Investigations

Question 1

Principles of Echocardiography

Answer 1

-Uses ultrasound to image cardiac structures
-Sound waves generated by the transducer
-Reflected waves detected and used to generate images
-Degree of reflection is dependent on a tissues: Acoustic Impedance
==Soft tissues (lung) = low impedance, dark
==Dense tissues (bone) = high impedance so reflects more sound waves, bright

Question 2

Types of ECHO

Answer 2

-Transthoracic
=safe and versatile
=image acquisition and quality of image reduced in increased body habitus, chest wall deformities/ hyperinflated lungs

-Transoesophageal (TOE)
= improved image quality as proximity, useful for assessing valve disease and endocarditis, better image of LA appendage and pulmonary veins
= risk of oropharyngeal & oesophageal injury as invasive, risk of sedation

-Stress echo (transthoracic before and after heart stressed):
= Assessment of myocardial perfusion (change in contraction), coronary territory of disease
= Change in contraction of myocardium “stressed” using exercise or dobutamine

Question 3

What can you see on a transthoracic echo?

Answer 3

-Basic views: parasternal, apical, subcostal, suprasternal
-4 chambers
-4 valves
-Pericardium and myocardium
-Aortic root and arch
-Inferior vena cava

Question 4

Common indications for ECHO

Answer 4

-Heart Failure
-Valve Disease
-Coronary Artery Disease/ Ischaemic HD
-Emergency echo

Question 5

What is assessed in echo heart failure?

Answer 5

-Heart function
=LV and RV function
=Ventricular size
=Thickness of myocardium
=Regional vs global impairment
=Identify cause of HF

Question 6

How is LV systolic function defined?

Answer 6

-Ejection fraction= percentage of blood pumped out of the LV each heart beat

-Normal: >-55%
-Mild HF: 45-54%
-Moderate: 36-44%
-Severe: <-35%

Question 7

How is ECHO used in ischaemic heart disease?

Answer 7

-Can identify areas of infarction (wall motion abnormalities)

-Regional myocardial contraction
=Normal: Normokinetic
=Impaired contraction: Hypokinetic
=No contraction: Akinetic

-Identify complications post ACS
=e.g. LV failure, papillary muscle rupture

Question 8

How is ECHO used in valve disease?

Answer 8

-Identify mechanism and severity
=e.g. calcification (bright), rheumatic, infective endocarditis (vegetation)

-Severe Aortic Stenosis
=Max velocity: Vmax >4m/s (Doppler)
=Valve Area: <1.0cm2

-Severe Mitral Regurgitation
=Jet area >40% LA
=Regurgitant volume >60ml

Question 9

How is ECHO used in emergency ECHO?

Answer 9

-Cardiac Tamponade
=Pericardial effusion
=Intrapericardial pressures> intracardiac pressures (less pressure on right)
=RA/RV collapse (impaired filling, decreased CO, haemodynamic compromise)
=Guiding pericardiocentesis

-Aortic Dissection (CT preferred)
=Dissection flap

-Large pulmonary embolism (CT preferred)
=RV dilation, raised pulmonary pressures

Question 10

Main reason for stress testing?

Answer 10

-Typical angina is diagnosed when someone has all three of the following:
=Central crushing chest pain
=Brought on by exertion
=Relieved with rest or nitrates

-Patients are not always clear on whether their pain is exertion driven.

-Exercise stress testing is an inexpensive, non-invasive and safe way to determine the exertional component of an individuals chest pain.

Question 11

Other reasons for exercise/ stress testing

Answer 11

-Risk stratification after myocardial infarction or hypertrophic cardiomyopathy
-Evaluation of revascularisation or drug treatment
-Evaluation of exercise tolerance and cardiac function
-Assessment of cardiopulmonary function in patients with dilated cardiomyopathy or heart failure
-Assessment of treatment for arrhythmia

Question 12

Sensitivity and specificity of exercise stress testing in chest pain (how useful)

Answer 12

-Sensitivity (i.e. correctly identifies patients with a disease) 39%.
-Specificity (i.e. correctly identifies patients who do not have the disease) 91%!!!
-Abnormal results associated with a nearly 15 fold increase in coronary revascularization and 3 fold increase in fatal or nonfatal myocardial infarction.

Question 13

Describe the Bruce Protocol

Answer 13

-Stage 1 (1.7mph, 10% elevation)
-Stage 2 (low intensity, 2.5mph, 12%)
-Stage 3 (moderate, 3.4mph, 14%)
-Stage 4 (max, 4.2mph, 16%)

-Depends on patient (deconditioning= alternative protocol)

Question 14

How is exercise/ stress testing carried out?

Answer 14

-Patient is first connected to the exercise ECG machine and resting ECGs sitting and standing taken.
-During the test the ECG machine provides a continuous of heart activity and 12 lead ECGs are recorded intermittently.
-Blood pressure recordings are taken before and at the end of each exercise stage. Blood pressure should RISE as exercise increases.

Question 15

Describe normal ECG changes during exercise

Answer 15

-P wave increases in height
-R wave decreases in height
-J point becomes depressed
-ST segment becomes sharply upsloping
-Q-T interval shortens
-T wave decreases in height

Question 16

What represents abnormal (myocardial ischaemia) ECG?

Answer 16

-PR segment= isoelectric baseline
-Changes in ST segment >/=1mm is significant (1 small box)

Question 17

How to measure down sloping ST depression

Answer 17

-Identify the J point (where QRS ends and ST segments begin)
-Measure 80ms (2 small squares) after J point

Question 18

Additional information that can be gained from exercise stress test

Answer 18

-Exercise capacity (additional prognostic value)
-Heart rate response to exercise
-Blood pressure response to exertion

Question 19

Exercise stress test vs pharmacological stress test

Answer 19

-Exercise
=gradually increasing exercise load to achieve maximal HR
-Safe (incidence death/MI 0.01%, dangerous arrhythmia 0.02%)

-Pharmacological
=Medications (dobutamine/adenosine) given intravenously to achieve maximal HR
=Used in those unable to exercise as physical disability/ mobility issues
=Relatively safe, higher risk

Question 20

Calculate maximal HR

Answer 20

Age-220
-Satisfactory HR achieved on reaching 85% of maximal

Question 21

Contraindications of exercise stress testing

Answer 21

-Acute myocardial infarction (within 4-6 days)
-Unstable angina (rest pain in previous 48 hours)
-Uncontrolled heart failure
-Acute myocarditis or pericarditis
-Acute systemic infection
-Deep vein thrombosis
-Uncontrolled malignant hypertension
-Severe aortic stenosis

Question 22

Situations in which exercise ECG can be difficult to interpret

Answer 22

-If the resting ECG has pre-existing ST abnormalities
=Left ventricular hypertrophy
=Left bundle branch block
=Drugs such as digoxin

-In those with atrial arrhythmias (particularly atrial fibrillation)

-Inability to achieve maximal heart rate
=Due to deconditioning
=Due to medications such as beta blockers (if unable to stop)

Question 23

Technical factors of Cardiac CT

Answer 23

-X-ray imaging (ionising radiation) to create isometric 3D dataset of heart
-Requires the use of intravenous iodinated contrast to delineate coronary arteries
-Image acquisition takes place when heart (coronary arteries) most still – DIASTOLE, fast enough for SINGLE BREATH HOLD (eliminates respiratory motion)
-Length of diastole inversely related to heart rate
-Heart rate should be regular and <65 bpm for good quality images (longer diastole so more time to image)

Question 24

Cardiac CT Imaging techniques

Answer 24

-Multiplanar reconstructions= each artery identified and lengthened out to see entire length in one plane
=Rotate around centre of artery to assess for narrowing/ stenosis

-Advanced computational methods calculate flow of blood through each artery with respect to any narrowing present

Question 25

Cardiac CT pathology techniques

Answer 25

-Plaque analysis
=visualise all layers of arteries to examine for atherosclerotic plaques (lipid accumulation= outward expansion/ positive remodelling without encroaching lumen)
=Plaque morphology, low attenuation (darker)= necrosis

-Calcification
=CT can make areas of calcium look larger than they really are (blooming)= overestimate severity of stenosis

Question 26

Pros of Cardiac CT

Answer 26

-Offers excellent assessment of coronary arteries with proper patient selection (rule out obstructive coronary disease)
-Quick (<15 mins)
-First line test for investigation of patients with suspected stable angina (SIGN 151 guideline)
-Improves patient outcome (rate of cardiac death/MI) versus standard care (SCOT-HEART 5 year results)

Question 27

Cons of Cardiac CT

Answer 27

-Ionising radiation (small cancer risk)
-Iodinated contrast (risk of renal failure, allergy)
-Non-diagnostic images in some patients
=Tachycardia / irregular heart rate (cannot be controlled accurately with beta blockers)
=Obesity (higher radiation dose)
=Elderly (lots of calcium which creates artefact)
=Previous coronary stents and extensive vascular calcification

Question 28

How does cardiac MRI work?

Answer 28

-Uses strong magnetic fields and radiofrequency energy to create images of the heart
-Essentially generates signal from water (protons) to make images
-To achieve optimal spatial resolution need to combine data from multiple cardiac cycles – ECG gating mandatory

Question 29

Safety concerns with cardiac MRI

Answer 29

-The magnet is always on
-Ferromagnetic objects will move with great force as they get closer to the isocentre of the scanner

Question 30

Cardiac MRI imaging techniques

Answer 30

-Black blood axial sequences (series of slices cutting down through the chest)
= assess ANATOMY of the great vessels (aorta, pulmonary)
= extra-cardiac incidental findings (liver, spine or breast area)

• Long axis cines (single cardiac cycle)
  =Qualitatively assess LV function
  =REGIONAL variation in contractility (Previous MI wall thinning with lack of wall thickening during systole)
  =Visual assessment of valve function

-Short axis stack (series of equally spaced cuts through the left ventricle)
=Calculate LV and RV volumes and ejection fractions

-Late gadolinium enhancement
=TISSUE CHARACTERISATION (scar or fibrosis=white/ normal heart muscle= black)
=MI= classically subendocardial
=Myocarditis inflammation= sub epicardial late enhancement
=Mid wall patchy late enhancement can be seen in various cardiomyopathies
=Diffuse pattern may be seen in infiltrative cardiomyopathies such as amyloidosis.

Question 31

Cardiac MRI pathology

Answer 31

-Thrombus detection
-Myocarditis
-Infarction

Question 32

Pros of Cardiac MRI

Answer 32

-High spatial resolution
-No ionising radiation
-Tissue characterisation

Question 33

Cons of Cardiac MRI

Answer 33

-Expensive
-Small bore (obesity)
-Long scan time (45-60 mins) with need for breath-holding 15-20 secs (respiratory disease)
-No metal allowed - artefacts
-Cannot detect calcium

Question 34

What is Cardiac MRI useful for?

Answer 34

-Assessing cardiac function when poor image quality on echo
-Accurate volume / ejection fraction measures are required to plan clinical care
-Detailed assessment of right ventricle
-Tissue characterisation (e.g. fibrosis / scarring / infiltration / infarction)
-Abnormal cardiac anatomy (congenital heart disease)
-Troponin rise but normal coronary arteries

Question 35

What is PET?

Answer 35

-Positron Emission Tomography
-Molecular imaging using a radiolabelled isotope (e.g. 18F-fluorodeoxyglucose)- behaves like glucose
=higher in areas of high glucose metabolism (infection/inflammation)
-Co-localise PET activity using anatomical reference imaging (e.g. CT)

Question 36

Major uses of PET in cardiology

Answer 36

-Diagnosis of endocarditis / infection of prosthetic material
-Diagnosis of cardiac sarcoidosis

Question 37

Most common indication for CT cardiac?

Answer 37

Assess for the presence and extent of coronary atherosclerosis in suspected ischaemic HD