Mechanical Complications of Myocardial Infarction

1. Mechanical Complications of Myocardial Infarction • Armed Forces Academy of Medical Sciences

2. Epidemiology • 1.5 Million MI’s yearly in U.S. • 30% mortality • decline by 30% in last decade • In hospital mortality ~5% • 50% of deaths occur in first hr. secondary to ventricular arrhythmias- later lecture • Mechanical complications responsible for 15% of deaths

3. Mechanical Complications • Free Wall Rupture • Pseudoaneurysm • Rupture of Intraventricular septum • Rupture of Papillary Muscle

4. LV Free Wall Rupture • Mean Age 69 • 8-15% of all deaths from MI • 10% of hospital deaths • Peaks 3-6 days post MI, 25% within 24 hrs.

5. Ventricular Free Wall Rupture

7. LV Free Wall RupturePathophysiology • Usually involves anterior or lateral walls in distribution of terminal LAD • Large, transmural MI’s involving > 20% of myocardium. • Tear in myocardium or dissecting hematoma at junction of infarct and normal muscle. Shearing effect produces laceration of myocardial microstructure

8. LV Free Wall RuptureRisk Factors • Sustained HTN • AGE, Female sex • First MI, Normal LV function • Increased shearing forces • Corticosteroids, NSAID’s • Impaired wound healing • Late use of Thrombolytics • decreased incidence with early therapy • Persistent occlusion, lack of collaterals

9. LV Free Wall RuptureClinical Course • Ruptured free wall leads to hemopericardium and death through tamponade, cardiogenic shock • Nausea, hypotension, pericardial pain, agitation • ? prodromal bleeding, seen in 80% of pts with rupture • 25% have new murmur • Deviation from expected Evolutionary T-wave pattern- 94% of pts. • EMD, Bradydysrhythmias, AIVR common

10. Free Wall Rupture T-Waves

11. LV Free Wall RuptureDiagnosis • Death often occurs prior to imaging . SCD 70% • Echo shows pericardial effusion, tamponade • Organized thrombus in pericardial space • Incomplete rupture may be missed by TTE, TEE • PA catheter shows equalization of pressures-tamponade

12. LV Free Wall RuptureManagement • 90% medical mortality; sugical case reports of correction • Inotropic agents • Volume Loading • Pericardiocentesis

13. LV Free Wall RuptureManagement • IABP, hemodynamic stabilization • Coronary Angiography controversial • Blind bypass of palpable lesions • Infarctectomy with closure of viable myocardium • avoid suture in infarcted tissue • Dacron, Teflon or Pericardial patch

14. Free Wall Rupture Repair

15. Ruptured Papillary Muscle

16. Rupture Papillary Muscle

17. Papillary Muscle Rupture • MR Transiently present in up to 80% of MI pts. • usually of no hemodynamic significance • Mitral Annular Dilitation, Wall motion asynergy, Papillary muscle dysfunction/rupture • 0.9-5% of all deaths from MI • 50% mortality within 24hrs., 80% within 2 weeks

18. Papillary Muscle Rupture • Inferior MI leads to rupture of Postero-medial pap muscle/AMI-antero-lateral pap muscle (rare) • PM pap muscle single supply from PDA • AL pap muscle dual supply from LAD/Cx • Complete transection incompatible with life • Occurs with small infarctions, moderate CAD • 50% have subendocardial infarct, single vessel dz • Greater shearing forces • Length of coronary vessels, subendocardial location may predispose to ischemia

19. Papillary Muscle RupturePresentation • Mean age 65 • Peak incidence 3-5 days post-MI • 75% Inferior MI • New Holosytolic Murmur in 50% • pressure equalization may blunt murmur • Acute hemodynamic decompensation, pulmonary edema

20. Papillary Muscle RuptureDiagnosis • Physical exam often non-diagnostic • Echo may visualize chordal rupture, head of pap muscle, flail leaflet • LV fxn well preserved in setting of hemodynamic decompensation • Coronary angiography prior to surgery if condition permits

21. Papillary Muscle RuptureManagement • 33% immediate death, 50% at 24 hrs., 80% within 2 weeks • Afterload reduction, vasodilators • IABP-afterload reduction • MV replacement or repair • may be delayed up to 6 weeks if pt. stable to allow myocardial healing s/p MI • 50% of those initially stabilized will decompensate

22. Papillary Muscle Repair

23. Interventricular Septal Rupture

24. Interventricular Septal Rupture • 0.5-2 Percent of MI’s • 5 % of peri-infarction deaths • Mean Age 63 • Hypertension • Poor collateral network

25. Interventricular Septal RuptureRisk Factors • Large Transmural Infarctions • Anterior-Apical, Inferior-Basal • Virtually all patients have severe, multi-vessel CAD • First MI

26. Interventricular Septal RuptureClinical Features • Harsh, Loud Holosystolic Murmur at LLSB with thrill (50%) • Acute right sided heart failure • May have increased chest pain, SOB • Cardiogenic Shock

27. Interventricular Septal RuptureDiagnosis • Step up in oxygen saturation of RV • Angiography if hemodynamically stable for coronary anatomy, ventriculography • Echo • Highly sensitive (96%) with careful apical-basal, and anterior-posterior sweeps of septum • doppler to detect complex defects

28. Intraventricular Septal RuptureManagement • Diuretics, Ionotropes, Vasodilators-enhance forward flow, decrease shunting. • IABP • Surgical repair • 25% mortality at 24 hrs., 65% at 2 weeks without surgery • Cardiogenic shock 100% mortality without surgery • LV Fxn, magnitude of shunt do not correlate with outcome

29. VSD Repair

30. Percutaneous VSD Repair

31. LV Pseudoaneurysm • Rare complication of MI • Results from incomplete rupture of wall sealed by thrombus and pericardium

32. Pseudoaneurysm

33. Pseudoaneurysm

34. LV PseudoaneurysmDiagnosis • Difficulty to distinguish from true anuerysm • To and Fro murmur • Pericardial friction rub • Enlarging LV bulge on lateral or posterior wall • Narrow neck seen on Echo, or LV gram

35. LV pseudoaneurysmManagement • High propensity rupture • Urgent surgical repair indicated • Technique similar to free wall rupture • Survival 90% in stable pts.