Cardiac imaging

Question 1

For what reasons might cardiac catheterization be performed?

Answer 1

1. Sample blood to assess oxygen saturation and measure pressures
2. Inject radiopaque contrast medium to image cardiac anatomy and blood flow
3. Performing angioplasty (+/- stenting) or valvuloplasty (if patient is too ill or declines valve surgery)
4. Perform intervascular ultrasound or ECG

Question 2

What pre-procedure checks are necessary for cardiac catheterization?

Answer 2

1. Is the patient taking a blood thinner e.g. warfarin? This should ideally be stopped 2-3 days before the procedure
2. Nil by mouth for 6 hours prior to the procedure
3. Oral hypoglycaemics e.g. metformin should be withheld from one day before the procedure to 3 days after. This is because renal function may be temporarily reduced by the dye used- and metformin is excreted by the kidneys
4. If the patient has reduced renal function, dye should be used minimally

Question 3

What are the possible complications of cardiac catheterization?

Answer 3

1. Bruising at site of insertion (groin or arm)
2. Haemorrhage
3. Contrast reaction- rare and usually mild with modern contrast agents
4. Loss of peripheral pulse. May be due to: dissection, thrombosis or arterial spasm. Occurs in <1 in 1000 in most centres

Question 4

What is the normal cardiothoracic ratio in adults?

Answer 4

<50%

Question 5

Why is a PA x-ray preferable to an AP? Why is an AP sometimes done?

Answer 5

1. PA is preferable as heart size can be reliably assessed (heart appears enlarged on AP)
2. An AP may be done in emergency situations to image the chests of patients who are unable to stand with their arms out in front of them (necessary for PA)