Björn Sonesson

The chimney graft: a technique for preserving or rescuing aortic branch vessels in stent-graft sealing zones.

Purpose: To report an alternative to the fenestrated stent-graft for preserving blood flow to side branches in the sealing zones of aortic stent-grafts. Technique: A covered stent is deployed parallel to the main aortic stent-graft, protruding somewhat proximally, like a chimney, to preserve flow to a vital side branch covered by the aortic stent-graft. Use of a chimney graft makes it possible to use standard off-the-shelf stent-grafts to instantly treat lesions with inadequate fixation zones, providing an alternative to fenestrated stent-grafts in urgent cases, in aneurysms with challenging neck morphology, and for reconstituting an aortic side branch unintentionally compromised during endovascular repair. This technique has been used successfully in 10 patients, combining chimney grafts in the renal, superior mesenteric, left subclavian, left common carotid, and innominate arteries with stent-grafts in the abdominal (n=6) or thoracic (n=4) aorta. There has been no late chimney graft—related endoleak on imaging studies up to 8 months. Conclusion: The use of chimney grafts is feasible in the renal and superior mesenteric arteries, as well as in the supra-aortic branches, to facilitate stent-graft repair of thoracic or abdominal aortic lesions with inadequate fixation zones.

Diameter and compliance in the human common carotid artery--variations with age and sex.

In this study, age and sex differences in diameter and compliance of the common carotid artery (CCA) were evaluated in 119 healthy subjects with a phase-locked echo-tracking system. The diameter and pulsatile diameter changes were measured, and pressure strain elastic modulus (Ep) and stiffness (beta) were calculated and used as the inverse estimate of compliance. The carotid diameter increased more rapidly in males and was larger than in females from 25 years of age. The relative diameter change was equal in both sexes, and decreased from 12% to 14% in younger subjects to approximately 5% in elderly subjects. Compliance decreased almost linearly and in parallel in males and females up to 45 years of age. Between 45 and 60 years the decrease was more marked in females than in males, whereas it was by far more marked in males between 60 and 70 years of age.

Compliance and diameter in the human abdominal aorta--the influence of age and sex.

OBJECTIVES Females develop cardiovascular diseases and abdominal aortic aneurysms later in life than males. In this study we investigated the diameter and compliance of the distal abdominal aorta in healthy females of varying ages. The results were compared with those obtained previously from healthy males in order to assess potential sex-related differences in the aging process of the abdominal aorta. METHODS An ultrasound phase-locked echo-tracking system was used to determine differences in diameter and pulsatile diameter change of the distal abdominal aorta in 69 Caucasian females from 4 to 74 years. Pressure strain elastic modulus (Ep) and stiffness (beta) were calculated from diameter, pulsatile diameter change and blood pressure obtained by the auscultatory method. Compliance was defined as the inverse of Ep and beta. The pressure dependence of Ep and beta was evaluated in 10 females with intraarterial blood pressure measurement at rest and during isometric exercise. RESULTS The diameter of the distal abdominal aorta increased not only in the period between the ages of 5 and 25 years, but also by about 24% between 25 and 70 years (p < 0.0001). From about the age of 25 years the diameter was smaller in females than in males (p < 0.01). Ep and beta increased nearly linearly with advancing age in females from 0.18 x 10(5) to 1.17 x 10(5) N/m2 (Ep) and from 1.85 to 8.51 (beta). In males the increase in Ep and beta was greater and exponential in nature (p < 0.001). Ep but not beta increased significantly during blood pressure increase (p < 0.05). Stiffness (beta) may therefore be a more useful index of arterial compliance than Ep. CONCLUSIONS This investigation demonstrates age and sex-related differences in diameter and compliance in the normal human abdominal aorta and implies that degenerative changes appear later in females than in males.

Diameter and compliance in the male human abdominal aorta: influence of age and aortic aneurysm.

In this study changes in the diameter and compliance of the distal abdominal aorta (76 healthy Caucasian males, 5-71 years old) were determined non-invasively and related to age by means of an ultrasound phase-locked echo-tracking system. The diameter of the aorta increased not only in the period between 5 and 25 years of age, but also by about 30% between the ages of 25 and 71. The pressure diameter curves at 25, 51 and 70 years were non-linear with flattening between 90 and 110 mmHg, and the slope of the curves declined with age. Thus, the pressure strain elastic modulus (Ep) and stiffness (beta) increased (i.e. compliance decreased) in an exponential manner according to age. A group of 37 males with aneurysmal widening of the distal abdominal aorta had a significant increase in Ep when compared to an age-matched control group. Furthermore, the ranges for both Ep and beta were much larger in the aneurysm group than in the control group, indicating diversity in the pathogenesis of the disease. The non-invasive ultrasonic method of phase-locked echo-tracking is an appropriate method for studying compliance in major arteries under a variety of pathophysiological conditions.

Infrarenal Aortic Diameter in the Healthy Person

In order to determine the relevance of abdominal aortic dilatation, knowledge of the normal aortic diameter and its relation to age, sex and body size (height, weight, body surface area) is essential. The diameter of the infrarenal aorta was measured in 146 healthy males and females 4-74 years old with ultrasonography and the influence of the aforesaid factors on aortic diameter was analysed by means of a multiple stepwise regression model. The infrarenal aorta was found to increase steadily in diameter throughout life. From about 25 years the diameter was larger in males than in females (p < 0.01) though this difference vanished if corrected for differences in body surface area. Significant correlations were found between aortic diameter and weight (r = 0.84, p < 0.001), height (r = 0.77, p < 0.001) and body surface area (r = 0.83, p < 0.001). Age followed by body surface area were the factors most influencing aortic diameter in both males (r = 0.92, p < 0.001) and females (r = 0.94, p < 0.001). Nomograms predicting aortic diameters in relation to age, sex, and body surface area are presented.

The diameter of the common femoral artery in healthy human: Influence of sex, age, and body size

PURPOSE To determine the relevance of dilatations of the common femoral artery (CFA), knowledge of the normal CFA diameter is essential. The diameter of the CFA in healthy male and female subjects of different ages was investigated. METHODS The diameter of the CFA was measured in 122 healthy volunteers (59 male, 63 female; 8 to 81 years of age) with echo-tracking B-mode ultrasound scan. The influence of age, sex, height, weight, body surface area (BSA), and systolic blood pressure was analyzed by means of a multiple regression model. RESULTS The CFA increased steadily in diameter throughout life. From 25 years onwards, the diameter was larger in men than in women. Significant correlations were found between the CFA diameter and weight (r = 0.58 and r = 0.57 in male and female subjects, respectively; P <.0001), height (r = 0.49 and r = 0.54 in male and female subjects, respectively; P <.0001), and BSA (r = 0.60 and r = 0.62 in male and female subjects, respectively; P <.0001). Age and BSA were used to create a model for prediction of the CFA diameter (r = 0.71 and r = 0.77 in male and female subjects, respectively; P <.0001). CONCLUSION The diameter of the CFA increases with age, initially during growth but also in adults. This is related to age, body size, and sex male subjects have larger arteries than female subjects. It is now possible to predict the normal CFA diameter, and nomograms that may be used in the study of aneurysmal disease are presented.

Sex difference in the mechanical properties of the abdominal aorta in human beings

PURPOSE A previous study has shown age- and sex-related differences in abdominal aortic compliance. In that study blood pressure determined by auscultation in the brachial artery was assumed to be equal to blood pressure in the abdominal aorta. To validate our findings we investigated the pressure-diameter (P-D) relationship of the abdominal aorta. METHODS Diameter and pulsatile diameter change of the abdominal aorta were determined noninvasively by an ultrasound phase-locked echo-tracking system with simultaneous measurement of aortic pressure resulting in P-D curves in 27 healthy male and female volunteers 23 to 72 years of age. The degree of error in aortic compliance as calculated from blood pressure determined by auscultation of the brachial artery rather than from direct measurement of aortic pressure was evaluated. Compliance was defined as the inverse of pressure strain elastic modulus (Ep) or of stiffness (beta). RESULTS There was no significant difference in the systolic pressure at the two sites, but the diastolic pressure was systematically overestimated by approximately 10 mm Hg when determined by the auscultatory method (p < 0.01) leading to a 15% to 20% underestimation of Ep and stiffness (beta). The individual P-D curves exhibited hysteresis, were nonlinear, and revealed that the aorta is more distensible at lower than at higher pressures. The steepness of the P-D curve decreased with increasing age and this occurred at an earlier age in men than in women. CONCLUSION This investigation demonstrates a decrease in abdominal aortic wall distensibility with age, which occurs at an earlier age in men, and confirms earlier results by use of the indexes Ep and stiffness (beta). This implies that the abdominal aorta in men is more prone to degenerative changes, which may be one of the factors responsible for the sex difference in aortic vascular disease.

Balloon occlusion of the aorta during endovascular repair of ruptured abdominal aortic aneurysm.

Purpose: To describe a technique of aortic clamping during endovascular aneurysm repair (EVAR) in patients with ruptured abdominal aortic aneurysms (AAA) and circulatory collapse. Technique: A balloon catheter is inserted percutaneously from the femoral artery and inflated in the suprarenal aorta. An introducer sheath must support the balloon. The stent-graft is passed from the contralateral groin and deployed beneath the balloon. The sheath makes it possible to retrieve the balloon after the endograft has been deployed. Carbon dioxide facilitates angiography while the aortic blood flow is arrested. Conclusions: The aortic stent-graft can be deployed while the aorta is continuously “clamped” from a transfemoral approach. This may allow EVAR in patients with circulatory collapse due to aneurysm rupture.

Endovascular repair of ruptured abdominal aortic aneurysms: logistics and short-term results.

PURPOSE To report our experience in establishing a treatment protocol for endovascular aneurysm repair (EVAR) of ruptured abdominal aortic aneurysms (rAAA), including an investigation of the reasons for patient exclusion and a report of our short-term results. METHODS Between 1997 and July 2002, 21 patients with rAAA underwent endovascular repair according to our protocol and were followed prospectively. A retrospective analysis was also conducted of 23 rAAA patients treated with open repair from January 2001 through June 2002. Procedural and clinical data from this sample were compared to 14 contemporaneous emergent EVAR cases and analyzed to determine why the open repair patients were not treated with an endovascular approach. RESULTS Among the 21 patients treated with emergent EVAR since the beginning of this protocol, 6 (29%) procedures were performed under local anesthesia and 6 were performed percutaneously. Thirty-day mortality was 19%. In the comparison of 14 emergent EVAR cases to 23 open rAAA repairs, the mean duration of symptoms prior to intervention was 12 hours for the EVAR patients and <1 hour for OR patients. No significant difference was found in operating time, but the EVAR group had significantly less blood loss (p=0.0001) and transfusion needs (p=0.02); duration of intensive care unit stay was significantly shorter in the EVAR group (p=0.02). Thirty-day mortality was 29% (4/14) for EVAR and 35% for OR (8/23) (p>0.05). Reasons for not performing EVAR were unavailability of adequate equipment (n=11) or trained staff (n=7), hemodynamically unstable patient (n=2), mycotic aneurysm (n=2), and unfavorable anatomy in a 60-year old patient with a <5-mm-long, sharply angled infrarenal neck. CONCLUSIONS Endovascular repair of ruptured aortic aneurysms is feasible, and short-term results are promising. Good logistics, adequate training of physicians and staff in an elective setting, and versatile endografts are prerequisites for this type of treatment program.

NONINVASIVE MEASUREMENT OF DIAMETER CHANGES IN THE DISTAL ABDOMINAL AORTA IN MAN

An ultrasound phase-locked, echo-tracking system was used to determine the dynamic properties of the distal abdominal aorta in 10 Caucasian male subjects (mean age, 25 years). Recordings were made at rest and during the blood pressure increase resulting from isometric exercise. The pressure diameter curve was nonlinear with an inflection at about 90-110 mmHg. Above this pressure range, the vessel was stiffer (less compliant), but the pressure diameter relationship was roughly linear above as well as below the inflection. Individual pressure diameter curves showed hysteresis, i.e., the aorta had a smaller diameter during expansion than during retraction at corresponding pressures. The pressure strain elastic modulus (Ep) and stiffness (beta) were at rest [Mean Arterial Pressure (MAP), 81 mmHg] 0.70 10(5) N/m2 and 6.0, respectively. During isometric exercise (MAP, 122 mmHg), Ep increased significantly by 91% and stiffness (beta) nonsignificantly by 27%. The variability of the compliance determinations was 5% when the ultrasonic system was combined with intra-arterial blood pressure measurements and less than 7% when combined with auscultatory blood pressure measurements. It is concluded that the phase-locked, echo-tracking system fulfills clinical requirements for routine measurements of vascular compliance.