Why people with Angioplasty and Stents face problem of low Hemoglobin

After the angioplasty it is seen in some cases that the haemoglobin slightly reduces though it varies from the individual to individual. The medicines given for blood thinning could be a reason for that but that is not established so far. There have been some research in this area and it is observed that in some cases the haemoglobin level reduced slightly and on an average it reduced in the range 0.6 to 1.0 g/dl which is not very significant but if it goes further down then it is a matter of concern. The matter is still under research.

Haemoglobin Drift After Cardiac Surgery. There were some studies on this subject and some papers were also published. After seeing this question I was going through such papers. A team of doctors from The Johns Hopkins
Medical Institutions, Baltimore, Maryland conducted a study and reported. The maximum drift that was observed in the cases they have studied is s1.8 +_1.1 g/dL.
Haemoglobin levels initially dropped in all most all the patients. But 79% of patients reached normal levels by the time they are getting discharged. They conducted a multivariable analysis and found that increasing cardiopulmonary bypass time was the main reason for this drift.
If the author is interested in knowing the full details of this study he can go through the given below URL.
https://www.annalsthoracicsurgery.org/article/S0003-4975(12)00655-8/pdf.

An experiment was undertaken to show that anemia is a risk factor which predicts non fatal coronary event including elevation of MI, targeting revascularization and the post PCI. The findings did not suggest any role of MI or PCI. leading to loss of haemoglobin. It was finally concluded that there had been a drop of oxygen supply within the circulation system which caused underlying inflammation. Because inflammation response is the critical mechanism of ISR, it is reasonable to infer that anemia could contribute to the progression of ISR in addition to the dysfunction of endoethical cell. This will ultimately speed up the chances of formation of ISR.
The final conclusion was arrived at showing that the patient with the baseline anemia before PCI have higher incidences of ISR after PCI than their non animatic counterparts.