BOSTON – Medical therapy for acute uncomplicated type B aortic dissections was effective in the short term, but was associated with low 6-year intervention-free survival in a review of 298 cases.

Furthermore, patients who received medical therapy without operative intervention had increased mortality at 6 years, compared with those who received intervention, Dr. Christopher A. Durham reported at the Vascular Annual Meeting.

During a mean follow-up of nearly 4.3 years, medical therapy failed in almost 60% of the patients; 114 died after an average of 2.7 years, and 87 required aortic intervention.

Aneurysmal degeneration was the indication for intervention in 65% of patients requiring intervention, and six of these patients experienced a ruptured aneurysm. "Only six of these patients underwent stent placement, with the remainder receiving open aortic replacement," said Dr. Durham of Massachusetts General Hospital, Boston.

The average time to operation in this subset of patients was 2.3 years. Visceral malperfusion was the indication for intervention in 18 patients (21%), and most underwent an endovascular intervention including either stenting or endovascular fenestration. A less common indication for intervention was retrograde type A dissection development in two patients. These patients underwent open replacement.

The average time to intervention in the subset of patients whose indication was not aneurysmal degeneration was 24 days. Early treatment failure – within 15 days of presentation – occurred in 37 patients (12%) and included 12 deaths and 25 interventions.

"In this group of patients who ultimately required an intervention within the acute period, aneurysmal degeneration was the indication in 25% of patients, all of whom were treated with an open approach," Dr. Durham said. Visceral malperfusion was the indication in half of the early interventions.

The 30-day mortality rate among patients with early intervention after initial medical therapy was 12%.

Freedom from intervention was 74% at 6 years, with most interventions occurring within the first 12 months. Intervention-free survival was 55% at 3 years and 41% at 6 years. Only end-stage renal disease was found to be predictive of failure, and age over 70 years was protective against failure (hazard ratio, 0.97), Dr. Durham said, adding that no variables associated with progression to intervention were identified.

Notably, although survival was similar during the first 3 years in those who remained on medical management and those who required intervention (73% and 78%, respectively), survival at 6 years was 58% and 76% in the groups, respectively.

"These data join emerging data demonstrating a survival benefit in patients undergoing intervention when compared to those who are treated with medical therapy alone," he said.

Study subjects were all patients who were initially managed medically for acute uncomplicated type B aortic dissection between March 1999 and March 2011 in a health care system. The patients had a mean age of 66 years at presentation, about 62% were men, and most were white. Nearly 75% had hypertension, and most of those were on therapy. About 5% had end-stage renal disease.

Failure of medical therapy was defined as any death or aortic-related intervention. Early failure was defined as failure within 15 days of presentation.

"Aortic dissection is the most common catastrophic event affecting the aorta, with an incidence exceeding that of ruptured abdominal aortic aneurysm.

"The majority of patients with type B aortic dissections, where the entry tear originates distal to the left subclavian artery, are treated with medical therapy," he said. In fact, medical management aimed at lowering the systolic blood pressure and pulse remains the standard of care, and a number of studies have demonstrated a favorable 1-year survival – ranging from 70% to 90% – with medical therapy alone in this population.

"However, at what cost?" Dr. Durham asked.

"The principal late complication of aortic dissection is aneurysmal degeneration of the outer wall of the false lumen, which has been reported to occur in up to 40% of medically treated patients," he said, adding that, because of a paucity of contemporary data regarding the natural history of medically treated patients, it has been unclear whether the natural history has been altered with current medical therapy.

The current findings suggest that operative intervention is associated with a survival benefit.

As Food and Drug Administration "approval has just been granted for thoracic stent grafts to be used in aortic dissection, it is clear that endovascular coverage of proximal aortic entry tears will become more common in the acute phase. As such, further study is needed to determine which patients presenting with type B dissections will benefit from early intervention," he said.

Dr. Durham reported having no disclosures.

Editor’s Note: The treatment of type B dissection is a controversial subject and this controversy will be addressed in an upcoming Point/Counterpoint article in Vascular Specialist.

Meds fall short for type B dissection