Prognosis of Acute Low-Tone Hearing Loss Without Vertigo: A Scoping Review

OBJECTIVE

Despite its relatively high prevalence, our understanding of the natural clinical course of acute low-tone hearing loss (ALHL) without vertigo remains incomplete. The purpose of this study is to summarize the findings of studies that evaluated recovery from hearing loss (HL), recurrence and/or fluctuation of HL, and progression to Meniere's Disease (MD) of patients presenting with ALHL without vertigo.

METHODS

A scoping review of the English literature was performed. On May 14, 2020 and July 6, 2022, MEDLINE, Embase, and Scopus were searched to identify articles related to the prognosis of ALHL. To be included, articles had to present outcomes that were clearly distinguishable for patients with ALHL without vertigo. Two reviewers evaluated articles for inclusion and extracted data. Disagreements were adjudicated by a third reviewer.

RESULTS

Forty-one studies were included. There was extensive heterogeneity between studies in regard to defining ALHL, treatment methods, and time of follow-up. Most of the cohorts (39 out of 40) reported partial or complete recovery of hearing in the majority (>50%) of patients, although reports of recurrence were relatively common. Progression to MD was infrequently reported. Shorter time from onset of symptoms to treatment predicted better hearing outcomes in 6 of 8 studies.

CONCLUSION

The literature suggests that although the majority of patients with ALHL experience hearing improvement, recurrence and/or fluctuation are common, and progression to MD occurs in a minority of patients. Additional trials utilizing standardized inclusion and outcome criteria are needed to determine the ideal treatment for ALHL.

LEVEL OF EVIDENCE

NA Laryngoscope, 133:2457-2469, 2023.

Delayed Luminescence in 2-Methyl-5-(penta(9-carbazolyl)phenyl)-1,3,4-oxadiazole Derivatives

2,5-Diphenyl-1,3,4-oxadiazole has been widely used as an acceptor portion of donor-acceptor fluorophores that exhibit thermally activated delayed fluorescence (TADF), but analogous 2-alkyl-5-phenyl-1,3,4-oxadiazoles have been much less widely investigated. Here the properties of carbazole-substituted 2-methyl-5-phenyl-1,3,4-oxadiazoles are compared to those of their 2,5-diphenyl analogues. The fluorescence of each of the former compounds is blue-shifted by ca. 50-100 meV relative to that in the latter, while similar estimated values of the singlet-triplet energy separation (ΔE_ST) are maintained. In particular, 2-methyl-5-(penta(9-carbazolyl)phenyl)-1,3,4-oxadiazole and 2-methyl-5-(penta(3,6-di-tert-butyl-9-carbazolyl)phenyl)-1,3,4-oxadiazole exhibit solution fluorescence maxima of 466 and 485 nm and estimated ΔE_ST values of 0.12 and 0.03 eV, respectively. In both cases the reverse intersystem crossing (RISC) rates inferred from their solution fluorescence behavior are over twice those of the corresponding 2-phenyl derivatives. Organic light-emitting diodes (OLEDs) in which the 2-methyl derivatives are used as emitters yield external quantum efficiency (EQE) values of up to 23%. OLEDs with 2-methyl-5-(penta(9-carbazolyl)phenyl)-1,3,4-oxadiazole and 2-methyl-5-(penta(3,6-di-tert-butyl-9-carbazolyl)phenyl)-1,3,4-oxadiazole emitters show reduced efficiency rolloff at high current densities relative to their 2-phenyl counterparts, the latter exhibiting an EQE of 16% at 1000 cd m^-2.

Determining the source of unusual xenon isotopes in samples

Three unusual radioactive isotopes of xenon-¹²⁵Xe, ¹²⁷Xe, and ^129mXe-have been observed during testing of a new generation radioxenon measurement system at the manufacturing facility in Knoxville, Tennessee. These are possibly the first detections of these isotopes in environmental samples collected by automated radioxenon systems. Unfortunately, the new isotopes detected by the Xenon International sampler can interfere with quantification of the radioactive xenon isotopes used to monitor for nuclear explosions. Xenon International sampling data collected during February through September 2020 were combined with an atmospheric transport model to identify the possible release location. A source-location analyses using sample counts dominated by ¹²⁵Xe strongly supports the conclusion that the release point is near (within 20 km) the sampler location. Wind patterns are not consistent with releases coming from more distant nuclear power plants. The High Flux Isotope Reactor (HFIR) and the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory are located in the region of most likely source locations. The source-location analysis cannot rule out either facility as a release location, and some of the samples may contain a combination of releases from both facilities. The source-location results using ¹²⁵Xe are not unexpected because Klingberg et al. (2013) previously published the production rate of radioactive xenon isotopes from neutron activation of stable xenon in the air at the HFIR. Up to 10¹² Bq of ¹²⁵Xe could be produced per operational day and other xenon isotopes would be produced in lesser quantities.

Electron spin resonance resolves intermediate triplet states in delayed fluorescence

Molecular organic fluorophores are currently used in organic light-emitting diodes, though non-emissive triplet excitons generated in devices incorporating conventional fluorophores limit the efficiency. This limit can be overcome in materials that have intramolecular charge-transfer excitonic states and associated small singlet-triplet energy separations; triplets can then be converted to emissive singlet excitons resulting in efficient delayed fluorescence. However, the mechanistic details of the spin interconversion have not yet been fully resolved. We report transient electron spin resonance studies that allow direct probing of the spin conversion in a series of delayed fluorescence fluorophores with varying energy gaps between local excitation and charge-transfer triplet states. The observation of distinct triplet signals, unusual in transient electron spin resonance, suggests that multiple triplet states mediate the photophysics for efficient light emission in delayed fluorescence emitters. We reveal that as the energy separation between local excitation and charge-transfer triplet states decreases, spin interconversion changes from a direct, singlet-triplet mechanism to an indirect mechanism involving intermediate states.

Reducing the risk of cerebrospinal fluid rhinorrhea following translabyrinthine surgery of the posterior fossa

Objective

To describe the procedure and results of an adapted closure and reconstruction technique for translabyrinthine surgery that focuses on identifying and managing potential pathways for CSF egress to the middle ear and Eustachian tube.

Methods

Retrospective review of a cohort of translabyrinthine acoustic neuroma cases that were reconstructed using this technique.

Results

In addition to meticulous packing of potential conduits using soft tissue, hydroxyapatite cement is used to seal opened air cell tracts prior to obliteration of the mastoid defect using adipose tissue. Early results of a small patient cohort using this technique are encouraging and there were no wound infections. There was a single case of CSF rhinorrhea associated with incomplete sealing of opened petrous apex cells, with no recurrence after appropriate implementation of the described protocol during revision surgery.

Conclusion

Proactive management of potential conduits of CSF egress including opened air cell tracts has a high likelihood of reducing rates of rhinorrhea and need for revision surgery after the translabyrinthine approach to the posterior fossa.

Host-Free Yellow-Green Organic Light-Emitting Diodes with External Quantum Efficiency over 20% Based on a Compound Exhibiting Thermally Activated Delayed Fluorescence

Thermally activated delayed fluorescent (TADF) materials are advantageous as emitters in organic light-emitting diodes (OLEDs) due to their ability to utilize all excited states formed by charge recombination for light emission, potentially leading to 100% internal quantum efficiency. As in conventional fluorescent or phosphorescent OLEDs, TADF emitters are commonly doped at a relatively low concentration in a host matrix. However, increasing evidence suggests that balanced ambipolar transport properties and small aggregation-induced fluorescence quenching allow TADF emitters to be used alone in so-called host-free OLEDs. Here, we report host-free OLEDs in which the emissive layers (EMLs) consist solely of a yellow-green-emitting TADF compound, 5,5'-(2,3,5,6-tetra(carbazol-9-yl)-1,4-phenylene)bis(2-(4-( tert-butyl)phenyl)-1,3,4-oxadiazole), TCZPBOX. Devices with this host-free EML yield a maximum external quantum efficiency (EQE) of 21%, current efficacy (CE) of 73 cd/A, and power efficacy (PE) of 79 lm/W at a luminance of 10 cd/m². At a high luminance of 10,000 cd/m², a high EQE of 13% is maintained. A maximum luminance of 120,000 cd/m² is reached at an applied voltage of 9.8 V. When TCZPBOX was doped in the host 2,6-di(carbazol-9-yl)-pyridine (PYD2) at 40 wt %, the device yielded a maximum EQE of 28%, CE of 94 cd/A, and PE of 100 lm/W at 10 cd/m².

Control of Singlet Emission Energy in a Diphenyloxadiazole Containing Fluorophore Leading To Thermally Activated Delayed Fluorescence

2-(4-(9,9-Dimethylacridin-10(9H)-yl)phenyl)-5-phenyl-1,3,4-oxadiazole has an energy difference between the lowest excited singlet and triplet states (ΔE _ST) of ca. 0.24 eV. Introduction of two electronegative fluorine atoms onto the acceptor portion of the molecule to give 2-(4-(9,9-dimethylacridin-10(9H)-yl)-3,5-difluorophenyl)-5-phenyl-1,3,4-oxadiazole lowers the energy of the singlet emission with a negligible effect on the corresponding triplet energy, leading to a donor-acceptor compound with decreased ΔE _ST of ca. 0.13 eV that displays thermally activated delayed fluorescence. Organic light-emitting diodes fabricated using the latter compound display high EQE_max of 21.9% at a luminance of 10 cd/m² and sky-blue emission, however, they suffer from a large efficiency roll-off at increased luminance.

Measurements of Argon-39 at the U20az underground nuclear explosion site

Pacific Northwest National Laboratory reports on the detection of ³⁹Ar at the location of an underground nuclear explosion on the Nevada Nuclear Security Site. The presence of ³⁹Ar was not anticipated at the outset of the experimental campaign but results from this work demonstrated that it is present, along with ³⁷Ar and ⁸⁵Kr in the subsurface at the site of an underground nuclear explosion. Our analysis showed that by using state-of-the-art technology optimized for radioargon measurements, it was difficult to distinguish ³⁹Ar from the fission product ⁸⁵Kr. Proportional counters are currently used for high-sensitivity measurement of ³⁷Ar and ³⁹Ar. Physical and chemical separation processes are used to separate argon from air or soil gas, yielding pure argon with contaminant gases reduced to the parts-per-million level or below. However, even with purification at these levels, the beta decay signature of ⁸⁵Kr can be mistaken for that of ³⁹Ar, and the presence of either isotope increases the measurement background level for the measurement of ³⁷Ar. Measured values for the ³⁹Ar measured at the site ranged from 36,000 milli- Becquerel/standard-cubic-meter-of-air (mBq/SCM) for shallow bore holes to 997,000 mBq/SCM from the rubble chimney from the underground nuclear explosion.

Source term estimation of radioxenon released from the Fukushima Dai-ichi nuclear reactors using measured air concentrations and atmospheric transport modeling

Systems designed to monitor airborne radionuclides released from underground nuclear explosions detected radioactive fallout across the northern hemisphere resulting from the Fukushima Dai-ichi Nuclear Power Plant accident in March 2011. Sampling data from multiple International Modeling System locations are combined with atmospheric transport modeling to estimate the magnitude and time sequence of releases of (133)Xe. Modeled dilution factors at five different detection locations were combined with 57 atmospheric concentration measurements of (133)Xe taken from March 18 to March 23 to estimate the source term. This analysis suggests that 92% of the 1.24 × 10(19) Bq of (133)Xe present in the three operating reactors at the time of the earthquake was released to the atmosphere over a 3 d period. An uncertainty analysis bounds the release estimates to 54-129% of available (133)Xe inventory.

Structural influences impacting the role of the 9-ylidene bond in the electronic tuning of structures built upon 9-fluorenylidene scaffolds

A structure–effect study is presented pertaining to the HOMO–LUMO tuning of compounds built upon the 9-fluorenylidene scaffold frequently incorporated as a moiety within organic-based semiconducting materials. The results represent the first reported analysis employing an ensemble of spectroscopy, electrochemistry, and crystal structure data to elucidate and compare the electronic properties of 9-fluorenones, 9-fluorenylidenes, and 9-fluorenimine derivatives. The results also provide the first spectroscopically and crystallographically measured description of exciton coupling within 9,9′-bifluorenylidenes. The 9-ylidene bond is seen to play a key role impacting the electronic properties, and an examination of the effects of substituents, conjugation, heteroatoms, and steric strain on the 9-ylidene bond in a diverse set of structures with representative structural variations relevant to the HOMO–LUMO tuning is presented. Increasing conjugation decreased the HOMO–LUMO gap (HLG), increased the HOMO energy (EHOMO), but decreased the LUMO energy (ELUMO). Substituent effects were observed to produce only slight changes that tended to decrease the HLG and increase both EHOMO and ELUMO, while heteroatom inclusion at the 9-ylidine bond tended to decrease the HLG, EHOMO, ELUMO, and the extinction coefficient. In the sterically hindered 9,9′-bifluorenylidenes, increased steric strain that promoted either an increase in the torsion angle or bond length of the 9-ylidene bond was seen to decrease the HLG via exciton coupling. These results elucidate the HOMO–LUMO tuning of systems containing a 9-fluorenylidene moiety and may assist in developing materials with specifically tuned HLGs and HOMO–LUMO levels for a variety of applications.

Non-surgical embryo transfer in cattle

Embryos collected surgically from donors superovulated with PMSG and synchronized with either prostaglandin F(2)alpha or progestagen impregnated sponges were transferred non-surgically to prostaglandin or progestagen synchronized recipients. One embryo was transferred to the uterine horn ipsilateral to the corpus luteum either through a flexible catheter introduced through a steel tube and passed to the uterine tip, or through a Cassou inseminating gun passed approximately 6 cm into the horn. Of 16 recipients receiving 5 or 6 day old embryos through the catheter (1976), 6 (38%) were palpated pregnant at 42 days and 4 (25%) subsequently calved. Of 16 recipients receiving 7 or 8 day old embryos through the straw and 16 through the catheter (1977), 10 (63%) and 3 (19%), respectively, were palpated pregnant (P<0.05) and 8 (50%) and 3 (19%), respectively, had normal embryos at slaughter 4 to 29 days after palpation (P reverse similar0.10 ). Forty 7 to 9 day old embryos were transferred through the straw in 1978. Eighteen (45%) of the recipients were palpated pregnant and 16 (40%) had normal embryos at slaughter 98 to 168 days after palpation. The success of the transfers in 1978 was affected by embryo quality [good vs poor embryos; 64% vs 22% recipients pregnant (P<0.01) and 59% vs 17% embryos surviving to slaughter (P<0.05)]. Also, in 1978, pregnancy rate was affected by the time taken to transfer the embryo with the highest rate achieved with the fastest transfers (P<0.10, b = -0.47). Injection of Indomethacin near the time of transfer, synchronization between donor and recipient onset of estrus and embryo age did not affect pregnancy rates. The pregnancy rate achieved after the transfer of good quality embryos by the straw technique was equal to that expected from surgical techniques.

New approach for measuring properties of rp-process nuclei

A new experimental approach was developed that can reduce the uncertainties in astrophysical rapid proton capture (rp) process calculations due to nuclear data. This approach utilizes neutron removal from a radioactive ion beam to populate the nuclear states of interest. Excited states were deduced by the gamma-decay spectra measured in a semiconductor Ge-detector array. In the first case studied, 33Ar, excited states were measured with uncertainties of several keV. The 2 orders of magnitude improvement in the uncertainty of the level energies resulted in a 3 orders of magnitude improvement in the uncertainty of the calculated 32Cl(p,gamma)33Ar rate that is critical to the modeling of the rp process. This approach has the potential to measure key properties of almost all interesting nuclei on the rp-process path.

Use of ultrasonography to characterize ovarian status in chicken

Much research has been conducted to investigate the effects of environmental and nutritional treatments on ovarian development in poultry. However, to investigate the ovary, the hen must be killed, and thus, lifelong egg production can only be inferred. To date, the ability to noninvasively determine ovarian status has not been available. Improvements in ultrasound technology now make it possible to observe ovarian condition in vivo, thereby allowing for repeated sampling of the same bird over an entire egg production cycle. In the current study, large yellow follicles (LYF; diameter greater than 10 mm) were characterized in broiler breeder hens using Aloka ultrasound diagnostic equipment. Ultrasound images were used to determine the number and diameter of the LYF as well as the presence of an egg in the oviduct. Immediately following ultrasonography, hens were killed and dissected to determine the number and diameter of LYF. From the ultrasound images, the number of LYF +/- 1 was predicted with 96.3% accuracy in Experiment 1 and 93.3% accuracy in Experiment 2. Diameter measurements were used to classify follicles hierarchically. Of the birds determined via dissection to have multiple hierarchies, 77.8% were identified with ultrasound. All regressing or regressed ovaries were correctly identified with ultrasound.

The gastroenterologist and his endoscope: the embodiment of technology and the necessity for a medical ethics

The purpose of this essay is to argue for the necessity of an ethics of the practice of the specialist-technologist in medicine. In the first part I sketch three stages of medical ethics, each with a particular viewpoint regarding the technology of medicine. I focus on Brody's consideration of the "physician's power" as a example of contemporary medical ethics which explicitly excludes the specialist-technologist as a locus of development of medical ethics. Next, the philosophy of Heidegger is examined to suggest an approach to the problem, and, finally, some of Levinas' contributions regarding the "other" are introduced to suggest a preliminary approach to a medical ethics of the specialist-technologist.

Transient entrainment: the evolution of a medical concept from description to prescription

Entrainment is a phenomenon that has come to have considerable utility in cardiac electro-physiology diagnosis and treatment; specifically, to identify a zone of slow conduction in a reentrant circuit, a zone hypothetically vulnerable to intervention from the application of RF energy. The observation of entrainment has gone through an evolutionary sequence in the literature, from the initial simple observations of the phenomenon to the present stage of relatively fixed criteria of identification. This article follows the evolution of the specific features of the criteria of entrainment to their current crystallization into features that are suggested to prescribe sites for attempted ablation. This examination of the evolutionary course of the development of the conception of entrainment is of interest not only to cardiac electrophysiology, but also to philosophers of science, by illustrating how scientists emphasize and develop certain observations with the ultimate aim of applying the observations for successful intervention in pathological entities.

Arterial oxygen saturation during upper gastrointestinal endoscopy in elderly patients: the role of endoscope diameter

The effect of endoscope diameter upon arterial oxygen saturation was investigated in 52 elderly patients by comparing two groups of 26 patients examined with different diameter endoscopes (PQ20 and Q10). In the group of 26 patients examined with the larger endoscope (Q10), the baseline oxygen saturation values and those during intubation were significantly higher than in the group examined with the smaller instrument (PQ20). There was no significant difference in oxygen saturation between the two groups after sedation or during the procedure as a whole. Our findings suggest that the examination of elderly patients using a standard diameter endoscope does not pose any greater risk.

Clinical and electrophysiologic features and role of catheter ablation techniques in adult patients with automatic atrioventricular junctional tachycardia

A total of 8 patients with junctional tachycardia (JT) were included for study. Patients with JT had a supraventricular arrhythmia that was initiated by a junctional complex without PR prolongation and episodes of atrioventricular (AV) dissociation. JT could not be initiated by pacing and occurred either spontaneously (3 patients) or with isoproterenol (5 patients). Tachycardia could be consistently terminated by either carotid sinus massage (1 patient), intravenous adenosine (2 patients), or critically timed ventricular premature complexes (3 patients). In 6 of the 8 other patients, tachycardia foci (atrial or ventricular) or mechanisms (AV node reentry) were found. Two patients underwent complete AV junctional ablation and 2 had termination of tachycardia without change in the AV conduction by perinodal application of radiofrequency lesions. AVJT appears to be due to abnormal automaticity and may be successfully ablated by application of radiofrequency energy to perinodal areas.

Is medicine hermeneutics all the way down?

Several recent publications have suggested that hermeneutics, the method of literary criticism, might prove to be useful in medicine. In this essay I consider this thesis with particular attention to the claim that medicine "is hermeneutics all the way down". After examining an anti-positivist critique of positivist medicine and arguing that hermeneutic interpretation involves a more radical critique of modern medicine, I examine the supposed consequences of hermeneutical universalism: relativism, skepticism and antirealism which further evaluation reveals to be only potential consequences of hermeneutics. A brief discussion of phronesis and of the possible "texts" of medicine concludes the article.

Postextrasystolic potentiation. Do we really know what it means and how to use it?

Postextrasystolic potentiation (PESP), the increase in contractility that follows an extrasystole, is an interesting phenomenon that has been known for almost 100 years. The literature on this effect is reviewed. It is found that there is significant evidence that the phenomenon is independent of muscle loading and represents a distinct property of the myocardium. Examination of the literature pertaining to the cause of the effect suggests that calcium shifts within the sarcoplasmic reticulum are responsible, although there are some conflicts with this conclusion. Regarding the utility of PESP as a diagnostic test of latent viability of ischemic myocardium, the literature review reveals contradictions and conflicts with several methodological problems of the experiments. Finally, concerning the utility of continuous PESP (paired-pacing) to augment ventricular function in the failing ventricle, the studies again are inconclusive and methodologically suspect. Conditions for the proper analysis of the PESP response are reported, and suggestions for future studies are introduced.

Should physicians be bayesian agents?

Because physicians use scientific inference for the generalizations of individual observations and the application of general knowledge to particular situations, the Bayesian probability solution to the problem of induction has been proposed and frequently utilized. Several problems with the Bayesian approach are introduced and discussed. These include: subjectivity, the favoring of a weak hypothesis, the problem of the false hypothesis, the old evidence/new theory problem and the observation that physicians are not currently Bayesians. To the complaint that the prior probability is subjective, Bayesians reply that there will be ultimate convergence, but the rebuttal to this is that there will not be uniform convergence. Secondly, since the Bayesian scheme favors a weak hypothesis, theories turn out to be a gratuitous risk. The problem with the false hypothesis comes out in the denominator of the theorem, revealing that a factor which is not a theory at all is being considered in the reasoning. On the old evidence/new theory problem old evidence cannot confirm a new theory so that the posterior probability will equal the prior probability. Finally, empiric studies have shown that current physicians are not Bayesians. But on consideration of Bayesian inference as a system of inference, it can be reasoned that physicians should be Bayesians. However, the problem of physicians' and patients' own subjectivity continue to plague this system of medical decision making.

A real-time analysis of growth cone-target cell interactions during the formation of stable contacts between hippocampal neurons in culture

Mechanisms of cell-cell recognition and structural changes of growth cones (g.c.) and target membranes during contact formation are poorly understood. To examine these issues, we obtained a high magnification, real-time record of stable contact formation in cultured cells from the hippocampal CA1 area in the newborn rat. We used differential interference contrast (DIC) optics coupled to a video microscope for periods of over 24 h of continuous time-lapse recording. Our goal was to observe the sequential changes exhibited by afferent and target cells as they form a stable contact. Understanding the process of how stable contacts are made is important because such contacts are the first step in synapse formation. Four principal observations emerged from our study: (1) The target cell was receptive to a contact on a specific patch on its surface defined by the presence of lamellae and filopodia. This specific patch (named target site) was invariably present on the target cell surface before the time the growth cone arrived. (2) Stable adhesion between filopodia on the two cells initiated events leading to cell-cell contact formation. Specifically, the remaining filopodia on the growth cone and target cell were redirected toward the adhering filopodia, and the growth cone size decreased dramatically. (3) The axonal process then grew at a significantly accelerated rate (up to 50 times its baseline growth rate). (4) In addition, a number of observations were obtained on axonal turns towards the target cell, induction of target sites, and architectural remodelling of cells after the formation of a new contact. Our findings indicate that in this neuronal system, filopodia are the means used by cells to interact at stages prior to and during contact formation. We speculate that the molecules involved in cell recognition and the machinery that initiates contact formation are embedded in the fine structure of filopodia. Finally, our results provide possible clues as to some of the stages that may be involved in synapse formation in the mammalian central nervous system.

Comparison of ionic and non-ionic contrast agents in cardiac catheterization: the effects of ventriculography and coronary arteriography on hemodynamics, electrocardiography, and serum creatinine

We compared two nonionic contrast agents (ioxaglate and iohexol) with an ionic agent (Renografin-76) on the effects of ventriculography and coronary arteriography on the hemodynamics, electrocardiography, and serum creatinine in one hundred consecutive patients. Patients were randomized to nonionic or ionic groups and were further evaluated regarding the effect of fluid loading prior to catheterization. The ionic agent more often produced subjective reactions (rash, nausea/vomiting). Following ventriculography, both ionic and non-ionic agents produced an increase in left ventricular end diastolic pressure and this effect was undetermined by fluid loading. Nonionic agents decreased aortic diastolic pressure following ventriculography and this effect was unaltered by fluid loading. In contrast, the ionic agent produced profound hemodynamic changes (drop in both systolic and diastolic pressures) following coronary arteriography and these effects were blunted by prior fluid loading. The ionic agent produced significantly greater heart rate slowing and prolongation of the QT interval than the nonionic agents, suggesting that the latter are potentially less arrhythmogenic. Comparing the two non-ionic agents, we found that both decreased aortic diastolic pressure and increased left ventricular end diastolic pressure following ventriculography. Iohexol produced greater heart rate slowing than did ioxaglate, though the increase was minor compared to the ionic agent. Neither nonionic agent appeared to significantly affect serum creatinine. In conclusion, the two nonionic agents appeared to offer significant advantages over the ionic agent in ventriculography and coronary arteriography.

Electrocardiography and postextrasystolic potentiation: utilization of the two methods to predict postrevascularization segmental myocardial function

We previously reported that postextrasystolic potentiation (PESP) is a useful predictor of changes in systolic wall function (SWF) following coronary revascularization. In the current study we analyzed ECG changes related to corresponding myocardial segments to determine their correlation with PESP and SWF. We found: (1) The PESP response in a jeopardized segment was a valid predictor of improved SWF even when Q waves, ST-segment changes, or T-wave changes were present. (2) However, when Q waves were present in two or more of the corresponding leads, positive PESP was less likely to be observed. (3) Thus Q waves in two leads predicted the least postrevascularization improvement. (4) Segments with no corresponding Q-wave postrevascularization usually improved SWF. (5) Furthermore, a continuum of responsiveness to PESP was found, ranging from T-wave changes, ST-segment changes to Q-wave changes, indicating dissociation between electrical and mechanical events. In conclusion, the ECG together with PESP provide good predictive information relative to the efficacy of revascularization. PESP is a more valuable predictive indicator. ECG alone may be of value in that the occurrence of Q waves in two or more corresponding leads predicts a low probability of improved SWF. Further studies are indicated to investigate the dissociation between electrical and mechanical events.

The cardiovascular effects of anticholinergic agents administered during halothane anaesthesia in children

The cardiovascular effects of anticholinergic agents administered during halothane anaesthesia were studied in 31 children aged 1-12 years undergoing peripheral orthopaedic surgery. Either normal saline, glycopyrrolate (10 micrograms.kg-1) or atropine (20 micrograms.kg-1) was administered in randomized double-blind fashion during the induction of anaesthesia with halothane while the electrocardiogram was continuously recorded. After induction, the children were paralyzed with atracurium, intubated, and ventilated. Anaesthesia was maintained with N2O/O2 and halothane (up to 2.5% inspired). The concentrations of expired CO2 and halothane were measured continuously using mass spectrometry. Sixty-one percent (19/31) of the children developed one or more dysrhythmias. Junctional rhythm occurred in 74% (14/19) of the children with dysrhythmias, developed early during induction (mean +/- s.d. time = 2.29 +/- 2.0 min after commencement of induction), and usually resolved before the administration of the study drug (8/14). All dysrhythmias initially occurred before or during induction and none developed during intubation, during incision, during the maintenance of anaesthesia, or after the administration of anticholinergic agents. The data suggest that: 1) a combination of factors present during halothane induction is highly dysrhythmogenic especially for junctional rhythm; 2) junctional rhythm will resolve spontaneously; 3) the administration of an anticholinergic agent during halothane induction is safe but may be unnecessary in children greater than 1 year of age; and 4) the dysrhythmogenic factors present during induction are attenuated during the maintenance of halothane anaesthesia.

Postextrasystolic potentiation: analysis of methods of induction

Studies were conducted in 15 patients with coronary artery disease to determine if the type of pacing used to induce an extrasystole had a bearing on subsequent postextrasystolic potentiation (PESP) and if the fact that these were evaluated in jeopardized or nonjeopardized portions of the ventricle altered the ability to assess PESP. Two types of pacing were used. In the first group, all beats in the test sequence (basic heart rate, extrasystole, and postextrasystole) were delivered from a programmed external pacemaker. This group was termed the "all-paced" (AP) group, and the postextrasystole was introduced before a compensatory pause could occur, so that loading conditions within the ventricle at the last regular beat and after the extrasystole were not different. In the second group, the extrasystole was coupled to the sensed intrinsic heart rate of the patient, and the postextrasystole was allowed to occur spontaneously. This group was termed the "sensed-paced" (SP) group. Despite differences in basic heart rates and postextrasystolic intervals between the two groups, comparable results were obtained with the two techniques. However, the postextrasystole in the SP group occurred much earlier than expected, probably due to intrinsic cardioacceleration during ventriculography. The net result was that loading conditions in this group before and after the extrasystole were also not different from each other. Results from the pacing techniques were not influenced by whether they were obtained from jeopardized or nonjeopardized segments.(ABSTRACT TRUNCATED AT 250 WORDS)

Postextrasystolic potentiation: regional wall motion before and after revascularization

We evaluated the augmentation of contractility which follows an extrasystole (postextrasystolic potentiation: PESP) in patients before and after coronary revascularization surgery for angina pectoris. PESP was induced by methods which result in essentially identical loading conditions of the ventricle for the beat before the extrasystole and the beat after the extrasystole. We evaluated regional ventricular function before and after revascularization in "jeopardized" segments (supplied by a coronary vessel with significant coronary disease) and "nonjeopardized" segments (supplied by a vessel without significant disease). All coronary lesions were proximal to all three anterior or all posterior segments. Those jeopardized segments with patent grafts which had augmented with PESP improved their baseline function following revascularization. Conversely, those jeopardized segments which failed to augment with PESP decreased their basic function following revascularization. Those segments in which the grafts were occluded failed to augment with PESP after attempted revascularization. Perioperative myocardial infarction resulted in a drop in ejection fraction and a failure to augment with PESP. The nonjeopardized segments responded to PESP similarly to the ischemic augmenting segments. The results of this study suggest that PESP does detect ventricular segments which will improve basic function following revascularization. Those segments which fail to augment with PESP are most likely more ischemic than the augmenting segments, will not improve, and may even decrease function following revascularization.

"Isolength" postextrasystolic potentiation as a predictor of functional restoration following surgical revascularization for myocardial ischemia

A previously developed method of programmed postextrasystolic potentiation (PESP) was assessed in eight patients with medically refractory unstable angina, as a predictor of functional restoration resulting from surgical revascularization. Prior to coronary arteriography, left ventricular segmental wall motion was determined during ventricular pacing and the first postextrasystolic beat following an extrasystole. The postextrasystole was induced at an interval calculated to occur at a time where ventricular preload was identical to the regular paced beat (isolength interval). The left ventricular wall was divided into six segments, each subscribing one area of the ventriculogram, and correction for rotation during systole was made. Of 48 segments, 21 were considered "jeopardized," due to greater than 70% reduction in cross-sectional lumen of the serving coronary arteries. Fifteen of these 21 responded to PESP, increasing their segmental area ejection fraction from 44 +/- 5 (paced "normal" beat) to 56 +/- 6 (postextrasystolic beat) (p less than 0.05). Following surgical revascularization, these segments showed an improvement in their baseline area ejection fraction from 44 +/- 6 to 58 +/- 5 (p less than 0.05). Six jeopardized segments that failed to respond to PESP prior to revascularization showed functional deterioration after revascularization. The 27 non-jeopardized segments (which were not revascularized) also showed functional improvement, suggesting improved collateral flow. This study demonstrates that isolength postextrasystolic potentiation obtained with a standardized pacing protocol may be used to predict the potential for improvement in cardiac function following surgical revascularization. Our results also show that lack of PESP predicts loss of left ventricular myocardial function following revascularization.

Sustained-release procainamide: use of serum concentrations to determine dosage

The utility of the antiarrhythmic drug procainamide (PA) is limited by the required dosage schedule (every three to four hours). A commercially available, slow release procainamide (P-SR) is recommended to be given every six hours. We compared procainamide capsules (P-Caps) given every four hours with P-SR given every six hours in a crossover study of 12 patients. Doses of P-Caps were chosen to produce a therapeutic result and serum drug concentrations within the therapeutic range. Doses of P-SR were adjusted until serum PA concentrations were similar to those when P-Caps were used. The dosage for P-Caps was 58 mg/kg/day +/- 24.6; P-SR dosage was 53 mg/kg/day +/- 15.18 (mean +/- SD) (P not statistically significant). The PA peak to trough variation for P-Caps was 2.2 micrograms/ml +/- 2.3 and for P-SR 1.5 micrograms/ml +/- 1.4 (P not significant). We conclude that P-SR given every six hours in the same daily dose as PA capsules given every four hours will provide similar therapeutic concentrations with no greater peak to trough variation.

Relationship between postextrasystolic potentiation and slow-phase force-frequency response in guinea-pig ventricular myocardium

Relationship between postextrasystolic potentiation and slow-phase force-frequency response in guinea-pig ventricular myocardium. Acta physiol. pol. 1985, 36 (2): 175-184. We investigated relationship between postextrasystolic potentiation (PESP) and a form of slow-phase force-frequency relation, namely the post-rest recovery of contractile force (CF). We found that although the degree of post-rest recovery of CF determines CF of the potentiated beats, PESP does not affect the time-course of post-rest recovery, even if it is sustained by means of paired stimulation. Moreover, PESP may be completely or almost completely inhibited by caffeine in 10 mmolar concentration, whereas post-rest recovery is not significantly affected by this drug. We conclude, that PESP and slow force-frequency relations are based on separate cellular mechanisms.

Recurrent supraventricular tachycardia induced by antitachycardia pacemaker

We report a case of sensing malfunction in which supraventricular tachycardia was repeatedly induced, then terminated appropriately, by an antitachycardia pacemaker.

Successful result from delayed streptokinase administration: subtotal thrombotic occlusion in a subsequently normal coronary artery

This report describes successful results from intracoronary streptokinase administered beginning 6 hr after onset of symptoms to a 32-year-old male with subtotal vessel occlusion by thrombus. Coronary angiography 26 days later demonstrated normal vessels. We conclude that 1) duration of symptoms beyond 3-4 hr should not preclude the use of thrombolytic therapy in evolving myocardial infarction, 2) this patient exemplifies the higher incidence of subsequently demonstrated normal coronary arteries in patients under age 35 with acute myocardial infarction; arterial spasm and platelet aggregation are the most likely causes of coronary occlusion in these patients.

Applicability of echocardiography in volume determinations in experimental animals

A method is described for the use of echocardiography in volume determinations in the experimental animal. Suitability of the technique in both acute and chronically implanted animals was tested. Stroke volumes derived from calculations based on echo data were compared with those obtained by an electromagnetic flow probe placed around the aorta. High correlation was found in both the acute (r = 0.96, P less than 0.001) and the chronic (r = 0.89, P less than 0.001) preparations. Cardiac output computed from echocardiographic data and compared with those based on either flow probe or indicator-dilution techniques also showed a high degree of correlation in both the acute (r = 0.91 and 0.95, respectively; P less than 0.001) and chronic (r = 0.98 and 0.94, respectively, P less than 0.001) preparations. It is suggested that echocardiography, because of the potential to measure many indicators of myocardial function in addition to volume, represents a significant improvement in the techniques available for basic cardiovascular experimentation.

Use of a programmable calculator for rapid, low-cost processing of echocardiographic records

A comparative study was performed to determine the accuracy of a programmable calculator with supplemental digitizer in echocardiographic analysis. Twenty separate measurements were collected per heart beat from five different dogs, taking five heart beats from each dog. The measurements were made by an echocardiographic technician (ET), echocomputer (EC), and by a programmable calculator (HP). In a triple comparison (ET-HP, ET-EC, HP-EC) there were no significant differences in the values obtained, suggesting that the programmable calculator can provide a highly accurate and rapid means of processing echocardiographic measurements, thereby providing the advantages of the echocomputer without the cost of such a device.

Postextrasystolic potentiation and contractile reserve: requirements and restrictions

These studies were conducted to examine the basic characteristics of postextrasystolic potentiation (PESP) and the relationship of loading effects to PESP. Measurements of left ventricular (LV) and aortic pressures, the rate of pressure rise, and echocardiographically determined LV dimensions were made in anesthetized open-chest dogs. The hearts were paced, and timed extrasystoles were introduced that were followed by postextrasystoles (PES). PES's were elicited after an interval equal to either a full compensatory pause or a time when the diastolic properties of the LV could not be distinguished from control (isolength). Potentiation of contraction for the PES's introduced after an isolength pause was dependent on both the heart rate and the extrasystolic interval, whereas the PES's that occurred after a full pause showed no dependence on either of these intervals. PESP elicited during the isolength period was not dependent on either preload and afterload. It is concluded that PESP depends on the combination of heart rate and extrasystolic and postextrasystolic intervals. Further, PESP may be inaccurate in assessing contractile reserve unless the heart rate and extrasystolic interval are known and the PES is introduced after an isolength pause.

Rib destruction: a neglected finding in malignant mesothelioma

Malignant mesothelioma is extensively described in the radiological literature, but the incidence and importance of rib destruction has not been emphasised. In this communication, four patients with extensive mesothelioma and contiguous rib destruction are described. They represent 12% of the collected series of 36 patients. The differential diagnosis of a pleural mass with rib destruction is discussed.

Elevated blood taurine levels in acute and evolving myocardial infarction

Blood samples obtained from 97 consecutive patients admitted to the hospital for chest pain were analyzed for taurine concentrations. The mean value of the maximum taurine concentration in whole blood from AMI patients were greater than the mean value of the maximum taurine concentration in patients without AMI. There was no difference in plasma taurine levels between AMI and non-AMI patients, indicating that a cellular component(s) of whole blood was sequestering taurine. The increased blood taurine concentrations in the AMI patients evolved over the course of 70 hr and paralleled the increase in total CK levels. Blood taurine concentrations, in general, did not rise in patients who had chest pain of unknown etiology, skeletal muscle trauma, pleuritic pain, SVT/VT plus CV, acute pericarditis, acute cholecystitis, or angina pectoris. It is concluded that blood but not plasma taurine concentrations rise after acute myocardial injury and tend to be higher the more extensive the infarction. The mechanism of the blood taurine rise is unknown, but a myocardial source is probable. Also, there is evidence that the myocardium selectively leaks taurine, and not other amino acids. Monitoring blood taurine concentration in AMI may provide useful diagnostic and prognostic information.