MUNI MED ECG - Electrocardiography 1 Fyziologický ústav, Lékařská fakulta Masarykovy univerzity Electrocardiography - Definition: recording the cardiac electrical activity from the surface of the body (el. heart activity can also be obtained from the esophageal leads or the heart surface itself, but these methods are used by other names) 2 Fyziologický ústav, Lékařská fakulta Masarykovy univerzity MUNI MED Cardiac conduction system branches fibers 3 Fyziologický ústav, Lékařská fakulta Masarykovy univerzity Cardiac conduction system Function: AP formation and preferential conduction The atriums are separated from the chambers by a non-conductive fibrous septum - the only way is through the AV - Sinoatrial node (SA) - natural frequency 100 bpm (mostly under parasympathetic damping effect), conduction velocity 0.05 m/s - Preferred internodal atrial ways - conduction velocity 0.8-1 m/s - Atrioventricular node - single conductive connection between atria and ventricles, natural frequency 40 - 55 bpm, conduction velocity only 0.05 m/s (nodal delay) - His bundle - conduction velocity 1-1,5 m/s Tawara (bundle) branches - conduction velocity 1 -1,5 m/s I natural frequencies of 20 - 40 bpm, they have slow Purkynje fibers - conduction velocity 3-3,5 m/s spontaneous depolarization Sinus rhythm - AP starts at the SA node Junction rhythm - AP is formed in the AV node or His bundle Tertiary (ventricular) rhythm - AP is formed in bundle branches or Purkynje fiber Ventricular myocardial activation - from inside to outside, markedly synchronized, determined by the onset of excitement Repolarization of ventricular myocardium - in the opposite direction, less sharp, repolarization isles Note: natural frequency is the frequency of AP formation unaffected by neural and hormonal control UNI E D Electric dipole - Electrode: records electrical potential (O) - Electrical lead: connection of two electrodes - It records the voltage between the electrodes - Voltage: difference of el. potentials (V=01-O2) electrode 5 Fyziologický ústav, Lékařská fakulta Masarykovy univerzity MUNI MED Einthoven triangle (standard, limb, bipolar leads) Bipolar leads: both electrodes are active (variable electrical potential) Electrode colors: R: red, L: yellow, F: green Fyziologický ústav, Lékařská fakulta Masarykovy univerzity Goldberger leads (augmented, limb, unipolar leads) - Unipolar leads: one electrode is active (variable electric potential) and the othe is inactive (constant electric potential, usually 0 mV) - The active electrode is always positive 7 Fyziologický ústav, Lékařská fakulta Masarykovy univerzity Wilsonova central terminal (W It is formed by the connection of limb electrodes through resistors electrically represents the center of the heart (it is actually led out or it is calculated) Inactive electrode (constant potential) Central terminal Real central terminal 8 Fyziologický ústav, Lékařská fakulta Masarykovy univerzity MUNI MED Chest leads - Chest lead: connection of chest electrode and central terminal - Unipolar leads: chest electrode is active (positive) and central terminal is inactive (0 mV potential) 9 Fyziologický ústav, Lékařská fakulta Masarykovy univerzity MUNI MED Leads according to Cabrera 90° 10 Fyziologický ústav, Lékařská fakulta Masarykovy univerzity Analysis of ECG 1. Heart action 2. Heart rhythm 3. Heart rate 4. Waves, segments and intervals - P wave - PQ interval - QRS complex - ST segment - T wave - QT interval 5. Electrical heart axis Ventricular depolarization Atrial depolarization Svod II Ir Q s Ventricular repolarization 11 Fyziologický ústav, Lékařská fakulta Masarykovy univerzity MUNI MED Analysis of ECG A millimeter grid of paper wi help in fast analysis See the paper speed (here 25 mm / s)v - How many ms is one mm? - It is good to know how much mV is one mm 25 mm/s 10 mm/mv 12 HR [1/min] P 68 ms PQ 136 ms 71 QRS 98 ms QT 356 ms RR 850 ms QTc 386 ms Seiva Servis_Praha 1) Heart action Regularity of distances between QRS complexes - RR intervals Calculate difference: RR - mean RR _rr (you only need to choose the shortest and longest RR in the record) Regular action: difference < 0,16 s Irregular action: difference > 0,16 s - Usually pathological - Beware of significant sinus respiratory arrhythmia - it is very physiological. If you are unsure, ask the patient to hold their breath during recording Note: if one extrasystole is present, but otherwise the action is regular, it is called regular 13 Fyziologický ústav, Lékařská fakulta Masarykovy univerzity MUNI MED 2) Heart rhythm - Heart rhythm is determined by the source of action potentials that lead to ventricular depolarization ventricular depolarization is crucial, because it determines cardiac output - Sinus rhythm - AP begins in SA node - On ECG: present P wave (atrial depolarization) before QRS - Junction rhythm - AP begins in AV node or His bundle, the frequency is usually 40-60 bpm - P wave is not before QRS, QRS is normal (narrow) - Heart rate is low (40-60 bpm) - Atrial depolarization can be present in the ECG if the ventricular impulses are transferred to the atria - wave is after QRS and has opposite polarity because it runs in opposite direction - Tertial (ventricular) rhythm - AP begins in other parts of the conduction system, frequency 30-40 bpm - QRS has a strange shape (wider), because it spreads in a non-standard direction in the ventricles UNI 3) Heart rate (HR) - Frequency of ventricular contraction (because it determines cardiac output); on ECG - frequency of ventricular depolarizations -HR = 1 / RR bpm - Physiological: 60 - 90 bpm at rest -Tachycardia: > 90 bpm in rest Can be sinus (increase sympathetic aktivity, medication, ...) - Tachyarrhythmias: rhythm is not sinus - Bradycardia: < 60 bpm - Can be sinus (increase sympathetic aktivity, sport heart - physiological) - HR < 50 bpm, rhythm probably is not sinus 15 Fyziologický ústav, Lékařská fakulta Masarykovy univerzity MUNI MED 4) Waves, segments, intervals 16 PQ interval Fyziologický ústav, Lékařská fakulta Masarykovy univerzity Name Norm wave P 80 ms interval PQ (PR) 120-200 ms segment PQ (PR) 50-120 ms Q - complex QRS 80-100ms R - S - segment ST 80-120 ms interval QT < 420ms wave T 160 ms Bazett's formula: QTc = QT depends on RR interval -correction of QT on RR QT tJřř UNI ED 4) Waves, segments, intervals name Place and description Physiological bacground Norm wave P First round wave (negative or positive) Atrial depolarization 80 ms Interval PQ(PR) Interval from beginning of P to beginning of Q (or R, if Q is not present) Time interval from SA node activation to the Purkynje fibers activation 120-200 ms segment PQ (PR) From P wave end to beginning of Q (or R, if Q is not present) Complete atrial depolarization, AP transfer from AV to ventricles 50-120 ms Q First negative deflection Depolarization of septum and papilar muscles - complex QRS From beginning of R to end of S Ventricular depolarization 80-100ms R Positive deflection Main ventricular depolarization - S Negative deflection after positive deflection. - segment ST Interval of isoelectric line between end of QRS and beginning of T wave Complete depolarization of ventricles 80-120 ms Interval QT From beginning of Q (or R) to the end of wave T Electrical systole < 420ms wave T Second round wave (negative or positive) Ventricular repolarization 160 ms 4) Waves Ventricular depolarization QRS R Atrial depolarization Lead II Ventricular repolarization 18 Wave P: - Is present? - Is positive/negative, one-peak/two-peak, high(>0,25mV)/normal/low? QRS: Examples: Q: first negative deflection R: first positive deflection S: negative deflection after positive deflection small deflection (pod 0,5 mV) - small letter Strong deflection - capital letter Second positive deflection Q) Wave T: - Is positive/negative/bipolar? - Does it have the same polarity as the strongest QRS deflection? - Yes: concordant (ok), No: discordant (pathology) - Bipolar T: Preterminal negative (-/+) Terminal negative (+/-) Fyziologický ústav, Lékařská fakulta Masarykovy univerzity UN I ED 5) F10Qt r j C31 h63 rt 3X J S E'ectr'ca' heart axis: average direction of the electric heart vector during ventricular El, heart axis aVL -30* I 0< aVR 30< vectocardiogram depolarization (QRS complex) (can also be determined for atrial depolarization: P, or ventricular repolarization: T, but in practice we will analyse ventricular depolarization) Heart axis is physiologically directed down, left, back -refers to the real placement of the heart in the chest. - Here we solve only the frontal plane (limb leads) Physiological range: Middle type 0° - 90° Left type -30° - 0° Right type 90° - 120° Pathological range: Right deviation: > 120 ° (P ventricular hypertrophy, dextrocardia) Left deviation: < -30° (L ventricular hypertrophy, pregnancy, obesity) UNI ED the axis is also changed when Tawara branches are blocked or after IM, missing el. activity of part of chambers Electrical heart axis - evaluation 25mm/s lOmm/mV TAC 50/60 Hzlfad 0.3 Hzl Lead ll:QM=-1; R„=17; SM=-1 QRS„=15 Lead INI: Qm=0; Rm=10; S„,=-1; QRS„,=9 Because the el. axis is related to ventricular depolarization in the frontal plane, use QRS in limb leads: I, II, III. Calculate the sum of QRS oscillations in i leads I, II, III. When the oscillation is down, it is negative. When the oscillation is up, it is positive. Use a millimeter grid - Lead I: Q,=-1; R,=6; S,=0; QRS,=5 Electrical heart axis - evaluation - Draw the Einthoven Triangle with Goldberger augmented Leads - Mark the angles around the triangle (in the circle) - Lead I: - 0 at lead I is in the center of lead - QRS, = 5, so from 0, measure 5mm towards the positive electrode, make a mark (or any other units, ratio is important) - If the sum of QRS is negative, you will go towards the negative electrode - Run a line from the mark perpendicular to the I lead (parallel to the aVF lead) 90 MED o Electrical heart axis - evaluation Lead II: - 0 at lead II is again in the center of lead - QRS I, = 15, so from 0, measure 15 mm towards the positive electrode, make a mark (again, if the sum of QRS is negative, you will go towards the negative electrode) - Run a line from the mark perpendicular to the II lead (parallel to the aVL lead) Electrical heart axis - evaluation Lead III: - The same way draw line for QRS „, = 9 ■ Draw an arrow that starts at the center of the triangle and passes the cross of the drawn lines This arrow shows the direction of the cardiac electrical axis in the frontal plane Note, logically, only lines from two leads are sufficient The cardiac electrical axis for ventricular depolarization in the frontal plane is 70 ° 60° MUNI ED 24 11 Rhythms Nurses Need to Know Basic EKG/ECG Rhythms ^^dentlSe? H O C V-Fib Ventricular Fibrillation Rste: UnmeaBurable V-Tach Ventricular Tachycardia AAAA/VWWWWW\ Wide OPS Rste: FBSt|10O-25O bpm) Torsade de Pointes Type Of Ventricular Tachycardia ^ Rot-:- Vs\~v F-ast <"2:00250 i:-i:-nv. TbII snd SMort Waves Irregular, NoP Wave, No QRS Regular, NoP Wave, Wide QRS Irregular, NoP Wave, Wide QRS *Synchronized Cardioversion possible for SVT if medication ineffective. SVT* Supraventricular Tachycardia STEMI ST Elevation Myocardial Infarction A-Fib Atrial Fibrillation A-Flutter Atrial Flutter Rate: Very Fast <150-25O bprn) ,-jv "\-——-,—j-vj"f""*\-_—"\-, ST Elevatron " T Erratic Waves I * QRS normally narrow but not always \ ^ "Sawtooth" Pattern ^ I «— No P Waves —* _j Rate: slow < Rate: Fast (> 100 tjpm> Rate: N:i mol .;ůO-IOO l:-|:-m; Regular, P Wave Hidden, Normal QRS Reg or Irreg, P Wave, ST Elevated Irregular, NoP Wave, Normal QRS* Reg or Irreg, NoP Wave, Normal QRS Irregular, NoP Wave, Wide QRS Regular, P Wave, Normal QRS Regular, P Wave, Normal QRS Regular, P Wave, Normal QRS UNI ED