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Biomedical subjects

B D Lindsay

Publications and source records attributed to B D Lindsay.

At least 37 records · Page 2Linked to original sources
PubMed1993

Long-term effectiveness of surgical treatment of ectopic atrial tachycardia.

OBJECTIVES: The purpose of this study was to determine the long-term clinical outcome of patients with ectopic atrial tachycardias treated surgically. BACKGROUND: Ectopic atrial tachycardia is an uncommon arrhythmia that can be symptomatic and is associated with the development of a cardiomyopathy. Management strategies are not well defined because of the paucity of data on the long-term effectiveness of pharmacologic and nonpharmacologic therapies. METHODS: The long-term clinical impact of medical and surgical therapy was determined in 15 consecutive patients with ectopic atrial tachycardia. All 15 patients were initially treated with antiarrhythmic drugs (mean 5.7 +/- 2.2 drugs/patient). An effective drug regimen was identified in only 5 (33%) of the 15 patients; the remaining 10 patients were treated surgically. In each, individualized surgical procedures were guided by computer-assisted intraoperative mapping, with atrial plaques comprising up to 156 electrodes. Focal ablation was performed in four patients and atrial isolation procedures in six. RESULTS: The 10 patients treated surgically were followed up a mean of 4 +/- 3.2 years. Ectopic atrial tachycardia recurred in one patient. A permanent pacemaker was implanted in two patients, one of whom also required reoperation for constrictive pericarditis. There were no operative deaths. Ectopic atrial tachycardia recurred in three (60%) of the five patients discharged on antiarrhythmic drug therapy during a mean follow-up interval of 6.4 +/- 4.3 years. There was one nonarrhythmic death. CONCLUSIONS: Map-guided surgery demonstrated long-term efficacy in abolishing symptoms in 9 of the 10 patients with ectopic atrial tachycardia. Results demonstrate that surgery is effective for patients with ectopic atrial tachycardias who are not easily treated with antiarrhythmic drugs.

Adolescent↗
PubMed1992

Improved detection of accessory pathways that bridge posterior septal and left posterior regions in the Wolff-Parkinson-White syndrome.

To improve the detection of accessory pathways that bridge the posterior septum and left posterior free wall, catheter maps of the coronary sinus from 21 patients (group I) who needed dissection of both these anatomic regions were compared with data from 23 (group II) with pathways confined to the posterior septum and from 9 (group III) with left posterior pathways. A decapolar catheter was used to map the coronary sinus in 0.5 to 1 cm steps. Intraoperative mapping was performed with a 16-electrode band. Catheter maps during atrial pacing and orthodromic supraventricular tachycardia were analyzed for the site of earliest activation and for differences in a new directional measure of conduction time between adjacent mapping sites. The site of earliest activation alone did not distinguish accessory pathways that bridged both anatomic regions, because 14 of 21 patients (66%) in group I would have been misclassified to either group II or III. In contrast, anterograde and retrograde directional conduction times distinguished patients in group I from those in groups II (p less than 0.01 to less than 0.0003) and III (p less than 0.04 to less than 0.0001). A multivariate model that incorporated the observed differences in directional interelectrode conduction times improved the identification of group I patients, with a sensitivity of 87% and a specificity of 90%. The results define new features in activation patterns measurable during catheter mapping that identify accessory pathways that bridge the posterior septum and left posterior free wall.

Adolescent↗
PubMed1992

Radiation exposure to patients and medical personnel during radiofrequency catheter ablation for supraventricular tachycardia.

Radiofrequency catheter ablation is an effective alternative to medical therapy for patients with supraventricular arrhythmias. The purpose of this study was to determine the risks to the patient and to medical personnel due to radiation exposure from fluoroscopy during radiofrequency ablation of supraventricular tachycardia. One hundred eight consecutive patients with Wolff-Parkinson-White syndrome or atrioventricular nodal reentry who underwent the ablation procedure were studied. The ablation procedure was successful in 95% of the patients studied. Preexcitation or supraventricular tachycardia recurred in 5% of the patients during a mean follow-up of 9 +/- 4 months. The mean fluoroscopy time was 50 +/- 31 minutes. An anthropomorphic radiologic phantom was used to determine organ exposure and the effective dose equivalents for the patient and medical personnel. The patient's effective dose equivalent during a representative ablation procedure was 1.7 rems, which is comparable to other invasive cardiovascular procedures. The risk of inducing a fatal cancer from this exposure is 1 chance in 745, which is 1% of the spontaneous risk. The risk of a serious birth defect is 1 chance in 80,000, which is 0.1% of the current incidence of serious birth defects in the United States. The cardiologist who receives the highest exposure among medical personnel, would incur 1.8 mrems per case or 450 mrems per year if 250 procedures were performed. This exposure is 9% of the recommended annual limit. These results demonstrate the efficacy of radiofrequency energy ablation of supraventricular tachycardia and confirm that radiation exposure to patients and medical personnel is within established guidelines.

Electrocoagulation↗
PubMed1992

Prospective detection of vulnerability to sustained ventricular tachycardia in patients awaiting cardiac transplantation.

This prospective study tested the hypothesis that abnormal signal-averaged electrocardiograms (ECGs) and inducible ventricular arrhythmias identify patients awaiting cardiac transplantation who are prone to sustained ventricular tachycardia (VT) or ventricular fibrillation (VF). Thirty-seven patients with advanced symptoms of heart failure and a mean left ventricular ejection fraction of 20 +/- 7 were studied. In response to programmed ventricular stimulation using up to 3 extrastimuli, sustained monomorphic VT was induced in 8 (22%) and polymorphic VT or VF was induced in 5 patients (13%). Patients with inducible arrhythmias underwent drug therapy guided by results of programmed ventricular stimulation or implantation of a defibrillator. Patients in whom ventricular arrhythmias could not be induced were not treated for arrhythmias. The signal-averaged ECG was abnormal and sustained VT or VF was induced in 10 patients (27%). Follow-up ranged from 1 to 33 months (mean 12). Four patients (11%) died suddenly and 4 (11%) had nonfatal sustained VT or VF. The positive predictive value for sudden death or nonfatal VT/VF was 27% for the signal-averaged ECG, 38% for programmed ventricular stimulation, and 50% if both tests were abnormal. The negative predictive values for these tests were 87, 88 and 88%, respectively. The actuarial incidence of arrhythmic events was significantly higher in patients with inducible ventricular arrhythmias (p = 0.017) and in patients in whom both the results of signal-averaged electrocardiographic analysis and the response to programmed ventricular stimulation were abnormal (p = 0.002). This study demonstrates that results of signal-averaged electrocardiographic analysis and the response to programmed ventricular stimulation improve risk stratification for sudden cardiac death in patients awaiting cardiac transplantation.

Actuarial Analysis↗
PubMed1992

Diagnosis and localization of accessory pathways.

The WPW syndrome is a curable disease. The evolution of nonpharmacological methods of accessory pathway ablation has had a significant impact on management strategies in patients with arrhythmias mediated by accessory pathways. Despite an incidence of preexcitation in the general population of 0.1% to 0.3%, curative therapy is underutilized. This review has highlighted the traditional and newer methods of diagnosing and localizing accessory pathways. The number of patients benefiting from definitive therapy will parallel increased physician awareness of these methods.

Cardiac Catheterization↗
PubMed1991

Successful surgical treatment of atrial fibrillation. Review and clinical update.

Atrial fibrillation is the most common of all sustained cardiac arrhythmias, yet it has no effective medical or surgical therapy. During the past decade, multipoint computerized electrophysiological mapping systems were used to map both experimental and human atrial fibrillation. On the basis of these studies, a new surgical procedure was developed for atrial fibrillation. Between September 25, 1987, and July 1, 1991, this procedure was applied in 22 patients with paroxysmal atrial flutter (n = 2), paroxysmal atrial fibrillation (n = 11), or chronic atrial fibrillation (n = 9) of 2 to 21 years' duration. All patients were refractory to all antiarrhythmic medications, and each patient failed to receive the desired therapeutic benefits of an average of five drugs administered preoperatively. There were no operative deaths and all perioperative morbidity resolved. All 22 patients have been successfully treated for atrial fibrillation with surgery alone. Three patients developed one late isolated episode of atrial flutter at 5, 6, and 15 months postoperatively, and each of these patient's symptoms is now controlled by a single antiarrhythmic drug. Preservation of atrial transport function has been documented in all patients postoperatively, and all have experienced marked clinical improvement.

Adult↗
PubMed1991

Operations for atrial fibrillation.

Atrial fibrillation is the most common of all sustained cardiac arrhythmias, yet it has no effective medical or surgical therapy. During the past decade, multipoint computerized electrophysiological mapping systems were used to map both experimental and human atrial fibrillation. On the basis of these studies, a new surgical procedure was developed for atrial fibrillation. Between September 25, 1987, and May 1, 1991, this procedure was applied in 22 patients with either paroxysmal atrial flutter (n = 2), paroxysmal atrial fibrillation (n = 11), or chronic atrial fibrillation (n = 9) of 2 to 21 years' duration. All patients were refractory to all antiarrhythmic medications and each patient failed an average of 5.2 drugs preoperatively. There were no operative deaths and all perioperative morbidity resolved. All 22 patients have been cured of atrial fibrillation with surgery alone. One late isolated episode of atrial flutter occurred in a patient who is now receiving encainide. Preservation of atrial transport function has been documented in all of the patients postoperatively and all have experienced marked clinical improvement.

Adult↗
PubMed1991

Diagnostic implications of spectral and temporal analysis of the entire cardiac cycle in patients with ventricular tachycardia.

BACKGROUND: Available methods for analysis of signal-averaged electrocardiograms (ECGs) have a low-positive predictive accuracy for identifying patients at risk for ventricular arrhythmias. Identification of the spectral and temporal features in ECGs that distinguish patients prone to ventricular tachycardia (VT) is a prerequisite to implementing refinements in methods that increase the diagnostic power of the signal-averaged ECG. METHODS AND RESULTS: Fast Fourier transforms and time-domain reconstructions based on inverse fast Fourier transforms were computed over the entire cardiac cycle of signal-averaged ECGs of sinus beats from 40 patients with myocardial infarction and sustained VT, 41 with infarction without VT, and 20 normal controls. Ventricular depolarization and repolarization were analyzed by procedures that obviate limited resolution due to short data segments and window functions. Spectral magnitudes of ECGs from patients in each group were compared, and the phase data were used for time-domain reconstructions to determine the temporal distributions of distinguishing frequency bands during the cardiac cycle. Magnitudes of 1-7-Hz frequencies were increased (from p less than 0.05 to p less than 0.00001), and magnitudes of 13-56-Hz and 70-128-Hz frequencies were decreased (from p less than 0.05 to p less than 0.00001) in the spectra of ECGs from patients with VT compared with patients without VT. Time-domain reconstructions demonstrated that 1-7-Hz frequencies were detectable throughout the QRS complex, ST segment, and T wave in ECGs from each group. The 13-56-Hz and 70-128-Hz frequency bands not only contributed to the terminal QRS and ST segment but were also detectable throughout the QRS complex of ECGs from patients with VT. CONCLUSIONS: Results define new spectral and temporal features in signal-averaged ECGs from patients with VT that are excluded from analysis by available techniques that limit the bandwidth or restrict interrogation to portions of the cardiac cycle. These findings provide an objective basis for developing new indexes for signal-averaged ECG analysis.

Electrocardiography↗
PubMed1991

The surgical treatment of atrial fibrillation. II. Intraoperative electrophysiologic mapping and description of the electrophysiologic basis of atrial flutter and atrial fibrillation.

Computerized mapping of atrial fibrillation was performed in animals and man. To study atrial fibrillation in a systematic manner, we developed a clinically relevant experimental model of atrial fibrillation. Chronic mitral regurgitation was created surgically in 25 dogs without opening the pericardium. After several months of chronic mitral regurgitation, the atria became enlarged and sustained atrial fibrillation could be induced by standard programmed electrical stimulation techniques. Computerized isochronous activation maps of the atria were recorded during atrial fibrillation from 208 bipolar electrodes simultaneously. In a parallel study, human atrial fibrillation was mapped with a separate 160-channel intraoperative mapping system in patients with paroxysmal atrial fibrillation who were undergoing surgical correction of the Wolff-Parkinson-White syndrome. The canine activation sequence maps demonstrated a spectrum of rhythm abnormalities ranging from simple atrial flutter to complex atrial fibrillation. They also showed that macroreentrant circuits within the atrial myocardium were responsible for the entire spectrum of arrhythmias. Atrial reentry was also documented during human atrial fibrillation. All patients had nonuniform conduction around regions of bidirectional block in both atria resulting in multiple discrete wave fronts. In addition, six patients had a single reentrant circuit in the right atrium in which bidirectional block of the activation wave front occurred along the sulcus terminals between the venae cavae. The left atrium in all patients demonstrated multiple wave fronts and conduction block, but left atrial reentry could not be detected. Both the experimental study and the clinical study demonstrated that multiple wave fronts, nonuniform conduction, bidirectional block, and large (macroreentrant) reentrant circuits occur during atrial fibrillation. The presence of macroreentrant circuits and the absence of either microreentrant circuits or evidence of atrial automaticity suggests that atrial fibrillation should be amenable to surgical ablation.

Adult↗
PubMed1990

Noninvasive detection of patients with ischemic and nonischemic heart disease prone to ventricular fibrillation.

Abnormalities in the fast Fourier transforms of signal-averaged electrocardiograms (ECGs) obtained during sinus rhythm appear to distinguish patients with ischemic heart disease and sustained monomorphic ventricular tachycardia from those without ventricular tachycardia. This study was performed to determine the power of frequency analysis to detect patients with a history of ventricular fibrillation, to determine the extent to which spectra of signal-averaged ECGs from patients with ischemic and nonischemic heart disease are comparable and to compare results of signal-averaged ECG analysis in patients with ventricular fibrillation with results of programmed ventricular stimulation. Signal-averaged ECGs were obtained during sinus rhythm from 60 patients with sustained ventricular tachycardia (Group I) and 34 patients with ventricular fibrillation (Group II). Results of signal-averaged ECG analysis were abnormal in 92% of patients with ventricular tachycardia and 85% of patients with ventricular fibrillation (p = NS). Abnormal spectra were detected in the signal-averaged ECGs from 90% of patients with ischemic and from 86% of patients with nonischemic heart disease (p = NS). In contrast, the results of programmed stimulation differed markedly between the two patient groups. Sustained ventricular arrhythmias were induced in 91% of the patients with ventricular tachycardia compared with only 46% of those with ventricular fibrillation (p less than 0.0001). Moreover, ventricular tachycardia was inducible in 81% of patients with ischemic heart disease compared with only 50% of those with nonischemic heart disease (p less than 0.02). Thus, abnormalities in the spectra of signal-averaged ECGs were found in the majority of patients with ventricular fibrillation and were detectable even in those whose arrhythmia was not inducible by programmed stimulation. These results broaden the potential clinical application of noninvasive interrogation of signal-averaged ECGs to include the prospective identification of patients with ischemic or nonischemic heart disease prone to ventricular tachycardia or ventricular fibrillation.

Cardiac Pacing, Artificial↗
PubMed1990

Perinodal cryosurgery for atrioventricular node reentry tachycardia in 23 patients.

Atrioventricular node reentry tachycardia is the most common cause of paroxysmal supraventricular tachycardia. Available nonpharmacologic therapies include (1) catheter ablation or cryosurgical ablation of the His bundle and insertion of a permanent pacemaker and (2) surgical dissection around the atrioventricular node or discrete cryosurgery of the perinodal tissues, in an attempt to divide or ablate only one of the dual atrioventricular node conduction pathways responsible for the tachycardia while leaving the other intact. This report describes 23 consecutive patients who underwent the discrete cryosurgical procedure between August 13, 1982, and March 16, 1989. The first patient in this series, a 38-year-old woman, is the first patient in whom refractory atrioventricular node reentry tachycardia was cured surgically by a procedure designed to treat this arrhythmia. The ages of the 13 female and 10 male patients ranged from 12 to 56 years with an average age of 29 years. Fourteen of the 23 patients (61%) had the Wolff-Parkinson-White syndrome. Other associated arrhythmias included atrial flutter/fibrillation (n = 2), right atrial reentrant tachycardia (n = 1), junctional tachycardia (n = 1), and a Mahaim fiber (n = 1). Associated anatomic abnormalities included Ebstein's anomaly in two patients and a large right atrial aneurysm in one patient. The perinodal cryosurgical procedure was performed through a right atriotomy in the normothermic beating heart. Multiple 3 mm diameter cryolesions were placed around the borders of the triangle of Koch on the lower right atrial septum to alter the input pathways of the atrioventricular node. There were no operative deaths in this series of patients. Postoperatively, all 23 patients had normal atrioventricular conduction, and no heart block has occurred in any patients during the follow-up period. All patients have remained free of atrioventricular node reentry tachycardia (and of the Wolff-Parkinson-White syndrome) and none has required postoperative antiarrhythmic drugs for either of these arrhythmias. We consider this simple, safe, easily performed, and uniformly successful operation to be the procedure of choice for the treatment of medically refractory atrioventricular node reentry tachycardia.

Adolescent↗
PubMed1988

Improved differentiation of patients with and without ventricular tachycardia by frequency analysis of multiple electrocardiographic leads.

Previously, these investigators have analyzed fast Fourier transforms of signal-averaged electrocardiograms (ECGs) to distinguish patients with from those without sustained ventricular tachycardia (VT). In these studies, analysis was performed on X, Y and Z ECG signals and patient to patient comparisons were based on an average of the X, Y and Z results. The purpose of this study was to determine the extent to which fast Fourier transform analysis of individual ECG leads and of the vector magnitude contribute to the differentiation of patient groups. Studies were performed in 28 normal subjects (group I), 38 patients with prior myocardial infarction but without VT (group II), 38 patients with anterior infarction and sustained VT (group III) and 29 patients with inferior infarction and sustained VT (group IV). Results in group I were used to define normal values for the area and peak magnitude ratios for the individual X, Y and Z leads and for the vector magnitude and to define normal values for the mean XYZ area and peak magnitude ratios. Spectra of the X, Y and Z leads, the vector magnitude and the mean XYZ results were significantly different in patients with VT compared with normal subjects and patients without VT (p less than 0.001). Results were abnormal in multiple leads from 71% of patients with VT and from only 5% of normal subjects (p less than 0.0001). In many patients with VT, abnormalities were identified in 2 of the 3 leads indicating a selective spatial distribution of altered ECG signals that elicit abnormal frequency components.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

Computerized global electrophysiological mapping of the atrium in a patient with multiple supraventricular tachyarrhythmias.

The first clinical experience and the potential benefit of intraoperative global atrial-activation mapping recorded from 156 electrodes simultaneously are demonstrated in a 14-year-old girl with an ectopic (automatic) right atrial tachycardia, junctional tachycardia, and atrial flutter secondary to a previous atriotomy. Cryoablation of the right atrial focus terminated the automatic tachycardia, and surgical interruption of the atrial flutter pathway temporarily terminated this arrhythmia. Persistence of the junctional tachycardia necessitated elective cryoablation of the bundle of His.

Atrial Flutter↗
PubMed1988

Identification of patients with sustained ventricular tachycardia by frequency analysis of signal-averaged electrocardiograms despite the presence of bundle branch block.

Previously, we have demonstrated distinguishing features in the fast Fourier transform (FFT) of signal-averaged electrocardiograms (ECGs) obtained during sinus rhythm in the absence of bundle branch block that differentiate patients with from those without sustained ventricular tachycardia (VT). The ECGs during sinus rhythm from many patients with sustained VT, however, exhibit intraventricular conduction abnormalities. Accordingly, this study was performed to determine whether the presence of bundle branch block during sinus rhythm precluded accurate identification of patients with sustained VT. Studies were performed in 28 normal subjects (group I) and 141 patients with organic heart disease grouped according to clinical characteristics. Group II comprised 40 patients without VT in whom the QRS duration during sinus rhythm was less than 120 msec. Group III included 21 patients without VT in whom the QRS duration during sinus rhythm was 120 msec or greater. Group IV comprised 43 patients with sustained VT having ECGs during sinus rhythm with QRS durations less than 120 msec. Group V included 37 patients with sustained VT in whom the QRS duration during sinus rhythm was 120 msec or greater. FFTs of the terminal QRS and ST segment of signal-averaged X, Y, and Z ECGs were computed. Transformed data were expressed as an FFT magnitude and the relative contribution and peak magnitudes of 20 to 50 Hz frequencies determined after first demonstrating that this FFT method was more appropriate, when compared with the energy spectrum, for analyzing ECG signals having a broad range of ST segment durations.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1987

Long-term efficacy and safety of beta-adrenergic receptor antagonists for supraventricular tachycardia.

The efficacy and safety of nadolol and atenolol, 2 new long-acting beta-adrenergic receptor antagonists, were evaluated in patients with recurrent supraventricular tachycardia (SVT). Intravenous and oral drug therapy was administered to patients with atrioventricular reentrant tachycardia and atrioventricular nodal reentrant tachycardia. Efficacy was judged on a short-term basis by programmed electrical stimulation and on a long-term basis by clinical parameters and serial ambulatory electrocardiographic recordings during long-term follow-up. In addition, the usefulness of programmed electrical stimulation to predict long-term efficacy was evaluated. Intravenous nadolol prevented induction of SVT in 6 of 8 (75%) patients with atrioventricular nodal reentrant tachycardia, and oral nadolol prevented induction of SVT in 5 of 6 (83%) responders to intravenous nadolol. No episodes of sustained SVT recurred in these 5 patients during follow-up. Intravenous nadolol also prevented induction of SVT in 2 of 17 (11%) patients with atrioventricular reentrant tachycardia. Both patients remained non-inducible during treatment with oral nadolol, and neither experienced recurrence of SVT during follow-up. Intravenous atenolol prevented induction of SVT in 5 of 6 (83%) patients with atrioventricular nodal reentrant tachycardia. Oral atenolol prevented induction of atrioventricular nodal reentrant tachycardia in 4 of 5 (80%) patients responding to intravenous atenolol, and none of these 4 patients experienced a clinical recurrence. Intravenous atenolol prevented induction of SVT in 1 of 4 (25%) patients with atrioventricular reentrant tachycardia. Oral atenolol prevented induction of SVT in this patient and the arrhythmia has not recurred during follow-up. During follow-up (1 to 37 months), drug tolerance and compliance have been excellent with a low incidence of adverse reactions (11%).(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗