First- or second-degree atrioventricular block as a risk factor in idiopathic dilated cardiomyopathy

Regulation of sinus node pacemaking and atrioventricular node conduction by HCN channels in health and disease

The funny current, I_f, was first recorded in the heart 40 or more years ago by Dario DiFrancesco and others. Since then, we have learnt that I_f plays an important role in pacemaking in the sinus node, the innate pacemaker of the heart, and more recently evidence has accumulated to show that I_f may play an important role in action potential conduction through the atrioventricular (AV) node. Evidence has also accumulated to show that regulation of the transcription and translation of the underlying Hcn genes plays an important role in the regulation of sinus node pacemaking and AV node conduction under normal physiological conditions - in athletes, during the circadian rhythm, in pregnancy, and during postnatal development - as well as pathological states - ageing, heart failure, pulmonary hypertension, diabetes and atrial fibrillation. There may be yet more pathological conditions involving changes in the expression of the Hcn genes. Here, we review the role of I_f and the underlying HCN channels in physiological and pathological changes of the sinus and AV nodes and we begin to explore the signalling pathways (microRNAs, transcription factors, GIRK4, the autonomic nervous system and inflammation) involved in this regulation. This review is dedicated to Dario DiFrancesco on his retirement.

Atrioventricular dromotropathy: evidence for a distinctive entity in heart failure with prolonged PR interval?

Heart failure (HF) is often accompanied by atrioventricular (AV) conduction disturbance, represented by prolongation of the PR interval on the electrocardiogram. Studies suggest that PR prolongation exists in at least 10% of HF patients, and it seems more prevalent in the presence of prolonged QRS duration. A prolonged PR interval may result in elevated left ventricular (LV) end-diastolic pressure, diastolic mitral regurgitation, and reduced LV pump function. This seems especially the case in patients with heart disease, in whom it is associated with an increased risk for atrial fibrillation, advanced AV heart block, HF, and death. These findings point towards the importance of proper AV coupling in HF patients. A few studies, strongly differing in design, suggest that restoration of AV coupling in patients with PR prolongation by pacing improves cardiac function and clinical outcomes. These observations argue for AV-dromotropathy as a potential target for pacing therapy, but other studies show inconsistent results. Given its potential clinical implications, restoration of AV coupling by pacing warrants further investigation. Additional possible future research goals include assessing different techniques to measure compromised AV coupling, determine the best site(s) of ventricular pacing, and assess a potential influence of diastolic mitral regurgitation in the efficacy of such therapy.

Heart failure and right ventricular pacing - how to avoid the need for cardiac resynchronization therapy

INTRODUCTION

Heart failure (HF) is a common finding in patients with pacemakers implanted for bradycardia, with cross-sectional and longitudinal studies contributing to the growing consensus that right ventricular pacing can cause adverse cardiac remodeling and left ventricular systolic dysfunction increasing the risk of hospitalization and death. An unselected approach using cardiac resynchronization therapy from the time of first implant in patients with heart block has produced equivocal results. Contemporary research has therefore begun to focus on the stratification of patients' risk of pacemaker-associated impairment to permit focused, personalized management.

AREAS COVERED

The present review will describe the incidence and relevance of HF in the pacemaker population and discuss current management options for such patients.

EXPERT COMMENTARY

At present there are few contemporary data to guide the identification of patients with and at risk of pacemaker-associated cardiac remodeling and dysfunction. Emphasis must be placed on precise and personalized treatment approaches which currently remain under-investigated due to a number of challenges, for example, small sample sizes, limited clarity on programmed settings, and short follow-up periods.

Atrioventricular Conduction Delay Predicts Impaired Exercise Capacity in Patients with Heart Failure with Reduced Ejection Fraction

Background

Atrioventricular conduction delay (AVCD) impairs left ventricular (LV) filling and consequently leads to a reduction of cardiac output. We hypothesized that in patients with severely depressed LV function and coexisting intraventricular conduction disturbances (IVCD), AVCD can affect exercise performance. Therefore, we evaluated the association of AVCD and exercise capacity in patients with heart failure (HFREF) and coexisting IVCD.

Material/Methods

We included patients with stable, chronic HFREF, LVEF <35%, sinus rhythm, and QRS ≥120 ms. PR interval and peak oxygen consumption (VO_{2 peak}) were specifically investigated. Multiple regression analysis was used to adjust the association between PR interval and VO_{2 peak} for possible confounders.

Results

Most (57.5%) of the 40 included patients [20% female, aged 63±12, 47.5% of ischemic etiology (IHD)] were in NYHA class III. Mean PR interval was 196±38.1 ms. There were 26 (65%) patients with PR interval ≤200 ms and 14 (35%) with >200 ms. Groups were similar in clinical, laboratory, echocardiographic parameters, QRS morphology, and treatment regimens. VO_{2 peak} was lower in patients with longer PR interval group as compared to shorter PR interval group (12.3±4.1 vs. 17.06±4.4, p=0.002). In the regression model, PR interval, female sex, and IHD remained important predictors of VO_{2 peak} (_partial=−0.50, p=0.003; r_partial=−0.48, p=0.005; r_partial=−0.44, p=0.01; R²=0.61).

Conclusions

Delayed AV conduction contributes to decreased exercise capacity in patients with HFREF and coexisting IVCD.

Prognostic value of T1-mapping in TAVR patients: extra-cellular volume as a possible predictor for peri- and post-TAVR adverse events

The benefit of a transcatheter aortic valve replacement (TAVR) can differ in patients, and therapy bears severe risks. High-degree aortic stenosis can lead to cardiac damage such as diffuse myocardial fibrosis, evaluable by extra-cellular volume (ECV) in CMR. Therefore, fibrosis might be a possible risk factor for unfavorable outcome after TAVR. We sought to assess the prognostic value of T1-mapping and ECV to predict adverse events during and after TAVR. The study population consisted of patients undergoing clinically indicated TAVR by performing additional CMR with native and contrast-enhanced T1-mapping sequences for additional evaluation of ECV. Study endpoints were congestive heart failure (CHF) and TAVR-associated conduction abnormalities defined as new onset of left bundle branch block (LBBB), AV-Block or implantation of a pacemaker. 94 patients were examined and followed. Median follow up time was 187 days (IQR 79-357 days). ECV was increased (>30 %) in 38 patients (40 %). There was no significant correlation between ECV and death, Hazard ratio (HR) 0.847 (95 % CI 0.335; 2.14), p = 0.72. ECV in patients with subsequent CHF was higher than in those without an event (33.5 ± 4.6 and 29.1 ± 4.1 %, respectively), but the difference just did not reach the level of significance HR 2.16 (95 % CI 0.969; 4.84), p = 0.06. Patients with post-TAVR conduction abnormality (LBBB, AV-block or pacemaker implantation) had statistically relevant lower ECV values compared to those without an event. Patients with an event had a mean ECV of 28.1 ± 3.16 %; patients without an event had a mean ECV of 29.8 ± 4.53, HR 0.56 (95 % CI 0.32; 0.96), p = 0.036. In this study, elevated myocardial ECV is a predictor of CHF by trend; CMR may be helpful in identifying patients with a high risk for post-TAVR cardiac decompensation benefitting from an intensified post-interventional surveillance. Patients with post-TAVR conductions abnormalities have a significantly decreased ECV. Nevertheless, it remains unclear which precise molecular tissue alteration is the protective factor or risk factor in this case.

Outcomes Related to First-Degree Atrioventricular Block and Therapeutic Implications in Patients With Heart Failure

The prevalence of first-degree atrioventricular block in the general population is approximately 4%, and it is associated with an increased risk of atrial fibrillation. Cardiac pacing for any indication in patients with first-degree heart block is associated with worse outcomes compared with patients with normal atrioventricular conduction. Among patients with heart failure, first-degree atrioventricular block is present in anywhere between 15% and 51%. Data from cardiac resynchronization therapy studies have shown that first-degree atrioventricular block is associated with an increased risk of mortality and heart failure hospitalization. Recent studies suggest that optimization of atrioventricular delay in patients with cardiac resynchronization therapy is an important target for therapy; however, the optimal method for atrioventricular resynchronization remains unknown. Understanding the role of first-degree atrioventricular block in the treatment of patients with heart failure will improve medical and device therapy.

Prolongation of atrio-ventricular node conduction in a rabbit model of ischaemic cardiomyopathy: Role of fibrosis and connexin remodelling

Conduction abnormalities are frequently associated with cardiac disease, though the mechanisms underlying the commonly associated increases in PQ interval are not known. This study uses a chronic left ventricular (LV) apex myocardial infarction (MI) model in the rabbit to create significant left ventricular dysfunction (LVD) 8 weeks post-MI. In vivo studies established that the PQ interval increases by approximately 7 ms (10%) with no significant change in average heart rate. Optical mapping of isolated Langendorff perfused rabbit hearts recapitulated this result: time to earliest activation of the LV was increased by 14 ms (16%) in the LVD group. Intra-atrial and LV transmural conduction times were not altered in the LVD group. Isolated AVN preparations from the LVD group demonstrated a significantly longer conduction time (by approximately 20 ms) between atrial and His electrograms than sham controls across a range of pacing cycle lengths. This difference was accompanied by increased effective refractory period and Wenckebach cycle length, suggesting significantly altered AVN electrophysiology post-MI. The AVN origin of abnormality was further highlighted by optical mapping of the isolated AVN. Immunohistochemistry of AVN preparations revealed increased fibrosis and gap junction protein (connexin43 and 40) remodelling in the AVN of LVD animals compared to sham. A significant increase in myocyte–non-myocyte connexin co-localization was also observed after LVD. These changes may increase the electrotonic load experienced by AVN muscle cells and contribute to slowed conduction velocity within the AVN.

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Chronic myocardial infarction (MI) causes changes in atrio-ventricular node (AVN) function.

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Isolated hearts post-MI show delays in ventricular activation due to slowed conduction via the AVN.

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Isolated AVN preparations demonstrated AVN electrical remodelling post-MI.

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Electrical remodelling is associated with fibrosis and altered expression of connexins in the AVN.

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AVN dysfunction post-MI is caused by localized functional and structural remodelling.

Normality index of ventricular contraction based on a statistical model from FADS

Radionuclide-based imaging is an alternative to evaluate ventricular function and synchrony and may be used as a tool for the identification of patients that could benefit from cardiac resynchronization therapy (CRT). In a previous work, we used Factor Analysis of Dynamic Structures (FADS) to analyze the contribution and spatial distribution of the 3 most significant factors (3-MSF) present in a dynamic series of equilibrium radionuclide angiography images. In this work, a probability density function model of the 3-MSF extracted from FADS for a control group is presented; also an index, based on the likelihood between the control group's contraction model and a sample of normal subjects is proposed. This normality index was compared with those computed for two cardiopathic populations, satisfying the clinical criteria to be considered as candidates for a CRT. The proposed normality index provides a measure, consistent with the phase analysis currently used in clinical environment, sensitive enough to show contraction differences between normal and abnormal groups, which suggests that it can be related to the degree of severity in the ventricular contraction dyssynchrony, and therefore shows promise as a follow-up procedure for patients under CRT.

Atrial pacing or ventricular backup-only pacing in implantable cardioverter-defibrillator patients

BACKGROUND

The need for pacing support in typical ICD patients is unknown.

OBJECTIVE

This study sought to determine whether atrial pacing with ventricular backup pacing is equivalent to ventricular backup pacing only in implantable cardioverter-defibrillator (ICD) patients.

METHODS

We randomized 1,030 patients from 84 sites with indications for ICDs, with sinus rhythm, and without symptomatic bradycardia to atrial pacing with ventricular backup at 60 beats/min (518) or ventricular backup pacing at 40 beats/min (512). The primary end points were time to death, heart failure hospitalization (HFH), and heart failure-related urgent care (HFUC).

RESULTS

Follow-up was 2.4 ± 0.8 years when the trial was stopped for futility. There were 355 end point events (103 deaths, 252 HFH/HFUC) in 194 patients favoring ventricular backup pacing (event-free rate 77.7% vs. 80.3% for atrial pacing at 30 months; hazard ratio 1.14, upper confidence bound 1.59, prespecified noninferiority threshold 1.21), therefore equivalence between pacing arms was not demonstrated. Overall HFH/HFUC rates were slightly higher during atrial pacing (event-free rate 85.4% vs. 86.4% for ventricular backup pacing). Exploratory analyses revealed that the difference in HFH/HFUC rates was largely seen in patients with a PR interval ≥230 ms. There were no differences between groups for atrial fibrillation, ventricular tachycardia/ventricular fibrillation, quality of life, or echocardiographic measurements. Fewer patients in the atrial pacing group were reported to develop an indication for bradycardia pacing (3.7% vs. 7.3%, P = .0053).

CONCLUSION

Equivalence between atrial pacing and ventricular backup pacing only could not be demonstrated.

CLINICAL TRIALS IDENTIFIER

NCT00281099.

Lamin A/C gene mutations in familial cardiomyopathy with advanced atrioventricular block and arrhythmia

Lamin A and C proteins, encoded by the lamin A/C gene (LMNA), are inner nuclear membrane proteins predominantly expressed in terminally differentiated cells. Mutations in LMNA can cause various forms of cardiomyopathy with arrhythmia in an autosomal dominant manner. We collected and evaluated the clinical characteristics of unclassified familial cardiomyopathy with advanced AV block and sporadic cases with advanced AV block. Mutation in LMNA was directly screened using the cycle sequencing method in 5 probands of the familial cardiomyopathy and 60 sporadic cases with advanced AV block. In four of the five familial cases (80%), we identified four distinct mutations: two protein-truncation mutations, R225X and 815_818delinsCCAGAC, and two missense mutations, Y259H and R166P. No sporadic cases carried LMNA mutation. Left ventricular end-diastolic diameter (LVEDD) was slightly enlarged in LMNA mutant carriers (123.5 +/- 9.5%) as well as in non-carriers (125.1 +/- 13.3%), while left ventricular fractional shortening (LVFS) was preserved in LMNA mutant carriers (32.3 +/- 4.8%) and non-carriers (37.6 +/- 6.8%). In LMNA mutation carriers, the average age at onset of advanced AV block is significantly lower than that in non-carriers (43.7 +/- 9.5 vs. 65.3 +/- 13 yr., p < 0.01). Ventricular tachycardia, sudden death, and poor prognosis were observed in LMNA mutation carriers. LMNA mutation could cause familial cardiomyopathy with insignificant LV remodeling, early-age onset of advanced AV block, and lethal ventricular arrhythmia. Screening of LMNA mutation might be beneficial for risk stratification and clinical management of this type of unclassified familial cardiomyopathy.

Health-e-Child project: mechanical dyssynchrony in children with dilated cardiomyopathy

OBJECTIVE

Left ventricular mechanical dyssynchrony has been poorly studied in the pediatric population with dilated cardiomyopathy. We investigated the degree of dyssynchrony in children with dilated cardiomyopathy using tissue Doppler imaging and speckle tracking strain.

METHODS

Twenty-five children with dilated cardiomyopathy were compared with healthy subjects. Left ventricular mechanical dyssynchrony was assessed by speckle tracking strain and tissue Doppler imaging. Both radial and longitudinal dyssynchrony were analyzed. Left ventricular end-diastolic diameter was measured to assess the relation between dyssynchrony and ventricular function and remodeling.

RESULTS

Radial and longitudinal dyssynchrony parameters were significantly higher in the dilated cardiomyopathy group and correlated with Z-score left ventricular end-diastolic diameter. A logarithmic correlation between left ventricular ejection fraction and left ventricular end-diastolic diameter parameters was found.

CONCLUSION

In children with dilated cardiomyopathy, tissue Doppler imaging and speckle tracking strain allowed the detection of dyssynchrony, which correlates with the severity of left ventricular function.

Relationship Between Intraventricular Cardiac Asynchrony and Degree of Systolic Dysfunction

OBJECTIVES

Cardiac asynchrony is an area of study becoming more relevant in the evaluation and management of heart failure. Our aim was to determine the prevalence of cardiac asynchrony by Doppler echocardiography and to evaluate its relationship with the degree of left ventricular (LV) systolic dysfunction.

METHODS

A total of 316 consecutive patients with LV ejection fraction less than 40% were enrolled. We divided them into 3 groups according to the degree of LV dysfunction: 31% to 40%, 21% to 30%, and less than 20%. Intraventricular asynchrony was evaluated using two methods: (1) measurement of the septal to posterior wall-motion delay (cut-off point 130 milliseconds); and (2) measurement of the difference between time from Q wave to LV ejection end, and the time from Q wave to the end of the systolic wave of the most delayed basal segment by Doppler tissue imaging (ejection- Doppler tissue imaging time; cut-off point 50 milliseconds).

RESULTS

Mean age was 62.14 +/- 13.5 years (75.7% men). No differences were found among clinical electrical and echocardiographic variables among the groups. Furthermore, no relationship was found between the existence of intraventricular cardiac asynchrony and the degree of LV systolic dysfunction. These were similar in patients with ischemic dilated cardiomyopathy and nonischemic dilated cardiomyopathy.

CONCLUSIONS

The degree of LV systolic dysfunction and its origin are not related to the presence of cardiac asynchrony. A specific echocardiographic Doppler study must always be performed to assess the existence of cardiac asynchrony in those who are candidates to resynchronization therapy.

[Cardiac resynchronization therapy for heart failure - from experimental pacing to evidence-based therapy]

Within the last decade, cardiac resynchronization therapy (CRT) has become an evidence-based cornerstone for a subset of patients with chronic heart failure. For those, who suffer from ischemic or non-ischemic cardiomyopathies at NYHA III or IV, have sinus rhythm, a left bundle branch block and a left ventricular ejection fraction below 35%, CRT has evolved as an important treatment option with promising results. Numerous studies have shown that in these patients pacemaker-mediated correction of intra- and interventicular conduction disturbances can improve not only clinical symptoms, exercise tolerance and the frequency of hospitalizations, but even more important the overall mortality. These clinical results are due to several functional aspects. In the failing heart characteristic intra- and interventricular alterations in electrical conduction result in mechanical asynchrony that leads to an abnormal contraction of the left ventricle with delayed activation of the lateral wall, a paradoxical septal movement, a reduced diastolic filling and a mitral regurgitation due to dyssynchrony of papillary muscle activation. It is conceivable that these functional changes have fatal consequences for the failing heart. AV-optimized left- or biventricular stimulation by modern pacemakers can correct the pathological dyssynchrony, thereby improving cardiac function and clinical outcome in these patients. Although tremendous progress in cardiac resynchronization therapy has been made during the last decade, a couple of questions still need to be resolved. Critical issues are the identification of patients, who will predictably benefit from CRT, the value of CRT-pacemakers versus CRT-ICDs, and the usefullness of CRT in patients with atrial fibrillation.

What can post market registries tell us about the use of cardiac resynchronization therapy?

Cardiac resynchronization therapy (CRT) has become an established therapeutic option for patients with dilated cardiomyopathies and New York Heart Association class III congestive heart failure symptoms who also have a widened QRS complex on their electrocardiograms (generally > 120 ms). Results from a number of clinical trials have shown that CRT improves patients' exercise tolerance, quality of life, and survival. There is further evidence that CRT has structural effects on the heart with improved cardiac function. Despite these salutary results, clinical trials in CRT study prespecified populations that fit the inclusion criteria for these trials. Many patients have been excluded from these clinical trials and yet may potentially benefit from CRT. Evaluation of the effects of CRT on these populations might reveal the potential to expand the use of this therapy in larger numbers of patients to CRT who may not have been included in the clinical trial. This review article will assess the limitations of some of the clinical trials in CRT and will discuss the potential for CRT registries that are presently underway to extend the patient population that may benefit from this therapeutic option.

Cardiac Resynchronization Therapy and Other New Approaches for the Treatment of Heart Failure in the Elderly

Approximately 15% to 20% of patients with systolic heart failure have a QRS duration greater than 120 ms, which is most commonly seen as left bundle-branch block (LBBB). In LBBB, the left ventricle is activated through the septum from the right ventricle, resulting in a significant delay between the onset of right (RV) and left ventricular (LV) contraction. In patients with LV dysfunction, ventricular dyssynchrony caused by LBBB places the already failing left ventricle at an additional mechanical disadvantage. Ventricular dyssynchrony appears to have a deleterious impact on the natural history of heart failure, as a wide QRS complex has been associated with increased mortality in patients experiencing heart failure. On the basis of these observations, investigators hypothesized that patients with LV dysfunction and delayed ventricular conduction would benefit from pacing at sites that achieve a more favorable contraction pattern, and correct interatrial and/or interventricular conduction delays to maintain optimal atrial-ventricular (AV) synchrony. Multiple clinical trials of cardiac resynchronization therapy have demonstrated that it is safe and effective, with patients achieving significant improvement in both clinical symptoms as well as multiple measures of functional status and exercise capacity. Moreover, it has reduced measures of morbidity and mortality in several studies. Thus, cardiac resynchronization therapy should be routinely offered to eligible patients experiencing heart failure.

Genetics of dilated cardiomyopathy

Dilated cardiomyopathy (DCM) is a myocardial disease characterized by dilatation and impaired systolic function of the left or both ventricles. The etiology of DCM is multifactorial, and many different clinical conditions can lead to the phenotype of DCM. During recent years it has become evident that genetic factors play an important role in the etiology and pathogenesis of idiopathic DCM. The genetics of DCM have been under intensive investigation lately, and thereby the knowledge on the genetic basis of DCM has increased rapidly. The genetic background of the disease seems to be relatively heterogeneous, and the disease-associated mutations concern mostly single families and only few affected patients. Disease-associated mutations have been detected e.g. in genes encoding sarcomere, cytoskeletal, and nuclear proteins, as well as proteins involved with regulation of Ca(2+) metabolism. The mechanisms, by which mutations eventually result in clinical heart failure, are complex and not yet totally resolved. DCM causes considerable morbidity and mortality. Better knowledge of the genetic background and disease-causing mechanisms would probably help us in focusing early treatment on right subjects and potentially also developing new treatment modalities and improving cardiac outcome in the affected patients. This review deals with DCM of genetic origin.

Usefulness of clinical, electrocardiographic, and echocardiographic parameters to detect cardiac asynchrony in patients with left ventricular dysfunction secondary to ischemic or nonischemic heart disease

OBJECTIVES

Specific evaluation using echocardiographic Doppler is superior to the measurement of the QRS complex to detect cardiac asynchrony. Nevertheless, no clinical, electrocardiographic, or echocardiographic parameters have been evaluated to obtain an accurate and easy-to-use marker of cardiac asynchrony in patients with depressed left ventricular (LV) ejection fraction. Our aim was to determine whether there is any marker of cardiac asynchrony in patients with LV systolic dysfunction that allows us to obviate the performance of a specific echocardiographic study before cardiac resynchronization therapy.

METHODS

In all, 316 consecutive patients with LV ejection fraction less than 40% were enrolled. Interventricular asynchrony was defined as an interventricular mechanical delay longer than 40 milliseconds. Intraventricular asynchrony was defined as the difference between time from Q wave to LV ejection end and the time from Q wave to the end of the systolic wave of the most delayed basal segment by Doppler tissue imaging greater than 50 milliseconds.

RESULTS

In all, 177 (56%) had ischemic and 139 (44%) had nonischemic heart disease. The logistic regression analysis showed that only the presence of left bundle branch block was an independent predictor of interventricular asynchrony despite the cause of the underlying disease (odds ratio and 95% confidence interval 7.2 [3.9-13.4], P < .001; 5.99 [2.7-13.2], P < .001; and 8.75 [3.2-23.8], P < .001 for the total population, ischemic and nonischemic groups, respectively). Nevertheless, none of the studied parameters was found as a predictor of intraventricular asynchrony.

CONCLUSIONS

The presence of left bundle branch block is a marker of interventricular asynchrony in patients with ventricular dysfunction despite the cause of the underlying cardiac disease. Nevertheless, intraventricular cardiac asynchrony cannot be detected using conventional parameters. A specific echocardiographic evaluation before cardiac resynchronization therapy must be performed in all these patients. Our aim was to determine whether there is any marker of cardiac asynchrony in patients with left ventricular systolic dysfunction that allows us to obviate the performance of a specific echocardiographic study before cardiac resynchronization therapy. Our results showed that only the presence of left bundle branch block was an independent predictor of interventricular asynchrony despite the cause of the underlying disease but none of the studied parameters was found as a predictor of intraventricular asynchrony.

Ventricular dyssynchrony in dilated cardiomyopathy: the role of biventricular pacing in the treatment of congestive heart failure

Despite advances in pharmacologic therapy, the prognosis of patients with advanced congestive heart failure (CHF) remains poor. Many of these patients have cardiac conduction abnormalities, such as left bundle-branch block or interventricular conduction delays, that can lead to ventricular dyssynchrony (abnormal ventricular activation that results in decreased ventricular filling and abnormal ventricular wall motion). Biventricular pacing is an alternative, nonpharmacologic therapy under active investigation for the treatment of CHF. Resynchronization devices with transvenous leads in the right atrium, right ventricle, and left ventricle (via the coronary sinus) have been implanted in patients to provide atrial triggered biventricular pacing. The use of such devices has been associated with improvement in ejection fraction, dP/dt, stroke work, and functional class. The proposed mechanisms involved in improving ventricular function with biventricular pacing include improved septal contribution to ventricular ejection, increased diastolic filling times, and reduced mitral regurgitation. This article reviews the pathophysiology of ventricular dyssynchrony and examine insights from clinical trials that are evaluating cardiac resynchronization therapy for CHF.

Cardiac resynchronization therapy: redefining the role of device therapy in heart failure

That cardiac dyssynchrony can contribute to a decline in cardiac efficiency has been recognized in one form or another for at least 50 years. Although revascularization and beta-blockers can improve cardiac synchrony, there was little interest in or awareness of this clinical entity until the advent of specific, highly effective therapy using atriobiventricular pacing, often described as cardiac resynchronization therapy. Over the last few years, significant advances in cardiac resynchronization therapy technology and the publication of large-scale clinical trials using cardiac resynchronization therapy devices in patients with heart failure have led to the widespread use of these devices. This review will briefly describe the complex nature of cardiac dyssynchrony, what is known about its epidemiology, the effects of cardiac resynchronization therapy, appropriate patient selection, practical aspects, such as implantation and monitoring, and some still unanswered questions.

[Is standard-echocardiography sufficient for identification of responders?]

During recent years cardiac re-synchronization has become an important tool in the treatment of patients with signs and symptoms of heart failure and de-synchronized contraction of the heart. This article describes the pathophysiological basis of de-synchronized contraction due to left bundle branch block and the use of conventional echocardiography to unmask whether the electrical abnormality is accompanied by an asynchronous contraction in the individual patient. The altered contraction in the de-synchronized heart is analysed on different levels: atrioventricular dyssynchrony describes the disturbed mechanical coupling of the ventricles and atria, interventricular dyssynchrony describes the disturbed mechanical coupling of the left and right ventricle, and intraventricular dyssynchrony describes the uncoordinated contraction of the left ventricle. Since tissue Doppler imaging is implemented only in the top level echo machines of the respective manufacturers, this article uses parameters derived from standard echo techniques to analyse the different aspects of dyssynchrony.

Cardiac resynchronization therapy and tools to identify responders

Heart failure is a major epidemic. Many people with heart failure struggle with refractory symptoms despite optimal medical therapy. Those with severe left ventricular dysfunction and ventricular conduction delay are at significant risk from either dying suddenly or dying from progression of their heart failure. Cardiac resynchronization therapy (CRT) improves hemodynamics and symptoms of heart failure and has recently been shown to improve survival. One problem facing the use of CRT is that 30% of patients fail to respond. The dominant theory is that QRS duration (electrical dyssynchrony) does not accurately reflect mechanical dyssynchrony. Echocardiographic tools have recently been developed that enable clinicians to assess the degree of mechanical dyssynchrony in patients being considered for CRT. These tools are able to predict with a significant amount of accuracy whether a patient will respond to CRT. This allows for a more refined approach to evaluating patients for CRT and optimizing the treatment of congestive heart failure.

Response of the ECG to short-term diuresis in patients with heart failure

BACKGROUND

Increase in the amplitude of electrocardiogram (ECG) QRS complexes has been observed in patients treated for heart failure (HF), but the underlying mechanism has not been delineated. Also, correlation of augmentation of the QRS potentials with loss of weight has been noted in patients recovering from anasarca of varying etiology, or after hemodialysis. We assessed the effect of diuresis-based fluid loss in patients treated for HF on the amplitude of ECG QRS complexes.

METHODS

This is a cohort study based on ECG and other data from a previously published investigation of patients with HF conducted at a university affiliated hospital, which used new measurements and analysis, performed by a totally blinded investigator based at another institution. Twenty-one patients (10 men) aged 70.5+/-12.7 years, 13 with ischemic, and 8 with nonischemic cardiomyopathy, were admitted to the hospital for management of exacerbated HF and were observed for 48 hours. The patients received diuresis, and had routine laboratory testing, documentation of the net fluid lost, and recording of ECGs prior to the initiation of therapy and at 24 and 48 hours. Percent change (%Delta) over the course of observation in the sums of the amplitude of QRS complexes from 12 leads (SigmaQRS12), 6-limb leads (SigmaQRS6), and leads 1+2 (SigmaQRS2) in mm of standard ECGs were correlated with net fluid loss corrected for admission weight in mL/kg.

RESULTS

Fluid loss amounted to 3204.9+/-1399.5 mL in the course of 40+/-23 hours of diuresis. SigmaQRS12 was 160.9+/-42.3 mm before and 170.0+/-50.7 mm after diuresis (P=0. 024). Percent change in SigmaQRS12, SigmaQRS6, and SigmaQRS2 correlated well with the net fluid loss (r=-0.70, -0.82, -0.61, and P=0.002, 0.0005, 0.001) correspondingly.

CONCLUSION

Changes in sums of the amplitude of QRS complexes of the standard ECG correlates well with net fluid loss in response to short-term diuresis in patients with HF. Change in the SigmaQRS12, SigmaQRS6, and SigmaQRS2 from ECGs before and after diuresis can be used as an easily obtainable and universally available bedside index of the net fluid loss experienced by bedridden patients with HF undergoing therapy.

Cardiac resynchronization therapy in pediatrics: Emerging technologies for emerging indications

Cardiac resynchronization therapy (CRT) has become the standard of care for the treatment of heart failure in adults with decreased ventricular function and conduction delay who remain symptomatic despite optimal medical therapy. Indications for CRT in adults include medically refractory heart failure with a QRS duration of >or=120 msec and a left ventricular end-diastolic dimension of >or=55 mm with ejection fraction <or=35%. No such consensus guidelines exist in pediatrics; however, recent preliminary data indicate that CRT is effective therapy for symptomatic heart failure in children in both the acute postoperative setting as well as in the ambulatory setting. CRT is a viable therapeutic option in children with decreased ventricular function and ventricular conduction delay. It is preferable to high-dose inotropic therapy and should be given serious consideration for the treatment of refractory heart failure prior to proceeding with heart transplantation.

Color Doppler tissue velocity imaging can disclose systolic left ventricular asynchrony independent of the QRS morphology in patients with severe heart failure

A QRS width greater than 120 ms is assumed to be a marker of inter- and intraventricular asynchrony in severe heart failure (HF) patients. Color Doppler tissue velocity imaging (c-TVI) with a time resolution of 10 ms was used to study regional left ventricular (LV) longitudinal systolic contraction pattern in HF patients with left and right bundle branch block (LBBB and RBBB) and in patients with normal QRS width. We studied 12 women and 23 men with severe HF, with a mean age of 66 +/- 11 years in New York Heart Association functional Class 2.9 +/- 0.6. Twenty patients had LBBB and 10 of those were accepted for cardiac resynchronization therapy by biventricular pacing (CRT). Ten patients had normal QRS width, and five had RBBB. In the echocardiographic apical four chamber view, regional peak LV tissue velocities and regional LV time differences of peak tissue velocities were compared at basal and mid-LV segments. There were no significant differences in regional mean peak tissue velocities among the patient groups. In patients with LBBB accepted for CRT, the LV lateral free-wall movement at basal LV was 29 ms delayed during main systole, almost significantly different from LBBB patients not accepted for CRT (P = 0.075). Even in HF patients with normal QRS width or RBBB, significant asynchronous longitudinal LV contraction was observed.

CONCLUSIONS

For the detection of regional longitudinal LV contraction asynchrony in patients with severe HF, supplementary methods to the surface ECG, such as c-TVI, are strongly recommended.

Update of implantable cardioverter/defibrillator and cardiac resynchronization therapy in heart failure

PURPOSE OF REVIEW

Heart failure prevalence is reaching epidemic proportion in the United States and is associated with significant morbidity and mortality. A large proportion of the mortality is the result of sudden cardiac death (SCD). Clinical trials have demonstrated the superiority of the implantable cardioverter/defibrillator (ICD) compared with antiarrhythmic drugs for secondary prevention of sudden cardiac death.

RECENT FINDINGS

Recently, several clinical trials in primary prevention of sudden cardiac death in both ischemic and nonischemic heart failure have been completed. The 2002 guidelines for implantable cardioverter/defibrillator implantation were recently released as well. Adjunct therapy consisting of antiarrhythmic drugs or radiofrequency ablation is necessary in the subset of patients with implantable cardioverter/defibrillator that have frequent or intractable ventricular arrhythmias. An emerging new therapy in the heart failure population is cardiac resynchronization therapy, which coordinates right and left ventricular pacing in a subset of patients with interventricular conduction delay.

SUMMARY

Several randomized clinical trials have demonstrated improvements in heart failure-related symptoms, exercise tolerance, and reversal of ventricular remodeling. Meta-analysis of these trials has also demonstrated mortality benefit. Patient selection, left ventricular pacing site, and optimal device programming are issues that need further investigation. Recent trials have also studied the compatibility between cardiac resynchronization therapy and implantable cardioverter/defibrillator as a single device. Finally, the DAVID trial has raised concerns of conventional right ventricular pacing and the risk of heart failure in a subset of patients.

Cardiac resynchronization by pacing: an electrical treatment of heart failure

Various modalities of cardiac pacing have been proposed in the past to improve hemodynamics, either directly or indirectly. Some of these are conventional ways of cardiac stimulation, others such as biventricular or left ventricular pacing, represent dedicated pacing techniques. Left ventricular and biventricular pacing are successfully applied in those patients with congestive heart failure who have conduction disturbances (i.e. left bundle branch block) as they correct the ensuing intra- and interventricular dyssynchrony. This is the reason why these pacing modalities are described as cardiac resynchronization therapy. According to the results of a series of studies, the cardiac resynchronization therapy seems to have a favourable clinical impact in terms of quality of life, morbidity and hospitalization rate. On-going and future studies should assess the impact of resynchronization therapy on overall mortality and its cost-effectiveness profile in specific subgroups of patients. Other open issues regard (i) the convenience of using biventricular pacing as a pacing-alone therapy or in combination with ventricular defibrillation capability, especially for potential candidates to heart transplantation, and (ii) the ways to identify properly the responders to resynchronization therapy.

Cardiac Resynchronization Therapy for Heart Failure Management

Heart failure (HF) is responsible for an immense burden on our healthcare system. The prevalence of this disease continues to increase as a result of an aging population, successful treatment of acute coronary syndrome, and the use of new pharmacotherapies. Although pharmacotherapy with angiotensin converting enzyme inhibitors and beta-blockers shows improvement in morbidity and mortality, the overall prognosis of these patients remains poor. Cardiac transplant has limited applicability. Conduction disturbances are frequent in patients with advanced heart failure and may cause worsening systolic function and ventricular dyssynchrony. Biventricular pacing to achieve cardiac resynchronization is a recent and promising therapy for HF patients with an intraventricular conduction defect. Randomized clinical trials have substantiated that cardiac resynchronization therapy (CRT) through biventricular pacing offers significant benefit in morbidity and mortality in a select group of HF patients. Because of the high incidence of sudden cardiac death in patients with severe HF, the combination biventricular pacing with implantable cardioverter defibrillator therapy will provide additional benefit. This article provides an overview of CRT with the intent of describing ventricular dyssynchrony, the benefits of CRT, and the implications for advanced practice nurses.

QRS duration: a simple marker for predicting cardiac mortality in ICD patients with heart failure

BACKGROUND

Patients resuscitated from ventricular tachyarrhythmias benefit from implantable cardioverter-defibrillators (ICDs) as opposed to medical treatment. Patients with increased QRS duration receiving an ICD in the presence of heart failure are at greatest risk of cardiac death and benefit most from ICD therapy.

OBJECTIVE

To determine whether an increased QRS duration predicts cardiac mortality in ICD recipients.

DESIGN

Consecutive patients with heart failure in New York Heart Association functional class III were grouped according to QRS duration (< 150 ms, n = 139, group 1; v > or = 150 ms, n = 26, group 2) and followed up for (mean (SD)) 23 (20) months.

PATIENTS

165 patients were studied (80% men, 20% women); 73% had coronary artery disease and 18% had dilated cardiomyopathy. Their mean age was 62 (10) years and mean ejection fraction (EF) was 33 (14)%. They presented either with ventricular tachycardia (VT) or ventricular fibrillation (VF).

MAIN OUTCOME MEASURES

Overall and cardiac mortality; recurrence rates of VT, fast VT, or VF.

RESULTS

Mean left ventricular EF did not differ between group 1 (33 (13)%) and group 2 (31 (15)%). Forty patients died (34 cardiac deaths). There was no difference in survival between patients with EF > 35% and < or = 35%. Cardiac mortality was significantly higher in group 2 than in group 1 (31.3% at 12 months and 46.6% at 24 months, v 9.5% at 12 months and 18.2% at 24 months, respectively; p = 0.04). The recurrence rate of VT was similar in both groups.

CONCLUSIONS

Within subgroups at highest risk of cardiac death, QRS duration-a simple non-invasive index-predicts outcome in ICD recipients in the presence of heart failure.

Colour tissue velocity imaging can show resynchronisation of longitudinal left ventricular contraction pattern by biventricular pacing in patients with severe heart failure

OBJECTIVE

To quantify ventricular resynchronisation by biventricular pacing using colour tissue Doppler velocity imaging (c-TVI).

DESIGN AND PATIENTS

c-TVI shows regional tissue velocity profiles with a very high time resolution (10 ms). Eighteen patients were studied from an apical four chamber view at baseline and after a one month follow up of biventricular pacing. Regional left ventricular peak tissue velocities and regional time differences during the cardiac cycle were compared in the basal and mid interventricular septal segments of the left ventricle, and in the corresponding segments in the left ventricular free wall.

RESULTS

From baseline to follow up, mean peak tissue velocities changed only during isovolumic contraction in the basal interventricular septum and the left ventricular free wall. At baseline the peak main systolic tissue velocities in the left ventricular free wall were typically delayed by an average of 42 ms in the basal left ventricular site and by 14 ms in the mid left ventricular site compared with the corresponding sites in the interventricular septum. After resynchronisation by biventricular pacing those regional movements were separated by an average of only 7 ms at the basal site, but there was still a 21 ms earlier movement of the left ventricular free wall in the mid left ventricular site. The diastolic movement pattern remained unchanged from baseline to follow up.

CONCLUSIONS

c-TVI showed a significant asynchronous regional longitudinal movement of basal left ventricular sites at baseline. A change to a more synchronous longitudinal left ventricular movement pattern during biventricular pacing was demonstrated.

Cardiac resynchronization therapy: overcoming ventricular dyssynchrony in dilated heart failure

Despite optimal medical therapy, dilated heart failure is associated with a dismal prognosis and relentless progression. Intraventricular conduction delay or bundle branch block is a marker of heart failure progression and worsening prognosis. Patients fitting this profile have been shown to benefit from a specific form of cardiac pacing now referred to as cardiac resynchronization therapy (CRT). This monograph is an in-depth review of the theory and consequences of ventricular dyssynchrony in dilated heart failure, and provides an overview of the major clinical trials of CRT. Practical considerations for achieving ventricular resynchronization are discussed, with an emphasis on biventricular pacing.

Heart failure patients with ventricular dysynchrony: management with a cardiac resynchronization therapy device

Despite an array of treatment modalities, the overall prognosis for patients with severe heart failure remains bleak. Biventricular pacing, or cardiac resynchronization therapy, is gaining increasing acceptance as a compelling treatment for those individuals with advanced heart failure (New York Heart Association functional class III or IV). This article provides a brief description of the atrial and ventricular conduction disturbances common in patients with advanced heart failure. Current indications for therapy are outlined, as are recent results of cardiac resynchronization therapy trials. The implant procedure is described to provide a comprehensive overview of this innovative approach to re-establishing normal electromechanical activity and synchronous right and left ventricular contractions. Patient care, before and after device implant, is also summarized. The focus on patient education throughout this article may allow it to serve as a reference for health care providers involved in the care of patients with severe heart failure.

Septal q waves as an indicator of risk of mortality in elderly patients with chronic heart failure

BACKGROUND

The absence of electrocardiographic septal q wave is a recognized marker of left ventricular disease. We aimed to investigate the prognostic significance of absent septal q waves in elderly (age >65 years) patients with chronic heart failure.

METHODS

A total of 110 patients (mean age 73 +/- 4 years) with New York Heart Association functional class II to IV and left ventricular ejection fraction of <45% were enrolled in the study. Standard 12-lead electrocardiograms were critically analyzed for the presence or absence of septal q waves in leads I, aVL, V5, and V6. Patient survival was determined from hospital and general practitioner records and National Statistics Registry at a mean follow-up of 4 years.

RESULTS

Septal q waves were absent in 71 and present in 39 patients. The overall mortality rate was 47% (43 patients). The incidence of death was 49% (36 patients) in the group with no septal q waves and 18% (7 patients) in those who demonstrated septal q waves. On univariate analysis by Cox proportional hazard method, absence of septal q waves was found to be a strong marker of poor prognosis in CHF (P =.003, hazard ratio 1.40, 95% CI 1.10-1.67). Kaplan-Meier survival curves showed a significant difference in survival independent of age, New York Heart Association functional class, peak VO2, and QRS duration between these 2 groups.

CONCLUSIONS

Absence of the normal septal q wave on 12-lead electrocardiography, which may indicate structural heart disease and myocardial fibrosis, is an independent predictor of poor prognosis in elderly patients with CHF.

Predictors of appropriate implantable cardioverter-defibrillator therapy in patients with idiopathic dilated cardiomyopathy

Evaluating predictors of appropriate implantable cardioverter-defibrillator (ICD) therapy in patients with idiopathic dilated cardiomyopathy (IDC) may be helpful in developing risk stratification strategies for these patients. Fifty-four patients with IDC underwent ICD implantation and were followed up. Twenty-three patients (42%) had a class I indication for ICD implantation; the remaining patients underwent implantation for multiple risk factors for sudden death including left ventricular dysfunction, nonsustained ventricular tachycardia, syncope, or positive electrophysiologic study results. Clinical, electrocardiographic, and electrophysiologic data were collected. Appropriate ICD therapy was defined as an antitachycardia pacing therapy or shock for tachyarrhythmia determined to be either ventricular tachycardia or ventricular fibrillation. Appropriate ICD therapy was observed in 23 patients (42%). There was a significant difference in use of beta-blocker therapy between patients who did and did not have appropriate ICD therapy (p <0.0003). Cox regression analysis identified the following univariate predictors (p <0.1): class I indication (p <0.005) and lack of use of beta-blocker therapy (p <0.0007). In multivariate analysis, only lack of beta-blocker use (relative risk 0.15, 95% confidence intervals 0.05 to 0.45; p <0.0007) was identified as a predictor of appropriate ICD therapy. Of the patients who received ICD therapy, only 4 (17%) were taking beta blockers, whereas 21 of the 31 patients (68%) who did not receive ICD therapy were treated with beta blockers (p <0.0003). In patients with IDC selected for ICD implantation, the most consistent predictor of appropriate ICD therapy was lack of beta-blocker use. Attempts should be made to administer beta blockers to these patients, if tolerated.

Outcome studies with device therapy in patients with heart failure

Heart failure is a common debilitating condition for which pharmacologic therapy thus far has provided only partial relief. Despite, and sometimes because of, medical therapy, the overall prognosis remains poor, with high rates of sudden death and death from progressive heart failure. Device-based therapies offer considerable promise for relief of symptoms and for improving prognosis. It is clear that implantable defibrillators should be considered for patients with heart failure who have been resuscitated from ventricular fibrillation or sustained ventricular tachycardia. Several large studies currently are investigating the effects of implantable defibrillators on total mortality in patients with major left ventricular systolic dysfunction but without other risk factors for sudden death. Cardiac resynchronization is a promising new therapy that may relieve the symptoms of heart failure in appropriately selected patients resistant to optimal pharmacologic therapy. Two large trials (CARE-HF and COMPANION) currently are investigating the effects of cardiac resynchronization therapy (CRT) on morbidity and mortality. It is important that those involved in these trials enroll patients quickly and minimize device implantation into patients who have not been assigned this therapy (cross-overs). Overenthusiasm for the benefits that doctors believe devices might bring could destroy the future basis for our clinical practice, denying future generations of patients and the doctors themselves access to what they believe to be effective treatments.

Implantable cardioverter defibrillators in heart failure

Implantable cardioverter defibrillators provide effective and reliable treatment of spontaneous VT and VF. These devices can be expected to decrease the risk for arrhythmic death in patients with heart failure but do not improve overall survival when death from severe pump dysfunction is imminent. Appropriate patient selection is a major aspect of arrhythmia management. Future devices will incorporate features that have the potential to reduce atrial arrhythmias, improve ventricular function, monitor hemodynamics, and prevent sudden arrhythmic death.

Cardiac resynchronization: a novel therapy for heart failure

Despite advances in medical therapy for patients with congestive heart failure, morbidity and mortality remain high. Conduction abnormalities, such as left bundle branch block, right bundle branch block, and nonspecific conduction delay, are observed commonly in patients with dilated cardiomyopathy. In patients with heart failure, the presence of intraventricular conduction delay is associated with more severe mitral regurgitation and worsened left ventricular systolic and diastolic function, and is an independent risk factor for increased mortality. Conventional dual-chamber (right atrial and right ventricular) pacing with a short atrioventricular delay was initially introduced as therapy for patients with advanced congestive heart failure to improve diastolic dysfunction and reduce mitral regurgitation. The acute beneficial hemodynamic effects observed in early, uncontrolled studies were not confirmed in subsequent randomized, controlled studies with longer follow-up. Cardiac resynchronization with novel biventricular (left and right ventricular) pacing systems has resulted in hemodynamic and functional benefits in patients with congestive heart failure and an underlying intraventricular conduction delay. Improvements in cardiac index, systolic blood pressure, and functional class have been reported with biventricular pacing, both acutely and at more than 1 year of follow-up. These encouraging preliminary results with biventricular pacing in patients with congestive heart failure will be validated in two prospective, randomized, controlled trials, Multicenter InSync Randomized Clinical Evaluation (MIRACLE) and Comparison of Medical Therapy, Pacing, and Defibrillation in Chronic Heart Failure (COMPANION). These studies are designed to evaluate the long-term efficacy of biventricular pacing in improving exercise capacity and in reducing morbidity and mortality in patients with advanced, symptomatic congestive heart failure. (c)2001 by CHF, Inc.

Electrotherapeutic management of patients with heart failure

Heart failure is associated with poor long term survival due to progressive refractory heart dysfunction and sudden cardiac death. Cardiac resynchronization through atrio-biventricular pacing has been introduced to treat patients affected by drug-refractory heart failure with desynchronized ventricular activation, as for complete left bundle branch block. The technique is aimed to overcome interventricular and intraventricular conduction delays leading to ventricular dysynchrony, paradoxical septal wall motion, presystolic mitral regurgitation and reduced diastolic filling times. Short term studies demonstrated that biventricular pacing (and perhaps left ventricular pacing alone) may improve both systolic and diastolic function. Initial studies in patients receiving long term pacing consistently showed significant QRS shortening associated with improvement in symptoms, left ventricular ejection fraction, exercise tolerance, quality of life and New York Heart Association functional class. As far as sudden cardiac death prevention in heart failure is concerned, implantable cardioverter defibrillator (ICD) implantation has been demonstrated to be the most effective therapy in patients with prior cardiac arrest due to ventricular fibrillation or poorly tolerated ventricular tachycardia. Low left ventricular ejection fraction, unsustained ventricular tachycardia and inducibility at electrophysiological study also may identify high risk patients requiring ICD implantation. Further studies are needed to evaluate the effect of cardiac resynchronization on hard end-points, such as survival and long term clinical outcome, and to upgrade risk stratification criteria to be used in selection of candidates for ICD implantation.

A pilot experience with permanent biventricular pacing to treat advanced heart failure

BACKGROUND

The prognosis and quality of life of patients with advanced heart failure remain poor. The purpose of this study was to evaluate new nonpharmacologic approaches. Biventricular pacing was proposed in this indication, based on the encouraging results of acute hemodynamics studies.

METHODS

Fifty patients with drug-resistant heart failure (New York Heart Association [NYHA] class III/IV, 16 of 34) were consecutively implanted with biventricular pacemakers. All patients had severe dilated cardiomyopathy and intraventricular conduction delay. Survival, NYHA class, electrocardiogram, echocardiographic data, and exercise tolerance were assessed over a mean follow-up period of 15.4 +/- 10. 2 months.

RESULTS

At the end of follow-up, 55% of patients were alive without heart transplantation or left ventricular assistance device. The mortality rate was significantly lower in class III (12. 5%) than in class IV patients (52.5%). In survivors, biventricular pacing significantly improved symptoms (NYHA class 2.2 +/- 0.5 at follow-up vs 3.7 +/- 0.5 at baseline) and exercise tolerance ((. )VO(2) peak 15.5 +/- 3.4 mL/min per kilogram at follow-up vs 11.1 +/- 3 mL/min per kilogram at baseline).

CONCLUSIONS

Biventricular pacing appears to improve the functional status of patients with dilated cardiomyopathy with advanced heart failure. The technique appears to be attractive as an additive treatment, especially in class III patients. Controlled randomized studies are needed to validate this novel concept.

Should stimulation site be tailored in the individual heart failure patient?

Right ventricular pacing at various sites and shortened atrioventricular (AV) delay has failed to demonstrate a convincing short-term and long-term improvement of left ventricular function. Left-ventricular-based stimulation offers a new therapeutic option for patients with symptomatic congestive heart failure and conduction disturbances, especially of left bundle-branch block configuration. Left ventricular mechanical improvement seems mainly dependent on the pacing site, in addition to optimizing the AV delay. Predominantly retrospective data suggest that pacing the posterolateral free wall results in the greatest hemodynamic improvement. Based on the evaluation of different pacing sites in 2 patients, we noted that site is of major importance for maximal improvement of left ventricular function, and pacing at a suboptimal site can even deteriorate left ventricular contractility. Moreover, lead technology has advanced rapidly and different areas of the left ventricle can now be reached transvenously for acute and chronic placement. Therefore, ongoing trials will help to identify the optimal pacing site and might indicate whether invasive testing will be required in the future.