ELECTROCARDIOGRAPHY Flashcards
(8 cards)
What is the electrocardiogram?
It is a graphic recording of changes of the total electromotive force of heart (a sum vector) during spreading excitation wave in the heart.
What functions of myocardium can be evaluated by the electrocardiography?
Functions of automatism, conductibility, excitability.
What functions of myocardium can be evaluated by the electrocardiography?
Functions of automatism, conductibility, excitability.
. List the main parts of conduction system of the heart.
Sinoatrial (SA) node, internodal tracts (anterior, medial, posterior), atrioventricular (AV) node and the His-Purkinje conduction system – trunk of His’ bundle, right and left bundle branches (left bundle branch is divided into anterior and posterior hemifascicles), Purkinje fibers.
In what sequence does the wave of excitation spread in the heart?
Atrial activation begins with impulse generation in the SA node. Once the impulse leaves this pacemaker site, atrial activation spreads in the right atrium and simultaneously impulse spreads along the atrial internodal tracts toward the left atrium and AV node. Upon exiting the AV node, the impulse traverses the bundle of His to enter the bundle branches and then Purkinje fibers to finally activate working muscle fibers. Sequence of ventricular activation: interventricular septum, lateral walls of the left and right ventricles (from endocardium to epicardium), the basal areas of the ventricles are the last to be activated.
List the leads for obligatory taking an electrocardiogram
The standard clinical ECG includes recordings from 12 leads: three bipolar limb leads (the standard leads I, II, and III), six unipolar precordial (chest) leads (leads V1 through V6), and three modified unipolar limb leads (the augmented limb leads aVR, aVL, and aVF).
Specify heart area which electric phenomena are represented by each of the standard leads
Lead I records potentials of the lateral wall of left ventricle; lead II displays a sum potential of heart on longitudinal axis; lead III represents potentials of the right ventricle and posterodiaphragmatic (inferior) areas of left ventricle.
Specify heart area which electric phenomena are represented by each of the augmented limb leads.
AVR records a sum potential of heart on longitudinal axis (the heart vector is oriented from this electrode, therefore Р wave, maximal wave of QRS complex and Т wave are negative); aVL represents the potentials of high areas of lateral wall of left ventricle; aVF displays the potentials of right ventricle and posterodiaphragmatic (inferior) areas of left ventricle.
