Outcomes of Hospitalized Patients with Myocardial Infarction and Immune Thrombocytopenic Purpura: A Cross Sectional Study over 15 Years

Background:

Immune Thrombocytopenic Purpura (ITP) is an autoimmune disorder characterized by low platelet counts and mucocutaneous bleeding. Antiplatelet agents are an essential component in the treatment of acute myocardial infarction (MI). Patients with ITP are not exempt from succumbing to acute myocardial infarction. Myocardial infraction in these patients is rare but poses a significant management challenge. The outcomes of hospitalized patients with ITP and acute MI have not been previously described and may help identify risk factors associated with adverse outcomes in this unique patient population.

Methods:

The International Classification of Diseases, 9th Edition, Clinical Modification codes were used to identify patients with ITP who were admitted with acute myocardial infarction. All data regarding such hospitalization was extracted from the National Inpatient Database for the years 2000 to 2014. Patient demographics of age, race and gender; hospital characteristics such as geographical location, teaching status, rural vs. urban location and bed size, medical comorbidities such as hypertension, hyperlipidemia, diabetes and coronary artery disease were studied. The Chi square test was used to determine associations with statistical significance and logistic regression was used to determine independent predictors of mortality.

Results:

A total of 753,732 hospitalized patients with ITP were identified over the time period of 2000 to 2014 of which 37695 patients had both ITP and acute MI. There were more females with ITP in general (60% females vs 40% males), but more males with ITP and acute MI (55.8% males vs 44.2% females; p =0.0000). Caucasians were affected the most (5.5%) amongst all races and the age group of 65-79 years had the highest percentage of patients with ITP and MI (7.3%). While hospitals located in the Northeast region of the country had the highest prevalence of MI in ITP, there was no statistical difference between prevalence in hospitals of different sizes (small vs. medium vs. large). A majority of patients with MI and ITP were covered by Medicare and were discharged home. 5572 patients received a stent and 3353 patients underwent coronary artery bypass grafting. The classical risk factors of hypertension, hyperlipidemia, and diabetes were also noted to be highly prevalent in patients with ITP and MI. 10.05% of patients with ITP and acute MI died during hospitalization, while 4% of all patients with ITP died during hospitalization (p<0.05). Multiple regression showed that stent placement, female gender, blood transfusions, platelet transfusion, 80+ age group and higher Charlson's score were independent predictors of mortality in patients with ITP who have MI (ORs: 0.3, 0.8, 1.9, 1.3, 5.9 and 5.5 respectively).

Conclusions:

ITP patients with MI have poor outcomes. Known risk factors for acute MI in the general population are also applicable to patients with ITP. Acute MI is associated with an increased rate of in-hospital death in patients with ITP. Both blood transfusions and platelet transfusions adversely affect outcomes and should be considered in the management of MI in ITP patients.