myocardial ischemia and infarction

Question 1

pathological Q wave

Answer 1

Q waves are considered pathological if:
> 40 ms (1 mm) wide
> 2 mm deep
> 25% of depth of QRS complex
Seen in leads V1-3

Pathological Q waves usually indicate current or prior myocardial infarction.

***Lead aVR should not be used to look for pathological Q wave since it usually shows this kind of waveform in normal hearts.

Question 2

hyperacute stage of infarction

Answer 2

“T en dome” where ST elevation is merged with a tall peaked T wave.

Question 3

Acute stgge

Answer 3

Pathological Q wave
and/ or R reduction ST elevation.
Negative T wave (the T wave is really biphasic, but the positive phase merges with the ST elevation)

Question 4

Subacute stage

Answer 4

pathological Q wave and/or R reduction,

Cornoary T wave (symmetric, deep, peaked, negative T wave).

Question 5

Definitive stage (old infarct)

Answer 5

The pathological Q wave usually remains life-long; the repolarization abnormalities may be normalized.

Question 6

what causes a discordant T wave?

Answer 6

• > A VPC, where the spread of re polarization will follow a tangenital way rather than the usual radial way.
• > Transient negative T waves seen during an angina attack, where the ion channels function changes significantly due to eg- ischemia.
• > Coronary T waves in a subacute infarct

Question 7

Why is there a ST segment changes?

Answer 7

ST segment changes from its normal isoelectric appearance is due to lesion.

Lesion is a state of severe hypoxia, however, it is temporary only, so will not cause necrosis. Lesion lowers the resting potential.

Question 8

Subendocardial lesion
Which occurs in patients with-
Typical angina pectoris
Small size infarcts (NoSTEMI)

Answer 8

the TP and PR segments are elevated, ST is depressed.
All these changes contribute to apparent ST depression.

**Pathological Q wave or R reduction can be observed.

Question 9

Subepicardial/ transmural lesion
occurs in patients with:
Prinzmetal angina and larger size infarcts.

Answer 9

TP and PR segments are depressed, ST is elevated.
All these changes contribute to an apparent ST elevation.

Pathological Q wave

Question 10

Anterior extensive (anterolateral) infarct

Answer 10

lead I, Avl
All pectoral leads( V1-V6).

Most typical is occlusion of the LEFT MAIN CORONARY ARTERY!!!

Question 11

Anteroseptal

Answer 11

V1, V2, V3, V4

Most commonly occurs in occlusion of LAD.
**Can also see poor R progression with lack of pathological Q waves.
This is not specific for MI but also for right ventricular hypertrophy and COPD.

Question 12

Lateral

Answer 12

Lead I, aVL, V5, V6.
Most common involves occlusion of the left circumflex artery.

Reciprocal changes can be seen in inferior leads.

Question 13

High Lateral

Answer 13

Lead I, aVL.

Question 14

Inferior (diaphragmatic surface)

Answer 14

Lead II, III, aVF

Often caused by occluson of the right coronary artery or its descending branch.
Might see reciprocal changes in the anterior and left lateral leads.

Question 15

Posterior

Answer 15

Reciprocal signs- V1, V2, V3.
Direct signs- V7, V8, V9.

Mostly due to occlusion of the right coronary artery.
Reciprocal images- ST depression and tall R waves in anterior leads.

Question 16

how to describe the findings of an MI on EKG?

Answer 16

1) What region of the heart is involved?
2) Where is the most likely location of the occlusion?
3) Approx. how old the infarct is
4) What is the overall impression?

Question 17

apical ballooning syndrome / broken heart syndrome.

Answer 17

Not that relevent.

New ECG changes (ST elevation or T wave inversion) or moderate troponin rise.
Transient akinesis / dyskinesis of left ventricle (apical and mid-ventricular segments) with regional wall abnormalities extending beyond a single vascular territory.
Absence of coronary artery stenosis >50% or culprit lesion.

Question 18

Myocardial ischemia

Answer 18

ST segment depression
T wave flattening or inversion

Incase of high troponin level it will be considered a NSTEMI rather than unstable angina pectoris.

Question 19

st depression causes

Answer 19

the most common cause of horizontal and descending st depression is myocardial ischemia.
ascending st depression are common in sinus tachycardia (ergometry).
The so called scooped (shallow, symmetrical) St depression are usually seen in patients treated with digitalis.

Question 20

negative U waves

Answer 20

Also indicate significant myocardial ischemia

Question 21

ST Elevation in aVR – LMCA occlusion

Answer 21

Widespread horizontal ST depression, most prominent in leads I, II and V4-6
ST elevation in aVR ≥ 1mm
ST elevation in aVR ≥ V1

Question 22

Right ventricular STEMI

Answer 22

How to spot right ventricular infarction

The first step to spotting RV infarction is to suspect it… in all patients with inferior STEMI!

In patients presenting with inferior STEMI, right ventricular infarction is suggested by the presence of:

ST elevation in V1 – the only standard ECG lead that looks directly at the right ventricle.
ST elevation in lead III > lead II – because lead III is more “rightward facing” than lead II and hence more sensitive to the injury current produced by the right ventricle.
ST depression in lead I.

Right ventricular infarction complicates up to 40% of inferior STEMIs. Isolated RV infarction is extremely uncommon.
Patients with RV infarction are very preload sensitive (due to poor RV contractility) and can develop severe hypotension in response to nitrates or other preload-reducing agents.
Hypotension in right ventricular infarction is treated with fluid loading, and nitrates are contraindicated.

Question 23

wellens syndrome (not really relevent)

Answer 23

Wellens’ syndrome is a pattern of deeply inverted or biphasic T waves in V2-3, which is highly specific for a critical stenosis of the left anterior descending artery (LAD).
Patients may be pain free by the time the ECG is taken and have normally or minimally elevated cardiac enzymes; however, they are at extremely high risk for extensive anterior wall MI within the next few days to weeks.
Due to the critical LAD stenosis, these patients usually require invasive therapy, do poorly with medical management and may suffer MI or cardiac arrest if inappropriately stress tested.

criteria:
Deeply-inverted or biphasic T waves in V2-3 (may extend to V1-6)
Isoelectric or minimally-elevated ST segment (< 1mm)
No precordial Q waves
Preserved precordial R wave progression
Recent history of angina
ECG pattern present in pain-free state
Normal or slightly elevated serum cardiac markers