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Biomedical subjects

L S Klein

Publications and source records attributed to L S Klein.

At least 19 recordsLinked to original sources
PubMed1992

Radiofrequency catheter ablation of ventricular tachycardia in patients without structural heart disease.

BACKGROUND: Radiofrequency energy has been used safely and successfully to eliminate accessory pathways in patients with the Wolff-Parkinson-White syndrome and the substrate for atrioventricular nodal reentrant tachycardia. However, this form of ablation has had only limited success in eliminating ventricular tachycardia in patients with structural heart disease. In contrast, direct-current catheter ablation has been used successfully to eliminate ventricular tachycardia in patients with and without structural heart disease. The purpose of this study was to test whether radiofrequency energy can safely and effectively ablate ventricular tachycardia in patients without structural heart disease. METHODS AND RESULTS: Sixteen patients (nine women and seven men; mean age, 38 years; range, 18-55 years) without structural heart disease who had ventricular tachycardia underwent radiofrequency catheter ablation to eliminate the ventricular tachycardia. Two patients presented with syncope, nine with presyncope, and five with palpitations only. Mean duration of symptoms was 6.7 years (range, 0.5-20 years). Radiofrequency catheter ablation successfully eliminated ventricular tachycardia in 15 of 16 patients (94%). Sites of ventricular tachycardia origin included the high right ventricular outflow tract (12 patients), the right ventricular septum near the tricuspid valve (three patients), and the left ventricular septum (one patient). The only ablation failure was in a patient whose ventricular tachycardia arose from a region near the His bundle. An accurate pace map, early local endocardial activation, and firm catheter contact with endocardium were associated with successful ablation. Radiofrequency ablation did not cause arrhythmias, produced minimal cardiac enzyme rise, and resulted in no detectable change in cardiac function by Doppler echocardiography. CONCLUSIONS: Radiofrequency catheter ablation of ventricular tachycardia in patients without structural heart disease is effective and safe and may be considered as early therapy in these patients.

Adolescent↗
PubMed1992

Surgery for atrioventricular node reentry tachycardia. Results with surgical skeletonization of the atrioventricular node and discrete perinodal cryosurgery.

Surgical treatment options for interruption of atrioventricular node reentrant tachycardia include (1) skeletonization of the atrioventricular node by dissecting it from most of its atrial inputs and (2) discrete cryosurgery of the perinodal tissues by applying a series of sequential cryolesions to the atrial tissues immediately adjacent to the atrioventricular node. Both these techniques attempt to interrupt one of the dual atrioventricular node conduction pathways while preserving the other. This report describes 17 consecutive patients who underwent surgical treatment, 10 patients with skeletonization of the atrioventricular node and seven patients with discrete perinodal cryosurgery. There were 10 female and seven male patients and their ages ranged from 28 to 56 years (mean 38). Two of the 17 patients had Wolff-Parkinson-White syndrome and their accessory pathways were interrupted before the atrioventricular nodal reentrant tachycardia was ablated. All the procedures were performed in a normothermic beating heart while atrioventricular conduction was monitored closely. In the skeletonization technique, the right atrial septum was mobilized and the atrioventricular node exposed anterior to the tendon of the Todaro. The perinodal cryosurgical procedure was also performed through a right atriotomy and a series of sequential 3 mm cryolesions were placed around the borders of the triangle of Koch on the inferior right atrial septum. There were no operative deaths. Two patients who underwent the skeletonization operation had heart block necessitating pacemaker therapy. At postoperative electrophysiologic study, no echoes or atrioventricular nodal reentrant tachycardia were inducible in any of the 17 patients. All patients have remained free of arrhythmia recurrence and have required no antiarrhythmic therapy after a follow-up of 5 to 28 months (mean 14). In conclusion, both atrioventricular node skeletonization and perinodal cryosurgery successfully ablate atrioventricular nodal reentrant tachycardia; however, perinodal cryosurgery appears to be safer in avoiding heart block, is more easily performed, and is our procedure of choice for the management of medically refractory atrioventricular nodal reentrant tachycardia.

Adolescent↗
PubMed1992

Catheter ablation of ventricular tachycardia using radiofrequency techniques in patients without structural heart disease.

It has been previously demonstrated that radiofrequency (RF) energy can be safely applied to successfully eliminate accessory pathways in patients with the Wolff-Parkinson-White syndrome. This technique may also be used to successfully eliminate atrioventricular (AV) nodal reentrant tachycardia by elimination of either the fast or slow AV nodal pathways. However, RF energy has achieved only limited success in eliminating ventricular tachycardia (VT) in patients with structural heart disease, such as coronary artery disease and dilated cardiomyopathy. Direct-current catheter techniques have successfully eliminated VT in patients with and without structural heart disease, but this technique is limited by the risk of barotrauma and proarrhythmia. We used RF catheter ablation techniques to eliminate VT in patients without structural heart disease. Our results from the basis of this report. 16 patients (nine women and seven men; mean age 38; range 18 to 55 years) who did not have any identifiable structural heart disease by echocardiography where included in this study. These patients underwent RF catheter ablation to eliminate VT. Two patients had presented with syncope, nine with presyncope and five with palpitations only. The mean duration of symptoms was 6.7 years (range 0.5 to 20 years). VT was successfully eliminated by RF catheter techniques in 15 of the 16 patients (a 94% success rate). Importantly, successful ablation sites included regions other than the right ventricular outflow tract. Areas of VT origin therefore included the high right ventricular outflow tract (twelve patients), right ventricular septum near the tricuspid valve (three patients), and the left ventricular septum (one patient). The only ablation failure was in a patient whose VT arose from a region near the His bundle. Successful ablation occurred in patients in whom an accurate pace map could be obtained and early local endocardial activation was obtainable. Further, firm catheter contact with endocardium was required for successful elimination of VT. RF ablation did not cause any identifiable arrhythmia and produced a minimal cardiac enzyme rise. It also resulted in no detectable change in cardiac function by Doppler echocardiography. Based on these findings, we conclude that RF catheter ablation of VT in patients without structural heart disease was highly effective and safe. It may therefore be considered as early therapy in these patients.

Adult↗
PubMed1991

Antitachycardia devices: realities and promises.

Nonpharmacologic therapy for ventricular arrhythmias has gained growing attention with the development of the implantable cardioverter-defibrillator. In addition, the reports of adverse effects of drug therapy from several studies, including the Cardiac Arrhythmia Suppression Trial (CAST), have supported the need for these devices. The development of new implantable cardioverter-defibrillators that have the capability of antitachycardia pacing, bradycardia pacing, cardioversion and defibrillation has enhanced their clinical utility. The currently available implantable cardioverter-defibrillators have been shown to significantly improve survival after sudden cardiac arrest in patients with life-threatening ventricular arrhythmias. Newer devices with expanded capabilities may reduce mortality even further. In this report the features of currently available antitachycardia devices and implantable cardioverter-defibrillators are reviewed and the features and current implant data on newer antitachycardia devices are discussed.

Arrhythmias, Cardiac↗
PubMed1991

Electrophysiologic and anatomic characteristics of ventricular tachycardia induced at the right ventricular outflow tract but not at the apex.

The site of ventricular stimulation is an important variable in the initiation of ventricular tachycardia (VT) by programmed ventricular stimulation. Among 169 patients studied consecutively, 17 (10%) had ventricular tachycardia induced by programmed electrical stimulation from the right ventricular outflow tract but not from the apex. Fourteen of these 17 patients had had prior myocardial infarction (12 had inferior, and two had both inferior and anterior myocardial infarction), two had a dilated cardiomyopathy, and one had a localized cardiomyopathy. Fourteen patients had echocardiograms suitable for analysis. Of these, 12 had posterior/inferior ventricular wall motion abnormalities located at the base of the heart. The ventricular effective refractory periods from the right ventricular outflow tract and right ventricular apex were 237 +/- 4 and 244 +/- 5 msec, respectively (p less than 0.05, mean +/- SEM). Induced VT had a cycle length of 229 +/- 4 msec and had the morphology of right bundle branch block in 12 patients, of left bundle branch block in three patients, and had both morphologies in two patients. In 14 patients the axis was superior. VT was initiated with two extrastimuli in 15 patients and with burst right ventricular pacing in two patients. Similar pacing techniques with identical pacing intervals did not induce VT at the right ventricular apex in 14 of these 17 patients. Further, among the 15 patients whose VT was induced at the right ventricular outflow tract with two extrastimuli, neither burst pacing (n = 13) nor two extrastimuli introduced at faster paced rates (n = 12) induced VT at the right ventricular apex.(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiac Pacing, Artificial↗
PubMed1990

Clinical features of amiodarone-induced pulmonary toxicity.

The incidence and clinical predictors of amiodarone pulmonary toxicity were examined in 573 patients treated with amiodarone for recurrent ventricular (456 patients) or supraventricular (117 patients) tachyarrhythmias. Amiodarone pulmonary toxicity was diagnosed in 33 of the 573 patients (5.8%), based on symptoms and new chest radiographic abnormalities (32 of 33 patients) and supported by abnormal pulmonary biopsy (13 of 14 patients), low pulmonary diffusion capacity (DLCO) (nine of 13 patients), and/or abnormal gallium lung scan (11 of 16 patients). Toxicity occurred between 6 days and 60 months of treatment for a cumulative risk of 9.1%, with the highest incidence occurring during the first 12 months (18 of 33 patients). Older patients developed it more frequently (62.7 +/- 1.7 versus 57.4 +/- 0.5 years, p = 0.018), with no cases diagnosed in patients who started therapy at less than 40 years of age. Gender, underlying heart disease, arrhythmia, and pretreatment chest radiographic, spirometric, or lung volume abnormalities did not predict development of amiodarone pulmonary toxicity, whereas pretreatment DLCO was lower in the group developing it (76.0 +/- 5.5% versus 90.4 +/- 1.4%, p = 0.01). There was a higher mean daily amiodarone maintenance dose in the pulmonary toxicity group (517 +/- 25 versus 409 +/- 6 mg, p less than 0.001) but no difference in loading dose. No patient receiving a mean daily maintenance dose less than 305 mg developed pulmonary toxicity. Patients who developed toxicity had higher plasma desethylamiodarone (2.34 +/- 0.18 versus 1.92 +/- 0.04 micrograms/ml, p = 0.009) but not amiodarone concentrations during maintenance therapy.(ABSTRACT TRUNCATED AT 250 WORDS)

Amiodarone↗
PubMed1990

Effect of atrioventricular interval during pacing or reciprocating tachycardia on atrial size, pressure, and refractory period. Contraction-excitation feedback in human atrium.

To determine whether a contraction-excitation feedback mechanism exists in human atrium, we investigated the effects of varying the atrioventricular (AV) interval from 0 to 360 msec during AV pacing at a cycle length of 400 msec on atrial pressure, size, and refractoriness in 10 patients (group 1, without supraventricular tachycardia). The same parameters were determined in another 10 patients (group 2, with different spontaneous AV relations) during AV reciprocating tachycardia or AV nodal reciprocating tachycardia and during high right atrial (RA) pacing at the tachycardia cycle length. In group 1 patients, peak and mean RA pressure, RA effective refractory period (RA-ERP), and left atrial (LA) size all decreased to minimal values at an AV interval of 120 msec and remained low as the AV interval was increased and approached 400 msec. The increase in each of the variables from its lowest to greatest value was as follows: Mean systemic blood pressure, 20.9 +/- 3.1 mm Hg; LA size, 0.55 +/- 0.05 cm; RA peak pressure, 10.4 +/- 1.8 mm Hg; RA mean pressure, 3.5 +/- 0.6 mm Hg; and RA-ERP, 22.5 +/- 3.0 msec, p less than 0.001 for each. The weighted mean correlation coefficient with RA-ERP was significant for RA peak pressure and LA size (p less than 0.001 for each). These same relations were investigated in five patients with the Wolff-Parkinson-White syndrome and AV reciprocating tachycardia and five patients with AV nodal reciprocating tachycardia (group 2).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

Methodological pluralism in clinical nursing research.

Clinical nursing research can benefit from an approach that blends discovery oriented qualitative methods with the objective, numerically based quantitative methods. This paper describes current approaches to clinical research in either the quantitative or qualitative paradigm. The strengths and weaknesses of each of these approaches are discussed. A rationale for methodological pluralism--the blending of the two methods--to understand clinical phenomena is presented.

Clinical Nursing Research↗
PubMed1989

The electrophysiologic effects of enoximone in patients with preexisting ventricular tachyarrhythmias.

Electrophysiologic and hemodynamic effects of intravenous enoximone were studied in 15 male patients, mean age 62.2 years, with New York Heart Association classes II to IV congestive heart failure (coronary artery disease in 10 and idiopathic dilated cardiomyopathy in five patients; mean ejection fraction, 0.19). All patients had spontaneous ventricular tachyarrhythmias; eight had sustained ventricular tachycardia (VT), one had ventricular fibrillation, and six had nonsustained VT. Hemodynamic and electrophysiologic parameters including VT induction were determined before and during an intravenous infusion of enoximone. The cardiac index increased (2.49 +/- 0.89 to 2.96 +/- 0.78), and the pulmonary capillary wedge pressure decreased (22.4 +/- 13.2 to 10.0 +/- 9.0) after enoximone per predefined protocol endpoints. There was a significant decrease in spontaneous sinus cycle length, corrected sinus nodal recovery time, AH interval during atrial pacing, shortest cycle length at which 1:1 atrioventricular nodal conduction occurred, and refractory periods of the atrium, ventricle, and atrioventricular node. Enoximone did not alter the cycle length of induced VT, and there was no consistent change in the number of extrastimuli required for VT induction. A baseline 24-hour ECG recording was obtained on 14 patients (while receiving a long-term antiarrhythmic drug regimen, if needed) and repeated after 1 week and 1 month of oral enoximone therapy. There was no significant increase in the number of premature ventricular complexes per hour or VT episodes per 24 hours after 1 week or 1 month of therapy with enoximone. However, if four patients who received amiodarone and may not yet have reached steady state were excluded from analysis, there was a significant increase in the frequency of premature ventricular complexes per hour 1 month after initiation of enoximone. We conclude that intravenous enoximone reduces pulmonary capillary wedge pressure and increases cardiac output in most patients. Intravenous enoximone in doses sufficient to have hemodynamic effects shortens atrial, ventricular, and atrioventricular nodal refractoriness and decreases AV nodal conduction time but has no consistent effect on VT induction or VT cycle length. The frequency of spontaneous ventricular ectopy may increase in some patients after oral enoximone, but its clinical significance is undefined. Enoximone may be administered cautiously to patients with congestive heart failure and preexisting ventricular tachyarrhythmias.

Administration, Oral↗
PubMed1988

Prospective evaluation of a discriminant function for prediction of recurrent symptomatic ventricular tachycardia or ventricular fibrillation in coronary artery disease patients receiving amiodarone and having inducible ventricular tachycardia at electrophysiologic study.

Induction of ventricular tachycardia (VT) at electrophysiologic study in patients taking amiodarone poorly predicts recurrence of VT. Consequently, a discriminant function was developed (using parameters based on retrospective data) that appeared to identify high-risk patients. These parameters included ventricular effective refractory period, corrected QT interval, initiation of a repetitive ventricular response and the mode of VT induction. In the present study these parameters were prospectively evaluated in 60 patients with coronary artery disease and sustained VT or ventricular fibrillation (VF), in whom VT was still induced at electrophysiologic study during amiodarone therapy. Thirteen patients had recurrent events (sudden death in 8 and sustained VT in 5) and 47 patients had no symptomatic arrhythmia recurrence (follow-up for 16 +/- 2 months, mean +/- standard error of the mean). The ventricular effective refractory period, corrected QT interval and presence of a repetitive ventricular response did not discriminate between patients with and without symptomatic arrhythmia recurrence. However, an easier mode of VT induction during amiodarone therapy versus control was highly predictive of arrhythmia recurrence: 9 of 13 (69%) recurrences were in this group. In contrast, only 4 of 44 (9%) patients who had either the same or harder mode of VT induction had a recurrent event. Overall, 9 of 16 (56%) patients with an easier mode of VT induction had a recurrence, including 6 of the 8 patients with subsequent sudden cardiac death. It is concluded that electrophysiologic testing during amiodarone therapy is useful to identify high-risk patients.

Administration, Oral↗
PubMed1978

Effect of O2 exposure on pulmonary metabolism of prostaglandin E2.

The effect of exposure to oxygen on lung metabolism of prostaglandin E2 to 15-keto-prostaglandin E2 and 13-14-dihydro-15-keto-prostaglandin E2 was studied in the isolated, perfused rat lung. During a 30-sec period, lungs were infused with varying concentrations of prostaglandin E2 labeled with hydrogen-3 and the fraction metabolized during one passage was determined. At a prostaglandin E2 concentration of 5 nM, which approximates that in normal mixed venous blood, an average of 93 per cent of infused prostaglandin was metabolized by normal lungs. At prostaglandin E2 concentrations of 2 to 70 micrometer, the fraction metabolized decreased. The computed concentration of prostaglandin E2 for half-maximal rate of metabolism was 4.2 micrometer. Metabolism of prostaglandin E2 by isolated lungs was unaffected by exposure of rats to greater than 97 per cent oxygen at 1 atmosphere absolute for 24 hours, but was markedly depressed after both 36 and 48 hours of hyperoxia. These results indicate that exposure of the rat to oxygen for 36 and 48 hours is associated with decreased ability of the lung to metabolize prostaglandin E2 to its keto derivatives and may result in increased concentration of prostaglandin E2 in the systemic arterial blood.

Animals↗