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In present day interventional cardiology practice, balloons (with / without mounted stent) are provided with manufacturers' sizing charts, based upon experiments performed in controlled environment, whereas in coronaries balloon size is influenced by the vessel wall compliance. Many operators rely on these charts to choose the stent / balloon size and use the inflation pressure during Percutaneous Coronary Intervention (PCI) to achieve expected stent size.
We have retrospectively collected data from 35 consecutive patients, who have undergone OCT after stent deployment. We measured stent diameter (d) and mean luminal area (MLA) at various points and compared them with the values provided on manufacturers' chart. Patients, who required stent overlap or stenting for in-stent restenosis were excluded.
Average stent diameter was 3.3 ± 0.2 mm, length was 21.1 ± 1.9 mm and deployment pressure was 14.0 ± 1.0 atm, which should have resulted in expected stent diameter of 3.5 ± 0.2 mm and mean luminal area (MLA) of 10.1 ± 1.0 mm2 as per the chart provided. Average inflation time was 30 seconds. OCT study demonstrated that the achieved average stent diameter was 3.2 ± 0.2 mm (92 ± 2 % of the expected diameter, P < 0.01). We found that stent was better expanded at both the ends in comparison to mid part. Average achieved MLA in stented segment was 8.1 ± 1.1 mm2 (80.2 ± 1.9 % of expected MLA, ranging from 69 to 88%). Minimum MLA through out the stented segment was 7.0 ± 1.0 mm2 (69.7 ± 3.2% of expected, ranging from 54 to 83%). Stents were well apposed in the area of minimum MLA, and under-expansion was not always related to presence of calcium in the vessel wall. Minimum MLA, in comparison to expected, was less of an issue in those, who were treated with post dilatation.
1. Mean stent diameter and MLA achieved in human subjects is significantly less than what is proposed by the manufacturers. 2. Operator has to be aware about these limitations / differences, and should take extra precaution to obtain satisfactory procedure result. 3. Post dilatation should be considered more often to achieve good sizing. Study limitations: 1. This was a retrospective study with limited numbers. 2. We have not compared differences between various stent platforms and different designs. 3. Balloon inflation was maintained for different time period in these subjects and that may have an impact on stent sizing.