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PPS - obesity > Heart function and imaging > Flashcards

Heart function and imaging Flashcards

1
Q

Examples of ways to image the heart

A

Echocardiography

Chest X-ray

Coronary CT Angiography

Invasive Coronary Angiogram

Coronary angioplasty

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2
Q

What are the advantages of echocardiogram?

A

Easy

Quick

Non-invasive

Non ionising radiation

To assess the heart

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3
Q

When is an echocardiogram ordered?

A

One of the first tests a cardiologist is likely to do to a patient admitted to the cardiac care unit

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4
Q

Who performs an echocardiogram?

A

Well trained cardiologist

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5
Q

What is an echocardiogram used for?

A

Identifying which areas of the heart have been damaged during MI

How that damage affects the heart’s function

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6
Q

What parameters are assessed during an echocardiogram?

A

LV function

RV funciton

Hypokinesis

Valve function

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7
Q

What about LV function can be observed during an echocardiogram?

A

Size

Well at pumping blood out the heart

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8
Q

What is hypokinesis?

A

Symmetry in the movement of the heart wall

May be damaged following MI

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9
Q

What is an ultrasound?

A

Uses sound waves in the megahertz range

1-15 MHz - inaudible to humans

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10
Q

How does an ultrasound work?

A

An ultrasound generates, detects and processes the ultrasound signal

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11
Q

Why is the image quality compromised in obese patients?

A

Image resolution is better with shorter wavelengths of sound, but this reduces the distance they can penetrate the tissue

Ultrasound image quality is compromised in patients with lots of adipose tissue

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12
Q

How does the ultrasound machine generate ultrasound?

A

Pizoelectric crystal cells generate and receive ultrasound signals

A very short electrical impulse is applied to the crystal-containing transducer

This generates a short pulse

The beam diverges and reflects off the surfaces it meets

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13
Q

What is a common pizoelectric crystal used in ultrasound?

A

Zirconate titanate

Changes dimension in response to an applied electric current

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14
Q

What is attenuation?

A

Sound waves lose energy to the medium they are travelling through

Velocity of the sound waves depend on the density of the medium

This is how we get different colours in the monitor image

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15
Q

What is a hyperechoic surface?

A

A highly reflective surface such as bone

Need to think carefully where to place the probe

Place the probe between the ribs to get a good image of the heart

Most of the ultrasound wave is reflected back, which casts an acoustic shadow behind the reflective structure

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16
Q

What is a hypoechoic or anechoic surface?

A

Very low or no reflection of the ultrasound wave

The probe’s inbuilt image compensation creates an area behind the surface of acoustic enhancement

Makes it appear brighter

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17
Q

What characteristics affect the reflected beams?

A

Reflected beams are altered by

  • the distance they travel
  • the structure they reflect from
  • the characteristics of the media through which they have travelled
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18
Q

What can be seen in an echocardiogram?

A

Apex of the heart and four chambers

Valves

In infection can get enough detail to see the build up of bacteria on the valves on the echo

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19
Q

What are the benefits of echocardiograms?

A

Images can be freeze-framed

Can build all the data from an echo to obtain 3D pictures of the heart

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20
Q

Why are echocardiograms used so often to assess heart health?

A

Good modality to assess the structure of the heart and synchrony of the muscle of the heart wall in real time

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21
Q

How common are chest X-rays?

A

Common technique used for most patients

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22
Q

Are chest x-rays often used for patients suspected of having MI?

A

If unsure of the history can look at the anatomy

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23
Q

Why are chest x-rays not the first test done on suspected MI patients?

A

Time needed for the test - need to ensure the patient is stable

Shouldn’t hold up urgent treatment

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24
Q

What is a disadvantage of CXR?

A

Ionising radiation = inherent risk to the patient

Damaging to DNA and cells

Risk of mutations leading to cancer

25
Q

What is another use for CXR in MI patients, other than diagnosis?

A

Used to check if complications have arisen from an MI

26
Q

What is an example of a complication that arises due to MI?

A

Pulmonary oedema

Buildup of fluid inside the lungs

Bilateral increase in opaqueness as the heart is not pumping well enough

27
Q

How much ionising radiation does a CT release compared to a CXR?

A

CT has 1000x more radiation than x-ray

28
Q

How does a CXR create an image of the tissues?

A

Electromagnetic radiation with heterogeneous beams of x rays from a x ray generator

Aimed at particular tissue

Place a photographic or digital film

X-rays pass through tissue

Different types of tissue absorb x-rays at different extents

Shadow created in 2D picture allow us to investigate the tissues

29
Q

What is a CT scan?

A

Imaging technique that takes multiple X-ray images around the craniocaudal axis

30
Q

What is craniocaudal?

A

Head-to-tail

31
Q

How does a CT make images of the body?

A

An X-ray machine is fixed opposite multiple rows of detectors

This rotates around the patient capturing X-ray images from different angles

Angles are computed using voxels

32
Q

What is a voxel?

A

3D pixel

33
Q

How are the x-ray images processed to form a CT image?

A

Axial slices are divided into grids of voxels

The attenuation in each is compared and calculated to reconstruct an optimised image

Post-processing algorithms can be used to highlight features and further optimise the image

34
Q

What is attenuation?

A

How much the tissues absorb the radiation

35
Q

What is a coronary CT angiography?

A

Newer technique of CT

Used to look for stenosis of the coronary arteries

36
Q

Why are coronary CT angiography techniques used less than CXR or Echocardiograms?

A

Need quick sequencing CT machines to be able to obtain clear pictures of the heart

37
Q

Which patients undergo cCTA?

A

Patients who present to A&E with low/intermediate probability for coronary artery disease

38
Q

What is needed to carry out a cCTA?

A

Trace contrast

39
Q

What is the advantage of cCTA?

A

Non-invasive

40
Q

What is a disadvantage of cCTA?

A

Use of ionising radiation due to using X-rays

Currently quite a new technique = expensive

41
Q

What happens if cCTA shows moderate or significant CAD?

A

Patients need further testes

  • functional tests
  • invasive coronary angiogram
42
Q

How do you conduct an ICA?

A

Iodine-based contrast dye used to highlight the coronary arteries on X-rays

43
Q

What is the aim of ICA?

A

Determine whether a blockage or narrowing has occurred in the coronary arteries

44
Q

How is an ICA carried out?

A

A catheter is inserted into a blood vessel usually in the groin

Catheter is guided into the coronary arteries using X-rays

Positioned in the heart so that its tip rests in a coronary artery

Contrast is then injected

Artery and small vessels leading from it are visualized by a series of X-rays

45
Q

What is the form of intervention that can be done during ICA?

A

Angioplasty

46
Q

Which patients undergo angioplasty?

A

Patients who present to A&E with typical angina routinely have an invasive coronary angiogram

Following MI - gold standard for treatment

47
Q

What is PCI?

A

Percutaneous Transluminal Coronary Angioplasty

Coronary Angioplasty

48
Q

When is PCI used?

A

For severe (stable) angina where medication is ineffective - outpatient cases

Acute STEMI

NSTEMI ACS

Haemodynamically significant lesions serving viable myocardium observed during angiography

49
Q

What are the complication risks of PCI?

A

Thrombosis occurs in 1-2% of patients

Usually presents as an MI, with high mortality

Restenosis occurs in up to 20% of patients, usually presents as a return of anginal pain

50
Q

When is PCI carried out?

A

Usually carries on in patient undergoing angiography - in the same procedure

51
Q

Steps of PCI

A

Performed under local anaesthetic

A catheter is inserted into an artery in the wrist or groin and guided into the affected coronary artery using continuous X-ray video

When catheter is in place a wire is guided into the affected coronary artery

Balloon is inflated to widen the artery

52
Q

What is a stent?

A

Metal mesh tube placed around the balloon inflated in the coronary artery

Holds artery open

53
Q

What are the complications of PCI?

A

Thrombosis occurs in 1-2% of the patients

Usually presents as MI, with high mortality

Restenosis occurs in up to 20% of patients

Bleeding in site of entry can lead to haematoma or aneurysm

Use serial x-rays images and dyes to visualise the arteries which causes increased risk of kidney damage

54
Q

What are the symptoms of restenosis?

A

Return of anginal pain

55
Q

What is restenosis?

A

Neointimal hyperplasia

Formation of thrombi

Another blockage = MI

56
Q

What is neointimal hyperplasia?

A

Re-closure of the artery due to proliferation of smooth muscle cells

57
Q

What are ways to prevent restenosis?

A

Coating stents in drugs to prevent complications

Localised amount of anti-clotting drugs

58
Q

What is an example of a drug used in drug-eluting stents?

A

Paclitaxel

Inhibits cell proliferation

PPS - obesity (6 decks)

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