ELECTROCARDIOGRAPHY = methods enabling to register electrical changes caused by heart activity from body surface. Willem Einthoven 1860- 1927 1893 Einthoven introduces the term 'electrocardiogram' 1895 Einthoven distinguishes five deflections - P, Q, R, S and T 1902 Einthoven publishes the first electrocardiogram 1905 Einthoven starts transmitting electrocardiograms from the hospital to his laboratory 1.5 km away via telephone cable 1924 the Nobel prize ELECTRICAL DIPOLE Local currents • Maximal in dipole axis (1) • Zero in the place of the centre (0) SPREADING OF DEPOLARIZATION FRONT ELECTRICAL FIELD OF THE HEART (vector) •Consists of sum of momentary dipoles on the depolarization front •Its size is a function of number of dipoles and steepness of boundary line •Direction from depolarized (-) to (re)polarized (+) area REGIONAL VECTORS INTEGRAL VECTOR during excitation is changing: •Size of momentary dipoles •Their direction •They are spreading to body surface - ELECTROCARDIOGRAPHY SA uzol Myokard predsieni AV uzol Hisov zväzok Tawarové ramienka Purkyňové *~-L vlákna y j Myokard komôr EKG [m s] 0 PQ interv. QRS QT 0,16 0,1 0,3 - i_ ! HR - dependent Atrial depol. Ventricular complex _I I_ (depol.) (repol.) ECG gives information about: Frequency (changes of HR in S A node or arrhythmias, sick sinus syndrome) 2. Conduction (blocks - SA, AV) 3. Rhythm (ES - supraventricular, ventricular) 4. Ventricular gradient (relationship between depolarization and repolarization: origin - metabolic, hemodynamic, anatomic, physical...ischemia, hypertrophy, dilatation, cardiomyopathy, inflammations, changes in electrolytes, drugs...) 3D LOOPS OF ELECTRICAL AXIS F - frontal plane H - horizontal plane 0 - elektricky střed srdce P - sinová depolarizace QRS - komorová depolarizace T - komorová repolarizace 2D PROJECTION OF HEART AXIS F - frontal plane H - horizontal plane ID PROJECTION OF HEART AXIS Projection on the chest surface into frontal plane (2D) And its projection to line (ID), axis of the I. ECG lead in time E - Einthoven triangle F Goldberger, 1947, aVR, aVL, aVF HEXAAXIAL SYSTEM aVF I It tmr TFÄns I Frontal projection of vector! CHEST LEADS PROJECTION PLANES OF CARDIAC VECTOR AND ECG LEADS Frontal plane limb leads L, IL, III., aVR, aVL, aVF Horizontal plane VI-V6 Both planes are shifted into the level of electrical centre of the heart (0) E - Einthoven triangle ELECTRICAL AXIS OF THE HEART Summary of all momentary vectors, which form ventricular depolarisation loop. Expresses the direction of ventricular activation. Reflects asymmetry in ventricular wall thickness and the position of the heart in the chest. ELECTRICAL AXIS - in the frontal plane (r-q-S) in lead I., II., III. triangle LEFT DEVIATION, RIGHT DEVIATION i -tl_A-_ I + \ 14/ \ 7 111 i ~r>ta~y— v+ 1 \ I*-*'-. / \ V ^ / \ v /111 Normal 12-lead electrocardiogram ECG - information about: 1. Magnitude and position of the heart (electrical axis) 2. Site of impulse origin (P, QRS) 3. Conduction path (P-Q, QRS) 4. Impulse regression (T) 5. Rhythm (P-P, R-R) 6. Action potential alterations (ST, T) 7. Effect of drugs, remedies, ion composition changes. RESPIRATORY (SINUS) ARRHYTHMIA 1847, Ludwig, ECG and breathing of dog - respiratory sinus arrhythmia Detectable already during prenatal life. Present in numerous species in animal kingdom - in all vertebrates. Physiological meaning ???? STABILISATION OF MEAN BP (protection against mechanical effect of intrathoracic pressure on arterial BP) Key effect of parasympathetic NS (decrease of its tonus), sympathetic NS only modulates!!! MECHANISMS: 1) CENTRAL 2) REFLEXES FROM LUNGS 3) REFLEXES FROM BARORECEPTORS 4) REFLEXES FROM RECEPTORS IN THE RIGHT ATRIUM 5) LOCAL EFFECTS ON SA NODE 6) EFFECT OF OSCILLATIONS OF pH, pa02, paC02 Central mechanisms • Central generator of RS A • Respiratory neurons in medulla oblongata hyperpolarise preganglionic vagal neurons • Vagal tonus decreases during inspiration - HR increases Reflexes from lungs - inflation reflexes • Stimulation of vagal stretch-receptors during inspiration supresses inspiratory centre and also cardio-inhibitory centre in medulla oblongata Reflexes from baroreceptors • Diverse opinions about the effect of arterial baroreceptors on RSA • Fluctuation of sensitivity of baroreceptors during respiratory cycle Reflexes from receptors in the right atrium • Bainbridge, 1915 • Reflex increase of HR during atria stretching • Applicable in explanted (denerved) heart Local effects on SA node • Stretching of SA node causes faster spontaneous depolarisation • Effect of mechanosensitive chloride channels • Changes of SA node perfusion (a. centralis) and possible compression of SA node by expanding lungs Effect of pH, pa02 and paC02 oscillations • Oscillatory activity of peripheral chemoreceptors contributes to formation of RSA and increases its amplitude ARRHYTHMIAS = disturbance of impulse generation or conduction RHYTHM and FREQUENCY: Regular 1) Normal HR range: 70 - 220 bpm; effect of age) 2) Sinus tachycardia (60 - 100 bpm; exercise; aging) 3) Sinus bradycardia (below 60 bpm; athletes' heart) 4) Nodal rhythm - below 40 bpm, ventricular rhythm - below 20 bpm) Irregular 1. sinus respiratory arrhythmia (physiological) 2. Sick sinus syndrome 3. Extrasystoles (ES) single or coupled (bigeminy, trigeminy), according to site or origin - sinus, atrial, junction, ventricular ARHYTMIAS SITE OF ORIGIN SINUS ATRIA JUNCTION VENTRICLES JL JL JU ju p+ p- (p-) (p-)^ •Polarity of P wave •PQ interval (QP) (physiological PQ interval: 0.12 - 0.2 s) BLOCKS SICK SINUS SYNDROM AV BLOCKS r PQ>0.2sec LBBB II O RBBB Wenckebach periods (phenomenon) III O A-V dissociation BUNDLE BRANCH BLOCK (BBB) - LEFT, RIGHT PREEXCITATION AV node is „by-passed"? fast conduction •„short nodus" •Wolf-Parkinson-White syndrome (WPW) - sensitive to paroxysmal tachycardia - see re-entry delta wave PQ<0,12s REENTRY Common mechanism of (paroxysmal) tachycardias, extrasystoles, bigeminy, etc. • Double pathway Diverging and converging of excitation pathways • Unidirectional block 1. Long refractory period 2. Slowed conduction 3. Reentry 1. 2. Loops most often at the level of AV junction Determinants of re-entry: Proper dimension of the loop Proper timing of the trigger ES TACHYARYTHMIA • SINUS TACHYCARDIA • PAROXYSMAL TACHYCARDIA (supraventricular, ventricular) • FLUTTER (>250/min; atrial) • FIBRILLATION (>600/bpm; atrial, ventricular; breakdown of electrical homogeneity) ATRIAL FLUTTER Frequency 250 - 600/bpm Atrioventricular block n:l ATRIAL FIBRILLATION lTEui Irregular ventricular rhythm + f-waves VENTRICULAR FIBRILLATION oVR VI V4 V2 V5 m V3 Y6 fiHVTHM STRtPi fl 25 ami/mo; I cm/mY COOOOtWJOOO -3 Frequency above 600/bpm, LETHAL HEART ISCHEMIA A: exercise angina pectoris B: acute non-Q myocardial infarction C: acute Q myocardial infarction ANTIARRHYTHMICS | • BLOCKERS OF Na CHANNEL - prolong inactivation of INa, e.g. refracterity, „blocking" fast ways • BLOCKERS OF Ca CHANNELS - „blocking" fast ways • BLOCKERS OF K CHANNEL - prolonging refractory period • ß-SYMPATOLYTICS - slowing HR Schémata a animace zpracovalo Servisní středisko pro e-learning na MU CZ.1.07/2.2.00/28.0041 Centrum interaktivních a multimediálních studijních opor pro inovaci výuky a efektivní učení EWť sv^Ký BU iv?r i (Ml I ioclalnl- MINISTERSTVO školství, opvnistrirí ^^i^f É^^^l fOndvCR EVROPSKÁ UNIE M LAD EÍE A TĚLOVÝCHOVY konkurenci: hDpn™t ^A.** INVESTICE DO ROZVOJE VZDĚLÁVÁNÍ