Discussion

Dr Chris Kwolek (Boston, Mass). I would like to congratulate Dr Greenstein and his coauthors on a very nice presentation and thank them for providing me with a copy of their manuscript well in advance of this meeting. The authors described the results of a contemporary series, although retrospective, of carotid endarterectomy and a large cohort of patients performed by 482 surgeons in over 167 hospitals within the state of New York with a very reasonable death and stroke rate for symptomatic and asymptomatic patients. In this era of increased concern about the role of carotid endarterectomy versus carotid angioplasty and stenting, and the management of the patients with carotid stenosis, I think this paper will be increasingly important. However, I am a little bit intrigued by the methodology and I will get to my question in a moment.

We have reported a 10% incidence of minor complications, including an incidence of 5.5% of cranial nerve injuries, 5% incidence of hematoma, one-third of which required surgical re-exploration. So, approximately 1.5% to 2% required a surgical re-exploration, and the author very interestingly notes that the existence of one of these complications also greatly increases the risk of concomitant stroke and potentially death, at least for the cranial nerve injuries both stroke alone and for hematoma, stroke, and death in a threefold to fourfold manner. You alluded to it in your presentation, but one wonders, what is the etiology of this relationship? It is that these are complex patients? I think very appropriately, patients who have combined carotid CABGs or redo procedures were factored out of the evaluation initially, but it begs the question. Is this merely a marker perhaps for operator experience?

So my first question is, do you have any data about the results of individual surgeons since you allude to it in your final slide and how did that play out with respect to results? And then the second question, we also know there has been some interest on a national level both by the American College of Surgeons and the NSQIP [National Surgical Quality Improvement Program] as to hospital dependent rates as well as surgeon independent rates. I would like you to comment on the higher incidence of significant complications in a very contemporary series albeit it across the large statewide registry. When we compare your results to such retrospective reviews that Bruce Perler has presented from the state of Maryland and the large retrospective reviews from similar databases in the state of California with over 40,000 patients, was it just that New York has more problems, or is it the methodology where much like the NSQIP, these are independent nurse reviewers going back and looking specifically at charts?

My final question, I think this lends itself to future investigation and, not being familiar with the New York statewide project, do the investigators or the Agency for Healthcare Research and Quality (AHRQ) have plans to perform future studies perhaps looking at carotid angioplasty and stenting and comparing that to the results of carotid endarterectomy in a contemporary series within the state of New York? I thank the society for the privilege of the floor.

Dr Alexander J. Greenstein (New York, NY). There are several possible explanations for the relationship that we detected between major and minor complications. First, higher rates of both types of complications might be more common in sicker patients. We think our CEA-specific risk adjustment model should have accounted for most of this variation. Second, the presence of anatomic variants or other technically difficult aspects of a case might lead to an increase of both complications. These data are not readily reported in the charts or easily extracted, so we were not able to discount this as a possibility. Third, a minor complication (eg, a large hematoma) could itself lead to death or stroke. This wouldn’t explain the sequence for the vast majority of major complications. Fourth, the risk of minor and major complications might reflect the technical quality and experience of the surgeon, operative team, and/or hospital. We think this is the most likely explanation, though this is difficult to prove with observational data.

We did observe significant variations in the rates of minor and major complications at both the individual surgeon and hospital level. In analyses done with the surgeon (or hospital) as the unit of analyses (not the patient as was done in this paper), surgeons (and hospitals) with higher rates of minor complications also had higher rates of major complications. These provider-level comparisons are tricky because those with very low volume will have unstable point estimates of adverse events based on chance alone. Excluding low-volume providers solves this problem, but then limits the generalizability of the results.

Dr Kwolek is correct that the methodology we used to ascertain adverse events was direct clinical chart review, much like the NSQIP. We had trained, independent research nurses carefully review the full inpatient medical chart, including admission, discharge, daily progress, and operative notes, and diagnostic imaging reports, and recorded information on minor and major complications. We also did chart review on any subsequent hospitalizations in the 30 days after surgery to detect late strokes or deaths. Studies that rely solely on administrative billing data or just the initial hospitalization tend to report lower rates of adverse outcomes.

Finally, the NYCAS Study reflects practice in 1998 and 1999, so we have no data on outcomes of carotid angioplasty and stenting.

Dr Vik Kashyap (Cleveland, Ohio). Can you explain the methodology again to me? There were 9500 charts. How much of the information was precoded or collected prospectively at the time of the operations versus how many variables did you have to go through and cull through these close to 10,000 charts to get?

Dr Greenstein. As we indicate in the article, all the data in the NYCAS Study were based on information documented in the hospital chart as part of usual care. Our trained research nurses retrospectively abstracted all clinical data from these hospital charts several years after the actual care occurred. There was no prospective coding of the data for this study as might be done in a randomized clinical trial.

Dr Kashyap. And then, in terms of the very specifics that you have on cranial nerve policies, these were confirmed by physicians or neurologists or were these all abstracted from the texts of the data that was built?

Dr. Greenstein. It was a combination of the research nurse looking at the medical chart and seeing a specific diagnosis of cranial nerve palsy or documentation of signs or symptoms suggestive of a nerve injury. If there is any question, the nurse abstractors discussed the details with the investigative team. Cases in which a stroke, TIA, or death was recorded by the nurses were reviewed by two physician reviewers (including a neurologist).

Dr Kwolek. I apologize, there was one more important point that did not come out of the presentation, but is in the manuscript, which will be important as we start comparing this, because this paper will be cited by the carotid angioplasty stenting advocates, since there is a higher incidence of cranial nerve injury. One of the subsets that needs to be broken out is temporary numbness around the ear or earlobe or facial numbness. After an endarterectomy, I would argue that larger number of our patients have that deficit and whether that is coded as significant or not, needs to be clarified.

Dr Greenstein. I have to look in to that. Thank you.

Unidentified speaker. I think my question is along the same lines. There is a lot of difference between having a deviation of tongue versus hoarseness of voice versus not being able to breathe versus losing a high pitch in your voice. So, it seems to me to be not as meaningful to have a big bucket of patients having cranial nerve deficiency, because it really is not going to get home the message of the intensity of the consequence or the significance. Did you segregate and then pool it together or did you just add it as a collective cranial nerve deficiency? Because there are studies that say that as high as 16% incidence of hypoglossal nerve palsy, but we do not take that as seriously as hoarseness of voice or inability to swallow and losing the glossopharyngeal function.

Dr Greenstein. Again, this is one of the limitations of a retrospective study of this nature. We have large numbers, but we do not have the richness of clinical detail about the severity or persistence of cranial nerve injuries that could answer this question.

Dr George Levinson (Bethesda, Md). Was there any correlation between the use of clopidogrel preoperatively and the incidence of early postoperative stroke due to thrombosis and bleeding? In other words, with Plavix [Sanofi-Aventis, Bridgewater, NJ], was there more bleeding and fewer strokes, and if one did not have Plavix immediately preoperatively, were there more strokes and fewer bleeding?

Dr Greenstein. The NYCAS database has data on the use of antiplatelet agents and anticoagulants, but their potential impact on risk of thrombotic or bleeding complications has not yet been analyzed.