cardiac problem, on her ECG show; tall R wave on V5 and V6, deep S on V1 and inverted T wave; sum of R and S equal or more than 35 small squires indicate the Left Ventricular Hypertrophy with strain (inverted T wave).

 

 

                                               Right or Left Bundle Branch Block

Delay conduction to ventricle due to block; conduction from healthy branch to selective ventricle then from this ventricle to another ventricle, that is why QRS complex is wide in both either left or right BBB; wide due to delay impulse to blocked ventricle.

When there is defective impulse transmission to ventricle through bundle Branch of heart muscles due to the cause.

Patient T, complaining of heart problem, her ECG show, rSR’ as wide QRS complex on V1 indicate RBBB.

 

For the LBBB, patient ECG show Wide QRS complex on V5 and V6 with Bizarre rSR’ that simulate on Limbs lead two, three and aVF.

                                                      In Case of Myocardial Infarctio

Check all chest leads V1 to V6. If there is very deep Q wave, raised or not ST segment and inverted T wave on any lead from V1 to V6 of Patient ECG indicate Anterior Myocardial Infarction.

 

Noted: raised ST segment indicate the Recent MI and baseline “S” indicate Old MI.  Deep Q wave here called pathological Q wave.

 

Same finding on Limb leads two; three and aVF, but this indicates Inferior myocardial Infarction.