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ECG Made Easy, Ch. 9
Introduction to the 12-Lead ECG
Question | Answer |
---|---|
Placement of right precordial leads is identical to the standard precordial leads except on the right side of the chest. | True |
In a patient experiencing an acute coronary syndrome, ST-segment elevation in the shape of a “smiley” face (upward concavity) is usually associated with an acute injury pattern. | False |
Consider the presence of right ventricular infarction if a patient with an inferior wall infarction becomes hypotensive after administration of nitrates. | True |
In most patients, the posterior wall of the left ventricle is supplied by the right coronary artery. | False |
The posterior wall of the left ventricle is supplied by the ________________ in most patients; however, in some patients it is supplied by the ________________. | 1. circumflex coronary artery 2. right coronary artery |
An abnormal (pathologic) Q wave indicates that presence of dead myocardial tissue. | True |
Leads V4R, V5R, and V6R are used to view the posterior wall of the left ventricle. | False |
The leads corresponding to the posterior wall of the left ventricle | V7, V8, V9 |
When you read a 12-lead ECG from left to right, the ECG tracing is continuous. | True |
“Poor R wave progression” is a phrase used to describe R waves that decrease in size from V1 to V4. | True |
The six limb leads view the heart in the frontal plane as if the body were flat. | True |
Each electrode placed on the chest in a “V” position is a (positive/negative) electrode. | positive |
0.12 second = | 20 milliseconds |
axes of leads I, II, and III form an equilateral triangle with the heart at the center (Einthoven’s triangle). If the augmented limb leads are added to this & the The axes of the six leads moved in a way in which they bisect each other, the result is the | hexaxial reference systes |
Lead V1, Heart surface viewed | Septum |
Lead V2, Heart surface viewed | Septum |
Lead V3, Heart surface viewed | Anterior |
Lead V4, Heart surface viewed | Anterior |
Lead V5, Heart surface viewed | Lateral |
Lead V6, Heart surface viewed | Lateral |
Lead located at the fourth intercostals space, left sternal border. | V2 |
Common ECG finding in hyperkalemia. | Tall, tented T waves |
The zone of ________ is typically characterized by ST segment elevation. | injury |
Lead 1 + Lead III | Lead II |
Occlusion of the left anterior descending coronary artery may result in a(n) __________ myocardial infarction. | anterior |
Leads that view the heart in the horizontal plane. | Chest |
Leads that view the inferior wall of the heart. | II, III, aVF |
Lead I is perpendicular to lead | aVF |
Occlusion of the right coronary artery may result in a(n)__________ myocardial infarction. | inferior |
Leads used to view the right ventricle. | V1R-V6R |
Lead located at the fourth intercostals space, right sternal border. | V1 |
Lead II is perpendicular to lead | aVL |
Leads that view the heart in the frontal plane. | Limb |
Lead located at the fifth intercostals space, left midclavicular line. | V4 |
Direction of the mean QRS vector. | Electrical axis |
Lead III is perpendicular to lead | aVR |
Leads that view the lateral wall of the heart. | I, aVL, V5, V6 |
The zone of __________ is typically characterized by Q waves. | infarction |
Indicator of the magnitude and direction of current flow. | Vector |
Leads that view the septum. | V1-V2 |
List two (2) other names for the “chest” leads. | 1. Precordial 2. V leads |
Axis, Lead 1 - QRS direction | normal positive, left positive, right negative, indeterminate negative |
Axis, Lead aVF - QRS direction | normal positive, left negative, right positive, indeterminate negative |
List three (3) acute coronary syndromes. | 1. Angina 2. non-ST-segment elevation myocardial infarction (MI) 3. ST-segment elevation MI |
List “the three ‘I’s” of an acute coronary event. | The processes of: 1. Ischemia 2. Injury 3. Infarction |
List four (4) causes of ST-segment elevation other than myocardial infarction. | 1. Ventricular hypertrophy 2. Conduction abnormalities 3. Pulmonary embolism 4. Spontaneous pneumothorax 5. Intracranial hemorrhage 6. Hyperkalemia 7. Pericarditis |
Explain what is meant by the phrase, “Poor R wave progression.” | Poor R wave progression is a phrase used to describe R waves that decrease in size from V1 to V4. |
In a 12-lead ECG, how long (in seconds) is the view of each lead? | A 12-lead provides a 2.5-second view of each lead. It is assumed 2.5 seconds is long enough to capture at least one representative complex. A 2.5-second view is not long enough to assess rate & rhythm. One continuous rhythm strip is usually at the bottom |
Differentiate a physiologic Q wave from a pathologic Q wave. | A physiologic Q wave in the limb leads is < 40 ms (0.04 second) in duration & < 1/3 of the amplitude of the R wave in that lead. An abnormal (pathologic) Q wave is > 40 ms in duration & equal or > 1/3 of the amplitude of the following R wave in that lead. |
When is the term “intraventricular conduction delay” used? | A QRS 100-120 ms is an incomplete r or l bundle branch block. A QRS > 120 ms is called a complete right or left bundle branch block. If the QRS is wide but there is no BBB, “wide QRS” or “intraventricular conduction delay” is used to describe the QRS. |
What causes the ST-segment elevation seen in acute myocardial infarction? | ST-segment elevation is caused by changes that affect ventricular repolarization and/or ventricular depolarization. MI produces ST-segment elevation because the infarction affects ventricular repolarization and/or depolarization. |
Explain “anatomically contiguous leads.” | refers to leads that “see” the same area of the heart. Two leads are contiguous if they look at the same area of the heart or they are numerically consecutive chest leads. |
Standard 12 lead is composed of | six limb leads and six chest leads |
Directions in frontal plane leads | superior, inferior, right and left |
Leads I, II, III are | bipolar |
Leads aVR, aVL, and aVF are | unipolar |
Leads I, II, III, aVR, aVL and AVF view the heart in the __________ plane. | frontal |
Directions in horizontal plane leads | anterior, posterior, right and left |
Chest leads V1-V6 view the heart in the ________ plane. | horizontal |
Lead I, II and III make up the standard _______ leads. | limb |
Imaginary line joining the positive and negative electrodes of a lead is called the | axis of the lead |
Distinct negative pole and distinct positive pole | bipolar |
Lead I views the _______ surface of the left ve3ntricle.. | lateral |
Leads II and III view the _______ surface of the left ventricle. | inferior |
aVR, aVL and aVF maker up the ________ limb leads. | augmented |
Augmented limb leads are | unipolar |
The a in aVR, aVL and aVF refers to | augmented |
The V in aVR, aVL and aVF refers to | voltage |
The R, L and F in aVR, aVL and aVF refers to the | Right arm, left arm and left foot (leg) |
Lead aVR view the heart from | the right shoulder (positive electrode) and views the base of the heart (primarily the atria and the great vessels) |
Lead aVR does not view | any wall of the heart |
Lead aVL views the heart from | the left shoulder (positive electrode) and is oriented to the lateral wall of the left ventricle. |
Lead aVF views the heart from | the left foot (leg) (positive electrode). |
Leads II an III in conjunction with aVF view | the inferior surface of the left ventricle. |
Six chest leads | Lead V1 thru V6 |
Each electrode place in a V position is a __________ electrode. | positive |
Chest leads are also known as the | precordial leads |
Chest leads V1 thru V6 are | unipolar with the heart as the theoretical negative electrode |