EKG for Lab PDF

An electrocardiogram (ECG) is a graphic representation of the electrical events of the cardiac cycle  Small Q waves can be seen in leads I, aVL, V5, and V6 and represent septal activation. Pathological Q waves (>¼ R-wave amplitude, >0.04 seconds) can signal old myocardial infarction (M...

An electrocardiogram (ECG) is a graphic representation of the electrical events of the cardiac cycle  Small Q waves can be seen in leads I, aVL, V5, and V6 and represent septal activation. Pathological Q waves (>¼ R-wave amplitude, >0.04 seconds) can signal old myocardial infarction (MI) or septal hypertrophy.  An increase in R-wave amplitude from lead V1 to its maximum amplitude in V5 is considered normal R-wave progression. The S wave represents late ventricular depolarization Depression or elevation of the ST segment can represent myocardial ischemia or infarction.  Normally, T waves are upright in every lead except aVR and V1 Inverted or broad T waves can indicate myocardial ischemia or infarction. Peaked T waves can signal hyperkalemia The QT interval is primarily a measure of ventricular repolarization. The QT interval varies with heart rate and its measurement can be adjusted accordingly using the corrected QT interval (QTc) https://pmc.ncbi.nlm.nih.gov/articles/PMC708 0915/#:~:text=The%20corrected%20QT%20int erval%20is,rise%20to%20abnormal%20myocar dial%20repolarisation.  A prolonged QTc interval can be a marker for ventricular arrhythmia and a risk factor for sudden cardiac death QTc = QT / √RR U waves are small waves following T waves and may be normal in some leads, especially the precordial leads V2 to V4. U waves can also signal hypokalemia and other metabolic conditions  This ECG tracing shows ST-segment depression and prominent R waves in the anterior precordial leads V1–V3 that may represent posterior Acute Myocardial Infarction.  ST-segment elevation of ≥1 mm in posterior leads V7–V9 is highly suggestive of posterior Acute Myocardial Infarction.  To investigate RV infarction, a right-sided ECG is obtained by placing leads V1R–V6R as a mirror image of the locations for V1–V6 on the left.  This right-sided ECG demonstrates ST-segment elevation in leads V1R–V6R.  Myocardial Infarctus MI is diagnosed by ECG, cardiac biomarkers, and/or imaging modalities that detect new loss of viable myocardium or new regional wall motion abnormality. In a patient with symptoms suggestive of acute coronary syndrome (ACS; eg, chest pain, dyspnea, diaphoresis, nausea, and vomiting), ST-segment elevation on ECG indicates complete occlusion of a coronary artery resulting in transmural infarction, or STEMI. Such electrocardiographic changes are dependent upon the location of infarction and the degree of coronary artery occlusion. Clinically significant ST-segment elevation is considered to be present if greater than 1 mm (0.1 mV) in at least two anatomically contiguous leads or 2 mm (0.2 mV) in two contiguous precordial leads  This ECG shows an anterior STEMI due to occlusion of a mid-LAD lesion.  This ECG shows ST-segment elevation in the high lateral leads (I, aVL); a result of circumflex artery occlusion.  This ECG reveals ST-segment elevation in the inferior leads (II, III, and aVF) with reciprocal changes in the anterior leads resulting from RCA occlusion.  This ECG shows ST-segment elevation in the inferior leads (II, III, and aVF) and subtle ST- segment depression in lead V2 after PDA occlusion. (PDA: Posterior decending artery)  a Left Bundle Bbranch Block pattern. A Sgarbossa criterion of ST-segment elevation of 1 mm or more that is concordant with the QRS complex (in leads I and AVL) is met.  T wave In the very early stages of a MI, the T waves corresponding to the affected myocardial territory will peak, becoming tall and narrow. This typically occurs within 15 minutes from the onset of transmural ischemia and is very transient, thus infrequently captured on ECG  T wave In patients with symptoms suggestive of myocardial ischemia, the presence of hyperacute, or peaked, T waves on ECG should prompt immediate concern for MI. After a brief period of persistent transmural ischemia, these T-wave changes may evolve into ST-segment elevations. Tall or peaked T waves can also be seen in healthy patients as a normal variant, typically in the precordial leads. The presence of tall, peaked T waves is also an electrocardiographic finding associated with hyperkalemia. As such, hyperacute T waves in a dialysis patient should prompt consideration of hyperkalemia in the appropriate clinical setting. Tall T waves can also be seen in LV hypertrophy, LBBB, and intracranial bleeding  T wave hyperacute T waves in an anterolateral distribution, suggesting a possible infarct of the LAD artery and an associated diagonal branch  ST segment depression While transmural ischemia classically results in ST-segment elevation in the corresponding leads, subendocardial ischemia typically results in the overall ST-segment vector pointing toward the inner ventricular layer and appears as ST-segment depression. Depression of the ST segment is a repolarization abnormality suggestive of myocardial ischemia. Horizontal or down-sloping depression >1 mm and up-sloping depression >2 mm is considered positive  ST segment depression isolated ST-segment elevation in AVR with deep ST-segment depression and T-wave inversion in nearly all other leads except V1. This ECG is worrisome for either left main or proximal (to the first diagonal branch) LAD occlusion.