Willem Einthoven was a Dutch physician and physiologist who made significant contributions to the field of electrocardiography. Some synonyms for his name include Willem Einthoven Jr., Willem Einthoven Sr., and Dr. Einthoven. Additionally, he is often referred to as the inventor of the electrocardiogram (ECG), which measures the electrical activity of the heart. Einthoven's work in this field brought forth many new understandings of heart function and cardiac disease. Today, the ECG remains a critical tool in diagnosing and monitoring heart conditions. Einthoven's legacy lives on, and his contributions continue to shape the medical field's understanding of heart health and disease management.