Usefulness of QRS prolongation in predicting risk of inducible monomorphic ventricular tachycardiain patients referred forelectrophysiologic studies

Repaired Tetralogy of Fallot: Have We Understood the Right Timing of PVR?

Despite many advances in surgical repair during the past few decades, the majority of tetralogy of Fallot patients continue to experience residual hemodynamic and electrophysiological abnormalities. The actual issue, which has yet to be solved, is understanding how this disease evolves in each individual patient and, as a result, who is truly at risk of sudden death, as well as the proper timing of pulmonary valve replacement (PVR). Our responsibility should be to select the most appropriate time for each patient, going above and beyond imaging criteria used up to now to make such a clinically crucial decision. Despite several studies on timing, indications, procedures, and outcomes of PVR, there is still much uncertainty about whether PVR reduces arrhythmia burden or improves survival in these patients and how to appropriately manage this population. This review summarizes the most recent research on the evolution of repaired tetralogy of Fallot (from adolescence onwards) and risk factor variables that may favor or delay PVR.

Electrocardiographic Features and Outcome: Correlations in 124 Hospitalized Patients With COVID-19 and Cardiovascular Events

OBJECTIVES

Electrocardiographic (ECG) changes have been associated with coronavirus disease 2019 (COVID-19) severity. However, the progression of ECG findings in patients with COVID-19 has not been studied. The purpose of this study was to describe ECG features at different stages of COVID-19 cardiovascular (CV) events and to examine the effects of specific ECG parameters and cardiac-related biomarkers on clinical outcomes in COVID-19.

DESIGN

Retrospective, cohort study.

SETTING

Major tertiary-care medical centers and community hospitals in Louisville, KY.

PARTICIPANTS

A total of 124 patients with COVID-19 and CV events during hospitalization.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Twelve-lead ECG parameters, biomarkers of cardiac injuries, and clinical outcomes were analyzed with Spearman correlation coefficients and Kruskal-Wallis 1-way analysis of variance. Atrial fibrillation/atrial flutter was more frequent on the ECG obtained at the time of the CV event when compared with admission ECG (9.5% v 26.9%; p = 0.007). Sinus tachycardia was higher in the last available hospital ECG than the CV event ECG (37.5% v 20.4%; p = 0.031). Admission ECG-corrected QT interval was significantly associated with admission troponin levels (R = 0.52; p < 0.001). The last available hospital ECG showed nonsurvivors had longer QRS duration than survivors (114.6 v 91.2 ms; p = 0.026), and higher heart rate was associated with longer intensive care unit length of stay (Spearman ρ = 0.339; p = 0.032).

CONCLUSIONS

In hospitalized patients with COVID-19 and CV events, ECGs at various stages of COVID-19 hospitalization showed significantly different features with dissimilar clinical outcome correlations.

Sodium dichloroacetate stimulates cardiac mitochondrial metabolism and improves cardiac conduction in the ovine fetus during labor

Previous studies in our laboratory have suggested that the increase in stillbirth in pregnancies complicated by chronic maternal stress or hypercortisolemia is associated with cardiac dysfunction in late stages of labor and delivery. Transcriptomics analysis of the overly represented differentially expressed genes in the fetal heart of hypercortisolemic ewes indicated involvement of mitochondrial function. Sodium dichloroacetate (DCA) has been used to improve mitochondrial function in several disease states. We hypothesized that administration of DCA to laboring ewes would improve both cardiac mitochondrial activity and cardiac function in their fetuses. Four groups of ewes and their fetuses were studied: control, cortisol-infused (1 g/kg/day from 115 to term; CORT), DCA-treated (over 24 h), and DCA + CORT-treated; oxytocin was delivered starting 48 h before the DCA treatment. DCA significantly decreased cardiac lactate, alanine, and glucose/glucose-6-phosphate and increased acetylcarnitine/isobutyryl-carnitine. DCA increased mitochondrial activity, increasing oxidative phosphorylation (P_CI, P_CI + II) per tissue weight or per unit of citrate synthase. DCA also decreased the duration of the QRS, attenuating the prolongation of the QRS observed in CORT fetuses. The effect to reduce QRS duration with DCA treatment correlated with increased glycerophosphocholine and serine and decreased phosphorylcholine after DCA treatment. There were negative correlations of acetylcarnitine/isobutyryl-carnitine to both heart rate (HR) and mean arterial pressure (MAP). These results suggest that improvements in mitochondrial respiration with DCA produced changes in the cardiac lipid metabolism that favor improved conduction in the heart. DCA may therefore be an effective treatment of fetal cardiac metabolic disturbances in labor that can contribute to impairments of fetal cardiac conduction.

Recommendations for the use of electrophysiological study: Update 2018

The field of cardiac electrophysiology has greatly developed during the past decades. Consequently, the use of electrophysiological studies (EPSs) in clinical practice has also significantly augmented, with a progressively increasing number of certified electrophysiology centers and specialists. Since Zipes et al published the Guidelines for Clinical Intracardiac Electrophysiology and Catheter Ablation Procedures in 1995, no official document summarizing current EPS indications has been published. The current paper focuses on summarizing all relevant data of the role of EPS in patients with different types of cardiac pathologies and provides up-to-date recommendations on this topic. For this purpose, the PubMed database was screened for relevant articles in English up to December 2018 and ESC and ACC/AHA Clinical Practice Guidelines, and EHRA/HRS/APHRS position statements related to the current topic were analyzed. Current recommendations for the use of EPS in clinical practice are discussed and presented in 17 distinct cardiac pathologies. A short rationale, evidence, and indications are provided for each cardiac disease/group of diseases. In conclusion, because of its capability to establish a diagnosis in patients with a variety of cardiac pathologies, the EPS remains a useful tool in the evaluation of patients with cardiac arrhythmias and conduction disorders and is capable of establishing indications for cardiac device implantation and guide catheter ablation procedures.

Up-regulated Cx43 phosphorylation at Ser368 prolongs QRS duration in myocarditis

Prolongation of QRS duration in electrocardiogram is one of the risk factors for morbidity and mortality in many kinds of cardiac diseases. However, its molecular mechanism is unknown. In this study, utilizing experimental autoimmune myocarditis (EAM) as a disease model, we show that the prolongation of QRS duration is accompanied by elevated phosphorylation of connexin 43 (Cx43) at Ser368 (p^S368Cx43). In cultured cells, inflammatory cytokine IL‐1β activates p38 MAPK to up‐regulate p^S368Cx43 and impairs cell‐to‐cell communication. In isolated hearts of normal rats, perfusion of IL‐1β not only increases p^S368Cx43 but also impairs cell‐to‐cell communication and prolongs QRS duration. Furthermore, blockade of p38 MAPK down‐regulates p^S368Cx43, improves cell‐to‐cell communication and reduces QRS duration in EAM. These findings suggest that up‐regulation of p^S368Cx43 by IL‐1β via p38 MAPK contributes to the prolongation of QRS duration and could be a therapeutic target for myocarditis‐induced prolongation of QRS duration.

Impact of QRS duration on survival benefit with prophylactic implantable cardioverter-defibrillators: a meta-analysis of randomized controlled trials

BACKGROUND

QRS duration is an important risk factor for both sudden cardiac death and all-cause mortality in patients with moderate to severe left ventricular systolic dysfunction. However, it is unknown whether baseline QRS duration can help predict the mortality benefit from implantable cardioverter-defibrillators (ICDs) when used for primary prevention purposes.

OBJECTIVE

Our objective was to examine the relationship between baseline QRS duration and mortality reduction with ICDs implanted for primary prevention by performing a meta-analysis of all available randomized clinical trials.

METHODS

A systematic literature search of SCOPUS (covering MEDLINE and EMBASE) was conducted for randomized controlled clinical trials involving ICDs. Primary prevention trials of systolic dysfunction that reported all-cause mortality according to subgroups on the basis of baseline QRS duration were included.

RESULTS

A total of four randomized controlled clinical trials enrolling 3561 patients were included. Patients with QRS durations less than 120 ms [n = 2002, hazard ratio 0.78, 95% confidence interval (CI) 0.63-0.96, P = 0.018] and at least 120 ms (n = 1559, hazard ratio 0.59, 95% CI 0.48-0.73, P = 0.0000009) had significant decreases in all-cause mortality. On heterogeneity analysis, a strong trend for greater magnitude of benefit in patients with QRS at least 120 ms was observed (22% risk reduction vs. 41% risk reduction, P = 0.066).

CONCLUSION

For primary prevention purposes, ICDs are effective in reducing all-cause mortality in moderate to severe systolic dysfunction regardless of QRS duration. However, patients with a baseline QRS duration of at least 120 ms seem to derive a greater mortality benefit from ICDs.

Prognostic Implication of QRS Variability during Hospitalization in Patients with Acute Decompensated Heart Failure

Background and Objectives

Heart failure (HF) patients display more varied QRS duration. We investigated whether QRS variability during hospitalization for acute decompensated HF is associated with poor clinical outcomes after discharge.

Subjects and Methods

One hundred seventy three patients (64% males; age 60±13 years) admitted for acute decompensated HF with severe left ventricular (LV) dysfunction (LV ejection fraction ≤35%) were consecutively enrolled. QRS variability was calculated by the difference between maximum and minimum QRS duration acquired during hospitalization. The prognostic implications on composite endpoints of death or urgent heart transplantation were analyzed.

Results

Forty-two patients (24.3%) died and three patients (1.7%) underwent urgent heart transplantation during the follow-up of 51±18 months. Patients who reached composite endpoints (n=45) showed greater QRS variability than those who did not (n=128) (20±23 ms vs. 14±14 ms, p=0.046). Patients who had high QRS variability (more than 22 ms; n=36) tended to have a higher event rate than those with QRS variability <22 ms {39% vs. 23%, hazard ratio (HR), 1.88; 95% confidence interval (CI) 1.001-3.539, p=0.05}. Adjusting with other variables, high QRS variability was an independent predictor for composite outcome (HR 1.94; 95% CI 1.023-3.683, p=0.042).

Conclusion

QRS variability measured during hospitalization for acute decompensated HF has a prognostic impact in HF patients with severe LV dysfunction.

Short- and long-term outcomes depending on electrical dyssynchrony markers in patients presenting with acute heart failure: clinical implication of the first-degree atrioventricular block and QRS prolongation from the Korean Heart Failure registry

BACKGROUND

Prolongations of PR interval and QRS duration on 12-lead electrocardiogram are associated with atrioventricular and interventricular/intraventricular dyssynchrony, respectively. However, their clinical significance remains unclear in real-world heart failure (HF) population. We assessed whether the presence of first-degree atrioventricular block and/or QRS prolongation (≥120 ms) is associated with worse short- and long-term outcomes in patients with acute HF.

METHODS

The Korean Heart Failure is a nationwide registry of 3,200 consecutive patients presenting with acute HF at 24 centers in South Korea between June 2004 and April 2009. We selected 1,986 patients with sinus rhythm and divided them into 4 groups depending on the presence of first-degree atrioventricular block and/or QRS prolongation; ED_Neither (n = 1,347), ED_PR (n = 217), ED_QRS (n = 329), and ED_Both (n = 93) groups, respectively.

RESULTS

During the median follow-up of 18.2 months, overall death rate (17%, 22%, 20%, and 29%, P < .01) tended to rise with increasing number of electrical dyssynchrony markers. Patients in ED_Both group showed worst outcomes regarding the requirement of invasive managements during the index admission, in-hospital mortality, postdischarge death/rehospitalization, and cardiac device implantation. In time-dependent Cox regression analyses, presence of both PR >200 ms and QRS ≥120 ms was independently associated with in-hospital death (P < .01), postdischarge death/rehospitalization (P = .03), cardiac device implantation (P < .01), and overall death (P < .01).

CONCLUSIONS

A combined analysis of electrical dyssynchrony markers (PR prolongation and QRS widening) might be useful for short- and long-term risk stratifications of patients with acute HF.

Common genetic variation modulating cardiac ECG parameters and susceptibility to sudden cardiac death

Sudden cardiac death (SCD) is a prevalent cause of death in Western societies. Genome-wide association studies (GWAS) conducted over the last few years have uncovered common genetic variants modulating risk of SCD. Furthermore, GWAS studies uncovered several loci impacting on heart rate and ECG indices of conduction and repolarization, as measures of cardiac electrophysiological function and likely intermediate phenotypes of SCD risk. We here review these recent developments and their implications for the identification of novel molecular pathways underlying normal electrophysiological function and susceptibility to SCD.

Syncope in adults: systematic review and proposal of a diagnostic and therapeutic algorithm

This review aims to provide a practical and up-to-date description on the relevance and classification of syncope in adults as well as a guidance on the optimal evaluation, management and treatment of this very common clinical and socioeconomic medical problem. We have summarized recent active research and emphasized the value for physicians to adhere current guidelines. A modern management of syncope should take into account 1) use of risk stratification algorithms and implementation of syncope management units to increase the diagnostic yield and reduce costs; 2) early implantable loop recorders rather than late in the evaluation of unexplained syncope; and 3) isometric physical counter-pressure maneuvers as first-line treatment for patients with neurally-mediated reflex syncope and prodromal symptoms.

On the relationship between block of the cardiac Na⁺ channel and drug-induced prolongation of the QRS complex

BACKGROUND AND PURPOSE

Inhibition of the human cardiac Na(+) channel (hNa(v) 1.5) can prolong the QRS complex and has been associated with increased mortality in patients with underlying cardiovascular disease. The safety implications of blocking hNa(v) 1.5 channels suggest the need to test for this activity early in drug discovery in order to design out any potential liability. However, interpretation of hNa(v) 1.5 blocking potency requires knowledge of how hNa(v) 1.5 block translates into prolongation of the QRS complex.

EXPERIMENTAL APPROACH

We tested Class I anti-arrhythmics, other known QRS prolonging drugs and drugs not reported to prolong the QRS complex. Their block of hNa(v) 1.5 channels (as IC(50) values) was measured in an automated electrophysiology-based assay. These IC(50) values were compared with published reports of the corresponding unbound (free) plasma concentrations attained during clinical use (fC(max)) to provide an IC(50) : fC(max) ratio. KEY RESULTS For 42 Class I anti-arrhythmics and other QRS prolonging drugs, 67% had IC(50) : fC(max) ratios <30. For 55 non-QRS prolonging drugs tested, 72% had ratios >100. Finally, we determined the relationship between the IC(50) value and the free drug concentration associated with prolongation of the QRS complex in humans. For 37 drugs, QRS complex prolongation was observed at free plasma concentrations that were about 15-fold lower than the corresponding IC(50) at hNa(v) 1.5 channels.

CONCLUSIONS AND IMPLICATIONS

A margin of 30- to 100-fold between hNa(v) 1.5 IC(50) and fC(max) appears to confer an acceptable degree of safety from QRS prolongation. QRS prolongation occurs on average at free plasma levels 15-fold below the IC(50) at hNa(v) 1.5 channels.

LINKED ARTICLE

This article is commented on by Gintant et al., pp. 254-259 of this issue. To view this commentary visit http://dx.doi.org/10.1111/j.1476-5381.2011.01433.x.

Chewing reduces sympathetic nervous response to stress and prevents poststress arrhythmias in rats

Reducing stress is important in preventing sudden death in patients with cardiovascular disease, as stressful events may cause autonomic imbalance and trigger fatal arrhythmias. Since chewing has been shown to inhibit stress-induced neuronal responses in the hypothalamus, we hypothesized that chewing could ameliorate stress-induced autonomic imbalance and prevent arrhythmias. To test this hypothesis, we analyzed changes in radiotelemetered electrocardiograms in rats that were allowed to chew a wooden stick during a 1-h period of immobilization stress. Chewing significantly reduced the occurrence of ventricular premature beats (VPBs) and complex ventricular ectopy after immobilization and prevented stress-induced prolongation of the QT interval of VPBs throughout the 10-h experimental period. It also prevented prolongation of the QRS complex and fluctuations in the QT interval in normal sinus rhythm beats preceding VPBs during both immobilization and in the poststress period. Fast Fourier transform-based spectral analysis of heart-rate variability further showed that chewing significantly inhibited the stress-induced increase in the power ratio of low-to-high frequency activity (LF/HF: a marker of sympathetic activity) during immobilization and in addition was associated with blunting of the stress-induced increase in plasma noradrenaline observed at the termination of immobilization. Similar suppressive effects on the occurrence of VPBs and the LF/HF were observed in rats that were administered the β-adrenergic blocker propranolol before immobilization. These results indicate that chewing can ameliorate sympathetic hyperactivity during stress and prevent poststress arrhythmias and suggest that chewing may provide a nonpharmacological and cost-effective treatment option for patients with a high risk of stress-induced fatal arrhythmia.

Clinical implications of QRS duration and QT peak prolongation in patients with suspected coronary disease referred for elective cardiac catheterization

BACKGROUND

The electrocardiogram (ECG) remains a simple, universally available, and prognostically powerful investigation in heart failure, and acute coronary syndromes. We sought to assess the prognostic utility of clinical, angiographic, and simple ECG parameters in a large cohort of patients undergoing elective cardiac catheterization (CC) for known or suspected coronary artery disease.

METHODS

Consecutive consenting patients undergoing CC for coronary disease were enrolled at a single tertiary center. Patient data, drug therapy, catheter reports, and ECG recordings were prospectively recorded in a validated electronic archive. The primary outcome measure was death or nonfatal myocardial infarction (MI) over 1 year or until percutaneous or cardiac surgical intervention. Independent prognostic markers were identified using the Cox proportional hazard model.

RESULTS

A total of 682 individuals were recruited of whom 17(2.5%) died or suffered a nonfatal MI in 1 year. In multivariate analysis QRS duration (ms) (HR 1.03 95% CI 1.01-1.05, P = 0.003), extent of coronary disease (HR 2.01 95% CI 1.24-3.58, P = 0.006), and prolonged corrected QT peak interval in lead I (HR 1.02 95% CI 1.00-1.03, P = 0.044) were independently associated with death or nonfatal MI. Receiver-operator characteristic (ROC) analysis for the multivariate model against the primary end point yielded an area under the curve of 0.759 (95% CI 0.660-0.858), P < 0.001.

CONCLUSIONS

QRS duration and QT peak are independently associated with increased risk of death or nonfatal MI in stable patients attending for coronary angiography.

Native QRS duration predicts the occurrence of arrhythmic events in ICD recipients

AIMS

Identification of implantable cardioverter/defibrillator (ICD) recipients at higher risk of future therapies may assist in pre-empting future shocks. Native QRS duration is an established predictor of overall mortality, but the role of this parameter as a clinical predictor of arrhythmic events warrants further investigation.

METHODS AND RESULTS

In an analysis of a single-centre, 13-year ICD implantation experience (1990-2002), multiple clinical parameters including QRS duration were analysed using a multiple logistic regression model. Of 562 patients followed for at least 1 year, 98 (17%) did not receive ICD therapies (event-free, group A). Comparisons were made with a randomly selected sample of 123 patients who received ICD therapies (arrhythmic events, group B). There were no significant differences in age, gender, frequency of coronary artery disease, and degree of left ventricular dysfunction. However, QRS duration was a significant determinant of arrhythmic events (> or =100 vs. <100 ms: adjusted OR 2.75, 95% CI 1.37-5.51; > or =120 vs. <120 ms: adjusted OR 1.77, 95% CI 0.97-3.23). QRS duration was also a predictor of overall mortality in the logistic regression models (> or =100 ms: adjusted OR 3.72, 95% CI 1.17-11.9; > or =120 ms: adjusted OR 3.09, 95% CI 1.39-6.85).

CONCLUSION

In this ICD population, consisting largely of secondary prevention ICD recipients, longer QRS duration predicted higher likelihood of arrhythmic events. Extent of QRS prolongation could guide the decision to initiate prophylactic anti-arrhythmic therapy in ICD patients.

Significance of QRS complex duration in patients with heart failure

Prolongation of QRS (> or =120 ms) occurs in 14% to 47% of heart failure (HF) patients. Left bundle branch block is far more common than right bundle branch block. Left-sided intraventricular conduction delay is associated with more advanced myocardial disease, worse left ventricular (LV) function, poorer prognosis, and a higher all-cause mortality rate compared with narrow QRS complex. It also predisposes heart failure patients to an increased risk of ventricular tachyarrhythmias, but the incidence of cardiac or sudden death remains unclear because of limited observations. A progressive increase in QRS duration worsens the prognosis. No electrocardiographic measure is specific enough to provide subgroup risk categorization for excluding or selecting HF patients for prophylactic implantable cardioverter-defibrillator (ICD) therapy. In ICD patients with HF, a wide underlying QRS complex more than doubles the cardiac mortality compared with a narrow QRS complex. There is a high incidence of an elevated defibrillation threshold at the time of ICD implantation in patients with QRS > or =200 ms. Mechanical LV dyssynchrony potentially treatable by ventricular resynchronization occurs in about 70% of HF patients with left-sided intraventricular conduction delay, a fact that would explain the lack of therapeutic response in about 30% of patients subjected to ventricular resynchronization according to standard criteria relying on QRS duration. The duration of the basal QRS complex does not reliably predict the clinical response to ventricular resynchronization, and QRS narrowing after cardiac resynchronization therapy does not correlate with hemodynamic and clinical improvement. Mechanical LV dyssynchrony is best shown by evolving echocardiographic techniques (predominantly tissue Doppler imaging) currently in the process of standardization.

Predictive Value of Ventricular Arrhythmia Inducibility for Subsequent Ventricular Tachycardia or Ventricular Fibrillation in Multicenter Automatic Defibrillator Implantation Trial (MADIT) II Patients

In the Multicenter Automatic Defibrillator Implantation Trial (MADIT) II, implantable cardioverter-defibrillator (ICD)-randomized patients underwent electrophysiologic testing. Both inducible and noninducible patients received an ICD. We correlated inducibility with the occurrence of subsequent ventricular tachycardia (VT) or ventricular fibrillation (VF). Intracardiac ICD electrograms for subsequent events were analyzed to categorize the spontaneous arrhythmia as VT or VF. The two-year Kaplan-Meier event rate for VT in inducible patients was 29.0% versus 19.3% in noninducible patients. However, ICD therapy for spontaneous VF was less common at two years in inducible patients (3.2%) than in noninducible patients (8.6%). In the MADIT II study, inducibility predicted an increased likelihood of VT but decreased VF.

OBJECTIVES

We correlated electrophysiologic inducibility with spontaneous ventricular tachycardia (VT) or ventricular fibrillation (VF) in the Multicenter Automatic Defibrillator Implantation Trial (MADIT) II.

BACKGROUND

In the MADIT II study, 593 (82%) of 720 implantable cardioverter-defibrillator (ICD) randomized patients underwent electrophysiologic testing. Patients received an ICD whether they were inducible or not.

METHODS

A "standard" inducibility definition included sustained monomorphic or polymorphic VT induced with three or fewer extrastimuli or VF induced with two or fewer extrastimuli. We compared a narrow inducibility definition (only monomorphic VT) and a broad definition (standard definition plus VF with three extrastimuli). We used ICD-stored electrograms to categorize spontaneous VT or VF.

RESULTS

Inducible patients (standard definition) had a greater likelihood of experiencing ICD therapy for VT than noninducible patients (p = 0.023). Unexpectedly, ICD therapy for spontaneous VF was less common (p = 0.021) in inducible patients than in noninducible patients. The two-year Kaplan-Meier event rate for VT or VF was 29.4% for inducible patients and 25.5% for noninducible patients. Standard inducibility did not predict the combined end point of VT or VF (p = 0.280, by log-rank analysis). The narrow inducibility definition outperformed the standard definition, whereas the broad definition appeared inferior to the standard definition.

CONCLUSIONS

In the MADIT II study patients, inducibility was associated with an increased likelihood of VT. Noninducible MADIT II study subjects using this electrophysiologic protocol had a considerable VT event rate and a higher VF event rate than inducible patients. Induction of polymorphic VT or VF, even with double extrastimuli, appears less relevant than induction of monomorphic VT.

Late Gadolinium Enhancement Cardiovascular Magnetic Resonance of the Systemic Right Ventricle in Adults With Previous Atrial Redirection Surgery for Transposition of the Great Arteries

Background— Patients treated for transposition of the great arteries by atrial redirection surgery have a right ventricle (RV) that sustains systemic pressures long term. Late RV dysfunction occurs in these patients; the reasons for this are unclear, but myocardial fibrosis may be important. Myocardial fibrosis can be visualized by late gadolinium enhancement (LGE) cardiovascular magnetic resonance (CMR). We hypothesized that LGE would be present in the systemic RV and relate to adverse clinical features.

Methods and Results— We performed CMR on 36 consecutive adult patients (mean age, 27 years) after atrial redirection surgery for transposition of the great arteries. Late gadolinium RV enhancement was seen in 22 patients (61%) with various patterns. Patients with RV LGE were older (30 versus 22 years; P <0.001) and had increased RV end-systolic volume index (43 versus 35 mL/m 2 ; P =0.03), decreased RV ejection fraction (57% versus 62%; P =0.02), increased QRS duration (108 versus 97 ms; P =0.01), and increased QT dispersion (93 versus 71 ms; P =0.002). The extent of LGE correlated with age ( r =0.59, P <0.001) and QRS duration ( r =0.67, P <0.001) and inversely with RV ejection fraction ( r =−0.76, P <0.001). The incidence of documented arrhythmia and/or syncope (10 of 36) was significantly higher in the late gadolinium-positive group (9/22 versus 1/14; P =0.03).

Conclusions— LGE CMR suggestive of myocardial fibrosis occurs in the systemic RV of patients after atrial redirection surgery. The extent of LGE correlates with age, ventricular dysfunction, electrophysiological parameters, and clinical events, suggesting prognostic importance that merits further investigation.

Usefulness of prolonged QRS duration to identify high-risk ischemic cardiomyopathy patients with syncope and inducible ventricular tachycardia

We evaluated 61 consecutive patients who had coronary artery disease, decreased left ventricular function, and syncope and underwent implantation of a cardioverter-defibrillator because sustained ventricular tachycardia was inducible at electrophysiologic testing. During a follow-up of 3.0 +/- 1.8 years, 23 patients (38%) developed ventricular tachycardia. Prolonged QRS duration (>/=120 ms) was the only significant predictor of arrhythmia. The 1- and 2-year rates without ventricular arrhythmia were 82% and 77%, respectively, in patients whose QRS duration was <120 ms. In contrast, 1- and 2-year rates without ventricular arrhythmia were only 64% and 51%, respectively, in patients whose QRS duration was >/=120 ms (risk ratio 3.7, 95% confidence interval 1.4 to 9.8, p = 0.0092).