Module 14 : Stress and Contrast Echo Flashcards
describe echo imaging of the coronaries
- two proximal stems of the coronaries can be seen
- cannot diagnose reliably
- not always visible (echo not modality of choice)
what is an angiography
- catheter inserted into artery
- dye injected into the artery to display the luminal contour of the artery
- measurement of the patent vs stenosed portion and percentage calculated
- performed before angioplasty
what is an angioplasty
- balloon is inserted into the coronary artery and the vessel is dilated while the plaque is displaced
what is the principle of a stress ECG test
- physical stress induces ischemia of the myocardium
how is a stress ECG test done
- patient with primary or secondary heart disease put on treadmill and exercised until target HR is reached
what is the target HR in a stress ECG
- 85-90% of max HR
how to calculate the Max HR
- max HR = 220 - age
how to calculate the target HR
target HR = 220 - age x 85%
what is the ischemic cascade
- myocardial O2 supply/demand imbalance
- perfusion abnormalities
- diastolic dysfunction
- systolic function
- increase LV filling pressures
- ECG changes
- angina
what ST segment depression measurement will indicate positive for ischemia
> 1mm
what is the metabolic equivalent of task METS
- assessment of workload is measured by metabolic equivalents
- workload is a reflection of oxygen consumption and hence energy use
how many METS is required to carry out activites of daily living an exercise
- 5
why is the specificity of ST segment depression as a main indicator for MI limited
- ST segment depression occurs in up to 20% of normal individuals
what are the normal electrocardiographic changesdurign exercise
- P wave increase in height
- R wave decreases in height
- J point becomes depressed
- ST segment becomes sharply up stroking
- QT interval shortens
- T wave decreases in height
what are the 6 ECG criteria to stop an ETT
- severe ST segment depression > 3mm
- onset of VT
- new afib or supra ventricular tachycardia
- development of new BBB
- new second or third degree AV block
- cardiac arrest
what are 4 signs and symptoms to stop an ETT
- patient requests stopping because of severe fatigue
- severe chest pain dyspnea or dizziness
- fall in systolic blood pressure > 200mmHg
- rise in blood pressure
6 positive signs of ischemia for ETT
- horizontal ST segment depression of = 2mm
- downsloping ST segment depression
- early positive response within 6 minutes
- perisitance of ST segment depression for more than 6 minutes
- persistence of ST depression for more than 6 minutes into recovery
- ST segment depression in five or more leads
- exertion hypotension
what is the primary use of stress echo
- assessment of cardiac perfusion
what is the principle of stress echo
- increased cardiac workload is used to unmask perfusion defects which may be silent at rest (increased O2 demand cannot be matched by insufficient coronary supply)
how is ischemia seen in a stress echo
- wall motion abnormality
what 2 tings can increase cardiac load
- exercise
- pharmaceutical
what are 3 other uses for stress echo
- viability of the myocardial muscle tissue after MI
- valvular studies
- assessment for cardiac transplants
what are the 2 exercise protocols for stress echo
- treadmill \+ bruce protocol = higher workload but acquire images at rest and after exercise - bicycle ergometer \+ usually recumbent/supine \+ acquire during exercise and rest
what are the 2. pharmaceutical protocols for stress echo
- dobutamine
+ increases contractility and O2 consumption and BP
+ atropine increases HR - dipyridamole
+ has similar effects as a vasodilator
+ must stop beta blockers before procedure
what are the 6 steps of stress echo prep
- NPO > 3 hours pre test
- obtain informed consent from patient
- explain procedure ( patient move directly to bed after exercise)
- set up 12 lead ECG and acquire resting trace
- measure resting BP
- set up test parameters
+ maximum workload
+ symptoms to be documented
what is the diagnostic sequence for a stress echo
- baseline echo images = resting wall motion abnormalities
- exercise test = exercise duration BP, HR, symptoms, ECG changes
- immediate post or maximal exercise image = compare baseline and stress images on quad screen cine loop
what are the 4 baseline set of images
- PLAX
- PSAX (pap)
- apical 4 chamber
- apical 2 chamber
what are 3 technical point for a stress echo
- need optimal endocardial definition
- acquire images quickly after exercise as workload declines rapidly
- use 3D/4D
steps to the post treadmill test
- begin recording images as soon as exercise ends
- have 60 seconds to obtain all 4 cine clips
+ PLAX/ A3C
+ PSAX (mid)
+ A4C
+ A2C - scan for at least 2 more minutes
- look for WMA and calculate WMSI
charcteristics of a dobutamine
- is a synthetic catecholamine
- infused gradually using automatic IV calibrated syringe
- used for patients who cannot exercise or for viability tissue studies
what are the effects of dobutatmine
- causes positive chronotropic and inotropic
- raises HR and contractility in viable myocardium
- non viable myocardium will not respond to the drug
- can cause high or low BP due to reflex peripheral effects
- increases O2 demand which can trigger ischemia
what is the the infusion protocol for a dobutamine stress test
- starts = 5
- 3 min = 10
- 6 min = 20
- 9 min = 30
- 12 min = 40
what is the data recording protocol for a dobutamine stress echo
- for baseline each stage/ dose and recovery document \+ HR \+ BP \+ symptoms : CP, SOB, syncope \+ ECG - echo images \+ PSAX at med and base \+ A4 \+ A2 \+ PLAX - doppler LVIT LVOT CO
what are the 6 complications of dobutamine stress echo
- PVC PAC = 10%
- non sustained VT or SVT = 4 %
- angina = if positive test but usually stopped
- hypotension = 10% due to peripheral drug effect
- MI or VF = 1/2000
what are the dobutamine stress test conditions
- supervising physician present
- trained personnel
- nurse
- crash cart
does dobutamine affect crontacitility more than HR and what can be given to augment the HR
- yes
- atropine used if
+ peripheral vasodilation occurs
+ patient on beta blockers
does dobutamine increase venous return
- no only exercise
what are the 7 endpoints for stopping a dobutamine stress test
- reaching maximum dose
- patient discomfort
- definite wall motion abnormality
- ST segment elevation on ECG
- reaching 85% of max heart rate for age
- systolic BP > 200 of diastolic BP > 120
- ventricular arrhythmias
when is a stress test echo done for valvular heart disease
- symptoms do not match echo assessed values
+ underestimate due to low flow state - dobutamine also used for valve stress echo
what 4 things does contrast asses with improved endocardial border delineation
- wall motion
- thrombus
- aneurysms
- TDS patients
what else can be studied with contrast echo
- study anomalous cardiac structures for blood flow
+ shunts
+ congenital abnormalities
+ larger vessel anomalies
what are 2 considerations that must be made before a contrast echo is done
- lower mechanical index to not burst any bubbles
- contrast injected into arm vein
+ agitated saline (right)
+ difinity (left heart)
what is agitated saline used to look for
- ASDs
- PFOs
- rt to lt shunts
how is the saline agitated
- pushed back and forth between syringes then injected into right arm vein
what would indicate a positive shunt with agitated saline contrast
- bubbles seen crossing septum
characteristics of tissue viability studies
- detects stunned or hibernating myocardium post MI to see if it will come back
what is an MIBI
- methoxy isobutyl isonitrile
- radioactive tracers display where they end in the heart
- binds to healthy heart muscle
- ## injected at peak exercise and then at rest
what is CT angio
- computed tomography angiography
- uses contrast to visualize coronaries
- patients with iodine allergies must use other contrasts
what is MRI
- magnetic resonance imaging
- uses echoes of radio frequency returning from structures with different properties within a strong magnetic filed that aligns magnetic poles of all atoms of tissues at that resonance
what 5 things can cardiac MRI reliably image
- coronary arteries
- wall structure
- cardiac chambers
- pharmaceutical stress
- contrast
