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Medicine > Cardiology > Flashcards

Cardiology Flashcards

0
Q

What is the usual rate for the sinoatrial node?

A

60 to 100 per minute

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1
Q

What is depolarization?

A

When cells lose their internal negativity and turn positive.

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2
Q

Distance of one horizontal large square on EKG paper?

A

0.2 seconds, one small square is 0.04 seconds

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3
Q

Distance of one large vertical square on EKG paper?

A

0.5 mV, one small square is 0.1 mV

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4
Q

What does the p wave represent?

A

First half represents right atrial depolarization, second half left atrial depolarization

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5
Q

What are the three parts of the ventricular conducting system?

A

Bundle of His, bundle branches, terminal Purkinje fibres

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6
Q

Three fascicles of left bundle branch?

A

Septal fascicle, anterior fascicle, and posterior fascicle

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7
Q

What does the q wave represent?

A

Septal depolarization

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8
Q

What does the T wave represent?

A

Ventricular repolarization

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9
Q

What is a segment on an EKG?

What is an interval?

A

Straight line connecting two waves is a segment.

An interval encompasses at least one wave plus the connecting line.

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10
Q

What does the PR interval represent?

A

The time from start of atrial depolarization to the start of ventricular depolarization

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11
Q

What does the PR segment represent?

A

Time from end of atrial depolarization to the start of ventricular depolarization.

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12
Q

What does the ST segment represent?

A

Time from end of ventricular depolarization until start of ventricular repolarization.

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13
Q

What does the QT interval measure?

A

Time from start of ventricular depolarization until end of ventricular repolarization.

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14
Q

What does the QRS interval measure?

A

Time of ventricular depolarization

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15
Q

If a wave of depolarization moves toward an electrode? Away from it?

A

Toward = positive deflection on EKG

Away = negative deflection on EKG

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16
Q

What does a wave of repolarization look like when moving toward an electrode?
Away?
Perpendicular?

A 
Toward = negative deflection on EKG
Away = positive
Perpendicular = biphasic
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17
Q

What are the inferior leads and their angles?

A

Lead II - +60
Lead III - +120
Lead aVF - +90

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18
Q

What are the left lateral leads and their angles?

A

Lead I - +0
Lead aVL - -30
V5
V6

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19
Q

What are/is the right sided lead(s)?

A

Lead aVR - -150

V1

20
Q

What are the anterior leads?

A

V2, V3, V4

21
Q

What plane are the limb leads in? The precordial leads?

A

Limb - frontal

Precordial - horizontal

22
Q

How can the EKG change web a chamber hypertrophied or enlarges?

A
  1. Can take longer to depolarize –> increase in duration
  2. Generate more current –> increase in amplitude
  3. Change in axis
23
Q

What is the range for a normal axis?

A

If the QRS axis lies within the shaded quadrant, between 0° and 90°, it is normal.

24
Q

If the QRS is positive in these leads it is normal.

A

If the QRS complex is positive in leads I and aVF, the QRS axis must be normal.

25
Q

How to precisely determine axis?

A
  1. Look for the limb lead in which the QRS complex is most nearly biphasic, that is, with equal positive and negative deflections (sometimes the deflections are so small that the wave appears flat, or isoelectric). The axis must then be oriented approximately perpendicular to this lead because an electrode oriented perpendicularly to the mean direction of current flow records a biphasic wave.
  2. You now have 2 choices - based on whether the QRS is positive in I and aVL you should be able to tell which way it lies.

Ex:The QRS complex in lead III is biphasic. The axis therefore must be either +30° or −150°. However, because the QRS complex is positive in both leads I and aVF, the axis must be normal, that is, it must lie within the shaded quadrant. The axis therefore can only be +30°.

26
Q

What will the leads look like with RAD?

A

Right axis deviation. The QRS complex is negative in lead I, whereas it is positive in aVF.

27
Q

What will the leads look like in LAD?

A

If the axis lies between 0° and −90°, we speak of left axis deviation. In this case, the QRS complex in lead I will be positive, but it will be negative in lead aVF.

28
Q

What will the leads show in extreme RAD?

A

In rare instances, the axis becomes totally disoriented and lies between −90° and 180°. This is called extreme right axis deviation. The QRS complex in both lead aVF and lead I will be negative.

29
Q

What are some causes of RAD?

A

In patients with chronic obstructive pulmonary disease sufficiently severe to cause pulmonary artery hypertension, or in patients with uncorrected congenital heart disease associated with profound volume or pressure overload of the right ventricle. If the right ventricle greatly hypertrophies, it can be detected on the EKG as a shift in the QRS axis. The mean electrical axis of current flow is drawn rightward, and the result is right axis deviation.

30
Q

What leads are useful and why when looking for atrial enlargement?

A

Virtually all of the information you need to assess atrial enlargement can be found in leads II and V1. Lead II is useful because it is oriented nearly parallel to the flow of current through the atria (i.e., parallel to the mean P wave vector). It therefore records the largest positive deflection and is very sensitive to any perturbations in atrial depolarization. Lead V1 is useful because it is oriented perpendicularly to the flow of electricity and is therefore biphasic, allowing easy separation of the right and left atrial components.

31
Q

What changes on EKG do you see with right atrial enlargement?

A

With right atrial enlargement, the amplitude of the first portion of the P wave increases. The width does not change because the terminal component of the P wave is left atrial in origin, and this remains unchanged.
Enlargement of the right atrium may also cause the right atrium to dominate the left atrium electrically. The vector of atrial depolarization may swing rightward, and the P wave axis may move rightward toward or even beyond +90°. The tallest P wave may therefore no longer appear in lead II, but in lead aVF or lead III.
The classic picture of right atrial enlargement is an increased amplitude in leads II and first half V1, and has been called P pulmonale because it is often caused by severe lung disease.

Right atrial enlargement is characterized by the following:

  1. P waves with an amplitude exceeding 2.5 mm in the inferior leads
  2. No change in the duration of the P wave
  3. Possible right axis deviation of the P wave.
32
Q

What does the EKG look like with left atrial enlargement?

A

With left atrial enlargement, the second portion of the P wave may increase in amplitude. The diagnosis of left atrial enlargement requires that the terminal (left atrial) portion of the P wave should drop more than 1 mm below the isoelectric line in lead V1.
However, a more prominent change in the P wave is an increase in its duration. This occurs because left atrial depolarization represents the terminal portion of the P wave, and prolonged depolarization can be readily seen (with right atrial enlargement, prolonged depolarization of the right atrium is hidden by the left atrial portion of the P wave). The diagnosis of left atrial enlargement, therefore, also requires that the terminal portion of the P wave should be at least one small block (0.04 seconds) in width.
The electrocardiographic picture of left atrial enlargement has been called P mitrale because mitral valve disease is a common cause of left atrial enlargement.

Left atrial enlargement is characterized by the following:

  1. The amplitude of the terminal (negative) component of the P wave may be increased and must descend at least 1 mm below the isoelectric line in lead V1.
  2. The duration of the P wave is increased, and the terminal (negative) portion of the P wave must be at least 1 small block (0.04 seconds) in width.
  3. No significant axis deviation is seen because the left atrium is normally electrically dominant.
33
Q

What are the usual causes of right ventricular hypertrophy?

A

The most common causes of right ventricular hypertrophy are pulmonary disease and congenital heart disease.

34
Q

What are the common causes

A

The leading causes of left ventricular hypertrophy are systemic hypertension and valvular disease.

35
Q

What are the criteria for right ventricular hypertrophy?

A

Right ventricular hypertrophy is characterized by the following:

  1. Right axis deviation is present, with the QRS axis exceeding +100°.
  2. The R wave is larger than the S wave in V1, whereas the S wave is larger than the R wave in V6.
36
Q

What are the criteria for left ventricular hypertrophy?

A

Left ventricular hypertrophy is characterized by voltage criteria and, not infrequently, secondary repolarization abnormalities. The two most useful voltage criteria are the following:
1.The R wave in V5 or V6 plus the S wave in V1 or V2 exceeds 35 mm.
2.The R wave in aVL exceeds 13 mm.
Secondary repolarization abnormalities include asymmetric, T wave inversion and down-sloping ST segment depression.
Left axis deviation exceeding −15° is also present.

Although the EKG pattern of left ventricular hypertrophy is easily recognized, it is present in only about 50% of patients whose echocardiograms demonstrate a thickened left ventricle. The sensitivity of the EKG criteria for left ventricular hypertrophy is thus fairly low. However, when the EKG pattern of left ventricular hypertrophy does appear, there is a 90% likelihood that a thickened ventricle will be seen on an echocardiogram. The specificity of the EKG criteria for left ventricular hypertrophy is thus quite high.

37
Q

What are some common causes of arrythmias?

A

H—Hypoxia: A myocardium deprived of oxygen is an irritable myocardium. Pulmonary disorders, whether severe chronic lung disease or an acute pulmonary embolus, are major precipitants of cardiac arrhythmias.
I—Ischemia and Irritability: We have already mentioned that myocardial infarctions are a common setting for arrhythmias. Angina, even without the actual death of myocardial cells associated with infarction, is also a major precipitant. Occasionally, myocarditis, an inflammation of the heart muscle often caused by routine viral infections, can induce an arrhythmia.
S—Sympathetic Stimulation: Enhanced sympathetic tone from any cause (e.g., hyperthyroidism, congestive heart failure, nervousness, exercise) can elicit arrhythmias.
D—Drugs: Many drugs can cause arrhythmias. Ironically, the antiarrhythmic drugs themselves, such as quinidine, are among the leading culprits.
E—Electrolyte Disturbances: Hypokalemia is notorious for its ability to induce arrhythmias, but imbalances of calcium and magnesium can also be responsible.
B—Bradycardia: A very slow heart rate seems to predispose to arrhythmias. One could include the brady-tachy syndrome (also called the sick sinus syndrome) in this category.
S—Stretch: Enlargement and hypertrophy of the atria and ventricles can produce arrhythmias. This is one way in which congestive heart failure and valvular disease can cause arrhythmias.

38
Q

How do you calculate HR from an EKG?

A

1.Find an R wave that falls on, or nearly on, one of the heavy lines.
2.Count the number of large squares until the next R wave.
3.Determine the rate in beats per minute as follows:
•If there is one large square between successive R waves, then each R wave is separated by 0.2 seconds. Therefore, over the course of 1 full second, there will be 5 cycles of cardiac activity (1 second divided by 0.2 seconds), and over 1 minute, 300 cycles (5 × 60 seconds). The heart rate is therefore 300 beats per minute.
•If there are two large squares between successive R waves, then each R wave is separated by 0.4 seconds. Therefore, over the course of 1 full second, there will be 2.5 cycles of cardiac activity (1 second divided by 0.4 seconds), and over 1 minute, 150 cycles (2.5 × 60 seconds). The heart rate is therefore 150 beats per minute.
By similar logic:
•Three large squares = 100 beats per minute
•Four large squares = 75 beats per minute
•Five large squares = 60 beats per minute
•Six large squares = 50 beats per minute
Notice that you can get the same answers by dividing 300 by the number of large squares between R waves (e.g., 300 ÷ 4 squares = 75). Even greater accuracy can be achieved by counting the total number of small squares between R waves and dividing 1,500 by this total.

39
Q

What are the five types of sustained supraventricular arrythmias?

A

There are five types of sustained supraventricular arrhythmias that you must learn to recognize:

  1. Paroxysmal supraventricular tachycardia (PSVT), sometimes also called AV nodal reentrant tachycardia
  2. Atrial flutter
  3. Atrial fibrillation
  4. Multifocal atrial tachycardia (MAT)
  5. Paroxysmal atrial tachycardia (PAT), sometimes also called ectopic atrial tachycardia.
40
Q

What are the 4 questions to ask when assessing rhythm on EKG?

A
  1. Are normal P waves present?
  2. Are the QRS complexes narrow or wide?
  3. What is the relationship between the P waves and the QRS complexes?
  4. Is the rhythm regular or irregular?
41
Q

What are the 5 types of rhythm disturbance?

A
  1. The electrical activity follows the usual conduction pathways we have already outlined, but it is either too fast, too slow, or irregular. These are arrhythmias of sinus origin.
  2. The electrical activity originates from a focus other than the sinus node. These are called ectopic rhythms.
  3. The electrical activity is trapped within an electrical racetrack whose shape and boundaries are determined by various anatomic or electrical myocardial features. These are called reentrant arrhythmias. They can occur anywhere in the heart.
  4. The electrical activity originates in the sinus node and follows the usual pathways but encounters unexpected blocks and delays. These are conduction blocks
  5. The electrical activity follows accessory conduction pathways that bypass the normal ones, providing an electrical shortcut, or short circuit. These arrhythmias are termed preexcitation syndromes.
42
Q

How to do carotid massage?

A
  1. Auscultate for carotid bruits. You do not want to cut off the last remaining trickle of blood to the brain nor dislodge an atherosclerotic plaque. If there is evidence of significant carotid disease, do not perform carotid massage.
  2. With the patient lying flat, extend the neck and rotate the head slightly away from you.
  3. Palpate the carotid artery at the angle of the jaw and apply gentle pressure for 10 to 15 seconds.
  4. Never compress both carotid arteries simultaneously!
  5. Try the right carotid first because the rate of success is somewhat better on this side. If it fails, however, go ahead and try the left carotid next.
  6. Have a rhythm strip running during the entire procedure so that you can see what is happening. Always have equipment for resuscitation available; in rare instances, carotid massage may induce sinus arrest.
43
Q

What are the characteristics of PSVT?

A

Regular

P waves are retrograde if visible

Rate: 150-250 bpm

Carotid massage: slows or terminates

44
Q

What are the characteristics of atrial flutter?

A

Regular, saw-toothed

2:1, 3:1, 4:1, etc., block

Atrial rate: 250-350 bpm

Ventricular rate: one half, one third, one quarter, etc., of atrial rate

Carotid massage: increases block

45
Q

What are the characteristics of atrial fibrillation?

A

Irregular

Undulating baseline

Atrial rate: 350-500 bpm

Ventricular rate: variable

Carotid massage: may slow ventricular rate

46
Q

What are the characteristics of MAT?

A

Irregular

At least three different P wave morphologies

Rate: 100-200 bpm; sometimes less than 100 bpm

Carotid massage: no effect

47
Q

What are the characteristics of PAT?

A

Regular

Rate: 100-200 bpm

Characteristic warm-up period in the automatic form

Carotid massage: no effect, or only mild slowing

Medicine (14 decks)

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