Effects of Septal Pacing on P Wave Characteristics: The Value of Three-Dimensional Echocardiography

SZILI-TOROK, T., et al .: Effects of Septal Pacing on P Wave Characteristics: The Value of Three-Dimensional Echocardiography. Interatrial septum (IAS) pacing has been proposed for the prevention of paroxysmal atrial fibrillation. IAS pacing is usually guided by fluoroscopy and P wave analysis. The authors have developed a new approach for IAS pacing using intracardiac echocardiography (ICE), and examined its effects on P wave characteristics. Cross-sectional images are acquired during pullback of the ICE transducer from the superior vena cava into the inferior vena cava by an electrocardiogram- and respiration-gated technique. The right atrium and IAS are then three-dimensionally reconstructed, and the desired pacing site is selected. After lead placement and electrical testing, another three-dimensional reconstruction is performed to verify the final lead position. The study included 14 patients. IAS pacing was achieved at seven suprafossal (SF) and seven infrafossal (IF) lead locations, all confirmed by three-dimensional imaging. IAS pacing resulted in a significant reduction of P wave duration as compared to sinus rhythm (   99.7 ± 18.7   vs   140.4 ± 8.8  ms; P < 0.01   ). SF pacing was associated with a greater reduction of P wave duration than IF pacing (   56.1 ± 9.9   vs   30.2 ± 13.6  ms; P < 0.01   ). P wave dispersion remained unchanged during septal pacing as compared to sinus rhythm (   21.4 ± 16.1   vs   13.5 ± 13.9  ms; NS   ). Three-dimensional intracardiac echocardiography can be used to guide IAS pacing. SF pacing was associated with a greater decrease in P wave duration, suggesting that it is a preferable location to decrease interatrial conduction delay. (PACE 2003; 26[Pt. II]:253–256)     

Fractional Flow Reserve: The Ideal Parameter for Evaluation of Coronary, Myocardial, and Collateral Blood Flow by Pressure Measurements at PTCA

To overcome the fundamental limitations of coronary arteriography to assess the functional significance of coronary artery disease, it is necessary to obtain direct information about coronary blood flow. Recently we validated three pressure flow equations, which enable calculation of maximum coronary, myocardial, and collateral flow by merely measuring aortic, central venous, and distal coronary pressures under the condition of maximum vasodilation and using an ultra thin pressure monitoring guide wire for distal coronary pressure recording. In this paper, the first clinical experiences of this method are described. For that purpose, the concept of fractional flow reserve (FFR) is important. Fractional coronary flow reserve (FFR_cor) is defined as the maximum achievable blood flow in a stenotic artery, divided by normal maximum flow in that same artery, i.e. maximum flow in that artery in the case that it would be completely normal. Fractional myocardial flow reserve (FFR_myo) is defined in a similar way, and recruitable collateral blood flow is expressed as a fraction of normal maximum myocardial flow. Fractional flow reserve, defined in this way, is easy to obtain at percutaneous transluminal coronary angioplasty (PTCA) by the pressure-flow equations, is independent of pressure changes, applicable to three vessel disease, and enables calculation of the separate contribution of coronary and collateral flow to total myocardial perfusion. In 18 patients a very close correlation was demonstrated between FFR_myo, calculated by pressure recordings at PTCA by the first pressure flow equation, and FFR_myo obtained by positron emission tomography, which is considered the gold standard for myocardial perfusion. In 60 other patients, maximum recruitable collateral blood flow at balloon inflation (Q_c/Q^N) was calculated according to the third pressure-flow equation and correlated to the presence or absence of ischemia. It could be demonstrated that Q_C/Q^N exceeds 22% in all 23 patients without ischemia, whereas Q_c/Q^N was less than 22% in 34 out of 37 patients who experienced ischemia during balloon inflation. This margin value of 22% is very close to the theoretically expected value of 20%. based upon a coronary flow reserve of 5 under standard physiologic conditions. It can be concluded that the concept of fractional flow reserve provides a rapid, accurate, and elegant way for quantitative assessment of maximum coronary and myocardial blood flow before and after PTCA. Moreover, this is the first method that enables quantitative calculation of collateral blood flow in clinical practice. (J Interven Cardiol 1993; 6:331–344)     

Changing cocaine smoking rituals in the Dutch heroin addict population

Recently the use patterns, circumstances and consequences of cocaine have become of interest to both researchers and policy makers in Europe. Currently only a few studies have been conducted of the social epidemiology of cocaine. In this article, focus is placed upon the use of cocaine in one subpopulation, heroin addicts. Based mainly upon ethnographic research conducted in the city of Rotterdam it can be estimated that the prevalence of cocaine use in this population has reached a very high level. The mode of ingesting cocaine parallels that of heroin; Injecting Drug Users inject cocaine-hydrochloride, heroin smokers smoke cocaine base. This cocaine base is mainly processed by users themselves. An exception to this rule of self-processing can be found in the most marginalized addicts who do not have access to the house addresses where both heroin and cocaine-hydrochloride are sold. In this group the selling of ‘cooked cocaine’, a crack-like product, has occurred. The circumstances and potential consequences of the emergence of ‘cooked cocaine’ are discussed.     

Different Mechanisms Underlying Consecutive, Postoperative Atrial TachyArrhythmias in a Fontan Patient

Introduction: Atrial tachyarrhythmias (AT) frequently develop later after a Fontan operation and can be successfully treated by ablative therapy. However, new arrhythmias often develop.
Methods and Results: Consecutive AT emerging in a Fontan patient were ablated using three-dimensional electro-anatomical mapping. During a 6-year period, nine different AT were ablated, including intraatrial reentrant AT (N = 5), focal AT (N = 3), and focal atrial fibrillation (N = 1) originating from distinct right atrial sites.
Conclusion: In a Fontan patient, successive AT can be caused by different mechanisms. These AT are most likely the result of progressive atrial cardiomyopathy and can be treated by catheter ablation.     

Fractional Flow Reserve: Who Needs the Pressure Wire?

Recently, the interest in coronary pressure measurements has been revived thanks to technical innovations (the development of pressure-measuring angioplasty guidewire) and theoretical progress (the concept of pressure derived fractional flow reserve). Fractional flow reserve (FFR) is the ratio of maximal flow in the myocardial region depending on a stenosis to maximal flow in that same region if the stenosis were absent. With the development of pressure guidewires, fractional flow reserve can be calculated rapidly and safely in the diagnostic and interventional setting. It has been shown that pressure derived FFR can be used as a surrogate for a stress test for on-line clinical decision making in the catheterization laboratory. Values < 0.75 are most often associated with exercise-inducible myocardial ischemia, while values > 0.75 exclude objective signs of ischemia during exercise. The accuracy of FFR for that purpose is approximately 95% and higher than that of any single noninvasive test taken alone. Of note, it has been shown that prognosis is favorable in patients in whom a planned angioplasty was deferred on the basis of a myocardial fractional flow reserve > 0.75. After regular balloon angioplasty, the combination of a good angiographic result and a FFR > 0.90 is associated with an event rate during a 2-year follow-up, which is similar to that after stenting. After stent implantation, FFR should normalize. A FFR < 0.94 after stent implantation appears to be as accurate as intravascular ultrasound (IVUS) to detect stent malposition. Thus, pressure derived FFR is a well-validated index of stenosis severity that has evolved from a physiological index to a clinical tool.     

Modulation of the acoustic startle response by film-induced fear and sexual arousal

The response matching model of Lang, Bradley, and Cuthbert (1992) predicts startle reflex facilitation during negative relative to positive emotional states. Using slide and imagery paradigms, larger eyeblink responses to startle probes for unpleasant than for pleasant conditions have consistently been reported. The present study extended the previously observed relationship between valence and startle to more complex stimuli, namely 1-min film fragments. Thirty-three subjects viewed a sequences of 27 film fragments with neutral, negative (fearful), and positive (sexual) contents, presented in one of three mixed orders. Blink magnitude to brief bursts of white noise was larger during fearful fragments than during sexual fragments. Blink magnitudes habituated across successive film fragments, but the positive-negative difference remained stable within film fragments and during the entire length of the videotape (approximately 40 min).     

Synthetic peptide vaccines: palmitoylation of peptide antigens by a thioester bond increases immunogenicity

Synthetic peptides have frequently been used to immunize animals. However, peptides less than about 20 to 30 amino acids long are poor immunogens. In general, to increase its immunogenicity, the presentation of the peptide should be improved, and molecular weight needs to be increased. Many attempts have been made to couple peptide immunogens to different carrier proteins [e.g. keyhole limpet haemocyanin (KLH) or ovalbumin]. This leads to very complex structures, however. We used a controlled conjugation of a peptide to a single long-chain fatty acid like palmitic acid by a thioester or an amide bond. It was found that these S-palmitoylated peptides were much more immunogenic than N-palmitoylated peptides and at least similar to KLH-conjugated peptides with respect to appearance and magnitude of induced antibodies (canine parvovirus) or immunocastration effect (gonadotropin-releasing hormone). For chemical synthesis of thioesters, we established conditions for solution and solid-phase synthesis. In both phases, Cys(SBu^t) could only be deprotected efficiently using phosphines, and S-acylation was accomplished using standard coupling at pH 5. We speculate that, in vivo, the presence of an appropriate fatty acid chain, chemically linked through a labile thioester bond, greatly enhances immunogenicity, because it represents a favourable substrate for cleavage by cellular thioesterases in cells of the immune system.