Clinical characteristics and outcomes of type A intramural haematoma and aortic dissection: a systematic review and meta-analysis of 6457 patients

BACKGROUND: Type A intramural haematoma (TAIMH) and type A aortic dissection (TAAD) are both managed surgically as acute aortic syndromes, but whether their clinical profiles and outcomes differ remains unclear. We performed the first comprehensive meta-analysis to compare patient characteristics, operative findings and complications between TAIMH and TAAD. METHODS: Systematic searches of six databases identified studies comparing TAIMH and TAAD, with data pooled using random-effects models and Hartung-Knapp-Sidik-Jonkman corrections for small samples. Subgroup and meta-regression analyses assessed the influence of treatment strategy, geography and baseline factors. The primary outcome was in-hospital mortality; secondary outcomes were 30-day, operative mortality and perioperative complications. RESULTS: 16 studies including 6457 patients (1288 TAIMH; 5169 TAAD) were analysed. Compared with TAAD, patients with TAIMH were older, more often female and had more hypertension but less connective-tissue disease, severe aortic regurgitation and malperfusion. TAIMH was associated with shorter aortic cross-clamp and cardiopulmonary bypass times and fewer total arch replacements. Perioperative mortality was significantly lower in TAIMH (in-hospital risk ratio (RR) 0.49, 95% CI 0.35 to 0.68; 30-day RR 0.59, 95% CI 0.40 to 0.88; operative RR 0.31, 95% CI 0.16 to 0.60), with fewer postoperative acute kidney injury (RR 0.57, 95% CI 0.42 to 0.76), consistent across eastern and western populations. CONCLUSIONS: TAIMH differs pathophysiologically and prognostically from classical TAAD, demonstrating lower perioperative mortality despite affecting an older population. These findings support distinct risk stratification and tailored surgical strategies for TAIMH and should inform updates to future aortic-disease guidelines. PROSPERO REGISTRATION NUMBER: CRD42024599964.