Evaluation of Fusion Beat Detection with a New Ventricular Automatic Capture Algorithm in ICDs

This study evaluated a newly developed automatic capture verification scheme for implantable cardioverter defibrillators (ICDs) regarding discrimination of capture, fusion, and noncapture beats, with an emphasis on fusion detection. The algorithm uses evoked response detection based on a sensing vector from right ventricular shocking coil to Can. Patients undergoing ICD implant or replacement were enrolled in this study. An external system was used for pacing and data acquisition. To provoke ventricular fusion beats, VVI patients were paced close to the rate of their intrinsic rhythm and DDD patients were paced close at their intrinsic PR interval. Surface ECG and wideband filtered intracardiac electrograms were recorded for off-line analysis. Each paced beat was independently classified visually by surface ECG and by the automatic detection algorithm. The algorithm performance was then evaluated by comparing the classification results. Twenty-seven patients (22 males, 5 females; 63.8 ± 12.5 years) were analyzed. Device and lead demographics were: 18 DDD/9 VVI; 16 dedicated bipolar, 11 integrated bipolar leads; 18 acute, 9 chronic (3.7 ± 2.0 years) leads. In total, 2064 beats were analyzed, including 1,477 fusion beats and 587 capture beats. Fusion detection sensitivity and specificity were 99.5% and 99.0%, respectively. Seven true-fusion beats (0.5%) were classified as capture and 6 capture beats (1.0%) were identified as fusions. Capture or fusion beats were never detected as non-capture beats. It is concluded that the algorithm was effective in detecting fusion beats. It could potentially be used in ICD applications that need accurate fusion detection.     

AGE AND SITE PREVALENCE OE HISTOLOGIC SUBTYPES OE BASAL CELL CARCINOMAS

Background. Basal cell carcinomas (bcc ) are the most frequently diagnosed skin cancers. The relationships between some clinical parameters, such as sex, age, and location of the tumor, and the histologic patterns play an important role as factors predictive of recurrence and treatment implications. Methods. A total of 693 patients with bcc , divided according to sex, age, and location of the tumor were studied. The histologic patterns considered were nodular, superficial, and morpheiform bcc and fibroepithelioma. The correlation between clinical and histologic parameters was analyzed. Results. All histologic patterns considered were most commonly represented in the 7th and 8th decades. There were no sex differences. A prevalence of a superficial pattern for sun-unexposed areas and of a nodular pattern for sun-exposed areas was observed. The morpheiform pattern showed no correlation with any body site. The fibroepithelioma showed an absolute prevalence for the lumbosacral region. Conclusions. Age does not seem to be a discriminant or permissive factor for a particular histologic pattern of bcc . The prevalence of some subtypes for a particular body area may be explained on the basis of local predisposing conditions affecting the histologic development of the tumor.     

Low Energy Internal Atrial Cardioversion in Atrial Fibrillation Lasting More Than a Year

The aim of this study was to evaluate the efficacy of low energy internal atrial cardioversion in restoring sinus rhythm (SR) in patients with chronic atrial fibrillation (AF) persisting > 1 year. Fifteen patients with chronic AF lasting > 1 year (from 13–48 months, mean 24 ± 13 months) were studied. R wave synchronized 3/3 ms biphasic shocks were delivered between right atrial and coronary sinus (left pulmonary artery in five patients) electrodes. Sedatives or anesthetics were administered only at the patient's request. Results: Stable SR was restored in 14 (93%)of 15 patients after shocks with a mean leading edge voltage of 377 ± 77 V (range 260–500) and a mean delivered energy of 7.3 ± 3.4 J (range 2.6–12.9). The procedure was performed without anesthesia in 6 (40%) patients. All successfully cardioverted patients were treated with flecainide, sotalol, or amiodarone. During a follow up of 7.7 ± 7.9 months (range 1–24) AF recurred in five (36%) patients. Three of five AF recurrences occurred within 3 days after conversion to SR. Conclusion: Internal low energy atrial cardioversion is highly effective in restoring SR even in patients with AF lasting > 1 year. The long-term results from the standpoint of freedom from AF recurrences, are satisfactory, although additional antiarrhythmic treatment is required, particularly in the first days after conversion.     

Intrapatient Comparison of Atrial and Ventricular Sensing, Pacing Threshold, and Impedance: Benefits with Steroid-Eluting Leads

We compared the atrial and ventricular bioelectrical effects relating to pacing threshold, pacing impedance, and pacing energy in each of 58 patients to determine the importance of pacing impedance in safe low energy stimulations. The study was conducted during 4 years of follow-up. Of the 58 patients in our study, 31 were stimulated in both chambers with steroid-eluting leads (Capsure 4503 and 4003) and 27 with platinum electrode catheters (Target Tip 4511 and 4011). The two groups were homogeneous in sex, age, cardiopathy, and reason for implant. At 6 months, the mean impedance values for the Target Tip were: 358 ± 72 Ω for the atrium and 443 ± 87 Ω for the ventricle (P < 0.00002): after 1 year, atrium = 386 ± 77 Ω, ventricle = 439 ± 42 Ω (P < 0.04); at 2 years, atrium = 409 ± 86 Ω, ventricle = 510 ± 94 Ω (P < 0.0001); at 3 years, atrium = 428 ± 81 Ω, ventricle = 494 ± 67 Ω (P < 0.02); and at 4 years, atrium = 424 ± 71 Ω and ventricle = 501 ± 69 Ω (P < 0.003). The mean impedance value (for the Capsure) was: atrium = 351 ± 43 Ω, ventricle = 431 ± 81 Ω at 6 months (P < 0.03); at 1 year, atrium = 359 ± 38 Ω, ventricle = 446 ± 83 Ω (P < 0.01); at 2 years, atrium = 304 ± 124 Ω, ventricle = 459 + 108 Ω (P <0.0003); at 3 years, atrium = 359 ± 108 Ω, ventricle = 461 ± 89 Ω (P < 0.02); and at 4 years, atrium = 419 ± 133 Ω and ventricle = 515 ± 75 Ω (P < 0.03;. In view of the chronic threshold, low energy stimulation was used at follow-up. The mean low energy stimulation values programmed for Target Tip were: atrium = 2.5 V/0.35 ms, ventricle = 2.5 V/0.30 ms; for Capsure, atrium = 2.5 V/0.25 ms, ventricle = 2.5 V/0.25 ms. The mean stimulation energy value was 31% higher in the atrium than in the ventricle with Capsure leads, and 39% higher with Target Tip. Pacing impedance was lower in the atrium than in the ventricle with both leads. Energy consumption in the atrium is significantly greater than in the ventricle with both leads, particularly with Target Tip.     

HIV-1 protease inhibitors containing a novel C2 symmetrical hydroxyalkylgem-diamino core structure

Two series of peptidomimetics containing a novel C₂ symmetrical hydroxyalkylgem-diamino core structure were prepared, from amino acid starting materials, and evaluated as inhibitors of HIV-1 protease (HIV-1 Pr). 1, 1-Diamino-3-hydroxypropane (gHse) derivatives showed weak inhibitory potency (IC₅₀> 10 μM). In the 1, 1-diamino-2-hydroxyethane (gSer) series, a compound containing P1/P1’benzyl and P2/P2’Fmoc substitueras, displayed a significant HIV-1 Pr inhibition (IC₅₀= 440 nM). © Munksgaard 1997.     

Cardiac Resynchronization Therapy:

In patients with heart failure and wide QRS complex, cardiac resynchronization therapy (CRT) is associated with improvement of symptoms and cardiac function. This study examined the effects of a 3-month period of CRT on left ventricular (LV) and right ventricular (RV) ejection fraction (EF) and on LV volumes, both at rest and during exercise. A CRT system was implanted in 15 patients with severe heart failure and wide QRS. Before implant and 3 months later, all patients underwent assessment of cardiac performance with equilibrium Tc⁹⁹ radionuclide angiography with imaging in the best septal left anterior oblique view. Exercise was performed on a bicycle ergometer. At 3 months, a significant improvement in New York Heart Association functional class was observed, and radionuclide angiography showed a significant decrease in LV volumes and a significant increase in LVEF at rest, as well as a significant increase in LVEF during exercise. The remodeling processes associated with CRT did not appear to include RV function, since RVEF did not improve, and changes in RVEF did not correlate with changes in LVEF, neither at rest nor during exercise.