SEARCH · PubMed Health

Results for “Magnetocardiography”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 recordsLinked to original sources

PubMed2005

[Magnetocardiography--a possible supplementary method for early detection of fetal distress in high-risk pregnancies].

Ever since the first report on fetal magnetocardiography by Kariniemi in 1974 numerous studies have examined cardiac activity in healthy fetuses using this technique. Recently there has been an increase in reports on the identification of fetal pathological states, in particular in the diagnosis of fetal arrhythmias, using magnetocardiography. Other possible applications of this non-invasive method include the assessment of intrauterine growth retardation and fetal stress. In a patient with gestational hypertension and asymmetric growth retardation without pathological ultrasound findings, fetal magnetocardiography showed a reduced beat-to-beat heart rate variability indicating signs of fetal stress. On the day following the magnetocardiographic recording, fetal Doppler ultrasonography findings indicated an incipient brain sparing effect. The fetal growth retardation was reflected in the duration of the fetal cardiac time intervals. We conclude that fetal magnetocardiography non-invasively enables the timely identification of pathological fetal conditions.

Adult↗

PubMed2001

Fetal heart rate patterns in normal and ritodrine-treated pregnancies, detected by magnetocardiography.

OBJECTIVE: The aim of the present study was to test the validity of magnetocardiography in the diagnosis of fetal heart rate arrhythmias in normal pregnancies, as compared to the number of arrhythmias reported in other series, which were detected by use of other diagnostic techniques. We also evaluated the influence of ritodrine on the fetal heart rhythm in pregnancies treated for the risk of preterm labor by means of magnetocardiography, in order to provide preliminary results that could be utilized in the future establishment of magnetocardiography as a screening procedure in the diagnosis and management of fetal arrhythmias. METHODS: We performed a prospective study on two subgroups of pregnant women: one of 84 women with normal healthy singleton pregnancies and one of 68 pregnant women treated with ritodrine for the risk of preterm labor. RESULTS: The prevalence of fetal arrhythmias in the first subgroup was 3.5% (3/84), while in the second subgroup the prevalence was 16% (11/68). CONCLUSIONS: The incidence of fetal arrhythmias detected in our population of normal pregnancies was comparable to that reported in previous studies by use of other techniques. Results gained from the second subgroup, although not comparable to others, owing to lack of similar reports, led us to believe that magnetocardiography's advantages over conventional methods of fetal cardiac surveillance could highlight the technique as a useful screening procedure for the detection of preterm fetuses, which should be submitted to closer investigation, because of the arrhythmias caused by ritodrine infusion.

Adult↗

PubMed2006

Fetal and maternal magnetocardiography during flecainide therapy for supraventricular tachycardia.

BACKGROUND: Fetal magnetocardiography is a noninvasive technique capable of identifying fetal arrhythmias and can simultaneously characterize the cardiac rhythm of the mother and fetus. CASES: Three patients, two singleton pregnancies and one twin pregnancy, were admitted for evidence of fetal supraventricular tachycardia. Fetal magnetocardiography was used to monitor the effects of flecainide therapy on the fetus and mother. Two singleton pregnancy fetuses showed improved heart rate and cardiac rhythm within 1 week of the initial dosing. Maintenance dosages controlled the conditions thereafter. Flecainide slowed the supraventricular tachycardia in the twin subject, but magnetocardiography revealed maternal adverse effects necessitating termination of flecainide therapy. CONCLUSION: Magnetocardiography is a valuable tool for rhythm diagnosis and for monitoring the maternal and fetal cardiac rhythms in a patient undergoing flecainide therapy for fetal supraventricular tachycardia.

Anti-Arrhythmia Agents↗

PubMed2005

Clinical application of magnetocardiography.

Magnetocardiography is a noninvasive contactless method to measure the magnetic field generated by the same ionic currents that create the electrocardiogram. The time course of magnetocardiographic and electrocardiographic signals are similar. However, compared with surface potential recordings, multichannel magnetocardiographic mapping (MMCG) is a faster and contactless method for 3D imaging and localization of cardiac electrophysiologic phenomena with higher spatial and temporal resolution. For more than a decade, MMCG has been mostly confined to magnetically shielded rooms and considered to be at most an interesting matter for research activity. Nevertheless, an increasing number of papers have documented that magnetocardiography can also be useful to improve diagnostic accuracy. Most recently, the development of standardized instrumentations for unshielded MMCG, and its ease of use and reliability even in emergency rooms has triggered a new interest from clinicians for magnetocardiography, leading to several new installations of unshielded systems worldwide. In this review, clinical applications of magnetocardiography are summarized, focusing on major milestones, recent results of multicenter clinical trials and indicators of future developments.

Arrhythmias, Cardiac↗

PubMed2005

Prenatal diagnosis of a long QT syndrome by fetal magnetocardiography in an unshielded bedside environment.

OBJECTIVE: The potentially life threatening long QT syndrome should be diagnosed during pregnancy to improve perinatal care. METHODS: A patient with a family history for a hereditary long QT syndrome presented at 30 weeks of her first pregnancy with fetal bradycardia and a narrow oscillation bandwidth on cardiotocography without structural abnormalities of the fetal heart. Fetal magnetocardiography was performed with a prototype biomagnetometer/gradiometer device in a magnetically unshielded environment. The cardiac time intervals were determined in the averaged PQRST complex. RESULTS: The QT time and the frequency-corrected QTc showed a marked prolongation to 380 ms and 0.52 s, respectively. The findings were confirmed in the postnatal electrocardiogram after spontaneous term delivery in a perinatal center. The causative mutation on chromosome 11 had been passed on to the newborn from his mother. CONCLUSION: Bedside fetal magnetocardiography revealed the exact diagnosis of the long QT syndrome in a period of the gestation when the fetus was electrically isolated by the vernix caseosa that hinders electrocardiography. To patients at risk of fetal cardiac abnormalities, magnetocardiography can be offered as a non-invasive diagnostic bedside procedure. The diagnosis should trigger closer surveillance and delivery in a perinatal center.

Adult↗

PubMed2001

Repolarization abnormalities detected by magnetocardiography in patients with dilated cardiomyopathy and ventricular arrhythmias.

INTRODUCTION: Abnormal repolarization is one of the acknowledged mechanisms leading to malignant ventricular arrhythmias. We used a novel magnetocardiographic technique to investigate the role of inhomogeneous repolarization in patients with nonischemic dilated cardiomyopathy prone to sustained ventricular arrhythmias. METHODS AND RESULTS: Forty-nine dilated cardiomyopathy patients were studied, 18 with a history of sustained ventricular tachycardia (n = 6) or ventricular fibrillation (n = 12) and 31 with no ventricular arrhythmias. The magnetocardiogram was registered and QT apex and QT end intervals were determined by a computer algorithm. Inhomogeneity of repolarization was characterized with indices describing QT apex and QT end dispersion, and T wave end duration. In addition, time-domain late fields of the QRS complex in magnetocardiography and QT dispersion in 12-lead ECG were determined. T wave end was longer in the arrhythmia group in patients with sinus rhythm (87 +/- 15 msec vs 73 +/- 12 msec; P = 0.005) and in those not having bundle branch block. Magnetocardiographic late fields of the QRS complex were not different between groups. QT apex and end dispersion on magnetocardiography or 12-lead ECG showed no difference. CONCLUSION: Prolongation of the end part of the T wave revealed by magnetocardiography is related to malignant ventricular arrhythmias in dilated cardiomyopathy. The results suggest that abnormal repolarization rather than delayed conduction underlies the arrhythmias in this disease.

Adult↗

PubMed2002

[Differentiation between vital heart muscle tissue and infarct scar using magnetocardiography].

Magnetocardiography provides touchless information about myocardial excitation propagation and repolarization. This evolving diagnostic technique has been used so far to risk-stratify patients in terms of sudden cardiac death and to detect myocardial ischemia. We evaluated its potential to assess myocardial viability in patients with coronary artery disease. Magnetocardiography was performed using a shielded prototype 49-channel LTS SQUID system. A specific algorithm was developed to calculate automatically a set of magnetocardiographic parameters. Regional myocardial viability was determined using 18F-labeled fluoro-2-deoxyglucose positron emission tomography. We found that magnetocardiography may contribute essentially to discriminate between viable myocardium and infarct scar.

Adult↗

PubMed2006

Comparison of magnetocardiography and electrocardiography: a study of automatic measurement of dispersion of ventricular repolarization.

AIMS: There is some dispute over the clinical significance of dispersion of ventricular repolarization measurements from the electrocardiogram. Recent studies have indicated that multichannel magnetocardiograms (MCGs), which non-invasively measure cardiac magnetic field strength from many sites above the body surface, may provide independent information from ECGs about ventricular repolarization dispersion. For this study, magnetocardiography and electrocardiography were compared from automatic measurements of dispersion of ventricular repolarization. METHODS AND RESULTS: Dispersion of ventricular repolarization time was determined in MCGs and standard ECGs recorded simultaneously from 27 healthy volunteers and 22 cardiac patients. Two automatic techniques were used to determine the interval of ventricular repolarization. There were significant differences in ventricular dispersion between ECG and MCG measurements, with multichannel MCG greater than ECG by 52 (47) ms [mean (SD)] (P<0.00001) and 12-channel MCG greater by 17 (40) ms (P<0.004) across techniques and all subjects. Magnetocardiograms had the greater discriminating power between normal and cardiac patients with differences of 46 (18) ms (P<0.017) for multichannel MCG and 44 (16) ms (P<0.005) for 12-channel MCG, compared with 16 (7) ms (P<0.04) for ECG. CONCLUSION: Magnetocardiography has the power to discriminate regional cardiac conduction differences.

Electrocardiography↗

PubMed2003

Magnetocardiography in coronary artery disease with a new system in an unshielded setting.

BACKGROUND: The noninvasive detection of coronary artery disease (CAD) remains a clinical challenge. Magnetocardiography is a completely noninvasive method that permits the registration of cardiac electrical activity at multiple sites in a plane above the chest cage without the need for electrodes. In contrast to the electrocardiogram (ECG) which suffers from boundary effects and a variety of potential artifacts (electrode placement, etc.) the MCG is unaffected by such impediments as the magnetic field is unaltered by surrounding tissues. HYPOTHESIS: Magnetocardiography with a newly developed single-channel system in an unshielded setting should be a better qualitative diagnostic tool than the standard ECG for the detection and assessment of CAD. METHODS: In all, 52 patients with angiographically documented CAD and unimpaired ventricular function as well as 55 controls were included in this study. A standard 12-lead ECG was obtained in all subjects. The MCG recordings were taken from 36 positions under resting conditions. From these, current density vector maps were generated during the ST-T interval. Each map was then classified using a classification system with a scale from 0 (normal) to 4 (grossly abnormal). RESULTS: While the ECG was normal in all subjects, the MCG in the controls was classified as category 0, 1, or 2. However, in patients with abnormal coronary angiograms, mainly maps in categories 3 and 4 were seen (p < 0.05). CONCLUSION: A single-channel magnetometer in an unshielded setting reveals significant differences between normals and patients with CAD with normal ECG on the basis of current density reconstruction during the ST segment when measured under resting conditions. This method might be suitable for the noninvasive detection of CAD.

Aged↗

PubMed1991

Clinical magnetocardiography. 10 years experience at the Catholic University.

Since the introduction, in 1982, of a Biomagnetic facility in the clinical environment, efforts were concentrated to investigate whether magnetocardiography could really provide new information of potential diagnostic use, even avoiding electromagnetic shielding to facilitate simultaneous biomagnetic and conventional cardiac investigations, including cardiac catheterization for invasive electrophysiological procedures. More than 350 patients have been magnetically investigated using a single-channel second-order gradiometer. Results of 281 MCG studies, whose data have been extensively analyzed with updated software programs, are reported. Magnetocardiographic (MCG) mapping during endocardial pacing was performed to quantify the accuracy of MCG localization of intracardiac dipolar sources. MCG classification of ventricular preexcitation has been attempted in 70 patients with overt preexcitation. MCG localization of the ventricular preexcited area was accurate and reproducible, provided that during mapping a sufficient degree of ventricular preexcitation was present. MCG mapping during orthodromic A-V re-entry tachycardia has been also employed to attempt the localization of retrograde atrial preexcitation as well as the site of origin of atrial and ventricular tachyarrhythmias. For validation, the results of catheter and epicardial mappings have been used. Other applications of clinical magnetocardiography are under evaluation. The use of the Relative smoothness index needs, in our opinion, a larger experience to define its reliability as a predictor of risk for sudden death. MCG follow-up study of patients with transplanted hearts seems to be a promising application, for early detection of acute graft rejection reaction. Our reported case strongly supports this potentiality. Present work is also addressed to develop an integrated system allowing easy MCG mapping during cardiac catheterization, as a new method to guide diagnostic and therapeutic procedures as close as possible to the arrhythmogenic substrate.

Electrocardiography↗

PubMed2000

Right ventricular volume unloading evaluated by tangential magnetocardiography.

OBJECTIVE: The evaluation of right ventricular volume overload in the presence of a right bundle branch block based solely on the results of an electrocardiogram is difficult. The purpose of this study was to purify acute right ventricular volume unloading from the tangential magnetocardiography. METHODS: We measured the tangential (x-y plane) magnetocardiogram and electrocardiogram simultaneously in nine patients with a secundum atrial septal defect. The magnetocardiograms were obtained before surgical closure and during the immediate postoperative period using the 32-channel superconducting quantum interference device system in a magnetically shielded room. RESULTS: The QRS duration on the surface electrocardiogram decreased significantly (p < 0.05) in the immediate postoperative period. The right ventricular depolarization time as measured by the magnetocardiogram was shortened from 40.3 +/- 6.1 to 25.3 +/- 7.4 milliseconds (p < 0.0005). The maximum peak amplitude during right ventricular depolarization decreased from 17.9 +/- 4.8 to 11.1 +/- 4.9 pT (p < 0.01). CONCLUSIONS: We conclude that acute volume unloading of the right ventricle was indicated quantitatively by shortening of the right ventricular depolarization time and a reduction in the amplitude of current vectors originating from the right ventricular depolarization on the tangential magnetocardiography.

Adolescent↗

PubMed2002

Clinical implications of fetal magnetocardiography.

OBJECTIVES: To test the usefulness and reliability of fetal magnetocardiography as a diagnostic or screening tool, both for fetuses with arrhythmias as well as for fetuses with a congenital heart defect. METHODS: We describe 21 women with either a fetal arrhythmia or a congenital heart defect discovered during prenatal evaluation by sonography. Four fetuses showed a complete atrioventricular block, two an atrial flutter, nine ventricular extrasystole, and one a complete irregular heart rate. Five fetuses were suspected to have a congenital heart defect. In all cases magnetocardiograms were recorded. RESULTS: Nine fetuses with extrasystole showed a range of premature atrial contractions, premature junctional beats or premature ventricular contractions. Two fetuses with atrial flutter showed typical flutter waves and four fetuses with complete atrioventricular block showed an uncoupling of P-wave and QRS complex. One fetus showed a pattern suggestive of a bundle branch block. In three of four fetuses with confirmed congenital heart defects the magnetocardiogram showed abnormalities. CONCLUSION: Fetal magnetocardiography allows an insight into the electrophysiological aspects of the fetal heart, is accurate in the classification of fetal arrhythmias, and shows potential as a tool in defining a population at risk for congenital heart defects.

Adult↗

PubMed1995

[Magnetocardiography for assessment of fetal heart actions].

Magnetocardiography provides a new, alternative method for fetal surveillance. This method allows the registration of changes in the magnetic field produced by the fetal cardiac system. In comparison to fetal ECG, the fetal magnetocardiogram (fMCG) is not affected by intermediate tissue, in particular by the insulating effect of the vernix caseosa. Furthermore fMCG's with a good signal noise ratio can be obtained in the second trimester. A multichannel biomagnetometer allows the non-invasive measurement of the magnetic signals produced by the fetus. Examples of dta and evaluation techniques are given. Signal processing software allows the identification of all fetal beats in a data set, permitting the calculation of an averaged beat and the evaluation of signal morphology and cardiac time intervals. Furthermore it is possible to produce a beat to beat time series with high temporal resolution, making the evaluation of heart rate variability with measures from the time, frequency, and phase domain accessible. Particularly the latter are of interest in investigating changes in temporal complexity of the fetal cardiac system. Magnetocardiography thus holds the promise of improved antenatal surveillance as of the second trimester.

Adult↗

PubMed1994

Antenatal fetal magnetocardiography: a new method for fetal surveillance?

OBJECTIVE: To establish the reliability of fetal magnetocardiography as a method of measuring the time intervals of the fetal heart during the antenatal period. DESIGN: A prospective study. SETTING: Wellcome Biomagnetism Unit, Southern General Hospital. SUBJECTS: One hundred and six low risk pregnant women at 20 to 42 weeks gestation. MAIN OUTCOME MEASURES: Success in obtaining QRS complexes, P waves and T waves. Correlation of time intervals with fetal outcome. RESULTS: The technique was acceptable to pregnant women. A QRS complex was successfully demonstrated in 68 (67%) of the unaveraged traces. Using off-line averaging techniques on these 68 cases, P waves were obtained in 75% and T waves in 72%. Although good quality traces were obtained throughout the range of gestational ages, in general it was more difficult below 28 weeks. QRS duration (R2 = 7%, P = 0.02) demonstrated a positive linear correlation with increasing gestation. Of the 35 (51%) cases with umbilical vein pH analysis available, only one result was less than 7.2. No significant relation was found between measurements of the fetal waveforms and the pH results. CONCLUSION: The technique of fetal magnetocardiography provides a significant advance in the technological field for the demonstration of QRS complexes and the full PQRST waveforms in gestations from 20 weeks onwards. With further technical improvements the clinical impact of this technique can be assessed more fully.

Adolescent↗

PubMed1999

Magnetocardiography in the diagnosis of fetal arrhythmia.

OBJECTIVE: To examine the possible use of magnetocardiography in the diagnosis of fetal arrhythmias. DESIGN: Investigation of routinely examined pregnant women, as well as women referred because of arrhythmias or other reasons. PARTICIPANTS: Sixty-three women between the 13th and 42nd week of pregnancy. METHODS: Recording of 189 fetal magnetocardiograms, of which 173 traces (92%) demonstrated sufficient fetal signal strength to permit evaluation. After digital subtraction of the maternal artefact, all fetal complexes were identified and the recording was examined for arrhythmic events. RESULTS: Short bradycardic episodes, not associated with any pathological condition, were found in 26% of all recordings, usually in mid-pregnancy. In 12 cases, isolated extrasystoles of no clinical importance could be identified. There were nine traces which revealed multiple arrhythmias including ventricular and supraventricular ectopic beats, bigeminy and trigeminy, sino-atrial block and atrio-ventricular conduction disturbances. Furthermore, two cases with tachycardia were found. CONCLUSION: Magnetocardiography offers a simple noninvasive method for examination of the fetal cardiac electrophysiological signal. It may thus be useful in the identification and classification of clinically relevant arrhythmia and aid in decisions concerning treatment.

Adult↗

PubMed2005

The value of magnetocardiography in patients with and without relevant stenoses of the coronary arteries using an unshielded system.

BACKGROUND: The diagnostic management of patients with chest pain remains a clinical challenge. Magnetocardiography (MCG) is a noninvasive method for the recording of cardiac electromagnetic signals at multiple sites above the chest cage. Contrary to electrocardiogram (ECG) the magnetic field is unaltered by surrounding tissues. The present study aimed to analyze the diagnostic value of an unshielded four-channel MCG for the detection of coronary artery disease (CAD) in patients with chest pain. METHODS: The study included 417 subjects: 177 patients with angiographically documented CAD (stenoses > or =50%), 123 symptomatic patients without hemodynamically relevant stenosis (nCAD) and 117 healthy subjects. Twelve-lead ECG was obtained in all subjects. The magnetocardiography recordings were taken from 36 positions at rest. From these current density vector maps were generated during the ST-T interval. Each map was classified using a classification system with a scale from 0 (normal) to 4 (grossly abnormal). RESULTS: While the ECG was normal in all subjects the MCG revealed typical differences. In normals most maps were classified as category 0, 1 or 2, in nCAD and more so in CAD patients the categories 3 and 4 prevailed. Using a cut-off value of 39.2% for the discrimination between normals and CAD patients sensitivity was 73.3%, specificity 70.1%. CONCLUSION: Contrary to ECG, unshielded MCG reveals significant differences between normals and symptomatic patients with and without relevant stenoses using current density reconstruction during repolarization at rest. This method might be a suitable noninvasive tool for the management of patients with chest pain.

Coronary Stenosis↗

PubMed2006

Increased intra-QRS fragmentation in magnetocardiography as a predictor of arrhythmic events and mortality in patients with cardiac dysfunction after myocardial infarction.

INTRODUCTION: Increased intra-QRS fragmentation score (FRA) in magnetocardiography (MCG) has shown association with sustained ventricular arrhythmias in post-MI patients suggesting its relation to arrhythmia substrate. The aim of this study was to investigate whether increased FRA in MCG predicts arrhythmic events and mortality after acute myocardial infarction (MI) with cardiac dysfunction. METHODS AND RESULTS: A series of 158 patients with acute MI and left ventricular ejection fraction (LVEF) <50% were studied. Their age was 60 +/- 10 years and LVEF 40 +/- 6%. MCG was registered and FRA was computed. For comparison, QRS duration in 12-lead ECG was measured. In a mean follow-up of 50 +/- 15 months, 32 (20%) patients died and 18 (11%) had an arrhythmic event. Both arrhythmic event rate and all-cause mortality were significantly higher in patients with increased FRA (P < 0.001 for both). In contrast, increased QRS duration in ECG predicted all-cause mortality (P < 0.05) but not arrhythmic events. In multivariate analysis, FRA was an independent predictor of both arrhythmic events and all-cause mortality. Using a combined criterion of increased FRA and LVEF < 30% yielded positive and negative predictive accuracies of 50% and 91% for arrhythmic events. CONCLUSION: In post-MI patients with left ventricular dysfunction, increased intra-QRS fragmentation in high-resolution magnetocardiography predicts arrhythmic events, whereas QRS duration in 12-lead ECG predicts all-cause mortality. Analysis of intra-QRS fragmentation by MCG may assist in guiding therapy of post-MI patients, for example, by selecting those who would benefit most from prophylactic implantable cardioverter-defibrillator therapy.

Arrhythmias, Cardiac↗

PubMed2001

Detection of cardiac hypertrophy in the fetus by approximation of the current dipole using magnetocardiography.

To determine the developmental changes in the myocardial current during fetal life, and to evaluate the clinical usefulness of magnetocardiography for prenatal diagnosis of cardiac hypertrophy or enlargement, we approximated the magnitude of the one-current dipole of the fetal heart using fetal magnetocardiography (fMCG). A total of 95 fetuses with gestational age of 20-40 wk were included in this study. fMCG was recorded with a nine-channel superconducting quantum interference device system in a magnetically shielded room. The magnitude of the dipole (Q) was calculated using an equation based on the fMCG amplitude obtained on the maternal abdomen and the distance between the maternal surface and fetal heart measured ultrasonographically. In uncomplicated pregnancies, the Q value correlated significantly with gestational age, reflecting an increase in the amount of myocardial current, i.e. myocardial mass. Moreover, the Q values in fetuses with cardiomegaly caused by various cardiovascular abnormalities tended to be higher than the normal values. Although there are some limitations of the methodology based on the half-space model, and fetal orientation may influence the magnitude of the dipole, making it smaller, fMCG recorded with a multichannel superconducting quantum interference device system is a clinically useful tool for noninvasive, prenatal, and electrical evaluation of fetal cardiac hypertrophy.

Cardiomegaly↗