First glimpse into the origin and spread of the Asian longhorned tick, Haemaphysalis longicornis, in the United States

Established populations of Asian longhorned ticks (ALT), Haemaphysalis longicornis, were first identified in the United States (US) in 2017 by sequencing the mitochondrial cytochrome c oxidase subunit I (cox1) 'barcoding' locus followed by morphological confirmation. Subsequent investigations detected ALT infestations in 12, mostly eastern, US states. To gain information on the origin and spread of US ALT, we (1) sequenced cox1 from ALT populations across 9 US states and (2) obtained cox1 sequences from potential source populations [China, Japan and Republic of Korea (ROK) as well as Australia, New Zealand and the Kingdom of Tonga (KOT)] both by sequencing and by downloading publicly available sequences in NCBI GenBank. Additionally, we conducted epidemiological investigations of properties near its initial detection locale in Hunterdon County, NJ, as well as a broader risk analysis for importation of ectoparasites into the area. In eastern Asian populations (China/Japan/ROK), we detected 35 cox1 haplotypes that neatly clustered into two clades with known bisexual versus parthenogenetic phenotypes. In Australia/New Zealand/KOT, we detected 10 cox1 haplotypes all falling within the parthenogenetic cluster. In the United States, we detected three differentially distributed cox1 haplotypes from the parthenogenetic cluster, supporting phenotypic evidence that US ALT are parthenogenetic. While none of the source populations examined had all three US cox1 haplotypes, a phylogeographic network analysis supports a northeast Asian source for the US populations. Within the United States, epidemiological investigations indicate ALT can be moved long distances by human transport of animals, such as horses and dogs, with smaller scale movements on wildlife. These results have relevant implications for efforts aimed at minimizing the spread of ALT in the United States and preventing additional exotic tick introductions.

Antithrombogenic Coating of Stents Using a Biodegradable Drug Delivery Technology

To reduce the thrombogenic properties of coronary artery stents, a biodegradable polylactic acid (PLA) stent coating with an incorporated thrombin inhibitor and a platelet aggregation inhibitor has been developed. In an ex vivo human stasis model, its effect on platelets, plasmatic coagulation and its release characteristics were studied using whole blood. Bare steel and bare gold-surface stents were compared to steel and gold-surface stents coated with PLA (30 kDa) containing 5% polyethyleneglycol (PEG)-hirudin and 1% iloprost, with an empty tube as control. Markers of activated coagulation (prothrombin fragment F1-2 and thrombin-antithrombin III complex, TAT), were assayed and the release of drugs from the coating was assessed by aPTT and collagen-induced platelet aggregation. Bare steel and gold stents were completely covered by a blood clot, and high levels of coagulation markers (F1-2 fragment and TAT) were detected. No differences in the thrombogenic properties were found between bare gold or steel stents. Coated stents were free of blood clots and only minor elevations of markers were detected. Release data from in-vitro studies over 90 days showed a gradual release of the drugs with an initial exponential release characteristic for PEG-hirudin, slow release of iloprost and a 10% degradation of the PLA carrier. This drug releasing biodegradable coating effectively reduced thrombus formation independent of the metallic surface.

Circulating serum CK level vs. muscle impairment for in situ monitoring burden of disease in Mdx-mice

BACKGROUND

Duchenne muscular dystrophy (DMD) consists of a lack in the expression of the subsarcolemmal protein dystrophin causing progressive muscle dysfunction. Among the widely applied animal models in DMD research is the C57BL/1010ScSn-Dmdmdx mouse, commonly referred to as the "mdx mouse". The potential benefit of novel interventions in this model is often assessed by variables such as functional improvement, histological changes, and creatine kinase (CK) serum levels as an indicator for the extent of in situ muscle damage.

OBJECTIVE

Our objective was to determine to what extent the serum CK-level serves a surrogate for muscle dysfunction.

METHODS

In this trial mdx mice were subjected to a four-limb wire-hanging test (WHT) to assess the physical performance as a reference for muscle function. As CK is a component of the muscle fiber cytosol, its serum activity is supposed to positively correlate with progressing muscle damage. Hence serum CK levels were measured to detect the degree of muscle impairment. The functional tests and the serum CK levels were analyzed for their specific correlation.

RESULTS

Although physical performance decreased during the course of the experiment, latency to fall times in the WHT did not correlate with the CK level in mdx mice.

CONCLUSION

Our data suggests that the serum CK activity might be a critical parameter to monitor the progression of muscle impairment in mdx mice. Further this study emphasizes the complexity of the DMD phenotype in the mdx mouse, and the care with which isolated parameters in this model should be interpreted.

Influence of systemic inflammation on efficiency of antiplatelet therapy in PAOD patients

Recently it was shown that inflammation adversely influences results obtained from the platelet function analyzer system, PFA-100, hypothesizing that inflammation could confound interpretation of platelet function results. We investigated the clinical relevance of these results in patients with peripheral arterial occlusive disease (PAOD), with and without signs of systemic inflammation. In 98 PAOD patients, all treated with acetyl-salicylic acid (ASA), we obtained PFA-100 values upon stimulation with epinephrine. C-reactive protein (CRP) values were investigated as indicator for systemic inflammation. Mean CRP levels were elevated in 23 patients (23%). There was no difference of mean PFA-100 results between patients with elevated CRP levels and those without. Our results indicate that the effect of ASA on platelet aggregation, as measured by the PFA-100, is not relevantly influenced in PAOD patients with elevated CRP.

Monitoring of antiplatelet therapy with the PFA-100 in peripheral angioplasty patients

BACKGROUND

In patients suffering from peripheral arterial occlusive disease (PAOD) the risk of restenosis after percutaneous transluminal angioplasty (PTA) might be influenced by platelet mediated factors.

OBJECTIVE

To look for a correlation between the effect of antiplatelet therapy and recurrence of disease after PTA by monitoring platelet function in 3-month intervals by the platelet function analyzer system, PFA-100, over a period of 1 year.

PATIENTS AND METHODS

A group of 98 patients (43 females, 55 males) with PAOD, treated with aspirin (n = 52), thienopyridine (n = 34) or combination therapy of both (n = 12) were followed over a period of 12 months after elective PTA of the lower extremities with regard to occurrence of restenosis or reocclusion at the site of angioplasty, to demonstrate inhibitory effects on platelets, induced by antiplatelet therapy.

RESULTS

PFA-100 proved suitable to identify 'non-responders' to antiplatelet therapy, in a 12-month follow-up period. In 'non-responders' to clopidogrel therapy, a higher incidence of restenosis or reocclusion after PTA of the lower limbs was detected compared with 'responders'.

CONCLUSION

PFA-100, upon stimulation with ADP, might predict patients under clopidogrel therapy with elevated risk for the development of complications following PTA of the lower limbs. This could offer the chance to switch to an alternative therapy or adapt the dose.

Carotid artery stenting: effect of learning curve and intermediate-term morphological outcome

PURPOSE

To assess the impact of learning on the rate of success and complications of carotid stenting in a single-center, one-operator series and prospectively follow a patient cohort with regard to restenosis.

METHODS

In 303 patients (mean age 70 +/- 8.8 years), 320 internal carotid arteries (ICA) were treated with carotid stenting for stenoses > or = 70%. Four groups of 80 consecutive interventions were compared with regard to primary technical success and periprocedural complications. Stent patency in follow-up was assessed using duplex scanning.

RESULTS

Stenting was successful in 298 (93%) arteries. The combined neurological complications (transient ischemic attacks and all strokes) and 30-day death rate was 8.2% (n = 25), but the all stroke and 30-day death rate was 3.0% (n = 9). A significant reduction in the frequency of neurological complications after the initial 80 interventions was observed (p = 0.03), but technical success was not appreciably improved with increasing experience thereafter. Over a median 12 months (interquartile range 6 to 24), cumulative patency rates were 91%, 90%, and 91% at 6, 12, and 36 months, respectively.

CONCLUSIONS

Elective carotid stenting can be performed with excellent technical success, an acceptable frequency of periprocedural complications, and good intermediate-term patency. However, our findings suggest that a larger number of interventions should be performed to overcome the negative effects of the initial learning phase.

Atorvastatin improves blood rheology in patients with familial hypercholesterolemia (FH) on long-term LDL apheresis treatment

To determine the effect of atorvastatin on blood rheology in patients with familial hypercholesterolemia (FH) on regular LDL apheresis, we prospectively studied the rheological variables fibrinogen, plasma viscosity, red cell aggregation, whole blood viscosity, hematocrit and platelet aggregation in 12 patients (two homozygous, ten heterozygous) before and during treatment with atorvastatin. Baseline values of red cell aggregation and whole blood viscosity were increased in FH patients on regular LDL apheresis compared with healthy controls (P<0.05), whereas fibrinogen, plasma viscosity and hematocrit were similar in the two groups. Treatment with atorvastatin reduced red cell aggregation (P<0.01), whole blood viscosity (P<0.01), plasma viscosity (P<0.01) and platelet aggregation (P<0.05), but caused a slight increase in plasma fibrinogen (by 5%; P<0.01). Our findings suggest that atorvastatin improves blood rheology in patients with FH on regular LDL-apheresis. This improvement in blood flow properties may contribute to the well-known beneficial effects of atorvastatin on cardiovascular risk in patients with severe hyperlipidemia and atherosclerotic vascular disease.

High prevalence of anal squamous intraepithelial lesions and squamous-cell carcinoma in men who have sex with men as seen in a surgical practice

INTRODUCTION

Anal high-grade squamous intraepithelial lesions are probable invasive anal squamous-cell cancer precursors, and although unproved, treatment of high-grade squamous intraepithelial lesions may prevent progression to anal squamous-cell cancer. Men who have sex with men are often treated for benign anorectal disorders without consideration given to the possibility of concurrent high-grade squamous intraepithelial lesions or anal squamous-cell cancer. We determined the prevalence of anal high-grade squamous intraepithelial lesions and anal squamous-cell cancer in an urban surgical practice of men who have sex with men referred for treatment of anal condyloma and other benign noncondylomatous anal disorders.

METHODS

One hundred thirty-one HIV-positive and 69 HIV-negative men who have sex with men referred for surgical treatment of presumed benign anorectal disease were evaluated by anal cytology, high-resolution anoscopy, and biopsy. Anal cytology and histology were reported with a modified Bethesda classification.

RESULTS

One hundred fifty-seven patients (79 percent) were referred for condyloma, 4 (2 percent) for anal squamous intraepithelial lesions (anal high-grade squamous intraepithelial lesions) diagnosed by primary care providers, and 39 (19 percent) for other benign anorectal disorders. One hundred forty-three patients (93 percent) had abnormal anal cytology, with 107 (54 percent) having high-grade squamous intraepithelial lesions on cytology. Biopsy results revealed 120 patients (60.0 percent) with high-grade squamous intraepithelial lesions and 5 patients (3 percent) with invasive squamous-cell carcinoma. Four of five men with anal squamous-cell cancer were HIV positive. Fourteen men (36 percent) who have sex with men referred for noncondylomatous benign anal disorders had high-grade squamous intraepithelial lesions, and three (8 percent) had anal squamous-cell cancer. High-grade squamous intraepithelial lesions and anal squamous-cell cancer were seen most often at the squamocolumnar junction.

CONCLUSIONS

Men who have sex with men referred for treatment of either condyloma or noncondylomatous benign anorectal disease had a high prevalence of anal high-grade squamous intraepithelial lesions and anal squamous-cell cancer. All men who have sex with men referred for treatment of benign anorectal disease should have high-resolution anoscopy and aggressive biopsy of all abnormal areas. Treatment of external lesions alone could miss high-grade squamous intraepithelial lesions or anal squamous-cell cancer.

[Development of a radioligand assay for quantifying specific prostaglandin E1 binding in ischemic ulcers]

Ulcers of the lower extremities are of immense socioeconomical importance. Prevention and therapy of these trophic lesion are hence of great interest. In granulation tissue of ischemic ulcers Laser Doppler flow was previously shown to be higher compared to that in ischemic/adjacent skin or in ulcer without granulation tissue. Intravenous infusion of prostaglandin E1 significantly increased Laser Doppler flow. The present study was designed to test the hypothesis whether the increased baseline and prostaglandin E1-stimulated perfusion of granulation tissue is due to an increased number of prostaglandin E1-receptors in granulation tissue. Therefore, a radioligand binding assay was developed. In an initial pilot study the density of the prostaglandin E1-receptors in granulation tissue of ulcers was compared to that in ischemic/adjacent skin in 8 patients suffering from peripheral arterial occlusive disease requiring debridement or amputation of limbs because of ischemic lesions. The amount of specific binding sites detected was not significantly different between granulation tissue and ischemic/adjacent ulcer tissue. However it cannot be excluded that a possible difference might be detectable with more sensitive assays. In the future we hope to establish a more sensitive assay in order to be able to answer the initial question, whether there is a difference concerning the density of prostaglandin E1 receptor sites in granulation tissue and ischemic/adjacent skin.

p-Hydroxyphenylacetaldehyde, the major product of tyrosine oxidation by the activated myeloperoxidase system can act as an antioxidant in LDL

The oxidative modification of low density lipoprotein (LDL) may play a significant role in atherogenesis. HOCl generated by the myeloperoxidase/H2O2/Cl- system of activated neutrophils may be operative in vivo making LDL atherogenic. Tyrosine has been found to be oxidized by HOCl to p-hydroxyphenylacetaldehyde (p-HA) capable of modifying phospholipid amino groups in LDL. As an amphiphatic phenolic compound, p-HA may have the potential to act as an antioxidant in the lipid phase of LDL. The present results show that (a) tyrosine exerts a protective effect on LDL modification by HOCl, (b) p-HA could act as antioxidant associated with the lipoprotein preventing cell- and transition metal ion-mediated LDL oxidation and (c) p-HA was able to scavenge free radicals.

Endovascular irradiation from beta-particle-emitting gold stents results in increased neointima formation in a porcine restenosis model

BACKGROUND

Recent studies have shown that ionizing radiation reduces neointima formation after balloon angioplasty and stent implantation in experimental models of restenosis and first clinical trials. The objective of this study was to determine the dose distribution of a new beta-particle-emitting radioactive gold stent and to evaluate the dose-dependent vascular response in the coronary overstretch pig model.

METHODS AND RESULTS

Sixteen Göttinger minipigs underwent placement of 11 nonradioactive and 36 beta-particle-emitting stents with activity levels of 10.4+/-0.6, 14.9+/-2.4, 22.8+/-1.3, 35.8+/-2. 8, and 55.4+/-5.3 microCi of (198)Au. Three months after implantation, the percent area stenosis, neointimal thickness, neointimal area, and vessel injury were analyzed by quantitative histomorphometry. The lifetime radiation doses at a depth of 1 mm were 3.3+/-0.2, 4.7+/-0.5, 7.2+/-0.4, 11.4+/-0.9, and 17.6+/-1.7 Gy for the different activity groups. No dose-response relationship was observed in the radioactive stents with respect to percent area stenosis (P=0.297), mean neointimal thickness (P=0.82), or mean neointimal area (P=0.65). Significantly lower neointima formation and less luminal narrowing was seen in the control group than in the beta-particle-emitting stents (P<0.001). Multilinear regression analysis revealed that only radioactivity made a significant independent contribution to the degree of percent area stenosis (P<0. 001).

CONCLUSIONS

Neointima formation in pigs is markedly increased by beta-particle-emitting stents with (198)Au as the radioisotope. This study provides evidence that dosages of 3 to 18 Gy of low-dose-rate beta-particle irradiation via endovascular stents cause pronounced luminal narrowing in the animal model at 3 months.

Coronary stent symmetry and vascular injury determine experimental restenosis

OBJECTIVE

To assess the impact of stent symmetry on restenosis using the coronary overstretch sheep model.

METHODS

Neointimal thickness, injury index, and percentage diameter and area stenosis were calculated by digital morphometry. The standard deviation of the angular burden was used to assess stent symmetry for each section.

MATERIALS

15 healthy Merino sheep (63-75 kg) underwent implantation of 30 slotted tube stents (7 mm). Restenosis was induced by calculated overstretch of the coronary artery. Twenty eight days after implantation, stents were excised and underwent histological examination using quantitative digital morphometry.

RESULTS

The severity of vessel injury was positively correlated with neointimal thickness and with percentage diameter and area stenosis (p < 0.001). Mean neointimal thickness and mean vascular injury per cross section were strongly related to the standard deviation of angular burden, with correlation coefficients of 0.6 and 0.8, respectively (p < 0.001).

CONCLUSIONS

The well known relation between vascular injury and restenosis was confirmed, and a new relation was discovered between stent asymmetry and restenosis. If these results apply to human coronary arteries, restenosis may also be dependent on the degree of asymmetric stent expansion. These results should influence the development of new stent designs to reduce asymmetric stent expansion, leading to a more homogeneous strain distribution in stented coronary segments.

Inhibition of neointima formation after experimental coronary artery stenting: a new biodegradable stent coating releasing hirudin and the prostacyclin analogue iloprost

BACKGROUND

To minimize acute stent thrombosis and development of restenosis, stents coated with biodegradable and nonbiodegradable polymers have been proposed to serve as sustained-release drug carriers.

METHODS AND RESULTS

In both a sheep and a pig model, we examined the vascular response to standard and high-pressure implantation of coronary Palmaz-Schatz stents coated with a 10-microm layer of polylactic acid (MW 30 kDa) releasing recombinant polyethylene glycol (r-PEG)-hirudin and the prostacyclin analogue iloprost, both drugs with antithrombotic and potentially antiproliferative effects. Study observation time was 28 days. Between the corresponding stent groups, no differences were observed with regard to preplacement and postplacement implantation parameters. The morphometric analysis demonstrated that the coating was associated with a greater lumen diameter through a reduction in the mean restenosis area by 22.9% (P<0.02) in the standard-pressure model (sheep) and by 24.8% (P<0.02) in the overstretch pig model compared with uncoated control stents without inducing a local inflammatory response.

CONCLUSIONS

The results from this study demonstrate beneficial effects of a polymeric stent coating with polylactic acid releasing r-PEG-hirudin and iloprost on the development of restenosis after coronary stent placement at 4 weeks, independent of the extent of vascular injury. Future studies are proposed to investigate the integration of other substances to further enhance the potential of the stent coating on reducing neointimal formation.

Hydrogen peroxide for prevention of bacterial growth on polymer biomaterials

BACKGROUND

Despite widespread use of potent antibiotics, infections of artificial implants and catheters are of increasing concern. We tested whether local treatment with 3% hydrogen peroxide (H2O2), long known as an inexpensive wound disinfectant, could prevent or reduce bacterial growth on polymer biomaterials.

METHODS

Two-centimeter-long pieces of polyurethane and silicone tubing were contaminated with a standardized solution of Staphylococcus epidermidis (10(5)/mL) and then rinsed and wiped with saline (0.9%) solution. Bacterial growth was assessed after incubation at 37 degrees C for 24 hours. Bacterial colonies were compared for the following treatments: wiping only with saline; wiping with 1.5%, 2%, or 3% H2O2; pretreating biomaterials with 3% H2O2 and subsequent contamination for 2 and 4 hours without treatment after contamination; and contamination of tubings 1 month after pretreatment with 3% H2O2. The effect of 3% H2O2 was also assessed on contamination with Escherichia coli.

RESULTS

Bacterial growth was reduced by more than 99% when the contaminated tubes were treated with 3% H2O2 compared with saline control (p < 0.001). Lower concentrations of H2O2 were less effective. The length of the contamination period had no influence on the effectiveness of H2O2 when used on polyurethane but did with silicone tubings. Pretreatment with H2O2 1 month before contamination still reduced bacterial growth rate by 90% on polyurethane and by 75% on silicone tubings. Comparable effects on bacterial growth rate were observed for staphylococci (-90%, p < 0.001) and escherichiae (-90%, p < 0.001).

CONCLUSIONS

Local treatment with 3% H2O2 significantly reduced bacterial growth on polymer biomaterials even for 1 month after treatment. This finding might influence clinical strategies of prevention of foreign body infection.

Marked reduction in atrial defibrillation thresholds with repeated internal cardioversion

OBJECTIVES

This study was performed to assess the atrial defibrillation threshold in patients with recurrent atrial fibrillation (AF) using repeated internal cardioversion.

BACKGROUND

Previous studies in patients with chronic AF undergoing internal cardioversion have shown this method to be effective and safe. However, current energy requirements might preclude patients with longer-lasting AF from being eligible for an implantable atrial defibrillator.

METHODS

Internal shocks were delivered via defibrillation electrodes placed in the right atrium (cathode) and the coronary sinus (anode) or the right atrium (cathode) and the left pulmonary artery. After cardioversion, patients were orally treated with sotalol (mean 189 +/- 63 mg/day). Eighty consecutive patients with chronic AF (mean duration 291 +/- 237 days) underwent internal cardioversion, and sinus rhythm was restored in 74 patients. Eighteen patients underwent repeated internal cardioversion using the same electrode position and shock configuration after recurrence of AF (mean duration 34 +/- 25 days).

RESULTS

In these 18 patients, the overall mean defibrillation threshold was 6.67 +/- 3.09 J for the first cardioversion and 3.83 +/- 2.62 J for the second (p = 0.003). Mean lead impedance was 55.6 +/- 5.1 ohms and 57.1 +/- 3.7 ohms, respectively (not significant). For sedation, 6.7 +/- 2.9 mg and 3.9 +/- 2.2 mg midazolam were administered intravenously (p = 0.003), and the pain score (0 = not felt, 10 = intolerable) was 5.1 +/- 1.9 and 2.7 +/- 1.8 (p = 0.001). Uni- and multivariate analyses revealed only the duration of AF before cardioversion to be of relevance, lasting 175 +/- 113 days before the first and 34 +/- 25 days before the second cardioversion in these 18 patients (p = 0.002).

CONCLUSIONS

If the duration of AF is reduced, a significant reduction in defibrillation energy requirements for internal cardioversion ensues. This might extend the group of patients eligible for an implantable atrial defibrillator despite relatively high initial defibrillation thresholds.

Influence of balloon pressure during stent placement in native coronary arteries on early and late angiographic and clinical outcome: A randomized evaluation of high-pressure inflation

BACKGROUND

High-pressure dilatation is considered a better stent placement strategy, but this has not yet been proved by appropriately designed studies. The objective of this randomized trial was to assess the role of high-pressure dilatation in the early and late outcome of patients undergoing coronary stent placement.

METHODS AND RESULTS

Consecutive patients with coronary stent placement were randomly assigned to high- (15 to 20 atm, 468 patients) or low- (8 to 13 atm, 466 patients) balloon-pressure dilatation. The primary end point of the study was the event-free survival at 1 year. Secondary end points were the incidence of stent thrombosis at 30 days and angiographic restenosis (>/=50% diameter stenosis) at 6 months. The incidence of stent thrombosis was 1.7% in the high-pressure and 1.9% in the low-pressure group (relative risk 0.89; 95% CI 0.30 to 2.56). During the first 30 days, although there was no significant difference in the incidence of Q-wave myocardial infarction, the incidence of non-Q-wave infarction was 6.4% in the high-pressure and 3.4% in the low-pressure group (relative risk 1. 87; 95% CI 1.02 to 3.42). The restenosis rate was 30.4% in the high-pressure and 31.4% in the low-pressure group (relative risk 0. 97; 95% CI 0.75 to 1.26). Event-free survival at 1 year was not significantly different between the groups, with 78.8% in high-pressure patients and 75.5% in patients assigned to low-pressure dilatation (hazard ratio 0.85; 95% CI 0.65 to 1.11).

CONCLUSIONS

The systematic use of high-balloon-pressure inflation (15 to 20 atm) during coronary stent placement is not associated with any significant influence on the 1-year outcome of patients undergoing this intervention.

Antithrombogenic coating of stents using a biodegradable drug delivery technology

To reduce the thrombogenic properties of coronary artery stents, a biodegradable polylactic acid (PLA) stent coating with an incorporated thrombin inhibitor and a platelet aggregation inhibitor has been developed. In an ex vivo human stasis model, its effect on platelets, plasmatic coagulation and its release characteristics were studied using whole blood. Bare steel and bare gold-surface stents were compared to steel and gold-surface stents coated with PLA (30 kDa) containing 5% polyethyleneglycol (PEG)-hirudin and 1% iloprost, with an empty tube as control. Markers of activated coagulation (prothrombin fragment F1-2 and thrombin-antithrombin III complex, TAT), were assayed and the release of drugs from the coating was assessed by aPTT and collagen-induced platelet aggregation. Bare steel and gold stents were completely covered by a blood clot, and high levels of coagulation markers (F1-2 fragment and TAT) were detected. No differences in the thrombogenic properties were found between bare gold or steel stents. Coated stents were free of blood clots and only minor elevations of markers were detected. Release data from in-vitro studies over 90 days showed a gradual release of the drugs with an initial exponential release characteristic for PEG-hirudin, slow release of iloprost and a 10% degradation of the PLA carrier. This drug releasing biodegradable coating effectively reduced thrombus formation independent of the metallic surface.

What is the ideal rate-adaptive sensor for patients with implantable cardioverter defibrillators: lessons from cardiac pacing

The development of implantable pacemakers in the clinical setting mirrors the implementation of advanced technical possibilities. In the United States, 83% of all pacemakers implanted in 1996 had rate response as a programmable option. A variety of sensors have been proposed and used for rate control. Among today's many concepts, accelerometer-controlled pacing is the most widely used rate-adaptive principle. Although the use of a second sensor is currently of proven benefit for only a limited number of patients, the concept of closed-loop pacing--implementing a negative feedback between pacing rate and the control signal--merits further investigation. This is of special importance in defibrillator patients whose myocardial contractility is generally limited. These patients are most sensitive to pacing rates that are too high for a given metabolic situation. The integration of rate-adaptive pacing into defibrillators is a natural consequence of the technical evolution.

Initial experience with a new balloon-guided single lead catheter for internal cardioversion of atrial fibrillation and dual chamber pacing

BACKGROUND

Based on the observation that internal cardioversion (IntCV) of atrial fibrillation is effective with electrodes in the right atrium and pulmonary artery, a new balloon-guided catheter and external defibrillation device with optional dual chamber pacing was evaluated.

METHODS

IntCV was attempted in 27 patients (age: 57 +/- 10 years, duration: 14 +/- 18 months, left atrial diameter 56 +/- 8 mm) using a new defibrillation device (Alert, EP MedSystems, Inc., NJ, USA) that allows the delivery of biphasic shocks (0.5-15 J, variable tilt), atrial and ventricular pacing, and online signal recording. Pacing and defibrillation shocks were applied via a 7.5 Fr balloon-guided catheter (EP MedSystems, Inc.). Pacing, sensing, and triggering were established through the proximal atrial array and an electrode ring between both defibrillation arrays and a single ventricular electrode ring. Catheters were inserted from the antecubital vein.

RESULTS

In 25 of 27 patients sinus rhythm was restored with a mean energy of 6.7 +/- 4.5 J. In five patients, atrial postshock pacing was required for bradycardia and atrial premature beats. The mean fluoroscopy time was 2.0 +/- 1.3 minutes.

CONCLUSION

The high success rate, ease of application, and backup dual chamber pacing suggest that this system is an alternative to established methods of cardioversion. In certain indications, such as failure of prior external cardioversion and situations in which a standard pulmonary balloon catheter is needed, this system would be advantageous.

Effect of glycoprotein IIb/IIIa receptor blockade on recovery of coronary flow and left ventricular function after the placement of coronary-artery stents in acute myocardial infarction

BACKGROUND

Apart from its established effects on vessel patency after percutaneous coronary revascularization, glycoprotein IIb/IIIa receptor blockade by abciximab may improve myocardial perfusion by inhibition of the interaction of platelets and platelet aggregates with the microvasculature. We investigated the effect of abciximab with stent placement in acute myocardial infarction.

METHODS AND RESULTS

In a prospective randomized trial, patients undergoing stenting in acute myocardial infarction within 48 hours after onset of symptoms were randomly assigned to receive either standard-dose heparin or abciximab plus low-dose heparin. Immediately after the procedure and at 14-day angiographic follow-up, we assessed flow velocity in the recanalized vessel with the Doppler wire and regional wall motion by the centerline method. End points were changes in papaverine-induced peak flow velocities and in wall motion indices. We assigned 98 patients to standard heparin and 102 to abciximab. We obtained 152 paired flow measurements and 151 paired left ventricular function studies. Residual stenoses of the treated lesions did not differ between the 2 groups. Improvement of peak flow velocity (mean [95% CI]: 18.1 cm/s [13.6 to 22.6 cm/s], n=80, versus 10.4 cm/s [5.4 to 15.4 cm/s], n=72, P=0.024) and wall motion index (0.44 SD/chord [0.29 to 0.59 SD/chord], n=79 versus 0. 15 SD/chord [0.00 to 0.30 SD/chord], n=72, P=0.007) was significantly greater in patients assigned to abciximab than in those on heparin alone. At follow-up, the abciximab group had a higher global left ventricular ejection fraction than the heparin group (62% [59% to 65%] versus 56% [53% to 59%], P=0.003).

CONCLUSIONS

Abciximab had important effects beyond the maintenance of large-vessel patency. It improved the recovery of microvascular perfusion and concomitantly enhanced the recovery of contractile function in the area at risk.

Internal cardioversion of atrial fibrillation with a single lead configuration in a patient with massive diaphragmatic herniation

An anatomically related circumstance is reported as indication for the internal low energy cardioversion instead of an external approach. A new single lead electrode configuration is described.

A comparative study of activity and dual sensor: activity and minute ventilation pacing responses to ascending and descending stairs

Previous studies with activity-based rate adaptive pacemakers have shown a somewhat paradoxical response when comparing ascending stairs to descending stairs. The objective of this investigation was to measure dual-sensor rate response provided by activity and minute ventilation (MV) compared with activity alone, and with a control group, during ascending and descending stairs. For dual sensor mode, measured mean peak pacing rate with 72 (92) steps per minute was 111 +/- 13 beats/min (124 +/- 14 beats/min) ascending stairs and 81 +/- 7 beats/min (97 +/- 13 beats/min) for descending. For activity mode alone, mean peak pacing rate was 90 +/- 12 beats/min (108 +/- 19 beats/min) ascending stairs and 97 +/- 12 beats/min (123 +/- 17 beats/min) descending. The mean peak control group heart rate ascending stairs for a step rate of 72 (92) steps/min were 116 +/- 11 beats/min (127 +/- 14 beats/min) ascending stairs and for descending 89 +/- 12 beats/min (95 +/- 11 beats/min). While for dual sensor controlled pacing there was a significant difference for ascending and descending stairs at both step rates, there was no difference between going upstairs and downstairs for activity mode alone. Rates with dual sensor did not significantly differ from respective rates of the control group. The mean correlation coefficient between MV and paced rate was 0.85. Pacing heart rates delivered by the dual sensor mode were appropriate for ascending and descending stairs. In contrast to activity mode alone, the peak heart rates for dual sensor mode are higher during ascending than during descending stairs.

Antithrombotic stent coatings: hirudin/iloprost combination

Neointimal formation after stent implantation can cause luminal narrowing, called restenosis. Restenosis is induced by initial platelet adhesion and thrombus formation followed by immunocyte adhesion on the stent surface and on the injured vessel wall. The thrombus releases factors, which activates the proliferation of smooth muscle cells. Stents, coated with an antithrombotic surface, may prevent platelet adhesion and subsequent smooth muscle cell proliferation. This paper will review stent coating with poly-LD-lactic acid, a biodegradable polymer containing Iloprost, a synthetic prostacycline, and PEG-Hirudin as a method for reducing of restenosis.

Unexpected recurrence of sinus rhythm in chronic atrial fibrillation due to sick sinus disease

A 60-years old patient with symptomatic sick sinus disease was implanted a dual-chamber pacemaker that did well during the following 13 years. Thereafter, the pacemaker had to be explanted because of a systemic infection, with the patient in constant chronic atrial fibrillation in the meantime. After another asymptomatic year, 6 arrhythmogenic syncopes occurred, apparently due to pre-automatic pauses prior to spontaneous conversions to sinus rhythm. Subsequently, the patient was implanted a VVI pacemaker, whereupon he did well henceforth. This case demonstrates the possibility of recurrence of sinus rhythm even after long-standing chronic atrial fibrillation.

Intra-atrial defibrillation for atrial fibrillation: animal data

Animal research in the area of atrial defibrillation has helped to bring about a greater understanding of the mechanisms and influencing factors of atrial defibrillation. Increased clinical interest in atrial tachyarrhythmias during the 1980s led to more intensive animal research in this area, in which concepts of intra-atrial cardioversion was only first described in 1974. Initially, the concept of one intracardiac catheter in conjunction with a subcutaneous electrode was evaluated. Further studies involved alternative waveforms, shock durations, electrode materials, and lead configurations to improve the percentage of successful cardioversions while reducing energy requirements. The results from ventricular defibrillation, in which the need for a homogenous field through the majority of fibrillating mass had been established, were applied to research for atrial defibrillation as well. An intracardiac vector with electrodes inside the heart was determined to be most efficient. Results concerning the feasibility, efficacy, and safety have been confirmed by clinical data. Further animal studies will help to evaluate new concepts for reducing energy requirements, such as new electrode materials and advanced shock timing. The clinical benefits of basic research in internal cardioversion of atrial fibrillation justifies additional animal research studies.

The immunohistological diagnosis of E. coli O157:H7 colitis: possible association with colonic ischemia

OBJECTIVE

E. coli O157:H7 may cause hemorrhagic colitis resembling ischemic colitis. Diagnosis is usually made by finding sorbitol-negative colonies on MacConkey agar that react with O157 and H7 antisera. Most ischemic colitis is idiopathic, but some may be caused by E. coli O157:H7, inasmuch as this organism can produce fibrin thrombi in colon vasculature. The objectives of this study were to determine whether E. coli O157:H7 infection can be diagnosed retrospectively from paraffin blocks of colon sections and whether an association exists between E. coli O157:H7 infection and colonic ischemia.

METHODS

Paraffin-embedded sections of normal colon (n = 2) and various colitides [ischemic (n = 11), E. coli O157:H7 (n = 2), IBD (n = 8) and pseudomembranous (n = 3)] were used. Sections were deparaffinized, rehydrated, incubated with 3% peroxide in methanol, rinsed, and incubated with peroxidase-labeled antibody isolated from goats immunized with whole E. coli O157:H7. Sections were stained with peroxidase chromagen reagent and counterstained with hematoxylin. Coarse, granular, orange-brown staining was considered positive. To determine the localization of the chromagen deposits, three cases that stained positive, including one of the culture-proved E. coli O157:H7 colitis and two of colonic ischemia, were processed for electron microscopy.

RESULTS

Both cases (100%) of E. coli O157:H7 colitis and three of 11 (27.3%) cases of ischemic colitis stained positive by light microscopy. In one culture-proved case, electron microscopy demonstrated staining of bacillary structures; in two cases of colonic ischemia, extensive deposits of chromagen material were present that were associated neither with inflammatory cells nor with bacterial forms.

CONCLUSIONS

Immunoperoxidase staining of archival sections may be used to diagnose E. coli O157:H7 infection. An etiological role for this organism is possible in some cases of colonic ischemia.

Efficacy of a new balloon catheter for internal cardioversion of chronic atrial fibrillation without anaesthesia

OBJECTIVE

To compare a new internal cardioversion system incorporated into a balloon guided catheter with a conventional two electrode system in patients with atrial fibrillation (AF).

DESIGN

Prospective study.

PATIENTS

74 patients with chronic AF treated by internal cardioversion.

MATERIALS

A 7.5 F balloon catheter with high energy electrode arrays each consisting of six 0.5 cm platinum rings. Brachial vein access enables one electrode array to be placed in the left pulmonary artery (distal pole) and the other at the lateral right atrial wall (proximal pole). The conventional two electrode system consists of 6 F electrodes placed in the proximal left pulmonary artery (anode) and the lower right atrium.

INTERVENTIONS

Internal cardioversion was performed by shocks delivered in 40 V incremental steps from an external defibrillator. Shocks were applied by the new device to 32 patients (group A) and by the conventional system to 42 patients (group B).

RESULTS

The groups differed with respect to system positioning (9.2 (7.3) upsilon 12.3 (8.1) minutes, p < 0.05) and fluoroscopy times (1.7 (1.0) v 3.3 (2.1) minutes, p < 0.01). Sinus rhythm was restored in 30 patients of group A and in 39 of group B (NS) with mean (SD) energy requirements of 8.4 (3.1) J and 7.2 (3.1) J, respectively (NS).

CONCLUSIONS

This new method of internal cardioversion has comparably high primary success rates and low sedation requirements with single and two lead systems.

New ICD-technologies: first clinical experience with dual-chamber sensing for differentiation of supraventricular tachyarrhythmias

Inappropriate ICD therapy for supraventricular arrhythmias remains an unsolved problem and may lead to serious clinical situations. Current algorithms for differentiation of supraventricular and ventricular arrhythmias are based on ventricular sensing solely and, therefore, lack sensitivity and specificity. This preliminary analysis from a multicenter trial comprises data from the first 26 patients who received a Res-Q Micron active-can ICD (Sulzer Intermedics) with a ventricular defibrillation lead and an additional bipolar lead for atrial sensing. Digitized atrial and ventricular waveform storage as well as interval charts from 102 induced and 30 spontaneous arrhythmia episodes were prospectively collected and analyzed with regard to appropriateness of ICD therapy. From all 132 arrhythmia episodes, high-quality stored dual-chamber intracardiac electrograms (IEGM) could be retrieved for further analysis: in 40 (30%) episodes, atrial fibrillation (AF with rapid ventricular response 22, AF with VT 9, AF with VF 9) was identified as the underlying intrinsic rhythm, and inappropriate ICD therapy was delivered in 4/22 (18%) episodes of AF with rapid ventricular response. In the remaining 92 (70%) episodes, sinus rhythm was the underlying atrial rhythm (SR with VT 13, SR with VF 79), and no inappropriate therapy was observed. Three of 22 (15%) high-energy shocks delivered for ventricular arrhythmias (VT 9, VF 9, rapid AF 4) terminated AF at the same time. In total, there were 3 complications (2 atrial lead dislodgments, 1 revision for bleeding). Both atrial lead dislodgments occurred in the 2 patients with passive-fixation leads compared to none in the 24 patients with active-fixation leads (p = 0.003). In conclusion, dual-chamber sensing and waveform storage of the new Res-Q Micron offer very helpful diagnostic tools for the detection of inappropriate ICD-therapy. Placement of an additional atrial lead is safe and does not interfere with proper ICD function. However, for avoidance of atrial lead dislodgment, active fixation leads are recommended. With the tested active-can lead configuration, the efficacy of successful atrial cardioversion by high-energy shocks delivered for ventricular arrhythmias seems to be low.

A comparison of treatment of atrial fibrillation with low-energy intracardiac cardioversion and conventional external cardioversion

AIM

Low-energy (1 to 15 J), catheter-based intracardiac cardioversion was compared with transthoracic external cardioversion (360 J) in a prospective, cross-over clinical trial.

METHODS AND RESULTS

In 187 consecutive patients with chronic atrial fibrillation, over a period of a mean of 10.0 +/- 7.3 (SD) months, 217 cardioversion attempts were made. Intracardiac shocks were randomly applied between two 6-F catheters located in either the right atrium and coronary sinus or between the right atrium and left pulmonary artery. When a cardioversion attempt with one method failed, the other method was implemented. After cardioversion, all patients were treated orally with sotalol with a mean daily dose of 174 +/- 54 mg. Internal cardioversion was more effective than external cardioversion (65/70 = 93% vs 92/117 = 79%, P < 0.01). The mean energy for successful cardioversion was 5.8 +/- 3.2 J for the internal and 313 +/- 71 J for the external cardioversion group. At a mean follow-up of 12.5 +/- 6.4 months, 48% (38%) of the patients treated with internal (external) cardioversion were in sinus rhythm (P < 0.05). In 22 of 25 patients in whom external cardioversion failed, sinus rhythm was restored with internal cardioversion at a mean energy of 6.5 +/- 3.0 J. Overweight patients had twice the risk of unsuccessful external cardioversion.

CONCLUSIONS

Internal cardioversion is effective in restoring sinus rhythm. It might be indicated in patients in whom external cardioversion had failed or in whom external cardioversion is assumed to be difficult or even contraindicated.

Patient characteristics and underlying heart disease as predictors of recurrent atrial fibrillation after internal and external cardioversion in patients treated with oral sotalol

The aim of this study was to identify predictors for recurrent atrial fibrillation after internal and external cardioversion in 157 patients. After cardioversion, patients were treated orally with sotalol (174 +/- 54 mg/day). Univariate predictors for recurrence included coronary artery disease (p < 0.05) and advanced age (p < 0.05). Multivariate adjusted risk for relapse increased with the presence of coronary artery disease (odds ratio [OR] 3.4, 95% confidence interval [CI] 1.6 to 8.0), presence of atrial fibrillation > 2 months before cardioversion (OR 2.3; 95% CI 1.4 to 4.5), left atrial diameter > 60 mm (OR 2.1; 95% CI 1.2 to 3.1), and age > 65 years (OR 1.6; 95% CI 1.3 to 3.3). In 26% of patients with lone atrial fibrillation, recurrence was observed compared with 51% of patients with underlying structural heart disease (p < 0.05). The mode of conversion, internal or external, had no impact on the recurrence rate. These findings might be useful for selection of the most appropriate therapy for the individual patient.

Evaluation of a new treadmill exercise protocol

STUDY OBJECTIVES

To confirm that a newly drafted treadmill exercise protocol designed on a theoretical basis to span a range of 0 to 200 W with approximately 25-W increments by alteration of either speed or grade from one stage to the next should correspond to a standard bicycle protocol consisting of 25-W steps.

DESIGN

Randomized, crossover study to compare both exercise test modes.

STUDY PARTICIPANTS

Twenty-one consecutive healthy volunteers.

INTERVENTIONS

Subjects underwent both exercise tests until either exhaustion or completion of the respective protocol, and cardiopulmonary exercise parameters were assessed during either of them. For comparison, correlation coefficients (r) were calculated.

RESULTS

Exercise tolerance time was 9% higher on the treadmill (p<0.05). Ten subjects completed the bicycle program, whereas 18 subjects did so on the treadmill. With both protocols, there were comparably linear increases in heart rate (r=0.885), oxygen uptake (r=0.925), oxygen uptake per body weight (r=0.944), carbon dioxide output (r=0.937), and minute ventilation (r=0.914). For the 2-min stage duration, a plateau in oxygen uptake was achieved with neither protocol. The ventilatory equivalent for oxygen, which is not linear, showed its minimum at comparable workloads, at the point of surpassing the anaerobic threshold. Correlation of oxygen pulse was fair (r=0.896).

CONCLUSIONS

There was an excellent correlation of the parameters with respect to both measured values at identical workloads and slopes of both protocols, thus enabling comparability of treadmill and bicycle ergometry. Due to its practical handling, the new protocol may facilitate acceptance, especially when used for elderly or disabled patients.

Effect of electrode position on outcome of low-energy intracardiac cardioversion of atrial fibrillation

The aim of this study was to evaluate the new method of low-energy, catheter-based intracardiac cardioversion in patients with chronic atrial fibrillation (AF) and to compare 2 different lead positions. Accordingly, we prospectively studied 80 consecutive patients with chronic AF (9.8 +/- 7.9 months) who were randomly assigned to undergo internal cardioversion either via defibrillation electrodes placed in the right atrium and coronary sinus (coronary sinus group) or via defibrillation electrodes placed in the right atrium and left pulmonary artery (pulmonary artery group). Intracardiac shocks were delivered by an external defibrillator synchronized to the QRS complex. After conversion, all patients were treated orally with sotalol (mean daily dose, 189 +/- 63 mg/day). For conversion to sinus rhythm, the overall mean energy requirement was 5.6 +/- 3.1 J. In the coronary sinus group, cardioversion was achieved in 35 of 38 patients at a mean energy level of 4.1 +/- 2.3 J (range 1.0 to 9.9), and in the pulmonary artery group in 39 of 42 patients with 7.2 +/- 3.1 J (range 2.5 to 14.8). Although there was no difference with regard to success rate, the energy differed significantly between the 2 groups (p < 0.01). Mean lead impedance was 56.4 +/- 7.0 omega and 54.6 +/- 8.5 omega, respectively (p = NS). No serious complications were observed in either lead group. At a mean follow-up of 14.2 +/- 7.0 months, 54% and 56%, respectively, of patients who had been converted successfully remained in sinus rhythm. Thus, low-energy biphasic shocks delivered between the right atrium and coronary sinus or pulmonary artery are equally effective for cardioversion of patients with chronic AF. The energy requirements for conversion from a pulmonary artery electrode position are higher than for the coronary sinus position.

Does reducing capacitance have potential for further miniaturisation of implantable defibrillators?

OBJECTIVE

To determine whether considerably smaller capacitors could replace 125 microF capacitors as the standard for use in implantable defibrillators.

METHODS

Measured energy, impedance, voltage, and current delivered were compared at defibrillation threshold in 10 mongrel dogs for defibrillation using 75 microF and 125 microF capacitors alternated randomly. Defibrillation was attempted with biphasic shocks of comparable tilt between an endocardial lead in the right ventricular apex and a "dummy" active can of an experimental implantable device placed in the subpectoral position.

RESULTS

A reduction of capacitor size of 40% was associated with an increase in voltage of 21% and in current of 22%. With a 65% tilt, no significant differences were found between the two capacitances with respect to the impedance or energy required for defibrillation.

CONCLUSIONS

Multiple advances in electrode material, electrode configuration, shock morphology, and shock polarity have reduced defibrillation energy requirements. Smaller capacitors could be used in implantable cardioverter/defibrillators without a major decrease in effectiveness.

[Internal defibrillation for cardioversion of atrial fibrillation during radiofrequency catheter ablation in a patient with WPW syndrome]

Although radiofrequency catheter ablation of accessory pathways during atrial fibrillation is possible (1), localisation of bypass tracts and delivery of radiofrequency current may be easier and safer in sinus rhythm. We report on a patient who developed atrial fibrillation with a fast ventricular response during mapping of a right posteroseptal atrioventricular pathway; after internal atrial defibrillation a successful radiofrequency ablation of the accessory pathway could be performed.Having venous sheaths already in place during electrophysiological studies, internal atrial cardioversion is a fast and uncomplicated procedure which may be the treatment of choice in case induced atrial fibrillation does not resolve spontaneously.

Pain threshold for low energy intracardiac cardioversion of atrial fibrillation with low or no sedation

Recent studies have shown that internal cardioversion of atrial fibrillation is safe and effective. In this randomized prospective study, we have tried to evaluate the influence of different waveforms on the perception of pain during internal cardioversion in patients with chronic atrial fibrillation.

METHODS

Internal cardioversion was performed with minimal or no sedation in 31 consecutive patients. R wave triggered, biphasic shocks of 6 ms/6 ms or 3 ms/3 ms duration (randomly selected) and approximately 65% tilt were used starting with a 50-V test shock. The shock intensity was increased in 40-V steps up to a maximum voltage of 520 V Shocks were applied via two custom-made catheters (Elecath, Rahway, NJ). In 16 patients (3 females, age 61 +/- 11 years, left atrium diameter 58 +/- 5 mm, duration of atrial fibrillation 4 +/- 4 months), 6/6 waveforms were used, and in 15 patients (1 female, age 62 +/- 5 years, left atrium diameter 59 +/- 4 mm, duration of atrial fibrillation 5 +/- 2 months), 3/3 waveforms were used. After cardioversion, each patient was asked to quantify their pain on a scale from 0-10 (0 = no pain, 10 = intolerable). Fourteen of the 15 patients in the 3/3 ms and 15 of the 16 patients in the 6/6 ms group were successfully cardioverted. Patients from the 6/6 waveform group were cardioverted with a lower mean voltage of 254/92 versus 355/127 V (P < 0.02), at lower pain score 1.8 +/- 1.3 versus 4.2 +/- 2.2 (P < 0.05) with equivalent energy (6.8 +/- 2.8 versus 6.2 +/- 1.5 J, n.s.) and required lower doses of midazolam of 2.2 +/- 1.9 versus 4.0 +/- 1.8 mg IV (P < 0.02). The waveform used in internal cardioversion seems to have a major impact on the patients' perception of pain. These results imply that energy determines the success of a shock, but voltage determines the pain perceived by the patient. The use of waveforms that deliver greater energy at lower peak voltages offers the possibility of internal cardioversion with less sedation and greater patient tolerance.

Coronary stent placement in patients with acute myocardial infarction: comparison of clinical and angiographic outcome after randomization to antiplatelet or anticoagulant therapy

OBJECTIVES

The Intracoronary Stenting and Antithrombotic Regimen (ISAR) trial is a randomized comparison of combined antiplatelet with anticoagulant therapy after coronary Palmaz-Schatz stent placement. The objective of this study was to compare early and late clinical and angiographic outcome in a subgroup of patients with stent placement for acute myocardial infarction.

BACKGROUND

Stenting has become a treatment option for acute myocardial infarction, but it is not known which antithrombotic regimen is more adequate after stent implantation.

METHODS

One hundred twenty-three patients with successful stenting after acute myocardial infarction were randomized to receive aspirin plus ticlopidine (n = 61) or intense anticoagulant therapy (n = 62). Six-month repeat angiography was performed in 101 (86.3%) eligible patients.

RESULTS

During the first 30 days after stenting, patients with antiplatelet therapy had a significantly lower clinical event rate (3.3% vs. 21.0%, p = 0.005) and stent vessel occlusion rate (0% vs. 9.7%, p = 0.03) and a trend to fewer cardiac events (1.6% vs. 9.7%, p = 0.12). After 6 months, the survival rate free of recurrent myocardial infarction was higher in patients with antiplatelet therapy (100% vs. 90.3%, p = 0.03), and the rate of stent vessel occlusion was lower (1.6% vs. 14.5%, p = 0.02). Both groups had comparable restenosis rates (26.5% vs. 26.9%, p = 0.87).

CONCLUSIONS

This study demonstrates that combined antiplatelet therapy after stent placement in patients with acute myocardial infarction is associated with an overall better clinical and angiographic outcome than anticoagulant therapy.

Improving accelerometer-based rate adaptive pacing by means of second-generation signal processing

Accelerometer-based rate adaptive pacing has gained widespread clinical use. Limitations exist for the distinction between walking upstairs and downstairs. It was the aim of this study to evaluate a new signal processing algorithm for more physiological rate adaptation. A custom-made pacemaker incorporating an accelerometer was randomly fixed to the left or right chest of 16 pacemaker patients (7 females, age: 64 +/- 11 years), 18 elderly study participants (6 females, age: 62 +/- 11 years), and 15 students (7 females age: 23 +/- 2 years). Study participants walked on level ground, upstairs and downstairs at five different step rates (72, 84, 96, 108, and 120 steps/min) controlled by an acoustic quartz metronome. The accelerometer signals, recorded on a portable data recorder, were analyzed with respect to frequency content, peak average of the mean acceleration, and morphology characteristics of the acceleration signal above and below zero baseline. By calculating the quotient of the signal's duration above and below zero baseline, a reliable discrimination between walking upstairs and downstairs was possible. A correction of the Leaky integrator signal by the new quotient yielded a more adequate rate adaptation to walking up and downstairs to represent at the patient's daily life activities. A more physiological rate adaptation can be achieved when using not only the accelerometer signal's amplitude, but applying additionally the morphology criterium of the acceleration signal's content in the positive and negative direction.

Initial experience with implantation of internal cardioverter/defibrillators under local anaesthesia by electrophysiologists

This study was designed to evaluate the implantation of internal cardioverter/defibrillators under local anaesthesia by electrophysiologists and to compare this to our former experience of implants with general anaesthesia. Forty-seven internal cardioverter/defibrillators were implanted at our institution by electrophysiologists. Twenty-nine operations were performed under general anaesthesia (isoflurane 0.4-0.6%), and 18 under local anaesthesia (mepivacain 1%). The defibrillator leads were introduced by venotomy of the cephalic vein (n = 25), puncture of the subclavian vein (n = 17) or both (n = 5). All devices were implanted beneath the pectoral muscles. The mean operation time was 99 +/- 29 min. In the group with local anaesthesia the operation time was significantly shorter than with general anaesthesia (86 +/- 20 min vs 107 +/- 31 min; P = 0.027). The defibrillation threshold with biphasic shock application was below 24 J in all patients; thus, the implantation of an additional subcutaneous patch electrode was unnecessary. There were no major complications in either group. However, modifications were required in four patients: in one a set screw had to be re-tightened after delivery of an erroneous shock in the early postoperative phase; in another, device migration occurred several weeks after implantation, but no therapeutic intervention was required; in another, a rise in pacing threshold and partial sensing loss were noted ten days postoperatively; in the fourth, a minor pneumothorax occurred after subclavian puncture, but no further treatment was necessary. There was no intra-operative or postoperative mortality in either group. Implantation of internal cardioverter/defibrillators under local anaesthesia and mild sedation is feasible, and can be safely performed by electrophysiologists experienced in basic surgery. The newly developed smaller devices allow implantation in the subpectoral region, and with "active can' configuration and biphasic shock application, subcutaneous patch electrodes become unnecessary.

Low energy intracardiac cardioversion after failed conventional external cardioversion of atrial fibrillation

OBJECTIVES

This study was designed to evaluate the efficacy of intracardiac cardioversion in patients with chronic atrial fibrillation after unsuccessful external cardioversion.

BACKGROUND

Previous studies in patients with atrial fibrillation undergoing intracardiac cardioversion have suggested that intracardiac cardioversion is highly effective and safe. However, the characteristics of patients who benefit most from this invasive technique are unknown.

METHODS

We prospectively studied 25 consecutive patients with chronic atrial fibrillation (11 +/- 9 months). All patients had undergone at least three attempts at conventional external transthoracic cardioversion by means of paddles in an anteroposterolateral position applying energies up to 360 J without success. Intracardiac shocks were delivered by an external defibrillator through defibrillation electrodes placed in the right atrium and coronary sinus or in the right atrium and left pulmonary artery. After conversion, all patients were treated orally with sotalol (mean 194 +/- 63 mg/day).

RESULTS

Internal cardioversion was successful in 22 of 25 patients at a mean defibrillation threshold of 6.5 +/- 3.0 J. Mean lead impedance was 56.4 +/- 7.4 omega. No severe complications were observed. At a mean follow-up of 15 +/- 12 months, 12 (55%) of the patients treated successfully remained in sinus rhythm.

CONCLUSIONS

In patients with failed external cardioversion, internal cardioversion offers a new option for restoring sinus rhythm. Intracardiac cardioversion is an effective and safe method and can be easily performed in patients with minimal sedation.

Ventricular tachycardia initiated solely by reduced pacing rate during routine pacemaker follow-up

Ventricular arrhythmias during a pacemaker follow-up have been previously reported, usually in conjunction with temporary asynchronous stimulation of a demand pacemaker through magnet application or by increased myocardial excitability, for example, following a myocardial infarction. The subject of this report, an 82-year-old pacemaker patient, had been VVI-paced without problems for the past 11 years. As an aid in determining the sensing threshold, the pacemaker lower rate was reduced from 70 to 40 beats/min. A ventricular tachycardia of 240 beats/min was induced, most likely following short-long cycles; syncope resulted. To our knowledge, this is the first report of induction of a ventricular tachycardia during pacemaker follow-up solely by reduction of pacing rate and not by asynchronous pacing. This case demonstrates an additional potential risk associated with pacemaker rate manipulation during pacemaker follow-up.

Activity controlled cardiac pacemakers during stairwalking: a comparison of accelerometer with vibration guided devices and with sinus rate

Activity controlled pacemakers are the most widely used rate adaptive systems. We studied second-generation activity controlled systems (accelerometer) in 21 patients with such an accelerometer controlled system implanted during walking level and stairs. We compared them to the rate of vibration controlled, first-generation activity pacemakers and to the sinus rate of a healthy control group. A metronome directed the speed during walking and climbing stairs at 92, 108, and 120 steps/min. At 92 steps/min, the new accelerometer controlled systems showed a significant (P < or = 0.001) pacing rate increase from 107 +/- 8 beats/min during walking level to 124 +/- 8 beats/min during climbing stairs, and a significant decrease to 105 +/- 12 beats/min during walking downstairs. In contrast, first-generation activity controlled pacemakers showed a less physiological rate behavior with higher pacing rate (113 +/- 7 beats/min) walking downstairs than walking upstairs (97 +/- 9). For everyday activities at normal walking speed, accelerometer controlled pacemakers show a more physiological rate behavior than first-generation pacemakers, but they lose this physiological response with faster walking.