In a 58‑year‑old man 22 days after mitral valve replacement (MVR) who presents to the emergency department with light‑headedness, nausea, vomiting, abdominal pain, normal vital signs, recent fish consumption, and new postoperative anticoagulant therapy, what diagnostic work‑up is indicated?

Diagnostic Work-Up for Post-Mitral Valve Replacement Patient with GI Symptoms

This patient requires immediate evaluation for prosthetic valve complications, anticoagulation-related bleeding, and infectious endocarditis, as these represent life-threatening conditions in the early post-operative period that can present with seemingly benign GI symptoms.

Critical Life-Threatening Diagnoses to Rule Out First

Prosthetic Valve Dysfunction and Hemolytic Anemia

• Obtain complete blood count with peripheral smear, reticulocyte count, lactate dehydrogenase (LDH), total and indirect bilirubin, and haptoglobin immediately to evaluate for mechanical hemolytic anemia, which can present with nausea, abdominal pain, and lightheadedness 1
• Hemolytic anemia after mitral valve replacement manifests with jaundice (72% of cases), dark urine (84%), and can cause acute kidney injury (44% of cases), hepatomegaly (60%), and splenomegaly (60%) 1
• Laboratory findings typically show hemoglobin around 70 g/L, elevated bilirubin (mean 72 μmol/L), and markedly elevated LDH (mean 2607 IU/L) 1
• Perform urgent transthoracic echocardiography to assess for paravalvular leak (present in 64% of hemolytic anemia cases), valve dehiscence, or abnormal leaflet motion 2, 1

Anticoagulation-Related Hemorrhage

• Check INR immediately and assess for signs of GI bleeding including hemoglobin/hematocrit, stool guaiac, and hemodynamic stability 3
• Bleeding during anticoagulant therapy warrants diagnostic investigation even when INR is therapeutic, as it may unmask previously unsuspected lesions such as ulcers or tumors 3
• Hemorrhagic complications from warfarin may present as abdominal pain, nausea, weakness, hypotension, or unexplained shock 3
• The possibility of hemorrhage should be considered in evaluating any anticoagulated patient with complaints that don't indicate an obvious diagnosis 3

Infective Endocarditis

• Obtain at least two sets of blood cultures from separate venipuncture sites before any antibiotic administration 4
• Prosthetic valve endocarditis can develop within weeks of surgery and presents with fever, but may initially manifest with nonspecific symptoms including nausea and malaise 5, 4
• Perform transthoracic echocardiography initially, with low threshold for transesophageal echocardiography if TTE is nondiagnostic, as TEE is superior for detecting vegetations on prosthetic valves 2
• Acute endocarditis requiring emergency surgery carries 30-day mortality of approximately 22-28% 5

Secondary Diagnostic Considerations

Metabolic and Infectious Causes

• Obtain comprehensive metabolic panel including electrolytes, renal function (creatinine, BUN), and liver function tests 1
• Creatinine levels negatively correlate with hemoglobin in hemolytic anemia (indicating renal dysfunction from hemolysis) 1
• Check complete blood count with differential to evaluate for infection or anemia from other causes 1
• Consider stool culture and ova/parasites if fish consumption suggests possible foodborne illness, but only after life-threatening diagnoses are excluded

Medication-Related Nausea

• Review all new postoperative medications for GI side effects 6
• Postoperative nausea is common but persistent morning nausea for 22 days warrants investigation for more serious causes 6

Imaging Studies

Immediate Echocardiography

• Transthoracic echocardiography is indicated to evaluate the mitral valve apparatus and left ventricular function after a change in signs or symptoms 2
• Assess for paravalvular regurgitation, abnormal leaflet motion, left ventricular function, and pulmonary artery pressures 2
• Transesophageal echocardiography should be performed if TTE provides nondiagnostic information regarding severity of complications or if endocarditis is suspected 2

Additional Imaging if Initial Work-Up Negative

• Consider abdominal ultrasound or CT if hepatosplenomegaly is suspected on physical examination (common in hemolytic anemia) 1
• Chest X-ray to evaluate for pleural effusions, which are common postoperative complications 2

Critical Pitfalls to Avoid

• Never dismiss seemingly minor GI symptoms in early post-valve replacement patients, as they may represent the initial presentation of catastrophic complications including hemolytic anemia, prosthetic valve dysfunction, or endocarditis 1
• Do not attribute symptoms solely to foodborne illness without excluding prosthetic valve complications first, as the temporal relationship to fish consumption may be coincidental 1
• Avoid delaying echocardiography in any post-valve surgery patient with new symptoms, as early detection of prosthetic valve dysfunction is critical 2
• Do not wait for fever to develop before investigating endocarditis, as initial presentations may be subtle with nonspecific symptoms 5, 4

Immediate Management Priorities

• Admit for continuous monitoring and expedited diagnostic work-up given the combination of lightheadedness, GI symptoms, and recent cardiac surgery 2
• Ensure therapeutic anticoagulation is maintained unless active bleeding is identified 2
• Hold oral intake until GI bleeding is definitively excluded 3
• Aggressive hydration may be needed if hemolysis or dehydration from vomiting is present 1