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31 Cards in this Set
- Front
- Back
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What is the normal variation of voltages measured in the standard 3 Bipolar limb leads?
(from Peak of R to bottom of S) |
Between .5 - 2.0 mV
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Which leads generally measure the highest or lowest voltages?
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Highest = Lead II
Lowest = Lead III |
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What defines a "High-Voltage EKG" in a patient?
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A sum of all voltages in the QRS complex greater than 4 mV.
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Most common cause of a HIGH voltage QRS complex:
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Hypertrophy of the muscle - most commonly left hypertrophy due to hypertension.
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What causes right ventricle hypertrophy?
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1. Lean tall person
2. Standing up 3. Pulmonary valve stenosis |
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What causes left ventricle hypertrophy?
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1. Short fat person
2. Lying down 3. Aortic valve stenosis |
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Why does hypertrophy cause increased voltage in the EKG?
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B/c the increased muscle mass generates increased electricity around the heart.
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What generally causes DECREASED voltage in the EKG leads?
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Cardiac myopathy
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What is a common cause of cardiac myopathy?
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Old Myocardial Artery infarcts with resulting diminished muscle mass.
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How exactly does cardiac myopathy alter the EKG (2 ways)?
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1. Prolonged QRS complex
2. Decreased voltage |
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What conditions surrounding the heart can cause decreased voltage on the EKG?
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1.Effusion- Fluid in pericardium
2. Pleural effusion 3. Pulmonary emphysema |
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How does Effusion cause decreased voltage?
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Fluid short-circuits the potentials generated by the heart b/c it is a great conductor and charge flows to the fluid instead of heart.
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How does Pulmonary Emphysema decrease EKG voltage?
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-Excess air in lungs
-Decreased current thru lungs -Chest cavity enlarges - lungs wrap around heart and insulate -Decreases spread of voltage in heart |
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3 Things that PROLONG the QRS complex:
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-Hypertrophy
-Dilatation -Purkinje system blocks |
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Length (time) of QRS complex:
-Normal -Prolonged |
Normal = 0.06 - 0.08
Prolonged = 0.09 - 0.12 |
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What happens to impulse conduction when Purkinje fibers are blocked? How does that affect the EKG?
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The ventricle muscle has to conduct it instead. Much slower, so QRS wave is prolonged.
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What is the usual QRS duration in a purkinje complex block?
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0.14 sec or longer
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What 2 Conditions most frequently cause Bizarre QRS complex patterns?
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1. Scar tissue from Cardiac muscle destructn in ventricles.
2. Multiple local conduction blocks in the purkinje system. |
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What is a "CURRENT OF INJURY"?
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When current flows between pathologically depolarized and normally polarized areas - EVEN BETWEEN HEARTBEATS
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What causes a Current of Injury?
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Damage to the heart muscle that makes a part remain partially or fully depolarized ALL THE TIME.
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What is the electrical state of the injured area in current of injury?
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NEGATIVE - depolarized so surface is negative.
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List 3 abnormalities that can cause current of injury:
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1. Mechanical trauma
2. Infection 3. Ischemia |
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Which is the most common cause of current of injury?
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Ischemia
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How does an injury to the base of the left ventricle alter the EKG?
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-Never completely repolarized, so current ALWAYS recorded.
-Lead I is always negative b/c vector points away from injury -Leads II/III are still pos |
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Does the voltage ever record as zero in a current of injury?
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Yes - when the heart is completely depolarized.
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Since current is never NOT flowing in the resting heart with a current of injury, how is the baseline of zero determined?
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By using the J point as a reference.
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What is the J point?
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The point right after ventricular depolarization when the complete heart is depolarized and Voltage is 0
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How does the Current of injury vector relate to the area of heart muscle injured?
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The NEGATIVE end of the vector points toward the permanently depolarized muscle section.
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What are the 3 reasons for why Ischemia depresses the metabolism of muscle?
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1. Lack of oxygen
2. Accumulation of CO2 3. Lack of sufficient nutrients |
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What is the consequence of severe ischemia in the heart?
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Repolarization of the membrane cannot occur.
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In what condition is Current of Injury an extremely important diagnostic feature?
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Coronary occlusion - causing acute ischemia
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