Biomedical subjects

M E Cain

Publications and source records attributed to M E Cain.

At least 19 recordsLinked to original sources

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↗

PubMed1992

Reentrant and focal mechanisms underlying ventricular tachycardia in the human heart.

BACKGROUND: To determine the mechanisms of ventricular tachycardia (VT) in humans, three-dimensional intraoperative mapping of up to 156 intramural sites was performed in 13 patients with healed myocardial infarction and refractory VT. METHODS AND RESULTS: Mapping was of sufficient density to define the mechanism of 10 VTs in eight patients. In five of 10 cases, sustained VT was initiated in the subendocardium or epicardium by intramural reentry with marked conduction delay as well as functional and anatomic block most prominent in the subendocardium and midmyocardium. The initiating beats of reentrant VT induced by programmed electrical stimulation arose in the endocardium or midmyocardium by progressive slowing of conduction leading to unidirectional block. Multiple simultaneous reentrant circuits can be present. In contrast, five of the 10 sustained VTs were initiated by a focal mechanism as defined by the absence of electrical activity between the termination of one beat and the initiation of the next despite the presence of multiple intervening intramural electrode recording sites. Comparisons of the mapping data with results of histopathological analysis of tissue demonstrated that the location of infarction as well as that of adjacent fibrotic muscle determined sites of both fixed and functional conduction block during macroreentrant VT and that slowing of conduction occurred in a direction transverse rather than longitudinal to fiber orientation. CONCLUSIONS: Both intramural reentry and a focal mechanism underlie sustained VT in patients with healed myocardial infarction.

Adult↗

PubMed1992

Contribution of myocardium responsible for ventricular tachycardia to abnormalities detected by analysis of signal-averaged ECGs.

BACKGROUND: Current methods of signal-averaged ECG analysis interrogate the terminal 40 msec of the QRS complex and/or the ST segment and have a low positive-predictive accuracy for detecting vulnerability to sustained ventricular tachycardia (VT). The extent to which abnormalities detected during these ECG intervals are generated by myocardial tissue responsible for VT has not been well defined. The purpose of this study was to determine when, during sinus rhythm, myocardium responsible for VT is activated. METHODS AND RESULTS: Three-dimensional ventricular activation maps were analyzed during sinus rhythm and during 10 VTs in eight patients with healed myocardial infarctions undergoing arrhythmia surgery for sustained monomorphic VT. The mechanism of VT was focal in five instances and macroreentrant in five. During sinus beats, myocardium responsible for all focal VTs activated 43 +/- 38 msec before the onset of the terminal 40-msec interval of the QRS complex. During sinus rhythm, activation of the myocardium critical to macroreentrant VT began 72 +/- 13 msec before the onset of the terminal QRS interval and in only three instances extended 2-25 msec into the terminal 40 msec of the QRS complex. Electrograms recorded during the ST segment represented late activation of epicardial sites overlying zones of infarction that were temporally and spatially remote from tissue critical to VT. CONCLUSIONS: Current methods of signal-averaged ECG analysis limiting interrogation to the terminal QRS/ST segment exclude detection of > 95% of the signals generated by myocardium responsible for sustained VT. These results establish a pathophysiological basis for expanding signal-averaged ECG analysis to include more of the cardiac cycle.

Electrocardiography↗

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

Periodicity of global ventricular activation of sinus beats in patients with coronary artery disease and sustained ventricular tachycardia.

Despite increasing clinical reliance on signal-averaged electrocardiograms for determining risk for development of sustained ventricular tachycardia (VT), the periodicity of global ventricular activation during sinus rhythm has not been defined. Accordingly, epicardial and transmural ventricular electrograms during 6 consecutive sinus beats were evaluated in 10 patients with abnormal signal-averaged electrocardiograms who were undergoing surgery for VT. Bipolar electrograms were recorded with sock and needle electrodes from up to 96 epicardial and 156 transmural sites. Electrogram morphology, duration and activation were compared on a beat-to-beat basis. In all, 9,816 electrograms were analyzed. Mean durations of epicardial and transmural electrograms were 33 +/- 16 ms (range 6 to 199) and 23 +/- 10 ms (range 6 to 72), respectively, with a beat-to-beat variation of 1.9 +/- 1.4 ms per site. Similarly, local activation times did not vary significantly during the 6 cardiac cycles analyzed (mean variation 1.7 +/- 2.0 ms). Local conduction failure was not observed. Although electrograms during the terminal 40 ms of the QRS were significantly longer (36 +/- 20 vs 26 +/- 12 ms, p less than 0.001) when compared with those recorded earlier during the QRS complex, beat-to-beat variation in duration (2.1 +/- 1.6 ms) and activation (1.7 +/- 2.3 ms) was not significant. Results demonstrate that epicardial and transmural electrograms recorded during sinus rhythm in patients with sustained VT are periodic signals and thus establish a physiologic basis for signal averaging of electrocardiographic waveforms in these patients.

Aged↗

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

Standards for analysis of ventricular late potentials using high-resolution or signal-averaged electrocardiography: a statement by a task force committee of the European Society of Cardiology, the American Heart Association, and the American College of Cardiology.

Sufficient data are available to recommend the use of the high-resolution or signal-averaged electrocardiogram in patients recovering from myocardial infarction without bundle branch block to help determine their risk for developing sustained ventricular tachyarrhythmias. However, no data are available about the extent to which pharmacological or nonpharmacological interventions in patients with late potentials have an impact on the incidence of sudden cardiac death. Therefore, controlled, prospective studies are required before this issue can be resolved. As refinements in techniques evolve, it is anticipated that the clinical value of high-resolution or signal-averaged electrocardiography will continue to increase.

Analog-Digital Conversion↗

PubMed1991

Standards for analysis of ventricular late potentials using high resolution or signal-averaged electrocardiography. A statement by a Task Force Committee between the European Society of Cardiology, the American Heart Association and the American College of Cardiology.

Sufficient data are available to recommend that the high-resolution or signal-averaged electrocardiogram can be used in patients recovering from myocardial infarction without bundle branch block to help to determine their risk for developing sustained ventricular tachyarrhythmias. However, no data are available regarding the extent to which pharmacologic or non-pharmacologic interventions in patients with late potentials have an impact on the incidence of sudden cardiac death. Therefore, controlled, prospective studies are required before this issue can be definitely answered. As refinements in techniques evolve, it is anticipated that the clinical value of high-resolution or signal-averaged electrocardiography will continue to increase in the future.

Arrhythmias, Cardiac↗

PubMed1991

Standards for analysis of ventricular late potentials using high-resolution or signal-averaged electrocardiography. A statement by a Task Force Committee of the European Society of Cardiology, the American Heart Association, and the American College of Cardiology.

American Heart Association↗

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↗

PubMed1991

The surgical treatment of atrial fibrillation. III. Development of a definitive surgical procedure.

On the basis of the known electrophysiologic mechanisms of atrial fibrillation, multiple surgical procedures were designed and tested in dogs to determine the feasibility of developing a surgical cure for human atrial fibrillation. These experimental studies culminated in a surgical approach that effectively creates an electrical maze in the atrium. The atrial incisions prevent atrial reentry and allow sinus impulses to activate the entire atrial myocardium, thereby preserving atrial transport function postoperatively. Since September 1987, this surgical procedure has been applied in seven patients, five with paroxysmal atrial fibrillation of 2 to 9 years' duration and two with chronic atrial fibrillation of 3 and 10 years' duration. All seven patients have been cured of atrial fibrillation and none is receiving any postoperative antiarrhythmic medications.

Adult↗

PubMed1990

Transmural ventricular activation during consecutive cycles of sustained ventricular tachycardia associated with coronary artery disease.

Although computerized mapping has enabled the intraoperative delineation of global ventricular activation from a single complex of ventricular tachycardia (VT), beat-to-beat reproducibility of isochronic maps has not been defined. To determine the reliability of single-beat analysis, epicardial and transmural ventricular electrograms during 6 consecutive VT cycles were analyzed in 10 patients during intraoperative mapping of sustained monomorphic VT. Bipolar electrograms were recorded simultaneously using sock and needle electrodes from up to 96 epicardial and 156 transmural sites. In each patient, at each electrode site, local activation time, electrogram duration and morphology were compared over 6 consecutive beats. A total of 9,816 electrograms were analyzed. For each patient, the isochronic activation map during VT was reproducible. Mean beat-to-beat variations in local epicardial and transmural activation times were only 1.7 +/- 1.7 and 2.04 +/- 1.9 ms, respectively (difference not significant). Moreover, electrogram duration did not vary significantly. Mean variations in epicardial and transmural electrogram durations were 2.1 +/- 1.8 and 1.4 +/- 1.9 ms, respectively (difference not significant). There were only 2 instances of 2:1 conduction failure; both occurred intramurally and adjacent to a site of VT origin. Thus, transmural ventricular activation during sustained monomorphic VT is reproducible regardless of electrode site or electrogram duration. These results demonstrate that analysis of a single beat of VT is a reliable and expedient method to delineate ventricular activation during intraoperative computerized mapping for the purpose of clinical decision-making in patients with sustained monomorphic VT.

Aged↗

PubMed1990

Computerized activation sequence mapping of the human atrial septum.

To delineate the propagation of electrical activation in the atrial septum, atrial epicardial and atrial septal maps were recorded intraoperatively using a 156-channel computerized mapping system in 12 patients during sinus rhythm (n = 10), supraventricular tachycardia associated with septal pathways in Wolff-Parkinson-White syndrome (n = 3), atrioventricular (AV) node reentrant tachycardia (n = 4), and atrial flutter (n = 5). The epicardial and septal data were recorded simultaneously from 156 atrial electrodes, digitized, analyzed, and displayed as isochronous maps on a two-dimensional diagram of the atria. During sinus rhythm, the activation wave fronts propagated most rapidly along the large muscle bundles of the atrial septum. During supraventricular tachycardia associated with Wolff-Parkinson-White syndrome, the earliest site of retrograde atrial activation usually corresponded to the position of atrial insertion of the septal pathways. However, the earliest site of activation during orthodromic supraventricular tachycardia was different from that during ventricular pacing in 1 patient with a posterior septal accessory pathway localized by the epicardial mapping study. The data document the rationale for dividing the ventricular end of the accessory pathways (ie, the endocardial technique) rather than the atrial end (ie, the epicardial technique) in patients with Wolff-Parkinson-White syndrome. During AV node reentrant tachycardia, atrial activation data suggested that atrial tissue lying outside the confines of the anatomical AV node is a necessary link in this common arrhythmia. Thus, these atrial septal maps explain why surgical dissection, or properly positioned small cryolesions placed in the region of the AV node, can ablate AV node reentrant tachycardia without altering normal AV node function. The maps recorded during atrial flutter suggest the importance of the atrial septum as one limb of a macroreentrant circuit responsible for the arrhythmia, and imply that atrial flutter is amenable to control by surgical techniques. These studies demonstrate the details of normal atrial septal activation, the importance of the atrial septum in a variety of different atrial arrhythmias, and the basis of and potential for surgical ablation of the most common types of supraventricular arrhythmias.

Adolescent↗

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↗