Comparison of the morphologic and vascular reactivity of the proximal and distal radial artery

Background. Variations in the morphology and vascular reactivity of the proximal and distal radial artery might influence its performance as a bypass conduit.

Methods. The morphologic and functional characteristics of the proximal and distal RAs were compared with those of the left and right internal mammary arteries by using histologic and in vitro organ bath techniques.

Results. Proximal RA had a significantly greater medial cross-sectional area compared with that of the distal RA (2.48 ± 0.27 mm² compared with 1.86 ± 0.21 mm², p < 0.05), which were both significantly greater than the left internal mammary artery (0.54 ± 0.09 mm²) or the right internal mammary artery (0.67 ± 0.03 mm²). Proximal RA had a significantly greater response to 90 mmol/L potassium chloride than that of distal RA (88.4 ± 7.3 compared with 60.2 ± 10.3 mN, p < 0.05), and both contracted more than the left internal mammary artery (30.3 ± 2.9 mN) and the right internal mammary artery (32.6 ± 4.1 mN). There was no difference in the response to noradrenaline and adrenaline between proximal and distal RA, both of which contracted more than the left and right internal mammary arteries.

Conclusions. When choosing a segment of RA for use as a bypass conduit, regional variations in biologic properties should be considered.     

SMA circuits reduce platelet consumption and platelet factor release during cardiac surgery

Background. Platelet count and function are particularly damaged by cardiopulmonary bypass (CPB). This study evaluated the effects of a novel CPB circuit in terms of platelet count and activation, and postoperative need for blood products.

Methods. One hundred patients undergoing coronary grafting were randomized in two groups: control group (n = 50) and test group (n = 50, surface modifying additives circuit, SMA group). Blood samples were taken before, during, and after CPB. Postoperative blood loss, number of transfused blood products, and postoperative variables were recorded.

Results. The platelet count decreased less in the SMA group compared to the control group (end of CPB: respectively, 165 ± 9 × 10³/mm³ vs 137 ± 8 × 10³/mm³; p < 0.01). This was paralleled by a reduction in β-thromboglobulin plasma levels in the SMA group. There was a trend to decreased blood loss in the SMA group, but the difference was significant only in patients taking aspirin preoperatively (p < 0.05). In the SMA group nearly 50% less fresh frozen plasma and platelet units were administered (p < 0.01). No operative deaths were observed.

Conclusions. The use of circuits with surface additives is clinically safe, preserves platelet levels, and attenuates platelet activation. This may lead to a reduced need for blood products.     

Automatic connector devices for proximal anastomoses do not decrease embolic debris compared with conventional anastomoses in CABG

Objective: Emboli generated during cardiac surgery have been associated with aortic clamping and manipulation. Proximal anastomotic devices are thought to be less traumatic by eliminating partial clamping, potentially resulting in fewer adverse outcomes. Intra-aortic filtration has been shown to effectively capture particulate debris. We compared the amount of debris released using intra-aortic filtration and the clinical outcomes between conventionally handsewn and automated proximal anastomoses. Methods: Seventy-seven patients undergoing primary coronary artery bypass grafting with cardiopulmonary bypass were enrolled in a prospective randomized study. Patients were assigned to the anastomotic device Group I (Symmetry™ Aortic Connector, n=39) or the conventional handsewn anastomosis control Group II (n=38). Proximal anastomoses were performed before cardiopulmonary bypass in both groups. Intra-aortic Filter 1 (EMBOL-X^TM) was deployed prior to partial clamping or puncturing the aorta for device application and removed after the proximal anastomosis was completed. Prior to cross-clamp removal, a second filter was inserted (Filter 2). A core laboratory performed quantitative and histologic analyses of the debris captured. Clinical outcomes included adverse events, neurocognitive test scores, graft patency, and mortality. Results: Preoperative variables and risk factors were not significantly different between Groups I and II (EuroSCORE 3.9±2.6 vs. 4.2±2.5). Filter analyses showed no significant difference between Groups I and II in Filter 1 or 2 for either surface area of particles or total number of particles (P>0.05). There was a significant decrease between Filters 1 and 2 in both Groups for surface area of particles (Group I: 18.5±23.8 mm² vs. 10.7±16.3 mm², P=0.017; Group II: 15.0±15.4 mm² vs. 6.9±.6.5 mm², P=0.004), and for total number of particles in Group II (8.6±3.7 vs. 7.1±2.4, P=0.023). No significant differences were observed between Group I (device) and Group II (control) outcomes for myocardial infarction, neurocognitive deficit, stroke, length of stay, graft occlusion, or mortality. Conclusions: The application of proximal aortic connectors without partial clamping does not reduce particulate emboli or affect clinical outcomes compared with conventional anastomoses. Cross-clamping during cardiopulmonary bypass produces less particulate debris than conventional or automated proximal anastomoses performed off-pump, suggesting a major source of emboli is the anastomotic process.     

Evidence for palliative enlargement of the right ventricular outflow tract in severe tetralogy of Fallot

Objective: If the pulmonary artery (PA) tree in patients with Fallot's tetralogy (TOF) is extremely hypoplastic, a shunt procedure may be difficult and not desirable because of side-effects. Moreover, the failing catch-up growth of the pulmonary annulus is well known. In patients with a severe form of TOF, we performed palliative transannular patching of the right ventricular outflow tract. The early and long-term follow-up was evaluated. Methods: Eleven patients (93 days (10–245 days); 3.5±0.7 kg (2.5–4.3 kg)) had highly symptomatic TOF (Hb: 18±2 g/dl, SO₂: 68±11%); angiographic diameters: RPA: 4.1 mm (2.5–6.4 mm), LPA: 3.4 mm (1.6–7.0 mm), PA trunc: 4.4 mm (2.5–7.0 mm). All 11 underwent transannular enlargement of the right ventricular outflow tract without closure of the ventricular septum defect. A PA index (cross-sectional area of the pulmonary arteries to BSA) was used to compare pre- and postoperative data. For follow-up, the patients were repetitively examined clinically and echocardiographically. Results: Preoperative PA index was 87±40 mm²/m² (normal: 330±35 mm²/m²). Postpalliation angiograms (age: 10–14 months) demonstrated a significant catch-up growth in nine patients (PA index from 99±40 to 310±54 mm²/m²) and inadequate growth in two patients (PA index 63 and 115 mm²/m²). Perioperative mortality was zero. Ten patients (43 months; 6–105 months) underwent elective repair. Six patients received pulmonary homograft valves (6–15 years after repair) because of severe pulmonary valve insufficiency and severe RV dilation. Complications: One patient died 10 months postpalliation due to pneumonia, one patient received a pacemaker after repair and died (2 months post-repair) due to pacemaker failure, a 5-year-old patient died 1 month after repair due to sepsis. All eight long-term survivors (12–17years) are in excellent clinical condition. Echocardiography revealed good RV function and near normal diameters at peak systolic pressures between 25 and 50 mmHg. Only one patient developed brady-arrhythmia; a pacemaker was implanted 8 years after repair and 2 years after homograft implantation. Conclusions: In a very severe form of TOF, palliative right ventricular outflow tract construction may provide the potential for complete repair. In the presented high-risk patient group, mortality was not related to the hypoplastic pulmonary arteries. Obviously, all patients need pulmonary valve implantation in the long run.     

Impaired distensibility of neoaorta after arterial switch procedure

Background. Although the arterial switch operation has become the standard surgical procedure for treatment of complete transposition, postoperative problems have not been fully appreciated. One such problem may be the postoperative function of great arteries that are manipulated radically.

Methods. The diameters at four levels of the aorta were measured in 36 patients who had undergone arterial switch operation and the distensibilities were calculated. The data were compared with that of age-matched controls.

Results. At the level of the Valsalva sinus, aortic diameters after one-staged and two-staged operations were 137.0% ± 21.3%N and 152.4% ± 17.7%N of the normal aorta, respectively. The distensibilities at the Valsalva sinus in patients after one-staged and two-staged operations were 1.2 ± 0.7 and 1.5 ± 0.8 cm² · dyn⁻¹ · 10⁻⁶, and at the supraaortic ridge were 2.5 ± 1.5 and 1.9 ± 1.5 cm² · dyn⁻¹ · 10⁻⁶, respectively.

Conclusions. In patients after arterial switch procedure, the distensibility of the base of aorta is decreased. Long-term follow-up is necessary to clarify the influence of the “stiffness” of the base of aorta.     

Clinical Results of the Staged Fontan Procedure in High-Risk Patients

Background. For high-risk Fontan candidates, the introduction of a bidirectional Glenn shunt before total cavopulmonary connection (a two-staged strategy) may extend the indications for the Fontan procedure. The clinical results of the two-staged and one-staged Fontan procedure were thus reviewed and compared.

Methods. Between November 1991 and July 1996, the two-staged strategy was performed in 40 high-risk Fontan candidates with a mean interval of 17.2 months after introducing the bidirectional Glenn shunt (staged group). We considered a young age (<2 years), high mean pulmonary arterial pressure (≥20 mm Hg), high pulmonary vascular resistance (≥3 Wood units), small pulmonary artery (Nakata index <200 mm²/m²), atrioventricular valve incompetence (≥ moderate), distortion of pulmonary artery, anomalous pulmonary venous return, and poor ventricular function as risk factors for the successful completion of Fontan circulation. During the same pe-riod, 68 patients underwent the modified Fontan procedure in a one-step fashion (primary group).

Results. In the staged group after the bidirectional Glenn shunt, the mean pulmonary arterial pressure and ventricular end-diastolic pressure were both found to have decreased significantly to the same level as those in the primary group, whereas the pulmonary artery demonstrated a significantly smaller size than that in the primary group. Operative morbidity was similar in both groups. Operative mortality was also similar and low in both groups (1.5% in the primary group and 0% in the staged group).

Conclusions. A bidirectional Glenn shunt was found to be a useful interim palliation in high-risk Fontan candidates. This two-staged strategy may extend the operative indications for the Fontan procedure.     

Effect of slow-release sodium fluoride on cancellous bone histology and connectivity in osteoporosis

We have previously demonstrated that a treatment regimen of slow-release sodium fluoride (SRNaF) and continuous calcium citrate increases lumbar bone mass, improves cancellous bone material quality, and significantly reduces vertebral fracture rate in osteoporotic patients. In order to assess whether such treatment also improves trabecular structure, we quantitated cancellous bone connectivity before and following 2 years of therapy with SRNaF in 23 patients with osteoporosis and vertebral fractures. In addition, we performed bone histomorphometry on the same sections used for connectivity measurements. There was a significant increase in L2-L4 bone mineral density during therapy (0.827 ± 0.176 g/cm² SD to 0.872 ± 0.166, p = 0.0004). Significant histomorphometric changes were represented by increases in mineral apposition rate (0.6 ± 0.4μm/d to 1.1 ± 0.7, p = 0.0078) and adjusted apposition rate (0.4 ± 0.3 μm/d to 0.6 ± 0.4, p = 0.016). On the other hand, trabecular spacing significantly declined (from 1375 ± 878 μm to 1052 ± 541, p = 0.05). Two-dimensional quantitation of trabecular struts on iliac crest histological sections disclosed significant increases in mean node number per mm² of cancellous tissue area (0.22 ± 0.12 vs. 0.39 ± 0.27, p = 0.0077), the mean node to free-end ratio (0.23 ± 0.21 vs. 0.41 ± 0.46, p < 0.05), and in the mean node to node strut length per mm² of cancellous area (0.098 ± 0.101 vs. 0.212 ± 0.183, p < 0.01). There were no significant changes in any of the measurements associated with free-end number or free-end to free-end strut length. When patients were divided into those with severe and mild-modest spinal bone loss (based upon initial lumbar bone density) the significant changes in connectivity occurred in patients with mild-moderate bone loss, but not in those with severe bone loss, suggesting that fluoride's effect is in part dependent on the presence of a certain critical amount of bone. This finding in combination with the previously reported increases in bone mass and bone material quality may explain the significant reduction in vertebral fracture rate observed with this particular fluoride regimen.     

Adjustable Model of Chronic Left Ventricular Dysfunction

Background. As an adjunct to the development of skeletal muscle-powered left ventricular assist devices, an adjustable model of chronic left ventricular failure was developed.

Methods. Implantation of a left ventricular balloon to induce heart failure was accomplished via left thoracotomy. Upon recovery, left ventricular failure was simulated by manipulation of left ventricular balloon volume to chronically raise left atrial pressure.

Results. Left atrial pressure increased from a baseline of 9.3 ± 0.7 mm Hg to 18.5 ± 1.2 mm Hg, 20.2 ± 1.8 mm Hg, and 26.0 ± 1.2 mm Hg by the 2nd, 6th, and 10th postoperative week, respectively. Cardiac index declined from a baseline of 4.4 ± 0.3 L · min⁻¹ · m⁻², reaching stability by the 8th postoperative week at 3.0 ± 0.4 L · min⁻¹ · m⁻². Stroke volume index declined from 1.12 ± 0.1 mL · kg⁻¹ · beat⁻¹ to 0.60 ± 0.1 mL · kg⁻¹ · beat⁻¹ by the 10th postoperative week. Mean survival was 75 ± 7 days. Causes of death included left ventricular failure, thromboembolism, and euthanasia.

Conclusions. This method of simulating chronic left ventricular dysfunction proved to be stable and adjustable and has been useful in the development of ventricular assist systems.     

Patient prosthesis mismatch is rare after aortic valve replacement: valve size may be irrelevant

Background. Although small valve size and patient-prosthesis mismatch are both considered to decrease long-term survival, little direct evidence exists to support this hypothesis.

Methods. To assess the prevalence of patient-prosthesis mismatch and the influence of small valve size on survival, we prospectively studied 1,129 consecutive patients undergoing aortic valve replacement between 1990 and 2000. Mean and peak gradients and indexed effective orifice area were measured by transthoracic echocardiography postoperatively (3 months to 10 years). Abnormal postoperative gradients were defined as those patients with mean or peak gradient above the 90th percentile (mean gradient ≥ 21 or peak gradient ≥ 38 mm Hg). Patient-prosthesis mismatch was defined as those patients with indexed effective orifice area below the 10th percentile (< 0.60 cm²/m²).

Results. A multivariable analysis identified internal diameter of the implanted valve as the only independent predictor of abnormal gradients postoperatively. However, there was no significant difference in actuarial survival between normal and abnormal gradient groups (7 years: 91.2% ± 1.5% versus 95.0% ± 2.2%; p = 0.48). Freedom from New York Heart Association class III or IV (7 years: 74.5% ± 3.1% versus 74.6% ± 6.2%; p = 0.66) and left ventricular mass index were not different between normal and abnormal gradient groups. Patients with and without patient-prosthesis mismatch were similar with respect to postoperative left ventricular mass index, 7-year survival (95.1% ± 1.3% versus 94.7% ± 3.0%; p = 0.54), and 7-year freedom from New York Heart Association class III or IV (79.3% ± 6.6% versus 74.5% ± 2.5%; p = 0.40). In patients with patient-prosthesis mismatch and abnormal gradients, the majority had prosthesis dysfunction owing to degeneration.

Conclusions. Severe patient-prosthesis mismatch is rare after aortic valve replacement. Patient-prosthesis mismatch, abnormal gradient, and the size of valve implanted do not influence left ventricular mass index or intermediate-term survival.     

Osteocyte density in aging subjects is enhanced in bone adjacent to remodeling haversian systems

The osteocyte is a candidate regulatory cell for bone remodeling. Previously, we demonstrated that there is a substantial (approximately 50%) loss of osteocytes from their lacunae in the cortex of the elderly femoral neck. Higher occupancy was evident in tissue exhibiting high remodeling and high porosity. The present study examines the distribution of osteocytes within individual osteonal systems at differing stages of the remodeling cycle. In 22 subjects, lacunar density, osteocyte density, and their quotient, the percent lacunar occupancy, was assessed up to a distance of 65 μm from the canal surface in six quiescent, resorbing, and forming osteons. In both forming (p = 0.024) and resorbing (p = 0.034) osteons, osteocyte densities were significantly higher in cases of hip fracture than controls. However, there were no significant between-group differences in lacunar occupancy. In both cases and controls, osteocyte density (p < 0.0001; mean difference ±SEM: 157 ± 34/mm²) and lacunar occupancy (p = 0.025; mean difference: 8.1 ± 3.4%) were shown to be significantly higher in forming compared with quiescent osteons. Interestingly, resorbing systems also exhibited significantly elevated osteocyte density in both the fracture and the control group combined (mean difference 76 ± 23/mm²; p = 0.003). Lacunar occupancy was also greater in resorbing compared with quiescent osteons (both groups combined: p = 0.022; mean difference: 5.7 ± 2.3%). Elevated osteocyte density and lacunar occupancy in forming compared with quiescent systems was expected because of the likely effects of aging on quiescent osteons. However, the higher levels of these parameters in resorbing compared with quiescent systems was the opposite of what we expected and suggests that, in addition to their postulated mechanosensory role in the suppression of remodeling and bone loss, osteocytes might also contribute to processes initiating or maintaining bone resorption.     

Predicting Feasibility of Biventricular Repair of Right-Dominant Unbalanced Atrioventricular Canal

Background. In right-dominant unbalanced atrioventricular (AV) canal, there are no criteria to judge adequacy of the left ventricle for biventricular repair. The purpose of this study was to test the hypothesis that right ventricular volume overload in this condition results in right-to-left septal bowing and contributes to the appearance of a small left ventricle.

Methods. Five consecutive neonates and young infants (age range, 23 days to 5 months; median age, 3 months) with right-dominant unbalanced complete AV canal underwent biventricular repair. Preoperative and postoperative echocardiographic measurements of left (LV) and right ventricular size and AV valve component size were made. Potential LV volume was assessed preoperatively using a theoretic model that assumed a normalization of septal bowing.

Results. There was no perioperative mortality; 1 patient died 71 days postoperatively of problems related to the left AV valve. Preoperatively, all patients had severe LV hypoplasia, with a mean end-diastolic indexed true LV volume of 14.8 ± 9.1 mL/m², indexed potential LV volume of 32.0 ± 18.8 mL/m², left AV valve to total AV valve ratio of 0.30 ± 0.06, and LV to right ventricular long-dimension ratio of 0.65 ± 0.1. Postoperatively, all patients had indexed true LV volumes greater than 30 mL/m² (mean volume, 35.6 ± 3.9 mL/m²), and the left AV valve to total AV valve ratio and the LV to right ventricular long-dimension ratio increased to 0.42 ± 0.03 and 0.88 ± 0.11, respectively. Both preoperative potential and true LV volumes correlated well with postoperative true LV volumes: r = 0.90 (p = 0.040) and r = 0.93 (p = 0.023), respectively. Increases in LV length and left AV annulus size indicated contributions of volume loading and surgical patching to the right of the ventricular crest to the increase in LV size.

Conclusions. In our small series, preoperative indexed potential LV volume of 15 mL/m² or greater (present in all patients) allowed biventricular repair of right-dominant unbalanced AV canal. Any previous criteria for LV hypoplasia in this condition need to be reconsidered. This study also has implications for other right-sided volume-loaded lesions in which the left ventricle initially is judged to be hypoplastic but in which biventricular repair may be feasible.     

Quantitative evaluation of gastric contents using ultrasound

Study Objectives: To describe a method of the authors' design for estimating gastric volume quantitatively using ultrasound and to evaluate the usefulness of this method in the clinical setting.

Design: Prospective, two-phase clinical study.

Setting: University hospital.

Patients and volunteers: Phase 1 study: 31 patients who were undergoing general anesthesia and had no gastrointestinal disorder. Phase 2 study: 8 healthy volunteers.

Interventions: With each subject in the sitting position, a cross-sectional view of the stomach was obtained via ultrasound along the median line of the epigastric region. The cross-sectional area of the stomach (CSA) was measured by the analysis unit on the basis of the trace-enclosure method, and a mean value was obtained from triplicate measurements.

Measurements and Main Results: In the phase 1 study, CSA was measured after the patient had fasted for 1 hour, 4 hours, and more than 8 hours. CSA (cm²) was 19.2 ± 0.9 cm² at 1 hour, 11.0 ± 0.7 cm² at 4 hours, and 5.5 ± 0.4 cm² at more than 8 hours. That is, CSA significantly decreased as fasting time was prolonged (p < 0.001 for 1 hour vs. more than 8 hours and 4 hours vs. more than 8 hours). Most of the patients (87%) who fasted for more than 8 hours had a CSA less than 8.0 cm². In the phase 2 study, after patients had fasted for more than 8 hours, CSA was measured both before and 5 minutes after the patient drank 50 ml of milk. CSA was 5.0 ± 0.5 cm² before and 8.5 ± 0.9 cm² after ingestion of the milk (p < 0.001). All subjects had a CSA less than 8.0 cm² before drinking the milk, whereas only 2 of 8 patients had a CSA less than 8.0 cm² after.

Conclusions: This method would be useful to estimate gastric contents quantitatively, and a CSA of 8.0 cm² might be a valid indicator of an empty stomach.     

Pulmonary thromboendarterectomy – risk factors for early survival and hemodynamic improvement

Objective: Pulmonary thromboendarterectomy (PTE) for chronic thromboembolic pulmonary hypertension is a challenging procedure with a considerable mortality. The aim of this investigation was to identify risk factors influencing mortality and operative results. Methods: Between October 1995 and August 2000, 69 patients (age 54 years; 34 women; mean New York Heart Association (NYHA) stage 3.4) underwent PTE. The preoperative pulmonary vascular resistance (PVR) was 988±554 dynes×s×cm⁻⁵, mean pulmonary artery pressure 50±12 mmHg, right atrial pressure (RAP) 11.5±4 mmHg. Hospital mortality was 10.1% (n=7/69). Mean postoperative PVR on the 2nd day was 324±188 dynes×s×cm⁻⁵. Pulmonary angiography was reviewed for number of involved segments (mean 9.3±2) and bronchial arteries diameter (BAD; mean 4.6±1.6 mm). A univariate and multivariate analysis was performed to determine preoperative risk factors for hospital death and inadequate hemodynamic improvement. Results: By univariate analysis, mortality was influenced by age (P=0.04), right atrial pressure (P=0.009), NYHA (P=0.02) and the number of angiographically involved segments (P=0.02). Sex, left ventricular function, presence of coronary artery disease and bronchial artery diameter did not show correlation with mortality. Inadequate hemodynamic improvement in a dichotomized analysis (PVR≥500 dynes×s×cm⁻⁵, n=11, and PVR <500 dynes×s×cm⁻⁵, n=58), assessed by univariate analysis, was significantly influenced by age (P=0.02), preoperative PVR (P=0.01), NYHA (P=0.002), RAP (P=0.02) and female sex (P=0.02). Multivariate analysis identified age (P=0.1), RAP (P=0.002) and female sex (P=0.007) as risk factors for inferior hemodynamic improvement. Conclusions: Preoperative parameters can be utilized to assess postoperative mortality and hemodynamic improvement after pulmonary thromboendarterectomy. Patient age and clinical deterioration of pulmonary hypertension are considerable preoperative factors influencing hospital mortality. Inadequate postoperative hemodynamic improvement is affected by severity of disease and female sex.     

Ultrastructural investigations of bone resorptive cells in two types of autosomal dominant osteopetrosis

In order to investigate the ultrastructure of bone resorptive cells in the two types of adult benign human osteopetrosis, iliac crest biopsies were obtained from 11 patients and 10 normal males, who served as a control group. Six patients had the radiological type I (4 women, 2 men, aged 23–58 years, MEAN = 36.5 years), and 5 type II disease (5 men, aged 20–48 years, MEAN = 29.8 years). The normal controls (aged 23–48 years, mean 34.1 years) were recruited from the medical staff. The biopsies were immediately divided. From each patient, half was embedded in paraffin for histochemistry and light microscopy, and half in epon for transmission electron microscopy.

The osteoclasts were markedly reduced in number and size hi Type I disease (0.2 ± .7 cells vs. 2.9 ± 1.0 cells per 2.7 mm² of bone area, p < 0.01) compared to controls, and stained only weakly for tartrate-resistant acid phosphatase (TRAP). At the ultrastructural level, no signs of active bone resorption were identified, whereas numerous mononuclear cells were observed at the bone surfaces.

In type II disease, the osteoclasts were large and highly multi-nucleated, with an increased number (8.3 ± 2.3 cells vs. 2.9 ± 1.0. cells per 2.7 mm² of bone area, p < 0.01) compared to controls. In all patients with this type, but never in type I or in the controls, a smooth, TRAP-positive substance was seen between the osteoclasts and the bone surface. Ultrastructurally, this substance was amorphous, with a condensation along the cell membrane. Neither ruffled borders nor clear zones were identified. Nuclear inclusions resembling tubular structures were observed in some osteoclasts in all patients with type II disease.

It is concluded that characteristic differences exist between the two types of adult human osteopetrosis at the ultrastructural level. Type I is morphologically similar to some murine mutations characterized by defective maturation of bone resorptive cells. In type II, a defect in the resorptive capacity of their giant osteoclasts is proposed. The pathogenetical significance of nuclear inclusions in type II osteoclasts is unknown.     

Bone strain and microcracks at stress fracture sites in human metatarsals

Microcracks in bone have been implicated in the development of stress fractures. The goal of this study was to evaluate bone strain and microcracks at locations where stress fractures are common (second metatarsal diaphysis) and rare (fifth metatarsal diaphysis) in an attempt to increase our understanding of the pathogenesis of stress fractures. A dynamic gait simulator was used to simulate normal walking with cadaver feet. The feet were loaded over the entire stance phase of gait and diaphyseal strains were recorded in second and fifth metatarsals. Microcrack density (Cr.Dn) and surface density (Cr.S.Dn) were determined in metatarsal cross sections from the contralateral feet. Bone strain was significantly higher in second metatarsals (−1897 ± 613 microstrain) than in fifth metatarsals (−908 ± 503 microstrain). However, second metatarsal Cr.Dn (0.23 ± 0.15 #/mm²) was not significantly different from fifth metatarsal Cr.Dn (0.35 ± 0.19 #/mm²). There was also no significant difference between Cr.S.Dn in second (17.64 ± 10.99 μm/mm²) and fifth (26.70 ± 15.53 μm/mm²) metatarsals. There were no significant relationships between the microcrack parameters and peak strain in either metatarsal. Cracks that occurred in trabecular struts (92 ± 33 μm) were significantly longer than those found ending at cement lines (71 ± 15 μm) and within osteons (57 ± 16 μm). There were no significant relationships between the microcrack parameters and age in either metatarsal. Peak strain was more than twofold greater in second metatarsals than in fifth metatarsals for simulations of normal walking; however, microcrack parameters were unable to explain the greater incidence of second metatarsal stress fractures.     

Successful biventricular repair after initial Norwood operation for interrupted aortic arch with severe left ventricular outflow tract obstruction

Background. Management of newborns with interrupted aortic arch (IAA) remains challenging. Associated severe left ventricular outflow tract obstruction (LVOTO) have often led to increased mortality with neonatal biventricular repair. We review our experience with an alternative approach for this complex surgical problem.

Methods. From May 1991 to June 1999, 28 neonates were treated for IAA. Thirteen of 28 neonates (46%) had type B IAA, ventricular septal defect (VSD) and severe LVOTO (Z value –2 to –7; mean –5 ± 1.7). Mean age was 8 days (3 to 23 days old) with average weight of 3.3 kg (2.4 to 4.2 kg). Eight of 13 (62%) had anomalous right subclavian artery. Ten of 13 (77%) had thymic aplasia and chromosome 22 region q11 deletion. All 13 patients were treated initially with a modified Norwood procedure.

Results. There were no perioperative deaths. Complications included 2 patients with recurrent arch stenosis treated with balloon dilatation. Two patients had systemic arterial shunt revision. Follow-up ranged from 2 to 99 months old (mean 39 months). There were 2 late deaths unrelated to any operation. Nine of 12 patients had a second stage palliation consisting of a bidirectional Glenn shunt. Six patients went on to have biventricular repairs (3 Ross-Konno, 2 Rastelli, 1 VSD closure with LVOT resection). One patient had a modified Fontan operation and 5 patients are awaiting potential biventricular repair.

Conclusions. Children with IAA and severe LVOTO may be managed by initial Norwood palliation with an excellent outcome likely. This initial “univentricular” approach has enabled eventual successful biventricular repair despite severe LVOTO.     

Effects of cerivastatin on vascular function of human radial and left internal thoracic arteries

Background. Statins may enhance vascular function independently of effects on cholesterol. This study investigated the ability of statins to modulate the vascular recovery of arteries used as coronary bypass grafts.

Methods. Specimens of radial artery and left internal thoracic artery were obtained during coronary artery bypass grafting. The specimens were divided into vascular rings, which were incubated in the absence or presence of cerivastatin (10⁻⁶ mol/L) for either 2 or 24 hours. Using an organ bath technique, endothelial function was examined using acetylcholine (10⁻⁹ to 10⁻⁵ mol/L) after contraction by 3×10⁻⁸ mol/L of endothelin-1.

Results. Time-related endothelial dysfunction was shown in the control group of radial artery but not in the cerivastatin group: maximal endothelium-dependent vasodilation in the control and cerivastatin groups were 56.8% ± 10.2% and 65.9% ± 10.1% at 2 hours and 39.4% ± 4.7% and 68.4% ± 5.0% (p < 0.01, vs control) at 24 hours, respectively. On the other hand, in the left internal thoracic artery, those in the control and cerivastatin groups were 38.3% ± 8.2% and 45.0% ± 5.5% at 2 hours and 38.1% ± 8.2% and 56.5% ± 8.8% at 24 hours, respectively (NS).

Conclusions. In radial artery, cerivastatin significantly preserved endothelium-dependent vasodilation, which diminished with time in the control group. This could have very important implications in the clinical practice of coronary artery bypass grafting.     

Univentricular repair: is routine fenestration justified?

Background. A decade after the introduction of baffle fenestration, the outcome of Fontan-type repair for hearts with a functional single ventricle finally looks promising. Our study was designed to assess the impact of fenestration on the outcome of univentricular repairs.

Methods. From January 1988 to December 1997, 348 patients (104 with tricuspid atresia and 244 with other morphological diagnoses) underwent univentricular repair at our institute. Since 1994, routine fenestration of the atrial baffle was performed in all patients (n = 126).

Results. The overall Fontan failure rate was 14% (50 of 348) and included 45 early deaths and five Fontan take downs. Absence of fenestration was the only and highly significant predictor of Fontan failure (risk ratio [RR] 3.3, 95% confidence interval [CI] 1.49 to 7.31, p = 0.002). Significant pleural effusion was seen in 27% of patients. Absence of fenestration of the atrial baffle (RR 3.97, 95% CI 2.17 to 7.26, p < 0.001) and aortic cross-clamp time more than 60 minutes (RR 2.15, 95% CI 1.3 to 3.5, p = 0.002) were found to be significant risk factors. The follow-up ranged from 6 to 120 months (mean 46.0 ± 18.0 months). There were 12 late deaths and 5 patients were lost to follow-up. Actuarial survival (Kaplan Meier) at 90 months was 81% ± 4%. Two hundred and fifty-eight patients (90%) were in New York Heart Association class I at their last follow-up visit. Oxygen saturation in the fenestrated group ranged from 85% to 94% (mean 89%). Thirty patients (26%) had spontaneous closure of the fenestration over a mean period of 34 months, and there has been no incidence of late systemic thromboembolism. In no instance has there been a need to close the fenestration.

Conclusions. Elective fenestration of the intraatrial baffle is associated with decreased Fontan failure rate and decreased occurrence of significant postoperative pleural effusions. Routine elective fenestration of the atrial baffle may, therefore, be justified in all univentricular repairs.     

Complement Activation and Cytokine Generation After Modified Fontan Procedure

Background. The modified Fontan procedure separates the systemic and pulmonary circulations in patients born with a functional single ventricle. Delayed recovery is frequently observed after this procedure. It was our hypothesis that complement activation or cytokine generation may contribute to the pathophysiology of this problem.

Methods. We measured activated complement C3, thromboxane B₂, interleukin-6, and tumor necrosis factor- levels by immunoassay in 16 patients undergoing Fontan procedure. Patient plasma samples were obtained preoperatively, on initiation of cardiopulmonary bypass, after administration of protamine, and 1, 4, 8, and 24 hours postoperatively.

Results. There was no early or late mortality in this cohort of patients. Low cardiac output developed in 3 of 16 patients, and pleural effusions developed in 5. The median length of hospital stay was 9 days. Activated complement C3 levels increased from a baseline of 1,486 ± 564 to 4,600 ± 454 ng/mL after cardiopulmonary bypass and administration of protamine, and returned to baseline by 24 hours. The level of interleukin-6 increased from 42 ± 32 to 176 ± 22 pg/mL and at 24 hours remained elevated at 71 ± 15 pg/mL. Neither thromboxane B₂ nor tumor necrosis factor- levels increased significantly.

Conclusions. The data demonstrate threefold to fourfold increases in activated complement C3 and interleukin-6, indicating that both humoral and cellular systems are affected. It is our conclusion that complement and cytokine activation may contribute to the delayed recovery observed after Fontan procedure.