Flashcards in Vasodilator Stress Testing Deck (18):
What are the qualities of Tc 99m-Sestamibi stress testing?
Uptake proportional to blood flow
Tissue uptake is fixed: true perfusion agent
Higher energy/better penetration and images
Tissue fixation permits gated LV angiogram: wall motion, EF
What are the qualities of an adenosine stress test?
Smooth muscle relaxation and direct coronary vasodilation: attenuated in coronary arteries, which have reduced coronary flow reserve and cannot further dilate in response to adenosine; in most cases coronary blood flow in diseased arteries does not decrease but in severe vessel stenosis or total occlusions with compensatory collateral circulation a decrease in coronary blood flow may occur, including ischemia via coronary steal phenomenon
What is the half-life of adenosine?
Approximately 6 seconds
What are the indications for adenosine/Tc 99 stress testing?
Physical limitations of exercise stress testing
Pts taking beta-blockers or other negative chronotropes
LBBB or V pacemakers
Severely diseased AV node or s/p AV node ablation unable to override ventricular pacing (often produces a false positive perfusion defect
What are the absolute contraindications of vasodilator stress testing?
Active bronchospastic lung disease or pts being treated for reactive airway disease
Pts with > first degree heart block, sinus node disease, or symtomatic bradycardia without V pacer (may lead to prolonged heart block or asystole)
SBP < 90mmHg
Hypersensitivity to adenosine
Pts using diphyridamole or methylxanthines (caffeine, aminophylline) because they are competitive inhibitors of adenosine at the receptor level (no caffeine for at least 24 hours, no dipyridamole or methylxanthines for 48 hours)
What are the relative contraindications of vasodilator stress testing?
Remote hx of RAD (COPD/asthma) quiescent for approx 1 year (Dobutamine may be safer)
History of SSS without vpacer
Severe bradycardia (HR<40)
What are the instructions to prepare a patient for a vasodilator stress test?
NPO after midnight except routine meds
Oral diabetic agents held; AM insulin doses may be given at half usual dose
No meds containing aminophylline for 48 hours
No caffeine for 24 hours
Wear comfortable loose fitting clothing and footwear appropriate for walking
What are indications for early termination of a vasodilator stress test?
Severe hypotension (SBP <90mmHg)
Symptomatic Mobitz I second degree heart block
Mobitz II or third degree heart block
Severe chest pain associated with ECG changes: >2 mm ST depression or any ST elevation in a non-Q wave lead
Adverse effects resolved or improve in <1 minute
What are the possible adverse effects experienced during a vasodilator stress test?
Non specific chest pain or tightness 34%
Symptomatic hypotension 3%
ST segment changes 13%
Tightness in throat
What can be done to decrease incidence of adverse effects during a vasodilator stress test?
Walk protocol - esp decreases flushing, nausea, H/A; less symptomatic hypotension and bradycardia
Improved image quality
Allows for immediate imaging
What occurs physiologically during a dobutamine stress MIBI?
Synthetic catecholamine stimulates beta 1 and 2 receptors
It is a positive inotrope and chronotrope
Dose-related increase in HR, BP, and myocardial contractility
Increases regional myocardial blood flow based on physiological principles of coronary flow reserve
Dose related increase in subepicardial and eubendocardial blood flow occurs within vascular beds supplied by significantly stenosed arteries with most of the increase occurring within the subepicardium rather than the subendocardium
Induces ischemia via increased HR, SBP, and contractility - DBP decreases as dose increases
What are the indications for dobutamine stress MIBI?
Second line pharmacologic stressor to be used in patients who cannot perform exercise stress and have a CI to vasodilator stress
Preferred agent if Persantine or Aggrenox on board, hx of asthma or COPD, critical carotid stenosis
What are the contraindications for a dobutamine stress mibi?
Ventricular arrhythmias, hx of VT
Atrial tachyarrhythmias with uncontrolled ventricular response
Recent MI (72 hours)
Hemodynamically significant LV outflow tract obstruction, obstructive cardiomyopathy
Thoracic aortic aneurysm or aortic dissection
What conditions should you ensure that a patient does not have prior to performing a dobutamine stress mibi in case Atropine is needed?
Glaucoma or obstructive uropathy
What are the indications for early termination of a dobutamine stress mibi?
Chest pain with 2 mm or more ST depression
Hypotension: 15 mmHg or more decreased SBP
Subside within 5-10 minutes of discontinuation
What are the possible side effects of a dobutamine stress mibi?
ST changes 50%
Significant SVT or ventricular tachyarrhythmia 8-10%
*Development of new WMA indicates ischemia
*Improvement of existing WMA indicates viable myocardium
*Wall motion may worsen at higher doses with onset of ischemia
What are the indications for coronary angiography over stress test?
High risk stress test based on ECG and hemodynamics
High risk perfusion study showing multiple defects, severe perfusion defects, or TID
Post MI angina
Vocational indication: pilots, truck/bus drivers
Prior nondiagnostic ECG stress test
High likelihood of false positive result
Conduction or repolarization abnormalities that make ECG stress test difficult to interpret: LBBB (exaggerates septal MA)
High pretest likelihood of disease
Permanent pacemaker (produces septal and apical WMAs)
For prognostic information post MI (preferably 48 hrs after uncomplicated MI)
Determine success of interventions