Electrogram width parameter analysis in implantable cardioverter defibrillators: Influence of body position and electrode configuration.

The "EGM width criterion" is a discrimination algorithm that was available in the last generation ICDs. It improved ventricular tachycardia detection by withholding inappropriate therapy deliveries in the presence of narrow QRS tachycardias. The accuracy of the algorithm depends on the optimal settings of the intracardiac EGM source, the "slew thresholds," and the "width threshold." The possible dependence of these parameters on body position may affect the detection efficacy. Whether these effects can be minimized by a proper choice of the electrode configuration used for signal analysis is still to be investigated. This study aimed to evaluate the stability of the slew threshold and width threshold obtained in the supine and orthostatic positions detected by the tip-to-ventricular coil and can-to-ventricular coil electrode configurations. Their time dependence was also evaluated at the 6-month follow-up. Fifty-eight patients who were recipients of an ICD (model Medtronic 7223cx and 7227cx) were included in the study. Changing from supine to orthostatic position caused a marked variation of slew and width thresholds (21.0 +/- 13.9 V/s and 10.1 +/- 9.6 ms, respectively) in 36% of patients with tip-to-ventricular coil and in 44% of patients with can-to-defibrillating coil (the mean slew threshold variation was in this case 17.6 +/- 15.8 V/s, while the mean width threshold variation was 18.8 +/- 21.0 ms). Width threshold variation was statistically significant (P < 0.02) with the latter electrode configuration. Slew thresholds settings changed between the 1- and 6-month follow-ups in the 75% of patients with can-to-defibrillating coil configuration and in 50% with tip-to-defibrillating coil. These time related variations were significantly larger with the tip-to-defibrillating coil configuration (P < 0.01). In conclusion, EGM width parameters may change between supine and orthostatic position and over time with tip-to-defibrillating coil configuration and can-to-defibrillating coil configuration. The former configuration was less sensitive to body position changes, but more sensitive to time related variations. These findings may be useful for optimal programming of the EGM width criterion, but if parameter programming based on these results can improve the discrimination specificity still needs to be investigated.

Four-Month Assessment of the Dentrust and Oral-B P35 Toothbrushes in Orthodontic Patients.

The efficacy and safety of two manual toothbrushes (Dentrust and the Oral-B P35) were evaluated in orthodontic patients classified by their treating orthodontist as having established gingivitis. Fifty-seven healthy adolescent subjects, who were fully bonded and banded with fixed orthodontic appliances, were randomly assigned to use one of the two toothbrushes for the duration of the four-month study. The subjects were given instructions with their new assigned toothbrush and agreed to use only these products at home, twice a day between orthodontic visits. On evaluation days at one, two and four months the patients reported to the clinic having not brushed for 12-16 hours, and were evaluated for plaque area and gingivitis in this single blind study. Gingivitis scores decreased significantly in the Dentrust group from baseline to the conclusion of the study. There was no significant statistical decline in gingivitis in the Oral-B P35 group until the four-month evaluation. Overnight plaque formation scores were similar for both groups during the study. After brushing for a timed one-minute period, both toothbrushes removed significant plaque area throughout the study. On total plaque levels, the Dentrust group was significantly lower on after-toothbrushing plaque area mean scores compared to the Oral-B P35 group at two and four months. No side effects were reported or observed during the study attributed to the use of the assigned toothbrushes.

Clinical evaluation of the Plak Trac toothbrush.

Three separate studies have been conducted to evaluate the clinical safety and efficacy of the Plak Trac mechanical toothbrush. In an exaggerated use study, volunteers used the product a minimum of five times a day for eight days. Soft tissue evaluations were conducted before and at various times after use of the Plak Trac brush throughout the study. No tissue irritation related to product use was observed or reported at any time in the study. In a thirty-day at-home use study the Plak Track brush was compared to the Colgate ADA-approved manual toothbrush. Plak Trac was consistently more effective than the Colgate brush on plaque removal, at higher statistical levels. Both brushes were effective in decreasing the gingival index during the study. In a one-time use test, Plak Trac, Interplak, and the Oral B 35 manual brush were evaluated for plaque removal efficacy. All brushes significantly reduced both smooth surface and interproximal plaque scores. On total smooth surfaces Plak Trac was significantly more effective than the Interplak brush.