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

Emerging Technologies in Cardiac Pacing

Cardiac pacing to treat bradyarrhythmias has evolved in recent decades. Recognition that a substantial proportion of pacemaker-dependent patients can develop heart failure due to electrical and mechanical dyssynchrony from traditional right ventricular apical pacing has led to development of more physiologic pacing methods that better mimic normal cardiac conduction and provide synchronized ventricular contraction. Conventional biventricular pacing has been shown to benefit patients with heart failure and conduction system disease but can be limited by scarring and fibrosis. His bundle pacing and left bundle branch area pacing are novel techniques that can provide more physiologic ventricular activation as an alternative to conventional or biventricular pacing. Leadless pacing has emerged as another alternative pacing technique to overcome limitations in conventional transvenous pacemaker systems. Our objective is to review the evolution of cardiac pacing and explore these new advances in pacing strategies.

Progress in Cardiac Resynchronisation Therapy and Optimisation

Cardiac resynchronisation therapy (CRT) has become the cornerstone of heart failure (HF) treatment. Despite the obvious benefit from this therapy, an estimated 30% of CRT patients do not respond ("non-responders"). The cause of "non-response" is multi-factorial and includes suboptimal device settings. To optimise CRT settings, echocardiography has been considered the gold standard but has limitations: it is user dependent and consumes time and resources. CRT proprietary algorithms have been developed to perform device optimisation efficiently and with limited resources. In this review, we discuss CRT optimisation including the various adopted proprietary algorithms and conduction system pacing.

Cardiac resynchronization therapy: present and future

Cardiac resynchronization therapy (CRT) via biventricular pacing (BVP) is a well-established therapy for patients with heart failure with reduced ejection fraction and left bundle branch block, who remain symptomatic despite optimal medical therapy. Despite the long-standing clinical evidence, as well as the familiarity of cardiac electrophysiologists with the implantation technique, CRT via BVP cannot be achieved or may result ineffective in up to one-third of the patients. Therefore, new alternative techniques, such as conduction system pacing and left ventricular pacing, are emerging as potential alternatives to this technique, not only in case of BVP failure, but also as a stand-alone first choice due to several potential advantages over traditional CRT. Specifically, due to its procedural characteristics, left bundle branch area pacing appears to be the most convincing technique, showing comparable efficacy outcomes when compared with traditional CRT, not increasing short-term device-related complications, as well as improving procedural times. However, transvenous leads remain a major limitation of all these pacing modalities. To overcome this limit, a leadless left ventricular endocardial pacing has been developed as an additional tool to achieve a left endocardial activation, although being still associated with non-negligible pitfalls, limiting its current use in clinical practice. This article focuses on the current state and latest progresses in cardiac resynchronization therapy.

Adverse effects of right ventricular pacing on cardiac function: prevalence, prevention and treatment with physiologic pacing

Right ventricular (RV) pacing is the main treatment modality for patients with advanced atrioventricular (AV) block. Chronic RV pacing can cause cardiac systolic dysfunction and heart failure (HF). In this review, we discuss studies that have shown deleterious effects of chronic RV pacing on systolic cardiac function causing pacing-induced cardiomyopathy (PiCM), heart failure (HF), HF hospitalization, atrial fibrillation (AF) and cardiac mortality. RV apical pacing is the most widely used and studied. Adverse effects of RV pacing appear to be directly related to pacing burden and are worse in patients with pre-existing left ventricular (LV) dysfunction. Chronic RV pacing is also associated with heart failure with preserved ejection fraction (HFpEF). Mechanisms, risk factors, clinical and echocardiographic features, and strategies to minimize RV pacing-induced cardiac dysfunction are discussed in light of the latest data. Studies on biventricular (Bi-V) pacing upgrade in patients who develop RV PiCM, use of alternate RV pacing sites, de novo Bi-V pacing, and physiologic pacing using HIS bundle pacing (HBP) and left bundle area (LBBA) pacing in patients with an anticipated high RV pacing burden are discussed.

Graphene Oxide-Gold Nanosheets Containing Chitosan Scaffold Improves Ventricular Contractility and Function After Implantation into Infarcted Heart

Abnormal conduction and improper electrical impulse propagation are common in heart after myocardial infarction (MI). The scar tissue is non-conductive therefore the electrical communication between adjacent cardiomyocytes is disrupted. In the current study, we synthesized and characterized a conductive biodegradable scaffold by incorporating graphene oxide gold nanosheets (GO-Au) into a clinically approved natural polymer chitosan (CS). Inclusion of GO-Au nanosheets in CS scaffold displayed two fold increase in electrical conductivity. The scaffold exhibited excellent porous architecture with desired swelling and controlled degradation properties. It also supported cell attachment and growth with no signs of discrete cytotoxicity. In a rat model of MI, in vivo as well as in isolated heart, the scaffold after 5 weeks of implantation showed a significant improvement in QRS interval which was associated with enhanced conduction velocity and contractility in the infarct zone by increasing connexin 43 levels. These results corroborate that implantation of novel conductive polymeric scaffold in the infarcted heart improved the cardiac contractility and restored ventricular function. Therefore, our approach may be useful in planning future strategies to construct clinically relevant conductive polymer patches for cardiac patients with conduction defects.

A comparison of the different features of quadripolar left ventricular pacing leads to deliver cardiac resynchronization therapy

INTRODUCTION

Cardiac Resynchronization therapy (CRT) improves the quality of life and reduces morbidity and mortality of certain patients with heart failure. However, not all patients respond positively after CRT and about one third of cases do not experience benefit. Suboptimal biventricular pacing may account for this and quadripolar left ventricular (LV) leads have emerged in the last years to address issues relating to inadequate delivery of CRT.

AREAS COVERED

This review article concisely summarizes the main technical characteristics of the quadripolar LV leads either currently available in the market today or under final stages of development. Focus is given in recent advancements in the area and challenging aspects and controversies, future implications as well as opportunities for further development.

EXPERT COMMENTARY

Quadripolar LV pacing leads have now become the standard of care in CRT. Currently a multitude of lead options is available to the clinician. The selection process of the most appropriate lead is far from the 'one size fits all' concept. Further development of quadripolar LV leads is currently ongoing and it is anticipated to contribute towards the release of more technologically advantageous leads which will enable the delivery of optimal CRT therapy with the lowest rate of complications.

Cardiac Resynchronization Therapy: An Overview on Guidelines

Cardiac resynchronization therapy (CRT) is included in international consensus guidelines as a treatment with proven efficacy in well-selected patients on top of optimal medical therapy. Although all the guidelines strongly recommend CRT for LBBB with QRS duration greater than 150 milliseconds, lower strength of recommendation is reported for QRS duration of 120 to 150 milliseconds, especially if not associated with LBBB. CRT is not recommended for a QRS of less than 120 milliseconds. No indication emerges for guiding the implant based on echocardiographic evaluation of dyssynchrony. Many data indicate that CRT is underused and there is heterogeneity in its implementation.

Cardiac Resynchronization Therapy: An Overview on Guidelines

Cardiac resynchronization therapy (CRT) is included in international consensus guidelines as a treatment with proven efficacy in well-selected patients on top of optimal medical therapy. Although all the guidelines strongly recommend CRT for LBBB with QRS duration greater than 150 milliseconds, lower strength of recommendation is reported for QRS duration of 120 to 150 milliseconds, especially if not associated with LBBB. CRT is not recommended for a QRS of less than 120 milliseconds. No indication emerges for guiding the implant based on echocardiographic evaluation of dyssynchrony. Many data indicate that CRT is underused and there is heterogeneity in its implementation.

Effect of study design on the reported effect of cardiac resynchronization therapy (CRT) on quantitative physiological measures: stratified meta-analysis in narrow-QRS heart failure and implications for planning future studies

Background

Biventricular pacing (CRT) shows clear benefits in heart failure with wide QRS, but results in narrow QRS have appeared conflicting. We tested the hypothesis that study design might have influenced findings.

Method and Results

We identified all reports of CRT‐P/D therapy in subjects with narrow QRS reporting effects on continuous physiological variables. Twelve studies (2074 patients) met these criteria. Studies were stratified by presence of bias‐resistance steps: the presence of a randomized control arm over a single arm, and blinded outcome measurement. Change in each endpoint was quantified using a standardized effect size (Cohen's d). We conducted separate meta‐analyses for each variable in turn, stratified by trial quality. In non‐randomized, non‐blinded studies, the majority of variables (10 of 12, 83%) showed significant improvement, ranging from a standardized mean effect size of +1.57 (95%CI +0.43 to +2.7) for ejection fraction to +2.87 (+1.78 to +3.95) for NYHA class. In the randomized, non‐blinded study, only 3 out of 6 variables (50%) showed improvement. For the randomized blinded studies, 0 out of 9 variables (0%) showed benefit, ranging from −0.04 (−0.31 to +0.22) for ejection fraction to −0.1 (−0.73 to +0.53) for 6‐minute walk test.

Conclusions

Differences in degrees of resistance to bias, rather than choice of endpoint, explain the variation between studies of CRT in narrow‐QRS heart failure addressing physiological variables. When bias‐resistance features are implemented, it becomes clear that these patients do not improve in any tested physiological variable. Guidance from studies without careful planning to resist bias may be far less useful than commonly perceived.

Cardiac resynchronization therapy in patients with chronic Chagas cardiomyopathy: long-term follow up

INTRODUCTION

Chagas disease is a major cause of cardiomyopathy and sudden death in our country. It has a high mortality when their patients develop New York Heart Association (NYHA) class IV.

OBJECTIVE

The objective of this study is to analyze the clinical outcome of patients with Chagas' cardiomyopathy with congestive heart failure with optimized pharmacological therapy, undergoing cardiac resynchronization therapy.

METHODS

Between January 2004 and February 2009, 72 patients with Chagas' cardiomyopathy in NYHA class III and IV underwent cardiac resynchronization therapy and were monitored to assess their clinical evolution. We used the t test or the Wilcoxon test to compare the same variable in two different times. A P value < 0.05 was established as statistically significant.

RESULTS

The average clinical follow-up was 46.6 months (range 4-79 months). At the end of the evaluation, 87.4% of patients were in NYHA class I or II (P<0.001). There was response to therapy in 65.3% of patients (P<0.001), with an overall mortality of 34.7%.

CONCLUSION

In patients with chronic Chagas cardiomyopathy undergoing cardiac resynchronization therapy, we found the following statistically significant changes: improvement in NYHA class and increase of left ventricle ejection fraction, a decrease of the systolic final diameter and systolic final left ventricle volume and improvement of patient survival.

Prognostic significance of left ventricular dyssynchrony by phase analysis of gated SPECT in medically treated patients with dilated cardiomyopathy

PURPOSE

The study aimed to investigate the value of clinical variables and rest gated single-photon emission computed tomography (SPECT) in predicting cardiac deaths in medically treated dilated cardiomyopathy (DCM) patients.

METHODS

This is a retrospective study. Fifty-six consecutive hospitalized DCM patients who underwent rest gated SPECT myocardial perfusion imaging were initially recruited. Patients were further excluded for receiving heart transplantation, cardiac resynchronization treatment, and noncardiac death during follow-up. The remaining 48 medically treated DCM patients were selected into the final analysis. Phase analysis of gated SPECT was conducted to identify left ventricular (LV) dyssynchrony. Cardiac death during follow-up was considered as the only endpoint. Univariate and multivariate Cox proportional hazards regression analysis were performed to identify the independent predictors of cardiac death. Kaplan-Meier cumulative survival analysis with stratification was performed, and survival curves were compared by log-rank test.

RESULTS

The mean age was 47.5 ± 15.8 years (range, 15-76 yrs) and 85.4% were men. The mean LV ejection fraction was 22.2 ± 7.7%. During the follow-up period (22.7 ± 5.1 mos), 12 (25.0%) cardiac deaths occurred. Compared to survivors, patients with cardiac death had lower body mass index (BMI, P = 0.010), higher percent of prolonged QRS duration (QRSD, P = 0.043), and severe LV dyssynchrony (P = 0.002). Multivariate Cox analysis demonstrated that severe LV dyssynchrony [hazard ratio = 9.607, 95% confidential interval (95% CI) 2.064-44.713, P = 0.004] and BMI (hazard ratio = 0.851, 95% CI 0.732-0.989, P = 0.036) were predictive of cardiac death.

CONCLUSION

Left ventricular dyssynchrony assessed by phase analysis of gated SPECT and BMI are predictive of cardiac death in medically treated DCM patients.

Long-term independent predictors of positive response to cardiac resynchronization therapy

AIMS

Cardiac resynchronization therapy (CRT) is currently considered an important breakthrough in the treatment of selected patients with refractory heart failure. However, long-term predictors of mortality, morbidity and time to recovery of ventricular function for those patients who respond positively to CRT remain poorly investigated.

METHODS

This is a retrospective follow-up study involving one hospital. Between August 2004 and October 2008, 211 consecutive patients with refractory heart failure received a CRT device in the Cardiology Division of Ospedale Civile Maggiore in Verona. The clinical characteristics studied were age, sex, heart rhythm, left ventricular end-systolic volume/body surface area (LVESV/BSA), left ventricular ejection fraction, QRS duration, type of bundle-branch block, cause, New York Heart Failure Association functional class, pharmacological therapy and lead position. The objective of this study was to evaluate the effect of several baseline characteristics on long-term prognosis in heart failure patients treated with CRT.

RESULTS

Nonischemic cause, left bundle-branch block and a basal LVESV/BSA of 106 ml/m or less were the only independent predictors of a positive response to CRT (P < 0.005). Additionally, a reduction in LVESV/BSA after CRT was associated both with increased survival and reduced rehospitalization for heart failure (P < 0.005).

CONCLUSION

A better selection of patients on the basis of cause, type of bundle-branch block and basal LVESV/BSA can increase the number of patients that would benefit from CRT.

The effects of right ventricular apical pacing on ventricular function and dyssynchrony implications for therapy

Cardiac pacing is the only effective treatment for patients with sick sinus syndrome and atrioventricular conduction disorders. In cardiac pacing, the endocardial pacing lead is typically positioned at the right ventricular (RV) apex. At the same time, there is increasing indirect evidence, derived from large pacing mode selection trials and observational studies, that conventional RV apical pacing may have detrimental effects on cardiac structure and left ventricular function, which are associated with the development of heart failure. These detrimental effects may be related to the abnormal electrical and mechanical activation pattern of the ventricles (or ventricular dyssynchrony) caused by RV apical pacing. Still, it remains uncertain if the deterioration of left ventricular function as noted in a proportion of patients receiving RV apical pacing is directly related to acutely induced left ventricular dyssynchrony. The upgrade from RV pacing to cardiac resynchronization therapy may partially reverse the deleterious effects of RV pacing. It has even been suggested that selected patients with a conventional pacemaker indication should receive cardiac resynchronization therapy to avoid the deleterious effects. This review will provide a contemporary overview of the available evidence on the detrimental effects of RV apical pacing. Furthermore, the available alternatives for patients with a standard pacemaker indication will be discussed. In particular, the role of cardiac resynchronization therapy and alternative RV pacing sites in these patients will be reviewed.

Interatrial conduction time and left atrial function in patients with left ventricular systolic dysfunction: effects of cardiac resynchronization therapy

BACKGROUND

Prolonged interatrial conduction time (IACT) can be associated with abnormal left atrial (LA) function but has not been characterized in patients with left ventricular (LV) systolic dysfunction (LVSD) and QRS intervals >130 ms.

METHODS

Two-dimensional Doppler echocardiography and Doppler tissue imaging (DTI) were performed in 41 patients with LVSD (mean LV ejection fraction, 26 +/- 5%) and 41 similarly aged normal controls. Two-dimensional measurements included LV volume and ejection fraction and LA volume for the determination of LA emptying fraction and LA ejection fraction. IACT was defined as the time from the onset of the P wave to the onset of the DTI-derived late diastolic (A') velocity at the lateral mitral annulus. Two-dimensional Doppler measurements were reassessed in patients with LVSD 4 +/- 2 months after cardiac resynchronization therapy (CRT).

RESULTS

IACT was longer in patients with compared to controls (105 +/- 25 vs 74 +/- 12 ms, P < .001); none of the controls had an IACT > 100 ms. In patients with LVSD, IACT was correlated modestly with measurements of LA volume (r = .41-.48, all P values < .009) but not with measurements of LA function. Patients with LVSD with IACTs > 100 ms (n = 20) prior to CRT had larger LA volumes and lower indices of LA function after CRT compared to those with IACTs < or = 100 ms. Significant reductions in LV end-systolic volumes and increases in LV ejection fractions occurred in both groups after CRT.

CONCLUSION

DTI-derived IACT can be prolonged in patients with severe LVSD and wide QRS intervals. An IACT > 100 ms can affect LA remodeling and function at early follow-up after CRT but does not influence the response in LV end-systolic volume or ejection fraction.

Nonischemic dilated cardiomyopathy: results of noninvasive and invasive evaluation in 310 patients and clinical significance of bundle branch block

BACKGROUND

The survival of patients with idiopathic dilated cardiomyopathy (IDCM) at III and IV stages of New York Heart Association (NYHA) is decreased in those with a bundle branch block (BBB) compared to those without BBB. Less is known on the prognosis of patients at earlier stages of NYHA and who had a left BBB (LBBB) or right BBB (RBBB). We sought to evaluate the prevalence and the clinical significance of LBBB or RBBB in patients with IDCM and classes I and II of NYHA.

METHODS

Clinical data, noninvasive, and invasive studies were consecutively collected in 310 patients, with IDCM, followed up to 4.8+/-3.7 years.

RESULTS

Seventy-six patients (25%) had LBBB, 21 (7%) had RBBB, and 212 had no BBB. Patients with BBB were older than other patients (P < 0.009). Left ventricular ejection fraction (LVEF) was lower in LBBB than in RBBB and other patients (P < 0.05). Syncope was more frequent in BBB than in absence (P < 0.05). Incidence of spontaneous ventricular tachycardia (VT) and atrial fibrillation, VT induction, total cardiac events, and sudden death were similar in the presence or absence of BBB. Deaths by heart failure and heart transplantations tended to be more frequent in BBB than in absence.

CONCLUSIONS

LBBB was present in 25% of patients with IDCM; RBBB was rare. Patients with BBB were older and had more frequent syncope than patients without BBB; LVEF was lower in LBBB than in RBBB or in absence of BBB. BBB did not increase the risk of spontaneous VT, VT induction, or sudden death, and tended to increase deaths by heart failure and the indications of heart transplantation.

Assessment of Early Changes in the Segmental Functions of the Left and the Right Ventricles After Biventricular Pacing in Heart Failure: A Study With Tissue Doppler Imaging

Tissue Doppler imaging allows assessment of systolic and diastolic regional ventricular function. The aim of this study was to assess early changes in regional systolic and diastolic functions and differences in transition time to contraction between the ventricles after cardiac resynchronization therapy. Fourteen patients were included, who underwent echocardiography before and 1 month after resynchronization. The difference between transition time to contraction of left and right ventricles decreased to 24.4 ± 10.7 milliseconds from 65.3 ± 18.2 milliseconds after resynchronization therapy ( P = .001). There was a significant relation between the decrease in difference between transition time and increase in ejection fraction (r = 0.80, P = .002). Early or late diastolic myocardial motion increased in 7 segments of left and 2 segments of right ventricles. Systolic myocardial motion increased in 7 segments of left and in all segments of right ventricles. Resynchronization therapy improved systolic and diastolic functions in both ventricles. The difference between transition time to contraction of ventricles might be helpful in estimating optimal resynchronization.

Biventricular Upgrading in Patients with Conventional Pacing System and Congestive Heart Failure:Results and Response Predictors

BACKGROUND

There are few studies on cardiac resynchronization therapy (CRT) in heart failure (HF) patients with preexisting right ventricular (RV) pacing. The purpose of this study was to determine the efficacy of CRT upgrading in RV-paced patients and the predictivity of electromechanical dyssynchrony parameters (EDP) evaluated by standard echocardiography (ECHO) and tissue Doppler imaging (TDI).

METHODS

Thirty-eight consecutive patients with HF [New York Heart Association (NYHA) class III or IV, LVEF < 35%], prior continuous RV pacing, and absence of atrial fibrillation were enrolled in the presence of a paced QRS > or = 150 ms and evaluated by ECHO and TDI. A responder was defined as a patient with a favorable change in NYHA class and neither HF hospitalization nor death, plus an absolute increase of LVEF > or = 10 units.

RESULTS

At six-months follow-up, the whole study population had significant improvement in symptoms, systolic function, and QRS duration (P < 0.001); 32 (84%) patients had a favorable clinical outcome, 25 (66%) were considered responders according to the previous definition. Postimplant QRS was similarly reduced in both responders and nonresponders, whereas EDP had a significant improvement only in responders (P < 0.05). Using EDP, 23 (79%) patients were responders compared with 2 (22%) patients without mechanical dyssynchrony (P = 0.002).

CONCLUSIONS

In HF patients with previous RV pacing, CRT is effective to improve clinical, functional outcome, and LV performance and to reduce electromechanical dyssynchrony in a large proportion of patients. Dyssynchrony evaluated by standard and TDI ECHO can be useful for CRT selection of paced patients.

Upgrading from Single Chamber Right Ventricular to Biventricular Pacing in Permanently Paced Patients with Worsening Heart Failure: The RD-CHF Study

BACKGROUND

Biventricular (BiV) stimulation lowers morbidity and mortality in patients with drug-refractory congestive heart failure (CHF), depressed left ventricular (LV) function, and ventricular dyssynchrony in absence of indication for permanent cardiac pacing. This pilot, single-blind, randomized, cross-over study examined the safety and efficacy of upgrading conventional pacing systems to BiV stimulation in patients with advanced CHF.

METHODS

We included 56 patients in New York Heart Association (NYHA) functional classes III or IV despite optimal drug treatment and ventricular dyssynchrony (interventriclar delay > 40 ms or LV preejection delay > 140 ms) in need of pacemaker replacement. We compared the patients' functional status, arrhythmias, and standard echocardiographic measurements during 3 months of conventional, single right ventricular (RV) versus 3 months of BiV stimulation.

RESULTS

There were 44 patients in the cross-over phase. QRS duration was shortened by 23% and LV preejection delay by 16% with BiV stimulation. NYHA functional class, 6-minute hall walk and quality of life score were significantly improved with BiV stimulation compared with single RV pacing by 18%, 29%, and 19%, respectively. No significant difference was observed in the ventricular arrhythmia burden or LV reverse remodeling between the 2 periods.

CONCLUSIONS

This pilot study showed that upgrading from RV pacing to BiV pacing significantly improves symptoms and exercise tolerance in chronically paced patients with advanced CHF and mechanical dyssynchrony.

A futuristic perspective on clinical studies of cardiac resynchronization therapy for heart failure patients

PURPOSE OF REVIEW

Heart failure is a major public health problem. Many heart failure patients have electrical and mechanical ventricular dyssynchrony, which are risk factors for death in heart failure patients.

RECENT FINDINGS

Cardiac resynchronization therapy, by stimulating both ventricles, is a strategy to improve ventricular dyssynchrony.

SUMMARY

This paper describes the historic development of this therapy; reviews the results of completed clinical cardiac resynchronization therapy studies, and discusses ongoing and future studies.

FDG PET as a predictor of response to resynchronisation therapy in patients with ischaemic cardiomyopathy

PURPOSE

Although resynchronisation therapy (CRT) is a promising addition to heart failure therapy, a substantial number of patients do not respond to CRT. As FDG PET has routinely been used for prediction of improvement after revascularisation in ischaemic cardiomyopathy, it was hypothesised that there is also a relationship between the extent of viable tissue and improvement as a result of CRT.

METHODS

Thirty-nine patients with ischaemic cardiomyopathy (ejection fraction 27 +/- 9%) and a wide QRS complex underwent temporary pacing to determine the optimal pacing combination, i.e. that with the highest increase in cardiac index (CI) compared with baseline (measured by Doppler echocardiography). All patients also underwent FDG PET imaging. In 19 patients, CI measurements were repeated 10-12 weeks after permanent biventricular pacemaker implantation.

RESULTS

Echocardiography (13-segment model) showed a mean of 9.8 +/- 1.6 dyssynergic segments, with preserved FDG uptake in 4.1 +/- 2.4 segments. CI improvement at the optimal pacing site was 20 +/- 9%. There was a linear relationship between the extent of viable tissue and CI improvement during pacing (p < 0.001). Using a cut-off value of more than three viable segments (ROC analysis), FDG PET had a sensitivity of 72% and a specificity of 71% for detection of the presence of haemodynamic improvement (i.e. a CI improvement >15%). The relation between CI improvement and viable tissue was similar at follow-up.

CONCLUSION

A correlation was found between the extent of viable tissue and the haemodynamic response to CRT in patients with ischaemic cardiomyopathy, suggesting that FDG PET imaging may be useful to discriminate between responders and non-responders to CRT.

Comparison of the haemodynamics of different pacing sites in patients undergoing resynchronisation treatment: need for individualisation of lead localisation

BACKGROUND

Biventricular pacing is a new therapy for the treatment of heart failure. However, a substantial number of patients do not respond to this therapy.

HYPOTHESIS

Individually determined maximal pacing sites will improve the haemodynamic response and increase the number of responders.

METHODS

In 48 patients with heart failure, the acute haemodynamic effects of nine different pacing configurations were studied, using two right and left ventricular pacing sites and their combinations. Cardiac index was measured using Doppler echocardiography. For further analysis, the combination with the highest cardiac index improvement was compared with baseline. Moreover, the number of responders was calculated using a cut-off value of 10% increase in cardiac index.

RESULTS

The mean (SD) increase in cardiac index ranged between 3.8% (6.0%) and 11.1% (8.6%). The pacing site with maximal cardiac index was highly variable between patients, and here the cardiac index increased to 14.8% (7.6%; (p<0.001). The number of responders varied between 15% and 64%, increasing to 75% at the site with maximal increase in cardiac index. In a subset of patients, the haemodynamic improvement after pacemaker implantation correlated well with the acute haemodynamics.

CONCLUSION

Individualisation of pacing configuration for biventricular pacing leads to further haemodynamic improvement in patients with heart failure and reduces the number of patients not responding to this therapy.

Cardiac resynchronisation therapy in heart failure: Current status

Cardiac resynchronization in heart failure already has a history of 12 years. However, the major advances have been the result of large multi center trials dating from 2001. In all these trials patients with a LVEF < or = 35% were included, and a QRS above 120 msec. Follow up was from 3-36 months. The majority of these trials showed a positive effect in reduction of composite and points of death or hospitalization for major cardiovascular events. Many of these trials also showed a diminution of left ventricular and systolic diameter or volume. Even in NYHA class II patients an improvement was seen. Some unanswered questions still remain as regards the agreement on electrical or electromechanical dyssynchrony criteria. There is a number of patients with "wide" QRS who do not improve and conversely a number of patients with a narrow QRS who witness improvement. The benefit in patients with atrial fibrillation also remains unanswered. Finally the value of this modality in patients with mild heart failure or asymptomatic left ventricular systolic dysfunction, NYHA class I-II remains to be determined in large on going trials. Another question is whether biventricular or left ventricular patient is preferable. Finally whether biventricular patient should be complemented by a defibrillator insertion is being currently studied. Cardiac resynchronization therapy along or in combination with an ICD improves symptoms, reduces major morbidity and mortality in patients with a left ventricular EF<35%, ventricular dilatation and a QRS > or = 120 msec in NYHA class III-IV. Further indications are currently being examined.

Upgrade to biventricular pacing in patients with pacing-induced heart failure: can resynchronization do the trick?

Dyssynchrony imposed on ventricular function by right ventricular (RV) apical pacing may lead in some cases to worsening or appearance of heart failure (HF) symptoms. This is a result of an altered pattern of activation, leading to several histological and functional adjustments of the left ventricle, including inhomogeneous thickening of the ventricular myocardium and myofibrillar disarray, fibrosis, disturbances in ion-handling protein expression, myocardial perfusion defects, alterations in sympathetic tone and mitral regurgitation. Studies of mid- and long-term effects of RV apical pacing on left ventricular (LV) function have demonstrated a progressive decline in ejection fraction and other indices of LV functional competence. Upgrading RV pacing systems to biventricular resynchronization modalities is a theoretically promising option for paced patients with worsening HF. The potentially favourable effect of upgrading on LV functional indices and patient clinical status has been demonstrated in few, non-randomized trials. Apart from the scantiness of existing clinical data, issues concerning technical aspects of the procedure and selection of eligible patients are raised. Is pacing-induced dyssynchrony equivalent to the indigenous dyssynchrony in unpaced patients with HF? What selection criteria should be applied in order to identify potential responders to cardiac resynchronization therapy in this patient population? Answers to these and more questions are still lacking.

Biventricular Pacemaker Upgrade in Previously Paced Heart Failure Patients—Improvements in Ventricular Dyssynchrony

BACKGROUND

Cardiac resynchronization therapy (CRT) reduces symptoms and mortality in patients with left bundle branch block (LBBB) and severe chronic heart failure. There are few data demonstrating the effects of CRT on contemporary dyssynchrony variables in patients with advanced heart failure who have been chronically paced from the right ventricle (RV).

METHODS AND RESULTS

We reviewed baseline and follow-up clinical and echocardiographic data on patients receiving CRT in a single centre. Indices of global left ventricular (LV) function and dyssynchrony before and after CRT were measured. Patients were then divided into those receiving their first device (n = 39) and those receiving CRT as an upgrade to existing RV pacemakers (n = 32). Baseline demographic variables, indices of global LV function, symptomatic status, renal function, hemodynamics, and diuretic requirements were not different between previously paced patients and nonpaced patients. Mean length of RV pacing in the previously paced patients was 59 months (range 12-167 months). Patients in the previously paced group had a broader QRS complex than patients with intrinsic LBBB. Aortopulmonary delay of longer than 40 ms was present in 68% of all subjects, 67% had intraventricular septal and posterior wall motion delay longer than 130 ms, and 59% had an intraventricular delay as measured by tissue Doppler imaging of longer than 65 ms. There was no difference between paced and nonpaced patients for any of these measures of dyssynchrony. QRS duration was reduced to a greater extent in the previously paced patients than those with no previous device therapy. CRT led to important reductions in each dyssynchrony variable in both patients with previous RV pacing and those with intrinsic LBBB. The magnitude of these changes in measures of dyssynchrony was not different between the 2 groups. In all patients undergoing CRT, 50% had a reduction in furosemide dose at 3 months, 56% an improvement of at least 1 grade in New York Heart Association status, and 66% an improvement of at least 5% in LVEF. Divided by group, previously paced patients were no more or less likely than newly implanted patients to achieve one or more of these clinical outcomes.

CONCLUSION

Our data suggest that patients with RV pacing and heart failure have similar dyssynchrony as patients with intrinsic LBBB. CRT leads to improvements in LV global function, dyssynchrony variables and symptoms in patients chronically paced from the RV that are similar to those observed in patients with LBBB without preexisting devices.

Significance of QRS complex duration in patients with heart failure

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

Time course of left ventricular volumes in severe congestive heart failure patients treated by optimized AV sequential left ventricular pacing alone--a 3-dimensional echocardiographic study

BACKGROUND

This study evaluates the acute and chronic resynchronizing effects of AV sequential left ventricular (LV) pacing on LV function in patients with impaired cardiac function and conduction disorders by 3-dimensional transesophageal echocardiography.

METHODS AND RESULTS

Twenty-nine patients with congestive heart failure, with LV ejection fraction (LVEF) < or = 30%, QRS duration > or = 120 milliseconds, and New York Heart Association Class II to IV, were implanted with a cardiac resynchronization device using an LV lead only, according to the invasively determined hemodynamic optimal pacing site and AV delay. Patients underwent 3-dimensional transesophageal echocardiography before randomization to treatment (baseline) and at 12-month follow-up (resynchronization--12 months). Three-dimensional volumes were acquired on resynchronization and during intermittent switch-off at intrinsic depolarization. The values of stroke volume were 43.2 +/- 13.3 (intrinsic-baseline), 51.7 +/- 17.4 (intrinsic--12 months), 57.2 +/- 15.6 (resynchronization-baseline), and 64.6 +/- 18.9 (resynchronization--12 months). Analysis of variance demonstrated a significant effect of resynchronization at different periods (P < .001) and a significant time effect (P < .05) for stroke volume. Similar results were observed with ejection fraction (LVEF). No effect was observed with LV end-diastolic volume, whereas a therapy effect with no time effect was observed with LV end-systolic volume.

CONCLUSIONS

A significant acute increase of LV stroke volume and LVEF was found by resynchronization by LV pacing alone. A continuous improvement of LV stroke volume and LVEF occurred with time of follow-up (reverse remodeling). The initial therapeutic effect persisted during 12-month follow-up independently of time of follow-up and QRS width. No significant decrease of LV end-diastolic size during chronic resynchronization was detected in contrast to previous studies with resynchronization by biventricular pacing.

Biventricular pacing and heterogeneity of ventricular repolarization in heart failure patients

OBJECTIVE

The aim of our study was to evaluate the effect of cardiac resyncronization therapy (CRT) on QT dispersion (QTd), JT dispersion (JTd) and transmural dispersion of re-polarization (TDR), markers of heterogeneity of ventricular repolarization in a study population with severe heart failure.

METHODS AND RESULTS

Fifty patients (43 male, 7 female, aged 60.2 ± 3.1 years) suffering from congestive heart failure (N = 39 NYHA class III; N = 11 NYHA class IV) as a result of coronary artery disease (N = 19) or of dilated cardiomyopathy (N = 31), sinus rhythm, QRS duration >130 ms (mean QRS duration >156 ± 21 ms), an ejection fraction < 35%, left ventricular end-diastolic diameter >55 mm, underwent permanent biventricular DDDR pacemaker implantation. A 12-lead standard electrocardiogram was performed at baseline, during right-, left-, and biventricular pacing and QTd, JTd and TDR were assessed. Biventricular pacing significantly reduced QTd (73.93 ± 19.4 ms during BiVP vs 91 ± 6.7 ms at sinus rhythm, p = 0.004), JTd (73.18 ± 17.16 ms during BiVP vs 100.72 ± 39.04 at baseline p = 0.003), TDR (93.16 ± 15.60 vs 101.55 ± 19.08 at baseline; p<0.004), as compared to sinus rhythm. Right ventricular endocardial pacing and left ventricular epicardial pacing both enhanced QTd (RVendoP 94 ± 51 ms, p<0.03; LVepiP 116 ±71 ms, p<0.02) and TDR (RVendoP 108.13 ± 19.94 ms; p<0.002; LVepiP 114.71 ± 26.1; p<0.05).There was no effect on JTd during right and left ventricular stimulation.

CONCLUSIONS

Biventricular pacing causes a statistically significant reduction of ventricular heterogeneity of ripolarization and has an electrophysiological antiarrhythmic influence on arrhythmogenic substrate of dilatative cardiomiopathy.

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.

Safety of Transvenous Cardiac Resynchronization System Implantation in Patients With Chronic Heart Failure

OBJECTIVES

The purpose of this study was to evaluate the safety of implanting a cardiac resynchronization therapy (CRT) system.

BACKGROUND

Clinicians and patients require data on the safety of the CRT implant procedure to estimate procedural risk.

METHODS

We evaluated outcomes of transvenous CRT system implantation in 2,078 patients from the Multicenter InSync Randomized Clinical Evaluation (MIRACLE) study, the MIRACLE Implantable Cardioverter-Defibrillator (ICD) study, and the InSync III study. We compared the MIRACLE study to the InSync III study and the MIRACLE ICD study randomized phase to its general phase to evaluate the effect of new technologies.

RESULTS

The implant attempt succeeded in 1,903 of 2,078 (91.6%) patients. Implant time decreased from 2.7 h in the MIRACLE study to 2.3 h in the InSync III study (p < 0.001), and from 2.8 h in the MIRACLE ICD study randomized phase to 2.4 h in the general phase (p < 0.001). The implant procedure produced 62 perioperative complications in 53 (9.3%) MIRACLE trial patients; 159 in 135 (21.1%) MIRACLE ICD study randomized phase patients and 71 in 62 (13.9%) general phase patients (p < 0.05 vs. randomized); and 41 in 37 (8.8%) InSync III study patients (p = NS vs. the MIRACLE study). We observed 73 postoperative complications in 62 (11.7%) MIRACLE trial patients, 77 in 68 (11.9%) MIRACLE ICD study randomized phase patients and 56 in 45 (11.0%) general phase patients (p = NS), and 37 in 34 (8.6%) InSync III study patients (p = NS). A total of 8% of patients required reoperation to treat lead dislodgement, extracardiac stimulation, or infection during follow-up.

CONCLUSIONS

Transvenous CRT system implantation appears safe, well-tolerated, has a high success rate, and improves with operator experience and the addition of new technologies.

Determinants of Mortality in Patients Undergoing Cardiac Resynchronization Therapy: Baseline Clinical, Echocardiographic, and Angioscintigraphic Evaluation Prior to Resynchronization

BACKGROUND

In dilated cardiomyopathy (DCM) patients (pts) with cardiac resynchronization therapy (CRT) for ventricular dyssynchrony, long-term predictors of mortality and morbidity remain poorly investigated.

METHOD AND RESULTS

We reviewed data of 102 pts, 68 +/- 10 years, NYHA Class II-IV (14 Class II, 67 Class III, 21 Class IV), who benefited from CRT (69 CRT, 33 CRT-ICD). Fifty-two patients had an ischemic DCM, 36 a previously implanted conventional PM/ICD, 29 a permanent atrial fibrillation, and 19 needed dobutamine in the month preceding implant. QRS duration was 187 +/- 35 ms, left ventricular end-diastolic diameter 72 +/- 10 mm, mitral regurgitation severity 1.9 +/- 0.8, echographic aorto-pulmonary electromechanical delay 61.5 +/- 25 ms and septo-lateral left intraventricular delay 86 +/- 56 ms, pulmonary artery pressure (PAP) 43 +/- 11 mmHg, angioscintigraphic left ventricular ejection fraction (EF) 20 +/- 9%, and right ventricular EF 30.5 +/- 14%. Over a mean follow-up of 23 +/- 20 months, 26 pts died (18 heart failures (HFs), 1 arrhythmic storm, 7 noncardiac deaths). Positive univariate predictors of death from any cause were NYHA Class IV (P < 0.001), and need for dobutamine the month preceding CRT (P < 0.008), while use of beta-blocking agents (P < 0.08) and left ventricular EF (P < 0.09) were negative ones. NYHA Class IV was the only independent predictor at multivariate analysis (P < 0.01). Survival at 24 months was 85% in Class II, 80% in Class III, and 37% in Class IV (II vs III, P = ns; III vs IV, P < 0.001). When using a composite endpoint of death from any cause and unplanned rehospitalization for a major cardiovascular event, there were 48 events (14 HF deaths, 3 noncardiac deaths, 26 HF rehospitalizations, 2 paroxysmal atrial fibrillation, 2 sustained ventricular tachycardia, 1 nonfatal pulmonary embolism). Predictors of death from any cause/unplanned rehospitalization for a major cardiovascular event in the follow-up were NYHA Class IV (P < 0.001), need for dobutamine during the month preceding CRT (P < 0.002), and PAP (<0.02). NYHA Class IV was the only independent predictor at multivariate analysis (P < 0.05). Event-free proportion at 24 months was 70% in Class II, 64% in Class III, and 37% in Class IV (II vs III, P = ns; III vs IV, P < 0.01). When considering determinants of mortality only in NYHA Class IV patients, no variable was significantly correlated to mortality. Need for dobutamine during the last month preceding CRT did not add an adjunctive mortality risk.

CONCLUSION

Baseline NYHA Class IV at implantation appears as the most important determinant of a poor clinical outcome in terms of both mortality and morbidity. No predictive criteria seem available for NYHA Class IV patients, in order to discriminate who will die after CRT and who will not. NYHA Class IV strongly influences the clinical outcome, suggesting that, in future studies planned on mortality and rehospitalization as major endpoints, baseline NYHA Class IV should be separately taken into account.

New insights into cardiac resynchronization therapy

Ventricular dyssynchrony plays a central role in the expression and progression of heart failure (HF). An independent risk factor for cardiac mortality, ventricular dyssynchrony is characterized by delay in left ventricular (LV) lateral wall contraction. This leads to decreased pumping efficiency, with resulting fluid retention and impaired exercise tolerance. Cardiac resynchronization therapy (CRT) attempts to improve cardiac efficiency by restoring the normal mechanical relationship between right and left ventricular contraction. Cardiac output increases with resynchronization, while ventricular filling pressure decreases without increasing cardiac oxygen consumption. Cardiac resynchronization therapy can also reverse LV dysfunction and reduce mitral regurgitation in patients with HF. Since 1999, the efficacy of implantable CRT devices has been evaluated in clinical trials enrolling more than 4,000 patients with heart disease. In the CARE-HF trial, CRT reduced the risk of death by 36% relative to standard pharmacologic therapy. Combining CRT with a defibrillator might produce an added benefit. In the COMPANION trial, all-cause mortality in patients randomized to a CRT-defibrillator combination was less than in patients receiving CRT therapy alone. Cardiac resynchronization therapy has also been found to decrease morbidity and improve functional status and quality of life. At the present time, the indications for CRT are limited and include symptomatic HF despite optimal medical therapy, prolonged QRS interval, and LVEF < or = 35%. However, indications for CRT are still evolving and may be expanded as further studies identify those most likely to benefit.

Ventricular reverse remodeling and 6-month outcomes in patients receiving cardiac resynchronization therapy: analysis of the MIRACLE study

OBJECTIVE

The objective of this analysis was to determine if there were differences in ventricular reverse remodeling and 6-month outcome with cardiac resynchronization therapy (CRT) among specific subgroups enrolled in the Multicenter InSync Randomized Clinical Evaluation (MIRACLE) Study.

BACKGROUND

Analysis of major subgroups receiving CRT is important in determining who may be most likely to benefit, since all patients who receive CRT do not demonstrate improvement.

METHODS

Differences in response to CRT between subgroups based on baseline echocardiographic parameters, New York Heart Association (NYHA) class, age, gender, beta blocker use, and etiology of heart failure (HF) were analyzed for the clinical end points of the study as well as 6-month HF re-hospitalization or death.

RESULTS

The benefit of CRT over control was similar in all subgroups with respect to all clinical endpoints. However, non-ischemic HF patients had greater improvements with CRT compared to ischemic HF patients in left ventricular end diastolic volume (P < 0.001) and ejection fraction (EF) (6.7% increase vs. 3.2% [P < 0.001]). Greater improvements in EF were also seen in those patients with less severe baseline mitral regurgitation (MR) (P < 0.001). Women but not men receiving CRT were more likely to be event-free from first HF hospitalization or death compared to the control group (Hazard Ratio = 0.157).

CONCLUSIONS

The benefits of CRT with respect to EF and reverse remodeling were greater in patients with non-ischemic HF and less severe MR. Women may also derive more benefit than men with respect to the occurrence of HF hospitalization or death.

Long-Term Follow-Up of Cardiac Resynchronization Therapy in Patients with End-Stage Heart Failure

Long-term follow-up of cardiac resynchronization therapy.

INTRODUCTION

Cardiac resynchronization therapy (CRT) has been introduced to treat patients with end-stage heart failure, and results of this technique are promising. The aim of our study was to assess the sustained benefit of CRT in a large patient cohort with end-stage heart failure at long-term follow-up. In addition, the prognosis of responders and nonresponders was evaluated.

METHODS AND RESULTS

125 patients with end-stage heart failure, NYHA class III or IV, LVEF<35%, QRS duration>120 msec and left bundle branch block morphology received a biventricular device. At baseline and 6 months after implantation the following parameters were evaluated: NYHA class, Minnesota Quality of life score, QRS duration on surface ECG, 6-minute walking distance and LVEF. Follow-up was obtained up to 3 years. After 6 months, patients were divided in clinical responders and nonresponders according to improvement in NYHA class. All clinical parameters improved significantly at 6-month follow-up. Hospitalization for heart failure was 3.8+/-4.9 days/year before and 0.7+/-1.6 days/year after CRT. Survival at 1-, 2-, and 3-year follow-up was 93%, 88%, and 85%, respectively. Responders (78%) showed a significantly better survival than nonresponders at 2- and 3-year follow-up (96% and 93% for responders versus 81% and 73% for nonresponders, P<0.05).

CONCLUSION

The improvement in functional status and symptoms after CRT is maintained at long-term follow-up (up to 3 years). The clinical improvement was associated with a significant reduction in hospitalization rate which was also maintained over the years. Preimplantation selection of responders may result in even better long-term survival.

Minimally Invasive Left Ventricular Epicardial Lead Placement: Surgical Techniques for Heart Failure Resynchronization Therapy

BACKGROUND

Epicardial lead placement for biventricular pacing is often a rescue procedure after failed coronary sinus cannulation. This study aims to determine perioperative and early postoperative outcome of minimally invasive left ventricular lead placement as a management strategy for heart failure, comparing minithoracotomy and endoscopic approaches.

METHODS

From October 2002 through October 2003, 41 patients underwent minimally invasive left ventricular lead placement, 23 (56%) by minithoracotomy and 18 (44%) endoscopically. Thirty-one (76%) were males, 19 (46%) had previous cardiac surgery, 21 (51%) had ischemic cardiomyopathy, 17 (41%) were in New York Heart Association class III or IV, and 28 (65%) had implantable cardioverter-defibrillators.

RESULTS

There were no in-hospital deaths, intraoperative complications, or failures to implant the left ventricular lead. Median operative time was longer for the endoscopic approach (188 minutes) than for minithoracotomy (151 minutes; p = 0.006). Preoperatively, the endoscopic group had more mitral regurgitation (median, 2.5 versus 1.0, respectively; p = 0.009). QRS duration was shorter postoperatively (mean change from preoperative, -32 +/- 24 ms; p < 0.0001); this change was unrelated to surgical approach. Impedance also was less postoperatively (mean change, -490 +/- 300 ohms; p < 0.0001), and the change was unrelated to surgical approach. Changes were greater the larger their preoperative values (p < 0.0001). Threshold increased with follow-up time (adjusted p < 0.0001), but impedance decreased (adjusted p = 0.0009); these trends were similar for both approaches. No changes were evident in left ventricular dimensions.

CONCLUSIONS

Minimally invasive left ventricular epicardial lead placement is safe and effective, offering selection of the best pacing site with minimal morbidity; it can be considered a primary option for resynchronization therapy.

Device Therapy in the Management of Congestive Heart Failure

Despite significant advancements in the treatment of heart failure over the past 2 decades, this patient population is still subject to considerably high morbidity and mortality rates. In recent years, the field of device therapy as adjunctive treatment to the medical management of congestive heart failure has grown in the wake of the large number of randomized trials that have demonstrated the safety and efficacy of these devices. The implantable defibrillator currently represents the standard of care in certain segments of the heart failure population, even in those without a prior arrhythmic event. Biventricular pacing systems appear to have a role in heart failure patients with prolongation of their QRS duration in improving ventricular performance and symptoms, if not mortality. Last, the shortage of organs available for orthotopic transplant has heightened interest in using ventricular-assist devices as destination therapy, and although there is evidence for the feasibility for this approach at the current time, there is a next generation of devices that appear even more promising.

Clinical and electrocardiographic predictors of a positive response to cardiac resynchronization therapy in advanced heart failure

AIMS

Cardiac resynchronization therapy (CRT) is an effective treatment for refractory congestive heart failure (CHF). However, up to 30% of patients do not respond to CRT. The aim of this study was to identify clinical and electrocardiographic (ECG) predictors of a positive response to CRT.

METHODS AND RESULTS

This retrospective study included 139 consecutive patients successfully implanted with a CRT device (mean age, 68+/-9 years, 113 men). At baseline, 69% of patients were in New York Heart Association (NYHA) functional class III, and 31% in class IV, mean left ventricular ejection fraction was 21+/-6%, and mean QRS duration was 188+/-28 ms. In each patient, left and right ventricular leads were placed to attain the shortest QRS duration during biventricular stimulation. Patients were classified at 6 months as responders to CRT (n=100) if they were alive, they had not been re-hospitalized for management of CHF, and the NYHA class had decreased by 1 point, and/or peak VO(2) or 6 min hall-walk increased by >10%. All others were classified as non-responders (n=38; one patient was lost to follow-up). Uni- and multivariate logistic regression analyses were performed to detect a pre- or intra-operative predictor of a positive response to CRT. Among multiple demographic, clinical, and ECG variables, the amount of QRS shortening (DeltaQRS) associated with biventricular stimulation was the only independent predictor of a positive (37+/-23 ms) vs. negative (11+/-23 ms) response to CRT (P<0.001).

CONCLUSION

A positive response to CRT was observed in 73% of patients at 6 months and predicted only by DeltaQRS.

Novel Steerable Telescoping Catheter System for Implantation of Left Ventricular Pacing Leads

Advances in left ventricular transvenous lead delivery systems for biventricular pacing are leading to more refined techniques, shorter procedure times and higher implant success rates. Despite these advances, the inability to successfully cannulate the coronary sinus and deliver a lead to a distal location are still major causes of prolonged procedures times and implant failures. The pathophysiologic process of heart failure results in dilatation of the right atrium as well as other morphological changes in cardiac anatomy. Additionally, cannulation can be further complicated by congenital anomalous cardiac anatomy. This report describes the implant of a biventricular pacing system using a novel, steerable 7 French catheter system developed to aid in the cannulation of the coronary sinus ostium and its venous branches. The steerable catheter is used in conjunction with a 9 French braided sheath and guide-wire to create a telescoping system. The use of new tools and methods as described provides insight into available options for left ventricular transvenous lead implantation and dealing with difficult anatomy.

Detrimental ventricular remodeling in patients with congenital complete heart block and chronic right ventricular apical pacing

BACKGROUND

Although dual-chamber pacing improves cardiac function in patients with complete congenital atrioventricular block (CCAVB) by restoring physiological heart rate and atrioventricular synchronization, the long-term detrimental effect of asynchronous electromechanical activation induced by apical right ventricular pacing (RVP) has not been well clarified.

METHODS AND RESULTS

Twenty-three CCAVB adults (24+/-3 years) with a DDD transvenous pacemaker underwent conventional echocardiography before implantation and, after at least 5 years of RVP, an exercise test and echocardiography coupled with tissue Doppler imaging and tissue tracking. They were compared with 30 matched healthy control subjects. After 10+/-3 years of RVP, CCAVB adults had significantly higher values versus controls in terms of intra-left ventricular (LV) asynchrony (respectively, 59+/-18 versus 19+/-9 ms, P<0.001), extent of LV myocardium displaying delayed longitudinal contraction (39+/-15% versus 10+/-7%, P<0.01), and septal-to-posterior wall-motion delay (84+/-26 versus 18+/-9 ms, P<0.01). The ratio of late-activated posterior to early-activated septal wall thickness was higher after long-term RVP than before (1.3+/-0.2 vs 1+/-0.1, P=0.05) and was higher than in controls (1+/-0.1, P<0.05). The percentage of patients with increased LV end-diastolic diameter was higher after long-term RVP than before implantation and was higher than in controls (57% versus 13%, P<0.05, and 57% versus 0%, P<0.01, respectively). CCAVB patients with long-term RVP had a lower cardiac output than controls (3.8+/-0.6 versus 4.9+/-0.8 L/min, P<0.05) and lower exercise performance (123+/-24 versus 185+/-39 W, P<0.001).

CONCLUSIONS

Prolonged ventricular dyssynchrony induced by long-term endovenous RVP is associated with deleterious LV remodeling, LV dilatation, LV asymmetrical hypertrophy, and low exercise capacity. These new data highlight the importance of the ventricular activation sequence in all patients with chronic ventricular pacing.

Cardiac resynchronization therapy and automatic implantable cardiac defibrillators in the treatment of heart failure: a review article

PURPOSE

To review the use of cardiac resynchronization therapy (CRT) and automatic implantable cardiac defibrillators (AICDs) in heart failure (HF) patients.

DATA SOURCES

Selected scientific literature.

CONCLUSIONS

New developments in device therapy for HF patients are helping to decrease morbidity and mortality in this challenging patient population. CRT improves left ventricular (LV) ejection fraction, quality of life, 6-min walk distances, and New York Heart Association scores in select patients. AICDs can prevent sudden cardiac death in those who have LV dysfunction and are at risk for ventricular arrhythmias. Cardiac devices are now becoming a standard of care for those with HF who meet certain criteria.

IMPLICATIONS FOR PRACTICE

Despite advances in medical therapy for treating LV dysfunction, newly diagnosed patients face a 50% mortality rate in 5 years. The natural history of HF leads to continual deterioration of function unless adverse cardiac remodeling is reversed. Until recently, the only means for improving symptoms and cardiac function has been through the optimization of standard medicines that are indicated for LV dysfunction, such as angiotensin-converting enzyme inhibitors and beta-blockers. However, not all patients benefit from medical management alone. Cardiac devices may now be considered when significant symptoms persist after standard medicines are optimized. When practitioners use a multiple-modality approach, careful patient selection based on the inclusion criteria used in the trials outlined in this article will likely lead to improved management of those with LV dysfunction.

Is right ventricular outflow tract pacing an alternative to left ventricular/biventricular pacing?

The right ventricular apex has been used as the traditional pacing site since the development of transvenous pacing in 1959. Some studies suggest that pacing the right ventricular apex may cause remodeling and is harmful. In the past decade, there have been a multitude of studies of the hemodynamic, electrophysiological, electrocardiographic, and clinical effects of ventricular pacing at other sites. Pacing of the left ventricle singly or with biventricular pacing has emerged as an effective and safe therapy for moderate to severe congestive heart failure in patients with prolonged QRS complexes. Studies of alternate right ventricular sites, like the right ventricular outflow tract, have given mixed results. Not all patients can be treated with left ventricular pacing, which is a time-consuming and difficult procedure. Right ventricular pacing is easier and less expensive than left ventricular pacing and further study of additional right ventricular sites seems warranted.

Intra- and interatrial conduction delay: implications for cardiac pacing

Atrial conduction disorders are frequent in elderly subjects and/or those with structural heart diseases, mainly mitral valve disease, hyperthrophic cardiomyopathies, and hypertension. The resultant electrophysiological and electromechanical abnormalities are associated with a higher risk of paroxysmal or persistent atrial tachyarrhythmias, either atrial fibrillation, typical or atypical flutter or other forms of atrial tachycardias. Such an association is not fortuitous because intra- and interatrial conduction abnormalities delays disrupt (spatial and temporal dispersion) electrical activation, thus promoting the initiation and perpetuation of reentrant circuits. Preventive therapeutic interventions induce variable, sometimes paradoxical effects as with the proarrhythmic effect of class I antiarrhythmic drugs. Similarly, atrial pacing may promote proarrhythmias or an antiarrhythmic effect according to the pacing site(s) and mode. Multisite atrial pacing was conceived to correct, as much as possible, abnormal activation induced by spontaneous intra- or interatrial conduction disorders or by single site atrial pacing, which are situations responsible for commonly refractory arrhythmias. Atrial electrical resynchronization can also be used to correct mechanical abnormalities like left heart AV dyssynchrony resulting from intraatrial conduction delays.