What are the possible causes of mortality in a patient post-cardiac surgery (CS) with a co-morbidity of a perimembranous ventricular septal defect (VSD)?

Mortality Causes in Post-Cardiac Surgery Patients with Perimembranous VSD

The primary causes of mortality in patients following cardiac surgery for perimembranous VSD are postoperative pulmonary hypertensive crises (PHC), right ventricular failure from acute elevation in pulmonary vascular resistance after defect closure, cardiogenic shock, and infective endocarditis—with mortality rates ranging from 20-50% when PHC occurs and approaching 100% when emergency surgery is performed within 3 days of cardiogenic shock. 1, 2

Immediate Postoperative Mortality Mechanisms

Pulmonary Hypertensive Crisis (PHC)

• PHC represents the most critical immediate postoperative complication, occurring in 2-7% of patients undergoing congenital cardiac surgery, with associated mortality of 20% in recent series 1
• PHC accounts for 8% mortality within the first month after repair of certain defects, and PHC episodes are strongly associated with high risk for late death 1
• The pathophysiology involves sudden inability of the right ventricle to decompress after VSD closure—preoperatively, cardiac output was maintained through the septal shunt, but postoperatively the RV must carry the entire burden of elevated pulmonary vascular resistance 1

Right Ventricular Failure

• When RV pressure rises above aortic pressure in systole and diastole, coronary perfusion becomes impaired, causing cardiac ischemia and dysfunction 1
• This is exacerbated by surgical factors including right ventriculotomy, transient myocardial dysfunction, tricuspid valve regurgitation, pulmonary valve regurgitation, and loss of sinus rhythm 1
• The presence of severely elevated pulmonary vascular resistance incurs high perioperative risk, particularly when pulmonary vascular resistance exceeds 2/3 systemic levels 1

Cardiogenic Shock

• Patients requiring urgent repair within 3 days of intractable cardiogenic shock have 100% mortality 2
• Cardiogenic shock remains the most important factor affecting early surgical results 2
• The mortality for patients in cardiogenic shock was 20% in one series, with all deaths occurring in shock patients who had three-vessel coronary artery disease 3

Timing-Related Mortality Factors

Early Surgery Complications

• Operative mortality is dramatically higher when patients undergo surgery within the first 6 hours (75%) or first 24 hours (61.3%) from index myocardial infarction 4
• All patients who underwent surgical repair later than day 36 after myocardial infarction survived, suggesting delayed operation is the most beneficial strategy when possible 2
• The time interval from infarct to rupture averages 8.7 days, and from rupture to surgery averages 23.1 days 2

Anatomic and Hemodynamic Risk Factors

Defect Location

• Posterior VSDs carry twice the operative mortality compared to anterior VSDs 3
• The mortality of patients with anterior VSD was 29.6% versus 42.8% for posterior VSD 2
• Perimembranous defects specifically carry risk for complications including aortic valve prolapse with progressive aortic regurgitation, infective endocarditis, aneurysm rupture, and right ventricular outflow tract obstruction 5

Pulmonary Vascular Disease Severity

• Closure of nonrestrictive VSD in adults with Eisenmenger syndrome who do not demonstrate left-to-right shunting carries high mortality risk and should not be performed 1
• Larger defects may be repaired only in the absence of severe pulmonary hypertension and severely elevated pulmonary vascular resistance, the presence of which incurs high perioperative risk 1
• Surgery is contraindicated when PA systolic pressure exceeds 2/3 systemic and pulmonary vascular resistance exceeds 2/3 systemic 5

Late Mortality Causes

Infective Endocarditis

• Infective endocarditis occurs in up to 2 per 1000 patient-years in patients with small residual VSDs 6
• At least 22% of patients with surgically repaired VSDs who developed IE had known residual VSD leaks 6
• The risk increases 6-fold compared to the general population, with 13.7% of patients with aneurysmal perimembranous VSD experiencing bacterial endocarditis 5
• In unrepaired VSD, there is increased risk of IE typically involving the tricuspid and pulmonic valves 1

Residual Hemodynamic Lesions

• Residual shunts at or adjacent to prosthetic patches that inhibit endothelialization remain high-risk for complications 6
• The presence of aortic regurgitation independently increases the risk of IE in patients with VSD, whether managed medically or surgically 6
• 6% of patients with small supracristal or perimembranous defects may develop aortic valve prolapse and resultant progressive aortic regurgitation 1

Additional Risk Stratification

Patient-Specific Factors

• Three-vessel coronary artery disease was the only variable predictive of operative mortality in univariate analysis, with 27% mortality in this subgroup 3
• Older age, renal failure, previous percutaneous coronary intervention, and urgent/emergent operations are associated with higher odds of mortality 4
• Patients with genetic syndromes, chromosomal abnormalities, or extracardiac anomalies have high incidence of lung hypoplasia and difficult postoperative courses complicated by simplified pulmonary vascular bed 1

Arrhythmic Complications

• Complete heart block requiring permanent pacemaker implantation occurs in approximately 2-5% of cases 7
• Ventricular arrhythmias, while less common than in other congenital heart diseases, can contribute to sudden cardiac death in the late postoperative period 1

Critical Pitfalls to Avoid

• Do not proceed with emergency surgery in cardiogenic shock within 72 hours if mechanical circulatory support can stabilize the patient—mortality approaches 100% with immediate surgery versus improved outcomes with delayed repair 2, 4
• Never assume complete surgical repair eliminates endocarditis risk—carefully assess for residual shunts postoperatively, as these patients retain elevated IE risk comparable to unrepaired defects 6
• Avoid closure in patients with Eisenmenger physiology and non-reactive pulmonary vascular disease—this carries prohibitively high mortality 1
• Maintain vigilance for respiratory management issues including pulmonary edema, atelectasis, ventilation-perfusion mismatch, and bronchoconstriction, as maintaining adequate functional residual capacity and avoiding acidosis is crucial for preventing PHC 1