Time course for reversal of electrophysiological and ultrastructural abnormalities in subendocardial Purkinje fibers surviving extensive myocardial infarction in dogs

Stellate Ganglia: A Key Therapeutic Target for Malignant Ventricular Arrhythmia in Heart Disease

Malignant ventricular arrhythmias (VAs), such as ventricular tachycardia and ventricular fibrillation, are the cause of approximately half a million deaths per year in the United States, which is a common lethal event in heart disease, such as hypertension, catecholaminergic polymorphic ventricular tachycardia, takotsubo cardiomyopathy, long-QT syndrome, and progressing into advanced heart failure. A common characteristic of these heart diseases, and the subsequent development of VAs, is the overactivation of the sympathetic nervous system. Current treatments for VAs in these heart diseases, such as β-adrenergic receptor blockers and cardiac sympathetic ablation, aim at inhibiting cardiac sympathetic overactivation. However, these treatments do not translate into becoming efficacious as long-term suppressors of ventricular tachycardia/ventricular fibrillation events. As a key regulatory component in the heart, cardiac postganglionic sympathetic neurons residing in the stellate ganglia (SGs) release neurotransmitters (such as norepinephrine and NPY [neuropeptide Y]) to perform their regulatory role in dictating cardiac function. Growing evidence from animal experiments and clinical studies has demonstrated that the remodeling of the SG may be intimately involved in malignant arrhythmogenesis. This identifies the SG as a key potential therapeutic target for the treatment of malignant VAs in heart disease. Therefore, this review summarizes the role of SG in ventricular arrhythmogenesis and updates the novel targeting of SG for clinical treatment of VAs in heart disease.

The Accuracy of Cardiac Surface Conduction Velocity Measurements

BACKGROUND

Conduction velocity (CV) is a measure of the health of myocardial tissue. It can be measured by taking differences in local activation times from intracardiac electrodes. Several factors introduce error into the measurement, among which ignoring the 3-dimensional aspect is a major detriment.

OBJECTIVES

The purpose of this study was to determine if, nonetheless, there was a specific region where CV could be accurately measured.

METHODS

Computer simulations of 3-dimensional ventricles with a realistic His-Purkinje system were performed. Ventricles also included a dense scar or diffuse fibrosis.

RESULTS

A finer spatial sampling produced better agreement with true CV. Using an error limit of 10 cm/s as a threshold, measurements taken within a region <2 cm from the pacing site proved to be accurate. Error increased abruptly beyond this distance. The Purkinje system and tissue fiber orientation played equally major roles in leading to a surface CV that was not reflective of the CV propagation through the tissue.

CONCLUSIONS

In general, surface CV correlates poorly with tissue CV. Only surface CV measurements close to the pacing site, taken with an electrode spacing of ≤1 mm, give reasonable estimates.

Fragmented QRS complex could predict all-cause mortality in patients with connective tissue disease-associated pulmonary arterial hypertension

OBJECTIVES

To investigate the prognostic impact and pathophysiological characteristics of fragmented QRS complex (fQRS) on patients with CTD-associated pulmonary arterial hypertension (CTD-PAH).

METHODS

This was a multicentre retrospective study recruiting 141 patients with CTD-PAH diagnosed by right heart catheterization (114 cases in the discovery cohort and 27 cases in the validation cohort). fQRS and ST-T change were detected on conventional 12-lead ECG. Patients were followed up every 3 months to update their status and the primary endpoint was all-cause death. Clinical information and ECG characteristics were compared between survival and death groups and Kaplan-Meier curve was used for survival analysis.

RESULTS

There were significant differences in age, gender, 6-min walk distance, N-terminal pro-brain natriuretic peptide, World Health Organization class, presence of fQRS, and presence of ST-T change in inferior leads between survival group and death group. Inferior fQRS and ST-T change were significantly associated with right ventricular dilatation and reduced right ventricular ejection fraction. Kaplan-Meier curve showed that all-cause mortality was higher in CTD-PAH with fQRS (P = 0.003) and inferior ST-T change (P = 0.012). Low- and intermediate-risk CTD-PAH with inferior ST-T change had higher all-cause mortality (P = 0.005). The prognostic value of fQRS and inferior ST-T change was validated in external validation cohort.

CONCLUSION

The presence of inferior fQRS and ST-T change could predict poor prognosis in CTD-PAH.

CLINICAL TRIAL REGISTRATION

NCT05980728, https://clinicaltrials.gov.

Dynamic Changes in Ion Channels during Myocardial Infarction and Therapeutic Challenges

In different areas of the heart, action potential waveforms differ due to differences in the expressions of sodium, calcium, and potassium channels. One of the characteristics of myocardial infarction (MI) is an imbalance in oxygen supply and demand, leading to ion imbalance. After MI, the regulation and expression levels of K+, Ca2+, and Na+ ion channels in cardiomyocytes are altered, which affects the regularity of cardiac rhythm and leads to myocardial injury. Myocardial fibroblasts are the main effector cells in the process of MI repair. The ion channels of myocardial fibroblasts play an important role in the process of MI. At the same time, a large number of ion channels are expressed in immune cells, which play an important role by regulating the in- and outflow of ions to complete intracellular signal transduction. Ion channels are widely distributed in a variety of cells and are attractive targets for drug development. This article reviews the changes in different ion channels after MI and the therapeutic drugs for these channels. We analyze the complex molecular mechanisms behind myocardial ion channel regulation and the challenges in ion channel drug therapy.

Fragmented QRS complex on a 12-lead electrocardiogram predicts cardiovascular and all-cause mortality in dialysis patients

BACKGROUND

Cardiovascular disease (CVD) is the most common cause of mortality in end-stage renal disease (ESRD) patients. Fragmented QRS complex (fQRS) has been reported as a helpful marker in evaluating various cardiovascular pathologies. We aimed to investigate the value of the fQRS complex clinical decision of ESRD patients receiving dialysis.

METHODS

This prospective observational study included 411 patients receiving hemodialysis (HD) or continuous ambulatory peritoneal dialysis (CAPD) between 2016-01-01 and 2020-12-31. The primary outcomes were all-cause and cardiovascular (CV) mortality.

RESULTS

HD patients have elevated values of fQRS complex compared to CAPD patients (39.1% vs. 28.2%, P = 0.027). Significantly, fQRS complex in the anterior/lateral leads is associated with all-cause and CV mortality stronger than fQRS in the inferior leads (P = 0.008). In a multivariate Cox regression analysis, HD patients with fQRS complex had a higher incidence of all-cause mortality (hazard ratio [HR] = 1.860; 95% confidence interval [CI]: [1.032, 3.349]; p = 0.041) and CV mortality (HR = 2.989; 95% CI [1.357, 6.584]; p = 0.007). For CAPD patients, fQRS complex was also associated with increased risk of all-cause mortality (HR = 1.593; 95% CI [1.023, 2.580]; p = 0.049) and increased risk of CV mortality (HR = 2.392; 95% CI [1.348, 4.173]; p = 0.013).

CONCLUSIONS

The presence of the fQRS complex was an independent predictor of all-cause and CV mortality in HD and CAPD patients. We suggested a potential role of the fQRS complex in CV risk strata for dialysis patients and the choice of dialysis modality.

Electrophysiologic Changes and Their Effects on Ventricular Arrhythmias in Patients with Continuous-Flow Left Ventricular Assist Devices

Ventricular arrhythmias (VAs) continue even after left ventricular assist device (LVAD) implantation. The effect of LVAD on VAs is controversial. We investigated electrophysiologic changes after LVAD and its effects on VAs development. A total of 107 implantable cardioverter-defibrillator (ICD) patients, with LVAD, were included in this study. Electrocardiographic parameters including QRS duration (between the beginning of the QRS complex and the end of the S wave), QT duration (between the first deflection of the QRS complex and the end of the T wave) corrected QT (QTc), QTc dispersion, fragmented QRS (F-QRS), and ICD recordings before, and post-LVAD first year were analyzed. All sustained VAs were classified as polymorphic ventricular tachycardia (PVT) or monomorphic VT (MVT). The QRS, QT, QTc durations, and QTc dispersion had decreased significantly after LVAD implantation (p < 0.001 for all). Also MVT increased significantly from 28.9% to 49.5% (p = 0.019) whereas PVT decreased from 27.1% to 4.67% (p = 0.04) compared to pre-LVAD period. A strong correlation was found between QT shortening and the decrease in PVT occurrence. Besides, the increase in the F-QRS after LVAD was associated with post-LVAD de nova MVT development. Finally, F-QRS before LVAD was found as an independent predictor of post-LVAD late VAs in multivariate analysis. Pre-existing or newly developed F-QRS was associated with post-LVAD late VAs, and it may be used to determine the risk of VAs after LVAD implantation.

Prognostic impact of multiple fragmented QRS on cardiac events in idiopathic dilated cardiomyopathy

AIMS

To evaluate the prognostic impact of fragmented QRS (fQRS) on idiopathic dilated cardiomyopathy (DCM).

METHODS AND RESULTS

We conducted a prospective observational study of 290 consecutive patients with DCM (left ventricular ejection fraction ≤ 40%) and narrow QRS who underwent cardiac magnetic resonance. We defined fQRS as the presence of various RSR' patterns in ≥2 contiguous leads representing the anterior (V1-V5), inferior (II, III, and aVF), or lateral (I, aVL, and V6) myocardial segments. Multiple fQRS was defined as the presence of fQRS in ≥2 myocardial segments. Patients were divided into three groups: no fQRS, single fQRS, or multiple fQRS. The primary endpoint was a composite of hard cardiac events consisting of heart failure death, sudden cardiac death (SCD), or aborted SCD. The secondary endpoints were all-cause death and arrhythmic event. During a median follow-up of 3.8 years (interquartile range, 1.8-6.2), 31 (11%) patients experienced hard cardiac events. Kaplan-Meier analysis showed that the rates of hard cardiac events and all-cause death were similar in the single-fQRS and no-fQRS groups and higher in the multiple-fQRS group (P = 0.004 and P = 0.017, respectively). Multivariable Cox regression identified that multiple fQRS is a significant predictor of hard cardiac events (hazard ratio, 2.23; 95% confidence interval, 1.07-4.62; P = 0.032). The multiple-fQRS group had the highest prevalence of a diffuse late gadolinium enhancement pattern (no fQRS, 21%; single fQRS, 22%; multiple fQRS, 39%; P < 0.001).

CONCLUSION

Multiple fQRS, but not single fQRS, is associated with future hard cardiac events in patients with DCM.

Complex Re-Entrant Arrhythmias Involving the His-Purkinje System: A Structured Approach to Diagnosis and Management

OBJECTIVES

This study sought to characterize the presentations, electrophysiological features and diagnostic maneuvers for a series of unique arrhythmias involving the HPS.

BACKGROUND

By virtue of its unique anatomy and ion channel composition, the His-Purkinje system (HPS) is prone to a variety of arrhythmic perturbations.

METHODS

The authors present a collaborative multicenter case series of 6 patients with HPS-related arrhythmias. All patients underwent electrophysiological studies using standard multipolar catheters.

RESULTS

In 3 patients, both typical and reverse bundle branch re-entry were seen, with 1 patient demonstrating "figure of 8" re-entry likely involving the septal fascicle. One patient presented with systolic dysfunction associated with a high premature ventricular complex burden, with the mechanism being bundle-to-bundle re-entrant beats masquerading as dual response to a single sinus impulse. Two patients were diagnosed with interfascicular re-entry. Diagnosis was aided by careful assessment of HV interval in sinus rhythm and ventricular tachycardia, multipolar catheters to assess the activation sequence of the His-right bundle branch, and fascicles and entrainment of different components of the HPS. Cure of the arrhythmia was achieved by ablation of the right bundle branch block in 3 patients, the left septal fascicle in 2 patients, and the left posterior fascicle in 1 patient.

CONCLUSIONS

Proper diagnosis of re-entrant arrhythmias involving the HPS may prove challenging. We emphasize a structured approach for diagnosis and effective therapy.

Cardiac transmembrane ion channels and action potentials: cellular physiology and arrhythmogenic behavior

Cardiac arrhythmias are among the leading causes of mortality. They often arise from alterations in the electrophysiological properties of cardiac cells and their underlying ionic mechanisms. It is therefore critical to further unravel the pathophysiology of the ionic basis of human cardiac electrophysiology in health and disease. In the first part of this review, current knowledge on the differences in ion channel expression and properties of the ionic processes that determine the morphology and properties of cardiac action potentials and calcium dynamics from cardiomyocytes in different regions of the heart are described. Then the cellular mechanisms promoting arrhythmias in congenital or acquired conditions of ion channel function (electrical remodeling) are discussed. The focus is on human-relevant findings obtained with clinical, experimental, and computational studies, given that interspecies differences make the extrapolation from animal experiments to human clinical settings difficult. Deepening the understanding of the diverse pathophysiology of human cellular electrophysiology will help in developing novel and effective antiarrhythmic strategies for specific subpopulations and disease conditions.

Eliciting α7-nAChR exerts cardioprotective effects on ischemic cardiomyopathy via activation of AMPK signalling

Our previous studies have reported that agonist of α7 nicotinic acetylcholine receptors prevented electrophysiological dysfunction of rats with ischaemic cardiomyopathy (ICM) by eliciting the cholinergic anti‐inflammatory pathway (CAP). Adenosine monophosphate‐activated protein kinase (AMPK) signalling is widely recognized exerting cardioprotective effect in various cardiomyopathy. Here, we aimed to investigate whether the protective effects of the CAP are associated with AMPK signalling in ICM. In vivo, coronary artery of rats was ligated for 4 weeks to induce the ICM and then treated with PNU‐282987 (CAP agonist) and BML‐275 dihydrochloride (AMPK antagonist) for 4 weeks. In vitro, primary macrophages harvested from rats were induced inflammation by Lipopolysaccharide (LPS) treatment and then treated with PNU‐282987 and BML‐275 dihydrochloride. In vivo, exciting CAP by PUN‐282987 elicited an activation of AMPK signalling, alleviated ventricular remodeling, modified the cardiac electrophysiological function, reduced the cardiac expression of collagens and inflammatory cytokines and maintained the integrity of ultrastructure in the ischemic heart. However, the benefits of CAP excitation were blunted by AMPK signaling antagonization. In vitro, excitation of the CAP was observed inhibiting the nuclear transfer of NF‐κB p65 of macrophages and promoting the transformation of Ly‐6C^high macrophages into Ly‐6C^low macrophages. However, inhibiting AMPK signalling by BML‐275 dihydrochloride reversed the CAP effect on LPS‐treated macrophages. Finally, our findings suggest that eliciting the CAP modulates the inflammatory response in ICM through regulating AMPK signalling.

Changes in the spatial distribution of the Purkinje network after acute myocardial infarction in the pig

Purkinje cells (PCs) are more resistant to ischemia than myocardial cells, and are suspected to participate in ventricular arrhythmias following myocardial infarction (MI). Histological studies afford little evidence on the behavior and adaptation of PCs in the different stages of MI, especially in the chronic stage, and no quantitative data have been reported to date beyond subjective qualitative depictions. The present study uses a porcine model to present the first quantitative analysis of the distal cardiac conduction system and the first reported change in the spatial distribution of PCs in three representative stages of MI: an acute model both with and without reperfusion; a subacute model one week after reperfusion; and a chronic model one month after reperfusion. Purkinje cells are able to survive after 90 minutes of ischemia and subsequent reperfusion to a greater extent than cardiomyocytes. A decrease is observed in the number of PCs, which suffer reversible subcellular alterations such as cytoplasm vacuolization, together with redistribution from the mesocardium—the main localization of PCs in the heart of ungulate species—towards the endocardium and perivascular epicardial areas. However, these changes mainly occur during the first week after ischemia and reperfusion, and are maintained in the chronic stages. This anatomical substrate can explain the effectiveness of endo-epicardial catheter ablation of monomorphic ventricular tachycardias in the chronic scar after infarction, and sets a basis for further electrophysiological and molecular studies, and future therapeutic strategies.

Predictive value of a fragmented QRS complex in diagnosing patients with myocardial ischemia

Background

A fragmented QRS complex (fQRS) is caused by conduction abnormalities of the ventricle secondary to myocardial ischemia and/or scar in patients with myocardial infarction. However, the implications of the fQRS in the development of coronary artery disease with myocardial ischemia in those without a scar remain unknown.

Methods

We studied electrocardiograms (ECGs) obtained from 150 patients (60.5 ± 8.5 years, 102 men) with myocardial ischemia, which was confirmed by performing both, a nuclear exercise stress test and coronary angiography. We also studied ECGs obtained from 601 patients (58.5 ± 10.0 years, 315 men) who showed a negative nuclear exercise stress test (control group). Patients in whom the nuclear exercise stress test showed a myocardial scar were excluded.

Results

An fQRS was more commonly observed in patients with myocardial ischemia (n = 48, 32.0%) than in the control group (n = 133, 22.1%) (P = 0.011). The sensitivity, specificity, positive, and negative predictive values of fQRS in diagnosing myocardial ischemia were 32.0, 77.9, 26.5, and 82.1%, respectively. The fQRS (odds ratio 1.580, 95% confidence interval 1.020‐2.446, P = 0.040) was an independent predictor of myocardial ischemia after adjusting for age, sex, current smoking habits, ST‐T changes on ECG, as well as histories of hypertension, diabetes, and dyslipidemia. Moreover, the fQRS showed an incremental prognostic value over conventional risk factors (χ² = 5, P = 0.032) and over a combination of conventional factors and ST‐T changes (χ² = 9, P = 0.014).

Conclusions

The fQRS is a moderately sensitive and independent predictor of myocardial ischemia.

Ventricular arrhythmias involving the His-Purkinje system in the structurally abnormal heart

His-Purkinje-related ventricular arrhythmias are a subset of ventricular tachycardias that use the specialized cardiac conduction system. These arrhythmias can occur in various different forms of structural heart disease. Here, we review the basic science discoveries and their analogous clinical observations that implicate the His-Purkinje system as a crucial component of the arrhythmia circuit. While mutations serve the molecular basis for arrhythmias in the heritable cardiomyopathies, transcriptional and posttranslational changes constitute the adverse remodeling leading to arrhythmias in acquired structural heart disease. Additional studies on the electrical properties of the His-Purkinje network and its interactions with the surrounding myocardium will improve the clinical diagnosis and treatment of these arrhythmias.

Prognostic significance of fragmented QRS in patients with ST-elevation myocardial infarction undergoing revascularization

BACKGROUND & OBJECTIVES

This longitudinal study was carried out to evaluate the prognostic significance of fragmented QRS (fQRS) in patients with acute ST elevation myocardial infarction (STEMI) undergoing revascularization.

METHODS

This study included 103 STEMI patients belonging to Killip class I and II who underwent primary revascularization. All patients underwent twelve lead ECG at admission before PCI. Serial ECG were done after PCI at 3 hours, 6 hours, 24 hours, 48 hours and at discharge for detection of fQRS and echocardiography on day 3 post revascularization. Patients developing fQRS within 48 hours and with persistence of fQRS till discharge were included in "persistent fQRS" group. They were followed up after 30 days for major adverse cardiac events (MACE) and assessment of LV function by echocardiography.

RESULTS

fQRS was present in 64 patients (61.5%) of study population with 37 patients (57.8%) having persistent fQRS. MACE rates were low (4.8%) and did not differ with respect to fQRS. fQRS significantly correlated with LV dysfunction at 30 days on univariate analysis (p-0.003) but not on multivariate analysis (p -0.10). fQRS was significantly related to impaired myocardial reperfusion as assessed by ΣSTR (percent of total ST segment resolution) (adjusted odds ratio, 95% CI [4.265 (1.034 - 17.58)], p = 0.04).

CONCLUSION

In our study, fQRS did not predict MACE and LV dysfunction in acute STEMI patients belonging to Killip class I and II on short term follow-up of 30 days. But, fQRS independently predicted impaired microvascular myocardial reperfusion as assessed by ΣSTR.

Purkinje physiology and pathophysiology

There has always been an appreciation of the role of Purkinje fibers in the fast conduction of the normal cardiac impulse. Here, we briefly update our knowledge of this important set of cardiac cells. We discuss the anatomy of a Purkinje fiber strand, the importance of longitudinal conduction within a strand, circus movement within a strand, conduction, and excitability properties of Purkinjes. At the cell level, we discuss the important components of the ion channel makeup in the nonremodeled Purkinjes of healthy hearts. Finally, we discuss the role of the Purkinjes in forming the heritable arrhythmogenic substrates such as long QT, heritable conduction slowing, CPVT, sQT, and Brugada syndromes.

Ventricular Tachycardia in Ischemic Heart Disease

Ventricular arrhythmias are a significant cause of morbidity and mortality in patients with ischemic structural heart disease. Endocardial and epicardial mapping strategies include scar characterization channel identification, and recording and ablation of late potentials and local abnormal ventricular activities. Catheter ablation along with new technology and techniques of bipolar ablation, needle catheter, and autonomic modulation may increase efficacy in difficult to ablate ventricular arrhythmias. Catheter ablation of ventricular arrhythmias seem to confer mortality and morbidity benefits in patients with ischemic heart disease.

The relation between coronary artery disease severity and fragmented QRS complex in patients with left bundle branch block

Background

The diagnosis of coronary artery disease (CAD) in patients with LBBB represents a clinical challenge. The presence of fragmented QRS (fQRS) complex on surface ECG may be related to myocardial ischemia, scarring or fibrosis.

Objectives

To investigate the relation between fQRS and the presence and severity of CAD in patients with LBBB.

Patients and methods

56 patients with symptoms suggesting CAD and complete LBBB were submitted to full history taking and clinical examination, complete 12-leads electrocardiography (ECG) to confirm the diagnosis of LBBB and to diagnose the fragmented wide QRS (f-wQRS) complex, echocardiography, and coronary angiography; lesions with ⩾70% narrowing in major epicardial artery or ⩾50% narrowing in the left main coronary artery were considered significant; and Gensini score was calculated. Patients were classified into two groups according to the presence or absence of f-wQRS.

Results

There were significantly more patients with obstructive CAD among patients with f-wQRS (p = 0.000053). Gensini score was significantly higher in patients with than in patients without fwQRS (p < 0.00001). f-wQRS was the only significant independent predictor of obstructive CAD. Sensitivity of f-wQRS in predicting obstructive CAD was 80.1%, specificity was 73.3%, positive predictive value was 72.4%, negative predictive value was 81.5%, and overall accuracy was 76.8%, p = 0.0022.

Conclusion

Seeking for f-wQRS in patients with LBBB and suspected CAD is a simple, easy, available, method that may be helpful in noninvasive prediction of obstructive CAD.

A review of the literature on cardiac electrical activity between fibroblasts and myocytes

Myocardial injuries often lead to fibrotic deposition. This review presents evidence supporting the concept that fibroblasts in the heart electrically couple to myocytes.

Fragmented QRS on Admission Electrocardiography Predicts Long-Term Mortality in Patients with Non-ST-Segment Elevation Myocardial Infarction

BACKGROUND

Early diagnosis and identification of high-risk non-ST elevation myocardial infarction (NSTEMI) is an important issue. Fragmented QRS (fQRS) complexes are defined as various RSR' patterns on 12-lead resting electrocardiography (ECG). Previous studies revealed that fQRS is related with increased ventricular arrhythmias and cardiovascular mortality. The relation between fQRS and mortality in acute coronary syndromes, mitral valve disease severity and structural heart disease has been shown in different studies. The aim of this study was to investigate relation between fQRS and long-term cardiovascular mortality in NSTEMI patients.

METHODS

Patients who admitted to our emergency unit and diagnosed NSTEMI between 2012 and 2013, 433 patients were included prospectively. fQRS complexes determined in 85 patients. Patients were divided into two groups according to fQRS existence. All patients evaluated for their clinical, laboratory, electrocardiographic, and echocardiographic characteristics. Angiographic features of 315 patients who underwent coronary angiography was also recorded. In-hospital, 30-day and 12-month mortality was compared between these groups.

RESULTS

Demographic characteristics and cardiovascular risk factors were similar in both groups except hyperlipidemia. GRACE risk score was higher in patients with fQRS and positively correlated with existence of fQRS. In hospital and 30-days mortality were similar but late mortality was higher in fQRS group. Predictors of late mortality were found to be age, heart rate, male sex in addition to fQRS.

CONCLUSION

We found a relation between fQRS and late mortality. Fragmented QRS may be seen as a cautionary signal for extensive myocardial damage and thereby increased long-term mortality for patients with NSTEMI.

Fragmented QRS complex is a diagnostic tool in patients with left ventricular diastolic dysfunction

Fragmented QRS complex (fQRS) on 12-lead ECG is associated with myocardial fibrosis and ischemic scar. Interstitial fibrosis is one of the histological characteristics of left ventricular diastolic dysfunction (LVDD). However, the clinical importance of fQRS in patients with LVDD remains unclear. Here, we assessed the hypothesis that the presence of fQRS is associated with disease severity in patients with LVDD, and could be used as an additional parameter to differentiate patients with heart failure with preserved ejection fraction (HFpEF) from LVDD. We analyzed 12-lead ECG of 239 patients with LVDD. The patients were divided into two groups according to the presence or absence of fQRS; 88 patients had fQRS (fQRS group) and 151 patients did not have fQRS (non-fQRS group). The percentage of patients with heart failure in the fQRS group was significantly higher than that in the non-fQRS group. The levels of B-type natriuretic peptide (BNP) and high-sensitive troponin T were significantly higher in the fQRS group than those in the non-fQRS group. In univariate logistic regression analysis, fQRS was associated with the presence of heart failure in patients with LVDD. Multivariate logistic regression analysis identified fQRS and BNP as independent indicators for HFpEF. In conclusion, the presence of fQRS on the ECG could be used as an additional tool to differentiate HFpEF from LVDD.

The importance of fragmented QRS in the early detection of cardiac involvement in patients with systemic sclerosis

Objective:

Systemic sclerosis (SSc) is an autoimmune connective tissue disorder characterized by fibrosis. The prognosis of the disease is bad when clinically symptomatic cardiac dysfunction is occurred, therefore early detection of cardiac dysfunction is important in patients with SSc. The aim of this study was to investigate the frequency of fQRS in superficial electrocardiography in cardiacally asymptomatic patients with SSc and its relation to the systolic pulmonary artery pressure (sPAP).

Methods:

This study included 31 cardiacally asymptomatic patients with SSc (23 females, 40.4±9.2 years) and 41 healthy volunteers as the control (31 females, 38.2±11.8 years). The ECGs with 12 derivations and transthoracic echocardiographies of the patients were evaluated. The presence of fQRS in the superficial ECG, and its relation to systolic pulmonary artery pressure (sPAP) were investigated.

Results:

The mean sPAP value in the SSc group was observed to be higher than that of the control group (26 mm Hg and 20 mm Hg, respectively, p<0.001). The presence of fQRS in the SSc group was more frequent than the control group (55% and 10%, respectively, p<0.001). In SSc patients presence of fQRS become relevant with ≥24 mm Hg sPAP by 88% sensitivity and 79% specificity.

Conclusion:

In our study, the presence of fQRS in SSc patients, were more frequent than in the normal population. Since pulmonary hypertension is the primary cause of mortality in patients with SSc, the correlation of fQRS with sPAP should also be considered.

Assessment of the relationship between fragmented QRS and cardiac iron overload in patients with beta-thalassemia major

Objective:

Beta-thalassemia major (TM) is a genetic hemoglobin disorder causing chronic hemolytic anemia. Since cardiac insufficiency and arrhythmias are the primary causes of mortality in such patients, monitoring of cardiac iron load is important in management of the disorder. The purpose of this study was to investigate the importance of fragmented QRS (fQRS) and its relation to the cardiac T2* value for the evaluation of cardiac iron load in TM patients.

Methods:

This retrospective study included 103 TM patients. The patients’ T2* values, measured by cardiac MRI and 12-lead surface ECGs, were interpreted. The cardiac T2* values under 20 were considered as cardiac iron overload. The relationship between the cardiac T2* value and fQRS in ECG was investigated.

Results:

The median age of the patients was 22.6±6.6 years. All patients were on regular blood transfusions and iron chelators. The patients had no risk factors for coronary artery disease. In 50 (48%) patients fQRS was detected, and in 37 (74%) of these the T2* values were low. 86% of patients with cardiac involvement (37) had fQRS, but 22% of patients with non-involvement (13) had fQRS (p<0.001).

Conclusion:

Since cardiac involvement is the primary cause of mortality in TM patients, the early diagnosis of cardiac dysfunction is of vital importance. The search for fQRS in the ECGs of these patients, particularly when cardiac T2* values cannot be determined and followed, is a non-expensive and easy-to-attain method for therapy management.

Assessment of the relationship between red cell distribution width and fragmented QRS in patients with non-ST elevated acute coronary syndrome

Background

Red cell distribution width (RDW) and fragmented QRS (fQRS) complexes have also been reported to be predictors of cardiac events and all-cause mortality in coronary artery disease (CAD). We aimed to investigate the association of serum red cell distribution width (RDW) levels and fQRS in patients with non-ST elevated acute coronary syndrome (NST-ACS).

Material/Methods

We retrospectively evaluated a total of 251 patients (191 men and 60 women) with NST-ACS. The NST-ACS consisted of unstable angina (UA) and non-ST elevated myocardial infarction (NSTEMI). The fQRS pattern was defined as the presence of an additional R’ or crochetage wave, notching in the nadir of the S wave or fragmentation of the RS or QS complexes in 2 contiguous leads corresponding to a major coronary artery territory. The relationships between the RDW and fQRS were assessed.

Results

The patients in the fQRS group were older, left ventricular ejection fraction (LVEF) levels were significantly lower, and baseline RDW and troponin levels were significantly higher than in the group without fQRS. There were positive correlations between age, number of coronary arteries narrowed, and RDW, and negative correlations between triglyceride, LVEF, and RDW in study patients. There were positive correlations between number of fQRS leads, age, and RDW, and negative correlations between triglyceride, LVEF, and RDW in NSTEMI patients.

Conclusions

Our results indicate that an elevated RDW values is associated with fQRS in NST-ACS. Elevated RDW values and fQRS together may be useful for identifying NSTEMI patients in NST-ACS.

Ankyrin-G participates in INa remodeling in myocytes from the border zones of infarcted canine heart

Cardiac Na channel remodeling provides a critical substrate for generation of reentrant arrhythmias in border zones of the infarcted canine heart. Recent studies show that Nav1.5 assembly and function are linked to ankyrin-G, gap, and mechanical junction proteins. In this study our objective is to expound the status of the cardiac Na channel, its interacting protein ankyrinG and the mechanical and gap junction proteins at two different times post infarction when arrhythmias are known to occur; that is, 48 hr and 5 day post coronary occlusion. Previous studies have shown the origins of arrhythmic events come from the subendocardial Purkinje and epicardial border zone. Our Purkinje cell (Pcell) voltage clamp study shows that INa and its kinetic parameters do not differ between Pcells from the subendocardium of the 48hr infarcted heart (IZPCs) and control non-infarcted Pcells (NZPCs). Immunostaining studies revealed that disturbances of Nav1.5 protein location with ankyrin-G are modest in 48 hr IZPCs. Therefore, Na current remodeling does not contribute to the abnormal conduction in the subendocardial border zone 48 hr post myocardial infarction as previously defined. In addition, immunohistochemical data show that Cx40/Cx43 co-localize at the intercalated disc (IDs) of control NZPCs but separate in IZPCs. At the same time, Purkinje cell desmoplakin and desmoglein2 immunostaining become diffuse while plakophilin2 and plakoglobin increase in abundance at IDs. In the epicardial border zone 5 days post myocardial infarction, immunoblot and immunocytochemical analyses showed that ankyrin-G protein expression is increased and re-localized to submembrane cell regions at a time when Nav1.5 function is decreased. Thus, Nav1.5 and ankyrin-G remodeling occur later after myocardial infarction compared to that of gap and mechanical junctional proteins. Gap and mechanical junctional proteins remodel in IZPCs early, perhaps to help maintain Nav1.5 subcellular location position and preserve its function soon after myocardial infarction.

Epicardial ablation for ventricular tachycardia

Epicardial ablation has lately become a necessary tool to approach some ventricular tachycardias in different types of cardiomyopathy. Its diffusion is now limited to a few high volume centers not because of the difficulty of the pericardial puncture but since it requires high competence not only in the VT ablation field but also in knowing and recognizing the possible complications each of which require a careful treatment.

This article will review the state of the art of epicardial ablation with special attention to the procedural aspects and to the possible selection criteria of the patients

Absence and Resolution of Fragmented QRS Predict Reversible Myocardial Ischemia With Higher Probability of ST Segment Resolution in Patients With ST Segment Elevation Myocardial Infarction

BACKGROUND AND OBJECTIVES

Fragmented QRS complexes (fQRS) are associated with increased morbidity and mortality. The causative relationship between fQRS and cardiac fibrosis has been shown, but whether the presence and the number of fQRS on admission of electrocardiogram (ECG) predicts ST segment resolution in patients undergoing primary percutaneous coronary intervention (p-PCI) has not been investigated until now.

SUBJECTS AND METHODS

This study included one hundred and eighty-four consecutive patients with ST elevation myocardial infarction (STEMI) who underwent p-PCI. The presence or absence of fQRS on pre and post-PCI ECG and their relation with myocardial infarction and reperfusion parameters were investigated.

RESULTS

Patients with fQRS on admission of ECG or newly developed fQRS after p-PCI had increased inflammatory markers, higher cardiac enzyme levels, increased pain to balloon time, prolonged QRS time, more extended coronary involvement and more frequent Q waves on ECG in comparison to patients with absence or resolved fQRS. The presence and higher number of fQRS on admission or post-PCI ECGs were significantly related with low percent of ST resolution and myocardial reperfusion parameters. The area under the receiver operating characteristics curve values for the presence and number of fQRS to detect Thrombolysis in Myocardial Infarction Blush Grade 0 and 1, were 0.682 and 0.703.

CONCLUSION

In our study, fQRS was significantly related to infarction and myocardial reperfusion parameters before and after p-PCI. Successful myocardial reperfusion by p-PCI caused the reduction in number of fQRS and QRS time with higher ST resolution. fQRS may be useful in identifying the patients at higher cardiac risk with increased ischemic jeopardized or infarcted myocardium, and persistent or newly developed fQRS may predict low percent of ST segment resolution in patients undergoing p-PCI.

QRS fragmentation and the risk of sudden cardiac death in MADIT II

BACKGROUND

QRS fragmentation (fQRS) has been reported as a useful ECG parameter in predicting mortality in high-risk postinfarction patients. Its prognostic value for sudden cardiac death (SCD) and ventricular arrhythmias in ischemic cardiomyopathy (ICM) remains unknown.

METHODS

MADIT II enrollment 12-lead ECGs were analyzed for fQRS defined as RSR' patterns (≥1 R' or notching of S or R wave) in patients with a normal QRS duration and >2 notches on the R or S wave in patients with abnormal QRS duration, present in 2 contiguous leads. Exclusion criteria included a paced rhythm and an uninterpretable or incomplete ECG. Study endpoints included SCD, SCD or appropriate implantable cardioverter defibrillator (ICD) shock, and total mortality (TM).

RESULTS

Of the 1,232 ECGs reviewed, 1,040 were of suitable quality for fQRS analysis. QRS fragmentation was found in 33% of patients in any leads, in 10% of patients in anterior leads, in 8% of patients in lateral leads and in 21% of patients in inferior leads. Anterior and lateral location of QRS fragmentation was not associated with follow-up events. Inferior location of fQRS was found to be predictive of SCD/ICD shock (hazard ratio [HR] 1.46, P = 0.032), SCD (HR 2.05, P = 0.007), and TM (HR 1.44, P = 0.036). This association was driven primarily by the increase in events found in LBBB patients: SCD/ICD shock (HR 2.05, P = 0.046), SCD (HR 4.24, P = 0.002), and TM (HR 2.82, P = 0.001).

CONCLUSIONS

Fragmented QRS, especially identified in inferior leads, is predictive of SCD, SCD or appropriate ICD shock, and all-cause mortality in patients with ICM. Identifying inferior fQRS in patients with LBBB is of particular prognostic significance and should reinforce the use of ICD therapy in this high-risk group.

The independent relationship of systemic inflammation with fragmented QRS complexes in patients with acute coronary syndromes

BACKGROUND AND OBJECTIVES

QRS complex fragmentations are frequently seen on routine electrocardiograms with narrow or wide QRS complex. Fragmented QRS complex (fQRS) is associated with increased morbidity and mortality, sudden cardiac death and recurrent cardiovascular events. In this study, we aimed to interrogate the relationship of systemic inflammation with the presence of fQRS in patients with acute coronary syndromes (ACS).

SUBJECTS AND METHODS

Two-hundred and twenty eligible patients with ACS that underwent coronary angiography were enrolled consecutively in this study. Patients with significant organic valve disease and those with any QRS morphology that had a QRS duration ≥120 ms as well as patients with permanent pacemakers were excluded from this study.

RESULTS

Patients with fQRS were of a higher age (p=0.02), had increased C-reactive protein (CRP) levels (p<0.001), prolonged QRS time (p<0.001), extent of coronary artery disease (CAD) (p<0.001), creatine kinase-MB (CK-MB) levels (p=0.006) and Q wave on admission electrocardiography (p<0.001) in comparison to patients with non-fragmented QRS. When we performed multiple logistic regression analysis, fQRS was found to be related to increased CRP levels {odds ratio (OR): 1.2, 95% confidence interval (CI): 1.045-1.316, p=0.007}, QRS duration (OR: 1.1, 95% CI: 1.033-1.098, p<0.001), extent of CAD (OR: 1.5, 95% CI: 1.023-2.144, p=0.037), Q wave (OR: 2.2, 95% CI: 1.084-4.598, p=0.03) and CK-MB levels (OR: 1.0, 95% CI: 1.001-1.037, p=0.04) independently.

CONCLUSION

In our study, we found that fQRS was independently related to increased CRP. Fragmented QRS that may result as an end effect of inflammation at cellular level can represent increased cardiac risk by different causative mechanisms in patients with ACS.

Relationship of fragmented QRS complexes with inadequate coronary collaterals in patients with chronic total occlusion

BACKGROUND

Fragmented QRS (fQRS) complexes are defined as various RSR' patterns (≥1 R' or notching of S wave or R wave) in two contiguous leads corresponding to a major coronary artery territory. In previous studies, fQRS has been associated with increased morbidity and mortality, sudden cardiac death and recurrent cardiovascular events (CVEs). The causative relationship between fQRS and cardiac fibrosis has been shown in prior studies. The association between inadequate (poor) coronary collaterals and presence of fQRS has not comprehensively been studied in patients with chronic total occlusion (CTO) until now. We tested the hypothesis that the presence of fQRS is associated with inadequate coronary collateral growth.

METHODS

This study had a cross-sectional observational design. The study population consisted of patients who underwent coronary angiography with the suspicion of coronary artery disease at our institution in an outpatient manner. Patients who had CTO in at least one major epicardial coronary artery were included. Coronary angiograms of 148 eligible patients from our database were analyzed again. Ninety-three patients had good and 55 had poor collateral development according to the Cohen-Rentrop method.

RESULTS

Patients with poor collateral development had higher plasma glucose (130 ± 54 vs. 116 ± 33 mg/dl, P = 0.047) and an older age (65 ± 10 vs. 61 ± 10  years, P = 0.042) in comparison to patients with good collateral growth. The presence and number of fQRS were higher in the poor collateral group than the good collateral group (64 vs. 32%, P < 0.001 and 2.3 ± 2.4 vs. 1.2 ± 2.0, P = 0.002, respectively). Left ventricular ejection fraction was significantly lower in the poor collateral group than the good collateral group (45 ± 11 vs. 51 ± 13, P = 0.014). There was a significant correlation between number of fQRSs and the echocardiographic wall-motion abnormality score (r = 0.662, P < 0.001). In multivariate analysis, only the presence of fQRS was independently related to poor collateral development (odds ratio, 3.559; 95% confidence interval, 1.708-7.415, P = 0.001).

CONCLUSION

We found that fQRS was independently related to inadequate coronary collaterals in patients with CTO. fQRS, which may be derived from the effects of myocardial ischemia or scar on myocardial electricity at the cellular level, can represent inadequate coronary collateral development in patients with CTO.

Relationship of fragmented QRS with prognostic markers and in-hospital MACE in patients undergoing CABG

BACKGROUND

Fragmented QRS complex (fQRS) is associated with increased morbidity and mortality, sudden cardiac death and recurrent cardiovascular events. However, its prognostic role has not been studied comprehensively in patients undergoing coronary artery bypass graft (CABG) surgery. In this study, we investigated the relationship between the presence of fQRS, and the prognostic markers and in-hospital major adverse cardiovascular events (MACE).

METHODS

Two hundred and forty two eligible patients who underwent CABG surgery at our institution were enrolled consecutively. In analysis of fragmentations on electrocardiograms, presence of fQRS was defined as various RSR' patterns (≥ 1 R' or notching of S wave or R wave) with or without Q waves without a typical bundle-branch block in two contiguous leads corresponding to a major coronary artery territory. MACE was defined as cardiac death, recurrent myocardial infarction, heart failure, cerebrovascular event, sustained ventricular tachycardia or fibrillation.

RESULTS

Patients with fragmented QRS had older age (64 ± 10 vs. 61 ± 9 years, p = 0.03), prolonged QRS time (99 ± 11 vs. 87 ± 11 ms, p < 0.001), higher rate of Q wave on ECG (29% vs. 12%, p = 0.001), higher European system for cardiac operative risk evaluation (EUROSCORE) (4.0 ± 1.9 vs. 2.6 ± 1.6, p < 0.001) and lower left ventricular ejection fraction (LVEF)% (43 ± 12 vs. 60 ± 12, p < 0.001) in comparison to patients with non-fragmented QRS. In addition, the patients with fQRS had longer cross-clamp time (67 ± 23 vs. 55 ± 20 minutes, p = 0.001) and extracorporeal circulation (105 ± 31 vs. 91 ± 30 minutes, p = 0.003), increased inotropic usage (p < 0.001) and prolonged cardiac surgery intensive care unit (53 ± 25 vs. 35 ± 12 hours, p < 0.001) and in-hospital stay after CABG.

CONCLUSION

FQRS may have additional value in the assessment of cardiac function and in prediction of intra- and post-operative hemodynamic instability and adverse cardiovascular events. Fragmentations on admission ECG may be useful for identifying patients with higher risk who will need additional support after CABG surgery.

Fragmented QRS complexes are associated with cardiac fibrosis and significant intraventricular systolic dyssynchrony in nonischemic dilated cardiomyopathy patients with a narrow QRS interval

BACKGROUND

Myocardial scar causes heterogeneous ventricular activation, which results in fragmentation of QRS complexes on ECG. Myocardial fibrosis in patients with nonischemic cardiomyopathy (NDCM) can be identified as late gadolinium enhancement (LGE) areas on cardiac magnetic resonance (CMR) studies. We investigated the association of fragmented QRS (fQRS) complexes with systolic dyssynchrony and myocardial fibrosis in patients with NDCM.

METHODS

Twenty patients with NDCM and sinus rhythm who had fQRS complexes were evaluated with CMR. The association of fQRS complexes with LGE and systolic dyssynchrony was investigated.

RESULTS

Nineteen patients had significant systolic dyssynchrony with echocardiography. Among 19 patients with significant dyssynchrony, 14 (74%) patients had fQRS complexes in the most delayed contracting segment or one of the dyssynchronous segments, whereas five patients (26%) had fQRS complexes in a lead which is discordant with the dyssynchronous segment on echocardiography. Seventeen patients had LGE in their CMR. Among the 17 patients with LGE; 13 patients (76%) had fQRS complexes concordant with LGE present segments.

CONCLUSION

Fragmentation of QRS complexes on ECG is associated with intraventricular systolic dyssynchrony and subendocardial fibrosis in NDCM patients with a narrow QRS interval and sinus rhythm.

The utility of fragmented QRS complexes to predict significant intraventricular dyssynchrony in nonischemic dilated cardiomyopathy patients with a narrow QRS interval

BACKGROUND

Fragmented QRS complexes in the electrocardiograms (ECGs) of patients with coronary artery disease are associated with adverse cardiac events. However, there are limited data on its predictive usefulness in patients with nonischemic dilated cardiomyopathy. Left ventricular dyssynchrony is common in heart failure patients who have wide QRS intervals, but its frequency in patients with narrow QRS intervals is uncertain.

OBJECTIVES

To investigate the relationship between fragmented QRS complexes and intraventricular dyssynchrony in patients with nonischemic dilated cardiomyopathy in sinus rhythm.

METHODS

Sixty nonischemic dilated cardiomyopathy patients with sinus rhythm and narrow QRS intervals were recruited. Forty patients had a fragmented QRS in their basal ECG, and 20 patients did not have a fragmented QRS. Patients were analyzed for correlation between fragmented QRS complexes and intraventricular dyssynchrony.

RESULTS

The maximal difference in time to the peak myocardial systolic velocity between any two left ventricular segments (Max-ASE Sys), and maximal difference between Max-ASE Sys and the mean value of all segments (Max-ASE to Mean Sys) were significantly higher in patients with fragmented QRS complexes (P=0.001 and P=0.003, respectively). Seventy-two per cent of the patients with fragmented QRS complexes had significant left ventricular dyssynchrony; 15% of patients without fragmented QRS complexes had significant left ventricular dyssynchrony (P<0.0001). The presence of fragmented QRS complexes in leads corresponding to the specific ventricular segment in basal ECG was found to detect intraventricular dyssynchrony with 90.6% sensitivity (negative predictive value of 85%).

CONCLUSION

Fragmentation in the resting ECG is associated with significant intraventricular dyssynchrony in patients with nonischemic cardiomyopathy, narrow QRS and sinus rhythm. Fragmentation in ECG might be useful in identifying patients who could benefit from cardiac resynchronization therapy.

Fragmented QRS on a 12-lead ECG: a predictor of mortality and cardiac events in patients with coronary artery disease

BACKGROUND

Fragmented QRS (fQRS) on a 12-lead electrocardiogram (ECG) is associated with myocardial scar in patients with coronary artery disease (CAD).

OBJECTIVE

We postulated that fQRS is a predictor of cardiac events and mortality in patients who have known CAD or who are being evaluated for CAD.

METHODS

The cardiac events (myocardial infarction, need for revascularization, or cardiac death) and all-cause mortality were retrospectively reviewed in 998 patients (mean age 65.5 +/- 11.9 years, male 967) who underwent nuclear stress test. The fQRS on a 12-lead ECG included various RSR' patterns (> or =1 R' prime or notching of S wave or R wave) without typical bundle branch block in 2 contiguous leads corresponding to a major coronary artery territory.

RESULTS

All-cause mortality (93 [34.1%] vs 188 [25.9%]) and cardiac event rate (135 [49.5%] vs 200 [27.6%]) were higher in the fQRS group compared with the non-fQRS group during a mean follow-up of 57 +/- 23 months. A Kaplan-Meier survival analysis revealed significantly lower event-free survival for cardiac events (P <.001) and all-cause mortality (P = .02). Multivariate Cox regression analysis revealed that significant fQRS was an independent significant predictor for cardiac events but not for all-cause mortality. The Kaplan-Meier survival analysis showed no significant difference between fQRS and Q waves groups for cardiac events (P = .48) and all-cause mortality (P = .08).

CONCLUSION

The fQRS is an independent predictor of cardiac events in patients with CAD. It is associated with significantly lower event-free survival for a cardiac event on long-term follow-up.

Mapping of epicardial activation in a rabbit model of chronic myocardial infarction:

INTRODUCTION

This study examines the consequences of a large transmural apical infarct on the epicardial electrical activity in isolated rabbit hearts.

METHODS AND RESULTS

Hearts were isolated 8 weeks after coronary artery ligation. Membrane voltage from the epicardial surface of the left ventricle (LV) including the infarct was monitored using the voltage sensitive dye RH237. Optical action potentials were detected from the epicardial surface of the infarct; the signal amplitude was approximately 20% of those in the noninfarcted zone (NZ). Epicardial activation mapping of the LV free wall showed that during right atrial (RA) pacing, the activation sequence was not significantly different between infarcted and sham-operated groups. However, direct stimulation of the epicardium in the NZ revealed an area of slow conduction velocity (CV approximately 5 cm/s(-1), approximately 10% of normal values) at the margin of the infarct zone (IZ). Within the IZ, CV was approximately 50% of normal. A prominent endocardial rim of myocardium in the infarct was not the source of epicardial optical signals because chemical ablation of the endocardium did not affect the epicardial activation pattern.

CONCLUSION

Therefore, remnant groups of myocytes in the mid-wall and epicardium of the infarct scar support normal electrical activation during RA pacing. Areas of delayed conduction emerge only on epicardial stimulation.

Arrhythmogenic Ion-Channel Remodeling in the Heart: Heart Failure, Myocardial Infarction, and Atrial Fibrillation

Rhythmic and effective cardiac contraction depends on appropriately timed generation and spread of cardiac electrical activity. The basic cellular unit of such activity is the action potential, which is shaped by specialized proteins (channels and transporters) that control the movement of ions across cardiac cell membranes in a highly regulated fashion. Cardiac disease modifies the operation of ion channels and transporters in a way that promotes the occurrence of cardiac rhythm disturbances, a process called “arrhythmogenic remodeling.” Arrhythmogenic remodeling involves alterations in ion channel and transporter expression, regulation and association with important protein partners, and has important pathophysiological implications that contribute in major ways to cardiac morbidity and mortality. We review the changes in ion channel and transporter properties associated with three important clinical and experimental paradigms: congestive heart failure, myocardial infarction, and atrial fibrillation. We pay particular attention to K+, Na+, and Ca2+channels; Ca2+transporters; connexins; and hyperpolarization-activated nonselective cation channels and discuss the mechanisms through which changes in ion handling processes lead to cardiac arrhythmias. We highlight areas of future investigation, as well as important opportunities for improved therapeutic approaches that are being opened by an improved understanding of the mechanisms of arrhythmogenic remodeling.

Fragmented left sided QRS in absence of bundle branch block: sign of left ventricular aneurysm

BACKGROUND

A left ventricular aneurysm (LVA) occurs between 3.5% and 9.4% of all cases of acute myocardial infarction. A fragmented left sided QRS (RSR; pattern or its variant RSr;, rSR;, or rSr;) without evidence of bundle branch block (QRS duration <or=120 ms) on the ECG may be associated with a significant myocardial scar, which is the characteristic of a LVA. We, therefore, postulate that fragmented QRS (RSR; pattern or its variant) in the left sided leads (I, aVL, V(3) to V(6)) may be a useful sign of LVA.

METHODS

ECGs of 110 consecutive patients with LVA documented by left ventricular angiography (30 degrees right anterior oblique view) was compared with 220 patients without LVA (110 patients with and 110 patients without coronary artery disease (CAD)), who were evaluated for CAD by symptoms and signs.

RESULTS

The sensitivity of the fragmented QRS for identification of LVA was 50% (55 of 110 patients) and specificity was 94.6% (209 of 220). Within the study population, the positive predictive value of the fragmented QRS for LVA was 83.3% (55 of 66) and the negative predictive value was 79.2% (209 of 264). Based on the range of prevalence of LVA in postmyocardial infarction population (3.5-9.4%) and on observed sensitivity and specificity, the positive predictive value of fragmented QRS for LVA after infarction can be estimated at 29-53% and the negative predictive value can be estimated at 95-98%.

CONCLUSION

The sensitivity of fragmented QRS in left precordial leads for LVA was only 50%, whereas the specificity was 94.5%. It has a relatively low to moderate positive predictive value and high negative predictive value.

[Sudden death (II). Myocardial ischemia and ventricular arrhythmias in experimental models: triggering mechanisms]

Metabolic and electrolytic alterations generated in the acute ischemic myocardium, such as an increase in extracellular potassium or acidosis, are responsible for the occurrence of ventricular arrhythmias. In the first 5-10 minutes following coronary occlusion, reentry seems to have an important role, although not in the next 15 minutes. If the patient survives, a subacute arrhythmia period appears, 6 to 72 hours after the onset of ischemia, probably due to abnormal automaticity in the surviving Purkinje fibers. Finally, reentry in the epicardial border zone is the most likely mechanism for chronic arrhythmias. In this review we focus on the studies dealing with the mechanisms of ischemia-induced arrhythmias, with special reference to those conducted in experimental models.