Complete heart block associated with paraneoplastic hypercalcemia: a case report.

Area of Science:

• Cardiology
• Endocrinology
• Oncology

Background:

• Complete heart block (CHB) is a rare but serious cardiac condition characterized by a lack of electrical signal conduction between the atria and ventricles.
• Hypercalcemia, an electrolyte imbalance, is an uncommon cause of CHB, often necessitating investigation into underlying etiologies.

Observation:

• A 59-year-old male presented with weakness and ECG findings of CHB, short QT interval, and ST elevation.
• Initial lab results revealed severe hypercalcemia (15.8 mg/dL) with normal parathyroid hormone, vitamin D, and phosphorus levels.
• A chest CT scan identified a large cavitary lung mass, leading to a diagnosis of lung cancer with paraneoplastic hypercalcemia.

Findings:

• Treatment with saline, calcitonin, and zoledronic acid successfully reduced serum calcium levels to 10.4 mg/dL within 4 days.
• Resolution of hypercalcemia correlated with the normalization of pathological ECG findings, including CHB.
• This case underscores the potential for paraneoplastic hypercalcemia, particularly from lung cancer, to manifest as severe cardiac conduction abnormalities.

Implications:

• This case adds to the limited literature on hypercalcemia-induced complete heart block, emphasizing the importance of considering electrolyte disturbances in cardiac emergencies.
• Early recognition and management of paraneoplastic hypercalcemia are crucial for reversing potentially life-threatening cardiac complications.
• Further research into the mechanisms linking paraneoplastic syndromes to cardiac dysfunction is warranted.