What is the best course of action for a 43-year-old male with a history of Transposition of the Great Arteries (TGA) and a heart murmur, who experiences palpitations upon physical activity, such as standing up or bending down, that resolve when sitting down?

Immediate Referral to Adult Congenital Heart Disease Specialist Required

This 43-year-old male with transposition of the great arteries experiencing exertional palpitations must be referred urgently to a specialized Adult Congenital Heart Disease (ACHD) center for comprehensive evaluation, as these symptoms likely represent exercise-induced arrhythmias or hemodynamic decompensation that require expert assessment to prevent sudden cardiac death or progressive heart failure. 1

Critical Diagnostic Workup Needed

Immediate Evaluation at ACHD Center

• All patients with TGA, regardless of surgical history, should be seen at least annually in a specialized ACHD center, and this patient's new symptoms mandate urgent evaluation rather than waiting for routine follow-up 1

• Exercise-provoked palpitations in TGA patients indicate possibly elevated risk of arrhythmias, requiring immediate exercise testing and arrhythmia monitoring 1

• The positional nature of symptoms (occurring with standing/bending, resolving with sitting) suggests either orthostatic arrhythmias or hemodynamic compromise that warrants urgent investigation 1

Essential Diagnostic Studies

Arrhythmia Assessment:

• Holter monitoring, event recorder, and potentially electrophysiology testing are required for patients with suspected or clinical arrhythmia 1

• ECG should be obtained immediately to assess for conduction abnormalities, as TGA patients have abnormally positioned AV nodes and bundle of His leading to conduction abnormalities, prolonged PR intervals, or complete heart block 1

• Exercise stress testing is specifically recommended to document arrhythmias provoked by physical activity, which is precisely what this patient describes 1

Structural and Functional Assessment:

• Comprehensive echocardiography must be performed at a regional ACHD center to evaluate systemic ventricular function and AV valve regurgitation 1

• Systemic right ventricular failure and/or severe systemic AV valve regurgitation typically cause dyspnea and exercise intolerance in the fourth or fifth decade, which matches this patient's age and symptom profile 1

• Cardiac MRI is indicated for quantification of ventricular volumes, mass, and ejection fraction if echocardiography is inconclusive 1

High-Risk Features to Assess

Age-Related Complications

• Patients with TGA in their fourth or fifth decade are at particular risk for systemic (subaortic) ventricular failure, which may be misdiagnosed as dilated cardiomyopathy 1

• The mismatch between myocardial blood supply and workload of the systemic ventricle contributes to heart failure at this age 1

• Arrhythmias, progressive AV block, and risk assessment for sudden cardiac death require particular attention in this population 1

Surgical History Matters

• If this patient had an atrial baffle procedure (Mustard or Senning), he faces risks of systemic RV failure, systemic tricuspid regurgitation, baffle obstruction, and conduction disturbances with potential for sudden death 1

• If he had an arterial switch operation, complications include coronary artery stenosis, neoaortic insufficiency, and arrhythmias 2

• Patients with congenitally corrected TGA (ccTGA) may develop complete heart block, which could explain positional palpitations 1

Activity Restrictions Pending Evaluation

Until comprehensive evaluation is complete:

• Patients with symptoms or history of arrhythmias should be counseled carefully on an individual basis because of possibly elevated risk of arrhythmias provoked by exercise 1

• Extremes of exertion or competitive contact sports should be avoided, though regular medium- or low-intensity physical activity can continue if symptoms allow 1

• The patient should avoid activities that provoke symptoms until arrhythmia evaluation is complete and risk stratification performed 1

Common Pitfalls to Avoid

• Do not dismiss positional palpitations as benign in TGA patients, as they may herald serious arrhythmias or hemodynamic decompensation requiring intervention 1

• Do not perform evaluation at a general cardiology clinic rather than an ACHD center, as these complex patients require specialized expertise in congenital heart disease 1

• Do not delay evaluation thinking annual follow-up is sufficient—new symptoms mandate urgent reassessment 1

• Do not misinterpret ECG findings as myocardial infarction, as TGA patients may have deep Q waves in II, III, aVF, and V1-V3 due to inverted bundle branches and abnormal septal activation 1

Prognosis Context

• With proper management at specialized centers, long-term survival is approximately 90% at 15 years post-surgery, though exercise performance and quality of life may be impaired 3

• Patients with uncomplicated TGA may live a normal life span with proper management, but this requires ongoing specialized surveillance 4

• The development of new symptoms at age 43 represents a critical juncture requiring immediate expert intervention to prevent morbidity and mortality 1