Ventricular Septal Rupture Following Myocardial Infarction 

Ventricular septal rupture (VSR) is a rare but lethal complication of myocardial infarction (MI). The event occurs 2-8 days after an infarction and often precipitates cardiogenic shock.^[1] The differential diagnosis of postinfarction cardiogenic shock should exclude free ventricular wall rupture and rupture of the papillary muscles. To avoid the high morbidity and mortality associated with this disorder, patients should undergo emergent surgery.^{[2, 3, 4, 5]} Concomitant coronary artery bypass may be required. Developments in myocardial protection and improved prosthetic materials have contributed greatly to successful management of VSR.^[6] Long-term survival can be achieved in patients who undergo prompt surgery.

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Latham first described this condition at autopsy in 1847, but he did not make the association between acquired VSR and coronary artery disease (CAD). Brunn made the first antemortem diagnosis of acquired VSR in 1923, and, in 1934, Sager established the clinical association between MI and VSR.

No surgical treatment was available until 1957, when Cooley et al performed the first successful surgical repair of VSR in a patient 9 weeks after the diagnosis. Unfortunately, the patient died 6 weeks later.

Principal treatment of postinfarction VSR during the early 1960s consisted of aggressive medical management, although it was well known that survival was rare after medical treatment alone. Surgical therapy was generally reserved for patients who survived at least 6 weeks, primarily to allow for scarring of the edges of the defect. A secure and long-lasting closure was thought to occur if the edges of the VSR were strong enough to hold the sutures.

By the late 1960s, early surgical repair was proposed for patients whose conditions were deteriorating despite medical therapy. The timely introduction of better prosthetic material significantly contributed to the successful surgical repair of acute VSR.^[6]

More recently, improved surgical techniques (eg, infarctectomy), myocardial protection, and better perioperative mechanical and pharmacological support have helped to lower mortality rates. In addition, the development of surgical techniques to repair perforations in different areas of the ventricular septum have led to improved results in the management of patients with postinfarction VSR.

Frequency

Rupture of the interventricular septum is an uncommon complication of MI. Although autopsy studies reveal an 11% incidence rate of myocardial free wall rupture after MI, septal wall perforation is much less common, occurring at rate of approximately 1-2%.

VSR occurs in a zone of necrotic myocardial tissue, and it usually occurs within the first 10-14 days. Clinical studies report an average time of 2.6 days from infarction to septal rupture. However, recent data suggest that the initial treatment of MI with thrombolytics may affect both the time between infarction and septal rupture and outcome. The early use of thrombolytic agents may lead to reopening of the occluded vessels, thus reducing the incidence of VSR.

The age range of patients who sustain a postinfarction VSR is wide, from 44-81 years. Men are affected more commonly than women, although septal rupture is more common in women than would be predicted based on the prevalence of CAD alone.

The blood supply to the septum originates from branches of the left anterior descending coronary artery, the posterior descending branch of the right coronary artery, or the circumflex artery when it is dominant. An infarction associated with a VSR is usually transmural and extensive. Approximately 60% of septal ruptures occur with infarction of the anterior wall; 40% occur with infarction of the posterior or inferior wall. Posterior VSR may be accompanied by mitral valve insufficiency secondary to papillary muscle infarction or dysfunction. At autopsy, patients with VSR usually show complete coronary artery occlusion with little or no collateral flow. The lack of collateral flow may be secondary to associated arterial disease, anatomic anomalies, or myocardial edema. Sometimes, multiple septal perforations occur. These may occur simultaneously or within several days of each other.

Ventricular aneurysms are commonly associated with postinfarction VSR and contribute significantly to the hemodynamic compromise in these patients. The reported incidence rate of ventricular aneurysms ranges from 35-68%, whereas the incidence of ventricular aneurysms alone following MI without VSR is considerably less (12.4%).

Natural history

The natural history of postinfarction VSR is greatly influenced by hypertension, anticoagulation therapy, advanced age, and, possibly, thrombolytic therapy. The natural course in patients with postinfarction VSR is well documented and short. Most patients die within the first week; almost 90% die within the first year. Reports indicate that fewer than 7% of patients are alive after 1 year. This grim prognosis results from an acute volume overload exacted on both ventricles in a heart already compromised by a large MI and occasionally by extensive CAD in sites other than that already infarcted. In addition, superimposed ischemic mitral valve regurgitation, a ventricular aneurysm, or a combination of these conditions may be present, which further compromises heart function. The depressed left ventricular function commonly leads to impaired peripheral organ perfusion and death in most patients.

A few sporadic reports indicate that some patients with medically treated postinfarction VSR live for several years. Although many medical advances have been made in the nonsurgical treatment of these patients, including intra-aortic balloon counterpulsation (IABCP), these methods have not replaced the need for surgery.

Differential diagnosis

An important diagnostic test for differentiating VSR from mitral valve insufficiency is catheterization of the right heart with a Swan-Ganz catheter. In the presence of a VSR, oxygen concentration between the right atrium and the pulmonary artery is stepped up. In addition, a pulmonary capillary wedge pressure tracing is beneficial for differentiating acute mitral regurgitation from VSR. Left- and right-sided pressure measurements help estimate the degree of biventricular failure and are useful in monitoring the response to perioperative therapy. Although right-sided failure is more common in patients with postinfarction VSR, left-sided failure and refractory pulmonary edema are more prominent in patients with ruptured papillary muscle. However, a third of patients with postinfarction VSR also have some mitral regurgitation secondary to left ventricular dysfunction. Only rarely is VSR also associated with ruptured papillary muscle.

History and physical examination

Upon auscultation, a loud systolic murmur is heard, usually within the first week after an acute MI. This is the most consistent physical finding of postinfarction VSR. Prior to the development of the murmur, the patient may have been stable after the acute MI. Coincident with the onset of the murmur, the patient's clinical course undergoes a sudden deterioration, with the development of congestive heart failure and, often, cardiogenic shock. The typical harsh systolic murmur is audible over a large area, including the left sternal border and apical area. The murmur sometimes radiates to the left axilla, thereby mimicking mitral regurgitation. A thrill is palpable in approximately 50% of patients.

Almost 50% of patients have recurrent chest pain. The differential diagnosis includes VSR and mitral insufficiency secondary to papillary muscle rupture, papillary muscle dysfunction, or left ventricular dilatation.

Summary of features of postinfarction VSR

• Occurrence is typically 3-8 days after an MI.
• The sites of rupture are the anterior septum (60%) and the posterior septum (40%).
• The most consistent finding is a murmur.
• In the differential diagnosis, exclude mitral regurgitation from papillary muscle rupture.
• Diagnosis is confirmed with the aid of echocardiography and the presence of a left-to-right shunt.
• Catheterization results help determine the extent of CAD.
• Of patients treated without surgery, 90% die.
• Surgery must be emergent, even if the patient is stable.^[3]
• All VSRs are closed with a patch and associated coronary artery bypass grafting.
• The surgical mortality rate for anterior defects is 10-15% and for posterior defects is 30-35%.

In view of the grim prognosis of medically treated patients, simply the diagnosis of postinfarction ventricular septal rupture (VSR) is an indication for operation. The previous controversy surrounding the timing of surgical intervention is no longer an issue, and most surgeons agree that early surgery should be performed in order to incur the lowest risk of mortality and morbidity. The success of the surgery depends on the prompt medical stabilization of the patient and the prevention of cardiogenic shock.

The relative safety of repair 2-3 weeks or more after perforation is apparent from the previous data. Because the edges of the defect have become firmer and fibrotic, repair is more secure and easily accomplished. A successful clinical outcome is related to the adequacy of closure of the VSR; therefore, if possible, search for multiple defects preoperatively and certainly at the time of surgery. Only when the patient is hemodynamically stable should repair be initially delayed, but there must be high degree of certainty that the patient is hemodynamically stable. These patients can suddenly deteriorate and die.

The criteria for a delay in surgery include adequate cardiac output, no evidence of cardiogenic shock, an absence of signs and symptoms of congestive heart failure or minimal use of pressor agents to control initial symptoms, an absence of fluid retention, and good renal function. The natural history of the disease is such that few patients present with these signs and symptoms.

In most patients, postinfarction VSR rapidly leads to a worsening of the hemodynamic state, with cardiogenic shock, marked and intractable symptoms of congestive heart failure, and fluid retention. Immediate surgery is usually indicated.^[7] The high surgical risk of early repair is accepted because of the even higher risk of death without surgery under such circumstances.

Occasionally, a delay in diagnosis and referral occurs. These patients are usually critically ill, and the prognosis is very grim; thus, allowing the natural history of the disease to take its course is prudent.^[7]

Generally, most patients who experience a postinfarction ventricular septal rupture (VSR) need emergent surgery. However, because of either delayed diagnosis or referral, an occasional patient may be in a state of multiorgan failure and may not be a candidate for surgery. The chances of such a patient surviving an operation are minimal; in these circumstances, supportive medical therapy may be adequate. Patients who are comatose and in cardiogenic shock have a particularly poor prognosis after surgery, and surgery is best avoided in such circumstances.