Biomedical subjects

J A Matos

Publications and source records attributed to J A Matos.

At least 19 recordsLinked to original sources

PubMed2005

Adaptive response of a new radioresistant strain of Chlamydomonas reinhardtii and correlation with increased DNA double-strandbreak rejoining.

In order to study the relationship between radioresistance and the adaptive response, we aimed to produce a new strain of Chlamydomonas reinhardtii with characteristics of high radioresistance coupled with a protoplast structure typical for the genus, and the cell-wall-less phenotype to facilitate rapid cell lysis in DNA double-strand break (DSB) assays. The adaptive response of the new strain was investigated using clonogenic and DSB assays. Strain H-3 was derived by mating a radioresistant strain (AK-9-9) with the cell-wall-less mutant CW15 strain and selecting for radioresistance by clonogenic assay. The random amplification of polymorphic DNA (RAPD) molecular marker system was used to evaluate genetic polymorphisms between H-3 and other related C. reinhardtii strains. DSB were estimated using constant-field electrophoresis. Of several mutant strains tested, strain H-3 was shown to be most radioresistant on the basis of dose to give a 90% lethality (LD90) rate and dose to give a 99% lethality rate (LD99). In addition to its high radioresistance and thinner cell wall as compared with that of the other parental strain AK-9-9, H-3 also expressed a radiation-induced adaptive response measured by clonal survival when given a priming dose before a test dose. DSB were also rejoined more rapidly in cells exposed to a priming dose 4 h previously. It is concluded from split-dose experiments that the already highly radioresistant strain H-3 is further capable of 'over recovery' or adaptation to radiation exposure. Accelerated DSB rejoining in cells given a priming dose may underlie the cellular adaptive response in this organism.

Adaptation, Physiological↗

PubMed2000

Chloroplast evolution in the Pinus montezumae complex: a coalescent approach to hybridization.

This study addresses the evolutionary history of the chloroplast genomes of two closely related pine species, Pinus hartwegii Lindl. and P. montezumae Lamb (subsect. Ponderosae) using coalescent theory and some of the statistical tools that have been developed from it during the past two decades. Pinus hartwegii and P. montezumae are closely related species in the P. montezumae complex (subsect. Ponderosae) of Mexico and Central America. Pinus hartwegii is a high elevation species, whereas P. montezumae occurs at lower elevations. The two species occur on many of the same mountains throughout Mexico. A total of 350 individuals of P. hartwegii and P. montezumae were collected from Nevado de Colima (Jalisco), Cerro Potosí (Nuevo León), Iztaccihuatl/Popocatepetl (México), and Nevado de Toluca (México). The chloroplast genome of P. hartwegii and P. montezumae was mapped using eight restriction enzymes. Fifty-one different haplotypes were characterized; 38 of 160 restriction sites were polymorphic. Clades of most parsimoniously related chloroplast haplotypes are geographically localized and do not overlap in distribution, and the geographically localized clades of haplotypes include both P. hartwegii and P. montezumae. Some haplotypes in the clades occur in only one of the two species, whereas other haplotypes occur in both species. These data strongly suggest ancient and/or ongoing hybridization between P. hartwegii and P. montezumae and a shared chloroplast genome history within geographic regions of Mexico.

Altitude↗

PubMed1999

Vascular permeability increase and plasma volume loss induced by endotoxin was attenuated by hypertonic saline with or without dextran.

Endotoxin given intravenously is known to cause plasma leakage and subsequent loss of circulating plasma volume. Hypertonic saline resuscitation has been successfully applied in hemorrhagic and traumatic shock, but its application for the treatment or prevention of septic or endotoxin shock is less well studied. Our aim was to investigate the effects of endotoxin on plasma leakage in hamsters when administered in two different ways: applied locally to the hamster cheek pouch microcirculation or systemically by i.v. injection. The cheek pouch was studied by intravital microscopy using FITC-labeled dextran as a tracer of plasma leakage. Escherichia coli lipopolysaccharide (LPS) was continuously added into the superfusion buffer of the cheek pouch preparation during 120 min in two control groups (each n = 6) and two further groups (each n = 6) treated with either hypertonic saline (HS) or hypertonic saline and dextran (HSD). Treatment was given as an i.v. injection 0.35 mL NaCl 7.5%/100 g b.w. during 4 min starting 15 min prior to the start of endotoxin application. Endotoxin caused a reversible increase in the number of postcapillary venular leaks with a maximal response at 70 min after start of endotoxin application. The maximal responses were reduced to 36% in the HS-treated and to 37% in the HSD-treated group in comparison to what was seen in the control groups. In the second part of the study endotoxin was given i.v. 0.3 mg/kg to anesthetized hamsters (n = 41) and arterial blood samples were collected at 0, 60, 120, and 180 min after endotoxin injection for measurement of hematocrit and plasma FITC-dextran concentration. Hamsters were divided into seven groups: untreated control group (n = 6); HSC control group given only an i.v. injection of hypertonic saline (n = 6); LPS group given endotoxin 0.3 mg/kg during 1 min (n = 9); HSp group given hypertonic saline (NaCl 7.5%) 10 min prior to i.v. endotoxin (n = 6); HSa group given hypertonic saline 10 min after i.v. endotoxin (n = 6); HSD group given hypertonic saline with dextran 40, 10 min prior to i.v. endotoxin (n = 6); HSD control group given only i.v. hypertonic saline + dextran and no endotoxin (n = 2). Injection of endotoxin caused a significant increase in hematocrit, which was counteracted by hypertonic saline treatment, with or without dextran, probably due to reduced extravasation of plasma in postcapillary venules.

Animals↗

PubMed1991

Blood lymphocytes are sensitized to branchial plexus nerves in patients with neuralgic amyotrophy.

The percentage of lymphocytic subsets in the blood of cases with neuralgic amyotrophy (NA), and the proliferative response of blood lymphocytes cultured with different nerve extracts, obtained from normal subjects at postmortem, were examined in 6 patients with NA and in 18 age-matched controls with shoulder pain not related to NA. Most (5/6) NA patients had decreased CD3 values and increased CD4/CD8 ratios due to a decreased of the CD8 subset. Lymphocytes of NA patients increased their blastogenic activity in cultures with nerve extracts from different brachial plexus nerves and its branches, but not in cultures with extracts of sacral plexus nerves. Cultures did not respond to nerve extracts in any of the control cases, although mitogenic activity was similarly elicited in cultured lymphocytes stimulated with phytohemagglutinin in both control cases and NA patients. These results suggest that NA is probably an immune mediated disease.

Adolescent↗

PubMed1987

Disopyramide-pyridostigmine interaction: selective reversal of anticholinergic symptoms with preservation of antiarrhythmic effect.

This double-blind, randomized, placebo crossover study was used to evaluate the effects of a cholinesterase inhibitor--slow-release pyridostigmine (180 mg orally every 12 hours)--on the anticholinergic and antiarrhythmic properties of disopyramide. Quantitative side effects questionnaire scores were used to guide disopyramide administration in 20 men with ventricular tachycardia. Disopyramide was given to each patient both with placebo and with active pyridostigmine. The maximal administered dose for each regimen was used in conjunction with corresponding questionnaire scores to calculate an index or estimate of the maximal tolerable dose of disopyramide. Additional evaluations performed at baseline and at each maximal administered dose regimen included tear and saliva quantitation, 24 hour electrocardiogram (ECG), exercise testing and programmed ventricular stimulation. Results showed that the maximal administered dose of disopyramide was greater with active pyridostigmine than with placebo: 295 +/- 75 versus 245 +/- 100 mg every 6 hours (p less than 0.05). The calculated maximal tolerable dose was substantially greater in the presence of pyridostigmine: 355 +/- 90 versus 260 +/- 115 mg every 6 hours (p less than 0.001). Maximal side effects questionnaire scores also reflected decreased anticholinergic activity in the presence of pyridostigmine compared with placebo: 101.9 +/- 2.2 versus 104.6 +/- 2.8, respectively (p less than 0.005). Baseline tear and saliva production was significantly reduced during disopyramide therapy, but was restored toward normal by the addition of pyridostigmine.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1987

Automatic implantable cardioverter/defibrillator: inadvertent discharges during permanent pacemaker magnet tests.

A patient with an automatic implantable cardioverter defibrillator (AICD) received two inadvertent shocks when a magnet was placed over the pacer during a routine permanent pacer check. Analysis of the rhythm strip suggested that both patients' QRS complexes (133 beats/minute) and asynchronous pacer artifacts (70 beats/minute) were counted by the AICD sensing system and exceeded the rate criteria of 153 beats/minute. This resulted in shocks from the AICD during sinus rhythm at 133 beats/minute. To avoid possible inadvertent shocks, an AICD should be deactivated while a magnet is placed over the pacemaker during a permanent pacer check.

Electric Countershock↗

PubMed1986

Discordance between ambulatory monitoring and programmed stimulation in assessing efficacy of mexiletine in patients with ventricular tachycardia.

UNLABELLED: Programmed electrical stimulation (PES) and 24-hour Holter monitoring were compared in 30 patients with ventricular tachycardia (VT) or ventricular fibrillation (VF) before and during treatment with mexiletine. Before treatment, all patients had greater than or equal to 30 ventricular premature complexes (VPCs)/hr and 22 patients had nonsustained VT on Holter. All had inducible sustained VT by PES (one to three extrastimuli). Mexiletine was effective in only 23% by PES criteria (VT no longer inducible or less than or equal to 15 beats in duration and effective in 57%, 57%, and 73% by Holter criteria I, II, and III, respectively (Holter I greater than or equal to 50% reduction of VPCs, greater than or equal to 90% reduction of couplets and abolition of nonsustained VT; Holter II greater than or equal to 83% reduction of VPCs and abolition of VT; Holter III abolition of VT in patients who had VT during baseline Holter). Results of PES and Holter were discordant in 67%, 60%, and 55% (PES vs Holter I, II, and III, respectively). The majority (greater than or equal to 75%) of the discordance occurred due to mexiletine appearing effective by Holter criteria but ineffective by PES criteria (suggesting insensitivity of efficacy by Holter criteria and/or nonspecificity of induced VT during treatment with mexiletine). CONCLUSIONS: PES and Holter are discordant in assessing efficacy of mexiletine (p less than 0.05). Efficacy of mexiletine by Holter criteria is easier to achieve than efficacy by PES. The discordance between the two methods, both with very good reported predictive values, calls for randomized clinical follow-up studies to determine sensitivity and specificity of each method in assessing efficacy of mexiletine.

Drug Evaluation↗

PubMed1986

Comparison of ramp and stepwise incremental pacing in assessment of antegrade and retrograde conduction.

Conventional assessment of antegrade (AV) and retrograde (VA) conduction involves stepwise increments in pacing rates until block in conduction is observed. This study was designed to establish the comparative characteristics of ramp pacing, in which the rate is continuously and smoothly incremented until block occurs. Two hundred and ten patients participated in portions of this study. Stepwise pacing was performed in 10 beat/minute steps, with the rate held for at least 15 seconds at each step; if marked prolongation or variability in conduction was observed, the rate was held constant for up to 60 seconds to allow for accommodation. With ramp pacing, the rate was gradually increased at a steady 2-4 beats/minute/second. Whenever possible, both stepwise and ramp pacing were performed for assessment of both antegrade and retrograde conduction. All patients had conducted sinus rhythm as their baseline mechanism. Antegrade conduction was similar using incremental stepwise and ramp pacing. The AH interval at a cycle length (CL) of 500 ms, the maximum AH increment, the cycle length at AV block were all remarkably similar (p = NS). Assessment of retrograde conduction produced similar results, with insignificant differences between maximum conducted VA intervals, and cycle length at VA block using the two pacing techniques. Ramp pacing provides a useful and rapid alternative to conventional stepwise incremental pacing in the assessment of antegrade and retrograde conduction in patients using both normal and accessory pathways. Ramp pacing was better tolerated, and some correlations between antegrade and retrograde conduction were stronger with the ramp pacing technique.

Atrioventricular Node↗

PubMed1985

Combination of procainamide and quinidine for better tolerance and additive effects for ventricular arrhythmias.

The efficacy and tolerance of quinidine and procainamide used individually and in combination were studied in 19 patients with frequent ventricular premature complexes (VPCs). During single-drug treatment, the maximum tolerated dose of quinidine without extracardiac dose-related side effects was 1.6 +/- 0.21 g/day and that of procainamide was 4.1 +/- 1.05 g/day. During combination therapy with smaller doses (p less than 0.05) of quinidine (1.16 +/- 0.26 g/day) and procainamide (2.80 +/- 0.98 g/day), no patient had side effects. Before treatment, all patients had frequent (more than 60 per hour) VPCs and 17 had ventricular tachycardia on Holter monitoring. The frequency of VPCs was reduced to 22 +/- 19% with quinidine, 47 +/- 40% with procainamide and 9 +/- 11% with combination therapy (p less than 0.05, combination vs procainamide or quinidine alone). Individually, an effective regimen (more than 83% reduction of VPCs and abolition of ventricular tachycardia) was found in 5 patients (26%) receiving quinidine alone at maximal tolerated dose, in 4 (21%) receiving procainamide alone at maximal tolerated dose, and in 14 (74%) receiving combination therapy (p less than 0.01 vs quinidine or procainamide). Thus, the antiarrhythmic effects of quinidine and procainamide are additive. When quinidine or procainamide are additive. When quinidine or procainamide is ineffective because dose-related extracardiac side effects limit the maximal tolerated dose, combination therapy in smaller and tolerable doses avoids side effects and is more effective than either drug alone at the maximal tolerated dose.

Adult↗

PubMed1985

The value of electrophysiologic studies in syncope of undetermined origin: report of 150 cases.

A prospective study examined the diagnostic yield and therapeutic efficacy of electrophysiologic studies in patients with SUO. We defined SUO as those syncopal or near-syncopal events remaining unexplained after a standardized, noninvasive evaluation that included a history, physical examination, routine laboratory screening, EEG, nuclear brain scan or CAT scan, 12-lead ECG, chest x-ray, orthostatic vital signs, bedside carotid sinus massage, and at least 24 hours of continuous ECG monitoring. The 150 SUO patients included 95 men and 55 women (mean age 62.0 years); 35 had recurrent SUO, 75 (50%) had organic heart disease, and 129 (86%) had abnormal ECGs. There were 162 abnormal electrophysiologic findings that could explain the SUO uncovered in 112 patients, a diagnostic yield of 75%: one finding in 71 patients, two findings in 32, and three findings in nine. These findings were: His-Purkinje disease in 49 patients (30%), inducible ventricular arrhythmias in 36 (22%), AV nodal disease in 20 (12%), sinus node disease in 19 (12%), inducible supraventricular arrhythmias in 18 (11%), carotid sinus hypersensitivity (not elicited by carotid sinus massage prior to electrophysiologic studies) in 15 (9%), and hypervagotonia in five (3%). When electrophysiologic study findings were classified as clearly abnormal or borderline, 54 patients had at least one clearly abnormal finding, a diagnostic yield of 36%. Subgroups of patients presenting with only a single SUO event, no evidence of organic heart disease, or normal baseline ECGs all had substantial diagnostic yields during electrophysiologic studies. Follow-up data in 137 patients (91%) (mean 31 months) showed recurrences in 16 of 34 patients (47%) without and 15 of 103 patients (15%) with electrophysiologic findings despite therapy directed by electrophysiologic testing (p less than 0.0005). This study and a review of the literature indicate that electrophysiologic testing is useful in elucidating the causes of SUO and directing therapy. A significant number of patients benefit from electrophysiologic studies, even when only clearly abnormal findings are considered diagnostic, when only a single syncopal event has occurred, or whether or not organic heart disease or an abnormal ECG is present.

Adult↗

PubMed1985

Activation mapping in patients with coronary artery disease with multiple ventricular tachycardia configurations: occurrence and therapeutic implications of widely separate apparent sites of origin.

Catheter or intraoperative activation mapping studies, or both, were performed in 17 patients with coronary artery disease with two to four distinct configurations of ventricular tachycardia, resistant to a mean of 12.1 +/- 6.0 antiarrhythmic drug trials per patient. Mapping studies were performed to guide anticipated surgical ablation of arrhythmias. Activation map data were adequate to determine sites of origin of 30 (64%) of 47 observed tachycardia configurations. These 30 ventricular tachycardias (26 observed clinically) were mapped to 22 separate endocardial sites of origin. Sites of origin of distinct tachycardias were identical or closely adjacent (within 3 cm) in six patients and widely separate (greater than or equal to 4 cm) in eight patients (47% of the group). Activation maps were not adequate to determine sites of origin of 17 (36%) of the 47 tachycardias, including all configurations in three patients. Fifteen patients underwent surgery for control of ventricular tachycardia: aggressive, map-guided endocardial resection (mean 26.5 +/- 14.2 cm2) in 12 patients with identified sites of tachycardia origin and extensive resection of visible endocardial scar (2 patients) or encircling endocardial ventriculotomy (1 patient) in those in whom the sites of origin of all clinical tachycardias remained undetermined. Two inoperable patients were treated with amiodarone. During postoperative electrophysiologic tests (11 of 13 surgical survivors), ventricular tachyarrhythmias were initially uninducible in only 4 of 11 patients. However, in two patients only nonclinical arrhythmias (ventricular flutter) were induced. Six (21%) of 29 clinical tachycardias whose sites of origin were either not determined or not resected (right septum or papillary muscle) remained inducible in five patients. Using previously ineffective antiarrhythmic drugs, initially inducible arrhythmias became uninducible (two patients), or harder to induce than preoperatively (five patients). As a result of surgical resections alone or in combination with previously ineffective drugs (and amiodarone in two inoperable patients), there were no recurrences of ventricular tachycardia in 14 (93%) of 15 patients discharged during 19.0 +/- 14.3 months of follow-up study. Thus, activation mapping may commonly reveal separate apparent sites of origin for clinically observed, morphologically distinct, highly drug-refractory ventricular tachycardias in patients with coronary artery disease with multiple tachycardia configurations. Extensive surgical resection of identified sites of origin may be required to ablate arrhythmias in these patients.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗

PubMed1985

Bethanidine sulfate: efficacy in prevention of ventricular tachyarrhythmias during programmed stimulation. Report of a multicenter study of 56 patients.

Twelve cardiac electrophysiology centers conducted an open label prospective trial of bethanidine sulfate, an oral bretylium analog, for the prevention of ventricular tachyarrhythmias during programmed electrical stimulation. The study group included 56 patients (44 men, 12 women; mean age 60 years; 55 with structural heart disease). Sixteen patients had both ventricular tachycardia and fibrillation, 30 had ventricular tachycardia alone and 10 had ventricular fibrillation alone. Programmed stimulation on no antiarrhythmic drugs induced sustained ventricular tachycardia in 46 patients, nonsustained ventricular tachycardia in 4 patients and ventricular fibrillation in 6 patients. During programmed ventricular stimulation after 59 trials of 20 to 30 mg/kg body weight of oral bethanidine (acute dosing in 40 patients, and divided dosing over 24 hours in 19 patients), no ventricular tachyarrhythmias were inducible in 6 patients (11%), sustained ventricular tachycardia was converted to nonsustained ventricular tachycardia in 3 patients (5%), ventricular tachyarrhythmias remained inducible in 39 patients (70%) and spontaneous ventricular tachyarrhythmias occurred more frequently in 4 patients (7%). Side effects prevented repeat testing in four patients. The 10 patients presenting with only ventricular fibrillation appeared to have a higher response rate: no ventricular tachyarrhythmias were inducible in 2 patients and sustained ventricular tachycardia was converted to nonsustained ventricular tachycardia in 2 patients. Despite protriptyline administration in 54 of 59 bethanidine trials, symptomatic hypotension occurred in 30 trials (51%). In conclusion, the efficacy of bethanidine for preventing ventricular tachyarrhythmias as assessed by programmed stimulation is low. Patients presenting with only ventricular fibrillation may have a more favorable response to bethanidine sulfate. Symptomatic hypotension occurs frequently despite concomitant use of protriptyline.

Adult↗

PubMed1985

Discordance between ambulatory monitoring and programmed stimulation in assessing efficacy of class IA antiarrhythmic agents in patients with ventricular tachycardia.

Concordance between programmed stimulation and 24 hour ambulatory electrocardiographic (Holter) monitoring was studied in 54 patients with sustained ventricular tachycardia during 84 therapeutic trials with class IA antiarrhythmic agents. During baseline studies before treatment, all patients had frequent (greater than or equal to 30/h) ventricular premature complexes on Holter recordings and sustained ventricular tachycardia inducible by one to three extrastimuli. During treatment, programmed stimulation and Holter monitoring were repeated. Efficacy of treatment determined by programmed stimulation (ventricular tachycardia no longer inducible or nonsustained) was compared with three Holter criteria of efficacy: I = 83% or more reduction of ventricular premature complexes and abolition of ventricular tachycardia; II = 50% or more reduction of ventricular premature complexes and 90% or more reduction of couplets and abolition of ventricular tachycardia; III = abolition of ventricular tachycardia in patients with ventricular tachycardia during a baseline Holter recording. Treatments were judged effective by programmed stimulation criteria in only 25% of cases but in 51, 63 and 75% of cases by Holter criterion I, II and III, respectively. Results of programmed stimulation and Holter monitor were discordant (effective by one criterion but ineffective by the other) in 50% of cases using Holter criterion I, in 54% using Holter criterion II and in 61% using Holter criterion III. In the majority of discordant results, treatments appeared efficacious by Holter criteria but ineffective by programmed stimulation criteria, suggesting insensitivity of efficacy by Holter criteria or nonspecificity of induced ventricular tachycardia during treatment, or both.

Aged↗

PubMed1985

Prediction of sudden death and spontaneous ventricular tachycardia in survivors of complicated myocardial infarction: value of the response to programmed stimulation using a maximum of three ventricular extrastimuli.

The prognostic significance of ventricular arrhythmias induced by programmed electrical stimulation was evaluated in 50 survivors of acute myocardial infarction complicated by a major new conduction disturbance (38 patients), congestive heart failure (33 patients) or sustained ventricular tachyarrhythmias (22 patients), alone or in combination. Programmed stimulation was performed in patients in stable condition 7 to 36 days (mean 16) after infarction using one to three extrastimuli at four times diastolic threshold at a maximum of two right ventricular sites. Two groups were identified by the response to programmed stimulation: 17 patients with sustained (greater than 15 seconds) or nonsustained (greater than 7 beats but less than or equal to 15 seconds) ventricular tachycardia (group I), and 33 patients with 0 to 7 intraventricular reentrant complexes in response to maximal stimulation efforts (group II). Group I patients had a higher incidence of anterior infarction than that of patients in group II (71 versus 42%), had lower left ventricular ejection fraction (mean 0.35 versus 0.48) and were more often treated with antiarrhythmic drugs (47 versus 18%, p less than 0.05). There were no significant differences between groups in the occurrence of congestive failure, new conduction disorders or sustained ventricular arrhythmias with infarction, or in the proportions treated with a beta-receptor blocking agent, coronary bypass grafting or a permanent pacemaker. Total cardiac mortality was 24% during a mean follow-up period of 23 months and did not differ between groups; however, the response to programmed stimulation identified a group at high risk of late sudden death or spontaneous ventricular tachycardia: 7 (41%) of 17 group I patients compared with 0 of 33 group II patients (p less than 0.001). The induction of sustained or nonsustained ventricular tachycardia identified all patients who died suddenly or had spontaneous tachycardia (sensitivity 100%), but triple extrastimuli were required to induce prognostically significant arrhythmias in five of these seven patients; the specificity of this protocol was only 57%. When the clinical variables of the group were evaluated individually, the response to programmed stimulation had a stronger association with occurrence of late sudden death than did any other factor (Fisher's exact test, p less than 0.001); however, a type II error could not be excluded.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗

PubMed1985

Catheter ablation of tachycardias.

Non-surgical electrode catheter ablation appears to be a useful technique for the treatment of selected patients with resistant supraventricular and ventricular tachycardias. Many problems remain, including the need for improved methods of tachycardia localization, the need for permanent pacing with A-V junctional ablation, a variety of potential and demonstrated complications, and the need for specially designed equipment. The relative role of electrical ablation versus other new techniques such as those employing lasers, remains unsettled. The clearly demonstrated benefits of electrical ablation in a growing number of patients ensures that continued development and refinement will occur.

Animals↗

PubMed1984

Attempted nonsurgical electrical ablation of accessory pathways via the coronary sinus in the Wolff-Parkinson-White syndrome.

Previous canine experiments suggested that transvenous catheters placed in the coronary sinus could be used to deliver limited energy shocks, resulting in fibrosis in the atrial wall and coronary sulcus with sparing of the coronary artery. From the distribution of the fibrosis, it appeared that this approach could be used for attempted ablation of accessory pathways in patients with the Wolff-Parkinson-White syndrome. Eight patients with symptomatic Wolff-Parkinson-White syndrome underwent electrophysiologic testing with attempted ablation of 10 accessory pathways. Shocks were limited to 40 to 80 J, except in one patient who received shocks of 100 and 150 J. From 2 to 26 shocks were given to each accessory pathway. All the accessory pathways were blocked completely immediately after the shocks. Subsequently, evidence of accessory pathway conduction recurred in each patient. Three had early promise of long-term improvement after the procedure, with prolongation of the refractory periods of the accessory pathways during the remainder of the initial hospitalization. Several weeks later, however, there was evidence of return toward original values in two of these. Another patient who appeared not to benefit during her initial hospitalization returned 7 weeks later with very depressed accessory pathway conduction, possibly due to developing fibrosis. The only significant complication occurred in the patient receiving shocks of 100 and 150 J; he had apparent rupture of the coronary sinus requiring pericardial drainage. In two patients in whom nonsurgical ablation was not successful, intraoperative mapping showed that the accessory pathway was located in an area of fibrosis at the site of the attempted ablation. In summary, nonsurgical electrical ablation of accessory pathways via the coronary sinus may be successful using limited energy levels in a few patients. The procedure remains experimental, and widespread application must await more effective means of delivering the shocks.

Adolescent↗

PubMed1984

Nonsurgical electrical ablation of tachycardias: importance of prior in vitro testing of catheter leads.

Nonsurgical electrical ablation of tachycardia pathways or foci has been attempted or carried out using a variety of temporary pacing catheter leads. To determine the ability of such leads to withstand the high energies used in such procedures, 34 leads were suspended in saline, and subjected to repeated electrical shocks. Small (4 French) temporary pacing leads made by a variety of manufacturers tolerated multiple shocks up to 100 joules; above this level, failures became increasingly common, although usually the failure mode was benign with respect to patient care implications. Testing of 6, 7, and 8 French leads revealed considerable inter-and intra-manufacturer differences in the ability to withstand higher energy shocks, reflecting differences in materials and fabrication techniques. It is concluded that careful in vitro lead testing is required prior to using identical models in humans for arrhythmia ablation procedures.

Cardiac Catheterization↗

PubMed1984

DDD/DDT pacemakers in the treatment of ventricular tachycardia.

The possibility of adapting multimode dual-chamber pacemakers for programmed and burst stimulation was explored in a group of patients with ventricular tachycardia. The potential usefulness and pitfalls of these pacemakers were exemplified in one patient, presented in detail. The implanted DDD pacemaker was programmed to an all-synchronous mode (DDT), permitting programmed ventricular stimulation through synchronization with chest wall stimulation provided by a standard external programmable stimulator. With the ventricular sensing refractory period shortened to 200 ms, both programmed electrical stimulation and burst pacing for termination of induced tachycardias were possible. When medications failed to offer protection against the patient's tachycardias, the ventricular sensing refractory period (and minimum stimulation interval) was increased to 300 ms, thereby permitting burst pacing at up to 200 beats/minute for termination of spontaneous episodes. After many trials to confirm the efficacy of such stimulation, and the lack of muscle potential triggering, the patient was discharged home with the pacemaker in the DDT mode. He was instructed to go to his local emergency room, and was equipped with a portable device to trigger his implanted unit. Subsequently, the patient had successful termination of several spontaneous episodes of ventricular tachycardia in an emergency room. Later, he began to experience palpitations during certain exercises, and it was found that the implanted unit was being triggered by pectoral myopotentials. The unit was therefore reprogrammed to decrease the sensitivity, and the patient was again discharged. The need for careful evaluation and close follow-up is emphasized to maximize the benefits and to minimize the very serious potential risks of this pacing mode.

Action Potentials↗