Significance of ventricular tachycardia in idiopathic dilated cardiomyopathy: observations in 35 patients

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.

In-hospital ventricular arrhythmia in heart failure patients: 7 year follow-up of the multi-centric HEARTS registry

Aims

The aim of this study was to determine the incidence, predictors, and short‐term and long‐term outcomes associated with in‐hospital sustained ventricular tachycardia (VT) and ventricular fibrillation (VF) collectively termed ventricular arrhythmia (VA) in the heart failure (HF) patients.

Methods and results

The HEart function Assessment Registry Trial in Saudi Arabia (HEARTS registry) is a prospective national registry of patients with chronic HF from18 tertiary care hospitals across Saudi Arabia. Diagnosis of HF was in accordance with American Heart Association/European Society of Cardiology definition criteria. The registry had enrolled 2610 HF patients during the 14 month recruitment period between October 2009 and December 2010. Occurrence of in‐hospital cardiac events, prognosis, and outcome were monitored during the 7 year follow‐up period. The incidence of in‐hospital VA in HF was 4.2%. VA was more common among men, and mean age was lesser than non‐VA patients (58.5 ± 16: 61.5 ± 15 years; P = 0.042). Smoking and family history of cardiomyopathy were significant risk factors of VA. Previous history of arrhythmia, ST elevated myocardial infarction, infections, and hypotension remained significant predictors of in‐hospital VA associated with three to seven times more risk. Patients with VA had higher rates of in‐hospital events like recurrent HF, haemodialysis, shock, sepsis, major bleeding, intra‐aortic balloon pump, and stroke compared with those without VA, all being highly significant (P < 0.001). After adjustment for age, gender, and co‐morbidities, in‐hospital VA increased the risk of cardiogenic shock by 24 times, dialysis and major bleeding by 10 times, and recurrent congestive HF and pacing by five times. Survival analysis showed that all‐cause mortality was significantly higher in the VA patients (P < 0.001). Presence of VA increased in‐hospital and 1 month mortality to 23 and 17 times, respectively.

Conclusions

Lower mean age of VA complicated HF patients is a matter of concern in the Saudi population. HF associated with VA increased in‐hospital events and all‐cause mortality indicating poor prognosis and survival. These findings enable risk stratification and reflect on the importance of early recognition of the clinical markers and predictors of VA prompting immediate management.

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.

Sudden death in dilated cardiomyopathy

The purpose of this review is to examine the potential contribution of arrhythmia to the occurrence of sudden death in dilated cardiomyopathy (DCM) and to discuss current treatment options. We performed a search of the MEDLINE database from 1985 to the present and the reference citations of selected articles pertaining to the prognostic significance, management, and pathophysiology of arrhythmias in DCM. A large proportion of patients with DCM die suddenly, most secondary to ventricular arrhythmia and a smaller proportion due to bradyarrhythmia. The presence and severity of ventricular ectopy may predict risk for sudden death, but the role of electrophysiologic study and signal-averaged electrocardiography in further risk stratifying patients remains uncertain. Abnormalities of the autonomic nervous system and renin-angiotensin-aldosterone axis appear to promote the occurrence of ventricular arrhythmias. Angiotensin-converting enzyme inhibitors improve overall mortality in congestive heart failure, and the use of direct angiotensin-receptor antagonists is currently being studied. In addition, beta-receptor antagonists appear to improve morbidity and may prove to improve mortality in heart failure as well. Other interventions still under investigation include amiodarone and the implantable cardioverter-defibrillator. The underlying pathophysiology of sudden death in DCM involves primarily ventricular tachyarrhythmia. Angiotensin-converting enzyme inhibitors remain a mainstay of improving overall mortality, while further study on the roles for newer drugs and devices is ongoing.

[Long term electrocardiography (Holter monitoring)]

During the past almost 50 years Holter monitoring has become an established non-invasive diagnostic tool in clinical electrophysiology. It allows ECG recording independent of stationary monitoring facilities during daily life and, therefore, contains much information. In the beginning the main interest was directed towards quantitative and qualitative assessment of arrhythmias, their circadian behaviour, and the circadian behaviour of the heart rate. With advances in technology the analysis spectrum of Holter monitoring expanded, and it was used also for detection of silent myocardial ischaemia. New digital recorders and computers with large capacities made it possible to measure every single heart beat very accurately, which was a prerequisite for heart rate variability and QT-interval analysis, which provided new knowledge about the autonomic modulation of the heart rate and the circadian dynamicity of the QT interval, respectively. Beyond arrhythmia analysis Holter monitoring was increasingly used to assess prognosis in different cardiac conditions. It can also be valuable in assessing transient symptoms possibly related to arrhythmias or device dysfunction, which will not necessarily be revealed by simple device control.

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.

Long-term continuous external electrocardiographic recording: a review

Ambulatory electrocardiographic (AECG) monitoring is an essential tool in the diagnostic evaluation of patients with cardiac arrhythmias. Recent advances in solid-state technology have improved the quality of the ECG signals and new dedicated algorithms have expanded the clinical application of software-based AECG analysis systems. These advances, in addition to the availability of inexpensive large storage capacities, and very long-term continuous high-quality AECG monitoring, have opened new potential uses for AECG. New digital recorders have the capability of multichannel simultaneous recordings (from 3 to 12 leads) and for telemetred signal transduction. These possibilities will expand the traditional uses of AECG for arrhythmia detection, as arrhythmia monitoring to assess drug and device efficacies has been further defined by new studies. The analysis of transient ST-segment deviation still remains controversial, but considerably more data are now available, especially about the prognostic value of detecting asymptomatic ischaemia. Heart rate variability analysis has shown promise for predicting mortality rates in cardiac patients at high risk. We review recent advances in this field of non-invasive cardiac testing.

Left ventricular end-systolic stress/diameter relation as a contractility index and as a predictor of survival. Independence of preload after normalization for end-diastolic diameter

The independence of the slope of the left ventricular (LV) end-systolic stress/end systolic diameter (ESS/ESD) relation of preload (PL) after normalization for end-diastolic diameter (EDD), and the reliability of both the original and the normalized slope as contractility and prognostic indices, were assessed. We studied echocardiographically, hemodynamically, and with carotid pulse tracing, 25 normal subjects, 18 patients with coronary artery disease having a normal ejection fraction (EF), and 30 patients with idiopathic dilated cardiomyopathy (DCM). The arterial pressure was changed with intravenous infusion of phenylephrine. To investigate the effect of PL on the ESS/ESD slope, in 12 normals the PL was decreased with intravenous infusion of 40 mg of furosemide and increased with 1 l isotonic NaCl. The studied population was followed up for 18-61 months. The mean values of the slope after furosemide and after NaCl differed significantly but when the above values were divided by the EDD the differences were nullified. The mean values of the slope differed highly significantly between the three groups. The normalized slope increased the sensitivity in the discrimination. During the follow-up period 10 patients with DCM died. The original and the normalized slopes separated the deceased and survivors significantly (P < 0.002 for both indices) as compared to EF (P < 0.05). The ESS/ESD slope is a very sensitive contractility index and is also superior to EF as a prognostic parameter. The normalization of the slope eliminates its dependence on PL and improves the sensitivity in assessing decreased contractility, although it slightly decreases its prognostic value.

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.

Clinical characteristics of induced nonclinical ventricular tachycardia in nonischemic cardiomyopathy

The clinical significance of induced nonclinical ventricular tachycardia (NCVT) in nonischemic dilated cardiomyopathy (DCM) remains controversial. Twenty-eight patients with sustained VT or ventricular fibrillation related to DCM underwent programmed ventricular stimulation (PVS) to induce VT. However, VT was not induced in four patients. Based on the morphology of induced ventricular arrhythmia, we classified the remaining 24 patients into NCVT (n = l1 ) and clinical VT (CVT) groups (n = 13), then evaluated the prognosis for a mean follow-up period of 22 months. The cycle length of induced NCVT was significantly shorter than that of induced CVT (277 +/- 38 ms vs 325 +/- 63 ms, P < 0.05). Appropriate antiarrhythmic agents were selected by serial PVS in 36% of the NCVT group and in 38% of the CVT group (4/11 vs 5/13). Among patients who had been treated by PVS guided drug therapy, arrhythmic events were observed in 75% of the NCVT group and 80% of the CVT group (3/4 vs 4/5). The total incidence of sudden death in the NCVT group was higher than that in the CVT group (5/11: 45% vs 4/13: 31%). In conclusion, induced NCVT and CVT are refractory to pharmacological therapy and both have an important characteristic value in DCM.

Primary prevention of sudden cardiac death in idiopathic dilated cardiomyopathy: the Cardiomyopathy Trial (CAT)

BACKGROUND

Patients with idiopathic dilated cardiomyopathy (DCM) and impaired left ventricular ejection fraction have an increased risk of dying suddenly.

METHODS AND RESULTS

Patients with recent onset of DCM (< or =9 months) and an ejection fraction < or =30% were randomly assigned to the implantation of an implantable cardioverter-defibrillator (ICD) or control. The primary end point of the trial was all-cause mortality at 1 year of follow-up. The trial was terminated after the inclusion of 104 patients because the all-cause mortality rate at 1 year did not reach the expected 30% in the control group. In August 2000, the vital status of all patients was updated by contacting patients, relatives, or local registration offices. One hundred four patients were enrolled in the trial: Fifty were assigned to ICD therapy and 54 to the control group. Mean follow-up was 22.8+/-4.3 months, on the basis of investigators' follow-up. After 1 year, 6 patients were dead (4 in the ICD group and 2 in the control group). No sudden death occurred during the first and second years of follow-up. In August 2000, after a mean follow-up of 5.5+/-2.2 years, 30 deaths had occurred (13 in the ICD group and 17 in the control group). Cumulative survival was not significantly different between the two groups (93% and 80% in the control group versus 92% and 86% in the ICD group after 2 and 4 years, respectively).

CONCLUSIONS

This trial did not provide evidence in favor of prophylactic ICD implantation in patients with DCM of recent onset and impaired left ventricular ejection fraction.

Role of implantable cardioverter defibrillators in dilated cardiomyopathy

Idiopathic dilated cardiomyopathy (DCM) accounts for about 10,000 deaths per year in western countries. Of these deaths, 8% to 51% occur suddenly, with more than half of the events due to a ventricular arrhythmia. Improvement in diagnostic techniques and therapeutic strategies, together with changes in secular trends, have likely contributed to the reported trend toward improved survival in recent years. Identification of DCM patients at higher risk of sudden death is difficult. Poor left ventricular function is the strongest predictor of all-cause death, whereas a history of sustained unstable ventricular arrhythmia or cardiac arrest identifies patients at high risk of sudden death. Recent data suggest that a history of syncope, regardless of inducibility at programmed electrical stimulation, may be a risk factor of sudden death. Despite the absence of controlled studies, use of implantable cardioverter defibrillator therapy for primary prevention can be considered in patients with unexplained syncope as well as subgroups of DCM patients awaiting transplantation. In patients who survive a cardiac arrest or an unstable ventricular tachycardia, use of implantable cardioverter defibrillator therapy is associated with improved survival during follow-up and should be considered as a first-line therapy.

Therapeutic options in patients with reduced ejection fraction and nonsustained ventricular tachycardia

The patient with a reduced ejection fraction and nonsustained ventricular tachycardia represents a common management problem for the physician. This article reviews the supporting evidence for the therapeutic options available for these patients according to the etiology of the reduced ejection fraction. In postinfarction patients, electrophysiology-guided implantable cardioverter defibrillator therapy improves survival more than antiarrhythmic therapy. In patients with nonischemic cardiomyopathy, the best therapy is yet undetermined. Ongoing clinical trials will hopefully direct future therapy.

Nonsustained ventricular tachycardia. A guide to the clinical significance and management

The patient with nonsustained ventricular tachycardia represents a common management problem for the cardiologists and internists. Treatment is sometimes needed for the suppression of symptoms. More commonly, nonsustained ventricular tachycardia is asymptomatic, and the clinician must determine the prognostic importance. The prognostic implications, the role of electrophysiologic study, and the potential role of pharmacologic and defibrillator intervention depend on the underlying cardiac substrate present in the individual patient.

An animal model of arrhythmogenesis in congestive heart failure

Background: Patients with congestive heart failure (CHF) frequently die from arrhythmias, but models to study arrhythmogenic mechanisms during progressive CHF are lacking. Consequently we examined the feasibility of using dogs with an ischemic insult followed by rapid pacing to study ventricular arrhythmias in CHF. Methods: Eighteen chronically instrumented dogs had ischemic damage induced by inflating a balloon tipped catheter in a coronary artery for 90 min. After 2 weeks recovery, electrophysiologic studies were performed on no drugs, during esmolol infusion, and during isoproterenol infusion. The pacer was turned on at 250 bpm in 12 dogs, but not in six controls, and studies repeated bi-weekly for up to 6 weeks. Results: Serial echocardiograms documented progressive CHF, and serial signal averaged electrocardiograms demonstrated prolongation of total QRS, increased duration of terminal QRS<40 mv, and decreased RMS voltage of the terminal 20 ms of QRS in paced dogs. Arrhythmia severity increased as CHF progressed, but responses were quite variable, unaffected by esmolol, and minimally altered by isoproterenol. Conclusions: Ischemic left ventricular damage followed by rapid ventricular pacing in dogs produces a model that closely mimics patients with CHF and ventricular arrhythmias, including a heterogeneous pathophysiologic response to intervention.

Recovery time dispersion measured from 87-lead body surface potential mapping as a predictor of sustained ventricular tachycardia in patients with idiopathic dilated cardiomyopathy

INTRODUCTION

The clinical usefulness of QT dispersion in 12-lead ECG has been controversial in identifying subjects at risk for sustained ventricular tachycardia (VT) in patients with idiopathic dilated cardiomyopathy (DCM). We hypothesized that increasing the spatial resolution of the ECG improves the accuracy of risk stratification. The purpose of this study was to test the ability of recovery time dispersion measured from 87-lead body surface potential mapping (BSPM) to identify patients at risk for sustained VT in idiopathic DCM.

METHODS AND RESULTS

We obtained 87-lead BSPM and 12-lead ECG in 33 patients with idiopathic DCM (15 patients with a history of sustained VT [VT(+) group] and 18 patients without a history of sustained VT [VT(-) group]) and in 20 normal control subjects. We measured the corrected QT dispersion and corrected recovery time dispersion from 12-lead ECG (QTc-12 dispersion and RTc-12 dispersion, respectively) and 87-lead BSPM (QTc-87 dispersion and RTc-87 dispersion, respectively). Signal-averaged ECG also was recorded in 25 patients. Neither the QTc-12 nor QTc-87 dispersion discriminated between the VT(+) and VT(-) groups patients. The VT(+) group patients had a larger but insignificant RTc-12 dispersion than the VT(-) group patients. In contrast, the RTc-87 dispersion was significantly larger in the VT(+) group patients than in the VT(-) group patients (236 +/- 39 msec vs 184 +/- 28 msec, P < 0.001). Receiver operating curve analysis indicated that the RTc-87 dispersion was as good as late potentials in predicting susceptibility to sustained VT; its sensitivity, specificity, and negative predictive value were 73%, 76%, and 76%, respectively (cutoff value 200 msec). RTc-87 dispersion >200 msec combined with positive late potentials provide high sensitivity (92%) and high negative predictive value (88%) for sustained VT.

CONCLUSION

The RTc-87 dispersion is a useful tool to identify subjects at risk for sustained VT in patients with idiopathic DCM.

Sudden cardiac death syndrome and pump dysfunction: the link

Clearly, sudden cardiac death syndrome in heart failure is linked to severely perturbed neurohumoral, hemodynamic, and mechanical systems. Routine antiarrhythmic drug therapy has not proven beneficial and, therefore, there is no justification for using these agents in unselected heart failure patients who are without significant symptomatic ventricular arrhythmia. Aggressive treatment of the failure syndrome seems most important. Because many of the problematic arrhythmias arise from triggering automaticity, which is known to occur in excessive ventricular stretch and wall stress, systemic vascular "unloading" with vasodilators and angiotensin-converting enzyme inhibitors is likely helpful. The most recent American College of Cardiology/American Heart Association Guidelines regarding therapeutic management of heart failure suggest that aggressive pharmacologic treatment of asymptomatic ventricular arrhythmias is best avoided. To be considered strongly for pharmacologic prescription or for implantation of a tachyarrhythmia termination device, a patient should have symptomatic ventricular tachycardia with an episode of syncope or sudden cardiac death syndrome rather than simply having palpitations of asymptomatic, unsustained ventricular tachycardia. Indeed, aggressively treating congestive heart failure with medication often eliminates potentially life-threatening arrhythmias. Appropriate use of vasodilators and, particularly, angiotensin-converting enzyme inhibitors is important. Correction of fluid balance and electrolyte disorders may be helpful to address symptoms and certainly is likely to decrease the potential for morbidity and mortality. On occasion it may be necessary to consider bradyarrhythmia pacemaker insertion or the use of atrioventricular nodal-ablation techniques with subsequent ventricular or atrioventricular pacer insertion. Obviously, sudden cardiac death due to sudden heart block or asystole might be attenuated with this strategy.

Application of noninvasive and invasive tests for risk assessment in patients with ventricular arrhythmias

Sudden cardiac death remains a major public health problem in western society. Because most patients who experience cardiac arrest are not successfully resuscitated, primary prevention of sudden death remains an important challenge. A number of noninvasive risk stratification techniques have been suggested as providing useful information in patients with underlying structural heart defects. Unfortunately, the positive predictive value of most of these techniques has been limited. Left ventricular ejection fraction, the presence of nonsustained ventricular tachycardia on Holter monitoring, and inducible sustained ventricular tachycardia at electrophysiologic testing in patients with coronary artery disease remain the best established prognostic test. However, with the exception of two ICD studies using the combination of these markers, prospective studies have not yet completely validated the use of these and other prognostic markers. Further understanding of the pathophysiology of ventricular fibrillation and other risk stratification techniques will be necessary before a clear algorithm can be developed for application to patients at risk for sudden death.

Nonsustained ventricular tachycardia

The patient with nonsustained ventricular tachycardia represents a common management problem for the cardiologist. The challenges posed by this type of arrhythmia differs from those posed by other arrhythmias, because most instances of nonsustained ventricular tachycardia do not cause symptoms. This article reviews common situations in which nonsustained ventricular tachycardia occurs and their appropriate management.

Significance of accelerated idioventricular rhythm in idiopathic dilated cardiomyopathy

Holter monitoring was performed in 202 patients with idiopathic dilated cardiomyopathy, which revealed accelerated idioventricular rhythm in 16 patients (8%) and nonsustained ventricular tachycardia in 70 patients (35%). During 32 +/- 15-month prospective follow-up, no significant difference was observed for major arrhythmic events and transplant-free survival between patients with and without accelerated idioventricular rhythm, whereas patients with nonsustained ventricular tachycardia had a significantly higher incidence of major arrhythmic events and a lower transplant-free survival rate.

Arrhythmias in heart failure: current concepts of mechanisms and therapy

About one half of deaths in patients with heart failure are sudden, mostly due to ventricular tachycardia (VT) degenerating to ventricular fibrillation or immediate ventricular fibrillation. In severe heart failure, sudden cardiac death also may occur due to bradyarrhythmias. Other dysrhythmias complicating heart failure include atrial and ventricular extrasystoles, atrial fibrillation (AF), and sustained and nonsustained ventricular tachyarrhythmias. The exact mechanism of the increased vulnerability to arrhythmias is not known. Depending on the etiology of heart failure, different preconditions, including ischemia or structural alterations such as fibrosis or myocardial scarring, may be prominent. Reentrant mechanisms around scar tissue, afterdepolarizations, and triggered activity due to changes in calcium metabolism significantly contribute to arrhythmogenesis. Furthermore, alterations in potassium currents leading to action potential prolongation and an increase in dispersion of repolarization play a significant role. Treatment of arrhythmias is necessary either because patients are symptomatic or to reduce the risk for sudden cardiac death. The individual history, left ventricular function, electrophysiologic testing, and the signal-averaged ECG give useful information for identifying patients at risk for sudden cardiac death. The implantable cardioverter defibrillator (ICD) has evolved as a promising therapy for life-threatening arrhythmias. A potential role may exist for antiarrhythmic drugs, mainly amiodarone. There is growing evidence that patients with sustained VT or a history of resuscitation have the best outcome with ICD therapy regardless of the degree of heart failure. Many of these patients require additional antiarrhythmic therapy because of AF or nonsustained VTs that may activate the device. Catheter ablation or map-guided endocardial resection are additional options in selected patients but seldom represent the only therapeutic strategy.

Remodeling of lung interstitium but not resistance vessels in canine pacing-induced heart failure

We previously showed that pacing-induced heart failure in dogs results in an enhancement of pulmonary vascular reactivity. In the present study we hypothesized that enhanced matrix deposition and structural remodeling of lung resistance microvessels would underlie these functional changes. Using biochemical measures, we found no difference in the normalized lung content of hyaluronan, uronic acid, and collagen between control dogs and dogs paced for 1 mo, although lung dry weight and noncollagen protein content increased significantly in the paced group (P < 0.05). From separate Formalin-fixed lung lobes, 5-microm frozen sections were prepared and stained with Masson's trichrome, and vascular structure was evaluated using standard morphometric techniques. When perivascular fluid cuffs were excluded from the measure of wall thickness, collagen and media volume fractions in any size range did not differ between paced and control groups. Similarly, in the paced group, medial thickness in <400-microm arterial or venular microvessels did not vary significantly from that in the controls. In contrast, the relationship of interstitial fluid pressure to lung water was significantly shifted to the right in the paced group, such that normal tissue pressures were observed, despite the increased water content. We conclude that although 1 mo of pacing-induced heart failure results in altered interstitial function, the attendant pulmonary hypertension and/or hormonal responses are insufficient to induce medial hypertrophy or other remodeling of the extra-alveolar microvasculature.

The top ten fallacies of nonsustained ventricular tachycardia

Nonsustained ventricular tachycardia (NSVT) continues to remain a subject of controversy. This is true despite a wealth of epidemiologic and basic/clinical laboratory findings that have accumulated during the past 2 decades. However, these data not only generate the impetus to conduct further research, but also provide compelling arguments against continued adherence to time honored precepts about NSVT that evolved since the inception of the "PVC Hypothesis," although never substantiated by rigorous scientific inquiry. This paper discusses the "top ten" fallacies of NSVT and details the data that support abandonment of them.

Ion channel blockers in the treatment of chronic heart failure

Strategies for pharmacological treatment of chronic congestive heart failure (CHF) are discussed from the viewpoint of cardiac ion channel modulations. It remains controversial as to whether Na channel blockers, which are the most effective drugs to suppress ventricular arrhythmias, can improve the prognosis of chronic CHF. As far as recent knowledge of interactions between the Na channel and its blocker is concerned, lidocaine-like agents such as mexiletine, which inhibit the Na channel current by binding to the channel in the inactivated state, are recommended because they can suppress premature ventricular contractions without prolongation of QRS complexes of sinus beats. To develop a new agent for the treatment of chronic CHF, we extracted the common features of electropharmacologic actions shared by amiodarone and vesnarinone, both of which have been reported to reduce the mortality of patients with chronic CHF. It is concluded that increases in the action potential duration (APD) of ventricular muscle mediated through an inhibition of the delayed rectifier K channel (IK channel) and a reduction of sinus node firing through an inhibition of L type Ca channel in addition to IK channel inhibition, are essential for the treatment of chronic CHF.

Therapy of ventricular tachycardia in patients with nonischemic cardiomyopathies

In patients with IDCM and sustained VT, every effort should be made to exclude bundle branch reentrant tachycardia. We strongly believe that this mechanism of VT remains underdiagnosed despite electrophysiologic evaluation. In appropriate candidates with cardiomyopathies and "nonbundle branch reentrant VT," ICD implantation is frequently the treatment of choice, especially if the clinical presentation is that of hemodynamic collapse, or there is significant left ventricular systolic dysfunction. The role of amiodarone versus ICD, especially for patients with well-tolerated VT and milder forms of cardiomyopathies, is yet to be defined.

Antiarrhythmic drug therapy for ventricular arrhythmias: current perspectives

Pharmacologic therapy for ventricular arrhythmias has undergone a remarkable change recently. Recognition of the importance of underlying structural heart disease on prognostic implications of ventricular arrhythmias has resulted in the refinement of the clinical classification of these arrhythmias. With refinement of techniques of risk stratification, it is now possible to identify patients ventricular arrhythmias at high risk for sudden death. Retrospective analyses of prior antiarrhythmic drug trials and new data from prospective randomized trials are now available and can more directly define the risks and benefits of antiarrhythmic therapy. Prevention of sudden death, reduction in total mortality, or improvement in symptoms remain the only benefits of antiarrhythmic drugs. With inclusion of total mortality as the major endpoint for assessment of pharmacologic interventions in high-risk patients, the potential for excess mortality due to antiarrhythmic agents is now recognized. The pharmacologic diversity of newly released antiarrhythmic agents and others under development has resulted in a re-evaluation of the traditional classification of these drugs. Multiple ongoing clinical trials will define the risks and benefits of antiarrhythmic therapy and other nonpharmacologic interventions in patients with ventricular arrhythmias.

Dynamic cardiomyoplasty in the treatment of dilated cardiomyopathy: current results and perspectives

BACKGROUND

The purpose of this article is to provide an overview of the current indications, results, and perspectives of dynamic cardiomyoplasty in the treatment of patients with dilated cardiomyopathy. Particular emphasis is placed on the clinical experience with 36 patients operated at the São Paulo Heart Institute between 1988 and 1995.

METHODS

Based on several clinical reports, the mechanisms of action of dynamic cardiomyoplasty in these patients include the enhancement of left ventricular systolic function, by the direct action of synchronized skeletal muscle flap contraction and the reversion of chamber remodeling. Moreover, both mechanisms seem to be responsible for improved diastolic function properties and for the decrease of ventricular wall stress. Besides the acceptable hospital mortality observed for patients with dilated cardiomyopathy ranging from 0% to 8% with this surgical procedure, clinical improvement after dynamic cardiomyoplasty has been demonstrated as a prevailing and significant outcome.

RESULTS

Nevertheless, the 1-year survival for these patients ranges from 82% to 86% and the 5-year survival on the order of 41% to 49%. In addition, the analysis of factors influencing the outcome showed that cardiomyoplasty long-term survival was significantly affected by the severity of preoperative clinical compromise and cardiac function impairment. On the other hand, patients with dilated cardiomyopathy who were operated in functional Class III or intermittent Class IV and with pulmonary vascular resistance below 4 Wood units, present survival rates on the order of 79% at 2 years and of 64% at 5 years of follow-up, which are similar to those reported after cardiac transplantation.

CONCLUSIONS

Furthermore, technological advances incorporated in the new cardiomyostimulators may ameliorate skeletal muscle flap performance at long term. Other developments are also discussed in this field.

Fractionated electrograms in dilated cardiomyopathy: origin and relation to abnormal conduction

OBJECTIVES

We sought to investigate the origin of the fractionated electrogram and its relations to abnormal conduction in cardiomyopathic myocardium.

BACKGROUND

Patients with dilated cardiomyopathy have a high incidence of ventricular tachycardias. Electrograms recorded in these patients are often fractionated.

METHODS

High resolution mapping (200-microM interelectrode distance) of the electrical activity was carried out in 11 superfused papillary muscles and 6 trabeculae from 7 patients who underwent heart transplantation because of dilated cardiomyopathy. Similar measurements were taken in four papillary muscles from dog hearts in which electrical barriers had been artificially made. Ten human preparations were studied histologically.

RESULTS

All preparations revealed sites with fractionated electrograms. In three human preparations, activation patterns showed a discernible line of activation block running parallel to the fiber direction. Fractionated electrograms were recorded at sites contiguous to the line of block. In five preparations, fractionated electrograms were recorded at sites where lines of block were not identified. In these preparations, electrical barriers consisted of short stretches of fibrous tissue. In the remaining nine preparations, fractionated electrograms were recorded, both from sites contiguous to distinct obstacles and sites without evidence of a barrier.

CONCLUSIONS

Our observations showed that fractionated electrograms recorded in myocardium damaged by cardiomyopathy were due to both distinct, long strands and short stretches of fibrous tissue. Delayed conduction was caused by curvation of activation around the distinct lines of block and by the wavy course of activation between the short barriers. The latter reflects extreme nonuniform anisotropy.

Bradycardia-associated episodic weakness, syncope, and aborted sudden death in cardiomyopathic Doberman Pinschers

Paradoxical sinus bradycardia and cardiac asystole resulted in episodic weakness, syncope, or aborted sudden cardiac death during exertion in 8 cardiomyopathic Doberman Pinschers. Bradycardias persisted for 1 to 2 minutes in 5 of 8 dogs, and were often followed by sinus tachycardia. Syncope was prolonged on multiple occasions in 5 dogs, and was accompanied by white, then cyanotic mucous membranes, mydriasis, and apparent sudden death.

Cardiovascular effects of the combination of OPC-18790 and dopamine in halothane-anesthetized dogs

OPC-18790, (+/-)-6-[3-(3,4-dimethoxybenzylamino)-2-hydroxypropoxy]-2(1H)-quin olinone, is a novel positive inotropic agent, and its mechanism of positive inotropic action involves not only phosphodiesterase inhibition, but also a prolongation of action potential duration in ventricular muscle. Prolongation of action potential duration is also a property of class III antiarrhythmic agents; therefore, we examined the cardiohemodynamic effects and arrhythmogenicity of a combination of OPC-18790 and dopamine in halothane-anesthetized dogs. Dopamine (5 micrograms/kg/min) alone increased the peak of the first derivative of left ventricular pressure (LVdP/dtmax) and cardiac output (CO) by 43-48% and 16-20%, respectively, while OPC-18790 (10 micrograms/kg/min) increased these parameters by 56% and 22%, respectively. The combination of OPC-18790 (10 micrograms/kg/min) and dopamine (5 micrograms/kg/min) and dopamine alone at an increased dose of 10 micrograms/kg/min further increased LVdP/dtmax and CO by 104-113% and 29-30%, respectively. Thus, positive inotropic effects were equally observed in both groups, and the effects of OPC-18790 and dopamine seemed to be additive. The other hemodynamic effects were similar among all groups. Arrhythmias such as premature ventricular contraction developed in 5 out of 7 dogs (71.4%) in the 10-micrograms/kg/min dopamine group, while only one premature ventricular contraction was observed in 1 of 7 dogs (14.3%) in the OPC-18790 (10 micrograms/kg/min) and dopamine (5 micrograms/kg/min) combination group. These results suggest that the combination of OPC-18790 and dopamine may provide new therapeutic options for the treatment of heart failure.

Prognostic importance of the length of ventricular tachycardia in patients with nonischemic congestive heart failure

In patients with congestive heart failure the frequency of ventricular arrhythmias poorly predicts mortality. It is unknown whether the length of ventricular tachycardia is a better predictor of mortality in these patients. We therefore investigated the prognostic importance of the length of the longest run of ventricular tachycardia, the frequency of ventricular tachycardia, and the frequency of ventricular premature depolarizations with 24-hour ambulatory electrocardiographic recordings in 122 patients with heart failure. We also determined whether the cause of heart failure affects the prognostic importance of these parameters. Each ambulatory electrocardiographic recording was evaluated for the frequency of ventricular premature depolarizations and ventricular tachycardia and for the length of the longest run of ventricular tachycardia. For each electrocardiographic parameter patients were divided into groups based on the median value of that parameter. Mortality among groups was compared in all patients and then separately for nonischemic and ischemic patients. Neither the frequency of ventricular premature depolarizations nor the frequency of ventricular tachycardia predicted mortality whether or not cause was considered. When all patients were examined, the length of ventricular tachycardia did predict an increased risk of death. However, when cause was considered, length of ventricular tachycardia predicted mortality only in the nonischemic patients and not in the ischemic patients. We conclude that the length of ventricular tachycardia may be the best electrocardiographic predictor of mortality in patients with nonischemic heart failure.

Effect of amiodarone therapy on mortality in patients with left ventricular dysfunction and asymptomatic complex ventricular arrhythmias: Argentine Pilot Study of Sudden Death and Amiodarone (EPAMSA)

The efficiency of prophylactic antiarrhythmic treatment with amiodarone in reducing 1-year mortality in patients with reduced left ventricular ejection fraction ( < 35%) and asymptomatic ventricular arrhythmias (Lown classes 2 and 4) was investigated in a prospective, multicenter, randomized, controlled study. Among 127 patients who entered the study, 61 were assigned to no antiarrhythmic therapy (control group [CG] and 66 to amiodarone treatment (amiodarone group [AG]). Amiodarone was administered at a dosage of 800 mg/day for 2 weeks followed by 400 mg/day thereafter. A 12-month follow-up was completed for 106 patients (57 in the AG and 49 in the CG). Amiodarone reduced the overall mortality rate, which was 10.5% in the AG versus 28.6% in the CG (odds ratio [OR] 0.29; 95% confidence interval [CI] 0.10 to 0.84; log-rank test 0.02) and sudden death rate, which was 7.0% in the AG versus 20.4% in the CG (OR 0.29; 95% CI 0.08 to 1.00; log-rank test 0.04). Side effects were rare, and in only three patients did amiodarone treatment have to be discontinued.

Lack of long-term ventricular arrhythmia reduction by enalapril in heart failure. SOLVD Investigators

Previous studies have indicated that angiotensin-converting enzyme inhibitors may reduce the frequency of ventricular arrhythmias in patients with heart failure. These reports were mostly small and of short duration. We prospectively studied 734 patients recruited in 11 universities for 1 year who were enrolled in the Studies of Left Ventricular Dysfunction (SOLVD) to determine the long-term effects of enalapril and placebo on the frequency and complexity of ventricular arrhythmias in patients with symptomatic (treatment trial) or asymptomatic (prevention trial) heart failure and depressed left ventricular function (ejection fraction < or = 35%). Five hundred fifty-three patients from the prevention trial and 181 from the treatment trial of SOLVD underwent ambulatory electrocardiographic monitoring at baseline, and then at 4 and 12 months of double-blind therapy with either placebo or enalapril (2.5 to 10 mg twice daily). The prospectively defined primary analysis was by intent-to-treat and revealed no significant differences in ventricular premature complexes between the placebo and enalapril groups at baseline (87 +/- 13 vs 84 +/- 13/hour), 4 months (100 +/- 15 vs 85 +/- 12/hour), or 12 months (80 +/- 12 vs 90 +/- 14/hour). Likewise, there was no difference between the placebo and enalapril groups in runs of nonsustained ventricular tachycardia: baseline (8.3 +/- 4.1 vs 1.9 +/- 0.4 runs/day), 4 months (16 +/- 12 vs 7.2 +/- 4.1 runs/day), or after 12 months of blinded therapy (11 +/- 7.0 vs 6.1 +/- 4.4 runs/day).(ABSTRACT TRUNCATED AT 250 WORDS)

Cardioverter defibrillator therapy as a bridge to heart transplantation

The prognosis of patients with severely impaired left ventricular function is poor, with an annual mortality rate of about 50%, and the majority die from sudden cardiac death. Heart transplantation is an accepted therapy for patients with end-stage heart disease; however, about 30% of candidates for transplantation die from sudden cardiac death while on the waiting list. It has been shown that implantable cardioverter defibrillator (ICD) therapy has a low surgical mortality and is highly effective in the prevention of sudden death. Therefore, prophylactic ICD implantation may prevent sudden death in patients with end-stage heart disease while on the waiting list, and it is highly probable that patients with an ICD have a greater chance of survival until a donor heart becomes available. However, this hypothesis still has to be proven by prospective studies.

Idiopathic dilated cardiomyopathy in dogs: survival and prognostic indicators

To further define the prognosis and identify clinical findings predictive for survival in dogs with dilated cardiomyopathy (DCM), we performed Kaplan Meier survival analysis of 37 dogs with idiopathic DCM. Survival analysis showed that the 50% probability of survival occurred at 2.3 months. Probability of survival at 1 year was 37.5% and at 2 years was 28%. Bivariate Cox proportional hazard ratios identified pleural effusion and pulmonary edema, both signs of congestive heart failure, as independent prognostic indicators for dogs with DCM (P < .01). Hazard ratios for these prognostic indicators were 2.354 and 3.291, respectively. Multivariate Cox stepwise regression identified pleural effusion, left ventricular free-wall thickening fraction, ventricular ectopy, and weight loss as significant prognostic indicators for dogs with DCM. Because of the retrospective nature of this study, the effects of different drug treatments were not evaluated. The type of cardiac-related death, progressive failure versus sudden death, was not addressed in this study and requires further evaluation.

Initiation of ventricular extrasystoles by myocardial stretch in chronically dilated and failing canine left ventricle

BACKGROUND

Stretch-induced arrhythmias (SIAs) can be elicited in normal canine left ventricles by transient diastolic dilatation. Since clinically important ventricular arrhythmias arise most commonly in failing and dilated ventricles, we hypothesized that the arrhythmogenic effect of transient diastolic stretch would be enhanced in chronically dilated failing canine hearts.

METHODS AND RESULTS

Heart failure was induced in seven dogs by right ventricular pacing at 250 min-1 for 20.2 +/- 1.6 days. Left ventricular (LV) mechanical properties were measured in vivo with serial echocardiograms in these seven dogs with the dogs awake and tranquilized to confirm the development of LV dilation and failure. By the third week of pacing, average short-axis area ejection fraction decreased by 64.3% (P < .001) as end-diastolic and end-systolic diameters increased by 25.9% and 50.7%, respectively (P < .001). After heart failure was established, the hearts were harvested and in vitro data were obtained as an isolated, blood-perfused ventricle preparation. A computerized servo pump system connected to an LV intracavitary balloon was used to measure and control LV volume. Results were compared with in vitro data obtained from eight ventricles not subjected to pacing (controls). LV contractility, quantitated in vitro as the slope of the peak isovolumic pressure-volume relation (Emax) normalized to LV cavity size, was much lower in the heart failure group than in controls (182 +/- 18 versus 365 +/- 38 mm Hg, P < .001). In all isolated hearts, SIAs were induced using an electromechanical stimulation protocol in which eight paced beats at 2 Hz were followed by a transient increase in LV volume during early diastole. Prestretch volume (Vi) was selected to yield end-diastolic pressures of 4 to 8 mm Hg in all hearts. The fractional increase in LV volume (delta V) that produced SIAs 50% of the time (delta V 50/Vi) was smaller in failing hearts than in controls (0.78 +/- 0.04 versus 1.18 +/- 0.17, P = .009), indicating an increased sensitivity to SIAs in the failing hearts. Although ventricular pairs were occasionally induced in both groups, the great majority of the arrhythmias induced in both groups were single extrasystoles, and nonsustained runs of ventricular tachycardia were never elicited in either group. LV end-diastolic and peak stretch pressures were similar in the two groups, but LV end-diastolic wall stress was higher by 35.7% (P = .029) in the dilated failing ventricles because LV hypertrophy, which tends to normalize wall stress as the heart dilates, did not occur during the 3 weeks of pacing. For stretch stimuli of comparable arrhythmogenic effectiveness, peak LV wall stress during stretch was similar in the two groups, whereas the fractional increase in volume was significantly smaller in the heart failure group, indicating impaired viscoelastic properties in the failing ventricles. In five control ventricles, acute exposure to 0.5 mumol/L dobutamine increased ventricular sensitivity to the induction of SIAs, as shown by a decrease in delta V50/Vi from 1.27 +/- 0.16 to 1.06 +/- 0.11 (P = .04).

CONCLUSIONS

Altered mechanical properties and/or neurohumoral adaptations associated with chronic dilation and failure predispose the ventricle to induction of ventricular extrasystoles by transient LV diastolic stretch.