Stress Echo - week 13

What is stress echo?

non-invasive diagnostic method to assess known or suspected CAD

What is one basic form of stress echo?

Using a treadmill or an ergometer (upright or supine) to exercise the heart

What is the other basic form of stress echo?

Using various drug agents to simulate exercise (inotropic positive) = pharmacologic stress test

What is the goal of stress echo?

to induce myocardial ischemia by augmentation of oxygen demand to the heart in the absence of adequate supply

During the stress echo test what is recorded?

EKG and BP

Why are ultrasound images captured?

To detect changes in wall motion that may occur

What are the types of stress tests performed?

• ETT

• SE

• DSE

What is ETT?

exercise treadmill test

• recording EKG and BP changes during exercise

What is SE?

stress echocardiography

• in addition to EKG and BP changes, capture of US images before and after exercise is performed to indirectly assess coronary perfusion to different wall segments of the LV

What is DSE?

dobutamine stress echocardiography

• pharmacologically induced high HR to mimic exercise with recording of EKG, BP and US images

What are the objectives for stress echo?

• Evaluation of known or suspected CAD

• Risk stratification of patients before non-cardiac surgery after MI or interventional procedures and prior to start an exercise/diet program

• Evaluation of LV systolic function - global and segmental

• Identification of viable, hibernating or stunned myocardium with LV dysfunction

• Evaluation of the LV function and valvular hemodynamics and/or cardiomyopathies

At rest, the myocardium is well supplied with?

oxygenated blood through the coronary artery and LV systolic function is normal

As stress and demand for oxygen ____ during exercise or drug induced ______ __, the region supplied by specific vessels will display ____

• Increases

• increased HR

• WMA (hypokinesis, akinesis, dyskinesis) if lesions are present in vessels or their branches

What do WMA generally precede?

EKG changes

How can WMA be assessed?

From the wall score index

What are the 2 categories of contraindications?

Absolute and relative

What are 3 absolute contraindications?

• Acute MI less than 72 hours old

• Unstable angina

• Hemodynamic instability ( systolic BP > 210 mmHg or < 90 mmHg; diastolic BP >110 mmHg)

What are 3 more absolute contraindications?

• Uncontrolled cardiac arrhythmias

• Symptomatic aortic or subaortic stenosis with pressure gradient > 50 mmHg

• Uncontrolled symptomatic HF

What are 3 more absolute contraindications?

• Acute myocarditis, pericarditis and infective endocarditis

• Acute aortic dissection/large aortic aneurysm

• Acutely ill patients

What are 4 more absolute contraindications?

• Patients with ambulation problems

• Pregnancy

• Combative patients or patients who are otherwise judged uncooperative

• Patients who refuse the procedure and/or consent may not be obtained

What are relative contraindications?

risk/benefit assessment is performed by the physician

What are 3 relative contraindications?

• Unstable angina but asymptomatic for the previous 12 hours

• Left main coronary artery disease

• Severe arterial hypertension ( systolic BP>170 mmHg, diastolic BP > 100 mmHg)

What are 3 more relative contraindications?

• Increased cardiac enzyme levels or electrolyte abnormalities 

• Significant ischemic EKG changes

• Hypertrophic obstructive CM or other forms of outflow obstruction

What are 3 more relative contraindications?

• PHTN with MPAP > 50 mmHg or SPAP > 70 mmHg

• Tachyarrhythmias/Bradyarrhythmias - high degree of A-V block

• Mental or physical impairment leading to inability to exercise

If the echo images are suboptimal, it should be the cardiologist’s decision to? (relative contraindications)

to abort, use contrast agents or continue the SE

Maximal HR =

220 - age

Target HR (85% of age predicted MHR) =

MHR x 0.85

% maximal HR achieved =

MHR achieved/MHR calculated

Double product =

MHR achieved x systolic BP

Rate pressure product =

HR x systolic BP

What is the procedure of flow?

1. Explain test to the patient

2. Position EKG electrodes to ensure that echo windows are not obstructed

3. Obtain resting echo images (digital capture)

4. Exercise patient

5. Prepare probe and system for immediate post exercise study

6. Obtain and record post images rapidly

7. Select post exercise images, shuffle and review pre and post exercise images

For patient prep, pt should be NPO for?

3 hours prior to test

What is the short cardiac patient hx questionnaire for pt prep?

• risk factors for CAD

• previous CAD (PTCA, MI, CABG)

• previous tests/procedures, medications, indication

• goal of the test

What should the pt sign for pt prep?

• consent form

• informed of procedure

What should be obtained for pt prep?

• Resting BP supine and standing

• a resting 12 lead EKG

What are the exercise protocol?

• Standard Bruce protocol

• Modified Bruce protocol

• Naughton protocol

What is the modified Bruce protocol utilized in?

in pts with lower exercise capacity

Resting images =

Baseline images

What does the Bruce standard protocol do?

will run on stages of 3 minutes when the treadmill settings change to higher speed and incline and BP is recorded at min 2:30 of every stage until termination

What happens when the endpoint is reached?

the patient is moved quickly on the bed and post-exercise images are acquired promptly ( within 60 seconds) with HR maintained at high rate

What are 2 of the end points?

• When target or predicted HR is achieved = 90% of MHR for 1 minute

• Intolerable symptoms

What are 3 more end points?

• Significant ST segment changes occur

• elevation of >1mm or depression of >2 mm when compared to baseline EKG

• Severe angina pectoris

What are 2 more end points?

• Sustained SVT, ventricular arrhythmias or A-V block

• Hypertensive or hypotensive response

In recovery what do you monitor and obtain?

• monitor vital signs

• obtain EKG recordings

When do you obtain EKG recordings for recovery?

every 2 minutes for 10 minutes or until the BP and HR return to baseline

For interpretation, what do you note?

patient symptoms during exercise

For interpretation, what do you record?

• EKG changes

• arrhythmias

For interpretation, what do you evaluate?

global and segmental LV systolic function pre and post exercise

For interpretation, what is assigned?

• Assign a wall score to each segment well visualized

• calculate a wall motion score index

What is a normal response?

All walls become hyperdynamic with symmetric wall thickening and equal excursion in all segments

What are 2 more normal responses?

• EF increases minimum 5% post exercise

• LV end -systolic dimension decreases

What is an abnormal response?

Resting hypokinetic wall segment that worsens with exercise may represent hibernating myocardium

What are 2 more abnormal responses?

• New segmental WMA using wall motion score index

• Decreased EF and longitudinal strain - global LV systolic dysfunction

What is a Dobutamine Stress Echo?

pharmacologic alternative to exercise echocardiography for those who are unable to exercise or have specific indications

What are the advantages of Dobutamine Stress Echo?

• useful for myocardial viability assessment

• allows Doppler interrogation during the test and allows immediate detection of an abnormal response and facilitates cessation of testing

How long should a pt be NPO for dobutamine stress echo?

3 hours prior to test

What should be obtained for pt prep (dobutamine)?

Cardiovascular history

What should be explained and signed for pt prep (dobutamine)?

• The procedure

• side effects Dobutamine

• potential complications explained

• Patient consent form signed

What should be placed and recorded for pt prep (dobutamine)?

• Placement of EKG leads

• resting EKG recorded

What should be started and prepared for pt prep (dobutamine)?

Starting IV access

What is Dobutamine?

synthetic catecholamine that augments myocardial contractility

What is the dobutamine calculation?

to determine the number of ml/hr which equals 1mcg/kg/min, determine the patient’s weight in kilograms (pounds/2.2)

What is the equation for the dobutamine calculation?

Weight x 60 min/100 mg/ml

What will the answer of the dobutamine calculation provide and determine?

The answer will provide the ml/hr and to determine the amount of the Dobutamine to be administered

• multiply the ml/hr by 5, 10, 20, 30 and 40 respectively

What are the views for resting images (after a baseline echo)?

• PLAX

• PSAX

• AP-4Ch

• AP-2Ch

• AP-3Ch (optional)

• Views demonstrating valvular color flow

What is the first step of a dobutamine procedure?

Infuse Dobutamine with a starting rate of 5 mcg/kg/min or 10 mcg/kg/min

What is the 2nd and 3rd step of the procedure (dobutamine)?

• At 2:30 min begin obtaining views, BP, EKG

• Increase Dobutamine infusion to 10 mcg/kg/min at 3 min

What is the 4th and 5th step of the procedure (dobutamine)?

• At 5:30 min obtain a second set of views, BP and EKG

• Increase Dobutamine to 20 mcg/kg/min at 6 min

What is the 6th and 7th step of the procedure (dobutamine)?

• at 8:30 min obtain third set of views, EKG, BP

• Increase Dobutamine to 30 mcg/kg/min at 9 min

What is the 8th, 9th and 10th step of the procedure (dobutamine)?

• At 11:30 min obtain fourth set of views, BP, EKG

• Increase Dobutamine to 40 mcg/kg/min at 12 min

• At 14:30 obtain a fifth set of views, BP and EKG

What is the last step of the procedure (dobutamine)?

At 15 min obtain 12 lead EKG, note HR and increase Dobutamine infusion up to 50mcg/kg/min until peak HR is achieved

What is the procedure for dobutamine stress echo?

1. Infuse Dobutamine with a starting rate of 5 mcg/kg/min or 10 mcg/kg/min

2.  At 2:30 min begin obtaining views, BP, EKG

3. Increase Dobutamine infusion to 10 mcg/kg/min at 3 min 

4. At 5:30 min obtain a second set of views, BP and EKG

5. Increase Dobutamine to 20 mcg/kg/min at 6 min

6. At 8:30 min obtain a third set of views, BP and EKG

7. Increase Dobutamine to 30 mcg/kg/min at 9 min 

8. At 11:30 obtain a fourth set of views, BP and EKG 

9. Increase Dobutamine to 40 mcg/kg/min at 12 min 

10. At 14:30 obtain a fifth set of views, BP and EKG 

11. At 15 min obtain 12 lead EKG, note HR and increase Dobutamine infusion up to 50mcg/kg/min until peak HR is achieved

What happens if no endpoint is reached?

Dobutamine infusion is continued up to 50mcg/kg/min with atropine sulfate administered to increase HR

• (additional doses of 0.25 to 0.5 may be repeated at 1 min intervals to a maximum of 2mg)

What may be the remaining images for dobutamine?

a combination of

• low stress

• intermediate stress

• post atropine images or recovery images

What are 3 endpoints for dobutamine?

• Development of new segmental WMA or worsening preexisting segmental WMA

• > 1mm downsloping ST segment depression with segmental WMA

• Angina pectoris

What are 3 more endpoints for dobutamine?

• Achievement of >85% of MPH determined by age

• BP > 210/120 mmHg

• Symptomatic hypotension with a fall >40 mmHg

What are 3 more endpoints for dobutamine?

• Tachyarrhythmias

• Significant increase in valvular pressure gradient

• Maximum dose of Dobutamine at 50 mcg/kg/min

What are 2 more endpoints for dobutamine?

• Side effects due to Dobutamine (nausea, vomiting, headache)

• Patient request to end test

What is the recovery for dobutamine?

• Evaluate BP

• 12 lead EKG at 2 min interval until back to baseline or HR below 100 bpm

• finalize US images.

What is a normal response for dobutamine?

hyperdynamic wall motion and increased EF

What are 2 abnormal responses for dobutamine?

• Hypokinesia, akinesia or dyskinesia or failure of a wall to increase systolic thickening and excursion or increase in LV volume

• Improvement of a hypokinetic, akinetic segment during administration of low dose Dobutamine (5 or 10 mcg/kg/min) suggests the presence of viable myocardium

What are 2 more abnormal responses for dobutamine?

• Determine wall motion index

• Determine E/e’ ratio at rest and peak dose - LV diastolic function

What is the determination of myocardial viability performed to evaluate?

evaluate if revascularization can improve myocardial contractility and LV systolic function

What are the 4 different clinical scenarios when evaluating myocardial response to low and high dose of dobutamine, with resting akinetic hypokinetic segment?

• Monophasic (sustained) response

• Biphasic response

• Nonphasic response

• Ischemic response

What is a monophasic (sustained) response?

• if the myocardium is viable with NO stenosis of the coronary artery perfusing the akinetic/hypokinetic segment

• myocardial contractility increases continuously with low/high dose of Dobutamine

What is the biphasic response?

• if the myocardium is viable but the coronary artery that perfuses the segment is severely stenotic

• myocardial contractility improves initially with low dose of Dobutamine but worsens with higher dose

What is a biphasic response a typical response for?

hibernating myocardium

• suggests increased potential for recovery of function

What is a nonphasic response?

• when the myocardium is scarred, with NO myocardial viability

• there is NO myocardial thickening at rest or with low/high dose of Dobutamine

What is an ischemic response?

a worsening of function without contractile reserve suggests a stress-induced ischemic myocardium due to flow limiting stenosis of the corresponding coronary artery

(restenosis)

What is Diastolic function evaluation for stress echo in non-ischemic HD evaluation?

in patients with HF to detect diastolic filling impairment with exercise

(restrictive CM)

What is cardiomyopathy for stress echo in non-ischemic HD evaluation?

hypertrophic and dilated CM

What is native valvular disease for stress echo in non-ischemic HD evaluation?

mild to moderate AS, MR or stenosis severity evaluation