Low blood pressure can cause high pulse rate. Also, in certain types of arrhythmias high pulse rate can result in fall in the blood pressure. High pulse rate refers to pulse greater than 100 per minute, and is also referred to as tachycardia.
High pulse rate or tachycardia is often associated with low blood pressure. Tachycardia is a reflex response to fall in blood pressure. When the blood pressure is low and the tissues of the body are not receiving adequate perfusion, the body raises heart rate in order to compensate for the low perfusion. Therefore, almost all causes of low blood pressure will result in low blood pressure with tachycardia.
Normal person with no symptoms and no primary disease condition (that could cause hypotension) will usually have normal pulse rate. In athletes and those who do regular exercise, both blood pressure and pulse rate might be low. This also is absolutely normal finding and requires no treatment.
Many cardiac arrhythmias can result in a high pulse rate and a low blood pressure. In this case, it is the high pulse rate that is causing the low blood pressure. The pulse rate in such cases is very high, and thus the heart is beating so fast, that it is not getting enough time adequately fill itself with the blood. An example of such condition is atrial fibrillation. In this condition there is arrhythmia in the upper chamber (atria) of the heart which stimulates the heart to beat at very fast rate. The lower chambers (ventricles) are not adequately filled with blood, resulting in a fall in blood pressure.
Further evaluation is always necessary to ascertain the cause of low blood pressure and tachycardia. Treatment is dependent upon the primary condition resulting in the hypotension and tachycardia.