By Samuel Zeng, MD – UCLA
Posted on April 4, 2025
When chest pain strikes a patient with a history of heart disease, acute coronary syndrome (ACS) often tops the differential. But as Samuel Zeng, MD, a second-year internal medicine resident at UCLA, discovered in a recent case study, immune checkpoint inhibitors (ICIs) can complicate the picture. In his poster presentation, “ICI-Induced Myocarditis: When Chest Pain Is Not Due to a Blocked Vessel,” Dr. Zeng unravels a rare and lethal complication that challenges conventional thinking. Here’s what clinicians need to know.
A Complex Patient Profile
The case centers on an 84-year-old woman battling stage III non-small cell lung cancer. Treated with chemotherapy and durvalumab—an ICI—she presented to the emergency department with chest pain just three weeks after starting the immunotherapy. With a robust cardiac history, including eight stents, her symptoms screamed ACS. Initial tests reinforced this suspicion: elevated troponin levels, though no EKG changes, prompted a swift cardiology consult.
The Cardiology Conundrum
Dr. Zeng’s team watched as cardiology performed a left heart catheterization, revealing a partial blockage in a marginal artery. A stent was placed, yet the chest pain persisted—a red flag. Within 24 hours, the patient progressed to a second-degree heart block, followed by a complete heart block, requiring a pacemaker. These developments baffled the team. Was this still ACS, or something else?
Unraveling Triple M Syndrome
On day 12, the patient’s condition took a turn. New symptoms—droopy eyelids, shoulder weakness, and worsening breathing—prompted a neurology consult. The diagnosis? Myasthenia gravis. Combined with her earlier chest pain and heart block, Dr. Zeng and his colleagues identified triple M syndrome: myocarditis, myositis, and myasthenia gravis. This rare ICI-induced complication, linked to durvalumab, explained her atypical presentation. Tragically, the late diagnosis led to her passing.
Key Lessons for Clinicians
Dr. Zeng’s case highlights a critical takeaway: ICI-induced myocarditis can mimic ACS, especially in patients with cardiac histories. Search terms like “ICI side effects” or “myocarditis symptoms” might lead clinicians here, and for good reason. The American Society of Clinical Oncology (ASCO) guidelines recommend early prednisone—within 24 hours—if ICI-related myocarditis is suspected, even empirically. The stakes are high: untreated, it’s often fatal, while steroid risks are minimal by comparison.
Subtle clues were missed, Dr. Zeng notes. Elevated transaminases hinted at ICI-related hepatitis, and a creatine kinase (CK) test could have flagged myositis sooner. For patients on immunotherapy, expanding the chest pain differential is non-negotiable.
Why This Matters
With ICIs revolutionizing cancer treatment, cases like this are a wake-up call. Keywords like “immune checkpoint inhibitor complications” or “myocarditis diagnosis” underscore the need for awareness. Patients with pre-existing heart disease on ICIs are particularly vulnerable, and standard ACS protocols may fall short. Dr. Zeng’s work urges clinicians to think beyond blocked vessels and consider immunotherapy’s broader impact.
Conclusion
Samuel Zeng, MD, of UCLA, offers a compelling reminder through this case: chest pain in the context of ICIs demands a nuanced approach. By sharing this story, he hopes to equip healthcare providers with the insight to act swiftly and save lives. For more on ICI-induced myocarditis or differential diagnoses for chest pain, explore related resources or consult the latest ASCO guidelines.
About the Author: Samuel Zeng, MD, is a second-year internal medicine resident at UCLA, dedicated to advancing clinical education through complex case studies.
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