Mechanical Complications of Mechanical Complications of Myocardial InfarctionMyocardial Infarction

Armed Forces Academy of Medical Sciences

EpidemiologyEpidemiology

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

Mechanical ComplicationsMechanical Complications

Free Wall RupturePseudoaneurysmRupture of Intraventricular septumRupture of Papillary Muscle

LV Free Wall RuptureLV Free Wall Rupture

Mean Age 698-15% of all deaths from MI10% of hospital deathsPeaks 3-6 days post MI, 25% within 24 hrs.

Ventricular Free Wall RuptureVentricular Free Wall Rupture

LV Free Wall RuptureLV Free Wall RupturePathophysiologyPathophysiology

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

LV Free Wall RuptureLV Free Wall RuptureRisk FactorsRisk Factors

Sustained HTNAGE, Female sexFirst 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

LV Free Wall RuptureLV Free Wall RuptureClinical CourseClinical 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 murmurDeviation from expected Evolutionary T-wave

pattern- 94% of pts.EMD, Bradydysrhythmias, AIVR common

Free Wall Rupture T-WavesFree Wall Rupture T-Waves

LV Free Wall RuptureLV Free Wall RuptureDiagnosisDiagnosis

Death often occurs prior to imaging . SCD 70%

Echo shows pericardial effusion, tamponadeOrganized thrombus in pericardial spaceIncomplete rupture may be missed by TTE,

TEEPA catheter shows equalization of

pressures-tamponade

LV Free Wall RuptureLV Free Wall RuptureManagementManagement

90% medical mortality; sugical case reports of correction

Inotropic agentsVolume LoadingPericardiocentesis

LV Free Wall RuptureLV Free Wall RuptureManagementManagement

IABP, hemodynamic stabilizationCoronary Angiography controversialBlind bypass of palpable lesionsInfarctectomy with closure of viable

myocardium– avoid suture in infarcted tissue

Dacron, Teflon or Pericardial patch

Free Wall Rupture RepairFree Wall Rupture Repair

Ruptured Papillary MuscleRuptured Papillary Muscle

Rupture Papillary MuscleRupture Papillary Muscle

Papillary Muscle RupturePapillary 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

Papillary Muscle RupturePapillary 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

Papillary Muscle RupturePapillary Muscle RupturePresentationPresentation

Mean age 65Peak incidence 3-5 days post-MI75% Inferior MINew Holosytolic Murmur in 50%

– pressure equalization may blunt murmur

Acute hemodynamic decompensation, pulmonary edema

Papillary Muscle RupturePapillary Muscle RuptureDiagnosisDiagnosis

Physical exam often non-diagnosticEcho may visualize chordal rupture, head of

pap muscle, flail leafletLV fxn well preserved in setting of

hemodynamic decompensationCoronary angiography prior to surgery if

condition permits

Papillary Muscle RupturePapillary Muscle RuptureManagementManagement

33% immediate death, 50% at 24 hrs., 80% within 2 weeks

Afterload reduction, vasodilatorsIABP-afterload reductionMV 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

Papillary Muscle RepairPapillary Muscle Repair

Interventricular Septal RuptureInterventricular Septal Rupture

Interventricular Septal RuptureInterventricular Septal Rupture

0.5-2 Percent of MI’s5 % of peri-infarction deathsMean Age 63HypertensionPoor collateral network

Interventricular Septal RuptureInterventricular Septal RuptureRisk FactorsRisk Factors

Large Transmural InfarctionsAnterior-Apical, Inferior-BasalVirtually all patients have severe, multi-

vessel CADFirst MI

Interventricular Septal RuptureInterventricular Septal RuptureClinical FeaturesClinical Features

Harsh, Loud Holosystolic Murmur at LLSB with thrill (50%)

Acute right sided heart failureMay have increased chest pain, SOBCardiogenic Shock

Interventricular Septal RuptureInterventricular Septal RuptureDiagnosisDiagnosis

Step up in oxygen saturation of RVAngiography if hemodynamically stable for

coronary anatomy, ventriculographyEcho

– Highly sensitive (96%) with careful apical-basal, and anterior-posterior sweeps of septum

– doppler to detect complex defects

Intraventricular Septal RuptureIntraventricular Septal RuptureManagementManagement

Diuretics, Ionotropes, Vasodilators-enhance forward flow, decrease shunting.

IABPSurgical repair

– 25% mortality at 24 hrs., 65% at 2 weeks without surgery

Cardiogenic shock 100% mortality without surgeryLV Fxn, magnitude of shunt do not correlate with

outcome

VSD RepairVSD Repair

Percutaneous VSD RepairPercutaneous VSD Repair

LV PseudoaneurysmLV Pseudoaneurysm

Rare complication of MIResults from incomplete rupture of wall

sealed by thrombus and pericardium

PseudoaneurysmPseudoaneurysm

PseudoaneurysmPseudoaneurysm

LV PseudoaneurysmLV PseudoaneurysmDiagnosisDiagnosis

Difficulty to distinguish from true anuerysmTo and Fro murmurPericardial friction rubEnlarging LV bulge on lateral or posterior

wallNarrow neck seen on Echo, or LV gram

LV pseudoaneurysmLV pseudoaneurysmManagementManagement

High propensity ruptureUrgent surgical repair indicatedTechnique similar to free wall ruptureSurvival 90% in stable pts.