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CVPR - CV Unit 1 > ECG > Flashcards

ECG Flashcards

1
Q

P wave

A

Atrial depolarization (sum of R + L)

Smaller amplitude due to less total muscle mass

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2
Q

QRS Complex

A

Ventricular depolarization; occurs simultaneously as atrial repolarization, obscuring the signal

Upward deflection of R wave corresponds to phase 0 of action potential; isoelectric ST segment links QRS to T wave and corresponds to phase 2 of the action potential (long plateau)

Normal duration is 0.06-0.10s

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3
Q

T wave

A

Repolarization of the ventricles, corresponding to phase 3 of the action potential

T wave (hyperpolarization moving away from the lead) should deflect in the same direction as QRS (depolarization moving toward the lead)

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4
Q

QT Interval

A

Total duration of ventricular depolarization and repolarization

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5
Q

PR interval

A

Spans from the onset of the P wave to the onset of the QRS complex

Represents AV node conduction time

Normal duration is 0.12-0.20s

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6
Q

ECG paper speed

A

25 mm/s

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7
Q

ECG chronology - small vs. large squares

A

Thin lines (small squares) are spaced 0.04s apart

Thick lines (large squares) are spaced 0.2s apart

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8
Q

Unipolar leads

A

Measure the difference in electrical potential between one point on the body and a virtual reference point set at 0 electrical potential, located in the center of the heart

aVR, aVL, aVF
V1-V6

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9
Q

Bipolar leads

A

Measure the difference in electrical potential between two different points on the body

Standard Limb Leads I, II, and III

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10
Q

ST depression - Interpretation

A

Caused by ischemia due to sudden high oxygen demand in the presence of a fixed coronary obstruction

Resting ST segment is normal but during exercise there is a ST depression due to transient ischemia

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11
Q

T wave inversion - Interpretation

A

Caused by ischemia due to acute coronary artery obstruction during low oxygen demand; ischemia may be transient or result in tissue injury

Recall that normally T waves deflect in the same direction as QRS complex

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12
Q

ST elevation - Interpretation

A

Sign of transmural cardiac injury in an acute coronary syndrome, usually acute myocardial infarction

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13
Q

Significant Q wave - Definition & Interpretation

A

Defined as a Q wave that is:

  1. Greater than or equal to 1/4 the amplitude of the R wave
  2. Greater than or equal to one small box (0.04s) wide
  3. Seen in at least 2 leads reflecting the same region of the ventricle

Absence of normal transmural vector produces a negative deflection in leads over infarcted tissue

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14
Q

Lateral Leads

A

I and AVL

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15
Q

Inferior Leads

A

II, III, and AVF

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16
Q

Right Chest Leads

A

V1 and V2

Monitor the RV

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17
Q

Left Chest Leads

A

V5 and V6

Monitor the LV

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18
Q

ECG features of transmural myocardial infarction

A

ST elevation with Q waves

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19
Q

ECG features of subendocardial myocardial infarction

A

ST depression without Q waves

20
Q

QT Interval - Definition & Causes

A

Defined as a QT interval that is more than half of the RR interval

Caused by: 
Hypocalcemia, hypokalemia, hypomagnesemia
Class 1A or 3 anti-arrhythmic drugs
Hypothermia
Congenital Long QT Syndrome
21
Q

ECG features of Left Ventricular Hypertrophy

A

Big R waves in L-sided leads:

I, aVL, V5, V6

22
Q

ECG features of Right Ventricular Hypertrophy

A

Big R waves in R-sided leads:

V1, V2

23
Q

ECG features of Hypercalcemia

A

Shortened QT interval

24
Q

ECG features of Hypocalcemia

A

Prolonged QT interval

25
U wave
A small, variable wave following the T wave; thought to represent repolarization of the Purkinje fibers
26
Sinus Tachycardia
Regular, fast heart rate > 100bpm with normal P and QRS features Commonly occurs during exercise or emotional stress; increased cardiac oxygen demand may precipitate angina in patients with coronary artery disease No treatment usually needed; may be treated with beta blockers, if severe
27
Sinus bradycardia
Regular, slow heart rate ( seen in the elderly Treatment with atropine or cardiac pacemaker
28
1st degree AV block
Defined as a PR interval > 0.2 seconds; interpreted as delayed conduction through the AV node Caused by drugs (B-blockers, digitalis) and conduction system disease
29
2nd degree AV block
Some P waves conduct normally to the ventricles but others do not and therefore are not followed by R waves Rate may be too slow to support adequate CO, resulting in syncope or confusion requiring the use of a pacemaker Caused by conduction system disease and high vagal tone
30
3rd degree AV block
P waves and QRS show regular rhythm but occur at different rates with P rate > QRS rate Caused by AV node failure secondary to severe conduction system disease; may cause syncope or sudden death, usually requires a pacemaker
31
Atrial Flutter
P waves flutter at rate of 240-320 bpm; pulse may be regular or irregular and ventricular rates vary but are typically rapid Some risk of embolic stroke due to clot in the left atrium; treated with Warfarin for anti-coagulation and B-blockers, Ca2+ channel blockers, or Digoxin for rate control
32
Atrial Fibrillation
Irregular ventricular rhythm without P waves Risk of embolic stroke due to atrial thrombi, heart failure due to rapid heart rate and loss of atrial kick Treatment: Anti-coagulation, cardioversion (electrical or medical), and rate control with drugs
33
Atrial Tachycardia
Characterized by rapid HR (>180 bpm) with narrow QRS complexes and abnormal P waves Terminated by adenosine infusion; recurrence prevented by ablation of re-entry pathway
34
Junctional Rhythm
Regular rhythms arising from the AV node; usually characterized by a narrow QRS without P waves, which are buried within the QRS signal When P waves are present they are usually inverted because the wave is conducted upward from the AV node rather than downward from the SA node
35
Ventricular Tachycardia
Ectopic ventricular focus conducted by slow myocardium; caused by fibrosis, infiltrate, dilation - long path allows re-entry Characterized by repetitive wide-abnormal QRS without preceeding P wave
36
Lead I
Standard (Bipolar) Limb Lead L. arm (+) R. arm (-)
37
Lead II
Standard (Bipolar) Limb Lead L. foot (+) R. arm (-)
38
Lead III
Standard (Bipolar) Limb Lead L. foot (+) L. arm (-)
39
aVF
Augmented (Unipolar) Limb Lead L. foot (+)
40
aVR
Augmented (Unipolar) Limb Lead R. arm (+)
41
aVL
Augmented (Unipolar) Limb Lead L. arm (+)
42
V1 & V2
Precordial Chest Leads R. ventricle + septum
43
V3 and V4
Precordial Chest Leads Septum
44
V5 and V6
Precordial Chest Leads L. Ventricle
45
Evolution of ECG in transmural myocardial infarct
1. Peaked T wave ("hyperacute T wave") 2. T-wave inversion - sign of ischemia 3. ST elevation - sign of transmural, ischemic injury occurring within 1-2 hours of insult 4. Q wave + ST elevation + T inversion - typical of transmural infarcts OR 5. ST depression with no Q wave - typical of subendocardial infarcts
46
Atrial Premature Beats
P wave occurs too early following the last T wave and looks slightly different from other P waves; QRS is normal Mostly benign
47
Premature Ventricular Contraction (PVC)
Depolarization originates in the ventricle and contraction occurs via contractile myocytes Characterized by wide QRS signal without P waves Common in normal subjects; treatment usually not required

CVPR - CV Unit 1 (13 decks)

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