The ability to identify cardiac ischemiaThe ability to identify cardiac ischemia, injury and infarction is vital in the management of the majority of cardiac emergencies. Most sudden cardiac deaths are associated with an ischemic episode. Patient deaths due to an acute myocardial infarction (MI) typically..., injury and infarctionThe necrosis of tissue; acute myocardial infarction involves the acute death of myocardial cells. 1. Six Second ECG Guidebook (2012), T Barill, p. 198 is vital in the management of the majority of cardiac emergencies. Most sudden cardiac deaths are associated with an ischemic episode. Patient deaths due to an acute myocardial infarctionThe necrosis or death of myocardial tissue due to insufficient supply of oxygen to the infarcted region. The ability to identify cardiac ischemia, injury and infarction is vital in the management of the majority of cardiac emergencies. Most sudden cardiac... (MI) typically occur within the first 2 hours of symptoms. The 12 lead ECGElectrocardiogram; also called an EKG; a representation of electrical voltage measured across the chest over a period of time. 1. Six Second ECG Guidebook (2012), T Barill, p. 196 is a superior diagnostic tool to quickly identify various degrees of ischemiaInsufficient supply of oxygen to meet the oxygen demands of tissue. Anaerobic metabolism becomes increasingly important during periods of ischemia. Ischemia results from an inadequate blood flow that fails to meet the oxygen demands (energy demands) of tissues. If tissues....
“Time is muscle” should prompt an immediate 12 lead ECG for any patient suspected of having cardiac ischemia. Identifying regions of the heart that are ischemic, injured and/or infarcting requires a close inspection for Q waves, ST deviationWhile ST deviations may be a normal occurrence for a subset of the population, most often ST deviation is a sign of either myocardial ischemia, myocardial infarction and/or cardiac disease. It makes sense, then, to report any finding of ST..., dynamic T waveThe wave that arrives after the QRS; is a graphical presentation of ventricular repolarization. Expect a T wave to follow every QRS complex. The T wave is a graphic representation of the repolarization of the ventricle. The T wave is... changes and even R wave progressionThe phenomenon of R wave progression utilizes the following six leads: V1, V2, V3, V4, V5, V6. The chest leads provide information on the sagittal plane from the anterior surface across to the lateral surface of the heart. Notice in....
In the search for signs of cardiac ischemia, identify both the abnormal waveforms as well as the region of the heart that is affected. For example, the presence of abnormal Q wavesQ waves are a normal phenomenon when they are narrow (less than 1 mm in width) and shallow (less than 25% the height of the R wave). Q waves that exceed any of these criteria are evidence of prior ST... in leads II, III and aVF is sufficient evidence to confidently claim that the patient has had an inferior MI. Generally, abnormal findings must be present in two contiguous leadsContiguous leads in a 12-Lead ECG refer to a group of leads that are sequentially connected on the body surface, with a common view of a region of the heart. For example, leads II, III and aVF are contiguous in... before arriving at a diagnosis. Note that a solitary abnormal Q waveA Q wave is the first negative deflection of the QRS complex that is not preceded by a R wave. A normal Q wave is narrow and small in amplitude. Note that a wide and/or deep Q wave may signify... is sufficient evidence of a previous MI of indeterminate age (in leads other than aVR).
Dynamic T wave inversions often result from ischemic zones. The appearance of ST depressionThe downward placement of the ST segment greater than 1 mm from the isoelectric line; suggestive of cardiac ischemia, but also may point to ventricular hypertrophy, digoxin use, and pericarditis among other possibilities. Between the QRS complex and the T... is typical of cardiac ischemia, injury and possibly even infarction. The presence of ST elevationThe upward placement of the ST segment greater than 1 mm from the isoelectric line; suggestive of cardiac infarction or ischemia. Between the QRS complex and the T wave, lies the ST segment. The ST segment usually follows the isoelectric... of 1 mm or more in two contiguous leads (lead viewsLocating the positive electrode is crucial to determining which area of the heart is viewed electrically. Metaphorically, the positive electrode serves as a mini-video camera aimed at the heart in the direction of the negative electrode. These leads and their... proximate to each other) is diagnostic of an acute myocardial infarction.
Upon discovery of ischemic indicatorsEquipped with a carefully formed clinical impression of the patient, a systematic approach to 12 lead ECG interpretation makes the 12 lead ECG a reliable assessment tool. Mindful of false positives and false negatives, the patient’s old 12 lead ECG..., identify the affected region of the heart (see Table 6.4). Visually progress through other leads that also monitor the affected region to support your findings i.e. from lead II to leads III and aVF. This is a simple process of putting all the evidence together to complete the clinical picture.
Table 6.4 organizes ECG leads into specific monitored regions of the heart. Note that V2 and V4 are considered transitional leads because they straddle two regions. Reciprocal changesOccasionally, a lead view provides a mirror-like representation for the opposite surface of the heart. For example, ST elevation in anterior leads (V1-V4) may present as reciprocal changes in the posterior leads (opposite surface of the heart) as ST depression... – mirror changes that reflect the opposite surface of the heart – are also included for reference.
1. Six Second ECG GuidebookA Practice Guide to Basic and 12 Lead ECG Interpretation, written by Tracy Barill, 2012 Introduction The ability to correctly interpret an electrocardiogram (ECG), be it a simple six second strip or a 12 lead ECG, is a vital skill... (2012), T Barill, p. 144-145