Imaging in Cardiology Flashcards
Limitations of stress ECHO
False negative: single vessel disease. Rapid resolution of symptoms following exercise prior to acquisition of images
False positive: hypertensive response following exercise
Examples of anatomical imaging in cardiology
- CTCA
- Coronary artery scoring
- Coronary angiography - gold standard anatomy test
- Cardiac MRI
Notes on CTCA
Indications
* Uninterpretable or equivocal stress test results in evaluation of chest pain syndrome
* Evaluation of chest pain syndrome w/ intermediate pre-test probability of CAD w/ uninterpretable ECG (e.g. LBBB) or unable to exercise
* Acute CP w/ intermediate pre-test probability of CAD w/ no ECG changes and serial enzymes negative
- Very high sensitivity and specificity for coronary artery stenosis
- Very high negative predictive value - if normal/negative - very high confidence no CAD
- PPV lower - if coronary artery stenosis identified - exact degree of stenosis may not correlate with an invasive angiogram
- Calcium plaques can cause excessive blooming artefact -> false positive result
- Can be used to rule out aortic dissection or PE
- Appropriate for assessing CABG graft patency (100% sensitivity)
- Not so sensitive for native coronary arteries - or arteries stented with stent < 3mm in diameter
Notes on coronary artery scoring
- Different to CTCA. Non-contrast
- All calcified plaques taken into accound -> measure of total atherosclerotic burden
Consider in
* Asymptomatic patients, 45-75 years with intermediate CVS risk (10-20% FRS)
* Possible role in same age group with lower risk if diabetic, strong family history premature CHD, or indigenous patients
When to avoid
* Very low risk (< 5%)
* High risk - doesn’t change management
* Symptomatic or previously documented cad
Scores and risk of cardiac events/death at 10 years
* 0 = < 1%
* 1-100 - low risk < 10%
* 101-400 = 299 intermediate, 10-20% ( start aspirin and statin)
* 101-400 nd >76th centile = moderately high, 15-20%
* >400 = high risk >20%
Notes on Cardiac MRI
- Superior to CT in imaging myocardium - but not coronary arteries
- Delayed gadolinium enhancement = scar tissue/infarcted - more than 50% thickness enhancement unlikely myocardium is viable - may not benefit from suregry or coronary stenting
- Scar imaging - MRI superior to SPECT
- **Gold standard for diagnosis of LV thrombus
- **Generally not used for screening due to cost and availability, TTE preferred in 1st instance
- TOE good at visualising posterior cardiac structures, it is not good at assessing ventricular apices
Options for functional imaging in Cardiology
- Invasive fractional flow reserve
- Stress ECG
- Stress ECHO
Notes on Invasive Fractional Flow Reserve
- Gold standard functional imaging test
- Invasive coronary angiogram - pressure wire to detect fractional flow reserve
- < 0.8 = functionally significant stenosis that will result in ischaemia
Notes on Stress ECG
- Original method of functional assessment
- Myocardial ischaemia = stress induced ST segment changes
- Sensitivity 68%, specificity 77%
Notes on Stress ECHO
Pre-stress ECHO: assess LVEF, diastology, valves, wall motion
Stress ECG: ECG changes, symptoms, haemodynamics, exercise capacity, arrhythmias
Post stress: wall motion, diastologies, RVSP
Myocardial ischaemia defined as:
* Exercise induced ST segement changes +/- exercise induced wall motion abnormalities - more sensitive and specific than stress ECG as wall motion abnormalities precede ECG changes
* Cascade -> ischaemia, diastolic dysfunction, regional systolic dysfunction (RWMA), ECG changes, chest pain
Wall motion analysis during exercise, % wall thickening
○ >50% = normal
○ <50% = hypokinetic
○ < 10% = akinetic
○ Dyskinetic = opposite direction
Calculation of ejection fraction
Stroke volume/LV end diastolic volume
Stroke volume = LV end diastolic volume - LV end systolic volume
Notes on speckle tracking and global longitudinal strain
Assessment of strain using speckles - how much movement of speckles towards apex in systole, the less movement -> LV failure
Global longitudinal strain - the more negative the more normal
- Note bullseye pattern i.e. apical sparing pattern -> think cardiac amyloid
- If infiltrative disease suspected -> need Cardiac MRI
Features of amyloid on cardiac MRI
- Increased native T1 mapping
- Increased extracellular volume
- Abnormal gadolinium kinetics
- Widespread late gadolinium enhancement
Notes on cardiac involvement in amyloidosis
- Two most prevalent forms:
1. Light chain immunoglobulin (AL)
2. Transthyretin (ATTR) amyloidosis - includes wild type (> 90%) and the hereditary or variant type (< 10%) cases
Treatment
* Maintainence of euvolaemia - loop diuretic, possibly MRA
* Usual HFreF meds may be poorly tolerated due to hypotension
* Avoid CCBs
When to investigate for cardiac amyloid
Heart failure and wall thickness >12mm
AND
Age > 65 years OR red flag
Red flags
* Polyneuropathy
* Dysautonomia
* Skin bruising
* Macroglossia
* Deafness
* Bilateral carpal tunnel
* Ruptured biceps tendon
* Lumbar spinal stenosis
* Vitreous deposits
* Family history
* Renal insufficiency/proteinuria
Notes on bone scintigriphy in assessment for cardiac amyloid
Notes on assessment of diastolic function in ECHO
- First part of diastole is energy requiring active relaxation - can be impaired with aging, LV hypertrophy, ischaemia
- Second part is passive stretch and can be impaired by contrictive or restrictive process
E/A
See diagram
E = passive filling
A = atrial contraction, no atrial contraction in AF makes measurement tricky in this setting
ECHO criteria for diagnosis of HFpEF
- Structural risk factors - mainly LV hypertrophy
- Evidence of high LA pressure over the longer term
- Evidence of high LA pressure now
Structural abnormalities
* Increased LV wall thickness
* Normal <= 11mm
* Can formally calculate LV mass
* Relative wall thickness
* RWMA
Notes on Bernoulli equation
- Change in pressure across an orifice is proportional to square of velocity of fluid flowing through the orifice
- Does not apply if there is a change in the viscosity of the blood e.g. severe blood loss
Pressure = 4 x velocity squared
To calculate RVSP = RA pressure + TR jet pressure
i.e RA + 4(TR jet velocity squared)
Normal Right Atrial Pressures
* < 5 mmHg = NORMAL
* 5-10 = INTERMEDIATE
* > 10 = HIGH
Contraindications to TOE
Absolute
Esophageal - tumour, stricture, fistula, perforation
Active upper GI bleed
Perforated bowel or bowel obstruction
Unstable cervical spine
Uncooperative patient
Relative contraindications
Barrett’s oesophagus, history of dysphagia (requires GI evaluation first)
Active oesophagitis
High grade eosaphageal varices, active peptic ulcer disease
Neck immobility
Severe coagulopathy or thrombocytopaenia
Severe hiatus hernia
Prior neck or chest radiation
Prior GI surgery
Esophageal diverticulum
Loose teeth
Indications for TOE
Most common
* Lip injury
* Hoarseness
* Dysphagia - 1.8%
Very uncommon
Major bleeding, esophageal perforation, bronchospasm, laryngospasm, minor pharngeal bleeding, dentla injury, heart failure, arrhythmia
Indications for TOE
- Infective endocarditis
- Pre-cardioversion/ablation of AF/A flutter
- Cardiac source of embolus
- Suspected acute aortic syndrome e.g. aortic dissection
- Non diagnostic TTE
- Pre and intra cardiac surgical assessment
- Percutaneous structural cardiac procedures - TAVI, MitraClip, left atrial appendage occlusion
Echo finding in infective endocarditis
1. Vegetations
* Mobility independent of valve motion, echogenic density, lobulated, located upstream side of valve, in path of jet or on prosthetic material
2. Abscess
* Echodense or lucent sapce, usually adjacent to valve annulus
* Aortic > mitral
3. New dehiscence of prosthetic valve
* Rocking motion > 15 degress in any noe plane
* Associated with perivalvular regurgitation
Limitations of TOE in assessment for infective endocarditis
- Suboptimal visualisation or aortic prosthetic valves due to reflective properties
- Poor visulation of anterior aortic root due to acoustic shadow
Mimickers of vegetations of ECHO
- Fibroelastoma on aortic valve
- Lambl’s excresence
- Calcific valvular degenerative changes
- Thrombi
- Myxomatous valves
- Redundant/ruptured chordae
- False tendon
- Chiari network
- Non-infective vegetations - Libman-Sacks endocarditis
Notes on role of ECHO in acute aortic syndrome
TOE findings
* Aortic dissection - intimal flap, tear site
* Involvement of valves/coronary arteries -> aortic regurgitations, RWMAs
* Peripcardial effusion
* Sensitivity 98%, specificity 63-96%
* TTE sensitivity 78- 90%
How to distinguish between constrictive pericarditis (e.g. TB) vs restrictive cardiomyopathy (e.g. amyloid)
- Ventricular interdependence in constrictive pericardiditis - deep inspiration causes a rise in RV pressure and a fall in lV pressure
- E’ (relaxation velocity) is low in restrictive, and high in constrictive
Both have raised right atrial pressures, and low voltage complexes on ECG
