Final answer:
The upper limit of the normal R-wave axis on a 12-lead ECG is 90 degrees. This axis represents the direction of electrical impulses during depolarization in the heart. Deviations from the normal range can indicate various cardiac conditions or abnormalities.
Step-by-step explanation:
The upper limit of the normal R-wave axis on a 12-lead ECG is 90 degrees. The R-wave axis is the direction in which the electrical impulses are traveling through the heart during depolarization. In a normal heart, the electrical impulse travels from the upper right to the lower left, resulting in a positive deflection of the R-wave in the lead II ECG.
If the R-wave axis deviates from the normal range, it can indicate various cardiac conditions or abnormalities. For example, if the R-wave axis is shifted to the right, it may be indicative of right ventricular hypertrophy or chronic obstructive pulmonary disease. On the other hand, if the R-wave axis is shifted to the left, it may be suggestive of left ventricular hypertrophy or heart block.
It is important to note that the upper limit of the normal R-wave axis can vary slightly depending on individual factors such as age and body habitus. However, a range of 0 to 90 degrees is generally considered to be within the normal limits.