ECG Final

Definition of Ischemia

Lack of oxygenated blood flow

Definition of injury

lack of blood supply causing injury to muscle

Definition of infarction

death or necrosis of tissue/ irreversible

What are the major coronary arteries?

• right coronary artery

• Left main coronary artery

• circumflex

• left anterior descending

For ischemia, where does the lack of oxygenated blood go to?

The left ventricle

What are the characteristics of ischemia on an ECG?

ST depression or inverted T waves

What is the magnitude of ischemia determined by?

• the degree of ST depression

• the number of ECGs leads

• Duration of the ST depression in recovery

What is the criteria for upsloping ischemia?

1 mm (0.08 sec after QRS)

30% to 40% error rate

What is the criteria for horizontal ischemia?

1 mm (0.08 sec after QRS)

Very low error rate

What is the criteria for down sloping ischemia?

1 mm (0.08 sec after QRS)

5% to 10% error rate

What is the characteristics of injury?

• Stage beyond ischemia

• ECG: ST elevation, reversible

What are the characteristics of infarction?

• Necrosis of tissue

• ECG: significant Q waves

What is the Q to R ratio for infarction?

>0.25 or > 40ms duration in two or more leads (excluding III and aVR

What is acute transmural infarction?

ST elevation

tall positive T waves

What is evolving transmural infarction?

deep T wave inversions

How does the electrical signal move with ST depression?

it take longer to move through the myocardium

What results during an exercise test when the ST segment is depressed?

there is evidence of possible myocardial ischemia

What happens due to ST elevation?

insufficient blood to myocardium

What results during an exercise test when the ST segment is elevated?

it is caused for immediate concern especially if patient is symptomatic.

Where is the infarct located?

Where in the ECG hyperacute T waves appear.

What leads anterior MI are located in?

V1 - V6

Lead 1 & AVL

What leads inferior MI are located in?

Lead 2 & 3 & AVF

When do abnormal Q waves of an MI appear?

within the first day

What is the criteria for bundle branch blocks

 Rhythm: regular

 Rate: that of the underlying rhythm

 P waves: sinus

 PR interval: normal (0.12-0.20 sec)

 QRS: wide > 0.12 sec

What is the criteria for a right bundle branch block?

• V1 and V2

• Rabbit ears

What is the criteria for left bundle branch block

• V5 and V6

• notched or rabbit ears (R & R’)

• T wave inverted

• Predominantly negative QRS

What is the criteria for PVC (premature ventricular contraction)?

• Rhythm: underlying rhythm usually regular; irregular with PVC

 Rate: underlying rhythm

 P waves: None associated w/ PVC; P waves might be seen before, after the PVC or in ST segment on T wave, or hidden in QRS

 PR: not measurable

 QRS: premature, abnormal shape and wide (> 0.12sec)

What is a ventricular bigeminy?

every other beat is a PVC

What is a unifocal PVC?

identical shapes

What is a quadrigeminal PVC?

every fourth beat is a PVC

What is the Idioventricular Rhythm criteria?

• originates in ventricles

• QRS is wide, bizarre, no p waves

• Rhythm: Regular

• Rate: 20 - 40 bpm

What is the Accelerated Idioventricular Rhythm criteria?

• Originates in ventricles

• QRS is wide, bizarre. and no p waves

• Rhythm: regular

• Rate: 40 - 110 bpm

What is the cause of an Accelerated Idioventricular rhythm?

myocardial Infarction

What is the cause Idioventricular Rhythm?

End-stage cardiac disease

What is the Ventricular Tachycardia criteria?

• Originates in ventricles

• QRS is wide and bizarre

• Rhythm: regular

• Rate: >110 bpm

What is the cause of a Ventricular Tachycardia?

Coronary Artery Disease

What are the characteristics of Ventricular Fibrillation?

• Chaotic electrical activity

• No organized impulse or ventricular contraction

• #1 cause of cardiac arrest

What is the criteria for Ventricular Fibrillation?

Heart rate: 300-600 bpm

Rhythm: Extremely Irregular

P wave: absent

PR interval: N/A

QRS: Fibrillatory baseline

What is the criteria for Ventricular Asystole?

Heart Rate: absent

Rhythm: absent

P wave: absent or present

PR interval: N/A

QRS: absent

What is a battery?

powered devices designed to electrically stimulate the heart

What are the two types pacemakers?

Temporary and Permanent

What is a temporary pacemaker?

pacing wire is connected to a battery outside the body

What is a permanent pacemaker?

Inserted subcutaneously

What is a pacemaker spike?

sharp vertical deflection, followed by QRS

what is an atrial pacemaker?

spike followed by the P wave

What is a Ventricular Pacing fixed rate pacemaker?

fires at specific preset rate, regardless of patient’s own HR

What is a Ventricular Pacing demand pacemaker?

newer, work when it is needed; only when patient’s HR falls below preset value

What are the dual-chamber pacing disadvantages?

atrial electrodes easy to dislodge, facilitate tachycardia, no good for setting of atrial fib or flutter, very expensive

What is the dual-chamber pacing?

Electrodes in right atrium and ventricle, therefore sensing and pacing and allows for AV delay similar to PR interval.

What is a atrial pacemaker (single chamber)?

One spike producing an abnormal P wave, followed by a normal QRS

What is a ventricular pacemaker (single chamber)?

One spike producing a wide QRS

What is an AV sequential pacemaker?

One spike followed by an abnormal P wave, followed by a second spike producing a wide QRS

What are electronic pacemaker spikes?

Artificially induces electronic stimulus that paces the patient’s rhythm causing a blip or spike on the ECG waveform.

What is a Paced Fusion Beat?

The artificial pacemaker and the patient’s own cardiac rhythm occurs simultaneously producing a combination of a paced beat and normal beat.

What are indications for cardiac pacing?

• Symptomatic bradyarrhythmia

• Syncope, light-headedness, weakness

• CHF, complete heart block, 2nd degree AV block

• atrial flutter or fib with slow ventricular response

What are the diagnosis of MI with pacemakers?

• Difficult or impossible because of the LBBB configuration

• After insertion of pacemaker it might show ECG changes- deep non-infarctional T waves