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Cardio Exam 1 > 14 - ECG Recognition II > Flashcards

14 - ECG Recognition II Flashcards

1
Q

What is an escape rhythm?

A

When a latent pace maker has been called into action

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2
Q

What is an atrial premature beat?

A
  • The atria are depolarizing differently
  • Morphology might or might not be different, it’s just coming before a normal p wave should come
  • The premature atrial beat is followed by a pause period
  • This is a protective mechanism by the heart
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3
Q

What are the features of a junctional escape rhythm?

A
  • The depolarization is NOT coming from the SA node, but rather the level of the junction (AV junction)
  • When the ventricles and atria receive depolarization impulse simultaneously: P wave can occur just before QRS (with a short PR interval), inside QRS complex (P wave buried), or just after QRS.
  • QRS will be narrow (not wide)
  • Retrograde P wave = after QRS
  • Inverted P wave = down instead of up
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4
Q

Why do juncitonal escape rhythms occur?

A

If you depolarize the junction (AV junction) middle of the heart, it will spread in BOTH directions if the tissue is excitable

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5
Q

Why does bradycardia often accompany a junctional escape rhythm?

A

Latent pace makers are slower

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6
Q

In junctional escape rhythm, why are there sometimes QRS complexes without p waves?

A

Absence of a p wave before a QRS means that the impulse is not being generated at the SA node, but rather at the AV node

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7
Q

Describe the features of atrial fibrillation

A
  • Fibrillation (f) waves vary in shape and polarity (come from multiple sites throughout atrial muscle)
  • Irregularly irregular: variable f-f intervals and irregular ventricular (QRS) response
  • Differentiate from atrial flutter
    o Identical flutter (F) waves that time out regularly
    o Constant QRS response (e.g. 2 F:1 QRS or 4 F:1 QRS)
  • Can increase risk for thrombo-embolus, due to uncoordinated movement of blood (especially stroke) and heart failure, due to short-term decrease in cardiac output and long-term mechanisms activated to compensate for reduced cardiac output
  • Control rate, by pharmaceuticals or pacemaker; control rhythm, by ablation or cardioversion
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8
Q

Describe the features of supraventricular premature beats

A
  • Can precede other supraventricular arrhythmias
  • In atrial premature beat (APB), atrial depolarization occurs before next sinus p wave, termed p’ wave
  • QRS complex of APB preceded by P wave that looks different from other P waves on strip (different morphology or PR interval); PR interval may be longer or short; P wave could be obscured by T wave
  • After APB, a slight pause occurs before the normal sinus beat resumes (contrasted to the fully compensatory pause often seen after ventricular premature beats)
  • QRS complex will be narrow (if no additional defects are present)
  • May reach junction during refractory period and be blocked
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9
Q

Describe the features of multifocal atrial tachycardia

A

Multifocal Atrial Tachycardia

  • multiple sites of atrial stimulation (ectopic foci)
  • 3 or more consecutive non-sinus P waves with different shapes
  • PR intervals vary
  • Ventricular rate is irregular (some beats get through, some do not) and rapid.
  • MAT can compromise filling and clinical symptoms of reduced perfusion (dizziness, shortness of breath) may be seen
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10
Q

Describe the features of a first degree AV block

A

First Degree AV Block

  • P wave (usually sinus) followed by QRS complex with a PR interval > 200 msec
  • PR interval is uniformly prolonged; all PR intervals are similar
  • The number of P waves equals the number of QRS complexes
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11
Q

Describe the features of a second degree AV block (Type I)

A

Second Degree Type I AV Block (Wenckebach)

  • Intermittently “dropped” QRS complexes (P wave not followed by a QRS complex)
  • Each stimulus has progressively harder time traversing AV node until atrial stimulus is not conducted; PR interval will change progressively
  • The pattern of conducted: dropped beats is regular (e.g. 3 P waves: 2 QRS complexes)
  • Produces a strip with grouped or clustered beats
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12
Q

Describe the features of second degree AV block (Type II)

A

Second Degree Type II AV Block

  • Sudden appearance of a single, “dropped” beat (P wave not followed by a QRS complex)
  • Random (not progressive) lengthened (to infinity!) PR interval
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13
Q

Describe the features of a third degree AV block

A

Third Degree AV Block
- Complete heart block: no conduction from atria to ventricles; AV dissociation
- Atria continue to be paced by SA node, regular P waves
- Escape rhythm must pace ventricles (variable morphology, depending on location of escape pacemaker)
o Nodal pacemakers can generate higher rate of impulses and better coordinated (narrow QRS) depolarizations than infranodal escape rhythms
- More P waves than QRS complexes

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14
Q

Describe the features of a right bundle branch block (RBBB)

A

Right Bundle Branch Block (RBBB)
- Conduction occurs much more slowly in the right ventricle as compared to the left, generating a wide QRS complex
- Late QRS forces point toward the right ventricle (positive in V1 and negative in V6)
o V1: rSR’ complex with a broad R’ wave
o V6: qRS-type complex with broad S wave
o SECONDARY changes in T wave: inversions in right chest leads
- Found in pathologies that affect the right side of the heart (e.g., pulmonary embolism, COPD)

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15
Q

Describe the features of a left bundle branch block (LBBB)

A

Left Bundle Branch Block (LBBB)
- Conduction occurs much more slowly in the left ventricle as compared to the right, generating a wide QRS complex
o Septal depolarization occurs from right to left due to the lag (lack) of impulse from the left side
o “Entire” ventricular depolarization event occurs right to left
- V1: wide QS complex (can be notched like an “M”)
- V6: wide R wave (can be notched like an “M”)

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16
Q

Describe the features of sinus tachycardia

A

Sinus Tachycardia

  • Sinus rhythm with a HR exceeding 100 bpm
  • Each P wave is followed by a QRS complex
  • Can be related to sympathetic nervous stimulation or parasympathetic (vagal) withdrawal
  • Causes can be multifactorial: physiologic, pain response, drug response (especially autonomic drugs), fever, volume or blood loss, CHF, pulmonary embolism, MI, hyperthyroidism, pheochromocytoma
17
Q

Describe the features of sinus bradycardia

A

Sinus Bradycardia

  • Sinus rhythm with a HR less than 60 bpm
  • Each P wave is followed by a QRS complex
  • Can be related to augmented vagal tone
  • Causes can be multifactorial: physiologic, drug response (increasing parasympathetic tone or decreasing sympathetic tone), MI, hypothyroidism, hyperkalemia, sick sinus syndrome, age, hyper-vagotonia syndromes (vasovagal reactions, carotid sinus hypersensitivity, intracranial hypertension)
  • Useful to assess the HR response to exercise to determine whether aggressive correction of bradycardia necessary
18
Q

Describe the features of unifocal and multifocal premature ventricular complexes

A

Unifocal and Multifocal Premature Ventricular Complexes (PVC)

  • PVC with similar appearance in any one lead (uniform) and different appearance (multifocal)
  • PVC comes from ventricles, so the spread of depolarization is slow
  • Usually precede sinus P wave, sometimes followed by retrograde (non-sinus) P wave
  • 3 in a row is considered ventricular tachycardia (VT); can occur regularly or irregularly
  • If the focus is in the LV, the QRS may appear as a RBBB; if in the RV, the QRS may appear as a LBBB
  • QRS complex widens as origin is away from the middle of the heart
  • Repolarization after PVC is discordant and ST segment can be elevated (differentiate from concordant T waves and ST segment elevation with myocardial injury)
  • R on T Phenomenon: PVC falls near T wave, may precipitate VT or ventricular fibrillation
  • Can be “normal” (benign) or abnormal (symptom of heart disease)
19
Q

Describe the features of ventricular tachycardia

A

Ventricular Tachycardia

  • 3 or more PVC’s in a row at a rate of 100 bpm
  • Can be result of focal or reentrant mechanism, usually initiated by PVC
  • Can be nonsustained (less than 30 sec) or sustained, monomorphic or polymorphic (with or without QT interval prolongation)
  • Torsades de Pointes: usually from R on T due to prolonged QT interval
20
Q

Describe the features of ventricular fibrillation

A

Ventricular Fibrillation

  • Completely disorganized ventricular rhythm
  • No cardiac output
  • Coarse or fine nomenclature refers to amplitude of waves
  • If left untreated, progresses to from coarse to fine VF to asystole
21
Q

Describe the features of right atrial abnormality

A

Right Atrial Abnormality

  • Results in abnormal amplitude of P wave (tall, > 2.5mm) but does not change duration
  • Sometimes called P pulmonale due to association with pulmonary disease
22
Q

Describe the features of left atrial abnormality

A

Left Atrial Abnormality

  • Results in wide (>0.12 sec), sometimes notched P wave in one or more extremity leads and wide biphasic P waves in lead V1
  • Can occur in the setting of valvular heart disease, hypertensive heart disease, cardiomyopathies and coronary artery disease
23
Q

Describe the features of right ventricular hypertrophy

A

Right Ventricular Hypertrophy

  • Tall right precordial R waves
  • Right axis deviation
  • Right precordial T wave inversions
  • Can occur with pulmonary hypertension or pulmonic stenosis (increased pressure load); confirm by echocardiography
24
Q

Describe the features of left ventricular hypertrophy

A

Left Ventricular Hypertrophy

  • High voltage (abnormally tall) R waves in left chest leads; prominent S waves in right chest leads
  • Exact voltage criteria vary
  • Occurs with pressure overload on the left side of the heart: valvular disease, cardiomyopathies, systemic hypertension; confirm by echocardiography
25
Q

Describe the features of a STEMI

A

STEMI
- Some MIs will occur without ST elevation. We will ignore these in our discussion.
- ST elevation most commonly occurs with transmural MI: ischemia and necrosis of a large area encompassing the entire ventricular wall
- Acute phase: ST segment elevation, sometime hyperacute T waves in 2 or more leads
- Evolving phase: hours or days later, deep T wave inversions in the leads that previously showed ST elevation
- Anterior infarct: ST elevation in anterior leads (chest leads); loss of normal R wave progression; prominent Q waves in area(s) of tissue death
o Antero-lateral infarct: ST elevation in V1→V4-6
- Inferior infarct: ST elevation in leads II, III, aVF; Q waves denote death of tissue and are found in the leads with ST segment elevation
- Reciprocal changes: inverse changes (ST depression) in the leads opposite the injury

Cardio Exam 1 (15 decks)

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