Microwave, Irrigated, Pulsed, or Conventional Radiofrequency Energy Source: Which Energy Source for Which Catheter Ablation?

ERDOGAN, A., et al .: Microwave, Irrigated, Pulsed, or Conventional Radiofrequency Energy Source: Which Energy Source for Which Catheter Ablation? The aim of the study was to compare the diameter of endomyocardial lesions induced with the delivery of microwave, cooled, or pulsed energy versus conventional RF energy. In vitro tests were performed in fresh endomyocardial preparations of pig hearts in a 10-L bath of NaCl 0.9% solution at 37°C and constant 1.5 L/min flow. Ablation 7 Fr catheters with 4-mm tip electrodes were used, except for the delivery of microwave energy. Energy delivery time was set to 60 s/50 W in all experiments. Cooled energy delivery was performed with a closed irrigation catheter. Pulsed energy delivery was performed using a special controller with a duty-cycle of 5 ms. Microwave energy was delivered with a 2.5-GHz generator and 10-mm antenna. Electrode temperature and impedance were measured simultaneously. After ablation, lesion length, width, and depth were measured with microcalipers, and volume calculated by a formula for ellipsoid bodies. Each energy delivery mode was tested in ten experiments. The deepest lesions were created with cooled energy delivery, and the largest volume by microwave energy delivery. Pulsed RF produced significantly deeper lesions than conventional RF energy delivery. Cooled or pulsed RF energy delivery created deeper transmural lesions than conventional RF. To create linear lesions at anatomically complex sites (isthmus), microwave energy seemed superior by rapidly creating deep and long lesions. (PACE 2003; 26:[Pt. II]:504–506)     

Effect of Biphasic Waveform Pulse on Endocardial Defibrillation Efficacy in Humans

Several clinical studies have proved increased defibrillation efficacy for implantable cardioverter defibrillators with biphasic pulse waveforms compared to monophasic pulse waveforms. This difference in defibrillation efficacy depends on the type of defibrillation lead system used. The influence of biphasic defibrillation pulse waveforms on the defibrillation efficacy of purely endocardial defibrillation lead systems has not yet been sufficiently examined, we, therefore studied 30 consecutive patients with drug refractory ventricular tachyarrhythmias during the implantation of a cardioverter defibrillator. After implanting an endocardial "integrated" sensing/defibrillation lead we performed a prospective randomized comparison of the defibrillation efficacy of monophasic and biphasic defibrillation waveform pulses. For endocardial defibrillation with the biphasic waveform the mean defibrillation threshold was 12.5 ± 4.9 joules and for the monophasic waveform 22.2 ± 5.6 joules (P < 0.0001). There was a decrease in the required defibrillation energy of biphasic defibrillation in 29/30 patients. Thus considering purely endocardial defibrillation a statistically significant and clinically relevant increase in defibrillation efficacy can be demonstrated for biphasic defibrillation waveform pulses.     

Experimental hypersensitivity in the rabbit; effect of inhibition of antibody formation by X-radiation and nitrogen mustards on the histologic and serologic sequences,and on the behavior of serum complement,following single large injections of foreign Proteins

X-radiation and nitrogen mustard administration inhibit the formation of precipitins for whole bovine serum and bovine serum gamma globulin in the rabbit. When specific antibody formation is inhibited by these agents, intravenous injection of a single large dose of bovine serum gamma globulin is not usually followed by the development of tissue lesions 9 to 11 days later, as occurs fairly regularly in control animals. A fall in titre of serum complement to very low levels for 3 to 5 days is closely correlated in time with the disappearance of antigen from the circulation following the intravenous injection of single large doses of bovine serum albumin and bovine serum gamma globulin. A rise in complement titre to normal levels occurs as antibodies appear in the serum. This sudden fall in complement titre is correlated with the development of characteristic lesions, and does not occur when antibody formation is inhibited. The data presented are interpreted as evidence in favor of the concept that the lesions are due to a reaction between antigen fixed in or on tissue cells and circulating antibody. The possible significance of serum complement in the pathogenesis of anaphylactic tissue lesions is discussed.     

Safety and Efficacy of Angiographic Guided Elective Palmaz-Schatz Stent Implantation Without Coumadin: Comparison of Stent Implantation and Angioplasty

This study was designed to evaluate the safety and efficacy of routine high-pressure Palmaz-Schatz coronary stenting in patients with symptomatic coronary heart disease with only angiographic guidance without coumadin for poststenting treatment. Intracoronary stenting reduces restenosis rate after coronary angioplasty. High pressure stent deployment with intravascular ultrasound guidance reduces the incidence of stent thrombosis, despite reduction of anticoagulation. However, the feasibility of routine stent implantation with only angiographic guidance and without coumadin for poststenting treatment has not yet been determined. Patients undergoing coronary angioplasty for symptomatic coronary heart disease received stent implantation for abrupt or threatening vessel occlusion, vessel dissection without compromised antegrade blood flow (but at high risk for subacute occlusion and early restenosis), unsatisfactory angioplasty result with > 30% residual stenosis, and elective stent implantation in de novo lesions, restenotic lesions, and lesions in bypass grafts. Quantitative coronary analysis was performed before the procedure, immediately after, and at follow-up 6 ± 1 (SD) months later. This patient group was matched for clinical and angiographic characteristics with those patients who underwent balloon angioplasty during the same period. Patients who underwent coronary stenting had larger net gain (1.95 ± 1.0 vs 1.42 ± 0.9; P < 0.001) resulting in a larger minimal luminal diameter (2.48 ± 1.19 vs 1.78 ± 1.01; P < 0.001) at follow-up as compared with balloon angioplasty. Restenosis, defined as > 50% diameter stenosis at follow-up, occurred in 35.0% in the PTCA group and in 16.1% in the stent group (P < 0.001). Subacute stent thrombosis occured in one patient (0.8%) due to angiographically evident suboptimal stent expansion. Routine coronary high pressure Palmaz-Schatz stenting with angiographie guidance without coumadin for poststenting treatment represents a safe and effective option in patients with symptomatic coronary heart disease without increasing the incidence of (sub)acute stent thrombosis.     

Evaluation of the dose-effect relationship of a new ace inhibitor (perindopril) by an automatic blood pressure recorder

Repeated blood pressure recordings by non-invasive devices areof better predictive value than single measurements in the evaluationof antihypertensive treatment. Such a method has been used toestablish the dose-effect relationship of perindopril. Aftera two-week placebo run-in period, 40 patients with essentialhypertension (age 56.6 ± 1.5 years, 31 males, nine females)were treated with placebo or 2, 4 or 8 mg of perindopril oncedaily for one month following a randomized double-blind design.They were included if at least 75% of diastolic blood pressurerecordings, made over an 8 h diurnal period using an automaticblood pressure recorder, were > 95 mmHg on placebo. Values (mean ± SEM) before and after treatment were assessedusing analysis of variance. These data showed a significantlygreater reduction of blood pressure with 4 mg and 8 mg dailydoses compared to placebo and the 2 mg daily dose. Such resultswere not obtained with blood pressure levels recorded by a mercurysphygmomanometer, confirming the value of an automatic bloodpressure recorder as a tool in therapeutic trials.     

Incidence of T Wave Alternation After Acute Myocardial Infarction and Correlation with Other Prognostic Parameters: Results of a Prospective Study

Tachycardia induced alternation of the T wave (TWA) has been associated with arrhythmia morbidity in mixed patient populations. However, less is known concerning the general incidence of TWA and its usefulness in risk stratification early after acute myocardial infarction (MI). TWA was prospectively and systematically assessed in 140 consecutive patients 15 +/- 6 days after acute MI and prior to discharge. Results of TWA measurements were compared to other noninvasive risk markers, LV function, and coronary angiography. Sustained TWA was present at rest or inducible during exercise in 27% of patients. The patient-specific heart rate for the onset of TWA was 98 +/- 9 beats/min. After multivariate analysis, TWA correlated with age (P = 0.02) and LV function (P = 0.002) and occurred more often in patients after nonanterior MI (P = 0.03). Acute results of Holter monitoring, late potentials by signal-averaged ECG, and heart rate variability were unrelated to the TWA status. During follow-up (451 +/- 210 days) two major arrhythmic events occurred. The incidence of TWA early after MI is about 25%. TWA is related to age and LV function but not to other common arrhythmia markers. Although TWA does not appear to be related to excessive cardiac morbidity, evaluation of the prognostic significance of TWA requires further study.     

Radiation Exposure of Patient and Physician during Implantation and Upgrade of Cardiac Resynchronization Devices

Background: Cardiac resynchronization therapy (CRT) is often associated with extended fluoroscopic exposure during placement of the devices. The objective of this study was to measure the radiation exposure sustained by different parts of the body of patients and operators during fluoroscopically guided cardiac resynchronization device implantation. Methods: Dosimetry data were prospectively recorded in a series of 104 consecutive patients, who underwent resynchronization device implantation or upgrade in our cardiac catheterization laboratory. Five Chipstrate dosimeters were fixed to the patient's skin around the thorax (right and left paravertebral, right and left parasternal, and sternal positions), one dosimeter was attached to the forehead, and one to the pubis. The operator was equipped with one dosimeter on the forehead at eye level and a ring dosimeter was worn on the right hand. Results: Based on the maximum radiation dose of 9.2 mSv measured at the operator's hand in a single implantation session, it might be recommended to conservatively limit the number of implantations to four per month (an annual limit value of 500 mSv). At a mean dose of 1.2 mSv, this number can be increased sevenfold. Conclusion: In patients, incipient deterministic radiation effects can theoretically be observed at dose area product >400 Gy?cm², a dose applied in 2.9% of CRT implantation procedures. Special follow‐up programs are considered necessary for these patients and for operators, as the latter may be exposed over many years given the unknown long‐term impact of chronic radiation exposure and the nature of current complex electrophysiology and device procedures. (PACE 2010; 1003–1012)