Journal of Electrocardiology

International Congress on Electrocardiology 2011 in Kingston, Ontario, Canada

Adrian Baranchuk, Alejandro Barbagelata — 2012-05-01

The 38th International Congress on Electrocardiology (ICE) was hosted in Kingston, Ontario, Canada, in June 8 to 11, 2011. With the financial help of Queen's University, the Kingston Economic Development Corporation and the device and drug industry, we have been able to organize a rich scientific agenda. We also had time to enjoy some of the Kingston pearls: the Gala Night was hosted at Fort Henry, built in 1812 near the mouth of the Cataraqui River where it flows into the St Lawrence River, at the upper end of the Thousand Islands. ICE meetings are characterized by broad areas of interest, and ICE 2011 was not the exception. Topics on clinical arrhythmias, inherited arrhythmic disorders, mathematical modeling, and new diagnostic imaging alternatives were discussed at the highest possible scientific level.

Why the sudden PR prolongation?

Laszlo Littmann, Rehan Khan — 2012-02-22

Coexisting early repolarization pattern and Brugada syndrome: recognition of potentially overlapping entities

2011-12-19

Abstract: The Brugada type 1 electrocardiographic (ECG) pattern and the early repolarization pattern (ERP) are 2 ECG patterns characterized by the appearance of J waves. Although Brugada type 1 ECG pattern in the context of the Brugada syndrome (BrS) is well known for predisposing to life-threatening ventricular arrhythmias, it has only recently come to light that ERP, which was previously believed to be benign, may also be a marker for arrhythmogenic potential. ERP and BrS share many remarkable cellular, ionic, and ECG similarities and behave comparably in terms of their response to heart rate, pharmacologic agents, and neuromodulation. The extent to which ERP and BrS may overlap remains unclear.Here, we present an illustrated case of a symptomatic patient whose ECG signature evolved spontaneously from ERP alone to ERP with a concomitant Brugada type 1 ECG pattern over a short number of days. This case lends further strength to the notion that these 2 ECG patterns may be more closely related than had been initially thought.

Ventricular flutter triggered by fever in a patient with Brugada syndrome

2012-02-10

Abstract: Brugada syndrome is a clinical-electrocardiographic entity predisposing to malignant ventricular arrhythmias. The typical arrhythmia is polymorphic ventricular tachycardia, which can potentially degenerate to ventricular fibrillation. Monomorphic ventricular tachycardia is uncommon. Our group is reporting the case of a 39-year-old man with known Brugada syndrome who developed ventricular flutter while febrile. Fever has previously been shown to unmask Brugada changes and to induce ventricular arrhythmias. The appearance of monomorphic ventricular tachycardia potentially attributable to sodium-channel dysfunction further confounds the mechanism of arrhythmogenesis in Brugada syndrome. This curious occurrence further underlines the likely complex nature of arrhythmogenesis in Brugada syndrome.

Long-term results of slow pathway ablation in patients with atrioventricular nodal reentrant tachycardia: simple approach

Francisco Femenía, Mauricio Arce, Martín Arrieta, Jorge Palazzolo, Emilce Trucco — 2012-01-19

Abstract: Aims: The aim of this study was to report the short- and long-term results of slow pathway radiofrequency (RF) ablation in patients with atrioventricular (AV) nodal reentrant tachycardia (AVNRT) using a simplified approach (2 catheters and short applications of RF).Materials and Methods: This was a retrospective study that included consecutive patients with AVNRT. We used an anatomical approach with only 2 catheters. Decremental AV nodal conduction and atrial-His conduction interval jump were measured. To detect the onset of the QRS, we used surface lead II. During the stimulation protocol, we performed S2-QRS and S3-QRS measurements. An increase in the S3-QRS3 interval of 50 milliseconds or greater in response to a decrease in the S2-QRS2 coupling interval of 10 milliseconds was defined as a discontinuous AV nodal function curve and taken as evidence of dual antegrade AV pathways. Atrioventricular nodal reentrant tachycardia was demonstrated by the presence of dual AV nodal physiology, atrial echoes, and tachycardia induction with a 1:1 AV relationship and a VA interval of less than 70 milliseconds. Short RF applications (10-15 seconds) were delivered at an intermediate point between the posteroseptal and medioseptal regions of the Koch triangle. The applications were considered effective when junctional rhythm appeared. The end point was the demonstration of slow pathway modification without AVNRT induction.Results: Three hundred forty-four patients (age, 49.22 ± 17.47 years; 254 were female) were included. Discontinuous AV nodal function curves were found in 271 patients (78.77%), and short-term success was achieved in all patients. The anterograde jump in AV nodal conduction was abolished after RF in 222 patients (81.91%), and discontinuous AV nodal conduction and single AV nodal echo beats persisted in 49 cases (18%). The mean number of RF application was 7.79 ± 2.23, the mean number of effective applications was 4.63 ± 0.62, and the mean RF application time was 54.92 ± 8.03 seconds. The total procedure and fluoroscopy time was 29.45 ± 9.6 and 10.87 ± 2.36 minutes, respectively. After the procedure, all patients were followed up for a mean of 46.44 ± 18.89 months, and 7 patients (2%) presented AVNRT recurrences. Complications were observed in 4 patients (1.16%); no permanent AV block was observed.Conclusion: In this study, slow pathway RF ablation using a simplified approach technique is an effective and safe approach for the treatment of AVNRT.

Optimized electrocardiographic criteria for prior inferior and anterior myocardial infarction

Robert A. Warner, Norma E. Hill — 2012-01-04

Abstract: Background and Purpose: The first purpose of the study was to optimize empirically the detection of prior inferior myocardial infarction (IMI) and prior anterior myocardial infarction (AMI) by electrocardiogram (ECG). The second purpose was to compare the diagnostic performances of the new criteria with those of 3 widely used commercial diagnostic ECG algorithms.Materials and Methods: We analyzed the digital ECG data from 1138 subjects with suspected coronary artery disease in whom the presence or absence of prior IMI or AMI was documented by coronary angiography and left ventriculography. We used receiver operating characteristic curves to develop the new criteria for prior IMI and AMI using a training set of 562 subjects and then tested their diagnostic performances using a separate test set of 576 subjects. In both the training and test sets, we used χ2 test to compare the performances of the new criteria with those of 3 commercial computerized diagnostic algorithms.Results: The best criterion for prior IMI was the algebraic sum of the Q and T amplitudes in leads III and aVF. Its sensitivities/specificities were 71%/98% and 74%/98% in the training and test sets, respectively. The best criterion for prior AMI was the algebraic sum of the Q, R, and T amplitudes minus the Q duration in leads V2, V3, and V4. Its sensitivities/specificities were 68%/98% and 65%/98% in the training and test sets, respectively. In both the training and test sets, these diagnostic performances were generally superior to those of the 3 commercial algorithms.Conclusions: Using digital ECG data, we developed and tested new criteria for prior IMI and AMI whose diagnostic performances are generally superior to each of 3 widely used commercial ECG diagnostic algorithms.

Exercise training slows down heart rate and improves deceleration and acceleration capacity in patients with heart failure

Roberto Ricca-Mallada, Eduardo R. Migliaro, Jaroslaw Piskorski, Przemyslaw Guzik — 2012-02-17

Abstract: Controlled physical training has been shown to be a valuable therapeutic addition to a pharmacological treatment in patients with chronic heart failure (CHF). It is speculated that repeated physical training can improve the autonomic modulation of the cardiovascular system in patients with CHF. The present study evaluates autonomic function in patients with CHF by means of heart rate variability and the phase-rectified signal averaging of heart rate that allows the quantification of the acceleration capacity and deceleration capacity. Two groups of patients with CHF treated with comparable pharmacological medications were enrolled into this study. One group entered a 24-week training program, whereas another group remained without it. After the completion of the study, there was a significant increase of mean RR interval, high- and low-frequency power of heart rate variability, and the magnitudes of deceleration capacity and acceleration capacity only in patients who underwent the cardiac rehabilitation program with controlled physical training.

Compensatory properties of heart rate asymmetry

Jaroslaw Piskorski, Przemyslaw Guzik — 2012-05-01

Abstract: Background: Heart rate asymmetry (HRA) is a physiologic phenomenon that reflects a systematic and 1-directional difference between heart rate accelerations and decelerations. In terms of variance-based descriptors, HRA causes the contributions from heart rate decelerations to contribute more to short-term variability than accelerations, and for the long-term variability, the relation is reversed. The hypothesis tested in the present article is that this reversal is caused by a compensatory mechanism whose function is to keep the system in relative balance.Methods: Thirty-minute electrocardiographic recordings from 420 young healthy volunteers were analyzed. The variance-based HRA descriptors were calculated. Cases with both short- and long-term HRAs were considered to show compensation. In the binomial test, we looked for statistically significant departures from independence in the distribution of cases possessing both types of asymmetry.Results: Short-term asymmetry was observed in 77.6% of subjects (P < .0001), and long-term asymmetry, in 69.3% (P < .0001); both types of HRA coexisted in 66.9% (P < .0001) of the whole group. This result is significantly different (P < .0001) from the independent case (53.78%).Conclusion: The compensation effect between the short- and long-term asymmetries is present in supine resting electrocardiographic recordings in young healthy people.

Semiautomated QT interval measurement in electrocardiograms from a thorough QT study: comparison of the grouped and ungrouped superimposed median beat methods

2012-02-24

Abstract: Introduction: We postulated that it may be easier to identify earliest Q onset and latest T offset when the median beats from 12 leads are separated vertically by 5 to 10 mm (ungrouped superimposed median beat [SMB] method) rather than when their baselines closely (but rarely perfectly) overlap (grouped SMB method).Methods: Three readers manually adjudicated annotations placed by an automated algorithm, using grouped (gSMB) and ungrouped (uSMB) methods in 2658 electrocardiograms (ECGs) recorded in 38 subjects in a crossover design thorough QT study at predose and 6 time points postdosing with placebo or moxifloxacin.Results: Placebo-subtracted, moxifloxacin-induced QTcF prolongation was comparable with both methods. Maximum QTcF prolongation was seen at 2 hours—10.5 milliseconds (90% confidence interval, 7.9-13.1 milliseconds) with gSMB and 12.9 milliseconds (90% confidence interval, 9.9-15.8 milliseconds) by uSMB. Both methods showed good agreement; mean QT was 4 milliseconds greater by uSMB. Interreader variability of absolute differences in QT measurements was 1 millisecond lower with the uSMB method (6.8 ± 5.7 milliseconds by gSMB and 5.9 ± 4.5 milliseconds by uSMB).Conclusion: Mean QT was 4 milliseconds longer, and interreader variability, 1 millisecond lower with uSMB. Otherwise, both methods were comparable and detected the moxifloxacin effect.

Individualized model of torso surface for the inverse problem of electrocardiology

Jana Lenkova, Jana Svehlikova, Milan Tysler — 2012-03-09

Abstract: Purpose: We studied the implementation of a patient-specific torso model created without the use of magnetic resonance imaging in the inverse problem of electrocardiology.Method: Three types of inhomogeneous numerical torso models were created, with different degrees of adjustment of the outer surface to patients, whereas the heart and lung models remained unchanged. The torso models were used in the inverse localization of small areas with repolarization changes from simulated difference integral QRST maps. The localization error (LE) was evaluated as the distance between the centers of the modeled and the inversely found area with repolarization changes.Results: The mean LE was 1.88 cm with the standard torso model. After adapting the torso shape, the mean LE was 1.83 cm, whereas after adapting both, the shape and electrode positions, the mean LE was 1.02 cm.Conclusion: If torso imaging is not available, a torso model with adapted shape and electrode positions gives only slightly less accurate results.

Sodium-channel blockers might contribute to the prevention of ventricular tachycardia in patients with long QT syndrome type 2: a description of 4 cases

2012-03-09

Abstract: Four patients with long QT type 2, aged 11 to 18 years from unrelated families, with recurrent syncope and polymorhic ventricular tachycardia were studied. Long QT syndrome was diagnosed in these children at ages 4 to 7 years. Syncope, QT prolongation on electrocardiogram (corrected QT interval ≥490 milliseconds), notched T-wave morphology, bradycardia, and polymorphic ventricular arrhythmia were found in all of the patients. The KCNH2-L586M; KCNH2-G604S, KCNH2-L1045F; and a combined mutation KCNH2 T613M + SCN5A R190G were genotyped. Syncope, implantable cardioverter-defibrillator shocks, and tachycardia persisted in these patients, although they were receiving a full dose of β-blocker therapy. Adding a sodium-channel blocker (IC class) led to a reduction in the polymorphic ventricular arrhythmia. No syncope episodes were registered during the patients' 8 to 60 months of follow-up on the combined antiarrhythmic therapy. Further studies are needed to better define the possible role of sodium-channel blockers in patients with long QT type 2.

Alterations in the QRS complex in the offspring of patients with metabolic syndrome and diabetes mellitus: early evidence of cardiovascular pathology

Ljuba Bacharova, Zora Krivosikova, Ladislava Wsolova, Martin Gajdos — 2012-05-01

Abstract: Objective: This study was undertaken to evaluate the nature and onset of changes in the QRS complex in the offspring of patients with diabetes mellitus (DM) and metabolic syndrome (MetS).Methods and Methods: A total of 529 subjects, divided into 5 groups, were included in the study: (i) group DM (n = 92), patients with DM; (ii) group MetS (n = 125), patients with MetS; (iii) group O-DM (n = 109), offspring of patients with DM; (iv) group O-MetS (n = 122), offspring of patients with MetS; and (v) group HO (n = 81), offspring of healthy subjects. QRS parameters analyzed included amplitude, maximum QRS spatial vector magnitude, electrical axis (EA), and 3 electrocardiogram (ECG) criteria for left ventricular hypertrophy based on amplitude criteria: Sokolow-Lyon index, Cornell voltage, and Gubner criterion.Results: Patients with DM and MetS showed a significant leftward shift of the EA when compared with the control group. A modest but significant leftward shift of EA was also observed in both offspring groups. These EA and maximum QRS spatial vector magnitude changes were reflected in the individual leads of the 12-lead ECG. The prevalence of a positive diagnosis by accepted electrocardiographic criteria (ECG left ventricular hypertrophy) was low.Conclusion: Patients with DM and MetS displayed significant changes in QRS complex that suggest depolarization sequence deterioration. Similar changes were observed also in the offspring of patients with DM and MetS, which suggests early subclinical cardiovascular damage. These findings have implications for prevention, early diagnosis, and treatment in the offspring of patients with DM and MetS.

Characteristics of electrocardiographic repolarization in acute myocardial infarction complicated by ventricular fibrillation

2012-01-12

Abstract: Background and Purpose: Some de- and re-polarization patterns can reflect an increased risk of ventricular tachyarrhythmias. We studied whether some electrocardiographic (ECG) patterns are able to predict the development of ventricular fibrillation (VF) during acute myocardial infarction (MI).Methods: We compared the patterns of ST-T segment of 78 patients who developed VF during acute MI (patient with VF) vs 170 comparable patients with acute MI but with no VF complications.Results: Of the VF group, 47 developed out-of-hospital VF and 31 developed VF after their admission to the hospital. A steep downsloping ST segment toward a negative T wave with or without a short, flat, or rising portion at the initial portion was observed in 69.2% of the 78 patients: 61.3% in patients with pre-VF and 74.5% in patients with post-VF, vs 9.4% of patients who did not develop VF (P < .0001). In 90.6% of the latter, a typical upward-concave or convex “ischemic” pattern of the ST segment was observed. Thus, the characteristic ST-T patterns were highly associated with VF with a specificity greater than 90%.Conclusions: A steep downsloping ST segment may characterize the ECGs of patients who develop VF during acute MI.

Prognostic value of high sensitive C-reactive protein in subjects with silent myocardial ischemia

2012-01-04

Abstract: Objectives: The aim of this study was to evaluate the prognostic value of high sensitive C-reactive protein (CRP) in subjects with silent myocardial ischemia (SMI).Design: In total, 678 healthy men and women aged 55 to 75 years with no history of cardiovascular disease or stroke were included. High-sensitive CRP and 48-hour ambulatory ECG monitoring were performed. The primary endpoint was the combined endpoint of death and myocardial infarction.Results: The median follow-up time was 76 months. Seventy-seven subjects (11.4%) had SMI. The combined endpoint occurred in 26% of the subjects with SMI and 14% of the subjects without SMI (P = .005). SMI had a poor prognosis in the group with an elevated CRP ≥3.0 μg/mL (hazard ratio, 3.46; 95% confidence interval, 1.67-7.16; P = .001) compared with the group of subjects with SMI and a low CRP <3.0 μg/mL (hazard ratio, 1.37; 95% confidence interval, 0.63-2.98; P = .54).Conclusions: In apparently healthy subjects, a low level of CRP <3.0 μg/mL selects a low-risk subgroup, despite the presence of SMI.

Mason-Likar electrode configuration can confound the recognition of electrode cable interchange

Velislav N. Batchvarov, Dilshat Djumanov, Jorg Taubel, A. John Camm — 2011-03-02

Prehospital 12-lead ST-segment monitoring improves the early diagnosis of acute coronary syndrome

2011-11-24

Abstract: Aims/Methods: We studied 620 patients who activated “911” for chest pain symptoms to determine the sensitivity and specificity of 12-lead electrocardiogram (ECG) ST-segment monitoring in the prehospital period (PH ECG) for diagnosing acute coronary syndrome (ACS) and to assess whether the addition of PH ECG signs of ischemia/injury to the initial hospital 12-lead ECG obtained in the emergency department would improve the diagnosis of ACS.Results: The sensitivity and specificity of the PH ECG were 65.4% and 66.4%. There was a significant increase in sensitivity (79.9%) and decrease in specificity (61.2%) when considered in conjunction with the initial hospital ECG (P < .001). Those with PH ECG ischemia/injury were more than 2.5 times likely to have an ACS diagnosis than those who had no PH ECG ischemia/injury (P < .001).Conclusions: Prehospital ECG data obtained with 12-lead ST-segment monitoring provides diagnostic information about ACS above and beyond the initial hospital ECG.

Electrocardiographic patterns of proximal left anterior descending artery occlusion in ST-elevation myocardial infarction may be modified by 3-vessel coronary artery disease

2012-01-16

Abstract: Background: The electrocardiographic (ECG) pattern of ST-segment deviation in myocardial infarction is integral to the proper assessment of the location, extent, and functional significance of the infarct but may be modified by the underlying coronary artery anatomy.Methods: We describe the ECG findings in 2 cases of proximal left anterior descending (LAD) artery occlusion in ST-elevation myocardial infarction (STEMI) associated with 3-vessel coronary artery disease.Results: Both patients had atypical ECG patterns of ST-segment elevation in leads V2, I, and aVL and ST-segment depression with positive T waves suggestive of extensive subendocardial ischemia in leads II, III, aVF, and V3 through V6; acute proximal LAD occlusion and concomitant 3-vessel coronary artery disease were observed angiographically.Conclusion: Electrocardiographic changes in proximal LAD STEMI may be modified by the presence of significant atherosclerotic disease elsewhere in the coronary vasculature. Recognition of this ECG pattern may aid the clinician in the rapid identification of high-risk STEMI.

Acute ischemia manifestation in a patient with coronary slow flow phenomenon

Blendi Horjeti, Artan Goda — 2011-08-16

Abstract: A patient with anginal chest pain and electrocardiographic changes suggesting ischemia was referred to our hospital. Coronary angiography revealed no significant stenosis or ectasia but only slow flow in all 3 coronary arteries. After infusion of unfractionated heparin for 24 hours, negative T waves became less deep, and repeated coronary angiography showed significant improvement of the coronary flow. The coronary slow flow phenomenon, together with the associated ischemic electrocardiographic changes, should be considered as a separate entity in the differential diagnosis of acute coronary syndromes. Additional clinical research is required to better understand the syndromes of chest pain with normal coronary arteries.

Isolated spontaneous septal myocardial infarction

Janos Tomcsanyi, Bela Bozsik, Andras Zsoldos, Tamas Simor — 2011-09-12

Abstract: Isolated occlusion of the septal perforating branch of the left anterior descending coronary artery is extremely rare. As a result, little is known about its electrocardiographic manifestations compared with those of an anteroseptal myocardial infarction. We present the case of an isolated septal myocardial infarction with ST-segment elevation.

Non–ST-segment elevation acute coronary syndrome presenting with ST-segment elevation in aVR and dual antiplatelet therapy

2011-12-08

A 74-year-old woman was admitted to our emergency department because of severe chest pain lasting more than 2 hours. The initial triage included a ph ysical examination and a 12-lead electrocardiogram, which showed ST-segment elevation (>2.0 mm) in the aVR lead and diffuse ST-segment depression (>2.0 mm) in leads I, II, III, aVF, and V2 through V6 (A).

Acute myocardial infarction with isolated conus branch occlusion

2012-01-04

Abstract: There are few reports of acute myocardial infarction (AMI) relating to the occlusion of the conus branch, most of which are iatrogenic in nature. So far as we are concerned, this is the first case of spontaneous AMI with isolated conus branch occlusion. Electrocardiogram (ECG) showed mild elevation of ST segment in leads V1 through V3. Cardiac makers of myocardial infarction were positive. Right coronary angiography revealed an isolated occlusion of the conus branch. Penetration of the guidewire in the occluded lesion was attempted, and recanalization was successfully achieved. The patient was discharged without any adverse events.

Graphical representation of QT rate correction formulae: an aid facilitating the use of a given formula and providing a visual comparison of the impact of different formulae

Derek J. Rowlands — 2012-02-23

Abstract: The QT interval on the electrocardiogram is an increasingly important measurement, especially in relation to drug action and interaction. The QT interval varies inversely as the heart rate and numerous rate correction formulae have been proposed. It is difficult to compare the effect of applying different formulae at different heart rates and for different measured QT intervals. A simple graphical display of the results from different formulae is proposed. This display is dependent on the concept of the absolute correction factor. This graphical presentation is useful (a) in comparing the effect of the application of different formulae and (b) in directly reading the correction produced by any individual formula.

Overly excited over preexcitation

Sanjiv M. Baxi, Nora Goldschlager — 2011-12-15

T-wave alternans and the confounding role of the T-wave amplitude

John E. Madias — 2012-01-20

Abstract: The interpretation of the electrocardiogram (ECG) T-wave alternans (TWA) as positive or negative depends on its magnitude, regardless whether the frequency domain or the time domain analysis is employed. The author argues that a number of cardiac and extracardiac influences can confound the magnitude of TWA. The amplitude of the ECG T waves, considered in the measurement/calculation of TWA, and possibly myocardial edema are examples of cardiac influences. Peripheral edema with its effect in attenuating the amplitude of all components of the ECG, including the T waves, is an example of extracardiac influence. Another concern is the variation in the evolution of the T-wave amplitudes during the 3- to 6-month period after an acute myocardial infarction, and whether such variation confounds the results of the TWA testing, which often is undertaken at that time bracket. The T-wave amplitude changes may impact the sensitivity and specificity of TWA testing after an acute myocardial infarction. Perhaps the measured TWA magnitude should be adjusted to the amplitude of the T waves or voltage-time integral of the J-T interval, depending on the method used for the calculation of TWA. These issues need to be considered and investigated in an effort to render TWA testing more reliable in predicting sudden cardiac death.

Correlations among the frequencies of atrial activity on the surface electrocardiogram, intracardiac atrial electrograms, and the atrial effective refractory period in patients with atrial fibrillation

Merritt H. Raitt, Walter Kusumoto — 2012-01-27

Abstract: Background: The frequency of surface atrial electrocardiogram (ECG) depolarization has been postulated to reflect the atrial effective refractory period (AERP).Methods: Frequency analysis of surface ECGs after QRST subtraction and of electrograms from 4 right atrium and 4 coronary sinus electrode pairs was performed in 38 patients in atrial fibrillation. The AERP was measured in the right atrium and coronary sinus 10 minutes after cardioversion.Results: The correlation between the dominant frequencies of intracardiac electrograms and atrial activity in leads I, II, and V1 were 0.89, 0.85, and 0.88, respectively (all P < .001). The correlation between the average AERP and the frequency of atrial activity in the surface leads was 0.50, 0.45, and 0.47 (all P < .005).Conclusion: In atrial fibrillation, the frequency of atrial depolarization measured from the surface ECG is highly correlated with intracardiac atrial frequency. However, the correlation between the frequency of surface atrial activity and atrial refractoriness, although significant, is not strong.

ECG quiz

2012-05-01

Triphasic and quadriphasic waveforms are superior to biphasic waveforms for synchronized beating of cardiomyocytes

2012-02-15

Abstract: Background and Purpose: Within pacemaker research few attempts have been made to find an optimal waveform phase sequence that synchronizes beating of cardiomyocytes at an electrode. Multielectrode arrays (MEAs) offer electrophysiological screening of cardiomyocytes serving as a system for preliminary screening of pacing waveform design.Materials and Methods: The HL-1 cell line was cultured in MEAs until confluence and stimulated with biphasic, triphasic, and quadriphasic waveforms. The amplitudes required for synchronized beating of the cells were determined.Results: Triphasic and quadriphasic waveforms were more efficient in eliciting synchronized beating of the HL-1 cells compared with the biphasic waveform because it allows significant reductions in synchronizing voltage amplitudes and reductions in supplied stimulus.Conclusion: The MEA system allows for a straightforward manner to investigate effects of waveform design on synchronized beating in cardiomyocytes in vitro. Increased number of phase changes in a pacing waveform seems to be the major reason for the reduction in synchronizing amplitudes.

Diagnosis and mortality prediction in pulmonary hypertension: the value of the electrocardiogram-derived ventricular gradient

2012-01-24

Abstract: Purpose: The aim of this study was to investigate the use of the electrocardiogram-derived ventricular gradient, projected on the x-axis (VGx), for detection of pulmonary hypertension (PH) and for prediction of all-cause mortality in PH patients.Methods: In patients referred for PH screening (n = 216), the VGx was calculated semiautomatically from the electrocardiogram and was defined as abnormal when less than 24 mV·ms. The VGx of PH patients was compared with the VGx of patients without PH. The association between a reduced VGx and mortality was investigated in PH patients.Results: Patients with PH (n = 117) had a significantly reduced VGx: 14 ± 27 vs 45 ± 23 mV·ms, P < .001. Furthermore, a severely reduced VGx (<0 mV·ms) was associated with increased mortality in PH patients: hazard ratio, 1.025 (95% confidence interval, 1.006-1.045; P = .012) per mV·ms VGx decrease.Conclusion: Reduced VGx is associated with the presence of PH and, more importantly, within PH patients, a severely reduced VGx predicts mortality.

Specificity of the wide QRS complex tachycardia algorithms in recipients of cardiac resynchronization therapy

Marek Jastrzebski, Piotr Kukla, Danuta Czarnecka, Kalina Kawecka-Jaszcz — 2011-10-10

Abstract: Background: We assessed the specificity of wide QRS complex tachycardia (WCT) differentiating algorithms in patients with preexistent left bundle branch block (LBBB) and heart failure.Methods: Three hundred fourteen patients with resynchronization devices were retrospectively screened. electrocardiograms with supraventricular LBBB rhythm were used as a surrogate for supraventricular tachycardia QRS morphology. The Pava lead II criterion, ventricular activation velocity ratio (Vi/Vt) ratio in V2, Vereckei aVR, Brugada, Griffith, and Bayesian algorithms were investigated.Results: The WCT algorithms had a lower specificity (33%-69%) in patients with LBBB than in general WCT populations. The Pava lead II criterion and Brugada algorithm had higher specificity than other algorithms (P < .05). Several of the single criteria (absence of an RS complex in V1 through V6, initial R wave in aVR, Vi/Vt < 1 in V2) had specificities of 92% to 99%.Conclusions: In patients with heart failure and LBBB, an electrocardiographic diagnosis of ventricular tachycardia should be based on selected, specific criteria rather than on WCT algorithms.

Outcome after implantable cardioverter-defibrillator in patients with Brugada syndrome: the Gulf Brugada syndrome registry

2011-11-11

Abstract: Background and Objective: Among patients with Brugada syndrome (BS) and aborted cardiac arrest, syncope, or inducible ventricular fibrillation at electrophysiologic study (EPS), the only currently recommended therapy is an implantable cardioverter-defibrillator (ICD), but these are not without complications. We assessed the total number of shocks (appropriate and inappropriate) and complications related to ICD in patients with BS.Methods and Results: Twenty-five patients implanted with ICD for BS in 6 Gulf centers between January 1, 2002, and December 31, 2010, were reviewed. Implantable cardioverter-defibrillator indication was based on aborted cardiac arrest (24%), syncope (56%), or in asymptomatic patients with positive EPS (20%). During a follow-up of 41.2 ± 17.6 months, 3 patients (all with prior cardiac arrest) had appropriate device therapy. Four patients developed complications; 3 of them had inappropriate shocks.Conclusion: In our cohort, appropriate device therapy was limited to cardiac arrest survivors, whereas none of those with syncope and/or positive EPS had arrhythmias. Overall complication rate was relatively high, including inappropriate ICD shocks.

Very late stent thrombosis immediately after recurrent inappropriate shock delivery by an implantable cardioverter defibrillator

John Groarke, Dermot Phelan, David Burke, Peter Crean, Brendan Foley — 2011-12-26

Abstract: The case of a 49-year-old man who developed an ST segment elevation myocardial infarction because of very late stent thrombosis occurring in the immediate aftermath of a “storm” of recurrent inappropriate implantable cardioverter defibrillator (ICD) shocks caused by a fracture of a Medtronic Sprint Fidelis (Medtronic Inc., Minneapolis, MN) right ventricular lead is described. A causal relationship between recurrent ICD shocks and stent thrombosis is proposed. This deleterious association is an important observation given the increasing population of patients who receive both coronary stents and ICDs.

Pacemaker-mediated tachycardia initiated by an atrioventricular search algorithm to minimize right ventricular pacing

S. Serge Barold, Roland X. Stroobandt — 2012-01-27

Abstract: We report the initiation of pacemaker-mediated tachycardia by a St Jude implantable cardioverter-defibrillator with a programmed Ventricular Intrinsic Preference algorithm used for minimizing or inhibiting right ventricular pacing. This feature prolongs the atrioventricular (AV) delay periodically to determine if ventricular sensed events follow atrial events. Retrograde ventriculoatrial conduction and pacemaker-mediated tachycardia were initiated by long extended AV delays of 300 and 400 milliseconds. The 400-millisecond AV delay consisted of the programmed sensed AV delay (100 milliseconds) plus the Ventricular Intrinsic Preference increment (200 milliseconds) plus 100 milliseconds imposed by the AutoCapture algorithm when it detected loss of ventricular capture.

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