Includes a complete e-book, video lectures, clinical management, guidelines and much more. The normal T-wave is slightly asymmetric, with a steeper downward slope. Two small septal q-waves can actually be seen in V5–V6 in Figure 10 (left-hand side). Pathological Q-waves have duration ≥0,03 sec and/or amplitude ≥25% of the R-wave amplitude. This is seen in ischemia, electrolyte disorders (calcium, potassium), tachycardia, increased sympathetic tone, drug side effects etc. ECG interpretation always includes assessment of the QT (QTc) duration. The transition from ST segment to T-wave is smooth, and not abrupt. The ventricular septum receives Purkinje fibers from the left bundle branch and therefore depolarization proceeds from its left side towards its right side. Lateral ventricular infarction. Volgman AS(1), Winkel EM, Pinski SL, Furmanov S, Costanzo MR, Trohman RG. The difference between the shortest and the longest QT interval is the QT dispersion. Pacing from the different PVs produced distinct P-wave characteristics. If R-wave in V1 is larger than S-wave in V1, the R-wave should be <5 mm. A U-wave is occasionally seen after the T-wave. A biphasic T-wave has a positive and a negative deflection (Figure 37, panel C). ScienceDirect ® is a registered trademark of Elsevier B.V. ScienceDirect ® is a registered trademark of Elsevier B.V. Morphological characteristics of P waves during selective pulmonary vein pacing. avolgman@rpslmc.edu Rejection remains the Achilles heel of orthotopic cardiac transplantation (OHT). S ingh (2006) Effects of soil layering on the characteristics of basin-edge induced surface waves and differential ground motion, Jr. of Earthquake Engineering 10, 595-616. T-waves with very low amplitude are common in the post-ischemic period. Refer to Figure 4 (second panel). Similarly, a person with chronic obstructive pulmonary disease (COPD) often displays diminished QRS amplitudes due to hyperinflation of thorax (increased distance to electrodes). Comprehensive tutorial on ECG interpretation, covering normal waves, durations, intervals, rhythm and abnormal findings. In the setting of chest discomfort (or other symptoms suggestive of myocardial ischemia) ST segment elevation is an alarming finding as it indicates that the ischemia is extensive and the risk of malignant arrhythmias is high. P waves are the fastest seismic waves and can move through solid, liquid, or gas. Causes of prolonged QTc duration: antiarrhythmics (procainamide, disopyramide, amiodarone, sotalol), psychiatric medications (tricyclic antidepressants, SSRI, lithium etc); antibiotics (macrolides, kinolones, atovaquone, klorokine, amantadine, foscarnet, atazanavir); hypokalemia, hypocalcemia, hypomagnesemia; cerebrovascular insult (bleeding); myocardial ischemia; cardiomyopathy; bradycardia; hypothyroidism; hypothermia. The final vector stems from activation of the basal parts of the ventricles. The amplitude of this Q-wave typically varies with ventilation and it is therefore referred to as a respiratory Q-wave. The second positive wave is called “R-prime wave” (R’). This may be explained by right bundle branch block, right ventricular hypertrophy, hypertrophic cardiomyopathy, posterolateral ischemia/infarction (if the patient experiences chest pain), pre-excitation, dextrocardia or misplacement of chest electrodes. Below follows a discussion which aims to clarify some of the common misunderstandings. Method Patient population . 2) Explain how wind-generated waves, swell, rogue waves, and tsunamis are formed. Post-ischemic T-wave inversion is caused by abnormal repolarization. A negative T-wave is also called an inverted T-wave. Depolarization of the ventricles generates three large vectors, which explains why the QRS complex is composed of three waves. These waves travel in the speed range of 1.5-13 km/s. These ST segment depression should resolve within minutes after termination of the tachycardia. These calculations are approximated simply by eyeballing. Smooth contour; Monophasic in lead II; Biphasic in V1; Axis. If these Q-waves do not fulfill criteria for pathology, then they should be accepted. Normalization of T-wave inversion after myocardial infarction is a good prognostic indicator. It is a positive wave occurring after the T-wave. Such an accessory pathway is an embryological remnant which may be located almost anywhere between the atria and the ventricles. Match. They can still propagate through the solid inner core: when a P wave strikes the boundary of molten and solid cores at an oblique angle, S waves will form and propagate in the solid medium. The existence of pathological Q-waves in two contiguous leads is sufficient for a diagnosis of Q-wave infarction. Electromagnetic Wave are waves composed of undulating electrical fields and magnetic fields. T-wave changes are frequently misunderstood in clinical practice, which the discussion below will attempt to cure. The different kinds of electromagnetic waves, such as light and radio waves, form the electromagnetic spectrum. Prolonged QT duration may either be congenital (genetic mutations, so-called long QT syndrome) or acquired (medications, electrolyte disorders). It is measured from the onset of the QRS complex to the end of the T-wave. The longer the Q-wave duration, the more likely that infarction is the cause of the Q-waves. The PR segment serves as the baseline (also referred to as reference line or isoelectric line) of the ECG curve. If myocardial infarction leaves pathological Q-waves, it is referred to as Q-wave infarction. Sinus Tachycardia. ECG interpretation includes an assessment of the morphology (appearance) of the waves and intervals on the ECG curve. Assessment of the T-wave represents a difficult but fundamental part of ECG interpretation. The P-wave reflects atrial depolarization (activation). Author information: (1)Section of Cardiology, Rush Medical College, Chicago, Illinois 60612, USA. The P-wave is always positive in lead II during sinus rhythm. T-wave inversions that are secondary to these conditions are typically symmetric and there is simultaneous ST-segment depression. If the atria are depolarized by impulses generated by cells outside of the sinoatrial node (i.e by an ectopic focus), the morphology of the P-wave may differ from the P-waves in sinus rhythm. It is important to assess the amplitude of the R-waves. Hence, ECG leads with net positive QRS complexes will show ST segment depressions (as well as T-wave changes). A common cause of abnormally large T-waves is hyperkalemia, which results in high, pointed and asymmetric T-waves. For this purpose, it is wise to subdivide ST-T changes into primary and secondary. However, the distance between the heart and the electrodes may have a significant impact on the amplitudes of the QRS complex. It is called Wave Propagation Direction. Although heart rhythm will be discussed in detail in the next chapters, fundamental aspects of rhythm will also be covered in this discussion (refer to Normal Rhythm and Arrhythmias). The term ST segment deviation refers to elevation and depression of the ST segment. Women have a more symmetrical T-wave, a more distinct transition from ST segment to T-wave and lower T-wave amplitude. The P-wave vector is slightly curved in the horizontal plane. First, realize that this “radially-directed” plane wave is in fact a plane wave, and not a cylindrical wave. Three criteria were used to distinguish right from left PV: 1) a positive P-wave in lead aVL and the amplitude of P-wave in lead I ≥50 μV indicated right PV origin (specificity 100% and 97%, respectively); 2) a notched P-wave in lead II was a predictor of left PV origin (specificity 95%); and 3) the amplitude ratio of lead III/II and the duration of positivity in lead V1were also helpful in distinguishing left versus right PV origin. To analyze P waves superimposed on T waves during spontaneous ectopics, the algorithm should be used in combination with an ECG subtraction … Chronic cor pulmonale (COPD, pulmonary hypertension, pulmonary valve stenosis). The vector is directed forward and to the right. Non-ischemic ST segment elevations are typically concave (Figure 16, panel B). If the ectopic focus is located close to the sinoatrial node, the P-wave will have a morphology similar to the P-wave in sinus rhythm. Acute cor pulmonale (pulmonary embolism). The P-wave will display higher amplitude in lead II and lead V1. Numerous conditions can diminish the capacity of the atrioventricular node to conduct the atrial impulse to the ventricles. Note that the first vector in Figure 7 is not discussed here as it belongs to atrial activity. The straight ST segment can be either upsloping, horizontal or (rarely) downsloping. It is crucial to differentiate normal from pathological Q-waves, particularly because pathological Q-waves are rather firm evidence of previous myocardial infarction. Secondary T-wave inversions are illustrated in Figure 19 (as well as Figure 18 D). Normal R-wave progression implies that the R-wave gradually increases in amplitude from V1 to V5 and then diminishes in amplitude from V5 to V6 (Figure 10, left-hand side). As noted above, the small r-wave in V1 is occasionally missing, which leaves a QS-complex in V1 (a QRS complex consisting of only a Q-wave is referred to as a QS-complex). Bazett’s formula has traditionally been used to calculate the corrected QT duration. The term ST-T segment changes (or simply ST-T changes) is used to refer to such ECG changes. Left anterior fascicular block is diagnosed if the axis is between -45° and 90° with qR complex in aVL and QRS duration is 0,12 s, provided that other causes of left axis deviation have been excluded. Many of these conditions cause rather characteristic ST segment changes. Thus, a biphasic T-wave should be classified accordingly. The height of the U-wave is typically one-third of the T-wave. If the stenosis/occlusion is located in the left circumflex artery or right coronary artery, the flat T-waves are seen in leads II, aVF and III. An algorithm based on these characteristics identified 93% of left versus right PVs, 85% of superior versus inferior PVs, and in all 79% of the specific PVs paced. Particle motion is parallel Positive T-waves are rarely higher than 6 mm in the limb leads (typically highest in lead II). Among following: these, the fundamental forward space-harmonic wave and 1) angular positions of the dielectric helix-support rods the first backward space-harmonic wave crossing over at the around the helix (angular offset of the rods); π-point frequency (Fig. As noted above, the transition from the ST segment to the T-wave should be smooth. If the axis is more negative than –30° it is referred to as left axis deviation. P waves are also called pressure waves for this reason. The p wave is positive in II and AVF, and biphasic in V1. An algorithm predicting the paced PV was developed and prospectively evaluated in a different population of 20 patients. Large waves are referred to by their capital letters (Q, R, S), and small waves are referred to by their lower-case letters (q, r, s). ECG changes in ischemia are discussed in detail in section 3 (Acute & Chronic Myocardial Ischemia & Infarction) and a specific chapter discusses ST elevation in detail. The following rules apply: Normal in newborns. P waves are the fastest seismic waves and can move through solid, liquid, or gas. Right axis deviation: Net negative QRS complex in lead I but positive in lead II. Low amplitudes may also be caused by hypothyreosis. These waves travel in a transversal direction. These waves can travel through solid, liquid, and gas. Please refer to Figure 37. Figure 15 B. Pacemaker stimulation in the (right) ventricle. Switched arm electrodes (negative P and QRS-T in lead I). Normal P wave axis is between 0° and +75° P waves should be upright in leads I and II, inverted in aVR; Duration < 0.12 s (<120ms or 3 small squares) Amplitude < 2.5 mm (0.25mV) in the limb leads < 1.5 mm (0.15mV) in the precordial leads Its amplitude is generally one-fourth of the T-wave’s amplitude. R-wave amplitude in V6 + S-wave amplitude in V1 should be <35 mm. In the setting of circulatory collapse, low amplitudes should raise suspicion of cardiac tamponade. Therefore to determine whether the QT interval is within normal limits, it is necessary to adjust for the heart rate. Pre-excitation. The ST segment corresponds to the plateau phase (phase 2) of the action potential. Before discussing each component in detail, a brief overview of the waves and intervals is given. Recall that the P-wave in V1 is often biphasic, which is also shown in Figure 3. It is often biphasic in lead V1. 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