Mortality drops for acute type A aortic dissection, still high for patients not receiving surgery

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The chance of a patient surviving after an acute type A aortic dissection has improved significantly, but mortality remains high if not recognised early and repaired surgically. This is according to new research from a team at Michigan Medicine at the University of Michigan (Ann Arbor, USA).

A team of researchers examined early mortality rates for over 5,600 patients admitted to the hospital and examined hourly with acute type A aortic dissection between 1996 and 2018 from the International Registry for Acute Aortic Dissection (IRAD).

Findings published in JAMA Cardiology reveal that 5.8% of patients with acute type A aortic dissection died within the first two days after hospital arrival, a mortality rate of 0.12% per hour. The rate is significantly lower than that reported in the 1950s, which estimated that 37% of patients died within the first 48 hours, with an increasing mortality rate of 1–2% per hour.

“We believe that advances in diagnosis and management, especially a focus on early surgical repair, may have contributed in part to these improvements in mortality for acute aortic dissection,” said Kim Eagle, senior author of the paper and director of the University of Michigan Health Frankel Cardiovascular Center.

Of all the patients, 91% either received surgery or were intended for surgery, with the others managed medically due to advanced age and complications, such as stroke and kidney failure. Nearly 24% of those receiving medical treatment alone died within two days, compared to 4.4% of patients treated with surgical repair—a death rate more than 5 times higher.

“Patients who were managed medically were likely not surgical candidates due to their comorbidities,” said Bo Yang, a professor of cardiothoracic surgery at University of Michigan Medical School, in a press release announcing the results of the study. Yang was not involved in the study, the release notes. “The medically managed patients could die from aortic dissection-associated complications—such as malperfusion, cardiac tamponade, aortic rupture and acute aortic insufficiency, which can be treated with surgery—or from their existing medical conditions which could be worsened by the aortic dissection.”

Only 1% of patients deemed suitable for surgery died before the procedure. These patients died after an average of nearly nine hours from being admitted to the hospital, exceeding the six-hour median time to surgery for all patients.

Interhospital transfer is needed in more than 70% of aortic dissection cases, causing inherent delays. Before this study, Eagle says, it was thought that early death from this condition was so prohibitive that operating urgently, even in hospitals with limited volume of aortic dissection surgery and resources, was the preferred strategy.

However, there is evidence that surgery at a low-volume hospital can double the risk of dying while undergoing repair compared to the highest volume providers. Additionally, mortality rates for open repair of acute type A aortic dissection are nearly three times higher when the operation is not performed by a dedicated aortic surgeon.

“Hospital mortality at a high-volume centre like U-M [University of Michigan], where aortic dissection patients are taken care only by highly experienced aortic surgeons, can be as low as 5%, while the same patient operated on at a low-volume centre may be 20% or higher,” Eagle said. “With this new information, it is clear that the ‘cost’, or risk, of a four-to-six-hour delay caused by transfers is more than offset by the lower risk of surgery at experienced hospitals.”

Cases are rare. Approximately three in 100,000 people suffer aortic dissection each year. The condition most commonly affects older men, and a person experiencing the tear may feel a “knifelike, tearing pain through the back,” according to IRAD.

It is estimated that up to 50% of patients will die before ever reaching the hospital, making the overall mortality for aortic dissection substantially higher, the press release from Michigan Medicine notes.

“There is a need to identify the high-risk population of aortic dissection, such as those with a family history of aortic aneurysm and dissection, especially at a younger age, or known pathogenic genetic variants, so that we can replace the proximal aorta electively to prevent acute type A aortic dissection,” Yang said. “For young people under 55 years old with severe chest pain, we have to prove if patients have aortic dissection or otherwise.”


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