Inferior Wall Infarction

Inferior wall MI is caused by occlusion of the right coronary artery (RCA). This type of infarction is manifested by ECG changes in leads II, III, and aV_F (See image below).

Conduction abnormalities are expected with an inferior wall MI and are r/t the anatomy of the coronary arterial circulation supply. The RCA perfuses the sinoatrial (SA) node in slightly more than 50% of the population, supplies the proximal bundle of His and atrioventricular (AV) node in more than 90% of individuals, heart block and other conduction disturbances should be anticipated.

Inferior wall infarction has a mortality rate of about 6%. If the right ventricle is involved, the mortality rate rises to 25% to 30%.

The images below show changes seen on a 12-lead ECG with an inferior wall MI. A.   Infarction location on cardiac wall.
B.   ECG leads with expected ST-segment elevation.
C.   A 12-lead ECG from a patient experiencing inferior wall MI.

Correlations Among Ventricular Surfaces, EKG Leads, & Coronary Arteries

Below is a table which list corresponding surface area of the heart with EKG leads and the coronary artery usually involved. The location of infarction is determined by correlating the ECG leads with Q waves and the ST-segment T-wave abnormalities.  Infarction most commonly affects the left ventricle and the interventricular septum; however, the right ventricle can be infracted, and many patients who sustain an inferior MI have some right ventricular damage. The ECG manifestations that are used to diagnose an MI and pinpoint the area of damaged ventricle include inverted T waves, ST-segment elevation, and pathologic Q waves in specific lead groupings as described subsequently.

Surface of Left Ventricle	EKG Leads	Coronary Artery Usually Involved
Inferior	II, III, aVF	Right coronary artery (RCA)
Lateral	V5-V6, I, aVL	Left circumflex (CIRC)
Anterior	V2-V4	Left anterior descending (LAD)
Anterior lateral	V1-V6, I, aVL	Left main coronary artery (L MAIN)
Septal	V1-V2	Left anterior descending (LAD)
Posterior	V1-V2	Left circumflex or right coronary artery (reciprocal changes)
	V7-V9 (direct)

Coronary Circulation

The above image is the coronary circulation. Please print out and review the coronary arteries. It is important to know coronary circulation. If a patient is having an heart attack, the initial treatment is different based on location of infarction.


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CCRN Test Plan

Clinical judgement comprises 80% of the CCRN exam. The other 20% represents professional caring and ethical practice. Listed below is the breakdown of the 80% by system.  This BlogSpot is a guideline to help focus your studying and prepare you will questions. We will start with the cardiovascular system and work our way through the other systems overs the next several months.  Scroll below to find the breakdown of the cardiovascular system by disease specifics.

System Breakdown
A. Cardiovascular (20%)                                      
B. Pulmonary (18%)                                            
C. Endocrine (5%)                                                
D. Hematology/Immunology (2%)
E.  Neurology (12%)                         
F.  Gastrointestinal (6%)
G.  Renal (6%)
H.  Multi-system (8%)
I.  Behavior & Psycho-social 4%

Cardiovascular Breakdown
1. Acute coronary syndromes (including unstable angina)
2. Acute myocardial infarction/ischemia (including papillary muscle rupture)
3. Acute peripheral vascular insufficiency (e.g.,acute arterial occlusion, carotid artery stenosis, endartarectomy, peripheral stents, Fem-Pop bypass)
4. Acute pulmonary edema
5. Cardiac surgery (e.g., valve replacement, CABG)
6. Cardiac trauma
7. Cardiogenic shock
8. Cardiomyopathies (e.g., hypertrophic, dilated, restrictive, idiopathic)
9. Dysrhythmias
10. Heart failure
11. Hypertensive crisis
12. Hypovolemic shock
13. Interventional cardiology (e.g., catheterization)
14. Myocardial conduction system defects
15. Ruptured or dissecting aneurysm (e.g., thoracic, abdominal, thoraco-abdominal)
16. Structural heart defects (acquired and congenital, including valvular disease)

LOOK FOR THE QUESTIONS & ADVANCED PATHO TO START WITHIN THE NEXT WEEK!

You can do it!!! Take 30 minutes everyday to review material and complete at least 10 questions a day and you will be prepared to take the CCRN exam in a few months.