title: Aortic dissection type A versus type B: a different post-surgical death hazard?
abstract: OBJECTIVE
  Patients with type B aortic dissection differ from patients with type A dissection in age, hypertension prevalence, indications and timing of surgical treatment, yet reported long-term results have been rather similar (see Doroghazi et al. J Am Coll Cardiol 1984;3:1026-1034).
  
  
  METHODS
  With the aim of comparing the post-surgical history, we have reviewed our results in 288 dissections, 213 type A and 75 type B, operated consecutively between 1 January 1970 and 31 November 1994. Follow-up was 100% complete. Empirical survival of both groups was interpolated with a fully parametric method and the shape and scale of the hazard function was investigated.
  
  
  RESULTS
  Survival was not significantly different between type A and type B. Parametric survival was, respectively, 0.52% (70% C.L.: 0.48-0.55) vs. 0.56% (0.51-0.62) at 5 years, 0.44% (0.40-0.47) vs. 0.28% (0.23-0.25) at 10 years, 0.37% (0.33-0.41) vs. 0.25% (0.19-0.32) at 15 years, and 0.31% (0.26-0.35) vs. 0.24% (0.18-0.31) at 20 years. Following the high perioperative risk phase in type A dissection, the intermediate and late risk remains constant at a rate of 0.0033 events/month (3.9% patient-years (pt.-years)). By contrast, the postoperative course of type B dissection shows an intermediate risk phase between 4 and 10 years with an average linearized risk of 9.3% pt.-years and a peak of 20%. This determined lower survival rates (24 vs. 31% at 20 years, P = NS).
  
  
  CONCLUSIONS
  We conclude that patients with type B dissection have a steeper postoperative death hazard as compared to type A dissection patients. Age confounding or late entry do not explain the difference. This could be possibly related to a greater propensity for expansion, higher risk of malperfusion complications or to limitations of our current surgical treatment.
authors.affiliation: Istituto Chirurgia Cardiocascolare, University of Padova, Italy.
authors.forename: G
authors.initials: G
authors.lastname: Rizzoli
authors.forename: D
authors.initials: D
authors.lastname: Scalia
authors.forename: D
authors.initials: D
authors.lastname: Casarotto
authors.forename: E
authors.initials: E
authors.lastname: Tiso
mesh_terms: D000328:Adult; D017677:Age Distribution; D000368:Aged; D000784:Aortic Dissection / Q000145:classification* / Q000453:epidemiology / Q000401:mortality / Q000601:surgery*; D001019:Aortic Rupture / Q000453:epidemiology / Q000401:mortality / Q000601:surgery*; D002423:Cause of Death; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007558:Italy / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D016012:Poisson Distribution; D011183:Postoperative Complications / Q000401:mortality*; D015995:Prevalence; D016016:Proportional Hazards Models; D012307:Risk Factors; D017678:Sex Distribution; D015996:Survival Rate