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Cardiac rhythm, rate and ventricular repolarization properties in infants at risk for sudden infant death syndrome: comparison with age- and sex-matched control infants.

Using 24-hour ambulatory electrocardiographic recordings and 120-lead body surface potential maps, prevailing cardiac rate and rhythm, incidence and frequency of dysrhythm and rate and pattern of ventricular repolarization at the body surface were compared in 17 infants at risk for sudden infant death syndrome (SIDS) and 17 age- and sex-matched control subjects. Sinus rhythm was the prevailing rhythm in both study groups and there were no intergroup differences in average overall awake or asleep sinus rates, nor in temporal variability of sinus rate. Atrial and ventricular ectopic activity were equally uncommon in both study groups. Although there were smooth and bipolar body surface distributions of ST-T and QRST time integrals in both study groups, the average rate of ventricular repolarization (QTc), measured from the 12-lead electrocardiogram, 120-lead body surface potential maps and 24-hour electrocardiography, was consistently shorter in the at-risk group than in the control group. However, temporal variability of QTc was not different between the 2 groups. Thus, significant cardiac dysrhythm and QT prolongation are not found in infants at increased risk for SIDS. Rather, there is an abbreviated ventricular repolarization interval in at-risk infants. In combination with the findings of intergroup similarity of average sinus rate and temporal variability of sinus rate and ventricular repolarization rate, the data suggest a subtle, constant difference in cardiac autonomic activity, most likely an increase in sympathetic tone, in at-risk subjects. The role of this altered cardiac autonomic activity in the causation of SIDS remains undetermined.

Electrocardiography↗

Application of the single moving dipole inverse solution to the study of the Wolff-Parkinson-White syndrome in man.

The single moving dipole (SMD) inverse solution was performed in 28 patients with the Wolff-Parkinson-White preexcitation syndrome to see if the calculated position of the SMD during the initial delta wave could indicate the site of the underlying accessory pathway. This site was first estimated to be at one of eight locations around the atrioventricular ring, from the patient's QRS and ST segment body surface potential maps, as has been described by others. Next, SMD parameters were calculated during the delta wave so as to approximate, on a numerical torso model, the patient's body surface potential map. Visualization of the calculated position of the SMD around the atrioventricular ring was done by projecting it on a plane parallel to this ring. This plane corresponded to the most basal transverse section of a heart model present in the torso model. One limitation was the use of non-varying heart and torso models for all patients. As a result, the SMD technique lacked the precision to separate accessory pathway sites into eight atrioventricular locations. However it was capable of distinguishing between patients belonging to the larger classes of right-sided, posterior, and left-sided preexcitation, formed by combining adjacent atrioventricular accessory pathway locations. With more accurate heart and torso models, it may be possible to increase SMD resolution so as to locate accessory pathway sites deep within the heart. This would represent an advantage over the surface potential map approach which only identifies the site of earliest epicardial breakthrough associated with the accessory pathway.

Adolescent↗

The processed map of the body surface potential.

As the processed maps, the variance map and the residue which was the ratio of the nondipolar cardiac field were introduced. The variance map was made from the root mean square of the distance from the mean value of QRS, T or QRST. The variance map may be useful to find the area of the peak variation of QRS, T or QRST on the body surface. The residue is the expression how much was the nondipolar component included in the body surface potentials. This may be relevant to detect the abnormal cardiac potentials included in the body surface potentials.

Electrocardiography↗

QRS alterations in body surface potential distributions during percutaneous transluminal coronary angioplasty in single-vessel disease.

Body surface QRS potentials were recorded with 63 chest leads in 20 patients with proximal single-vessel disease located on either the left anterior descending coronary artery (n = 10), the right coronary artery (n = 6), or the left circumflex coronary artery (n = 4) before, during, and after percutaneous transluminal coronary angioplasty. In each case, three consecutive inflations of relatively short duration (37 +/- 14 seconds) were carried out. Electrical activity was displayed as unipolar electrograms and body surface potential maps. The total QRS complex duration decreased in 14 of the 20 patients. Focal conduction disturbances were observed in six cases; all six had left anterior descending coronary artery occlusion and two were also accompanied by a clear shortening of the right epicardial breakthrough time. In these two cases, an initial activation loss seemed to be characteristic, whereas in the other four cases, a rather diffuse slowing of intraventricular conduction, especially during the terminal portion of the QRS, could be observed. Individual and group mean isointegral difference body surface potential maps (during-minus-before dilation) were considered valuable for the interpretation of localized changes in intraventricular conduction during percutaneous transluminal coronary angioplasty, and their individual variations could, at least partly, be explained by the presence or absence of collateral circulation. Two different hypotheses are suggested to account for the QRS complex shortening observed during short-term myocardial ischemic injury: (1) coronary artery occlusion delayed activation of the portion of the septal region that is normally activated early during the QRS, and/or (2) coronary artery occlusion increased the speed of propagation within the ventricles. Both of these hypotheses are discussed in light of earlier clinical and experimental results.

Angioplasty, Balloon, Coronary↗

Two-dimensional Fourier spectrum of QRST integral maps in classification of patients prone to ventricular arrhythmia.

Two-dimensional Fourier spectra of QRST integral maps, obtained by body surface potential mapping, were analyzed to identify subjects prone to ventricular arrhythmia, when they have not been identified by the extrema count method. The diagnostic performance (84.38 percent) of the peak value of the Fourier spectrum as a classifier for subjects prone to ventricular arrhythmia showed an improvement of 3.65 percent over the use of the extrema count method as a classifier.

Arrhythmias, Cardiac↗

Body surface isopotential mapping of the entire QRST complex in the Wolff-Parkinson-White syndrome. Correlation with the location of the accessory pathway.

Body surface potential maps were recorded during sinus rhythm and during atrial pacing at the time of electrophysiologic studies in 42 patients with Wolff-Parkinson-White syndrome. The locations of the accessory pathways were determined by epicardial mapping during surgery in 34 patients and by multicatheter endocavitary electrophysiologic studies in eight additional patients. During delta wave inscription, the shape and extension of areas of the negative and positive potentials on the thorax correlated better with the preexcitation site (69% of patients) than with the localization of the minimum potential alone (45.2% of patients). Typical potential distributions were present from the beginning of the delta wave and remained stationary during the first half of the QRS complex. During marked preexcitation, the superposition of atrial activity on the delta wave produced a mixed pattern in the earliest maps. However, these alterations of early delta thoracic potential distribution did not persist longer than 30 msec. The spread of the negative potentials during the last half of the QRS complex also characterized each localization: right-sided preexcitation reproduced the depolarization sequence of left bundle branch block, left-sided preexcitation reproduced that of right bundle branch block, and posterior pathways resembled left anterior fascicular block. Anterior left ventricular and more anterior left lateral ventricular preexcitations mimicked a right bundle branch block-left posterior fascicular block pattern. There was good correlation between the body surface potential map obtained during the ST segment and the site of the right-sided preexcitation. However, in left-sided preexcitations, ST patterns concordant with delta wave patterns were found less frequently than in right-sided preexcitations.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

[Departure map].

Departure maps were developed for the easy recognition of abnormalities on the body surface potential maps. To construct departure maps, mean (m) and standard deviation (SD) was calculated for each lead to a value, such as potential, time-integral value, ventricular activation time, etc. For a measured value (x) of each lead, departure index was calculated as (x-m)/SD. The departure maps demonstrated body surface distribution of the departure index. Areas of departure index > 2 or < -2 were considered abnormal. Departure maps represent the location and extent of abnormal increase or decrease, and are useful for the assessment of myocardial infarction, ventricular hypertrophy, and myocardial ischemia. This technique may be applied to various parameters of body surface mapping.

Body Surface Potential Mapping↗

Spatial resolution of body surface potential and Laplacian pace mapping.

The spatial resolution (SR) of the body surface Laplacian map (BSLM) was assessed using a three-dimensional, realistically shaped, heart-torso model. The BSLMs were estimated from the body surface potential maps (BSPMs) generated by pacing different sites of the ventricle of a three-dimensional computer heart model using a novel three-dimensional spline Laplacian algorithm. Pacing was performed at a total of 88 myocardial units in five regions of the AV ring (anterior, left wall, posterior, right wall, and septum) and three regions adjacent to the AV ring in the middle anterior and posterior of the ventricles. The SR of the BSPMs and BSLMs were investigated by means of the correlation coefficient (CC) of maps. When 5 microV and 10 microV Gaussian white noises were added into the simulated BSPMs, the SR, at 36 ms after the onset of pacing, was about 5.0 +/- 1.2 mm and 5.4 +/- 1.3 mm for the BSPMs, and 3.3 +/- 0.8 mm and 4.0 +/- 0.9 mm for the BSLMs, respectively. The results of the present simulation study suggest that the BSLM has higher SR and may provide a more accurate means than the BSPMs for differentiating between the accessory pathways or the sites of other ectopic cardiac beats along the AV ring and in its neighboring regions.

Atrial Premature Complexes↗

The effects of unilateral stellate ganglion blockade on human cardiac function during rest and exercise.

INTRODUCTION: Left-sided stellate ganglion predominance has been proposed as a mechanism responsible for lethal ventricular arrhythmias, due to heterogenous ventricular repolarization. To determine the cardiovascular effects of such asymmetric sympathetic ganglion innervation in man, studies were performed in 15 patients undergoing unilateral stellate ganglion blockade for the management of chronic arm pain. METHODS AND RESULTS: Standard 12-lead ECGs, systemic blood pressure, body surface potential mapping, and radionuclide angiography were performed during rest and graded exercise before and after blockade. Successful unilateral blockade was accomplished in 13 of the patients, 11 of whom had right-sided blockade and two left-sided blockade. No significant changes due to blockade of stellate ganglia, including QT intervals, were detected during rest or graded exercise in standard ECGs. No cardiac rhythm disturbances occurred in these states. Body surface potential maps and arterial blood pressure were similar during resting supine and upright positions, as well as immediately after exercise before and after blockade. Unilateral ganglionic blockade did not modify resting or exercise cardiac ejection fractions. CONCLUSION: Unilateral stellate blockade in man does not induce untoward cardiovascular effects during rest or exercise.

Adult↗

Implantable cardioverter-defibrillator patch shunting effect manifestations on the body surface map.

The purpose of this study was to demonstrate the known shunting effect of implantable cardioverter-defibrillator patches using the body surface map. Using a 32-lead body surface mapping computer system (Corazonix Predictor, Oklahoma City, OK) we recorded body surface potential maps both prior to and 7 days after implantable cardioverter-defibrillator patch placement in a patient during right ventricular pacing at 60 beats/minute. This study demonstrated a marked shunting effect from the patches to the body surface during electrical depolarization as well as repolarization. In addition, patch orientation and configuration were evaluated by this method. Specifically, the waveforms were affected by the presence of insulator patches. This may be an important explanation, which may prevent appropriate transthoracic defibrillation using standard configurations. Further research is necessary to elucidate the true effect of the depolarization and repolarization waveform and defibrillator patches.

Aged↗

Surface reflections of cardiac excitation and the assessment of infarct volume in dogs. A comparison of methods.

Ventricular depolarization was analyzed in intact dogs by simultaneously recording body surface potential maps, McFee axial vectorcardiograms, and a 5 X 4 lead precordial grid of QRS complexes. The purpose of this study was to compare the effectiveness of subtraction approaches, using the simultaneously acquired data. The totally closed chest approach avoided the problem of volume conductor alteration by thoracotomy. Infarct volume was calculated morphologically from measurements of serial ventricular sections. The maximal correlation with anatomic infarct size using the precordial QRS grid approach was 0.51, using cumulative difference data between 1 and 38 msec when the postinfarction grid was substracted from the preinfarction grid. A correlation coefficient of 0.80 was achieved using the numerically integrated data between 1 and 31 msec from the vectorcardiogram, and the body surface potential map achieved a correlation coefficient above 0.88 when the electrical difference of msec 16 was used. These data suggest that estimates of infarct size from selected surface reflections of the activation process are feasible if some sort of preinfarction control data are available. Caution must be exercised to avoid inclusion of electrical effects late in the activation process which contain contamination by highly variable alterations in the excitation sequence due to delayed conduction or alteration in conduction pathway in or near the infarct zone.

Action Potentials↗

[ST-T isointegral map].

In this paper, clinical application of isointegral analysis on body surface potential maps during ST-T segment was reviewed. ST-T integral, which was defined as the time integral value during ST-T segment, gives an important information about the abnormalities in ventricular recovery and reflects the recovery sequence. Post-exercise recording of the ST-T isointegral maps well reflects the presence and the location of myocardial ischemia in patients with 1) angina pectoris and 2) previous myocardial infarction. The combined analysis of QRST and ST-T isointegral map in left ventricular hypertrophy can determine, whether the ST-T abnormality suggests the myocardial damages or not.

Body Surface Potential Mapping↗

Vulnerability to ventricular arrhythmia: assessment by mapping of body surface potential.

It is now well established that the vulnerability of the ventricular myocardium to repetitive dysrhythm increases in the presence of greater than normal disparity local recovery times. Local recovery is reflected in the electrocardiographic waveform as an area of the ventricular deflection (QRST time integral), and thus disparate ventricular recovery may be manifested in the body surface distribution of this quality. To assess this possibility, we obtained simultaneous 120-lead electrocardiograms from both the anterior and posterior torso in 140 subjects (ages 8 to 75) grouped as follows: group A, 97 normal subjects; group B, 16 patients resuscitated from ventricular fibrillation or sustained ventricular tachycardia; and group C, 27 patients 6 to 12 months after myocardial infarction but without clinically significant arrhythmia. In each subject, the QRST integral was evaluated for each lead and isointegral contour maps were plotted. A score was assigned to each map, based on the number of extrema; each maximum or minimum scored one point, with the exception of simultaneously occurring anterior and posterior minima on the right shoulder (frequently occurring in normal subjects), which scored together only one point. All but one group A subject had dipolar QRST integral maps (mean +/- SD score 2.11 +/- 0.2). Conversely, 10 of 16 (62.5%) group B patients had scores of 3 or more (mean 3.16 +/- 1.08; p less than .01 vs group A). Group C patients had intermediate values, with eight of 27 (29.6%) scoring 3 or more (mean 2.46 +/- 83); this was less than in group B (p less than .01), but more (p less than .05) than in group A.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

Characterization of the spatial distribution of late ventricular potentials by body surface mapping in patients with ventricular tachycardia.

Low-level activity at the end of the QRS complex was analyzed from 63 thoracic leads in 15 normal subjects and in 21 patients with ventricular tachycardia (VT). The latter had old myocardial infarction and no conduction disturbances and had not been receiving antiarrhythmic drugs. In both normal subjects and patients with VT, isopotential maps of the time-averaged and filtered (25 Hz high-pass) electrocardiograms during the terminal portion of the QRS were dipolar, i.e., they showed single positive and negative regions. For patients with VT, the extrema were either distant, with one over the precordial area and the other over the back, or close together in the precordial region. In 10 patients, maps recorded after administration of antiarrhythmic drugs remained the same while QRS duration was prolonged. In six patients, maps recorded before antiarrhythmic surgery showed distant extrema for septal or posterobasal VT sites of origin and close extrema for anterior or posteroapical sites. Generally, QRS duration was reduced and maps were modified after surgery. Late potentials can be well detected with only three orthogonal leads because their distributions are dipolar, but maps provide additional information about their distribution, which may be related to conduction delay sites and possibly to VT sites of origin. Sources near the torso surface would produce close extrema, whereas deeper sources would produce distant extrema.

Adult↗

The role of initial minimum potentials on body surface maps in predicting the site of accessory pathways in patients with Wolff-Parkinson-White syndrome.

Forty-one patients (23 men and 18 women, ages 20 to 66 years) with Wolff-Parkinson-White syndrome were studied with isopotential body surface maps during sinus rhythm to find the most reliable index for predicting the sites of single accessory pathways. The sites predicted by surface maps were compared with those confirmed by multicatheter electrophysiologic study or in the course of surgical operation. Location of the initial minimum by a time criterion, 40 msec after onset of the QRS complex, was not reliable enough for prediction in patients with the small delta wave on their electrocardiograms, because ventricular activation via the normal conduction pathway significantly influenced the location of the minimum. Location of the minimum by an amplitude criterion, -0.15 mV or slightly deeper, was influenced minimally by fusion of ventricular activation, the patient's body size, or age and corresponded well to the site of the accessory pathway in 36 of 41 patients. Those minima appeared on circumscribed areas of the map in accordance with the anatomic subdivisions of the atrioventricular ring. Thus location of the minimum by the amplitude criterion was an excellent index for predicting the site of the accessory pathway, regardless of the degree of ventricular fusion. These amplitude-based map features suggest that nonstandard electrocardiograms recorded from selected positions on the body surface can be used as accurate predictors of the sites of accessory pathways.

Adult↗

Anterior infarctional changes occurring during mid and late ventricular activation detectable by surface mapping techniques.

This is a comparative body surface potential map study of 26 patients with a recent acute anterior myocardial infarction. The mean plus or minus two standard deviations (+/- 2 SD) for the voltage distribution was established at 5 msec intervals throughout the cardiac cycle in 30 normal subjects at each of 142 recording sites. Instances in which a patient's potential distribution fell outside the normal range were analyzed as to location, duration and intensity against the expected time course of ventricular activation. Only four patients had departures from the normal distribution confined to the Q time zone. Twenty patients had not only Q time zone abnormalities, but had areas of both positivity and negativity exceeding +/- 2 SD, which occurred well after 30 msec. Two patients with clearly documented diagnostic Q waves during the first few days of hospitalization had lost these findings by the date of body surface mapping. They did retain, however, departure map findings demonstrating significant abnormalities occurring between 30 and 60 msec after onset of ventricular activation. These changes occurring in the mid and late time zones of the activation sequence are not detectable by conventional electrocardiography or vectorcardiography, yet present a strikingly apparent finding by this technique of analysis and display.

Action Potentials↗