Arrhythmic Risk in Biventricular Pacing Compared With Left Bundle Branch Area Pacing: Results From the I-CLAS Study

BACKGROUND

Left bundle branch area pacing (LBBAP) may be associated with greater improvement in left ventricular ejection fraction and reduction in death or heart failure hospitalization compared with biventricular pacing (BVP) in patients requiring cardiac resynchronization therapy. We sought to compare the occurrence of sustained ventricular tachycardia (VT) or ventricular fibrillation (VF) and new-onset atrial fibrillation (AF) in patients undergoing BVP and LBBAP.

METHODS

The I-CLAS study (International Collaborative LBBAP Study) included patients with left ventricular ejection fraction ≤35% who underwent BVP or LBBAP for cardiac resynchronization therapy between January 2018 and June 2022 at 15 centers. We performed propensity score-matched analysis of LBBAP and BVP in a 1:1 ratio. We assessed the incidence of VT/VF and new-onset AF among patients with no history of AF. Time to sustained VT/VF and time to new-onset AF was analyzed using the Cox proportional hazards survival model.

RESULTS

Among 1778 patients undergoing cardiac resynchronization therapy (BVP, 981; LBBAP, 797), there were 1414 propensity score-matched patients (propensity score-matched BVP, 707; propensity score-matched LBBAP, 707). The occurrence of VT/VF was significantly lower with LBBAP compared with BVP (4.2% versus 9.3%; hazard ratio, 0.46 [95% CI, 0.29-0.74]; P<0.001). The incidence of VT storm (>3 episodes in 24 hours) was also significantly lower with LBBAP compared with BVP (0.8% versus 2.5%; P=0.013). Among 299 patients with cardiac resynchronization therapy pacemakers (BVP, 111; LBBAP, 188), VT/VF occurred in 8 patients in the BVP group versus none in the LBBAP group (7.2% versus 0%; P<0.001). In 1194 patients with no history of VT/VF or antiarrhythmic therapy (BVP, 591; LBBAP, 603), the occurrence of VT/VF was significantly lower with LBBAP than with BVP (3.2% versus 7.3%; hazard ratio, 0.46 [95% CI, 0.26-0.81]; P=0.007). Among patients with no history of AF (n=890), the occurrence of new-onset AF >30 s was significantly lower with LBBAP than with BVP (2.8% versus 6.6%; hazard ratio, 0.34 [95% CI, 0.16-0.73]; P=0.008). The incidence of AF lasting >24 hours was also significantly lower with LBBAP than with BVP (0.7% versus 2.9%; P=0.015).

CONCLUSIONS

LBBAP was associated with a lower incidence of sustained VT/VF and new-onset AF compared with BVP. This difference remained significant after adjustment for differences in baseline characteristics between patients with BVP and LBBAP. Physiological resynchronization by LBBAP may be associated with lower risk of arrhythmias compared with BVP.

Early-Onset Cardiomyopathy After Pacemaker Implanted in a Preterm Infant With Congenital Complete Heart Block and Anti-Ro/SSA Antibodies

Congenital complete heart block is a potentially fatal complication that can occur in neonates whose mothers have autoimmune disorders; it has rarely been reported in the presence of Sjögren syndrome. Pacemaker implantation is recommended to treat rhythm abnormalities in these neonates. We report the case of a late-preterm infant with Sjögren-syndrome-antibody-induced complete heart block who underwent temporary bipolar epicardial pacing as a bridge to permanent pacemaker implantation. Soon after the pacemaker was implanted, takotsubo cardiomyopathy developed. To our knowledge, this is the first report of reversible cardiomyopathy after pacemaker implantation in an infant.

Minimally Invasive Implantation of a Micropacemaker Into the Pericardial Space

BACKGROUND

Permanent cardiac pacemakers require invasive procedures with complications often related to long pacemaker leads. We are developing a percutaneous pacemaker for implantation of an entire pacing system into the pericardial space.

METHODS

Percutaneous micropacemaker implantations were performed in 6 pigs (27.4-34.1 kg) using subxyphoid access to the pericardial space. Modifications in the implantation methods and hardware were made after each experiment as the insertion method was optimized. In the first 5 animals, nonfunctional pacemaker devices were studied. In the final animal, a functional pacemaker was implanted.

RESULTS

Successful placement of the entire nonfunctional pacing system into the pericardial space was demonstrated in 2 of the first 5 animals, and successful implantation and capture was achieved using a functional system in the last animal. A sheath was developed that allows retractable features to secure positioning within the pericardial space. In addition, a miniaturized camera with fiberoptic illumination allowed visualization of the implantation site before electrode insertion into myocardium. All animals studied during follow-up survived without symptoms after the initial postoperative period.

CONCLUSIONS

A novel micropacemaker system allows cardiac pacing without entering the vascular space or surgical exposure of the heart. This pericardial pacemaker system may be an option for a large number of patients currently requiring transvenous pacemakers but is particularly relevant for patients with restricted vascular access, young children, or those with congenital heart disease who require epicardial access.

Chronotropic Incompetence in Chronic Heart Failure

Chronotropic incompetence (CI) is generally defined as the inability to increase the heart rate (HR) adequately during exercise to match cardiac output to metabolic demands. In patients with heart failure (HF), however, this definition is unsuitable because metabolic demands are unmatched to cardiac output in both conditions. Moreover, HR dynamics in patients with HF differ from those in healthy subjects and may be affected by β-blocking medication. Nevertheless, it has been demonstrated that CI in HF is associated with reduced functional capacity and poor survival. During exercise, the normal heart increases both stroke volume and HR, whereas in the failing heart, contractility reserve is lost, thus rendering increases in cardiac output primarily dependent on cardioacceleration. Consequently, insufficient cardioacceleration because of CI may be considered a major limiting factor in the exercise capacity of patients with HF. Despite the profound effects of CI in this specific population, the issue has drawn limited attention during the past years and is often overlooked in clinical practice. This might partly be caused by a lack of standardized approach to diagnose the disease, further complicated by changes in HR dynamics in the HF population, which render reference values derived from a normal population invalid. Cardiac implantable electronic devices (implantable cardioverter defibrillator; cardiac resynchronization therapy) now offer a unique opportunity to study HR dynamics and provide treatment options for CI by rate-adaptive pacing using an incorporated sensor that measures physical activity. This review provides an overview of disease mechanisms, diagnostic strategies, clinical consequences, and state-of-the-art device therapy for CI in HF.

Leadless Cardiac Pacemakers: The Next Evolution in Pacemaker Technology

Implantable pacemakers stand as a mainstay in our therapeutic arsenal, affording those suffering from advanced cardiac conduction system disease both an improved quality of life and reduced mortality. Annually, over 225,000 new pacemakers are implanted in the United States for bradyarrhythmias and heart block. The first implantable transvenous pacemakers appeared in 1965; they were bulky devices, hobbled by a short battery life, and a single pacing mode. Modern transvenous pacemakers have evolved considerably with significant improvements in battery life, pacing options, and lead technology but are still subject to a spectrum of complications stemming from either the subcutaneous pocket or the leads, including: hematoma, infection, wound dehiscence, pneumothorax, cardiac tamponade, lead dislodgment, upper extremity deep vein thrombosis, lead failure, venous obstruction, tricuspid valve insufficiency, and endocarditis. Single-chamber right ventricular (RV) leadless cardiac pacemakers, a concept from the past, has been revitalized to address these complications. Improvements in battery life, device miniaturization, catheter-based delivery tools, and advanced programming have made leadless cardiac pacemakers a viable option. In this review, we will discuss single-component leadless cardiac pacemaker technology, provide an overview of the two approved devices, and discuss their benefits as well as their limitations. [Full article available at http://rimed.org/rimedicaljournal-2017-11.asp].

Long-term follow-up shows excellent transmural atrial lead performance in patients with complex congenital heart disease

BACKGROUND

Many patients with congenital heart disease require permanent pacing for rhythm management but cannot undergo transvenous lead placement. In others, epicardial scarring prohibits adequate sensing and pacing thresholds using epicardial leads. This study describes long-term lead performance using a transmural atrial (epicardial to endocardial) pacing approach in patients with congenital heart disease.

METHODS AND RESULTS

For transmural atrial (TMA) lead access, a bipolar, steroid-eluting transvenous lead was placed from the epicardium via purse-string incision or atriotomy and affixed to atrial endocardium. Records were reviewed for patient data and acute and long-term lead performance for TMA leads placed 1998 to 2004. Forty-two of 48 TMA leads remain active at last follow-up. Two leads fractured, 4 were functional at >5-year follow-up but no longer active. Freedom from lead failure 98% (95% confidence interval, 86%-100%) at mean follow-up 7.8 years. TMA leads gave excellent sensing and pacing characteristics at implant and chronically. Median acute and chronic sensing thresholds were 3 and 2.8 mV, respectively; median acute and chronic pacing thresholds at 0.5 ms were 0.9 and 0.7 V, respectively. TMA leads performed similarly in Fontan patients. Overdrive pacing for intra-atrial re-entrant tachycardia was successful in 7 of 8 patients. One patient with high baseline risk died of stroke 7 years after implant. No lead-associated thrombi were observed.

CONCLUSIONS

TMA pacing leads had excellent longevity, initial, and chronic functional properties and provide an alternative to epicardial leads in patients with congenital heart disease. Patients who cannot receive transvenous leads, have epicardial scarring or have intra-atrial re-entrant tachycardia could benefit most from routine use of this technique.

Inappropriate implantable cardioverter-defibrillator shocks attributed to alternating-current leak in a swimming pool

Implantable cardioverter-defibrillators (ICDs) are the standard of care for preventing sudden cardiac death in patients who are predisposed to malignant ventricular arrhythmias. Causes of inappropriate ICD shock include equipment malfunction, improper arrhythmia evaluation, misinterpretation of myopotentials, and electromagnetic interference. As the number of implanted ICDs has increased, other contributors to inappropriate therapy have become known, such as minimal electrical current leaks that mimic ventricular fibrillation. We present the case of a 63-year-old man with a biventricular ICD who received 2 inappropriate shocks, probably attributable to alternating-current leaks in a swimming pool. In addition, we discuss ICD sensitivity and offer recommendations to avoid similar occurrences.

Prospective randomized study to assess the efficacy of site and rate of atrial pacing on long-term progression of atrial fibrillation in sick sinus syndrome: Septal Pacing for Atrial Fibrillation Suppression Evaluation (SAFE) Study

BACKGROUND

Atrial-based pacing is associated with lower risk of atrial fibrillation (AF) in sick sinus syndrome compared with ventricular pacing; nevertheless, the impact of site and rate of atrial pacing on progression of AF remains unclear. We evaluated whether long-term atrial pacing at the right atrial (RA) appendage versus the low RA septum with (ON) or without (OFF) a continuous atrial overdrive pacing algorithm can prevent the development of persistent AF.

METHODS AND RESULTS

We randomized 385 patients with paroxysmal AF and sick sinus syndrome in whom a pacemaker was indicated to pacing at RA appendage ON (n=98), RA appendage OFF (n=99), RA septum ON (n=92), or RA septum OFF (n=96). The primary outcome was the occurrence of persistent AF (AF documented at least 7 days apart or need for cardioversion). Demographic data were homogeneous across both pacing site (RA appendage/RA septum) and atrial overdrive pacing (ON/OFF). After a mean follow-up of 3.1 years, persistent AF occurred in 99 patients (25.8%; annual rate of persistent AF, 8.3%). Alternative site pacing at the RA septum versus conventional RA appendage (hazard ratio=1.18; 95% confidence interval, 0.79-1.75; P=0.65) or continuous atrial overdrive pacing ON versus OFF (hazard ratio=1.17; 95% confidence interval, 0.79-1.74; P=0.69) did not prevent the development of persistent AF.

CONCLUSIONS

In patients with paroxysmal AF and sick sinus syndrome requiring pacemaker implantation, an alternative atrial pacing site at the RA septum or continuous atrial overdrive pacing did not prevent the development of persistent AF.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. UNIQUE IDENTIFIER: NCT00419640.

Implantable cardioverter-defibrillators: indications and unresolved issues

Since the implantable cardioverter-defibrillator was first used clinically in 1980, several large randomized controlled trials have shown that therapy with this device can be beneficial in various patient populations. Evidence suggests that this therapy is useful in the secondary prevention of sudden cardiac death among patients who have survived arrhythmic events. Several trials have also shown the usefulness of implantable cardioverter-defibrillator therapy in the primary prevention of sudden cardiac death in patients with coronary artery disease and nonischemic cardiomyopathy. Other data support the use of this device for various infiltrative and inherited conditions. When used with cardiac resynchronization therapy, implantable cardioverter-defibrillators have improved survival rates and quality of life in patients with severe heart failure. Further research is needed to examine the potential benefits of implantable cardioverter-defibrillators in elderly, female, and hemodialysis-dependent patients, and to determine the optimal waiting period for implantation after myocardial infarction, coronary revascularization, and initial heart-failure diagnosis.

Rituximab-induced polymorphic ventricular tachycardia

The anti-CD20 monoclonal antibody rituximab is an effective treatment for small lymphocytic lymphoma; however, it has been associated with infusion reactions, including cardiac arrhythmias. Severe cardiac arrhythmia is an adverse reaction that is related to rituximab chemotherapy, and more investigation is warranted into the adverse reactions of rituximab that involve cardiac conduction abnormalities. Herein, we report what we believe to be the 1st case of symptomatic polymorphic ventricular tachycardia to have occurred during an initial infusion of rituximab.

Electrical storm in patients with implantable cardioverter-defibrillators: can it be forecast?

The aim of this retrospective study was to determine the prevalence and predictors of electrical storm in 227 patients who had received implantable cardioverter-defibrillators (ICDs) and had been monitored for 31.7 +/- 15.6 months. Of these, 174 (77%) were men. The mean age was 55.8 +/- 15.5 years (range, 20-85 yr), and the mean left ventricular ejection fraction (LVEF) was 0.30 +/- 0.14. One hundred forty-six of the patients (64%) had underlying coronary artery disease. Cardioverter-defibrillators were implanted for secondary (80%) and primary (20%) prevention. Of the 227 patients, 117 (52%) experienced events that required ICD therapy. Thirty patients (mean age, 57.26 +/- 14.3 yr) had > or = 3 episodes requiring ICD therapy in a 24-hour period and were considered to have electrical storm. The mean number of events was 12.75 +/- 15 per patient. Arrhythmia-clustering occurred an average of 6.1 +/- 6.7 months after ICD implantation. Clinical variables with the most significant association with electrical storm were low LVEF (P = 0.04; hazard ratio of 0.261, and 95% confidence interval of 0.08-0.86) and higher use of class IA antiarrhythmic drugs (P = 0.018, hazard ratio of 3.84, and 95% confidence interval of 1.47-10.05). Amiodarone treatment and use of beta-blockers were not significant predictors when subjected to multivariate analysis. We conclude that electrical storm is most likely to occur in patients with lower LVEF and that the use of Class IA antiarrhythmic drugs is a risk factor.

Dual atrioventricular-nodal physiology, elicited by pacing and leading to a reversible cardiomyopathy

Atrioventricular nodal re-entry tachycardia is the most common form of regular paroxysmal tachycardia in the adult population. This tachycardia is a re-entrant rhythm that uses the anatomic location of the atrioventricular node and its surrounding perinodal atrial tissue. The simplest concept regarding the atrioventricular nodal physiology that allows re-entry is founded upon the postulated existence of 2 atrioventricular nodal pathways with different conduction velocities and refractory periods. Herein, we present the case of a 64-year-old man who had a history of paroxysmal atrial fibrillation; he had a permanent pacemaker for sick-sinus syndrome. He developed a tachycardia-induced cardiomyopathy with a perpetual dual response to the pacemaker stimulus. The tachycardia displayed characteristic dual atrioventricular-nodal physiology that was suppressed by amiodarone therapy, leading to a reversal of the cardiomyopathy. We discuss the mechanisms that surround such phenomena.

Predictors of permanent pacemaker implantation during the early postoperative period after valve surgery

The ability to preoperatively identify patients who may require permanent pacemaker implantation is rather poorly understood. The aim of this study is to determine the current incidence of permanent pacing after valve surgery and to determine which factors place the heart valve patient at risk of requiring permanent pacemaker implantation. We audited the records of 2,392 consecutive adult patients who underwent cardiac valve surgical procedures by the same surgical team from 25 April 1998 through 31 March 2003. Of these, 118 patients (group A) required the postoperative implantation of permanent pacemakers during the same hospitalization; they were compared with 1,959 heart valve patients (group B) who did not require pacemaker placement. Multivariate logistic regression analysis showed that reoperations (odds ratio [OR], 8.23; P <0.001), longer cumulative cross-clamp times (OR, 5.9; P <0.001), multiple-valve surgical procedures (OR, 3.46; P <0.05), and absence of preoperative sinus rhythm (OR 2.52; P <0.001) were independent predictors of the need for permanent pacemaker implantation after valve surgery. These results suggest that patients who display these risk factors for arrhythmias that require permanent pacemaker implantation receive closer observation and advance counseling about the likelihood of such implantation.

Pacemakers in children: medical and surgical aspects

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Indications and choices in pacemaker therapy

During their 33-year history of clinical use, cardiac pacemakers have evolved from devices primarily intended to save lives into complex systems designed to improve the cardiac patient's overall quality of life. To help physicians cope with this rapidly changing field, this review outlines current indications for pacemaker therapy and examines the wide range of options available. After describing the standard nomenclature for identifying the various systems, the author discusses pacemaker selection on the basis of cardiac rhythm alone, as well as rate-modulated therapy.

Electrophysiologic testing: predictive of amiodarone efficacy in recurrent sustained ventricular tachycardia?

The role of programmed ventricular stimulation (PVS) was evaluated in 12 patients with recurrent sustained ventricular tachycardia (VT) who were treated with amiodarone as the sole antiarrhythmic agent. At control PVS, sustained VT was induced in 11 patients and nonsustained VT was induced in one patient, as compared with late PVS (mean, 8.6 weeks) when sustained VT was induced in six patients and nonsustained VT was induced in five. Amiodarone significantly prolonged the patients' RR, PR, QRS, and QTc intervals, VT cycle length, and right ventricular effective refractory period. During a mean follow-up of 16 +/- 13.6 months, two patients had recurrent clinical VT. In the patients in whom amiodarone therapy failed (1) sustained VT was induced during late PVS, (2) VT cycle length and symptoms during late PVS and during recurrent clinical VT were similar, and (3) the QTc failed to be prolonged significantly (32.5 +/- 1.6 ms in amiodarone failure vs. 84.1 +/- 27.1 ms in amiodarone success, P<0.05). It is concluded that (1) amiodarone in high-risk patients is clinically effective (88.3%), (2) patients with noninducible VT or nonsustained VT during late PVS did not have recurrent clinical VT, (3) late PVS is probably predictive of electrophysiologic and hemodynamic consequences in patients with recurrent spontaneous VT, and (4) failure of the QTc interval to be prolonged substantially is probably predictive of clinical recurrence of VT.