Biomedical subjects

Guy DeRose

Publications and source records attributed to Guy DeRose.

12 recordsLinked to original sources

PubMed2006

Gender differences in relative dilatation of abdominal aortic aneurysms.

It has been postulated that gender differences in abdominal aortic aneurysm (AAA) rupture risk are due to variation in proportional dilatation. This study's purpose was to examine differences in relative dilatation of AAAs as related to rupture risk and repair thresholds. During a recent 20-month period (August 2003-March 2005), all patients receiving elective endovascular repair of an AAA underwent computer-generated computed tomographic measurements, including suprarenal aortic diameter (D1) and maximum aneurysm diameter (D3). As a measure of proportional dilatation, a D3/D1 ratio was calculated for each patient and compared between genders. Values for males and females were plotted separately (D3 vs. D3/D1), and the resulting linear regression equations allowed for the comparison of proportional dilatation of aneurysms between genders. In 129 patients (108 males, 21 females), mean D3 did not differ between genders (62 +/- 9.0 vs 63.4 +/- 10.8 mm, p = 0.89), while relative dilatation (D3/D1) was significantly greater in females compared to males (2.82 +/- 0.52 vs. 2.55 +/- 0.42, p = 0.02). Linear regression analysis allowed for comparison of D3 as a function of D3/D1 and correlated a 55 mm AAA in males with one of 52 mm in females. These differences became greater with increasing AAA diameters (e.g., 60 and 70 mm AAAs in a male were proportionally similar to 56 and 62 mm AAAs in a female). AAAs of equal diameter represent a greater proportional dilatation in females than in males. This supports the recommendation for a smaller aneurysm diameter (52 mm) threshold for repair in females rather than the commonly used 55 mm threshold in males. Also, these data suggest that the gender difference in rupture risk widens exponentially as aneurysm diameter, and thereby proportional dilatation, increases above this repair threshold.

Angioplasty↗

PubMed2006

Endograft treatment of ruptured abdominal aortic aneurysms using the Talent aortouniiliac system: an international multicenter study.

OBJECTIVE: To understand the potential of endovascular aneurysm repair (EVAR) in patients presenting with a ruptured abdominal aortic aneurysm (rAAA), the proportion in whom this procedure was applicable was assessed. Mortality and morbidity was also determined in patients treated with emergency EVAR (eEVAR) when anatomic and hemodynamic conditions allowed (ie, in the entire cohort with patients receiving endovascular and open repair combined). In addition, a comparison was made between the treatment group with eEVAR and open repair. METHODS: Between February 2003 and September 2004, 10 participating institutions enrolled a representative sample of 100 consecutive patients in whom eEVAR was considered. Patients in the New Endograft treatment in Ruptured abdominal aortic Aneurysm (ERA) trial were offered eEVAR or open repair in accordance with their clinical condition or anatomic configuration. Written informed consent was obtained from all patients or their legal representatives. The study included patients who were treated by stent-graft technique or by open surgery in the case of adverse anatomy for endoluminal stent-grafting or severe hemodynamic instability, or both. Data were collated in a centralized database for analysis. The study was sponsored and supported by Medtronic, and eEVAR was uniquely performed with a Talent aortouniiliac (AUI) system in all patients. Crude and adjusted 30-day or in-hospital and 3-month mortality rates were assessed for the entire group as a whole and the EVAR and open repair category separately. Complication rates were also assessed. RESULTS: Stent-graft repair was performed in 49 patients and open surgery in 51. No significant differences were observed between these treatment groups with regard to comorbidity at presentation, hemodynamic instability, and the proportion of patients who could be assessed by preoperative computed tomography scanning. Patients with eEVAR more frequently demonstrated a suitable infrarenal neck for endovascular repair, a longer infrarenal neck, and suitable iliac arteries for access than patients with open repair. The primary reason to perform open aneurysm repair was an unfavorable configuration of the neck in 80% of the patients. In patients undergoing eEVAR, operative blood loss was less, intensive care admission time was shorter, and the duration of mechanical ventilation was shorter (P < or = .02, all comparisons). The 30-day or in-hospital mortality was 35% in the eEVAR category, 39% in patients with open repair, and 37% overall. There was no statistically significant difference between the treatment groups with regard to crude mortality rates or rates adjusted for age, gender, hemodynamic shock, and pre-existent pulmonary disease. The cumulative 3-month all-cause mortality was 40% in the eEVAR group and 42% in the open repair group (no significant differences at crude and adjusted comparisons). The 3-month primary complication rate in the two treatment groups was similar at 59%. CONCLUSIONS: In approximately half the rAAA patients, eEVAR appeared viable. An unsuitable infrarenal neck was the most frequent cause to select open repair. In dedicated centers using a Talent AUI system, eEVAR appeared to be a feasible method for treatment of a rAAA. The overall first-month mortality did not differ across treatment groups (patients with endovascular and open repair combined), yet was somewhat lower than observed in a recent meta-analysis reporting on open repair.

Aged↗

PubMed2005

Risk-adjusted analysis of outcomes following elective open abdominal aortic aneurysm repair.

The purpose of this study was to describe a method to analyze outcomes following open abdominal aortic aneurysm (AAA) repair while considering the variability in patients' preoperative risk. Consecutive patients undergoing elective open infrarenal AAA repair during a 4-year period (2000-2003) were reviewed. Thirty-day or in-hospital mortality was the major outcome variable. Preoperative mortality risk was estimated for each patient using a validated scoring system that considers age, renal dysfunction, and coronary artery and cerebrovascular disease. A risk-adjusted cumulative sum method was used to compare observed versus predicted outcomes by assigning a risk-adjusted score, based on log-likelihood ratios, to each patient. These cumulative scores were sequentially plotted with preset control limits to allow for "signaling" when results were substantially different than expected (doubling or halving of odds ratios). Four hundred and sixty-three patients were studied with an overall early mortality rate of 4.5% (n = 21). Patients were allocated to three different preoperative risk groups (low, n = 89; medium, n = 160; high, n = 214) according to a medical comorbidity-based scoring system. Predicted (P) and observed (O) mortality rates for each group were as follows: low, 2.4% (P) and 2.2% (O); medium, 4.1% (P) and 4.4% (O); high, 9.3% (P) and 5.6% (O). The resulting risk-adjusted scores for each patient were plotted sequentially. This plot was flat for the first year and then adopted a negative slope crossing the lower control limit after 266 patients, indicating improved results compared to those expected. This coincided with the adoption of routine intraoperative cell saver use in our practice. This form of analysis allows for the prospective evaluation of results while considering patient-mix variabilities.

Aged↗

PubMed2005

Midterm follow-up of inflammatory abdominal aortic aneurysms following endovascular repair.

The role of endovascular therapy in the management of inflammatory aneurysms of the infrarenal abdominal aorta has been controversial. Review of our endovascular database identified six patients who have undergone treatment for preoperatively diagnosed inflammatory abdominal aortic aneurysms. Outcomes measured were primary success of the procedure, variation in computed tomographic (CT) scan-defined perianeurysmal fibrosis, change in aneurysm size, development of endoleak, requirement of reintervention, aneurysm rupture, and progression or resolution of symptoms. At a median follow-up of 20 months (range 4-56 months), endovascular repair has been successful in all six patients. All patients demonstrated CT reduction of perianeurysmal fibrosis, with a median of 47% absolute reduction (range 33-69%, p = 0.014). All patients had aneurysm sac shrinkage, with a mean of 41% (range 6-86%, p = 0.04). There were no aneurysm ruptures or persistent endoleaks. Of the three patients who presented with abdominal or back pain, all are now symptom-free. One patient required reintervention for limb thrombosis of a bifurcated graft after 2 years. In conclusion, endovascular treatment of an inflammatory abdominal aortic aneurysm is safe and effective and the treatment of choice in anatomically suitable patients.

Aged↗

PubMed2005

Endovascular management of traumatic thoracic aortic injuries.

BACKGROUND: Endovascular surgery has recently been extended to the treatment of blunt traumatic aortic injuries. Since most of these injuries occur at the aortic isthmus, graft fixation in proximity to the origin of the left subclavian artery (LSA) has been a concern. Covering the LSA with graft fabric lengthens the proximal fixation site and should minimize proximal endoleaks. We therefore wished to evaluate the feasibility and safety of endovascular repair of thoracic aortic injuries after blunt trauma, both with and without deliberate coverage of the LSA. METHODS: At a tertiary care teaching hospital in London, Ont., we reviewed our experience with endovascular repair of 7 traumatic aortic injuries. We reviewed the technical success rate and the incidence of left subclavian coverage. Major morbidity, including rates of paraplegia and death were noted. The patients were followed-up with serial CT to look for endoleaks, stent migration or aneurysm growth and to determine whether they had symptoms related to left subclavian coverage. RESULTS: The time from injury to treatment ranged from 7 hours to 7 days (mean 36 h). The mean Injury Severity Score was 36. All injuries were at the aortic isthmus, and among the 7 patients treated, 6 had deliberate coverage of the LSA. One patient underwent carotid-to-subclavian artery bypass, but the other 5 did not. There were no cases of paraplegia; 1 patient had symptoms of claudication in the left arm but did not want revascularization. No procedure-related complications occurred, and all patients survived the event. Follow-up ranged from 2 to 30 (mean 13) months, and no endoleaks, stent migration or aneurysm expansion were noted in follow-up. CONCLUSIONS: Although long-term results are unknown, we conclude that endovascular repair of traumatic aortic injuries after blunt trauma can be performed safely with low morbidity and mortality and that coverage of the LSA without revascularization is tolerated by most patients.

Accidents, Traffic↗

PubMed2004

Low-threshold two-dimensional annular Bragg lasers.

Lasing at telecommunication wavelengths from annular resonators employing radial Bragg reflectors is demonstrated at room temperature under pulsed optical pumping. Submilliwatt pump threshold levels are observed for resonators with 0.5-1.5-wavelength-wide defects of radii 7-8 microm. The quality factors of the resonator modal fields are estimated to be of the order of a few thousand. The electromagnetic field is shown to be guided by the defect. Good agreement is found between the measured and the calculated spectra.

Journal Article↗

PubMed2004

Cumulative sum failure analysis of the learning curve with endovascular abdominal aortic aneurysm repair.

PURPOSE: The purpose of this study was to evaluate the importance of experience and the learning curve with endovascular abdominal aortic aneurysm (AAA) repair. METHODS: A retrospective analysis was performed of all elective endovascular AAA repairs attempted by an individual surgeon and radiologist over a 4-year period. The primary outcome variable was achievement and 30-day maintenance of initial clinical success as defined by the Society for Vascular Surgery/American Association of Vascular Surgery reporting standards. Following standard statistical analysis, the cumulative sum (CUSUM) method was used to analyze the learning curve, with a predetermined acceptable failure rate of 10% and calculated 80% alert and 95% alarm lines. RESULTS: Ninety-six elective endovascular AAA repairs were attempted by this team between 1998 and 2002 (mean age 74 +/- 0.8 years; mean aneurysm diameter 5.98 +/- 0.8 cm). Initial clinical success was achieved and maintained in 85 of 96 patients (88.5%). Although results were acceptable throughout the study period, improved results with respect to the target failure rate (10%) were not achieved until 60 patients were treated. The learning or CUSUM curves did not differ for different device manufacturers, with improved results being achieved following 20 implantations of each device. The results did differ when comparing aortouniiliac grafts (n = 27) and bifurcated grafts (n = 64). Results with bifurcated grafts remained consistent throughout the study period, whereas with aortouniiliac grafts, results improved after only a few procedures in comparison with the target failure rate. CONCLUSION: Success rates with endovascular aneurysm repair will improve with an individual's experience. The CUSUM method is a valuable tool in the evaluation of this learning curve, which has credentialing and training implications. Although acceptable results were obtained throughout the study period, this analysis indicates that 60 endovascular aneurysm repairs, or 20 with an individual device, are necessary before optimal rates of initial clinical success can be achieved. These results can be achieved more readily with aortouniiliac grafts than with bifurcated grafts.

Aged↗

PubMed2004

Implementation of a successful endovascular surgical program in a non-teaching tertiary-care centre in Ontario.

Endovascular surgical techniques have become an accepted standard of care for high-risk patients with abdominal aortic aneurysms and for certain patients with thoracic aortic pathology and peripheral arterial aneurysms. In Canada, endovascular surgery has been concentrated in tertiary-care academic teaching institutions. As the technology evolves and as expertise advances, the applicability of endovascular techniques will expand. With time, and as the demand for endovascular techniques rises, this expertise will increasingly need to be delivered by dedicated vascular surgical services in nonteaching institutions. The dissemination of endovascular surgical capabilities represent a unique challenge. We report the successful implementation of an endovascular surgical program in a tertiary-care nonteaching institution using a carefully planned preceptorship model. We review our initial 49 cases and discuss 6 factors important to the successful establishment of an endovascular surgical service: education, teamwork, strict selection of patients, use of a single stent-graft manufacturer, industry support and endovascular preceptorship. Our experience may be used as a model by other institutions in Canada.

Aged↗

PubMed2004

Chronic lower extremity ischemia: a human model of ischemic tolerance.

BACKGROUND: Ischemic preconditioning (IPC) has been found in animals to have a protective effect against future ischemic injury to muscle tissue. Such injury is unavoidable during some surgical procedures. To determine whether chronic ischemia in the lower extremities would imitate IPC and reduce ischemic injury during vascular surgery, we designed a controlled clinical study. PATIENTS AND METHODS: Two groups of patients at a university-affiliated medical centre with chronic lower-extremity ischemia served as models of IPC: 6 patients awaiting femoral distal bypass (FDB) and 4 scheduled for aortobifemoral (ABF) bypass grafting for aortoiliac occlusive disease. Seven patients undergoing elective open repair of an infrarenal abdominal aortic aneurysm (AAA) were chosen as non-IPC controls. Three hematologic indicators of skeletal-muscle injury, lactate dehydrogenase (LDH), creatine kinase (CK) and myoglobin, were measured before placement of the proximal clamp, during surgical ischemia, immediately upon reperfusion, 15 minutes after and 1 hour after reperfusion, and during the first, second and third postoperative days. RESULTS: Baseline markers of skeletal-muscle injury were similar in all groups. In postreperfusion samples, concentrations of muscle-injury markers were significantly lower in the 2 PC groups than in the control group. For example, at day 2, LDH levels were increased by about 30% over baseline measures in the elective AAA (control) group, whereas levels in the FDB and ABF groups remained statistically unchanged from baseline. Myoglobin in controls had increased by 977%, but only by 160% in the FDB and 528% in the ABF groups. CK levels, in a similar trend, were 1432% higher in the control group and only 111% (FDB) and 1029% (ABF) in the study groups. Taken together, these data represent a significant level of protection. CONCLUSIONS: Patients with chronic lower-extremity ischemia suffered less severe ischemic injury after a period of acute ischemia than those with acute ischemia alone. Ischemic preconditioning is one proposed mechanism to help explain this protective effect.

Aged↗

PubMed2004

Is intensive care necessary after elective abdominal aortic aneurysm repair?

BACKGROUND: To review morbidity and mortality of patients undergoing elective, open repair of infra-renal abdominal aortic aneurysms and were admitted postoperatively to a surgical stepdown unit rather than routinely to the intensive care unit (ICU), we carried out a retrospective review. METHODS: All patients undergoing this type of repair in our centre, a division of vascular surgery in a tertiary-care teaching hospital in Ontario, over a 27-month period were reviewed. A consecutive 230 patients who underwent aneurysm repair from September 1999 through November 2001 were routinely admitted to a surgical stepdown unit postoperatively, with only a minority of patients requiring admission to ICU. We reviewed the rate of initial ICU admission and that of subsequent ICU admission after stepdown-unit admission. We also assessed morbidity, mortality and length of hospital stay for patients admitted to ICU as well as those admitted to the stepdown unit. RESULTS: ICU admission was avoided in 204 (89%) of these patients. The remaining 26 patients (11%) required ICU admission at some point during their hospital stay. Only 3 patients (1%) originally admitted to the stepdown unit subsequently required postoperative admission to ICU. CONCLUSIONS: Our experience demonstrates that proper preoperative assessment and selection allows the majority of elective infra-renal aneurysm repairs to be safely cared for postoperatively in a stepdown unit, and that subsequent ICU admissions are rare.

Aged↗

PubMed2002

Is long-term anticoagulation after acute thromboembolic limb ischemia always necessary?

OBJECTIVE: After thromboembolectomy, patients with acute limb ischemia often receive anticoagulant therapy to prevent recurrent events. Patients with atrial fibrillation or cardiac thrombus have a higher risk of recurrent emboli than those without these risk factors. This study examines the importance of long-term anticoagulation in these 2 groups. DESIGN: A review of patients presenting with acute limb ischemia over a 5-year period (1994-1999). SETTING: A university-affiliated medical centre. PATIENTS: Fifty patients divided into 2 groups: 19 (38%) patients with atrial fibrillation (group 1) and 31 (62%) patients with no atrial fibrillation or cardiac thrombus (group 2) as confirmed by transthoracic echocardiography. INTERVENTION: All patients underwent surgical thromboembolectomy and received postoperative anticoagulant therapy. OUTCOME MEASURES: Mortality, limb loss, further thromboembolic events and bleeding complications as determined by telephone survey. RESULTS: There was a significant difference in 5-year survival (group 1, 84%; group 2, 64%) and early limb loss (group 1, 0%; group 2, 13%). Further thromboembolic events and bleeding complications were rare but were more common in group 1. In group 2 there were no instances of recurrent thromboemboli and no bleeding complications although only 39% of patients in this group were taking angicoagulants at the end of the study period. CONCLUSIONS: Patients with extremity thromboemboli without atrial fibrillation or cardiac thrombus may not be at the same risk for recurrent events as those with these risk factors, and long-term anticoagulant therapy may not be as necessary in this group.

Adult↗

PubMed2002

A cost-effectiveness analysis of standard versus endovascular abdominal aortic aneurysm repair.

OBJECTIVE: To compare endovascular and standard open repair of abdominal aortic aneurysms in terms of initial in-hospital costs and the costs of secondary interventions and surveillance. DESIGN: A retrospective study. SETTING: A university-affiliated tertiary care medical centre. PATIENTS: Seven patients who underwent elective endovascular (EV) repair of an abdominal aortic aneurysm in 1998 and 31 patients anatomically suitable for endovascular repair who underwent standard (STAN) elective repair. Follow-up ranged from 2 to 14 months. INTERVENTIONS: Elective repair of an abdominal aortic aneurysm with use of the standard technique or endovascular technology. OUTCOME MEASURES: Costs common to both groups were not determined. Costs were determined for total hospital stay, preoperative or postoperative embolization, grafts, additional endovascular equipment, and follow-up computed tomography. RESULTS: Groups were similar with respect to demographic data and aneurysm size (EV = 6.23 cm v. STAN = 6.05 cm). All patients were in American Society of Anesthesiologists class III or IV. Vanguar bifurcated grafts and extensions were used in the EV group. The total cost for both groups in Canadian dollars included: cost of stay (EV, 5.6 d, $2092.63 v. STAN, 10.7 d, $4449.19; p = 0.009); cost of embolization (EV, n = 3; $900/procedure); cost of follow-up CT (EV, 5.4 per patient; $450/CT); cost of grafts (EV = $8571.43, STAN = $374); additional radiologic equipment costs (EV = $1475). The mean total cost differed significantly between the 2 groups (EV = $14,967.63 v. STAN = $4823.19; p = 0.004). The additional cost associated with a reduction in hospital stay was calculated by determining the incremental cost-effectiveness ratio (ICER, difference in mean costs/difference in mean length of stay = $1604.51). CONCLUSIONS: Endovascular repair continues to be more expensive than standard open repair determined according to procedural and follow-up costs. The technology is still in the developmental stage, but as it evolves and follow-up protocols are streamlined, it is hoped that there will be an eventual reduction in the costs associated with the endovascular procedure.

Aortic Aneurysm, Abdominal↗