Showing papers on "QRS complex published in 1998"

Asynchronous Electrical Activation Induces Asymmetrical Hypertrophy of the Left Ventricular Wall

Abstract: Background—Asynchronous electrical activation, induced by ventricular pacing, causes regional differences in workload, which is lower in early- than in late-activated regions. Because the myocardium usually adapts its mass and structure to altered workload, we investigated whether ventricular pacing leads to inhomogeneous hypertrophy and whether such adaptation, if any, affects global left ventricular (LV) pump function. Methods and Results—Eight dogs were paced at physiological heart rate for 6 months (AV sequential, AV interval 25 ms, ventricular electrode at the base of the LV free wall). Five dogs were sham operated and served as controls. Ventricular pacing increased QRS duration from 47.2±10.6 to 113±16.5 ms acutely and to 133.8±25.2 ms after 6 months. Two-dimensional echocardiographic measurements showed that LV cavity and wall volume increased significantly by 27±15% and 15±17%, respectively. The early-activated LV free wall became significantly (17±17%) thinner, whereas the late-activated septum ...

Prognostic significance of the initial electrocardiogram in patients with acute myocardial infarction

Abstract: Context.—Early risk stratification of patients with myocardial infarction is critical to determine optimum treatment strategies and enhance outcomes, but knowledge of the prognostic importance of the initial electrocardiogram (ECG) is limited.Objective.—To assess the independent value of the initial ECG for short-term risk stratification after acute myocardial infarction.Design.—Retrospective analysis of the Global Utilization of Streptokinase and t-PA (alteplase) for Occluded Coronary Arteries (GUSTO-I) clinical trial database.Setting.—A total of 1081 hospitals in 15 countries.Patients.—From the 41021 patients enrolled in the overall study, we selected those who presented within 6 hours of chest pain onset with ST-segment elevation and no confounding factors (paced rhythms, ventricular rhythms, or left bundle-branch block) on the ECG performed before thrombolysis was administered (n=34166).Main Outcome Measure.—Ability of initial ECG to predict all-cause mortality at 30 days.Results.—Most ECG variables were associated with 30-day mortality in a univariable analysis. In a multivariable analysis combining the initial ECG variables and clinical predictors of mortality, the sum of the absolute ST-segment deviation (both ST elevation and ST depression: odds ratio [OR], 1.53; 95% confidence interval [CI], 1.38-1.69), ECG, heart rate (OR, 1.49; 95% CI, 1.41-1.59), QRS duration (for anterior infarct: OR, 1.55; 95% CI, 1.43-1.68), and ECG evidence of prior infarction (for new inferior infarct: OR, 2.47; 95% CI, 2.02-3.00) were the strongest ECG predictors of mortality. A nomogram based on the multivariable model produced excellent discrimination of 30-day mortality (C-index, 0.830).Conclusions.—In patients presenting with myocardial infarction accompanied by ST-segment elevation, components of the initial ECG help predict 30-day mortality. This information should be valuable in early risk stratification, when the opportunity to reduce mortality is greatest, and may help in assessing outcomes adjusted for patient risk.

Acute effects of intraoperative multisite ventricular pacing on left ventricular function and activation/contraction sequence in patients with depressed ventricular function.

Abstract: Multisite Pacing Effect on LV Function Introduction: We hypothesized that simultaneous right and left ventricular apical pacing would result in improvement in left ventricular function due to improved coordination of segmental ventricular contraction Structural changes in ventricular muscle present in dilated cardiomyopathy compromise ventricular excitation and mechanical contraction Methods and Results: Eleven patients with depressed left ventricular function having cardiac surgery underwent epicardial multisite pacing with continuous transesophageal echocardiographic imaging Quantitative measurement of percent fractional area change was performed, and segmental changes in contraction sequence resulting from simultaneous right and left ventricular pacing were assessed by application of phase analysis to recorded transesophageal images There was no statistically significant difference between the paced QRS duration achieved with simultaneous right and left ventricular apical pacing and the native QRS duration (139 ± 39 msec vs 106 ± 18 msec, P = NS), but all other paced modes resulted in longer QRS durations Percent fractional area change improved with simultaneous right and left ventricular apical pacing hut not with other paced modes (415 ± 119 vs 343 ± 97, P < 001) Phase analysis demonstrated a resequencing of segmental left ventricular activation/contraction when compared to baseline ventricular activation Conclusion: Simultaneous right and left ventricular apical pacing results in acute improvements in global ventricular performance in patients with depressed ventricular function Improvements may result from pacing-induced global coordination through recruitment of left and right ventricular apical and septal segments critical to effective ventricular contraction

Electrocardiographic findings in a healthy biracial population

Abstract: It has been well documented that the prevalence of certain electrocardiographic (ECG) findings among individuals free of coronary heart disease (CHD) differs by race. However, it is not known whether these differences exist independently of CHD risk factors (e.g., hypertension). We examined the ECG tracings of 2,686 apparently healthy, middle-aged African-American and white men and women who participated in the Atherosclerosis Risk in Communities Study and were at low risk of CHD. Using the Minnesota Code, among men, 46% of African-Americans, but only 25% of whites, had a minor ECG finding (p < 0.001). In women, 32% of African-Americans and 23% of whites had a minor ECG finding (p < 0.01). Specifically, the age-adjusted prevalences of high-amplitude R wave, ST elevation, T-wave findings, and prolonged P-R interval were statistically significantly higher in African-Americans. As for continuous ECG measurements, the R wave in leads V5 and V6, the S wave in V1, the J-point amplitude in leads V2 and V5, the P-R interval, and the Cornell voltage (?S V3? + R aVL) for left ventricular hypertrophy were all significantly greater in African-Americans than in whites. However, in both men and women, the heart rate corrected QT interval was shorter in African-Americans than in whites. All of these findings remained statistically significant after further adjustment for traditional CHD risk factors. These results suggest that racial differences in electrocardiograms may not be explained entirely by differences in established CHD risk factors, and because current diagnostic ECG criteria are largely based on data from middle-aged white men and women, race should be considered in the interpretation of ECG findings.

ANN-based QRS-complex analysis of ECG.

Abstract: Reliable detection of the QRS complex in either a normal or an abnormal ECG and its analysis is the first and foremost task in almost every ECG signal analysis system aimed at the diagnostic interp...

Verapamil‐Sensitive Left Anterior Fascicular Ventricular Tachycardia: Results of Radiofrequency Ablation in Six Patients

Abstract: Verapamil-Sensitive Left Anterior Fascicular VT. Introduction: Verapamil-sensitive left ventricular tachycardia (VT) with a right bundle branch block (RBBB) configuration and left-axis deviation bas been demonstrated to arise from the left posterior fascicle, and can be cured by catheter ablation guided by Purkinje potentials. Verapamil-sensitive VT with an RBBB configuration and right-axis deviation is rare, and may originate in the left anterior fascicle. Methods and Results: Six patients (five men and one woman, mean age 54 ± 15 years) with a history of sustained VT with an RBBB configuration and right-axis deviation underwent electrophysiologic study and radiofrequency (RF) ablation. VT was slowed and terminated by intravenous administration of verapamil in all six patients. Left ventricular endocardial mapping during VT identified the earliest ventricular activation in the anterolateral wall of the left ventricle in all patients. RF current delivered to this site suppressed the VT in three patients (ablation at the VT exit). The fused Purkinje potential was recorded at that site, and preceded the QRS complex by 35, 30, and 20 msec, with pace mapping showing an optimal match between the paced rhythm and the clinical VT. In the remaining three patients, RF catheter ablation at the site of the earliest ventricular activation was unsuccessful. In these three patients, Purkinje potential was recorded in the diastolic phase during VT at the mid-anterior left ventricular septum. The Purkinje potential preceded the QRS during VT by 66, 56, and 63 msec, and catheter ablation at these sites was successful (ablation at the zone of slow conduction). During 19 to 46 months of follow-up (mean 32 ± 9 months), one patient in the group of ablation at the VT exit bad sustained VT with a left bundle branch block configuration and an inferior axis, and one patient in the group of ablation at the zone of slow conduction experienced typical idiopathic VT with an RBBB configuration and left-axis deviation. Conclusion: Verapamil-sensitive VT with an RBBB configuration and right-axis deviation originates close to the anterior fascicle. RF catheter ablation can be performed successfully from the VT exit site or the zone of slow conduction where the Purkinje potential was recorded in the diastolic phase.

Time-voltage QRS area of the 12-lead electrocardiogram: detection of left ventricular hypertrophy.

Abstract: Identification of left ventricular hypertrophy (LVH) using 12-lead ECG criteria based primarily on QRS amplitudes has been limited by poor sensitivity at acceptable levels of specificity. Because the product of QRS voltage and duration, as an approximation of the time-voltage area of the QRS complex, can improve accuracy of the 12-lead ECG for LVH, we examined the diagnostic value of true time-voltage area measurements of QRS complexes from the standard 12-lead ECG. Standard 12-lead ECGs and echocardiograms were obtained in 175 control subjects without LVH and in 74 patients with regurgitant valvular heart disease and LVH defined by echocardiographic criteria (indexed LV mass >110 g/m2 in women and >125 g/m2 in men). Standard voltage criteria, voltage-duration products (voltage multiplied by QRS duration), and true time-voltage areas of the QRS were calculated for Sokolow-Lyon criteria (SV1 +RV(5/6)) and the 12-lead sum of voltage criteria. Test sensitivities were compared using gender-specific partitions with matched specificity of 98% in the 175 subjects without LVH. Measurement of the time-voltage area significantly improved sensitivity for both criteria. The 76% sensitivity of the 12-lead sum area and 65% sensitivity of Sokolow-Lyon area were significantly greater than the 54% sensitivity of the approximation of QRS area provided by each voltage-duration product (P<.001 and P=.021) and than the 46% and 43% sensitivities of the respective simple voltage criteria (each P<.001). Comparison of receiver operating characteristic curves confirmed the superior overall performance of time-voltage area criteria compared with both voltage-duration products and simple voltage criteria. These results suggest that use of time-voltage areas can dramatically improve identification of LVH by 12-lead ECG. Further study of this approach is needed to identify optimal criteria for LVH based on the time-voltage area measurements from the 12-lead ECG.

Circadian rhythm of the signal averaged electrocardiogram and its relation to heart rate variability in healthy subjects

Abstract: Objective To examine the circadian variation in the signal averaged electrocardiogram (saECG) and heart rate variability and investigate their relations in healthy subjects. Methods 24 hour ECGs were obtained with a three channel recorder using bipolar X, Y, and Z leads in 20 healthy subjects. The following variables were determined hourly: heart rate, filtered QRS (f-QRS) duration, low and high frequency components of heart rate variability (LF and HF), and the LF/HF ratio. Results Heart rate, f-QRS duration, HF, and the LF/HF ratio showed significant circadian rhythms, as determined by the single cosinor method. Heart rate and the LF/HF ratio increased during daytime, and f-QRS duration and HF increased at night. f-QRS duration was negatively correlated with heart rate ( r = 0.95, p r = 0.94, p r = 0.93, p Conclusions f-QRS duration has a significant circadian rhythm in healthy subjects and is closely related to the circadian rhythm of autonomic tone.

Familial Sudden Cardiac Death Associated with a Terminal QRS Abnormality on Surface 12‐Lead Electrocardiogram in the Index Case

Abstract: Familial Sudden Death and ECG Abnormalities. A case is presented of an 18-year-old male who had been resuscitated following an episode of sudden death due to ventricular fibrillation. The patient was noted to have an abnormal deflection in the terminal QRS on surface ECG and an abnormal signal-averaged KCG demonstrating a late potential coincident with the terminal QRS abnormality on the ECG. The patient had easily inducible polymorphic ventricular tachycardia during electrophysiologic study, which was suppressed by quinidine but not by procainamide or beta blockers. The surface ECG and signal-averaged ECG also were normalized by quinidine but not by procainamide or beta blockers. The patient had no further arrhythmias on quinidine for 6 years until he inexplicably discontinued his medication and died suddenly shortly thereafter. The present case may represent a unique familial sudden death syndrome or possibly a variant of the sudden death syndrome associated with right bundle branch block and ST elevation in V1, through V3, Currently available data suggest that, in such patients, an implantable cardioverter defibrillator may provide better protection from sudden death than does antiarrhythmic drug therapy.

Specific electrocardiographic features of manifest coronary vein posteroseptal accessory pathways

Abstract: Coronary Vein Accessory Pathways. Introduction: Some posteroseptal accessory pathways (APs) can be successfully ablated by radiofrequency current only from inside the coronary sinus (CS) or its branches, because of an absolute or relatively epicardial location. The aim of this study was to identify ECG features of manifest posteroseptal APs requiring ablation in the CS or the middle cardiac veins (MCVs). Methods and Results: One hundred seventeen consecutive patients with manifest posteroseptal APs successfully ablated: (1) ≥ 1 cm deep inside the MCV (group MCV: n = 13); (2) inside the CS, including the area adjacent to the MCV ostium (group CS: n = 10); (3) at the right (group R: n = 60); or (4) the left posteroseptal endocardial region (group L: n = 34) were included. We reviewed delta wave polarity (initial 40 msec) and QRS morphology during sinus rhythm and atrial pacing as well as electrogram characteristics in these patients. The local target site electrogram in groups MCV and CS was characterized by a longer atrial to ventricular electrogram interval, suggesting a longer course of the pathway and more frequent recording of a presumptive AP potential compared to the group ablated at the right or left endocardium. The most sensitive ECG feature for group CS or group MCV was a negative delta wave in lead II in sinus rhythm (87%), but specificity (79%) and positive predictive value (50%) were relatively low. A steep positive delta wave in aVR during maximal preexcitation possessed the highest specificity and positive predictive value (98% and 88%, sensitivity 61%) which increased to 99% and 91%, respectively, when combined with a deep S wave in V6 (R wave ≤ S wave). Conclusion: These data suggest that posteroseptal APs ablated inside the coronary venous system have highly specific features, including the combination of a steep positive delta wave in lead aVR and a deep S wave in lead V6 (R wave ≤ S wave) during maximal preexcitation. The highest sensitivity is provided by a negative delta wave in lead II. These findings may be helpful for anticipating and planning an epicardial ablation strategy.

Signal-averaged ECG abnormalities in haemodialysis patients. Role of dialysis.

Abstract: Background. Late potentials (LP) on the signal-averaged electrocardiogram (SAECG) are predictive of malignant ventricular arrhythmias and sudden cardiac death in patients with ischaemic and non-ischaemic cardiomyopathy. Cardiac dysfunction, both regional and global, as well as supraventricular and ventricular arrhythmias are reported in a high percentage of patients with end-stage renal failure (ESRF). The aim of the study was to assess the prevalence of LP and the effects of haemodialysis on the SAECG of ESRF patients. Methods. SAECG was recorded immediately before and within 30min after the end of dialysis in 48 patients in sinus rhythm, free of conduction disturbances on ECG and of signs of congestive heart failure. Serum electrolytes were sampled together with the SAECG recordings. An echo-Doppler exam was performed within 2 weeks of the study. SAECGs were adequate for analysis in 45/48 patients. LP were present when at least two of the following criteria were fulfilled: QRS duration ≤ 115 ms, LAS 40 ≤38 ms, RMS 40 ≥ 38 μV at 40 Hz high pass bidirectional filter, and noise <0.7 μV. Results. LP were detected in 12/45 patients (25%) on the SAECG before dialysis; of these 12 patients, seven had a history of a previous myocardial infarction and two had documented coronary artery disease (CAD). A significant greater wall motion score index-calculated on a 16 segment model-was reported in patients with LP (1.20±0.20 vs 1.01±0.03, P<0.01), while left ventricular mass was comparable in the two groups of patients. At the end of dialysis, a significant prolongation of fQRS duration was found both at 25 and 40 Hz filters (from 98±11 to 106±16 ms and from 97±12 s to 102±13 ms, respectively, P < 0.001). A significant inverse relationship was seen between the percentage of dialysis-induced serum potassium reduction and fQRS changes at 40 Hz (r = - 0.68, P<0.001). Conclusions. LP were detected in a significant proportion of dialysis patients, probably related to underlying CAD with left ventricular dysfunction. Prolongation of fQRS after dialysis could be explained by the acute reduction in serum potassium levels.

The heart remembers.

Abstract: Time for primary review 21 days. Cardiac memory was characterized by Rosenbaum et al. in 1982 as ST-T wave changes induced by ventricular pacing or arrhythmia that persist long after normal ventricular activation has resumed [1]. Rosenbaum's work enlarged upon the earlier studies of Chatterjee et al. [2]who reported persistent postpacing changes in T wave morphology. The key aspects of cardiac memory were that the magnitude and persistence of the postpacing T wave changes increased with the duration of abnormal ventricular activation (referred to as ‘accumulation’) (Fig. 1), and the subsequent normalization of the T wave occurred slowly, requiring hours to months, depending on the duration of the inciting stimuli. Fig. 1 (A) T wave changes in a human subject in complete heart block before and after siting a ventricular pacemaker, and then with the pacemaker turned off after 15 minutes and 3, 8 and 15 days after the onset of pacing. Note the progressive evolution of the T wave change (reprinted from reference [2], by permission). (B) Cardiac memory evolution over 21 days of ventricular pacing (VP). Depicted are leads I and aVR from one dog during control, during VP, and at the end of 1 hour after pacing was discontinued on days 7, 14, and 21. In both leads, evolution of the T wave is such that it tracks the vector of the paced QRS complex (reprinted from reference [15], by permission). (C) Frontal plane vectorcardiographic depiction of cardiac memory from the same dog presented in Figure 1B. A shows P, QRS, and T wave vectors in control, before the onset of pacing. B: The QRS and T vectors during ventricular pacing. C: The T wave vector alone (note enlarged scale as well as dotted line indicating the change in vector) during sinus rhythm in control … * Corresponding author. Tel.: +1-212-305-8754; fax: +1-212-305-8351; e-mail: emf3@columbia.edu

Electrocardiographic changes after alcohol septal ablation in hypertrophic obstructive cardiomyopathy

Abstract: Objective—To report acute and mid-term electrocardiographic changes in patients with hypertrophic obstructive cardiomyopathy (HOCM) after alcohol ablation of the first large septal branch of the left anterior descending coronary artery; and to relate electrocardiographic data with the left ventricular outflow tract pressure gradients. Patients—Nine consecutive symptomatic patients with HOCM (mean (SD) age 45 (12) years). Methods—Analysis of baseline and postprocedure ECGs and 24 hour ambulatory monitoring (up to six months). ECG data were related to left ventricular outflow tract pressure gradients. Results—One patient developed complete atrioventricular block requiring permanent pacing. The PR interval was significantly prolonged up to third month after ablation. Immediately after the procedure all patients developed right bundle branch block. At the sixth month of follow up, right bundle branch block was present in four patients. New anterior ST elevation developed immediately after ablation in five of the nine patients, and new Q waves in four. The QRS duration was significantly prolonged immediately after ablation and during follow up. There was significant but transient prolongation of QT-mean and QTc-mean intervals. QT dispersion, QTc dispersion, and JTc-mean interval were not affected. JT and JTc dispersions were transiently prolonged. No serious ventricular arrhythmias were recorded during Holter monitoring, either before or after the procedure. There were no significant correlations between the left ventricular outflow tract pressure gradient and QTc, QT-d, QTc-d, JTc, JT-d, JTc-d, or QRS duration before and after ablation. Conclusions—Alcohol septal ablation for HOCM induces significant changes in the resting ECG in most patients, despite the occlusion of a relatively small artery. The changes include new Q waves, new bundle branch block, transient anterior ST segment elevation, atrioventricular block, and transient prolongation of QT interval. Keywords: hypertrophic obstructive cardiomyopathy; alcohol septal ablation; electrocardiography; QT interval

Abnormal ventricular activation and repolarisation during dobutamine stress echocardiography in coronary artery disease

Abstract: Objective—To assess possible ECG changes caused by dobutamine stress and their relation to wall motion disturbances in patients with coronary artery disease. Design—Prospective recording and analysis of 12 lead ECG at rest and during each stage of dobutamine stress echocardiography, and correlation with wall motion changes. Setting—A tertiary referral centre for cardiac disease equipped with noninvasive facilities for pharmacological stress tests. Subjects—27 patients, mean (SD) age 60 (8) years, with documented evidence of coronary artery disease in whom dobutamine stress echo was clinically indicated, and 17 controls of similar age. Results—In controls, all ECG intervals shortened with increasing heart rate but in the patient group only PR and QT intervals shortened while QRS duration broadened and QTc interval prolonged progressively. In the 27 patients, 16 developed chest pain, 15 with reduced left ventricular long axis systolic excursion (p < 0.001), and all showed reduced peak lengthening rate; ST segment shift appeared in 16, 13 of whom developed chest pain, but did not correlate with reduction of either systolic long axis excursion or peak lengthening rate; QRS duration broadened in 20, 16 with reduction of long axis excursion (p < 0.02) which was more often seen at the septum (p < 0.005); QTc interval prolonged in 19, all of whom had associated reduction of peak long axis lengthening rate (p < 0.02). Conclusions—QRS duration and QTc interval both normally shorten with dobutamine stress, while in coronary artery disease they both lengthen: changes in QRS duration correlate with systolic and QTc interval with diastolic left ventricular wall motion disturbances. ST segment shift also occurred in most patients, but without consistent correlation with wall motion abnormalities. It was thus less discriminating than the other two abnormalities in this respect. (Heart 1998;79:468‐473)

Intracardiac QRS Electrogram Width—An Arrhythmia Detection Feature for Implantable Cardioverter Defibrillators: Exercise Induced Variation as a Base for Device Programming

Abstract: Delivery of inappropriate therapy of implantable cardioverter defibrillators (ICD) due to inaccurate arrhythmia detection represents a major clinical problem. Different arrhythmia detection criteria such as the "stability" of the cycle length or the suddenness of "onset" of tachycardia have been implemented in ICD software to prevent inappropriate therapy. The new Medtronic model 7223Cx ICD offers an additional detection parameter (QRS width), which reflects changes in the duration of ventricular depolarization as a tool to distinguish supraventricular from ventricular tachycardias. Although this criterion can be programmed based on ECG parameters derived from resting ECGs, this may not be sufficient since QRS width is subject to considerable changes due to transient myocardial ischemia, changes in autonomic tone, or frequency dependent effects of antiarrhythmic drugs. The present study aimed to determine frequency dependent changes in QRS width in individual patients at rest and during symptom-limited exercise testing in 16 patients with documented ventricular tachycardia (N = 13) or ventricular fibrillation (N = 3). The optimal EGM slew threshold and the individual variation of QRS width were determined. Measurements obtained at the end of the implantation procedure were compared to those performed at hospital discharge. The majority of patients showed a wider variation in QRS duration as measured from 30 consecutive cycles during exercise as compared to rest. For example, the QRS range (i.e., the difference between the maximal and the minimal QRS width measured) averaged 7 +/- 3 ms at rest and increased to 11 +/- 3 ms during exercise (P = 0.004) with an increase of > or = 4 ms observed in 11 (69%) of 16 patients. In 13 (81%) of 16 patients a reprogramming of at least one QRS width parameter from its value at the time of implantation was necessary. Thus, the QRS width measured from the intracardiac EGM shows significant intraindividual variations in different physiological conditions. For optimal programming of the QRS width parameter, measurements obtained during exercise are important.

Solitary Papillary Muscle Hypertrophy as a Possible Form of Hypertrophic Cardiomyopathy

Abstract: Patients can present with hypertrophied papillary muscles in the left ventricle, even without hypertrophy in other segments, and they have electrocardiographic (ECG) abnormalities suggestive of hypertrophic cardiomyopathy (HCM). This study was performed to evaluate whether the solitary papillary muscle hypertrophy was related to HCM. By analyzing 6731 echocardiographic studies between 1990 and 1994, the incidence of patients with papillary muscle hypertrophy was retrospectively examined, as well as the ECG features and family history related to HCM in these patients. After the normal size of the anterolateral and posteromedial papillary muscles was obtained from echocardiographic studies in 40 healthy subjects (0.7 +/- 0.2 cm for each of the vertical and horizontal axis), papillary muscle hypertrophy was defined as follows: either the vertical or horizontal diameter of at least one of the 2 papillary muscles was more than 1.1 cm (mean+2SD in the normal subjects). Using this definition, 29 patients with papillary muscle hypertrophy were identified, of whom 14 (48%) showed high voltage QRS complexes, 10 (34%) showed T wave inversion, and 6 (21%) showed abnormal Q waves. Ten patients (34%) had a family history of HCM. In 2 patients that were followed for 18 and 11 years, respectively, the voltages of the QRS complexes and inverted T waves progressed with the hypertrophy of the papillary muscle. These findings suggest that solitary papillary muscle hypertrophy is related to HCM and that papillary muscle hypertrophy is a newly identified subtype of or an early form of HCM.

Radiofrequency catheter ablation of left ventricular outflow tract tachycardia: report of two cases.

Abstract: Idiopathic ventricular tachycardia (VT) originating from the left ventricular outflow tract (LVOT) is rare. We report two patients whose QRS configuration during VT commonly showed an inferior axis and monophasic R waves in all the precordial leads. The mechanism of these VTs appeared to be triggered activity. From mapping and ablation, the origin of these VTs was determined to be in the most posterior LVOT, corresponding to the aortomitral continuity (left fibrous trigone).

«El corazón del deportista»: hallazgos electrocardiográficos más frecuentes

Abstract: The morphological and functional cardiac adaptations induced by physical training may be reflected in several athlete's electrocardiographic variants. Rhythm and heart rate disturbances are the most common findings, and sinus bradycardia is the most frequent adaptation. Non-specific intraventricular conduction delay and incomplete right bundle branch block are also frequent, but other bundle branch and fascicular blocks are extremely rare. While the atrioventricular conduction may be prolonged, the occurrence of first degree and type I second degree atrioventricular blocks depends on the individual's susceptibility. Advanced second and third degree atrioventricular blocks are exceptional, and when present, the possibility of underlying heart disease must be excluded. High QRS voltage is more frequent in male athletes, but its correlation with left ventricular hypertrophy is low. The ST segment elevation in the so called "early repolarization" pattern is typical of the athlete's electrocardiogram. Vagotonic or high T wave voltages and U waves are also frequent when sinus bradycardia is present. Tachyarrhythmias and increased automatism arrhythmias are rare and usually benign. The increased vagal tone is responsible for the suppression of the physiological and ectopic pacemakers. While Wolff-Parkinson-White syndrome per se does not exclude an athlete from sports activity, the risk of a sudden death makes it mandatory to perform an exhaustive cardiac evaluation. We may conclude that no sport can be considered arrhythmogenic or as a predisposing factor for malignant ventricular arrhythmias.

Electrocardiographic and morphometric features in patients with ventricular tachycardia of right ventricular origin

Abstract: Objective—To study differences between repetitive monomorphic ventricular tachycardia (RMVT) of right ventricular origin, and ventricular tachycardia in arrhythmogenic right ventricular dysplasia (ARVD). Patients—Consecutive groups with RMVT (n = 15) or ARVD (n = 12), comparable for age and function. Methods—Analysis of baseline, tachycardia, and signal averaged ECGs, clinical data, and right endomyocardial biopsies. Pathological findings were related to regional depolarisation (QRS width) and repolarisation (QT interval, QT dispersion). Results—There was no difference in age, ejection fraction, QRS width in leads I, V1, and V6, and QT indices. During ventricular tachycardia, more patients with ARVD had a QS wave in V1 (p < 0.05). There were significant differences for unfiltered QRS, filtered QRS, low amplitude signal duration, and the root mean square voltage content. In the absence of bundle branch block, differences became non-significant for unfiltered and filtered QRS duration. Mean (SD) percentage of biopsy surface differed between RMVT and ARVD: normal myocytes (74(3.4)% v 64.5(9.3)%; p < 0.05); fibrosis (3(1.7)% v 8.9(5.2)%; p < 0.05). When all patients were included, there were significant correlations between fibrosis and age (r = 0.6761), and fibrosis and QRS width (r = 0.5524 for lead I; r = 0.5254 for lead V1; and r = 0.6017 for lead V6). Conclusions—The ECG during tachycardia and signal averaging are helpful in discriminating between ARVD and RMVT patients. There are differences in the proportions of normal myocytes and fibrosis. The QRS duration is correlated with the amount of fibrous tissue in patients with ventricular tachycardia of right ventricular origin. Keywords: arrhythmogenic right ventricular dysplasia; electrocardiography; endomyocardial biopsy; ventricular arrhythmias

Acute posterior wall myocardial infarction: Electrocardiographic manifestations

Abstract: Myocardial infarction (MI) of the posterior wall of the left ventricle involves occlusion of either the left circumflex or the right coronary artery. Posterior wall MI most often occurs along with acute inferior or lateral MI; isolated posterior wall MI, however, does occur. Electrocardiographic abnormalities suggestive of acute posterior wall MI include the following (in leads V1, V2, or V3): (1) horizontal ST segment depression; (2) a tall, upright T wave; (3) a tall, wide R wave; and (4) and R/S wave ratio greater than 1.0 (in lead V2 only). Further, the combination of horizontal ST segment depression with an upright T wave increased the diagnostic accuracy of these two separate electrocardiographic findings. The additional-lead electrocardiogram using left posterior thorax leads is potentially helpful; ST segment elevation greater than 1 mm in this distribution suggests an acute posterior wall MI>

Localization of Optimal Ablation Site of Idiopathic Ventricular Tachycardia from Right and Left Ventricular Outflow Tract by Body Surface ECG

Abstract: Background—Idiopathic ventricular tachycardia (VT) is known to arise from the right ventricular (RV) and left ventricular outflow tracts (LVOT). However, reliable noninvasive methods to localize the optimum ablation site for VT have not been reported. Methods and Results—Body surface maps (BSM) and 12-lead ECGs were investigated in 35 VTs from the RVOT and 5 VTs from the LVOT in which the origin was confirmed during the ablation procedure. The RVOT was classified into 8 subdivisions with the use of a 3-dimensional anatomic relation: anterior (A)–posterior (P), right (R)–left (L), and superior (S)–inferior (I). On the BSM, the following 3 indexes differentiated each location of the origin, with a diagnostic accuracy of 88% (A-P), 92% (R-L), and 77% (S-I): (1) the location of the minimum at the early-to-mid QRS (right, A; left, P), (2) the isopotential distribution in the left shoulder area after 30 ms of QRS (positive, R; negative, L), and (3) the downward moving time of the minimum at the early-to-mid QRS...

Effects of postmyocardial infarction scar size, cardiac function, and severity of coronary artery disease on QT interval dispersion as a risk factor for complex ventricular arrhythmia.

Abstract: The aim of the study was to determine the relation between QT dispersion and ventricular arrhythmia after myocardial infarction, as well as the effects of postinfarction scar size, cardiac function, and severity of coronary artery disease on QT dispersion. Three hundred three patients, 3 months after myocardial infarction, and a group of 21 healthy subjects were evaluated. QT dispersion was the difference between maximal and minimal QT interval in 12-ECG leads. Postinfarction scar size was determined by Selvester's QRS scoring system. Cardiac function was evaluated by echocardiography and exercise stress test, and the severity of coronary artery disease by the number and degree of coronary artery stenoses. QT dispersion increased significantly in relation to the severity of arrhythmia ( 80 ms was associated with ventricular tachycardia with the sensitivity of 68% and specificity of 88%. QT dispersion also increased significantly, dependent on the postinfarction scar size (0% vs > or = 33% of left ventricular myocardium; 61.8 [+/- 16.4] vs 74.7 [+/- 16] ms, P 0.05). In conclusion, QT dispersion is a risk marker of complex ventricular arrhythmia in the chronic stage of myocardial infarction. Multiple regression analysis indicates that only the postinfarction scar size has an independent effect on QT dispersion (R2 = 0.39, P < 0.05).

Evidence for an influence of mechanical restitution on beat-to-beat variations in haemodynamics during chronic atrial fibrillation in patients

Abstract: Objective : We tested the hypothesis that beat-to-beat changes in haemodynamics during atrial fibrillation include an effect of each preceding R–R interval through the interval–strength relationship (mechanical restitution). Background : The variation in stroke volume and pulse pressure characteristic of atrial fibrillation is usually ascribed to time dependent ventricular filling. Methods : We measured the maximum rate of rise of left ventricular pressure (LVd P /d t max), and aortic blood velocity and its integral in patients with atrial fibrillation undergoing cardiac catheterisation. The contractile response of isometric human myocardial trabeculae to sequences of atrial fibrillation was also studied, using the recorded ECGs as stimuli. The trabeculae were obtained from the resected right ventricular outflow tracts of patients with Fallot's tetralogy undergoing operative correction. Results : Beat-to-beat variations in contractile function during atrial fibrillation in the patients were recorded as LVd P /d t max and left ventricular ejection (ascending aortic) velocity integral (proportional to stroke volume). Both these indices correlated well with the response to the same ECG (R wave) sequences in the isometric model measured as the maximum rate of rise of force, d F /d t max, r =0.72 to 0.81, p <0.0001. When short pre-preceding intervals were excluded (minimizing the effect of post-extrasystolic potentiation), these variables showed a positive curvilinear relationship to preceding interval typical of mechanical restitution. Conclusions : Mechanical restitution, which causes beat-to-beat changes in inotropic state, accounts in part for the changes in stroke volume in atrial fibrillation.