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Echocardiography in the Evaluation of Intracardiac Sources of Embolism

Echocardiography in the Evaluation of Intracardiac Sources of Embolism. Airley E. Fish, MD Imaging Conference Wednesday May 13, 2009. Introduction. Intracardiac sources of CVA Account for 75-100k of 500k strokes/year in U.S. TEE

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Echocardiography in the Evaluation of Intracardiac Sources of Embolism

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  1. Echocardiography in the Evaluation of Intracardiac Sources of Embolism Airley E. Fish, MD Imaging Conference Wednesday May 13, 2009

  2. Introduction • Intracardiac sources of CVA • Account for 75-100k of 500k strokes/year in U.S. • TEE • Search for source of cardiac emboli is the leading clinical indication for TEE • More cost effective than TTE • Superior to TTE for most cardiac sources of emboli • Exceptions • Assessment of LV systolic function • Identification of LV apical thrombi

  3. Superiority of TEE vs TTE • Pearson et al 1991 in JACC • 79 patients with cryptogenic stroke • TEE ID’ed source in 57% • TTE ID’ed source in only 15% • Rauh et al 1996 in Stroke • 30 patients with CVA and low-risk for embolism • Sinus rhythm • No cardiac disease related to embolism • Minimal carotid artery stenosis • TTE showed no embolic sources • TEE showed • Aortic plaques in 19 • PFO in 7 • LAA thrombus in 3 • Atrial septal aneurysm in 2

  4. Major Sources of Emboli • Masses • LA/LV Thrombi • Atherosclerotic plaques • Vegetations • Tumors • Propensity for Thrombus Formation • LA spontaneous echo contrast • MAC • Passageways for Paradoxical Embolism • PFO/ASD

  5. Major Cardioembolic Sources Aortic Atherosclerotic Plaques Atrial myxoma LA Thrombus -Atrial fibrillation -Sustained atrial flutter PFO/ASD Rheumatic Mitral (MAC) or Aortic Valve Disease LA Spontaneous Echo Contrast LV Thrombus -Recent AMI -EF < 30% Mechanical or Bioprosthetic Valve Vegetations Tumors

  6. Most Common Sources of Emboli • LA Thrombi • LA Spontaneous Echo Contrast • Aortic Atherosclerosis • LV Thrombi • Prosthetic Valve Thrombi • Abnormalities of the Interatrial Septum

  7. LA Thrombi • Account for 45% of cardiogenic thromboemboli • Manning et al 1995, Annals of Internal Medicine • Intraoperative visualization vs TEE LA/LAA • Sensitivity and specificity TEE 100%, 99% • TTE LA/LAA • Sensitivity and specificity TTE 39%, 65% • Most often associated with • Atrial fibrillation and/or • Rheumatic mitral stenosis

  8. LA Thrombi – AF vs NSR • Leung et al 1997, Am Journal of Cardiology • 2894 patients underwent TEE for various indications • 94/2894 patients with LA thrombus • 83/94 in AF • Stoddard et al 1995, J American College of Cardiology • TEE looking for LA thrombus in patients with AF • Acute AF - 14% with thrombus • Chronic AF – 27% with thrombus • AF and clinical thrombus - 43% with thrombus (?up to 57% with migration) • Omran et al 2000, American Heart Journal • 869 patients with embolic CVA or TIA • If NSR, no MV disease, and normal LA function • Only 1% with LA thrombus • Therefore, routine TEE in sub-population not recommended

  9. LA Thrombi

  10. LA Thrombi FIGURE 21.34. In a patient with untreated rheumatic heart disease, a very large LA thrombus (arrows) is seen. The RA is also severely dilated.

  11. LAA Thrombi FIGURE 11.32. TEE image of the left atrial appendage (LAA) in a patient with rheumatic MS and a LAA thrombus. Irregular echo density mass filling the LAA (thin arrows). Boundary of the wall of the LAA is as noted by the heavier arrows.

  12. LA Thrombi FIGURE 21.41. A, B: Thrombus straddling the interatrial septum through a PFO and extending into the LA (small arrows). Thrombus was highly mobile & likely originated in the lower extremities. Increased mobility of atrial septal tissue indicated by large arrow.

  13. LA Thrombi

  14. LA Spontaneous Echo Contrast (SEC) • “Smoke-like” echoes seen within LA during TEE • Most common TEE finding in work up of thrombus source • Especially if AF or LAE • May also be seen in NSR • 26/1288 with SEC • 3/26 with LA thrombus (LAE, decreased LAA emptying velocity) • 2º RBC aggregation in low shear rate conditions • RBC aggregation mediated by plasma proteins • Particularly fibrinogen • Promote RBC rouleaux formation (via elimination of normal negative electrostatic forces of RBC’s aggregation) • Increased plasma fibrinogen levels • Hypercoagulable state – Mitral stenosis • >2/3 patients with MS have TEE e/o SEC • Atrial blood stasis • Increased LA levels of prothrombin 1 and 2 (procoagulants) • MR may spontaneous echo contrast frequency

  15. LA Spontaneous Echo Contrast FIGURE 11.30. TEE in a patient with rheumatic MS, LAE, and marked stasis of the blood within the LA and LAA. In the real-time image, the stasis of the blood appears as a dense swirling cloud of “smoke'' filling the LA and LAA.

  16. LA Spontaneous Echo Contrast FIGURE 22.48. Expanded view of the LAA in a patient with AF. No distinct thrombus but vague swirling smoke-like echoes suggesting stagnant blood in the body of the LAA.

  17. LA Spontaneous Echo Contrast FIGURE 21.39. Small thrombus within the LAA

  18. Aortic Atherosclerosis • TEE sensitive for visualization of aortic intima • CT/MRI experience limited, cannot characterize plaque mobility • Aortic atherosclerotic plaques source of • Thromboemboli (relatively common) • Unstable atherosclerotic plaque, superimposed thrombi embolize • Tend to be single, lodge in small or medium arteries • Often resulting in CVA/TIA • Can also result in limb and organ (kidney, GI, etc.) ischemia • Atheroemboli/Cholesterol Emboli (fairly rare) • Arterio-arterial embolism of small pieces of atheromatous material • Multiple small artery occlusions tissue/organ damage • Ischemic digits, retinal ischemia, intestinal infarction, etc. • Patients with • Unexplained CVA • TIA • Arterial embolization

  19. Aortic Atherosclerosis: Thromboembolism

  20. Aortic Atherosclerosis: Thromboembolism Postmortem specimen of a terminal aorta with a thromboembolus from a cat with HCM and an acute onset of caudal limb pain and paresis. Thromboembolus lodged at the terminal aorta ("saddle" thromboembolus), with portions extending into the external iliac arteries

  21. Aortic Atherosclerosis: Thromboembolism

  22. Aortic Atherosclerosis: Thromboembolism • Thoracic aortic plaque/plaque mobility – TEE • Complex aortic plaque • > 4 mm thick (more likely to be lipid-laden) • Mobile • Ulcerated • Pedunculated

  23. Aortic Atherosclerosis: Thromboembolism

  24. Aortic Atherosclerosis: Thromboembolism FIGURE 20.49. Suprasternal notch TTE in a patient with atheromatous involvement of the proximal descending thoracic aorta. Notice the relatively normal aortic arch (Ao) and the distinct echo density protruding into the lumen of the proximal descending thoracic aorta that represents focal pedunculated atheroma.

  25. Aortic Atherosclerosis: Thromboembolism FIGURE 20.51A. TEE in short-axis view of the descending thoracic aorta. Note the relatively circular aorta into which there is marked protrusion by pedunculated atheroma

  26. Aortic Atherosclerosis: Thromboembolism FIGURE 20.52. TEE recorded in the longitudinal plane of a descending thoracic aorta with aneurysm. The arrows outline the external boundary of the aorta with all space in between representing an aneurysm with complex atheroma. Note the markedly complex atheroma with multiple pedunculated and mobile components filling the dilated lumen.

  27. Aortic Atherosclerosis: Thromboembolism • Treat for 2º prevention of CVD if • Complex aortic plaque (regardless of CVA/peripheral embolism) • or Simple aortic plaque and unexplained CVA/peripheral embolism • 2º Prevention of CVD • Aspirin (or other antiplatelet agents) – ARCH trial underway in Europe • If CVA and plaque > 4 mm and/or mobile • ?Warfarin with goal INR 2-3 + statin • ?Aspirin 325 mg PO q day + statin • If no CVA and plaque mobile • ?Warfarin with goal INR 2-3 + statin • If no CVA and plaque > 4 mm • ?Aspirin 325 mg PO q day + statin • Statins (recommend same goal as for known CAD, no RCT’s to date) • Blood pressure control • Smoking cessation • If diabetic, glycemic control

  28. Aortic Atherosclerosis: Thromboembolism • Possible benefit of aortic arch replacement • Prophylactic atherectomy ? ‘ed CVA risk • Undergoing cardiac surgery consider • Intraoperative U/S to guide aortic manipulation sites • Use of off-pump CABG may be beneficial • Cross-clamping & performance of proximal anastamosis may risk of embolization 2º mechanical disruption

  29. Aortic Atherosclerosis: Cholesterol Emboli

  30. Aortic Atherosclerosis: Cholesterol Emboli

  31. Aortic Atherosclerosis: Cholesterol Emboli Light micrograph of an atheroembolus in a muscular renal artery showing cleft-like spaces (arrow) due to washout of the cholesterol crystals during histologic processing

  32. TEE descending thoracic aorta Massive atherosclerotic plaque Images on the right (1A, 2A, 3A) taken 1-2 seconds after their respective pictures on the left Arrows point to small particles of embolic material moving in transit in the aortic lumen Patient died from Intestinal infarction Renal failure Aortic Atherosclerosis: Cholesterol Emboli

  33. Aortic Atherosclerosis: Cholesterol Emboli • Risk factors for atheroembolic disease • Age • Smoking • Hypercholesterolemia • Hypertension • Agmon et al 2000, in Circulation • Population-based study of those with aortic plaque • Odds of complex plaque increased as ambulatory SBP increased • OR 1.43 for each 10 mmHg increase • Obesity • Diabetes • CRP

  34. Aortic Atherosclerosis: Cholesterol Emboli • Often blamed on Rx with anticoagulant drugs • ?plaque hemorrhage as precipitant • Tunick et al 2002, in Am J Cardiology • 519 with severe aortic plaque • Cholesterol emboli in only 5/519 over > 3 years • No difference between anticoagulation and events • 2/206 on warfarin • 3/313 off warfarin

  35. Aortic Atherosclerosis: Cholesterol Emboli • 2º Prevention of CVD • Aspirin (or other antiplatelet agents) • Statins (same goal as for 2º CAD, no RCT’s to date) • ?Lower LDL • ?Pleotrophic effects of plaque stabilization • In above retrospective trial of 519 patients, statins associated with a significantly lower rate of recurrent CVA & thromboembolism • Blood pressure control • Smoking cessation • If diabetic, glycemic control

  36. LV Thrombi – Background & Incidence • Among most common complications of STEMI • Dependent upon infarct location and size • Large, anterior STEMI’s • Aneurysm formation and akinesis or dyskinesis • Reduced LVEF • Increased WMA’s • Develop early (within 2 weeks, median 5 days), embolization within 1st 4 months • Incidence in reperfusion era – (predominantly thrombolytic therapy) • 8326 patients GISSI-3 database • LV thrombus 5.1%, overall • Anterior infarct 11.5% with LV thrombus • Other infarcts 2.3% with LV thrombus • May be underestimate (excluded severe CHF and SBP < 100 mmHg) • Incidence in reperfusion era – (primary PCI) • 163 patients • LV thrombus 4.3%, overall • Anterior infarct 10.4% with LV thrombus • Other infarcts 0% with LV thrombus

  37. LV Thrombi – Incidence and Risk Factors • In reperfusion era (incidence decreasing) • LV aneurysm 8-15% of Q wave infarctions • Mural thrombus ID’ed in >50% of these cases • Two factors contribute to clot formation • Stasis of flow in aneurysm cavity • Contact of blood with fibrous tissue in aneurysm (rather than normal endocardium)

  38. LV Thrombi - Diagnosis • TTE is a Class I indication for assessment of mural thrombus after acute STEMI • Presence of thrombus • Risk factors for embolization

  39. LV Thrombi - Appearance • Thrombus appearance • Very fresh/red • Protrude into cavity center • Highly mobile • Difficult to differentiate from effect of slowly moving cavitary blood seen within LV aneurysms (highly reflective, luminescent) • Older • Smooth cavitary surface (resemble liver tissue) • Less likely to change or embolize

  40. LV Thrombi – Risk for Embolization • High risk for embolization • Mobile thrombi • Embolization in 26/119 with LV thrombus s/p STEMI • Free mobility in 58% of patients with embolization • 15/18 patients with free mobility (83% vs 11%) embolized • Free mobility in 3% of patients without embolization • Protruding thrombi (into LV cavity) • Protrusion in 88% of patients with emboli • 23/40 patients with protruding thrombi embolized (58% vs 4%) • Protrusion in 18% of patients without emboli

  41. LV Thrombi - Prevention • ACE-I thought to result in fewer LV thrombi via preservation of LVEF and wall motion • No difference in patients on/off lisinopril in GISSI-3 • Short-term (10 days) • Unfractionated Heparin vs Heparin SQ • Out of 221 patients, LV thrombus in 11% vs 32% • 2004 ACC/AHA STEMI guidelines • Warfarin reasonable with severe LV dysfxn/WMA’s for the prevention of LV thrombus formation

  42. LV Thrombi – Embolization Prevention • No RCT’s • Warfarin reduces risk of embolization • May prevent thrombus extension • May prevent thrombus endothelialization • May not promote thrombus resolution • 2004 ACC/AHA STEMI guidelines - LV thrombus • Warfarin 3-6 months • Indefinitely, if no increased risk of bleeding • 2006 AHA/ASA – prevention of ischemic CVA • Warfarin 3 months – 1 year • Goal INR 2-3 • Also recommend concurrent ASA Rx for 2º prevention • Consider increased risk of bleeding in PCI (triple Rx)

  43. LV Thrombi FIGURE 4.24. Apical view in a patient with a vague echo density on noncontrast imaging. After IV injection of a perfluorocarbon-based agent, a distinct spherical filling defect is noted in the apex, consistent with a pedunculated apical thrombus

  44. LV Thrombi FIGURE 15.39. Apical four-chamber view recorded in a patient with an acute anterior apical MI and early thrombus formation. Note the regional dilation of the LV at the apex and the pedunculated, multilobulated mass protruding into the cavity of the LV.

  45. LV Thrombi FIGURE 15.64. Apical four-chamber view recorded in a patient with an acute anteroapical MI and a pedunculated, slightly mobile apical thrombus

  46. LV Thrombi FIGURE 15.65. Apical two-chamber view recorded in a patient with an anteroapical MI & multiple large pedunculated & mobile thrombi. Note multiple masses protruding into the cavity of the LV apex & the mobile nature of these thrombi in the real-time image.

  47. Prosthetic Valve Thrombi • Common in patients with mechanical valves • Especially if mitral/tricuspid valves (“low-flow”) • Especially if suboptimal anticoagulation • Goal INR 2.5-4.9 • Best evaluated by TEE • Although often assumed clinically • No other obvious cause • Sub-therapeutic INR • Confirmatory, but doesn’t change Rx • Unless valvular dysfunction 2º to a massive thrombus

  48. Prosthetic Valve Thrombus – Aorta FIGURE 14.39A. Even a small thrombus, if properly located, can result in obstruction. A: A St. Jude aortic prosthesis is shown. A thrombus was not visualized. B: Color Doppler imaging demonstrates increased turbulence and significant aortic regurgitation (arrow). C: From the transthoracic study, a peak pressure gradient of 95 mm Hg confirms the presence of significant obstruction.

  49. Prosthetic Valve Thrombus – Mitral FIGURE 14.37A. In this example, a large thrombus was visualized on transthoracic (A) imaging. The thrombus can be seen on the LA aspect of the mitral prosthesis.

  50. Abnormalities of the Interatrial Septum • Thromboemboli via 2 mechanisms • R L shunting via PFO/ASD • Interatrial septal aneurysm

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