Body Surface Mapping System Research Articles

Significance of left posterior extension of early repolarization in patients with J-wave syndrome

J waves in the inferior or lateral leads are characteristic electrocardiographic (ECG) changes in patients with early repolarizationsyndrome (ERS). However, the presence of J waves in the left posterior region has not yet been evaluated. The purpose of this study was to clarify the significance of J waves in the posterior left ventricle using leads V7-V9 and a body surface mapping (BSM) system. Forty patients diagnosed with ERS were included. All patients exhibited J waves in either the contiguous inferior, lateral, or posterior leads. We evaluated the incidence of J waves in the inferolateral and posterior leads using a 15-lead ECG with synthesized V7-V9 and an 87-lead BSM. Additionally, we assessed the arrhythmogenicity of the posterior regions based on the morphology ofthe premature ventricular complexes (PVCs) associated with ventricularfibrillation (VF). J waves were observed in the lateral, inferior, and posterior leads of 26 (65%), 31 (78%), and 39 (97%) patients, respectively. J waves were found only in the posterior leads of 5 patients. BSM was evaluated in 9 patients, all of whom exhibited a positive area on the posterior region. PVCs associated with VF were recorded in 5 patients. Among patients with inferolateral and posterior J waves, all except 1 patient who displayed left bundle branch block morphology showed PVCs originating from the posterior left ventricular region. Posterior J waves are common in ERS patients. This abnormality can be detected using leads V7-V9 and the BSM system and may be associated with arrhythmogenesis.

Body Surface Mapping system - a potential diagnostic tool for unmasking delayed right ventricular epicardial activation in ARVC patients and phenotype-negative gene-carriers

Abstract Funding Acknowledgements Type of funding sources: Private grant(s) and/or Sponsorship. Main funding source(s): Selanders stiftelsen Background Life-threatening ventricular arrhythmias can occur at any stages of ARVC – the detection of early manifestations of the disease may have prognostic implications. Purpose The purpose was to explore the usefulness of a 252-leads noninvasive Body Surface Mapping (BSM) system for the detection of delayed epicardial activation in ARVC patients and phenotype-negative gene-carriers (GC). Methods Twelve patients with ARVC, 20 GC and 8 genotype and phenotype negative family members served as controls (C) were included. 12-lead ECG, signal-averaged-electrocardiogram, echocardiography, 252-lead BSM recordings and thoracic CT scan were performed in all subjects. The noninvasively reconstructed epicardial signals of the right ventricle (RV) were analysed using the Activation Time Editing tool of the BSM system. Local depolarisation was defined as the steepest negative dV/dt of the local epicardial signal. The time from the start of RV epicardial signals to the earliest local depolarisation (ELD) and to the latest local depolarisation (LLD), were measured for the whole RV and separately for the anterior free wall (AW) and inferior wall (IW). The duration of the activation, defined as LLD-ELD, was calculated for AW, IW and the whole RV. Results The ELDs was similar in all study groups whereas the LLD in the IW and whole RV was significantly longer among ARVC patients compared to C. Although the activation durations in the AW and IW did not differ between the groups, the activation duration of the whole RV was significantly longer in ARVC patients. A LLD cut off of 81ms in RV and an activation duration cut off of 49msec in RV discriminated ARVC patients from C with highest sensitivity and specificity. Based on these cut-offs, 35% of GC group had longer LLD times and 70 % had longer activation duration (figure 1). Conclusions ARVC patients as well as the majority of GC demonstrated prolonged LLD and/or activation duration times in RV compared to C, suggesting that the 252-leads noninvasive BSM system may be a useful tool for early detection of delayed RV epicardial activations. Larger studies are required to confirm our results.

Abnormal patterns of noninvasively reconstructed epicardial signals and right ventricle activations in patients with Arrhythmogenic Right Ventricular Cardiomyopathy and gene-carriers

Abstract Funding Acknowledgements Type of funding sources: Private grant(s) and/or Sponsorship. Main funding source(s): Selanders stiftelsen Background ARVC primarily affects the epicardium resulting in electrical abnormalities and ventricular arrhythmias that can appear before its clinical correlate with structural changes, which is often hard to evaluate non-invasively. Purpose To evaluate whether a 252-leads Body Surface Mapping (BSM) system can reveal RV activation abnormalities by non-invasively reconstructed epicardial signals of the right ventricle (RV) in ARVC patients and non-affected gene-carriers (GC). Methods Twelve ARVC patients, 20 GC and 8 genotype-negative family members serving as controls (C) underwent 12-leads ECG, signal-average ECG, echocardiography and 10 minutes recording with a non-invasive 252-leads BSM System. A thoracic CT scan was required for the construction of anatomically adapted epicardial signals. The reconstructed epicardial signals were studied using the Activation Time Editing tool of the BSM system. The morphologies of QRS complexes and T waves in predefined areas, including anterior free wall (AW), apex, RV base, RV inferior wall (IW) and RVOT, were studied. The pattern of RV activation was also studied. Results In controls the QRS morphology showed a rS pattern in most RV regions except for in the RVOT showing a rSr’ pattern and the IW where the signals had either a rS or rSr’ morphology. The T waves were positive in all areas, except for in the RV basis and in the IW, where 6 and 3 controls, respectively, had negative/isoelectric T waves. The earliest activation of the RV occurred in the anterior paraseptal region in 7/8 C, while the latest activation occurred in RVOT in 7/8 C (figure 1). ARVC patients also more commonly had a rS pattern in all regions except for in the RVOT (rSr’ pattern) and IW (rS or rSr’ pattern), but had a higher variation in the QRS morphology. Fractionated signals were seen in 7/12 cases. The epicardial T waves were negative/ isoelectric in 11/12 cases. Even though the RV activation more commonly started in the anterior paraseptal region and ended at the RVOT, 58% of ARVC patients had different areas of earliest and/or latest activation (figure 1). GC had the same distribution of QRS morphology as in C, but up to 75% of the T waves were negative or isoelectric, particularly in the RV base and IW. Fractionated signals were seen in two cases. In 60% of GC the earliest and/or latest activation location differed from those see in C. Conclusions Using the 252-leads BSM system, distinct characteristics of reconstructed epicardial signals and RV activation patterns were detected in ARVC patients, distinguishing them from C. The observation that similar changes were observed in epicardial signals and activation patterns among GC suggest that the 252-leads BSM system may be useful as a non-invasive tool evaluating genetically predisposed subjects for early manifestations of the disease.

PO-714-02 RIGHT VENTRICULAR EPICARDIAL ACTIVATION DELAY IN ARRHYTHMOGENIC RIGHT VENTRICULAR CARDIOMYOPATHY PATIENTS AND GENE CARRIERS UNMASKED BY BODY SURFACE MAPPING SYSTEM

ARVC is afflicted by life-threatening ventricular arrhythmias even before the manifestations of right ventricular (RV) structural abnormalities. Therefore, an early diagnosis is crucial albeit still challenging. To investigate whether a 252-leads noninvasive Body Surface Mapping (BSM) system could detect epicardial conduction delays in ARVC patients and unaffected gene-carrying family members (GC). Twelve ARVC patients, 20 GC and 8 gene-negative family members serving as controls (C) underwent 12-lead ECG, signal-averaged-electrocardiogram (SAECG), echocardiography, 252-lead BSM recordings and thoracic CT scan. Reconstructed epicardial signals were analysed using the Activation Time Editing tool of the activation map. Local depolarisation was defined as the steepest negative dV/dt of the unipolar local epicardial signal. The time from the earliest start of RV epicardial activation to the earliest local depolarisation (ELD) and to the latest local depolarisation (LLD), respectively, were measured separately for the RV free wall (RFW), inferior wall (RIW) and the whole RV. The activation duration, defined as LLD-ELD, was calculated for RFW, RIW and the whole RV. The ELD was similar in all study groups whereas the LLD in the RFW and whole RV was significantly longer among ARVC patients compared to C, but similar in the RIW. Similarly, the activation durations in the RFW and whole RV were significantly longer in ARVC patients but did not differ in the RIW among the groups. A 43ms LLD cut off in the RV and 20 msec activation duration cut off in the RV discriminated ARVC patients from C with highest sensitivity and specificity. Based on these cut-offs, 40% of GC group had longer LLD times and 20 % had also longer activation duration (figure 1). ARVC patients demonstrated prolonged LLD and activation duration times in the RFW and whole RV compared to C. The finding that prolonged conductions could be demonstrated in the GC group as well suggest that the 252-leads noninvasive BSM system may be used as screening tool for the detection of early delays of the RV epicardial activation. Larger studies are required to confirm our results.View Large Image Figure ViewerDownload Hi-res image Download (PPT)

Repolarization abnormalities unmasked with a 252‐lead BSM system in patients with ARVC and healthy gene carriers

Background: Diagnosing arrhythmogenic right ventricular cardiomyopathy (ARVC) at an early stage can be challenging even after ECG recording and a combination of several imaging techniques. The purpose of this study was to explore if a body surface mapping (BSM) system with 252‐leads could identify repolarization abnormalities and thereby diagnose early stages of ARVC.Methods: ARVC patients, gene carriers without signs of ARVC and controls underwent a 12‐lead resting ECG, signal‐averaged ECG, echocardiography, 24‐hours Holter monitoring, and BSM with electrocardiographic imaging (ECGI). All 252‐leads, divided into four quadrants of the vest, were analyzed regarding concordances between T wave polarity and QRS main vector.Results: Of 40 patients included there were 12 ARVC patients, 20 gene carriers, and 8 controls. The ARVC patients had two different repolarization patterns, one with more pronounced negative T waves at the lower left panel and another with mixed changes that clearly differed from the controls, all of whom had a normal 12 lead ECGs and consistent repolarization patterns on their BSM recordings. The patterns observed in ARVC patients were also present in 5/20 (25%) gene carriers, three of whom had normal resting ECG. A novel repolarization index successfully detected all ARVC patients and 88% of gene carriers with pathologic repolarization pattern.Conclusions: The finding that abnormal repolarization patterns could be unmasked by BSM in 25% of healthy gene carriers, suggests that it may potentially be a useful tool for identifying early manifestations of ARVC. Further and larger studies are warranted to assess its diagnostic accuracy.

QRS Complex Detection and Measurement Algorithms for Multichannel ECGs in Cardiac Resynchronization Therapy Patients.

We developed an automated approach for QRS complex detection and QRS duration (QRSd) measurement that can effectively analyze multichannel electrocardiograms (MECGs) acquired during abnormal conduction and pacing in heart failure and cardiac resynchronization therapy (CRT) patients to enable the use of MECGs to characterize cardiac activation in such patients. The algorithms use MECGs acquired with a custom 53-electrode investigational body surface mapping system and were validated using previously collected data from 58 CRT patients. An expert cohort analyzed the same data to determine algorithm accuracy and error. The algorithms: 1) detect QRS complexes; 2) identify complexes of the most prevalent morphology and morphologic outliers; and 3) determine the array-specific (i.e., anterior and posterior) and global QRS complex onsets, offsets, and durations for the detected complexes. The QRS complex detection algorithm had a positive predictivity and sensitivity of ≥96% for complex detection and classification. The absolute QRSd error was 17 ± 14 ms, or 12%, for array-specific QRSd and 12 ± 10 ms, or 8%, for global QRSd. The absolute global QRSd error (12 ms) was less than the interobserver variation in that measurement (15 ± 10 ms). The sensitivity, positive predictivity, and error of the algorithms were similar to the values reported for current state-of-the-art algorithms designed for and limited to simpler data sets and conduction patterns and within the variation found in clinical 12-lead ECG QRSd measurement techniques. These new algorithms permit accurate, real-time analysis of QRS complex features in MECGs in patients with conduction disorders and/or pacing.

P5513Rotor distribution and stability in atrial fibrillation using a non invasive body-surface mapping system

P5513Rotor distribution and stability in atrial fibrillation using a non invasive body-surface mapping system

P291Rotor distribution and stability in atrial fibrillation using a non invasive body-surface mapping system

P291Rotor distribution and stability in atrial fibrillation using a non invasive body-surface mapping system

177-01: Use of a Novel Noninvasive ECG Body Surface Mapping System to Identify Line of Block and Optimal CRT Setting

177-01: Use of a Novel Noninvasive ECG Body Surface Mapping System to Identify Line of Block and Optimal CRT Setting

136-25: Rotor Distribution and stability in Atrial Fibrillation Using a Non invasive Body-Surface Mapping System

136-25: Rotor Distribution and stability in Atrial Fibrillation Using a Non invasive Body-Surface Mapping System

Detection of regional myocardial ischaemia by a novel 80-electrode body surface Delta map in patients presenting to the emergency department with cardiac-sounding chest pain

Presentation with acute chest pain is common, but the conventional 12-lead ECG has limitations in the detection of regional myocardial ischaemia. The previously described method of the body surface mapping system (BSM) Delta map, derived from an 80-electrode BSM, as well as a novel parameter total ischaemic burden (IB), may offer improved diagnostic sensitivity and specificity in patients with myocardial ischaemia. The feasibility of using the novel BSM Delta map technique, and IB, for transient regional myocardial ischaemia was assessed in comparison with 12-lead ECG in 49 patients presenting to the emergency department (ED) with cardiac-sounding chest pain. The sensitivity and specificity of 12-lead ECG for the diagnosis of acute coronary syndrome (ACS) was 67 and 55%, respectively, positive likelihood ratio (+LR) 1.52 [95% confidence interval (CI) 0.86, 2.70] and negative likelihood ratio (-LR) 0.58 [95% CI 0.30, 1.12]. The sensitivity and specificity of the BSM Delta map for the diagnosis of ACS was 71 and 78%, +LR 3.19 [95% CI 1.31, 7.80], -LR 0.37 [95% CI 0.20, 0.68]. There was a significantly positive correlation between peak troponin-I concentration and IB (r=0.437; P<0.002). This pilot study confirms the feasibility of using the Delta map for the diagnosis of ACS in patients presenting to the ED with cardiac-sounding chest pain and suggests that it has promising diagnostic accuracy and has superior sensitivity and specificity to the 12-lead ECG. The novel parameter of IB shows a significant correlation with troponin-I and is a promising tool for describing the extent of ischaemia. The use of the BSM Delta map in the ED setting could improve the diagnosis of clinically important ischaemic heart disease and furthermore presents the result in an intuitive manner, requiring little specialist experience. Further larger scale study is now warranted.

Detection of transient regional myocardial ischemia using body surface Delta map in patients referred for myocardial perfusion imaging—A pilot study

BackgroundThe diagnosis of transient regional myocardial ischemia (TRMI) in patients presenting with stable chest pain is a challenge. Exercise Tolerance Test (ETT) is no longer recommended in most cases due to its flaws. Alternative tests are more expensive and less readily available. The BSM Delta map is an intuitive color display of digitally subtracted ST-segment shift derived from two 80-electrode BSM recordings at baseline and at peak stress, and has shown promise as a tool for detection of TRMI. ObjectivesThe purpose of this pilot study was to assess the feasibility of BSM Delta map as a tool to detect TRMI using dobutamine stress ECG gated single-photon emission computed tomography myocardial perfusion imaging (MPI) as a reference. MethodForty consecutive patients were recruited who were referred for MPI with a history of angina-like symptoms. The BSM Delta map was derived from two 80-electrode body surface mapping system recordings carried out simultaneously with MPI at (a) baseline and (b) peak dobutamine stress. Standard 12-lead ECGs were also recorded at the same time points. ResultsThe mean patient age was 68±7.1years, and 52% (21/40) were female. Using MPI as the reference the sensitivity of BSM Delta map was 82% (9/11) and specificity was 86% (25/29) (95% CI 0.688–0.992), positive likelihood ratio 5.93 (95% CI 2.29–15), negative likelihood ratio 0.21 (95% CI 0.06–0.75). The sensitive of the 12-lead ECG was 36% (4/11) and specificity was 76% (22/29) (95% CI 0.356–0.767), positive likelihood ratio 1.51 (95% CI 0.55–4.15), negative likelihood ratio 0.84 (95% CI 0.51–1.37). BSM Delta map is more sensitive and specific (McNemar's chi-square test p=0.03 (95% CI, 0.448–0.924). The PPV and NPV for BSM Delta map were 69% (9/13) and 93% (25/27) respectively, compared with 36% (4/11) and 76% (22/29) for 12-lead ECG. ConclusionThis pilot study confirms the feasibility of using Delta map in this context and suggests that it has promising diagnostic accuracy and is superior to the 12-lead ECG. It could potentially represent a clinically suitable screening tool for TRMI in patients presenting with stable chest pain, since it is near patient and requires little specialist training for acquisition and interpretation. A larger clinical study is now required.

Site Specific Effects of Quinidine on Repolarization Abnormalities in Patiens with Brugada Type ECG by Using Body Surface Mapping System

Site Specific Effects of Quinidine on Repolarization Abnormalities in Patiens with Brugada Type ECG by Using Body Surface Mapping System

Performance of a body surface mapping system using emergency physician real-time interpretation

Objective We compared the performance characteristics of the 12-lead electrocardiography (ECG) with body surface mapping (BSM) in patients presenting for evaluation of symptoms suggestive of acute coronary syndromes. Methods The diagnostic test characteristics (sensitivity, specificity, likelihood ratios, and predictive values) for 12-lead ECG and BSM were computed using 3 different criterion standards. Results Of the 150 patients enrolled, 19 were positive for acute coronary syndromes using the criterion standard of cardiac troponin T >0.1 ng/mL, percutaneous coronary intervention, more than 70% stenosis, abnormal noninvasive testing, and coronary artery bypass graft. Changes not known to be old on ECG and BSM had sensitivities of 10.5 (95% confidence interval [CI 95], 1.8-34.5) and 15.8 (CI 95, 4.2-40.5), and specificities of 90.1 (CI 95, 83.3-94.4) and 86.3 (CI 95, 78.9-91.4), respectively. Conclusion In this emergency department population, both the BSM and the 12-lead ECG exhibited similar test characteristics.

PRIME ECG improves emergency department diagnosis and management in moderate- to high-risk unstable angina/non–ST elevation myocardial infarction patients

Study objectives: The 12-lead ECG is the current criterion standard for the diagnosis and early evaluation of patients with chest pain. A significant proportion of patients with unstable angina (UA) or non–ST elevation myocardial infarction (NSTEMI) do not manifest ischemic changes on the 12-lead ECG. The recently developed PRIME 80-lead ECG Body Surface Mapping System (Meridian) may be clinically useful in the diagnosis and management of UA/NSTEMI. Recent studies have looked at this 80-lead ECG to see if sensitivity and specificity for acute coronary syndromes could improve with this instrument. Some researchers have shown in 53 patients with enzymatically confirmed acute myocardial infarction (AMI) that the 80-lead ECG doubled the diagnostic sensitivity of AMI compared with 12-lead ECG. Other researchers compared 18 patients with left bundle-branch block and enzymatically confirmed AMI and showed that the sensitivity of 80-lead ECG for early detection of AMI was double that of the 12-lead ECG. The objective of this study is to determine whether 80-lead ECG can improve early detection of ischemic changes in emergency department (ED) patients with UA/NSTEMI over 12-lead ECG. Our hypothesis is that the PRIME ECG body map compared with the 12-lead ECG improves the diagnosis and management of ED patients with acute coronary syndromes. Methods: This is a prospective study performed on a convenience sample of suspected moderate- to high-risk UA/NSTEMI ED patients, defined as a Thrombolysis in Myocardial Infarction (TIMI) risk score of 3 or greater, positive biomarkers, or new (or not known to be old) ischemic ECG changes, who present within 12 hours of the most recent ischemic symptom. Enrolled patients had a 12-lead ECG and also a PRIME 80-lead ECG performed oof 4), blinded to patient data other than medical history and physical examination, interpreted the ECG and PRIME for their effect on patient disposition and therapy including the probability of AMI and cardiac care unit or cardiac step-down admission. The physicians recorded whether the PRIME ECG after evaluation of the 12-lead ECG changed either the patient therapy or disposition. Outcomes were 1-month major adverse coronary events (MACEs), defined as death, AMI, percutaneous transluminal coronary angioplasty or stent, coronary artery bypass graft surgery (CABG), or coronary stenosis greater than 50%. Data were analyzed using descriptive statistics. Results: Thirty-four patients have been enrolled to date. Sixty-eight percent of those enrolled had 1 of the prespecific MACEs, (32% NSTEMI, 41% PCI, 18% CABG, 17% >50% stenosis). The PRIME ECG added additional information to the 12-lead ECG in 59% (20/34) of patients. The PRIME ECG changed ED disposition or therapy in 21% (7/34) of patients. Of the 13 patients for whom the PRIME ECG added additional data without changing management, 62% (8/13) had a MACE. Of the 7 patients for whom the PRIME ECG changed management, 86% (6/7) had a MACE. The 1 patient of the 7 without a MACE was post-CABG, had significant stenosis (80% to 100%) thought to be old, and was treated with aggressive therapy. Conclusion: The use of the PRIME ECG in moderate- to high-risk UA/NSTEMI patients improved the ED diagnosis and management.

A novel method for the detection of transient myocardial ischaemia using body surface electrocardiac mapping

Background: The limitations of the 12-lead ECG in the detection of myocardial ischaemia are well known. This study sought to test the hypothesis that a Body Surface Mapping (BSM) system can detect and localise the transient regional ischaemia induced by elective percutaneous coronary intervention (PCI) in patients with stable angina. Methods and Results: 25 patients undergoing elective single vessel PCI were studied: 11 with RCA lesions, 9 with LAD lesions and 5 with circumflex lesions. Patients had BSM readings every 30 s following the inflation of a dilating balloon in the target vessel for 1 min. BSMs were analysed for ST segment change at 60 ms after the J point (ST60). Peak ST changes were analysed and colour map reconstruction made. Characteristic ST segment changes in each arterial domain were observed following inflation of the balloon. Maximal change occurred in a standard V lead on only 2/46 occasions. Statistically significant rapid rise and fall of ST 60 readings were observed indicating the onset recovery and location of the transient ischaemia. A novel method for the presentation of colour map reconstruction that removes baseline noise has been developed. Conclusions: These data confirm the hypothesis that this BSM system can detect and display transient myocardial ischaemia. BSM may represent a novel clinical tool for the assessment of clinical ischaemia.

Body Surface Mapping

Recent advances in biomarkers have improved the evaluation of patients with acute chest pain, but current critical care pathways may still lead to important delays in early diagnosis and, hence, treatment of acute myocardial infarction (AMI). Electrocardiographic changes may occur within seconds of an ischemic insult, but the conventional 12-lead electrocardiogram (ECG) typically has only 50% to 60% sensitivity for diagnosis of AMI. Recording of multiple ECGs over a larger thoracic surface area, including the right ventricular, high left lateral, and posterior regions, by body surface mapping (BSM) has been made feasible in the setting of acute coronary syndromes by novel developments in electrode technology and simultaneous multichannel ECG data acquisition. Clinical studies of an Food and Drug Adminstration-approved BSM system (PRIME-ECG) have demonstrated improved early diagnosis of AMI in patients without 12-lead ST elevation and improved detection of right ventricular or posterior involvement in ST elevation MI. The improved diagnostic sensitivity compared with the conventional 12-lead ECG coupled with the potential reduction of delay to diagnosis compared with biomarkers suggest that BSM may have an important role as part of a chest pain critical care pathway for evaluation of patients with ischemic type chest pain.

Development of an interactive computer-guided method for radiofrequency catheter ablation of ventricular tachycardia.

The purpose of this study was to develop a simple computer-guided approach to localizing ventricular tachycardias during ventricular mapping. Six patients with sustained monomorphic ventricular tachycardia were connected to a 32-lead computer body surface mapping system. Isoarea maps of induced ventricular tachycardia were recorded. Then a pacing probe was placed in either the right or left ventricle, and maps were generated from a variety of sites. Differences between ventricular tachycardia and pace map maxima X, Y coordinates were utilized to guide catheter manipulation and localization. In 6 of 6 patients (100%) this method appeared to provide a systematic approach to ventricular tachycardia localization. Computer-generated correlations as well as the X, Y coordinates of the QRS isoarea maxima were used to determine proximity to the ventricular tachycardia foci and direct catheter manipulation. In the next three patients this method was applied prospectively to help guide catheter manipulation during ventricular tachycardia (two right ventricular outflow tract tachycardias, and one left ventricular tachycardia). After a mean of 4.0 +/- 1.7 radiofrequency applications, ventricular tachycardia was no longer inducible, and at 7 +/- 0 months follow-up there have been no arrhythmia recurrences. We conclude that online computerized body surface mapping can assist in localizing ventricular tachycardia. Differences in maxima during pace maps and in-situ ventricular tachycardias can help with catheter manipulation as well as with more precise identification of focal tachycardias. This technique appears to hold the promise of a simple computer-guided method that may facilitate radiofrequency catheter ablation.

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.

Signal-averaged body surface mapping for the assessment of low-amplitude potentials: Detailed maps during early ventricular activation in normal subjects

Body surface isopotential maps around early ventricular activation were investigated in 30 normal subjects by the use of the authors' signal-averaged body surface mapping system. The number of beats averaged was 96–154 (mean, 127). Two distinct patterns were recognized in the appearance of a maximum at the onset of ventricular activation: the maximum in the first type (n = 16) was located on the right anterior chest; the maximum in the second type (n = 14) was on the central or left anterior chest. The site of the earliest ventricular activation was considered to be different in each of these types. During early ventricular activation, 25 subjects (83%) had two minima: one was on the left lateral chest and the other was on the left back. The two minima probably reflect two different receding activation fronts in the ventricles. The data in the present study are important to the understanding of the early ventricular activation process, as well as the diagnosis of heart diseases in which this process is disturbed.