B P3 C18 Nuclear Cardiology Flashcards
Advantages of PET
High spatial and contrast resolution
Capability for tomographic dynamic imaging with high temporal resolution
Accurate and depth-independent attenuation correction
High count sensitivity, making possible rapid protocols
Low radiation dose protocols (due to short half-life of the PET tracers)
Quantitation of absolute radiotracer concentration in tissue, including myocardial blood flow
CT hybrid imaging for quantification of atherosclerotic burden and localizing hot spot imaging tracers
Availability of a wide array of molecularly targeted clinical and research radiotracers that can image molecular processes in the pico and nano molar concentrations
Indications for Cardiac Positron Emission Tomography Myocardial Perfusion Imaging and Myocardial Blood Flow Measurements
Rest-stress myocardial perfusion PET is a first-line preferred test for patients with known or suspected CAD who meet appropriate criteria for a stress imaging test and are unable to complete a diagnostic-level exercise stress imaging study
Indications for Cardiac Positron Emission Tomography Myocardial Perfusion Imaging and Myocardial Blood Flow Measurements
Rest-stress myocardial perfusion PET is recommended for patients with suspected active CAD, who meet appropriate use criteria for a stress imaging test, and who also meet one or more of the following criteria:
• Prior stress imaging study that is of poor quality, equivocal or inconclusive, affected by attenuation artifact, or discordant with clinical impressions or other diagnostic test results including findings at coronary angiography
• Body characteristics that commonly affect image quality such as large breasts, breast implants, obesity, etc.
• High-risk patients in whom diagnostic error carries even greater clinical implications, such as chronic kidney disease stages 3, 4, or 5; diabetes mellitus; and high-risk CAD
• Young patients with established CAD who are expected to need repeated exposures to radiation associated cardiac procedures
• Patients in whom myocardial blood flow quantitation is needed
• Patients without known CAD who present with symptoms suspicious for myocardial ischemia
• Increased suspicion of multivessel CAD
• Suspected heart transplant vasculopathy
• Patients with known CAD in whom more specific physiologic assessment is desired
A low-dose, noncontrast, ungated free tidal b ing scan of the chest.
Attenuation correction CT
A noncontrast, prospectively gated CT scan for dose reduction, acquired during an inspiratory breath-hold
Calcium score CT
Plays a major diagnostic role, particularly in the evaluation of patients without prior known coronary artery disease (CAD) and with normal MPI
Calcium score
Radionuclide imaging has limited anatomic resolution and hybrid CT imaging (without or with iodinated CT contrast) provides localization of the tracer uptake, which is helpful in hot spot imaging:
________________ for amyloidosis
________________ for sarcoidosis or infection imaging
99m Tc-pyrophosphate
2-deoxy-2-[18 F] fluoro-D-glucose [18 F-FDG]
There are four common modes of image acquisition with SPECT or PET:
List mode, static, ECG gated, or dynamic
____________ allow assessment of regional wall motion and quantification of left ventricular (LV) volumes and EF
ECG-gated images
___________ allows tracking of radiotracer transit through the blood vessels and the heart starting with the time of radiotracer injection
Myocardial blood flow estimates can be derived by this approach
Dynamic imaging
This can be performed at rest and during peak pharmacologic stress to compute rest and stress myocardial blood flow, respectively.
The ratio of stress to rest myocardial blood flow is termed ________________
Myocardial flow reserve (MFR)
Dynamic imaging for myocardial blood flow quantitation requires pharmacologic stress testing with _____________ (preferred) or dobutamine.
Vasodilators
An ideal radiotracer for MPI should be extracted by the myocardium at a rate that is ____________
Linearly related to myocardial blood flow
Most SPECT and PET perfusion radiotracers demonstrate ____________, as in the resting state, or when there is significant obstructive CAD with a reduction in stress myocardial blood flow.
Linear extraction at relatively low blood flow rates
As myocardial blood flow increases with exercise or pharmacologic stress, radiotracer extraction falls off and, consequently, myocardial blood flow is underestimated.
Accuracy can be increased by using radiotracers with greater extraction at high flow rates; this is particularly important for the evaluation of nonobstructive CAD, diffuse CAD, or microvascular dysfunction.
FDA-approved SPECT myocardial perfusion tracers
99mTc-sestamibi
99mTc-tetrofosmin
201thalium
99mTc is produced by a 99mmolybdenum generator and then compounded into 99mTc-sestamibi or 99mTc-tetrofosmin; have a half-life of ___________
6 hours
99mTc perfusion tracers passively diffuse into cardiomyocytes at rates proportional to blood flow and bind to the mitochondria within the first _________ after injection.
60 to 90 seconds
Mechanism of uptake of
99mTc-sestamibi
99mTc-tetrofosmin
Mitochondrial uptake
201thallium is produced by a cyclotron, emits lower energy photons (80 keV), and has a half-life of ___________.
73 hours
201Thallium circulates to the heart at a rate proportional to blood flow and enters the cardiomyocytes via the ____________
Na+/K +ATPase pump
Early perfusion defects on 201thallium images represent _____________ from ischemia or scar.
Perfusion defects may resolve over time because of redistribution of 201 thallium in ischemic and hibernating regions; therefore poststress 201thallium images are obtained ______________ after injection
Reduced blood flow
Within 10 to 15 minutes
Because of its long half-life and relatively low photon energy, 201 thallium imaging is associated with a ________________
For this reason, it is currently not recommended for _____________; instead, it is used for ________________ at sites without access to other viability tests
Higher radiation dose
Perfusion imaging
Viability assessment
Highest extraction ratio among spect tracers
201Thallium - 85% (lowest photon energey 69-81 keV)
Sestamubi - 65% (140 keV)
Tetrofosmin - 60% (140 keV)
FDA-approved PET perfusion tracers
82Rubidium
13N-ammonia
Monovalent cation that enters the cardiomyocyte via the Na+/K +ATPase pump
82Rubidium
Half life of Rubidium
76 seconds
What is not feasible because of the short half life of Rubidium?
Exercise stress imaging is not feasible
Other considerations due to short half life:
(1) it is produced from a 82 strontium/82 rubidium generator housed in an infusion cart next to the PET scanner
(3) rapid sequential imaging is possible
Enters the cardiomyocytes passively where it is c verted into 13N-glutamine and trapped in the glutamate pool.
13N-ammonia
Half life of N-ammonia
9.96 minutes
Advantage of N-ammonia’s its short (9.96 minutes) half-life:
Exercise PET is feasible
Other considerations:
(1) an on-site cyclotron is required
(3) lower injected doses are administered
Exercise PET does not allow for quantitation of ________________, which is an important advantage of PET MPI.
Myocardial blood flow
During treadmill exercise stress, radiotracer injection occurs outside the PET gantry. Postexercise myocardial blood flow quantification is not feasible because of the lack of an arterial input function.
The superior extraction characteristics of PET tracers, compared with SPECT perfusion tracers, makes them more suitable for ___________
Quantifying myocardial blood flow
Highest extraction fraction among PET MPI tracers
15Oxygen-water - 100% (not approved by FDA in the US)
13N-ammonia - 75%
82 Rubidium(82Rb) - 55% (only generator as source, others cyclotron)
The only clinically available FDA approved tracer to image myocardial metabolism is ______
18F-FDG
Glucose analog used to image myocardial glucose metabolism.
18F-FDG
The primary clinical applications of cardiac 18F-FDG PET are for
Imaging myocardial viability
Myocardial and vascular inflammation
Infective endocarditis
18F-FDG enters the cardiomyocytes through glucose transporters ( ______ and ______ ), where it is phosphorylated by the enzyme hexokinase and trapped as 18F-FDG-6-phosphate.
GLUT 1 and 4
Unlike glucose-6-phosphate, 18 F-FDG-6-phosphate cannot be metabolized.
Insulin, ischemia, and hypoxia induce translocation of glucose transporters to the plasma membrane and increase myocyte glucose uptake
Cells which preferentially uses glucose for their metabolic needs independent of insulin
Ischemic and hypoxic cells
Malignant and inflammatory cells
Dietary preparation to switch myocardial metabolism to glucose or fatty acids forms the basis for the use18 F-FDG to image _____________ (glucose load with IV insulin) and cardiovascular inflammatory conditions (low-carbohydrate, high-fat diet followed by prolonged fasting) such as ________, _________, __________
Myocardial viability
Sarcoidosis, infective endocarditis, and vasculitis
The heart extracts oxygen nearly maximally at rest (__________)
60% to 80%
With exercise stress (or dobutamine infusion) there is a severalfold increase in oxygen demand from high heart rate, contractility, and ventricular work that is met physiologically by increased blood supply from _____________
Metabolic vasodilation
Normal coronary arteries have a coronary blood flow at rest of _________, which can increase three- to fivefold during maximal vasodilation.
0.7 to 1 mL/min
Coronary blood flow remains constant over a wide range of coronary perfusion pressures through dynamic changes in tone in arterioles and other resistance vessels, and it only falls in the presence of very severe upstream coronary stenosis ( _______ luminal narrowing)
> 90%
Augmentation of myocardial blood flow in response to exercise/vasodilator stress is __________ and forms the basis for the use of stress radionuclide MPI for detection of obstructive CAD.
Progressively blunted with increasing severity of upstream coronary stenosis
Earliest event in the ischemic cascade
Reduced regional myocardial perfusion
In contrast to exercise stress, vasodilator stress does not ____________
Increase oxygen demand
The diseased and nondiseased territories manifest differential hyperemic responses due to ___________.
Differences in resting microvascular dilation
In myocardial territories supplied by coronary arteries with critical stenosis (>90%), where the microvasculature is maximally vasodilated at rest, vasodilation of the epicardial coronaries by vasodilator stress agents can redistribute flow away from the subendocardium causing _________, which can often manifest as ischemic ST depression during vasodilator stress testing.
Coronary steal
If there is severe multivessel obstructive CAD and coronary blood flow is reduced in all vascular territories, this can result in an apparently normal appearing relative myocardial perfusion image with no perfusion defects, also known as _________
Balanced ischemia
____________ safe and is the preferred mode of stress in conjunction with radionuclide MPI.
Stress testing using exercise stress with treadmill or bicycle
Preferred as it is physiologic, providing information on symptoms, functional capacity, and hemodynamic and ECG changes with stress.
The most widely used protocol in exercise testing
Standard Bruce treadmill exercise
______________ provides an excellent alternative if exercise stress is not feasible (orthopedic or other limitations), contraindicated (recent acute coronary syndrome [ACS], or recent deep vein thrombosis, very large aortic aneurysm, etc.), or if patients are unable to exercise maximally.
Pharmacologic stress testing
To evaluate anginal symptoms on maximal medical therapy in patients with known prior CAD, a ___________ irrespective of heart rate is often adequate if a reasonable workload of at least 5 metabolic equivalents (METS) is achieved.
Symptom-limited stress test
To evaluate anginal symptoms in patients without documented prior CAD, _____________ is desirable with exercise stress.
If not, the radiotracer is not administered, and stress test is converted to a vasodilator stress.
In those instances, ____________, a non–weight-based fixed dose stress agent is well suited for administration on the treadmill or soon after termination of exercise.
Maximal heart rate response
Regadenoson
____________ preferred stress modality for radionuclide MPI (SPECT and PET) in patients who are unable to exercise adequately, and for evaluation of residual ischemia in patients with recent ACS/myocardial infarction (MI)
Pharmacologic stress testing
The three most commonly used vasodilator stress agents
Adenosine, dipyridamole, and regadenoson
Binds to four types of adenosine receptors.
Effects after binding to the receptors
A2A
A1
A2B
A3
Adenosine
A2A - coronary vasodilation
A1- heart block
A2B - wheezing
A3 - peripheral vasodilation
Causes coronary vasodilation by increasing endogenous adenosine levels.
Dipyridamole
A specific A 2Areceptor agonist
Regadenoson
Contraindications to vasodilator agents
Active wheezing
High-grade atrioventricular (AV) block without a functioning pacemaker
Systolic blood pressure (BP) <90 mm Hg
Any contraindications for stress testing (acute MI, unstable angina, aortic dissection, acute pulmonary embolism).
Regadenoson stress testing is associated with __________
Seizures
Contraindicated in patients with a history of seizures that are not well controlled or in those with structural brain injury
Doses of vasodilator agents
Adenosine
Dipyridamole
Regadenoson
Adenosine - 140 mcg/kg/min x 4mins
Dipyridamole - 0.56 mg/kg x 4 minutes
Regadenoson - 0.4 mg/5 mL prefilled solution administered as a rapid bolus over 10 seconds (fixed dose)
Vasodilator stress agents often cause symptoms of hyperemia in about 50% of patients including
Urge to breathe deeply
Chest tightness
Headache, flushing
10 to 20 beat increase in heart rate
10-mm Hg decrease in systolic BP.
What improves improves symptoms and reduces heart block during vasodilator testing
Exercise, including swinging the legs on the side of the bed, hand grip exercise, or low-level treadmill exercise
Unlike exercise, which shunts blood to the exercising muscles, vasodilator agents cause ____________ and intense radiotracer uptake in the liver that may scatter into the inferior wall of the left ventricle;
Splanchnic hyperemia
Competitive agonists of the adenosine receptors and can reverse the vasodilatory effects of adenosine, dipyridamole, and regadenoson
They need to be held for at least _______ before vasodilator stress
Methylxanthines
12 hours
used as an antidote for side effects of vasodilator stress agents
IV Aminophylline (1 to 2 mg/kg slow push over 1 to 2 minutes)
Vasodilator stress has been shown to be safe for evaluation of myocardial ischemia within _______ after presentation with ACS or uncomplicated MI.
24 to 48 hours
Administered as a weight-based graded infusion starting at 10 mcg/kg/min and escalating every 3 minutes by 10 mcg/ kg/min to a maximum of 40 mcg/kg/min.
Dobutamine
When vasodilators are contraindicated or cannot be used because of caffeine intake, dobutamine stress testing is used.
The infusion is terminated 1 minute after injection of the radiotracer.
If target heart rate is not achieved, ________ is administered as 0.5 mg IV followed by increments of 0.25 mg IV to a maximum of 2 mg IV
Atropine
Dobutamine plus atropine stress testing with maximal heart rate response has been shown to increase myocardial blood flow equivalently to vasodilator stress.
Atropine is contraindicated in patients with angle closure glaucoma and prostatism.
Tracers for evaluation of Amyloidosis
99mTc-pyrophosphate,
3,3-diphosphono-1,2-propanodicarboxylic acid (DPD)
Hydroxymethylene diphosphonate (HMDP)
_________ are the mostly widely used protocols
Stress first and single-day rest followed by stress MPI
In a _____________, stress MPI is performed first and only followed by rest imaging when stress images are abnormal.
This protocol is preferred for patients without prior CAD because it is most efficient and associated with the lowest radiation dose to the patient.
Stress-first protocol
this protocol is most effective with attenuation correction and advanced scanners.
Most patients referred for SPECT MPI are candidates for stress-first imaging, except for patients with
Documented prior MI
Those needing viability assessment
Those presenting with ACS who may benefit from rest and stress imaging.
For ___________, the low rest radiotracer dose (4 to 8 mCi) is typically followed by a larger stress radiotracer dose (12 to 25 mCi, approximately three times the initial dose) to overcome the shine through of the first injection.
Single-day 99m Tc-rest-first MPI
____________ provide the lowest possible radiation dose and optimal image quality because there is no shine through of rest radiotracer activity.
Two-day protocols
SPECT and PET perfusion tracers are administered intravenously and extracted by cardiomyocytes _________ after injection
within 60 to 90 seconds
Therefore it is important to maintain maximal stress (exercise or vasodilator) for at least 1 minute after injection of the radiotracer
SPECT MPI scans are typically acquired _________ after stress radiotracer injection
15 to 45 minutes
Hence, most patients with reversible perfusion defects do not demonstrate regional wall motion abnormalities on the gated SPECT studies, unless ischemia is severe leading to postischemic stunning
In contrast, PET MPI-gated images are obtained ___________ after completion of vasodilator stress and during peak dobutamine infusion.
Immediately
A _____________ or a ______________ with 82rubidium PET has been shown to be a marker of significant obstructive multivessel CAD
Lack of increase in LVEF with vasodilator stress
Decrease in LVEF post vasodilator stress
For PET, ___________ is performed with82 rubidium or 13N-ammonia
A single-day rest and stress MPI
F-FDG Metabolic Imaging Protocols
Viability
Cardiac sarcoidosis, infection or vasculitis
For viability imaging, glucose/insulin preparation is necessary. Then, 18 F-FDG (5 to 10 mCi) is administered intravenously and cardiac PET/CT images are acquired 60 minutes later.
For cardiac sarcoidosis, infection, or vasculitis imaging, patients undergo the high-fat/low-carbohydrate dietary preparation. Cardiac and partial or full-body PET/CT images are acquired 90 minutes after IV injection of 18F-FDG.
The perfusion images are reviewed visually and semiquantitatively. Interpretation is performed in a segmental fashion using a 17-segment heart model and a 0 to 4 scale (where each of the 17 segments are scored using 0 = normal, 1 = mild, 2 = moderate, 3 = severe, and 4 = absent tracer uptake).
Identify the pattern of myocardial perfusion
Ischemia
Perfusion - reversible defect
Wall motion - normal or abnormal
Identify the myocardial perfusion images
Fixed defect
Abnormal wall motion
Scar
Pattern of myocardial perfusion and viability
Defect with normal/abnormal wall motion and partial FDG uptake
Nontransmural scar
High risk features in MPI
Large single or multiterritorial fixed and/or reversible myocardial perfusion defects involving >15% of the LV mass
Transient ischemic dilation of the left ventricle
Stress-induced myocardial stunning with a drop in LVEF poststress
Transient RV tracer uptake
Increased pulmonary tracer uptake
High risk features in stress test
Significant (>3 mm) ST-segment depression
Prolonged ST-segment depression
ST depression at low workload
Multilead ST depression
ST-segment elevation (>1 mm)
Hypotension (>10 mm Hg) with exercise
Sustained ventricular tachycardia
Hot-spot images (sarcoidosis, amyloidosis, and infective endocarditis) are quantified using target to background ratio (myocardium to rib uptake in _______ and myocardium to blood activity in ________),
Amyloidosis
Sarcoidosis
The basic principle of radionuclide MPI for detecting CAD is based on the ability of a radiotracer to _________ in a myocardial region subtended by a coronary artery with a flow-limiting stenosis.
Identify a transient regional perfusion deficit
A ________ myocardial perfusion defect is indicative of ischemia, whereas a _________ perfusion defect generally reflects scarred myocardium from prior MI
Reversible
Fixed
Myocardial segments with ________ peak activity of perfusion tracer are considered viable, those with ________ peak activity are considered nonviable, and those with __________ of peak activity are further evaluated for myocardial viability.
> 60%
<40%
40% to 60%
Generally, myocardial perfusion defects during stress develop downstream to a epicardial stenosis with ___________ luminal narrowing and become progressively more severe with increasing degree of stenosis.
≥50% to 70%
It is noteworthy that coronary stenosis of intermediate severity (e.g., 50% to 90%) is associated with significant variability
For any degree of intermediate luminal stenosis, the observed physiologic variability is multifactorial and includes geometric factors of coronary lesions not accounted for by a simple measure of minimal luminal diameter or percentage of stenosis.
These factors include
Shape, eccentricity, and length, which are known to modulate coronary resistance
Collateral blood flow
Presence of diffuse coronary atherosclerosis and microvascular dysfunction.
A recognized limitation of semiquantitative visual assessment of radionuclide myocardial perfusion images with SPECT and PET often uncovers only coronary territories supplied by coronary arteries with the most severe stenosis.
Consequently, it is relatively insensitive to accurately delineate the extent of obstructive angiographic CAD, especially in the setting of __________
Multivessel CAD
A number of studies have demonstrated a relationship between myocardial blood flow and flow reserve and percentage diameter stenosis on angiography; that is, there is a progressive reduction in _________ and _________ with increasing severity of angiographic stenosis
Myocardial blood flow and flow reserve
An MFR ________is associated with a >97% negative predictive value for ruling out high-risk angiographic CAD.
MFR >2.0
The power of radionuclide MPI (including SPECT and PET) for risk stratification is based on the fact that major determinants of prognosis in patients with CAD are readily available from gated MPI. These include
The amount of myocardial scar
The extent and severity of stressinduced ischemia
Gegree of LV dilatation
Reduced LVEF
A normal or low-risk rest/stress radionuclide MPI with SPECT or PET was associated with an annual risk of MACE of ____________ respectively.
0.85% and 0.4%
The absolute quantification of ___________ by PET (an integrated marker of epicardial stenosis, diffuse atherosclerosis, and microvascular dysfunction) is a definite advantage in higher-risk patients
Myocardial blood flow and flow reserve
In such patients, a relatively preserved MFR identifies truly low-risk individuals among high-risk patients
_______ (and the presence of often associated __________) are associated with a greater risk of cardiac death
Fixed perfusion defects
LV dilatation and reduced LV function
Reversible or ischemic defects are more closely associated with the occurrence of ________________
Nonfatal MI
The constellation of ____________, ______________, ____________ represents the highest risk subgroup.
Extensive myocardial scar (fixed defects), LV remodeling, and reduced EF
For any amount of ischemic and/or scarred myocardium, a ______ is associated with a higher risk of death than in the setting of relatively preserved MFR
Severely reduced global MFR
The increased risk of adverse events in patients with reduced MFR (<2.0) also applies to patients with visually normal radionuclide MPI.
In the majority of these patients, the reduced MFR reflects a combination of ________ and _______ and is found frequently in symptomatic men and women without overt obstructive CAD (51% and 54%, respectively).
Diffuse nonobstructive atherosclerosis and CMD
Importantly, the noninvasive PET measure of MFR improves risk reclassification, especially among high-risk cohorts (e.g., patients with diabetes, non-ST elevation MI [NSTEMI], chronic renal impairment, and high coronary calcium scores).
The relative frequency and severity of CMD is similar in women and men, but numerically there is a larger number of _______ with CMD than men.
Women
Because it is a diffuse process, conventional exercise stress testing and stress imaging tests, such as with echocardiography or SPECT imaging, lack sensitivity and specificity for detecting ___________ and thus have a relatively limited role in its diagnosis.
Coronary microvascular dysfunction
Direct interrogation of coronary microvascular function is necessary to establish the diagnosis of CMD.
This is the most accurate and reproducible noninvasive technique in diagnosis of CMD
PET imaging
_____________ reflects the combined effects of altered coronary fluid dynamics caused by diffuse atherosclerosis and microcirculatory dysfunction
Reduction of stress myocardial blood flow and MFR
The combined effects of extensive nonobstructive a sclerosis and CMD increases the clinical risk compared to the risks associated with either one alone.
Give the clinical diagnosis
Myocardial ischemia from nonobstructive atherosclerosis and coronary microvascular dysfunction
Cardiac PET/CT images of a 76-year-old woman with dyslipidemia, hypertension, and nonobstructive angiographic coronary artery disease who presented with atypical chest pain and dyspnea. Vasodilator-stress and rest13 N ammonia PET images demonstrate visually normal myocardial perfusion. The ECG gated images demonstrated a rest left ventricular (LV) ejection fraction of 71% that increased to 73% during stress with normal LV volumes (not shown). The CT transmission scan showed severe coronary artery calcification (lower left). Quantitative stress myocardial blood flow and myocardial flow reserve was moderately reduced in all coronary territories and globally.
Radionuclide MPI is appropriate for Prior PCI/CABG and Recurrent Symptoms
Radionuclide MPI provides __________ that helps with risk prediction and management decisions regarding the potential need for targeted revascularization
Localization and quantification of myocardial ischemia
Among patients with known CAD, both PET and SPECT MPI offer high sensitivity. However, PET has higher specificity compared with SPECT, and consequently higher diagnostic accuracy.
it is important to avoid ___________ in cases of known CAD as this reduces the sensitivity of the test for detection of myocardial ischemia.
Submaximal exercise
In such cases, conversion to vasodilator stress helps avoid nondiagnostic tests.
The addition of quantitative myocardial blood flow information is useful in patients with prior PCI but less so in those with ___________, as they have extensive disease in the native vessels, which can lead to a blunted flow response to vasodilator-stress despite patent grafts.
Prior CABG
__________ was an independent predictor of major arrhythmic events, whereas other perfusion PET variables including ischemic burden, the presence of nontransmural scar/hibernation, peri-infarct ischemia, and MFR were not.
Myocardial scar
Identify the pattern of MPI
Myocardial scar
Mildly dilated left ventricle and a large perfusion defect of severe intensity throughout the inferior and inferolateral and basal anterolateral walls, which was irreversible.
64-year-old man with known chronic total occlusion (CTO) of the LAD coronary artery
Interpret the MPI
Transient left ventricular (LV) dilatation with stress and a large perfusion defect of severe intensity throughout the anteroseptal and anterior walls and LV apex, showing complete reversibility
There is a small but severe perfusion defect involving the basal inferolateral wall, also showing complete reversibility
Consistent with postischemic stunning
The study shows complete viability of the LAD territory with evidence of severe stressischemia, and a small area of moderate stress-induced ischemia in the inferolateral wall.
In patients with congenital heart disease, CMR is suitable to provoke ischemia
False
CMR is also often used to study anatomy, but stress CMR is limited to pharmacologic stress, which is not suitable to provoke ischemia in compressive physiologies.
Exercise stress is preferable in these patients and is feasible with SPECT and with 13N-ammonia PET
Absence of perfusion defects involving a typical coronary artery territory and normal MFR would support a diagnosis of __________
Nonischemic cardiomyopathy
In patients without angina but a history of MI, radionuclide MPI helps define the ___________________, which in turn helps inform patient management
Extent of scarred and viable myocardium and the magnitude of residual stress-induced ischemia
A reversible state of regional contractile dysfunction that can occur after restoration of coronary blood flow following a brief episode of ischemia despite the absence of myocardial necrosis.
Myocardial stunning
Most common form of stunning in patients with chronic LV dysfunction caused by CAD
Chronic coronary stenoses who experience recurrent episodes of ischemia (symptomatic or asymptomatic) in the same territory.
Myocardial stunning is considered a form of ______________, in which reintroduction of oxygen after a period of ischemia induces a transient calcium overload that damages the contractile apparatus
Reperfusion injury
This refers to a state of persistent LV dysfunction associated with chronically reduced blood flow but preserved viability.
Myocardial hibernation
A 74-year-old woman with hypertension, diabetes, and chronic kidney dysfunction who presented with new-onset exertional dyspnea. ECG showed left bundle branch block (LBBB). EF 15%.
Interpret the MPI
Nonischemic cardiomyopathy
PET MPI shows a severely dilated left ventricle and a small septal perfusion defect showing apparent reversibility, likely secondary to LBBB. The ECG-gated images demonstrated an ejection fraction of 15% that rose to 20% during peak stress, and evidence of septal dyssynchrony. Myocardial flow reserve was preserved in all coronary territories.
The evaluation of patients with severe LV dysfunction and angiographic CAD often requires the combination of stress testing to ___________ and metabolic imaging to ________________
Quantify the extent of myocardium at risk
Distinguish viable from nonviable myocardium
SPECT MPI can be used to assess the extent and severity of myocardial ischemia using exercise or pharmacologic stress in combination with 99mTc-labeled radiotracers or 201thallium
For viability assessment, _________ is preferable.
Attenuation-corrected SPECT MPI
One advantage of _________ is that it provides a more accurate assessment of viable myocardium, especially in the setting of severe resting hypoperfusion
A common approach to improve detection of hibernating myocardium is the use of _________ to improve collateral flow at rest and enhance radiotracer uptake in areas of severe hypoperfusion.
201thallium
Nitrates
PET imaging provides a more comprehensive approach for the evaluation of patients with ischemic cardiomyopathy
The advantages of PET include its more accurate quantitative assessment of ischemia and the use of _________ to assess myocardial metabolism and myocardial viability.
18 FFDG
68/M with prior MI presenting with worsening HF symptoms. EF 30%
Interpret the MPI
Ischemic cardiomyopathy
Myocardial perfusion images MPI demonstrate a large and severe perfusion defect throughout the inferior and inferolateral walls, which was irreversible and consistent with prior MI. However, the quantitative myocardial blood flow and flow reserve (MFR) data show blunted augmentation of flow during stress, resulting in a severe reduction in MFR in all three vascular territories.
70-year-old man with progressive dyspnea, hypotension, and new severe biventricular systolic dysfunction with elevated natriuretic peptides
Interpret the MPI
Ischemic cardiomyopathy with hibernating myocardium (LCx and RCA - mismatch) and flow limiting stenosis in LAD
Clinically m ful changes in global LV function can be expected after revascularization only in patients with relatively large areas of hibernating and/or stunned myocardium (_______ of the LV mass)
~ 20%
A protein misfolding disorder in which misfolded proteins deposit in various organs as fibrils causing a diffuse infiltrative cardiomyopathy
Cardiac amyloidosis
The two common forms of a dosis that affect the heart are
Immunoglobulin light chain amyloidosis (AL amyloidosis, a plasma cell dyscrasia)
Transthyretin amyloidosis (wild-type ATTR or hereditary ATTR)
AL amyloidosis is treated with ________
Chemotherapy
Wild-type TTR-CA is treated by TTR stabilization (____________) and for hereditary TTR neuropathy is treated by silencing TTR gene products (_______________)
Tafamidis
Patisiran and Inotersen
Bone avid radiotracers in cardiac amyloidosis has been recognized for almost 40 years, it is now established that such increased uptake is more consistently seen in ________________
ATTR-CA
Exclusion of AL amyloidosis using serum free light chain assay, serum, and urine immunofixation electrophoresis is thus critical to maintain the high specificity of ______________ for ATTR-CA and to ensure timely consideration of chemotherapy if AL amyloidosis is diagnosed.
99m Tc-PYP/ DPD/HMDP scan
Cardiac AL amyloidosis can be diagnosed by ___________
Cardiac ATTR amyloidosis can be diagnosed by ____________
Biopsy or clinical measures
Biopsy or by imaging
Indications for 99mTc-P DPD/HMDP imaging include
Black patients age >60 with HFpEF or LV thickening
Non-Black patients age >60 with HFpEF and LV thickening
Heart failure with unexplained peripheral sensory neuropathy
Known or suspected hereditary ATTR-CA
Follow-up of progressive symptoms in known AL amyloidosis or ATTR-CA
Diagnostic criteria for Cardiac Amyloidosis
Endomyocardial biopsy: documenting amyloid deposits with Congo red positivity and immunohistochemistry or mass spectrometry typing of fibril
Extracardiac biopsy: documenting amyloid deposits with Congo red positivity and immunohistochemistry or mass spectrometry typing of fibril AND
Cardiac AL or ATTR amyloidosis can be diagnosed by typical imaging features* (echo wall thickness >12 mm, late gadolinium enhancement, or expanded extracellular volume >0.40) OR
Cardiac AL amyloidosis can be diagnosed by elevated cardiac biomarkers* (age-adjusted NT proBNP or troponin T)
Clinical diagnosis of Cardiac Amyloidosis:
Cardiac ATTR amyloidosis can be diagnosed by ____________ in patients with typical imaging features* and without a plasma cell dyscrasia (normal serum free light chain assay as well as serum and urine immunofixation electrophoresis).
Endomyocardial biopsy or a strongly positive bone-avid cardiac scintigraphy (PYP/DPD/HMDP)
99mTc-PYP/DPD/HMDP images are typically interpreted visually comparing radiotracer uptake in myocardium in relation to that in the ________
Ribs
Bone-avid scintigraphy can detect early amyloid deposition in the heart before increase in myocardial wall thickening,
A granulomatous disorder of unknown etiology that effects multiple organs and cardiac involvement is present in approximately 20% to 25% of patients
Sarcoidosis
Focal noncaseating granulomas with m ated giant cells and macrophages formed as a result T cell-mediated immune response to an unknown trigger.
Sarcoidosis
______ has a low yield because of frequent sampling errors given the focal nature of the cardiac sarcoidosis most frequently affecting the left ventricle
RV endomyocardial biopsy
_______ is typically the first test when cardiac s coidosis is suspected with specific features that may suggest sarcoidosis
CMR
However, the presence of late gadolinium enhancement does not differentiate fibrosis from active inflammation, and T2-weighted edema signal is insensitive to diagnose active cardiac sarcoidosis
The only clinical test to image myocardial inflammation
F-FDG PET
18 F-FDG PET imaging has a significant advantage over endomyocardial biopsy in identifying cardiac and systemic involvement, identifying extracardiac sites for biopsy, and facilitating the evaluation of response to anti-inflammatory therapy
________ is necessary, when CMR unavailable, contraindicated, or inconclusive; and even when CMR is positive,to guide the potential need of anti-inflammatory therapy
F-FDG PET
18 F-FDG PET uptake in the heart, however, is not specific for sarcoidosis and can represent normal myocardium, inflamed myocardium, malignancy, or hibernating myocardium. Hence the 18 F-FDG PET scan is performed with a special diet of ________ for 24 hours before the test followed by prolonged fasting of at least 12 hours.
Low-carbohydrate and high-fat meals
18F-FDG PET and cardiac CTA are emerging as important adjuncts to echocardiography to identify ________
Complications of endocarditis, prosthetic valve/device infection, and systemic embolization
18F-FDG PET is also a useful method to image response to therapy in patients in whom ______________ (e.g., conduits or descending aortic stents)
Removal of the infected prosthetic material is not feasible
The presence of _______ (as opposed to diffuse) and intense radiotracer uptake is consistent with infection.
Focal
_____________ is the test of choice to ascertain the presence of inflammation in large-vessel vasculitis
18F-FDG PET/CT
F-FDG PET/CT can guide the most appropriate site of biopsy, identify disease at an inflammatory stage where it may be more amenable to therapy, and can quantify the extent and severity of inflammation that is useful in the evaluation of response to anti-inflammatory therapy.
Typically, 18 F-FDG PET/CT is used in conjunction with ___________ to evaluate the anatomic abnormalities from the vasculitis.
MRA or CTA
In conjunction with magnetic resonance imaging (MRI) images, give the vasculitis pattern of a PET uptake > liver uptake and abnormal MRI
Inflammatory (PET uptake > liver uptake and abnormal MRI)
Other patterns:
Normal (both MRI and PET normal)
Fibrous (abnormal MRI, but PET uptake ≤ liver uptake)
Patients at increased risk for ventricular dysfunction and heart failure include
Those Receiving high-dose anthracycline therapy (e.g., doxorubicin ≥ 250 mg/m2 )
Those receiving concomitant high-dose radiation therapy (≥30 Gy) with the heart is in the treatment field
Those receiving lower-dose anthracycline therapy in combination with lower-dose radiation therapy where the heart is in the field
Those receiving lowerdose anthracycline or trastuzumab therapy alone and have any of the following risk factors including ≥2 cardiovascular risk factors
Age ≥60
Known cardiovascular disease
Those receiving treatment with lower-dose anthracycline followed by trasutuzmab
Discontinuation of doxorubicin is recommended if there is an absolute decrease in LVEF of ______ from baseline to ______.
≥10%
≤50%
