Electrocardiography (ECG) Flashcards Preview

01 CARDIOVASCULAR MEDICINE > Electrocardiography (ECG) > Flashcards

Flashcards in Electrocardiography (ECG) Deck (28):
1

Reading

Rate, Rhythm (P before each QRS)

Axis

Intervals

P-R (120-200ms or 3-5 little boxes)

QRS < 120ms (3 little boxes)

Segments

QT (50-500ms or < .5 R-R 

Hypertrophy

P wave for atrial

R wave for ventricular

Infarction

Q waves

Inverted T

ST elevation/depression

 

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A-V block

First Degree: Prolonged P-R interval (0.2 second)

Second Degree: Dropped QRS; not all P waves transmit to produce ventricular contraction

Mobitz type I (Wenckebach), with progressive prolongation of the PR interval until the dropped beat

Mobitz type II, with a constant PR interval and periodic dropped beats.

Third Degree: Complete A-V dissociation; random P wave and QRS

Lyme carditis can manifest by acute-onset, high-grade atrioventricular conduction defects that occasionally may be associated with myocarditis. Carditis occurs in 5% to 10% of patients with Lyme disease, usually within a few weeks to months after infection.  Atrioventricular block can present in any degree, and progression to complete heart block is often rapid. 

Acute-onset, high-grade atrioventricular conduction defects that occasionally may be associated with myocarditis. Carditis occurs in 5% to 10% of patients with Lyme disease, usually within a few weeks to months after infection. Atrioventricular block can present in any degree, and progression to complete heart block is often rapid. The prognosis is good, usually with resolution of atrioventricular block within days to weeks. The presence of the characteristic skin rash, erythema migrans, with or without a history of tick bite in an endemic region, has a greater than 80% probability of being caused by Borrelia burgdorferi infection and is sufficient to support a decision to treat Lyme disease empirically without laboratory confirmation of the diagnosis.

3

AV Block

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First Degree: Prolonged P-R interval (0.2 second)

Second Degree: Dropped QRS; not all P waves transmit to produce ventricular contraction

Mobitz type I (Wenckebach): Progressive prolongation of the PR interval until the dropped beat

Mobitz type II: Constant PR interval and periodic dropped beats.

Third Degree: Complete A-V dissociation; random P wave and QRS

 

Lyme carditis can manifest by acute-onset, high-grade atrioventricular conduction defects that occasionally may be associated with myocarditis. Carditis occurs in 5% to 10% of patients with Lyme disease, usually within a few weeks to months after infection.  Atrioventricular block can present in any degree, and progression to complete heart block is often rapid. 

4

RBBB

Right Bundle Branch Block: wide QRS complex (>120 msec), RSR’ pattern in lead V1, and a wide negative S wave in leads I, V5, and V6.

5

ECG Criteria for STEMI

Two or More Contiguous ECG Leads

ST-segment elevation

II, III, aVF ≥0.1 mVa at J-point for most leads

V1-V3 ≥0.15 mV for V2-V3 for women

V4-V6 ≥0.2 mV for V2-V3 for men ≥ 40 y

I, aVL ≥0.25 mV for V2-V3 for men <40 y

ST-segment depression (indicates true posterior wall MI)

V1-V3 ≥0.1 mV  (Often has tall R waves in V1-V3)

New LBBB  New finding or presumed new

6

Q Wave

Significant Q wave is one millimeter (one small square) wide, which is .04 sec. in duration or 1/3 the amplitude (or more) of the QRS complex.

Note those leads (omit AVR) where significant Q’s are present.

Old infarcts: significant Q waves (like infarct damage) remain
for a lifetime.

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7

LBBB

Associated with absent Q waves in leads I, aVL, and V6; a large, wide, and positive R wave in leads I, aVL, and V6; Wide QRS and “rabbit ears” or RSR' in V5 or V6.

and prolongation of the QRS complex to greater than 0.12 seconds.

The presentation of acute coronary syndrome with new left bundle branch block should be considered equivalent to ST-elevation myocardial infarction and is an indication for acute reperfusion therapy

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8

LBBB

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Acute myocardial infarction manifesting as a new left bundle branch block on electrocardiogram and complicated by ischemic mitral regurgitation and heart failure. Electrocardiographically, left bundle branch block is associated with absent Q waves in leads I, aVL, and V6; a large, wide, and positive R wave in leads I, aVL, and V6; and prolongation of the QRS complex to greater than 0.12 seconds. Repolarization abnormalities are present and consist of ST-segment and T wave vectors directed opposite to the QRS complex.

9

Ischemia

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ST-segment depression and T-wave inversion (anterolateral leads)

10

sick sinus syndrome (SSS) 

SSS comprises a collection of pathologic findings that result in bradycardia. These include sinus arrest, sinus exit block, and sinus bradycardia. SSS is common in the elderly, and because symptoms can be intermittent or nonspecific, misdiagnosis can occur.

11

DDx: Supraventricular Arrhythmias:

Supraventricular tachycardias (SVTs) are rapid heart rhythms that require atrial tissue or the atrioventricular node for initiation and maintenance. 

Sinus Tachycardia

Atrial Tachycardia

Atrioventricular Nodal Reentrant Tacycardia

Atrioventricular Reciprocating Tachycardia

Multifocal Atrial Tachycardia

Atrial Fibrillation

Atrial Flutter

12

Sinus Tachycardia

Hx: Fever, exercise, anxiety, pain, anemia, thyrotoxicosis, hypoxemia, cocaine use, and alcohol withdrawal are common causes of sinus tachycardia.

Dx: The P waves have normal morphologic features but can become difficult to see with heart rates greater than 140/min because the P waves begin to merge with the preceding T waves. 

Slowing the heart rate with carotid sinus massage often shows the hidden P waves and establishes the diagnosis.

13

Atrial Tachycardia

Heart rate is between 150/min and 200/min.

Commonly occurs in patients with coronary artery disease or cor pulmonale. 

Atrial tachycardia often terminates without intervention once the underlying cause is treated. First-line drug therapies for stable atrial tachycardia are β-blockers and non-dihydropyridine calcium channel blockers (eg, verapamil, diltiazem).  If atrial tachycardia fails to respond to first-line therapy, more advanced antiarrhythmic therapy may be needed with agents such as amiodarone, flecainide, and sotalol. 

Atrial tachycardia is distinguished from atrial flutter by its somewhat slower atrial rate (150-250 bpm as opposed to 250-350 bpm).  

14

Atrioventricular Reciprocating Tachycardia

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Heart rate is typically between 140/min and 250/min.

AVRT is associated with an accessory pathway between the atria and ventricle that is not contained within the AV node itself. 

Dx: A short PR interval and the presence of a delta wave (a sloping upstroke initiating the QRS complex, which may be wide due to sequential rather than parallel depolarization of the ventricles).  This pattern on ECG is referred to as preexcitation, and when present with symptomatic tachycardia, it is called the Wolff-Parkinson-White syndrome.

WPW: Delta wave = slurred upswing on QRS; Ventricular preexcitation by an accessory atrioventricular connection, with a short P-R interval, prolonged QRS duration, and slurred onset of the QRS (delta wave) interval. With paroxysmal tachyarrhythmias.

Tx: Patients with narrow-complex AVRT are treated in the same manner as those with AVNRT. 

15

Atrioventricular nodal reentrant tachycardia (AVNRT)

AVNRT accounts for approximately 60% of all SVTs that present as a regular rhythm.

Dx: P wave either is seen just after the QRS complex, which accounts for a short RP interval or is concealed within the QRS complex (no visible P wave) 

Tx: VNRT may be terminated by maneuvers to increase vagal tone, such as Valsalva or unilateral carotid massage (after careful carotid artery auscultation for bruits). 

Rx: Intravenous adenosine, a non-dihydropyridine calcium channel blocker, and β-blockers are often successful in terminating AVNRT not responding to vagal maneuvers. Intravenous adenosine has a very rapid onset and is extremely short-acting, with a half-life of 10 seconds, making it an excellent first therapeutic choice. Adenosine is contraindicated in patients with severe bronchospastic disease. β-Blockers and non-dihydropyridine calcium channel blockers can also be used long term to prevent frequent recurrence of AVNRT.

In refractory cases, catheter radiofrequency ablation is between 95% and 99% successful in preventing AVNRT recurrence.

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16

Multifocal Atrial Tachycardia

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Hx: Occurs most often in patients with severe chronic obstructive pulmonary disease (COPD), but it may also occur in patients with pulmonary embolism, congestive heart failure, and hypoxemia.

Dx: Discrete P waves with at least three morphologic patterns with varying P-P, P-R, and R-R intervals and a heart rate between 100/min and 140/min.  The morphologic features of P waves are generally best seen in leads II, III, and V1.

Tx: Minimizing or discontinuing agents that may precipitate MAT (such as β-agonist therapy). If MAT persists despite the appropriate treatment of underlying causes, metoprolol or even high-dose magnesium may improve the tachycardia.

17

Atrial Fibrillation

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Atrial fibrillation is classified as paroxysmal (lasting <7 days), persistent (lasting >7 days), or long-standing persistent (permanent) (lasting >1 year or associated with failed cardioversion). 

Hx: Associated with structural heart disease, such as valvular disease (especially mitral valve disease), dilated cardiomyopathy, hypertension, and coronary artery disease. Heart failure, pulmonary hypertension, and increasing age are also strongly associated.  Noncardiac causes include substance abuse (eg, alcohol, caffeine, cocaine, amphetamines), inhaled β-agonists, hypoxemia, COPD, pulmonary embolization, obstructive sleep apnea, and hyperthyroidism.

In patients with atrial fibrillation, assess rate control by asking about easy fatigability and exertional dyspnea, and measure their heart rate after walking.

Dx: Disorganized atrial activity at a rate of 350 to 600/min, with no discernible P waves. It is characteristically associated with an irregularly irregular rhythm, and the fibrillatory waves vary in amplitude, morphologic pattern, and interval, creating a rough, irregular baseline between QRS complexes.

Tx: Rate control, restoration/maintenance of sinus rhythm, and stroke prevention. 

Atrial fibrillation with a rapid (irregular) ventricular response and hemodynamic compromise is treated acutely with electrical cardioversion (to sinus rhythm).

Rhythm control approach:  The antiarrhythmic agents amiodarone, flecainide, ibutilide, propafenone, and sotalol are used to maintain patients in sinus rhythm following cardioversion.

If the heart rate is >110/min, the degree of AV nodal blockade should be increased.

Rx: Includes intravenous non-dihydropyridine calcium channel blockers (diltiazem or verapamil) or β-blockers (metoprolol or esmolol). 

Rate control approach: patients aged >65 years 

The CHADS2 risk score is used to predict the likelihood of stroke in patients with nonvalvular atrial fibrillation.stroke risk factors (ie, Congestive heart failure, Hypertension, Age >75 years, Diabetes mellitus, and prior Stroke or TIA). 

Score of 1: either anticoagulation or antiplatelet therapy

Score of 2 or greater: oral anticoagulation (warfarin) is recommended for stroke prevention.  Direct thrombin inhibitors are another option.

Warfarin (target international normalized ratio [INR] of 2.0-3.0) reduces the risk of stroke by an average of 64% in patients with nonvalvular atrial fibrillation.

Maintain the INR at 2.0 to 3.0 in patients with nonvalvular atrial fibrillation or at 2.5 to 3.5 in patients with valvular atrial fibrillation.

The HAS-BLED score can be used to identify patients at high risk of bleeding.

Pulmonary vein catheter radiofrequency ablation or "maze" procedure in those treated unsuccessfully

18

Atrial flutter

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The underlying causes of atrial flutter are similar to those for atrial fibrillation and often result from atrial dilation.

Hx: Typical causes include pulmonary embolism, septal defects, mitral or tricuspid valve disease, and chronic left ventricular failure. Atrial flutter may occur in patients without underlying heart disease, however, such as those with thyrotoxicosis or alcoholism.

Dx: Characterized by a saw-tooth pattern on electrocardiogram that is most noticeable in the inferior leads.

The atrial rate is between 240/min and 300/min and is usually associated with a 2:1 or 3:1 AV block, resulting in a ventricular rate of approximately 100/min to 150/min.

Irregular rate and a saw-tooth pattern in lead II

Tx: Follows the same principles as atrial fibrillation. Patients with hemodynamic instability due to atrial flutter should be immediately electrically cardioverted. In others, rate control involves the use of a non-dihydropyridine calcium channel blocker or a β-blocker.  Preventing stroke and cardiac embolization is identical to atrial fibrillation as mentioned previously.

19

Ddx: Ventricular Arrhythmias

Premature ventricular contractions (PVCs)

Ventricular tachycardia (VT)

Ventricular fibrillation (VF)

20

Premature ventricular contractions (PVCs)

May be a marker of underlying heart disease, they have minimal prognostic significance if left ventricular function is preserved. 

Hx: Rarely have symptoms but may complain of palpitations or a sensation that the heart has stopped, owing to the post-PVC compensatory pause. 

Tx: If the patient's symptoms are tolerable, no therapy is indicated. If not, β-blockers, such as metoprolol, are reasonably effective at suppressing premature ventricular complexes

21

Ventricular tachycardia (VT)

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VT is a potentially life-threatening arrhythmia due to rapid, depolarizing impulses originating from the His-Purkinje system, the ventricular myocardium, or both.

Hx: VT often accompanies structural heart disease (prior MI), most commonly ischemic heart disease, and it is associated with electrolyte disorders (eg, hypokalemia, hypomagnesemia), drug toxicity, valvular heart disease, nonischemic cardiomyopathy, and long QT syndrome. In a patient with a wide-complex tachycardia with a history of coronary artery disease or cardiomyopathy, ventricular tachycardia is the most likely diagnosis.

Nonsustained VT: has ≥3 beats but is <30 seconds in duration. 

Hx: Usually are asymptomatic but may experience palpitations, dizziness, or syncope.

Sustained VT: Persists >30 seconds or requires termination due to hemodynamic collapse.

Hx: Syncope or near syncope and can also present with sudden cardiac death.

Dx: Ventricular rate typically ranges from 140/min to 250/min

Long QT syndrome is characterized by prolonged ventricular repolarization and a predisposition to the development of polymorphic VT and sudden cardiac death.

Torsades de pointes is a special subset of polymorphic VT where the ventricular rate ranges from 200/min to 300/min.

Rx: Epinephrine or vasopressin is recommended for hemodynamic support,

Sustained: Amiodarone has largely replaced other antiarrhythmic agents (sotalol) for resistant (sustained?) VT in the acute setting, although lidocaine can be useful in patients with coronary ischemia.  Procainamide and sotalol are also acceptable, and lidocaine can be used as a second-line agent.

Nonsustained: Medical therapy does not improve survival in patients with nonsustained VT, and thus pharmacologic therapy is avoided unless the patient has a history of structural heart disease or long QT syndrome or (rarely) intolerable symptoms.

β-Blockers are the mainstay of treatment for those with symptomatic nonsustained VT, although non-dihydropyridine calcium channel blockers may also be used in patients with structurally normal hearts.

Tx: Patients in whom drug therapy for nonsustained VT fails or is not tolerated can be referred for catheter-directed radiofrequency ablation or ICD placement. 

Implantable cardioverter-defibrillator (ICD) is an internal defibrillator that senses dangerous cardiac arrhythmias and automatically converts the rhythm to sinus rhythm by either administering a high-energy shock or delivering a short series of paced beats. 

An ICD is also indicated in patients with sustained VT in the setting of structural heart disease or when a completely reversible risk factor cannot be identified (such as in patients with hypertrophic cardiomyopathy at increased risk for sudden cardiac death).  ICD placement is also indicated for the primary prevention of sudden cardiac death in patients with (1) NYHA Class II or III heart failure and an ejection fraction of less than 35% or (2) a prior MI and an ejection fraction of less than 30% (after a waiting period of 40 days).

Catheter-directed radiofrequency ablation of VT is useful in patients with idiopathic VT (those without structural heart disease or another clear etiology) as well as those with frequent recurrences of VT.

22

Ventricular fibrillation (VF)

Dx: Rate is typically >300/min

Hx: Sudden cardiac death.

23

Symptomatic bradycardia (heart rate <40 bpm) or sinus pauses

Symptomatic complete heart block or second-degree heart block (type 1 or 2)

Asymptomatic complete heart block or advanced second-degree heart block

Atrial fibrillation with pauses of ≥5 seconds

Alternating bundle branch block

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II, III, aVF

Inferior

RCA

25

V1-V3

Anteroseptal

LAD

26

V4-V6; possible elevations in I and aVL

Lateral and apical

LCx

27

V1-V3 (ST depression)

Posterior walla

“Dominant” vessel (RCA or LCx)

28

V4Rb

Right ventriclea

Right coronary artery

aOften associated with inferior and/or lateral ST-elevation infarctions and tall R wave in V1.

bIndicates a precordial lead placed at the V4 position on the right side of the chest.