2025 ECG Quiz 5 Flashcards
Myocardial Ischemia and Infarction
WHAT IS MYOCARDIAL
INFARCTION
Occlusion of coronary arteries = acute
coronary syndrome
* Causes myocardial hypoperfusion resulting in
cellular death
AKA: “Heart attack”
May lead to:
* Arrhythmias
* Heart failure
* Cardiogenic shock
* Heart rupture
* Cardiac arrest
* Death
WHAT CAUSES
MYOCARDIAL INFARCTION
Coronary Artery Disease
* Narrowing caused by build up of plaque (atherosclerosis)
Coronary Thrombosis
* Blood clot blockage.
* Commonly associated with
coronary narrowing due to
atherosclerosis.
Coronary Artery Spasm
* Cocaine, stress, cold, etc.
ACUTE CORONARY
SYNDROME
Any condition brought on by a sudden reduction or
blockage of blood flow to the heart
Stable angina vs Unstable
angina
NSTEMI vs STEMI
STABLE VS UNSTABLE
ANGINA
Stable angina: vessel unable
to dilate enough to allow
adequate blood flow
STABLE VS UNSTABLE
ANGINA
Unstable angina: Thrombus
forms on ruptured plaque
causing partial occlusion
NSTEMI VS STEMI
Non-STEMI
* Partial occlusion
* Cellular death occurs in
subendocardial tissue
NSTEMI VS STEMI
STEMI
* Total occlusion
* True emergency
* Cellular death occurs
throughout entire wall of
heart, or transmural
3 COMPONENTS OF MI
DIAGNOSIS
History and physical exam
Cardiac enzymes
ECG changes
HISTORY AND PHYSICAL
EXAM
Prolonged, severe chest pain
* Classic symptom of cardiac ischemia
* Diffuse chest pain
* May radiate to jaw, neck, left arm, back
* Angina: ischemic chest pain
* Generalized weakness
* Lightheadedness and syncope
* Shortness of breath
* Diaphoresis and pallor
* Nausea and vomiting
* Anxiety/”feeling of impending doom”
Woman and Diabetics can show Atypical signs… dont see the crushing chest pain
CARDIAC ENZYMES
Troponin (TnI, TnT)
* Most important cardiac marker
* High sensitivity and specificity
* Rises early and stays elevated
longer than other enzymes
* Valuable for early/late detection
* Provides information pertaining to
acute MI severity and reperfusion
Myoglobin
* Limited specificity, but
high sensitivity makes it
useful for early
detection.
Creatine kinase MB isoenzyme (CKMB)
* High sensitivity & specificity = valuable in assessment of AMI severity & reperfusion
* Limited value early/late
ELECTROCARDIOGRAM
During an AMI, the ECG evolves
through 3 stages:
* T wave peaking followed by T wave inversion
* ST segment elevation
* Appearance of new Q waves
* Changes begin immediately after
infarct.
* 12-lead EKG can help aid in localization of infarct.
TREATMENT OF MI
THROMBINS2
* Thienopyridines
* P2Y12 receptor blockers
* Heparin/enoxaparin, Reninangiotensin
system blockers
* Oxygen
* Morphine
* Beta blocker
* Intervention
* Nitroglycerin
* Statin
* Salicylate (Aspirin)
Management:
* IV Access, ECG, Cardiac
Monitoring, SpO2, CXR
* Send Cardiac Enzyme Labs
* Begin THROMBINS2 if suspected MI from ECG
* Consider revascularization
interventions:
Percutaneous coronary
Intervention (PCI)
Intra-coronary stent (ICS)
Coronary artery bypass graft (CABG)
ST SEGMENT
ELEVATION
MI (STEMI)
T WAVE ALTERATIONS
1st sign: T waves peak
* Changes due to local hyperkalemia in ischemic myocardium.
* At this point ischemia can be reversible if blood flow is restored promptly
* Must be in two sequential anatomical leads i.e. V1,V2; V5,V6
Hours later: T waves invert
* May persist for months to years.
* Note: T-wave inversion can occur due to causes other than MI. However, in MI, T waves invert symmetrically.
Young kids might have inverted T-Wave normal???
T WAVE ALTERATIONS
Young kids might have inverted T-Wave normal???
ST SEGMENT ELEVATION
Q WAVE APPEARANCE
WHY Q WAVES FORM
Myocardium dies and cannot conduct
electrical current.
Electrical forces move away from area of infarction.
Causes deep negative deflection, a Q wave.
RECIPROCAL CHANGES
Electrical forces move toward sites distant from infarction.
Affect ST segment (depression), Q waves,
and T waves.
STEMI SUMMARY
T wave “peaks”
Signifies myocardial ischemia
ST segment elevation; merges with T wave
Signifies myocardial injury
Signifies to baseline within a few hours
T Wave inverts
* Inverts symmetrically
* May resolve or persist for months/years
New Q waves appear
Signifies permanent myocardial
infarction
* Persist for lifetime of patient
PEAKED T
WAVES
ST SEGMENT
ELEVATION
Q WAVE
APPEARANCE
Q-Waves can persist for life
STEMI-LOCALIZING THE
INFARCT
Location of infarct affects prognosis and
treatment.
Two major systems of blood supply to
myocardium:
* Right coronary artery
- Left coronary artery (left main coronary artery):
- Left anterior descending artery
- Left circumflex artery
ANATOMICAL
CATEGORIES OF
INFARCTION
Inferior
Lateral
Anterior
Posterior
ANATOMICAL
CATEGORIES OF
INFARCTION
Inferior
Lateral
Anterior
Posterior
LOCALIZING
ACS AND
INFARCTION
INFERIOR
INFARCTION
LATERAL
INFARCTION
ANTERIOR
INFARCTION
POSTERIOR
INFARCTION
Since no ECG lead reflects posterior electrical activity, changes are reciprocal of those in anterior leads
Can attach V8 and V9??? Look at more
RIGHT VENTRICULAR
INFARCTIONS
PRACTICE
V6 - large ST elevation
Also in aVF and aVL
Lateral infarction
PRACTICE
V2 and V3 - ST elevation
Peaked T-Waves
Anterior infarction
PRACTICE
Lead II - ST Elevation
Lead I and aVF - small ST Elevation
Inferior and Lateral Infarction
PRACTICE
Inferior and Lateral Infarction
NON-STEMI
More common than STEMIs.
NO ST-segment elevation or deep Q waves.
Only changes are T-wave inversion and ST depression
Usually caused by either:
* Nonocclusive thrombosis of major
coronary artery
* Complete occlusion of small offshoot
Involve less than entire thickness of heart muscle
Lower initial mortality; higher later re-infarction mortality
DISTINGUISHING ANGINA
FROM NON-STEMI
EKG findings resemble those of a non- STEMI
* ST-segment depression
* T-wave inversion
Distinction is made by measuring cardiac
enzymes:
* Significantly elevated with a non-
STEMI
* Normal with uncomplicated angina
Angina associated with ST elevation and normal enzymes, the T is different though? = Crinsmetal Ingina? From the book… look at more
SORTING OUT THE DIFFERENT ISCHEMIC
SYNDROMES
LIMITATIONS OF THE ECG
IN DIAGNOSING INFARCTION
Diagnosis of myocardial infarction with
EKG relies on:
* T-wave changes
* ST-segment changes
* Q-wave formation
Some underlying cardiac conditions
mask these effects:
* Wolff–Parkinson–White
* Left ventricular hypertrophy
* Left bundle branch block… if see on ECG, need to rule out infarction before can do anything (will never show the ST changes)
