Understanding Complications of Acute Myocardial Infarction

1. Complications of Acute M.I. Douglas Burtt, M.D.

2. Coronary atherosclerosis

3. Schematic of an Unstable Plaque

4. Cross section of acomplicated plaque

5. Journey down a coronary…

6. Frank Netter: View of the Heart

7. Left Anterior Descending Occlusion Occlusion of the left anterior descending coronary artery

8. Experimental Data • Canine studies – transient artery clamping or ligation • Balloon angioplasty studies • Time dependent series of events • Chest Pain as a late event

9. ACUTE M.I.THE “ISCHEMIC CASCADE” Diastolic dysfunction Chest pressure, etc. Acute MI Release of CPK Ischemic EKG changes Localized systolic dysfunction

10. ACUTE M.I.THE “ISCHEMIC CASCADE” • Diastolic dysfunction • Localized systolic dysfunction • Ischemic EKG changes • Chest pressure, etc. • Release of CPK

11. Time course of cell death • 20 - 40 minutes to irreversible cell injury • ~ 24 hours to coagulation necrosis • 5 - 7 days to “yellow softening” • 1 - 4 weeks: ventricular “remodeling” • 6 - 8 weeks: fibrosis completed

12. Think Anatomically!! • Left main coronary artery supplies two-thirds of the myocardium • LAD supplies ~ 40% of the L.V., including apex, septum and anterior wall • RCA supplies less L.V. myocardium, but all of the R.V. myocardium

13. Blood supply of the septum

14. Think Anatomically!!! • LAD supplies most of the conduction system below the A-V node(i.e. the His-Purkinje system) • RCA supplies most of the conduction system at or above the A-V node(i.e. the A-V node and, usually, the S-A node)

15. Conduction System of the Heart

16. Conduction System: detail

17. ACUTE M.I.Anatomical correlates LAD occlusion causes extensive infarction associated with: • LV failure • High grade heart block • Apical aneurysm formation • Thrombo-embolic complications

18. ACUTE M.I.Anatomical correlates RCA occlusion causes moderate infarction associated with: • RV failure • Bradyarrhythmias • Occasional mechanical complications

19. ACUTE M.I.Arrhythmias • Sinus bradycardia • Sinus tachycardia • Atrial fibrillation • PVCs / ventricular tachycardia /ventricular fibrillation • Heart block

20. Arrhythmias:Inferior M.I. • Sinus bradycardia -- S.A. nodal artery and increased vagal tone • Heart block -- A-V nodal artery1st degree A-V blockWenckebach 2nd degree A-V blockA-V dissociation • Atrial fibrillation -- L.A. stretch • Ventricular tachycardia / fibrillation -- via “re-entry” or increased automaticity

21. Arrhythmias:Anterior M.I. • Sinus tachycardia -- low stroke volume • Heart block -- His-Purkinje systemLeft or Right Bundle branch blockComplete Heart Block • Ventricular tachycardia / fibrillation due to “re-entry” or increased automaticity

22. ACUTE M.I.Hypotension • Identify hemodynamic subset • Distinguish decreased preload from decreased cardiac output • Think about hemodynamic monitoring

23. Hemodynamic subsets • Starling curves to plot “preload” versus cardiac output • Identification of high risk subgroups • Definition of cardiogenic shock Cardiac Output L.V.E.D.P.

24. 1 3 Cardiac Index (L/min/m2) 2 4 L.V.E.D.P. Hemodynamic Subsets

25. Acute M.I.Mechanical Complications • Rupture of free wall Tamponade Pseudoaneurysm • Rupture of papillary muscle Acute Mitral regurgitation • Rupture of intraventricular septum Acute V.S.D.

26. ACUTE M.I.Papillary Muscle RuptureLeading to Acute M.R.

27. ACUTE M.I.Papillary Muscle RuptureLeading to Acute M.R. • Systolic murmur • Giant V - waves on PC Wedge tracing • Echo/Doppler confirmation • RX with Afterload reduction • Intra-aortic balloon pump

28. “Flail” Mitral Leaflet

29. Echo/Color Doppler of Acute M.R. LV RA LA

30. Development of giant “V waves” P.C. Wedge pressure P. A. pressure V-wave

31. Acute Mitral Regurgitation:Treatment • Rapid diagnosis • Afterload reduction • Inotropic support • Intra-aortic balloon pump • Surgical valve replacement

32. ACUTE M.I.Acute Ventricular Septal Defect • Can occur with either anterior or inferior MI • Peak incidence on days 3-7 • Causes an abrupt left-to-right “shunt”

33. ACUTE M.I.Acute Ventricular Septal Defect • Abrupt onset of a harsh systolic murmur, often with a “thrill” • Detected by an oxygen saturation “step-up”

34. Oxygen saturation “step-up”

35. Acute V.S.D.:Treatment • Rapid diagnosis • Afterload reduction • Inotropic support • Intra-aortic balloon pump • Surgical repair of ruptured septum

36. Intra-Aortic Balloon Pump • Augments coronary blood flow during diastole • Decreases afterload during systole by deflating at the onset of systole • Reduces myocardial ischemia by both mechanisms

37. Intra aortic balloon pump

38. Intra-aortic balloon pump

39. Cardiac TamponadeEqualization of diastolic pressuresHypotensionJ.V.D.Clear lung fields Pulsus paradoxus Pseudoaneurysm Enlarged cardiac silhouette Echocardiographic diagnosis Free Wall Rupture

40. ACUTE M.I.Apical Aneurysm • Associated with large, transmural antero-apical MI • Can lead to LV apical thrombus • Is associated with ventricular arrhythmias

41. ACUTE M.I.Apical Aneurysm • Causes “dyskinesis” of the apex • Can be detected by cardiac echo • Can lead to systemic emboli • Anticoagulants may prevent embolization

42. Right Heart Failure • Very commonly a sequela of Left Heart Failure • LVEDP • PCW • PA pressure • Right heart pressure overload • Cardiac causes • Pulmonic valve stenosis • RV infarction • Parenchymal pulmonary causes • COPD • ILD • Pulmonary vascular disease • Pulmonary embolism • Primary Pulmonary hypertension

43. ACUTE M.I.Right Ventricular Infarction • Jugular venous distention with clear lungs • Equalization of right atrial and PCW pressures • ST elevation in right precordial leads • Therapy with fluids

44. 1 3 Cardiac Index (L/min/m2) 2 4 L.V.E.D.P. Hemodynamic Subsets

45. ACUTE M.I.Pericarditis • Pleuritic chest pain • Radiation to the trapezius ridge • Fever • Pericardial friction rub

46. ACUTE M.I.CARDIOGENIC SHOCK • Large area of myocardial necrosis • Consider mechanical complications • Exclude correctable causes -- i.e. hypovolemia or R.V. infarct • I.A.B.P. C.A.B.G. OR P.T.C.A.

49. Think anatomically!!! LAD vs. RCA Think hemodynamic subsets!!! Summary Watch for mechanical complications

50. THE END