Clinical magnetocardiography: the unshielded bet-past, present, and future.

Magnetocardiography (MCG), which is nowadays 60 years old, has not yet been fully accepted as a clinical tool. Nevertheless, a large body of research and several clinical trials have demonstrated its reliability in providing additional diagnostic electrophysiological information if compared with conventional non-invasive electrocardiographic methods. Since the beginning, one major objective difficulty has been the need to clean the weak cardiac magnetic signals from the much higher environmental noise, especially that of urban and hospital environments. The obvious solution to record the magnetocardiogram in highly performant magnetically shielded rooms has provided the ideal setup for decades of research demonstrating the diagnostic potential of this technology. However, only a few clinical institutions have had the resources to install and run routinely such highly expensive and technically demanding systems. Therefore, increasing attempts have been made to develop cheaper alternatives to improve the magnetic signal-to-noise ratio allowing MCG in unshielded hospital environments. In this article, the most relevant milestones in the MCG's journey are reviewed, addressing the possible reasons beyond the currently long-lasting difficulty to reach a clinical breakthrough and leveraging the authors' personal experience since the early 1980s attempting to finally bring MCG to the patient's bedside for many years thus far. Their nearly four decades of foundational experimental and clinical research between shielded and unshielded solutions are summarized and referenced, following the original vision that MCG had to be intended as an unrivaled method for contactless assessment of the cardiac electrophysiology and as an advanced method for non-invasive electroanatomical imaging, through multimodal integration with other non-fluoroscopic imaging techniques. Whereas all the above accounts for the past, with the available innovative sensors and more affordable active shielding technologies, the present demonstrates that several novel systems have been developed and tested in multicenter clinical trials adopting both shielded and unshielded MCG built-in hospital environments. The future of MCG will mostly be dependent on the results from the ongoing progress in novel sensor technology, which is relatively soon foreseen to provide multiple alternatives for the construction of more compact, affordable, portable, and even wearable devices for unshielded MCG inside hospital environments and perhaps also for ambulatory patients.

Compliance in weight control reduces atrial fibrillation worsening: A retrospective cohort study.

BACKGROUND AND AIM: Obesity plays a dominant role in the etiology of atrial fibrillation (AF), and the maintenance of a normal body mass index (BMI) seems to prevent and even reduce the incidence of the arrhythmia's recurrence. We selected 270 patients (pts) to assess whether this therapeutic effect was statistically significant even in Mediterranean patients. METHOD AND RESULTS: In this retrospective cohort study, we analyzed every symptomatic AF relapse during a total follow-up of 657 patient-years. Clinical data, BMI variations, and pts' history were available in our clinical database. We divided the pts in four groups (Gs), according to their BMI variation during the follow-up: G1, normal weight pts, maintaining their weight; G2, overweight pts, losing weight; G3, overweight pts, maintaining their weight; G4, pts gaining weight. Their follow-up (in months) was normalized according to their AF relapses, thus obtaining a mean AF-free period for each patient. Among the overweight groups, G2 showed the best AF-free period (9.7 months). However, G3 and G4 showed a reduced AF-free interval (4.6 and 1.7 months, respectively). G1, predictably, had the longest AF-free period (10 months). CONCLUSION: The results of the present study confirm that simple non-invasive intervention aimed to normalize BMI and to control risk factors through appropriate lifestyle can be highly effective in reducing the AF burden, by acting on comorbidities and proarrhythmic mechanisms. Therefore, serious attempt should be made to correct risk factors before an ablation therapy is proposed.

From 3D to 4D imaging: is that useful for interventional cardiac electrophysiology?

Three-dimensional electroanatomical imaging is increasingly used in interventional cardiac electrophysiology, to guide catheter ablation of cardiac arrhythmias. At the same time, there is a growing interest for non-invasive methods, such as magnetocardiographic mapping (MCG), to localize the arrhythmogenic substrates, to test their reproducibility and to plan the most appropriate interventional approach. So far electroanatomical imaging has relayed on static mathematical modeling of the heart and more recently on direct merging with three-dimensional rendering of cardiac anatomy from multidetector computer tomography or magnetic resonance imaging. Merging electrophysiological information with static anatomical structures, can surely be a source of uncertainty for MCG-based pre-interventional localization of the arrhythmogenic substrate and causes mismatch between the real-time imaging of moving catheters and the static geometry of the cardiac chambers reconstructed with invasive electroanatomical imaging. The implementation of recent realistic numerical models of the beating heart in a breathing thorax can improve accuracy and fill the gap between non-invasive and interventional electroanatomical imaging.

Management of bladder, prostatic and pelvic floor disorders with botulinum neurotoxin.

Since its introduction in the late 1970s for the treatment of strabismus and blepharospasm, botulinum toxin (BoNT) has been increasingly used in the interventional treatment of several other disorders characterized by excessive or inappropriate muscle contractions. The use of this pluripotential agent has extended to a plethora of conditions including: focal dystonia; spasticity; inappropriate contraction in most sphincters of the body such as those associated with spasmodic dysphonia, esophageal achalasia, chronic anal fissure, and vaginismus; eye movement disorders; other hyperkinetic disorders including tics and tremors; autonomic disorders such as hyperhidrosis; genitourinary disorders such as overactive and neurogenic bladder, non-bacterial prostatitis and benign prostatic hyperplasia; and aesthetically undesirable hyperfunctional facial lines. In addition, BoNT is being investigated for the control of the pain, and for the management of tension or migraine headaches and myofascial pain syndrome. BoNT injections have several advantages over drugs and surgical therapies in the management of intractable or chronic disease. Systemic pharmacologic effects are rare; permanent destruction of tissue does not occur. Graded degrees of relaxation may be achieved by varying the dose injected; most adverse effects are transient. Finally, patient acceptance is high. In this paper, clinical experience over the last years with BoNT in urological impaired patients will be illustrated. Moreover, this paper presents current data on the use of BoNT to treat pelvic floor disorders.

Non-invasive electrophysiologic study with amagnetic transesophageal pacing during unshielded multichannel magnetocardiographic mapping.

UNLABELLED: Multichannel magnetocardiographic (MCG) mapping is a non-invasive method, which can provide reproducible three-dimensional (3D) localization of accessory pathways (AP) and ventricular arrhythmias, before ablation procedures. More recently MCG imaging of intra-atrial reentry circuits has also been reported. So far, reported cases of MCG localization and imaging of arrhythmias were investigated during spontaneous rhythm only, although more relevant information can be obtained during dynamic electrophysiologic study (EPS). For cardiac pacing one could use an amagnetic intracardiac catheter; but this, however, would add invasivity to a non-invasive method. The aim of this study was to validate a novel approach for dynamic non-invasive EPS based on MCG in combination with amagnetic transesophageal pacing (TEP). METHOD: A tetrapolar 7 French amagnetic catheter was developed, which provides effective TEP (with an average stimulation threshold of 10-15 mA) and simultaneous recording of two esophageal atrial electrograms. MCG data were acquired at rest, with a 36-channel MCG system (sensitivity of 20 fT/Hz(1/2)), for 90 to 300 seconds (sampling rate of 1 KHz; bandwidth of DC Hz to 100 Hz), as a function of the type of pacing procedure. 10 patients were investigated, during both continuous and programmed TEP. RESULTS AND CONCLUSIONS: MCG during TEP was feasible and reproducible. It provided: 1) more accurate localization of AP during pacing-induced maximal preexcitation; 2) inducibility of supraventricular AR and imaging of atrial reentry circuits, not spontaneously present; 3) stabilization of the heart rate to improve the accuracy of quantitative estimate of ventricular repolarization parameters.

Magnetocardiographic study of ventricular repolarization in hypertensive patients with and without left ventricular hypertrophy.

UNLABELLED: Previous studies in magnetically shielded rooms have shown that magnetocardiographic (MCG) mapping can be useful to detect early signs of left ventricular hypertrophy (LVH). The aim of this study was to evaluate ventricular repolarization parameters in patients with essential hypertension, associated or not with LVH, by means of unshielded multichannel MCG mapping. METHODS: 31 patients with pharmacologically treated essential hypertension (average BP systolic: 147.8+/-11.2, diastolic: 92.2+/-4.9) since 6.5+/-5.6 years, 13 without and 18 with evidence of LVH (4 by ECG, 11 by echocardiography, and 3 at both), were studied with a 36-channel MCG system (sensitivity of 20 fT/square root of Hz1/2) and with 12-lead ECG, in an unshielded hospital setting. To assess ventricular repolarization, HR-corrected, QTend, JTpeak, JTend, Tpeak-end intervals and QT dispersion (QTd) were measured from both MCG and ECG waveforms. The magnetic field gradient orientation (alpha angle) during the ST interval and at the Tpeak was also computed. 20 normal age-matched volunteers were used for comparison. RESULTS: As compared to normal volunteers, MCG JTend, QTend, Tpeak-end and QTd were significantly longer in hypertensive patients. The difference was not significant, if only patients with essential hypertension but no LVH were considered. The magnetic field alpha angle during the ST was significantly abnormal in patients with essential hypertension (p < 0.01). CONCLUSIONS: In patients with essential hypertension, MCG detects alterations of ventricular repolarization, not evidenced by 12-lead ECG.

Magnetocardiographic differences of ventricular repolarization parameters between Wistar rats and guinea pigs.

UNLABELLED: The morphology and range of duration of the action potential (AP) in normal Wistar rat's (WR) myocyte markedly differ from those of guinea pigs (GP), whose plateau (phase 2) duration is longer. Thus a clear-cut T wave can be easy defined in GP but not in WR. Aim of this study was to differentiate magnetocardiographic (MCG) ventricular repolarization (VR) parameters of healthy adult WR and GP. METHODS: 10 female animals (5 Guinea pigs and 5 Wistar rats) were studied with a 36-channel MCG system (sensitivity of 20 fT/square root of Hz1/2) and with one ECG lead, in an unshielded hospital room. To assess VR, HR-corrected, JTpeak, JTend, Tpeak-end and QTend, intervals were measured from both MCG waveforms. Timing was improved by MCG maps analysis. Magnetic field orientation (MFO), its dynamics (MFD) and stability (JTS) during the JT interval, were also automatically computed from MCG maps. RESULTS: All repolarization intervals were significantly shorter in WR than in GP, except the Tpeak-end, which was longer. MFO and MFD also differed. CONCLUSIONS: MCG estimate of VR parameters, in adult WR and GP, is precise enough to evidence breed-related differences, consistent with physiological heterogeneity of duration during phases 2 and 3 of the AP, and with an higher degree of transmural dispersion of repolarization in WR.

Effects of filtering on computer-aided analysis for detection of chronic ischemic heart disease with unshielded rest magnetocardiographic mapping.

UNLABELLED: Recent studies have reported better sensitivity of magnetocardiographic (MCG) mapping, as compared to ECG, in detecting ventricular repolarization (VR) abnormalities due to myocardial ischemia in patients (pts) with Ischemic Heart Disease (IHD). For quick data reduction, automatic analysis of MCG mapping is mostly used. The aim of our study was to evaluate if filtering modality could alter automatic analysis of MCG. METHOD: 39 subjects were studied: 20 normals and 19 IHD pts, with angiography-documented >70% coronary stenosis, positive stress/SPECT and ischemic 12-lead ECG in 12/19 (63%). Rest MCG was recorded with a 36-channel system (at 1 kHz; bandwidth DC-100 Hz). To assess VR, Hänninen's STalpha angle and three magnetic field dynamics parameters, [i.e. +/- poles: angle (A), distance (D) and ratio (R)] during the T-wave interval, were computed from the same MCG maps: 1) after digital 20 Hz low-pass filtering (LPF) and 2) after digital 50 Hz adaptive filtering (AF). The baseline was unchanged. Three quantitative MCG scores of the T-wave (EXT, ML, Q) were automatically calculated (with 20 Hz LPF only). RESULTS: Whereas the filtering modality didn't affect the predictivity of the STalpha angle, the predictive values of A, D, and R were different and partially contradicting. Automatic MCG scores had a predictive values ranging between 73% and 92%. CONCLUSIONS: The diagnostic power of unshielded MCG for detection of chronic IHD, with T-wave parameters (A, D and R) might be affected by LPF. The STalpha angle is not affected by LPF. Automatic EXT, ML and Q scores have better predictivity than ECG.

Clinical multichannel MCG in unshielded hospital environment.

UNLABELLED: From November 5th, 2001 to May 19th, 2004, 545 patients (177 with arrhythmias, 67 with WPW syndrome, 60 with Ischemic Heart Disease (IHD), 129 with different kinds of cardiomyopathy, 106 normals, 6 FMCG) have been consecutively investigated at the Catholic University of Rome, with unshielded Multichannel Magnetocardiographic Mapping (MMCG): 20 with the 9-channel system only and 525 with the 36-channel system (207 of them with both systems). 107 patients were investigated also after physical stress, carried out with a standard bicycle ergometer. In all patients MMCG was recorded at least three times, to check for reproducibility and/or for clinical follow-up, for a total of more than 1600 recordings. METHOD: MMCG was performed, with both the 9-channel and the 36-channel systems, at 1 kHz in the bandwidth DC-100 Hz. In the last 200 pts, 12-lead ECG was simultaneously recorded with amagnetic electrodes. On each patient file, post-processing and signal analysis for the quantitative assessment of ventricular repolarization and for 3D localization and electroanatomical imaging of cardiac arrhythmias, were carried out independently with two different approaches and software programs developed by CMI and by Neuromag (Finland). RESULTS: The results with the two methods have been compared. For 3D electroanatomical integration of MMCG localization results, 3D cardiac models have been used, constructed from patient MRI and/or from orthogonal fluoroscopic images taken at the moment of MCG recording. CONCLUSIONS: Qualitative reproducibility of MMCG was satisfactory. However the estimate of quantitative parameters has shown a certain degree of variability, which deserves further evaluation.

Cardiovascular adaptation during action pistol shooting.

BACKGROUND: Action Pistol Shooting, implies high degree of physical and psychological stress, however cardiovascular adaptation during competition has not been studied so far. METHODS: We studied six healthy males athletes, during the Italian National Dynamic Pistol Shooting Championship. ECG was monitored and blood pressure (BP) manually measured along the match. RESULTS: Mean heart rate (HR) was close to 100 bpm per minute in all but one shooters. Marked tachycardia, above 180 beats per minute was recorded in four shooters, during "field course" stages. In two cases the heart rate under stress reached about 200 bpm, for the occurrence of paroxysmal atrial arrhythmias. BP behavior was different among the six shooters with mean systolic values ranging between 140 and 170 mmHg and maximal systolic values between 160 e 240 mmHg. CONCLUSIONS: Action Pistol Shooting induces acute elevation of HR and BP, which may reach abnormal values and can be associated with impaired performance and score. Further study is warranted in shooters undergoing combat-like tournaments to evaluate unperceived cardiovascular stress and their coping capability.

Identification of anti-endothelial cell antibodies in patients with chronic anal fissure.

BACKGROUND: Recent studies demonstrate that chronic anal fissure can be the consequence of a local ischemic process. Thus hypothesizing that at the perianal level the interaction of immune component with endothelium could constitute a mechanism determining ischemia and hypertonia, the presence or absence of circulating anti-endothelial cell antibodies (AECAs) was determined in the serum of patients with anal fissure. METHODS: The study was carried out on 30 patients: 10 with posterior chronic anal fissure (group 1), 10 with grades III and IV hemorrhoids (group 2), and 10 without previous or active anorectal disease, or both (group 3). An indirect immunofluorescence assay on sections of rat kidney tissue was used to identify AECA in the peripheral blood. RESULTS: The assay result was positive for AECAs in 12 patients, all with anorectal disease when compared to the control group (P = .001). The basal anal tone was higher in the AECA-positive patients than in the AECA-negative patients (P = .001). CONCLUSIONS: Only the patients with anal fissure or hemorrhoids were AECA positive. All healthy controls tested negative for AECA. Although the number of subjects studied is small, the presence of auto-antibodies directed against the endothelial cells in the serum of these patients supports the hypothesis that the endothelium is involved in the anal disease.