post CABG Myocardial Infarction : Latest Diagnostic and Therapeutic Approach

1. post CABG Myocardial Infarction : Latest Diagnostic and Therapeutic Approach Susana G. Garcia MD

2. No Disclosure

3. Objectives • Review the current definition, risk factors, clinical impact and incidence of PMI • Describe the different clinical presentation of PMI and how this dictate the goal and approach to diagnosis and treatment of PMI • Describe the use and limitation of different diagnostic tools in the evaluation of perioperative ischemia and infarction • Present current data on novel diagnostic tools and therapies used in PMI

4. Objectives • Present algorithmic approach to post CABG patients with signs of ongoing ischemia • Discuss the recent guideline on: • Resuscitation of cardiac arrest after cardiac surgery • Mechanical Circulatory Support • Mgt of Early Graft Failure

5. Universal Definition of Perioperative Myocardial Infarction “ an increase in biomarker values to > 5x the URL during the first 72 h ff CABG, when associated with: • the appearance of new pathological Q-waves or new LBBB or • angiographically documented new graft or native coronary artery occlusion or • imaging evidence of new loss of viable myocardium” ESC-ACCF-AHA-WHF Universal Definition of Myocardial Infarction

6. Pre-op Risk factors of PMI • Age >70 years (ESC) • Female gender • Renal Failure • Diabetes • Peripheral artery disease • Emergency CABG • Repeat CABG • Preop MI • Preop Ischemia • Cardiomegaly • Diastolic dysfunction • Prior MI • Use of nsaid • No bb , no statin, no asa • Severe LVdysfsn(EF<35%) or cardiogenic shock

7. Intraoperative Risk factors of PMI • Long CPB time • CABG combined with other surgery • Intraop ischemia • Surgical technique • Inadequate protection

8. Post-op Risk factors of PMI • High Hct(Spiess B. D. et al.; J ThoracCardiovascSurg 1998;116:460-46) • Rapid arrhythmias • Hypertension • Hypotension • Tachycardia from • Volume depletion • Blood loss • Inotropes. Pressores • Pain

9. Significance of PMI • PMI is associated with adverse outcome • Available data suggests a direct correlation between : • the amount of myonecrosis • the likelihood of reduced survival

10. Incidence of PMI • Because of the wide variability in the definitions used, the incidence of reported MI is highly variable • Incidence= of 2–40%

11. Diagnosis of PMI • is not straightforward • In the early period the critical issue is : • to determine whether there is acute severe ischemia/infarction due to • Early Graft Failure • Acute Native Coronary Thrombosis • that warrants urgent intervention.

12. Diagnosis of PMI • Some degree of myocardial injury virtually always occurs after CABG • At one end of the spectrum, the myocardial injury is manifested as a small troponin release with no clinical sequelae • Troponin release may be from: • Myocardial trauma • Imperfect myocardial protection

13. Diagnosis of PMI • At the other end of the spectrum, is severe myocardial ischemia or infarction that is associated with hypotension, LCOS and ventricular arrhythmias • This latter situation demands urgent investigation because it may represent an acute obstruction of a coronary graft or native coronary vessel • Timely intervention may be life saving

14. Initial Goal in theEvaluation of PMI • To search for signs of ischemia/infarction which may be due to • Early Graft Failure • Acute Native Coronary Thrombosis • that warrants urgent intervention.

15. Clinical Assessment of PMI • Angina (not reliable): • Pain from myocardial ischemia is very difficult to distinguish from wound pain • Most are sedated and ventilated during the early post op period • Cannot report symptoms • Hemodynamic Instability: • Has many causes • But one important to consider is ischemia

16. Clinical Assessment of PMI • Hemodynamic Instability • Acute ischemia of severity sufficient to cause hypotension or low cardiac output state : • implies a large region of threatened myocardium • warrants urgent intervention and treatment • Swan Ganz Catheter Measurements suggestive of LCOS • Increased in PA pressure • Increased PCWP • Low CO

17. Signs of Ongoing Ischemia

18. 39 patients with post op suspicion of graft failure

19. ECG Diagnosis • New significant Q waves • ≥ 0.04 second duration in any two leads except III and aVR • may be indicative of full-thickness MI • but they take 24 to 48 hours to develop • therefore not useful in the assessment of suspected ischemia • ST segment depression • ≥ 1 mm, measured 0.06 sec after the J point • if it occurs, develops concurrently with myocardial ischemia. • ST segment elevation, with the subsequent new Q waves after CABG surgery • may provide a useful marker of acute ischemia.

20. ECG Diagnosis • Diffuse upsloping ST elevation • Pericarditis • do not mply ischemia. • New LBBB or AV block • may indicate acute ischemia, • but they too are common following cardiac surgery. • Recurrent Ventricular Tachycardia • strongly suggestive of severe acute ischemia.

21. ECG Diagnosis • Despite the limitations of ECG analysis, • the finding of ST segment depression or elevation that is limited to a specific coronary territory • + hemodynamic instability / ventricular arrhythmias • is strongly suggestive of acute ischemia.

22. Echocardiography • All patients with suspected myocardial ischemia after CABG surgery should undergo urgent echocardiograms • —preferably a transesophageal echocardiogram examination looking SWMAs • SWMAs • are more sensitive and specific for myocardial ischemia than ECG changes • but they can be difficult to interpret in postoperative patients.

23. Biochemical Markers • Troponin I • a value > 20 μg/l is associated with prolonged hospital stay • indicative of early graft failure Salamonsen RF,. ClinChem 2005; 51:40-46. • Troponin T • a value > 1.58 μg/l at 18 to 24 hours after surgery is predictive of adverse outcome, including death. Januzzi JL. J Am CollCardiol 2002; 39:1518-1523.

24. Biochemical Markers • A limitation of making judgments based on troponins is that peak levels occur at about 24 hours after an ischemic event • Troponin T peaks a little later than troponin I • Thus, these markers are not ideal for the evaluation of acute ischemia soon after surgery.

25. Biochemical Markers • CKMB • is less sensitive and specific than the troponins • takes nearly 24 hours to reach peak levels. • Myoglobin levels • peak within 6 to 12 hours of ischemic injury • but are poorly predictive of outcome. Costa MA(ARTS trial). Circulation 2001; 104:2689-2693.

26. cTnI elevation after CABG discriminates patients: • with graft-related PMI • non-graft-related PMI • without PMI • however, not earlier than 12 h after surgery. • This detection window is far too long to enable timely rescue strategies

27. New Biomarkers for Ischemia • Reported to detect ischemia within the first 30 minutes: • Heart type fatty acid binding protein(hFABP) • Ischemia Modified Albumin • May enable early intervention aimed at restoring myocardial flow

28. Interventions for Suspected Postoperative Myocardial Ischemia

29. Approach to Diagnosis and Treatment PMI • If ischemia is suspected on the basis of hemodynamic instability or ECG changes • urgent transesophageal Initiate Mgt for Arrhythmia, Ischemia. LCOS

30. 2010 ESC Guideline in Myocardial Revasc

31. Approach to Diagnosis and Treatment PMI • If ischemia is suspected on the basis of hemodynamic instability or ECG changes • urgent transesophageal Initiate Mgt for Arrhythmia, Ischemia. LCOS

33. Management of MyocardialIschemia: • Class I Recommendations • to reduce the risk of perioperative myocardial ischemia and infarction, management targeted at optimizing the determinants of coronary arterial perfusion • heart rate • diastolic or mean arterial pressure, and • right ventricular or LV end-diastolic pressure • is recommended (Level of Evidence: B) 2011 ACC AHA CABG Guideline

34. Intraoperative Evaluation of Myocardial Ischemia Intraoperative TEE PA Cath ECG Intraoperative Graft Assessment

35. TEE vs PA Cath • TEE : useful for evaluation of • LVEDA/LVEDV • EF and CO • LVEDP • Valve Function • PHTN • Shunts • Complications • Ischemia ( New RWMA) • guide surgical therapy • lead to • revison of failed conduit • placement of additional grafts not originally planned • Potentially superiority over Swan PCWP or PADP in assessment of LVEDP in the early post op period Fontes ML, Bellows W, Ngo L, et al. Assessment of ventricular function in critically ill patients: limitations of PAC J CardiothoracVascAnesth. 1999;13:521–7.

36. Live 3DTEE • Time to minimal regional volumes • normal subject • synchronous • in a heart failure patient • dispersed Translational Research Volume 159, Number 3

37. New TEE Technologies for Detection of Ischemia • Doppler Tissue Imaging • Real Time 3D TEE • Speckle Tracking • Cost effectiveness has not been determined • Too complex for routine use

38. Intraoperative Graft Assessment • Graft patency strongly influences early and late outcomes after CABG. • Transit Time Flow Measurement • quantitative volume flow technique, • cannot • define the degree of graft stenosis

39. A randomized comparison of intraoperative ICG angiography and transit-time flow measurement to detect technical errors in coronary bypass grafts Journal of Thoracic and Cardiovascular Surgery,Volume 132, Issue 3, September 2006, Pages 585-594Nimesh D. Desai Indocyanine Green Angiography • Diagnostic accuracy for detecting clinically significant graft failure • ICG > Transit-time US flow measurement. LIMA Anastomosis LAD

40. Indocyanine Green Angiography • High inter-rater reliability for graft patency between surgeons. • For graft stenosis >50% • Sn=100% • Sp=100% LIMA Anastomosis LAD Desai JACC Vol 46, Issue 8, 18 Oct 2005, pp 1521-25

41. The Hybrid Suite • has the capability of serving both as: • a complete surgical OR • a cath laboratory. • It allows for • routine completion angiogram following CABG surgery • identifies abnormal grafts, providing the opportunity to revise them with PCI surgery before leaving the OR. • SeminThoracCardiovascSurg 21:207-212

42. The Graft Imaging to Improve Patency (GRIIP) clinical trial results The Journal of Thoracic and Cardiovascular Surgery, Volume 139, Issue 2, February 2010, Pages 294-301.e1 * Steve K. Singh, MD, MS • Yes • No • Is Routine intraoperative graft assessment safe? • Does it lead to a marked reduction in graft occlusion 1 year after CABG?

43. Interventions for Suspected Postoperative Myocardial Ischemia

44. Cardiac Arrest / Shock from PMI

45. 2010 European Resuscitation Council Guideline: Cardiac Arrest Following Cardiac Surgery • Incidence 0.7-2.9% • Potentially reversible • If treated promptly has a high survival rate • 54-79% • Key to successful resuscitation • Early resternotomy • esp if + tamponade (external chest compression not effective)

47. During witnessed arrest of post cardiac surgery patients, Can I start chest compression?

48. 2010 ESC CPR Guideline: • External chest compression should be started immediately in all patients who collapse without a pulse • Correct reversible cause (K, volume, bleeding, O2, acidosis, ischemia) • During CPR… • IABP changed to pressure trigger • If unable to attain SBP of at least 80mmHg with effective compression: may indicate tamponade • Do early resternotomy

49. Witnessed and Monitored VF/VT Arrest 3 quick defibrillation  3 failed shocks  Emergency Resternotomy  Further defibrillation as indicated should be performed with internal paddles at 20 joules after resternotomy  Amiodarone 300mg after 3rd failed defibrillation attempt (but don’t delay resternotomy)

50. “An irritable myocardium ff cabg is caused most commonly by myocardial ischemia Correction of Ischemia, rather than giving Amiodarone, is more likely to achieve myocardial stability”