Based on data collected from 2002–2020, Dominic Howard (Oxford University Hospitals NHS Trust, Oxford, UK) spoke at the 2020 UK Vascular Societies’ Annual Scientific Meeting (VS ASM; 24–27 November, virtual) on changing patterns of thoracic aortic disease. He stressed the significance of uncontrolled hypertension as a treatable risk factor for acute aortic dissection, predicted that dissections will increase “significantly” in the elderly over the next 30 years, and noted that further research is required to understand why women with aortic disease have poorer outcomes than men.
“Currently, there are very few data on risk factors, incidence, and outcomes of thoracic aortic disease,” Howard began, detailing that existing studies are mainly retrospective, restricted to certain cohorts, limited by age and gender, and have excluded out-of-hospital events and deaths, resulting in “potentially inaccurate” data.
Howard and colleagues set up the Oxford Vascular study (OxVasc) in 2002. He informed the VS ASM audience that, over the last 18 years, the team has analysed a population of around 90,000 patients, with daily ascertainment of acute vascular events. In addition, the team have the benefit of “extensive” pre-morbid primary care data, Howard detailed, including information on social deprivation, blood pressure, medication history, family history, and other cardiovascular events and comorbidities.
“The aim of OxVasc has always been to provide the most accurate data on incidence, risk factors, and outcomes for all vascular events,” the presenter explained, adding that the team have also extrapolated their incidence rates on to the UK population, in order to predict the number of cases that are going to occur over the next four decades for a variety of vascular conditions.
Ten-year results show benefit of prospective, population-based methodology
Howard relayed that the team published 10-year results on acute dissection back in 2014, which showed that, firstly “a prospective, population-based methodology is far superior to HES [Hospital Episode Statistics] coding”. In fact, he stated that if HES coding is used to detect acute dissections, “you will miss approximately one-third of cases”.
The 10-year results also revealed that, overall, ruptured aneurysms—both thoracoabdominal and abdominal—have a higher incidence per 100,000 people than acute dissection, and that both of these conditions are more common in men than women. The team also observed that the age at index event for acute dissection is 72 years, compared to 79 years for an index ruptured aneurysm.
Howard mentioned that the 10-year results revealed a gender difference that is more significant with acute aneurysmal disease, with three-quarters of these events being in men, whereas for acute dissection, 60% are in men and 40% are in women.
Furthermore, Howard shared the finding that the first event in women for acute aortic dissection tends to be a decade later than the first even for men, whereas this is not the case for ruptured aneurysms, where both men and women can have their first event at a similar age.
Ten-year results confirmed that smoking status is the “driving” risk factor for ruptured aneurysms, Howard relayed, adding that current smokers tend to have their index event “approximately a decade younger than non-smokers,” whereas he noted that the main risk factor for acute aortic dissection is uncontrolled hypertension.
Looking at overall annual mortality for both acute aortic dissection and ruptured aneurysms, their results confirmed that these two conditions “have some of the worst outcomes of all cardiovascular events”.
Ruptured abdominal aortic aneurysms “continue to have the highest incidence” of all aortic conditions, 18-year results reveal
Howard detailed that the team can now present the 18-year results of the OxVasc study. “First of all, we can show that ruptured abdominal aortic aneurysms continue to have the highest incidence of all aortic conditions, and are more common in men than women,” he revealed.
In addition, the team found that abdominal aneurysms are of a lower incidence and are as common in women as they are in men. Both type A and type B dissection increase in incidence with age, and both are slightly more common in men than women, “but this is not as marked as for aneurysmal disease”.
Considering the time trends in incidence over the last 18 years, Howard detailed that the team have confirmed ruptured aneurysms are slowly declining in incidence, which he said is most probably due to smoking cessation. He stated that acute aortic dissection is relatively stable in incidence, which is likely due to “ongoing, poorly-controlled” hypertension in the background population.
Going into more detail regarding ruptured aneurysm incidence, Howard pointed out that for ruptured abdominal aortic aneurysms, the incidence has slowly declined over the last 18 years, while for thoracoabdominal aneurysms the incidence has remained quite static, “but it is lower”.
Regarding type A and type B dissection, Howard reported that these have both slowly decreased in incidence.
Ageing population to witness increasing incidence of aortic dissection
Based on UK population predictors from the Office of National Statistics (ONS), Howard detailed that by 2050, 40% of the UK population will be aged over 65. “Interestingly,” he stated, “since 1987, the number of people living to over 90 has increased from around 200,000 to 600,000 currently”.
Therefore, when the OxVasc incidence rates are mapped by age for acute aortic dissection on to the UK population predictions, just under 4,000 are occurring per year currently, with the majority in men and women aged 65–75. However, by 2040, Howard stated that this number will increase to just under 6,000.
Primary care data on blood pressure elucidate role in aortic dissection
Howard explained that both ruptured aneurysm patients and acute dissection patients have a “similar profile” of risk factors. However, he noted that smoking status is more associated with aneurysmal disease. In particular, current smoking status is far more associated with ruptured aneurysms than it is with acute dissection.
The team wanted to investigate the relationship between blood pressure and aortic dissection in more detail, and so they went thought the primary care data and collected all blood pressure measurements 15 years prior to index aortic dissection event. Howard reported that they managed to achieve this for 96% of patients. During the 15-year period, just under 50% had regular blood pressures of greater than 180 systolic, Howard reported.
In addition, they wanted to know how uncontrolled hypertension was associated with poor outcomes, and so looked at those patients with type A dissection and compared those who died immediately, at home, versus those who survived until after hospital admission. “We found that the age was similar in these two groups, but, interestingly, of those patients who died immediately, at home, fare more were female, and also the blood pressure five years prior to the event was worse in those who had immediate death versus those who survived”.
Selected intervention “may be warranted” in type B dissection and mortality “significantly higher” for women
Looking at five-year outcome data for mortality, the team observed that type A dissection has a “very high” up front mortality, “partly because over 50% of them die at home, before getting to hospital”. Type B has a lower 30-day mortality of around 15–20%. However, over a five-year period, the mortality increases for type B dissection due to ongoing cardiovascular events and aortic complications.
Regarding type B dissections in those who had early interventions versus those treated with medical therapy, although those who had early intervention had a higher 30-day and one-year mortality, at five years, this was potentially lower than those who had medical therapy. However, Howard noted that this analysis is biased by intervention selection, as often those who are intervened on have a complicated dissection compared to those who are treated with medical therapy having uncomplicated dissections. Nevertheless, it does suggest that early intervention “may be warranted in selected patients”.
In terms of 10-year outcomes, Howard showed that ruptured aneurysms, both abdominal and thoracoabdominal, have a “very high” overall mortality, as does type A dissection, whereas type B has a gradual increase in mortality over a 10-year period.
Finally, when the team went on to look at whether there were any differences in outcome for women versus men, they found that for acute aortic dissection, immediate death, 30-day mortality, and five-year mortality were all “significantly higher” in women, and this is adjusted for age.
Summarising, Howard highlighted that uncontrolled hypertension is the “most significant, treatable” risk factor for acute aortic dissection, adding that type A dissection has a “very high” mortality, with 50% of cases dying at home.
In addition, he noted that type B dissection has a “significant” mortality at five and 10 years, and it is possible that selected intervention, even in those with uncomplicated dissection, may be necessary.
While observing that acute aneurysmal cases are declining, likely as a result of smoking cessation, the incidence of acute aortic dissection remains stable, probably as a result of uncontrolled hypertension in the background population.
Due to the population ageing, dissections will increase “significantly” in the elderly over the next 30 years, and women with aortic disease—and particularly aortic dissection—have poorer outcomes than men. “More research is required to understand why this is,” Howard remarked.