Predictive modeling of drug effects on electrocardiograms.

Whole electrocardiogram (ECG) waveform analysis is a technique for evaluating aggregate arrhythmic risks of drugs. In this paper, we propose methods for exploring changes to ECG morphology due to drug effects using Gaussian model parameters, and predict patient specific post-drug ECG based on pre-drug ECG. We evaluate the proposed methods using clinical ECG recordings from subjects under the effect of anti-arrhythmic drugs Dofetilide, Quinidine, Ranolazine, and Verapamil, from the ECGRVDQ database on PhysioNet. Paired-sample t-test p-values (>0.05) suggest the proposed method can achieve similar results when compared to expert annotated J to Tpeak and Tpeak to Tend intervals for all four drug states. We employed a leave-one-out cross validation strategy to train the prediction model and produce the results. Mean Pearson correlations between all predicted and recorded post-drug waveform morphologies for all drug states across both the vector magnitude lead and Lead II is 0.94±0.05, with p-values <0.01 for all predictions; indicating significant predictions. Parameters from ECG models with Gaussian basis can be used to calculate clinically useful information and to capture or predict changes in cardiac signals due to drug effects.

Lower limb muscle strength and physical activity in healthy individuals approaching retirement.

The purpose of this study was to examine knee extensor/flexor muscle strength and physical activity in healthy males and females approaching retirement. Peak torques of the knee extensor and knee flexor muscle groups were measured bilaterally in 95 individuals (mean age 59.4 years) using an isokinetic dynamometer. Isokinetic concentric contractions were performed at angular velocities of 1.05 and 3.14 rad x s(-1). Physical activity, including household, leisure, and sporting activities, was assessed. The results show that the average peak torques exhibited were lower than previously reported in studies using the same methodology with different populations of similar age and body size. Over one-third of the participants were sedentary, with just 13% being active enough to obtain health benefits. The poor muscle strength and low physical activity of this self selecting group of healthy working adults were surprising, and potentially a cause for concern. The combination of retirement being a potential watershed for a decrease in physical activity and the known age-related decline in physical performance indicates that some of these participants are at risk of losing their functional independence fairly early in the retirement stage. We recommend the introduction of effective health promotion interventions for individuals approaching retirement, encouraging them to become more physically active.

Referrals for movement disorder surgery: under-representation of females and reasons for refusal.

OBJECTIVE: Referral of movement disorder patients for deep brain stimulation surgery was examined to determine whether referred patients were representative of gender proportions in our population, and reasons why patients do not proceed to surgery. METHODS: Demographic information on referrals to the surgical program was retrospectively reviewed from our database and from a detailed chart review. RESULTS: Although almost equal numbers of movement disorder patients are male and female, of the 91 patients referred for surgery, only 31% were female. Sixty-one percent of referred patients did not undergo surgery. Of these, the majority were denied for medical reasons, including cognitive decline (21%), psychiatric concerns (5%) and neurological reasons (42%). CONCLUSIONS: Almost one-third of patients referred for movement disorder surgery were denied for medical reasons. This underscores the importance of evaluation of all potential patients by a multidisiplinary team to fully assess suitablity for stereotactic surgery. Interestingly, women were under-represented in those referred. In order that all appropriate patients have the opportunity to consider surgery, education of both physicians and patients, and different strategies to approach females regarding surgery may allow more patients to benefit from this treatment.

Gender differences in balance performance at the time of retirement.

BACKGROUND: Impairments in balance performance are a commonly accepted risk factor for falling in older people. Since there is a higher reported incidence of falling in women, it is of interest to test whether this correlates with poorer balance performance in women than men at the time of retirement in order to plan health promotional strategies. The purpose of this study was to investigate whether any gender differences exist in balance performance in people approaching retirement age. METHODS: Ninety-seven healthy volunteers (44 males, 53 females) planning to retire shortly were enrolled in the study (age range 50-67 years). Balance assessments during quiet standing were performed under various conditions; feet together eyes open, feet together eyes closed and single limb stance eyes open. The range of centre of pressure displacement in both the anterior-posterior and medial-lateral planes was collected for each task using a force platform. FINDINGS: For several of the balance tasks the men exhibited a statistically significant larger range of centre of pressure displacement than the women (P<0.01). However, after normalising the data for height, no gender differences were seen. Over half of the group failed to complete all three single limb stance trials on both limbs. INTERPRETATION: When the data was normalised for height, no differences were found in static balance performance between men and women of retirement age. A number of participants demonstrated balance impairments whilst performing the single limb stance likely to affect functional activities. Health promotional messages should be targeted equally at men and women.

Constructing a tissue-specific model of ventricular microstructure.

Simulations of cardiac electrical activity are generally computed in idealized or generic domains. We have developed a semi-automated technique for imaging an extended volume of cardiac ventricular tissue at a resolution of approximately 1 microm, and constructing from those images a geometric and structural model with 10 microm resolution suitable for solving the bidomain equations. This technique enables experimental modeling and computer simulation to be integrated by constructing a tissue-specific structural model in less than one week. We demonstrate the use of this procedure applied to a sample of rat ventricle.

Normalisation of gait EMGs: a re-examination.

The purpose of this study was to compare four different methods of normalising electromyograms (EMGs) recorded during normal gait. Comparisons were made between the amplitude, intra-individual variability and inter-individual variability of EMGs. Surface EMGs were recorded from the biceps femoris, semitendinosus, vastus lateralis and vastus medialis of ten males and two females while they walked on a treadmill at a self-selected speed. EMGs from the same muscles were subsequently recorded during isometric maximal voluntary contractions (MVCs) and concentric, isokinetic MVCs that were performed between 0.52 and 7.85 rad x s(-1) on a BIODEX dynamometer. EMGs were also recorded during eccentric, isokinetic MVCs between 0.52 and 2.62 rad x s(-1). Gait EMGs were then normalised at 2% intervals of the gait cycle by expressing them as a percentage of the following reference values: the mean (mean dynamic method) and the peak (peak dynamic method) EMG from the intra-individual ensemble average; the EMG from an isometric MVC (isometric MVC method); and the EMG from an isokinetic MVC that occurred with the same muscle action, length and velocity of musculotendinous unit as the gait EMGs (isokinetic MVC method). The isokinetic MVC method produced significantly greater (P<0.05) intra-individual variability compared to the other methods when it was measured using the variance ratio. Inter-individual variability of gait EMGs, again measured using the variance ratio, was also greatest when they were normalised using the isokinetic MVC method. The pattern and amplitude of EMGs normalised using the isometric MVC method and the isokinetic MVC method were very similar (root mean square difference and absolute difference both less than 3%). It was concluded that the isokinetic MVC method should not be adopted by gait researchers or clinicians as it does not reduce intra- or inter-individual variability anymore than existing normalisation methods, nor does it provide a more representative measure of muscle activation during gait than the isometric MVC method.

Effect of group therapy for breast cancer on healthcare utilization.

PURPOSE: The purpose of this study was to determine whether participation in a group psychosocial intervention by patients with breast cancer would result in an improvement in psychological measures and in reduced billings in general medical expenses. DESCRIPTION OF STUDY: Eligible women who had completed treatment for stage 0, I, or II primary breast cancer were prospectively and randomly assigned to either the intervention (n=46) or control (n=43) group. Both groups received the usual psychosocial care; however, the intervention group also participated in six weekly cognitive/behavioral psychosocial meetings. All were assessed on psychiatric symptoms, mood, depression, and coping strategies at four time periods: pre-intervention, post-intervention, 1-year follow-up, and 2-year follow-up. Alberta Healthcare billing records were obtained covering the 2-year follow-up period to determine the amount billed per person over the course of the study. RESULTS: Women in the intervention group had less depression, less overall mood disturbance, better overall quality of life, and fewer psychiatric symptoms than those in the control group, beginning immediately post-intervention and remaining so at 2 years post-intervention. Billing in the intervention group was an average of $147 less than in the control group, a 23.5% reduction. CLINICAL IMPLICATIONS: This is the first study to show that a psychosocial intervention can reduce direct healthcare billings in a sample of patients with cancer. Importantly, these findings help to justify the routine availability of such programs in cancer treatment facilities worldwide.

Multiwatt continuous-wave adaptive laser resonator.

We present, for what we believe is the first time, results of continuous-wave diode-pumping of a Nd:YVO (4) laser with an adaptive gain-grating resonator. The system is shown to produce more than a 7-W output in a TEM>(00) single longitudinal mode with a laser beam propagation parameter M(2) of <1.3 and <1.1 in the x and y axes, respectively. We demonstrate the self-adaptive abilities of the resonator by spatial correction of an intracavity aberrator for both injected and self-starting versions of the cavity.

High-phase-conjugate reflectivity (<800%) obtained by degenerate four-wave mixing in a continuous-wave diode-side-pumped Nd:YVO(4) amplifier.

High-phase-conjugate reflectivities of >800% have been achieved through degenerate four-wave mixing in a cw diode-side-pumped Nd:YVO(4) amplifier. Reflectivity curves are shown as a function of input pump-beam intensity for three values of small-signal amplifier gain, and comparison is made with a numerical simulation.

Multidisciplinary approach to management of a hereditary neurodegenerative disorder: Huntington disease.

Huntington Disease is a well known autosomal dominant inherited disease resulting in emotional problems, abnormalities of movement, and eventually dementia. It stands out as one of the most devastating illnesses, not only for its neurodegenerative progression but also for its impact on families. Care often becomes fragmented due to the person's response to symptoms and/or family breakdown. The successful interaction of health care disciplines working with Huntington Disease in our centers, namely, the family physicians, nursing, Genetics, Neurology, Psychiatry, Social Work, and Long Term Care has resulted in a comprehensive program of care for our patients and their families. This article will describe the history, structure and interaction of the multidisciplinary group. It will describe the difficulties we have overcome and offer suggestions for the implementation of similar programs for the care of people with other disorders.

Predictive testing for Huntington disease in Canada: adverse effects and unexpected results in those receiving a decreased risk.

By January 1, 1991, a total of 388 persons had enrolled in the Canadian collaborative study of predictive testing for Huntington disease (HD). Of these participants, 105 persons have been given a decreased risk result. Contrary to expectations, approximately 10% of persons with a decreased risk result have had psychological difficulties coping with their new status. Here, we describe the individual responses of 6 such persons and experimental themes emerging after following these persons for up to 2 years. Individuals who are more likely to suffer an adverse reaction to a decreased risk result include those persons who have made irreversible decisions based on the belief they would develop HD or those who had unrealistic overoptimistic expectations of the positive effects of a decreased risk result. In contrast to those receiving an increased risk result, the most vulnerable time for persons receiving a decreased risk result is between 2 and 12 months after learning the outcome. The need for assessment and counselling of participants in predictive testing programs, even when there is a decreased risk result, is emphasized.

Compliance with follow-up of patients treated for non-seminomatous testicular cancer.

Many patients with Stage 1 non-seminomas are now treated by orchidectomy and close follow-up along. Chart review indicated that a group of such patients, compared with patients treated with chemotherapy, tended to be less compliant with follow-up. A questionnaire given to a second sample of patients confirmed that surgical patients underestimated the dangers of the disease and chances of relapse, and doubted the value of follow-up.