ACC/AHA/HRS 2008 Guidelines for Device-Based Therapy of Cardiac Rhythm Abnormalities: Executive Summary

Hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy is a common inherited cardiovascular disease present in one in 500 of the general population. It is caused by more than 1400 mutations in 11 or more genes encoding proteins of the cardiac sarcomere. Although hypertrophic cardiomyopathy is the most frequent cause of sudden death in young people (including trained athletes), and can lead to functional disability from heart failure and stroke, the majority of affected individuals probably remain undiagnosed and many do not experience greatly reduced life expectancy or substantial symptoms. Clinical diagnosis is based on otherwise unexplained left-ventricular hypertrophy identified by echocardiography or cardiovascular MRI. While presenting with a heterogeneous clinical profile and complex pathophysiology, effective treatment strategies are available, including implantable defibrillators to prevent sudden death, drugs and surgical myectomy (or, alternatively, alcohol septal ablation) for relief of outflow obstruction and symptoms of heart failure, and pharmacological strategies (and possibly radiofrequency ablation) to control atrial fibrillation and prevent embolic stroke. A subgroup of patients with genetic mutations but without left-ventricular hypertrophy has emerged, with unresolved natural history. Now, after more than 50 years, hypertrophic cardiomyopathy has been transformed from a rare and largely untreatable disorder to a common genetic disease with management strategies that permit realistic aspirations for restored quality of life and advanced longevity.

Symptomatic complete heart block leading to a diagnosis of Kearns-Sayre syndrome

Kearns-Sayre syndrome (KSS) is a rare syndrome characterized by the triad of progressive external ophthalmoplegia, pigmentary retinopathy and cardiac conduction system disturbances; it is a mitochondrial encephalomyopathy with which usually presents before the patient reaches the age of 20. Here we present a case report of a patient with KSS who presented with symptomatic complete heart block.

Sudden cardiac death in dialysis: do current guidelines for implantable cardioverter defibrillator therapy apply to patients with end-stage kidney disease?

Arrhythmic mechanisms account for one in four deaths in end-stage kidney disease. Large-scale randomized controlled trials have demonstrated a mortality benefit from implantable cardioverter defibrillator therapy in carefully selected patient groups at high risk for sudden cardiac death. Unfortunately, patients with end-stage kidney disease were systematically excluded from these trials. Consequently, the applicability of American College of Cardiology (ACC)/American Heart Association (AHA)/Heart Rhythm Society (HRS) guidelines on implantable cardioverter defibrillator therapy to dialysis patients remains uncertain. Observational data suggest that secondary preventative implantable cardioverter defibrillator therapy following resuscitated cardiac arrest prolongs the lives of dialysis patients. This intervention may also offer a survival advantage as a primary preventative strategy in end-stage kidney disease. However, competing risk from co-morbidity can negate any perceived benefit. Device-related complications also negatively impact outcome. The recommendation that primary preventative device implantation be reserved for patients with severely impaired left ventricular function may be excessively restrictive in this high-risk population. Trials of implantable cardioverter defibrillator therapy that include dialysis patients are required to validate existing device eligibility criteria in this unique population. Novel indications for this intervention in dialysis patients should also be identified.

Multimodality imaging in interventional cardiology

'Multimodality' imaging--the side-by-side interpretation of data obtained from various noninvasive imaging techniques, such as echocardiography, radionuclide techniques, multidetector CT (MDCT), and MRI--allows anatomical, morphological, and functional data to be combined, increases diagnostic accuracy, and improves the efficacy of cardiovascular interventions and clinical outcomes. During the past decade, advances in software and hardware have allowed co-registration of various imaging modalities, resulting in cardiac 'hybrid' or 'fusion' imaging. In this Review, we discuss the roles of both multimodality and hybrid imaging in three broad areas of cardiology--coronary artery disease (CAD), heart failure, and valvular heart disease. In the evaluation of CAD, integration of either single-photon emission computed tomography (SPECT) or PET with CT coronary angiography provides both morphological and functional data in a single procedure. Accordingly, the functional consequences (myocardial hypoperfusion on SPECT or PET) of anatomical pathology (coronary anatomy on MDCT or MRI) can be assessed. Co-registration of PET and MRI data sets to provide cellular and molecular information on plaque composition and stability is now possible. Furthermore, novel imaging modalities have been implemented to guide electrophysiological and transcatheter-based procedures, such as cardiac resynchronization therapy (an established treatment for patients with heart failure), and transcatheter valve repair or replacement procedures.

Newer applications of nuclear cardiology in systolic heart failure: detecting coronary artery disease and guiding device therapy

Radionuclide-based imaging techniques can be applied to the heart failure population to derive clinically useful information. This review discusses the specific role of myocardial perfusion imaging for determining heart failure etiology, and the potential application of radionuclide-based imaging techniques for the optimal selection of patients with heart failure for device therapy.

Sudden cardiac death risk stratification in patients with heart failure

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

Defibrillation testing during implantable cardioverter-defibrillator implantation in Italian current practice: the Assessment of Long-term Induction clinical ValuE (ALIVE) project

BACKGROUND

Clinical practice with regard to defibrillation threshold (DFT) testing during implantable cardioverter-defibrillator (ICD) implantation varies considerably, even among experienced implanting centers. International guidelines do not as yet mandate DFT testing.

OBJECTIVE

The objective of this project is to assess current clinical decision making regarding DFT testing during ICD implantation.

METHODS

The ALIVE project collected data on DFT testing from a multicenter network of Italian clinicians sharing a common system for the collection, management, analysis, and reporting of clinical and diagnostic data from patients with Medtronic (Minneapolis, MN) implantable devices.

RESULTS

Data on 2,082 consecutive patients implanted with a Medtronic ICD in 111 Italian centers, over the period 2007 to 2010, were analyzed. Defibrillation threshold testing was performed in 33% of cases (678/2,082). The main reasons for performing the test were physician's clinical practice ("I always perform DFT") (80%) and secondary prevention implantation (12%). The main reasons for not performing DFT testing were centers' practice (44%), primary prevention (31%), and device replacement (15%). In 22 patients, ventricular fibrillation induction was not achieved; 656 patients completed DFT testing: 633 patients (96%) performed a single test, 19 patients (3%) performed a second induction test, and 4 patients (0.6%) underwent an additional induction test.

CONCLUSIONS

The preliminary results of the ALIVE project show that a great number of implant procedures are performed without DFT testing in the common practice of the participating centers. We also measured an inhomogeneous, center-dependent DFT testing behavior, which suggests the importance of defining a common guideline for ICD implant testing. Follow-up data on our patients will provide more information on the clinical value of the test.

Clinical factors and echocardiographic techniques related to the presence, size, and location of acoustic windows for leadless cardiac pacing

AIMS

Temporary leadless cardiac pacing using ultrasound energy is feasible in patients. An implantable left ventricular stimulation system being developed for cardiac resynchronization therapy transfers energy from a subcutaneous transmitter to an endocardial receiver through tissue free of interfering lung or rib ('acoustic window'). The aim was to use transthoracic echocardiography to evaluate acoustic window (AW) locations and sizes to determine the implant site for a transmitter, and to investigate clinical predictors of AW location and size.

METHODS AND RESULTS

Inclusion criteria were ejection fraction ≤35%, and New York Heart Association functional class III or IV. Acoustic windows were evaluated in intercostal spaces (ICSs) measured in the supine, right lateral, sitting, and standing position during normal respiration and held inspiration. Among 42 patients, at least one adequate AW (≥2 cm(2)) was identified in 41, 19 patients had adequate AWs in 2 ICSs and 20 patients had adequate AWs in 3. Acoustic window areas were generally smallest in the lateral position with held inspiration and largest in the standing position with normal respiration. Patients with ischaemic cardiomyopathy compared with non-ischaemic cardiomyopathy had smaller heart size [left ventricular end-systolic volume index (LVESVI) 78 ± 38 mL/m(2) vs. 104 ± 46 mL/m(2), P = 0.03] but larger AWs in the right lateral position (11.4 ± 6.5 cm(2) vs. 7.3 ± 3.4 cm(2), P = 0.01) and standing position (14.0 ± 7.2 cm(2) vs. 9.4 ± 3.3 cm(2), P = 0.02).

CONCLUSIONS

Adequate AWs were present in nearly all patients. Despite smaller hearts, ischaemic cardiomyopathy patients had adequate AWs. A simple procedure performed as an adjunct to pre-implant echocardiography can screen patients and identify transmitter implant locations for an ultrasound-mediated leadless pacing system.

Event-free survival following CRT with surgically implanted LV leads versus standard transvenous approach

BACKGROUND

While surgical epicardial lead placement is performed in a subset of cardiac resynchronization therapy patients, data comparing survival following surgical versus transvenous lead placement are limited. We hypothesized that surgical procedures would be associated with increased mortality risk.

METHODS

Long-term event-free survival was assessed for 480 consecutive patients undergoing surgical (48) or percutaneous (432) left ventricle (LV) lead placement at our institution from January 2000 to September 2008.

RESULTS

Baseline clinical and demographic characteristics were similar between groups. While there was no statistically significant difference in overall event-free survival (P = 0.13), when analysis was restricted to surgical patients with isolated surgical lead placement (n = 28), event-free survival was significantly lower in surgical patients (P = 0.015). There appeared to be an early risk (first approximately 3 months postimplantation) with surgical lead placement, primarily in LV lead-only patients. Event rates were significantly higher in LV lead-only surgical patients than in transvenous patients in the first 3 months (P = 0.006). In proportional hazards analysis comparing isolated surgical LV lead placement to transvenous lead placement, adjusted hazard ratios were 1.8 ([1.1,2.7] P = 0.02) and 1.3 ([1.0,1.7] P = 0.07) for the first 3 months and for the full duration of follow-up, respectively.

CONCLUSIONS

Isolated surgical LV lead placement appears to carry a small but significant upfront mortality cost, with risk extending beyond the immediate postoperative period. Long-term survival is similar, suggesting those surviving beyond this period of early risk derive the same benefit as coronary sinus lead recipients. Further work is needed to identify risk factors associated with early mortality following surgical lead placement.

Clinical and echocardiographic predictors of nonresponse to cardiac resynchronization therapy

BACKGROUND

Lack of response to cardiac resynchronization therapy (CRT) ranges between 30% to 40% of heart failure (HF) patients. The present study aimed to evaluate the clinical and echocardiographic determinants of nonresponse to CRT.

METHODS

A total of 581 patients (66.4 ± 10.0 years, 77.9% male) with advanced HF scheduled for CRT implantation were included. Clinical and echocardiographic evaluations were performed at baseline and 6 months of follow-up. Nonresponse was defined as no improvement in the New York Heart Association functional class, death from worsening HF or heart transplantation, and <15% reduction in left ventricular (LV) end-systolic volume.

RESULTS

At 6 months of follow-up, 254 patients (44%) did not respond to CRT. The nonresponders were more frequently male (81.9% vs 74.3%, P = .030) and had ischemic cardiomyopathy (69.7% vs 53.2%, P < .001), shorter QRS duration (150.6 ± 29.9 milliseconds vs 156.0 ± 32.5 milliseconds, P = .041), worse New York Heart Association functional class (2.8 ± 0.6 vs 2.7 ± 0.6, P = .008) and shorter 6-minute walk distance (297.9 ± 110.7 m vs 331.8 ± 112.6 m, P = .001), larger left atrial volumes (44.9 ± 16.9 mL/m(2) vs 40.9 ± 17.6 mL/m(2), P = .006), less baseline LV dyssynchrony (56.2 ± 41.3 milliseconds vs 69.1 ± 39.9 milliseconds, P < .001), and, more frequently, anterior LV lead position (12.4% vs 4.0%, P = .007). At multivariate analysis, only the ischemic etiology of HF (odds ratio [OR] 2.264, P = .005), shorter 6-minute walk distance at baseline (OR 0.998, P = .030), less baseline LV dyssynchrony (OR 0.989, P < .001), and anterior LV lead position (OR 3.713, P < .010) remained independent predictors of nonresponse to CRT.

CONCLUSIONS

Ischemic etiology of HF, shorter baseline 6-minute walk distance, less baseline LV dyssynchrony, and anterior LV lead position are independent determinants of nonresponse to CRT.

Relative merits of left ventricular dyssynchrony, left ventricular lead position, and myocardial scar to predict long-term survival of ischemic heart failure patients undergoing cardiac resynchronization therapy

BACKGROUND

The relative merits of left ventricular (LV) dyssynchrony, LV lead position, and myocardial scar to predict long-term outcome after cardiac resynchronization therapy remain unknown and were evaluated in the present study.

METHODS AND RESULTS

In 397 ischemic heart failure patients, 2-dimensional speckle tracking imaging was performed, with comprehensive assessment of LV radial dyssynchrony, identification of the segment with latest mechanical activation, and detection of myocardial scar in the segment where the LV lead was positioned. For LV dyssynchrony, a cutoff value of 130 milliseconds was used. Segments with <16.5% radial strain in the region of the LV pacing lead were considered to have extensive myocardial scar (>50% transmurality, validated in a subgroup with contrast-enhanced magnetic resonance imaging). The LV lead position was derived from chest x-ray. Long-term follow-up included all-cause mortality and hospitalizations for heart failure. Mean baseline LV radial dyssynchrony was 133±98 milliseconds. In 271 patients (68%), the LV lead was placed at the latest activated segment (concordant LV lead position), and the mean value of peak radial strain at the targeted segment was 18.9±12.6%. Larger LV radial dyssynchrony at baseline was an independent predictor of superior long-term survival (hazard ratio, 0.995; P=0.001), whereas a discordant LV lead position (hazard ratio, 2.086; P=0.001) and myocardial scar in the segment targeted by the LV lead (hazard ratio, 2.913; P<0.001) were independent predictors of worse outcome. Addition of these 3 parameters yielded incremental prognostic value over the combination of clinical parameters.

CONCLUSIONS

Baseline LV radial dyssynchrony, discordant LV lead position, and myocardial scar in the region of the LV pacing lead were independent determinants of long-term prognosis in ischemic heart failure patients treated with cardiac resynchronization therapy. Larger baseline LV dyssynchrony predicted superior long-term survival, whereas discordant LV lead position and myocardial scar predicted worse outcome.

Predictors of death and occurrence of appropriate implantable defibrillator therapies in patients with ischemic cardiomyopathy

Most patients with chronic ischemia and an implantable cardiac defibrillator (ICD) for primary prevention do not experience therapies for ventricular arrhythmias on follow-up. The present study aimed to identify independent clinical, electrocardiographic, and echocardiographic predictors of death and occurrence of ICD therapy in patients with chronic ischemic cardiomyopathy and ICD for primary prevention. A total of 424 patients with chronic ischemic cardiomyopathy, ejection fraction ≤ 35%, and New York Heart Association (NYHA) class ≥ II were recruited. All patients underwent echocardiography before ICD insertion. Primary outcome was all-cause mortality; secondary outcome was occurrence of appropriate ICD therapy on follow-up. Primary and secondary outcomes occurred in 84 and 95 patients, respectively. Patients who died were more likely to have diabetes (hazard ratio [HR] 1.67, 95% confidence interval [CI] 1.00 to 2.79, p = 0.049), higher NYHA class (HR 1.96, 95% CI 1.15 to 3.33, p = 0.013), lower peri-infarct strain on echocardiogram (HR 1.25, 95% CI 1.07 to 1.46, p = 0.005), and lower glomerular filtration rate (HR 1.01, 95% CI 1.00 to 1.03, p = 0.022). Only peri-infarct strain (HR 1.22, 95% CI 1.09 to 1.36, p < 0.001) predicted the occurrence of ICD therapy on follow-up. In conclusion, in chronic ischemic patients with an ICD for primary prevention, the presence of diabetes, renal dysfunction, higher NYHA class, and impaired peri-infarct zone function were predictors of all-cause mortality. In contrast, only impaired peri-infarct zone function determined the occurrence of appropriate ICD therapy on follow-up.

Effect of renal function on survival after implantable cardioverter defibrillator placement

Implantable cardioverter defibrillators (ICDs) are effective at reducing arrhythmic death in patients with left ventricular dysfunction, but few studies have investigated the outcomes after ICD implantation in patients with chronic kidney disease (CKD). We conducted a 2-center retrospective study of 958 patients who had undergone ICD placement for primary prevention from the 2000 to 2006. The patients were stratified into 5 groups according to the CKD stage (stage 1, glomerular filtration [GFR] 90 to 120 ml/min; stage 2, GFR 60 to 89 ml/min; stage 3, GFR 30 to 59 ml/min; stage 4, GFR 15 to 29 ml/min; and stage 5, GFR 0 to 14 ml/min). The primary end point was death at 1 year. Of the 958 patients included in our analysis, 73 (7.6%) had died at 1 year. The mortality rate at 1 year increased with worsening CKD (1.8%, 5.3%, 9.0%, 22%, and 38% for stage 1 to 5, respectively, p <0.0001 for group). CKD was an independent predictor of mortality; hazard ratio 1.0, 1.075 (95% confidence interval 0.578 to 2.0), 1.372 (95% confidence interval 0.736 to 2.556), 3.092 (95% confidence interval 1.52 to 6.29), and 10.15 (95% confidence interval 4.25 to 24.23) for stage 1 to 5, respectively (p <0.0001 for group). Patients with CKD and left ventricular dysfunction have a poor prognosis despite ICD placement. The 1-year mortality increased as the renal function decreased. In conclusion, physicians should be cognizant of the prognosis when considering whether an ICD should be implanted in patients with CKD.

Use of implantable cardioverter-defibrillators

The implantable cardioverter-defibrillator (ICD) is the most effective treatment for patients with life-threatening ventricular tachycardia or ventricular fibrillation not due to reversible causes. The American College of Cardiology/American Heart Association class I and IIa indications for an ICD are discussed. Patients with ICDs who need pacing should be treated with biventricular pacing, not with dual-chamber rate-responsive pacing, at a rate of 70/min. Patients with ICDs should be treated with β-blockers, statins and angiotensin-converting enzyme inhibitors or angiotensin receptor blockers.

Bundle-branch block morphology and other predictors of outcome after cardiac resynchronization therapy in Medicare patients

BACKGROUND

Clinical trials of cardiac resynchronization therapy (CRT) have enrolled a select group of patients, with few patients in subgroups such as right bundle-branch block (RBBB). Analysis of population-based outcomes provides a method to identify real-world predictors of CRT outcomes.

METHODS AND RESULTS

Medicare Implantable Cardioverter-Defibrillator Registry (2005 to 2006) data were merged with patient outcomes data. Cox proportional-hazards models assessed death and death/heart failure hospitalization outcomes in patients with CRT and an implantable cardioverter-defibrillator (CRT-D). The 14 946 registry patients with CRT-D (median follow-up, 40 months) had 1-year, 3-year, and overall mortality rates of 12%, 32%, and 37%, respectively. New York Heart Association class IV heart failure status (1-year hazard ratio [HR], 2.23; 3-year HR, 1.98; P<0.001) and age ≥ 80 years (1-year HR, 1.74; 3-year HR, 1.75; P<0.001) were associated with increased mortality both early and late after CRT-D. RBBB (1-year HR, 1.44; 3-year HR, 1.37; P<0.001) and ischemic cardiomyopathy (1-year HR, 1.39; 3-year HR, 1.44; P<0.001) were the next strongest adjusted predictors of both early and late mortality. RBBB and ischemic cardiomyopathy together had twice the adjusted hazard for death (HR, 1.99; P<0.001) as left BBB and nonischemic cardiomyopathy. QRS duration of at least 150 ms predicted more favorable outcomes in left BBB but had no impact in RBBB. A secondary analysis showed lower hazards for CRT-D compared with standard implantable cardioverter-defibrillators in left BBB compared with RBBB.

CONCLUSIONS

In Medicare patients, RBBB, ischemic cardiomyopathy, New York Heart Association class IV status, and advanced age were powerful adjusted predictors of poor outcome after CRT-D. Real-world mortality rates 3 to 4 years after CRT-D appear higher than previously recognized.

Brugada syndrome associated with supraventricular tachycardia: diagnostic and therapeutic strategies

We report the case of a patient with Brugada syndrome and a history of palpitations who presented with an episode of syncope and developed supraventricular tachycardia in the electrophysiological study. The patient was treated with radiofrequency ablation for the supraventricular tachycardia and an implantable cardioverter defibrillator for the Brugada syndrome. At 18 months following implantation of the defibrillator an electrical storm with ventricular fibrillation episodes occurred followed by appropriate discharges of the defibrillator.

Prevalence and predictors of off-label use of cardiac resynchronization therapy in patients enrolled in the National Cardiovascular Data Registry Implantable Cardiac-Defibrillator Registry

OBJECTIVES

The purpose of the study was to define the extent and nature of cardiac resynchronization therapy (CRT) device usage outside consensus guidelines using national data.

BACKGROUND

Recent literature has shown that the application of CRT in clinical practice frequently does not adhere to evidence-based consensus guidelines. Factors underlying these practices have not been fully explored.

METHODS

From the National Cardiovascular Data Registry's Implantable Cardiac-Defibrillator Registry, we defined a cohort of 45,392 cardiac resynchronization therapy-defibrillator (CRT-D) implants between January 2006 and June 2008 with a primary prevention indication. We defined "off-label" implants as those in which the ejection fraction was >35%, the New York Heart Association functional class was below III, or the QRS interval duration was <120 ms in the absence of a documented need for ventricular pacing. The relationships between patient, implanting physician, and hospital characteristics with off-label use were explored with multivariable hierarchical logistic regression models.

RESULTS

Overall, 23.7% of devices were placed without meeting all 3 implant criteria, most often due to New York Heart Association functional class below III (13.1% of implants) or QRS interval duration <120 ms (12.0%). Atrial fibrillation/flutter, previous percutaneous coronary intervention, and the performance of an electrophysiology study before implant were independently associated with increased odds of off-label use, whereas diabetes mellitus, increasing age, and female sex were associated with decreased odds. Physician training and insurance payer were weakly associated with the likelihood of off-label use.

CONCLUSIONS

Nearly 1 in 4 patients receiving CRT devices in the study time frame did not meet guideline-based indications. Given the evolving evidence base supporting the use of CRT, these practices require careful scrutiny.

Long-term outcomes and clinical predictors for pacemaker-requiring bradyarrhythmias after cardiac transplantation: analysis of the UNOS/OPTN cardiac transplant database

BACKGROUND

Pacemaker-requiring bradyarrhythmias after cardiac transplantation are common, and rarely can lead to sudden cardiac death. Prior outcomes studies have been limited to single-center data.

OBJECTIVE

This study sought to define the long-term outcomes and clinical predictors for pacemaker-requiring bradyarrhythmias in the cardiac transplant population.

METHODS

This study used multivariable analysis of the United Network for Organ Sharing/Organ Procurement and Transplantation Network (UNOS/OPTN) database of sequential U.S. cardiac transplant recipients from 1997 to 2007 stratified by postoperative bradyarrhythmias requiring a pacemaker. The primary end point was all-cause mortality.

RESULTS

Among 35,987 cardiac transplant recipients (age 46.1 ± 18.3 years, 76% male, 22% bicaval technique) with a follow-up of 6.3 ± 4.7 years, pacemaker-requiring bradyarrhythmias occurred in 3,940 patients (10.9%). Pacemaker recipients demonstrated improved survival (median 8.0 years vs. 5.2 years, P < .001), decreased 5-year mortality (13.8% vs. 17.7%, P < .001), and overall crude mortality (42.9% vs. 45.9%, P < .001). Multivariable propensity-score-adjusted analysis demonstrated improved survival among pacemaker recipients (adjusted hazard ratio 0.84, 95% confidence interval [CI] 0.80 to 0.88, P < .001) after adjustment for donor/recipient age, UNOS listing status, donor heart ischemic time, surgical technique, graft rejection, and other common comorbidities. The bicaval surgical technique was strongly protective against a postoperative pacemaker requirement (odds ratio [OR] 0.33, 95% CI 0.29 to 0.36, P < .001) in multivariable analysis. Among the other variables studied, only increasing donor age (OR 1.04, 95% CI 1.00 to 1.09, P < .001) and recipient age (OR 1.09, 95% CI 1.0 to 1.12, P < .001) were associated with a permanent pacemaker requirement.

CONCLUSION

Cardiac transplant recipients with pacemaker-requiring bradyarrhythmias have an excellent long-term prognosis. Increased mortality in the nonpacemaker group merits further investigation. Biatrial surgical technique and increasing donor/recipient age are associated with postoperative pacemaker requirement.

Management of ventricular tachycardia in patients with structural heart disease

Patients with structural heart disease and ventricular tachycardia (VT) can be difficult to manage clinically. Many treatment options are available, but no single approach can be applied to every patient. This review aims to discuss the current options available for the management of this population. VT can be associated with cardiomyopathy of any etiology, both ischemic and nonischemic. Antiarrhythmic drugs have not been shown to decrease mortality in this patient population, but they can help reduce episodes. While the advent of the implantable cardioverter-defibrillator has revolutionized the treatment of VT, patients with recurrent shocks for VT have high morbidity and mortality. The development of catheter ablation over the past few decades has greatly aided the ability to control VT in these patients. The approach to patients with VT and structural heart disease is multifaceted. Often, a combination of therapeutic techniques is required to obtain the best result.

Will imaging assist in the selection of patients with heart failure for an ICD?

Sudden cardiac death remains the leading cause of death in the U.S. A left ventricular ejection fraction (LVEF)<30% to 35% identifies a population of patients at increased risk for sudden cardiac death. Once identified, an implantable cardioverter-defibrillator (ICD) is effective in reducing the occurrence of sudden cardiac death. Yet in a substantial proportion of patients who receive an ICD based on reduced LVEF, the device never delivers therapy. Furthermore, the majority of patients who die suddenly do not qualify for ICD placement under current LVEF-based criteria in the guidelines. This review considers the potential role of cardiac imaging in improving the selection of patients most likely to benefit from an ICD. The presence of myocardial scar and/or unrevascularized myocardial ischemia provides an important substrate for the occurrence of potentially fatal ventricular arrhythmias. The presence of clinical heart failure further increases the risk of ventricular arrhythmia. The sympathetic nervous system provides an important trigger for major arrhythmic events, both through global overactivity and through regional heterogeneity of sympathetic activity. A mismatch of myocardial perfusion and innervation may pose a particularly great risk. Imaging modalities provide unique opportunities to investigate the anatomic and pathophysiologic substrates, as well as the triggering effects of cardiac sympathetic innervation. Combining imaging and electrophysiologic modalities offers promise for improved accuracy in future selection of patients with heart failure for ICD placement.

Value of right ventricular-left ventricular interlead electrical delay to predict reverse remodelling in cardiac resynchronization therapy: the INTER-V pilot study

AIMS

Few studies have systematically evaluated the value of intra-procedural parameters in predicting response to cardiac resynchronization therapy (CRT). We investigated whether intracardiac (electrogram) measurements of electrical delays between the positioned right ventricular (RV) and left ventricular (LV) leads at implantation could predict the mid-term CRT response.

METHODS AND RESULTS

Fifty-two patients underwent CRT implantation according to standard techniques and clinical indications. The RV-LV interlead electrical delay measured during spontaneous rhythm and the difference between the pacing-induced (Deltap) RV-LV interlead electrical delays measured during RV and LV pacing were defined intraoperatively using the electrical depolarizations registered at the ventricular leads on the device programmer. At 6 months, a reduction of LV end-systolic volume > or = 15% was used to define CRT responders. Responders (62%), when compared with non-responders, showed a higher proportion of ischaemic aetiology (P = 0.007) and a lower value of DeltapRV-LV interlead electrical delay (22.1 +/- 18.4 vs. 46.3 +/- 15.0 ms, P = 0.0001). At multivariate analysis, the DeltapRV-LV interlead electrical delay was the only independent predictor of response to CRT (P = 0.001). For such a parameter, the receiving operating characteristic curve analysis identified a cut-off value of 42 ms corresponding with the highest accuracy: sensitivity 90.6%; specificity 70%; positive and negative predictive value 83% and 82%, respectively. Conversely, no difference was ascertained between responders and non-responders when RV-LV interlead electrical delay was measured during spontaneous rhythm (76.1 +/- 28.5 vs. 89.6 +/- 21.2, P = 0.078).

CONCLUSION

Intraprocedural measuring of paced RV-LV interlead electrical delay obtained during RV and LV pacing predicts mid-term CRT response.

[Catecholaminergic polymorphic ventricular tachycardia]

BACKGROUND

CPVT (catecholaminergic polymorphic ventricular tachycardia) is a condition characterized by syncopes and cardiac arrest that was first described in 1975. CPVT has later been classified as a genetic disease with a great risk for life-threatening arrhythmias that are mainly caused by mutations in the ryanodine receptor 2 gene. Starting with a case report, we present an overview of CPVT.

MATERIAL AND METHODS

The literature reviewed was identified through a non-systematic search in PubMed.

RESULTS

Diagnosing CPVT may be difficult, as resting ECG is normal and the syncopes may be misdiagnosed as epilepsy. Information about syncopes related to physical or emotional stress and occurrence of unexplained syncopes or cardiac arrest among family members, is important in the diagnostic evaluation. An exercise stress test often reveals the classical pattern of ventricular arrhythmias at heart rates above 100 beats/min. The diagnosis can be confirmed by genetic testing. By beta-blocker treatment and, if necessary, an ICD (implantable cardioverter defibrillator) the prognosis can be improved.

INTERPRETATION

CPVT is a serious disease with a poor prognosis when left untreated. It is a rare but important differential diagnosis in young individuals with syncopes or cardiac arrest. Genetic screening of relatives has made it possible to identify mutation carriers in affected families in order to provide them with preventive therapy.

Mortality risk score in primary prevention implantable cardioverter defibrillator recipients with non-ischaemic or ischaemic heart disease

AIMS

To assess survival and to construct a baseline mortality risk score in primary prevention implantable cardioverter defibrillator (ICD) patients with non-ischaemic or ischaemic heart disease.

METHODS AND RESULTS

Since 1996, data of all consecutive patients who received an ICD system in the Leiden University Medical Center were collected and assessed at implantation. For the current study, all 1036 patients [age 63 (SD 11) years, 81% male] with a primary indication for defibrillator implantation were evaluated and followed for 873 (SD 677) days. During follow-up, 138 patients (13%) died. Non-ischaemic and ischaemic patients demonstrated similar survival but exhibited different factors that influence risk for mortality. A risk score, consisting of simple baseline variables could stratify patients in low, intermediate, and high risk for mortality. In non-ischaemic patients, annual mortality was 0.4% (95% CI 0.0-2.2%) in low risk and 9.4% (95% CI 6.6-13.1%) in high risk patients. In ischaemic patients, mortality was 1.0% (95% CI 0.2-3.0%) in low risk and 17.8% (95% CI 13.6-22.9%) in high risk patients.

CONCLUSION

Utilization of an easily applicable baseline risk score can create an individual patient-tailored estimation on mortality risk to aid clinicians in daily practice.

Echocardiographic evaluation of systolic heart failure

Echocardiography is the most commonly used modality for evaluating left ventricular size and function in the context of systolic heart failure. Traditional techniques, though extensively used, have their limitations and more recently several newer technologies have emerged that are more reproducible, provide prognostic information, guide therapies and have an important role in monitoring progress. This review will evaluate the traditional and more novel techniques used and briefly provide an overview of the role of echocardiography in guiding and monitoring therapies in patients with systolic heart failure.

The intravenous adenosine test: a new test for the identification of bradycardia pacing indications? A pilot study in subjects with bradycardia pacing indications, vasovagal syncope and controls

BACKGROUND

Intravenous adenosine has recently been used in the diagnosis of unexplained syncope, but there is no consensus as to the meaning of a 'positive' test. The objective is to determine the sensitivity and specificity of intravenous adenosine testing in the diagnosis of bradycardia-pacing indications [sinus node dysfunction(SND), atrio-ventricular block (AVB) and cardio-inhibitory carotid sinus syndrome (CSS)].

DESIGN

Pilot cohort study.

METHODS

Patients-(i) Bradycardia-pacing group: Consecutive patients referred for pacing for SND, AVB and CSS; (ii) Consecutive head-up tilt (HUT)-positive VVS patients. Controls-(i) Simple controls (S-Con: normal examination/ECG) and (ii) Electrophysiology controls (EP-Con: consecutive subjects referred for accessory pathway ablation). Pacing referrals and EP-Con had electrophysiology studies to confirm referral diagnosis and exclude others. All subjects had bolus injection of 20 mg intravenous adenosine during continuous ECG and blood pressure monitoring (positive test: >or=6 s asystole, >or=10 s high-degree AVB post-injection). Sensitivity, specificity, safety and tolerability of the test were measured.

RESULTS

Of 264 potential participants (4 SND, 8 AVB, 7 CSS, 10 VVS, 10 EP-Con and 11 S-Con) 50 were studied. All (100%) of the bradycardia-pacing group were adenosine test-positive, as were 6 (60%) VVS. None (0%) and 3 (27%) of the EP- and S-Con groups were positive. Adenosine testing was 100% sensitive and 86% specific for bradycardia-pacing indications, and 100% specific using the diagnostically 'clean' EP-Con results. There were no significant adverse or side effects.

CONCLUSION

Adenosine testing reliably identified patients with definitive bradycardia-pacing indications in whom alternative diagnoses were excluded. Further work is needed to evaluate the role of this test in the diagnosis of unexplained syncope.

Risk of failure of transvenous implantable cardioverter-defibrillator leads

BACKGROUND

Despite the positive effect on mortality in selected patients, implantable cardioverter-defibrillator therapy is also associated with potential malfunction of the implanted system. The present study provides the long-term lead failure rate in a large single-center cohort.

METHODS AND RESULTS

Since 1992, a total of 2068 implantable cardioverter-defibrillator patients with 2161 defibrillation leads were prospectively collected. Data of the implant procedure and all follow-up visits were recorded. All cases of lead removal or capping or placing of an additional pace or sense lead were noted and analyzed. Lead models were grouped by manufacturer and approximate lead diameter in French. During a mean follow-up of 36 months, 82 (3.8%) cases of lead failure were identified. Cumulative incidence of lead failure at 1 year was 0.6%; at 5 years, 6.5%; and at 10 years, 16.4%. The highest risk of lead failure was found in small-diameter leads. Adjusted hazard ratio was 6.4 (95% CI, 3.2 to 12.8) for Medtronic 7F leads, when compared with all other leads.

CONCLUSIONS

In this large single-center experience, the overall incidence of lead failure was 1.3 (95% CI, 1.0 to 1.6) per 100 lead-years. Comparison of different groups of leads shows major differences in event rates. Specific manufacturer's small-diameter defibrillation leads may have a higher risk of early lead failure.

[Latest proceedings: remote medicine - ready for clinical practice?!]

Changes in the demographic structure, increasing multimorbidity in connection with a rise in the number of chronic illnesses and the absence of an effective coordination of the different levels of healthcare services with its discontinuous processes and redundancies will increase the economic burdens in the German health-care system. Recent developments and appropriate logistic premises nowadays offer a realistic basis for implementing remote medicine as a central service and information tool as well as an instrument controlling the information and data flow between patient, hospital and medical practitioner. This article highlights current and future strategies including diagnostic and therapeutic options. The focus will concentrate on patients with heart rhythm disturbances, advanced congestive heart failure, and patients with implantable devices, i.e., pacemaker and implantable cardioverter defibrillator (ICD).