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Background: Health-care organizations around the world are striving to achieve transformational performance improvement, often through adopting process improvement methodologies such as lean management. Indeed, lean management has been implemented in hospitals in many countries. But despite a shared methodology and the potential benefit of benchmarking lean implementation and its effects on hospital performance, cross-national lean benchmarking is rare. Health-care organizations in different countries operate in very different contexts, including different health-care system models, and these differences may be perceived as limiting the ability of improvers to benchmark lean implementation and related organizational performance. However, no empirical research is available on the international relevance and applicability of lean implementation and hospital performance measures. To begin understanding the opportunities and limitations related to cross-national benchmarking of lean in hospitals, we conducted a cross-national case study of the relevance and applicability of measures of lean implementation in hospitals and hospital performance.Methods: We report an exploratory case study of the relevance of lean implementation measures and the applicability of hospital performance measures using quantitative comparisons of data from Hospital District of Helsinki and Uusimaa (HUS) Helsinki University Hospital in Finland and a sample of 75 large academic hospitals in the USA.Results: The relevance of lean-related measures was high across the two countries: almost 90% of the items developed for a US survey were relevant and available from HUS. A majority of the US-based measures for financial performance (66.7%), service provision/utilization (100.0%) and service provision/care processes (60.0%) were available from HUS. Differences in patient satisfaction measures prevented comparisons between HUS and the USA. Of 18 clinical outcome measures, only four (22%) were not comparable. Clinical outcome measures were less affected by the differences in health-care system models than measures related to service provision and financial performance.Conclusions: Lean implementation measures are highly relevant in health-care organizations operating in the USA and Finland, as is the applicability of a variety of performance improvement measures. Cross-national benchmarking in lean healthcare is feasible, but a careful assessment of contextual factors, including the health-care system model, and their impact on the applicability and relevance of chosen benchmarking measures is necessary. The differences between the US and Finnish health-care system models is most clearly reflected in financial performance measures and care process measures. [ABSTRACT FROM AUTHOR]

Background: Many infants under 4 months suffer from infantile colic. Infants with colic cry a lot, appear to be in pain, and it is difficult to sooth them. Colic is a painful condition for the infant and very stressful to parents. Parents in Finland get advice to try reflexology treatment for their infant, but there are no studies in Finland to support this advice. Aim: The aim of the pilot study was to treat infants with reflexology and find out parents' experiences of the effects of the treatment on colic symptoms and parental stress. Method: A total of 33 parents of 35 infants diagnosed with colic participated to the pilot study. Three certified reflexologists with health care education background and extensive experience in infant reflexology were trained to give the reflexology treatment in a standardised manner. They treated each infant 3–4 times. The whole body reflexology treatment session consisted of gentle pressure treatment of soles and feet, hands, head, face, ears, back, neck and whole stomach area. One treatment session lasted about 20–30 minutes, and treatments were delivered within 8–12 days. The data were collected from the parents with semi‐structured questionnaires. Results: The series of the treatments helped reduce the suffering of all the babies with infant colic. The colic symptoms disappeared on 43% of infants and decreased on the remaining 57%. The parents reported having pleasant experiences with the treatment, regardless whether the colic symptoms disappeared or continued. Parents stated that the treatment reduced the most typical colic symptoms; infants' body tension, colic crying and restless movements, poor sleep quality and irregular bowel movements. Conclusions: Reflexology treatment seems to be a safe and effective way to treat infants with colic when conducted by a health care professional with reflexology training and experience. [ABSTRACT FROM AUTHOR]

Abstract: Background: Plasma B-type natriuretic peptide (BNP), as well as the N-terminal part of the prohormone (Nt-BNP), are frequently elevated in aortic valve stenosis (AS). Yet, their release from the heart into the circulation has never been directly studied in AS. Aim: To assess the release of Nt-BNP in AS with focus on the identification of its main determinants. Methods: We studied 49 adult patients undergoing preoperative cardiac catheterization for isolated AS. Blood was sampled from the aortic root and the coronary sinus for Nt-BNP determination by immunoassay. Results: The mean (±S.E.) transcardiac Nt-BNP step-up averaged 79±53 pmol/l in 11 control patients free of structural heart disease, 75±32 pmol/l in 31 AS patients free of heart failure (HF), 236±62 pmol/l in 8 AS patients with diastolic HF (ejection fraction ≥50%, pulmonary wedge pressure >14 mm Hg) and 469±66 pmol/l in 7 AS patients with systolic HF (ejection fraction <50%, wedge pressure >14 mm Hg) (p<0.001). The transcardiac Nt-BNP gradient was independently associated with left ventricular (LV) end-diastolic pressure (β=0.47, p<0.001) and ejection fraction (β=−0.29, p<0.019) and with co-existent coronary artery disease (β=0.23, p=0.050). Conclusion: LV diastolic and systolic dysfunction along with coronary artery disease are likely to be the key determinants of cardiac Nt-BNP release in AS. The transcardiac Nt-BNP gradient increases on average three-fold with the development of diastolic HF and six-fold in systolic HF. [Copyright &y& Elsevier]

Abstract: Conventional electrocardiogram criteria for myocardial infarction (MI) rely on QRS features, but ST-T segment is also affected. We recorded body surface potential mapping in 24 patients with prior MI and in 24 controls. T-wave maximum amplitude and QRS and ST-T integrals were automatically determined. Old MI was verified by magnetic resonance imaging. ST-T integral and T-wave maximum amplitude outperformed QRS integral in detecting MI, with area under receiver operating characteristic curve of 94%, 95%, and 83%, respectively. ST-T integral performed better in non–Q-wave than Q-wave MI, with area under receiver operating characteristic curve of 97% and 92%, respectively. QRS integral correlated negatively with ST-T integral in patients with MI (r = −0.58, P < .001) and positively in controls (r = 0.45, P < .001). In conclusion, ST-T integral proved equal to QRS integral in old MI detection. Inclusion of ventricular repolarization phase and development of electrocardiographic analysis over larger chest area may improve the QRS-based diagnosis of old myocardial infarction. [Copyright &y& Elsevier]

Abstract: Prehospital thrombolysis for acute ST-elevation myocardial infarction (STEMI) has been shown to improve recovery from myocardial function. We describe prehospital thrombolytic treatment in two patients suffering from STEMI complicated by ventricular fibrillation (VF) on a passenger ship. The importance of a functioning Emergency Medical Service (EMS) system providing guidance for paramedical personnel is discussed briefly. Both our patients survived and returned back to normal life. It is concluded that EMS physician guided prehospital thrombolytic treatment may offer an important therapeutic option for nurses or paramedics in locations out of reach of ordinary EMS services. [Copyright &y& Elsevier]

Background: Delayed electrical activity necessary for re-entrant ventricular tachycardia (VT) is detectable noninvasively with high resolution techniques. We compared high resolution signal-averaged analysis of magnetocardiography (MCG), body surface potential mapping (BSPM), and orthogonal three-lead ECG (SA-ECG) in the identification of patients prone to VT after myocardial infarction (MI).Methods: Patients with remote myocardial infarction and cardiac dysfunction were studied, 22 with (VT group) and 22 without VT (control group). MCG with seven channels and BSPM with 63 and SA-ECG with three orthogonal leads were registered. After signal-averaging and highpass filtering, three time domain analysis (TDA) parameters describing late electrical activity were computed: QRS duration (QRSd), root mean square amplitude (RMS) of the last 40 ms of QRS, and the duration of the low-amplitude QRS end (LAS).Results: All parameters by each method were significantly different between the patients' groups. For example, LAS parameter in MCG was 59 (SD 22) ms in the VT group vs. 37 (SD 13) ms in controls (P < 0.001), 77 (SD 22) ms vs. 56 (SD 19) ms in BSPM (P = 0.002), and 60 (SD 24) ms vs. 39 (SD 22) ms in SA-ECG (P = 0.005). The combination of LAS parameter in MCG and SA-ECG resulted in improved performance in comparison to any single parameter with 95% sensitivity and 68% specificity.Conclusions: All three high resolution methods identified VT propensity among post-MI patients with cardiac dysfunction and between-method differences were small. Information in MCG and SA-ECG may be complementary and their combination could be of value in postinfarction arrhythmia risk assessment. [ABSTRACT FROM AUTHOR]

Objectives. In LQT1 subtype of inherited long QT syndrome, repolarization abnormalities originating from defective IKs render patients vulnerable to ventricular arrhythmia during sudden sympathetic activation. Experimental studies show lower IKs density and longer action potential duration in left (LV) than in right (RV) ventricle. We studied interventricular dispersion of repolarization in patients with IKs defect during autonomic tests. Design. We measured interventricular (difference of QT intervals between LV and RV type leads) and transmural electrocardiographic dispersion of repolarization from 25-lead electrocardiograms in nine asymptomatic KCNQ1 mutation carriers (LQT1) and eight controls during rest, Valsalva maneuver, mental stress, sustained handgrip and supine exercise. Results. LQT1 carriers showed increased interventricular dispersion of repolarization (13±9 ms vs. 4±4 ms, p=0.03) during all tests. Valsalva strain increased the difference between the study groups. In LQT1 carriers, interventricular dispersion of repolarization correlated weakly with electrocardiographic transmural dispersion of repolarization. Conclusions. Asymptomatic KCNQ1 mutation carriers exhibit increased and by abrupt sympathetic activation augmented interventricular difference in electrocardiographic repolarization times. Interventricular and transmural repolarization dispersion behave similarly in patients with IKs defect. [ABSTRACT FROM AUTHOR]

Abstract: Magnetocardiography (MCG) is a method complementary to electrocardiography (ECG). We examined recording and reproducibility of atrial depolarization signal by MCG. Multichannel MCG over anterior chest and orthogonal 3-lead ECG were recorded in 9 patients who had paroxysmal lone atrial fibrillation and in 10 healthy subjects in duplicate at least 1 week apart. Data were averaged using atrial wave template and high-pass filtered at 25, 40, and 60 Hz. Atrial signal duration with automatic detection of onset and offset and root mean square amplitudes of the last portion of atrial signal were determined. Coefficient of variation of atrial signal duration by MCG at 40 Hz was 3.3% and difference between the measurements was 3.5 milliseconds on average. The corresponding figures obtained by signal-averaged ECG (SAECG) were 6.1% and 6.9 milliseconds. Coefficient of variation for root mean square of the last 40 milliseconds of atrial signal were 16% in MCG and 17% in SAECG. Reproducibility was best at 40-Hz filter and similar in patients and healthy subjects. In conclusion, the reproducibility of atrial signal variables in MCG is adequate and somewhat better than in SAECG and equal in patients with lone atrial fibrillation and healthy subjects. Magnetocardiography seems to be a potentially valuable method to evaluate features of atrial depolarization in patient studies. [Copyright &y& Elsevier]

Time-domain late field and intra-QRS fragmentation parameters in magnetocardiography (MCG) identify patients prone to VT after myocardial infarction. This study investigated if they are related to slow ventricular conduction and affected by arrhythmia surgery. Twenty-two patients with old myocardial infarction undergoing map-guided subendocardial resection to treat sustained VT were included. Bipolar electrograms were recorded during operation using an epicardial jacket and endocardial balloon electrode array. The time from the QRS onset to the end of local ventricular excitation in each electrogram was measured during sinus rhythm. Multichannel MCG was recorded before and after operation and filtered QBS duration (QRSd), root mean square amplitude of the magnetic field strength during the last 40 ms of the QRS complex (RMS40) duration of the low amplitude signal < 300 fT (LAS300), fragmentation index M (M), and fragmentation score S (S) were determined. All patients had one or two VT foci localized and resected. MCG parameters correlated with time to the latest end of ventricular excitation; r = 0.45 for QRSd (P = 0.035), r = 0.64 for M (P = 0.001), and r = 0.73 for S (P < 0.001). The correlations were even better in patients with anterior infarction (e.g., r = 0.87 for QRSd, P < 0.001; r = 0.91 for M, P < 0.001). The operation reduced the abnormalities in MGG parameters and 20 of the 21 patients tested postoperatively became noninducible. MCG parameters indicating postinfarction arrhythmia propensity are related to delayed ventricular conduction. Abolition of the arrhythmia substrate reverses the abnormality of these parameters. [ABSTRACT FROM AUTHOR]

BACKGROUND AND AIM. Magnetocardiography (MCG) is a novel, non-contact mapping technique to record cardiac magnetic field. We evaluated MCG criteria for myocardial ischemia in stress testing. METHODS. Multichannel MCG over frontal chest was performed in 44 patients with coronary artery disease (CAD) and 26 healthy controls during supine bicycle exercise test. Of the 44 patients 16 had anterior, 15 posterior, and 13 inferior ischemia documented by coronary angiography and exercise thallium scintigraphy. ST amplitude, ST slope, T-wave amplitude, and ST-T integral were measured. The optimal sites for detecting the ischemiainduced changes on MCG were sought. The orientation of the magnetic field was also determined. RESULTS. The optimal sites for the decrease of ST slope, ST amplitude, T-wave amplitude, and ST-T integral were over the abdomen. The reciprocal increase of these parameters was found over the left parasternal area. The optimal sites were approximately the same for all patient groups. In single-vessel disease patients without previous myocardial infarction (MI), ST slope increase and ST elevation performed the best (area under the receiver operating characteristic curve 92% and 90%, respectively). In post-MI patients with triple-vessel disease the decrease of T-wave amplitude and ST slope performed the best (area under curve 91%, for both). The magnetic field orientation at ST segment performed equally well as the other ST parameters. In stepwise logistic regression analysis, by use of the presence of CAD as the dependent parameter, ST slope increase and ST peak gradient orientation entered the model. CONCLUSIONS: Various ST segment and T-wave parameters detect ischemia in MCG. ST amplitude performs especially well in non-MI patients with less severe CAD. In advanced CAD late development of T-wave amplitude might be more sensitive to ischemia than ST amplitude. [ABSTRACT FROM AUTHOR]

Introduction: Experimentally, both delayed ventricular conduction and nonhomogeneous ventricular repolarization contribute to reentrant arrhythmias. We tested the hypothesis that increased T wave dispersion is independent of delayed ventricular conduction associated with arrhythmia vulnerability in postmyocardial infarction (post-MI) patients. Methods and Results: We studied 32 post-MI patients with clinical or inducible monomorphic ventricular tachycardia (VT group), 28 post-MI patients without arrhythmias (MI group), and 13 healthy controls, using magnetocardiographic (MCG) mapping with signal averaging. Twelve-lead ECG was the reference. Filtered QRS duration (fQRS) and T wave peak to T wave end interval (TPE) were used as measures of ventricular conduction and nonhomogeneity in ventricular repolarization, respectively. In MCG, the VT group showed the longest fQRS (135 ± 34 msec vs 114 ± 22 msec in the MI group: P = 0.012). Mean TPE and maximum TPE in VT versus MI groups were 78 ± 9 msec versus 70 ± 6 msec (P < 0.001) and 117 ± 23 msec versus 104 ± 19 msec (P = 0.020), respectively. Maximum TPE did not correlate with fQRS in the VT group (r = 0.063; P = NS) but did correlate in the MI group (r = 0.396; P = 0.037). For identification of post-MI patients prone to VT, selection of cutoff values for fQRS > 140 msec and mean TPE >81 msec gave sensitivity and specificity of 41% and 89%, and 31% and 96%, respectively. Their combination increased sensitivity to 63% while maintaining 89% specificity. Conclusion: Post-MI patients susceptible to VT show increased T wave dispersion independent of delayed ventricular conduction. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate if magnetocardiographic (MCG) analysis of cardiac micropotentials within the QRS complex can identity patients prone to ventricular arrhythmias, and to compare it to MCG time-domain, late-field analysis. The study population consisted of 136 patients with remote MI, 53 with and 83 without a history of VT. After averaging and high pass filtering of multichannel MCG signals, time-domain parameters describing the end-QRS activity and fragmentation index M and score S describing the whole QRS complex were computed. Fragmentation and time-domain parameters differed between the VT and control groups: fragmentation index M was 12 ± 3 versus 9 ± 2 (P < 0.001), fragmentation score S was 83 ± 42 versus 56 ± 21 (P < 0.001), and filtered QRS duration was 144 ± 32 versus 114 ± 19 ms (P < 0.001) in VT and control groups, respectively. A combination of fragmentation parameters yielded 87% sensitivity and 61 % specificity in VT identification. Corresponding figures for a time-domain parameter combination were 81% and 72%. Sensitivity of time-domain analysis was 88% and specificity was 75% in a subgroup with anterior Ml. In multivariate analysis, fragmentation and time-domain analyses discriminated VT patients from controls independently of the extent of coronary artery disease or left ventricular dysfunction. MCG in postinfarction patients reveals pathology associated with propensity to ventricular arrhythmias inside and not only at the end of the QRS complex. MGC seems most accurate in the anterior infarct location. [ABSTRACT FROM AUTHOR]

Introduction: Abnormal repolarization is one of the acknowledged mechanisms leading to malignant ventricular arrhythmias. We used a novel magnetocardiographic technique to investigate the role of inhomogeneous repolarization in patients with nonischemic dilated cardiomyopathy prone to sustained ventricular arrhythmias. Methods and Results: Forty-nine dilated cardiomyopathy patients were studied, 18 with a history of sustained ventricular tachycardia (n = 6) or ventricular fibrillation (n = 12) and 31 with no ventricular arrhythmias. The magnetocardiogram was registered and QT apex and QT end intervals were determined by a computer algorithm. Inhomogeneity of repolarization was characterized with indices describing QT apex and QT end dispersion, and T wave end duration. In addition, time-domain late fields of the QRS complex in magnetocardiography and QT dispersion in 12-lead ECG were determined. T wave end was longer in the arrhythmia group in patients with sinus rhythm (87 ± 15 msec vs 73 ± 12 msec; P = 0.005) and in those not having bundle branch block. Magnetocardiographic late fields of the QRS complex were not different between groups. QT apex and end dispersion on magnetocardiography or 12-lead ECG showed no difference. Conclusion: Prolongation of the end part of the T wave revealed by magnetocardiography is related to malignant ventricular arrhythmias in dilated cardiomyopathy. The results suggest that abnormal repolarization rather than delayed conduction underlies the arrhythmias in this disease. [ABSTRACT FROM AUTHOR]

Introduction: Magnetocardiographic (MCG) mapping is a new method to record cardiac signals. This study examined the association of MCG late fields with the propensity to sustained ventricular tachycardia (VT) after myocardial infarction (MI). Methods and Results: One hundred patients with remote MI were studied, 38 with and 62 without history of VT. High-resolution MCG and signal-averaged ECG (SAECG) as a comparative method were recorded. Time-domain parameters describing the abnormal low-amplitude end QRS activity, MCG late fields, and SAECG late potentials were analyzed. Late field parameters differed significantly between the patient groups: filtered QRS duration was 137 ± 26 msec in the VT group and 110 ± 18 msec in the control group (P < 0.001), and root mean square amplitude of the last 40 msec was 260 ± 170 and 510 ± 360 fT (P < 0.001), respectively. The optimal MCG parameter combination yielded a sensitivity of 92% and a specificity of 61% in classification to the VT group, whereas those for SAECG were 63% and 66%. In a subgroup of 63 patients with marked left ventricular dysfunction and comparable stage of coronary heart disease, only MCG (sensitivity 73%, specificity 67%) but not SAECG could assign a patient to the VT group. Conclusion: Late fields of the MCG QRS complex indicate propensity to life-threatening arrhythmias in post-MI patients. This discriminative ability persists in the presence of severe left ventricular dysfunction where ECG late potentials lose their informative value. MCG late field analysis is a potential new method for noninvasive risk assessment in post-Ml patients. [ABSTRACT FROM AUTHOR]

Background: Detection of myocardial ischemia was studied with multichannel exercise magneto-cardiography (MCG). A surface gradient method was applied to analyze cardiac magnetic fields. Methods: We studied 27 patients with single vessel coronary artery disease (CAD) and 17 healthy volunteers. The MCG was recorded over anterior chest during supine bicycle ergometry. The two-dimensional direction of the maximum spatial magnetic field gradient was determined during the ST segment and at the T-wave apex at different phases of stress test. Results: The CAD patient group was separated from controls by the orientation of the magnetic field gradient during the ST segment at cessation of exercise (CAD 167 ± 68° vs controls 106 ± 49°; P < 0.005) and at 4 minutes postexercise, but not at rest. The-CAD patient group was separated from controls also by the orientation of the magnetic field gradient at the T-wave apex at 4 minutes postexercise (CAD 87 ± 60° vs controls 58 ± 18° P < 0.05), but not at rest. The change in the orientation of the field gradient at the T-wave apex 4 minutes postexercise, compared to baseline, was greater in CAD patients (31 ± 43°) than in controls (9 ± 8° P < 0.05). This change was larger in the patient group with stenosis in the right than in the left coronary artery (P < 0.05). Conclusions: Transient acute myocardial ischemia causes well-recognizable changes in the magnetocardiogram at the ST segment and the T wave. The orientation of the maximum spatial gradient of the magnetic field can be used as a parameter to determine these changes. [ABSTRACT FROM AUTHOR]

This study was performed to: (1) evaluate the accuracy of noninvasive magneto-cardiographic (MCC) localization of an amagnetic stimulation catheter; (2) validate the feasibility of this multipurpose catheter; and (3) study the characteristics of cardiac evoked fields. A stimulation catheter specially designed to produce no magnetic disturbances was inserted into the heart of five patients after routine electrophysiological studies. The catheter position was documented on biplane cine x-ray images. MCG signals were then recorded in a magnetically shielded room during cardiac pacing. Noninvasive localization of the catheter's tip and stimulated depolarization was computed from measured MCG data using a moving equivalent current-dipole source in patient-specific boundary element torso models. In all five patients, the MCG localizations were anatomically in good agreement with the catheter positions defined from the x-ray images. The mean distance between the position of the tip of the catheter defined from x-ray fluoroscopy and the MCG localization was 11 ± 4 mm. The mean three-dimensional difference between the MCC localization at the peak stimulus and the MCC localization, during the ventricular evoked response about 3 ms later, was 4 ± 1 mm calculated from signal-averaged data. The 95% confidence interval of heat-to-beat localization of the tip of the stimulation catheter from ten consecutive beats in the patients was 4 ± 2 mm. The propagation velocity of the equivalent current dipole between 5 and 10 ms after the peak stimulus was 0.9 ± 0.2 m/s. The results show that the use of the amagnetic catheter is technically feasible and reliable in clinical studies. The accurate three-dimensional localization of this multi-purpose catheter by multichannel MCG suggests that the method could be developed toward a useful clinical tool during electrophysiological studies. [ABSTRACT FROM AUTHOR]

This study was performed to evaluate the accuracy of multichannel magnetocardiographic (MCG) and body surface potential mapping (BSPM) in localizing three-dimensionally the tip of an amagnetic catheter for electrophysiology without fluoroscopy. An amagnetic catheter (AC), specially designed to produce dipolar sources of different geometry without magnetic disturbances, was placed inside a physical thorax phantom at two different depths, 38 mm and 88 mm below the frontal surface of the phantom. Sixty-seven MCG and 123 BSPM signals generated by the 10 mA current stimuli fed into the catheter were then recorded in a magnetically shielded room. Non- invasive localization of the tip of the catheter was computed from measured MCG and BSPM data using an equivalent current dipole source in a phantom-specific boundary element torso model. The mean 3-dimensional error of the MCG localization at the closer level was 2 ± 1 mm. The corresponding error calculated from the BSPM measurements was 4 ± 1 mm. At the deeper level, the mean localization errors of MCG and BSPM were 7 ± 4 mm and 10 ± 2 mm, respectively. The results showed that MCG and BSPM localization of the tip of the AC is accurate and reproducible provided that the signal-to-noise ratio is sufficiently high. In our study, the MCG method was found to be more accurate than BSPM. This suggests that both methods could be developed towards a useful clinical tool for nonfluoroscopic 3-dimensional electroanatomical imaging during electrophysiological studies, thus minimizing radiation exposure to patients and operators. [ABSTRACT FROM AUTHOR]

Background During recent years artificial neural networks have been proposed as a diagnostic tool in different fields of cardiology. Most of the studies have utilized the multilayer perceptron with backpropagation learning rule for the design of the network. As a new approach, Learning Vector Quantization (LVQ) which belongs to the class of competitive learning networks, was developed particularly for classification problems. So far there are no data available on the application of LVQ for classification tasks in cardiology. The present study aims at investigating the performance of LVQ for localization of myocardial infarction (Ml) based on ST elevations in the standard 12-lead ECG. Methods Altogether, 769 male patients (age 53 ± 7 years) with an acute Ml were included into the study. Three hundred fifty-three patients (46%) presented with anterior and 416 patients (54%) with inferior Ml based on typical changes in the standard 12-lead ECG. Standardized ST elevations in all 12 leads were used as input structure for the network. The performance of the network was studied using two different learning and test sets. The influence of the number of reference vectors and training steps on the classification accuracy for infarct location was investigated. Results The highest classification accuracy of 88.6% for infarct location was achieved using the learning set with 66% of all patients. This setup was based on five reference vectors and 200 training steps. The best accuracies for anterior Ml were higher as compared to inferior infarctions in both the test and training set. Using more than 50 reference vectors resulted in a decrease of classification accuracy due to overtraining of the network. Conclusion Appropriately initialized and trained artificial neural networks based on LVQ give a high accuracy for localization of Ml using only ST elevations of the standard 12-lead ECG. [ABSTRACT FROM AUTHOR]

Objective: The objective of this study was to investigate the prognostic significance of the wavelet decomposition (WD), when applied to single leads of the signal-averaged ECG (SAECG) of postinfarction patients, as well as to compare it with conventional time-domain (TD) analysis in order to optimize the utility of high resolution ECG techniques in risk stratification. Comparisons with clinical variables were also performed. Methods: SAECGs of 769 patients were analyzed (mean age 53 ± 7 years). A total of 42 arrhythmic events occurred within 54 months. For numerical calculations of WD, relative energies of the QRS complex were obtained in seven frequency bands. Conventional parameters of late potential analysis in TD were calculated at 25 and 40 Hz high pass filter. Results: No significant correlation was found between parameters of both methods. Several parameters of the WD of single leads showed slightly higher sensitivity (e.g., 52% vs 36%) and positive predictive values (e.g., 13.3% vs 10.2%) compared with those obtained with the QRS duration of TD analysis. In multivariate analysis, combination of QRS duration with WD parameters (relative risk [rr] =4.55, P < 0.0001), followed by the WD of single leads (rr = 4.19, P < 0.0001), nonsustained ventricular tachycardia in the long-term ECG (rr = 3.72, P = 0.0005) and the history of previous infarction (rr = 2.72, P = 0.0035) were the most significant predictors in risk stratification. Conclusion: Time domain and wavelet transform of SAECG resulted in an improvement in postinfarction risk stratification compared with the clinical variables included in this study. Wavelet parameters may not be vastly superior to QRS duration, but they are a new index measuring intra-QRS phenomena. [ABSTRACT FROM AUTHOR]