Abnormal ECG in Skin Cancer: Should You Be Concerned?

An abnormal ECG (electrocardiogram) in someone with skin cancer can have several possible explanations, and the level of concern often depends on your symptoms, the specific ECG change, and the treatments you are receiving. Many modern skin cancer therapies can affect the heart’s rhythm or function, so an abnormal ECG may reflect a treatment-related effect rather than permanent heart disease. ^[1] Targeted therapies and immunotherapies sometimes cause ECG changes like QT interval prolongation, arrhythmias, or ST–T wave changes, which need monitoring but are often manageable when detected early. ^[2] [PM14]

Why ECGs Matter in Cancer Care

• Baseline and follow‑up ECGs help detect heart rhythm changes early, especially if you are starting therapies known to affect the heart. ^[3]
• Heart monitoring may be advised during treatment, including ECGs, blood pressure checks, and blood tests like electrolytes and cardiac biomarkers (e.g., troponin). ^[4]
• If you have pre‑existing heart disease or are taking medicines that can affect heart rhythm, closer ECG monitoring is generally recommended. ^[5]

Common Treatment-Related ECG Changes

• QT interval prolongation: Some targeted therapies for melanoma (e.g., BRAF or MEK inhibitors like vemurafenib or dabrafenib) can lengthen the heart’s electrical recovery time, raising arrhythmia risk. Clinics often avoid starting certain drugs if the QTc is very high (for example, >500 ms), and they correct electrolytes such as potassium and magnesium. ^[2]
• Bradycardia or conduction blocks: A few cancer drugs can slow the heart rate or affect the heart’s electrical pathways, leading to ECG abnormalities. This typically prompts dose adjustment or cardiology review if symptoms occur. ^[3]
• ST–T changes and arrhythmias: Immune checkpoint inhibitors (ICIs) can rarely inflame the heart (myocarditis), showing new arrhythmias, ST‑segment changes, or low voltage on ECG. These changes are not always due to blocked arteries but may reflect inflammation, and they warrant urgent evaluation when accompanied by symptoms. [PM14]

Immunotherapy and Myocarditis: What to Know

• ICIs can, in uncommon cases, cause myocarditis that shows up with ECG changes, elevated troponin, and sometimes heart block or dangerous arrhythmias. [PM14]
• Early detection is key: programs that check troponin, ECGs, and echocardiograms regularly in the first weeks after starting ICIs have identified myocarditis early and prevented fatal outcomes. [PM15]
• Severe cases can progress quickly, with conduction problems and ventricular arrhythmias; rapid specialist care is crucial if red‑flag symptoms appear. [PM17]

Targeted Therapy in Melanoma: QT and Heart Function

• BRAF/MEK inhibitor regimens (e.g., vemurafenib with cobimetinib, or encorafenib with binimetinib) have recognized cardiotoxicity risks, including QT prolongation and reductions in left ventricular ejection fraction (LVEF). ^{[2] [6] [7]}
• Care teams often perform baseline cardiac assessments and may repeat ECGs and echocardiograms during treatment; dose changes or temporary holds are used if significant abnormalities develop. ^[6]

How Concerned Should You Be?

• If you feel well and the abnormality is mild (for example, a borderline QTc with no symptoms), your team may simply monitor and correct reversible factors like low potassium or magnesium. ^[8]
• If you have new chest pain, shortness of breath, palpitations, fainting, or swelling, an abnormal ECG is more concerning and should prompt immediate medical review. ^[9]
• Your specific therapy matters: QT prolongation on a BRAF/MEK inhibitor or new conduction abnormalities on immunotherapy may call for closer testing, possibly temporary treatment holds, and cardiology input. ^[2] [PM14]

What Usually Happens Next

• Repeat ECGs and lab checks for electrolytes (potassium, magnesium, calcium) are common first steps, since correcting imbalances can normalize ECGs. ^[8]
• Troponin testing and an echocardiogram may be ordered to look for heart muscle injury or function changes, particularly if you are on or starting immunotherapy. [PM15]
• Medication review is important to identify other drugs that might also prolong QT or interact with cancer therapies. ^[10]

Practical Tips You Can Use

• Know your regimen: Ask your oncology team whether your treatment has known heart rhythm effects and what monitoring is planned. ^[1]
• Track symptoms: Report any chest pain, shortness of breath, rapid or irregular heartbeat, dizziness, or fainting immediately. These are red flags when paired with an abnormal ECG. ^[9]
• Keep electrolytes stable: Follow guidance on hydration and nutrition, and take supplements only as advised; low potassium or magnesium can worsen QT prolongation. ^[8]
• Coordinate care: If advised, meet a cardio‑oncology or cardiology specialist; shared care helps tailor treatment while protecting heart health. ^[9]

Bottom Line

An abnormal ECG in the setting of skin cancer is not uncommon and can be due to many factors, including cancer therapies, electrolytes, or underlying heart conditions. It can be a manageable signal especially when found early that your care team should review, monitor, and address to keep treatment safe and effective. ^[1] Staying alert to symptoms and following recommended monitoring (ECGs, labs, echocardiograms) helps catch serious issues like QT prolongation or myocarditis before they become dangerous. ^[2] [PM15]