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
