Cardiovascular Noninvasive Imaging Flashcards
Echocardiography definition
A group of tests that utilize ultrasound to ezamine the heart and record information in the form of echoes (reflected sonic waves).
What is the greatest limitation of echocardiography?
Lack of adequate access to the heart: distance, air in lungs or between transducer and skin/bone), Image acquisition and interpretation user dependent.
Ultrasound definition
Imaging technique using high-frequency sound waves to produce images of the organs and structures of the body. Sent through using a transducer placed directly on top of skin by air-free contact). Sound waves sent by transducer and reflected by internal structures as echoes and return to transducer/receiver. Painless and harmless. Displayed on a screen recorded on videotape/digital.
Where is the cardiac outline?
Extends from junction of 2nd left costal cartilage with sternum at sternal angle to apex beat in 5th intercostal space on midclavicular line.
What is the primary cover of the heart anteriorly?
Bony structures: sternum, ribs, lungs. Impenetrable to ultrasound.
Where is the best access to heart view for echo?
Parasternal view: Beneath 3,4,5 intercostal space, between 2-3cm left of the sternal border and left parasternal area.
Types of echocardiography used clinically
M-mode, 2-D B-mode/real time, Doppler (color, CW, PW)
M-mode echocardiography
1-dimentional view of heart: parallel rays/beams as depth. Represent echoes from tissue interfaces along axis of beam, mostion along single scan line through heart, time along x-axis (1s/arrow), depth along y-axis (1cm space between marks)
What action can be seen in M-mode echo of the ventricles?
Contraction during systole, changes in diameter atrial kick.
How can information from an isolated M-mode view be augmented to see more?
By changing the direction of the ultrasonic beam as in an arc or sector.
How does a 2-D echo relate to individual M-mode views?
Beam moved so that about 30 slices/second obtained.
Where is the long axis plane?
Perpendicular to sternal plane and runs from right shoulder to left kidney. Transects heart from aortic root left ventricular apex (includes aortic and mitral valves). Going through septum of heart.
Where is the short axis plane?
At right angle to sternal plane from left midclavicle to right hip
Where is the 4 chamber plane?
Right angles to long and short axes, includes both apex and right shoulder. Runs from apex to base of heart and approximately perpendicular to both posterior interventricular septum and interatrial septum.
Orthogonal planes for imaging of heart
What is doppler echocardiography?
Detects direction and velocity of moving blood within the heart.
What is doppler echo used to detect?
Cardiac valvular insufficiency and stenosis, shunts and abnormal flows.
What does doppler echo measure?
Direction, velocity and turbulence.
What color is blood moving towards the transducer in color Doppler flow?
Yellow and red shades
What color is blood moving away from the transducer?
Blue shades
What is the structure of the continuous wave Doppler?
Two crystal mounted on the same transducer, one continuously seending, other continuously receiving ultrasound.
What is the capability and limitation of the continuous wave Doppler?
Quantification of high velocity flow but cannot localize where along the scan line the flow originates. Can be used to calculate pressure.
What is the advantage of a pulsed wave Doppler (PW)?
Ability to localize source of velocity selectively from a small segment along the ultrasound beam (sample volume).
What is the disadvantage of a pulsed wave Doppler?
Inability to accurately measure high blood flow velocities-aliasing. Inability of pulsed Doppler to faithfully record velocites about 2m/s.
What does the tissue doppler echo measure?
Velocity of myocardium
How does the velocity of the myocardium relate to the velocity of moving red blood cells?
Several magnitudes lower.
What is the benefit of analysis of tissue doppler echo?
Allows for quantification of regional myocardial contraction and relaxation. But not very useful.
Clinical uses of 2-D echo
Cardiac chambers (size, LV hypertrophy, regional wall motion abnormalities), valve morphology and motion, pericardial effusion and tamponade, masses, great vessels.
What are the clinical uses of Doppler Echo?
Valve stenosis (gradient and valve area), Valve regurgitation (semiquantitation), intracardiac pressures, volumetric flow, diastolic filling, intracardiac shunts
What are the clinical uses of stress echo?
2-D: myocardial ischemia and viable myocardium. Doppler: valve disease.
Clinical uses of Transesophageal echo (TEE)
Inadequate transthoracic images, aortic disease, infective endocarditis, source of embolism, valve prosthesis, intraoperative
What is emergency echocardiography?
Ability to obtain instantaneous images of cardiac structures for immediate interpretation at patient’s bedside is a major advantage.
What is regional wall motion?
Division of LV into 16 or 17 segments and evaluation of contraction of all segments to see if normal, hypokinetic, akinetic, dyskinetic, aneurysmatic, etc.
How is diastolic measured (by which parameters)?
Abnormal relaxation time, reversal of flow pattern over mitral valve, restrictive pattern.
What is fractional shortening?
Measure of systolic function by LVED and LVES diameter (A-B)/A, End diastole-end systole/end diastole=measurement of shortening of LV
How is global left ventricular function measure by ejection fraction?
LV border is traced in end diastole and end systole in 2 vertical planes (4/2 chamber views). Volumes calculated by machine. EF=(LVEDV-LVESV)/LVEDV
How can 2-D echo measure cardiac valves?
Morphology: thickened, calcified, stenotic prolapsing.
How can Doppler echo measure cardiac valves?
Flow: high velocities (stenosis) or incompetence by regurgitant jets.
What is the structure of a TEE?
2-D transducer at the end of a flexible endoscrope.
What is the image from a TEE?
High-quality 2-D images via the esophagus in multiple planes and also to obtain Doppler information.
When should TEE be performed?
When further information is required usually after 2D and Doppler transthoracic echocardiograms (too much space, air, bone, etc).
For what conditions is TEE useful?
Diagnosing endocarditis and source of emboli, assessing prosthetic valves, aortic disease, including dissection and intracardiac masses (myxoma, thrombus or vegetation). Afib to exclude LA clot before cardioversion.
When is TEE useful in the OR?
During open-heart surgery (assessing cardiac morphology and function before, during, and after surgical repair of valvular or congenital conditions). Monitoring myocardial ischemia during noncardiac surgery.
Advantages of echo
Painless, harmless, less costly than other sophisticated imaging techniques.
Limitations of echo
Technical difficulties exist that require expertise on the part of the examiner and interpreter. The principal problem is posed by the poor transmission of ultrasound through bony structures or air-containing lungs.
What is the purpose of a stress test?
To diagnose or know prognosis of coronary artery disease.
What determines myocardial oxygen consumption (MO2)
Heart rate, systolic BP, LVEDV, wall thickness, contractility
What is the main significant mechanism for the heart to increase oxygen consumption?
Increase perfusion by decreasing resistance at the coronary arteriolar level.
Progression of myocardial ischemic response after atherosclerotic narrowing of epicardial vessels
An ischemic threshold occurs beyond which exercise can produce abnormalities in diastolic and systolic LV function, ECG, chest pain.
What does the metabolic equivalent (MEET) refer to?
Resting VO2, respiratory oxygen uptake, for a 70kg, 40yo male. 1 MET=3.5mL/min/kg
What is the range of METs
3-5 light, 5-7 medium, >9 is heavy labor or running 6mph
What is the calculation for age predicted maximum heart rate?
220-age
Why is maximum HR and CO decreased in older individuals?
Decreased beta adrenergic responsivity
Indications for ECG/exercise stress test
- Diagnosis of CAD 2. Assess prognosis and functional capacity in patients with known CAD 3. Evaluate after therapy such as coronary revascularization 4. Evaluate prognosis and functional capacity after an uncomplicated MI 5. Assess symptomatic, exercise-induced arrhythmias 6. Assess severity of valvular disorders.
Absolute contraindications to exercise testing
Acute myocardial infarction (within 2 d)
Unstable angina not previously stabilized by medical therapy†
Uncontrolled cardiac arrhythmias causing symptoms or hemodynamic compromise
Symptomatic severe aortic stenosis
Uncontrolled symptomatic heart failure
Acute pulmonary embolus or pulmonary infarction
Acute myocarditis or pericarditis
Acute aortic dissection
Relative contraindications to exercise testing
Left main coronary stenosis
Moderate stenotic valvular heart disease
Electrolyte abnormalities
Severe arterial hypertension‡
Tachyarrhythmias or bradyarrhythmias
Hypertrophic cardiomyopathy and other forms of outflow tract obstruction
Mental or physical impairment leading to an inability to exercise adequately
High-degree atrioventricular block
What is the principle of the Bruce Protocol?
Multistage maximal treadmill (slope and speed increases) with 3 minute periods to allow achievement of steady-state before increased workload.
Indications for terminating an exercise test
- Achievement of target heart rate 2. Progressive angina 3. Other limiting symptoms (dyspnea, fatigue, lightheadedness,claudication) 4. ST segment elevation >2 mm 5. Severe ST segment depression 6. Nonsustained ventricular tachycardia 7. New onset of atrial fibrillation, atrial flutter or SVT 8. Development of second or third degree AV block 9. Development of a new left bundle branch block 10. A 10 mm Hg drop in systolic blood pressure 11. Extreme elevation of systolic or diastolic blood pressure 12. A progressive drop in heart rate with continued exercise 13. Equipment problems, such as loss of ECG signal.
What does exercise-induced ST segment depression indicate?
NOT the site of MI nor which coronary artery involved. Severe aortic stenosis, glucose load, hypertension LV hypertrophy, cardiomyopathy hyperventilation, anemia, mitral valve prolapse, hypokalemia, IV conduction disturbance, severe hypoxia, preexcitation syndrome, digitalis, severe volume overload (aortic, mitral, regurgitatino), sudden excessive exercise, supraventricular tachyarrhythmias.
Exercise parameters associated with adverse prognosis and multivessel coronary artery disease
Duration of symptom-limiting exercise (< 6 METs) Failure to increase systolic blood pressure >120 mmHg, or a sustained decrease >10 mm Hg, or below rest levels, during progressive exercise. ST segment depression >2 mm, downsloping ST segment, starting at < 6 METs, involving >5 leads, persisting >5 minutes into recovery. Exercise-induced ST segment elevation (aVr excluded). Angina pectoris during exercise. Reproducible sustained (> 30 sec) or symptomatic ventricular tachycardiA.
How is the sensitivity and specificity of exercise testing?
Not great but not awful (68 and 77%)
When is the maximum diagnostic power of the exercise test?
When pretest probability of CAD is intermediate (30-70%).
What are the primary indications for a stress echo?
Confirm suspicion of CAD and estimate severity. Valvular heart disease with Doppler echo at rest and exercise for hemodynamic to stress.
Why is it important that images be obtained as soon as possible after exercise is stopped?
Regional wall motion abnormalities may dissipate rapidly with time.
What are indicators of myocardial ischemia in stress echo?
New regional wall motion abnormalities, decline in EF, increase in ESV.
What infusion can be used for patients not able to exercise?
Dobutamine. Low dose for increased perfusion, high dose for increased myocardial demand and decreased contraction if perfusion impaired
What are predictors of risk in stable angina patients for stress test?
Presence of redistribution (reversible defects) Extent of ischemia Extent of perfusion deficit (reversible and fixed) Severity of perfusion deficit Increased lung thallium uptake Number of vascular territories with perfusion defects Left ventricular dilation (transient or fixed).
What should determine the choice of initial stress test?
Evaluation of the patient’s resting ECG, physical ability to perform exercise, local expertise and technology available in an institution.
Initial mode exercise ECG test for standard CAD assessment
Normal ECG, no digoxin, able to exercise. On pretest probability of diease.
What determines the imaging modality (nuclear imaging/echo)
If resting ECG abnormalities (ST depression >1 mm, LVH, bundle branch block, pacing) / patient taking digoxin / prior coronary revascularization give nuclear imaging with pharm agent.
When is pharmacologic stress testing preferred?
Patients unable to exercise.
What are the benefits and limitations of echo stress testing?
Provides additional structural information. Limited diagnostic images in some patients (COPD, obese). No irradiation.
What are the benefits and limitations of nuclear imaging stress testing?
Preferred If patient had previous infarction and the question is if a specific myocardial area is ischemic. Nuclear imaging using 99mTc-labeled compounds is preferred in obese patients and those with severe lung disease. Nuclear imaging is more sensitive and less specific than echocardiography for the detection of myocardial ischemia.
What may show up as false positive in stress tests?
LBBB or provoked abnormalities in regional perfusion and regional ventricular function in the absence of CAD.
Flowchart for stress test
