Critical medicine topic-CMT 010
LEFT VENTRICULAR (LV)
ANEURYSM
FOLLOWING ACUTE
MYOCARDIAL INFARCTION (AMI)
Introduction
Left ventricular (LV) aneurysm is a well-recognized
mechanical complication of transmural acute myocardial infarction (AMI),
particularly after a large anterior wall infarction. It results from
thinning and outward bulging of infarcted myocardium during systole and
diastole, leading to impaired ventricular function, heart failure, arrhythmias,
and thromboembolic complications.
Incidence and Risk Factors
·
The incidence
depends on the frequency of transmural MI and congestive heart
failure.
·
Most commonly
develops after large anterior wall myocardial infarction.
·
Approximately 75%
of patients have multivessel coronary artery disease.
Location of LV Aneurysms
Anterior (True) Aneurysm
·
Accounts for more
than 80% of LV aneurysms.
·
Usually located anterolaterally
near the cardiac apex.
·
Most are true
aneurysms, containing thinned but intact myocardial wall.
Posterior (Pseudoaneurysm)
·
Represents 5–10%
of cases.
·
Nearly half
are false aneurysms (pseudoaneurysms).
·
Result from contained
myocardial rupture, with hemorrhage limited by pericardial adhesions.
·
No myocardium
is present in the aneurysm wall.
·
Pseudoaneurysms
have a much higher risk of rupture.
Clinical Manifestations
Heart Failure
·
Occurs in
approximately 50% of patients with moderate or large aneurysms.
·
May occur with or
without associated angina.
Angina
·
Present as the
predominant symptom in about 30% of patients.
Ventricular Arrhythmias
·
Approximately 15%
present with ventricular tachyarrhythmias.
Thrombus Formation and Embolism
·
Left
ventricular mural thrombi occur in
approximately 50% of patients.
·
Systemic
embolic events occur most frequently
during the first 4–6 months after MI.
·
Therefore, anticoagulation
(usually warfarin) is recommended during this high-risk period.
Diagnosis
Most Sensitive Investigation
·
Biplane left
ventriculography is the most
sensitive method for diagnosis and assessment of ventricular function.
Supportive Diagnostic Tests
·
Persistent ST-segment
elevation on ECG.
·
Bulge on the
cardiac silhouette on chest X-ray.
·
Radionuclide
ventriculography.
·
Two-dimensional
echocardiography.
These investigations can suggest the diagnosis but are
less accurate in assessing the aneurysm's effect on left ventricular
systolic function.
Indications for Surgery (Aneurysmectomy)
Surgical aneurysmectomy is recommended in symptomatic
patients with:
·
Congestive heart
failure.
·
Refractory
ventricular tachycardia.
·
Recurrent
systemic thromboembolism.
·
Refractory
angina.
Timing of Surgery
·
Whenever
possible, surgery should be delayed after the acute MI.
·
Waiting allows
the aneurysm wall to mature into firm scar tissue, facilitating safer
and more effective surgical repair.
Prognosis After Aneurysmectomy
Surgical treatment significantly improves outcomes:
·
70–80% of patients improve by at least one New York Heart
Association (NYHA) functional class.
·
Improvement in left
ventricular ejection fraction is common.
·
Long-term outcome
depends primarily on the preserved contractile function of the remaining
non-aneurysmal myocardium.
Key Facts
·
Most LV aneurysms
develop after large anterior transmural MI.
·
>80% are anterior true aneurysms.
·
5–10% are posterior; many are pseudoaneurysms.
·
50% develop heart failure.
·
50% have mural thrombus.
·
Embolic risk is
greatest during the first 4–6 months.
·
Biplane
ventriculography is the most
sensitive diagnostic test.
·
Aneurysmectomy is indicated for heart failure, refractory angina,
ventricular arrhythmias, or recurrent embolism.
·
Prognosis depends
on the function of the remaining left ventricular myocardium.
DR.C.GANESAN
M.D.,
PROFESSOR
OF MEDICINE
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