Association of left ventricular remodeling and nonuniform electrical recovery expressed by nondipolar QRST integral map patterns in survivors of a first anterior myocardial infarction. Captopril and Thrombolysis Study Investigators

Myocardial scar characteristics based on cardiac magnetic resonance imaging is associated with ventricular tachyarrhythmia in patients with ischemic cardiomyopathy

OBJECTIVES

We hypothesized that myocardial scar characterization using cardiac magnetic resonance imaging (CMR) may be associated with the occurrence of ventricular tachyarrhythmia (VT), appropriate implantable cardioverter-defibrillator (ICD) therapy and mortality.

BACKGROUND

Since a minority of patients with prophylactic ICD implantation receive appropriate ICD therapy, there is a need for more effective risk stratification for primary prevention in patients with ischemic cardiomyopathy.

METHODS AND RESULTS

In 99 patients with ischemic cardiomyopathy, CMR was performed prior to ICD implantation. We assessed if CMR indices (cardiac mass, LVEF) and CMR scar characteristics (infarct core mass, peri-infarction mass and the ratio's between left ventricular mass, infarct core mass and peri-infarction mass) were associated with outcome. The primary endpoint was sustained VT and/or appropriate ICD therapy. The secondary endpoint was all-cause mortality. During a median follow-up of 5.4 years (IQR 4.5-6.6 years), 34 patients reached the primary end-point (17 appropriate ICD shocks) and 26 patients died. In multivariable Cox regression analysis, peri-infarction to core-infarction ratio (HR 2.01, 95%CI: 1.17-3.44, p=0.01) was independently and significantly associated with the primary endpoint, whereas NYHA-class and lower LVEF were not. Conversely, age (HR 1.06, 95% CI: 1.01-1.12, p=0.02) and lower LVEF (HR 0.95, 95% CI: 0.91-1.00, p=0.04) were independently associated with all-cause mortality, mainly due to heart failure.

CONCLUSION

A relatively large peri-infarction mass is associated with sustained VT and/or appropriate ICD therapy, whereas age and lower LVEF are associated with mortality. CMR based tissue characterization could aid in the prediction of specific outcome measures and in clinical decision making.

Diagnostic accuracy of a new cardiac electrical biomarker for detection of electrocardiogram changes suggestive of acute myocardial ischemic injury

OBJECTIVE

A new cardiac "electrical" biomarker (CEB) for detection of 12-lead electrocardiogram (ECG) changes indicative of acute myocardial ischemic injury has been identified. Objective was to test CEB diagnostic accuracy.

METHODS

This is a blinded, observational retrospective case-control, noninferiority study. A total of 508 ECGs obtained from archived digital databases were interpreted by cardiologist and emergency physician (EP) blinded reference standards for presence of acute myocardial ischemic injury. CEB was constructed from three ECG cardiac monitoring leads using nonlinear modeling. Comparative active controls included ST voltage changes (J-point, ST area under curve) and a computerized ECG interpretive algorithm (ECGI). Training set of 141 ECGs identified CEB cutoffs by receiver-operating-characteristic (ROC) analysis. Test set of 367 ECGs was analyzed for validation. Poor-quality ECGs were excluded. Sensitivity, specificity, and negative and positive predictive values were calculated with 95% confidence intervals. Adjudication was performed by consensus.

RESULTS

CEB demonstrated noninferiority to all active controls by hypothesis testing. CEB adjudication demonstrated 85.3-94.4% sensitivity, 92.5-93.0% specificity, 93.8-98.6% negative predictive value, and 74.6-83.5% positive predictive value. CEB was superior against all active controls in EP analysis, and against ST area under curve and ECGI by cardiologist.

CONCLUSION

CEB detects acute myocardial ischemic injury with high diagnostic accuracy. CEB is instantly constructed from three ECG leads on the cardiac monitor and displayed instantly allowing immediate cost-effective identification of patients with acute ischemic injury during cardiac rhythm monitoring.

Changes in dipolar structure of cardiac magnetic field maps after ST elevation myocardial infarction

BACKGROUND

Pathological changes in cardiac electrophysiology have been investigated in coronary artery disease using magnetocardiography. Aim of this work was to examine the structure of cardiac magnetic field maps (MFM) during ventricular depolarization and repolarization in patients with acute ST elevation myocardial infarction (STEMI).

METHODS

Magnetocardiograms were recorded in 39 healthy subjects and 97 patients who had been successfully revascularized after STEMI. Using the Karhunen-Loeve transform, 12 eigenmaps were constructed for six intervals within the QT interval of each subject's signal-averaged data. The relative information content of the eigenmaps was compared between STEMI patients and healthy subjects.

RESULTS

Relative nondipolar content was between 0.03% and 0.52% higher in the STEMI group, (P < 0.001 for the repolarization intervals). Information content of the first dipolar eigenmap in the STEMI group was reduced by 2.6%-11.7% (P < 0.001 for the repolarization intervals). STT interval was best able to discriminate between groups: area-under-the-curve for nondipolar content was 85.8% (P < 0.001), for the first eigenmap 91.7% (P < 0.001). Severity of infarction was reflected in lower STT interval map 1 content for patients with anterior versus posterior infarction (83%± 11% vs. 87%± 10%, P < 0.05), with wall motion disturbances (84%± 11% vs. 92%± 7%, P < 0.001) and with microvascular obstruction (81%± 12% vs. 87%± 10%, P < 0.05). Regression analysis showed that patients with lower ejection fraction tended to have less information content (P < 0.001).

CONCLUSION

STEMI is associated with a loss of spatial coherence during repolarization, as quantified by principal component analysis of cardiac MFM.

Local depolarization abnormalities are the dominant pathophysiologic mechanism for type 1 electrocardiogram in brugada syndrome a study of electrocardiograms, vectorcardiograms, and body surface potential maps during ajmaline provocation

OBJECTIVES

We sought to obtain new insights into the pathophysiologic basis of Brugada syndrome (BrS) by studying changes in various electrocardiographic depolarization and/or repolarization variables that occurred with the development of the signature type 1 BrS electrocardiogram (ECG) during ajmaline provocation testing.

BACKGROUND

BrS is associated with sudden cardiac death. Its pathophysiologic basis, although unresolved, is believed to reside in abnormal cardiac depolarization or abnormal repolarization.

METHODS

Ajmaline provocation was performed in 269 patients suspected of having BrS with simultaneous recording of ECGs, vectorcardiograms, and 62-lead body surface potential maps.

RESULTS

A type 1 ECG was elicited in 91 patients (BrS patients), 162 patients had a negative test result (controls), and 16 patients had an abnormal test result. Depolarization abnormalities were more prominent in BrS patients and were mapped to the right ventricle (RV) by longer right precordial filtered QRS complex durations (142 +/- 23 ms vs. 125 +/- 14 ms, p < 0.01) and right terminal conduction delay (60 +/- 11 ms vs. 53 +/- 9 ms, p < 0.01). Repolarization abnormalities remained concordant with depolarization abnormalities as indicated by steady low nondipolar content (12 +/- 8% vs. 8 +/- 4%, p = NS), lower spatial QRS-T integrals (33 +/- 12 mV.ms vs. 40 +/- 16 mV.ms, p < 0.05), similar spatial QRS-T angles (92 +/- 39 degrees vs. 87 +/- 31 degrees , p = NS), similar T(peak)-T(end) interval (143 +/- 36 ms vs. 138 +/- 25 ms, p = NS), and similar T(peak)-T(end) dispersion (47 +/- 37 ms vs. 45 +/- 27 ms, p = NS).

CONCLUSIONS

The type 1 BrS ECG is characterized predominantly by localized depolarization abnormalities, notably (terminal) conduction delay in the RV, as assessed with complementary noninvasive electrocardiographic techniques. We could not define a separate role for repolarization abnormalities but suggest that the typical signs of repolarization derangements seen on the ECG are secondary to these depolarization abnormalities.

Reducing the Risk of Sudden Death in Heart Failure With β-Blockers

BACKGROUND

Heart failure (HF) is a serious cardiovascular syndrome that affects nearly 5 million people in the United States. A review of clinical data demonstrates that sudden cardiac death (SCD) accounts for approximately one-third of all HF deaths. This fatal outcome typically involves an unexpected electrical event leading to sustained cardiac arrhythmias resulting in cardiovascular collapse.

METHODS AND RESULTS

A systematic review of the literature was performed to serve as the basis for this review. Factors contributing directly to incidence of SCD in the HF population may include significant remodeling of the left ventricle (hypertrophy, dilation, and fibrosis) in addition to increased sympathetic activation. Using specific therapies to limit these mechanisms are beneficial in the HF patient by preventing SCD. Beta-blockers play a key role in the prevention of SCD for patients with HF by limiting the effects of circulating norepinephrine and by reducing left ventricular remodeling.

CONCLUSIONS

This review outlines the potential mechanisms and contributing factors of SCD in patients with HF and the impact of beta-blocker usage in the prevention of this fatal outcome for this growing patient population.

Ventricular arrhythmias: antiadrenergic therapy for the patient with coronary artery disease

Patients who have had a recent myocardial infarction (MI) are at high risk of ventricular arrhythmias that often cause sudden cardiac death. It is believed that sympathetic overactivity in the peri-infarction period may alter the electrophysiology and structure of the myocardium, thus placing these patients at risk of developing rhythm disturbances. A number of pharmacologic and nonpharmacologic therapies have been shown to reduce the risk of post-MI mortality, including sudden cardiac death. beta-Adrenergic blockers are recommended for all post-MI patients without contraindications because of overwhelming clinical evidence of their benefit in reducing mortality in this patient population. Recent clinical trials of implantable cardioverter defibrillators have provided compelling support that they are effective in both the primary and secondary prevention of sudden cardiac death. In addition, several studies have shown that combination therapy with beta-blockers and implantable cardioverter defibrillators have synergistic effects that optimize the benefits of both therapies.

The effect of mental stress on the non-dipolar components of the T wave: modulation by hypnosis

OBJECTIVE

Mental or emotional stress-induced ventricular arrhythmias and sudden cardiac death are thought to be mediated by the autonomic nervous system and ischemia. In the absence of ischemia, increased inhomogeneity of repolarization is thought to be important. We tested the hypotheses that in the absence of ischemia, mental stress may modulate repolarization by changing autonomic balance; and mental relaxation induced by hypnosis may offset the potentially adverse effects of stress on the cardiac electrophysiology.

METHODS

Twelve healthy volunteers (6 male, age 18-35, mean 25 years) experienced a series of different emotions intended to induce a wide range of autonomic response (42 test epochs) on two separate occasions, with and without hypnosis, with continuous electrocardiogram recording. Low- (LF) and HF (high-frequency) heart rate variability was measured and ventricular repolarization was assessed using the relative T-wave residua (proportion of nondipolar components of the T wave) calculated for the T-onset - T peak (TWR-peak T), T peak -T end (TWR-end T), and the whole T wave (TWR).

RESULTS

Emotionally induced changes in LF and LF/HF ratio correlated with changes in TWR, e.g., (R = 0.51, p < .001; R = 0.59, p < .0001; and R = 0.59, p < .0003, for LF/HF versus TWR, TWR-Peak T, and TWR-end T, respectively. Mental relaxation induced by hypnosis increased LF power (1,205 ms2) versus 624 ms2, p < .003 for hypnotized versus nonhypnotized state), HF power (1,619 ms2 versus 572 ms2), p < .0004), and reduced LF/HF ratio (1.0 versus 1.5, p = .052) and was associated with a marked reduction in the changes in repolarization in response to emotion, e.g., 10.7 x 10(-6) versus 5.0 x10(-6), p < .03 for TWR.

CONCLUSIONS

a) Mental stress in the absence of ischemia altered repolarization inhomogeneity via change in the autonomic balance. b) Mental relaxation induced by hypnosis greatly reduced the effect of mental stress on repolarization. c) These findings may have implications for arrhythmogenesis.

Software design for analysis of multichannel intracardial and body surface electrocardiograms

Analysis of multichannel ECG recordings (body surface maps (BSMs) and intracardial maps) requires special software. We created a software package and a user interface on top of a commercial data analysis package (MATLAB) by a combination of high-level and low-level programming. Our software was created to satisfy the needs of a diverse group of researchers. It can handle a large variety of recording configurations. It allows for interactive usage through a fast and robust user interface, and batch processing for the analysis of large amounts of data. The package is user-extensible, includes routines for both common and experimental data processing tasks, and works on several computer platforms. The source code is made intelligible using software for structured documentation and is available to the users. The package is currently used by more than ten research groups analysing ECG data worldwide.

Recovery time dispersion measured by body surface mapping: noninvasive method of assessing vulnerability to ventricular tachyarrhythmias

To assess the significance of recovery time (RT) dispersion measured by body surface mapping, we investigated body surface RT isochrone maps of 40 patients with anterior old myocardial infarction (OMI), 40 patients with dilated cardiomyopathy (DCM), and 40 controls. Among the OMI and DCM groups, 20 patients per group had sustained ventricular tachycardia (VT). The dispersion of corrected recovery time (RTc) by Bazett's formula significantly increased in OMI patients (169 +/- 38 ms) and DCM patients (163 +/- 22 ms) compared with controls (147 +/- 10 ms) (P <.01). RTc dispersion was greater in OMI patients with sustained VT than in those without sustained VT [184 +/- 43 ms vs. 155 +/- 24 ms (P <.05)], as well as in DCM patients with sustained VT compared with those without sustained VT [170 +/- 25 ms vs. 156 +/- 17 ms (P <.05)]. The results suggest that RTc dispersion determined by body surface mapping can be useful for assessing vulnerability to sustained VT.

Effects of antiarrhythmic drugs on QT interval dispersion--relationship to antiarrhythmic action and proarrhythmia

Class IA, IC, and III antiarrhythmic drugs prolong ventricular repolarization (VR) which is manifest as QT interval prolongation on the surface electrocardiogram. These drugs may prolong VR in a spatially heterogeneous manner which results in increased dispersion of VR. This may be manifest as increased QT interval dispersion. Antiarrhythmic drug-induced decreases in QT interval dispersion are associated with antiarrhythmic efficacy in patients with the long QT syndrome and in patients with sustained ventricular tachycardia. Antiarrhythmic drug-induced increases in QT interval dispersion are associated with ventricular proarrhythmia secondary to torsades de points ventricular tachycardia. A number of factors may modulate the effects of antiarrhythmic drugs on dispersion of VR, including the disease state, transient ischemia, electrolyte abnormalities, changes in autonomic tone, and hemodynamic stress.

Evolution of QRS duration after myocardial infarction: clinical consequences

The natural history of late potentials after acute myocardial infarction (AMI) has been studied in the first 2 years following myocardial infarction (MI). The purpose of the study was to assess the influence of some time delays since MI, including a time delay longer than 2 years on signal-averaged ECG (SAECG). SAECG was recorded at 40-Hz high pass filtering in 40 patients 10 days after acute MI (SAECG 1), then repeated 6-12 months later (mean 9 +/- 3 months) (SAECG 2), and then, 2-4 years later (mean 3 +/- 2 years) (SAECG 3). QRS duration, root mean square voltage of the last 40 ms of QRS (RMS 40), and low amplitude signal duration (LAS) were measured at the first (1), second (2), and third recording (3).

RESULTS

(***P < 0.001) [table: see text] The analysis of individual results showed a lengthening QRS duration at the third recording only in patients who had a decreased left ventricular ejection fraction (LVEF) at the third recording. In 12 patients with LVEF > 40%, QRS duration did not change at the first and third recording (104 +/- 15 vs 101 +/- 12 ms). In all 28 patients, but one with LVEF < 40%, QRS duration increased from 107 +/- 12 to 128 +/- 18 ms***. There was no correlation between QRS duration and LVEF at the second recording and no correlation between QRS duration increase at the third recording and the presence or not of late potentials at the first recording. QRS duration lengthening at the third recording was significantly correlated with a left ventricular (LV) dilatation occurrence at the two-dimensional echocardiogram. All arrhythmic events, but two, occurred in patients who developed a QRS duration prolongation and were significantly correlated (P < 0.01) to a mean longer QRS duration (132 +/- 20 ms) than in patients without arrhythmic events (113 +/- 17 ms). In conclusion, the patients with a LV impairment, and who developed a LV dilatation several months after AMI, presented a delayed lengthening of QRS duration noted only at least 2 years after infarction. These patients are at risk of arrhythmic events.

Value of magnetocardiographic QRST integral maps in the identification of patients at risk of ventricular arrhythmias

It has been shown that regional ventricular repolarization properties can be reflected in body surface distributions of electrocardiographic QRST deflection areas (integrals). We hypothesize that these properties can be reflected also in the magnetocardiographic QRST areas and that this may be useful for predicting vulnerability to ventricular tachyarrhythmias. Magnetic field maps were obtained during sinus rhythm from 49 leads above the anterior chest in 22 healthy (asymptomatic) control subjects (group A) and in 29 patients with ventricular arrhythmias (group B). In each subject, the QRST deflection area was calculated for each lead and displayed as an integral map. The mean value of maximum was significantly larger in the control group A than in the patient group B (1,626+/-694 pTms vs. 582+/-547 pTms, P<0.0001). To quantitatively assess intragroup variability in the control group A and intergroup variability of the control and patient groups, we used the correlation coefficient r and covariance sigma. These indices showed significantly less intragroup than intergroup variation (e.g., in terms of sigma, 28.0x10(-6)+/-12.3x10(-6) vs. 3.4x10(-6)+/-12.5x10(-6), P<0.0001). Each QRST integral map was also represented as a weighted sum of 24 basis functions (eigenvectors) by means of Karhunen-Loeve transformation to calculate the contribution of the nondipolar eigenvectors (all eigenvectors beyond the third). This percentage nondipolar content of magnetocardiographic QRST integral maps was significantly higher in the patient group B than in the control group A (13.0%+/-9.1 % vs. 2.6%+/-2.0%, P<0.0001). Discriminations between control subjects and patients with ventricular arrhythmias based on magnitude of the maximum, covariance sigma, and nondipolar content were 90.2%, 90.2%, and 86.3% accurate, with a sensitivity of 89.7%, 93.1%, and 75.9%, and a specificity of 90.9%, 86.4%, and 100%. We have shown that magnitude of the maximum and indices of variability and nondipolarity of the magnetocardiographic QRST integral maps may predict arrhythmia vulnerability. This finding is in agreement with earlier studies that used body surface potential mapping and suggests that magneticfield mapping may also be a useful diagnostic tool for risk analysis.

QT dispersion as a predictor of long-term mortality in patients with acute myocardial infarction and clinical evidence of heart failure

BACKGROUND

QT interval dispersion is a marker of inhomogeneous ventricular repolarization, and therefore has the potential to predict re-entry arrhythmias. Following acute myocardial infarction, increased QT dispersion has been associated with a higher risk of ventricular arrhythmias. However, whether or not QT dispersion predicts prognosis post-acute myocardial infarction is not clear. We addressed this issue by analysing the AIREX study registry.

METHODS

AIREX was a follow-up study of 603 post-acute myocardial infarction patients who exhibited clinical signs of heart failure and were randomly allocated to ramipril or placebo. An interpretable 12-lead ECG obtained between day 0 and day 9 after the index infarction (median time 2 days) was available in 501 patients. We examined whether QT dispersion was a predictor of all-cause mortality in the AIREX study registry (mean follow-up 6 years).

RESULTS

QT dispersion measurements were significantly increased in patients who subsequently died (QT dispersion: 92.0 +/- 38.5 ms vs 82.7 +/- 34.3 ins. P=0.005; rate corrected QT dispersion: 105.7 +/- 42.7 ms vs 93.1 +/- 35.9 ms, P<0.001). Univariate analysis showed that QT dispersion as a predictor of all-cause mortality risk (QT dispersion: hazard ratio per l0 ms 1.05, [95% CI 1.02 to 1.09]. P= 0.004; rate corrected QT dispersion: 1-07 [1.03 to 1.10], P<0.001): an increase of 10 ms added a 5-7%, relative risk of death. QT dispersion remained an independent predictor of all-cause mortality risk on multivariate analysis (QT dispersion: 1.05 [1.01 to 1.09], P=0.027; rate corrected QT dispersion: 1.05 [1.01 to 1.09]. P=0.022).

CONCLUSION

QT dispersion. measured from Li routine 12-lead ECG following acute myocardial infarction complicated by heart failure provides independent information regarding the probability of long-term survival. However. the low sensitivity of this electrocardiographic marker limits its usefulness for risk stratification if used in isolation.

Spatial features in body surface potential maps of patients with ventricular tachyarrhythmias with or without coronary artery disease

Body surface potential maps (BSPM) from patients with coronary artery disease or no structural heart disease were analyzed with respect to their spatial features and QT/QTc dispersion in order to determine whether BSPM allows identification of patients with ventricular fibrillation. QRST integral maps and QT/QTc dispersion were acquired from simultaneous recordings of 62 ECG leads during sinus rhythm in patients with idiopathic ventricular fibrillation (n=13), ventricular fibrillation and coronary artery disease (n=22), coronary artery disease without ventricular fibrillation (n=21) and healthy controls (n=18). The Karhunen-Loeve transformation was applied to reduce the dimensionality of the data matrix of the QRST map to eight coefficients. Linear discriminant analysis allowed discrimination between idiopathic ventricular fibrillation patients and controls with high sensitivity (85%) and specificity (89%). However, discrimination between coronary artery disease patients with or without ventricular fibrillation was poor (68% and 67%, respectively). QTc dispersion calculated from BSPM was longer in idiopathic ventricular fibrillation patients than in controls (99+/-30 ms vs 70+/-14 ms, P=0.009) in contrast to QTc dispersion taken from 12-lead ECG (53+/-21 ms vs. 47+/-12 ms, P=n.s.). No significant difference was noted for coronary artery disease patients with or without ventricular fibrillation. In conclusion, repolarization disturbances detected by BSPM allow identification of ventricular fibrillation patients without structural heart disease. However, our results do not suggest a major impact of QT/QTc dispersion or QRST integral mapping for identification of ventricular fibrillation patients with coronary artery disease.

Characteristic findings of body surface potential map during ventricular repolarization in patients with coronary heart disease

The objective of the present study was to investigate the characteristics of body surface potential map (BSPM) findings during ventricular repolarization in patients with coronary artery disease (CAD). A total of 108 consecutive patients, 99 men and 9 women with angina pectoris and positive treadmill exercise test results as well as angiographically documented CAD underwent BSPM study in a fasting state. Their ages ranged from 30 to 70 years. There were 13 patients with right coronary artery (RCA) lesions, 37 with left anterior descending artery (LAD) lesions, 5 with left circumflex artery (LCX) lesions, 17 with both RCA and LAD lesions, 12 with both LCX and LAD lesions, and 24 with 3-vessel disease. The BSPMs were obtained by using the heart potential map system designed by Toyama et al. There were 59 lead points on the anterior chest wall and 28 on the back. The BSPMs in isopotential distribution were made every one msec throughout the ventricular activation period. The distribution of positive and negative potentials, potential maximum and potential minimum, polarity of potential distribution, and the reversal of potential distribution during ventricular repolarization were analyzed. The following information on BSPMs was obtained: (1) In early ventricular repolarization, the negative potential and the potential minimum appeared abnormally on the anterior thorax. The potential abnormality displayed on the right portion or the inferior portion in patients with RCA lesions, on the middle portion or the left portion in patients with LAD lesions, and on the left-superior portion or the left-middle portion in patients with LCX lesions. In patients with multi-vessel disease, the abnormal potential distribution showed a combined pattern of individual vessel lesions. (2) In some cases, the multipolar potential distribution appeared abnormally during the initial stage and the peak of the T wave. (3) The reversal of potential distribution was observed in about half of the patients. The characteristic findings of the BSPM during ventricular repolarization, including abnormal potential distribution, multipolar potential distribution and reversal of potential distribution, will be of clinical value in patients with CAD.

Ramipril reduces QT dispersion in patients with acute myocardial infarction and heart failure

In a cohort of 67 patients from the Acute Infarction Ramipril Efficacy study, we showed that ramipril therapy was associated with a significant reduction in QT dispersion over a 2-month period after acute myocardial infarction. This reduction of ventricular repolarization inhomogeneity indicates an antiarrhythmic effect and may be an important additional mechanism for the reduced all-cause mortality and sudden death incidence achieved with angiotensin-converting enzyme inhibition after acute myocardial infarction.

Electrocardiographic identification of abnormal ventricular depolarization and repolarization in patients with idiopathic ventricular fibrillation

OBJECTIVES

We sought to gain more insight into the arrhythmogenic etiology of idiopathic ventricular fibrillation (VF) by assessing ventricular depolarization and repolarization properties by means of various electrocardiographic (ECG) techniques.

BACKGROUND

Idiopathic VF occurs in the absence of demonstrable structural heart disease. Abnormalities in ventricular depolarization or repolarization have been related to increased vulnerability to VF in various cardiac disorders and are possibly also present in patients with idiopathic VF.

METHODS

In 17 patients with a first episode of idiopathic VF, 62-lead body surface QRST integral maps, QT dispersion on the 12-lead ECG and XYZ-lead signal-averaged ECGs were computed.

RESULTS

All subjects of a healthy control group had a normal dipolar QRST integral map. In patients with idiopathic VF, either a normal dipolar map (29%,), a dipolar map with an abnormally large negative area on the right side of the thorax (24%) or a nondipolar map (47%) were recorded. Only four patients (24%) had increased QT dispersion on the 12-lead ECG and late potentials could be recorded in 6 (38%) of 16 patients. During a median follow-up duration of 56 months (range 9 to 136), a recurrent arrhythmic event occurred in 7 patients (41%), all of whom had an abnormal QRST integral map. Five of these patients had late potentials, and three showed increased QT dispersion on the 12-lead ECG.

CONCLUSIONS

In patients with idiopathic VF, ventricular areas of slow conduction, regionally delayed repolarization or dispersion in repolarization can be identified. Therefore, various electrophysiologic conditions, alone or in combination, may be responsible for the occurrence of idiopathic VF. Body surface QRST integral mapping may be a promising method to identify those patients who do not show a recurrent episode of VF.

Cardiac memory in patients with intermittent Wolff-Parkinson-White syndrome

This study used body surface mapping to evaluate the ventricular repolarization process in the absence of delta waves in 13 patients with the intermittent Wolff-Parkinson-White (WPW) syndrome. The findings were compared with data from 30 normal individuals and 50 patients with the overt WPW syndrome. The QRST isointegral maps of patients with the overt WPW syndrome exhibited abnormal areas and the QRST departure maps showed a peculiar distribution to each accessory pathway site. The QRST isointegral map exhibited abnormal areas in 11 of the 13 cases (85%) of the intermittent WPW syndrome in the absence of delta waves. In 8 of these 11 cases (73%), the distribution of the departure map resembled that in the overt WPW syndrome. These findings suggest that abnormal ventricular repolarization due to cardiac memory is present in patients with the intermittent WPW syndrome even in the absence of delta waves.

[Analysis of QRST integral and QT dispersion by body surface potential mapping in patients with malignant ventricular arrhythmias]

In a retrospective analysis in 74 patients with coronary artery disease or no obvious heart disease, the value of "body surface potential mapping" for the identification of repolarization abnormalities was investigated compared to the standard 12-lead ECG. In patients with idiopathic ventricular fibrillation the number of extrema in the QRST integral map was significantly higher than in the control group (3.15+/-0.99 vs. 2.17+/-0.51, p<0.001) and the QT dispersion was also higher (0.10+/-0.03 vs. 0.07+/-0.01, p<0.001), whereas there was no difference between either group in the 12-lead ECG QT dispersion. In patients with coronary artery disease the number of extrema in the QRST integral map and QT dispersion were also higher compared to the control group, but there were no significant differences between patients with or without aborted sudden cardiac death.In conclusion, BSPM identifies repolarization abnormalities not detected by 12-lead ECG, thereby identifying a potential reason for cardiac arrest in patients without overt heart disease. The usefulness of this technique for risk stratification in patients with coronary artery disease remains to be elucidated.