SEARCH · PubMed Health

Results for “Body Surface Potential Mapping”

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 289 records · Page 16Linked to original sources

PubMed1987

[The Italian Group for the Study of Streptokinase in Myocardial Infarct: Changes in surface cardiac potentials. Study with chest electromaps].

The electrocardiographic changes during and after the thrombolytic treatment with streptokinase (SK) were assessed by means of body surface potential mapping. The aim of the study was to identify potential patterns suggesting reperfusion and revealing possible short-term effects on the infarct size of the recanalization. We studied 23 patients enrolled in the G.I.S.S.I. trial; 11 had an anterior and 12 had an inferior myocardial infarction; 14 were treated with SK and 9 were controls. Body surface maps were recorded from 105 lead points located on the anterior thoracic surface using an automated instrument. The maps were obtained immediately before the SK infusion (or at the time of randomization in the control patients), 30, 60, 120 minutes thereafter and then 24 hours and 7 days after the onset of the infarct symptoms. In each patient the surface potential distribution at 100 msec after the end of QRS was considered and the sum of all the positive potential values was calculated (sigma ST). In addition, the potential time integrals relating to two intervals of the cardiac cycle (first 100 msec of ST and first 40 msec of QRS) were calculated at each lead point and transferred to diagrams representing the chest surface explored (isointegral map). With respect to Q-40 maps, deviation index maps were calculated as follows: the mean Q-40 map (obtained from 30 normal subjects) was subtracted from the map of each patient; the value obtained at each lead point was then divided by the standard deviation of the normal values for that point. An area where the integral values were at least 2 SD lower than normal was considered a reliable index of infarct. By considering as index of reperfusion an early peak of CPK (less than 12 hours from the onset of infarct symptoms), we divided the patients into 2 subsets: reperfused (R) and not reperfused (NR). The mean values of sigma ST at 100 msec progressively decreased in all patients from the baseline to the subsequent recordings in both control and SK groups, without significant differences; nevertheless, the highest percent reductions of sigma ST were observed only in some R patients. The maximum on the ST-100 isointegral maps also showed a similar behaviour.(ABSTRACT TRUNCATED AT 250 WORDS)

Clinical Trials as Topic↗

PubMed1986

[Left axis deviation investigated by body surface mapping and phase image analysis].

Relationship between left axis deviation and left anterior fascicular block (LAFB) was investigated by estimating the ventricular excitation and contraction sequence using body surface potential mapping and phase image analysis by radionuclide ventriculography. This study included seven normal persons, eight patients with complete right bundle branch block (RBBB) without left axis deviation (LAD), twelve with RBBB and unblocked axis (determined by the first half of the QRS complex) of 0 degrees or farther deviated to the left (RBBB with LAD), and three with isolated LAD. The isochrone ventricular activation maps (VAT maps) were obtained by body surface mapping technique. Planar phase images in the left anterior oblique projection and short-axis ventricular tomographic phase images using a seven-pinhole collimator were constructed by ECG-gated equilibrium blood pool scintigrams. On the VAT maps of RBBB, there was a markedly delayed conduction to the right ventricle, however, in the left ventricle, the excitation was initiated in the anterior paraseptal region, and it proceeded rapidly toward the lateral and posterior walls, and in the same direction as normal. The VAT maps of RBBB with LAD were categorized in three types according to the activation sequence in the left ventricle. Type I, the same as maps of RBBB, consisted of three cases. Type II, four cases, showed excitation starting from the apex and ascending in the anterior wall. There were five cases of type III, which showed the earliest excitation in the basal posteroparaseptal region, proceeding toward the apex and ascending in the anterior wall. Type II was considered compatible with block of the left anterosuperior fascicle, and type III was that of left anterosuperior and midseptal fascicles. In types II and III, the phase delay in the left anterior wall was recognized in tomographic phase images, and the difference between right and left ventricular mean phase angles in planar phase images was significantly smaller than in cases of isolated RBBB, These were thought to support the existence of LAFB. The range of the unblocked axis of RBBB with LAD was -3 degrees approximately 13 degrees (-7.7 +/- 5.0 degrees) in type I, -8 degrees approximately -30 degrees (-19.8 +/- 9.1 degrees) in type II, and -33 degrees approximately -60 degrees (-51.0 +/- 10.9 degrees) in type III. All cases with left axis deviation beyond -30 degrees were of type III, and suspected to have extensive damage, including the midseptal fascicle.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗

PubMed1996

Comparison between electrocardiographic and magnetocardiographic inverse solutions using the boundary element method.

The accuracy of imaging cardiac sources using electrocardiographic and magnetocardiographic signals is influenced by thoracic inhomogeneities, e.g. the lungs and cardiac blood masses. The effects is investigated of such inhomogeneities on the body-surface potential maps (BSPM) and magnetic-field maps (MFM) inverse solutions for a single moving dipole as the source model and a realistic torso model as the volume conductor, by employing a node-based boundary element method. Using the same number and placement of the body-surface potential and magnetic field leads, a comparison is obtained of the numerical accuracy of body-surface potential and magnetic field leads. The results show that, with no noise added, the body-surface potential solution is less sensitive to the exclusion of the inhomogeneities than the magnetic field solution. The influence of noise on the BSPM and MFM localization is comparable for x (left-right) and y (foot-head) oriented dipoles, and the BSPM localisation is more accurate than the MFM localisation for z (anterior-posterior) oriented dipoles.

Electrocardiography↗

PubMed1993

Body surface Laplacian mapping of cardiac excitation in intact pigs.

Relating body surface electrocardiographic signals to regional myocardial events has been a major effort in cardiac electrophysiology. Conventional electrocardiographic means do not provide sufficient spatial resolution to resolve distributed cardiac electrical activity. The purpose of this investigation was to evaluate and study the validity of a new technique--body surface Laplacian mapping--in a well-controlled experimental setting, and to test the hypothesis that the body surface Laplacian map (BSLM) can resolve normal and abnormal ventricular depolarization patterns and localize the initial site of ventricular depolarization with high spatial resolution. In this study, BSLMs were constructed from direct measurements of the surface Laplacian of the body surface potentials using an array of 64 concentric bipolar Laplacian electrodes. BSLMs were compared to body surface potential maps (BSPMs) during normal and ectopic ventricular activation in intact anesthetized pigs. The BSLM displayed highly localized images of cardiac electrical activity, indicating its ability to resolve myocardial events. The BSLM in pigs identified the pacemaking focus overlying the known location of the epicardial pacing electrode, and imaged the activation sequence associated with exogenous ventricular pacing. In contrast, in all cases the BSPM revealed a diffuse distribution of activity over the chest. The present results suggest that the BSLM provides sufficient spatial resolution to relate body surface recordings to regional myocardial events and is able to detect ventricular depolarization patterns with greater resolution than the conventional BSPM.

Animals↗

PubMed1988

Diagnostic value of Q waves outside standard precordial lead points in left anterior myocardial infarction undetectable by standard 12-lead electrocardiogram.

Body surface potential maps were recorded for 52 patients with solitary anterior myocardial infarction and 57 normal subjects. All patients had pure anterior wall asynergy on a left ventriculogram but no diagnostic Q wave on the standard 12-lead electrocardiogram. Q wave (greater than 30 msec) distributions on the body surface of the patients and normals were compared. The frequency of Q waves in the area above V1-V2 and in the right middle chest was significantly higher in patients than in normals. The sensitivity of Q waves for asynergy in leads from both these areas was 19-60%. The positive predictive value was 67-94%. The frequency of Q waves was significantly higher in severe asynergy than in mild asynergy. A combination of two selected unipolar leads from these areas yielded a sensitivity and specificity of 33% and 95%, respectively. With a combination of three leads, these values were 42% and 93% and with four leads 48% and 88%, respectively. The results indicate that several unipolar leads from the area above V1-V2 and from the right middle chest in addition to the standard 12-lead electrocardiogram may improve the electrocardiographic diagnostic accuracy of myocardial infarction.

Electrocardiography↗

PubMed2000

Relation between spatial distribution of late potentials and location of origin of premature ventricular complexes on body surface map in patients with postinfarction ventricular tachycardia.

We studied the relationship between the spatial distribution of late potentials (LPs) and the origin of premature ventricular complexes (PVCs) using body surface maps in 55 patients with postinfarction sustained ventricular tachycardia (VT). Body surface maps were recorded from 87 leads to construct departure maps during sinus rhythm and signal-averaged ECGs were recorded from 32 unipolar leads to construct a LP map. The root-mean-square values during 40 ms intervals behind the QRS end were computed as LPs. The PVC map was recorded simultaneously in 14 patients presenting PVC with similar morphology to VT during LP detection. The origin of PVC was localized at the site of isopotential minimum when the potential exceeded -0.5 mV during the early QRS period. The LP area and the departure area showed a similar distribution. However, the PVC origin was closer to the site of LP maximum than the departure minimum in 11 (79%) patients, and the spatial correlation between the LP maximum and the PVC origin was good in 12 (86%) patients. LP and PVC mapping from the body surface is feasible and of worth to predict noninvasively the site of origin of ventricular arrhythmias in patients with remote myocardial infarction and sustained VT.

Adult↗

PubMed1989

Relation between the ventriculographic silhouette and topography of thoracic potential in coronary artery disease.

The body surface potential map obtained within 30 days of cardiac catheterization was examined in 180 patients with coronary artery disease. Radii to the systolic and diastolic boundaries of the right anterior oblique ventriculogram were measured at 18 degrees intervals; isointegral voltages were tabulated for early and late halves of the QRS complex at 35 definitive electrode sites. Multivariate analysis showed all ray lengths depended on all 70 voltage values. Linear transformation matrices to predict ray length from voltage distribution were calculated for a training set which was successively expanded from 80 to 160 at increments of 20 patients. Training set expansion led to a progressive decrease in the error of reproduction of the ray lengths for patients outside the training set. There is a strong relation between ventriculographic contours in patients with coronary artery disease and body surface potential values during early and late QRS complexes. Even in simplified linear formulation, the relation is detectable throughout a large population despite interindividual variations in anatomic geometry.

Adult↗

PubMed1989

Anatomic localization of a single electrical source within the boundary of the human torso.

A closed prolate ellipsoid was used to approximate the surface of the Rush torso model to permit recovery of the site and orientation of known dipoles in 15 cardiac locations. Localization was found to be reasonably close, usually within 2 cm. When body surface potential maps of 37 subjects with right ventricular pacemakers were similarly treated, the discrepancy between known pacemaker site and the site of earliest activation was relatively large (mean, greater than 4 cm) and rapidly increased within the ensuing millisecond. The discrepancy not only emphasizes the wide variation in body shape and tissue distribution in living subjects, but also points to probable physical separation between stimulus site and earliest detectable activation site because of ischemia, infarction, or myocardial response to variation in current strength of the stimulus.

Cardiac Pacing, Artificial↗

PubMed1999

[Heterogeneities of ventricular repolarization and vulnerability to arrhythmia. How to detect them with noninvasive methods?].

Vulnerability to arrhythmias can be influenced by two conditions: a dynamic (beat-to-beat) variation of repolarization sequence, and a state of heterogeneity of repolarization, i.e. a greater than normal dispersion of recovery time. The first condition is well reflected by T-wave alternans, a phenomenon characterized by alternation on every other beat basis of amplitude and morphology of T waves. Experimental studies provided evidences of close temporal correlations between ischemia-induced alternans, dispersion of repolarization and susceptibility to ventricular fibrillation. Gross T-wave alternans can be occasionally observed in patients with long QT syndrome or during acute ischemia before the onset of arrhythmias. Recent studies have demonstrated that measurement of microvolt level T-wave alternans at rest and during exercise is a promising technique for the identification of patients at risk of ventricular arrhythmias and sudden death. A state of repolarization inhomogeneity can be revealed by methods which analyze a single cardiac beat. The QT dispersion, defined as the difference between maximum and minimum QT interval measured at 12 lead ECG, is the most simple and widely used index of repolarization inhomogeneity. The major limitation is that this measure cannot be related to the actual spatial heterogeneity of repolarization, since each surface lead reflects, in different degree, the electrical activity of the whole heart. The majority of studies reported that, in various pathological conditions, the QT dispersion is higher in patients with than without ventricular arrhythmias. On the other hand, a recent large prospective study in post-myocardial infarction patients failed to demonstrate the predictive value of QT dispersion, even when measured with the best available methodology. Body surface potential mapping has proven to be a useful method for detecting repolarization inhomogeneities not revealed by the analysis of conventional ECG leads. Different methods of analysis of the potential maps have been used. By applying principal component analysis of the ST-T waves, we computed the similarity index, defined as the ratio of the first principal component to the sum of all remaining components. A low value of similarity index suggests a high degree of repolarization inhomogeneity. The similarity index was found significantly lower in patients with idiopathic long QT syndrome and in patients with arrhythmogenic right ventricular dysplasia with episodes of ventricular tachycardia than in normal subjects. Future researches should aim at identifying novel reliable indices of repolarization inhomogeneity, first deduced from extensive body surface mapping, then possibly computed from digital recording of the 12 conventional leads.

Arrhythmias, Cardiac↗

PubMed1994

ESTRACE--1: a stethoscope for functional checking of electrostimulators and low cost body surface mapping system.

In a project on the mapping of body surface potentials evoked by implanted spinal cord stimulators and transcutaneous electrostimulators, a simple device was developed for use in polyclinical practice for easy checking of the function of these stimulators. The device is an electrical stethoscope and consists of an instrumentation amplifier, bandpass filter, a distortion circuit and a headphone. In vivo measurements demonstrate the generation of an amplitude-dependent tone by the distortion circuit. The apparatus is in many aspects similar to a stethoscope: simple to understand and a practical tool for a fast Go/No-Go test. The device can be optionally connected with a PC and enables body surface mapping documentation within a few minutes.

Adult↗

PubMed1993

Comparison of measured and computed epicardial potentials from a patient-specific inverse model.

This study reports the first direct comparison of measured and computed epicardial potentials in which the specific anatomy of a test subject has been used to calculate the inverse electrocardiographic model. It is now feasible to obtain low-noise body surface potential maps and to incorporate accurate anatomic data into inverse procedures for the purpose of computing epicardial potential distributions. The direct verification of computed human epicardial distributions remains an important goal. The experiment reported here obtained direct measurements from six transcutaneous pacing wires that were attached to points on the epicardial surface of the human heart in an intact subject. From the same subject, a magnetic resonance scan was used to produce a specific thoracic model consisting of 5-mm cubes. The forward model uses the finite difference method to compute a forward transfer matrix that relates each of 26 epicardial regions to body surface measurements. The inverse computation was performed by zero-order Tikhonov regularization. Body surface potentials were used in the inverse procedure to compute epicardial potentials, which were then compared with direct epicardial measurements. The computed epicardial potentials were compared to the measured ones by correlation, which gave an amplitude-independent measure of similarity. Amplitude differences and time delays in computed potentials were observed, but the morphologic trend was generally well recovered. The results obtained indicate the sensitivity of the inverse model to a number of factors. The robustness of computed epicardial distributions to errors in assumed lung conductivity is shown. Results from a nonpatient-specific, but realistic, torso model are presented.(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiac Pacing, Artificial↗

PubMed1991

Localization of cardiac arrhythmias: conventional noninvasive methods.

Noninvasive localization of the accessory pathway (AP) in patients with the Wolff-Parkinson-White syndrome and of the site of origin of ventricular tachycardia (VT) is reviewed. 12-lead electrocardiography (ECG) is the most readily available method for localization of both the AP and the site of VT origin. Many published ECG criteria are introduced. The application of body surface potential mapping, vectorcardiography, nuclear phase imaging, echocardiography, computed tomography, nuclear magnetic resonance, and signal-averaged ECG in the localization of these arrhythmogenic substrates is also described. We believe that ECG is the most sensitive noninvasive method for AP localization as well as being convenient and simple; it may be used as the only noninvasive method for the initial evaluation. The left lateral AP, which occurs with an incidence of more than 40%, could be localized preoperatively by noninvasive methods only. For localization of the site of VT origin, none of the noninvasive methods is accurate enough for guiding the surgical and catheter-mediated ablative therapies so far.

Action Potentials↗

PubMed1994

Forward problem of electrocardiography: construction of human torso models and field calculations using finite element method.

Finite element models of the human torso were constructed using anatomical data measured by serial computerised tomography scans in a subject. A first set of three models with a mesh resolution of 5517 nodes and 29810 elements included an homogeneous conductivity, lungs inhomogeneity, and heart, lungs and spinal region inhomogeneities. A second set comprised similar models with a mesh resolution of 12084 nodes and 67045 elements. A cylindrically shaped volume conductor was also constructed to evaluate the convergency and accuracy of the finite element solutions by comparison with the analytical solution. Forward simulations were performed using different excitation sites on the cardiac surface. The inclusion of conductivity inhomogeneities altered the maximum and minimum values of the body surface potentials, but did not substantially modify the pattern of the potential distributions. The greatest effect was due to the inclusion of the lungs. Increasing the mesh resolution from 5517 to 12084 nodes did not change noticeably the shape or amplitude of the simulated body surface potential maps. These models can readily be used for other bioelectromagnetic problems.

Electrocardiography↗

PubMed1986

Wolff-Parkinson-White VCG patterns that mimic other cardiac pathologies: a correlative study with the preexcitation pathway localization.

Vectorcardiograms (VCGs) of 44 patients with a Wolff-Parkinson-White (WPW) syndrome have been analyzed with the aim to correlate the QRS loop patterns with specific preexcitation sites. The VCG QRS loops were analyzed to determine whether conduction abnormalities and myocardial infarction (MI)-like patterns observed in the WPW syndrome could be related to specific preexcitation sites identified by surgery as well as by body surface potential mapping (BSPM). Left bundle branch block pattern was observed with anteroseptal (AS) preexcitation, anterior MI pattern was seen with lateral right ventricle (LRV) preexcitation, left anterior fascicular block was observed with posterior right ventricle (PRV) preexcitation, inferoposterior and strictly posterior MI pattern was found with posteroseptal (PS) and posterior left ventricle (PLV) preexcitation, right bundle branch block was seen in lateral left ventricle (LLV) preexcitation, and right bundle branch block was observed with left posterior fascicular block in anterior left ventricle (ALV) preexcitation. These VCG criteria seem to identify accurately the preexcitation sites as observed by delta wave BSPM and at surgery investigations. Consequently, they could be useful in localizing the preexcitation site in cases of ambiguous delta vector orientation.

Adult↗

PubMed1982

Effect of ventricular hypertrophy on conduction velocity of activation front in the ventricular myocardium.

To study the effect of ventricular hypertrophy on conduction velocity of the activation front noninvasively, transmural conduction indexes were obtained from findings of echocardiography and body surface potential mapping performed in 40 patients with right bundle branch block uncomplicated by the left anterior fascicular block. Because in these patients, left ventricular activation proceeds radially without being modified by right ventricular activation, the index was obtained by dividing ventricular septal thickness measured from the echocardiogram by transmural conduction time, which was taken as the time interval from the onset of the QRS complex to the time when the left ventricular epicardial breakthrough minimum appeared on the potential map. The indexes, ranging from 11 to 45 cm/s, has a good positive linear correlation with the septal thickness (Y = 2.37X - 1.33, correlation coefficient [r] = 0.83) and were abnormally small in some failed hearts. Further, both the mean ventricular activation times in lead V5 and the mean value for total duration of left ventricular activation did not differ significantly in patients with and without left ventricular hypertrophy. These findings suggest that conduction velocity was increased in the hypertrophied ventricle and decreased in the failed hearts. Because there were no significant differences in the mean serum sodium and potassium concentrations in the patients with and without left ventricular hypertrophy, it is concluded that hypertrophy itself most likely caused greater conduction velocity. Enlarged cells and multiple intercalated discs abundant in hypertrophied ventricle would have facilitated intercellular current flow and, hence, conduction velocity and impaired cellular connection in the failed heart would have reduced them. Thus, the transmural conduction index is suggested to be an important aid in interpreting electrocardiograms as well as in estimating the pathologic state of the heart.

Adolescent↗

PubMed1991

Dispersion of ventricular repolarization in the long QT syndrome.

To identify markers of dispersion of the ventricular repolarization in the idiopathic long QT syndrome, body surface potential maps were analyzed in 40 such patients (mean age +/- standard deviation 21 +/- 11 years) and in 30 healthy control subjects (mean age 24 +/- 7 years). In each subject, 117 chest leads were recorded and maps of the integral values of the QRST interval were calculated. A multipolar distribution of the values, a marker of gross electrical inequalities of repolarization, was found only in 4 patients. To detect minor regional disparities of ventricular recovery, all the ST-T waveforms were analyzed in each subject. The ST-T waves were represented by a discrete series of potential values. The "similarity index" was computed by applying a principal component analysis, which represents (in percent) to what extent 1 fundamental pattern of ST-T reproduces all the recorded waveforms. The mean value of the similarity index was significantly lower in patients with long QT syndrome than in control subjects (49 +/- 10 vs 77 +/- 8%, p less than 0.0001). A value less than 61% (corresponding to 2 standard deviations below the mean value for controls) was found in 35 of 40 patients and in only 1 control subject (sensitivity 87%, specificity 96%). Thus, the similarity index is a more sensitive marker than the multipolar distribution of QRST integral maps in revealing electrical disparities of the ventricular recovery times.(ABSTRACT TRUNCATED AT 250 WORDS)

Action Potentials↗

PubMed1990

Complementary nature of electrocardiographic and magnetocardiographic data in patients with ischemic heart disease.

High resolution body surface potential maps (BSPM) and magnetic field maps (MFM) for study groups consisting of 11 Q wave and 11 non Q wave myocardial infarct (MI) patients as well as 9 normal subjects, were recorded in a magnetically and electrically shielded room. A control group of 22 normal subjects provided group mean normal time integral maps for selected QRST time intervals. The difference between magnitudes of extrema in each map defined the normal mean data range R for that time interval. The root mean square sum of the differences between the time integral map of a study subject and the normal group-mean map provided an estimate of individual map variability, V. Subsequent calculation of group-mean map variability, V, and group-mean normalized variability, V/R, for specific time intervals of the cardiac cycle, were used to test the abilities of BSPM and MFM techniques to distinguish between the normal and MI study groups. Results indicate that BSPM V/R differences between MI and normal groups are most pronounced during Q wave and Q zone activity; between inferior MI's and normals (p less than 0.05) and between anterior MI's and normal (p less than 0.01). Significant differences in MFM V/R occur during repolarization; between inferior MI's and non Q wave MI's (p less than 0.05), between anterior MI's and normals (p less than 0.05), between non Q wave MI's and normals (p less than 0.05) and between all MI's and normals (p less than 0.01). It is concluded that high resolution BSPM and MFM provide complementary means of discriminating between normal subjects and MI patients.

Coronary Disease↗

PubMed1993

A computer heart model incorporating anisotropic propagation. I. Model construction and simulation of normal activation.

Present-day computer models of the entire heart, capable of simulating the activation isochrones and subsequently the body surface potentials, focus on considerations of myocardial anisotropy. Myocardial anisotropy enters into play at two levels, first by affecting the spatial pattern of activation owing to faster propagation along cardiac fibers and second by altering the equivalent dipole sources used to calculate the surface potentials. The construction of a new and detailed model of the human heart is described, based on 132 transverse sections obtained following a computed tomography scan of a frozen human heart whose chambers were inflated with pressurized air. The entire heart anatomy was reconstructed as a three-dimensional array of approximately 250,000 points spaced 1 mm apart. Conduction in the thin-walled atria was assumed isotropic from the sinus node region to the atrioventricular node, where it was subject to a 50 ms delay. A two-tier representation of the specialized conduction system was used, with the initial segments of the left and right bundles represented by a system of cables that feeds to the second tier, which is a sheet of conduction tissue representing the distal Purkinje system. Approximately 1,120 "Purkinje-myocardium" junctions present at the terminations of the cables and sprinkled uniformly over the sheet, transmit the excitation to the ventricles. A stylized representation of myocardial fiber rotation was incorporated into the ventricles and the local fiber direction at each model point used to compute the velocity of propagation to its nearest neighbors. Accordingly, the activation times of the entire ventricular myocardium could be determined using the 1,120 or so Purkinje-myocardium junctions as start points. While myocardial anisotropy was considered in the ventricular propagation process, it was ignored in the computation of the equivalent dipole sources. Nevertheless, the computed electrocardiogram, vectorcardiogram, and body surface potential maps obtained with the new heart model properly positioned inside an inhomogeneous torso model were all within normal limits.

Anisotropy↗