DIAGNOSTIC VALUE OF STRESS TESTING (SENSITIVITY & SPECIFICITY) Designed to test how effectively a test separates subjects with disease from healthy individuals ST segment depression has 84% specificity for angiographically significant CAD(assumes 85% heart rate)
Prognostic Value of Testing Post MI Stable CAD Post CABG(3 mos.) Post intervention(6 mos.) High Risk(Diabetics*******) Hypertension
ASSESSING THE APPROPRIATE TEST FOR THE APPROPRIATE PATIENT Treadmill Treadmill with imaging Pharmacologic Echocardiography
PHARMACOLOGIC Indications Patients unable to exercise Preoperative risk stratification Early postinfarct risk stratification Left bundle branch block Fixed-rate pacemakers
PHARMACOLOGIC TESTING Persantine/Adenosine Persantine/Adenosine Needs nuclear augmentation Coronary vasodilation Bronchospastic Not for acute asthmatic’s or severe COPD Dobutamine Dobutamine Inotrope Vasodilator Afterload reducer Increase heart rate May require atropine No bronchospastic component(COPD)
PERSANTINE IV dosing of.56ml/kg over 4 minutes 5 fold increase in coronary blood flow velocity Acts by indirectly increasing intravascular adenosine levels Precursor to adenosine Reverse effects with Aminophylline(dosing from 50-250mg iv injection
ADENOSINE Actively transported across cell to activate the A1 and A2 receptors, stimulates adenocine cyclase in smooth muscle and produces vasodilatation Leads to increase in cAMP, causes increase in Ca levels leading to smooth muscle relaxation
PERSANTINE/ADENOSINE- CONTRAINDICATIONS Bronchospasm- active lung disease AV block Taking caffine or methalxanthines Hypotention- <90mm hg
DOBUTAMINE Dobutamine is a synthetic catecholamine, which directly stimulates both beta-1 and beta-2 receptors. A dose-related increase in heart rate, blood pressure, and myocardial contractility occurs.
DOBUTAMINE increases regional myocardial blood flow based on physiological principles of coronary flow reserve. A similar dose-related increase in subepicardial and subendocardial blood flow occurs within vascular beds supplied by significantly stenosed arteries, with most of the increase occurring within the subepicardium rather than the subendocardium. Thus, perfusion abnormalities are induced by the development of regional myocardial ischemia.
DOBUTAMINE- CONTRAINDICATIONS Patients with recent (1 wk) myocardial infarction; unstable angina; significant aortic stenosis or obstructive cardiomyopathy; atrial tachyarrhythmias with uncontrolled ventricular response; history of ventricular tachycardia, uncontrolled hypertension, or thoracic aortic aneurysm; or left bundle branch block should not undergo dobutamine stress testing.
Treadmill Stress Testing Must be able to walk!! Can be used alone for low risk cases Augmentation can be with nuclear or echo Physiologic response Blood pressure response to exercise Exercise prescription
STRESS ECHO Can be done with treadmill or dobutamine Assesses wall motion Evaluates regional and global wall motion Fast answers No radiation exposure
STRESS ECHO STRESS NUCLEAR Cardiac function Real-time imaging Additional information (LVH, valves) Patient convenience Cost Relative perfusion More objective interpret. Quantitation of extent of perfusion abnorm. of perfusion abnorm. More extensive literature on prognosis