Electrophysiology of the Heart 1 PDF

Electrophysiology of the heart 1 Writer/reviser : Jawad Alnaj jar Warning : if you want to be an expert in ECG , watch this video https://youtu.be/CNN30YHsJw0 Electrocardiography is a process which we convert cardiac electricity to waves on a paper During depolarization, the norma...

Electrophysiology of the heart 1 Writer/reviser : Jawad Alnaj jar Warning : if you want to be an expert in ECG , watch this video https://youtu.be/CNN30YHsJw0 Electrocardiography is a process which we convert cardiac electricity to waves on a paper During depolarization, the normal negative potential inside the fiber reverses and becomes slightly positive inside and negative outside. ECG : graphical recording of electrical activity of the heart.  Note especially that no potential is recorded in the ECG when the ventricular muscle is either completely polarized or completely depolarized. Only when the muscle is partly polarized and partly depolarized does current flow from one part of the ventricles to another part, and therefore current also flows to the surface of the body to produce the ECG. ECG : graphical recording of electrical activity of the heart.  he P wave is caused by electrical potentials generated when the atria depolarize before atrial contraction begins. he QRS complex is caused by potentials generated when the ventricles depolarize before contraction—that is, as the depolarization wave spreads through the ventricles. here- fore, both the P wave and the components of the QRS complex are depolarization waves. he T wave is caused by potentials generated as the ventricles recover from depolarization. his process normally occurs in ventricular muscle 0.25 to 0.35 second after depolarization. The T wave is ECG : graphical recording of known as a repolarization wave. electrical activity of the heart. ECG helps us read heart rate and rhythm. Segment : region between two wave. Starts in the end of a wave and ends in the beginning in the next wave. P- Q or P- R Interval. he time between the beginning of the P wave and the beginning of the QRS complex is the interval between the beginning of electrical excitation of the atria and the beginning of excitation of the ventricles. his period is called the P-Q interval. Name : PR interval is more better than PQ interval because sometime there will no be Q wave in ECG.  One large square = 0.2 s ‫رقام‬%‫ركزوا على ا‬ One small square = 0.04 s How can we calculate heart rate 1500 / numbers of small squares between one R wave to another R wave Normal heart rate = 72 beats per minute Rhythm is normal when there are equal spaces between t wave , QRS and P wave Different ways to calculate heart rates When the impulses transmit from SA node to AV node , the atria will be completely depolarized Then the impulses transmit to interventricular septum through right and left AV bundles Then impulses transmit to purkinje fibers and depolarize the ventricles After complete depolarization ,the ventricles will be contract. When ventricles relax , repolarization happens Relationship between ECG and cardiac cycle Always the depolarization and repolarization from the conductive system preceded the contraction and relaxation If you interested in heart sounds https://youtu.be/s4RzKhu2mjc S1 sound ( lub ) : mitral and tricuspid valves close S2 sound ( dub ) : aortic and pulmonary valves close S3 ( not necessary existed ) : due to passive flow of bloode from atria to ventricles S4 : always abnormal When atria contract , ventricles relax. And vise H Isoelectric line  Einthoven’s triangle, is drawn around the area of the heart. his triangle illustrates that the two arms and left leg form apices of a triangle surrounding the heart. he two apices at the upper part of the triangle represent the points at How to memorize these which the two arms connect electrically with the luids around the heart, and the lower apex is the point at which 1- aVR —-> R = right the left leg connects with the fluids. 2- aVL ——> L = left 3- aVF —-> F = foot Lead is specific arrangement of each pair of connection. Positive in one area and negative in one area. By this arrangement we can see the heart in fiddle to directions Positive and negative show us the flow of currents Leads of ecg helps use to see the heart in all direction. For example , if we have infarction in specific area ,ecg can help us to know where this area is important Toknow For previous slides For the next slides 1- when calculate the heart rate , you will see that it is more than 100 —> tachycardia. 2- when calculate the heart rate , you will see that it is less than 60 —> bradycardia 3- you see the beats and the spaces between waves are abnormal —> arrhythmia  The reason from SA node Due to increase metabolic activity To practice how to calculate heart rate , try with this picture 1500 / small boxes between 2 R wave Also try to calculate now Sympathetic normally increases heart rate Parasympathetic decrease heart rates When a person takes a deep breath ( inspiration ) , , there will be out flow of signal from medulla to vasomotor to lung which leads to increase heart rate