Theophylline reverses high-grade atrioventricular block resulting from cardiac transplant rejection.
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Graft Rejection↗
Biomedical subjects
A B Curtis
Publications and source records attributed to A B Curtis.
Modification of atrioventricular conduction using a combined laser-electrode catheter.
Ablation of the AV junction is an accepted technique for the management of selected supraventricular tachyarrhythmias. Radiofrequency ablation appears to be safe and effective for AV junction ablation in most patients, but the need for firm tissue contact may make it less effective for ventricular tachycardia and certain ectopic/atrial tachycardias. Laser energy can also be delivered through a catheter, and thus it may be an attractive alternative energy source for ablation. A new laser-electrode catheter was developed for modification of conduction through the AV node as a model for ablation of an arrhythmia substrate. A window for delivery of continuous-wave Nd:YAG laser energy was placed between the two electrodes of a bipolar electrode catheter. In vitro studies using a matrix of power versus time were performed to determine the energy that would create lesions of the appropriate size in vivo. Using this information, advanced AV block was successfully created in 16 of 17 dogs (94%) with the laser-electrode catheter. Advanced AV block was successfully created in all four dogs in the chronic study, and it persisted for 1-24 weeks of follow-up until sacrifice of the animals. Histologic examination demonstrated discrete thermal damage at the AV junction with no instances of septal perforation in the acute studies or progressive necrosis in chronically maintained dogs. Advanced AV block may be produced consistently and safely in dogs using a combined laser-electrode catheter.
Aluminum Silicates↗
Syncope and sinus arrest associated with the upper limb-cardiovascular (Holt-Oram) syndrome.
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Adult↗
Catheter entrapment in the mitral valve apparatus during radiofrequency ablation.
Catheter ablation of accessory atrioventricular pathways in patients with Wolff-Parkinson-White syndrome has become an increasingly popular therapeutic option. Catheter technology is rapidly evolving, allowing physicians to tailor the choice of catheter to the location of the pathway. We describe catheter entrapment in the mitral valve apparatus while using a valve mapping catheter with a peanut shaped tip to approach a left free-wall pathway retrogradely across the aortic valve.
Adult↗
Amiodarone: should we use it more than we do?
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Amiodarone↗
Antiarrhythmic therapy in patients with congestive heart failure.
Current information suggests that in patients with congestive heart failure (CHF) who have asymptomatic ventricular arrhythmias, coronary artery disease (dilated ischemic cardiomyopathy), and a positive signal-averaged electrocardiogram, electrophysiologic studies are useful for stratifying risk and guiding therapy. Therapy with amiodarone hydrochloride (Cordarone) appears to improve survival in patients after myocardial infarction. In CHF patients with asymptomatic ventricular arrhythmias and dilated nonischemic cardiomyopathy, electrophysiologic studies are of little value in risk stratification because of their low yield of sustained monomorphic tachycardias. There is little evidence that therapy with conventional antiarrhythmic agents improves survival. Although amiodarone can suppress ventricular ectopic beats, no trial yet conducted has detected an effect on mortality. Randomized, controlled trials with low-dose amiodarone are needed for more definitive information. Most symptomatic patients should undergo electrophysiologic testing and receive guided therapy, either with antiarrhythmic drugs or with an implantable cardioverter-defibrillator.
Amiodarone↗
Adenosine-induced atrioventricular block: a rapid and reliable method to assess surgical and radiofrequency catheter ablation of accessory atrioventricular pathways.
Adenosine has been shown to inhibit anterograde and retrograde conduction through the atrioventricular (AV) node while having little or no effect on accessory pathway conduction. Its rapid onset of action and short half-life make it particularly suitable for repetitive measurements. In this study, the utility of adenosine was tested in assessing completeness of accessory pathway ablation. Sixteen patients with an accessory pathway were studied (eight surgical ablations, eight catheter ablations with radiofrequency energy). Before ablation, no accessory pathway was sensitive to adenosine. Twelve patients with pre-excitation showed high grade AV node block with maximal pre-excitation on the administration of adenosine during atrial pacing. Four patients with a concealed accessory pathway demonstrated high grade AV block without evidence of latent anterograde accessory pathway conduction. Preablation ventriculoatrial (VA) block was not observed in any of the 16 patients in response to adenosine during ventricular pacing. Immediately after accessory pathway ablation, all patients developed AV and VA block with the administration of adenosine during atrial and ventricular pacing, respectively. These findings were confirmed during follow-up study 1 week later. Atrioventricular block during atrial and ventricular pacing with adenosine affords a reliable and immediate assessment of successful pathway ablation.
Adenosine↗
Atrial fixation leads--a visual aid confirming actual fixation.
Various active fixation mechanisms are available for atrial lead implantation. Confirmation of actual fixation of the lead tip in the myocardium is sometimes difficult with standard techniques such as fluoroscopy. Our observation of organized clockwise/counterclockwise motions of the fixation stylet in synchrony with atrial systole confirms adequate positioning of the Accufix model #330-801 atrial lead in the right atrial appendage, which is helpful when the screw is difficult to visualize under fluoroscopy. This observation was confirmed in nine patients.
Electrodes, Implanted↗
Accelerated idioventricular rhythm detected during elective surgery in a healthy man.
Accelerated idioventricular rhythm (AIVR) is found most commonly in the presence of underlying heart disease. It is characterized by acceleration of a latent pacemaker that normally depolarizes slowly. We describe a 30-year-old man who was found to have episodes of accelerated idioventricular rhythm (AIVR) on cardiac monitoring during elective orthopedic surgery. Noninvasive evaluation including two-dimensional echocardiography was unremarkable. No late potentials were detected on a signal-averaged electrocardiogram. During an exercise tolerance test, AIVR was suppressed as heart rate increased. A 24-h Holter monitor revealed that the AIVR rate was consistently 73-76 beats/min, which appeared whenever the sinus rate slowed to this level. The patient has been asymptomatic, and the rhythm has persisted at least through a 5-month follow-up period.
Accelerated Idioventricular Rhythm↗
ACC policy statement. Recommended guidelines for training in adult clinical cardiac electrophysiology. Electrophysiology/ Electrocardiography Subcommittee, American College of Cardiology.
Training in clinical cardiac electrophysiology should take place in an Accreditation Council for Graduate Medical Education accredited cardiology program, and the electrophysiology training program itself should be accredited by the Council. Each trainee must be eligible for board certification in Internal Medicine and either eligible for certification in Cardiovascular Diseases or in a program leading to eligibility. Training faculty should be certified in clinical cardiac electrophysiology or demonstrate equivalent credentials. At least two training faculty members are preferred. The faculty must be dedicated to teaching, active in performing or promoting research and must spend a substantial portion of their time in research, teaching and practice of clinical electrophysiology. A curriculum of training should be established. Faculty experts in the related basic sciences should be available and involved in teaching. The institution should have a fully equipped clinical electrophysiology laboratory and complete noninvasive capabilities. A close working relation with a cardiac surgery faculty member skilled in surgical treatment of arrhythmias is required. Training in application of pharmacologic and all current nonpharmacologic therapies, in the outpatient and inpatient setting, is necessary. The clinical exposure must include all facets of arrhythmia diagnosis and treatment and must be quantitatively sufficient to allow the trainee to develop proficiency. The period of training should not be less than one year in addition to the period of cardiology fellowship required by the ABIM for board eligibility. A continuous period of training is preferred.
Anti-Arrhythmia Agents↗
A method for analysis of the local atrial evoked response for determination of atrial capture in permanent pacing systems.
We developed a method for detection and analysis of the local atrial evoked response. Eleven patients undergoing permanent dual chamber pacemaker implantations for standard clinical indications were included in the study. Using a pacing system emulator, charge balancing using a variable triphasic stimulus waveform to reduce polarization artifact amplitude was performed first. This could not be completed in one patient because of a poor signal-to-noise ratio. Subsequent analysis of the local atrial evoked response in the remaining ten patients showed the typical signal to be a biphasic waveform with an initial negative deflection followed by a positive deflection nearly equal in amplitude. The mean amplitude of the atrial evoked response was 3.1 +/- 1.4 mV, while the intrinsic P wave amplitude in these same patients averaged 5.6 +/- 3.0 mV. The summed evoked response, a parameter that is directly proportional to the area of the signal, was used to determine atrial pacing threshold. The median atrial pacing threshold determined by the algorithm was 1.00 V. There was no instance of failure to detect loss of capture, nor was loss of capture inaccurately determined when there was still successful atrial pacing. Atrial capture in permanent pacing systems can thus be determined using an algorithm to record and analyze the local atrial evoked response. This method could potentially be useful in the automatic determination of atrial pacing threshold.
Algorithms↗
A new algorithm for minimizing pacemaker polarization artifact: universally applicable in permanent pacing systems.
Polarization artifacts that result from pacing may interfere with analysis of paced evoked responses during, e.g., automatic threshold tracking. We have developed a method for reduction of such artifacts that relies on the introduction of pacing stimuli during the refractory period of unipolar or bipolar paced captured beats after previous identification of a refractory period "template" or baseline. The refractory pacing stimuli cannot capture the heart, and thus any deviation from the template is due to polarization artifact alone. The artifact amplitude is measured and the precharge duration of the triphasic stimulus waveform is changed each time until artifact is minimized, as detected by repeated reversals in the polarity of the polarization artifact. In a series of 11 patients with unipolar and bipolar permanent pacing leads, mean initial artifact before balancing was 1.44 +/- 0.84 mV, which was reduced to 0.44 +/- 0.30 mV after balancing (P = 0.001). Initial precharge duration was 3.2 msec by design; mean final precharge duration was 3.30 +/- 0.34 msec. This algorithm is universally applicable in permanent pacing systems, as it is valid in unipolar and bipolar pacing and it does not require an intrinsic cardiac rhythm.
Algorithms↗
Automatic reduction of stimulus polarization artifact for accurate evaluation of ventricular evoked responses.
The ventricular evoked response, the cardiac depolarization generated in response to a pacing stimulus, is potentially useful as a sensor for rate responsive pacing and automatic threshold tracking. It is necessary to minimize the polarization artifact that results from pacing in order to sense cardiac depolarizations from the same electrodes that pace the heart. To accomplish this, a triphasic stimulus waveform consisting of precharge, stimulus, and postcharge was used. An algorithm was developed that introduced pacing stimuli during the refractory period of sensed beats, when cardiac depolarization could not occur by definition and polarization artifact could be evaluated. Precharge duration was varied until the amplitude of the polarization artifact was small compared to the evoked response. In 18 patients with temporary electrode catheters, polarization artifact was reduced from 6.8 +/- 3.4 mV to 1.9 +/- 1.1 mV after balancing (P less than 0.005). Initial precharge duration was 3200 mu sec and the mean final precharge duration was 3551 +/- 516 mu sec. In 14 patients with permanent bipolar pacing leads, polarization artifact was reduced from 3.2 +/- 3.5 mV to 0.7 +/- 0.6 mV (P less than 0.025). Final precharge duration averaged 3440 +/- 310 mu sec. Under a wide variety of pacing conditions, this algorithm simply and quickly reduces polarization artifact to a minimum to allow accurate analysis of evoked responses.
Algorithms↗
Characteristic variation in evoked potential amplitude with changes in pacing stimulus strength.
The evoked potential, the intracardiac signal generated by a pacing stimulus, shows promise as a sensor for rate-responsive pacing and automatic threshold determinations. Thus, it is important to understand factors that may alter the morphology of evoked potentials and affect accurate signal analysis. Using a computer-based pacing system emulator, stimuli at 2.5, 5.0 and 6.9 V were delivered to 12 patients through permanent bipolar pacing leads. At 2.5 V, the evoked potential amplitude measured -12.63 +/- 7.79 mV. When the pacing amplitude was increased to 5.0 and 6.9 V, the signal diminished in size or reversed in polarity, or both, averaging -0.83 +/- 7.82 mV and 0.64 +/- 7.0 mV, respectively (p less than 0.01 vs 2.5 V). Pacing at 2.5 V was performed in an additional 8 patients with temporary quadripolar electrode catheters. With the distal pole of the catheter as the cathode and the proximal 3 poles as a common anode, the evoked potential averaged -9.01 +/- 5.44 mV. With the proximal 2 poles of the catheter disconnected to make the anode equal in size and current density to the cathode, the evoked potential diminished to -0.94 +/- 11.27 mV (p less than 0.05). There is thus a decrease in the evoked potential at high stimulus amplitudes compared to that obtained at the cathodic threshold. This finding can be reproduced by manipulation of the size and current density of the anode, suggesting that anodal stimulation at the ring of permanent pacing leads may be responsible.
Cardiac Pacing, Artificial↗
Pentamidine-induced torsades de pointes in a renal transplant recipient with Pneumocystis carinii pneumonia.
Pentamidine isethionate, an important agent used to treat Pneumocystis carinii pneumonia, has been shown to be associated with the development of torsades de pointes in patients with AIDS. We have described a case of pentamidine-induced polymorphous ventricular tachycardia in a renal transplant recipient whose renal insufficiency may have prolonged the duration of arrhythmias. Careful ECG monitoring should be done during pentamidine administration, especially in patients with renal insufficiency. Physicians should be aware that this variety of polymorphous ventricular tachycardia can occur well within the recommended dose of pentamidine. More data are needed to define the relationship between renal dysfunction, plasma levels, and pentamidine cardiotoxicity.
Acquired Immunodeficiency Syndrome↗
Correction of reentrant atrioventricular tachycardia by surgical ablation of accessory pathways.
Patients with reentrant atrioventricular (AV) tachycardia have an accessory connection in addition to the normal conduction pathway, AV node and His-Purkinje system. This pathway predisposes some patients to recurrent, disabling supraventricular tachyarrhythmias. Although it is found with other associated cardiac conditions, most patients are healthy with no underlying structural heart disease. Interest has developed in surgically dividing the accessory pathway in patients with arrhythmias poorly controlled with medications or at risk for potentially fatal tachyarrhythmias. Surgery is safe and effective and should be considered for patients with rapid AV conduction during atrial fibrillation, those refractory to pharmacologic therapy, and young patients who otherwise would require lifelong antiarrhythmic therapy. This report describes surgical correction of reentrant AV tachycardia in five patients ranging in age from six months to 23 years.
Adolescent↗
Wide complex tachycardia due to coexistent supraventricular and ventricular tachycardia.
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Aged↗
Transvascular argon laser ablation of atrioventricular conduction in dogs: feasibility and morphological results.
The purpose of this study was to ablate atrioventricular (AV) conduction in dogs with an argon laser using a transvascular approach. Six dogs were anesthetized and underwent a right thoracotomy and atriotomy. A bipolar #7 French lumen catheter containing a 400 u silica fiber was used to map the region of the AV junction. When a stable His deflection was obtained, the silica fiber was extruded from the end of the catheter and argon laser radiation was delivered for up to 20 s at 3.0-4.5 watts. In five of six dogs, complete heart block was successfully created after 3 to 15 lasings. A continuous His bundle electrogram in one dog showed gradual prolongation of the HV interval before the development of complete infrahisian block. The mean R-R intervals in the five dogs with complete heart block increased from 435 +/- 56 ms to 1216 +/- 197 ms (P less than 0.001), and the QRS duration increased from 78 +/- 26 ms to 91 +/- 19 ms (P = ns). Gross inspection showed multiple 1-2 mm2 craters in the atria just above the tricuspid valve ring. Complications included one instance each of aortic root perforation and creation of a small ventricular septal defect. These lesions were so small that there was no hemodynamic compromise in either animal in which they occurred and the lesions themselves were only detected on careful postmortem examination. Histology revealed two patterns of injury involved in conduction ablation. One was direct vaporization of tissue resulting in a wedge shaped incision and the other was formation of a hematoma and thermal necrosis at the lasing site with little evidence of tissue vaporization. Although catheter modifications are necessary to avoid perforation, this study demonstrates that ablation of conduction can be successfully accomplished using an argon laser.
Animals↗