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STRESS ECHO

Stress echo is a family of cardiovascular stress examinations involving echocardiographic monitoring before, during, and after stress induction through exercise or pharmacological agents. Learn about coronary blood flow, coronary blood flow reserve, cellular mechanisms of ischemia, and basic principles of stress echo. Discover the differences between treadmill and supine bicycle protocols, advantages, disadvantages, indications for pharmacological stress echocardiography, and details about stress agents like dobutamine, dipyridamole, and adenosine.

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STRESS ECHO

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  1. STRESS ECHO DEEPAK NANDAN

  2. Stress echo is a family of examinations in which 2D echocardiographic monitoring is undertaken before , during & after cardiovascular stress • Cardiovascular stress  exercise pharmacological agents

  3. PHYSIOLOGY • Coronary blood flow – pulsatile & phasic • Precapillary arterioles – resistance vessels * principal contributor of resistance * main controller of coronary blood flow • ↑ CBF on ↑ demand occurs through reduction in resistance at this level

  4. CORONARY BLOOD FLOW RESERVE • Maximal CBF / basal CBF • Magnitude of bf ↑ secondary to any stress relative to resting flow • In discrete stenosis – CFR begins to ↓ when stenosis reaches 50% dm • CFR is abolished when stenosis reaches 90% • Resting bf remains constant up to 85- 90% of the stenosis

  5. Cellular Mechanism of Ischemia • Consequence(s) of Mechanical Dysfunction • Mechanical Dysfunction • Abnormal Contraction and Relaxation •  Diastolic Tension • Diastolic Wall Tension (Stiffness) Extravascular Compression   Blood Flow to Microcirculation ( O2 delivery to Myocytes) O2 Consumption (to maintain tonic contraction)  ATP Hydrolysis  O2 Demand  O2 Supply Modified from: Belardinelli et al. Eur Heart 8 (Suppl. A):A10-A13, 2006

  6. BASIC PRINCIPLES OF STRESS ECHO • ↑ Cardiac work load - ↑O2 demands- demand supply mismatch- ischemia • Impairment of myocardial thickening and endocardial motion

  7. Treadmill protocol

  8. Stress echo-Standard-format

  9. Supine bicycle ergometry

  10. Supine bicycle standard format

  11. Treadmill vs supine bicycle advantage • Add information • Wide spread availability • Simple protocol • High work load • > Sensitive Disadvantage • Imaging post ex only Advantage • Image through out the exercise- peak • Onset of RWMA • Better image quality • Contrast stress echo • > Specific Disadvantage • Lower work load • Supine position affects ex.physio

  12. Information obtained from Exercise Stress but not available with Pharmacological Test • Exercise Duration/Tolerance • Reproducibility of Symptoms with Activity • Heart rate response to exercise • Blood Pressure response • Detection of Stress Induced Arrhythmias • Assess control of angina with medical therapy • Prognosis

  13. Indication pharmacological stress echocardiography • Inadequate exercise • Left bundle branch block • Paced ventricular rhythm • pre-excitation or conduction abnormality • Medication: beta-blocker, calcium channel blocker • Evaluation of patients very early after MI(<3 days) or • angioplasty stent(<2weeks) • Poor image degradation with exercise • Poor patient motivation to exercise

  14. Pharmacologic Stress Agents Inotropic agents Dobutamine Arbutamine Coronary vasodilator Dipyridamole Adenosine Stress agents

  15. DOBUTAMINE STRESS ECHO • Dobutamine- synthetic catecholamine • Inotropic & chronotropic- β1,β2 & α • Action: onset – 2 min half life – 2 min: continous IV • Metabolizd by cathechol-o-methyl transferase • Excretion: hepatobiliary system and kidney

  16. Dobut-protocol

  17. Protocol for Dobutamine Stress Echo.

  18. End points to terminate

  19. Works by inducing myocardial ischemia • Modest ↑ SBP and ↓DBP • May be arrhythmogenic (0.7% rate in 8500 consecutive studies performed at Mayo Clinic) • Usually ineffective in patients on beta blockers • High rate of side effects • Hypotension induced does not have prognostic value unlike TMT • Does not interact with dipyridamole

  20. Dipyridamole Potent coronary vasodilator Provoke anginal attack in angina patients Vasodilation effect inhibition of reuptake of adenosine by the endothelial cell CBF increases 4 to 5 times in normal vessel Reduction of subendocardial blood flow in stenotic coronary artery

  21. Dipyridamole Coronary steal phenomenon Standard protocol: 0.54 mg/kg for 4 min High dose protocol: 0.84mg/kg Antidote: theophylline

  22. CORONARY STEAL

  23. Dipyridamole Contraindication active wheezing high degree AV block hypotension(SBP<90 mmHg) recent use of dipyridamole(<24 hours) Relative contraindication Hx of reactive airway disease sick sinus syndrome severe sinus bradycardia

  24. Adenosine Naturally occuringagent Types of receptors A1: slowing HR and conduction A2a: c-AMP – decrease calcium uptake by SR -- smooth muscle relaxation vasodilation Half life: 2 seconds need constant IV infusion Rapidly removed from RBC and endothelial cell

  25. Adenosine – side effect Flushng: 37% Dyspnea: 35% GI discomfort: 15% Headache:14% Light-headedness 9% Most side effect – short-lived and mild

  26. Myocardial contrast in stress echo • Left vent opacification for border enhancement • Myocardial perfusion imaging • Perfusion at resting state-stress is performed and perfusion imaging is done at peak stress

  27. Vasodilator stress echo-perfusion imaging

  28. Stress Echo Stress Echocardiography Diagnosis Prognosis Viability Treatment

  29. Exercise –preferred-add information • > sensitive in CAD compared to dobutamine • Treadmill >sensitive, Bicycle>specific • Bicycle –during stress-> accurate presence and extend of disvs pat choice,availability etc. • Dobutamine is limited to pats who cant exert adequately & when the Q of viability is addressed • In pharmaclogical stress dobutamine is the agent- produces true ischemia than a flow mismatch

  30. INTERPRETATION OF STRESS ECHO • Subjective assessment of regional wall motion • Compares wall thickening & endocardial excursion at baseline and stress • Limitation- subjective & nonquantitative • Measures like EF, ESV change, and strain rate to overcome limitations

  31. Strain rate-myocardial velocity gradient -postsystolic shortening • TDI/Strain imaging> sensitive • Ischemia delays onset & rate of regional myo relaxation • Time quantified using TDI • QRS-onset of relaxation-350-400ms • Interval↓ by 34+/_10% in nl segments in response to high dose dopamine • ↓in interval is <12+/-18% in ischemic seg

  32. Grade 1-normal 2-hypokinesis 3-akinesis 4-dyskinesis • Nl WMSI-1 at baseline and stress • Any score>1-abnormal • Good prognostic value

  33. Hypokinesia-<5 mm of endocardial excursion • Akinesis - -vesyst thickening & endo excursion • Dyskinesis –systolic thinning & outward motion • nlresp-hyperkinesis • Absence –low work load, β blockade, cardiomyopathy & delayed post stress imaging • Localisation>specific in multivessel dis & in LAD than RCA/LCX

  34. Normal- hyperkinesis during stress test

  35. DYSKINESIA OF THE APEX IN STRESS

  36. Prognostic value A new wall motion abnormality,rest & exercise WMSI,ESV response-correlated with risk

  37. Chamber dilatation in resp to stress

  38. Prognostic value of stress echo • Independent predictors of cardiac events a)WMSI with exercise b) ST ↓≥1 mm c) treadmill time • Risk Index(RI)=1.02(WMSI)+1.04(ST change)− 0.14(Treadmilltime) • RI in upper quartile(+0.66 to+2.02)– risk was highest(30%) • Prognostic value is comparable in women and men

  39. Stress echo after revascularisation

  40. PRE-OPERATIVE RISK STRATIFICATION WITH DOBUTAMINE STRESS ECHO *Mayo Clinic, 530 Patients

  41. Perioperative marker of coronary event • patients with a positive electrocardiographic response to treadmill stress test but no inducible wall motion abnormality on stress echocardiogram have a very low rate of adverse cardiovascular events during follow-up

  42. VIABILITY OF MYOCARDIUM • That has the potential for functional recovery;- either stunned/hibernating myocardium • >6mm thickness -viable segment • Stunned or hibernating improved contractility with dobutamine , not in infarcted myocardium • Biphasic response – low dose ↑contractility(10 to 20 mcg/kg), at higher dose CBF ↓-- contractility ↓

  43. Biphasic response is the most predictive of the functional recovery after revascularisation • Sustained improvement/no change-nonviable • For viability assessment – nuclear techniques are more sensitive dobut stress echo more specific PPV-similar NPV- favoursdobut stress echo

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