Risks of endovascular or open repair for aneurysms reviewed

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A new scoring system may help surgeons determine risk levels in Medicare patients when considering endovascular repair for abdominal aortic aneurysms, according to a study in the December 2009 issue of the Journal of Vascular Surgery, published by the Society for Vascular Surgery.

Researchers reviewed a population-based dataset (66,943 cases from 2000–2006 of patients 65 to 85 years and older) and noted that there was only a very small cohort at high risk for endovascular surgery. “We believe that EVAR is safe and effective in the majority of the elderly population, even for those with multiple comorbidities,” said Natalia N Egorova, assistant professor in the department of health policy at Mount Sinai School of Medicine in New York City. “The scoring system we developed can be useful to perioperatively identify risk factors for older adults, even those who may be unfit for even minimally invasive treatment of their aneurysm.”


The scoring system, designed by Egorova and colleagues from the Mount Sinai School of Medicine, Columbia Weill Cornell Division of Vascular Surgery and the department of surgery at the University of Wisconsin School of Medicine and Public Health in Madison, rated risk factors from one to seven with 7 being the highest number for predicting mortality for any one factor.


Significant baseline factors were renal failure with dialysis (seven), renal failure without dialysis (three), clinically significant lower extremity ischaemia (five), age of 85 or more (three), age of 75–84 (two), age of 70–74 (one), heart failure (three), chronic liver disease (three), female gender (two), neurological disorders (two), chronic pulmonary disease (two), surgeon experience of less than three EVAR procedures (one) and hospital annual volume in EVAR  of less than seven procedures (one).


“These preoperative characteristics all increased the potential of death within the 30 days following EVAR. However, the overall mortality was low – 1.6%,” said Egorova. “Fortunately the majority of Medicare patients who were treated (96.6%) each had a combined score of 9 or less, which correlated with a mortality rate of less than 5%. Only 3.4% of patients had a mortality rate 5% or more and 0.8% of patients had a score of 13 or higher, which correlated with a mortality rate of 10% or higher.”


It also was noted that 30-day mortality among females was higher than among males (2.5% vs. 1.4%) and perioperative mortality increased with patient age becoming statistically significant for patients 70 years of age or older.


Baseline comorbidities were associated with 30-day mortality and common risk factors and included chronic pulmonary diseases (37.1%, with mortality 2%), cardiac arrhythmia (25.2%, mortality 2.3%) and heart failure (14.4%, mortality 3.5%). Patients with renal failure with dialysis represented only 1.1% of the cohort; however their risk of dying after EVAR was the highest at 11.8%. Another less common risk factor associated with mortality was clinically significant lower extremity ischemia (2.1%, mortality, 6.2%). Neurological disorders, including prior history of cerebrovascular accident and transient ischemic attack, were present in 11.2 of the cohort and found to increase periprocedural complications and mortality.


Mortality at 30 days declined from 2.3% to 1.4% with growing hospital annual volume from less than seven procedures vs. volume greater than 73 EVARs. Also, EVAR performed by surgeons with total experience of two or less procedures had higher mortality rate of 2.4% whereas the mortality was in the range of 1.3% to 1.6% for surgeons with cumulative EVAR experience of three or more procedures.


 Past studies have shown that in open repair (like in EVAR) renal failure heads the list as the main factor that impacts mortality. It is followed by myocardial disorders, such as ischemia and congestive heart failure; pulmonary disease; age; and female gender. According to researchers, major heart and/or lung disease has been reported as a less relevant risk factor for EVAR because the surgical intervention (groin cut-downs) has less profound physiologic demand on the heart and lungs.


 Study authors said that there were some limitations in their current study: administrative datasets knowledge of the severity of comorbidities is often lacking; diagnosis codes can be broad and vague and provide limited detail about a specific patient’s disease state (e.g. if someone has a chronic condition between hospitalisation or there is no code available); and there is a lack of information regarding patient’s complex arterial anatomy (e.g. size of the aneurysms treated).


“However, our study is one of the largest Medicare administrative basis ever published and we feel it is rich in information regarding diagnoses, procedures and demographics and is a true representation of clinical practice in the United States,” said Egorova.


Source: Society for Vascular Surgery

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