You asked an interesting question. More information is needed to provide a definite answer.
For example, exactly how high is the heartrate while showing a blood pressure of 90/60?
It is abnormal to have such a blood pressure coupled with a heart rate in excess of 100 beats per minute.
Tacycardia (technically, a fast heart rate in excess of 100 beats per minute) can be divided into two categories (a) compensatory or (b) idiopathic.
A high heart rate and low blood pressure is common in cases of shock, when the blood vessels are widely dilated, increasing body capacitance. In such a case the dilation (widining of the interior diameters) could be due to septicemia,or a generalized infection.
An idiopathic tachcardia could be due to a malfunction in the atrial pacemaker node. But even so the blood pressure should be higher unless the heart is not functioning optimally. For example, with very high heart rates the heart will not fill completely with blood between contractions. Sometimes the etiology cannot be determined.
Hi
Welcome to the MedHelp forum!
Slightly lower BP can cause tachycardia. It can also be due to anemia, hyperthyroidism (in your case ruled out), fever, low blood sugar, anxiety and panic disorder, heart causes like sinus tachycardia and palpitations, alcohol, coffee, effect of certain drugs etc. Discuss with your doctor. Take care!
90/60 would be considered hypotensive vs. normal.