The role of the transvenous catheter electrophysiologic study in the evaluation and management of ventricular tachyarrhythmias associated with ischemic heart disease

The transvenous-catheter electrophysiologic (EP) study has occupied a central position in the investigation and management of patients with ischemic heart disease and a propensity to ventricular tachycardia (VT) or ventricular fibrillation (VF) for more than 25 years. However, demonstration of the superiority of the implantable cardioverter defibrillator (ICD) compared to other approaches to the management of VT/VF has resulted in a decrease in the frequency of use of the EP study in these patients. Nevertheless, the EP study remains a value-added procedure for many patients in this setting. These advantages include demonstration that the clinical arrhythmia is VT/VF when the diagnosis is uncertain, identification of those patients whose VT/VF is actually the result of a supraventricular tachyarrhythmia, identification of VT mechanisms readily amenable to catheter ablation, assessment of the response of a patient's VT to attempts at pace-termination, evaluation of candidacy for ablative VT therapy, prediction of the efficacy of approaches to prevention of VT/VF episodes, risk stratification of patients who have not yet experienced a sustained episode of VT/VF, and continued enhancement of our understanding of the mechanisms and therapeutics of VT/VF. The purpose of this review is to outline our present understanding of the techniques and indications for an EP study in patients with ischemic heart disease.     

抗链球菌溶血素O及类风湿因子定量测定

目的建立胶乳增强免疫比浊法在全自动生化分析仪上定量测定血清中抗链球菌溶血素O(ASO)、类风湿因子(RF)的方法。方法用胶乳增强免疫比浊法定量测定ASO、RF,并对其重复性、准确性、线性范围、试剂稳定性加以评价。结果二种浓度ASO、RF批内CV分别为1.96%,1.06%和2.08%,1.19%;批间CV分别为3.83%,2.89%和3.18%,2.04%;线性范围分别为65U/L~520U/L,25U/L~200U/L;平均回收率分别为99.7%和101.5%;试剂在仪器2℃~8℃的条件下放置至少可用20d。结论本次实验较好的把胶乳增强免疫比浊法和全自动生化分析仪结合在一起,定量测定血清中ASO、RF的含量,特异性强、重复性好、检测灵敏度高、线性范围宽、自动化程度高、操作简便快速。     

Temperature quantification using the proton frequency shift technique: In vitro and in vivo validation in an open 0.5 tesla interventional MR scanner during RF ablation

Open magnetic resonance (MR) scanners allow MR-guided targeting of tumors, as well as temperature monitoring of radio frequency (RF) ablation. The proton frequency shift (PFS) technique, an accurate and fast imaging method for temperature quantification, was used to synthesize thermal maps after RF ablation in an open 0.5 T MR system under ex vivo and in vivo conditions. Calibration experiments with 1.5% agarose gel yielded a chemical shift factor of 0.011 +/- 0.001 ppm/ degrees C (r2 = 0.96). Three gradient echo (GRE) pulse sequences were tested for thermal mapping by comparison with fiberoptic thermometer (Luxtron Model 760) readings. Temperature uncertainty decreased from high to low bandwidths (BW): +/-5.9 degrees C at BW = 15.6 kHz, +/-1.4 degrees C at BW = 3.9 kHz, and +/-0.8 degrees C at BW = 2.5 kHz. In vitro experiments (N = 9) in the paraspinal muscle yielded a chemical shift factor of 0.008 +/- 0.001 ppm/ degrees C. Temperature uncertainty was determined as +/-2.7 degrees C (BW = 3.9 kHz, TE = 19.3 msec). The same experiments carried out in the paraspinal muscle (N = 9) of a fully anesthetized pig resulted in a temperature uncertainty of +/-4.3 degrees C (BW = 3.9 kHz, TE = 19.3 msec), which is higher than it is in vitro conditions (P < 0.15). Quantitative temperature monitoring of RF ablation is feasible in a 0.5 T open-configured MR scanner under ex vivo and in vivo conditions using the PFS technique.     

数字胃肠机升级方案的选择与特殊运用

本文介绍了数字胃肠机升级方案的选择原则和需要考虑的主要因素及方法,并阐述了升级系统在胃肠造影以外的应用。合理选择数字胃肠机升级系统方案,可以让数字成像完全满足临床诊断的需求,同时又极大地节约医院的运行成本。     

RA患者血清CK组分定量检测及其临床意义

目的:探讨RA病人血清CK组分定量检测及临床意义。方法:采用美国全自动免疫散射速率比法,对32名RA患者和30名正常人血清分析测定RF、Ig组分和CRP水平。结果:CRP和IgG-CO水平均高于正常对照组水平。结论:分析Ig和CRP水平可用于RA的病情判断及其预后判断,有十分重要实用价值。     

Hypoperfusion as a possible factor in the development of gastrointestinal complications after cardiac surgery

This study has presented the spectrum of postoperative gastrointestinal system complications after open heart surgery at the University of Washington from 1980 through 1983. The frequent necessity for operative intervention and a mortality rate of 17 percent in our study of gastrointestinal complications in patients who have undergone open heart surgery indicates the need for early diagnosis and treatment. The data suggest that bypass times approaching 100 minutes and the presence of postoperative cardiogenic shock are important risk factors in the development of such complications in elective cardiac surgery patients. An incidence of gastrointestinal complications of 8.6 percent in those undergoing repair of acute aortic dissections makes gastrointestinal complaints particularly suspicious in this subgroup.     

Quantitative single-voxel spectroscopy: the reciprocity principle for receive-only head coils

PURPOSE: To correct MR spectra for local changes in the coil sensitivity for a widely used coil setup, consisting of a transmitting body coil and a receive-only head coil. MATERIALS AND METHODS: The method relies on the reciprocity principle for the body coil and a correction factor for signal amplitudes between body coil and head coil. The correction is based either on the local flip angle dependence of the stimulated echo acquisition mode signal (TFC) or on the automatic RF calibration (RFC). Water phantoms of different volumes were used to simulate variable coil loads, and B1 field inhomogeneities were assessed by varying the voxel position. Furthermore, the correction was tested by longitudinal measurements in one volunteer. RESULTS: The correction in vitro yields a reduction of the variation coefficient of the water signal by about 77% (TFC) and 66% (RFC) for different coil loads, as well as 55% (TFC) for variable voxel positions. Slightly lower reductions were assessed for the variation coefficients of the metabolite signals in vivo. CONCLUSION: This approach adequately compensates for local changes in coil sensitivity, when acquiring MR spectra with a receive-only head coil.     

Magnetic resonance imaging in neonatal encephalopathy

Magnetic resonance imaging may provide invaluable information in the term born neonate with encephalopathy. However, both hardware and sequences may need adaptation from normal adult protocols. Sedation is often required to obtain good quality imaging, but anaesthesia is not necessary in this population. The perinatal history may predict the pattern of brain lesions, which, in turn, may be used to predict the neurodevelopmental outcome. Image interpretation is not easy and requires a full clinical history in addition to experience of both normal and abnormal neonatal brain appearances. Lesions evolve rapidly, and perinatally acquired leasions are at the most obvious 1-2 weeks from delivery. Early imaging in the first few days from presentation should always include diffusion-weighted sequences to identify early ischaemic change. Advanced techniques such as venography, angiography and perfusion-weighted imaging may be useful in certain situations, and serial imaging may help differentiate perinatal-acquired lesions from other pathologies.     

B(1) destructive interferences and spatial phase patterns at 7 T with a head transceiver array coil.

RF behavior in the human head becomes complex at ultrahigh magnetic fields. A bright center and a weak periphery are observed in images obtained with volume coils, while surface coils provide strong signal in the periphery. Intensity patterns reported with volume coils are often loosely referred to as "dielectric resonances," while modeling studies ascribe them to superposition of traveling waves greatly dampened in lossy brain tissues, raising questions regarding the usage of this term. Here we address this question experimentally, taking full advantage of a transceiver coil array that was used in volume transmit mode, multiple receiver mode, or single transmit surface coil mode. We demonstrate with an appropriately conductive sphere phantom that destructive interferences are responsible for a weak B(1) in the periphery, without a significant standing wave pattern. The relative spatial phase of receive and transmit B(1) proved remarkably similar for the different coil elements, although with opposite rotational direction. Additional simulation data closely matched our phantom results. In the human brain the phase patterns were more complex but still exhibited similarities between coil elements. Our results suggest that measuring spatial B(1) phase could help, within an MR session, to perform RF shimming in order to obtain more homogeneous B(1) in user-defined areas of the brain.     

Occupational safety: effects of workplace radiofrequencies on hearing function

BACKGROUND: The effects of radio frequency (RF) and microwave radiation on humans have been the subject of continuous investigation. Clinical investigations related to occupational RF/microwave exposure have been reported by investigators (1). Since one of the major groups occupationally exposed to RF and microwave radiation includes those working in radio broadcasting and TV transmitter stations, this study investigates whether RF affects auditory systems of people exposed to RF. METHODS: The study is carried out with people working in radio broadcasting stations and living in employee residential houses close to the broadcasting stations. All subjects in the control group were similar in age, work regime, socioeconomic status, and lack of experience in working with RF sources. Brainstem Evoked Response Audiometer (BERA) and Pure Tone Audiometry (PTA) were used to measure the effects of RF under investigation on hearing functions of the subjects. In BERA measurements, I-III, III-V and I-V interpeak latencies were evaluated. In pure tone audiometric measurements, 250 Hz, 500 Hz, 1000 Hz, 2000 Hz, 4000 Hz and 8000 Hz frequencies of hearing threshold were measured in subjects of experimental and control groups. Interpeak latencies and bone conduction hearing thresholds of subjects in the experimental group were compared with those of the control group. RESULTS: BERA results showed that I-III, I-V and III-V interpeak latencies of people occupationally exposed to RF were not higher than subjects in control groups (p>0.05). Results of BERA indicated no statistically significant differences between exposure and control subjects. In audiometric evaluation, hearing threshold of people occupationally exposed to RF were found higher than the control group subjects for frequencies of 4000 Hz and 8000 Hz in terms of bone and air conduction of right and left ear (p < 0.01). CONCLUSIONS: The results of traditional audiometer indicated that RF promotes sensorineural hearing loss and affects cochlea parts related to 4000 Hz and 8000 Hz. These findings may have immediate implications and considerations for workplace safety in order to provide an occupationally safe environment to employees working in such settings.