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‘David technique’ may enhance aortic repair

Key clinical point: An operation to repair type A aortic dissection that involves three specific steps achieves better outcomes than do other surgical approaches.

Major finding: Survival rates at 5 years were 86% for the group that had operations in which the surgeons used the three specific steps vs. 56% for the other group.

Data source: Retrospective analysis of single-center population of 146 patients who had repairs for type A aortic dissection.

Disclosures: None of the study coauthors had any relationships to disclose.

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Different strategies make interpretation difficult

Whether or not to use a cross-clamp in type A aortic dissection repair is a critical question, but a major concern of this study was the wide variability of techniques used in the comparison group, Dr. Richard J. Shemin said in his invited commentary (J. Thorac. Cardiovasc. Surg. 2015 [doi:10.1016/j.jtcvs.2015.04.038]). “The variety of approaches attests to the lack of institutional agreement on the surgical principles tested in the study,” he said. “The large variety of techniques in the control group makes the comparison and interpretation of this study difficult.”

“There are more questions to consider from this study than answers derived from the data about the clamp strategy,” he said

But, Dr. Shemin said, using the cross-clamp with axillary antegrade perfusion is “not a major issue.” And the use of clamping during the cooling period can save overall cardiac arrest time during the operation.

“If one does use femoral cannulation, then not applying the cross-clamp until achieving circulatory arrest is prudent,” he said. “With axillary cannulation, one achieves antegrade perfusion so early cross-clamping can be safely performed with the advantages of saving operative time.”

The clamp site must be inspected during circulatory arrest. Antegrade cerebral perfusion is proven to be an excellent technique and is facilitated by right axillary cannulation, Dr. Shemin said. “Most importantly, establishing antegrade CPB [cardiopulmonary bypass] perfusion after circulatory arrest is mandatory in all cases to minimize distal aorta trauma,” he said.

Dr. Richard J. Shemin is a cardiothoracic surgeon at UCLA Medical Center, Santa Monica, Calif.


 

References

Many techniques for repair of aortic dissection have evolved, but no trials have compared those techniques to determine which is the best. However, a study team has attempted to evaluate a surgical approach (the “David technique”) that includes three specific steps – no aortic cross clamp, the use of deep hypothermic circulatory arrest (DHCA), and the antegrade resumption of cardiopulmonary bypass. They found that this approach yielded significantly better long-term outcomes than did other approaches tried.

The study investigators, led by Dr. Jennifer S. Lawton of Washington University in St. Louis, reported their findings in the Journal of Thoracic and Cardiovascular Surgery (J. Thorac. Cardiovasc. Surg. 2015 [doi:10.1016/j.jtcvs.2015.03.023]). “We hypothesized that a surgical strategy to prevent cross-clamp injury or false lumen pressurization would be associated with reduced morbidity, mortality, persistent false lumen patency, and improved survival,” Dr. Lawton and her coauthors wrote. “This study was designed to determine the differences in outcomes between operative techniques.”

The study evaluated 196 patients who had surgery for acute type A aortic dissection over 17 years. Group 1, which comprised 49 patients, had the operation according to the protocol that involved the three specific steps, as Dr. Tirone David of the University of Toronto first reported in 1999 (Ann. Thorac. Surg. 1999;67:1999-2001) — the “David technique,” as the study authors called it. Group 2 consisted of patients whose repair involved a variety of techniques, including one or two steps of the David technique but not all three.

Study endpoints were 30-day mortality rate, postoperative adverse events, presence of a false aortic lumen, and overall survival, the latter defined as the time from the date of surgery to the date or death or last follow-up. The evaluation included examination of patients’ latest CT scan or MRI that was at least 6 months after the operation for false lumen, but only 78 patients had imaging at that interval.

Patients in Group 1 had a higher rate of persistent false lumen – 74% vs. 68% in Group 2. Thirty-day mortality was 6.1% in Group 1 and 15.7% in Group 2, but Dr. Lawton and her coauthors said this difference was not statistically significant.

Survival rates at 1, 5 and 10 years among both groups were “consistent with published ranges,” the authors said. At 5 years, the predicted survival was 86% for Group 1 and 56% for Group 2; and at 10 years, 72% and 37% respectively.

The study authors acknowledged the controversy that surrounds the use of retrograde resumption of cardiopulmonary bypass after replacement of the ascending aorta and that there’s no consensus on which method is best for resuming cardiopulmonary bypass after repair of a type A aortic dissection.

The study also found no difference in the incidence of false lumen between the two groups, but again, this is a source of controversy. “Persistence of a false lumen following repair for type A aortic dissection has been reported to be associated with poor prognosis and reduced long-term survival,” Dr. Lawton and her colleagues said.

“Others have reported a patent false lumen was not an independent predictor of late reoperation, but was a predictor of aortic growth following repair of type A aortic dissection.”

The study authors said one limit of their findings is its retrospective nature, but they also said that a prospective, randomized trial would be difficult to conduct.

None of the study coauthors had any relationships to disclose. They presented their original data at the American Association for Thoracic Surgery Aortic Symposium, April 24-25, 2014, in New York.

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