What is your diagnosis? Transverse subchondral bone fragments resulting from a fracture and dislocation of the proximal metaphyses of the third and fourth metatarsal bones.
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Animals↗
Biomedical subjects
D L Jones
Publications and source records attributed to D L Jones.
Biphasic versus sequential pulse defibrillation: a direct comparison in pigs.
It has recently been demonstrated that both biphasic and sequential pulse defibrillation shocks are superior to monophasic defibrillation shocks in animals and humans. There is little information directly comparing these two waveforms when pulse characteristics, subject, and total electrode surface area are kept constant. Pigs were randomized in a cross-over design for triplicate determinations of defibrillation threshold using biphasic and sequential pulse shocks and both large and small epicardial electrodes. Anesthetized pigs weighing 18 to 28 kg had sets of defibrillating electrodes (TX-7) with total surface areas of 13 cm2 (group 1, n = 16) and 26 cm2 (group 2, n = 16), respectively, attached to the heart. Leading edge delivered voltage, current, and energy were significantly lower with sequential pulse shocks than with biphasic shocks for both electrode sets (delivered energy means +/- standard error of the mean: 13.3 +/- 1.6 versus 22.4 +/- 3.0 joules, and 9.9 +/- 1.5 versus 14.2 +/- 1.6 joules, respectively). In addition, six of the pigs could not be defibrillated with 900 stored V using biphasic shocks, although all pigs were defibrillated with less than 800 stored V using sequential pulse defibrillation. We conclude that sequential pulse defibrillation using three defibrillating electrodes provides an important current delivery system not matched by biphasic shocks using two electrodes when subject, waveform characteristics, and total electrode surface area are kept constant.
Animals↗
Effects of acute and prolonged administration of propafenone on internal defibrillation in the pig.
Some antiarrhythmic sodium channel blocking drugs have been found to increase the energy necessary for internal defibrillation. Propafenone is a new drug that has been shown to be efficacious in the therapy of supraventricular and ventricular arrhythmias, and is of potential use in patients with defibrillators. The effects of short-term and prolonged propafenone administration on the internal defibrillation threshold (DFT) were determined in 43 pigs randomized to one of four groups: saline infusion (n = 10); propafenone infusion (n = 10); placebo administration for 8 days (n = 10); or propafenone administration for 8 days (n = 13). Two mesh electrodes were sutured on the right lateral and left lateral epicardial surface and current was delivered from the right electrode to the left electrode. Triplicate DFTs were obtained before and at 40 and 80 minutes after infusion of drug or placebo. In pigs receiving long-term administration, after baseline DFTs were obtained the electrodes were removed and the chest was closed. Following 8 days of drug or placebo administration, DFTs were redetermined. No changes were observed in the short- or long-term control groups. DFTs were lower after propafenone administration: either short-term infusion (20 +/- 6.2 joules at baseline; 15.6 +/- 5 joules at 40 minutes, p less than 0.05; 10.2 +/- 6 joules at 80 minutes, p less than 0.001) or long-term administration (17.8 +/- 2.6 joules at baseline versus 12 +/- 3.2 joules on drug, p less than 0.002). Decreased ventricular cycle lengths were found with acute administration of propafenone. Three pigs died during long-term administration of propafenone.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
Advanced time-frequency methods for signal-averaged ECG analysis.
Frequency-domain techniques have been extensively investigated for the analysis of high-resolution electrocardiograms (ECGs), although the merit of frequency-domain analysis is still subject to controversy. Time-frequency analysis methods, which estimate the frequency content of a signal as a function of time, potentially provide even more information for improved ECG analysis. Some researchers report impressive results in predicting the outcome of electrophysiologic studies using the short-time Fourier transform (spectrogram). Other time-frequency representations, such as the Wigner distribution, short-time spectral estimators, and the wavelet transform, have also been investigated. The authors present a unified overview of time-frequency representations, showing that only four classes characterize most time-frequency representations. The authors describe the advantages and drawbacks of the various approaches and speculate on their promise for ECG analysis. Very preliminary experiments in applying some of these techniques to the prediction of the outcome of electrophysiologic studies have suggested some possible new research directions.
Electrocardiography↗
Electrophysiological assessment of human inferior alveolar nerve function.
This study describes a technique for making electrophysiological recordings from the inferior alveolar nerve of conscious human subjects. Recordings were obtained from 6 of 10 subjects, with consistent waveform latencies and amplitudes across subjects. The neurogenic origin of the responses was verified by blocking the nerve with 2% xylocaine, resulting in a loss of the waveform. The method is relatively simple, tolerated well by patients, and yields consistent electrophysiological information. Proposed refinements of the technique could result in a clinically useful method of objectively assessing the functional state of the inferior alveolar nerve following injury or surgical intervention.
Action Potentials↗
Electrophysiologic substrate associated with pacing-induced heart failure in dogs: potential value of programmed stimulation in predicting sudden death.
To investigate the possible mechanisms of sudden death and the potential role of electrophysiologic testing in congestive heart failure, this study evaluated the electrophysiologic substrate in a model of heart failure induced by rapid pacing. Seventeen mongrel dogs underwent cardiac pacing at 220 to 240 beats/min for 5 weeks (paced group) and 11 other dogs served as a sham-operated control group. Rapid pacing of the right ventricle produced clinical and hemodynamic features of congestive heart failure. Dogs in the paced group had prolonged cardiac conduction time as reflected by longer epicardial activation time (36.1 +/- 2.4 vs. 30.8 +/- 0.8 ms, p less than 0.05). The ventricular effective refractory period was significantly prolonged after the development of heart failure (141 +/- 4 vs. 177 +/- 5 ms, p less than 0.01, at a basic pacing cycle length of 300 ms), whereas no significant change was found in the control group (140 +/- 4 vs. 145 +/- 4 ms, p = NS). The prolongation of the ventricular effective refractory period correlated with an increase in left ventricular end-diastolic pressure (r = 0.55, p less than 0.001) and the ventricular effective refractory period correlated inversely with cardiac index (r = -0.49, p less than 0.025). The rest membrane potential of ventricular muscle was less negative in the paced group compared with the control group (-80.7 +/- 2.2 vs. -85.6 +/- 2.2 mV, p less than 0.05). Intracellularly recorded action potential duration of ventricular muscle was longer in the paced than in the control group (236 +/- 9.8 vs. 198.9 +/- 2.6 ms, p less than 0.01), action potential duration at 90% repolarization).(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
Prolactin and total lactogenic hormone measured by microbioassay and immunoassay in breast cancer.
Basal prolactin (PRL) and total lactogenic hormone (TLH) levels were measured using a new microbioassay (BA) and conventional immunoradiometric assay (IRMA) in patients with breast cancer and compared to an age-matched control group. No significant differences were found using the IRMA, but BA lactogenic levels were significantly elevated in breast cancer patients compared controls, leading to a markedly elevated BA/IRMA ratio for both PRL (2.7 vs 1.4, P less than 0.0001) and TLH (2.8 vs 1.4, P less than 0.0001) which was greatest for postmenopausal women. Using the mean +2 standard deviations as the upper limit of normal, there was no significant difference between breast cancer patients and controls for IRMA, but BA and BA/IRMA PRL levels were elevated in 42% and 61% of the patients, respectively. There was a weak negative correlation of BA and IRMA PRL with age for normals (r = -0.53 for both) but no correlation was evident for breast cancer patients (r = 0.06 and -0.13, respectively) implying a sustained absolute and relative bioactive hyperprolactinaemia at all ages. These results show increased lactogenic bioactivity in breast cancer and suggest that different forms of bioactive prolactin undetected by IRMA (or enhancing serum factors) are present in the sera of these patients.
Adult↗
Bioactive and immunoactive prolactin levels after TRH-stimulation in the sera of normal women.
The availability of an improved microbioassay for lactogenic hormone measurement has enabled comparison of basal and dynamic prolactin bioactivity (BA) and immunoactivity (IRMA) in normal human serum. Serum from 16 normal females aged 22-74 years was assayed and revealed a mean BA/IRMA prolactin ratio of 1.6 for basal and 1.8 for peak TRH-stimulated levels. Basal prolactin levels in postmenopausal women measured by bioassay were lower than in premenopausal women showing a relative and absolute decrease in prolactin bioactivity with age, but there was no significant difference in dynamic levels. There was also no significant difference in BA or IRMA levels following the stress of venepuncture. These findings indicate that, as previously described for basal levels, there is a good correlation between dynamic prolactin bioactivity and immunoactivity in human serum.
Adult↗
Programming of single movements in Parkinson's disease: comparison with Huntington's disease.
The preparation of individual finger movements was examined in Parkinson's disease (PD), in comparison with a similar study of Huntington's disease (HD). Motor programming was varied by increasing the amount of information available in advance of each movement. PD patients had particular difficulty when there was no cue light in advance of the movement, and when two upcoming movements were cued ahead of the current movement. Such difficulties suggest that PD patients may have difficulty in performing movements without sensory cuing, and in maintaining and organising a future sequence of movements. HD patients had been previously shown to have similar deficits. Commonalities in these once contrasted disorders probably arise from disruption of common mechanisms.
Adult↗
Effects of defibrillation shocks delivered directly over a major coronary artery.
This study investigated the influence of defibrillator shocks delivered directly over a coronary artery, independent of ventricular fibrillation, on cardiac hemodynamics. Thirty-six open chest, halothane anesthetized pigs were randomized to receive six shocks at one of 5.0, 7.5, or 10.0 joules (J). Shocks were delivered between two mesh electrodes (Medtronic TX-7) sutured onto the epicardium, one over the left anterior descending coronary artery and the second directly opposite on the posterobasal ventricular surface. Shock delivery was synchronized to the R wave of the cardiac cycle, to reduce the risk of inducing fibrillation, with a 5-minute stabilization period between successive shocks. Pressure from the left ventricle, the left anterior descending coronary artery, distal to the mesh electrode and the left circumflex (control) artery and contractility in the regions perfused by both arteries were measured. The shocks invariably produced an immediate (2-second postshock), but transient, depression in systolic pressure of the same magnitude for the left anterior descending coronary artery, circumflex artery and the left ventricle that recovered by 5-minute postshock. There was no dose dependent relationship to energy. Also there was no clear difference in myocardial wall motion between the area perfused by the left anterior descending coronary artery and that perfused by the circumflex artery. These results suggest that shocks up to 10 J delivered over an epicardial artery do not cause arterial spasm and do not compromise coronary artery blood flow.
Animals↗
Impairment in bilateral alternating movements in Parkinson's disease?
Although problems in bilateral simultaneous movements in Parkinson's disease (PD) are well known, such deficits have not been reported to be any more impaired than simultaneous movements within the same limb. This is surprising, since (a) the parallels between supplementary motor area (SMA) damage and PD are well documented and (b) the SMA seems to play a special role in bilateral motor control. Bilateral versus unilateral movements in PD were examined by using a task that compared alternating movements of fingers of the same hand with alternating movements of fingers of the opposite hands. PD patients showed particular problems in programming and transferring motor activity to fingers on the opposite side of the body, as opposed to switching motor activity between fingers on the same side of the body. These findings outline the relevance of SMA dysfunction to PD.
Aged↗
A permanent transvenous lead system for an implantable pacemaker cardioverter-defibrillator. Nonthoracotomy approach to implantation.
A transvenous lead system for implantable defibrillators would obviate a surgical thoracotomy and reduce the morbidity and mortality associated with implantation. We evaluated the clinical performance of a new nonthoracotomy lead system that included a defibrillation lead in the coronary sinus. At the time of defibrillator implantation, transvenous defibrillation leads were inserted percutaneously through the left subclavian vein into the right ventricular apex (RVA), superior vena cava (SVC), and distal coronary sinus (CS) under fluoroscopic guidance. A subcutaneous patch electrode (SQ) was also available if required. The first single- or dual-pathway electrode configuration that successfully terminated three of four ventricular fibrillation episodes using 18 J or less was implanted. Eleven men and three women aged 39-77 years (60.0 +/- 10.1 years) with left ventricular ejection fraction ranging from 16% to 63% (33.4 +/- 13.1%) were evaluated. Nine presented with ventricular tachycardia, three had ventricular fibrillation, and two had both. A totally transvenous lead system (RVA/CS/SVC) was implanted in seven patients (50%) with a mean defibrillation threshold of 15.6 +/- 2.9 J (10-18 J). Four patients received a partial transvenous lead system (RVA/CS/SQ). An effective nonthoracotomy lead system was not found in three patients; they received epicardial electrodes. After cumulative follow-up of 73 patient-months, nine patients remain alive and free of problems related to the implanted nonthoracotomy leads. One patient died of respiratory failure 3 months after defibrillator implant, and the leads from another patient were removed at 9 months because of bacterial infection. A transvenous lead system that includes a defibrillation lead in the coronary sinus is a safe, reliable, and, at least in the short term, effective nonthoracotomy approach for automatic defibrillator implantation.
Adult↗
Effect of a fluoride solution on dentinal hypersensitivity.
This two-phase experiment assessed the effects over time of a solution containing 1.09% sodium fluoride, .40% stannous fluoride, and .14% hydrogen fluoride (.717% fluoride solution, DentinBloc) on pain associated with dentinal hypersensitivity. During phase I, 30 subjects demonstrating dentinal hypersensitivity to a blast of cool air were divided into three double blind experimental groups. After baseline data were collected for all subjects, one group was instructed to apply the .717% fluoride solution twice a day. A second group was instructed to apply a gel containing .04% stannous fluoride (Gel-Kam) twice a day. A third group was instructed to apply distilled water. Each subject was assessed at 2, 4, 8, and 16 weeks utilizing the "method of limits" with a standardized, repeatable cold thermal stimulus. The results of a two factor repeated ANOVA indicated that those subjects who applied the .717% fluoride solution reported significantly less sensitivity at the 2-week period than the other groups (P < .05). In addition, those subjects whose solution contained the 0.4% stannous fluoride reported significantly less sensitivity at the 4- to 8-week periods (P < .05). Phase II of the study assessed the .717% fluoride solution on a more precise time course. These included: immediately, 15 minute, 1 day, 1 week and 2 weeks. A one factor repeated ANOVA revealed that this effect presented 15-minute post application (P < .05) and continued throughout the testing periods. It was concluded that the fully active 0.717% fluoride solution was an effective agent in the control of dentinal hypersensitivity after two 1-minute applications.
Analysis of Variance↗
Results of multidisciplinary management of bilateral cleft lip and palate at the Iowa Cleft Palate Center.
Bilateral cleft of the lip and palate is by many standards the most complex and severe form of the defect. The complexity and severity of the defect require an unusual degree of cooperation among all specialists and especially between the surgeon and the orthodontist. There are no published findings that we know about in which comprehensive data from a number of disciplines are reported for the same group of bilateral cleft patients. Fifty randomly selected patients with bilateral complete clefts were examined by the Iowa team and two orthodontists from other institutions. The evaluations revealed that a large number of patients over the age of 10 have multiple residual problems requiring further treatment. Only 23 percent of the older patients studied were judged to have had treatment completed by the surgeon, speech pathologist, and orthodontist. It is very difficult to state whether the results obtained by our team can be considered satisfactory because there are no comparable studies that have attempted to evaluate the same parameters in multidisciplinary management.
Adolescent↗
Effects of lidocaine and verapamil on defibrillation in humans.
Patients with automatic defibrillators frequently require chronic antiarrhythmic drug therapy or receive acute therapy with the onset of symptoms. The effects on energy requirements for defibrillation of lidocaine hydrochloride and verapamil hydrochloride, two commonly used antiarrhythmic agents, were examined in 20 successive patients undergoing corrective arrhythmia surgery. The minimum energy requirement for ventricular defibrillation before and 5 minutes after the administration of 150 mg of lidocaine intravenously (n = 8), or 10 minutes after 10 mg of verapamil intravenously (n = 12), were determined. Each patient was assigned to receive either verapamil or lidocaine. Three mesh coil defibrillating electrodes (Medtronic 6891, 6892) were sutured to the epicardium of the right and left ventricles. Ventricular fibrillation was induced using alternating current. After a minimum of 10 seconds of fibrillation, the minimum energy for defibrillation was established using sequential pulse defibrillation. The preselected drug was then infused and the ventricular defibrillation energy was again determined after 5 or 10 minutes circulation time. Lidocaine did not alter the minimum energy for defibrillation (3.0 +/- 1.4 J vs. 3.0 +/- 1.8 J, mean +/- SD), despite plasma levels of lidocaine that averaged 13.2 +/- 1.9 mumol/l. In contrast, verapamil significantly increased (3.9 +/- 2.2 J vs. 6.5 +/- 2.9 J) the minimum energy necessary for defibrillation. The difference in defibrillation energy was significantly correlated to the fall in systolic blood pressure induced by verapamil administration (r = 0.72). These data reinforce the necessity for determining efficacy of defibrillation when medication changes are instituted. Verapamil should be used with caution in patients with automatic defibrillators and marginal defibrillation threshold.
Adult↗
Effects of lidocaine on defibrillation threshold in the pig: evidence of anesthesia related increase.
Some antiarrhythmic drugs may influence the ability of a shock to defibrillate a patient but the effect of lidocaine on defibrillation efficacy has been controversial, suggesting multiple influencing factors. We determined the effects of three doses of lidocaine on defibrillation thresholds, using single and sequential shocks, in 36 open chest halothane-anesthetized pigs. An additional eight pigs were anesthetized with barbiturate and received the highest infusion regime of lidocaine. Shocks were delivered through three mesh electrodes sutured over the anterior right ventricle, posterior right ventricle, and lateral left ventricle for sequential pulse shocks and between a lateral right to a lateral left ventricular mesh electrode for single pulse shocks. Triplicate defibrillation thresholds (DFTs) were obtained before and after lidocaine (n = 32) or saline (n = 12) administration, either with halothane or barbiturate anesthesia. Lidocaine did not alter DFT at any dose with either the single pulse (control 17.4 +/- 3.7 joules [J], highest dose of lidocaine 13.5 +/- 1.7 J, P = NS) or sequential pulse shocks (control 7.6 +/- 0.8 J, highest dose lidocaine 6.6 +/- 0.7 J, P = NS), when halothane anesthesia was used. Similar results were obtained with lower doses. In contrast, lidocaine in pentobarbital anesthetized pigs produced a significant increase of the DFT with single (control 13.7 +/- 1.9, during lidocaine 16.6 +/- 3.1, P less than 0.01) and sequential shocks (control 11.1 +/- 2.2, during lidocaine 14.5 +/- 3.4, P less than 0.01). Interaction between barbiturates and lidocaine, and/or pH may account for the inconsistency in previous studies and must be considered for animal and clinical experiments.
Anesthesia↗
Defibrillation shocks increase myocardial pacing threshold: an intracellular microelectrode study.
Defibrillation is known to cause inability to pace the heart acutely, but the mechanism is unknown. This study used microelectrode techniques to directly evaluate the effect of defibrillation shocks on the pacing threshold and membrane potentials from superfused guinea pig papillary muscles. Failure of pacing stimuli to induce action potentials (pacing failure) followed shocks of 50-200 V/cm, with pacing failure duration correlated with shock intensity. Increasing pacing strength from one to three times diastolic threshold decreased the incidence and duration of pacing failure. Decreased extracellular calcium concentration and verapamil added to the superfusate increased the duration of pacing failure. Membrane potential depolarization occurred after shock, but pacing failure did not correlate with depolarization magnitude. We conclude that defibrillation shocks directly cause shock intensity-dependent increase of myocardial pacing threshold. The pacing threshold of the myocardium can be increased after defibrillation shock independent of hypoxia or shock-induced depolarization and may involve membrane changes in calcium handling.
Action Potentials↗
Defibrillation efficacy. Comparison of defibrillation threshold versus dose-response curve determination.
When an automatic defibrillator is implanted, it is essential to determine the efficacy of the defibrillating system accurately, while balancing the need to keep the number of fibrillation episodes to a minimum. Two methods have evolved to assess defibrillation efficacy: 1) the "defibrillation threshold," which requires few ventricular fibrillation episodes, and 2) the "dose-response curve," which requires many ventricular fibrillation episodes and relates percent success to energy. The purpose of this study was to compare these two methods directly. Twenty open-chest anesthetized pigs had triplicate defibrillation threshold determinations. To produce a dose-response curve, six shocks then were delivered at 0.5, 0.75, 1.0, 1.25, 1.5, and 2.0 times the mean defibrillation threshold, in a balanced randomized order, during separate episodes of ventricular fibrillation. The data were fitted by logistic regression, conversions of the logistic regression, and a saturable exponential and nonsaturable growth exponential. A comparison was made of the mean defibrillation threshold and the 50% point on the dose-response curve (ED50) for each model, for each animal. In addition, the reliability of each measure was assessed by comparing the coefficients of variation. There was no statistical difference between the group defibrillation threshold (6.6 +/- 0.5 J) and group ED50 values (ED50 range of the models, 5.7 +/- 1.9 to 7.0 +/- 0.9 J). However, the variability about the defibrillation threshold was less than that of the ED50 values for all mathematical models except the true logistic equation, which was virtually the same.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗