| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
J Thorac Cardiovasc Surg 2007;134:545-547
© 2007 The American Association for Thoracic Surgery
Letter to the Editor |
Division of Cardiac Surgery, University of Verona Medical School, Verona, Italy
To the Editor:
We read with interest the article by Reece and associates1
supporting the feasibility and implying the potential advantage of direct cannulation of the dissected aorta (central cannulation) compared with peripheral cannulation (femoral or axillary) in the management of patients with acute type A aortic dissection. The authors compared retrospectively the results achieved in 24 patients cannulated via the dissected ascending aorta versus 46 cannulated via the femoral artery (n = 31) or the axillary artery (n = 15).
The authors claimed the groups to be comparable on the basis of age and preoperative comorbidities. Similarly, they reported no differences in bypass time, crossclamp time, or hypothermic circulatory arrest time between the two groups. The peripheral group had more cardiac events (peripheral 15% vs central 0%; P < .05) and a higher mortality than the central group (peripheral 19.5% vs central 4.2%; P < .05). The authors conclude that direct cannulation of the dissected aorta is safe and, used with the appropriate indication, might optimize postoperative outcomes in this disease entity.
The complete cardiothoracic surgeon must be adaptable to change and open to new predicaments. It would help, however, if these new thoughts, which often revolutionize much of what has been previously asserted for decades, would result from impeccable studies. Indeed, great methodologic vigilance and lack of bias outline the basic difference between evidence-based medicine and anecdotal experience or simplistic observations.
Is this the case with the study by Reece and colleagues?
Overall, the study reports a single institutional experience collected retrospectively over a 1-decade time period, all these being widely recognized methodologic limitations. In retrospective institutional studies arbitrarily limited to a given time period, data are retrieved by homologous observers from chart review rather than being recorded as they occur. Unrecognized group differences and observer bias constitute major problems.
Criteria to choose the site of cannulation are not reported in the article and are said to vary over time and among different surgeons, which implies that different patient subgroups might have undergone different approaches over time.
Most patients are said to have been cooled to a core body temperature of 18°C to allow 20 to 30 minutes of circulatory arrest time. Antegrade perfusion was reported to be used only recently and in some axillary cannulations, but retrograde cerebral perfusion was generally employed. A variety of neuroprotective pharmacologic strategies were reported to be used during the study period.
Indeed, it appears that many different variables might have affected neurologic outcome. Three different methods of cerebral protection were adopted (sole deep hypothermia and circulatory arrest, antegrade selective perfusion, and retrograde cerebral perfusion), together with a variety of nonspecified neuroprotective pharmacologic strategies. This, also in view of the limited patient sample size, makes interpretation of data about neurologic outcome totally unfeasible. Should any of the 30-day mortality be due to neurologic causes, it would be very hard to relate them to the cannulation site.2
Surgeons’ preferences are said to have dictated the adjunct procedures, including coronary artery bypass grafting (CABG).
Indication for myocardial revascularization in type A aortic dissection is controversial.3 Apart from cases with evidence of coronary dissection, for which the indication often goes without saying, it may be difficult to establish an indication for CABG. Compounding the problem is the rare availability of a coronary angiograms in this often urgent situation. The criteria adopted to perform a CABG are therefore important to know. They become crucial when the rate of postoperative myocardial infarction is outlined as presenting with a statistically significant difference between the two groups and supposed to be linked somehow to the site of cannulation.
Just as an example, since the criteria to perform a CABG have not been outlined in the article, should the presence of a history of coronary artery disease (as reported in Table 1) have been one of the criteria, it would appear that 6 of 7 (86%) patients with coronary artery disease among the central cannulation group versus 9 of 22 (41%) in the peripheral group underwent a concomitant CABG. This might have significantly contributed to the different coronary outcomes, independently from the cannulation site.
The two study groups were reported as similar with regard to the chosen preoperative comorbidities.
Many studies, including one from our own group on 311 acute type A dissections managed over a 25-year period,4,5 stressed the importance of a few specific preoperative variables on surgical outcome. Therefore, judging risk adjustment and clinical outcomes including mortality, some variables (eg, mesenteric ischemia) definitely have more relevance than others (eg, rheumatic disease). Many of these universally recognized as valuable data were missing (date of surgery, hypertension, obesity, redo surgery, abrupt onset of pain, angina, acute myocardial infarction, renal failure, and any sign of malperfusion [pulse deficit, neurologic deficit or stroke, paraplegia, mesenteric ischemia, limb ischemia]), again making comparison between the two groups and interpretation of outcomes, particularly 30-day mortality, difficult and simplistically attributed to the cannulation site.
In the reported experience, the use of central cannulation was said to have increased at the same time with the comfort for valve preservation procedures. This statement implies a different distribution over time of one approach (central cannulation) with respect to the other. Also, as reported in the meeting discussion, it implies that more experienced surgeon(s) may have preferentially adopted the central cannulation approach, which adds another potentially crucial variable to the analysis of results.
Hospital mortality for the central cannulation group was as low as 4% (1/24), with a reported 30-day mortality of 0%, despite the fact that 62% of the patients were operated on on an emergency basis. These excellent results offer mortality figures far below those even recently reported worldwide for the surgical management of acute type A aortic dissection.6 Without at all minimizing the authors’ fine management, such results elicit some concern about the possible biased selection of this group.
Reece and coauthors should be congratulated for the excellent results achieved in their central cannulation group of patients. We share the conviction that when properly tailored for the patient, direct cannulation of the dissected ascending aorta by the reported technique is feasible, reproducible, and probably safe, as we also occasionally experienced in our series. We believe, however, that based on the presented data, a comparative analysis with more conventional techniques (peripheral cannulation) might be misleading and potentially hazardous.
Therefore, although the authors stress that the presented data are not meant to advocate central cannulation approaches over peripheral cannulation techniques, their comparison of complications and disposition between the two groups might indeed lead to the misconception that the former procedure has potential advantage in terms of clinical outcome over the latter. This conclusion does not seem to be supported by sufficient evidence.
References
Related Article
This article has been cited by other articles:
|
|
 |
|
  N. Luciani, A. Anselmi, F. Glieca, G. Lauria, R. de Geest, and G. Possati Femoral Cannulation With Long Arterial Cannula in Aortic Dissection Ann. Thorac. Surg., February 1, 2012; 93(2): e45 - e47. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 R. S. Bonser, A. M. Ranasinghe, M. Loubani, J. D. Evans, N. M. A. Thalji, J. E. Bachet, T. P. Carrel, M. Czerny, R. Di Bartolomeo, M. Grabenwoger, et al. Evidence, Lack of Evidence, Controversy, and Debate in the Provision and Performance of the Surgery of Acute Type A Aortic Dissection J. Am. Coll. Cardiol., December 6, 2011; 58(24): 2455 - 2474. [Abstract] [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| ANN THORAC SURG | ASIAN CARDIOVASC THORAC ANN | EUR J CARDIOTHORAC SURG |
| J THORAC CARDIOVASC SURG | ICVTS | ALL CTSNet JOURNALS |
