Clinical Evaluation of Morphology Discrimination: An Algorithm for Rhythm Discrimination in Cardioverter Defibrillators

The aim of this study was to test the new morphology discrimination diagnostic algorithm for ICDs that differentiates supraventricular tachycardias (SVTs) from VTs by analysis of ventricular depolarization complexes morphology. Twenty-five patients implanted with a St. Jude Ventritex single chamber ICD were studied during electrophysiological evaluation at predischarge and were followed for 7 +/- 4 months. Sensitivity and specificity for VT detection and overall diagnostic accuracy of the morphology discrimination algorithm were calculated on 326 detected events. At electrophysiological evaluation, the algorithm was tested during 67 episodes of right atrial pacing, during 119 episodes of RV pacing (at basal interventricular septum and RV apex) and during 27 episodes of sustained AF: specificity was 98%, sensitivity was 66%, and diagnostic accuracy was 80%. All episodes of AF were correctly diagnosed as SVT. Exclusion of detections related to pacing at the basal interventricular septum, resulted in a specificity of 98%, a sensitivity of 85%, and a diagnostic accuracy of 93%. During follow-up, evaluation of the morphology discrimination algorithm on 113 spontaneous episodes (31 VTs, 31 AF, 7 SVTs, and 44 sinus tachycardias) exhibited a specificity of 89%, a sensitivity of 100%, and a diagnostic accuracy of 92%. In conclusion, the morphology discrimination algorithm exhibits a high specificity in discriminating VTs from SVTs, although with a corresponding reduction in sensitivity. The preliminary experience on spontaneous episodes is promising. To correct for the reduction in sensitivity, it is advisable to use this algorithm in parallel with other algorithms for rhythm discrimination (sudden onset, stability) coupled with extended high rate.     

Local Activation Time Derived from Stored EGM is Associated with Failure of Antitachycardia Pacing in Patients with Implantable Defibrillator

Background : Antitachycardia pacing (ATP) is an effective treatment of ventricular tachycardia (VT). However, persistent failure of ATP in some patients is well recognized. Methods : A method of deriving the local activation time from stored intracardiac electrograms in implantable cardioverter defibrillators is described. Using a case‐control design, the local activation times were compared between patients with persistent unsuccessful ATP with comparable controls with successful ATP. Results : The local activation times during VT in patients with failed ATP were longer at 120–180 ms compared with corresponding control patients with successful ATP (60–80 ms). The local activation time expressed as a proportion of VT cycle length in patients with failed ATP compared with patients with successful ATP were 0.40 ± 0.08 versus 0.19 ± 0.08 (P = 0.012). Conclusion : A novel method of deriving local activation time is described, and delayed local activation time may explain failure of ATP in terminating VT in some patients. (PACE 2010; 549–552)     

Opioid peptides Synthesis and binding properties of dermorphin related heptapeptides

C-Terminal amino acid residues of dermorphin (H-Tyr-D-Ala-Phe-Gly-Tyr-Pro-Ser-NH₂) were replaced by N^α-methyl- or D-amino acids in order to examine the effect on opioid activity. In binding studies based on displacement of μ, Δ, and κ opioid receptor selective radiolabels from guinea pig brain membranes, the 13 new analogues showed, like dermorphin, a negligible affinity for the κ binding site. The introduction of N^α-methyl- or D-amino acid residues at position 5, 6, or 7 of dermorphin, when matched with C-terminal amide function modifications, generally produced analogues with reversed μ/δ specificity.     

Solid-phase synthesis of the native sequence of horse heart cytochrome c-(66–104)-nonatriacontapeptide and of a C-terminal carboxyamide analog selectively modified at Met-80

The peptide corresponding to the (66–104) sequence of horse heart cytochrome c and its carboxyamide analog, selectively modified at the critical Met⁸⁰ residue, have been synthesized by stepwise solid-phase methods on PAM and BHA resins respectively. The correctness of the growing peptide chain as well as the homogeneity of the final products have been monitored by several analytical methods including quantitative Edman degradation. After HF cleavage both peptides were purified by semipreparative HPLC. The overall yields were 24% for the native (66–104) and 10% for the carboxyamide analog. The homogeneity of the purified synthetic peptides have been determined by different criteria including HPLC, amino acid composition, Edman degradation, electrophoresis, and tryptic peptide mapping. The synthetic fragments have been utilized for preliminary semisynthesis experiments with the native [Hse〉⁶⁵](1–65)H heme-sequence.     

The significance of a positive cutaneous immunofluorescence test in systemic lupus erythematosus

Direct cutaneous immunofluorescence microscopical examination of uninvolved skin is an important diagnostic test in systemic lupus erythematosus. Its prognostic significance is undetermined. In twenty-four patients there was an increased incidence of leukopenia, hypocomplementaemia, and LE cells in patients with positive skin immunofluorescence. Positive cutaneous immunofluorescence of uninvolved skin was correlated with the most severe forms of lupus renal disease, membranous glomerulonephritis, and diffuse proliferative glomerulonephritis.     

INFLUENCE OF LIGHT CURING SOURCE ON MICROHARDNESS OF COMPOSITE RESINS OF DIFFERENT SHADES

Introduction:

The evolution of light curing units can be noticed by the different systems recently introduced. The technology of LED units promises longer lifetime, without heating and with production of specific light for activation of camphorquinone. However, further studies are still required to check the real curing effectiveness of these units.

Purpose:

This study evaluated the microhardness of 4 shades (B-0.5, B-1, B-2 and B-3) of composite resin Filtek Z-250 (3M ESPE) after light curing with 4 light sources, being one halogen (Ultralux – Dabi Atlante) and three LED (Ultraled – Dabi Atlante, Ultrablue – DMC and Elipar Freelight – 3M ESPE).

Methods:

192 specimens were distributed into 16 groups, and materials were inserted in a single increment in cylindrical templates measuring 4mm x 4mm and light cured as recommended by the manufacturer. Then, they were submitted to microhardness test on the top and bottom aspects of the cylinders.

Results:

The hardness values achieved were submitted to analysis of variance and to Tukey test at 5% confidence level. It was observed that microhardness of specimens varied according to the shade of the material and light sources employed. The LED appliance emitting greater light intensity provided the highest hardness values with shade B-0.5, allowing the best curing. On the other hand, appliances with low light intensity were the least effective. It was also observed that the bottom of specimens was more sensitive to changes in shade.

Conclusion:

Light intensity of LED light curing units is fundamental for their good functioning, especially when applied in resins with darker shades.     

Effect of Steroid Eluting Versus Conventional Electrodes on Propafenone Induced Rise in Chronic Ventricular Pacing Threshold

The aim of this study was to evaluate chronic ventricular pacing threshold increase after oral propafenone therapy. Eighty-three patients affected by advanced atrioventricular hJock and sick sinus syndrome were studied at least 3 months after pacemaker implantation, before and after oral propafenone therapy (450–900 mg/day based on body weight). The patients were subdivided into three groups according to the type of unipolar electrode that was implanted: group I (41 patients)Medtronic CapSure 4003, group II(30 patients)Medtronic Target Tip 4011, and group III (12 patients)Osypka Vy screw-in lead. In all cases a Medtronic unipolar pacemaker was implanted: 30 Minix, 23 Activitrax, 14 Elite, 12 Legend, and 4 Pasys. Propafenone biood level was measured in 75 patients 3–5 hours after propafenone administration. The pacing autothreshoid was measured at 0.8 V, 1.6 V, and 2.5 V by reducing puise width. At the three different outputs before and after propafenone, threshold increments were significantly lower in group I in comparison with group II and group III (propafenone ranging from < 0.001 to < 0.05). No significant difference was found in pacing impedance or in propafenone plasma concentration in the three groups. Strength-duration curves were drawn for each group at baseline and after propafenone administration. Before propafenone, in group I, the knee was markedly shifted to the left and downward as compared to the classic curve, so that the steep part was predominant; in group II and group III this shift was progressively less evident. After propafenone we found the curve shifted to the right with the flat part progressively more evident in group II and group III as compared to group I. We conclude that steroid eiuting leads cause less threshold increase than conventionol and screw-in ones after oral propafenone, thus leading to safer chronic pacing. Chronic pacing at 2.5-V amplitude and 0.6-msec width was feasible in 97% of group I patients and in 80% of group II patients, but not in group III due to an insufficient safety margin. propafenone, pacing threshold     

Low Energy Intracardiac Cardioversion of Persistent Atrial Fibrillation

The aims of the study were to verify the efficacy and safety of low energy internal Cardioversion (LEIC) in patients with persistent at rial fibrillation (AF) and to identify the factors affecting the at rial defihrillation threshold (ADT). Forty-nine patients with persistent (lasting ≥ 10 days) AF underwent LEIC. In each patient, two 6 Fr custom-made catheters with large active surface areas were positioned in the coronary sinus (cathode) and the lateral right wall (anode), respectively, for shock delivery, and a tetrapolar lead was placed in the fight ventricular apex for R wave synchronization. Truncated, biphasic (3 ms+3 ms). exponential shocks were used, beginning at 50 V and increasing in steps of 50 V until sinus rhythm had been restored. Mild sedation (diazepam 5 mg IV) was administered to 12 patients. Sinus rhythm was restored in all the subjects with mean voltage and energy levels of 352.0 ± 80.3 V and 8.2 ± 3.4 J, respectively. The ADT in patients pretreated with amiodarone (6.4 ± 1.8 J) was lower than that of patients who had not received any antiarrhythmic drugs (9.2 ± 3.7) (P = 0.04). No ventricular arrhythmias were induced by any of the atrial shocks, and no other complications were observed. During a mean follow-up of 162.9 ± 58.7 days, AF recurred in 21 (43%) patients; 71% of these occurred in the first week after Cardioversion. LEIC is effective in restoring sinus rhythm in patients with persistent AF. The technique seems to be safe and does not require general anesthesia or, in most cases, sedation. Patients pretreated with amiodarone have lower ADTs.