Chapter 6 Myocardial ischemia and infraction Flashcards
define angina?
a condition marked by severe pain in the chest, often also spreading to the shoulders, arms, and neck, caused by an inadequate blood supply to the heart
define Stable angina?
chest pain is brought about only by a given level of exertion (walking up stairs) and relieved with rest
patient is not at immediate risk of Myocardial infraction.
define acute coronary syndrome?
caused by acute rupture or erosion of atherosclerotic plaque which forms a thrombus. If complete blocking of the coronary occurs, it is called: UNSTABLE ANGINA, or Myocardial infraction.
Define unstable angina?
similar to a stable angina but it occurs with little to no physical exertion, and is more severe and last longer.
what varieties of myocardial infractions occur?
- ST-segment elevation myocardial infraction or STEMI occurs if the coronary is completely occluded
- if the coronary is partially occluded then unstable angina or NON-ST-segment myocardial infraction (non-STEMI or NSTEMI) In this case the ST segment is not elevated but could be depressed.
what are the 3 components to the diagnosis of a myocardial infraction?
- history and physical examination (sudden crushing chest pain radiating to jaw, shoulder, left arm, nausea, diaphoresis and shortness of breath)
- Cardiac enzyme determinations (creatine kinase CK-MB and troponin)
- EKG
what are the 3 stages of STEMI (ST-segment elevation myocardial infractions). In order.
- T-wave peaking followed by T-wave inversion
- ST-segment elevation
- The appearance of new Q-waves.
describe what happens to the T-wave shortly after a myocardial infraction.
T-wave elevation to the level matching the QRS complex (peaking) often referred to a hyperacute T-waves. Shortly after (2-hours later) the T-wave inverts.
what are some other reasons for the T-wave flip other then Myocardial infraction?
And how to differentiate between them?
- both bundle branch block
- ventricular hypertrophy with repolarization abnormalities associated with T-wave inversion.
In myocardial infraction the ischemia are inverted symmetrically while in the case of hypertrophy they are asymmetrical.
What is pseudonormalization?
In patients whose T-waves are already inverted ischemia may case them to revert to normal. Thus it should be compared to previous ECG tracings.
what is persistent juvenile T-wave pattern?
Normal inverted T-waves seen in leads V1, V2 and V3 in children and young adults.
Describe the ST-segment during myocardial infraction?
Elevation of the ST segment occurs which returns to normal after a few hours of MI.
Persistent ST-segment elevation often indicates the formation of a ventricular aneurysm.
what is J-point elevation? how does it differ from ST-elevation
a common type of ST-segment elevation that can be seen in normal hearts (junction point) is where the ST segment takes off from the QRS complex
Commonly seen in V1, V2, V3 in young healthy individuals.
In contrast to ST elevation. Myocardial injury the elevated ST segment has a distinctive configuration; it is bowed upward and tends to merge imperceptibly with the T-wave.
J-point elevation the T-wave maintains its independent waveform.
what are Q-wave during a myocardial infraction?
Q-wave indicate and irreversible myocardial cell death had occurred. The presence of Q-waves is diagnostic of myocardial infraction.
May take hours to day to evolve after a STEMI, but ST-segment returns to baseline and Q-wave persists a lifetime.
why do Q-waves appear?
the dead heart tissue will show up as a deep negative in the electrode overlying the infarct.
Besides the Q-waves there are also “reciprocal changes” during myocardial infraction, what are they?
Leads located some distance from the site of infraction, will see an apparent increase in the electrical forces moving toward them, they will record a tall R-wave.
These are called reciprocal changes.
Leads distant from an infraction may record ST-segment depression.
Q-waves are present in Lead III normally, so what is considered a “significant Q-wave” that indicates infraction?
- Q-wave must be greater than 0.04 seconds in duration
- Q-wave depth must be at least 25% the height of the R-wave in the same QRS complex.
DO NOT consider lead aVR when looking for infractions, beacuse it normally has a very deep Q-wave. As does Lead III. aVR Q-wave are NEVER significant
infraction Q-waves are often present in multiple leads.
in which leads are Q-waves never significant?
aVR.
and Lead III also normally has them. Look for wide Q-waves.
what is the optimal window for restoring blood flow in myocardial infraction?
90 minutes
in which leads can an inferior infraction be seen?
Right coronary is affected and seen in:
Leads II, III, and aVF.
T-wave inversion in lead aVL
in which leads can an Lateral infraction be seen?
Left circumflex artery is affected.
changes will occur in the left lateral leads: I, aVL, V5 and V6.
in which leads can an anterior infraction be seen?
Left anterior descending (LAD) artery. Any of the V1 to V6 leads can show changes.
anterolateral infraction will show changes in Lead I and aVL.
POOR R-WAVE PROGRESSION (can also be seen in right ventricular hypertrophy, chronic lung disease and obese patients)
in which leads can an posterior infraction be seen?
these infraction can be accompanied by inferior or lateral infraction since they are supplied by the same right coronary artery. (posterior infractions rarely occur in isolation)
Right coronary artery is affected
Reciprocal changes should be seen. Tall R-waves in leads V1, V2, or V3.
posterior infraction is a mirror image of anterior infractions on the EKG. we CANNOT look for ST-segment elevation and Q-waves in non-existent posterior leads.
ST-segment DEPRESSION and TALL R-waves in anterior leads should be seen. mostly V1.
Large R wave in lead V1 is also seen for right ventricular hypertrophy. However hypertrophy requires axis deviation not seen in posterior infraction.
Describe Right ventricular hypertrophy?
These infractions are virtually always accompanying inferior infractions.
similar changes as that of inferior infraction:
ST-elevation and so forth in leads II, III and aVF. Also: T-wave changes and ST-segment elevation in Lead V1. and some ST elevation in lead V2 of lower magnitude but ST-depression may also be seen in this lead.
Lead III will see a greater ST-elevation then lead II since because Lead III lies farther right.
