Significance of ventricular arrhythmias in idiopathic dilated cardiomyopathy

Long-term prognosis and prognostic factors after primary prophylactic implantable cardioverter-defibrillator therapy

BACKGROUND

Little is known regarding which patients with ischemic cardiomyopathy (ICM) should be considered for prophylactic therapies, such as an implantable cardioverter-defibrillator (ICD), in the primary percutaneous intervention era. The aim of this study was to investigate the influence of non-sustained ventricular tachycardia (NSVT) on major adverse cardiac events (MACE) in heart failure with reduced ejection fraction (HFrEF) patients.

METHODS

We retrospectively analyzed patients of ICM and non-ICM who underwent ICD implantation at our institute from October 2006 to August 2020. MACE were defined as composite outcome of cardiovascular death, heart failure hospitalization, and appropriate ICD therapies.

RESULTS

A total of 167 patients were enrolled [male, 138 (83 %); age, 62.1 ± 11.7 years; left ventricular ejection fraction, 23.5 ± 6.1 %; left ventricular diastolic diameter, 67.4 ± 9.0 mm; atrial fibrillation, 47 (28 %); NSVT, 124 (74 %); use of class III antiarrhythmic drugs, 55 (33 %); ischemic cardiomyopathy, 56 (34 %); cardiac resynchronization therapy, 73 (44 %)]. The median follow-up duration was 61 months. MACE occurred with 71 patients (43 %). When comparing baseline characteristics of the patients, left ventricular ejection fraction (p = 0.02) and atrial fibrillation (p = 0.04) were significantly associated with MACE. The multivariable Cox analysis for the target variable MACE identified atrial fibrillation (hazard ratio 2.00; 95 % confidence index 1.18-3.37; p = 0.01) as an independent predictor for MACE.

CONCLUSIONS

Prior NSVT before ICD implantation was not an independent predictor of future MACE in patients with HFrEF with primary prophylactic ICD. In contrast, atrial fibrillation was associated with worse prognosis. To predict the prognosis of patients with primary prophylactic ICD, these factors should be assessed as comprehensive risk stratification factors for MACE.

Left ventricular dyssynchrony as marker of early dysfunction in premature ventricular contraction-induced cardiomyopathy

Background

Strain imaging has been suggested as a tool to detect early left ventricular (LV) dysfunction due to frequent premature ventricular contractions (PVCs) in patients with preserved LV ejection fraction (EF). However, the progression of intraventricular dyssynchrony (IVD), radial, and circumferential strain (RS, CS) in PVC-cardiomyopathy (CM) are unknown. The aim of this study was to elucidate the progression patterns of CS, IVD, and electro-mechanical latency (EML) in PVC-CM.

Methods and results

Pacemakers were implanted in 20 canines to reproduce ventricular bigeminy at 200ms (PVCs n = 11) for 12 weeks and compared to a sham group (n = 9). We obtained echocardiograms at baseline, 4-, 8- and 12-weeks. RS and CS were obtained at the LV mid-cavitary level. IVD was defined as the time between the earliest and latest peak RS. EML was defined as the time between the onset of QRS and the earliest peak RS. LVEF (62 ± 5 to 42 ± 7%, p < 0.01), CS (-18 ± 3 to -12 ± 3, p < 0.01), and EML (219 ± 37 to 283 ± 46ms, p = 0.02) changed significantly in the PVC group. Peak CS (-18 ± 3 to -14 ± 4, p = 0.02) and IVD (49 ± 31 to 122 ± 103, p = 0.05) had a significant change at 4-weeks despite preserved LVEF (51 ± 5%). IVD normalized while EML increased at weeks 8 and 12.

Conclusion

Our findings consolidate the existing theory that changes in strain precede changes in LVEF in PVC-CM. While IVD becomes abnormal early in the development of PVC-CM, it pseudo-normalizes at advanced stages due to further increases in EML suggestive of cardiac contractility remodeling. These findings are consistent with recent published data where abnormal LV mechanics could be part of a substrate that can predispose to worse outcome in PVC-Cardiomyopathy.

Detrimental proarrhythmogenic interaction of Ca2+/calmodulin-dependent protein kinase II and NaV1.8 in heart failure

An interplay between Ca²⁺/calmodulin-dependent protein kinase IIδc (CaMKIIδc) and late Na⁺ current (I_NaL) is known to induce arrhythmias in the failing heart. Here, we elucidate the role of the sodium channel isoform Na_V1.8 for CaMKIIδc-dependent proarrhythmia. In a CRISPR-Cas9-generated human iPSC-cardiomyocyte homozygous knock-out of Na_V1.8, we demonstrate that Na_V1.8 contributes to I_NaL formation. In addition, we reveal a direct interaction between Na_V1.8 and CaMKIIδc in cardiomyocytes isolated from patients with heart failure (HF). Using specific blockers of Na_V1.8 and CaMKIIδc, we show that Na_V1.8-driven I_NaL is CaMKIIδc-dependent and that Na_V1.8-inhibtion reduces diastolic SR-Ca²⁺ leak in human failing cardiomyocytes. Moreover, increased mortality of CaMKIIδc-overexpressing HF mice is reduced when a Na_V1.8 knock-out is introduced. Cellular and in vivo experiments reveal reduced ventricular arrhythmias without changes in HF progression. Our work therefore identifies a proarrhythmic CaMKIIδc downstream target which may constitute a prognostic and antiarrhythmic strategy.

Evaluation and treatment of premature ventricular contractions in heart failure with reduced ejection fraction

Premature ventricular complexes (PVCs) are often observed in patients presenting with heart failure with a reduced ejection fraction (HFrEF). PVCs may in some patients be considered to be the cause of heart failure, while in others it may be the consequence of heart failure. PVCs are important prognostic markers in HFrEF. The uncertainty whether PVCs are the cause or effect in HFrEF impacts clinical decision making. In this review, we discuss the complexity of the cause-effect relationship between PVCs and HFrEF. We demonstrate a workflow with the use of a trial period of amiodarone that may discover whether the reduced LVEF is reversible, the symptoms are due to PVCs and whether biventricular pacing can be increased by the reduction of PVCs. The use of non-invasive and invasive (high-density) mapping techniques may help to improve accuracy and efficacy in the treatment of PVC, which will be demonstrated. With these results in mind, we conclude this review highlighting the future directions for PVC research and treatment.

SOD2 deficiency in cardiomyocytes defines defective mitochondrial bioenergetics as a cause of lethal dilated cardiomyopathy

Electrophilic aldehyde (4-hydroxynonenal; 4-HNE), formed after lipid peroxidation, is a mediator of mitochondrial dysfunction and implicated in both the pathogenesis and the progression of cardiovascular disease. Manganese superoxide dismutase (MnSOD), a nuclear-encoded antioxidant enzyme, catalyzes the dismutation of superoxide radicals (O2•-) in mitochondria. To study the role of MnSOD in the myocardium, we generated a cardiomyocyte-specific SOD2 (SOD2Δ) deficient mouse strain. Unlike global SOD2 knockout mice, SOD2Δ mice reached adolescence; however, they die at ~4 months of age due to heart failure. Ultrastructural analysis of SOD2Δ hearts revealed altered mitochondrial architecture, with prominent disruption of the cristae and vacuole formation. Noninvasive echocardiographic measurements in SOD2Δ mice showed dilated cardiomyopathic features such as decreased ejection fraction and fractional shortening along with increased left ventricular internal diameter. An increased incidence of ventricular tachycardia was observed during electrophysiological studies of the heart in SOD2Δ mice. Oxidative phosphorylation (OXPHOS) measurement using a Seahorse XF analyzer in SOD2Δ neonatal cardiomyocytes and adult cardiac mitochondria displayed reduced O2 consumption, particularly during basal conditions and after the addition of FCCP (H+ ionophore/uncoupler), compared to that in SOD2fl hearts. Measurement of extracellular acidification (ECAR) to examine glycolysis in these cells showed a pattern precisely opposite that of the oxygen consumption rate (OCR) among SOD2Δ mice compared to their SOD2fl littermates. Analysis of the activity of the electron transport chain complex identified a reduction in Complex I and Complex V activity in SOD2Δ compared to SOD2fl mice. We demonstrated that a deficiency of SOD2 increases reactive oxygen species (ROS), leading to subsequent overproduction of 4-HNE inside mitochondria. Mechanistically, proteins in the mitochondrial respiratory chain complex and TCA cycle (NDUFS2, SDHA, ATP5B, and DLD) were the target of 4-HNE adduction in SOD2Δ hearts. Our findings suggest that the SOD2 mediated 4-HNE signaling nexus may play an important role in cardiomyopathy.

The relationship between electrocardiographic data and mortality in children diagnosed with dilated cardiomyopathy

The mortality causes of patients followed up due to dilated cardiomyopathy (DCM) include complications related to heart failure, ventricular arrhythmia, and transplantation. This study aims to evaluate the electrocardiographic findings of patients diagnosed with dilated cardiomyopathy and determine its relationship with mortality. The electrocardiographic, clinical, and laboratory findings of patients diagnosed with dilated cardiomyopathy between January 1, 2012, and September 1, 2018, in our university's pediatric cardiology department were retrospectively evaluated. The electrocardiographic findings of surviving and exitus dilated cardiomyopathy patients were compared and their effect on mortality was investigated. Twelve of the total 85 patients diagnosed with dilated cardiomyopathy were deceased. According to the electrocardiographic findings of surviving and exitus patients, there was a statistically significant difference in terms of P maximum (Pmax), P dispersion (Pdis), QT dispersion (QTdis), QTc maximum (QTcmax), QTc dispersion (QTcdis), Tp-e maximum (Tp-emax), Tp-e dispersion (Tp-edis), and QRS time. Hypertrophy and ischemia findings of electrocardiography were also statistically significant. There was a statistically significant difference between the two groups according to the echocardiographic findings of left ventricular ejection fraction (LVEF), left ventricular shortening fraction (LVSF), left ventricular end-diastolic diameter (LVEDd), and left ventricular end-systolic diameter (LVESd) measurements. It is well known that children diagnosed with dilated cardiomyopathy are at greater risk of arrhythmia compared with normal children. Although previous studies have determined the relationship between mortality and a limited number of electrocardiographic findings, especially in adults, the relationship between electrocardiography findings of children diagnosed with DCM and mortality has not been investigated before in such detail, as in our study.Conclusion: In this study, the significant difference between the electrocardiographic data of deceased and surviving dilated cardiomyopathy patients suggests that electrocardiographic data should be evaluated in detail in order to determine the low and high risk of mortality in patients with dilated cardiomyopathy.What is Known:• Previous studies on the relationship between limited electrocardiography data of adult patients diagnosed with DCM and mortality have been determinedWhat is New:• ECG data has not been investigated in such detail in child DCM patients, as in our study.

Clinical significance of precedent asymptomatic non-sustained ventricular tachycardias on subsequent ICD interventions and heart failure hospitalization in primary prevention ICD patients

Background

The prognostic implications of non-sustained ventricular tachycardia (NSVT) and their significance as therapeutic targets in patients without prior sustained ventricular arrhythmias remain undetermined. The aim of this study was to investigate the prognostic significance of asymptomatic NSVT in patients who had primary prevention implantable cardioverter-defibrillator (ICD) implantation due to ischemic or non-ischemic cardiomyopathy (ICM, NICM).

Methods

We enrolled 157 consecutive primary prevention ICD patients without previous appropriate ICD therapy (AIT). Patients were allocated to two groups depending on the presence or absence of NSVT in a 6-month period prior to enrollment. The incidence of AIT and unplanned hospitalization due to decompensated heart failure (HF) were assessed during follow-up.

Results

In 51 patients (32%), precedent NSVT was documented. During a median follow-up of 1011 days, AIT occurred in 36 patients (23%) and unplanned HF hospitalization was observed in 32 patients (20%). In precedent NSVT patients, the incidence of AIT and unplanned HF hospitalization was significantly higher as compared to patients without precedent NSVT (AIT: 29/51 [57%] vs. 7/106 [7%], P < 0.001, log-rank; HF hospitalization: 16/51 [31%] vs. 16/106 [15%], P = 0.043, log-rank). Cox-regression demonstrated that precedent NSVT independently predicted AIT (P < 0.0001). In subgroup analyses, precedent NSVT predicted AIT in both ICM and NICM (P < 0.0001, P = 0.020), but predicted HF hospitalization only in patients with ICM (P = 0.0030).

Conclusions

Precedent non-sustained VT in patients with primary prevention ICDs is associated with subsequent appropriate ICD therapies, and is an independent predictor of unplanned heart failure hospitalizations in patients with ischemic cardiomyopathy.

Arrhythmia-Induced Cardiomyopathy: JACC State-of-the-Art Review

Arrhythmias coexist in patients with heart failure (HF) and left ventricular (LV) dysfunction. Tachycardias, atrial fibrillation, and premature ventricular contractions are known to trigger a reversible dilated cardiomyopathy referred as arrhythmia-induced cardiomyopathy (AiCM). It remains unclear why some patients are more prone to develop AiCM despite similar arrhythmia burdens. The challenge is to determine whether arrhythmias are fully, partially, or at all responsible for an observed LV dysfunction. AiCM should be suspected in patients with mean heart rate >100 beats/min, atrial fibrillation, and/or premature ventricular contractions burden ≥10%. Reversal of cardiomyopathy by elimination of the arrhythmia confirms AiCM. Therapeutic choice depends on the culprit arrhythmia, patient comorbidities, and preferences. Following recovery of LV function, patients require continued follow-up if an abnormal myocardial substrate is present. Appropriate diagnosis and treatment of AiCM is likely to improve quality of life and clinical outcomes and to reduce hospital admission and health care spending.

Arrhythmic risk stratification in non-ischaemic dilated cardiomyopathy beyond ejection fraction

Sudden cardiac death and arrhythmia-related events in patients with non-ischaemic dilated cardiomyopathy (NICM) have been significantly reduced over the last couple of decades as a result of evidence-based pharmacological and non-pharmacological therapeutic strategies. Nevertheless, the arrhythmic stratification in patients with NICM remains extremely challenging, and the simple indication based on left ventricular ejection fraction appears to be insufficient. Therefore, clinicians need to go beyond the current criteria for implantable cardioverter-defibrillator implantation in the direction of a multiparametric evaluation of arrhythmic risk. Several parameters for arrhythmic risk stratification, ranging from electrocardiographic, echocardiographic, imaging-derived and genetic markers, are crucial for proper arrhythmic risk stratification and a multiparametric evaluation of risk in patients with NICM. In particular, integration of cardiac magnetic resonance parameters (mostly late gadolinium enhancement) and specific genetic information (ie, presence of LMNA, PLN, FLNC mutations) appears fundamental for proper implementation of the current arrhythmic risk stratification. Finally, a novel approach focused on both arrhythmic risk and prediction of left ventricular reverse remodelling during follow-up might be useful for effective multiparametric and dynamic arrhythmic risk stratification in NICM. In the future, a complete and integrated evaluation might be mandatory to implement arrhythmic risk prediction in patients with NICM and to discriminate the competing risk between heart failure-related events and life-threatening arrhythmias.

Arrhythmogenic Left Ventricular Cardiomyopathy: A Clinical and CMR Study

The clinical features, CMR characteristics and outcomes of arrhythmogenic left ventricular cardiomyopathy (ALVC), which is a very rare nonischemic cardiomyopathy, are currently not well studied. The purpose of the study is to investigate the clinical and cardiovascular magnetic resonance (CMR) imaging characteristics of arrhythmogenic left ventricular cardiomyopathy (ALVC). Fifty-three consecutive patients with ALVC were divided into two groups: ALVC patients without right ventricular (RV) involvement (n = 36, group 1) and those with RV involvement (n = 17, group 2). Clinical symptoms, cardiac electrophysiological findings, and CMR parameters (morphology, ventricular function, and myocardial fibrosis and fatty infiltration) were evaluated in both groups. The two groups showed no significant difference in age, gender, or presenting symptoms (P > 0.05). Right bundle branch block ventricular arrhythmia was less common in patients without RV involvement (50.0% vs.64.7%, P = 0.031). There were no significant differences in left ventricular function between the two groups, however right ventricular ejection fraction was significantly lower in group 2 (40.1 ± 4.0% vs. 48.7 ± 3.9%, P < 0.001). Inverse correlations of left ventricular ejection fraction with fat volume (r = −0.883, p = 0.001), late gadolinium enhancement (LGE) volume (r = −0.892, 0.013), ratio of fat/LGE (r = −0.848, p < 0.001), indexed left ventricular end diastolic volume (r = −0.877, p < 0.001) and indexed left ventricular end systolic volume (r = −0.943, p < 0.001) were all significant. ALVC is a rare disease with fibro-fatty replacement predominantly in the left ventricle, impaired left ventricular systolic function, and ventricular arrhythmias originating from the left ventricle. ALVC with right ventricular involvement may have a worse prognosis.

Association between changes in the intrathoracic impedance and ventricular arrhythmias in patients with heart failure

BACKGROUND

Ventricular arrhythmias (VAs) are independently related to mortality risk in patients with heart failure (HF). The wide availability of implantable cardioverter defibrillators and cardiac resynchronization therapy devices now offers an opportunity to clinically correlate the two disease processes. We hypothesized that there is an association between changes in the intrathoracic impedance and episodes of VA.

METHODS

Nonconcurrent prospective study of adults (age >20 years) with known HF with reduced ejection fraction (<35%). The OptiVol threshold was categorized as follows: 0-30 Ω-days, 31-60 Ω-days, 61-90 Ω-days, 91-120 Ω-days, and >120 Ω-days. Patients with OptiVol values at 0-30 Ω-days were used as the reference group. Receiver operating characteristic analysis was used to estimate the sensitivity and specificity at each threshold.

RESULTS

Of the 87 eligible patients, 65.5% were males. The mean age of the sample was 73.3 years (±12.7). Compared to patients in the 0-30 Ω-days category, those in the 31-60, 61-90, 91-120, and >120 Ω-days groups had, on average, 1.48, 1.64, 2.24, and 1.6 more VAs, respectively (P = 0.002, 0.009, 0.010 and 0.009, respectively). The sensitivity and specificity of each threshold were as follows: 82.6% and 61.7% at 31-60 Ω-days, 43.5% and 78.3% at 61-90 Ω-days, 30.4% and 85.0% at 91-120 Ω-days, and 21.7% and 88.3% at >121 Ω-days.

CONCLUSION

Our study found a significant positive relationship between changes in intrathoracic impedance and episodes of VAs in patients with HF.

Ventricular Arrhythmias in the Patient with a Structurally Normal Heart

Ventricular arrhythmias (VAs) are among the most common cardiac rhythm disturbances encountered in clinical practice. Patients presenting with frequent ventricular ectopy or sustained ventricular tachycardia represent a challenging and worrisome clinical scenario for many practitioners because of concerning symptoms, frequent associated acute hemodynamic compromise, and the adverse prognostic implications inherent to these cases. While an underlying structural or functional cardiac abnormality, metabolic derangement, or medication toxicity is often readily apparent, many patients have no obvious underlying condition, despite a comprehensive diagnostic evaluation. Such patients are diagnosed as having an idiopathic VA, which is a label with specific implications regarding arrhythmia origin, prognosis, and potential for pharmacologic and invasive management. Further, a subset of patients with otherwise benign idiopathic ventricular ectopy can present with polymorphic ventricular tachycardia and ventricular fibrillation, adding a layer of complexity to a clinical syndrome previously felt to have a benign clinical course. Thus, this review seeks to highlight the most common types of idiopathic VAs with a focus on their prognostic implications, underlying electrophysiologic mechanisms, unique electrocardiographic signatures, and considerations for invasive electrophysiologic study and catheter ablation. We further address some of the data regarding idiopathic ventricular fibrillation with respect to the heterogeneous nature of this diagnosis.

Predictors of Sudden Cardiac Death in Doberman Pinschers with Dilated Cardiomyopathy

Background

Doberman Pinschers with dilated cardiomyopathy (DCM) are at high risk of sudden cardiac death (SCD). Risk factors for SCD are poorly defined.

Aim

To assess cardiac biomarkers, Holter‐ECG, echocardiographic variables and canine characteristics in a group of Doberman Pinschers with DCM dying of SCD and in a DCM control group to identify factors predicting SCD.

Methods/Animals

A longitudinal prospective study was performed in 95 Doberman Pinschers with DCM. Forty‐one dogs died within 3 months after the last cardiac examination (SCD‐group) and were compared to 54 Doberman Pinschers with DCM surviving 1 year after inclusion. Holter‐ECG, echocardiography, measurement of N‐terminal prohormone of brain‐natriuretic peptide (NT‐proBNP), and cardiac Troponin I (cTnI) concentrations were recorded for all dogs.

Results

Volume overload of the left ventricle (left ventricular end‐diastolic volume (LVEDV/BSA) > 91.3 mL/m²) was the single best variable to predict SCD. The probability of SCD increases 8.5‐fold (CI_0.95 = 0.8–35.3) for every 50 mL/m²‐unit increment in LVEDV/BSA. Ejection fraction (EF), left ventricular end‐systolic volume (LVESV/BSA) and NT‐proBNP were highly correlated with LVEDV/BSA (r = −0.63, 0.96, 0.86, respectively). Generated conditional inference trees (CTREEs) revealed that the presence of ventricular tachycardia (VT), increased concentration of cTnI, and the fastest rate (FR) of ventricular premature complexes (VPC) ≥260 beats per minute (bpm) are additional important variables to predict SCD.

Conclusion

Conditional inference trees provided in this study might be useful for risk assessment of SCD in Doberman Pinschers with DCM.

Outcomes of Catheter Ablation of Ventricular Tachycardia in the Setting of Structural Heart Disease

Sustained ventricular tachycardias are common in the setting of structural heart disease, either due to prior myocardial infarction or a variety of non-ischemic etiologies, including idiopathic dilated cardiomyopathy, hypertrophic cardiomyopathy, and arrhythmogenic right ventricular cardiomyopathy. Over the past two decades, percutaneous catheter ablation has evolved dramatically and has become an effective tool for the control of ventricular arrhythmias. Single and multicenter observational studies as well as several prospective randomized trials have begun to investigate long-term outcomes after catheter ablation procedures. These studies encompass a wide range of mapping and ablation techniques, including conventional activation mapping/entrainment criteria, substrate modification guided by pacemapping, late potential and abnormal electrogram ablation, scar de-channeling, and core isolation. While large-scale, multicenter prospective randomized clinical trials are somewhat limited, the published data demonstrate favorable outcomes with respect to a reduction in overall ventricular tachycardia (VT) burden, reduction of implantable cardioverter defibrillator (ICD) shocks, and discontinuation of anti-arrhythmic medications across varying disease subtypes and convincingly support the use of catheter ablation as the standard of care for many patients with VT in the setting of structural heart disease.

Rapid and Potent Antiarrhythmic Effect of Cardiac Resynchronization Therapy in a Patient with Advanced Dilated Cardiomyopathy and a Large Ventricular Arrhythmia Burden

We report a case demonstrating a rapid and potent antiarrhythmic effect of biventricular pacing. A 67-year-old male patient with dilated cardiomyopathy was admitted for heart failure. The initial surface electrocardiogram revealed a left bundle branch block with a QRS complex duration of 200 ms. Echocardiographic examination revealed a left ventricular ejection fraction of 16%, a left ventricular end-diastolic dimension of 91 mm, and marked interventricular dyssynchrony. Continuous rhythm monitoring revealed frequently-recurring non-sustained monomorphic ventricular tachycardia (VT). Polymorphic VT, which persisted for 27 seconds, occurred on the third day after admission, and the R on T phenomenon recurred every two to three days thereafter. Optimal medical therapy for four weeks failed to suppress the recurrence of ventricular arrhythmias or ameliorate heart failure. Cardiac resynchronization therapy was initiated for an anticipated antiarrhythmic effect of biventricular pacing. Three days after the initiation of biventricular pacing, the ventricular arrhythmias disappeared almost completely.

Mechano-chemo-transduction in cardiac myocytes

The heart has the ability to adjust to changing mechanical loads. The Frank-Starling law and the Anrep effect describe exquisite intrinsic mechanisms the heart has for autoregulating the force of contraction to maintain cardiac output under changes of preload and afterload. Although these mechanisms have been known for more than a century, their cellular and molecular underpinnings are still debated. How does the cardiac myocyte sense changes in preload or afterload? How does the myocyte adjust its response to compensate for such changes? In cardiac myocytes Ca²⁺ is a crucial regulator of contractile force and in this review we compare and contrast recent studies from different labs that address these two important questions. The 'dimensionality' of the mechanical milieu under which experiments are carried out provide important clues to the location of the mechanosensors and the kinds of mechanical forces they can sense and respond to. As a first approximation, sensors inside the myocyte appear to modulate reactive oxygen species while sensors on the cell surface appear to also modulate nitric oxide signalling; both signalling pathways affect Ca²⁺ handling. Undoubtedly, further studies will add layers to this simplified picture. Clarifying the intimate links from cellular mechanics to reactive oxygen species and nitric oxide signalling and to Ca²⁺ handling will deepen our understanding of the Frank-Starling law and the Anrep effect, and also provide a unified view on how arrhythmias may arise in seemingly disparate diseases that have in common altered myocyte mechanics.

Recognition and Management of Cardiac Arrhythmias: Part II. Ventricular Arrhythmias and Bradyarrhythmias

This review discusses the treatment of ventricular arrhythmias and bradyarrhythmias. Recent studies addressing the management of nonsustained ventricular arrhythmias in patients with congestive heart failure and those recovering from myocardial infarction are discussed. Determination of the origin of wide QRS complex tachycardia is usually possible at the bedside and the diagnostic criteria are provided. Therapy to prevent recurrent ventricular tachycardia or ventricular fibrillation is difficult and controversial. A widely accepted approach based on electrophysiologic testing and implantable defibrillators appears to be the most effective. Recognition and management of common bradyarrhythmias including the indications for pacemakers are discussed.

Prognostic Significance of Nonsustained Ventricular Tachycardia Episodes Occurring Early After Implantable Cardioverter-Defibrillator Implantation Among Patients With Left Ventricular Dysfunction

Nonsustained ventricular tachycardias (NSVTs) are frequently observed in patients with left ventricular (LV) dysfunction. The prognostic implications of such NSVTs are conflicting. Our objective was to determine the relation between the burden of NSVT occurring early (within the first 6 months after ICD implant) and prognosis among ICD patients with LV dysfunction. We followed 416 ICD patients (age: 65 ± 11 years; LV ejection fraction: 30 ± 8; ischemic origin: 62%; primary prevention: 63%) with LV dysfunction for 41 ± 27 months. ICD programming was standardized. NSVT was defined as any VT of ≥5 beats at ≥150 beats/min which did not meet the detection criteria occurring within the first 6 months after ICD implant. A total of 250 patients (60%) presented at least one NSVT (median = 2; interquartile range 0 to 7). We classified the patients into 3 groups according to the number of NSVTs: no NSVT (n = 166); 1 to 5 NSVTs (n = 130); and >5 NSVTs (n = 120). The incidence of cardiac mortality (7.2% vs 17.7% vs 31.7%; p = 0.003), hospitalizations for heart failure (10.6% vs 24.4% vs 44.7%; p <0.001), and appropriate shock (15.7% vs 24.8% vs 43.8%; p <0.001) increased significantly with the number of NSVTs. By multivariate analysis, >5 NSVTs were found to be an independent predictor of cardiac mortality (hazard ratio [HR] 1.75; p = 0.03), hospitalization due to heart failure (HR 1.72; p = 0.001), and appropriate shock (HR 1.89; p <0.001) but not of inappropriate therapy (HR 0.9; p = 0.6). In conclusion, among ICD patients with LV dysfunction, NSVT episodes occurring in the first 6 months after implant are independently associated with a poor prognosis. Subjects with >5 NSVTs are at the highest risk.

The evaluation of non-ischemic dilated cardiomyopathy with T1 mapping and ECV methods using 3T cardiac MRI

PURPOSE

The aim of this study was to examine the correlation between ventricular function and the extracellular volume fraction (ECV) in patients with non-ischemic dilated cardiomyopathy (NIDCM) using 3.0 T magnetic resonance imaging (MRI). We also hypothesized that native T1 and ECV values would be increased in patients with NIDCM, independent of the left ventricular ejection fraction (LVEF). The findings of our study could lead to further studies of the follow-up protocols.

MATERIALS AND METHODS

In total, 53 consecutive dilated cardiomyopathy patients who had undergone cardiac MRI were functionally evaluated and underwent tissue characterization.

RESULTS

The mean native T1 value was 1235 ± 10 ms, and the mean ECV value was 35.4 ± 2.7% in the myocardia. The LVEF values ranged from 29 to 44%. No significant correlations were observed between functional analysis measurements and native T1 or ECV values.

CONCLUSIONS

Our results showed that myocardial fibrosis is unrelated to cardiac functional findings in NIDCM patients. Therefore, we propose that these patients should be evaluated using MRI and tissue characterization techniques, in addition to cardiac functional analysis.

Advances in the Management of Tachyarrhythmias

Recent developments of both diagnostic and therapeu tic techniques in the management of tachyarrhythmias have broadened the options available to physicians car ing for patients with tachyarrhythmias. Newer diag nostic methods allow more precise identification of the arrhythmia and better understanding of its mechanism. Long-term epidemiologic studies have identified groups of patients who do and do not require antiarrhythmic therapy. Antitachycardia pacemakers and automatic im plantable defibrillators allow effective treatment for pa tients for whom drugs were ineffective or in whom in tolerable side effects developed. Finally, several new antiarrhythmic agents have become available recently. Proper use of these new techniques and drugs requires greater understanding of the pathophysiology of cardiac arrhythmias.

Role of cardiac TBX20 in dilated cardiomyopathy

Dilated cardiomyopathy (DCM) is an important cause of heart failure and sudden cardiac death worldwide. Transcription factor TBX20 has been shown to play a crucial role in cardiac development and maintenance of adult mouse heart. Recent studies suggest that TBX20 may have a role in pathophysiology of DCM. In the present study, we examined TBX20 expression in idiopathic DCM patients and in an animal model of cardiomyopathy, and studied its correlation with echocardiographic indices of LV function. Endomyocardial biopsies (EMBs) from intraventricular septal from the right ventricle region were obtained from idiopathic DCM patients (IDCM, n = 30) and from patients with ventricular septal defect (VSD, n = 14) with normal LVEF who served as controls. An animal model of DCM was developed by right renal artery ligation in Wistar rats. Cardiac TBX20 mRNA levels were measured by real-time PCR in IDCM, controls, and in rats. The role of DNA promoter methylation and copy number variation (CNVs) in regulating TBX20 gene expression was also investigated. Cardiac TBX20 mRNA levels were significantly increased (8.9 fold, p < 0.001) in IDCM patients and in RAL rats as compared to the control group. Cardiac TBX20 expression showed a negative correlation with LVEF (r = -0.71, p < 0.001) and a positive correlation with left ventricular end-systolic volume (r = 0.39, p = 0.038). No significant difference in TBX20 CNVs and promoter methylation was observed between IDCM patients and control group. Our results suggest a potential role of TBX20 in pathophysiology of DCM.

Non-sustained wide complex tachycardia: an underappreciated sign to aid in diagnosis

AIMS

The electrocardiographic (ECG) signs used to differentiate ventricular tachycardia (VT) from supraventricular tachycardia (SVT) with aberrancy are specific but not highly sensitive. The purpose of this study was to define the utility of an underappreciated form of atrioventricular (AV) dissociation at the onset of tachycardia, a single dissociated P wave, in the differentiation of non-sustained monomorphic wide complex tachycardia (WCT) in hospitalized patients.

METHODS AND RESULTS

We prospectively analysed tracings from 102 consecutive hospitalized patients who had an episode of non-sustained (≥5 beats, <30 s), monomorphic, WCT (≥100 b.p.m.) on telemetry. WCT was classified as VT, SVT with aberrancy, or undifferentiated WCT based on predefined criteria. Of 102 patients with WCT, 3 (3%) had SVT with aberrancy, 43 (42%) had an undifferentiated WCT, and 56 (55%) had VT. ECG evidence of a single dissociated P wave at the onset of tachycardia (i.e. AV dissociation at the onset) was identified in 29 patients (28%) compared with less frequent traditional signs of VT including second-degree ventriculoatrial (VA) block in 18 patients (18%), AV dissociation during tachycardia in 17 patients (17%), fusion beats in 10 patients (10%), and capture beats in 3 patients (3%). On multivariate analysis, only the prematurity index predicted the occurrence of AV dissociation at the onset of the tachycardia (odds ratio 1.239, 95% confidence interval 1.033-1.486, P = 0.021).

CONCLUSION

When evaluating WCT in hospitalized patients, a single dissociated P wave at the onset of tachycardia is an easily recognizable diagnostic sign of VT, and is observed more frequently than the other accepted criteria for VT.

Arrhythmias in dilated cardiomyopathy

Patients with dilated cardiomyopathies (DCM) face a significant burden of arrhythmias, including conduction defects such as atrioventricular block and interventricular delay in the form of left bundle branch block, resulting in altered electromechanical coupling that can exacerbate heart failure. Atrial fibrillation is common and carries an adverse prognosis. Ventricular arrhythmias and sudden cardiac death generally occur late in the disease course. Sustained monomorphic ventricular tachycardia accounts for most of the sustained ventricular arrhythmias in DCM. This article summarizes common forms of arrhythmias encountered in patients with DCM, and reviews the relevant electrophysiologic basis of these arrhythmias and their management.

Multiple autonomic and repolarization investigation of sudden cardiac death in dilated cardiomyopathy and controls

BACKGROUND

Prophylactic defibrillator implantation is recommended in dilated, nonischemic heart disease and left ventricular ejection fraction of ≤0.30 to 0.35. Noninvasive testing should improve accuracy in decision making of prophylactic defibrillator implantation.

METHODS AND RESULTS

We enrolled 60 patients (median age, 57 years) with dilated cardiomyopathy and left ventricular ejection fraction ≤0.50, and 30 control subjects (median age, 59 years) with left ventricular ejection fraction >0.50. The protocol included an initial assessment, a second assessment after 3 years, and a final follow-up: pharmacological baroreflex testing (baroreceptor reflex sensitivity), short-term spectral analysis of heart rate variability (low frequency/high frequency), and long-term time domain analysis (SD of all normal-to-normal R-R intervals), exercise microvolt T wave alternans, and signal-averaged ECG, and corrected QT-time. The median follow-up was 7 years. End points were cardiac death, resuscitated cardiac arrest, and arrhythmic death. Cardiac death was observed in 21 patients. Resuscitated cardiac arrest and arrhythmic death caused by ventricular tachyarrhythmias ≥240 per minute was observed in 7 and 10 patients, respectively. In the single time point analysis, microvolt T wave alternans, baroreceptor reflex sensitivity, and SD of all normal-to-normal R-R intervals at initial testing added significant information regarding cardiac death. Microvolt T wave alternans added information on resuscitated cardiac arrest or arrhythmic death at multiple time points (P<0.001). False-negative microvolt T wave alternans results were seen in 8% of patients.

CONCLUSIONS

Noninvasive testing and left ventricular ejection fraction could not reliably identify patients with dilated cardiomyopathy at risk of fatal ventricular tachyarrhythmias. Therefore, the strategy to confine prophylactic implantable cardioverter-defibrillator implantation to patients with dilated cardiomyopathy and severely reduced LV function should be reconsidered.

Sudden cardiac death in patients with nonischemic cardiomyopathy

Sudden cardiac death (SCD) is an important cause of mortality worldwide. Although SCD is most often associated with coronary heart disease, the risk of SCD in patients without ischemic heart disease is well-established. Nonischemic cardiomyopathies, including idiopathic dilated cardiomyopathy, hypertrophic cardiomyopathy and arrhythmogenic right ventricular cardiomyopathy represent three unique disease entities that have been shown to be highly associated with SCD and ventricular arrhythmias. A variety of risk stratification tools have been investigated, although the optimal strategy remains unknown. Identification of the arrhythmogenic substrate and treatment of ventricular arrhythmias in these subgroups can be challenging. Herein, we aim to discuss the current understanding of the anatomic and electrophysiologic substrate underlying ventricular arrhythmias and highlight features that may be associated with a higher risk of SCD in these 3 conditions.

Nonsustained ventricular tachycardia

Nonsustained ventricular tachycardia (NSVT) has been recorded in a wide range of conditions, from apparently healthy individuals to patients with significant heart disease. In the absence of heart disease, the prognostic significance of NSVT is debatable. When detected during exercise, and especially at recovery, NSVT indicates increased cardiovascular mortality within the next decades. In trained athletes, NSVT is considered benign when suppressed by exercise. In patients with non-ST-segment elevation acute coronary syndrome, NSVT occurring beyond 48 h after admission indicates an increased risk of cardiac and sudden death, especially when associated with myocardial ischemia. In acute myocardial infarction, in-hospital NSVT has an adverse prognostic significance when detected beyond the first 13 to 24 h. In patients with prior myocardial infarction treated with reperfusion and beta-blockers, NSVT is not an independent predictor of long-term mortality when other covariates such as left ventricular ejection fraction are taken into account. In patients with hypertrophic cardiomyopathy, and most probably genetic channelopathies, NSVT carries prognostic significance, whereas its independent prognostic ability in ischemic heart failure and dilated cardiomyopathy has not been established. The management of patients with NSVT is aimed at treating the underlying heart disease.

Right ventricular arrhythmogenesis in failing human heart: the role of conduction and repolarization remodeling

Increased dispersion of repolarization has been suggested to underlie increased arrhythmogenesis in human heart failure (HF). However, no detailed repolarization mapping data were available to support the presence of increased dispersion of repolarization in failing human heart. In the present study, we aimed to determine the existence of enhanced repolarization dispersion in the right ventricular (RV) endocardium from failing human heart and examine its association with arrhythmia inducibility. RV free wall preparations were dissected from five failing and five nonfailing human hearts, cannulated and coronary perfused. RV endocardium was optically mapped from an ∼6.3 × 6.3 cm(2) field of view. Action potential duration (APD), dispersion of APD, and conduction velocity (CV) were quantified for basic cycle lengths (BCL) ranging from 2,000 ms to the functional refractory period. We found that RV APD was significantly prolonged within the failing group compared with the nonfailing group (560 ± 44 vs. 448 ± 39 ms, at BCL = 2,000 ms, P < 0.05). Dispersion of APD was increased in three failing hearts (161 ± 5 vs. 86 ± 19 ms, at BCL = 2,000 ms). APD alternans were induced by rapid pacing in these same three failing hearts. CV was significantly reduced in the failing group compared with the nonfailing group (81 ± 11 vs. 98 ± 8 cm/s, at BCL = 2,000 ms). Arrhythmias could be induced in two failing hearts exhibiting an abnormally steep CV restitution and increased dispersion of repolarization due to APD alternans. Dispersion of repolarization is enhanced across the RV endocardium in the failing human heart. This dispersion, together with APD alternans and abnormal CV restitution, could be responsible for the arrhythmia susceptibility in human HF.

Relationship between late ventricular potentials and myocardial 123I-metaiodobenzylguanidine scintigraphy in patients with dilated cardiomyopathy with mild to moderate heart failure: results of a prospective study of sudden death events

PURPOSE

Late ventricular potentials (LPs) are considered to be useful for identifying patients with heart failure at risk of developing ventricular arrhythmias. (123)I-metaiodobenzylguanidine (MIBG) scintigraphy, which is used to evaluate cardiac sympathetic activity, has demonstrated cardiac sympathetic denervation in patients with malignant ventricular tachyarrhythmias. This study was undertaken to clarify the relationship between LPs and (123)I-MIBG scintigraphy findings in patients with dilated cardiomyopathy (DCM).

METHODS

A total of 56 patients with DCM were divided into an LP-positive group (n = 24) and an LP-negative group (n = 32). During the compensated period, the delayed heart/mediastinum count (H/M) ratio, delayed total defect score (TDS), and washout rate (WR) were determined from (123)I-MIBG images and plasma brain natriuretic peptide (BNP) concentrations were measured. Left ventricular end-diastolic volume (LVEDV), left ventricular end-systolic volume (LVESV), and left ventricular ejection fraction (LVEF) were simultaneously determined by echocardiography.

RESULTS

LVEDV, LVESV, LVEF and plasma BNP concentrations were similar in the two groups. However, TDS was significantly higher (35 ± 8 vs. 28 ± 6, p < 0.005), the H/M ratio was significantly lower (1.57 ± 0.23 vs. 1.78 ± 0.20, p < 0.005), and the WR was significantly higher (60 ± 14% vs. 46 ± 12%, p < 0.001) in the LP-positive than in the LP-negative group. The average follow-up time was 4.5 years, and there were nine sudden deaths among the 56 patients (16.1%). In logistic regression analysis, the incidences of sudden death events were similar in those LP-negative with WR <50%, LP-negative with WR ≥ 50% and LP-positive with WR <50% (0%, 10.0% and 14.3%, respectively), but was significantly higher (41.2%) in those LP-positive with WR ≥ 50% (p < 0.01, p < 0.05, and p < 0.05, respectively).

CONCLUSION

The present study demonstrated that the values of cardiac (123)I-MIBG scintigraphic parameters were worse in LP-positive DCM patients than in LP-negative DCM patients. Furthermore, in LP-positive DCM patients with a high WR, the incidence of sudden death events was higher than that in other subgroups of DCM patients.

Sudden cardiac death risk stratification in patients with heart failure

The multiplicity of mechanisms contributing to arrhythmogenesis in patients with heart failure carries obvious implications for risk stratification. If patients having the propensity to develop arrhythmias by these different mechanisms are to be identified, tests must be devised that reveal the substrates or other factors that relate to each mechanism. In the absence of this, efforts to risk stratify patients are likely to be neither cost-effective nor accurate. This article reviews the current knowledge base of risk stratification for sudden death in patients with heart failure, while acknowledging several limitations in the studies examined.

Epicardial Ablation of VT in Patients with Nonischemic LV Cardiomyopathy

The past decade has seen a remarkable period of discovery and refinement of ventricular tachycardia (VT) ablation in patients with left ventricular cardiomyopathy (LVCM). Patients with LVCM presenting with VT have a common substrate distribution involving predominantly the basal or perivalvular LV, which is often more dramatic on the LV epicardium. They typically present with multiple and often unstable tachycardias due to scar-based reentry. Percutaneous intrapericardial access can be safely performed in the electrophysiology laboratory and has greatly enhanced the efficacy of VT ablation in this setting by allowing detailed mapping. Epicardial ablation incurs unique procedural considerations that must be understood to safely and effectively perform the procedure.

Are nonsustained ventricular tachycardias predictive of major arrhythmias in patients with dilated cardiomyopathy on optimal medical treatment?

BACKGROUND

To evaluate the role of nonsustained ventricular tachycardias (NSVT) for the prediction of major ventricular arrhythmias (MVA) in patients with idiopathic dilated cardiomyopathy (DCM) after optimization of medical treatment.

METHODS AND RESULTS

Three hundred nineteen consecutive DCM patients were evaluated after adequate stabilization on optimal angiotensin-converting enzyme (ACE) inhibitor (88%) and beta-blocker (82%) therapy. Frequency, length, and rate of NSVT at 24-hour Holter monitoring were analyzed to assess their values in predicting MVA (unexpected sudden death, SVT, ventricular fibrillation, and appropriate implantable cardioverter defibrillator interventions). During follow-up (median 96 months, 1(st)-3(rd) interquartile range 52-130), MVA incidence was low, and not statistically different between patients with and without NSVT (3 and 2 per 100 patient-years, respectively, P = nonsignificant [NS] at log-rank analysis). At multivariable analysis, the number of NSVT was predictive of MVA only if left ventricular ejection fraction (LVEF) was > 0.35 (two NSVT/day vs no NSVT/day: hazard ratio [HR] 5.3, 95% confidence interval [CI] 1.59-17.85 in LVEF > 0.35 vs HR 0.93, 95% CI 0.3-2.81 in LVEF < or = 0.35). Consequently, in patients with LVEF < or = 0.35, MVA incidence rates were similar regardless of NSVT (3.6 and 4.1 patient-years, respectively, in those with and without NSVT, P = NS), while in patients with LVEF > 0.35, MVA incidence (3.1 per 100 patient-years vs 0.9 per 100 patient-years, P = 0.003) was significantly higher when NSVT were present.

CONCLUSIONS

After medical stabilization, NSVT did not increase the risk of MVA in patients with DCM and LVEF < or = 0.35. Conversely, the number and length of NSVT runs were significantly related to the occurrence of MVA in the patients with LVEF > 0.35.

Monitorização eletrocardiográfica ambulatorial por 24-horas em cães com cardiomiopatia dilatada idiopática

Caracterizou-se monitorização eletrocardiográfica ambulatorial por 24 horas (ou monitorização Holter) em cães com cardiomiopatia dilatada idiopática, visando principalmente à detecção de arritmias ventriculares não detectadas pela eletrocardiografia convencional (de repouso). Para tanto, avaliaram-se 40 pacientes com diagnóstico de cardiomiopatia dilatada idiopática, por meio de exame físico e mensuração indireta da pressão arterial, além de exames eletrocardiográfico, ecocardiográfico, radiográfico de tórax e da monitorização Holter. Extra-sístoles ventriculares foram detectadas, por monitorização Holter, em 97,5% dos animais e taquicardia ventricular, em 45%. Não houve correlação entre o número de extra-sístoles ventriculares e a fração de encurtamento. Considerando as manifestações clínicas, apenas houve associação entre presença de taquicardia ventricular e histórico de síncopes. Conclui-se que a incidência de arritmias ventriculares em cães com cardiomiopatia dilatada idiopática é bastante alta, sendo a taquicardia ventricular relativamente freqüente, ocorrendo mais sob a forma não sustentada.

QT intervals in metabolic dilated cardiomyopathy

OBJECTIVES

The present study determined the prevalence of dilated cardiomyopathy together with prolonged corrected QT (QTc) intervals in children. The study also examined whether an association exists between prolonged QTc intervals and ventricular dysrhythmia in a patient cohort with dilated cardiomyopathy.

BACKGROUND

The morbidity and mortality for pediatric patients with dilated cardiomyopathy remains high and is a clinical challenge. The patient population includes a significant number of Hutterite patients with metabolic disease associated with dilated cardiomyopathy.

METHODS

Thirty-eight pediatric patients with dilated cardiomyopathy were reviewed for the presence of prolonged QTc and dysrhythmias. Eleven patients had a metabolic etiology for their dilated cardiomyopathy.

RESULTS

Thirty-six per cent of the patient cohort had a long QTc interval. After 50 months of follow-up, the probability of survival for a child with a long QTc interval was approximately 50%. The probability of survival for a child with a normal QTc interval was 72%. Seventy per cent of the patients who died had a metabolic etiology for their dilated cardiomyopathy and a long QTc.

CONCLUSIONS

Dilated cardiomyopathy may be associated with a prolonged QTc and may increase the patient's risk for sudden death. The presence of a metabolic etiology for dilated cardiomyopathy increases the risk of death.

Nonsustained ventricular tachycardia in dilated cardiomyopathy

In patients with structural heart disease, ventricular arrhythmias are associated with an increased risk of overall mortality and sudden cardiac death (SCD). Nonsustained ventricular tachycardia (NSVT) is common in patients with dilated cardiomyopathy of both ischemic and nonischemic origin. Recent studies suggest that NSVT may be a marker, but not a significant predictor, of mortality and SCD in that suppression of NSVT in these patients using antiarrhythmic drugs is of questionable benefit. Additionally, indications for implantable cardioverter defibrillator implantation do not include NSVT. This article focuses on the prognostic significance and treatment of patients with NSVT and ischemic or nonischemic dilated cardiomyopathy.

Idiopathic dilated cardiomyopathy in children: a single medical center's experience

BACKGROUND

The prognosis of patients with idiopathic dilated cardiomyopathy (DCM) is poor. Most patients die while waiting for cardiac transplantation because of the small number of donors in Taiwan. The purpose of this study was to review our experience with pediatric patients diagnosed with idiopathic DCM and attempt to discover prognostic factors.

METHODS

Eighteen patients with idiopathic DCM presenting between 1990 and 2004 were identified. They were classified into 2 groups according to outcome: group 1 comprised 13 patients who died; group 2 comprised 5 who survived. Clinical findings and laboratory investigations were compared between the 2 groups.

RESULTS

The age at initial diagnosis for the 18 patients (11 males, 7 females) ranged from fetus to 13 years (median, 3 months). The follow-up period ranged from 12 days to 44 months (median, 7 months) in group 1, and from 1 to 48 months (median, 39 months) in group 2. Of the 18 patients, 13 (72%) died: 11 died from severe heart failure while waiting for cardiac transplantation. The cumulative survival rate was 50% at 1 year and 28% at 4 years. The presence of arrhythmia and low left ventricular ejection fraction were predictive of a poor outcome.

CONCLUSION

The diagnosis of idiopathic DCM in children is associated with a generally poor prognosis. The lack of available donors results in significant mortality for pediatric patients awaiting transplantation. Advocating organ donation to increase the size of the organ donor pool is needed to significantly reduce the mortality rate in such patients.

Prognostic value of ambulatory electrocardiography monitoring in patients with dilated cardiomyopathy

BACKGROUND

Performance of ambulatory electrocardiography (AECG) may provide data useful for counseling patients regarding prognosis and for selecting potential patients for defibrillator implantation, but this practice remains controversial.

METHODS

We reviewed clinical and AECG data on 355 patients diagnosed with dilated cardiomyopathy (DCM). Predictors of survival were identified in a multivariable analysis using a Cox proportional hazard model. Ability of the derived model to predict outcomes was tested using a second cohort of 144 patients.

RESULTS

Nonsustained ventricular tachycardia (NSVT) was present on AECG in 31% of the subjects. Ambulatory electrocardiography provided 3 independent predictors of mortality: NSVT (relative risk [RR], 1.63; 95% confidence interval [CI], 1.06-2.51; P = .02), mean heart rate (RR, 1.03; 95% CI, 1.02-1.04; P = .0001), and heart rate range (RR, 0.990; 95% CI, 0.982-0.997; P = .008). Performance of the multivariable model was validated (area under the curve = 0.83) on a second cohort of patients.

CONCLUSION

Ambulatory electrocardiography provides useful prognostic information in patients with DCM, identifying 3 independent predictors of mortality.

Effects of Repeated Sauna Treatment on Ventricular Arrhythmias in Patients With Chronic Heart Failure

BACKGROUND

The aim of the present study was to determine whether repeated 60 degrees C sauna treatment improves cardiac arrhythmias in chronic heart failure (CHF) patients, because ventricular arrhythmias are an important therapeutic target in CHF.

METHODS AND RESULTS

Thirty patients (59+/-3 years) with New York Heart Association functional class II or III CHF and at least 200 premature ventricular contractions (PVCs)/24 h assessed by 24-h Holter recordings were studied. They were randomized into sauna-treated (n=20) or non-treated (n=10) groups. The sauna-treated group underwent a 2-week program of a daily 60 degrees C far infrared-ray dry sauna for 15 min, followed by 30 min bed rest with blankets, for 5 days per week. Patients in the non-treated group had bed rest in a temperature-controlled room (24 degrees C) for 45 min. The total numbers of PVCs/24 h in the sauna-treated group decreased compared with the non-treated group [848+/-415 vs 3,097+/-1,033/24 h, p<0.01]. Heart rate variability (SDNN, standard deviation of normal-to-normal beat interval) increased [142+/-10 (n=16) vs 112+/-11 ms (n=8), p<0.05] and plasma brain natriuretic peptide concentrations decreased [229+/-54 vs 419+/-110 pg/ml, p<0.05] in the sauna-treated group compared with the non-treated group.

CONCLUSION

Repeated sauna treatment improves ventricular arrhythmias in patients with CHF.

Telemetrically monitored arrhythmogenic effects of doxorubicin in a dog model of heart failure

A model of chronic heart failure has been induced in dogs by repeated intracoronary infusion of doxorubicin, which is an antineoplastic medication that has dose-limiting cardiotoxic side effects. Although many of the dogs receiving doxorubicin develop typical signs of dilated cardiomypathy over 4-6 weeks, some of them suddenly die before completing the four weekly infusions of the drug. The present study was undertaken to determine whether such sudden death may be caused by the development of fatal arrhythmias during doxorubicin treatment. This was assessed by telemetrically monitoring the EKG of seven dogs, which received intracoronary infusion of 1 mg/kg doxorubicin given in four divided weekly doses. The recordings were obtained for 8-10 h on alternate days up to 4 weeks. Echo-cardiographic recordings were obtained once a week. The acute effects with each infusion of doxorubicin included a significant increase in heart rate, and no significant change in QRS complex. The cumulative prolonged effects of doxorubicin included slight reduction in QRS amplitude and duration, and marked arrhythmic changes. Four out of seven dogs showed a spectrum of arrhythmic events such as single or groups of premature ventricular complexes (PVCs), bigeminy, ventricular tachycardia (VTAC), ventricular fibrillations (VFIB), and asystole. All dogs did not show each of the events listed above and the same dog did not show all the events all the time. One of these four dogs developed VFIB for 25 min and then asystole leading to sudden death. These studies conclusively showed that fatal arrhythmias develop in some of the dogs receiving doxorubicin treatment accounting for the sporadic incidence of sudden death. Prophylactic treatment with antiarrhythmic agents may prevent such adverse events.

Amiodarone versus implantable cardioverter-defibrillator:randomized trial in patients with nonischemic dilated cardiomyopathy and asymptomatic nonsustained ventricular tachycardia--AMIOVIRT

OBJECTIVES

The purpose of this multicenter randomized trial was to compare total mortality during therapy with amiodarone or an implantable cardioverter-defibrillator (ICD) in patients with nonischemic dilated cardiomyopathy (NIDCM) and nonsustained ventricular tachycardia (NSVT).

BACKGROUND

Whether an ICD reduces mortality more than amiodarone in patients with NIDCM and NSVT is unknown.

METHODS

One hundred three patients with NIDCM, left ventricular ejection fraction < or =0.35, and asymptomatic NSVT were randomized to receive either amiodarone or an ICD. The primary end point was total mortality. Secondary end points included arrhythmia-free survival, quality of life, and costs.

RESULTS

The study was stopped when the prospective stopping rule for futility was reached. The percent of patients surviving at one year (90% vs. 96%) and three years (88% vs. 87%) in the amiodarone and ICD groups, respectively, were not statistically different (p = 0.8). Quality of life was also similar with each therapy (p = NS). There was a trend with amiodarone, as compared to the ICD, towards improved arrhythmia-free survival (p = 0.1) and lower costs during the first year of therapy ($8,879 US dollars vs. $22,039 US dollars, p = 0.1).

CONCLUSIONS

Mortality and quality of life in patients with NIDCM and NSVT treated with amiodarone or an ICD are not statistically different. There is a trend towards a more beneficial cost profile and improved arrhythmia-free survival with amiodarone therapy.

Can we predict which patients with implantable cardioverter defibrillators receive appropriate shock therapy? A study of 155 patients

BACKGROUND

Appropriate shock therapy (AST) occurs in the minority of patients with implantable cardioverter defibrillators (ICDs). We assessed which patients received AST and whether there were any predictive factors.

METHODS

We retrospectively analysed data from 155 patients implanted with ICDs at our institution from a period from February 1984 to February 2001. Stored electrogram data were analysed. We sub-divided patients on the basis of underlying cardiac disease. Various clinical echocardiographic and electrophysiological variables were studied.

RESULTS

AST occurred in 53 (34%) of patients (Group 1) and no AST in 102 (64%) of patients (Group 2). Impaired LV function was significantly associated with AST. Group 1 patients had a lower ejection fraction (EF) compared to Group 2 (37.5+/-13% vs. 47.8+/-14%, P<0.0001). Seventy-two percent of patients with AST had an EF <40% vs. 35% of patients in Group 2 (P<0.0001). NYHA Class was also associated with AST, 42% of Group 1 were in NYHA Class III/IV vs. 12% in Group 2 (P<0.001). Programmed electrical stimulation (PES) was a predictor of AST. PES was positive in a greater proportion of patients in Group 1 vs. 2 (88% vs. 64%, P<0.0006). Sub-group analysis showed that patients with dilated cardiomyopathy (DCM) had a high incidence of AST (80%). In these patients PES was a poor predictor of AST being positive in only 25%.

CONCLUSION

AST occurs in the minority of our patients. Certain pre-procedural variables predict AST. PES does not appear useful in predicting shock therapy in DCM patients and a negative PES should not preclude ICD implantation in this group.

Left ventricular dysfunction is a risk factor for sudden cardiac death in adults late after repair of tetralogy of Fallot

OBJECTIVES

The purpose of this study was to determine if left ventricular (LV) systolic dysfunction was also a predictor of sudden cardiac death (SCD) in adults late after repair of tetralogy of Fallot (TOF).

BACKGROUND

Previous studies looking at risk factors for SCD in adults with repair of TOF have focused on the right ventricle (RV).

METHODS

A retrospective chart review of patients assessed at the Toronto Congenital Cardiac Centre for Adults was performed. Twelve adult patients with repaired TOF and SCD were identified (SCD group). A total of 125 living adult patients with repaired TOF were randomly selected for comparison (control group).

RESULTS

Patients with SCD were more likely to exhibit moderate or severe pulmonary regurgitation (92% vs. 51%, p = 0.02), have a history of sustained ventricular tachycardia (42% vs. 6%, p < 0.01), and have a QRS > or =180 ms (56% vs. 13%, p = 0.02). Moderate or severe LV systolic dysfunction was also significantly more common in patients with SCD than in the control group (42% vs. 9%, p < 0.01) with a positive predictive value of 29%. The combination of moderate or severe LV systolic dysfunction and QRS > or =180 ms had a positive and negative predictive value for SCD of 66% and 93%, respectively.

CONCLUSIONS

Moderate or severe LV systolic dysfunction is significantly more common in adult patients with repaired TOF and SCD. The combination of QRS > or =180 ms and significant LV systolic dysfunction has high positive and negative predictive value for SCD. The implication of the role of prophylactic antiarrhythmic implantable cardiac defibrillator insertion in these patients needs further elucidating.