What is causing the shortness of breath in an elderly patient, status post pancreatic cancer surgery and chemotherapy, presenting with tachypnea, right lower extremity edema, sinus tachycardia, and mildly elevated troponin?

Pulmonary Embolism Secondary to Malignancy-Associated Hypercoagulability

This patient most likely has a pulmonary embolism (PE) caused by pancreatic cancer-associated hypercoagulability, compounded by recent surgery and prior chemotherapy exposure. The constellation of acute dyspnea, tachypnea (RR 24), unilateral lower extremity edema, sinus tachycardia, mildly elevated troponin, and oxygen requirement in a post-operative pancreatic cancer patient creates a classic presentation for venous thromboembolism.

Primary Etiology: Pancreatic Cancer-Associated Thromboembolism

Pancreatic cancer creates an intrinsic hypercoagulable state with thromboembolic disease occurring in 17-57% of patients. 1

• Pancreatic cancer cells directly activate platelets and express multiple procoagulant factors including tissue factor and thrombin, making thrombosis the second leading cause of death in these patients 2, 1
• Clinical manifestations include deep venous thrombosis, pulmonary embolism, disseminated intravascular coagulation, portal vein thrombosis, and arterial thromboembolism 1
• The right lower extremity edema strongly suggests DVT as the source of PE 1

Contributing Factors Amplifying Risk

Recent major abdominal surgery (2 weeks post-op) dramatically increases thrombotic risk in an already hypercoagulable cancer patient. 1

• Post-operative state combined with pancreatic malignancy creates a multiplicative thrombotic risk 2, 1
• Three months of prior chemotherapy may have contributed to endothelial injury and coagulation activation 1

Why This is NOT Primarily Cardiac

While chemotherapy can cause cardiac arrhythmias and the patient has sinus tachycardia, the clinical picture does not support a primary cardiac etiology:

• The troponin elevation (0.1) is mild and consistent with PE-related right ventricular strain rather than acute coronary syndrome or chemotherapy-induced cardiomyopathy 3
• Sinus tachycardia in this context is a physiologic response to hypoxemia and increased work of breathing, not a primary arrhythmia 3, 4
• Chemotherapy agents used for pancreatic cancer (gemcitabine, 5-FU, FOLFIRINOX components) can cause arrhythmias, but the patient's presentation with unilateral leg edema and acute dyspnea points away from primary cardiotoxicity 5, 6
• The ESC guidelines note that when heart rate is <150 bpm without ventricular dysfunction, tachycardia is likely secondary to an underlying condition 3

Critical Diagnostic Pitfall to Avoid

Do not dismiss this as simple post-operative tachypnea or chemotherapy-related dyspnea without imaging to rule out PE. 3

• The combination of unilateral leg edema with respiratory symptoms in a pancreatic cancer patient mandates CT pulmonary angiography or V/Q scan 1
• Missing PE in this population carries significant mortality risk, as thromboembolism is the second leading cause of death in pancreatic cancer patients 2

Immediate Management Algorithm

Obtain CT pulmonary angiography emergently while initiating therapeutic anticoagulation if no contraindications exist:

• Check D-dimer (though likely elevated and less specific in cancer patients) 1
• Perform lower extremity venous duplex ultrasound to confirm DVT 1
• Initiate low-molecular-weight heparin rather than warfarin, as studies demonstrate superior outcomes in cancer-associated thrombosis 1
• Assess bleeding risk given recent surgery (2 weeks post-op), though therapeutic anticoagulation is typically safe at this timepoint 2, 1

Alternative Considerations (Less Likely)

While PE is most probable, other etiologies to consider include:

• Post-operative atelectasis or pneumonia (but wouldn't explain unilateral leg edema) 7
• Chemotherapy-induced pulmonary toxicity (but timing doesn't fit—3 months post-chemo) 6
• Cardiac arrhythmia from chemotherapy (but sinus tachycardia is physiologic here, not pathologic) 5