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Aims Current data concerning the influence of X-ray contrast media on the incidence of thrombotic complications in interventional cardiology are controversial. The effect of ionic contrast media on acute (≤72h) and subacute (≤30 days) stent thrombosis has not been investigated.Methods Three thousand, nine hundred and ninety consecutive patients underwent coronary stent placement. Group I (n=1808) received non-ionic contrast media while group II (n=2182) was given the ionic Ioxaglate. All patients were treated with a standard regimen of aspirin and ticlopidine for 4 weeks post intervention.Results Both acute and subacute stent occlusion occurred more frequently in patients receiving non-ionic contrast media compared to ionic contrast media (acute stent occlusion: 1·3% in group I vs 0·3% in group II, P=0·001; subacute stent occlusion: 2·4% in group I vs 0·7% in group II, P=0·001). The incidence of the combined clinical end-point of coronary artery bypass grafting, target lesion revascularization, and overall mortality within 12 months was significantly reduced by the use of Ioxaglate (22·9% vs 16·3%,P =0·001).Conclusions Based upon these data, we recommend the use of Ioxaglate in coronary interventions when stent placement is anticipated. [ABSTRACT FROM PUBLISHER]

In a prospective, double-blind, randomized, placebocontrolled study we investigated the facilitating influence of intravenous procainamide on conversion of atrial flutter by rapid atrial pacing.Fifty consecutive patients with spontaneous sustained atrial flutter were 1:1 randomized into two homogenous groups: group A received 10 mg. kg−1 procainamide intravenously, group B placebo. After infusion there was a significant (P<0·01) lengthening of the flutter cycle with respect to baseline in group A, exceeding the flutter cycle length of the control group (P<0·05). The overall success rate of rapid atrial pacing in restoring sinus rhythm was significantly higher after pre-treatment with procainamide compared to placebo (100% vs 76% P<0·05): 20 patients of group A reverted immediately after pacing to sinus rhythm, the remaining five after a brief episode of atrial fibrillation. In the placebo group, 16 patients showed a prompt conversion to sinus rhythm and three after transient atrial fibrillation. In the remaining six patients, due to sustained pacing-induced atrial fibrillation, direct current cardioversion was necessary. After administration of procainamide a less aggressive stimulation protocol with significantly (P<0·01) longer paced cycles to interrupt atrial flutter was achievable.In conclusion, intravenous procainamide augments the efficacy of atrial pacing to convert atrial flutter to sinus rhythm. [ABSTRACT FROM PUBLISHER]

Milrinone exerts positive inotropic and dose-dependent vasodilatory effects that promote haemodynamic improvement after intravenous administration to patients with heart failure. Bolus doses of 12·5–75 μg kg−1 markedly increase cardiac output and cause a substantial reduction in cardiac filling pressure and in systemic vascular and pulmonary vascular resistance. There is no evidence of tolerance to these effects which are maintained during continuous infusion for up to 48 h. In contrast, there are minimal effects on heart rate or systemic blood pressure, except at very high doses. At lower filling pressures, milrinone increases cardiac output more markedly than equally hypotensive doses of pure vasodilators. This response is accompanied by an increased left ventricular dP/dtmax and a shift in the left ventricular performance is associated with a lower myocardial energy requirement. Despite a fall in mean arterial pressure and transcoronary driving pressure, coronary venous flow is increased and there is a reduction in the arterio-coronary venous oxygen difference. This reflects a global improvement in left ventricular diastolic function, characterized by accelerated early relaxation and greater chamber distensibility. Improved performance of the right ventricle is due primarily to reduced right ventricular afterload as milrinone produces minimal inotropic effects on the right ventricle. [ABSTRACT FROM PUBLISHER]

To verify favourable long-term effects, 14 patients with chronic congestive heart failure, NYHA class II-IV, who had been treated with oral amrinone for 8–15 months with apparent clinical benefit, had the drug with drawn according to a 12 week placebo controlled double-blind crossover protocol. Evaluation was performed noninvasively by means of exercise stress test, echocardiogram, radionuclide angiography and systolic time intervals. None of these variables were significantly changed after discontinuation of amrinone, regardless of whether placebo was introduced during the first (group B, N = 7) or the second 6 week period (group A, N = 5), nor when the medication was finally openly withheld for another 6 weeks. In 2 further group A patients, premature termination of the trial was due to deterioration of symptoms on blinded amrinone. Hence, no sustained drug related effects could be proven by controlled withdrawal of long-term amrinone in this trial. [ABSTRACT FROM PUBLISHER]

The intraindividual changes of ventricular late potentials and their possible determinants were examined prospectively in 88 consecutive patients (male: 75; mean age: 58 +/- 9 years) after thrombolytic therapy for acute myocardial infarction. Late potential analysis was performed 4 weeks and 12 months after acute myocardial infarction. At the same time, a left heart catheterization was performed to assess the extent of coronary heart disease and left ventricular ejection fraction. The incidence of late potential 4 weeks after acute myocardial infarction was 15% (13/88 patients). Eighteen percent (16/88) of the patients revealed changing results of late potential analysis: 9 patients lost late potential (late potential pos./neg.) 1 year after acute myocardial infarction and 7 patients presented new formation of late potential (late potential neg./pos.). Preserved late potentials were found in four patients (late potential pos./pos.). Late potential analysis remained negative in 68 patients (late potential neg./neg.). There was no influence of age, gender, site of infarction, clinical course, and medical treatment on the natural course of late potential. Changing results of late potential analysis seemed to be correlated with the evolution of left ventricular ejection fraction and the dynamics of coronary heart disease. In the group late potential pos./pos., comparable values for left ventricular ejection fraction were measured at both examinations, whereas late potential neg./neg. had a significant increase in ejection fraction. In the group late potential pos./neg., a significant improvement in left ventricular function was also measured. In contrast, the late potential neg./pos. group tended to have lower left ventricular ejection fractions 1 year after infarction. In the late potential neg./pos. and late potential pos./pos. groups, the extent of coronary artery disease returned to conditions comparable to baseline despite an initial reduction after coronary revascularization performed 4 weeks after infarction. Late potential neg./neg. and late potential pos./neg. revealed a stable benefit gained from coronary revascularization with a persistent reduction in the number of diseased vessels. Dynamic changes in the results of the signal-averaged ECG 1 year after thrombolytic therapy for acute myocardial infarction were observed in 18% of the patients. These changes seem to be correlated with the evolution of left ventricular function and the dynamics of coronary artery disease. [ABSTRACT FROM AUTHOR]

Purpose: Primary stenting leads to better short-term outcomes than does balloon angioplasty among patients with acute myocardial infarction, but there are no data available on long-term follow-up.Subjects and Methods: We designed a randomized study with long-term follow-up to compare primary angioplasty with angioplasty accompanied by implantation of a silicon carbide-coated stent in patients within 24 hours after the onset of acute myocardial infarction. All 88 patients had lesions that were suitable for coronary stenting.Results: There were 44 patients in each of the randomization groups. During long-term follow-up (mean +/- SD: 710+/-282 days), primary stenting was associated with a reduction in the combined endpoint of death, reinfarction, or target vessel revascularization (10 [23%] versus 19 [43%], P = 0.03); death (4 [9%] versus 8 [18%], P = 0.18); reinfarction (1 [2%] versus 4 [9%], P = 0.18); and target lesion revascularization (7 [16%] versus 15 [34%], P = 0.04). Rehospitalization due to ischemic events (unstable angina or reinfarction) was also less frequent in the stent group (6 [14%] versus 10 [23%], P = 0.20).Conclusion: Primary stenting in acute myocardial infarction is significantly superior to angioplasty alone in both short-term and long-term follow-up. [ABSTRACT FROM AUTHOR]

In 19 patients paced and medicated for bradycardia tachycardia syndrome (BTS), AAIR and DDDR pacing were compared with regard to quality of life (QoL), atrial tachyarrhythmia (AFib), exercise tolerance, and left ventricular (LV)function. Patients had a PQ interval < or = 240 ms during sinus rhythm, no second or third degree AV block, no bundle branch block, or bifascicular block. In DDDR mode, AV delay was optimized using the aortic time velocity integral. After 3 months, QoL was assessed by questionnaires, patients were investigated by 24-hour Holter, cardiopulmonary exercise testing (CPX) was performed, and LV function was determined by echocardiography. QoL was similar in all dimensions, except dizziness, showing a significantly lower prevalence in AAIR mode. The incidence of AFib was 12 episodes in 2 patients with AAIR versus 22 episodes in 7 patients with DDDR pacing (P = 0.072). In AAIR mode, 164 events of second and third degree AV block were detected in 7 patients (37%) with pauses between 1 and 4 seconds. During CPX, exercise duration and work load were higher in AAIR than in DDDR mode (423+/-127 vs 402+/-102 s and 103+/-31 vs 96+/-27 Watt, P < 0.05). Oxygen consumption (VO2), was similar in both modes. During echocardiography, only deceleration of early diastolic flow velocity and early diastolic closure rate of the anterior mitral valve leaflet were higher in DDD than in AAI pacing (5.16+/-1.35 vs 3.56+/-0.95 m/s2 and 69.2+/-23 vs 54.1+/-26 mm/s, P < 0.05). As preferred pacing mode, 11 patients chose DDDR, 8 patients chose AAIR. Hence, AAIR and DDDR pacing seem to be equally effective in BTS patients. In view of a considerable rate of high degree AV block during AAIR pacing, DDDR mode should be preferred for safety reasons.

Unlabelled: Balloon catheters filled with liquid radioisotopes provide excellent dose homogeneity for intracoronary radiation therapy but are associated with risk for rupture or leakage. We hypothesized that the safety of liquid-filled balloons may be improved once positron emitters with half-lives below 2 h are used instead of the high-energy beta-emitters 166Ho, 186Re, or 188Re, all of which have a longer half-life of at least 17 h., Methods: To support this concept, the suitability of 18F (half-life, 109.8 min), 68Ga (half-life, 67.6 min), 11C (half-life, 20.4 min), 13N (half-life, 9.97 min), and 15O (half-life, 2.04 min) for intracoronary radiation therapy was evaluated. Potential tissue penetration of positron radiation was assessed in a series of phantom experiments using Gafchromic film. Antiproliferative efficacy of positrons emitted by 68Ga was investigated in vitro using cultured bovine aortic smooth muscle cells (BASMCs), and was compared with gamma-radiation emitted by 137Cs. To characterize the remaining risk, we estimated radiotoxicity after accidental intravascular balloon rupture on the basis of tabulated isotope-specific doses (ICRP 53) and compared these values with 188Re., Results: Half-dose depth of tissue penetration measured in phantom experiments was 0.29 mm for 18F, 0.42 mm for 11C, 0.54 mm for 13N, 0.79 mm for 15O, and 0.9 mm for 68Ga. Irradiation of cultured BASMCs with positron radiation (68Ga) induced dose-dependent inhibition of proliferation with complete proliferative arrest at doses exceeding 6 Gy. ED(50) and ED(80) were 2.5 +/- 0.4 Gy (mean +/- SD) and 4.4 +/- 0.8 Gy, respectively. Antiproliferative efficacy was equal to that of the 662-keV gamma-radiation emitted by 137Cs (ED(50), 3.8 +/- 0.2 Gy; ED(80), 8.0 +/- 0.3 Gy). Estimates made for patient whole-body and organ doses were generally below 50 mSv/1.85 GBq for all investigated positron emitters. The same dose estimates for 188Re were 6-20 fold higher., Conclusion: Among the studied radioisotopes, 68Ga is the most attractive source for liquid-filled balloons because of its convenient half-life, sufficient positron energy (2.92 MeV), documented antiproliferative efficacy, and uncomplicated availability from a radioisotope generator. The safety profile for 68Ga is significantly better than that of 188Re, which suggests this radioisotope should be evaluated further in preclinical studies.

In 120 consecutive patients with standard pacing indications, we tested the feasibility of RV septal lead implantation technique guided by surface ECG and the degree to which this technique reduces paced QRS duration compared to RV apical stimulation when passive-fixation leads are used. During implantation, an ECG was recorded with a paper speed of 100 mm/s using the orthogonal Frank leads, and QRS was measured from the earliest to the latest deflection in any of the Frank leads. Pace-mapping of the septum was performed until QRS was minimal. The lead was attached, where QRS, pacing threshold, lead impedance, and EGM amplitude provided the best compromise. An average of 3.7 +/- 2.5 attempts (range 1-18, median 7) was needed until a final implantation site was found. There were no technical problems during implantation. QRS could be reduced by 5-55 ms (mean delta QRS 19 +/- 11 ms) in 83 (69%) of 120 patients. In 22 (18%) patients, QRS was identical with apical and septal pacing, and in 15 (13%) patients, QRS was 5-20 ms (10 +/- 4) longer despite septal stimulation. Average QRS was significantly shorter during septal pacing compared with apical pacing (151 +/- 20 vs 162 +/- 23 ms, P < 0.001). There was a tendency towards greatest QRS reduction when the high septum was stimulated (22 +/- 11 ms reduction) as compared with mid- (18 +/- 11 ms) or apical parts of the RV septum (16 +/- 10 ms). QRS reduction was most likely if apical QRS width was > 170 ms (P = 0.0002), and there was an inverse correlation between apical QRS and delta QRS (r = 0.53, P < 10(-7)). During a mean follow-up of 14 months, there was no pacing or sensing problem and no lead dislodgment occurred.

Unlabelled: Three bipolar atrial pacing leads from one manufacturer differing in a single electrode design characteristic were compared. Each lead had nonretractable screw and a microporous electrode tip made of activated carbon. Model S84F had a tip surface area of 8 mm2. In model S44F, the tip surface area was reduced to 4 mm2 by insulation of the screw, and in model BS45D, steroid elution was added to the 4 mm2 tip. Ten patients in each group received identical pulse generators. During implantation, atrial potentials (5.4 +/- 2.0, 4.2 +/- 2.0, 4.6 +/- 2.1 mV), pacing thresholds at 0.5 ms (0.47 +/- 0.14, 0.41 +/- 0.15, 0.55 +/- 0.33 V) and lead impedance at 2.5 V/0.5 ms (515 +/- 80, 575 +/- 152, 546 +/- 131 omega) were comparable among groups. The early postoperative threshold peak was significantly lower with the BS45D than with the S84F and S44F lead models. One year after implantation, charge threshold was significantly lower with the BS45D lead than with the S84F and the S44F model (0.34 +/- 0.11 vs. 0.68 +/- 0.20 and 0.56 +/- 0.21 microC; P < 0.05). Lead impedance at 2.5 V/0.5 ms (557 +/- 90, 549 +/- 36, 524 +/- 72 omega) and atrial sensing (4.3 +/- 2.1, 4.7 +/- 1.9, 4.7 +/- 0.9 mV) were not significantly different. One year postimplant, current drain of the pacing system was measured by pacemaker telemetry at chronic output settings in AAI mode/70 beats/min. Battery current measured among the three atrial lead models did not differ significantly (S84F: 11.9 +/- 0.90, S44F: 12.2 +/- 1.8, BS45D: 11.5 +/- 0.26 microA)., In Conclusion: reduction of the tip surface area by insulation of the screw did not improve pacing performance. Addition of steroid elution to the 4 mm2 tip significantly lowered the early threshold peak and the long-term pacing threshold. Lowering of the pacing threshold, however, did not lower the current drain of the pacing system.

Patients in intensive care may be at high risk of in vivo platelet activation because comorbid conditions, such as infections, septicemia, shock, disseminated intravascular coagulation, and cancer represent procoagulant states. Hyperreactivity of platelets with or without a decline of cell count may result in thromboembolic complications potentially associated with the phenomenon of heparin-induced thrombocytopenia. We analyzed the data of 10 patients highly suspected of having heparin-induced thrombocytopenia during their intensive care treatment of 29 plus or minus 22 days. In seven patients, thrombocytopenia coincided with thromboembolic complications. Six patients had additionally undergone fibrinolytic therapy before starting activated partial thromboplastin time-adapted alternative anticoagulation with r-hirudin. In three patients, the platelet count decreased without a clinical manifestation, of heparin-induced thrombocytopenia. R-Hirudin treatment monitored by activated partial thromboplastin time and prothrombin time (PT) was effective and safe. The target value for activated partial thromboplastin time was a twofold prolongation. In four of five patients with deep venous thrombosis, a partial recanalization of the lower extremity could be achieved. Three patients with pulmonary embolism associated with deep venous thrombosis in two cases and in one additional case with an acute myocardial infarction did clinically profit from fibrinolysis with recombinant tissue plasminogen activator (rtPA) and r-hirudin treatment. Two lethal events probably caused by the underlying multimorbidity could not be prevented. No recurrence of thrombosis occurred, and there were no severe bleeding complications attributed to r-hirudin treatment. Platelet counts were significantly reduced on day 9.4 plus or minus 6.4 of heparin administration in all cases (>50% decrease related to the initial values) from 224,000 plus or minus 126,000/microL to 96,000 plus or minus 61,000/microL, and increased during rhirudin treatment to mean values of 224,000 plus or minus 126,000/microL. The heparin-induced platelet activation assay (HIPAA) assay was positive in 8/10 cases, whereas the PF4 enzyme-linked immunosorbent assay showed a positive result in four of eight analyzed cases. In four cases, the assays were concordantly positive. The PF4 enzyme-linked immunosorbent assay was not performed in two cases.

Background: The rubidium 81/krypton 81m method was suggested for assessment of myocardial blood flow (MBF) three decades ago. This study investigates the novel concept of using 81Rb-/81mKr-labeled coronary guide wires with wire-attached 81Rb activity and diffusable 81mKr gas for assessment of lesion-specific impairment of MBF by evaluation of the 81Rb/81mKr activity ratio. The feasibility of wire production is tested, and application of the method is investigated in the canine model., Methods and Results: Conventional coronary guide wires for angioplasty (0.014 in) were labeled with radioactive 81Rb/81mKr by ion bombardment of the wire tip. A total of 16 of the 18 wires labeled in series showed successful 81Rb fixation in combination with free 81mKr gas diffusability during quality control measurements. The suitability of the wires to assess MBF in combination with an external gamma ray detector was investigated in open-chested dogs. Electromagnetic measurement of coronary blood flow (CBF) was used as reference, providing a signal that is directly linked to volumetric MBF. The 81Rb/81mKr ratio tracked changes in CBF reliably in all 6 dogs. The found linear dependence of measured 81Rb/81mKr count rates on measured CBF supports the modeling assumptions made to apply the theoretic basis of the 81Rb/81mKr technique to 81Rb-labeled coronary guide wires., Conclusion: 81Rb-/81mKr-labeled coronary guide wires provide a signal that indicates volumetric MBF directly. This unique capability may qualify the technique as a valuable tool for research purposes and as an attractive method for invasive cardiology at centers where the logistic arrangements for short-lived isotope supply are provided.

Background: The hemodynamic superiority of stentless valves at rest has been generally accepted, but there is a lack of studies on exercise hemodynamics., Methods: We assessed aortic valve hemodynamics at rest and during exercise in 10 patients with a 23-mm stentless aortic bioprosthesis (Medtronic Freestyle; Medtronic Europe SA/NV, St. Stevens Woluwe, Belgium), in 10 patients with a 23-mm stented aortic bioprosthesis (Carpentier-Edwards, SAV, model 2650; Baxter Edwards AG, Horw, Switzerland), and in 10 healthy volunteers (control group) by means of Doppler echocardiography., Results: Gradients at rest and gradients on comparable maximum exercise levels were significantly lower in patients with stentless valves compared to those with stented valves (rest: 6 +/- 2/11 +/- 4 mm Hg [mean/peak] versus 12 +/- 3/21 +/- 10 mm Hg; exercise: 9 +/- 3/18 +/- 6 mm Hg [mean/peak] versus 22 +/- 8/40 +/- 11 mm Hg). Patients with stentless valves revealed, in comparison to healthy young men, significantly higher gradients, but the small gradient difference of 3/7 mm Hg (mean/peak) at rest remained nearly unchanged throughout the exercise protocol (4/8 mm Hg [mean/peak] at 25 W, 4/9 mm Hg at 50 W and 4/9 mm Hg at 75 W). In contrast, the gradient difference between patients with stented and stentless valves increased significantly from one exercise level to the next (6/12 mm Hg [mean/peak] at rest, 8/14 mm Hg at 25 W, 12/17 mm Hg at 50 W, and 15/25 mm Hg at 75 W)., Conclusions: A stentless aortic bioprosthesis seems to be an appropriate aortic valve substitute, especially in patients who perform regular physical exercise.

In vitro studies suggest that ionic and nonionic X-ray contrast media have different effects on rheological parameters. The risk of thrombotic complications in coronary interventions was reported to be lower using ionic contrast media. The aim of the present study was to compare the effects of different types of contrast media on rheological parameters after coronary angiography. Sixty patients were randomized to four groups: ioxaglate 320 (dimeric, ionic, n = 18), iomeprol 400 (monomeric, nonionic, n = 12), iobitridol 350 (monomeric, nonionic, n = 12), and iodixanol 320 (dimeric, nonionic, n = 18). Blood samples were collected via the side port of the arterial sheath immediately before and at the end of coronary angiography. In our study, all types of contrast media caused a significant decrease in haematocrit (Hct), plasma viscosity (PV), erythrocyte aggregation (EA), and in the platelet reactivity index (PRI). The most pronounced decrease in Hct was found using the ionic dimer ioxaglate. There were no significant differences between the contrast media with respect to their effects on PV, EA, and PRI.

In an attempt to evaluate the prevalence and predisposing factors of bipolar ventricular far-field oversensing, 57 patients were studied who had a Medtronic dual chamber pacemaker implanted (models 7940: n = 6; 7960i: n = 41; 401: n = 3; 8968i: n = 7) and bipolar atrial leads with a dipole spacing from 8.6 to 60 mm attached to various parts of the atrial wall (lateral/anterior: n = 30; appendage: n = 10; atrial septum: n = 10; floating: n = 7). Median bipolar sensing threshold for P waves was 4.0 mV (2.8-4.0 mV, lower and upper quartile) with standard leads and 0.35 (0.25-1.4) mV with single pass (VDD) devices. At the highest sensitivity available, 43 of 50 DDD pacemakers but only two of seven VDD systems detected intrinsic R waves in the atrium (P < 0.01). Ventricular far-field oversensing occurred at 0.5 mV in 28 (56%) and at 1.0 mV in 16 of 50 DDD units (32%), respectively, and there was one observation in a septal implant at a sensitivity of even 2.8 mV. With ventricular pacing, VDD systems were as susceptible to far-field signals as DDD pacemakers. Outside the postventricular blanking period (100 ms), evoked R waves were detected by 27 of 57 systems (47%) at maximum atrial sensitivity, by 10 (18%) at 0.5 mV, and by 2 (4%) at a setting of 1.0 up to 1.4 mV, respectively. There was no definite superiority of any lead position, there was a trend in favor of the atrial free wall for better intrinsic R wave rejection, but just the opposite was the case for paced ventricular beats. Bipolar signal discrimination tended to be higher with short tip-to-ring spacing (1 7.8 mm) but the difference to larger dipole lengths (30-60 mm) was not significant in terms of the R to P wave ratio and the overall far-field susceptibility. In summary, bipolar ventricular far-field oversensing in the atrium is common with short postventricular blanking times and high atrial sensitivity settings that may be warranted for tachyarrhythmia detection and mode switching. A potentially more discriminant effect of shorter dipole lengths (< or = 10 mm) remains to be tested.

AV conduction with atrial rate adaptive pacing (AAIR) during exercise was investigated in 43 patients (28 men, 15 female, mean age 68 +/- 7 years) who were paced and medicated with antiarrhythmic drugs for the bradycardia tachycardia syndrome (BTS). Patients were included if they had no second- or third-degree AV block, no complete bundle branch or bifascicular block, and a PQ interval < or = 240 ms during sinus rhythm at rest. The interval between the atrial spike and the following Q wave (SQ) was measured in the supine position at rest (R) with maximum AAI pacing rate (Fmax) achieved below the Wenckebach point (SQ-R-Fmax). Bicycle ergometry was performed using the Chronotropic Assessment Exercise Protocol, and AAI pacing rate was increased stepwise by programming load-adapted increments. Seven patients showed intrinsic rhythm during exercise. In those 36 patients who were atrially paced throughout ergometry (E), SQ was measured with 70 beats/min on the lowest CAEP stage (SQ-E-70) and with Fmax at maximum work load (SQ-E-Fmax). During exercise, no second-degree AV block was observed, but 28 of 36 patients (78%) showed a nonphysiological increase of the SQ interval, and the average SQ-E-Fmax was significantly longer than SQ-E-70 (250 +/- 31 versus 228 +/- 32 ms, P < 0.01). There was only a weak correlation between SQ-R-Fmax and SQ-E-Fmax (r = 0.35824, P < 0.05). When Fmax obtained during exercise was kept during recovery, 14 patients (39%) developed a second-degree AV block between 15 and 240 seconds after ergometry, 8 patients within 90 seconds. Patients who had exhibited a P on T wave in the ECG with Fmax at the end of exercise (11 of 36 patients) were reevaluated by Doppler echocardiography. Using the same exercise protocol and identical, load-adapted rate increments, only 3 of 11 patients showed premature mitral valve closure. It is concluded that patients paced and medicated for BTS are prone to a nonphysiological prolongation of AV conduction with AAIR pacing during and after exercise. As this risk can hardly be predicted by rapid atrial pacing at rest, the pacing system should be dual chamber in this subset of patients. This especially applies to the patients in whom mechanical AV timing is affected by the conduction delay.

Steroid-eluting pacing leads are known to attenuate the threshold peaking early after implantation. Long-term performance, however, is not yet settled. The lead design tested in this prospective study combines a 5.8-mm2 tip of microporous platinum-iridium with elution of 1.0 mg of dexamethasone sodium phosphate and tines for passive fixation (model 5024, Medtronic Inc.). In 50 patients (mean age 69 +/- 10 years), the electrode was implanted in the right ventricular apex. Follow-up was performed on days 0, 2, 5, 10, 28, 90, 180 and every 6 months thereafter for 5-years postimplant. At each visit, pacing thresholds were determined as pulse duration (ms) at 1.0 V and as the minimum charge (microC) delivered for capture. Lead impedance (omega) was telemetered at 2.5 V-0.50 ms, and sensing thresholds (mV) were measured in triplicate using the automatic sensing threshold algorithm of the pacemaker implanted (model 294-03, Intermedics Inc.). On the day of implantation, mean values were 0.10 +/- 0.03 ms, 0.12 +/- 0.03 microC, 758 +/- 131 omega, and 13.1 +/- 1.8 mV, respectively. Beyond 1-year postimplant, pacing thresholds did not vary significantly. Sensing thresholds and lead impedance values were stable during long-term follow-up. Five years after implantation, mean values were 0.23 +/- 0.11 ms, 0.24 +/- 0.07 microC, 670 +/- 139 omega, and 11.6 +/- 3.1 mV for pulse width and charge threshold, lead impedance, and sensing threshold, respectively, and all leads captured at 1.0 V with the longest pulse duration available (1.50 ms). It is concluded that the bipolar steroid-eluting tined ventricular lead showed stable stimulation thresholds, lead impedance values, and sensing thresholds for 5 years after implantation.

It was shown in a series of studies that increased lipoprotein (a) concentration is a strong and independent risk factor for coronary artery disease. The goal of this study was to determine the significance of elevated lipoprotein (a) levels for the existence and the early manifestation of coronary artery disease by systematically recording cardiovascular risk factors in diagnostic coronary angiographies in a larger group of patients, whereby particular attention was paid to sex-specific differences. In 1011 consecutive patients who underwent coronary angiography (731 men, 280 women, mean age 59 +/- 10 years), fasting blood samples were taken immediately before the angiographies to determine the levels of cholesterol, low density lipoprotein-, high density lipoprotein-cholesterol, triglycerides and lipoprotein (a). In addition, further risk factors were qualitatively recorded. The data evaluation was carried out using the SPSSx software package univariately and multivariately with stepwise discriminant analysis. In 231 patients (144 men, 87 women) either no or only discrete coronary findings appeared, while in 780 cases (587 men, 193 women) coronary artery disease with stenoses > 50% were found. Women with coronary artery disease were significantly older than men and demonstrated higher lipoprotein levels. Women as well as men with coronary artery disease differed from healthy controls by having higher levels of lipoprotein (a) and other lipoproteins, lipoprotein (a) having the smallest error probability (P < 0.0005). The early manifestation of coronary artery disease (below the 18th age percentile) in men (< 50 years) was connected with significantly higher levels of cholesterol, triglycerides and lipoprotein (a), which emphasized their atherogenic significance in the general view. The most striking finding was that in young women (< 53 years), compared to older women with coronary artery disease--corresponding to the age-determined prevalence--significantly lower concentrations of cholesterol, triglycerides and lipoprotein (a) were found. Possible explanations include later manifestation of coronary artery disease, a steeper increase of the lipids with age, particularly of lipoprotein (a), but also a different valence of the risk factors in women.

Objectives: The study investigates the correlation between left ventricular function and QRS duration obtained by alternate right ventricular pacing sites., Background: 1. Right ventricular apical pacing is associated with alterations of left ventricular contraction sequence. 2. A stimulation producing narrow QRS complexes is supposed to provide for better left ventricular contraction patterns., Methods: Fourteen patients with third degree AV block received one ventricular pacing lead in apical position. The alternate lead was attached to that site on the septum that produced the smallest QRS complex as measured from the earliest to the last deflection in any of the orthogonal Frank leads (xyz). During atrial synchronous ventricular pacing, the AV delay was optimized individually and for each stimulation site using mitral valve doppler or impedance cardiography. By radionuclide ventriculography, the phase distribution histogram of left ventricular contraction was evaluated as area under the curve (AuC); systolic function was determined as ejection fraction (EF) and as absolute ejected counts (EC) in random order. The difference (delta) in QRS duration between apical and septal stimulation (deltaxyz) was correlated with the difference in phase distribution (deltaAuC) and ejection parameters (deltaEF, deltaEC)., Results: QRS duration was shorter with septal than with apical pacing in 9 out of 14 patients (64%); it was longer in 4 (29%), and no difference was seen in 1 patient. There was a significant positive correlation between the change in QRS duration (deltaxvz) and phase distribution (deltaAuC: r = 0.66393, p = 0.010) and a significant negative correlation to systolic function (deltaEF: r = 0.70931, p = 0.004; deltaEC: r = 0.74368, p = 0.002)., Conclusions: In atrial synchronous right ventricular pacing, if the AV delay is adapted individually, decreased QRS duration obtained by alternate pacing sites is significantly correlated with homogenization of left ventricular contraction and with increased systolic function in acute tests.

Recent studies have shown that transvenous atrial cardioversion is feasible with lead configurations primarily designed for implantable cardioverter defibrillators (ICD). The purpose of this study was to examine the influence of an active pectoral ICD can on the atrial cardioversion threshold (ADFT). Forty consecutive patients received a transvenous single lead system (Endotak DSP 0125, CPI, St. Paul, MN, USA) in combination with a left subpectoral ICD (Ventak Mini, CPI) for treatment of malignant ventricular tachyarrhythmias. Patients were randomized into two groups: 21 received a Hot Can 1743 and 19 patients a Cold Can 1741. Step-down testing of the ventricular defibrillation threshold (VDFT) was performed intraoperatively and evaluation of the ADFT for induced atrial fibrillation (AF) at predischarge. After testing, each patient received a 2-J shock and was asked to quantify discomfort on a numerical scale ranging from 0 to 10. Both groups were comparable with regard to all clinical parameters studied. The mean VDFT in patients with a Hot Can device was significantly lower than in patients with a Cold Can (7.5 +/- 2.3 J vs 9.8 +/- 3.8 J; P < 0.03). The mean ADFT in the Hot Can group tended to be lower than in the group with Cold Cans (3.4 +/- 1.4 J vs 4.5 +/- 2.4 J; P = 0.07), and the proportion of patients in whom atrial cardioversion was accomplished at low energies (< or = 3 J) was higher in patients with active compared with patients with inactive pulse generators (57% vs 26%; P < 0.04). The mean discomfort reported after delivery of a 2-J shock was comparable in both groups (Hot Can 5.2 +/- 1.9; Cold Can: 5.3 +/- 2.1; P = NS). We conclude that the inclusion of an active left subpectoral can in the defibrillation vector of a ventricular ICD seems to reduce the energy requirements for atrial cardioversion without increasing the discomfort caused by low energy shocks.

The prevalence and clinical significance of sleep-related breathing disorders (SRBDs) in patients with cardiac disease and a history of life-threatening ventricular tachyarrhythmias is unclear. Forty consecutive recipients of implantable cardioverter defibrillators (ICDs) with cardiac disease and a documented history of spontaneous, life-threatening, ventricular tachyarrhythmias underwent full night polysomnography. SRBDs were diagnosed if the apnea/hypopnea index was > 10. SRBD were diagnosed in 16 of 40 patients (40%): central sleep apnea (CSA) was present in 9 of these 16 patients (56%), 8 of whom had associated Cheyne-Stoke respiration. Seven of the 16 patients with SRBD (44%) had obstructive sleep apnea (OSA). Patients with and without SRBDs were comparable with respect to left ventricular ejection fraction, NYHA classification, underlying heart disease, ICD indications, and concomitant antiarrhythmic drug and beta-blocker therapy. Patients were followed prospectively for 2 years. ICD-treated ventricular tachyarrhythmias occurred in 10 of 24 patients (42%) without SRBD, in 4 of 9 patients (44%) with CSA, and in 3 of 7 patients (44%) with OSA (NS). The numbers and circadian distributions of episodes recorded during follow-up in patients without SRBD versus with CSA or OSA were not significantly different (14 +/- 25, median = 4 vs 4 +/- 5, median = 2.5 vs 15 +/- 15, median = 7, respectively). The 2-year mortality, which was entirely attributable to nonsudden cardiac events, was highest in patients with CSA (4/9 [44%], vs 0/7 [0%] with OSA, vs 3/24 patients (12.5%) without SRBD; P < 0.05).

In 42 patients (26 men, 16 women; mean age 69 +/- 10 years), who were paced and medicated with antiarrhythmic drugs for the bradycardia tachycardia syndrome, chronotropic response and AV conduction with rapid atrial pacing during exercise were studied. Patients were included if they had no second- or third-degree AV block, no complete bundle branch or bifascicular block, and a PQ interval < or = 240 ms during sinus rhythm at rest. The interval between the atrial spike and the following Q wave (SQ) was measured in the supine position at rest with an AAI pacing rate of 5 beats/min above the sinus rate (SQ-R + 5), and at the end of exercise with 110 beats/min (SQ-E110). Bicycle ergometry was performed using the Chronotropic Assessment Exercise Protocol with the pacemakers being programmed to AAI with a fixed rate of 60 beats/min. Chronotropic incompetence was defined as peak exercise heart rate: (1) < 100 beats/min; (2) < 75% of the maximum predicted heart rate; or (3) the heart rate at half the maximum workload < 60 + 2 beats/min per mL O2/kg per minute (calculated O2 consumption). During exercise, one patient developed atrial fibrillation. Chronotropic incompetence was present in 71% (29/41) of the patients according to definition 2, and in 76% (31/41) according to definition 1 or 3. Ten out of 41 patients (24%) exhibited a second-degree AV block with atrial pacing at 110 beats/min at the end of exercise. Only 9 out of the remaining 31 patients (29%) showed a physiological adaptation of the SQ-E110, and 21 patients (68%) exhibited a paradoxical increase of the SQ interval with rapid atrial pacing at the end of exercise as compared to the SQ-R + 5. These observations indicate that the pacing system to be used in most patients paced and medicated for the bradycardia tachycardia syndrome should be dual chamber, and the option of rate adaptation should be considered.

The analysis of endocardial signals obtained from an electrode located in the right atrium enabled by new dual chamber implantable cardioverter defibrillators may be helpful to provide additional therapies such as overdrive pacing or low energy atrial cardioversion for the treatment of concomitant atrial flutter (AFL) or atrial fibrillation (AF). Algorithms for discrimination of atrial tachyarrhythmias based on rate counting are of limited efficacy. The aim of this study was to assess the intersignal variability by using fast discrete wavelet transforms (FDWT) as a new method of discrimination of AF from AFL. Patients with spontaneous episodes of AF/AFL or patients who developed AF/AFL during an electrophysiological study were studied. The endocardial signals were recorded from the high right atrium using a transvenous 5 Fr bipolar electrode catheter (interelectrode spacing: 1 cm). The signals were digitized (2 kHz, 12-bit resolution) after amplification and filtering (40-500 Hz). Within data segments of 10-second duration, 25 consecutive signals were selected and normalized and FDWT was applied. Standard deviations of the wavelet coefficients (SD) from coarse scales (scale 4-8) were calculated. A total of 94 data segments (AF: 52, AFL: 42) from 28 patients were analyzed. SD at each considered scale was higher for AF than for AFL (P < 0.001). SD at scale 8 discriminated between AF from AFL with 100% sensitivity and specificity. We conclude that assessment of intersignal variability of bipolar endocardial recordings using FDWT is an effective method for the discrimination of AF from AFL. The implementation of this tool in a discrimination algorithm of an implantable device may help provide the appropriate differential therapy for atrial tachyarrhythmias.

In a prospective study, a low threshold screw-in electrode (Medtronic 5078, group I, n = 9) was compared to a conventional active fixation lead (Biotronik Y60BP, group II, n = 9) to investigate whether lower pacing thresholds really translate into longer projected service life of the pacemaker. The leads were implanted in the atrium and were connected to a dual chamber pacing system which included the same ventricular lead (Medtronic 5024) and the same pulse generator model (Intermedics 294-03) in both groups. Eighteen months after implantation, atrial and ventricular pacing thresholds were measured as the charge delivered per pulse [microC] at 0.5, 1.0, 1.5, 2.0, and 3.5 V, respectively. For chronic output programming in both channels, patients capturing at 0.5 V were set to 1.0 V, those capturing at 1.5 V were permanently programmed to 2.0 V with the double of the charge threshold as the safety margin for pacing ("safety charge"). A combination of atrial and ventricular output settings was optimal, if it resulted in minimum battery current drain (microA] as measured by pacemaker telemetry. In both groups, current consumption [microA] decreased significantly as output amplitude was decreased, exhibiting its lowest value at 1.0 V in either channel. All ventricular leads could be programmed to the optimum output amplitude of 1.0 V in groups 1 and 2. As the 2:1 "safety charge" values were almost identical, the ventricular channel essential contributes the same amount to the battery drain of the pacing system in both groups. In the atrium, all patients of group 1 could be programmed to the optimum output amplitude of 1.0 V with an average pulse duration of 0.42 +/- 0.15 ms. In group 2, however, all patients had to be programmed to 2.0 V with a mean pulse width of 0.52 +/- 0.15 ms. With the atrial and ventricular output being optimized, the average battery drain of the whole pacing system was 12.19 +/- 0.63 microA in group 1 versus 14.42 +/- 0.32 microA in group 2 (P < 0.001). As patients were chronically programmed to these output settings, this difference translates into a clinically relevant gain in projected pacemaker longevity of 17 months or 18.3% (121 +/- 4 vs. 104 +/- 2 months; P < 0.001). Thus, programming a 2:1 safety margin in terms of charge and optimizing the output parameters by real-time telemetry of the battery current is a useful approach to reduce battery current drain. Making the most of modern lead technology with a different performance in only one channel of an otherwise identical DDD pacing system translates into a significant prolongation of projected pacemaker service life which is of great importance with the increasing awareness of health care expenditures. The gain in projected longevity is mainly due to the option of reducing the output amplitude which is still significantly beneficial well below the nominal voltage of the power source.

The purpose of the study was to examine the pacing and sensing characteristics of two bipolar active fixation atrial leads with a coaxial and a coradial conductor design, respectively. One group of ten patients received the ELA model S44F (4 mm2 vitreous carbon tip, coaxial multifilar coils, silicone). Nine other patients received the Intermedics ThinLine EZ 438-10 (8 mm2 iridium oxide-coated titanium tip, parallel-wound bifilar coil, polyurethane). Both lead models had electrically insulated corkscrews. Intraoperatively, pacing threshold (PT) at 0.50 ms, unfiltered atrial potential (AP), slew rate (SR) and pacing impedance (Z) at 2.5 V, 0.50 ms were measured using a Medtronic 5311 PSA. On the day of implant, and 2, 5, 10, 28, 90, 180, and 360 days after implant, minimum charge threshold (delta Qmin), atrial sensing threshold (Asen) and Z were measured via telemetry of the pacemaker (Intermedics 294-03 and 294-09). Z was significantly lower (P < 0.01) in the ThinLine EZ group at implant (419 omega vs 576 omega, mean values, 438-10 vs S44F) and at each follow-up (317-426 omega vs 492-613 omega). Five of nine patients with the 438-10 lead had Z values < 300 omega during follow-up (minimum 234 omega). There was no significant difference between the two leads with respect to PT (0.42 V vs 0.41 V), AP (3.75 mV vs 4.25 mV), SR (0.56 vs 1.06), delta Qmin (0.19-1.23 microC vs 0.18-1.35 microC) and Asen (3.4-4.5 mV vs 2.7-4.7 mV), respectively. Two patients developed pericardial effusions after implantation of a ThinLine EZ lead. One of them, who had a transient drop of blood pressure during implant, subsequently developed acute exsudative pericarditis. Therefore, both leads had acceptable sensing and pacing thresholds, but the 438-10 lead developed unusually low long-term lead impedance values. The high incidence of perforations in our small group of 438-10 patients has not been observed, thus far, in other studies.

Atherosclerotic cardiovascular disease is generally accepted to be the result of metabolic disturbances. However, recent studies have suggested an infectious agent, especially Chlamydia pneumoniae or cytomegalovirus, to be involved in the pathogenesis of atherosclerosis. Atherosclerotic plaque specimens obtained from patients with coronary disease either by balloon dilatation catheter (13 cases) or atherectomy (16 patients) were examined for the presence of C. pneumoniae and cytomegalovirus. Using two primer pairs for C. pneumoniae, two primer pairs for the identification of unknown bacteria and primer pairs for the detection of immediate early gene E2 and the late genomic region of cytomegalovirus, we were unable to detect the suspected agents. The absence of C. pneumoniae, other bacteria and CMV in coronary atheromas is against the hypothesis of a pathogenetic role of these agents in coronary atheroma formation in the patients studied.

We studied retrospectively 60 consecutive recipients of an implantable cardioverter-defibrillator and identified 16 patients who were temporarily on and off beta-blockers (further medication unchanged). An intraindividual analysis revealed that 56% of the patients experienced more arrhythmic episodes during follow-up off beta-blockers compared to 44% while being on beta-blockers. Also, the mean episode frequency during follow-up time on and off beta-blockers was comparable (0.4+/-0.6 vs. 0.5+/-0.5, ns).

In a pilot study, alterations of polymorphonuclear neutrophil function during systemic thrombolysis in acute myocardial infarction have been investigated in humans. The following parameters of neutrophil function were measured before and at 15 and 45 minutes after initiation of systemic thrombolysis with a recombinant tissue-type plasminogen activator in 20 patients with acute myocardial infarction: (1) neutrophil adhesion and (2) neutrophil activation. During systemic thrombolysis a significant decrease was observed in neutrophil adhesion (5.5+/-6.4 to 3.2+/-3.3; p<0.05), in phagocyting neutrophil activation (39+/-18 to 25+/-14%; p<0.05), and in resting neutrophil activation (9+/-7 to 3+/-4%; p<0.05). Successful reperfusion coincided with a significantly higher reduction of phagocyting neutrophil activation (40+/-14 to 20+/-12% vs. 39+/-24 to 26+/-19% in unsuccessful reperfusion; p<0.05), and of neutrophil adhesion (6.2+/-5.7 to 2.7+/-3.0 vs. 4.1+/-3.8 to 3.5+/-4.0 in unsuccessful reperfusion; p<0.05) during thrombolysis. Systemic thrombolysis in acute myocardial infarction is accompanied by a reduction in neutrophil adhesion and activation dependent on thrombolytic success.

In patients with sinoatrial disease, unexpected atrial flutter (Af) or fibrillation (AF) is a common problem during implantation of atrial-based pacing systems. As an alternative approach to blind atrial lead placement, lead positioning could be optimized by atrial electrogram mapping. It was the object of this study to evaluate if atrial lead implantation according to this approach and during ongoing arrhythmia is reasonable or if it should be postponed until restoration of sinus rhythm (SR). Twenty-nine consecutive patients (group I) with sick sinus syndrome received a dual-chamber pacemaker during an episode of Af (n = 11) or AF (n = 18). All but two atrial leads were of the screw-in type and had bipolar sensing. Atrial lead position was optimized by mapping the electrogram under fluoroscopy to find locations with high potential amplitudes. The patients were followed for 15.1 +/- 9.8 months, and atrial sensing threshold (AST), atrial pulse width threshold (PWT) at 2.0 V, the pacing mode programmed, and the clinical outcome (OUT) were recorded. The control group consisted of 30 patients (group II) who equally had a history of AF or Af, but were in SR during implantation. The atrial peak-to-peak potential (APEAK) after final lead placement was lower for AF (median value 2.5 mV, lower-upper quartile: 1.7-3.1 mV) as compared to Af (3.8 mV, 2.7-4.9 mV, P < 0.05) and SR (4.1 mV, 3.3-6.2 mV, P < 0.001). There was a correlation (P < 0.01) between APEAK during Af/AF and the postoperative AST immediately after restoration of SR. No lead in any group had to be corrected due to improper sensing in the postoperative course. Median chronic AST was 2.8 mV (2.0-4.0 mV) in group I and 4.0 mV (2.8-4.0 mV) in group II. Median chronic PWT at 2.0 V was 0.15 ms (0.12-0.26 ms) in group I and 0.15 ms (0.09-0.20 ms) in group II. There was no significant difference in chronic AST and PWT between both groups. All but two patients in group I preserved SR as the basic rhythm. A stable SR was observed in 10 of 29 patients, intermittent Af/AF was documented in 17 of 29 patients, seven of whom were asymptomatic. There was no significant difference in OUT between group I and II. Hence, sinus rhythm is not a prerequisite of atrial lead implantation. Mapping the Af or AF waves appears to be useful to guide lead placement and to achieve sufficient sensing and pacing conditions after conversion to sinus rhythm.

Using a Poisson regression model the relative incidence of acute myocardial infarctions (AMI) prospectively registered in 8 hospitals within a radius of 50 km during a 2-year period was correlated with the outside conditions characterized by a complete thermophysiological model (Klima-Michel Model) defining thermal stress. An increase in the incidence of AMI related to thermal stress could be demonstrated neither by splitting the study period into 12 equally sized 'felt-temperature' classes by months of the year nor by single days. This was confirmed by correlation of the AMI rate with the mean felt-temperature level during the preceding 14 days. Thermal stress caused by the atmospheric conditions in a temperate climate may be too weak to influence significantly the incidence of AMI.

Introduction: Analysis of endocardial signals obtained from an electrode located in the right atrium as realized in newly designed dual chamber, implantable cardioverter defibrillators might be used to provide additional therapeutic options, such as overdrive pacing or low-energy atrial cardioversion for the treatment of concomitant atrial flutter (AFL) or atrial fibrillation (AF). Therefore, we developed a computer algorithm for discrimination of normal sinus rhythm (NSR), AFL, and AF that may lead to adequate differential therapy of atrial tachyarrhythmias in an automated mode., Methods and Results: During an electrophysiologic study, bipolar endocardial signals from the high right atrium were obtained in 28 patients during sustained AFL or AF and after restoration of NSR. A total of 286 data segments of 5-second duration were recorded (NSR: 96, AFL: 86, AF: 104). Mean atrial cycle length (MCL), standard deviation of mean atrial cycle length (SDCL), and index of irregularity (IR), defined as the ratio between MCL and SDCL, were calculated for each data segment. A cutoff of 315 msec for MCL allowed discrimination of NSR from atrial tachyarrhythmias with 100% sensitivity and specificity. For discrimination of AF from AFL by using SDCL, a cutoff value of 11.5 msec led to a sensitivity of 99% and a specificity of 90%. Best discrimination of AF from AFL was found for the criterion IR > or = 7.5%, resulting in a sensitivity of 100% with a specificity of 95% for AF detection., Conclusion: The investigated algorithm provides discrimination of NSR, AFL, and AF with high sensitivity and specificity. Incorporation of this algorithm in an implantable automated antitachycardia device may lead to adequate differential therapy in patients suffering from spontaneous episodes of AF and AFL.

Minimizing the geometric surface area of pacing electrodes increases impedance and reduces the current drain during stimulation, provided that voltage (pulse-width) thresholds remain unchanged. This may be feasible by coating the electrode surface to increase the capacity of the electrode tissue interface and to diminish polarization. Ten unipolar, tined leads with a surface area of 1.3 mm2 and a "fractal" coating of iridium (Biotronik SD-V137) were implanted in the ventricle, and electrogram amplitude (unfiltered), slew-rate, pacing threshold (0.5 ms), and impedance (2.5 V; 0.5 ms) were measured by the 5311 PSA (Medtronic). On days 0. 2. 5. 10, 28, 90, 180, 360 postimplant, sensing threshold (up to 7.0 mV, measuring range 1-14 mV on day 360 only) and the strength duration curve (0.5-4.0 V; 0.03-1.5 ms; steps: 0.5 V; 0.01 ms, respectively) were determined, the minimum charge delivered per pulse (charge threshold), and the impedance were taken from pacemaker telemetry (Intermedics 294-03). Data were compared with those of an earlier series of 20 unipolar, tined TIR-leads (Biotronik) with a surface area of 10 mm2 and a @actal" coating of titanium nitride. With the model SD-V137 versus TIR, intraoperative electrogram amplitudes were 15.1 +/- 6.1 versus 14.4 +/- 3.9 mV (NS), slew rates 3.45 +/- 1.57 versus 1.94 +/- 1.06 V/s (P < 0.05), pacing thresholds 0.16 +/- 0.05 versus 0.52 +/- 0.15 V (P < 0.01) and impedance measurements 1,136 +/- 175 versus 441 +/- 73 omega (P < 0.0001), respectively. During follow-up, sensing thresholds were the same with both leads. Differences in pulse width thresholds lost its significance on day 28 but resumed on day 360 (SD-V137; 0.08 +/- 0.04 ms; TIR: 0.16 +/- 0.06 ms at 2.5 V; P < 0.01). With an electrode surface of 1.3 mm2, charge per pulse and impedance consistently differed from control, being 0.15 +/- versus 0.66 +/- 0.20 microC (P < 0.001) and 1,344 +/- 376 versus 538 +/- 79 omega respectively, one year after implantation (P < 0.0001). In summary, "fractally" coated small surface electrodes do not compromise sensing; by more than doubling impedance against controls they offer pacing thresholds (mainly in terms of charge) that are significantly lower than with the reference electrode.

Appropriate animal models for intracoronary stenting are most important for improving understanding of the pathophysiology of acute occlusion and long-term re-stenosis, which currently limits the safety and efficacy of percutaneous transluminal coronary angioplasty in humans. Since the anatomy and physiology of swine coronary arteries closely resemble those of humans, the procine model should be ideal for testing of stents. This is a comprehensive report on an experimental set-up in pigs, communicating in detail the necessary techniques as well as some modifications facilitating safe intracoronary stent placement and successful follow-up studies for weeks or months. Stent procedure is performed in mechanically ventilated and haemodynamically monitored animals under balanced anaesthesia. Intracoronary application of flow wires allows the assessment of local flow conditions, flow properties and coronary flow reserve. Real-time intravascular ultrasonography (IVUS) provides detailed information on coronary morphology and enables the appropriate sizing of the coronary lumen. From our own experience, we like to propose that the use of the porcine model has the potential to gain new insights into the pathophysiology of intracoronary stent placement-associated complications and allows for the study of modifications in techniques and materials, and the development of novel pharmacological therapeutic strategies.

We analyzed spontaneous ventricular tachycardias treated by antitachycardia pacing during long-term follow-up in 138 recipients of an implantable cardioverter-defibrillator. An inverse circadian variation of the antitachycardia pacing termination and acceleration rates with the worst antitachycardia pacing success during the time period with the highest episode frequency (morning hours) was demonstrated.