Abdominal aortic aneurysm: a general defect in the vasculature with focal manifestations in the abdominal aorta?

Is non-specific aneurysmal disease of the infrarenal aorta also a peripheral microvascular disease?

OBJECTIVES

to examine whether aneurysmal disease of the aorta has a functional component in the peripheral microIvasculature.

MATERIALS

ten normal persons; and 15 patients who had been operated on for ruptured non-specific infrarenal aortic aneurysm months to years previously were studied.

METHODS

blood flow rates were measured: (a) in the subcutaneous adipose tissue of the forefoot by the(133)xenon local washout method (perfusion through nutritive capillaries supplied by arterioles with elastin in the tunica media); and (b) in the arteriovenous anastomoses of the pulp of the first toe as measured by the heat washout method (perfusion predominantly through thick-walled tubes without elastin). Perfusion rates were measured in supine subjects at heart level, at 30 cm above and at 30 cm below heart level.

RESULTS

in subcutaneous adipose tissue, the capillary blood flow rate was four times higher in patients with aneurysmal disease than in normal subjects. Both groups exhibited autoregulation of blood flow and a normal veno-arteriolar sympathetic axon reflex. Blood flow rates in the arteriovenous anastomoses of the pulp did not differ between aneurysm patients and normal subjects. Autoregulation and the axon reflex were absent in the arteriovenous anastomoses of normal subjects as well as in aneurysm patients.

CONCLUSIONS

non-specific aneurysmal disease of the infrarenal aorta has a peripheral functional component affecting arterioles but not arteriovenous anastomoses.

Abdominal aortic aneurysm wall mechanics and their relation to risk of rupture

PURPOSE

to see whether aneurysmal aortic wall mechanics can be used as a predictor of abdominal aortic aneurysm (AAA) rupture.

METHOD

among 285 individuals, followed conservatively for AAA and monitored for aneurysm growth and wall mechanics on at least one occasion at our institution between January 1991 and January 1998, eleven subsequently ruptured. Wall mechanics were estimated as stiffness (beta). This was calculated from diameter and pulsatile diameter change, determined non-invasively by an ultrasonic echo-tracking system and blood pressure obtained by the auscultatory method. The results were compared with those of 121 individuals electively operated on for AAA.

RESULTS

no difference in aortic stiffness was found between those that subsequently ruptured (beta=35, median) compared to those non-ruptured (beta=38, median) AAAs (p=0.855). There was no difference in diameter in ruptured (58.8 mm) compared with non-ruptured (54.1 mm) AAAs (p=0.129). All ruptured AAAs showed an expansion of diameter over time.

CONCLUSION

this study shows no difference in aneurysmal aortic wall mechanics in those AAAs that subsequently ruptured compared with electively operated AAAs. The results indicate that it is not possible to use aneurysmal aortic wall stiffness as a predictor of rupture.

Is there a relationship between abdominal aortic aneurysms and alpha1-antitrypsin deficiency (PiZ)?

OBJECTIVE

To determine if the frequency of alpha 1AT deficiency (PiZ) is increased in patients with abdominal aortic aneurysm (AAA), and, to investigate whether aneurysmal stiffness and other clinical characteristics differ in AAA patients with and without alpha 1AT deficiency.

METHODS

We identified alpha 1AT-deficient individuals by a monoclonal-antibody ELISA technique, in 102 consecutive patients with AAA. Positive ELISA samples were further phenotyped by isoelectric focusing to differentiate between the heterozygosity (PiZ) and homozygosity (PiZZ) state. Aneurysmal diameter and stiffness was measured using echotracking sonography and blood pressure measurements.

RESULTS

The frequency of heterozygous alpha 1AT deficiency (PiZ) in patients with AAA was similar to that in the general population (6.8% and 4.7%, respectively, p > 0.3). The frequency of popliteal and femoral aneurysm was similar in male PiZ-carriers and non-carriers with AAA, as were age at diagnosis of AAA, aneurysmal diameter, aneurysmal stiffness, and presence of factors that may be associated with AAA (i.e. smoking, hypertension, diabetes mellitus, and family history of AAA). Occurrence of ischaemic heart disease was more frequent in male non-PiZ-carriers than in male PiZ-carriers with AAA (p = 0.03).

CONCLUSIONS

The frequency of alpha 1AT deficiency (PiZ) was not increased in our series of patients with AAA and patients in whom the two disorders coexisted did not appear to have different clinical characteristics except for the lower occurrence of ischaemic heart disease among the PiZ-carriers.

Reduced pulsatile wall motion of abdominal aortic aneurysms after endovascular repair

PURPOSE

The reduced size of abdominal aortic aneurysms (AAAs) after endovascular repair suggests lowered intraaneurysmal pressure. In the presence of endoleaks, the size is not decreased. Although postoperative intraaneurysmal pressure is difficult to record, the pulsatile wall motion (PWM) of aneurysms can be measured noninvasively. The aim of this study was to assess the PWM of AAAs before and after endovascular repair and to relate the change in the PWM to aneurysmal size and presence of endoleaks.

METHODS

Forty-seven patients underwent endovascular repair of an AAA. The aneurysm diameter and PWM were measured with the use of ultrasonic echo-tracking scans preoperatively; at 1, 3, and 6 months; and thereafter biannually. Fifteen aneurysms developed endoleaks, whereas 32 were completely excluded. The leaks were characterized with the use of computed tomographic scanning and angiography. Median follow-up was 12 months (interquartile range, 5 to 24 months).

RESULTS

The preoperative PWM of the aneurysms was 1.0 mm (range, 0.8 to 1.3 mm). After complete endovascular exclusion, the PWM was 25% (range, 16% to 37%) of the preoperative value (p < 0.001), and aneurysm diameter decreased by 8 mm (range, 6 to 14 mm) (p < 0.001). After 18 months, no further diameter reduction occurred. In three patients without endoleaks but with enlarging aneurysms, the postoperative PWM showed less reduction (p < 0.05). Aneurysms with endoleaks showed no diameter decrease, and the postoperative PWM was 50% higher than that in the totally excluded cases (p < 0.01). In five patients with transient endoleaks, the PWM was reduced after leakage ceased (p < 0.05). Leaks of various sources displayed similar PWM.

CONCLUSION

The size and PWM of aneurysms are reduced after endovascular repair. The diameter reduction may cease after 1.5 years. Endoleaks are associated with higher PWM than expected. Pressure may be transmitted without evidence of leaks.