Showing papers on "QRS complex published in 1988"

Electrical alternans and cardiac electrical instability.

Abstract: We investigated the relationship between electrical alternans and cardiac electrical stability in a series of 20 dog experiments and in a pilot clinical study. Electrical alternans was detected in both the QRS complex and the ST-T wave by use of a novel multidimensional spectral technique. The magnitude of the alteration was expressed as the alternating electrocardiographic morphology index (AEMI), expressed as parts per million of waveform energy. Electrical stability in the dog preparations was assessed via the ventricular fibrillation threshold measurement, and in the clinical studies via programmed stimulation. In 10 dog experiments, systemic hypothermia resulted in a 60% decrease in ventricular fibrillation threshold (VFT) (p less than .0001) and a significant increase in both AEMI(QRS) form 3.7 +/- 3.0 to 1448 +/- 548 (p less than .0001) and AEMI(ST-T) from 43.9 +/- 18.4 to 19,178 +/- 5579 (p less than .0001). In 10 dog experiments, transient coronary artery ligation also resulted in a 60% decrease in VFT (p less than .0001), an increase from 76.3 +/- 46.5 to 245 +/- 11 in AEMI(QRS) (p less than .05), and an increase from 842 +/- 505 to 1365 +/- 392 in AEMI(ST-T) (p less than .002). In 119 observations in 20 animal experiments, the rank correlation between VFT and AEMI(QRS) was -.30 (p less than .001), with that between VFT and AEMI(ST-T) being -.55 (p less than .0001). In a double-blind pilot clinical trial consisting of 23 studies in 19 patients, the result of electrophysiologic testing was used as an independent measure of cardiac electrical stability. Alternation in waveform morphology identified the inducible patient population with a sensitivity of 92%, a positive predictivity of 70%, and a specificity of 50% (p less than .05). We conclude that analysis of subtle beat-to-beat variability in electrocardiographic morphology may provide a noninvasive measure of cardiac electrical stability.

Importance of lead selection in QT interval measurement.

Abstract: The influence of lead selection on QT estimation in the 12-lead electrocardiogram was assessed in 63 patients (21 control subjects, 21 with anterior myocardial infarction, 21 with inferior myocardial infarction). QT estimates varied between leads. The variation was greater in patients with myocardial infarction than in control subjects (mean dispersion of QT: control subjects, 48 ± 18 ms [± standard deviation]; anterior myocardial infarction, 70 ± 30 ms; inferior myocardial infarction, 73 ± 32 ms). The maximum QT in any lead (QTmax) was determined and the deviation of each lead from this maximum value calculated. In all 3 groups, anteroseptal leads (V2 or V3) provided the closest approximation to QTmax. Interlead variability was found to be mainly due to variation in timing of the end of the T wave, rather than the onset of the QRS complex. The variability due to leads was considerably greater than the variability due to cycles, observers or measurement error. Implementation of a variety of current lead selection practices resulted in widely divergent estimates of QT interval. It is concluded that there is a need for standardization of lead selection practice for QT measurement. If measurements are confined to one or a few leads, anteroseptal leads provide the closest approximation to QTmax.

Electrocardiographic criteria for ventricular tachycardia in wide complex left bundle branch block morphology tachycardias

Abstract: Four electrocardiographic criteria for ventricular tachycardia (VT) were proposed and evaluated. These included (1) an R wave in V1 or V2 of greater than 30-ms duration; (2) any Q wave in V6; (3) a duration of greater than 60 ms from the onset of the QRS to the nadir of the S wave in V1 or V2 and (4) notching on the downstroke of the S wave in V1 or V2. The data showed that all 4 criteria had high predictive accuracy (96 to 100%) and specificity (94 to 100%). The relatively low sensitivities of the 4 criteria alone (30 to 64%) might limit their efficacy. Grouped criteria, however, could differentiate VT from supraventricular tachycardias with high sensitivity, specificity and predictive accuracy. The amount of tracings having either electrocardiographic criteria (1) or (2) or (3) or (4) was determined. The proposed combined criteria had a sensitivity of 100%, specificity of 89% and a predictive accuracy of 96%. Left axis deviation alone was of no value in distinguishing VT from supraventricular tachycardia. Characteristic patterns were present for left bundle branch block pattern VT associated with anterior and inferior myocardial infarction. In conclusion, the 12-lead electrocardiogram alone, when systematically analyzed, can be used to accurately diagnose the origin of wide complex tachycardias with left bundle branch block pattern. Attention to these criteria may lead to more rapid and effective therapy.

Serial electrocardiographic changes in idiopathic dilated cardiomyopathy confirmed at necropsy

Abstract: Serial electrocardiographic changes in necropsy-proven idiopathic dilated cardiomyopathy are evaluated and a method of predicting heart weight using QRS amplitudes is described. In 34 patients with multiple electrocardiograms (mean 3/patient) progressive prolongation of PR interval (0.18 +/- 0.03 to 0.21 +/- 0.03, p less than 0.001) and QRS duration (0.10 +/- 0.02 to 0.13 +/- 0.03, p less than 0.0001) was noted. Progressive conduction abnormalities were common (82%). QTc interval and QRS- and T-wave axes did not change. In 50 patients with electrocardiograms within 60 days of death, total 12-lead QRS and V1 through V6 QRS amplitude correlated better with heart weight (r = 0.51, p less than 0.0001 and r = 0.55, p less than 0.0001) than the Estes-Romhilt score did. The mean total 12-lead QRS amplitude was 138 mm with a mean of 106 for V1 through V6. In 31 patients cardiac mass index was calculated and showed significant correlation with 12-lead and V1 through V6 QRS amplitudes (r = 0.68, p less than 0.0001 and r = 0.75, p less than 0.0001, respectively). The QRS amplitudes remained constant during the illness. By using total 12-lead QRS or frontal plane QRS amplitude, heart weight can be predicted as early as 2 years before death. Use of body surface area and QRS amplitude criteria increases the accuracy of heart weight prediction. Thus, progressive electrocardiographic changes are common in patients with idiopathic dilated cardiomyopathy and QRS amplitude criteria are more accurate in the prediction of left ventricular hypertrophy than standard criteria.

Wide QRS Complex Tachycardia: Reappraisal of a Common Clinical Problem

Abstract: BACKGROUND AND PURPOSE Despite available criteria, diagnosis of the mechanisms of wide complex tachycardia is often incorrect. We aimed in this study to identify reasons for misdiagnoses and the value and limitations of clinical and surface electrocardiographic criteria. DATA IDENTIFICATION The analyzed data of 150 consecutive patients with wide QRS tachycardia from this study and a literature search of key papers in English since 1960 on clinical and surface electrocardiographic criteria form the basis of this report. The final correct diagnosis was made with intracardiac electrograms. DATA EXTRACTION AND ANALYSIS Among the 150 patients, 122 had ventricular tachycardia, 21 had supraventricular tachycardia with aberrant conduction, and 7 had accessory pathway conduction. Only 39 of 122 patients with ventricular tachycardia were correctly diagnosed initially. In others, the diagnoses were supraventricular tachycardia with aberrant conduction (43 of 122) or simply a wide QRS tachycardia (40 of 122). Misdiagnosis in patients with aberrant or accessory pathway conduction was also common. Standard electrocardiographic criteria for ventricular tachycardia had unacceptable sensitivity, poor specificity, or both. Collectively such criteria allowed a correct diagnosis of ventricular tachycardia in 92% of cases. Diagnosis of ventricular tachycardia was also suggested by its association with structural heart disease. Criteria suggestive of ventricular tachycardia included atrioventricular dissociation, positive QRS concordance, axis less than -90 deg to +/- 180 deg, combination of left bundle branch block and right axis, QRS duration of greater than 140 ms with right bundle branch block and greater than 160 ms with left bundle branch block and, a different QRS during tachycardia compared to baseline preexisting bundle branch block. CONCLUSIONS Ventricular tachycardia is the commonest underlying mechanism for wide QRS tachycardia. A correct diagnosis can usually be made from clinical and surface electrocardiographic criteria.

Relationship between the 12-lead electrocardiogram during ventricular tachycardia and endocardial site of origin in patients with coronary artery disease.

Abstract: Previous studies in patients with sustained ventricular tachycardia (VT) have demonstrated the efficacy of surgical and catheter-mediated ablative procedures based on activation mapping during VT. Since extensive preoperative or intraoperative mapping may be impractical due to time constraints or patient intolerance, we sought to define characteristics of the 12-lead electrocardiogram (ECG) during VT that could suggest a particular endocardial region of origin and thus facilitate mapping studies. Endocardial mapping was performed during 182 VTs in 108 patients with prior myocardial infarction of either the anterior or inferior wall. Endocardial sites of origin (sites from which greater than or equal to 40 msec of presystolic electrical activity was consistently recorded) were identified with use of catheter (154 VTs) or intraoperative (85 VTs) activation mapping (both methods used in 57 Vts). Twelve-lead ECGs obtained during these VTs were characterized by four features: location of infarction, bundle branch block type configuration, quadrant of QRS axis, and precordial R wave progression pattern. A specific combination of these four features was associated with a particular endocardial region containing the mapped site of origin in 87 VTs (48% of total). An association (greater than or equal to 70% positive predictive accuracy) was more likely to be found in the presence of left, as opposed to right, bundle branch block type patterns (53/73 [73%] vs 34/109 [31%]; p less than .001) and in the presence of VT related to inferior, as opposed to anterior, infarction (40/54 [74%] vs 47/128 [37%]; p less than .001).(ABSTRACT TRUNCATED AT 250 WORDS)

Electrogram patterns predicting successful catheter ablation of ventricular tachycardia.

Abstract: Ventricular tachycardia in patients with remote myocardial infarction is thought to be due to reentry. To improve the efficacy of catheter ablation, we sought to identify electrograms identifying essential components of the reentrant circuit. In this study we compared the efficacy of shocks delivered at sites of early ventricular activation during tachycardia (presumably exit sites from the reentrant circuit) with that of shocks delivered at sites recording mid-diastolic potentials that were not continuous with the main ventricular potential recorded during the QRS complex, but that always remained associated with the tachycardia during initiation, termination, and resetting with extrastimuli (presumably activation of a segment of the slowly conducting region of the reentrant circuit). A total of 20 attempts was made to ablate 14 monomorphic ventricular tachycardias in 10 patients with remote myocardial infarction with use of one to five shocks of 50 to 370 J (200 J in 70%). All seven tachycardias in which isolated mid-diastolic potentials were targeted were successfully ablated, although one required a second attempt. Twelve attempts were made to ablate seven tachycardias by delivering shocks at sites of early activation during tachycardia when mid-diastolic potentials were not identified. Only three attempts (25%) were successful. Activation preceded the QRS complex by 60, 85, and 120 msec in the three successful attempts and by 20 to 110 msec (median 55 msec) in the nine unsuccessful attempts. For the total 20 attempts, there was no significant difference between successful and nonsuccessful ablation in the number of shocks or total energy delivered.(ABSTRACT TRUNCATED AT 250 WORDS)

Transient alterations of the QRS complex and ST segment during percutaneous transluminal balloon angioplasty of the left anterior descending coronary artery.

Abstract: Using continuous 3-lead electrocardiographic (ECG) recordings in 19 patients undergoing elective percutaneous transluminal coronary artery angioplasty (PTCA) of the left anterior descending (LAD) artery, this study described the dynamic changes of the ST segment and the R- and S-wave amplitudes that occur during transient myocardial ischemia. The waveforms from lead V2 were quantified at 10-second intervals during the length of the balloon inflation that produced the greatest extent of ST-segment deviation. The simultaneous changes that occurred in leads a VF and V5 were also observed, but not quantified. Measurements of R- and S-wave amplitudes were performed during maximal ischemia from both the PR- and the J-ST-segment baselines to determine which of these most nearly maintained its control position during ischemia. The results indicate that the R-wave amplitude is best determined from the PR-segment baseline (p = 0.0007), while the S wave is best determined from the J-ST-segment baseline (p = 0.03). However, only a portion of the QRS changes observed during PTCA could be accounted for by the baseline shift. There were additional QRS changes during ischemia in 11 of the patients (58%) suggestive of conduction disturbances in 3 endocardial sites: left septal, right septal and left anterosuperior. It is hypothesized that these changes may represent ischemia-induced delay in conduction (“periischemic block”) previously thought to occur only with myocardial infarction.

Identification of Ventricular Tachycardia Using Intracavitary Ventricular Electrograms: Analysis of Time and Frequency Domain Patterns

Abstract: LIN, D., ET AL.: Identification of ventricular tachycardia using intracavitary ventricular electrograms: analysis of time and frequency domain patterns. Tachycardia detection by impladtable antitachycardia devices using rate alone has major limitations. Several alternative methods have bden proposed to distinguish ventricular tachycardia or ventricular fibrillation from normal sinus rhythm using intracardiac electrograms. These methods have not been tested, however, for recognition ofventticular tachycardia in patients with abnormal surface QRS conduction during sinus rhythm or with antiarrhythrnic drug therapy. In this study, three techniques for the indentification of ventricular tachycardia from intracavitary bipolar ventricular electrograms were examined and compared: correlation waveform analpsis, amplitude distribution analysis, and spectral analysis using Fast Fourier transformation. Thirty episodes of induced monomorphic ventricular tachycardia were analyzed and compared sinus rhythm in four groups of patients with: 1. Normal surface QRS conduction during sinus rhythm without antidrrhythmic drug therapy [five episodes); 11. Intraventricular conduction delay or bundle branch block during sinus rhythm without antiarrhythmic drug therapy [nine episodes); III. Normal surface QRS conduction during sinus rhythm with antiarrhythmic therapy (six episodes); and N. Intraventricular conduotion delay or bundle branch block during sinus rhythm with antiarrhythmic drug therapy (ten episodes). Correlation waveform analysis had 100% sensitivity and specificity in distinguishing ventricular tachycardia from sinus rhythm, even in the presence of an intraventricular conduction delay, bundle branch block, and antiarrhythmic drug therapy. In contrast, amplitude distribution analysis differentiated 15/30 episodes (50.0%) ofventricular tachycardia from sinus rhythm, and a maximum of 18/30 episodes (60.0%) of ventricular tachycardia were identified by specal analysis using Fast Fourier transformation. Correlation waveform analysis appears to be a reliable technique to discriminate ventricular tachycardia from sinus rhythm using intracavitary ventricular electrograms. Its computational demands are modest, making it suitable for consideration in an implantable antitachycardia device. [PACE, Vol. 11, November 1988)

Supraventricular tachycardia mimicking ventricular-tachycardia during flecainide treatment

Abstract: As a class IC antiarrhythmic drug, flecainide can produce marked widening of the QRS complex. This effect is use dependent,1 indicating that widening of the QRS complex becomes more prominent during faster heart rates. Widening of the QRS complex during tachycardia in patients treated with flecainide can be extreme due to this use dependency. It may create difficulty in determining the origin of the tachycardia, especially if bundle branch block (BBB) supervenes. This report describes flecainide-induced wide complex tachycardias of supraventricular origin, mimicking ventricular tachycardia (VT).

Effect of conduction defects on the signal-averaged electrocardiographic determination of late potentials.

Abstract: To determine the effect of cardiac conduction defects on the signal-averaged electrocardiogram (ECG) and on its ability to noninvasively identify patients predisposed to ventricular tachycardia (VT), standard 12-lead ECGs and signal-averaged ECGs were obtained in 213 patients with normal conduction and 186 patients with various conduction defects. Sustained VT was induced by programmed stimulation or occurred spontaneously in 122 patients. Two-way analysis of variance showed that conduction defects and VT were associated with changes in 3 signal-averaged ECG parameters: duration of the filtered QRS, duration of the terminal QRS under 40 microV and the mean amplitude of the terminal 40 ms of the QRS. Stepwise multiple logistic regression identified 3 variables that distinguished the patient with VT with a sensitivity of 62%, a specificity of 63% and a positive predictive accuracy of 63%. These 3 variables, listed in order of importance, were conduction defect score, duration of the filtered QRS and mean amplitude of the terminal 40 ms of the QRS. These data indicate that conduction defects have systematic effects on signal-averaged ECG parameters independent of those seen in patients predisposed to VT. These effects mandate the adjustment of the definitions of late potentials in the presence of conduction defects.

Identification of patients with sustained ventricular tachycardia by frequency analysis of signal-averaged electrocardiograms despite the presence of bundle branch block.

Abstract: Previously, we have demonstrated distinguishing features in the fast Fourier transform (FFT) of signal-averaged electrocardiograms (ECGs) obtained during sinus rhythm in the absence of bundle branch block that differentiate patients with from those without sustained ventricular tachycardia (VT). The ECGs during sinus rhythm from many patients with sustained VT, however, exhibit intraventricular conduction abnormalities. Accordingly, this study was performed to determine whether the presence of bundle branch block during sinus rhythm precluded accurate identification of patients with sustained VT. Studies were performed in 28 normal subjects (group I) and 141 patients with organic heart disease grouped according to clinical characteristics. Group II comprised 40 patients without VT in whom the QRS duration during sinus rhythm was less than 120 msec. Group III included 21 patients without VT in whom the QRS duration during sinus rhythm was 120 msec or greater. Group IV comprised 43 patients with sustained VT having ECGs during sinus rhythm with QRS durations less than 120 msec. Group V included 37 patients with sustained VT in whom the QRS duration during sinus rhythm was 120 msec or greater. FFTs of the terminal QRS and ST segment of signal-averaged X, Y, and Z ECGs were computed. Transformed data were expressed as an FFT magnitude and the relative contribution and peak magnitudes of 20 to 50 Hz frequencies determined after first demonstrating that this FFT method was more appropriate, when compared with the energy spectrum, for analyzing ECG signals having a broad range of ST segment durations.(ABSTRACT TRUNCATED AT 250 WORDS)

Method for analysis of electrocardiographic signal QRS complex

Abstract: A method and apparatus for examining the QRS complex of ECG signals to detect minute late potentials. The system functions to filter the QRS signals bi-directionally, and further separately processes the two filtered signals through selected window functions before summation. The summed signal is then passed through a smoothing function to produce an output signal of ideal phase that delineates any late potentials within the QRS complex.

Evaluation of a QRS scoring system for estimating myocardial infarct size. VI: Identification of screening criteria for non-acute myocardial infarcts.

Abstract: Each of the 54 criteria in the Selvester 32-point QRS scoring system for estimation of myocardial infarct (MI) size has attained greater than or equal to 95% specificity in normal subjects. This study was performed to identify a subset of those criteria with cumulative specificity greater than or equal to 95% and maximal sensitivity for use in screening for the presence of non-acute MI. Coronary angiography and left ventriculography were used to identify 500 normal subjects, 60 patients with isolated anterior MI and 62 patients with isolated inferior MI. Patients with the QRS confounding factors of ventricular hypertrophy, fascicular block or bundle branch block on their electrocardiogram were not included. Using stepwise logistic regression analysis, the screening criteria identified were: (1) Q greater than or equal to 30 ms in aVF, (2) R less than or equal to 10 ms and less than or equal to 0.1 mV in V2 and (3) R greater than or equal to 40 ms in V1. Cumulatively, these 3 screening criteria achieved 84% and 77% sensitivities for inferior and anterior MI groups, respectively. Thus, a set of 3 criteria from the Selvester QRS scoring system is capable of identifying single non-acute anterior or inferior MI in 80% of patients, and falsely indicating presence of MI in only 5% of normal subjects.

The Only EKG Book You'll Ever Need

Abstract: Getting Started Chapter 1: THE BASICS Electricity and the Heart The Cells of the Heart Time and Voltage P Waves, QRS Complexes, T Waves, and Some Straight Lines Naming the Straight Lines Summary: The Waves and Straight Lines of the EKG Making Waves The 12 Views of the Heart A Word About Vectors The Normal 12-Lead EKG Summary: Orientation of the Waves of the Normal EKG Coming Attractions Chapter 2: HYPERTROPHY AND ENLARGEMENT OF THE HEART Definitions Axis Summary: Axis Axis Deviation, Hypertrophy, and Enlargement Atrial Enlargement Summary: Atrial Enlargement Ventricular Hypertrophy Secondary Repolarization Abnormalities of Ventricular Hypertrophy Summary: Ventricular Hypertrophy CASE 1 CASE 2 Chapter 3: ARRHYTHMIAS The Clinical Manifestations of Arrhythmias Why Arrhythmias Happen Rhythm Strips How to Determine the Heart Rate from the EKG The Five Basic Types of Arrhythmias Arrhythmias of Sinus Origin Ectopic Rhythms Reentrant Rhythms The Four Questions Supraventricular Arrhythmias Summary: Supraventricular Arrhythmias Ventricular Arrhythmias Summary: Ventricular Arrhythmias Summary: Rules of Malignancy for PVCs Supraventricular Versus Ventricular Arrhythmias Summary: Ventricular Tachycardia (VT) Versus Paroxysmal Supraventricular Tachycardia (PSVT) with Aberrancy Programmed Electrical Stimulation Implantable Defibrillators External Defibrillators CASE 3 CASE 4 CASE 5 Chapter 4: CONDUCTION BLOCKS What Is a Conduction Block? AV Blocks Summary: AV Blocks Bundle Branch Block Summary: Bundle Branch Block Hemiblocks Summary: Criteria for Hemiblock Combining Right Bundle Branch Block and Hemiblocks Summary: Criteria for Bifascicular Block Blocks That Underachieve The Ultimate in Playing With Blocks: Combining AV Blocks, Right Bundle Branch Block, and Hemiblocks Pacemakers CASE 6 Chapter 5: PREEXCITATION SYNDROMES What Is Preexcitation? Wolff-Parkinson-White Syndrome Lown-Ganong-Levine Syndrome Associated Arrhythmias Summary: Preexcitation CASE 7 Chapter 6: MYOCARDIAL ISCHEMIA AND INFARCTION What Is a Myocardial Infarction? How To Diagnose a Myocardial Infarction Summary: The EKG Changes of an Evolving Myocardial Infarction Localizing the Infarct Non-Q Wave Myocardial Infarctions Angina Summary: The ST Segment in Ischemic Cardiac Disease Limitations of the EKG in Diagnosing an Infarction Stress Testing CASE 8 Chapter 7: FINISHING TOUCHES Electrolyte Disturbances Hypothermia Drugs Other Cardiac Disorders Pulmonary Disorders Central Nervous System Disease The Athlete's Heart Summary: Miscellaneous Conditions CASE 9 Chapter 8: PUTTING IT ALL TOGETHER The 11-Step Method for Reading EKGs Review Charts Chapter 9: HOW DO YOU GET TO CARNEGIE HALL? (Practice, Practice, Practice!) Practice EKG Strips Subject Index

Quantitative analysis of the signal-averaged QRS in patients with arrhythmogenic right ventricular dysplasia.

Abstract: Temporal signal averaging of the surface QRS (VI + V3 + V5) was performed in 16 patients with arrhythmogenic right ventricular dysplasia and in 16 normal subjects. The differences between ARVD patients and normals were large for the filtered QRS duration (FQRSd) (146.2±18.9 vs. 91.8±4.1ms, P<000001), the late potential duration (LPd) (83.5±23.3 ms vs. 23.6±4.6ms, P< 0.00001), the LPd/ FQRSd ratio (53.9± 10.1% vs. 25.8±5.1%, P <0.00001), the filtered QRS amplitude (234.0±61.1μV vs. 429±942 fiV, P <0001), and the root mean square voltage of the signals in the terminal 40 and 50 ms of the FQRS (RMS40 and RMS50) (18.4± 10.0μV vs. 118.4±49.8p.V, P<0.0005 and 27.9± 19.2μV vs. 217.0±66.3fiV, P<0000002). RMS50 <40μV discriminated best between ARVD and normals (81% sensitivity and 100% specificity). The right-sided predominance of the abnormalities in ARVD was demonstrated by the significantly longer FQRSd and LPd, and the higher ratio LPd/FQRSd in right than in left precordial leads. The arrhythmia susceptibility did not seem to influence the presence of or properties ofLP in the ARVD group. Patients with multiple QRS morphologies during ventricular tachycardia (VT) had, compared with patients with only one type of VT, longer LPd (108.3 ±46.4 ms vs. 64.2 ±31.7 ms, P<0.02) and lower RMS40 voltage (9.4±9.9 μV vs. 25.4±21.6 μV, P<0.05). The relative heart volume was positively correlated with delayed activity, but an enlarged heart was not apre-requisitefor the presence ofLP. The method thus identifies changes which are specific to ARVD. The findings indicate that certain electrical or morphological conditions are required for the occurrence of arrhythmias.

Natural history of late potentials in the first ten days after acute myocardial infarction and relation to early ventricular arrhythmias.

Abstract: Serial signal-averaged electrocardiograms (ECGs) were performed every 48 hours in 50 patients admitted to the coronary care unit with acute myocardial infarction. The prevalence of late potentials was 32% at presentation (mean time to recording 12.4 ± 6.6 hours after onset of chest pain) and increased progressively throughout the hospital stay. New late potentials were recorded in patients with no prior acute myocardial infarction as early as 3 hours after the onset of chest pain and as late as 8 days. Late potentials appeared transiently in only 3 patients. The detection of late potentials in the initial signal-averaged ECG identified patients with clinically significant early ventricular arrhythmias with a sensitivity of 80% and specifity of 72%. The predictive accuracy was 38% for a positive test and 94% for a negative test. Patients with early ventricular arrhythmias had significantly lower voltage in the terminal 40 ms of the filtered QRS complex (16 ± 8 vs 32 ± 19 μV, p

Resetting of ventricular tachycardia with electrocardiographic fusion: incidence and significance.

Abstract: The incidence and significance of fusion of the QRS complex during resetting of sustained ventricular tachycardias (VTs) was determined in 53 VTs induced by programmed stimulation in 46 patients with prior myocardial infarction. All 53 VTs were reset with one or two extrastimuli delivered at the right ventricular apex (RVA); 29 (54.7%) demonstrated fusion of the VT QRS complex coincident with the extrastimulus resetting the VT. Activation time at the RVA during VT (measured from the onset of the VT QRS complex to the first rapid deflection of the RVA electrogram) was longer in VT reset with fusion compared with those without fusion (91 +/- 30 vs 33 +/- 32 msec; p less than .001). A right bundle branch block VT QRS morphology and a rightward and inferior axis were more common in VT reset with electrocardiographic (ECG) fusion. Additionally, the shortest return cycle following the extrastimulus resetting the VT was shorter in VT reset with ECG fusion compared with those without (327 +/- 66 vs 423 +/- 84 msec; p less than .001). Fusion of the endocardial electrogram recorded at the site of VT origin was noted in 11 of 15 VTs that were reset while a recording catheter was positioned at this site, including all eight VTs with evidence of surface ECG fusion and three of seven VTs without fusion. Seventeen VTs were reset from the right ventricular outflow tract as well as the RVA; eight demonstrated QRS fusion at both sites, five from the right ventricular outflow tract only, and four from neither site.(ABSTRACT TRUNCATED AT 250 WORDS)