The information revealed by different research studies about the impact of height on the heart rate is not consistent.
Generally, it is believed that people, with higher body weight, have an increased heart rate. This may occur because the extra weight puts more strain on the body and heart. It also increases the body’s need for oxygen and other nutrients.
The role of higher body weight in regulating heart rate
Taller people have a higher body weight compared to the shorter people of the same BMI (Body Mass Index). So, the heart of the shorter people does not have to contract as frequently as that of the taller people to be able to supply a sufficient amount of blood to all the organs continuously.
This could be one of the reasons why taller people are expected to have a higher heart rate compared to that of shorter people.
Also, the higher fat mass and weight in taller people might restrict the flow of blood through the arteries and veins. Hence, the heart might need to beat faster as well as more strongly in order to allow enough blood to be pumped to all the organs and tissues.
This explains why taller people might have a higher heart rate than the shorter people of the same BMI.
However, some studies have shown contradictory results.
Hemodynamic liabilities in shorter people
There is evidence showing that a shorter stature could be a hemodynamic liability, which means being short can put a person at a risk of abnormalities related to the heart rate, blood pressure, and other parameters that determine the cardiovascular health.
The explanation for the association of short height with unfavourable hemodynamic parameters including heart rate is linked to the calibre of the coronary arteries.
The arteries in short people are likely to have a narrower diameter. So, the heart has to pump harder and more frequently in order to pump blood through them. 
The effect of higher blood pressure in taller men
So, taller men are likely to have a lower heart rate and a significantly higher central and brachial diastolic blood pressure. Similar findings were evident in women. The heart rate was higher in women with less than the median height while women taller than the median height had a slower heart rate.
Another study that evaluated the heart rate of patients with varying heights also found that those with a shorter stature had a faster heart rate. It also showed that the increased heart rate could lead to the shortening of the diastole, which is the phase of heartbeats during which the ventricles contract. 
Keeping in mind the varying findings provided by different research studies, it is difficult to predict how exactly the height influences the heart rate.