Adverse events with transvenous implantable cardioverter-defibrillators: a prospective multicenter study. European 7219 Jewel ICD investigators

[History of the implantable cardioverter-defibrillator in Germany]

The implantable cardioverter-defibrillator (ICD) was a breakthrough in the prevention of sudden cardiac death. After years of technical development in the USA, Michel Mirowski succeeded in proving reliable automatic defibrillation of ventricular tachyarrhythmias through initial human implantations in 1980, despite many obstacles. Nearly 4 years later, the first patients received ICDs at multiple centers in Germany. Subsequently, outside the USA, Germany became the country with highest implantation rates. The absolute number of implantations remained small as long as implantations required epicardial defibrillation electrodes and therefore thoracotomy by cardiac surgeons. Pacemaker-like implantation using a transvenous defibrillation electrode with a pectoral ICD became feasible in the early 1990s pushing implantation rates to the next level. Technical advancements were accompanied by clinical research in Germany, and often, the first-in-human studies were conducted in Germany. In 1991, the first guidelines for indications were established in the USA and Germany. Several randomized studies on indications were published between 1996 and 2009, mostly led by American teams with German participation, but also under German leadership (CASH, CAT, DINAMIT, IRIS). The DANISH study in 2016 questioned the results of these long-standing studies. Instead of providing ICDs to patients using a broad indication, future efforts aim to identify patients who, despite optimal medical therapy, cardiac resynchronization therapy (CRT), and/or catheter ablation, need protection against sudden cardiac death. Risk scores incorporating myocardial scars in magnetic resonance imaging (MRI) and genetic information are expected to contribute to more individualized and effective indications.

UltraSound Axillary Vein Access (USAA): Learning curve and randomized comparison to traditional venous access for cardiac device implantation

BACKGROUND

Many techniques exist for venous access (VA) during cardiac implantable electronic device (CIED) implantation.

OBJECTIVE

We sought to evaluate the learning curve with ultrasound (US) guided axillary vein access (USAA).

METHODS

Single-center prospective randomized controlled trial of patients undergoing CIED implantation. Patients were randomized in a 2:1 fashion to USAA versus conventional VA techniques. The primary outcomes were the success rates, VA times and 30-day complication rates.

RESULTS

The study included 100 patients (age 68 ± 14 years, BMI 27 ± 4 kg/m² ). USAA was successful in 66/70 implants (94%). Initial attempts at conventional VA included 47% axillary (n = 14), 30% (n = 9) cephalic, and 23% (n = 7) subclavian. The median access time was longer for USAA than conventional access (8.3 IQR 4.2-15.3 min vs. 5.2 IQR 3.4-8.6 min, p = .009). Among the five inexperienced USAA implanters, there was a significant improvement in median access time from first to last tertile of USAA implants (17.0 IQR 7.0-21.0 min to 8.6 IQR 4.5-10.8 min, p = .038). The experienced USAA implanter had similar access times with USAA compared with conventional access (4.0 IQR 3.3-4.7 min vs. 5.2 IQR 3.4-8.6 min, p = .15). Venograms were less common with USAA than conventional access (2% vs. 33%, p < .0001). The 30-day complication rate was similar with USAA (n = 4/70, 6%) versus conventional (n = 3/30, 10%, p = .44).

CONCLUSION

Although the success rate with USAA was high, there was a significant learning curve. Once experienced with the USAA technique, there is the potential for reduced complications without adding to the procedure duration.

Ultrasound guided axillary vein access: An alternative approach to venous access for cardiac device implantation

INTRODUCTION

Ultrasound guided axillary vein access (UGAVA) is an emerging approach for cardiac implantable electronic device (CIED) implantation not widely utilized.

METHODS AND RESULTS

This is a retrospective, age and sex-matched cohort study of CIED implantation from January 2017 to July 2019 comparing UGAVA before incision to venous access obtained after incision without ultrasound (conventional). The study population included 561 patients (187 with attempted UGAVA, 68 ± 13 years old, 43% women, body mass index (BMI) 30 ± 8 kg/m² , 15% right-sided, 43% implantable cardioverter-defibrillator, 15% upgrades). UGAVA was successful in 178/187 patients (95%). In nine patients where UGAVA was abandoned, the vein was too deep for access before incision. BMI was higher in abandoned patients than successful UGAVA (38 ± 6 vs. 28 ± 6 kg/m² , p < .0001). Median time from local anesthetic to completion of UGAVA was 7 min (interquartile range [IQR]: 4-10) and median procedure time 61 min (IQR: 50-92). UGAVA changed implant laterality in two patients (avoiding an extra incision in both) and could have prevented unnecessary incision in four conventional patients. Excluding device upgrades, there was reduced fluoroscopy time in UGAVA versus conventional (4 vs. 6 min; IQR: 2-5 vs. 4-9; p < .001). Thirty-day complications were similar in UGAVA versus conventional (n = 7 vs. 26, 4 vs. 7%; p = .13, p = .41 adjusting for upgrades), partly driven by a trend towards reduced pneumothorax (n = 0 vs. 3, 0 vs. 1%; p = .22).

CONCLUSIONS

UGAVA is a safe approach for CIED implantation and helps prevent an extra incision if a barrier is identified changing laterality preincision.

Air Entrapment Causing Inappropriate Shock From a Subcutaneous Implantable Cardioverter Defibrillator

Subcutaneous implantable cardioverter defibrillator (S-ICD) is an accepted alternative to conventional transvenous devices. Their efficacy in arrhythmia management is comparable to ICDs. However, those devices also have limitations such as lack of anti-tachycardia pacing capability or higher occurrence of device oversensing associated with inappropriate shocks. Air entrapment inside one or more of subcutaneous pockets has been reported as one of uncommon causes of device malfunction. It is important to recognize the wandering or drifting baseline signals during device interrogation for timely diagnosis and appropriate treatment.

Implantable cardiac defibrillators for people with non-ischaemic cardiomyopathy

BACKGROUND

There is evidence that implantable cardioverter-defibrillator (ICD) for primary prevention in people with an ischaemic cardiomyopathy improves survival rate. The evidence supporting this intervention in people with non-ischaemic cardiomyopathy is not as definitive, with the recently published DANISH trial finding no improvement in survival rate. A systematic review of all eligible studies was needed to evaluate the benefits and harms of using ICDs for primary prevention in people with non-ischaemic cardiomyopathy.

OBJECTIVES

To evaluate the benefits and harms of using compared to not using ICD for primary prevention in people with non-ischaemic cardiomyopathy receiving optimal medical therapy.

SEARCH METHODS

We searched CENTRAL, MEDLINE, Embase, and the Web of Science Core Collection on 10 October 2018. For ongoing or unpublished clinical trials, we searched the US National Institutes of Health Ongoing Trials Register ClinicalTrials.gov, the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP), and the ISRCTN registry. To identify economic evaluation studies, we conducted a separate search to 31 March 2015 of the NHS Economic Evaluation Database, and from March 2015 to October 2018 on MEDLINE and Embase.

SELECTION CRITERIA

We included randomised controlled trials involving adults with chronic non-ischaemic cardiomyopathy due to a left ventricular systolic dysfunction with an ejection fraction of 35% or less (New York Heart Association (NYHA) type I-IV). Participants in the intervention arm should have received ICD in addition to optimal medical therapy, while those in the control arm received optimal medical therapy alone. We included studies with cardiac resynchronisation therapy when it was appropriately balanced in the experimental and control groups.

DATA COLLECTION AND ANALYSIS

The primary outcomes were all-cause mortality, cardiovascular mortality, sudden cardiac death, and adverse events associated with the intervention. The secondary outcomes were non-cardiovascular death, health-related quality of life, hospitalisation for heart failure, first ICD-related hospitalisation, and cost. We abstracted the log (hazard ratio) and its variance from trial reports for time-to-event survival data. We extracted the raw data necessary to calculate the risk ratio. We summarised data on quality of life and cost-effectiveness narratively. We assessed the certainty of evidence for all outcomes using GRADE.

MAIN RESULTS

We identified six eligible randomised trials with a total of 3128 participants. The use of ICD plus optimal medical therapy versus optimal medical therapy alone decreases the risk of all-cause mortality (hazard ratio (HR) 0.78, 95% confidence interval (CI) 0.66 to 0.92; participants = 3128; studies = 6; high-certainty evidence). An average of 24 patients need to be treated with ICD to prevent one additional death from any cause (number needed to treat for an additional beneficial outcome (NNTB) = 24). Individuals younger than 65 derive more benefit than individuals older than 65 (HR 0.51, 95% CI 0.29 to 0.91; participants = 348; studies = 1) (NNTB = 10). When added to medical therapy, ICDs probably decrease cardiovascular mortality compared to not adding them (risk ratio (RR) 0.75, 95% CI 0.46 to 1.21; participants = 1781; studies = 4; moderate-certainty evidence) (possibility of both plausible benefit and no effect). Implantable cardioverter-defibrillator was also found to decrease sudden cardiac deaths (HR 0.45, 95% CI 0.29 to 0.70; participants = 1677; studies = 3; high-certainty evidence). An average of 25 patients need to be treated with an ICD to prevent one additional sudden cardiac death (NNTB = 25). We found that ICDs probably increase adverse events (possibility of both plausible harm and benefit), but likely have little or no effect on non-cardiovascular mortality (RR 1.17, 95% CI 0.81 to 1.68; participants = 1781; studies = 4; moderate-certainty evidence) (possibility of both plausible benefit and no effect). Finally, using ICD therapy probably has little or no effect on quality of life, however shocks from the device cause a deterioration in quality of life. No study reported the outcome of first ICD-related hospitalisations.

AUTHORS' CONCLUSIONS

The use of ICD in addition to medical therapy in people with non-ischaemic cardiomyopathy decreases all-cause mortality and sudden cardiac deaths and probably decreases mortality from cardiovascular causes compared to medical therapy alone. Their use probably increases the risk for adverse events. However, these devices come at a high cost, and shocks from ICDs cause a deterioration in quality of life.

Computer Aided Clinical Trials for Implantaule Cardiac Devices

In this paper we aim to answer the question, "How can modeling and simulation of physiological systems be used to evaluate life-critical implantable medical devices?" Clinical trials for medical devices are becoming increasingly inefficient as they take several years to conduct, at very high cost and suffer from high rates of failure. For example, the Rhythm ID Goes Head-to-head Trial (RIGHT) sought to evaluate the performance of two arrhythmia discriminator algorithms for implantable cardioverter defibrillators, Vitality 2 vs. Medtronic, in terms of time-to-first inappropriate therapy, but concluded with results contrary to the initial hypothesis- after 5 years, 2,000+ patients and at considerble ethical and monetary cost. In this paper, we describe the design and performance of a Computer-aided Clinical Trial (CACT) for Implantable Cardiac Devices where previous trial information, real patient data and closed-loop device models are effectively used to evaluate the trial with high confidence. We formulate the CACT in the context of RIGHT using a Bayesian statistical framework. We define a hierarchical model of the virtual cohort generated from a physiological model which captures the uncertainty in the parameters and allow for the systematic incorporation of information available at the design of the trial. With this formulation, the estimates the inappropriate therapy rate of Vitality 2 compared to Medtronic as 33.22% vs 15.62% $(\mathrm{p}\lt 0.001)$, which is comparable to the original trial. Finally, we relate the outcomes of the computer- aided clinical trial to the primary endpoint of RIGHT.

Association between Microvolt T-Wave Alternans and Malignant Ventricular Arrhythmias in Chagas Disease

Background

Sudden cardiac death is the most frequent death mechanism in Chagas disease, responsible for 55% to 65% of the deaths of patients with chronic Chagas cardiomyopathy (CCC). The most often involved electrophysiological mechanisms are ventricular tachycardia and ventricular fibrillation. The implantable cardioverter defibrillator (ICD) has a beneficial role in preventing sudden death due to malignant ventricular arrhythmias, and, thus the correct identification of patients at risk is required. The association of microvolt T-wave alternans (MTWA) with the appearance of ventricular arrhythmias has been assessed in different heart diseases. The role of MTWA is mostly unknown in patients with CCC.

Objectives

To evaluate the association between MTWA and the occurrence of malignant ventricular arrhythmias in patients with CCC.

Method

This is a case-control study including patients with CCC and ICD, with history of malignant ventricular arrhythmias (case group), and patients with CCC and no history of those arrhythmias (control group). The MTWA test results were classified as negative and non-negative (positive and indeterminate). The significance level adopted was a = 0.05.

Results

We recruited 96 patients, 45 cases (46.8%) and 51 controls (53.1%). The MTWA test was non-negative in 36/45 cases (80%) and 15/51 controls (29.4%) [OR = 9.60 (95%CI: 3.41 - 27.93)]. After adjustment for known confounding factors in a logistic regression model, the non-negative result continued to be associated with malignant ventricular arrhythmias [OR = 5.17 (95%CI: 1.05 - 25.51)].

Conclusion

Patients with CCC and history of malignant ventricular arrhythmias more often have a non-negative MTWA test as compared to patients with no history of arrhythmia.

The Value of the Tei Index in Predicting Implantable Cardioverter Defibrillator Shocks

Objectives:

An implantable cardioverter defibrillator (ICD) decreases the risk of sudden death in the appropriate patients. However, a relationship between ICD shocks and increased mortality and morbidity has been suspected. This report is an investigation of an association between ICD shocks and the Tei index, an echocardiographic parameter now commonly used to predict cardiovascular events.

Methods:

The basic characteristics of 250 patients with chronic heart failure who had an ICD implanted and 2 years of follow-up device recordings were retrospectively analyzed. Patients who received shock therapy during follow-up were compared with those who did not, based on demographic and other characteristics and the Tei index.

Results:

The mean Tei index value of ICD shock recipients was significantly higher than the score of non-recipients of ICD shock (0.70±0.10 vs 0.56±0.10; p<0.001). The percentage of patients for whom it was primary prevention who received either appropriate or inappropriate ICD shocks was 28.9%, whereas in those who received an ICD for secondary prevention, the percentage was 71.1% (p<0.001). ICD shock recipient patients were older, and had a greater rate of hypertension and smoking pack-years compared with those to whom an ICD shock was not delivered (p<0.001).

Conclusion:

The results of this study demonstrated a relationship between the Tei index and ICD shocks, either appropriate or inappropriate. The Tei index is a simple method to predict ICD shocks.

Postmortem ICD interrogation in mode of death classification

BACKGROUND

The definition of sudden death due to arrhythmia relies on the time interval between onset of symptoms and death. However, not all sudden deaths are due to arrhythmia. In patients with an implantable cardioverter defibrillator (ICD), postmortem device interrogation may help better distinguish the mode of death compared to a time-based definition alone.

OBJECTIVE

This study aims to assess the proportion of "sudden" cardiac deaths in patients with an ICD that have confirmed arrhythmia.

METHODS

We conducted a literature search for studies using postmortem ICD interrogation and a time-based classification of the mode of death. A modified QUADAS-2 checklist was used to assess risk of bias in individual studies. Outcome data were pooled where sufficient data were available.

RESULTS

Our search identified 22 studies undertaken between 1982 and 2015 with 23,600 participants. The pooled results (excluding studies with high risk of bias) suggest that ventricular arrhythmias are present at the time of death in 76% of "sudden" deaths (95% confidence interval [CI] 67-85; range 42-88).

CONCLUSION

Postmortem ICD interrogation identifies 24% of "sudden" deaths to be nonarrhythmic. Postmortem device interrogation should be considered in all cases of unexplained sudden cardiac death.

Natural History of Implantable Cardioverter-Defibrillator Implanted at or after the Age of 70 years in a Veteran Population: A Single Center Study

Background

The median age of patients in major Implantable Cardioverter-defibrillator (ICD)trials (MUSTT, MADIT-I, MADIT-II, and SCD-HeFT) was 63-67 years; with only 11% ≥70 years. There is little follow-up data on patients over 70 years of age who received an ICD for primary/secondary prevention of sudden cardiac death, particularly for veterans.

Objective

The aim of this study was to study the natural history of ICD implantation for veterans over 70 years of age.

Methods

We retrospectively reviewed single center ICD data in 216 patients with a mean age at implantation 76 ± 4 years. The ICD indication was primary prevention in 161 patients and secondary prevention in 55 patients. The ICD indication was unavailable in 4 patients.

Results

Mean duration of follow up was 1686 ± 1244 days during which 114 (52%) patients died. Of these, 31% died without receiving any appropriate ICD therapy. Overall, 60/216 (28%) received appropriate therapy and 28/216 (13%) received inappropriate therapy. Patients who had ICD implantation for secondary prophylaxis had statistically more (p= 0.02) appropriate therapies compared to patients who had ICD implantation for primary prevention. Indication for implantation and hypertension predicted appropriate therapy, while age at the time of implantation and presence of atrial fibrillation predicted inappropriate therapies. Overall, 7.7% had device related complications.

Conclusions

Although 28% septuagenarians in this study received appropriate ICD therapy, they had high rates of mortality, inappropriate therapy, and device complications. ICD implantation in the elderly merits individualized consideration, with higher benefit for secondary prevention.

ECG-derived spatial QRS-T angle is associated with ICD implantation, mortality and heart failure admissions in patients with LV systolic dysfunction

Background

Increased spatial QRS-T angle has been shown to predict appropriate implantable cardioverter defibrilIator (ICD) therapy in patients with left ventricular systolic dysfunction (LVSD). We performed a retrospective cohort study in patients with left ventricular ejection fraction (LVEF) 31–40% to assess the relationship between the spatial QRS-T angle and other advanced ECG (A-ECG) as well as echocardiographic metadata, with all-cause mortality or ICD implantation for secondary prevention.

Methods

534 patients ≤75 years of age with LVEF 31–40% were identified through an echocardiography reporting database. Digital 12-lead ECGs were retrospectively matched to 295 of these patients, for whom echocardiographic and A-ECG metadata were then generated. Data mining was applied to discover novel ECG and echocardiographic markers of risk. Machine learning was used to develop a model to predict possible outcomes.

Results

49 patients (17%) had events, defined as either mortality (n = 16) or ICD implantation for secondary prevention (n = 33). 72 parameters (58 A-ECG, 14 echocardiographic) were univariately different (p<0.05) in those with vs. without events. After adjustment for multiplicity, 24 A-ECG parameters and 3 echocardiographic parameters remained different (p<2x10^-3). These included the posterior-to-leftward QRS loop ratio from the derived vectorcardiographic horizontal plane (previously associated with pulmonary artery pressure, p = 2x10^-6); spatial mean QRS-T angle (134 vs. 112°, p = 1.6x10^-4); various repolarisation vectors; and a previously described 5-parameter A-ECG score for LVSD (p = 4x10^-6) that also correlated with echocardiographic global longitudinal strain (R² = - 0.51, P < 0.0001). A spatial QRS-T angle >110° had an adjusted HR of 3.4 (95% CI 1.6 to 7.4) for secondary ICD implantation or all-cause death and adjusted HR of 4.1 (95% CI 1.2 to 13.9) for future heart failure admission. There was a loss of complexity between A-ECG and echocardiographic variables with an increasing degree of disease.

Conclusion

Spatial QRS-T angle >110° was strongly associated with arrhythmic events and all-cause death. Deep analysis of global ECG and echocardiographic metadata revealed underlying relationships, which otherwise would not have been appreciated. Delivered at scale such techniques may prove useful in clinical decision making in the future.

Implantable cardioverter defibrillator management: an update

Implantable cardioverter defibrillator (ICD) is the cornerstone of primary and secondary prevention of sudden cardiac death. In 35 years of technologic improvement and clinical trials, there has been a continuous increase in implantation rate. Purpose of this review is to point out and discuss every aspect related to actual ICD management, investigating implantation procedure and predischarge care, office and remote monitoring follow-up, diagnostic evaluations, management of patients with suspected therapies or malfunctions, heart failure, surgery, radiotherapy and endoscopic procedures. Also, ICD backface such as infections and other complications will be discussed. Finally, we will focus on interesting future perspectives for this setting of patients.

Implantable Cardioverter Defibrillator Therapy and the Need for Concomitant Antiarrhythmic Drugs

Implantable cardioverter defibrillators (ICDs) are increasingly used for the prevention of sudden cardiac death in patients with life-threatening ventricular arrhythmias (VAs); however, there is a potential for severe and debilitating anxiety caused by symptoms associated with ICD therapy and anticipation of shocks. Anxiety is a psycho-logic stressor, including physiologic components that may lead to adrenergic excitation triggering new arrhythmias and ICD therapies. This often requires concomitant antiarrhythmic medication to reduce the frequency of shocks and symptomatic arrhythmias treated by anti-tachycardia pacing. Although published studies have documented the efficacy of currently available antiarrhythmics, they have limitations in patients with heart failure, may affect the defibrillation threshold, and/or have been associated with major side-effects. In conclusion, for the patient with an ICD experiencing symptomatic ventricular tachycardia (VTs) episodes or ICD shocks, there is a need for pharmacologic therapy to reduce the incidence of such events without affecting the performance of the ICD or causing major side-effects.

Computational cardiology and risk stratification for sudden cardiac death: one of the grand challenges for cardiology in the 21st century

Risk stratification in the context of sudden cardiac death has been acknowledged as one of the major challenges facing cardiology for the past four decades. In recent years, the advent of high performance computing has facilitated organ-level simulation of the heart, meaning we can now examine the causes, mechanisms and impact of cardiac dysfunction in silico. As a result, computational cardiology, largely driven by the Physiome project, now stands at the threshold of clinical utility in regards to risk stratification and treatment of patients at risk of sudden cardiac death. In this white paper, we outline a roadmap of what needs to be done to make this translational step, using the relatively well-developed case of acquired or drug-induced long QT syndrome as an exemplar case.

A Subclavian Arteriovenous Fistula Associated with Implantable Cardioverter-Defibrillator Implantation

Subclavian arteriovenous fistulas (AVFs) should be considered in the differential diagnosis of a patient presenting with worsening CHF symptoms or unilateral edema immediately after device implantation. A palpable thrill may be present or a bruit may be auscultated in the region of the fistula. Ultrasonography has limitations in the subclavian region and definitive diagnosis is only made by angiogram. Percutaneous occlusion of the AVF is preferred as surgical repair is associated with significant morbidity and mortality.

Advances in implantable cardioverter defibrillator therapy

Since the first implant in 1980, implantable cardioverter defibrillator (ICD) technology has progressed rapidly. Modern ICD's have hundreds of programmable options with the general goal of preventing inappropriate shocks and providing shocks for truly life threatening symptomatic ventricular arrhythmias. New studies on ICD programming have shown the benefits of prolonged detection intervals in reaching this goal. Anti-tachycardia pacing (ATP) therapy has become an important adjunct to defibrillator shocks. Remote monitoring technologies have surfaced which have been shown to identify arrhythmias and problems with the device in an expedient fashion. The subcutaneous ICD offers the advantage of avoiding intravascular leads and their inherent risks. Lastly, the current understanding of the effects of MRI in ICD patients has advanced creating new opportunities to provide MRI safely to such patients.

Catheter ablation of atrial tachyarrhythmias causing inappropriate implantable cardioverter-defibrillator shocks

AIMS

Inappropriate shocks have been an important issue post-implantable cardioverter-defibrillator (ICD) implantation. Moreover, inappropriate ICD shocks are associated with increased mortality. The objective of this study was to evaluate the feasibility of catheter ablation therapy for atrial tachyarrhythmias (ATa) responsible for inappropriate ICD shocks.

METHODS AND RESULTS

Among 108 consecutive patients who underwent ICD implantations, 22, 5, and 3 experienced inappropriate ICD shocks due to ATa, sinus tachycardia, and T-wave oversensing, respectively. Among the 22 patients with ATa, 18 patients (55 ± 10 years, 15 men, structural heart disease in 9) underwent catheter ablation of ATa causing inappropriate shocks. The median duration between the ICD implantation and first inappropriate shock was 10.0 (3.0-24.5) months. The ATa were atrial fibrillation (AF), atrial flutter (AFL), and atrioventricular nodal reentrant tachycardia in 14, 2, and 2 patients, respectively. One patient underwent an atrioventricular nodal ablation for persistent AF associated with a venous anomaly. Among 13 patients who underwent pulmonary vein antrum isolation, 10 (76.9%) were free from AF for a median of 21.0 (13-37.3) months after an average of 1.3 ± 0.5 procedures. In four patients with AFL or a supraventricular tachycardia, none had any arrhythmia recurrence for a median of 6.0 (3.3-93.5) months after a cavotricuspid isthmus or slow pathway ablation, respectively. There were no procedural complications. During the median follow-up of 19.0 (9.5-37.3) months after the last procedure, no patients experienced any inappropriate shocks.

CONCLUSION

Catheter ablation is a feasible therapeutic option for treating ATa responsible for inappropriate shock(s) in patients with ICD.

Implantable cardioverter-defibrillators in patients with arrhythmogenic right ventricular cardiomyopathy: the course of electronic parameters, clinical features, and complications during long-term follow-up

PURPOSE

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a progressive cardiomyopathy characterized by myocardial atrophy and fibro-fatty replacement of the right ventricle (RV) and ventricular tachyarrhythmias in young patients. Our aim was to evaluate clinical course and electronic parameters in patients with implantable cardioverter-defibrillator (ICD) and ARVC, during long-term follow-up.

METHODS AND RESULTS

We report on 12 patients with ARVC (mean age 40 ± 13 years) who were treated with ICD implantation in our center. Although several RV sites were tested for proper lead positions, the amplitude of R-wave at implantation was quite low (7.4 ± 3.0 mV). After a mean follow-up of 91 ± 28 months, R-wave amplitude significantly decreased to a mean value of 5.4 ± 2.5 mV (p=0.03). We also found a noticeable, nearly significant increase in pacing threshold (p=0.052) and a moderate increase in defibrillation impedance (p=0.07). Six patients (46 %) experienced at least one appropriate ICD therapy; three patients (23 %) experienced inappropriate ICD shocks secondary to the supraventricular tachycardia, T-wave oversensing, and electromagnetic interference.

CONCLUSIONS

ICD in patients with ARVC has been demonstrated to be feasible and safe. In our case series, we found low R-wave amplitudes at implantation and a significant R-wave decrease during follow-up; a considerable and nearly significant increase in pacing threshold was also observed. These findings may be related to the progressive fibro-fatty replacement of RV myocardium. Multiple sites should be tested in the right ventricle if sensing or pacing values are not optimal, and all the electronic parameters should be carefully monitored throughout the entire follow-up.

Advances in sudden death prevention: the emerging role of a fully subcutaneous defibrillator

Randomized clinical trials support the use of implantable defibrillators for mortality reduction in specific populations at high risk for sudden cardiac death. Conventional transvenous defibrillator systems are limited by implantation-associated complications, infection, and lead failure, which may lead to delivery of inappropriate shocks and diminish survival. The development of a fully subcutaneous defibrillator may represent a valuable addition to therapies targeted at sudden death prevention. The PubMed database was searched to identify all clinical reports of the subcutaneous defibrillator from 2000 to the present. We reviewed all case series, cohort analyses, and randomized trials evaluating the safety and efficacy of subcutaneous defibrillators. The subcutaneous defibrillator is a feasible development in sudden cardiac death therapy and may be useful particularly to extend defibrillator therapy to patients with complicated anatomy, limited vascular access, and congenital disease. The subcutaneous defibrillator should not be considered in patients with an indication for cardiac pacing or who have ventricular tachycardia responsive to antitachycardia pacing. Further investigation is needed to compare long-term, head-to-head performance of subcutaneous defibrillators and conventional transvenous defibrillator systems.

Integrated approach for smart implantable cardioverter defibrillator (ICD) device with real time ECG monitoring: use of flexible sensors for localized arrhythmia sensing and stimulation

Arrhythmias are the most common cause of death associated with sudden death and are common in US and worldwide. Cardiac resynchronization therapy (CRT), evolving from pacemakers and development of implantable cardioverter defibrillator (ICD), has been adopted for therapeutic use and demonstrated benefits in patients over the years due to its design and intricate functionality. Recent research has been focused on significant design improvement and efforts are dedicated toward device size reduction, weight and functionality in commercially available ICD's since its invention in the 1960's. Commercially available CRT-D has shown advancement on both clinical and technical side. However, improved focus is required on the device miniaturization, technologically supported and integrated wireless based system for real time heart monitoring electrocardiogram (ECG). In the present report a concise overview for the state-of-the art technology in ICDs and avenues for future development are presented. A unique perspective is also included for ICD device miniaturization and integration of flexible sensing array. Sensor array integration along with its capabilities for identifying localized arrhythmia detection and targeted stimulation for enhancing ICD device capabilities is reviewed.

Cardiac ablation catheter guidance by means of a single equivalent moving dipole inverse algorithm

BACKGROUND

We developed and evaluated a novel system for guiding radiofrequency catheter ablation therapy of ventricular tachycardia. This guidance system employs an inverse solution guidance algorithm (ISGA) using a single equivalent moving dipole (SEMD) localization method. The method and system were evaluated in both a saline tank phantom model and in vivo animal (swine) experiments.

METHODS

A catheter with two platinum electrodes spaced 3 mm apart was used as the dipole source in the phantom study. A 40-Hz sinusoidal signal was applied to the electrode pair. In the animal study, four to eight electrodes were sutured onto the right ventricle. These electrodes were connected to a stimulus generator delivering 1-ms duration pacing pulses. Signals were recorded from 64 electrodes, located either on the inner surface of the saline tank or on the body surface of the pig, and then processed by the ISGA to localize the physical or bioelectrical SEMD.

RESULTS

In the phantom studies, the guidance algorithm was used to advance a catheter tip to the location of the source dipole. The distance from the final position of the catheter tip to the position of the target dipole was 2.22 ± 0.78 mm in real space and 1.38 ± 0.78 mm in image space (computational space). The ISGA successfully tracked the locations of electrodes sutured on the ventricular myocardium and the movement of an endocardial catheter placed in the animal's right ventricle.

CONCLUSION

In conclusion, we successfully demonstrated the feasibility of using an SEMD inverse algorithm to guide a cardiac ablation catheter.

Ivabradine for the prevention of inappropriate shocks due to sinus tachycardia in patients with an implanted cardioverter defibrillator

AIMS

Ivabradine is a specific blocker of the pacemaker current (I(f)) used to decrease the sinus rate. Several clinical trials have shown that it is beneficial, with or without concomitant beta-blocker therapy, in patients with stable angina or heart failure. We sought to take advantage of ivabradine's ability to decrease the maximal obtainable sinus rate in order to prevent inappropriate shocks due to sinus tachycardia in patients with an implanted cardioverter defibrillator (ICD).

METHODS AND RESULTS

Prospective open-label series including all our patients with an implanted ICD who, during the course of 2010-2011, received ivabradine with the only purpose of preventing inappropriate ICD shocks for sinus tachycardia. These are patients who received one or more inappropriate shocks for sinus tachycardia or were conceived to be at very high risk for developing such complication. Our series includes five patients who received ivabradine (5-10 mg/day) in addition to their usual beta-blocker therapy. During a follow-up of 14 months no inappropriate shocks due to sinus tachycardia were recorded.

CONCLUSION

It is sensible to recommend ivabradine for the prevention of inappropriate ICD shocks due to sinus tachycardia in carefully selected patients.

Three-dimensional computed tomography imaging of an implantable cardioverter-defibrillator lead fragment in the left ventricle of a heart transplant followed by successful transarterial extraction with a snare catheter

We report on a 51-year old heart transplant recipient in whom a pacing lead fragment of his old implantable cardioverter-defibrillator (ICD) had been detected in the left ventricle following successful heart transplantation. The patient was transplanted after 5 weeks on high urgent status. A postoperative routine chest X-ray and a subsequent cardiac three-dimensional (3D) computed tomography scan showed a metallic foreign body bending during systole below the posterior mitral valve leaflet within the left ventricle of the heart transplant. Transarterial extraction therapy was planned and the femoral artery was cannulated in the usual fashion. An 8F snare catheter was directed into the left ventricle under fluoroscopic guidance. Successful extraction revealed a 3-cm, uncoated ICD fragment (diameter = 0.025 in.). Following extraction of the fragment echocardiography showed mild mitral regurgitation but no further adverse events occurred. The patient was discharged 2 days later. Transarterial fragment extraction using a snare catheter is a feasible, minimally invasive procedure in this clinical scenario. Careful inspection of all explanted hardware is strongly recommended to ensure that no portion of an ICD lead is left behind.

Implantable cardioverter defibrillator therapy: a single center experience in saudi arabia

INTRODUCTION

Internal Cardioverter Defibrillators (ICD) has been shown to decrease mortality in patients such as those with structural heart disease or at high risk of sudden cardiac death. To date there is no data regarding the clinical features, and outcomes of ICD patients in Saudi Arabia. Accordingly, we explored the clinical features and outcomes of ICD therapy among Saudis.

METHODS

Patients who had ICD implantation in King Khalid University Hospital from November 2007 until January 2010 were enrolled.

RESULTS

One hundred and eight ICD were implanted between November 2007 and February 2010. The mean age was 58.6±13.2 years. The majority were male 94 (87%), the rate of Diabetes Mellitus (DM) was 58.3%, Hypertension (HTN) was 61.1%, and 63% were smokers. The mean ejection fraction (EF) was 24.5%. Of the 108 patient 90(83.3%) had ICD insertion for primary prevention and 18(16.7%) for secondary prevention. Of the 90 patients who ICD for primary prevention 62 (57.4%) had ischemic cardiomyopathy, 39(36.1%) had dilated cardiomyopathy and 7 (6.5%) had channelopathy. Over a mean follow-up of 18 months 4 (3.7%) died.

CONCLUSIONS

Our study describes for the first time patients characteristic and outcomes for ICD therapy in Saudi Arabia. Our patients are younger and have higher prevalence of risk factors that those in Western countries.

Cost-effectiveness of implantable cardioverter-defibrillators in Brazil: primary prevention analysis in the public sector

BACKGROUND

Several studies have demonstrated the effectiveness and cost-effectiveness of implantable cardioverter-defibrillators (ICDs) in chronic heart failure (CHF) patients. Despite its widespread use in developing countries, limited data exist on its cost-effectiveness in these settings.

OBJECTIVE

To evaluate the cost-effectiveness of ICD in CHF patients under the perspective of the Brazilian Public Healthcare System (PHS).

METHODS

We developed a Markov model to evaluate the incremental cost-effectiveness ratio (ICER) of ICD compared with conventional therapy in patients with CHF and New York Heart Association class II and III. Effectiveness was evaluated in quality-adjusted life years (QALYs) and time horizon was 20 years. We searched MEDLINE for clinical trials and cohort studies to estimate data from effectiveness, complications, mortality, and utilities. Costs from the PHS were retrieved from national administrative databases. The model's robustness was assessed through Monte Carlo simulation and one-way sensitivity analysis. Costs were expressed as international dollars, applying the purchasing power parity conversion rate (PPP US$).

RESULTS

ICD therapy was more costly and more effective, with incremental cost-effectiveness estimates of PPP US$ 50,345/QALY. Results were more sensitive to costs related to the device, generator replacement frequency and ICD effectiveness. In a simulation resembling the MADIT-I population survival and ICD benefit, the ICER was PPP US$ 17,494/QALY and PPP US$ 15,394/life years.

CONCLUSIONS

In a Brazilian scenario, where ICD cost is proportionally more elevated than in developed countries, ICD therapy was associated with a high cost-effectiveness ratio. The results were more favorable for a patient subgroup at increased risk of sudden death.

Supraventricular arrhythmia induction by an implantable cardioverter defibrillator in a patient with hypertrophic cardiomyopathy

A 23-year-old woman with obstructive hypertrophic cardiomyopathy and history of frequent unexplained syncope had undergone implantable cardioverter defibrillator implantation. She had experienced frequent inappropriate shocks since implantation due to T-wave oversensing. After one of the syncopal attacks, she was found to have an atrioventricular (AV)-reentrant tachycardia, induced by a high-voltage shock, with rapid degeneration to atrial fibrillation and then ventricular fibrillation. The AV-reentrant tachycardia was believed to be the cause of both syncopal attacks and inappropriate shocks. The patient has been asymptomatic after ablation of the accessory pathway. To the best of our knowledge, this is the first report of induction of an AV-reentrant tachycardia by a high-voltage implantable cardioverter defibrillator shock.