What could cause a long R-R interval on an ECG?

A long R-R interval on an ECG can be caused by bradycardia, which is a slower-than-normal heart rate, often due to increased vagal tone or certain medications. It may also indicate heart block, where the electrical signals are delayed or blocked in the conduction pathways of the heart. Other potential causes include certain arrhythmias, such as sinus arrest or atrial fibrillation with a slow ventricular response. Additionally, electrolyte imbalances, particularly high potassium levels, can contribute to prolonged R-R intervals.