Correspondence
Partial Thrombosis of the False Lumen in Aortic Dissection
N Engl J Med 2007; 357:1868-1869November 1, 2007
- Article
To the Editor:
The main limitation of the study of a large cohort of patients with type B acute aortic dissection from the International Registry of Acute Aortic Dissection (IRAD), reported by Tsai et al. (July 26 issue),1 is the exclusion of patients who died in the hospital. Fifty patients (24.9% of the 201 patients examined) died within 3 years after discharge from the hospital, whereas 66 patients must have died in the hospital because 466 of the 532 patients enrolled in the IRAD who had type B acute aortic dissection were discharged from the hospital alive. In a previous study of 384 patients with type B acute aortic dissection from the IRAD,2 the in-hospital mortality among patients with a patent false lumen, those with a partially thrombosed false lumen, and those with a completely thrombosed false lumen was 12.7%, 12.1%, and 8.3%, respectively (P=0.71). We would like to know the false-lumen status of the 66 patients who were excluded from the study by Tsai et al. and would like to know the midterm mortality with the in-hospital mortality included rather than excluded.
2 ReferencesHisato Takagi, M.D., Ph.D.
Norikazu Kawai, M.D.
Takuya Umemoto, M.D., Ph.D.
Shizuoka Medical Center, Shizuoka 411-8611, Japan
kfgth973@ybb.ne. jp 1
Tsai TT ,Evangelista A ,Nienaber CA , et al. Partial thrombosis of the false lumen in patients with acute type B aortic dissection. N Engl J Med 2007;357:349-359
Full Text | Web of Science | Medline2
Suzuki T ,Mehta RH ,Ince H , et al. Clinical profiles and outcomes of acute type B aortic dissection in the current era: lessons from the International Registry of Aortic Dissection (IRAD). Circulation 2003;108:Suppl II:II-312
CrossRef | Web of Science
To the Editor:
Tsai et al. report an independent adverse relationship between partial thrombosis of the false lumen and long-term mortality among hospital survivors of acute type B aortic dissection. However, focusing on postdischarge mortality rather than total mortality (i.e., both in-hospital and postdischarge mortality) provides an incomplete view. Hypothetically, there is less time for thrombosis of the false lumen among patients who die in the hospital. This may seem to contradict the theory proposed by Tsai et al. Do the authors have any information on this important subgroup of patients to either substantiate or refute their hypothesis? Furthermore, according to their conceptual risk model, the group of patients who had complete thrombosis of the false lumen should have had the lowest mortality during follow-up. However, this was true only up to about 600 days of follow-up, after which there was a rather steep rise in the mortality rate observed only in this group. This suggests that there were probably other, unexplained factors contributing to late mortality besides false-lumen status.
Brian Wong, M.D.
Sudbury Regional Hospital, Sudbury, ON P3E 3B6, CanadaAuthor/Editor Response
Takagi et al. request information on the false-lumen status of the 66 patients who were excluded from the study because they died in the hospital. Of these patients, 39 (59.1%) had a patent false lumen, 19 (28.8%) had partial thrombosis of the false lumen, and 8 (12.1%) had complete thrombosis of the false lumen. This distribution closely resembles the distribution of false-lumen status in the study population. With the inclusion of these patients in the survival analysis, the mean (±SD) 3-year mortality rate for patients with a patent false lumen was 14.7±7.3%, for those with partial thrombosis it was 32.4±12.2%, and for those with complete thrombosis it was 30.0±22.6% (median follow-up, 3.2 years; P=0.004 by the log-rank test). Partial thrombosis of the false lumen remained a strong independent predictor of death (relative risk, 2.58; 95% confidence interval, 1.41 to 4.71; P=0.002). Therefore, including patients who did not survive the initial hospitalization did not change our findings.
Nonetheless, we dispute the argument by Wong that focusing on postdischarge mortality rather than total mortality (i.e., both in-hospital and postdischarge mortality) “provides an incomplete view.” In-hospital outcomes are generally acceptable in patients with uncomplicated acute type B dissection, 90% of whom survive to hospital discharge.1 Among patients who die early, consistent predictors of death include hemodynamic instability and malperfusion syndromes, which may not be dependent on false-lumen physiology but may rather be a sign of aortic rupture or static obstruction of branch vessels.2,3 This is supported by previous studies, which have not shown false-lumen status to be a predictor of early death.2,4 Our conceptual model postulates an increase in mean arterial and diastolic pressure in a lumen with pulsatile inflow and impaired outflow. This has long-term implications with regard to increased wall tension and the risks of aneurysm expansion, redissection, and rupture. Furthermore, by presenting our survival analysis and multivariate models based on data from the patients who survived to hospital discharge, we focused exclusively on predictors of death during follow-up, which may have surveillance and management implications. With regard to the complete-thrombosis group, which appeared to have a mortality similar to that in the partial-thrombosis group, we emphasize that our study, like most others, had very small numbers in this group, impairing the statistical comparison.
4 ReferencesThomas T. Tsai, M.D., M.Sc.
Kim A. Eagle, M.D.
University of Michigan Medical Center, Ann Arbor, MI 48109-5853
hsianshi@umich.edu 1
Hagan PG ,Nienaber CA ,Isselbacher EM , et al. The International Registry of Acute Aortic Dissection (IRAD): new insights into an old disease. JAMA 2000;283:897-903
CrossRef | Web of Science | Medline2
Suzuki T ,Mehta RH ,Ince H , et al. Clinical profiles and outcomes of acute type B aortic dissection in the current era: lessons from the International Registry of Aortic Dissection (IRAD). Circulation 2003;108:Suppl II:II-312
CrossRef | Web of Science3
Umana JP ,Lai DT ,Mitchell RS , et al. Is medical therapy still the optimal treatment strategy for patients with acute type B aortic dissections? J Thorac Cardiovasc Surg 2002;124:896-910
CrossRef | Web of Science | Medline4
Trimarchi S ,Nienaber CA ,Rampoldi V , et al. Role and results of surgery in acute type B aortic dissection: insights from the International Registry of Acute Aortic Dissection (IRAD). Circulation 2006;114:Suppl I:I-357
CrossRef | Web of Science
