A comparison of the classical and modified forms of the continuity equation in the On-X prosthetic heart valve in the aortic position

BACKGROUND AND AIM OF THE STUDY

The use of echocardiography to determine prosthetic valve hemodynamics has become generally accepted; however, there are still many differing methodologies in use. The continuity equation, which uses the ratio of the subaortic and transaortic velocity-time integrals for determining aortic effective orifice area (EOA), has been established as an accurate method. Another method using the more easily measured peak velocities in ratio has also been employed. These methods were compared to determine if the simpler method gave equivalent results.

METHODS

Early postoperative echocardiographic data on prosthetic valves from the MCRI Multicenter Trial were used to compare the two methods of calculating EOA (A2). Results using the two methods were compared by paired t-tests, the Wilcoxon signed rank test, regression and Bland-Altman analysis.

RESULTS

Despite a good correlation between the two methods (r = 0.91), results were different when compared by a paired t-test. On average, results by the modified method were 0.2 cm2 lower, but in 28% of cases they were in fact higher than the classical method.

CONCLUSION

The modified continuity equation based on the peak velocity ratio does not give the same result as the classical formula based on the velocity-time ratio. The modified method cannot reliably be substituted for the classical method in normally functioning On-X valves.

5-Iodo-A-85380, an alpha4beta2 subtype-selective ligand for nicotinic acetylcholine receptors

In an effort to develop selective radioligands for in vivo imaging of neuronal nicotinic acetylcholine receptors (nAChRs), we synthesized 5-iodo-3-(2(S)-azetidinylmethoxy)pyridine (5-iodo-A-85380) and labeled it with (125)I and (123)I. Here we present the results of experiments characterizing this radioiodinated ligand in vitro. The affinity of 5-[(125)I]iodo-A-85380 for alpha4beta2 nAChRs in rat and human brain is defined by K(d) values of 10 and 12 pM, respectively, similar to that of epibatidine (8 pM). In contrast to epibatidine, however, 5-iodo-A-85380 is more selective in binding to the alpha4beta2 subtype than to other nAChR subtypes. In rat adrenal glands, 5-iodo-A-85380 binds to nAChRs containing alpha3 and beta4 subunits with 1/1000th the affinity of epibatidine, and exhibits 1/60th and 1/190th the affinity of epibatidine at alpha7 and muscle-type nAChRs, respectively. Moreover, unlike epibatidine and cytisine, 5-[(125)I]iodo-A-85380 shows no binding in any brain regions in mice homozygous for a mutation in the beta2 subunit of nAChRs. Binding of 5-[(125)I]iodo-A-85380 in rat brain is reversible, and is characterized by high specificity and a slow rate of dissociation of the receptor-ligand complex (t(1/2) for dissociation approximately 2 h). These properties, along with other features observed previously in in vivo experiments (low toxicity, rapid penetration of the blood-brain barrier, and a high ratio of specific to nonspecific binding), suggest that this compound, labeled with (125)I or (123)I, is superior to other radioligands available for in vitro and in vivo studies of alpha4beta2 nAChRs, respectively.

The tissue distribution of the human beta3-adrenoceptor studied using a monoclonal antibody: direct evidence of the beta3-adrenoceptor in human adipose tissue, atrium and skeletal muscle

OBJECTIVE

To develop a monoclonal antibody that recognises an epitope of the native beta3-adrenoceptor expressed on the extracellular surface of human cells and tissues.

DESIGN

A high affinity monoclonal antibody, Mab72c, was raised against the human beta3-adrenoceptor expressed on a transfected mammalian cell line.

RESULTS

In CHO (Chinese hamster ovary) cells transfected with beta3-adrenoceptor cDNA, antibody labelling was found to be proportional to receptor density measured by the binding of the radiolabelled beta-adrenoceptor antagonist, [125I]-iodocyanopindolol. The use of Mab 72c has demonstrated the expression of the beta3-adrenoceptor in a variety of human tissues, including gall bladder, prostate and colon, where a mRNA signal had been detected previously. This study also provides the first direct demonstration of the expression of beta3-adrenoceptors in human skeletal muscle, atrium and adipose tissue.

CONCLUSION

The development of this antibody represents an important addition to the armentarium of reagents that are available to study the localisation of beta3-adrenoceptors in human tissues.

Identification, molecular cloning, expression, and characterization of a cysteinyl leukotriene receptor

The cysteinyl leukotrienes (CysLTs) have been implicated in the pathophysiology of inflammatory disorders, in particular asthma, for which the CysLT receptor antagonists pranlukast, zafirlukast, and montelukast, have been introduced recently as novel therapeutics. Here we report on the molecular cloning, expression, localization, and pharmacological characterization of a CysLT receptor (CysLTR), which was identified by ligand fishing of orphan seven-transmembrane-spanning, G protein-coupled receptors. This receptor, expressed in human embryonic kidney (HEK)-293 cells responded selectively to the individual CysLTs, LTC(4), LTD(4), or LTE(4), with a calcium mobilization response; the rank order potency was LTD(4) (EC(50) = 2.5 nM) > LTC(4) (EC(50) = 24 nM) > LTE(4) (EC(50) = 240 nM). Evidence was provided that LTE(4) is a partial agonist at this receptor. [(3)H]LTD(4) binding and LTD(4)-induced calcium mobilization in HEK-293 cells expressing the CysLT receptor were potently inhibited by the structurally distinct CysLTR antagonists pranlukast, montelukast, zafirlukast, and pobilukast; the rank order potency was pranlukast = zafirlukast > montelukast > pobilukast. LTD(4)-induced calcium mobilization in HEK-293 cells expressing the CysLT receptor was not affected by pertussis toxin, and the signal appears to be the result of the release from intracellular stores. Localization studies indicate the expression of this receptor in several tissues, including human lung, human bronchus, and human peripheral blood leukocytes. The discovery of this receptor, which has characteristics of the purported CysLT(1) receptor subtype, should assist in the elucidation of the pathophysiological roles of the CysLTs and in the identification of additional receptor subtypes.

Melanin-concentrating hormone is the cognate ligand for the orphan G-protein-coupled receptor SLC-1

The underlying causes of obesity are poorly understood but probably involve complex interactions between many neurotransmitter and neuropeptide systems involved in the regulation of food intake and energy balance. Three pieces of evidence indicate that the neuropeptide melanin-concentrating hormone (MCH) is an important component of this system. First, MCH stimulates feeding when injected directly into rat brains; second, the messenger RNA for the MCH precursor is upregulated in the hypothalamus of genetically obese mice and in fasted animals; and third, mice lacking MCH eat less and are lean. MCH antagonists might, therefore, provide a treatment for obesity. However, the development of such molecules has been hampered because the identity of the MCH receptor has been unknown until now. Here we show that the 353-amino-acid human orphan G-protein-coupled receptor SLC-1 expressed in HEK293 cells binds MCH with sub-nanomolar affinity, and is stimulated by MCH to mobilize intracellular Ca2+ and reduce forskolin-elevated cyclic AMP levels. We also show that SLC-1 messenger RNA and protein is expressed in the ventromedial and dorsomedial nuclei of the hypothalamus, consistent with a role for SLC-1 in mediating the effects of MCH on feeding.

DNA microarrays of the complex human cytomegalovirus genome: profiling kinetic class with drug sensitivity of viral gene expression

We describe, for the first time, the generation of a viral DNA chip for simultaneous expression measurements of nearly all known open reading frames (ORFs) in the largest member of the herpesvirus family, human cytomegalovirus (HCMV). In this study, an HCMV chip was fabricated and used to characterize the temporal class of viral gene expression. The viral chip is composed of microarrays of viral DNA prepared by robotic deposition of oligonucleotides on glass for ORFs in the HCMV genome. Viral gene expression was monitored by hybridization to the oligonucleotide microarrays with fluorescently labelled cDNAs prepared from mock-infected or infected human foreskin fibroblast cells. By using cycloheximide and ganciclovir to block de novo viral protein synthesis and viral DNA replication, respectively, the kinetic classes of array elements were classified. The expression profiles of known ORFs and many previously uncharacterized ORFs provided a temporal map of immediate-early (alpha), early (beta), early-late (gamma1), and late (gamma2) genes in the entire genome of HCMV. Sequence compositional analysis of the 5' noncoding DNA sequences of the temporal classes, performed by using algorithms that automatically search for defined and recurring motifs in unaligned sequences, indicated the presence of potential regulatory motifs for beta, gamma1, and gamma2 genes. In summary, these fabricated microarrays of viral DNA allow rapid and parallel analysis of gene expression at the whole viral genome level. The viral chip approach coupled with global biochemical and genetic strategies should greatly speed the functional analysis of established as well as newly discovered large viral genomes.

The relation between transaortic pressure difference and flow during dobutamine stress echocardiography in patients with aortic stenosis

OBJECTIVE

To investigate the relation between transaortic pressure difference and flow in patients with aortic stenosis.

METHODS

50 asymptomatic patients with all grades of aortic stenosis were studied using dobutamine stress echocardiography. Individual plots of mean pressure drop against flow were drawn. Comparisons were made between grades of aortic stenosis as defined by the continuity equation.

RESULTS

A significant linear relation between pressure difference and flow was found in 34 patients (68%). There was a significant curvilinear relation in four (8%), while no significant regression line could be fitted in 12 (24%). In the 34 patients with linear fits, the slopes (mean (SD)) were 0.08 (0.07) in mild, 0.10 (0.04) in moderate, and 0.22 (0.16) in severe aortic stenosis (p = 0. 0055).

CONCLUSIONS

Transaortic pressure difference can be related directly to flow in many patients with all grades of aortic stenosis. However, there are individual differences in slope and intercept suggesting that resistance calculated at rest may not always be representative. Raw pressure drop/flow plots may be an alternative method of describing valve function.

Characterization of the mouse proteasome regulator PA28b gene

The proteasome regulator PA28, which can be upregulated by IFN, is important in the modulation of proteasome activity. Since the proteasome has been implicated in the processing of the major histocompatibility complex (MHC) class I antigens, it was of interest to determine the regulatory elements of PA28 at the genomic level. Although PA28 has been found in different species, the gene layout on the chromosome was not determined. In this study, the genetic organization of mouse PA28b was characterized. Two copies of the PA28b gene, namely b1 and b2, were found by restriction fragment mapping and Southern hybridization. By fluorescence in situ hybridization, the location of the two PA28b genes was determined on chromosomes 11 and 14. PA28b1 has 11 exons, whereas PA28b2 has no introns and appears to be a nonfunctional pseudogene. The 5' promoter region of PA28b1 contains several transcriptional factor binding sites including two IFN responsive elements. The expression levels of PA28 and other gene products involved in MHC class I antigen presentation appear to be correlated in various tissues. Notably, PA28 is expressed at high levels in immunological tissues such as spleen and peripheral blood leukocytes. Taken together, PA28 seems to be co-regulated with other molecules involved in MHC class I antigen presentation.

Pulmonary response of normal human subjects to inhaled vasodilator substances

1. Inhaled vasodilators such as nitric oxide and epoprostenol (prostaglandin I2) are now widely employed as supportive therapies to improve oxygenation and reduce pulmonary vascular resistance in patients with acute and chronic pulmonary hypertension. However, few data exist concerning their effects in normal individuals. The aim of this study was to characterize the response of the pulmonary circulation in normal individuals to inhaled nitric oxide and nebulized prostaglandin I2.2.Eight healthy volunteers were exposed to inhaled nitric oxide (0, 20 and 40 p.p.m.) and nebulized prostaglandin I2 (10 microgram/ml). Changes in effective pulmonary blood flow and diffusing capacity of the lung for carbon monoxide (TLCO) were measured using respiratory mass spectrometry. Bicycle ergometry was used to increase effective pulmonary blood flow as a positive control.3. Exercise produced significant increases in both effective pulmonary blood flow and TLCO, but neither nitric oxide nor prostaglandin I2 produced significant changes in either parameter.4.No significant change in pulmonary haemodynamics was demonstrated in response to inhaled nitric oxide or nebulized prostaglandin I2, using doses known to be effective in patients with acute and chronic pulmonary hypertension. These data suggest that the normal pulmonary vascular bed is not amenable to vasodilatation by inhaled drugs. The study further suggests that the normal pulmonary vasodilatation seen on exercise is not mediated pharmacologically, but is a secondary consequence to the mechanical effects of a rise in pulmonary blood flow. This study thus supports the view that there is no resting vasoconstrictor tone in the pulmonary vascular bed.

Early postoperative echocardiographic hemodynamic performance of the On-X prosthetic heart valve: a multicenter study

BACKGROUND AND AIMS OF THE STUDY

This study aimed to investigate the early postoperative Doppler-derived hemodynamic results from the first patients receiving the On-XR prosthetic heart valve, a new bileaflet, pyrolytic carbon valve.

METHODS

Data were derived from 111 patients included in a 10-center international trial between September 1996 and December 1997.

RESULTS

The effective orifice area (EOA) for the valve, when implanted in the aortic position, ranged from 1.5 to 2.7 cm2 in 19 mm to 25 mm valves. The corresponding mean pressure gradients ranged from 11.8 to 7.6 mmHg. Mitral EOA was 2.3 cm2 for all sizes, these values being combined because the housing was identical for all mitral valves used in this study. The mitral mean gradient was 4.7 mmHg.

CONCLUSIONS

Early results of the study show the good hemodynamic performance of the On-X valve when implanted in the aortic or mitral positions.

How often do we operate too late in aortic stenosis?

The management of asymptomatic severe aortic stenosis remains controversial. Despite a good outcome in terms of mortality, the left ventricle may not recover fully after aortic valve replacement and patients may have impaired exercise ability. Routine assessment of the left ventricle is dominated by transverse systolic function to the relative neglect of long-axis and diastolic function. Long-axis dysfunction develops earlier than transverse dysfunction and may correlate with exercise ability. Reported symptoms can be unreliable and exercise testing reveals significant limitation in many apparently asymptomatic patients. Exercise testing and echocardiographic markers of early LV systolic dysfunction may help to refine the timing of surgery in patients with apparently asymptomatic severe aortic stenosis.

Effect of omeprazole in patients with chest pain and normal coronary anatomy: initial experience

Gastroesophageal reflux is frequently found in patients with chest pain despite normal coronary anatomy, but little data on the effect of specific medication exist. After performing 24 h ambulatory pH monitoring and the Bernstein test on 23 patients with normal coronary anatomy, we gave omeprazole, 40 mg nocte, for six weeks to these and to a control group of ten patients with coronary disease. Pain episodes per fortnight fell from 16.2 to 12.0 (P=0.02) in the patients with normal anatomy and from 19.6 to 17.1 (nonsignificant) in the patients with coronary disease. Improvement occurred in seven (30%) of the patients with normal coronary anatomy compared with one (10%) of those with coronary disease, while complete resolution occurred in four (17%) and none, respectively. Improvement or complete resolution were not predicted by the results of 24 h pH monitoring, although there was a trend towards the prediction of efficacy by the Bernstein test. Omeprazole shows promise as a treatment for patients with chest pain despite normal coronary anatomy and larger placebo-controlled trials should now be undertaken.

Atypical chest pain: looking beyond the heart

Chest pain is common, and tends to be overinvestigated. Patients with normal coronary anatomy have a low mortality, but remain significantly incapacitated. We discuss ways of improving the management of such patients. An early diagnosis of a non-cardiac cause of pain should be made, ideally by the general practitioner, taking account of risk factors for cardiac as well as psychological disorders, the quality of the pain, the patient's concerns and worries and the presence of stressful life events. The minimum of investigation should be performed. Cardiological referral should be considered for patients with a high a priori risk of ischaemic heart disease. Otherwise referral, if necessary, should be to a gastroenterologist, psychiatrist or clinical psychologist, as appropriate. Treatment options are medications with musculoskeletal or oesophageal activity, simple or repeated reassurance, cognitive therapy, psychiatric drugs, and respiratory retraining. We suggest that a multidisciplinary chest-pain clinic may improve the care of such patients.

Is it safe to cardiovert atrial fibrillation without anticoagulation if the transoesophageal echocardiogram is normal?

The risk of thromboembolism after unprotected DC cardioversion for chronic atrial fibrillation is 5%. The use of transoesophageal echocardiographic guidance probably reduces this risk to around 1.3%. However, after conventional courses of anticoagulation, the risk is only 0.3 to 0.8%. Until there is further information from large randomised trials, the routine use of transoesophageal echocardiography cannot be recommended. However it should be considered in acute onset atrial fibrillation of less than 2 days duration in the presence of underlying structural heart disease or in individual patients who have previously suffered an embolic event.

The use of routine duplex scanning in the assessment of varicose veins

BACKGROUND

Clinical assessment has been shown to compare poorly with results of hand-held Doppler examination or venography in the evaluation of varicose veins. Although the use of duplex scanning has been well described in the assessment of varicose veins, there are few data comparing clinical and Doppler assessment with results of duplex scans.

METHODS

A total of 188 patients were referred with varicose veins to a sole specialist vascular surgeon over a 1-year period. After clinical and Doppler assessment, all patients were referred for a duplex scan which was performed by a trained vascular technician. The results of the duplex scan were compared retrospectively with the clinical and Doppler findings.

RESULTS

A total of 315 legs were assessed over this period, with 38.7% having recurrent disease and 31.4% having trophic skin changes or ulceration. On duplex scanning, 198 legs (62.9%) had saphenofemoral junction incompetence, 61 legs (19.4%) had saphenopopliteal junction incompetence, 94 legs (29.8%) had perforator incompetence and 24 legs (7.6%) had deep venous incompetence. The respective sensitivity of clinical and Doppler assessment at these sites was 71.2, 36.1, 43.6 and 29.2%. If patients who were felt to have sole saphenofemoral junction incompetence clinically were treated by high ligation, stripping to the knee and stab avulsions, 28.9% would have had sites of reflux untreated.

CONCLUSIONS

Clinical and Doppler assessment is unreliable. Routine duplex scanning is likely to reduce recurrence by identifying sites of reflux with greater accuracy.

Dyspnoea and exercise intolerance during cardiopulmonary exercise testing in patients with univentricular heart. The effects of chronic hypoxaemia and Fontan procedure

BACKGROUND

Patients with univentricular hearts have decreased exercise tolerance and may demonstrate exertional dyspnoea. It is not known if chronic hypoxaemia exacerbates exercise intolerance and contributes to symptomatic limitation. The extent to which surgical correction of a right-to-left shunt by a Fontan-type procedure can increase exercise tolerance by reducing arterial deoxygenation is not well documented. The cardiopulmonary exercise responses and the symptomatic status in two groups of univentricular patients, those who are cyanotic and those who are acyanotic with Fontan-type circulation, were compared.

METHODS AND FINDINGS

Cardiopulmonary exercise testing was performed in 10 univentricular patients with rest or stress-induced cyanosis (age 30.5 +/- 2.3 [SE] years; 5 men) who had palliative or no surgery and eight patients (age 29.4 +/- 1.5 years; 4 men) with Fontan-type circulation. Peak oxygen consumption was comparable in both groups of univentricular patients (21.7 +/- 2.5 vs 21.0 +/- 1.9 ml.kg-1.min-1, P = 0.85) but was less than an age-matched group of 10 healthy subjects (34.7 +/- 1.9 ml.kg-1.min-1, P < 0.001 for both). Arterial oxygen saturation was 90.6% at rest in the cyanotic patients compared with 95.1% in the Fontan patients (P < 0.001) and at peak exercise, 66.2% compared with 90.5% (P < 0.001). Using a modified Borg scale (0-10), the symptoms of dyspnoea and fatigue were also assessed during exercise in the patient groups. The Borg scores for dyspnoea in the cyanotic and the corrected univentricular patients were, respectively, as follows: Stage 1: 0.5 vs 1.7; P= 0.04; Stage 2: 1.8 vs 2.3, P = 0.5; Stage 3: 3.0 vs 3.5, P = 0.7; Peak Exercise: 4.9 vs 4.8, P = 0.9. In addition, the Borg scores for fatigue were: Stage 1: 0.4 vs 1.6, P = 0.08; Stage 2: 2.0 vs 2.2, P = 0.9; Stage 3: 3.0 vs 4.3, P = 0.5; Peak Exercise: 4.9 vs 5.4, P = 0.5. The major limiting symptom at peak exercise was dyspnoea in four cyanotic patients compared with one in the Fontan group (Chi-square 0.982, P > 0.10). The arterial oxygen desaturation at peak exercise in the cyanotic patients limited by dyspnoea was not different from those limited by fatigue (67.5 +/- 10.1% vs 66.7 +/- 13.7%, P = 0.92). Exercise tolerance was also not related to the arterial oxygen saturation at peak exercise (r = 0.47, P = 0.17) in these patients.

CONCLUSIONS

Despite correction with Fontan-type surgery, the exercise tolerance and symptoms of these univentricular patients remained similar to those who were cyanosed. Cyanotic patients have adjusted to chronic hypoxaemia and it does not appear to determine the exercise tolerance or the genesis of dyspnoea in these patients. Further randomized prospective studies are required to investigate the long-term benefits of Fontan-type procedures in these patients on exercise tolerance, symptoms and prognosis.

Contribution of peripheral chemoreceptors to ventilation and the effects of their suppression on exercise tolerance in chronic heart failure

OBJECTIVES

To assess the contribution of peripheral chemoreceptors to ventilation and the effects of continuous inspired oxygen on exercise tolerance in chronic heart failure patients. The role of peripheral chemoreceptors in mediating hyperpnoea in chronic heart failure is unknown. Hyperoxia is known to suppress the peripheral chemoreceptor drive. The magnitude of decrease in ventilation with transient inhalations of oxygen thus provides a measure of the contribution of the peripheral chemoreceptors to ventilation.

SETTING

Tertiary specialist hospital.

SUBJECTS AND METHODS

Three breaths of 100% oxygen were given at rest and also during cycle ergometry at 25 W to 8 healthy controls (age 52.0 (4.7) (SEM) years) and 13 patients with chronic heart failure (age 60.5 (2.1) years (P = NS); radionuclide left ventricular ejection fraction 25.5 (4.3)%). The peripheral chemoreceptor sensitivity was also measured by assessing the ventilatory response to hypoxia using transient inhalations of pure nitrogen. Another group of 12 patients with chronic heart failure (age 65.5 (1.5) years; left ventricular ejection fraction 21.3 (3.0)%) underwent treadmill exercise testing on 2 occasions, breathing air or 100% oxygen in a randomised single-blind manner, to examine the effects of continuous inspired oxygen on exercise tolerance.

RESULTS

The reduction in ventilation with transient hyperoxia was 18.1 (2.9)% v 17.9 (2.6)% (P = NS) at rest and 20.4 (2.8)% v 21.0 (1.6)% (P = NS) during cycle ergometry, for controls and patients respectively. The hypoxic chemosensitivity was higher in patients (0.232 (0.022) v 0.572 (0.082) 1/min/%SaO2; P = 0.002). Continuous inspired oxygen increased exercise time (517 (31) v 455 (27) seconds; P = 0.003), and a trend towards a reduction in the ventilatory response to exercise, characterised by the regression slope relating ventilation to carbon dioxide output, was evident (31.27 (2.60) v 34.19 (2.35); P = 0.08).

CONCLUSIONS

Despite an increased peripheral chemoreceptor sensitivity, the proportionate contribution of peripheral chemoreceptors to ventilation remained similar in heart failure patients (about 20%). This suggests that the peripheral chemoreceptors are not the main mediator of increased ventilation and there are other non-peripheral chemoreceptor-mediated mechanisms involved. Hyperoxia reduced ventilation at rest and during cycle ergometry. The increase in exercise duration with continuous inspired oxygen that was associated with a reduction in exercise ventilatory response suggests that suppression of the peripheral chemoreceptors may improve exercise tolerance; the effects of possible reduced skeletal muscle anaerobiosis cannot be excluded, however.

Mild traumatic brain injuries in low-risk trauma patients

BACKGROUND

Moderate or severe traumatic brain injury (TBI) resulting from cranial trauma is usually easily recognizable. Mild TBI (MTBI), however, may escape detection at presentation because of delayed symptoms and the absence of radiographic abnormalities. Despite its subtle or delayed presentation, the spectrum of symptoms often experienced after MTBI, collectively referred to as "postconcussive syndrome," may cause serious psychosocial dysfunction.

METHODS/RESULTS

To assess the sensitivity of emergency department screening for MTBI, a prospective follow-up study was conducted on a group of patients (N = 129) who had been evaluated at a regional trauma center after blunt trauma. None had symptoms or signs of TBI at presentation, nor any history of direct cranial trauma. All were discharged to home from the emergency department without a diagnosis of TBI. At 1 month after injury, 41 of 129 (32%) patients described an increase in symptoms consistent with MTBI. The most common symptoms were insomnia (62%), headaches (58%), irritability (56%) and fatigue (56%). At 2 months, most symptoms had decreased significantly, and none had increased in severity. Despite improvement in their symptoms over that time period, 11% of those with persistent symptoms remained unable to resume their premorbid daily activities.

CONCLUSIONS

These data, obtained from a population of patients considered to be at extremely low risk for TBI, indicate that MTBI occurs more often among blunt trauma patients than is commonly appreciated, even in busy trauma centers. Because early recognition of MTBI may expedite referral of these patients for appropriate outpatient follow-up care, thereby avoiding potentially serious social and financial repercussions, emergency department personnel should have a high index of suspicion for MTBI in any patient sustaining blunt systemic trauma. Current measures that screen for MTBI appear to be inadequate; follow-up protocols may prove to be more sensitive screening tools.

Cloning differentially expressed mRNAs

Differential gene expression occurs in the process of development, maintenance, injury, and death of unicellular as well as complex organisms. Differentially expressed genes are usually identified by comparing steady-state mRNA concentrations. Electronic subtraction (ES), subtractive hybridization (SH), and differential display (DD) are methods commonly used for this purpose. A rigorous examination has been lacking and therefore quantitative aspects of these methods remain speculative. We compare these methods by identifying a total of 58 unique differentially expressed mRNAs within the same experimental system (HeLa cells treated with interferon-gamma). ES yields digital, reusable data that quantitated steady-state mRNA concentrations but only identified abundant mRNAs (seven were identified), which represent a small fraction of the total number of differentially expressed mRNAs. SH and DD identified abundant and rare mRNAs (33 and 23 unique mRNAs respectively) with redundancy. The redundancy is mRNA abundance-dependent for SH and primer-dependent for DD. We conclude that DD is the method of choice because it identifies mRNAs independent of prevalence, uses small amounts of RNA, identifies increases and decreases of mRNA steady-state levels simultaneously, and has rapid output.

The potential role of external beam radiation in preventing restenosis after coronary angioplasty

The potential role of radiation in the prevention of coronary artery restenosis after angioplasty has generated much recent interest. Animal research and pilot clinical efforts have focused primarily on intraluminal methods of radiation delivery. This article reviews the experience to date with external beam radiation in restenosis prevention and suggests issues that should be considered from the standpoint of both external beam and intravascular radiotherapy. External beam radiation can certainly play an effective role in clinical studies of coronary artery restenosis, and a multicenter randomized trial of external beam radiation after coronary angioplasty has been initiated.

Echocardiography and the small aortic root

Two-dimensional echocardiography gives an estimate of the diameter of the annulus or sinotubular junction accurate to one millimeter. The diameter of the aortic annulus is related to body surface area or height, while the sinotubular junction is related additionally to age with a small effect from blood pressure and gender. A small aortic root may be defined theoretically as an annulus or sinotubular junction smaller than 1.0 cm/m2. If the aorta and replacement valve are considered as a unit, the effective area should be no less than 1.2 cm2/m2. The first gives an over-exclusive, the second an over-inclusive definition of prosthesis-patient mismatch. However, attention to hemodynamic or anatomic parameters alone may be biologically simplistic. We should probably incorporate an assessment of exercise ability, morbidity, mortality, LVH and measures of dynamic left ventricular diastolic and systolic function in the definition of patient-prosthesis mismatch.

Is pressure recovery an important cause of "Doppler aortic stenosis" with no gradient at cardiac catheterisation?

Images

Microalbuminuria as a marker of silent myocardial ischaemia in IDDM patients

Insulin-dependent diabetic (IDDM) subjects with microalbuminuria have an increased long-term risk of overt cardiovascular disease; however, the early exposure to cardiovascular risk factors may increase their predisposition to current silent myocardial ischaemia. The frequency of silent myocardial ischaemia detected by stress echocardiography and electrocardiography was significantly greater in 32 asymptomatic IDDM patients with microalbuminuria compared to 32 normoalbuminuric IDDM patients (25% [n = 8] vs 6.3% [n = 2]; p = 0.03, odds ratio [95% CI] 6.3 [1.2, 37.8]). Elective coronary artery bypass grafting was required in 1 patient with microalbuminuria and silent myocardial disease. Microalbuminuria and poorer autonomic function were independently associated with silent myocardial ischaemia in multivariate analysis (p = 0.03 and p = 0.02, respectively). Screening for silent myocardial ischaemia using these non-invasive tests may be warranted in microalbuminuric IDDM which patients could be of considerable clinical importance.