Medical management centered around anti-impulse therapy and serial imaging is recommended for uncomplicated type B aortic intramural hematoma (IMH). The aim of this study was to evaluate the natural history of medically treated aortic IMH and identify factors that portend failure of medical management. Data from consecutive patients diagnosed with type B IMH from 1995 to 2019 were retrospectively reviewed. Primary outcome was 30-day mortality. Secondary outcomes included all-cause and aortic-related mortality, and aortic-related surgical intervention for dissection or aneurysm. Demographics, clinical, and anatomic data and management details were analyzed. Ninety-one patients were identified with type B IMH: 78 acute, 6 subacute, 1 chronic, 5 incidental, and 1 traumatic. All patients received antihypertensive medications and pain control. The initial management was best medical therapy (BMT) in 85% (N = 77) and surgery in 13% (N = 12) of patients. Two patients declined intervention and died within 48 hours. Thirty-day mortality was 5% (N = 4) in the BMT and 17% (N = 2) in the surgery treatment group. All-cause 5-year mortality was comparable between groups (57% vs 50%, P = .8), with a median survival of 6.8 years (interquartile range [IQR]: 2.4-10.9 years) after BMT and 5.9 years (IQR: 1.4-7.7 years) after surgery. However, 5-year aortic-related mortality was higher in the surgical group (25%) compared with BMT (4%, P = .02, Fig) due to high perioperative mortality. Aortic-related intervention after initial medical management was required in 19% (N = 15) of patients, for dissection (N = 3) and aneurysm (N = 12). The median freedom from intervention was 4.6 (IQR: 1.4-9.2) years. On univariate analysis, coronary artery disease, hypertension, baseline creatinine level, peripheral artery disease, active smoking, IMH thickness, and maximum aortic diameter were independent risk factors for a subsequent need for surgery after medical management (Table). On multivariate analysis, chronic kidney disease with a creatinine >1.2 mg/dL, IMH thickness (>7.7 mm), and aortic diameter (>42 mm) were predictive risk factors. Reintervention after initial surgical management was required in 25% (N = 3), for aneurysm, endoleak, and infected endograft with a median freedom from reintervention of 5.2 (IQR: 3-7.9) years. Medical management of type B IMH is associated with low early mortality but a 19% risk of aortic-related intervention, primarily for proximal descending thoracic aneurysm. Elevated creatinine, IMH thickness, and aortic diameter at presentation portend eventual failure of medical management. Given the nearly 5-year time between IMH and need for surgery beyond 30 days, diligent follow-up is needed. These findings provide useful information to guide patient expectations and optimal treatment.TableUnivariate analysis of baseline risk factors for need for surgical intervention after medical managementVariableBMT onlyBMT + surgeryP valueDemographics N6215 Male sex34 (55%)10 (67%).2 Age at symptom onset, years77 (47-92)76 (56-88).3 BMI, kg/m227.2 ± 6.028.2 ± 4.4.7Baseline comorbidity status Coronary artery disease17 (27%)14 (93%).01 Myocardial infarction11 (18%)2 (13%).8 MI within past 30 days2 (3%)1 (7%).5 Unstable angina7 (11%)0.2 CABG5 (8%)1 (7%).9 CABG within past 6 weeks1 (2%)0.6 Arrhythmia13 (21%)3 (20%).9 CHF10 (16%)3 (20%).7 EF<30%3 (5%)0.4 Hypertension48 (77%)14 (93%).02 Hyperlipidemia22 (35%)7 (47%).4 Current smoker15 (24%)10 (67%).03 Former smoker12 (19%)4 (27%).7 COPD10 (16%)2 (13%).8 Severe COPD on steroids/home O23 (5%)0.4 Diabetes mellitus6 (10%)0.2 Stroke/TIA11 (18%)3 (20%).4 PAD9 (15%)0.04 Baseline creatinine1.1 ± 0.62.3 ± 1.0.01 Creatinine > 35 (8%)5 (33%).02Presentation Acute5114.7 Subacute41 Chronic10 Incidental imaging finding50 Traumatic10Aortic segments involved Distal arch36 (58%)10 (62%).8 Descending thoracic59 (95%)15 (9100%).4 Suprarenal22 (35%)3 (20%).3 Infrarenal7 (11%)0.1Imaging at presentation IMH thickness, mm7.6 ± 48.3 ± 4.04 Aortic diameter, mm40.1 ± 9.347.8 ± 6.2.03 Associated PAU30 (40%)9 (60%).4Vital signs at presentation Heart rate, per min76 ± 1574 ± 16.4 Systolic BP, mm Hg158 ± 35152 ± 35.3Boldface P values represent statistical significance. Open table in a new tab