ECG-synchronized cardiac MR imaging: method and evaluation

An electrocardiographic (ECG) sensing and gating device compatible with a 0.35-tesla (T) magnetic resonance (MR) imager has been developed and used to produce 802 MR images of the heart in 30 patients. The instrument consists of an isolated acquisition module, an electrically floating preamplifier, and a monitor gating module. Two spin-echo images were acquired for each of five, 0.7-cm thick, transaxial sections from the base to the apex of the heart during each ECG-synchronized imaging run. Image quality was assessed in a blind study by two investigators, on a scale from 0 to 3, as diagnostic [2-3] or nondiagnostic [0-1]. There was agreement in 91.4% of their assessments of diagnostic images (68.1% of the images studied). Resolution of heart anatomy on the MR images was adversely affected by prolonged spin-echo time delay, imaging in late diastole, image acquisition at the cardiac apex, irregular triggering, and artifacts. The synchronization of gradient pulses to the ECG at 0.35 T appears safe for patients, permits diagnostic resolution of images, allows image acquisition at distinct points during the cardiac cycle, and enables monitoring of patients during imaging.     

The development of central areolar choroidal dystrophy

Background: Central areolar choroidal dystrophy (CACD) is a hereditary macular disorder of which the development is poorly understood. Methods: One hundred and eight members of seven families with CACD underwent ophthalmological examination. If macular alterations were found or suspected, the patients underwent fluorescein angiography, electroretinography (ERG), electrooculography (EOG) and tests of colour vision and visual field. CACD was divided into four stages: I,. slight parafoveal changes of the pigment epithelium (RPE); II, RPE mottling encircling the fovea; III, additional atrophy of the choriocapillaris without central involvement; IV, as stage III with central involvement. Results: In 60 eyes of 30 patients, 8 with stage 1, 12 with stage II, 18 with stage III and 22 with stage IV CACD were found. The photopic ERG was subnormal in about half of the cases with stage II-IV Colour vision tests revealed diminished red sensitivity and pseudoprotanomaly in stages I and II and combined red-green and blue-yellow defect in stages III and IV. Parafoveal reduced sensitivity (stages I and II) and parafoveal and foveal reduced sensitivity (stages III and IV) were found in the visual field tests. Conclusion: We describe and expand the stages of development of CACD. Early recognition of patients may have a great influence on their subsequent life.Presented during the meeting of the Club Jules Gonin, Versailles, France, September 1994     

Evaluation of IBMX-enhanced ocular hypotension after adrenergic agonists in the rabbit eye

Background: 3-Isobutyl-1-methylxanthine (IBMX), a phosphodiesterase inhibitor, enhanced the reduction of intraocular pressure more after administration of norepinephrine and epinephrine than after isoproterenol. The question arises of whether or not the IBMX-induced enhancement of ocular hypotension is exclusively due to ₂-adrenoceptor/cAMP stimulation.Methods: In groups of eight rabbits the ocular hypotensive responses after selective adrenergic agonists were studied in the presence and absence of phosphodiesterase inhibition with IB-MX.Results: Pretreatment with IBMX I%, applied topically, did not enhance the ocular hypotensive responses after phenylephrine (₁), B-HT920 (₂) and dobutamine (₁). The ocular hypotensive responses induced by salbutamol (0.001–0.5%) and higher concentrations of terbutaline were significantly enhanced by IBMX. Combined treatments of terbutaline 0.01% and B-HT920 0.2%, dobutamine 3% and phenylephrine 2%, and dobutamine 3% and B-HT920 0.2% were not associated with enhanced ocular hypotensive responses in the presence of IBMX. The only combination that was associated with a significant enhancement of ocular hypotension when combined with 1% IBMX was phenylephrine 2% and terbutaline 0.01%. A subthreshold dose of phenylephrine 0.1 % further increased the enhanced ocular hypotensive responses induced by salbutamol 0.025, 0.2 and 0.5% in combination with IBMX.Conclusions: Phosphodiesterase inhibition with IBMX enhances the ocular hypotensive effect induced by catecholamines not only by ₂-adrenoceptor/CAMP stimulation, but also by simultaneous ₁-adrenoceptor stimulation.     

Results of a filtering procedure in low tension glaucoma

Twenty-six eyes of twenty patients with established low tension glaucoma, who had either a double flap Scheie filtering operation or a trabeculectomy, were followed over a period ranging from one to ten years, with a median of three years. These 26 eyes include two second eyes that served as a contralateral control eye until the visual field deteriorated. All 26 eyes showed progression of visual field defects preoperatively, while postoperatively only 2 eyes showed further progression. Of the 16 nonoperated contralateral eyes, 7 showed progression of visual field defects over the same follow-up period. Two of these 7 eyes had to be operated during the study-period. The difference in progression between the operated and the non-operated eyes was significant (P<0.01). The diltering procedure provided a reduction in IOP of 20% or more in 21 of 26 eyes. There was a significant difference in the mean intraocular pressure (IOP) between the operated and the non-operated contralateral eye of 6.8 mmHg (37%) at one year postoperatively. The diurnal variation decreased highly significantly from 4.3 to 2.1 mmHg (P<0.001). It is concluded that filtering surgery in low tension glaucoma may result not only in a significant lowering of IOP, but is also effective in slowing further deterioration of the visual fields.Supported in part by a grant from De Rotterdamse Vereniging Blindenbelangen.Presented in part by N. de Jong at the 180th Meeting of the Netherlands Ophthalmological Society, Apeldoorn, March 1986.     

Does prostacyclin mediate alpha-adrenergic induced hypotension?

We have extended our previous observations on the effect of tranylcypromine (TCP) on intraocular pressure (IOP), following topical administration of catecholamines is normal and chemically denervated rabbit eyes. In normal eyes, TCP inhibits the hypotensive phase after topical norepinephrine (nE); less after epinephrine (E); and not at all after isoproterenol. In denervated eyes, the inhibitory effect of TCP on the hypotensive phase of nE and E is enhanced. Phenoxybenzamine (PBA), but not timolol maleate or indomethacin, blocks the effect of TCP on -adrenergic induced hypotension.Prostacyclin-like activity was estimated by bioassay using ADP induced rat platelet aggregation. This activity is significantly reduced in the primary aqueous and in the iris after TCP but it is significantly increased in pooled data of aqueous samples after topical nE.We conclude that the inhibitory effect of TCP on the hypotensive phase after topical E and nE is the result of inhibition of prostacyclin synthesis and not of MAO inhibition nor blockade of -receptors. It is possible that the normal production of prostacyclin by the iris and ciliary body maintains (lower) basal levels of IOP.     

一氧化氮的脊髓作用对局麻药耐药反应的影响

目的 探讨一氧化氮（NO）在脊髓的作用与局麻药外围神经阻滞耐药的关系。方法 ①鼠随机分为3组，组1腹腔和蛛网膜下腔注射生理盐水（NS），组2接受NS腹腔和5个剂量之一的L－NAME蛛网膜下腔给药，组3接受5个测量之一的L－NAME腹腔和NS蛛网膜下腔注射。L－NAME剂量是1，10，100，1000，10000nmol(n=9)；②蛛网膜下腔注射NS，L－NAME或D－NMAE 1000nmol(n=9).③蛛网膜下腔注射NS，精氨酸25μmol跟 随L－NAME1000nmol或NS（n=9)。随后用3％氯普鲁卡因0．3ml依次3次阻滞鼠坐骨神经，用热板、触觉复位、单足跳和肌力测试记录阻滞时间。结果 L－NAME蛛网膜下腔和腹腔给药阻止局麻药耐药的作用与剂量有关，蛛网膜下腔ED50明显低于腹腔ED50比率超过20倍。D－NAME对局麻耐药无显著影响（P＞0．05），精氨酸显著增加局麻药耐药（P＜0．05）并抑制L－NAME抗耐药的作用。结论 该实验表明L－NAME通过NO脊髓受体作用抑制局麻药耐药反应的发生。