What is the upper limit of the normal R-wave axis in degrees?

The normal R-wave axis range in the frontal plane is typically considered to be from -30 degrees to +90 degrees. The upper limit specifically refers to the maximum degree on the normal axis scale that is still indicative of a normal heart’s electrical activity. Therefore, +90 degrees is the upper limit of the normal R-wave axis, suggesting that any value above this could indicate a deviation or an abnormality in the heart's electrical conduction pathways.

Understanding the R-wave axis is crucial in interpreting an electrocardiogram (ECG), as it provides insight into the orientation of the heart’s electrical activity, which can be affected by various factors including heart position, hypertrophy, or other cardiac conditions. R-wave axis measurements can help diagnose potential issues such as left or right axis deviation.