Nuclear cardiology methods in routine clinical practice
Lang O., Kamínek M.
Dept Nucl Med, School of Medicine, Praha, Olomouc
Materials for medical students
Nuclear cardiology
Set of non-invasive mostly imaging diagnostic methods of the cardiovascular system
Huge expansion during last 30 years, in Czech rep. during last 10 years
Examination of venous system of lower extremities and lung perfusion are included
Seminar includes
Imaging in nuclear cardiology (NC)NC methodsMyocardial perfusionMyocardial viabilityHeart functionExamination of pulmonary embolismNew trends
Ways of imaging in NC
Detectors of ionizing radiation – gamma camerasSource of radiation inside the patient body -
radiopharmaceutical, tracerWays of distribution - perfusion, metabolic
process, receptors, etc.Source of information - ionizing photon (gamma)Digital images - processing, archiving, transfer
planar, tomographic• SPECT (transversal), PET (coincidence)
Data collection by gamma cameras
PET camera
Way of tomography - SA slices
Other tomographic slices
Parts of left ventricle myocardium
Legenda:
1 - apex
2 - anterior wall
3 - lateral wall
4 - inferior wall
5 – septum
VLA SA
HLA Pollar map
Heart examination
Myocardium imaging perfusion during stress and rest (80%) viability necrosis, innervation, ischemia
Mechanical function assessment steady-state ventriculography (multigated - MUGA) Angiocardiography (first-pass) non-imaging systems
Myocardial perfusionrate of NC examinations
0
2
4
6
8
10
12
num
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CR 1999 EU 1994 EU 1998 USA 1994
Why stress?Pathophysiology of CADHemodynamic effect of coronary stenosesCollateralsIschemic cascade
Rest myocardial perfusion in CAD
Physiological compensatory arteriolar dilatation in the region supplied by narrowed artery
Blood flow remains the same as in the region supplied by normal artery
Radiopharmaceutical distribution remains homogenous
Stress myocardial perfusion in CAD
Arteriolar dilatation in the bed of normal artery for blood flow increase
Blood flow through the normal artery increasesArteriolae in the bed of narrowed artery are
already dilated - no further dilatation can occure, so blood flow remains as in the resting state
Non-homogenous perfusion (radiopharmaceutical distribution) as a result
Ischemic cascade
Type of stress
Mechanical dynamic stress ergometer (bicycle), tread-mill
Pharmacological stress vasodilators - adenosine, dipyridamole positively inotropic drugs - dobutamine,
arbutamine atropine
Combined of all mentioned above
Ergometer
Goal is to achieve at least 85% of maximal heart rate (220-age) or double-product more than 25000
Increase by 50 (25) W after every 3 (2) minutesRate of pedalling 40 to 60 per minuteRadiopharmaceutical injection at peak stress
distribution proportional to blood flow at the time of injection
Maintain this stress for at least 1 to 2 minutesWithdraw betablockers (BB), patient fasting
Dipyridamole stressActs indirectly via the adenosin (block its
removal)Dilates coronary resistant arteries - it makes
possible to assess coronary flow reserveMaximal effect is achieved 3 to 4 minutes after
stopping the 4 minutes infusionIts effect can be stopped with theophyllines
withdraw them before the test
Usually used in patients using BB, unable to exercise, with LBBB
Contraindications to perform dipyridamole stress
Patients with chronic obstructive pulmonary disease treated by theophyllines (dobutamine can be used)
Patients should avoid tee, cofee, cola before the test to prevent false negative results (insuficient or no vasodilation)
Dipyridamole stress
Side effects of dipyridamole
They occures in approximately 30% of patients headache neck tension warm feeling dizziness nausea, hypotension chest pain (very seldom)
Performance of dipy stress
Dipyridamole applied by intravenous infusionUsual dosage is 0.56 (0.75; 0.84) mg/kg Dose is diluted with saline to 50 ml
to prevent local side effects (arm pain)
Duration of infusion is 4 minutes If the patient is unable of any physical stress,
tracer is injected 3-5 min. after stopping infusion
Combined stress
Dipyridamole is infused according to previous rules to sitting or lying patient
3 to 6 min. bicycle stress follows better image quality lower frequency of side effects can be performed even in patients with hypotension
1 to 2 min. before stopping bicycle stress radiopharmaceutical is injected
Test arrangement
Right arm - tourniquet of tonometerLeft arm - infusion through the cannulaSaline is connected after stopping
dipyridamole for venous link for the case of any complication
Patient is sitting on the ergometer, ECG electrodes according to Mason and Likar
Dobutamine stress
If dipyridamole is contraindicatedDobutamine intravenously in the dose of 5 to 10
g/kg/min., increase every 3 min. up to dose of 40 g/kg/min.
Monitore ECG, HR and BP, if 85% of maximal HR is not achieved, add Atropine
Radiopharmaceutical is injected 1 to 2 min. before stopping stress
Contraindications: ventricular tachycardia, severe hypertension, hypertrophic cardiomyopathy
Myocardial perfusion protocols
One-day (Tl, Tc, FDG) - two-days (Tc, FDG, Tl)
Stress - rest or rest - stress (Tc, Tl-Tc)Stress - (redistribution) - reinjection (Tl)Stress - metabolism (Tc - FDG)Stress - rest - metabolism (Tc, FDG)Rest - redistribution - (late redistribution) (Tl)Rest - metabolism (Tc - FDG)
Radiopharmaceuticals for perfusion
Tl-201 chlorid or Tc-99m MIBI for SPECT, N-13H3 or H2O-15 for PETDistribution in the myocardium rely on cells perfusion Tl-201 has redistributionTc-99m MIBI does not have redistribution
Data processing
Quantitative analysis of myocadial perfusion distribution CEqual™ - uses pollar maps for standardization and
comparison with „normals“
Gated (synchronized) tomography (QGSPECT) divides cardiac cycle into 8 periods makes possible to evaluate mechanical function of
the heart (ejection fraction - EF)
Quantification of perfusion
QGSPECT
Basic patterns of myocardial perfusion imaging (MPI)
Normal finding homogenous perfusion during stress as well as rest
Sign of ischemia perfusion defect during stress which disappears on
rest (reversible defect)
Sign of scar perfusion defect on stress and rest (fixed defect)
Sign of ischemia and scar combination of both mentioned above
Main clinical indication of MPI
Detection of ischemic heart diseaseHemodynamic effect of coronary stenosesPrognosis of patients with konwn CADEvaluation of revascularization effect and
detection of restenosisRisk stratification of patients after MIMyocardial viabilityAcute coronary syndromesCardiac risk in non-cardiac surgery
Detection of CAD
66y old pt, atypical chest pain, ECHO difuse wall motion abnormality, Ao+mi reg, sci isch. of inferior wall, EF 40%
Detection of CAD basic parameters
Planar Tl-201 scintigraphy - qualitative evaluatioin
Group of 4.678 pts - sens. 82%, spec. 88% pts without MI - sens. 85% pts after MI - sens. 99% one-vessel disease - sens. 79% two-vessel disease - sens. 88% three vessel disease - sens. 92%
Detection of CAD basic parameters
Referral bias only patients with positive scintigraphy are referred to
coronarography patients with normal scintigraphy are not catheterized higher sensitivity but decline of specificity
Normalcy rate (used instead of specificity) negative scintigraphy in patients with very low pretest
probabilty of CAD based on history, symptoms, stress ECG
Detection of CAD basic parameters
SPECT Tl-201 scintigraphyGroup of 1.527 pts - sens. 90%, spec. 70%
(more false positives due to artefacts), normalcy rate 89% pts without MI - sens. 85% pts after MI - sens. 99% one-vessel disease - sens. 83% two-vessel disease - sens. 93% three-vessel disease - sens. 95%
Detection of CAD basic parameters
SPECT Tl-201 scintigraphyGroup of 704 pts
stenosis of 50 to 70% - sens. 63% stenosis of 75 to 100% - sens. 88%
Dipyridamole stress (1.272 pts) sens. 87% spec. 81%
Detection of CAD basic parameters
SPECT Tl-201 scintigraphyAsymptomatic pts
5.000 coronarograms normal scintigraphy exclude CAD positive scintigrapy has positive predictive
value (PPV) of 50% - does not confirm CAD
Detection of CAD basic parameters
SPECT Tl-201 scintigraphyIndividual arteries (1.200 pts)SPECT is better than planar scintigraphy
(better localisation) LAD - sens. 80%, spec. 83% LCx - sens. 72%, spec. 84% RCA - sens. 83%, spec. 84%
Detection of CAD basic parameters
SPECT Tc-99m MIBI scintigraphySensitivity 87%Specificity 73% (less artefacts using
GSPECT)Normalcy rate 92%Optimal indication for detection of CAD
pretest probability 0.15 to 0.50 + pos. stress ECG pretest probability 0.50 to 0.85
Detection of CAD basic parameters
Difference was not confirmed Tl-201 vs Tc-99m MIBI MIBI vs Myoview physical vs pharmacological stress men vs women
Improvement of accuracy was confirmed SPECT vs planar scintigraphy GSPECT, quantification, prone projection
Pts prognosis
Prognosis of pts with known CADbasic parameters
Good prognosis - normal scintigraphy 2.825 pts without MI
• annual increment of death 0.24%
• annual increment of MI 0.53%
Signs of poor prognosis more perfusion defects in more arterial territories increased uptake in lungs and transient LV dilatation reversible defects, large and severe defects
Pts after revascularizationdetection of culprit lesion
56 y old pt, typical AP, positive stress ECG
SCG arteries stenoses, way of treatmen:
1. CABG RIA, RMS I, III a IV
2. PTCA RMS III a IV
Pts after revascularizationassessment of the result moderate ischemia of the lateral wall, after PTCA LCx: perfusion and wall motion improvement, EF from 56% to 63%, stress ECG positive in both
Pts after revascularizationprognosis
8
2540
90
10
20
30
40
positive negative
yes
no
MPI
Cardiac events
chi - square = 26.76p = 0.00000023RR = 3.15
Pts after revascularizationsummary
Early after the procedure negative scintigraphy - good prognosis positive scintigraphy - no predictive value
Ability of long-term prognosisRestenosis detection
in symptomatic patients in asymptomatic patients with positive stress ECG
Pts after MI
Definition of infarct sizeAssessment of salvaged myocardium thanks
to different ways of therapyEvaluation of myocardial viability in
location of wall motion abnormalityRisk stratification using stress perfusion
scintigraphy
Pts after MIscintigrapnic findings
Group of 55 pts pos 38 (69%), borderline 3 (5%), neg 14 (26%)
Group after QMI (32 pts) pos 23 (72%), borderline 2 (6%), neg 7 (22%)
Group after nQMI (23 pts) pos 15 (65%), borderline 1 (4%), neg 7 (31%)
Group with positive enzymes kinetics (35 pts) pos 25 (71%), borderline 3 (9%), neg 7 (20%)
Pts after MI with positive scintitypes of impairment
Group of 41 pts scar 6 (15%), scar + ischemia 9 (22%), isch 26 (63%)
Group after QMI (25 pts) scar 5 (20%), scar + ischemia 7 (28%), isch 13 (52%)
Group after nQMI (16 pts) scar 1 (6%), scar + ischemia 2 (13%), isch 13 (81%)
Group with positive enzymes kinetics (25 pts) scar 4 (16%), scar + ischemia 8 (32%), isch 13 (52%)
74y old pt, nQIM 9/98, left - scinti before PTCA 2.11.98, then PTCA LAD and OM with stents, right - scinti after PTCA 17.12.98
Pts after MIsummary
High risk pts (shock, failure, persistent AP, previous MI) - coronarography
Without failure with EF < 40% - scintigraphy viability and residual ischemia
Moderate risk - stress scintigraphy conservative vs invasive therapy
Low risk - stress ECG
Myocardial viabilityclinical significance
Important before revascularization prediction of cardiac function improvement (>
25% of myocardium should be viable)
Patients with cardiac failure decline of mortality but increase of cardiac
failure due to CAD nowadays high prevalence of viable myocardium among
pts in waiting list for heart transplantation
Myocardial viabilitycharacteristics
Defined by perfusion, metabolism and functionStunned myocardium
wall motion abnormality but normal perfusion and preserved metabolism
Hibernating myocardium wall motion and perfusion abnormality but
preserved metabolism
Scar abnormality of all characteristics
Myocardial viabilityPET examination (mismatch = hibernation)
Myocardial viabilityprinciple of the assessment
Preserved function of ATP-ase late accumulation of Tl-201
Preserved glucose metabolism accumulation of F-18 FDG
Preserved mitochondrial function accumulation of Tc-99m MIBI
Preserved answer to dobutamine dobutamine echocardiography
50y old woman, QMI of anterior wall treated by rescue PTCA LAD with stent implant. 6/99, ECHO anterior wall motion abnorm., stress scinti 7/99 apico-antero-septal scar,
examination by Tl-201 9/99, F-18 FDG 10/99201Tl
rest
redistribution
VLA
99mTc MIBI rest
18F FDG
restVLA
50y old woman, QMI antero-septal 1995, after PTCA LAD 1997, recurrent AP, stress scinti 11/98 antero-septal scar, Tl-
201 1/99, F-18 FDG 2/99, ECHO unable to evaluate
99mTc MIBI rest
201Tl
redistribution
VLA
99mTc MIBI rest
18F FDG
restVLA
72y old woman, MI 4/00, PTCA LAD 5/00, exam. 7/00, viab. 8/00, PTCA LAD 9/00, follow up exam. 10/00 – perfusion improv. about 7% of myocardium of LV, EF as well as wall motion the same
Myocardial viabilityaccuracy of different methods
Acute coronary syndromes
Imaging of jeopardized myocardium injection on admission, imaging after stabilization PPV of perfusion defect 90% NPV of no defect 100%
Infarction size measurement examination before leaving (correlates with histology)
ViabilityRisk stratification
Acute coronary syndromes
Examination rest SPECT perfusion with Tc-99m MIBI
Indication non-diagnostic ECG
Limitation availability
Benefit cost
Cardiac risk assessment in non-coronary surgery
Separates group of pts with higher riskGroup of 2020 pts
perfusion defect - perioperative events in 20% of pts
no perfusion defect - perioperative events in 2% of pts
Radionuclide ventriculography(MUGA)
Information about regional and global ventricular function
Excellent reproducibility of the resultsIndications
cardiotoxicity of cytostatics alternative in pts non-evaluable with ECHO
Radionuclide angiocardiography
First-pass evaluation of right ventricle function quantification of central circulation shunts
Non-imaging devices can monitore EF on CCU can be used for ambulatory EF monitoring
Non-imaging devices
Post-stress ventriculography
Imaging of myocardial sympathetic receptor densityI-123 MIBG
Tracer accumulates in postganglionic praesynaptic vesicules
Non-invasive assessment of myocardial sympathetic tone prognosis of pts with cardiac failure
Rational treatment of cardiac failure with beta-blockers
New trends
New tracers for myocardial perfusion imaging
Imaging of myocardial ischemiaImaging of myocardial necrosisImaging of cells apoptosisImaging of endothellin receptorsImaging of gene expression
Conclusion Nuclear cardiology tests can display non-
invasively myocardial perfusion distribution during different pathophysiological conditions above all
They contribute to myocardial viability assessment in acute and chronic forms of CAD
Cooperation of cardiologists with nuclear medicine physicians is essential for proper use of this methods in favour of our patients
Radionuclide venography and lung scintigraphyMain clinical indication is suspicion of
pulmonary embolismMain clinical significance is negative finding
- can exclude embolismWidely available is perfusion scintigraphyCorrelation with chest radiograph is essentialVentilation scintigraphy is useful in embolism
of less than 50% of pulmonary circulation
Lung perfusion scintigraphy
Tc-99m MAA as a tracer capillary microembolism display pulmonary blood flow distribution
It does not increase pulmonary pressure Injection in supine positionPlanar or SPECT imagingProcedure takes approximately 30 min.Interpretation is visual - PIOPED criteria
Lung perfusion scintigraphypatient imaging
Lung perfusion scintigraphyplanar images - normal
Lung perfusion scintigraphy planar and SPECT slices - embolism
Lung perfusion and ventilationpulmonary embolism
anterior view, left - perfusion, right - ventilation
Lung perfusion and ventilation pulmonary embolism
ANT POST RPO LPO
perfusion
ventilation
Radionuclide venography
Displays patency/abrupt cutoff of lower limbs deep venous system
Displays abnormal collateralizationDisplays irregular or asymmetric fillingDoes not display thrombusInjection of Tc-99m MAA into dorsal pedal
veins - lung perfusion scintigraphy followsProcedure takes approx. 40 to 60 minutes
Radionuclide venography
injection and imaging
Radionuclide venography
left without, right with tourniquets
Radionuclide venography
pathological findings
New trends
Thrombi imagingLabeled thrombocytes
not readily available
Receptors imaging Acutect - not registered in the Czech rep.
• peptide binding to receptors of activated thrombocytes labelled with Tc-99m
Result available in the order of 4 to 6 hours