A CASE OF UNDERSIZED IABP BALLOON IN A CARDIAC ARREST PATIENT AFTER PERCUTANEOUS CORONARY INTERVENTION: A CASE REPORT Cardiac arrest during percutaneous coronary intervention is a rare but serious complication. Intra-aortic balloon pump (IABP) is often utilized to support hemodynamics after a return of spontaneous circulation (ROSC) due to cardiac problem. However, supply chain issues that arise limit the availability of the optimal balloon size. A 70-yearold-man with angina pectoris, despite optimal medical therapy (OMT), underwent an elective percutaneous coronary intervention (PCI). He developed cardiac arrest and achieved ROSC, but had low blood pressure despite inotropes and vasopressor. IABP support was necessary but ideal balloon size was unavailable due to supply chain problems. An undersized balloon (25 cc) was utilized instead. He was monitored in the ICU and began to improved and was finally discharged. An undersized balloon may still provide some benefit in increasing coronary blood flow and reducing cardiac workload in certain patients who need IABP support, especially when supply chain issues or lack of other circulatory devices limit such options. However, careful individualized assessment is required.