Jonathan M. Weiswasser

Predictors of lower extremity arterial injury after total knee or total hip arthroplasty.

OBJECTIVE Lower extremity arterial injury is a rare complication following total knee (TKA) or total hip arthroplasty (THA). To date, no multi-institutional study has identified preoperative factors that may portend increased risk for these injuries. We queried a large clinical database for the incidence and predictors of arterial injury and/or compromise following lower extremity arthroplasty. METHODS Prospectively collected preoperative and postoperative data by the National Surgical Quality Improvement Program (NSQIP) of the Veterans Affairs Medical Centers were analyzed. All patients from 1996 to 2003 in the NSQIP database who underwent TKA or THA were identified via CPT codes. NSQIP defined, 30-day, postoperative outcomes were analyzed. Data were compared using bivariable analysis, as well as limited multivariable logistic regression. RESULTS A total of 41,633 arthroplasties (24,029 TKA, 2077 redo-TKA, 13,494 THA, 2033 redo-THA) were identified in the NSQIP database. A total of 34 (0.08%) lower extremity arterial injuries were recognized (0.08% TKA, 0.19% redo-TKA, 0.04% THA, 0.20% redo-THA). Eighteen injuries were repaired on the same day of surgery (seven intraop, 11 postop), eight between postoperative days 1 and 5, and 8 between days 6 and 30. Only two patients underwent lower extremity amputation (overall limb loss rate of 5.9% of patients who had arterial injury). Statistically significant predictors of lower extremity arterial injury identified on logistic regression analysis included redo procedure (odds ratio [OR] 2.7, 95% confidence interval [CI] 1.2-6.0, P = .013) and African American race (OR 2.5, 95% CI 1.2-5.3, P = .02). CONCLUSION Lower extremity arterial injury was exceedingly rare after total knee or total hip arthroplasty. There is an increased incidence in African American patients and those undergoing redo arthroplasty. Among patients who sustain vascular injury, excellent limb salvage rates can be achieved with close postoperative surveillance to achieve early detection and repair of injuries.

Carotid Plaque Morphologic Characteristics

Carotid artery atherosclerosis is predominantly believed to mirror atherosclerosis elsewhere in the body. Endothelial injury results in expression of cell surface adhesion molecules with expression of sequence of genes involved in the inflammatory pathway and expression of proinflammatory cytokines. The combination of the inflammatory mediators and contribution by monocytes infiltrating the intima and vascular smooth muscle cell proliferation result in the development of atheromatous plaque with a lipid-rich necrotic core. Complications of these atheromatous plaques can lead to plaque instability, rupture, and subsequent hemorrhage or ulceration. The significant risk factors, characteristics associated with symptoms, and available diagnostic imaging modalities are also discussed with review of the relevant literature.

Evaluation of macrocirculatory endothelium-dependent and endothelium-independent vasoreactivity in vascular disease.

Macrocirculatory endothelium-dependent and independent vasodilatation is integral to tissue-bed oxygen delivery and homeostasis. Dysfunction of macrocirculatory vasoreactivity is a precursor to atherosclerosis and occurs in a similar fashion in multiple tissue beds long before the onset of symptoms. Impaired macrocirculatory vasodilatation has been shown to occur in certain disease states including diabetes mellitus, hypercholesterolemia, chronic renal failure, peripheral arterial atherosclerosis, and abdominal aortic aneurysms, as well as secondary to smoking, advanced age, menopause, high-fat diet, and sedentary lifestyle. Brachial artery vasoreactivity is a noninvasive means of assessing macrocirculatory vasodilatory capacity that may help identify patients at increased risk for peripheral and cardiovascular disease and allow for objective assessment and monitoring of treatment. Endothelium-dependent vasoreactivity, or flow-mediated dilatation, is measured after brachial artery occlusion with a pneumatic blood pressure cuff, and endothelium-independent vasoreactivity is measured after the administration of sublingual nitroglycerin. The accuracy of brachial artery vasoreactivity is dependent on hematologic variables, as well as diurnal, day-to-day, ultrasound operator, and reader variations; however, the overall coefficient of variation is only 1.8%. We discuss the importance of the macrocirculation, investigative methods for evaluating macrocirculatory vasoreactivity, and review the literature of vasoreactivity in these different states.

Effect of Folic Acid and Vitamins B6 and B12 on Microcirculatory Vasoreactivity in Patients With Hyperhomocysteinemia

Objective: Hyperhomocysteinemia (HHcy) has been identified as an independent risk factor for atherosclerotic vascular disease. The effect of high-dose folic acid or combination vitamin therapy for the treatment of HHcy on the microcirculation is unknown. The purpose of this study was to evaluate the effect of a combination of folic acid, vitamin B6, and vitamin B12 on endothelium-dependent and endothelium-independent vasoreactivity in patientswith HHcy. Methods: Baseline cutaneous microvascular vasoreactivity was measured in 20 patients with HHcy and 18 patients with normohomocysteinemia (NHcy). Laser Doppler scan imaging before and after iontophoresis of 1% acetylcholine chloride (endothelium-dependent response) and 1% sodium nitroprusside (endothelium-independent response) was performed for the measurement of forearm skin vasodilatation. Patients were then treated with 10 mg folic acid, 100 mg vitamin B6, and 1 mg vitamin B12 orally once a day for 6 months. Follow-up fasting serum homocysteine and cutaneous Laser Doppler scan imaging before and after iontophoresis were performed at 1, 2, 3, and 6 months. Statistical analysis was performed using Fishers exact test, paired t test, and Wilcoxon matched-pairs signed-ranks test, with significance set at P < .05. Results: The HHcy group was older than the NHcy group (70.89 ± 1.95 vs 61.78 ± 2.73 years, P = .02). Otherwise the groups were similar in terms of race, tobacco use, comorbid diseases, and serum lipoproteins. Over the 6-month period, fasting serum homocysteine levels decreased significantly in both the NHcy group (10.40 ± 0.59 µmol/L vs 8.97 ± 0.84 µmol/L, P = .01) and the HHcy group (19.80 ± 1.06 µmol/L vs 13.40 ± 0.86 µmol/L, P = .0002). There were no statistically significant changes in endothelium-independent vasoreactivity (voltage change from baseline) in either group. Endothelium-independent vasore activity decreased over the 6-month period in the HHcy group (0.20 ± 0.04 V vs 0.11 ± 0.03 V, P = .03). Subanalysis of HHcy with diabetes or age greater than 65 years both showed worsening trends in endothelium-independent vasoreactivity (P = .05 for both groups). There were no statistically significant changes in endothelium-independent vasoreactivity in the NHcy group. Conclusions: High doses of folic acid and vitamins B6 and B12 lower fasting serum homocysteine levels in patients with HHcy. Older and diabetic patients with HHcy tend to do worse possibly because of long-term fixed microvascular insult secondary to multiple sustained comorbidities.