Changes in TSH levels in athyreotic patients with differentiated thyroid cancer during levothyroxine therapy: influence on dose adjustments

PURPOSE

The aim of the study was to describe the spontaneous TSH level variations and levothyroxine dose adjustments in athyreotic patients with differentiated thyroid cancer (DTC) in real-life practice.

METHODS

Patients with DTC were retrospectively evaluated at a tertiary referral center between October 2006 and November 2013. Hormone measurements (TSH and FT4 serum levels), L-T4 prescription information (dose per kg per day) and other medications were recorded at 1 month and 3, 12, 24, 36 and 48 months after primary treatment (surgery ± radioiodine therapy).

RESULTS

The cohort was composed of 452 patients; about 20% of patients with stable levothyroxine dose have clinically meaningful spontaneous TSH variations (defined as ΔTSH > 2 mcUI/mL) at yearly follow-up visit. Furthermore, about 25% of athyreotic DTC patients with stable dose have a ΔTSH > 1.5 mcUI/mL and about 40% a ΔTSH > 1 mcUI/mL during each follow-up visit. We further investigated whether this TSH variation would lead to subsequent dose changes. About 19.9-37.7% of DTC patients on stable LT4 dose on the previous visit had their levothyroxine dose reduced, while 7.8-14.9% increased due to TSH variations. We further evaluated the decision to change the dose in relation with the age-specific TSH range. Up to 77.2% of patients had their dose adjusted due to TSH falling below the age-specific range.

CONCLUSIONS

Spontaneous serum TSH variations determine levothyroxine replacement therapy in athyreotic patients with DTC, requiring multiple dose changes.

Lack of association between obesity and aggressiveness of differentiated thyroid cancer

PURPOSE

Aim of this study was to evaluate the association between body mass index (BMI) and aggressive features of differentiated thyroid cancer (DTC) in a prospective cohort.

METHODS

Patients with DTC were prospectively enrolled at a tertiary referral center and grouped according to their BMI. Aggressive clinic-pathological features were analyzed following the American Thyroid Association Initial Risk Stratification System score.

RESULTS

The cohort was composed of 432 patients: 5 (1.2%) were underweight, 187 (43.3%) normal weight, 154 (35.6%) overweight, 68 (15.7%) grade 1 obese, 11 (2.5%) grade 2 obese and 7 (1.6%) grade 3 obese. No single feature of advanced thyroid cancer was more frequent in obese patients than in others. No significant correlation was found between BMI, primary tumor size (Spearman's ρ - 0.02; p = 0.71) and ATA Initial Risk Stratification System score (ρ 0.03; p = 0.49), after adjustment for age. According to the multivariate logistic regression analysis, male gender and pre-surgical diagnosis of cancer were significant predictors of cancer with high or intermediate-high recurrence risk according to the ATA system (OR 2.06 and 2.51, respectively), while older age at diagnosis was a protective factor (OR 0.98), and BMI was not a predictor. BMI was a predictor of microscopic extrathyroidal extension only (OR 1.06).

CONCLUSIONS

Obesity was not associated with aggressive features in this prospective, European cohort of patients with DTC.

Clinical predictors of fever in stroke patients: relevance of nasogastric tube

OBJECTIVES

Fever frequently occurs in stroke patients and worsens their prognosis. However, only few studies have assessed the determinants of fever in acute stroke, and no study has specifically addressed the possible prediction of the development of fever.

MATERIALS AND METHODS

This investigation included 536 patients with acute stroke and a body temperature <=37°C during the first 24 h of stay. Ninety-two of them (17.2%) subsequently developed fever (defined as a temperature >=37.5°C starting after 24 h). Among the clinical variables available during the first 24 h from admission, those predictive of the subsequent appearance of fever were searched for. One hundred further patients had a temperature >37°C during the first 24 h.

RESULTS

In univariate analysis, many variables were predictive of the subsequent development of fever, but in multivariate analysis, only the following four predictors remained significant (odds ratio [95% confidence interval], P value): nasogastric tube (4.0 [2.2-7.4], <0.0001), atrial fibrillation (2.3 [1.4-3.8], 0.001), total anterior circulation syndrome (2.0 [1.2-3.5], 0.01), and urinary catheter (1.9 [1.1-3.3], 0.01). Among the 52 (9.7%) patients with three or four predictors, 31 (59.6%) subsequently developed fever. In addition, the factors independently associated with a temperature >37°C during the first 24 h were as follows: National Institutes of Health Stroke Scale (P < 0.0001), hemorrhagic stroke (P = 0.0008), atrial fibrillation (P = 0.002), and total parenteral nutrition (P = 0.03).

CONCLUSIONS

In patients with acute stroke, four clinical variables were found to be independently associated with the risk of developing fever and, of them, nasogastric tube was the strongest and most significant one.

EDS and μ-XRF mapping of amalgam degradation products in ancient mirrors

An amalgam mirror is a mirror type, used from the fifteenth century until the end of the nineteenth century, where the reflective layer is constituted by a tin amalgam layer adhered to a glass sheet. In this work, two amalgam mirrors samples were studied by scanning electron microscopy with an energy dispersive spectrometer and by micro-X-ray fluorescence elemental mapping to go deeply into the understanding of the degradation mechanism of the amalgam layer of ancient mirrors. The investigation has been focused for the first time on the reflective surface of the amalgam layer adherent to the glass sheet to better understand the processes of amalgam corrosion. The two amalgam degradation compounds, romarchite and cassiterite, has been spatially differentiated by scanning electron microscope (SEM) and energy dispersive spectrometer (EDS) maps. SEM images and micro-X-ray fluorescence and EDS maps showed that the amalgam degradation products grow up to form hemispherical stratified calottes. This structure is probably due to a mechanism involves cyclic phases and oxygen radial diffusion from a superficial oxidation nucleus.

New experimental platform to study high density laser-compressed matter

We have developed a new experimental platform at the Linac Coherent Light Source (LCLS) which combines simultaneous angularly and spectrally resolved x-ray scattering measurements. This technique offers a new insights on the structural and thermodynamic properties of warm dense matter. The < 50 fs temporal duration of the x-ray pulse provides near instantaneous snapshots of the dynamics of the compression. We present a proof of principle experiment for this platform to characterize a shock-compressed plastic foil. We observe the disappearance of the plastic semi-crystal structure and the formation of a compressed liquid ion-ion correlation peak. The plasma parameters of shock-compressed plastic can be measured as well, but requires an averaging over a few tens of shots.

RAGE gene polymorphism in heart failure patients with and without angiographic evidence of significant coronary atherosclerosis

Heart failure (HF) is a multifactorial disorder in which clinical, environmental and genetic components take part. For this reason it is possible that common gene variants could affect development, progression and response to pharmacological therapy. In recent years the role of AGEs in the pathogenesis of cardiovascular diseases has become recognized but little is known about the role of the AGE–RAGE system in heart failure. The aim of the present study was to identify possible relationship between -374 T/A RAGE gene polymorphism with heart failure. The population in this study consists of 386 subjects with HF, selected according to the presence of depressed Left Ventricular Ejection Fraction (LVEF) less than45 percent, and 639 patients with CAD documented at coronary angiography. Within the population with HF there are 228 patients with disease secondary to not ischemic cause and 158 with post-ischemic condition. The sample of AA genotype was significantly lower in patients with post-ischemic HF in respect to HF secondary to non-ischemic causes (pless than0.001). A significant difference between the two groups was also observed regarding the allele frequency. In addition, differences in the allelic and the genotypic frequencies of homozygous genotypes were found between the HF patients free from evidence of coronary significant lesions and patients with at least one hemodynamically significant coronary lesion, both HF and CAD. In patients with at least one vessel compromised the presence of A allele and the homozygous AA genotype were significantly lower than in patients with lesion-free coronary. In conclusion, our research reveals that the -374 T/A polymorphism is related to the genesis of atherosclerotic coronary artery disease but not to its evolution. The protective role of AA genotype in respect to atheromatous disease is therefore confirmed also in the HF population with non-ischemic origin.

Diagnosis of growth hormone deficiency is affected by calibrators used in GH immunoassays

Growth hormone (GH) values vary among immunoassays depending on different factors, such as the assay method used, specificity of antibodies, matrix difference between standards and samples, and interference with endogenous GH binding proteins (GHBPs). We evaluated whether the use of different calibrators for GH measurement may affect GH values and, consequently, the formulation of GH deficiency (GHD) diagnosis in children. Twenty-three short children (5 F, 18 M; age 11.4±3.1 years), with the clinical characteristics of GHD (height:  -2.3±0.5 SDS; height velocity  -2.3±1.5 SDS; IGF-I  -1.2±0.9 SDS), underwent GH stimulation tests to confirm the clinical diagnosis of GHD. Serum GH values were measured with Immulite 2000, using 2 different calibrators, IS 98/574, a recombinant 22 kDa molecule of more than 95% purity, and IS 80/505, of pituitary origin and resembling a variety of GH isoforms. We found blunted GH secretion in 20 subjects with the Immulite assay using the IS 98/574 GH as a calibrator, confirming the diagnosis of GHD. Subsequently, using IS 80/505 GH as a calibrator, in the same samples only 14 children showed reduced GH levels. The total cost for the first year of GH therapy of patients diagnosed with IS 98/574 as a calibrator was higher than that for patients diagnosed with IS 80/505 as a calibrator. These data confirm that GH values may depend on different calibrators used in the GH assay, affecting the formulation of GHD diagnosis and the consequent decision to start GH treatment.

Galectin-3 plasma levels and coronary artery disease: a new possible biomarker of acute coronary syndrome

Inflammation plays a key role in atherosclerosis. Galectin-3 is a macrophage- and endothelium-derived mediator actively involved in the regulation of many aspects of inflammatory cell behaviour. The aim of this study is to quantify plasma Galectin-3 in patients with coronary artery disease (CAD) and different clinical manifestation at the moment of observation in order to verify whether Galectin-3 could be a useful biomarker of atherosclerotic state. We enrolled 125 patients affected by CAD, angiographically documented (70 stable, 55 unstable). They underwent accurate examinations and anamnestic data was collected. The most important traditional risk factors, such as age, hypertension, and body mass index, were reported. Plasma Galectin-3 was quantified using an ELISA kit. Unstable patients (n = 55) had a higher plasma Galectin-3 levels in respect to the stable subjects (27.75 ng/mL (19.27-39.09) vs 6.48 ng/ml (4.88-8.83), p&#x003C;0.001. A trend in correlation between plasma Galectin-3 levels and number of vessels compromised seems to be present: CAD patients with three-vessel disease had higher levels of Galectin-3 than patients with one-or two-vessel disease (17.39 ng/ml (10.75-29.82) vs 9.18 ng/ml (5.56-23.22), p= 0.058. The significantly higher plasma Galectin-3 levels in patients with unstable angina in respect to the stable angina confirm the involvement of Galectin-3 in promoting macrophage activation and monocyte attraction. Despite the distribution of CAD in patients with acute and chronic coronary disease being similar, we may hypothesize that Galectin-3 could be a useful biomarker of atherosclerotic plaque and in particular of its destabilization.

Apelin Plasma Levels Predict Arrhythmia Recurrence in Patients with Persistent Atrial Fibrillation

Low levels of the regulatory peptide apelin have been reported in patients with lone atrial fibrillation (AF). We evaluate the potential utility of assessing apelin plasma levels as a predictor of AF recurrence in individuals presenting for electrical cardioversion. Plasma levels of apelin, brain natriuretic peptide (BNP) and high-sensitivity C-reactive protein were measured in 93 patients, with persistent AF before successful external electrical cardioversion. Significantly lower apelin plasma levels were found in patients with AF recurrence as respect to population with persistence of sinus rhythm during a six months follow-up. The hazard increased with duration of AF, left atrial dimension, BNP concentrations. Subjects with apelin levels below the median had a hazard ratio of 3.1 of arrhythmia recurrence with respect to those with high apelin levels (p< 0.05). A significant difference in BNP levels was found between patients with and without AF recurrence during the follow-up. After adjusting for potential confounders, both BNP and apelin retained their statistical significance as independent predictors of arrhythmia recurrence. Patients with both low apelin and elevated BNP had a worse prognosis compared with those with either low apelin or elevated BNP alone. Low plasma apelin levels before external electrical cardioversion are an independent prognostic factor for arrhythmia recurrence in patients with AF treated with antiarrhythmic drugs. Apelin may be of particular value for the identification of high-risk patients in addition to BNP.

Glass-ceramics obtained by the recycling of end of life cathode ray tubes glasses

This work is concerned with open-loop recycling of end of life Cathode Ray Tubes glass (an unsolved problem when considering that in Europe almost 90% of EOL electronic goods is disposed of in landfills), focusing on the development of glass-ceramics from panel or funnel glass with dolomite and alumina, and the evaluation of the tendency towards crystallisation with particular attention on composition and thermal treatment. Glasses were melted at a temperature of about 1500 degrees C and transformed into glass-ceramics by different thermal treatments (900 degrees C to approximately 1100 degrees C temperature range and 0.5 to approximately 8h soaking time). By using the evaluation of thermal, mineralogical and microstructural data it has been pointed out that a good degree of crystallisation is reached at about 1000 degrees C and with a high proportion of waste glass (50-75%) if 40-45% of CaO and MgO bearer (dolomite) is introduced. In this way alkaline and alkaline-earth silicate and aluminosilicate mainly develop probably with a surface mechanism.

Multiinstitutional experience with the management of superior mesenteric artery injuries

BACKGROUND

Superior mesenteric artery (SMA) injuries are rare and often lethal injuries incurring very high morbidity and mortality. The purposes of this study are to review a multiinstitutional experience with these injuries; to analyze Fullen's classification based on anatomic zone and ischemia grade for its predictive value; to correlate the American Association for the Surgery of Trauma-Organ Injury Scale (AAST-OIS) for abdominal vascular injury with mortality; and to identify independent risk factors predictive of mortality, describing current trends for the management of this injury in America.

DESIGN

We performed a retrospective multiinstitutional study of patients sustaining SMA injuries involving 34 trauma centers in the US over 10 years. Outcomes variables, both continuous and dichotomous, were analyzed initially with univariate methods. For the subsequent multivariate analysis, stepwise logistic regression was used to identify a set of risk factors significantly associated with mortality.

RESULTS

There were 250 patients enrolled, with a mean Revised Trauma Score (RTS) of 6.44 and a mean Injury Severity Score (ISS) of 25. Surgical management consisted of ligation in 175 of 244 patients (72%), primary [corrected] repair in 53 of 244 patients (22%), autogenous grafts were used in 10 of 244 (4%), and prosthetic grafts of PTFE in 6 of 244 patients (2%). Overall mortality was 97 of 250 patients (39%). Mortality versus Fullen's zones: zone I, 39 of 51 (76.5%); zone II, 15 of 34 (44.1%); zone III, 11 of 40 (27.5%); and zone IV, 25 of 108 (23.1%). Mortality versus Fullen's ischemia grade: grade 1, 22 of 34 (64.7%). Mortality versus AAST-OIS for abdominal vascular injury: grade I, 9 of 55 (16.4%); grade II, 13 of 51 (25.5%); grade III, 8 of 20 (40%); grade IV, 37 of 69 (53.6%); and grade V, 17 of 19 (89.5%). Logistic regression analysis identified as independent risk factors for mortality the following: transfusion of greater than 10 units of packed RBCs, intraoperative acidosis, dysrhythmias, injury to Fullen's zone I or II, and multisystem organ failure.

CONCLUSION

SMA injuries are highly lethal. Fullen's anatomic zones, ischemia grade, and AAST-OIS abdominal vascular injuries correlate well with mortality. Injuries to Fullen's zones I and II, Fullen's maximal ischemia grade, and AAST-OIS injury grades IV and V, high-intraoperative transfusion requirements, and presence of acidosis and disrhythmias are significant predictors of mortality. All of these predictive factors for mortality must be taken into account in the surgical management of these injuries.

Constitutive activation of Stat3 by the Src and JAK tyrosine kinases participates in growth regulation of human breast carcinoma cells

Constitutive activation of signal transducer and activator of transcription (STAT) proteins has been detected in a wide variety of human primary tumor specimens and tumor cell lines including blood malignancies, head and neck cancer, and breast cancer. We have previously demonstrated a high frequency of Stat3 DNA-binding activity that is constitutively-induced by an unknown mechanism in human breast cancer cell lines possessing elevated EGF receptor (EGF-R) and c-Src kinase activities. Using tyrosine kinase selective inhibitors, we show here that Src and JAK family tyrosine kinases cooperate to mediate constitutive Stat3 activation in the absence of EGF stimulation in model human breast cancer cell lines. Inhibition of Src or JAKs results in dose-dependent suppression of Stat3 DNA-binding activity, which is accompanied by growth inhibition and induction of programmed cell death. In addition, transfection of a dominant-negative form of Stat3 leads to growth inhibition involving apoptosis of breast cancer cells. These results indicate that the biological effects of the Src and JAK tyrosine kinase inhibitors are at least partially mediated by blocking Stat3 signaling. While EGF-R kinase activity is not required for constitutive Stat3 activation in breast cancer cells, EGF stimulation further increases STAT DNA-binding activity, consistent with an important role for EGF-R in STAT signaling and malignant progression. Analysis of primary breast tumor specimens from patients with advanced disease revealed that the majority exhibit elevated STAT DNA-binding activity compared to adjacent non-tumor tissues. Our findings, taken together, suggest that tyrosine kinases transduce signals through Stat3 protein that contribute to the growth and survival of human breast cancer cells in culture and potentially in vivo.

Probing impulsive strain propagation with X-ray pulses

Pump-probe time-resolved x-ray diffraction of allowed and nearly forbidden reflections in InSb is used to follow the propagation of a coherent acoustic pulse generated by ultrafast laser excitation. The surface and bulk components of the strain could be simultaneously measured due to the large x-ray penetration depth. Comparison of the experimental data with dynamical diffraction simulations suggests that the conventional model for impulsively generated strain underestimates the partitioning of energy into coherent modes.

Penetrating esophageal injuries: multicenter study of the American Association for the Surgery of Trauma

OBJECTIVE

The purpose of this study was to define the period of time after which delays in management incurred by investigations cause increased morbidity and mortality. The outcome study is intended to correlate time with death from esophageal causes, overall complications, esophageal related complications, and surgical intensive care unit length of stay.

METHODS

This was a retrospective multicenter study involving 34 trauma centers in the United States, under the auspices of the American Association for the Surgery of Trauma Multi-institutional Trials Committee over a span of 10.5 years. Patients surviving to reach the operating room (OR) were divided into two groups: those that underwent diagnostic studies to identify their injuries (preoperative evaluation group) and those that went immediately to the OR (no preoperative evaluation group). Statistical methods included Fisher's exact test, Student's T test, and logistic regression analysis.

RESULTS

The study involved 405 patients: 355 male patients (86.5%) and 50 female patients (13.5%). The mean Revised Trauma Score was 6.3, the mean Injury Severity Score was 28, and the mean time interval to the OR was 6.5 hours. There were associated injuries in 356 patients (88%), and an overall complication rate of 53.5%. Overall mortality was 78 of 405 (19%). Three hundred forty-six patients survived to reach the OR: 171 in the preoperative evaluation group and 175 in the no preoperative evaluation group. No statistically significant differences were noted in the two groups in the following parameters: number of patients, age, Injury Severity Score, admission blood pressure, anatomic location of injury (cervical or thoracic), surgical management (primary repair, resection and anastomosis, resection and diversion, flaps), number of associated injuries, and mortality. Average length of time to the OR was 13 hours in the preoperative evaluation group versus 1 hour in the no preoperative evaluation group (p < 0.001). Overall complications occurred in 134 in the preoperative evaluation group versus 87 in the no preoperative evaluation group (p < 0.001), and 74 (41%) esophageal related complications occurred in the preoperative evaluation group versus 32 (19%) in the no preoperative evaluation group (p = 0.003). Mean surgical intensive care unit length of stay was 11 days in the preoperative evaluation group versus 7 days in the no preoperative evaluation group (p = 0.012). Logistic regression analysis identified as independent risk factors for the development of esophageal related complications included time delays in preoperative evaluation (odds ratio, 3.13), American Association for the Surgery of Trauma Organ Injury Scale grade >2 (odds ratio, 2.62), and resection and diversion (odds ratio, 4.47).

CONCLUSION

Esophageal injuries carry a high morbidity and mortality. Increased esophageal related morbidity occurs with the diagnostic workup and its inherent delay in operative repair of these injuries. For centers practicing selective management of penetrating neck injuries and transmediastinal gunshot wounds, rapid diagnosis and definitive repair should be made a high priority.

Periprosthetic breast capsules contain the fibrogenic cytokines TGF-beta1 and TGF-beta2, suggesting possible new treatment approaches

Periprosthetic breast capsules composed of fibrotic collagenous material with increased collagen production are not dissimilar to other fibrotic conditions occurring in other organs. Fibrosis in the lung, liver, kidney, and skin has been associated with overproduction of the fibrogenic isoforms of transforming growth factor beta (TGF-beta1 and TGF-beta2). If periprosthetic breast capsules contained high levels of these cytokines, possibly new treatment approaches for capsular contraction could be proposed. Breast implant capsules of 35 patients harvested at the time of explantation were examined using indirect immunohistochemistry. Staining intensity for TGF-beta1 and TGF-beta2 was measured in all specimens. Immunohistochemical staining for TGF-beta1 and TGF-beta2 revealed that these two cytokines were present in all capsules analyzed. Minimal TGF-beta1 and TGF-beta2 were found in normal breast tissue. Levels of control vs. TGF-beta1 and control vs. TGF-beta2 were significant (p = 0.004 and p < 0.001 respectively). The presence of TGF-beta isoforms that are known to be fibrogenic may suggest new therapeutic approaches, which are being investigated for other fibrotic conditions.

Screening for major deep vein thrombosis in seriously injured patients: a prospective study

The purpose of the study is to determine the prevalence of acute deep venous thrombosis (DVT) in severely injured trauma patients, to investigate the cost effectiveness of a noninvasive surveillance program, and to assess the merit of current methods of prophylaxis against DVT. One hundred and forty-eight patients (295 limbs) with a mean age of 36.5 years, mean trauma score of 13.3, mean injury severity score of 22.4 with predominantly blunt injuries (88.5%), were part of the study. The mean length of stay was 17.6 days. Venous duplex scans (VDS) were performed on inpatients on days 2-5, day 11, and day 30 following admission. Sequential compression device and/or subcutaneous heparin was used in 99% of patients with compliance being monitored by trauma nurse clinicians. A total of 272 VDS were performed with total charges of $111,520. DVT was found by VDS or venography in eight limbs (2.7%) of six patients (4%), our of the limbs being symptomatic. Two additional patients had pulmonary embolism, both with normal VDS. Routine serial VDS in severely injured patients who undergo aggressive prophylaxis against DVT is not cost effective and therefore not justified.

Experimental myocardial cryoinjury: local electromechanical changes, arrhythmogenicity, and methods for determining depth of injury

To characterize the electromechanical effects of acute and 2-week-old cryoinjury, programmed stimulation and epicardial M-mode echo mapping (7.5 mHz) were performed prior to, at 15 minutes and 15 +/- 2 days after cryoinjury in 10 dogs. Epicardial and intramural bipolar and unipolar electrograms were recorded in five of the dogs. Cryoinjury was produced with a 5 mm in diameter flat cryoprobe at -60 degrees C applied to the left ventricular epicardium for 10 minutes at each of six contiguous sites. Cryoinjury, acutely and at 2 weeks, was characterized by a loss of normal intramural systolic thickening and a decrease in echo density. The maximum depth of cryoinjury determined by echo ranged from .55 to .85 cm acutely, and .50 to .80 cm chronically and it correlated acutely and chronically (r = .80; r = .85) with pathologically documented depth of cryoinjury at 2 weeks. Acutely, the presence of either an abnormal intramural unipolar or bipolar electrogram also defined the depth of cryoinjury within .16 cm. In contrast, epicardial electrograms were not useful for judging depth of cryoinjury. A QS complex on the epicardial unipolar electrogram was recorded over the cryoinjury acutely and at 2 weeks in four of five dogs despite preserved subendocardial systolic wall thickening and normal histology extending 40 to 65% of the wall thickness. Epicardial bipolar electrograms uniformly showed a marked decrease in amplitude and slope of the intrinsic deflection, a small but insignificant increase in width and no multicomponent activity. Ventricular fibrillation was reproducibly initiated with three ventricular extrastimuli in five of 10 dogs at 2 weeks. No ventricular tachycardia was initiated.(ABSTRACT TRUNCATED AT 250 WORDS)

Mechanism of skeletal muscle underperfusion in a dog model of low-output heart failure

To investigate the mechanism responsible for underperfusion of working skeletal muscle in heart failure, we measured systemic and femoral bed hemodynamics during treadmill exercise and gracilis muscle resistance during contraction frequencies of 1-9 Hz in 8 dogs ventricularly paced at 260 beats/min for 3 wk to induce heart failure (HF) and in 9 control dogs. At peak treadmill exercise (4 mph, 10%), HF dogs had reduced cardiac outputs (control: 297 +/- 42 vs. HF: 212 +/- 16 ml X min-1 X kg-1) and femoral bed flows (control: 352 +/- 112 vs. HF: 229 +/- 95 ml/min) and elevated arterial lactates [control: 1.7 +/- 0.7 vs. HF: 4.1 +/- 0.7 mM (all P less than 0.04)], consistent with skeletal muscle underperfusion. This muscle underperfusion was associated with reduced mean arteriovenous pressure gradients [control: 119 +/- 12 vs. HF: 91 +/- 9 mmHg (P less than 0.001)] but with normal systemic vascular [control: 21 +/- 6 vs. HF: 23 +/- 5 U (P = NS)] and femoral bed resistances [control: 3.5 +/- 1.6 vs. HF: 4.4 +/- 2.3 X 10(2) U (P = NS)]. Both groups also had similar gracilis muscle minimal resistance during exercise (control: 2.0 +/- 1.1 vs. HF: 1.9 +/- 0.9 X 10(3) U/100 g) and following maximal vasodilation (control: 2.0 +/- 1.0 vs. HF: 2.1 +/- 1.0 X 10(3) U/100 g). These results suggest that 1) short-term rapid ventricular pacing in the dog produces a model of low output HF resembling HF in humans, and 2) skeletal muscle underperfusion in this model is due to a reduced muscle arteriovenous pressure gradient and not to impaired skeletal muscle arteriolar vasodilation.