The effect of supplemental oxygen on the transarterial wall oxygen gradients at a prosthetic vascular graft to artery anastomosis in the rabbit.

Artery wall hypoxia has been proposed to contribute to many kinds of artery wall pathology, including atherosclerosis and intimal hyperplasia. The purpose of this study was to determine the effect of supplemental oxygen on the transarterial wall oxygen gradients at a prosthetic vascular device (PVG)-to-artery anastomosis. The transarterial wall oxygen gradient in the infrarenal aorta of New Zealand White rabbits housed for 42 days in a 40% supplemental oxygen was measured with an oxygen microelectrode 2 mm distal to a PVG-to-artery anastomosis. Oxygen tensions were significantly increased throughout the artery wall at all time points in the supplemental oxygen groups compared to those in non-oxygen-supplemented groups. Within the oxygen-supplemented groups, the outer artery wall had diminished oxygen tensions immediately following creation of the anastomosis, with a slow return to control oxygen tensions on postanastomosis day 42 which correlated with a return of the vasa vasorum. These changes were noted without differences in blood pressure or arterial blood oxygen concentrations within the oxygen-supplemented group. Artery wall hypoxia noted following the creation of a PVG-to-artery anastomosis can be eliminated and artery wall oxygen tensions significantly increased by the administration of supplemental oxygen.

Transarterial wall oxygen gradients at a prosthetic vascular graft to artery anastomosis in the rabbit.

PURPOSE: Artery-wall hypoxia has been proposed to contribute to many kinds of artery-wall pathologic conditions, including atherosclerosis and intimal hyperplasia. Intimal hyperplasia is common at sites of arterial injury, including an anastomosis. The purpose of this study was to determine the effect of a prosthetic vascular graft (PVG)-to-artery anastomosis on the delivery of oxygen to the artery wall. METHODS: The transarterial wall oxygen gradient in the infrarenal aorta of New Zealand White rabbits 2 mm distal to a PVG-to-artery anastomosis was measured with an oxygen microelectrode. RESULTS: Oxygen tensions were significantly decreased in the outer artery wall immediately after the creation of the anastomosis and showed a further decrease in oxygen tensions at days 7 and 14, which correlated with the absence of a vasa vasorum. After day 14, the oxygen tensions gradually increased, returning to normal by postanastomosis day 42, correlating with a return of the vasa vasorum. These changes were noted without differences in blood pressure or arterial blood oxygen concentrations. CONCLUSION: The delivery of oxygen to the artery wall is altered by the creation of a PVG-to-artery anastomosis. Low arterial oxygen tensions at a PVG-to-artery anastomosis support a role for artery-wall hypoxia in the formation of intimal hyperplasia at the site of a PVG-to-artery anastomosis.

Myocardial renin is neither necessary nor sufficient to initiate or maintain ventricular hypertrophy.

We tested the hypothesis that the myocardial renin-angiotensin system (RAS) is both necessary and sufficient to initiate and maintain all classes of ventricular hypertrophy. Myocardial and plasma renin and angiotensinogen were measured in rats during initiation and maintenance of ventricular hypertrophy associated with DOCA implants and 1% NaCl drinking water, with and without the AT(1) ANG II receptor blocker losartan. Additional groups of rats were given a low-sodium diet (0.04%) for 3 wk. Ventricular hypertrophy was initiated within 7 days and maintained for 35 days in DOCA-treated rats despite significantly low myocardial and plasma renin, normal or low myocardial and plasma angiotensinogen, or the presence of losartan. Furthermore, there was no ventricular hypertrophy in low-salt diet-fed animals despite increased myocardial and plasma renin levels and normal angiotensinogen levels. Therefore, the myocardial RAS is not necessary to initiate or maintain cardiac hypertrophy in DOCA-treated rats and is not sufficient to initiate cardiac hypertrophy in low-salt diet-fed rats. Additionally, myocardial renin and angiotensinogen were significantly correlated with corresponding plasma levels.

Superficial femoral popliteal vein: An anatomic study.

OBJECTIVE: The superficial femoral popliteal vein (SFPV) has been used as an alternative conduit for both arterial and venous reconstructive surgery. Its popularity continues to grow, despite concern about the potential for venous morbidity after harvest. The purpose of this study was to determine an anatomic "safe" length of SFPV for harvest, assuming that the preservation of at least one valve and one significant collateral vein in the remaining popliteal vein (PV) segment can minimize venous morbidity. METHODS: Forty-four SFPVs were harvested from 39 cadaveric specimens. The length of both the superficial femoral vein (SFV) and PV was measured, and the number and location of valves and significant side branches (more than 2 mm in diameter) of the PV were measured. The Student two-tailed t test was used as a means of comparing vein lengths between the sexes. Correlation coefficients were determined for the effect of patient height on vein length, stratified by means of sex. RESULTS: Vein length (SFV mean, 24.4 +/- 4 cm; PV mean, 18.8 +/- 4 cm) varied with sex (male SFV mean, 28.1 +/- 5 cm; male PV mean, 21. 5 +/- 3 cm; female SFV mean, 22.6 +/- 4 cm; female PV mean, 18.4 +/- 3 cm; P =.01). Valve number (mean, 1.8 +/- 0.5) and location and collateral vein number (mean, 5 +/- 1.8) and location were variable and independent of height or sex. CONCLUSION: An anatomic "safe" length of SFPV for harvest to minimize venous morbidity would include all the SFV and 12 cm of PV in 95% of women and 15 cm of PV in 95% of men. We found that the male sex was a significant determinant for a longer safe length of vein that can be harvested.

Expansion rates and outcomes for iliac artery aneurysms.

PURPOSE: The expansion rates and outcomes of iliac artery aneurysms (IAAs) were determined. METHODS: A retrospective chart review was conducted to identify patients in whom IAAs had been diagnosed between June 1990 and March 1999 in a vascular surgery service at a large university-affiliated Veterans Affairs medical center. The patients were veterans, 187 men and two women, in whom the diagnosis of an IAA was made, as defined by the Ad Hoc Committee on Reporting Standards of The Society for Vascular Surgery and International Society for Cardiovascular Surgery, North American Chapter (IAA >/= 1.5 cm). Expansion rates relative to the size of IAAs and clinical outcomes were noted for all patients. RESULTS: One hundred eighty-nine patients (mean age, 72.3 +/- 0.5 years) with 323 IAAs (mean size, 2.34 +/- 0.7 cm) were found. The mean follow-up (96% of patients with B mode ultrasound scanning) period was 31.4 months, with each patient undergoing a mean of 4.2 studies. The 4-year life-table survival rate was 78.2%, with no patient deaths related to their IAAs. Symptoms were noted in six of 189 patients (3.1%; two ruptures, four chronic pain), who all had IAAs larger than 4 cm. IAAs were repaired in 34 of 189 patients (18%), in 25 of the 34 patients because of their associated abdominal aortic aneurysms and in nine of 34 patients because of their IAAs alone. All nine patients requiring operative treatment of indications related to the IAA had an IAA larger than 4 cm. Expansion rates were slow for IAAs smaller than 3 cm (0.11 +/- 0.02 cm/year) and significantly greater (P <.003) for IAAs 3 to 5 cm (0.26 +/- 0.1 cm/year). The correlation between B mode ultrasound scanning and computed tomography scanning was excellent. The size of the IAAs was underestimated by 0.03 +/- 0. 06 cm by means of B mode ultrasound scanning. CONCLUSION: The IAAs followed up by this contemporary Veterans Affairs vascular surgery service were small, rarely caused symptoms or rupture, and expanded at a slow rate. IAAs smaller than 3 cm could be followed up safely on an annual basis with B mode ultrasound scanning. IAAs that are 3 cm or larger and smaller than 3.5 cm should be carefully followed with B mode ultrasound scanning at 6-month intervals, whereas elective repair should be considered for IAAs 3.5 cm or larger in good-risk patients. Based on this report and currently available evidence and recommendations, asymptomatic IAAs that are 4 cm or larger and all other symptomatic IAAs should be considered for operative repair. Also, the reported high rupture rate of IAAs that are 5 cm or larger mandates prompt operative repair.

Myocardial and plasma renin-angiotensinogen dynamics during pressure-induced cardiac hypertrophy.

Plasma and left ventricular (LV) renin and angiotensinogen concentrations were assessed in a rat model of pressure-overload cardiac hypertrophy to determine if myocardial levels remained proportional to plasma levels over time. Three days after subdiaphragmatic aortic constriction (AC), LV hypertrophy was evident and renin concentrations in both plasma and LV, although not significantly elevated, were positively correlated with relative cardiac mass. After 42 days AC, LV hypertrophy remained, plasma and LV renin and angiotensinogen levels were not different from shams, and there was no correlation between renin and relative cardiac mass. Furthermore, LV renin and angiotensinogen concentrations remained at approximately 25 and 4%, respectively, of those in plasma throughout the experiment. Myocytes from 3-day AC and sham-treated rats contained little renin as did LV from 48-h anephric rats. Incubations using calculated concentrations of myocardial interstitial renin and angiotensinogen revealed significant angiotensin I generation. These data suggest that LV renin in this model varies directly with plasma renin, is confined to the interstitial space, and can generate significant intramyocardial angiotensin I.