Magnetocardiographic Mapping Research Articles

Feasibility of simultaneous multichannel magnetocardiographic mapping, multiple monophasic action potential recording and laser photocoagulation of isolated and perfused rabbit ventricular myocardium

Abstract Background Multichannel magnetocardiographic mapping (MCG) has been validated as an accurate non-invasive method for 3D localization of arrhythmogenic substrates suitable for ablation treatment and of intracardiac electrophysiology catheters (1,2). High resolution (HR) MCG-guided multiple simultaneous monophasic action potential (multi-MAP) recording and pacing with a single patented amagnetic catheter (AC) detects local arrhythmogenic mechanisms (3). Laser photocoagulation (LP) providing more controlled and homogeneous myocardial lesions (4), may be an alternative to radiofrequency (RF) ablation, without unwanted electromagnetic noise effect during real-time MCG. Purpose This study aimed to experimentally test the feasibility of simultaneous multi-MAP recording and LP guided by real-time MCG. Methods An unshielded 36 channels SQUID system (sensitivity of 30 fT/Hz1/2, at 1 Hz) (CMI, USA) was used to study Langendorff-perfused isolated rabbit heart with MCG (Figure 1A). Four epicardial MAPs were simultaneously recorded (inter MAP distance: 1 mm) with a single multi-MAP AC (bandpass: DC-500 Hz; sampling frequency: 2 kHz) (GE-Prucka Cardiolab). LP was performed with a NdYAG laser (Dornier Medilas 5100) and a catheter system for safe myocardium LP (5). The study was carried out according to NIH guidelines for animal care and use. Results MCG imaging of rabbit ventricular magnetic field distribution and inverse source localization with the magnetic dipole model are shown in Figure 1B. The difference in morphology of local HR ventricular multi-MAP signals was compatible with myocardial anisotropy (Figure 1C). With appropriate cooling of the optic fiber-tissue interface, no epicardial damage was induced by LP, whereas deeper well defined intramural myocardial lesions were appreciable, of different size as a function of the energy delivered (Figure 1D). Multi-MAP recording was not significantly disturbed by LP. Keeping the Medilas unit at least 5 meters away from the MCG sensors, no electromagnetic artifacts were observed during MCG. Conclusion MCG, single catheter multi-MAP recording and well-defined LP lesions of ventricular myocardium were simultaneously feasible on Langendorff-perfused isolated rabbit heart, without major electromagnetic interferences, in an unshielded catheterization laboratory. With appropriate technological developments, safe MCG-guided single-catheter laser ablation of focal arrhythmogenic substrates is foreseen as a possible minimally invasive alternative to current interventional approaches. Funding Acknowledgement Type of funding sources: None.

Розроблення та впровадження в медичну практику нових інформаційних технологій і метрик для аналізу малих змін в електромагнітному полі серця людини

The article details the concept of clinical information technology (IT), i.e. a set of methods and software and hardware combined into a technological chain, the product of which is an automated diagnostic report, prognostic report or recommendation on patient management tactics. There are several examples of innovative information technologies and metrics implemented by the authors in Ukraine and abroad, designed to register and evaluate subtle changes in the electromagnetic field of the heart for early diagnosis of the most common and dangerous heart diseases, especially coronary heart disease. It is shown that new metrics of analysis of spatial structure of 2D and 3D magnetocardiographic maps of current density distribution allow to diagnose with high accuracy various forms of myocardial ischemia. The new method of the electrocardiogram scaling is used in various areas of clinical medicine, sports medicine, occupational medicine, as well as in large-scale population studies.

P3748Reproducibility of magnetocardiographic imaging of atrial electrophysiology in patients with paroxysmal atrial fibrillation and healthy subjects

Abstract Since tangential currents are better detectable as magnetic than electric signals at the body surface, magnetocardiographic mapping (MCG) can be more sensitive than ECG to atrial electrophysiologic alteration, such as abnormal interatrial conduction and/or dispersion of atrial repolarization, as mechanisms underlying the occurrence of paroxysmal atrial fibrillation (PAF). We had previously reported that visual analysis of the magnetic field distribution (MFD) dynamics may evidence an inversion of atrial MFD early during the P-wave suggesting atrial repolarization overlapping depolarization along the descending limb of the P-wave (Guida et al 2018). Aim of this study was to systematically evaluate the reproducibility of such observation and to evaluate the reliability of non-invasive MCG imaging of atrial electrophysiology carried out in our unshielded hospital laboratory. Methods MCG was recorded, in sinus rhythm (SR), with an unshielded 36-channel SQUID-system providing about 30–40 fT/√Hz sensitivity in bandwidth DC-250Hz (sampling frequency 1kHz). MCG data of 40 patients with PAF (PAFp) and 40 age-matched healthy controls (HC), with at least two subsequent recordings to evaluate reproducibility and optimal S/N ratio, were retrospectively analyzed. The dynamics of atrial MFD was studied, at 1 ms time resolution, to identify the onset of atrial repolarization (AR), in respect of the P-wave and PR interval duration. To localize atrial sources, the inverse solution was calculated with the Effective Magnetic Dipole (EMD) model, also after subtraction of the atrial repolarization. MCG parameters of atrial electromagnetic vector (EMV) were also calculated. The reproducibility was evaluated with the intraclass correlation coefficient (ICC). Results High resolution analysis of atrial MFD dynamics confirmed that atrial repolarization field overlaps atrial depolarization during the last third of the P-wave in most investigated subjects. Thus, subtraction of average AR MFD is necessary to discover and image the left atrial depolarization pathway. The reproducibility of MCG estimate of atrial MFD and of EMV parameters was good (average ICC >0.7). In PAFp, MCG evidenced abnormality of AR MFD consistent with dispersion of atrial repolarization (Figure 1), as previously reported with simultaneous MCG and MAP recordings (Fenici & Brisinda, 2007); however, such evaluation is reliable only with optimal S/N ratio during the PR interval. Conclusions Unshielded MCG in SR is sensitive enough to non-invasively image atrial electrophysiology. Visual analysis of atrial MFD dynamics with high temporal resolution reproductively confirmed that AR MFD initiates early, within the descending limb of the P-wave, masking the deeper magnetic field generated by left atrial depolarization currents. MCG can image abnormality of AR MFD in PAFp, suggestive of dispersion of atrial action potential duration. Quantitative estimate of atrial EMV parameters differentiates PAFp from HC.

P3655Predictive accuracy of cardiac magnetic field dynamics and inverse solution to non-invasively detect ischemic heart disease with unshielded magnetocardiographic mapping at rest

P3655Predictive accuracy of cardiac magnetic field dynamics and inverse solution to non-invasively detect ischemic heart disease with unshielded magnetocardiographic mapping at rest

Predictive value of unshielded magnetocardiographic mapping to differentiate atrial fibrillation patients from healthy subjects

P-wave duration, its dispersion and signal-averaged ECG, are currently used markers of vulnerability to atrial fibrillation (AF). However, since tangential atrial currents are better detectable at the body surface as magnetic than electric signals, we investigated the accuracy of magnetocardiographic mapping (MCG), recorded in unshielded clinical environments, as predictor of AF occurrence. MCG recordings, in sinus rhythm (SR), of 71 AF patients and 75 controls were retrospectively analyzed. Beside electric and magnetic P-wave and PR interval duration, two MCG P-wave subintervals, defined P-dep and P-rep, were measured, basing on the point of inversion of atrial magnetic field (MF). Eight parameters were calculated from inverse solution with "Effective Magnetic Dipole (EMD) model" and 5 from "MF Extrema" analysis. Discriminant analysis (DA) was used to assess MCG predictive accuracy to differentiate AF patients from controls. All but one (P-rep) intervals were significantly longer in AF patients. At univariate analysis, three EMD parameters differed significantly: in AF patients, the dipole-angle-elevation angular speed was lower during P-dep (p<0.05) and higher during P-rep (p<0.001) intervals. The space-trajectory during P-rep and the angle-dynamics during P-dep were higher (p<0.05), whereas ratio-dynamics P-dep was lower (p<0.01), in AF. At DA, with a combination of MCG and clinical parameters, 81.5% accuracy in differentiating AF patients from controls was achieved. At Cox-regression, the angle-dynamics P-dep was an independent predictor of AF recurrences (p=0.037). Quantitative analysis of atrial MF dynamics in SR and the solution of the inverse problem provide new sensitive markers of vulnerability to AF.

Noninvasive mapping reveals recurrent and suddenly changing patterns in atrial fibrillation—a magnetocardiographic study

Objective: To study noninvasive magnetocardiographic (MCG) mapping of ongoing atrial fibrillation (AF) and, for the possible mapping patterns observed, to develop simplified but meaningful descriptors or parameters, providing a possible basis for future research and clinical use of the mappings. Approach: MCG mapping with simultaneous ECG was recorded during arrhythmia in patients representing a range of typical, clinically classical atrial arrhythmias. The recordings were assessed using MCG map animations, and a method to compute magnetic field map orientation (MFO) and its time course was created to facilitate presentation of the findings. All the data were segmented into four categories of ECG waveform regularity. Main results: In visual observation of the MCG animations, an abundance of clear spatial and temporal patterns with regularity were found, often perceived as rotations of the map. This rotation and its sudden reversals of direction were distinctly present in the time course of the MFO. The shortest segments with consistent rotation lasted for some hundreds of milliseconds, i.e. a couple of cycles, but segments lasting for tens of seconds were observed as well. In the ECG, all four categories of regularity were present. The rotation of the MFO was observed in all patients under study and regardless of the ECG categories. Further, a change in ECG category during a measurement was frequently, but not always, found to be simultaneous with a change in the rotation pattern of the MFO. Utilization of spatial information of MCG mapping could enable detection of both regularities and instantaneous phenomena during AF. Significance: Cardiac mapping may offer a useful noninvasive means to study the mechanisms of AF, including superior temporal resolution.

Unshielded magnetocardiography: Repeatability and reproducibility of automatically estimated ventricular repolarization parameters in 204 healthy subjects.

Magnetocardiographic mapping (MCG) provides quantitative assessment of the magnetic field (MF) induced by cardiac ionic currents, is more sensitive to tangential currents, and measures vortex currents undetectable by ECG, with higher reported sensitivity of MCG ventricular repolarization (VR) parameters for earlier detection of acute myocardial ischemia. Aims of this study were to validate the feasibility of in-hospital unshielded MCG and to assess repeatability and reproducibility of quantitative VR parameters, considering also possible gender- and age-related variability. MCG of 204 healthy subjects [114 males-mean age 43.4±17.3 and 90 females-mean age 40.2±15.7] was retrospectively analyzed, with a patented proprietary software automatically estimating twelve VR parameters derived from the analysis of the dynamics of the T-wave MF extrema (five parameters) and from the inverse solution with the effective magnetic dipole model giving the effective magnetic vector components (seven parameters). MCG repeatability was calculated as coefficient of variation (CV) ±standard error of the mean (SEM). Reproducibility was assessed as intraclass correlation coefficient (ICC). The repeatability of all MCG parameters was 16±1.2 (%) (average CV±SEM). Optimal (ICC>0.7) reproducibility was found for 11/12 parameters (mean values) and in 8/12 parameters (single values). No significant gender-related difference was observed; six parameters showed a strong/moderate correlation with age. Reliable MCG can be performed into an unshielded hospital ambulatory, with repeatability and reproducibility of quantitative assessment of VR adequate for clinical purposes. Wider clinical use is foreseen with the development of multichannel optical magnetometry.

Phantom Assessment of Unshielded Magnetocardiography Repeatability, Precision and Accuracy in Electric Sources Localization

Pre-interventional knowledge of arrhythmogenic substrate location may reduce interventional time and arrhythmias ablation risks. Magnetocardiographic Mapping (MCG) is a contactless method for non-invasive localization of intra cardiac sources used for Three-Dimensional (3D) Electro-Anatomical Imaging (EAI) of arrhythmogenic substrates. The aim of this study was to assess the repeatability, precision, and accuracy of MCG in localizing dipolar sources in an unshielded environment.

GW28-e0528 Coronary artery disease versus coronary microvascular disease: advanced analysis of magnetocardiographic maps

The diagnostic management of patients with chest pain remains a clinical challenge. In particular, existing non-invasive techniques may lack sensitivity and specificity to differentiate between epicardial and microvascular abnormalities. Magnetocardiography (MCG) is non-invasive evaluation of the

P793Non-invasive three-dimensional electro-anatomical imaging of the site of origin of outflow tract ventricular arrhythmias with magnetocardiographic mapping

P793Non-invasive three-dimensional electro-anatomical imaging of the site of origin of outflow tract ventricular arrhythmias with magnetocardiographic mapping

Percutaneous method for single-catheter multiple monophasic action potential recordings during magnetocardiographic mapping in spontaneously breathing rodents

To test the feasibility of a novel method to combine magnetocardiographic (MCG) estimate of ventricular repolarization (VR) and multiple monophasic action potential (MultiMAP) recording in spontaneously breathing rodents with percutaneous sub-xyphoid epicardial placement of a MCG-compatible amagnetic catheter (AC), ten Wistar rats (WRs) and ten guinea pigs (GPs) were studied. Under fluoroscopic control, the AC was moved until four stable MAPs were recorded (fixed inter-electrode distance of 1.2 mm). 36-channel DC-SQUID (sensitivity 20 fT Hz–½) were used for MCG mapping. MAPs, differentially amplified (BW: DC-500 Hz), were digitized at 1 kHz. AC pacing provided local ventricular effective refractory period (VERP) estimate. MAP duration (MAPd) was measured at 50% and 90% levels of repolarization. Simultaneous MCG mapping and MultiMAP recording were successful in all animals. Average MAPd50% and MAPd90% were shorter in WRs than in GPs (26.4 ± 2.9 ms versus 110.6 ± 14.3 ms and 60.7 ± 5.4 ms versus 127.7 ± 15.3 ms, respectively). VERP was 51 ± 4.8 ms in WRs and 108.4 ± 12.9 ms in GPs, respectively. The MAP amplitude was 16.9 ± 4.5 in WRs and 16.2 ± 4.2 in GPs. MAP and MCG parameters of VR were in good agreement. All animals survived the procedure. Two also survived a second invasive study; one was followed up until natural death at 52 months. Percutaneous MultiMAP recording is minimally invasive, usually avoids animal sacrifice, is compatible with simultaneous surface MCG mapping and might be used for experimental validation of MCG VR abnormality, to study the arrhythmogenic potential of new drugs and/or animal models of ventricular arrhythmias.

Karhunen-Loeve representation of magnetocardiographic QRST integral maps: a critical tutorial

Event Abstract Back to Event Karhunen-Loeve representation of magnetocardiographic QRST integral maps: a critical tutorial Rok Hren1* 1 University of Ljubljana, Institute of Mathematics, Physics, and Mechanics, Slovenia It is well recognized that regional disparities of ventricular primary repolarization properties are reflected in the QRST deflection areas (integrals) and that spatial features extracted from the electrocardiographic QRST integral maps can be a useful tool for identifying patients at risk of arrhythmia vulnerability [1]. However, the conclusions from the studies employing magnetocardiographic mapping are far from definitive [2-4]. In this report, we reviewed the classical method in terms of Karhunen-Loeve representation to reduce the dimensionality of the input magnetocardiographic data; we discussed the implementation of the methodology and its statistical evaluation. Specifically, we comprehensively and critically evaluated the published clinical data pertaining to the prediction of arrhythmogenic risk when using magnetic field maps. We have concluded that while research in noninvasive assssment of the potentially complex arrhythmogenic conditions is mandatory due to a well-known significance of the sudden cardiac death among world population, robust and simple vulnerability markers, which are on a par with conventional ECG analysis, need to be developed to be effectively used in the clinical setting.

Non-invasive detection of conduction pathways to left atrium using magnetocardiography: validation by intra-cardiac electroanatomic mapping

Alteration in conduction from right to left atrium (LA) is linked to susceptibility to atrial fibrillation (AF). We examined whether different inter-atrial conduction pathways can be identified non-invasively by magnetocardiographic mapping (MCG). In 27 patients undergoing catheter ablation of paroxysmal AF, LA activation sequence was determined during sinus rhythm using invasive electroanatomic mapping. Before this, 99-channel magnetocardiography was recorded over anterior chest. The orientation of the magnetic fields during the early (40-70 ms from P onset) and later part (last 50%) of LA depolarization was determined using pseudocurrent conversion. Breakthrough of electrical activation to LA occurred through Bachmann bundle (BB) in 14, margin of fossa ovalis (FO) in 3, coronary sinus ostial region (CS) in 2, and their combinations in 10 cases by invasive reference in total of 29 different P-waves. Based on the combination of pseudocurrent angles over early and late parts of LA activation, the MCG maps were divided to three types. These types correctly identified the LA breakthrough sites to BB, CS, FO, or their combinations in 27 of 29 (93%) cases. Magnetocardiographic mapping seems capable of distinguishing inter-atrial conduction pathways. Recognizing the inter-atrial conduction pattern may assist in understanding the pathogenesis of AF and identifying the subgroups for patient-tailored therapy.

High‐Resolution Signal‐Averaged Analysis of Atrial Electromagnetic Characteristics in Patients with Paroxysmal Lone Atrial Fibrillation

Abnormalities in the electromagnetic signal of the atria during sinus rhythm could serve as markers of triggering foci or substrate for atrial fibrillation (AF). We examined atrial electrophysiologic properties noninvasively by using magnetocardiographic mapping (MCG) in patients with paroxysmal lone AF to find whether any difference exists between those who have frequent triggers of AF and who don't. MCG was recorded over anterior chest during sinus rhythm in 80 patients with paroxysmal lone AF (44 +/- 12 years, 61 males) and 80 matched controls. Atrial wave duration (Pd) and root mean square amplitudes of the last 40 ms (RMS40) of the averaged filtered atrial complex were determined automatically. Patients expressing atrial arrhythmias triggering AF episodes were classified as focal AF. The Pd was 109 ms in patients and 104 ms in controls (P = 0.007). In focal AF (72%) the Pd was slightly prolonged and its proportion of the PR interval was larger, but RMS40 was normal compared to controls. In other patients, the Pd was close to controls, but the RMS40 was reduced (59 +/- 17 vs74 +/- 36 fT, P = 0.006). Pd and atrial RMS amplitudes were unrelated to duration of AF history or frequency of recurrences. Clinical subclasses of lone AF seem to possess distinct signal profiles of atrial depolarization. Differences in electrophysiological properties between these subclasses may reflect pathogenetic variation and could have implications on diagnostics and therapy.

Longitudinal study of cardiac electrical activity in anesthetized guinea pigs by contactless magnetocardiography

Guinea pigs (GPs) are used for preclinical evaluation of electrophysiologic effects of new drugs, because their myocytes have human-like action potentials and ventricular repolarization's (VR) ion currents. This study was aimed to assess the reliability of magnetocardiographic (MCG) mapping for longitudinal studies of GP cardiac electrical activity. Eighteen anesthetized GPs were investigated with an unshielded 36-channel MCG instrumentation, at the age of 5 months (268.1 ± 19 g). Twelve GPs survived and were restudied when 14 months old (595.6 ± 90.5 g). RR, PR, QRS, QTpeak, QTend, JTpeak, JTend and Tpeak-end intervals were measured from MCG waveforms. Magnetic field (MF) maps, equivalent current dipole (ECD) parameters and current density imaging were also analyzed. A significant prolongation of the PR (p < 0.05) and QRS (p < 0.001) intervals was found at 14 months. Gender-related differences of VR intervals were not significant. Ppeak and QRSpeak MFs were similar in all animals, while Tpeak MF varied interindividually at 5 months and showed a rotation in some animals, at 14 months. The ECD strengths, measured at the Ppeak, QRSpeak and Tpeak were stronger (p < 0.01) at the age of 14 months than at 5 months. In contrast to findings in Wistar rats, age-related and gender-related differences of MCG VR parameters were not significant in GPs. Further work is necessary to clarify the variability of VR MF observed in healthy GPs.

Predictive value of rest magnetocardiography in patients with stable angina

Abstract. Magnetocardiographic mapping (MCG) is increasingly used for non-invasive early detection of ischemia in patients with acute chest pain. This study was aimed to evaluate the predictive value of MCG, for the diagnosis of ischemia in patients with coronary artery disease (CAD) and stable angina (StA). 51 pts (age 63 ± 10.7 years) with CAD (all chest pain free at the time of MCG) and 52 healthy volunteers were studied at rest with an unshielded 36-channel MCG system (sensitivity: 20 fT/√Hz, above 1 Hz). 42 pts underwent coronary angiography (CAng) (21 after MCG scan). 39 pts had stress SPECT; 32 had both CAng and SPECT. Analysis of ventricular repolarization (VR) was performed utilizing different methods for interactive and automated analysis of T-wave dynamics and of the effective magnetic vector (EMV) parameters. For all pts, best sensitivity, specificity, PPV, NPV and predictive accuracy of the MCG for the detection of ischemia were 56%, 96%, 94%, 69% and 78%, respectively (with EMV). If pts with previous myocardial infarction (MI) were excluded, best sensitivity, specificity, PPV, NPV and predictive accuracy of the MCG for the detection of ischemia were 83%, 96%, 94%, 89% and 91%, respectively (detected with EMV). Comparative values calculated from ECG were 38%, 100%, 100%, 80% and 82%, respectively. As compared with previous results in pts with ACS, the T-wave analysis seems to be less sensitive in pts with chronic CAD and previous MI. Further work is needed to better define MCG parameters to be used for the diagnosis of myocardial ischemia in pts with CAD and to differentiate VR abnormalities due to coexistent ventricular hypertrophy, previous MI, or other cardiomyopathy.

Magnetocardiographic estimate of cardiac intervals in guinea pigs. Comparison between conscious and anesthetized conditions

The aim of this study was to assess the feasibility and reliability of Magnetocardiographic mapping (MCG), for the measurement of cardiac intervals and quantitative estimate of other MCG ventricular repolarization (VR) parameters, in unrestrained conscious Guinea pigs (GPs), taking into account possible gender-related differences, and in comparison with MCG of the same animals under anesthesia. 12 adult GPs (6 males and 6 females) were investigated with an unshielded 36-channel MCG system. Two sets of measurements were performed from each animal, at the age of 14 months: 1) awake (prone posture), 2) under anesthesia (supine). RR, PR, QRS, QT peak, QT end, JT peak, JT end and T peak-end intervals were measured. MCG imaging and quantitative analysis were automatically obtained as magnetic field maps (MFMs) and with the Equivalent Current Dipole (ECD) inverse solutions. As concerns interval durations, measured in the two sessions, a statistically significant difference was found only for the T peak-end interval. No gender-related differences of VR intervals were observed. Although MFMs were different as a function of the posture, the ECD localization at the QRSpeak, was properly centered in the heart and coincided within a 3-D uncertainty of less that 10 mm. MCG mapping is reliable for the assessment of cardiac intervals and VR, both in awake and in anaesthetized GPs. In non-aggressive rodents, MCG mapping does not require anesthesia and can be repeated multiple times, for circadian or long-term longitudinal pharmacological studies.

Magnetocardiographic mapping in patients with myocardial infarction during rehabilitation period

Abstract The purpose of this work was to study the possibilities for revealing and prognosis of electrophysiological changes into pathological myocardium. Patients with myocardial infarction (MI) were observed by non-invasive method of magnetocardiographic (MCG) mapping. MCG mapping was performed for 285 examined patients divided into 3 groups: 95 persons — healthy, 81 patients — coronary artery disease (CAD), 109 patients affected with myocardium infarction (MI). 14 numeric MCG indexes, which reflect the changing of electrophysiological processes into myocardial, have been tested. Among them, 5 indexes have accuracy more than 80% in recognition of CAD and 2 reliable for MI indexes have been found.

Magnetocardiographic findings and follow-up in an asymptomatic Brugada patient. Effects of Flecainide and of exercise tests

The Brugada syndrome (BS) is a genetically transmitted arrhythmogenic disease, which requires risk stratification, especially in asymptomatic subjects. Recent studies have shown that magnetocardiographic mapping (MCG) at rest can detect abnormal current distribution located in the RVOT. Here we describe an asymptomatic 28 years old BS patient, studied with 12-lead ECG and 36-channel MCG for three times at rest, under effort and during flecainide (Flec) tests, along a four years follow-up. He had a type 2 BS ECG at rest, but normal physical examination, echocardiogram and MRI. Molecular screening of the SCNC5A open reading frame revealed a de novo missense mutation in the DII–DIII linker, confirming the diagnosis of BS. For MCG assessment of ventricular repolarization (VR), magnetic field (MF) dynamics and MF gradient orientation, were computed during the ST interval and at the T wave peak. Current density reconstruction (CDR) and the strength of the equivalent current dipole (ECD) were calculated during the JT interval, to evidence potentially arrhythmogenic current flowing. In spite of Flec-induced ECG abnormality (typical type-1 ST elevation in V1–V3), MCG didn't show clear-cut variation of VR parameters, which didn't differ from those of healthy controls, at rest and under effort. After Flec, CDR, calculated every 10 ms from the J point, evidenced a change in the direction of the strongest current toward the right ventricular outflow tract, without a significant increase of the JT ECD strength. During the follow-up the patient was asymptomatic and no arrhythmia occurred. Further work is deserved to establish the predictive value of MCG for non-invasive risk stratification in asymptomatic BS patients with abnormal Flec test.

Magnetocardiographic study of patients with right and left bundle branch blocks

It has been recently proposed that magnetocardiographic mapping (MCG) can be useful for early diagnosis of IHD also in patients with LBBB; however, MCG patterns of cBBB in the absence of IHD have not so far extensively investigated. This study was aimed to define typical magnetic field distribution (MFD) patterns and several quantitative parameters of ventricular depolarization (QRS) and repolarization (VR), in patients with cBBB. 38 patients (pts) with cBBB at the ECG [15 RBBB, 19 LBBB, 4 RBBB + LAH] and 33 healthy subjects (HS) were consecutively investigated with an unshielded 36-channels DC SQUID MCG system (sensitivity is 20 fT/Hza1/2, above 1 Hz). Quantitative analysis of MFD maps was automatically performed during the QRS and VR intervals. In RBBB pts, the direction of septal depolarization was normal. A significant ( p < 0.001) difference of R peak effective magnetic dipole orientation (EMDo) was observed between RBBB pts with (52.8° ± 15) and without (− 50.8° ± 28.5) cardiac abnormalities (CaAb), or associated with LAH (− 148° ± 17.3). In pts with RBBB + LAH, average ST and T peak EMDo values were different ( p < 0.01 and p < 0.05, respectively) from those of pts with RBBB only. 8 pts with LBBB had dilated cardiomyopathy (DCM), 3 had IHD. As compared to HS, LBBB was characterized by inverted (from right-to-left) direction of septal activation, counterclockwise rotation of R peak EMDo (− 113.4° ± 7.6) and an inversion of ST and T peak EMDo (61.4° ± 14.1 and 57.9° ± 14.1, respectively). In the 3 IHD pts, T-wave parameters were not significantly different from those with non-ischemic LBBB. In one post-myocarditis DCM, ST and T peak EMDo rotated clockwise, toward more positive values. MCG differentiates RBBB associated with CaAb from those without CaAb. MCG criteria to detect ischemia in LBBB pts are not defined yet.