When a patient's blood pressure is 135/81, 135 refers to:

The reading of 135/81 in a blood pressure measurement reflects two key numbers, where the first value, 135, represents the systolic pressure. Systolic pressure is the force exerted by circulating blood on the walls of the arteries when the heart beats. It is the peak pressure in the arteries, occurring during ventricular contraction, when the heart pumps blood out.

In this context, a systolic value of 135 indicates that the heart is pumping effectively, and blood is being delivered with adequate pressure to the body's organs and tissues. The second value, 81, is the diastolic pressure, which measures the pressure in the arteries when the heart is at rest between beats. Understanding these values is crucial for assessing cardiovascular health adequately.

As for the other choices, pedal pulse refers to the pulse detected in the feet, and apical pressure pertains to measurements taken at the apex of the heart, both of which are unrelated to the actual blood pressure numbers provided.