Various types of arrhythmias may occur during cancer treatment, including tachyarrhythmias, bradyarrhythmias, ventricular and supraventricular arrhythmias, and conduction blocks. These arrhythmias may be related to direct myocardial injury or coronary artery disease caused by chemotherapy or radiotherapy. Additionally, the combined use of antibiotics, antiemetics, and psychotropic drugs during cancer treatment can also induce or exacerbate arrhythmias.
Atrial Fibrillation
The incidence of atrial fibrillation (AF) in cancer patients ranges from 5% to 16%, which is higher than in the general population. Risk factors for AF in cancer patients include:
- The frequent coexistence of cardiovascular comorbidities and risk factors in cancer patients.
- Systemic inflammatory responses and oxidative stress associated with cancer, which promote atrial remodeling.
- Autonomic nervous system dysfunction caused by pain or emotional stress.
- Comorbidities such as electrolyte imbalances, infections, anemia, and hypoxemia.
- Cancer therapy drugs (e.g., ibrutinib).
- Thoracic surgeries for cancers such as lung or esophageal cancer.
- Invasion of the myocardium or adjacent tissues by certain tumors (e.g., lung or mediastinal tumors).
The treatment of AF in cancer patients is similar to that in the general population, as detailed in arrhythmia management. However, specific considerations for cancer patients include:
- Risk assessment for thromboembolism and bleeding should take into account the type and stage of cancer as well as the cancer treatment regimen.
- For non-valvular AF, non-vitamin K antagonist oral anticoagulants (NOACs) are preferred. It should be noted that NOACs are transported via P-glycoprotein, and rivaroxaban and apixaban are metabolized by CYP3A4. Cancer therapies that inhibit or enhance P-glycoprotein or CYP3A4 may affect the anticoagulant effects of NOACs.
- Thromboembolism and bleeding risks should be dynamically evaluated during cancer treatment, and anticoagulant regimens should be adjusted accordingly.
- Non-dihydropyridine calcium channel blockers and digoxin may have potential drug interactions with cancer therapies. Beta-blockers are preferred for ventricular rate control.
- Ibutilide, which is not metabolized by CYP3A4, CYP2D6, or P-glycoprotein, can be used for AF cardioversion in cancer patients. Amiodarone and dronedarone are inhibitors of CYP3A4 and P-glycoprotein, while propafenone is primarily metabolized by CYP2D6. Potential interactions with cancer therapies should be considered when using these drugs.
QT Interval Prolongation
Many cancer therapies can prolong the QT interval. Additionally, cancer patients often have electrolyte imbalances or impaired liver and kidney function, further increasing the risk of QT prolongation. Common cancer therapies associated with QT prolongation include arsenic trioxide and cyclin-dependent kinase 4/6 inhibitors. The incidence of QTc > 500 ms related to arsenic trioxide therapy ranges from 25% to 60%.
Risk factors for QT prolongation in cancer patients include:
- Female.
- Electrolyte imbalances (e.g., hypokalemia, hypocalcemia, hypomagnesemia).
- Coexisting cardiovascular diseases (e.g., heart failure, left ventricular hypertrophy, coronary artery disease, bradycardia, or congenital long QT syndrome).
- Liver or kidney dysfunction.
- Concomitant use of other QT-prolonging drugs (e.g., antiemetics, psychotropic medications).
Baseline electrocardiograms (ECGs) should be routinely performed before cancer therapy. If the baseline QTc exceeds 480 ms, the use of QT-prolonging drugs should be approached with caution. During cancer treatment, regular ECG monitoring is necessary. If QTc is between 480 and 500 ms, reversible risk factors for QT prolongation should be corrected, and dynamic ECG changes should be closely monitored. If QTc exceeds 500 ms or increases by more than 60 ms from baseline, discontinuation of the current cancer therapy should be considered, and concurrent use of other QT-prolonging drugs should be avoided. Treatment should follow torsades de pointes (TdP) management if necessary.
Other Types of Arrhythmias
Ventricular Arrhythmias
Myocardial injury caused by cancer therapies can increase the incidence of ventricular arrhythmias. Some ventricular arrhythmias are also associated with QT interval prolongation.
Sinoatrial Node Dysfunction and Conduction System Abnormalities
Drugs such as arsenic trioxide, cyclophosphamide, and anthracyclines, as well as radiotherapy, can lead to sinoatrial node dysfunction and conduction system abnormalities. Radiotherapy-induced dysfunction is often irreversible.
The treatment of these conditions should follow an individualized approach, with efforts to eliminate precipitating factors. Decisions regarding permanent pacemaker implantation should consider the patient's expected survival, quality of life, and surgical risks.