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Electrocardiography > Concepts for Exam #1 > Flashcards

Concepts for Exam #1 Flashcards

1
Q

What is an EKG?

A

A recording of the heart’s electrical activity.

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2
Q

What is automaticity?

A

The ability to produce an electrical impulse without outside stimulation.

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3
Q

What is excitability?

A

The ability to respond to an outside stimulus.

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4
Q

What is conductivity?

A

The ability to transmit an electrical impulse signal from cell-to-cell.

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5
Q

What are the three types of cells in the heart?

A

(1) Pacemaker cells (SA node); (2) conducting cells (includes the rest of the conduction system); and (3) myocardial cells (muscle cells of the atria and ventricles).

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6
Q

What are the characteristics of pacemaker cells?

A

(1) They depolarize spontaneously; (2) they are located in the SA node; (3) they set the heart at 60-100 bpm; and (4) they are influenced by external neurohumoral input.

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7
Q

What are the two types of cardiomyocyte action potential?

A

(1) Fast-response (occurring in the atria, ventricles, and purkinje fibers); and (2) slow-response (occurring in the SA and AV nodes).

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8
Q

Describe the fast-response action potential:

A

Phase 4: Resting membrane potential; Phase 0: depolarization (Na+ influx); Phase 1: K+ efflux; Phase 2: plateau (Ca2+ influx/K+ efflux); Phase 3: repolarization (K+ efflux).

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9
Q

How do catecholamines (epinephrine/norepinephrine) influence the pacemaker rate?

A

They increase the rate of depolarization; and increase the heart rare.

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10
Q

How does acetylcholine (released during vagal stimulation) influence the pacemaker rate?

A

It decreases the rate of depolarization; and decreases the heart rate.

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11
Q

Describe the process of excitation-contraction coupling:

A

A wave of depolarization stimulates the release of calcium from the sarcoplasmic reticulum; calcium allows the interaction between actin and myosin; contraction occurs.

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12
Q

What are the components of the conduction pathway?

A

SA node; AV node; His bundle; left bundle branch (with anterior and posterior fascicles) and right bundle branch; purkinje fibers.

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13
Q

Describe the placement of the limb leads:

A

Right arm; left arm; left leg. This creates three standard limb leads and three augmented limb leads; these six leads provide a frontal view of the heart.

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14
Q

Describe the placement of the precordial (chest) leads:

A 
V1: 4th intercostal, right side.
V2: 4th intercostal; left side.
V4: 5th intercostal, mid-clavicular.
V6: 5th intercostal; mid-axillary.
V3 and V5 are placed inbetween; these leads provide a transverse view of the heart.
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15
Q

What are the three characteristics of an EKG waveform?

A

(1) Duration; (2) amplitude; (3) and configuration.

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16
Q

Describe the normal appearance of the P-wave:

A

The direction is variable, it is always negative in aVR, and it may be biphasic in some leads; it should be rounded (not tall or wide), and preceed each QRS complex; the first half represents right atrial depolarization, and the second half represents left atrial depolarization.

17
Q

What does the P-wave look like during atrial enlargement?

A

Right Atrial Enlargement: taller than 2.5mm; initial component is tall in biphasic waves; Left Atrial Enlargement: the wave is wide and often notched; amplitude is normal or increased.

18
Q

Describe the normal appearance of the PR-interval:

A

It should be smaller than 1 large box in duration; if prolonged, it indicates first-degree heart block.

19
Q

What does the Q-wave represents, and how can you tell if it is pathologic?

A

The Q-wave represents septal depolarization; pathologic Q-waves are deep and wide (deeper than 1/3 the height of the R-wave) and they often fall straight down. These occur hours to days after an infarct, and will remain for life.

20
Q

Describe the normal appearance of the QRS complex:

A

Narrow is normal (less than 3 small boxes); large positive R-waves are seen in the left lateral and inferior leads; large negative S-waves are seen in V1 and V2. R-wave amplitude should increase throughout the precordial leads.

21
Q

What are the two reasons for a wide QRS complex?

A

(1) The impulse is being generated in the ventricles; or (2) the impulse is taking an aberrant pathway through the ventricles.

22
Q

What does a STEMI look like?

A

ST elevations of at least 1 mm in the limb leads, or 2 mm in the precordial leads; shape should be rounded, not concave (concave elevation is due to J-point notching).

23
Q

What does a normal T-wave look like?

A

The are variable in appearance; deflection is typically in the same direction as the QRS complex.

24
Q

What does a normal QT interval look like, and what determines its duration?

A

It is normally half-way between two QRS complexes; the duration is proportionate to heart rate.

25
Q

Describe the three methods for calculating heart rate:

A

(1) 300/# of large boxes between R-waves; (2) 300-150-100-75-60-50 method; and (3) multiply the number of QRS complexes in a 30-box span by 10.

26
Q

What is hypertrophy?

A

Increased muscle mass due to pressure overload (such as in chronic hypertension); typically occurs in the ventricles.

27
Q

What is enlargement?

A

Dilation of a chamber due to fluid overload; typically occurs in the atria.

28
Q

Why do hypertrophied ventricles typically progress to dilation?

A

The greater the stress, the more forceful the recoil; eventually, the stretch is so great that the elasticity is lost (occurs faster in the right ventricle because there is less muscle here).

29
Q

What is a vector?

A

A vector represents an electrical force moving through the ventricles in a particular direction.

30
Q

What is a mean vector?

A

Summation of all the vectors; the direction of the mean vector is the axis of ventricular depolarization. Axis is defined in the frontal plane only.

31
Q

What are the two signs of right ventricular hypertrophy?

A

(1) Right axis deviation; (2) poor R-wave progression.

32
Q

How can you identify poor R-wave progression?

A

The R-wave is larger than the S-wave in V1; the S-wave is larger than the R-wave in V6.

33
Q

What are the three signs of left ventricular hypertrophy?

A

(1) Left-axis deviation; (2) increased R-waves over the left ventricle; (3) increased S-waves over the right ventricle.

34
Q

What is the most important criteria for dagnosing left ventricular hypertrohy?

A

The R-wave amplitude in leads V5 or V6 plus the S-wave amplitude in V1 or V2 exceeds 7 large boxes.

35
Q

What are the two signs of secondary repolarization abnormality?

A

(1) Down-sloping ST-segment; ans (2) T-wave inversion.

Electrocardiography (2 decks)

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