G Melillo

Biomagnetically localizable multipurpose catheter and method for magnetocardiographic guided intracardiac mapping, biopsy and ablation of cardiac arrhythmias

A multipurpose catheter, specially designed to be biomagnetically localizable and the method for magnetocardiographic (MCG) guided intracardiac electrophysiological recordings, endomyocardial biopsy and ablation of cardiac arrhythmias are described. The catheter features two non-polarizable non-ferrous magnetic electrodes, arranged in such a way that, connected to an external current generator, an electromagnetic field of dipolar configuration can be generated in the heart. The connection is done with twisted pairs of non-ferrous magnetic conductors, to avoid the occurrence of spurious magnetic fields along the catheter during current injection to the electrodes. With this assembly the tip of the catheter can be localized (and driven close to an arrhythmogenic area) by MCG mapping. The same electrodes are feasible for monophasic action potential (MAP) recordings.One or more lumen allow fluid infusion, blood sampling, pressure measurements and introduction of steerable wires, pacing or ablation electrodes, bioptic devices, or optic fibers.On the basis of preoperative MCG three-dimensional localization of the arrhythmogenic substrate, the biomagnetically localizable catheter is driven, under fluoroscopic control, as close as possible to the suspected arrhythmogenic zone. MCG mapping is then performed under pacing, with adjustments of the catheters tip, until the electrically induced magnetic field and catheters localization parameters fit those generated by the spontaneous arrhythmia. MAP is recorded. The catheter position is accepted for ablation when electrophysiological abnormalities are identified in the MCG localized area.

A comparison between sevoflurane and desflurane anesthesia in patients undergoing craniotomy for supratentorial intracranial surgery.

BACKGROUND: Desflurane in neurosurgery may be beneficial because it facilitates postoperative early neurologic evaluation. However, its use has been debated because of its capacity to promote cerebral vasodilatation. Sevoflurane has been extensively used in neurosurgical patients. In this prospective clinical trial, we compared early postoperative recovery and cognitive function in patients undergoing craniotomy for supratentorial expanding lesions and receiving sevoflurane or desflurane anesthesia. METHODS: One hundred twenty patients, ASA physical status I–III (66 men), Glascow Coma Scale 15, undergoing craniotomy for supratentorial expanding lesions were enrolled in the study. Patients were randomly allocated to two anesthetic regimens. In Group S (60 patients, 52 ± 16 yr), anesthesia was maintained using sevoflurane with end-tidal of 1.5%–2% and was age adjusted to obtain approximately 1.2 minimum alveolar anesthetic concentration. In Group D (60 patients, 60 ± 14 yr), anesthesia was maintained using desflurane with end-tidal of 6%–7% and was age adjusted to obtain approximately 1.2 minimum alveolar concentration. Emergence time was measured as the time from drug discontinuation to the time at which patients opened their eyes; tracheal extubation time was measured as the time from anesthetic discontinuation and tracheal extubation. Recovery time was measured as the time elapsing from discontinuation of anesthetic and the time when patients were able to recall their name and date of birth. Cognitive behavior was evaluated with the Short Orientation Memory Concentration Test. In the postanesthesia care unit, a blinded observer monitored the patients for 3 h; the incidence of hemodynamic events, pain, nausea, and shivering requiring rescue medication was recorded. RESULTS: The mean emergence time (12.2 ± 4.9 min in Group S vs 10.8 ± 7.2 min in Group D; P = ns) was similar in the two groups, whereas the mean extubation time and recovery time were longer in Group S (15.2 ± 3.0 min in Group S vs 11.3 ± 3.9 min in Group D and 18.2 ± 2.3 min in Group S vs 12.4 ± 7.7 min in Group D, respectively; P < 0.001). The Short Orientation Memory Concentration Test score differed between the two groups only at the earliest assessment (15 min after extubation). No difference between the two groups was found in pain, shivering, nausea, vomiting, and incidence of postoperative hemodynamic events. CONCLUSION: Patients who received desflurane had a shorter extubation and recovery time but similar intraoperative and postoperative incidence of complications compared with those who received sevoflurane.

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 than350 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.

Early postoperative complications after intracranial surgery: comparison between total intravenous and balanced anesthesia.

This prospective study was performed to compare the incidence of complications occurring after neurosurgical procedures in patients anesthetized with either sevoflurane-fentanyl or propofol-remifentanil anesthesia. We enrolled 162 American Society of Anesthesiologists (ASA) I to III patients (82 females and 80 males, Glasgow 15) undergoing elective neurosurgical procedures. Anesthesia was conducted using either propofol-remifentanil (T group; n=80 patients) or sevoflurane-fentanyl (S group; n=82 patients). All patients were monitored in the postanesthesia care unit for 6 hours after extubation. We analyzed and compared in both groups the incidence of high severity complications such as respiratory events (PaO2 <90 mm Hg; PaCO2 >45 mm Hg) and neurologic events (seizures, new motor or sensory deficit, unexpected delay of awakening) and the incidence of low severity complications such as hypertension (mean arterial pressure increase above 30% of baseline), hypotension (mean arterial pressure decrease below 30% of baseline), pain, shivering, nausea, and vomiting. A total of 162 complications occurred in 92 patients (57%) with 50 patients (31%) having had 1, 26 patients (16%) having had 2, and 16 patients (10%) having had 3 or more events. The most frequent complication was respiratory impairment (28%) which was frequently reported only in the first postoperative hour. Out of the total number of complicating events, 77 (48 %) were found in group S, and 85 (52%) in group T (P=ns). Severe complications were rarely reported and evenly distributed in the 2 anesthetic groups. Similarly, no difference could be demonstrated in the composite incidence of less serious complications between the 2 anesthetic regimens tested in this study. This study confirms that the recovery period after neurosurgical procedures remains a time of great potential danger to patients given the high incidence of postoperative complicating events independently from the anesthetic strategy.

Atrial and Ventricular Tachycardias : Invasive Validation and Reproducibility of Magnetocardiographic Imaging

Magnetic localization of the site of onset of cardiac arrhythmias both of atrial and ventricular origin was first reported in 1986 (Fenici et al, 1987–89). However the accuracy of such localization procedures had not been validated so far. In this paper the reproducibility of such measurements is reported in several patients. Moreover the validation of magnetic localisation of ventricular tachycardia with conventional invasive endocardial mapping is described in one patient with previous myocardial infarction (MI).

Magnetocardiographic localization of a pacing catheter

Magnetocardiographic mapping during cardiac endocardia1 pacing was initially attempted by us, in patients undergoing invasive electrophysiological study for clinical reasons, in order to ascertain the reliability of the biomagnetic method in localizing a dipolar source placed in the human heart (Fenici et a1 1985,1986a,b,c). Subsequently similar results have been reported, with measurements carried out in two patients with permanently implanted pacemakers (Schmitz 1988) and in animals (Costa Monteiro et a1 1987). Here we report present results of an ongoing systematic research, carried out in our catheterization laboratory to quantify the accuracy of MCG localization of a catheter pacing different sites of the heart.

Magnetocardiographic localization of Kent bundles

First MCG recording in one patient with WPW was reported by Erne’ and Fenici (1984). Since then several preliminary measurements have been published (Fenici et al 1985–88; Katila et al 1988; Novak el al 1988; Oeff et al 1989), demonstrating the accuracy of MCG to localize Kent type accessory pathways. Here we report present results of our ongoing perspective study carried out to interprete the MCG patterns and to compare the respective localization power of electrocardiographic and magnetocardiographic criteria.

Biomagnetic imaging in the cardiac catheterization laboratory

At the beginning of the eighties still no demonstration had been given that magnetocardiography could be performed in a noisy unshielded hospital environment. Furthermore, when the first so called “high resolution MCG measurements” were reported (Farrel et a1 1978; Fenici et a1 1980 ), their interpretation and potential diagnostic utility were questionable. Tentative interpretation and validation of the experimental measurements on the basis of mathematical models (Leoni et a1 1982; Erne’ et a1 1985; Lorenzana et a1 1985), although clearcut and impressively coherent with what expected from the anatomy and physiology of the heart, were strongly criticized. Few experimental animal investigation had given counterdicting results (Leifer et a1 1983). Both cardiac electrophysiologists and cardiologists asked for direct demonstration that magnetocardiography could really provide new information with respect to the less expensive and troubleless electric measurements and that the MCG could be easily recorded in an hospital setting. For this reason at the Clinical Physiology Laboratory of the Catholic University of Rome a perspective project was started in 1980 to set up a Cardiovascular Biomagnetism Unit in the hospital, which should feature both the characteristics of a Biomagnetism and Cardiac Catheterization laboratory, without the use of any electromagnetic shielding.

Clinical value of magnetocardiography

Magnetocardiography, that is to say the recording of the magnetic field generated by the electrical activity of the heart, was born in 1963 when Baule and McFee, using an induction coil, measured for the first time magnetic signals produced by a human heart [2]. Since then, the evolution from a pioneering experimental observation to the present state of art has passed through fundamental technological progress. First, in 1970, the introduction of superconducting instrumentation in the MIT shielded room demonstrated that magnetocardiograms of quality comparable with that of standard electrocardiograms could be recorded [6, 8, 36]. The next important step was the adoption of gradiometric detection coils which allowed MCG recording in unshielded laboratories [1, 3, 33,44, 47] and opened the way to pioneering clinical measurements [4, 16, 18]. During the same years MCG were also recorded without a superconducting instrumentation [9]. Since the beginning the question arose whether or not magnetic measurements could increase the diagnostic capability of cardiologists in respect to more conventional methods. Several different approaches were used to quantify the information [5, 8, 33, 39] and, although some authors still favour analysis of MCG signal in the time domain both at standard [7, 28, 49] as well as at high resolution [38] isofield contour maps are nowadays preferred to give images of the magnetic field distribution during depolarization and repolarization [10, 11, 13, 21, 22, 27, 29].

Biomagnetic study of cardiac arrhythmias

Clinical magnetocardiographic mapping was initiated in the Cardiovascular Biomagnetism Unit of the Catholic University of Rome about 10 years ago. Since then several hundred patients have been investigated. However, the most interesting data have been collected after the development, in 1984, of the present laboratory configuration, which allows simultaneous MCG mapping and invasive electrophysiological procedures. Perspective studies have been carried out to validate the accuracy of MCG for localisation of arrhythmogenic structures and for early detection of patients at risk of sudden death. Although the diagnostic applicability of the method is still under evaluation, preliminary results are reported, concerning 120 patients, investigated between 1985 and 1990, with cardiac arrhythmias associated with ventricular pre-excitation, ischaemic heart disease or cardiomyopathies.