Ventricular Aneurysm

Etiology

Schlichter et al. (1954) described in detail the etiological causes of ventricular aneurysms. The etiology of LV aneurysm is classified as follows:

• Congenital aneurysm: It is a sporadic type in either of the ventricles. These aneurysms are usually large and lined with thin fibrous tissue. They have broad-based communication with the ventricular cavity and contain unclotted blood.[6]
• Acquired aneurysm: which can be classified into[7]:
  • Ischemic: Almost 85% to 90% of the ventricular aneurysms occur in the setting of acute anterior wall myocardial infarction. 
  • Traumatic: They occur as a result of either accidental or surgical wounds.
  • Infective: Common causes include infective endocarditis, rheumatic fever, syphilis, tuberculosis, septic emboli, polyarteritis nodosa, etc.
  • Idiopathic: A ventricular aneurysm of unknown etiology usually occurs in Africans and occasionally in the white population. It is an unusual aneurysm often arising close to the mitral ring in the form of an annular subvalvular aneurysm. It stretches the mitral ring and interferes with the function of the papillary muscle, chordae tendinae, and cusps of the mitral valve.
  • Postpartum: Rarely left ventricular aneurysm can be seen secondary to postpartum cardiomyopathy.
  • Other causes: systemic hypertension, steroids, and NSAIDs use may predispose to aneurysm formation. Other causes include Chagas disease, sarcoidosis, etc.

Epidemiology

In the Coronary Artery Surgery Study (CASS), 7.6% of patients had a left ventricular aneurysm in a total population of 15000 patients. The LV aneurysm was found in 22% of the anterior wall myocardial infarction within 3 months of infarction. Ventricular wall aneurysm is associated with high cardiac mortality that can be around 67% and 80% for 3 months and 1 year, respectively.[8]

Pathophysiology

The transmural myocardial infarction due to the occlusion of either the left anterior descending artery or the dominant right coronary artery leads to the formation of a true left ventricular aneurysm. Two principal mechanisms are involved in its formation, the early expansion phase, and the late remodeling phase.[9]

Early Expansion Phase

A true left ventricular aneurysm following acute myocardial infarction can occur as early as 48 hours or two weeks post-infarction. 

Within hours of the infarction, the gross thinning of the infarct zone occurs. The migration of inflammatory cells in the infarct zone occurs by 2 to 3 days post-infarction. They contribute to the lysis of the necrotic myocytes by 5 to 10 days. Some viable myocytes are often present in the infarct area. There is a disruption of the collagen fibers, and along with the necrotic myocytes, it forms the nadir of myocardial tensile strength. Usually, in the infarcted zone, an extravascular hemorrhage can occur, leading to the decreased diastolic and systolic function of the heart. The factors contributing to the formation of the left ventricular aneurysm in the early phase include:

• Preserved contractility of the surrounding myocardium
• Transmural infarction
• Lack of collateral circulation
• Lack of reperfusion
• Elevated wall stress
• Hypertension
• Ventricular dilatation
• Wall thinning 

Late Remodeling Phase

About 2 to 4 weeks post-infarction, remodeling of the myocardium begins with the appearance of highly vascularized granulation tissue. It is replaced by fibrous tissue 6 to 8 weeks post-infarction. As the myocardium becomes replaced by fibrous tissue, it greatly decreases the ventricular wall thickness due to the loss of myocytes.

Histopathology

The aneurysmal wall examined at necropsy and in surgical specimens shows aneurysmal wall thickness between 0.3 to 5 mm. The wall is composed almost entirely of fibrous tissue, with a few strands only of elastic tissue and necrotic cardiomyocytes. Also, extensive calcification in the aneurysmal wall is the characteristic finding of a true ventricular aneurysm. The size of the aneurysm varies between 5 x 7 cm and 1O x 15 cm in diameter. The usual site of the aneurysm is anterior, with extension laterally towards the septum, owing to the occlusion of the left anterior descending artery in anterior myocardial infarction. An area of pericarditis is usually noted over the aneurysm. Further, a ventricular aneurysm consists of a laminated mural thrombus and consists of old and recent thrombotic elements.

History and Physical

History

Small aneurysms are usually asymptomatic and are typically diagnosed by routine investigations. However, large aneurysms present with signs and symptoms of thromboembolism, wall motion abnormalities, contractility defects, arrhythmias, and sudden cardiac death. Common symptoms associated with the ventricular aneurysm include:

• Fatigue
• Shortness of breath
• Chest pain
• Palpitations
• Syncope
• Fluid retention causes swelling of ankles, feet, or abdomen
• Stroke, or thromboembolic phenomenon to any organ in the body
• Limb or visceral ischemia

Physical Exam

Clinical examination of the cardiovascular system reveals abnormalities pertinent to associated complications with the ventricular aneurysm. The physical signs which should suspect the presence of ventricular aneurysm include:

• Tachycardia
• Arrhythmias
• Pericardial rub
• Abnormalities of cardiac impulse
• Paradoxical splitting of the S2
• S3 heart sound
• Pedal edema
• Fine inspiratory basal crept
• Murmurs

Complications

The following complications can occur after an LV aneurysm.[10]

Heart Failure and Ischemia

The LV dilation, paradoxical motion, and high end-diastolic pressure due to aneurysm result in ischemia and heart failure secondary to cardiac output loss. The long-standing volume overload can further cause worsening of LV aneurysm entering a loop that enforces worsening heart failure and ischemia with worsening LV aneurysm.

Ventricular Arrhythmias

The LV aneurysm can generate severe ventricular tachyarrhythmias leading to sudden cardiac death. The fibrous tissue at the LV aneurysm site or the transition zone of normal myocardium and the aneurysmal wall can be arrhythmia focus. 

Thromboembolization 

Stasis of blood at the aneurysmal site can increase the formation of a mural thrombus that can eventually dislodge and put the patient at risk of embolization to body organs, including the brain, to cause a stroke. 

Ventricular Rupture and Cardiac Tamponade

Mature LV aneurysms have fewer chances of rupture due to dense fibrous tissue, but early immature aneurysms can rupture with the potential to cause cardiac tamponade and shock. 

Evaluation

The evaluation can include the following diagnostic testings: [11]

Routine Investigations

Electrocardiogram

There are three key electrocardiographic features of LV aneurysm after acute myocardial infarction, including 1) Tall R wave in lead AvR known as Goldberger's sign. 2) Persistent ST-segment elevation with T wave inversion. 3) Small R waves in the leads of the distribution of the left ventricular wall. Other EKG findings can include ventricular arrhythmias that can be complications of LV aneurysm. 

Chest Radiograph

In an anteroposterior or slightly oblique view of chest x-ray, a ventricular aneurysm forms a well-circumscribed opacity projecting beyond the regular cardiac outline. In contrast, in the lateral view, it forms a rounded or oval shadow, partially or entirely superimposed upon that of the heart. 

Computed Tomography

CT scan is another reliable imaging modality for LV aneurysms. Cardiac CT can give a better view of the aneurysm wall and the presence of mural thrombus at the cost of risk of contrast-induced nephropathy (CIN). However, CIN can be prevented by prior hydration before giving contrast. In patients with ischemic heart disease, assessing LV segmental dysfunction in the form of wall-thinning and reduced wall motion is possible with electron-beam CT (EBCT).

Magnetic Resonance Imaging

The use of MRI as a noninvasive modality for identifying LV aneurysms and assessing resectability makes it a reliable test. For this purpose, dark-blood imaging may be employed to define the anatomy. It helps in delineating the bulging of the aneurysm. The blood pool motion in the aneurysm is characterized by dynamic bright-blood imaging.

Echocardiography

Two-dimensional echocardiography aids in a clear demonstration of a ventricular aneurysm. It may also help differentiate between a true and false type aneurysm by depicting a narrow neck compared to the size of the cavity. Color-flow echocardiographic imaging may identify abnormal flow within the aneurysm. This information may help identify a thrombus. A pulsed Doppler imaging can reveal an oscillatory to and fro motion of aneurysm that changes its variation with inspiration and expiration. Calculating LV systolic function and LV volume is possible with 3-D tomographic echocardiography. An echocardiogram showing a left ventricular aneurysm is seen in figure 1. 

Nuclear Imaging

Radionuclide ventriculography may demonstrate a ventricular aneurysm.

Angiography

Left ventriculography has become the "gold standard" and most accurate test for diagnosing and localizing the left ventricular aneurysm site. It demonstrates a large, discrete area of dyskinesia (or akinesia), generally in the anteroseptal-apical walls. Occasionally, left ventriculography also may demonstrate mural thrombus. A quantitative definition of left ventricular aneurysms has been accomplished using a centerline analysis of left ventricular wall motion on left ventriculography in the 30-degree right anterior oblique view. It defines the aneurysm as a hypocontractile segment contracting more than two standard deviations out of the normal range. The outer portion of the aneurysm is termed dyskinetic, and the remaining portion is akinetic. The fraction of the total left ventricular circumference occurring as an aneurysm is calculated as the value percent. 

Treatment / Management

The management of LV aneurysms includes medical and surgical.[10]

Medical Management:

Small or medium, or large LV aneurysms with no symptoms can be safely monitored with an expected five-year survival of up to 90%. The management can include optimization of coronary artery disease risk factors for ischemia prevention, afterload reduction with angiotensin-converting enzyme inhibitors or angiotensin receptor blockers, and anticoagulation to prevent thromboembolism. In patients with large LV aneurysms with symptoms, the management is the same as asymptomatic cases, plus specific treatment for complication/symptoms treatment and perform surgical management if there is any indication. In terms of anticoagulation, the risk of LV mural thrombus is highest within the first month after acute infarction; therefore, it is always prudent to employ anticoagulation in all patients using warfarin the first three months after LV infarction. Long-term anticoagulation should be reserved for patients with large, friable thrombi protruding into the ventricular cavity, documented systemic embolization beyond the three months, or while receiving anticoagulants, and globally impaired LV function.

Surgical Management

Relative indications for ventricular aneurysm operation include:

• Documented expansion
• Large size
• Angina
• Congestive heart failure
• Arrhythmia
• Rupture
• Pseudoaneurysm
• Congenital aneurysm
• Embolism 

All patients considered for surgery must undergo right and left cardiac catheterization with coronary arteriography and left ventriculography. An echocardiographic assessment of the mitral valve should be done with +2 mitral regurgitation with cardiac catheterization and should be evaluated for intrinsic valve disease not amenable for annuloplasty. The left ventricular aneurysmal repair constitutes aneurysmectomy, aneurysmorrhaphy, and ventricular restoration that requires cardiopulmonary bypass and a balanced anesthetic technique. The ultimate size of the left ventricular cavity at the end of the procedure is critical to patient outcomes. Using preoperative and postoperative three-dimensional techniques to image the left ventricle, Cherniavsky and colleagues proposed that the aneurysm resection or patch should produce a postoperative left ventricular end-diastolic volume of about 150 mL. 

The early surgical approaches, including nondirected aneurysmectomy or infarctectomy with or without revascularization for patients with LV aneurysm and drug-refractory ventricular tachycardia, were abandoned because of high operative mortality. With the advancement of electrophysiologic mapping techniques to demarcate the site of arrhythmogenic focus, a directed subendocardial ablation of the arrhythmia focus of LV aneurysm can be performed. This technique consists of an aneurysmectomy, along with excision of a 2-3 mm thick layer of subendocardial peri-infarcted tissue. With such an approach, tachycardia can be eliminated in 90% of patients with an operative mortality of about 10%.

Relative contraindications for left ventricular aneurysm correction surgery include greater anesthetic risk, myocardial dysfunction, cardiac index less than 2.0 liters/m2 per minute, severe mitral regurgitation, evidence of subendocardial infarction, and lack of a thin-walled aneurysm with prominent margins. 

Pseudoaneurysm

Untreated LV pseudoaneurysm can have a mortality of up to 50%. Surgery is the preferred treatment for pseudoaneurysm and holds perioperative mortality up to 10%. Percutaneous transcatheter device closure is preferred over open surgery.[12](B2)

Differential Diagnosis

A ventricular aneurysm can mimic a variety of clinical conditions, which include:

• Angina pectoris
• ST-elevation myocardial infarction
• Left ventricular pseudoaneurysm
• Ventricular wall rupture
• Pericarditis
• Myocarditis
• Cardiac tamponade
• Myocardial trauma
• Takotsubo cardiomyopathy

Prognosis

The natural history and prognosis of ventricular aneurysms are not well defined because most of the reports are based on retrospective data and autopsy studies. In two autopsy studies, in which the age of the aneurysm had to be estimated from a retrospective analysis of case notes, the 5-year mortality rates were 30 and 80%. The most common cause of death was recurrent myocardial infarction and not congestive heart failure. In clinical studies, the prognosis depends on the size of the aneurysm and the presence of symptoms. In the study of Mourdjinis et al., the 5-year mortality was 50% overall, but only 10% in patients with small aneurysms.

In the prospective CASS study, the cumulative 4-year survival rate in patients with angiographic LV aneurysms is 71%. The mortality was dependent on the extent of coronary disease and the degree of LV dysfunction. The presence of an aneurysm per se did not add to the risk of death. Whether surgical intervention with aneurysmectomy alters the natural history or outcome of the condition remains controversial. Large-scale prospective studies comparing conservative and surgical approaches are lacking.

The most recent reported 5-year survival figures following surgery range from 68 to 79%, with only 10% operative mortality. For conservatively treated patients, the survival data at five years is slightly different, ranging from 66.7 to 70%. In the CASS study, the comparison of patients with medically or surgically treated improved survival with surgery was reported only in selected high-risk subgroups, for example, those with triple-vessel disease. This study suggests that survival is determined primarily by revascularization and not aneurysmectomy. Cosgrove et al. demonstrated that the 7-year survival of patients undergoing aneurysmectomy was 65% in those undergoing complete revascularization, compared with 50% for those in whom revascularization was incomplete.

The prospective, randomized STICH (Surgical Treatments for Ischemic Heart Failure) trial may provide more definitive data regarding the effect of surgery for ventricular restoration on survival, ventricular size and function, quality of life, and exercise capacity. 

Complications

A left ventricular aneurysm can be associated with a variety of complications such as malignant arrhythmias, heart failure, cardiac ischemia, thromboembolism, and rupture of the ventricle. Almost one-third of the patients with ventricular aneurysms develop arrhythmias. The location of arrhythmogenic focus is usually between that of the normal myocardium and the affected myocardium.[13] This arrhythmogenic focus can be localized with the help of endocardial mapping within 2 cm of the origin. Unfortunately, in patients with polymorphous ventricular tachycardia and after myocardial infarction (within six weeks), the endocardial mapping may fail to localize the site. 

The common complications associated with the in-hospital repair of ventricular aneurysm include[14]:

• Low cardiac output
• Ventricular arrhythmias 
• Respiratory failure
• Bleeding 
• Dialysis-dependent renal failure 
• Stroke