Objectives <p>Pulmonary artery adventitial hematoma (PAAH) is a potential complication of aortic dissection (AD) that has been shown to have a deleterious effect on prognosis. However, the specific relationship between PAAH secondary to the rupture of type A AD with early mortality has not been fully characterised. We aimed to evaluate the relationship betweeen PAAH and the short-term prognosis of patients with this condition, and to determine how PAAH impacts the prognosis of patients with type A AD compared with other complications of type A AD.</p> Methods <p>We retrospectively studied 344 patients with type A AD who were hospitalised at a single institution (164 men and 180 women with a mean [SD] age of 71.0 [12.6] years). These patients were allocated to two groups, comprising those who died within 1 week of the onset of symptoms (early mortality group; <i>n</i> = 33) and those who survived (survival group; <i>n</i> = 311). PAAH was classified according to the CT findings as stage 1 (only in the mediastinum), stage 2 (extending into the lung field ± the interlobular septa), or stage 3 (extending into the alveoli).</p> Results <p>The patient cohort was comprised of 90 (26.2%) patients with PAAH of 344 patients with type A AD. 16 (48.5%) of 33 patients had PAAH in the early mortality group, and 74 (23.8%) of 311 patients had PAAH in the survival group. The early mortality group had higher prevalences of PAAH (<i>p</i> = 0.002), stage 3 PAAH (<i>p</i> &lt; 0.001), pericardial haemorrhage (<i>p</i> = 0.001), mediastinal haemorrhage (<i>p</i> &lt; 0.001), haemothorax (<i>p</i> &lt; 0.001), renal ischaemia (<i>p</i> = 0.002), limb ischaemia (<i>p</i> = 0.001) and myocardial ischaemia (<i>p</i> = 0.004) than the survival group. Furthermore, multivariate analysis showed that age (<i>p</i> = 0.002), stage 3 PAAH (<i>p</i> &lt; 0.001), limb ischaemia (<i>p</i> = 0.010), and myocardial ischaemia (<i>p</i> = 0.001) were risk factors for early mortality.</p> Conclusions <p>PAAH is not a rare complication of type A AD, and stage 3 PAAH is a risk factor for early mortality.</p> Key Points <p><Emphasis Type="BoldItalic">Question</Emphasis> <i>PAAH due to ruptured type A AD can occur and has been reported to correlate with prognosis</i>.</p> <p><Emphasis Type="BoldItalic">Findings</Emphasis> <i>PAAH is not a rare complication of Stanford type A AD, and Stage 3 PAAH is a risk factor with the greatest prognostic value on early mortality</i>.</p> <p><Emphasis Type="BoldItalic">Clinical relevance</Emphasis> <i>Knowing that PAAH often occurs with type A AD can help us avoid misdiagnosing stage 3 PAAH as pneumonia or pulmonary oedema</i>.</p> Graphical Abstract <p></p>