Abstract Body (Do not enter title and authors here): Case Description
A 42-year-old female with migraines and recent history of quitting smoking presented to the ED after two syncopal episodes within a month. Initial EKG and cardiac markers were normal. A Holter monitor showed paroxysmal AV block with occasional sinus pauses up to two seconds. Echocardiography showed preserved left ventricular function (EF: 71%) and a mildly enlarged right ventricle. Stress echocardiogram and cardiac MRI confirmed no ischemia or fibrosis. Lyme and Chagas tests were negative. She was referred for permanent pacemaker (PPM) placement. Concern arose due to her syncope often being preceded by diffuse substernal chest pain, suggesting CAD. Coronary angiography with vasoreactivity testing was performed, revealing mild diffuse atherosclerosis with right dominance. Intracoronary acetylcholine testing in the left coronary artery induced significant vasospasm and coinciding AV block. She was started on a non-dihydropyridine calcium channel blocker, and received an implantable loop recorder (ILR). No recurrence of syncope was noted.

Discussion
Syncope was linked to coronary microvascular dysfunction (CMD), a condition prevalent in women. Despite unremarkable findings on standard cardiac assessments, the presence of pre-syncopal chest pain and leading to positive vasoreactivity, highlights the need for clinical suspicion in diagnosing CMD. This case illustrates the importance of thorough patient history and specific provocative testing, as standard evaluations often fail to detect CMD. The administration of intracoronary acetylcholine to provoke coronary spasm proved crucial in identifying the underlying etiology of the patient's symptoms.

Conclusions
This case highlights the critical role of clinical vigilance in diagnosing CMD, particularly in female patients. Identifying CMD requires a high index of suspicion and specialized testing protocols in the cardiac catheterization laboratory. Given gender disparities in cardiovascular outcomes, standardized practices for CMD testing should be implemented to ensure timely and accurate diagnosis and management. This approach can help bridge the gap in outcomes between men and women and improve overall patient care. The successful management of this patient with calcium channel blockers and close monitoring via ILR emphasizes the importance of individualized treatment strategies in CMD.