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Biomedical subjects

Janette F Strasburger

Publications and source records attributed to Janette F Strasburger.

11 recordsLinked to original sources
PubMed2006

Fetal cardiac repolarization abnormalities.

Abnormal cardiac repolarization renders the heart susceptible to lethal ventricular tachyarrhythmias, increasing the risk of sudden cardiac death in all ages; however, little is known about the incidence and etiology of T-wave abnormalities in utero. In this study, magnetocardiography was used to better define fetal T-wave characteristics, including the QT interval in the normal fetus, and to characterize T-wave abnormalities in the fetus with arrhythmia. The QT interval and T-wave alternans were assessed from magnetocardiographic recordings obtained at 14 to 39 weeks' gestation from 120 fetuses. Of these fetuses, 78 were from uncomplicated pregnancies and 42 had various forms of fetal arrhythmia (supraventricular tachycardia in 14, congenital atrioventricular block in 17, long QT syndrome with Torsades de pointes in 1, ventricular tachycardia in 2, sinus bradycardia in 4, and bradycardia due to blocked premature atrial contractions in 4). Although the corrected QT interval in normal sinus rhythm was accurately described by Bazett's formula, the corrected QT interval in fetal arrhythmia exhibited a systematic deviation at heart rate extremes. The dependence of the QT interval on the RR interval in arrhythmia was approximately described by QT alpha RR0.8. T-wave alternans was detected in 7 fetuses with arrhythmia, often in association with QT prolongation, suboptimal outcome, or fetal demise. The results of our study have demonstrated that QT-interval abnormalities exist and can be detected in fetal patients. The potential importance of T-wave assessment in the fetus with cardiac arrhythmia was evidenced by the high incidence of marked QT prolongation and T-wave alternans in the fetuses with suboptimal outcomes.

Arrhythmias, Cardiac↗
PubMed2006

Conduction system disease in fetuses evaluated for irregular cardiac rhythm.

OBJECTIVES: To determine the prevalence of 1st and 2nd degree AV block in fetuses with an irregular cardiac rhythm, and to summarize outcome of these pregnancies. BACKGROUND: The diagnosis of irregular cardiac rhythm or 'skipped beats' includes isolated ectopy that resolves spontaneously. Recently, Doppler measurements of the 'mechanical' PR interval have been shown to identify AV conduction disease prenatally. Prenatal therapy of these conduction abnormalities may limit the progression to more advanced disease either in utero or after birth. METHODS: A retrospective review was performed of fetuses evaluated between 1996 and 2004 with the findings of irregular cardiac rhythm. 1st or 2nd degree AV block was diagnosed on Doppler and M-mode recordings, and confirmed using either fetal magnetocardiography (fMCG) or postnatal 12-lead ECG. Dexamethasone was administered to 4 mothers with abnormal fetal AV conduction in the setting of anti-Ro/anti-La antibodies. RESULTS: Of 702 fetuses initially referred for arrhythmia, 306 had an irregular rhythm. Eight (2.6%) had intermittent 1st or 2nd degree AV block confirmed by fMCG and/or postnatal 12-lead ECG. AV block was presumed idiopathic in 2, associated with congenital long QT syndrome in 2 or with clinically unsuspected maternal anti-Ro or anti-La antibodies in 4. During the intrauterine period there was no progression to complete AV block and all were born alive at 34-40 weeks of gestation. CONCLUSION: A small but clinically significant population of fetuses with irregular rhythm will have 1st or 2nd degree AV block. Transplacental therapy may limit the intrauterine progression to more advanced disease.

Antibodies↗
PubMed2005

Prenatal diagnosis of fetal arrhythmias.

Life-threatening fetal arrhythmias are rare and warrant sophisticated specialty prenatal care, often provided by maternal-fetal medicine obstetricians, and pediatric and adult cardiologists. This medical field is in quick transition, and new methods of diagnosis and treatment of the fetus with arrhythmias are emerging. In this article, the mechanisms of arrhythmias are presented in light of recent progress in the new field of fetal electrophysiology. Treatments are reviewed with recommendations based on the small number of series of fetal tachycardia and fetal atrioventricular (AV) block drug treatment strategies published to date. Finally, a summary of areas of potential future research is provided.

Arrhythmias, Cardiac↗
PubMed2004

Giant fetal magnetocardiogram P waves in congenital atrioventricular block: a marker of cardiovascular compensation?

BACKGROUND: Cardiogram signal amplitude is a key index of hypertrophy but has not been investigated extensively in utero. In this study, magnetocardiography was used to assess P and QRS amplitude in normal subjects and subjects with fetal arrhythmia. METHODS AND RESULTS: The study cohort consisted of 68 normal fetuses and 25 with various arrhythmias: 9 reentrant supraventricular tachycardia (SVT), 2 ventricular tachycardia (VT), 2 sinus tachycardia, 2 blocked atrial bigeminy, 2 congenital second-degree atrioventricular (AV) block, and 8 congenital complete AV block. Subjects with congenital AV block, all presenting with bradycardia, showed large QRS amplitude, exceedingly large P-wave amplitude, and long P-wave duration. The 2 subjects with VT, both with poor ventricular function, also exhibited large P waves. SVT was associated with only moderate signal amplitude elevation. CONCLUSIONS: The data imply that AV block in utero is accompanied by hypertrophy, which is more pronounced for the atria than the ventricles. We hypothesize that the hypertrophy results from a compensatory response associated with regulation of cardiac output and is likely to be observable in other arrhythmias and disease states. Magnetocardiography may be more sensitive than fetal echocardiography for detection of atrial hypertrophy in utero.

Bradycardia↗
PubMed2004

Amiodarone therapy for drug-refractory fetal tachycardia.

BACKGROUND: Fetal tachycardia complicated by ventricular dysfunction and hydrops fetalis carries a significant risk of morbidity and mortality. Transplacental digoxin is effective therapy in a small percentage, but there is no consensus with regard to antiarrhythmic treatment if digoxin fails. This study evaluates the safety, efficacy, and outcome of amiodarone therapy for digoxin-refractory fetal tachycardia with heart failure. METHODS AND RESULTS: Fetuses with incessant tachycardia and either hydrops fetalis (n=24) or ventricular dysfunction (n=2) for whom digoxin monotherapy and secondary antiarrhythmic agents (n=13) were not effective were treated transplacentally with a loading dose of oral amiodarone for 2 to 7 days, followed by daily maintenance therapy for <1 to 15 weeks. Digoxin therapy was continued throughout gestation. Newborns were studied by transesophageal pacing or ECG monitoring to determine the mechanism of tachycardia. Three fetuses were delivered urgently in tachycardia during amiodarone loading, and 3 required additional antiarrhythmic agents for sustained cardioversion. Amiodarone or amiodarone combinations converted 14 of 15 (93%) with reentrant supraventricular tachycardia, 2 of 2 with ventricular or junctional ectopic tachycardia, and 3 of 9 (33%) with atrial flutter. Amiodarone-related adverse effects were transient in 5 infants and 8 mothers. Mean gestational age at delivery was 37 weeks, with 100% survival. CONCLUSIONS: Orally administered amiodarone is safe and effective treatment for drug-refractory fetal tachycardia, specifically reentrant supraventricular tachycardia, junctional ectopic, or ventricular tachycardia, even when accompanied by hydrops fetalis or ventricular dysfunction.

Amiodarone↗
PubMed2004

Commotio cordis.

Commotio cordis is ventricular fibrillation that results from blunt chest trauma and is a life threatening condition; early resuscitation and defibrillation are critical. This may occur during sporting events or from child abuse and most patients are boys who are younger than 16 years. Commotio cordis' prognosis depends on the availability of cardiac defibrillation. Automatic defibrillators at convenient locations near sporting events, combined with improved cardiopulmonary resuscitation education, may improve chances of survival after this rare phenomenon. Transient cardiac conduction abnormalities and arrhythmias have been observed in survivors; therefore, cardiac clearance before resumption of sports is indicated.

Arrhythmias, Cardiac↗
PubMed2003

Location of accessory connection in infants presenting with supraventricular tachycardia in utero: clinical correlations.

The most common mechanism of fetal tachycardia is orthodromic reciprocating tachycardia utilizing an accessory atrioventricular connection, however, data regarding accessory connection location in patients with fetal tachycardia is limited. To investigate the location of accessory connections in fetal tachycardia, postnatal transesophageal electrophysiology studies were performed at one institution over a 10-year period in 24 infants with documented fetal tachycardia. The 18 infants with inducible orthodromic reciprocating tachycardia were grouped according to accessory connection location, and groups were compared regarding prenatal presentation and clinical course. Left-sided connections were found in 13 (72%) patients, while accessory connection location could not be determined in the remaining 5 (28%) patients. The presence of a left-sided accessory connection was associated with sustained tachycardia, depressed ventricular function, and the need for antiarrhythmic therapy in utero. No other difference in clinical or electrophysiologic data was found between groups. Our findings indicate that a high proportion of patients with fetal tachycardia have left-sided accessory connections, and a left-sided connection may adversely affect fetal hemodynamics and cardiac output.

Bundle-Branch Block↗