Clinical Cardiac MI Flashcards Preview

Cardiovascular System > Clinical Cardiac MI > Flashcards

Flashcards in Clinical Cardiac MI Deck (25):
1

MRI and CT scanning are relatively

recent

2

How does a MR scanner work?

-Very strong, superconducting magnet of 0.5-3T.
-Radio-frequency coils transmit signals into patient, and energy the body absorbs is received by surface coils.
-In a metal 'faraday' box to exclude internal RF (same as fm stations)

-A computer is then used to reconstruct the images
-ECG signal for cardiac imaging

3

Super conducting Magnets

Enormous tube of iron
-bathed in liquid helium
-zero-electrical Resistance
-Magnetic-field always on! only turned off when heated (dangerous)
-Large refrigeration plants required
-Emergency vent for He to boiled off

4

Safety concerns.

-Magnetic field strong enough to launch projectiles
-Risk to electronic implants: pacemakers/defibrillators, cochlear implants
-Metallic foreign bodies: eyes, pre-80s cerebral aneurysm clips.

5

Particular problems with cardiac imaging

-Small fast-moving structures

-Constant cardiac motion (gated images)

-Resp motion

-irregular cardiac rhythms (blurry heart)

-Patients inability to co-operate

-Claustrophobia

6

Simplest type of image to take?

Axial image

7

Calcium is

black

8

If patients don't hold their breath, you get a

Blurry image

9

Ventricular modeling

Take many images from different planes, and calculate volumes
green: endocardial surface
blue: epicardial surface

10

What happens when intima pulls away from aorta

Most people 50% die. New channel, can pull away right the way down.

11

Right ventricular cardiomyopathy

accumulate lipids in myocardial cells. liable sudden ventricular arrhythmias.

-Irregular crenulated ventricular lining.

12

Fibroma

Benign fibrous tumour

13

Delayed myocardial enhancement.

Give people contrast agents: Gd-contrast agents
-Image 10-30mins later
-how much GD depends on how much extracellular space is there, shows as white (normal should have very little!)

Used: in adult cardiology for MI and assessment of myocardial viability

Lesser Use: to assess cardiomyopathy and possible causes, degree of myocardial fibrosis, myocarditis

14

angiography

3D image

15

Coronary angiogram

-Dye injected
-can see small arteries, outline =the lumen!

16

How do we treat coronary artery disease?

Coronary Bypass
Take arteries/veins, attach one end to aorta and the other to coronary arteries

17

Metal stents

Hold arteries open

18

Vein vs arterial grafts

Vein grafts clot within 5-10 years, arterial grafts much better

19

Balloon coronary angioplasty

-Balloon dilation of an atheromatous stenosis
-Requires extensive anticoagulant therapy (aspirin and heparin)

-High risk of acute thrombosis at the angioplasty site

-High risk of re-stenosis long-term, more scar tissue (~4-6months post procedure)

20

Factors that promote restenosis

-Multiple lesions treated
-Lengthy lesions
-diabetes increase risk by 3x
-previous history of re-stenosis

21

Now what is done more the ballon coronary angioplasty?

ballon with drug covered stent

22

Coronary stents

-Placed to ensure continued patency at site
-Reduces re-stenosis effect and need for re-intervention
-Still risk of acute thrombosis or restenosis.

Done with large antiplatelet drug to reduce thrombus + one month oral therapy

Many varieties

23

Advantages of CT angiography

-Non-invasive, therefore cheap, and lower risk

-Images both vessel wall and lumen
-More pleasant for patient
-Visualised other thoracic pathology.
-Lower radiation and contrast load
-Non-specific so can be used for whatever

24

Disadvantages of CT angiography

-Need regular slow cardiac rhythm, (doesn't work with atrial fibrillation)
-Required patient co-op
-problems with heavily calcified vessels
-More difficult to interpret

25

Plaque in coronary artery

White calcified plaque with lipid out line