Comparison of total knee arthroplasty using computer-assisted navigation versus conventional guiding systems: a prospective study.

PURPOSE: To compare knee alignments in total knee arthroplasty (TKA) using computer-assisted navigation versus conventional guiding systems. METHODS: Five men and 49 women aged 49 to 79 years underwent TKA for primary osteoarthritis of the knee with varus deformity. All valgus knees were associated with inflammatory arthritis and thus excluded. Computer-assisted navigation was used for the first 35 TKAs, whereas conventional extramedullary tibial and intramedullary femoral guiding systems were used for the next 35 TKAs. The mechanical axis, coronal tibial and femoral angles, sagittal tibial and femoral angles in the 2 groups were compared. RESULTS: Sagittal tibial and femoral angles aligned more optimally in TKAs using computer-assisted navigation. In the respective computer-assisted navigation and conventional guiding systems, 33 (94%) and 26 (74%) of the TKAs attained a postoperative mechanical axis of <3 degrees varus/valgus. CONCLUSION: Computer-assisted navigation gives a more consistent alignment correction and reduces outliers during implant positioning.

Valuing the health benefits of improving indoor air quality in residences.

Unlike commercial premises, the indoor air quality of residences is more dynamic, uncontrolled, and prone to human behavioral changes. In consequence, measuring the health benefit gains derived from improving indoor air quality in residences is more complicated. To overcome this, a human thermal comfort model was first integrated with indoor microenvironment models, and subsequently linked with appropriate concentration-response and economic data for estimating the economic benefit gains derived from improving indoor air quality in residences for an adult and an elderly person. In this study, the development of the model is illustrated by using a typical residential apartment locating at the worst air quality neighborhood in Hong Kong and the daily weather profiles between 2002 and 2006. Three types of personal intervention measures were examined in the study: (i) using air cleaner in residence, (ii) changing time spent in residence, and (iii) relocating to a better air quality neighborhood. Our results revealed that employing air cleaners with windows closed in residence throughout the entire year was the most beneficial measure as it could provide the greatest annual health benefit gains. It would give a maximum of HK$2072 in 5-year cumulative benefit gain for an adult and HK$1700 for an elderly person. Employing air cleaners with windows closed in only cool season (October through March) could give the highest marginal return per dollar spent. The benefit gains would become smaller when windows were opened to a greater extent. By contrast, relocating to a better air quality neighborhood and changing the time spent in residence did not appeal to be beneficial intervention measures.

Evaluation of health benefits for improving indoor air quality in workplace.

In contrast to a majority of reported damage-cost literature being focused on outdoor pollution, this paper describes the development of a protocol that links population exposure data with reported epidemiological concentration-response coefficients. A change in indoor particulate level is expressed as a change in total exposure levels, which is then linked with a corresponding change in ambient particulate concentrations before evaluating the associated health benefits. In this study, the development of protocol is illustrated by using a typical office building environment and daily time activity patterns of office occupants in Hong Kong. Our results indicate that some benefit gains for the owners-employers and the society would be anticipated if certain filter set configurations had been adopted. However, the amount of benefit gains for the owners-employers is shown to be increased with the average salary level of employees and the duration of their stay in offices.

Definition of predicted effective antiarrhythmic drug therapy for ventricular tachyarrhythmias by the electrophysiologic study approach: randomized comparison of patient response criteria.

OBJECTIVES: We sought to compare efficacies of therapy for ventricular tachyarrhythmias selected by programmed stimulation using two different patient response efficacy criteria: <5 versus <16 repetitive ventricular responses. BACKGROUND: Therapy selection for ventricular tachyarrhythmias by programmed stimulation requires definition of a patient response that predicts long-term efficacy. Such definitions have not been previously compared prospectively. METHODS: Patients with sustained ventricular tachyarrhythmias were randomized to therapy selection using either the <5 or <16 repetitive response criterion of predicted effective therapy. The primary end point was sudden death or recurrence of ventricular tachyarrhythmia requiring intervention. RESULTS: Predicted effective drug therapy was found for 23 (34%) of 68 patients randomized to the <5 criterion and 29 (36%) of 81 patients randomized to the <16 criterion (p = NS). Definition of therapy required 3.0 +/- 1.6 drug trials (mean +/- SD) in patients randomized to the <5 criterion and 2.9 +/- 1.8 trials in patients randomized to the <16 criterion (p = NS). Patients randomized to the <5 criterion had a lower 2-year probability of the primary end point (0.20 +/- 0.05) than did patients randomized to the <16 criterion (0.33 +/- 0.05, one-tailed p = 0.004). The advantage of the <5 criterion was also seen in subgroup analyses involving patients with and without an initial drug efficacy prediction. CONCLUSIONS: The programmed stimulation approach to the selection of antiarrhythmic therapy for ventricular tachyarrhythmias using a patient response criterion of <5 repetitive ventricular responses results in a lower probability of recurrence of ventricular tachyarrhythmia than does use of a <16 repetitive response criterion.

Comparison of 5F and 7/8F catheters for left ventricular and coronary angiography.

Fifty-two patients were randomized into two groups of 26 to the use of either 5 or 7/8F catheters for their first left heart cardiac catheterization. Clinical characteristics for the two groups were similar. 5F catheters were significantly inferior to 7/8F catheters in terms of torque control (P less than .001), ease of engaging coronary ostia (P less than .001), and quality of angiograms (P less than .05). Nine patients in the 5F group required a change to 7/8F catheters for completion of the procedure. There was no difference in procedure time or fluoroscopy time between the groups. Time to haemostasis was significantly shorter in the 5F group (P less than .01), but there was no difference between groups with respect to haematoma formation or rebleed after haemostasis. We conclude the slight advantage of 5F catheters in terms of haemostasis is outweighed by many disadvantages. Their routine use in cardiac catheterization, at least at this time, cannot be recommended.

Conversion from intravenous procainamide to oral sustained release tablets in cardiac patients.

There is as yet no established method for converting from intravenous to oral sustained release procainamide (Procan SR; Parke-Davis Canada Inc). The pharmacokinetics of simultaneous discontinuation of intravenous procainamide and administration of oral sustained release procainamide was studied in six patients with ventricular tachyarrhythmias. Patients were converted after ensuring that steady-state concentrations were achieved with intravenous procainamide. Serum procainamide levels were obtained at the time of conversion and 0.5, 1.0, 1.5, 2.0, 3.0, 4.0 and 6.0 h after conversion. The mean steady-state concentration (23.7 +/- 8.9 mumols/L) and the adjusted mean serum procainamide concentration with Procan SR (25.3 +/- 7.9 mumols/L) were not significantly different. This indicated that the serum procainamide concentration obtained with the intravenous infusion was not compromised when the patients were switched to oral therapy. Although mean percentage serum procainamide concentration fluctuation was 102.6 +/- 92.5, all patients tolerated the conversion well. Therefore, the method used in this study is an acceptable method of conversion.

Melperone: electrophysiologic and antiarrhythmic activity in humans.

Previous studies in animals and in humans have shown that melperone, a neuroleptic butyrophenone, has class III electrophysiologic activity. However, its antiarrhythmic activity has not been assessed in humans. Accordingly, the electrophysiologic and antiarrhythmic effects of melperone were assessed in 23 patients with symptomatic ventricular tachyarrhythmias. Seventeen patients had electrophysiologic testing while receiving melperone. At oral daily dosages greater than or equal to 240 mg, melperone produced significant prolongations of QT intervals (385 +/- 11 vs. 355 +/- 22 ms, p less than 0.05), ventricular effective refractory periods (263 +/- 18 vs. 243 +/- 28 ms, p less than 0.05; 260 +/- 18 vs. 235 +/- 27 ms, p less than 0.01; and 243 +/- 23 vs. 222 +/- 28 ms, p less than 0.01; at 600-, 500-, and 400-ms pacing cycle lengths, respectively) and ventricular tachycardia (VT) cycle lengths (286 +/- 46 vs. 239 +/- 70 ms, p less than 0.05). Inducible VT was suppressed entirely in one patient. In three other patients, inducible sustained VT became nonsustained. No significant negative inotropic effects were observed. The majority of patients (70%) experienced some adverse effect, the commonest of which was neurologic. In conclusion, melperone had significant class III electrophysiologic and antiarrhythmic activity in humans. Its clinical use may be limited by the high incidence of adverse effects.

Interaction between systolic and diastolic time intervals in atrial fibrillation.

To assess determinants of left ventricular filling time at rest simultaneous phonocardiograms, M mode echocardiograms, and indirect carotid pulse traces were performed on 50 patients with atrial fibrillation. Thus the effect of random variation in RR interval in the absence of atrial contraction on the inter-relation between systolic and diastolic events could be seen. Left ventricular filling time was closely related to RR interval and affected by it to a much greater extent than ejection time, so that filling time became very short when heart rate was fast. Two mechanisms were, however, identified whereby filling time was preserved: (a) prolongation of filling during the pre-ejection period of the following cycle, so that when the RR interval was less than 400 ms all of ventricular filling frequently occurred at this time; and (b) abbreviation of the QA2 interval of the succeeding beat with reduced filling, so that mitral valve opening occurred early. Changes in the duration of isovolumic contraction or relaxation time were not involved, neither could alteration in left ventricular contractile state resulting from variation in the interval between beats be shown to affect time at rest. The striking sensitivity of left ventricular filling time to rapid heart rate in atrial fibrillation suggests that it may be a major factor limiting cardiac performance. Diastolic as well as systolic events should, therefore, be taken into account when the effects of drugs or other physiological manoeuvres are studied in these patients.

Mechanisms of reduced left ventricular filling rate in coronary artery disease.

To identify mechanisms underlying slow left ventricular filling in coronary artery disease, left ventriculograms from 93 patients and 18 normal subjects were digitised frame by frame and global and regional function analysed. In 54 patients peak normalised filling rates were above the lower 95% confidence limit of normal (2 X 9s-1) and in 39 they were below. Patients with slow filling had a lower ejection fraction, a higher end systolic volume, and less overall shape index change, although a larger percentage occurred during isovolumic relaxation owing to asynchronous relaxation. Stroke volume was not significantly different. Slow outward wall motion was associated with increased cavity volume and systolic hypokinesis. Wall motion was also appreciably asynchronous, with wide spreads in the times of peak outward velocity and termination of rapid outward movement between regions. Early outward movement usually started in the anterior region, with peak velocity occurring before mitral valve opening, and significantly earlier than that in the apex or the inferior region. Ventricular oscillations occurred during filling in 23 patients. This asynchronous wall movement was unrelated to the distribution of coronary artery disease, systolic hypokinesis, or Q waves on electrocardiograms but was similar to that occurring in mitral stenosis. The main causes of slow left ventricular filling in patients with coronary artery disease appear to be (a) failure to achieve a normal low end systolic volume, with associated loss of physiological changes in left ventricular cavity shape, and (b) incoordinate wall motion during isovolumic relaxation which dissipates energy normally coupled to rapid ventricular filling. The resulting slow and asynchronous wall motion may have clinical implications especially when the time available for left ventricular filling is short.

Pachydermoperiostosis, hypertrophic gastropathy, and peptic ulcer.

Two brothers with pachydermoperiostosis, an autosomal dominant syndrome characterized by digital clubbing, periosteal new bone formation, coarse facial features with thick, furrowed, and oily skin, presented in their twenties with severe complicated duodenal ulcer disease requiring multiple operations. Their father and one paternal uncle also had pachydermoperiostosis and a past history of ulcer dyspepsia. The mother, one sister, two maternal aunts, and one other paternal uncle were healthy. Both brothers had giant hypertrophic gastritis (Ménétrier's disease). Their pentagastrin-stimulated acid output and fasting and meal-stimulated serum gastrin levels were normal, but their serum pepsinogen I and II levels were markedly elevated. The father had hypochlorhydria and a low serum pepsinogen I/II ratio, suggesting atrophic gastritis. This family study raises the possibility that pachydermoperiostosis, hypertrophic gastropathy, and peptic ulcer may be genetically related.