PROTAMINES

The synthesis of peptides containing blocks of arginyl residues is proposed through amidination of the corresponding ornithyl analogs. In order to test this strategy the ornithyl analog of the C-terminal sequence 52–65 of galline was synthesized by the conventional method. The amidination reaction, performed on fragments of different length and ornithyl-residue content, quantitatively converts ornithines into arginines. The strategy proposed may represent a powerful tool for the synthesis of protamines and other basic proteins.     

Protected 1–3 segment of the peptaibol antibiotics alamethicin and hypelcin.

A study of the modes of folding and self-association of Z-Aib-l -Pro-Aib-OMe (the protected 1–3 segment of the peptaibol antibiotics alamethicin and hypelcin) in the solid state was performed using i.r. absorption and X-ray diffraction. The stereochemically constrained tripeptide molecules adopt a 4 ± 1 intramolecularly H-bonded form (β-turn), where the single intramolecular H-bond is found between the peptide N-H group of the Aib³ residue and the urethane C = O group of the N-blocking benzyloxycarbonyl moiety. This folded structure is stabilized by an intermolecular H-bond between the urethane N-H group of the Aib¹ residue and the peptide C = O group of the Pro² residue of a symmetry related molecule. According to the i.r. absorption data, in CH₂Cl₂ and TMP solutions the same intramolecularly H-bonded form occurs as that found in solid state. Compared to the situation in the solid state, in CH₂Cl₂ and TMP solvation of the urethane N-H group replaces self-association (through the same N-H group). The results are also discussed in relation to those obtained for other protected -Aib-X-Aib-(X = Aib, l -Ala, l -Val) tripeptide segments of peptaibol antibiotics.     

Concentric Remodeling Detection by Magnetocardiography in Patients with Recent Onset Arterial Hypertension

The aim of this work was to evaluate a number of magnetocardiographic (MCG) indices in their predictive ability for left ventricular (LV) concentric remodeling. Twenty-five male patients affected by essential hypertension for no longer than 15 months and presenting signs of LV remodeling participated in the study; 25 normal men volunteers of comparable age were evaluated as controls. All participants underwent echocardiography (ECHO), electrocardiography (ECG), and magnetocardiography (MCG). Several MCG based indices were evaluated, namely the QRS Integral, T Integral, QRS-T Integral, T/QRS Integral, RS Index, and the variations of the electrical cardiac axis (ECA) orientation. MCG indices were compared with ECHO parameters, i.e., left ventricular mass index (LVMI) and relative wall thickness (RWT), and with ECG parameters, i.e., 12-lead standard ECG LVH Sokolow-Lyon and Cornell voltages. QRS Integral values for patients and controls were significantly different (P = 0.03), whereas T Integral values showed only a tendency to differentiate between patients and controls (P = 0.15). No significant correlation between MCG and echocardiographic indices in patients was found; RWT showed a tendency to correlate with QRS Integral (r = 0.34, P = 0.17) and with RS Index (r = 0.49, P = 0.15), and LVMI showed a tendency to correlate with the variations of the ECA orientation (r = 0.38, P = 0.10). Our findings, also supported by preliminary results on patients affected by hypertension induced LV hypertrophy, suggest a potential role of MCG in the evaluation of early electrophysiological alterations due to LV concentric remodeling. (PACE 2004; 27[Pt. I]:709–718)     

Early Conduction Disorders Following Percutaneous Aortic Valve Replacement

Background: Percutaneous aortic valve replacement (PAVR) may be an alternative therapy for patients with severe aortic stenosis who are denied valve surgery because of age and comorbidity. Data are few regarding the incidence of early conduction disorders (CD) after PAVR. We examined the incidence and characteristics of CD in the immediate postoperative period after PAVR, and the need for permanent pacemaker (PPM) implantation.
Methods and Results: Between June 2007 and June 2008 30 patients (mean age = 82.1 ± 8.5 years) underwent PAVR in our institution. The incidence of new, postoperative CD, diagnosed by 12-lead or 24-hour Holter electrocardiogram, was 68.0%. Left bundle branch block was the most common conduction abnormality, with an incidence of 45.8%. The incidence of complete atrioventricular block requiring PPM implantation was 20%.
Conclusions: We observed a higher incidence of early conduction disorders and need for PPM implantation after PAVR than generally reported after surgery. Whether this observation is clinically important requires larger prospective studies and follow up.     

Atrioventricular Interval Optimization in the Right Atrial Appendage and Interatrial Septum Pacing: A Comparison Between Echo and Peak Endocardial Acceleration Measurements

PADELETTI, et al. : Atrioventricular Interval Optimization in the Right Atrial Appendage and Interatrial Septum Pacing: A Comparison Between ECHC and Peak Endocardial Acceleration. Interatrial septum pacing (IASP) reduces interatrial conduction time and consequently may interfere with atrioventricular delay (AVD) optimization. We studied 14 patients with an implanted BEST Living system device able to measure peak endocardial acceleration (PEA) signal. The aims of our study were to compare the (1) optimal AVD (OAVD) in right atrial appendage pacing (RAAP) and IASP, and (2) OAVD derived by the PEA signal versus OAVD derived by Echo/Doppler evaluation of the left ventricular filling time (LVFT) and cardiac output (CO). Measurements were performed in DDD VDD modes Eight patients (group A) had RAAP and six patients (group B) had IASP. In group A, OAVD measured by LVFT, CO, and PEA was 185 ± 23 ms , 177 ± 19 ms , and 192 ± 23 ms in DDD and 147 ± 19 ms , 135 ± 27 ms , and 146 ± 20 ms in VDD, respectively. OAVD measured by LVFT, CO, and PEA was significantly longer in DDD mode than in VDD (P < 0.01, P < 0.01, P < 0.001 ). In group B, OAVD measured by LVFT, CO, and PEA was 116 ± 19 ms , 113 ± 10 ms , and 130 ± 30ms in DDD and 106 ± 16 ms , 96 ± 15 ms , and 108 ± 26 ms in VDD, respectively. No statistical differences were observed between DDD and VDD. Significant correlations between OAVDs PEA derived and OAVDs LVFT and CO derived were observed (r = 0.71, r = 0.69, respectively ). When new techniques of atrial stimulation, as IASP, are used an OAVD shorter and similar in VDD and DDD has to be considered. The BEST Living system could provide a valid method to ensure, in every moment, the exact required OAVD to maximize atrial contribution to CO.     

Update on Dedicated Bifurcation Stents

Coronary bifurcation lesions represent an area of ongoing challenge in interventional cardiology. Contemporary studies using drug-eluting stents report a reduction in main vessel (MV) restenosis; however, residual stenosis and restenosis at side-branch ostium remain an issue. Multiple two-stent bifurcation strategies exist, including T-stenting, V-stenting, simultaneous kissing stenting, culotte stenting, and crush stenting technique. Each strategy has its own advantages and disadvantages, but on the basis of results of numerous randomized trials, the provisional approach of implanting one stent on the main branch has became the default approach to most bifurcation lesions. Dedicated bifurcation stents have been designed to specifically address some of the shortcomings of the conventional percutaneous approach to bifurcation intervention. The majority of the devices are aimed at facilitating the provisional approach. Dedicated bifurcation stents should enable all operators to treat the side-branch ostium simultaneously with the main branch, preserving a safe, permanent access to side branch during the procedure. In the future, the use of these new devices will probably enhance the interaction between adequate mechanical scaffolding and accurate delivery of the appropriate dosage of any new antirestenosis drugs. There are currently 11 devices available that either have completed or are undergoing first-in-man trials. The development of further drug-eluting platforms and larger controlled studies should demonstrate their clinical applicability, efficacy, and safety before they are widely incorporated into daily practice.