43. Mechanical Complications Post-MI- Indications and Guidelines

Dina Al Rameni MD, Hashim Sabet MD
Hartford Hospital/UConn Health
August 14^th, 2024

Abbreviations & Definitions

CABG – Coronary artery bypass graft

ECMO – Extracorporeal membrane oxygenation

EF – Ejection fraction

HF – Heart failure

IABP – Intra-aortic balloon pump

LV – Left ventricle

MCS – Mechanical circulatory support

MI – Myocardial infarction

MR – Mitral regurgitation

PMR – Papillary muscle rupture

VFWR – Ventricular free wall rupture

VSD – Ventricular septal defect

Indications & Guidelines for Management

Ventricular Septal Defect (VSD)

VSDs are a rare but serious complication of an MI, occurring in about 0.3% of cases, usually 3-5 days after a major heart attack.¹ Risk factors include older age, female sex, and delayed treatment of the MI.² VSDs can vary in location, with anterior heart attacks often causing defects near the apex of the heart and inferior or lateral heart attacks causing defects near the base. These defects result in abnormal shunting of blood from the left to the right ventricle, leading to increased blood flow to the lungs and potentially severe symptoms ranging from shortness of breath to life-threatening circulatory collapse. Treating these patients is challenging because inotropes, which increase cardiac output, can worsen the left-right shunt. Afterload reduction is key; however, it is limited by hypotension. The management of post-MI VSD remains a surgical emergency with high mortality if left untreated. Both the American Heart Association (AHA) and the European Society of Cardiology (ESC) have issued specific recommendations regarding its management.

Surgical repair remains the definitive treatment for VSD. The major indications for surgery include:

• Hemodynamic instability: Patients presenting with cardiogenic shock or significant left-to-right shunting require urgent surgical intervention.³
• Large defect size: A septal rupture greater than 15 mm is associated with significant shunting and hemodynamic compromise, necessitating early repair.³
• Progressive clinical deterioration: Worsening symptoms or end-organ dysfunction are indications for expedited surgery.⁴

Conversely, in hemodynamically stable patients, surgery may be delayed to allow the necrotic myocardium to mature and scar, facilitating better outcomes.

The optimal timing for VSD repair remains debated. Early surgical intervention (within 7 days of MI) is often necessary for unstable patients but carries a higher operative mortality due to the friability of necrotic myocardial tissue. Delayed surgery (after 7 days) allows for scar formation and significantly improves survival rates in stable patients.⁵ A large study by Arnaoutakis et al. found that operative mortality was 54.1% for repairs performed within 7 days of myocardial infarction compared to 18.4% for surgeries performed later.⁵

According to the 2013 ACCF/AHA guidelines for the management of ST-elevation MI (STEMI), immediate surgical intervention is strongly recommended upon diagnosis of VSD, irrespective of the patient’s hemodynamic status.⁶ The guidelines emphasize that medical therapy alone is associated with exceedingly high mortality rates; thus, surgical repair should not be delayed. The use of MCS, such as IABP therapy, may be employed to stabilize patients preoperatively; however, it is considered an adjunct rather than a definitive therapy.⁶

The 2017 ESC guidelines for the management of STEMI patients also advocate for early surgical repair in cases of hemodynamic instability or cardiogenic shock. However, in contrast to the AHA’s approach, the ESC guidelines recognize that in hemodynamically stable patients, delayed surgical intervention may be considered to allow time for infarct tissue maturation and fibrosis. This strategy is based on evidence suggesting that surgical outcomes may be improved if surgery is performed after tissue stabilization, as friable infarcted myocardium poses a significant technical challenge and increases perioperative risk when surgery is undertaken too early.⁷

Both organizations agree on the critical need for surgical intervention, though they differ slightly regarding the timing based on patient stability. Immediate repair is the standard in unstable patients, while delayed surgery may be selectively appropriate in stable individuals. Additionally, multimodality imaging, including ECHO and cardiac magnetic resonance, is emphasized for both diagnosis and surgical planning.^6,7

In summary, current guidelines support prompt surgical repair for VSD, with individualized consideration of timing based on hemodynamic status. While stabilization measures such as MCS are important, they should not replace surgical intervention.

Acute Papillary Muscle Rupture (PMR)

Acute severe mitral regurgitation (MR) from PMR presents with acute pulmonary edema, hemodynamic instability, and cardiogenic shock, often leading to multiorgan failure and death. The mitral valve’s two papillary muscles, the anterolateral and posteromedial, have different susceptibilities to rupture. Anterolateral PMR is rare due to its dual arterial supply from the left anterior descending and circumflex arteries. Posteromedial PMR, typically associated with inferior or lateral MIs, is more common due to its single blood supply from the posterior descending artery. PMR can be complete or partial, affecting the severity of clinical symptoms.⁸

PMR should be suspected in any patient with an acute MI who develops acute pulmonary edema, hypotension, or a new systolic murmur. Transthoracic echocardiogram is often the first-line imaging modality; however, transesophageal echocardiogram provides superior diagnostic sensitivity, especially in hemodynamically unstable patients.^7,9

Indications and timing of surgical intervention according to current guidelines:

• Emergent surgical intervention is indicated in all patients with papillary muscle rupture leading to severe, symptomatic MR (Class I recommendation).^9,10
• Surgical repair should not be delayed for complete diagnostic workup if clinical suspicion is high and hemodynamic instability is present.^7,9
• If available, MCS (e.g., IABP, ECMO) may be used as a bridge to surgery to stabilize the patient.^7,11
• Immediate surgery is recommended irrespective of hemodynamic status due to the rapid progression of cardiogenic shock and respiratory failure. Medical management alone is associated with an extremely high mortality (>90%).⁷

Mitral valve replacement is generally preferred over mitral valve repair because of the friability and destruction of surrounding infarcted tissue.^7,12 Chordal-sparing mitral valve replacement is preferred for its predictability and established durability. In younger patients, mechanical valve replacement may offer better long-term symptom-free survival compared to bioprosthetic valves. The choice between a bioprosthetic and mechanical valve is also influenced by the need for MCS or advanced HF therapies, where the risk of mechanical valve thrombosis is higher with LV assist devices and ECMO.¹³

CABG may be performed during mitral valve surgery if significant coronary artery disease is present (Class IIa recommendation).^9,11 However, the surgeon must balance the risks of prolonging the procedure against the potential benefits of revascularization. Large studies have not shown a significant difference in mortality with or without CABG.¹⁴ Failure to address severe multivessel disease during mitral valve replacement may complicate weaning from cardiopulmonary bypass. In some cases, transcatheter options like MitraClip have been used as a rescue strategy for patients in cardiogenic shock who are too unstable for surgery.¹⁵

MCS devices like IABP and ECMO may provide hemodynamic support and oxygenation prior to surgery, especially in cases of profound shock. These devices should be considered adjunctive, not definitive, therapy.^7,12

Free Wall Rupture

Ventricular free wall rupture (VFWR) is a devastating mechanical complication following acute MI, with an incidence ranging from 0.5% to 6%.¹⁶ Despite significant reductions in its occurrence due to advances in reperfusion strategies, VFWR remains associated with extremely high mortality when it does occur. It may present acutely with sudden hemodynamic collapse due to hemopericardium and cardiac tamponade, subacutely with a slower leak into the pericardial space, or as a contained rupture (pseudoaneurysm) where blood is temporarily restrained by the pericardium or thrombus. Clinical manifestations typically include chest pain, syncope, pulseless electrical activity, hypotension, and signs of tamponade.¹⁵ Immediate recognition and intervention are crucial to survival.

Diagnosis is predominantly made through echocardiogram, either transthoracic or transesophageal, which may reveal pericardial effusion, tamponade physiology, or occasionally direct visualization of the rupture.¹⁸ Emergent pericardiocentesis can be life-saving as a bridge to surgery, but does not represent definitive management.

Current guideline-based management emphasizes the urgency of surgical intervention in all cases of VFWR associated with tamponade or hemodynamic compromise. The AHA/ACC 2013 STEMI guidelines give a Class I recommendation for immediate surgical repair in such scenarios.⁶ Similarly, the ESC 2017 STEMI guidelines emphasize that early operative intervention is mandatory, regardless of initial hemodynamic stability.⁷

Medical therapy alone is insufficient and is associated with nearly universal mortality. Even patients with subacute presentations or contained ruptures require urgent surgery due to the high risk of sudden deterioration. Surgical techniques vary depending on the extent and location of the rupture. Direct suture closure may be possible if the surrounding myocardial tissue is relatively preserved, but more often, patch repair with autologous pericardium or synthetic materials such as Dacron or PTFE is necessary due to the friability of the infarcted myocardium.^7,19 Cardiopulmonary bypass is typically required, although in cases of extreme instability, off-pump repairs have been described. While CABG may be performed concomitantly if time and anatomy permit, the primary goal remains securing the rupture, as the mechanical failure takes precedence over revascularization.⁶ The most common technique involves resecting the infarcted area and closing the ventricular wall with a synthetic patch. It is crucial to place sutures through healthy myocardium when using this method, as bleeding around the repair site due to tearing of necrotic muscle is a dreaded complication. An alternative is the sutureless patch technique, which uses overlapping patches and biological glue to cover the infarcted area of the LV free wall.²⁰

The adjunctive use of MCS, including IABP or ECMO, may assist in stabilizing patients pre- or post-operatively, yet they should not delay definitive surgical repair.²¹ Overall, a conservative approach without surgery leads to poor outcomes, whereas early surgical intervention, even in extremely high-risk patients, provides the only realistic chance of survival.

In summary, VFWR is a rare but fatal complication of myocardial infarction requiring immediate diagnosis and emergent surgical repair. Both AHA/ACC and ESC guidelines stress the necessity of urgent surgical intervention, reinforcing that any delay substantially worsens outcomes. Surgery remains the cornerstone of management, and while supportive measures may temporize the clinical situation, they are no substitute for definitive operative therapy.

Table 1. Summary Recommendations

Guideline	Recommendation
Ventricular Septal Defect (VSD)
AHA/ACC 2013 STEMI	Immediate surgical repair recommended for post-MI VSR, regardless of hemodynamic stability (Class I). Early surgery preferred over delayed repair.
ESC 2017 STEMI	Surgical closure recommended as soon as possible after diagnosis. Hemodynamic stabilization with mechanical support (e.g., IABP) can be used as bridge, but surgery should not be delayed.
AHA/ACC 2020 Valvular Heart Disease	Emergency surgical repair recommended for mechanical complications post-MI, including VSR (Class I).
Papillary Muscle Rupture (PMR)
AHA/ACC 2014 Valve	Emergency mitral valve surgery recommended (Class I).
ESC 2017 STEMI	Emergency surgery without delay; MCS may be considered to stabilize patients preoperatively.
ACC/AHA 2020 Valvular Heart Disease	Immediate surgical intervention for PMR with severe MR is strongly recommended.
Ventricular Free Wall Rupture (VFWR)
AHA/ACC 2013 STEMI	Immediate surgical repair recommended for patients with mechanical complications post-MI, including VFWR (Class I).
ESC 2017 STEMI	Surgical repair is mandatory in all cases of VFWR. Urgent diagnosis and operative management are critical.

Expert Commentary

When PMR is complete, the patient typically presents in profound shock, and we treat it as a surgical emergency, even more urgently than an aortic dissection. We proceed directly to the operating room, sometimes without cardiac catheterization if they are in cardiogenic shock. The culprit is typically either two left-sided vessel disease or a total occlusion of the right coronary artery, without collateral circulation, and LV function is generally preserved. In these cases, we move quickly to perform a mitral valve replacement, without attempting a repair. Concomitant CABG is not prioritized; it’s considered a bonus if feasible. Ultimately, this is a mechanical problem requiring immediate surgical correction.

VSD presents a unique challenge. In these cases, the injury extends beyond the visibly damaged area into necrotic and friable tissue, leading to a high risk of recurrence even after surgical repair. Our current practice is to stabilize these patients with VA-ECMO, with or without an IABP, and list them for heart transplantation if no contraindications exist. Unfortunately, no single center has accumulated enough experience or volume to provide a clear consensus on managing these complex cases.

Sources

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