Occasionally, a lead view provides a mirror-like representation for the opposite surface of the heart. For example, 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... in anterior leads (V1-V4) may present as reciprocal changes in the posterior leadsPosterior views of the heart can be best seen via posterior leads placed below the scapula to the left of the spine. The inferior leads show the inferior aspects of the heart - the inferior aspects of the right ventricle... (opposite surface of the heart) as 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... and possibly even T wave inversionAn inverted T wave can point to cardiac ischemia among other causes. Ischemia to the epicardium prolongs ventricular repolarization to this area. This extended repolarization of the epicardium removes the delay between the repolarization of the endocardium and the repolarization....
Picture this. A 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 taken on a patient who is admitted with crushing midsternal chest pain. On inspection, the patient is in a sinus tachycardiaA cardiac rhythm that originates from the SA node with rates most often 101-180/minute. sinus tachycardia, HR 138/min 1. Six Second ECG Guidebook (2012), T Barill, p. 104, 206 with a heart rateThe number of QRS complexes per minute; note that HR may not equal perfused pulse rate. See also: - Step 1 Heart Rate - Rate - Rule of 300s (Triplicate Method) - Six Second Count - The Caliper Method 1.... of 108/minute. Five of the anterolateral leads (V3-V6, aVL) show ST elevation by as much as 4 mm. The inferior leadsThe inferior leads show the inferior aspects of the heart - the inferior aspects of the right ventricle and the left ventricle. Much of the inferior view of the heart is of the right ventricle. Precordial leads placed along the... present with ST depression of as much as 4 mm and inverted T waves. Is this patient experiencing an anterolateral MIAs a general rule, a patient experiencing a left ventricular infarction - anterior, lateral or anterolateral MI - should be managed with particular attention to preload. Fluids should be administered cautiously. Medications that reduce preload and afterload can be very... and further 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... to the inferior region of the heart? Is it likely to have multiple ischemic regions at the same instant?
No, it is unlikely that two regions are simultaneously ischemic just as it is unlikely that two vessels are occludin at the same time. Instead, the ST depression on this 12 lead is called a reciprocal change.
Why hunt for ST elevation? First, myocardial infarctions (MI) are associated with 12 lead findings of ST elevation (55% of all MI), ST depression (35%) and even with normal or non-specific findings (10%). In hospitals without the ability to perform angioplasties and/or to insert stents into narrowed coronary arteriesThe coronary arteries provide blood to the heart tissues, carrying blood first across the epicardium, then the myocardium and finally terminating in the endocardium. The epicardium forms the outer layer of the heart. The myocardium forms the middle layer and... (percutaneous coronary interventions – PCI), the use of fibrinolytics is administered ONLY to patients experiencing an ST elevation MI (STEMI). Patients receiving fibrinolytics have a 25% reduction in morbidity and mortality. Unfortunately, only those experiencing a STEMI benefit from fibrinolytics. Fibrinolytics are not administered to those experiencing an MI with normal ECG findings or with ST depression because the risk of stroke associated with the fibrinolytics (about 2%) outweighs the possible advantages. Hunt for ST elevation to identify those who would greatly benefit from fibrinolytics and save lives for your actions.
A more apt way to search for reciprocal changes is to conceptualize opposite regions of the heart i.e. anterior and posterior, lateral and inferior. If ST depression is found in lateral leads, ST elevation might be found in the inferior leads (or in the right ventricular leads – V4R – if a 15 lead ECG is obtained).
This brings up an important consideration. Should a 12 lead ECG that only reveals ST depression in two or more leads be followed by a 15/18 lead ECG to hunt for possible ST elevation in mirror leads? Most often the answer is yes. Equipped with the knowledge that reciprocal changes exist and that findings of ST elevation are required to administer fibrinolytics, it is prudent to obtain a 15/18 lead ECG in an effort to search for ST elevation in these alternate 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....
Possible reciprocal changes include ST depression and 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... inversion. Tall R waves in the anterior leads V1 and V2 (usually deep S waves dominate) may also be reciprocal changes that mirror deep Q waves in the posterior leads. Note that a right bundle branch blockA bundle branch block must satisfy two criteria - a wide QRS complex and a notch in the QRS complex. To distinguish between a RBBB and a LBBB, first make certain that the rhythm is indeed supraventricular (P waves before... also typically presents with upright R waves in leads V1 and V2.
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. 148-149