Which of the following detects heart disease or an irregular heartbeat?

The electrocardiograph is specifically designed to measure the electrical activity of the heart, providing vital information about its rhythm and any potential irregularities, such as arrhythmias. It records the electrical impulses that trigger heartbeats, allowing for the detection of heart disease and conditions like an irregular heartbeat. This tool generates an electrocardiogram (ECG or EKG), which is critical for diagnosing various cardiac issues.

The stethoscope, while useful for listening to heart sounds and detecting certain conditions, does not provide the detailed information about electrical activity necessary to diagnose heart disease comprehensively. A cardiac ultrasound, or echocardiogram, can visualize heart structures and assess function but does not specifically monitor electrical activity. Similarly, a chest X-ray can show the size and shape of the heart as well as other thoracic structures, but it cannot evaluate the heart's electrical signals or rhythm. Thus, the electrocardiograph stands out as the primary tool for detecting heart disease and irregular heartbeats.