Myocardial Ischemia

Question 1

MVO2 (mlO2/minper100g) used by arrested heart?

Answer 1

2

Question 2

MVO2 (mlO2/minper100g) used by resting heart?

Answer 2

8

Question 3

MVO2 (mlO2/minper100g) used by heart during heavy exercise?

Answer 3

70

Question 4

Equation for coronary perfusion pressure?

Answer 4

DBP - LVEDP

Question 5

What is the minimum CPP needed for perfusion of coronary arteries during cardiac arrest?

Answer 5

15mmhg

Question 6

What is equation for oxygen delivery?

Answer 6

O2 delivery = coronary blood flow x arterial O2 content

Question 7

When is the left side of the heart perfused and why?

Answer 7

During diastole. The coronary artery entrances are at the base of the aorta, and when the heart contracts, the arteries are compressed.

Question 8

When is the right side of the heart perfused and why?

Answer 8

During both systole and diastole. Not as much compression occurs on right coronary arteries.

Question 9

What part of the heart is most at risk of hypo-perfusion and why?

Answer 9

Sub-endocardial layer just outside of ventricular chamber because it is at the end of the coronary perfusion pathway.

Question 10

How might fluid overload cause decrease in CPP?

Answer 10

Increasing LVEDP can cause a decrease in CPP

Question 11

What is myocardial extraction ratio? What about in other tissues of the body?

Answer 11

Myocardial 50%, elsewhere 25-35%

Question 12

What are the components of myo O2 demand?

Answer 12

HR, contractility, wall stress

Question 13

What are some components of O2 supply?

Answer 13

coronary blood flow, arterial O2 content, extraction ratio

Question 14

Disease processes that can lead to ischemia?

Answer 14

atherosclerosis, hypotension, blood loss or anemia, spasms, electrical activity (arrythmias)

Question 15

Atherosclerosis risk factors?

Answer 15

male, homocysteine, OCP, aged, family hx, obesity, DM, smoking, hyperlipidemia, HTN, hx PVD/CVA

Question 16

What can coronary ischemia cause?

Answer 16

MI, wall motion abnormalities, acute valvular failure, malignant arrhythmias, cardiogenic shock

Question 17

What is the optimal treatment for cardiogenic shock?

Answer 17

counterpulsation

Question 18

Risk factors for cardiac complications?

Answer 18

recent MI, congestive heart failure, significant aortic stenosis, age 70+, poor general health

Question 19

What EKG abnormalities are risk factors for cardiac complications?

Answer 19

PAC’s, >5 PVC’s, rhythms other than sinus

Question 20

What surgery types put pts at increased risk for cardiac complications?

Answer 20

emergency surgery, intrathoracic, intraperitoneal or aortic surgery, OR time 3+ hrs, wide swings in intra-op hemodynamics

Question 21

What are some MAJOR cardiovascular risk factors that put pts at increased risk for cardiac complications?

Answer 21

unstable angina, recent MI w/ evidence of ischemia, severe valvular disease, decompensated CHF, significant arrhythmias

Question 22

What are some INTERMEDIATE cardiovascular risk factors that put pts at increased risk for cardiac complications?

Answer 22

Mild angina, compensated or prior CHF, DM

Question 23

What are some MINOR cardiovascular risk factors that put pts at increased risk for cardiac complications?

Answer 23

Advanced age, abnormal EKG (rhythm other than sinus), low functional capacity, history of CVA, uncontrolled HTN

Question 24

What are some components of a pre-op cardiac workup?

Answer 24

history, physical exam, EKG, functional tests

Question 25

What are some functional tests for the pre-op cardiac workup?

Answer 25

functional capacity, holter monitoring, exercise EKG, thalium perfusion test, echocardiogram, coronary angioplasty

Question 26

What is the thalium perfusion test?

Answer 26

Dilate coronary arteries and look at perfusion in the myocardium. Atherosclerotic arteries don’t dilate well and leads to steal phenomenon. Ones that do dilate get more blood.

Question 27

Questions to ask about chest pain:

Answer 27

Where is the chest pain? Does is radiate? What makes it worse? Better?

Question 28

What are some physical signs of ischemia?

Answer 28

Mental status change- Brain not perfused well. JVD- jugular venous distension. Veins in neck distend. Backup of fluid. Cardiac wheezing- Get fluid around lungs from the backup. Can lead to pulmonary edema.

Question 29

Difference between concentric and eccentric hypertrophy?

Answer 29

concentric - thickening of myocardium. Eccentric - more muscle but dilation in size of chamber, from volume overload. Both have more muscle tissue and more O2 required.