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.

Impact of synchronized left ventricular pacing rate on risk for ventricular tachyarrhythmias after cardiac resynchronization therapy in patients with heart failure

BACKGROUND

The adaptive cardiac resynchronization therapy (aCRT) algorithm automatically produces synchronized left ventricular pacing (sLVP) with intrinsic atrioventricular conduction to improve clinical outcomes. However, relationship between sLVP percentage and risk for ventricular tachyarrhythmia (VT/VF) remains unclear. This study aimed to evaluate the clinical impact of sLVP rate on VT/VF occurrence.

METHODS

In total, 1,419 device interrogation data from 42 consecutive patients who underwent new aCRT device implantation were retrospectively analyzed. The primary endpoint was the first time VT/VF episode after aCRT device implantation.

RESULTS

During a median follow-up of 34 months, 15 patients had VT/VF episodes. Patients were divided into a high sLVP (the average sLVP percentage of ≥ 51.5%, n = 27) or low sLVP group (< 51.5%, n = 15). The high sLVP group had a significantly lower VT/VF incidence (22% vs. 60%; p = 0.014) and an independent predictor for VT/VF occurrence on multivariate analysis (hazard ratio 0.21; p = 0.007). LV ejection fraction improvements after 6 months (12.3 ± 8.7% vs. 2.8 ± 10.3%; p = 0.004) and 12 months (13.8 ± 9.3% vs. 6.2 ± 11.1%; p = 0.030) were significantly greater in the high sLVP group than in the low sLVP group. Age, PR interval, and left atrial diameter were significantly associated with the sLVP rate after aCRT.

CONCLUSIONS

Patients with high sLVP percentage after aCRT had lower long-term risk of VT/VF incidence with a favorable response to CRT. A synchronized pacing algorithm using intrinsic conduction may prevent malignant arrhythmias, as well as recover cardiac functions.

QT interval measurement in ventricular pacing: Implications for assessment of drug effects and pro-arrhythmia risk

QT interval prolongation is a known risk factor for development of malignant ventricular arrhythmias. Measurement of the QT interval is difficult in the setting of ventricular pacing (VP), which can prolong depolarization and increase the QT interval, overestimating repolarization time. VP and cardiac resynchronization therapies have become commonplace in modern cardiac care and may contribute to repolarization heterogeneity and subsequent increased risk for ventricular arrhythmias including Torsades de Pointes. It is imperative for the clinician caring for acutely ill cardiac patients to understand the relationship between QT interval prolongation, both drug-induced and pacing-induced, and repolarization changes with subsequent ventricular arrhythmia risk. In this review, we discuss the components of QT interval assessment for arrhythmogenic risk including arrhythmogenic QT prolongation, methods for adjusting the QT interval to identify repolarization changes, methods to adjust for heart rate, and propose a framework for medication management to assess for drug-induced long QT syndrome in patients with VP.

The Ubiquitous Premature Ventricular Complex

Premature ventricular complexes (PVCs) are one of the most commonly encountered arrhythmias and are ubiquitous in clinical practice, both in the outpatient and inpatient settings. They are often discovered incidentally in asymptomatic patients, however, can cause myriad symptoms acutely and chronically. Long thought to be completely benign, PVCs have been historically disregarded without pursuing any further evaluation. Newer data have revealed that a high burden of PVCs with specific characteristics can significantly increase a patient's risk of developing PVC-induced cardiomyopathy. The aim of this literature review is to provide further clarification on the identification of high-risk PVCs, subsequent workup, and the currently available treatment options. PVCs arise from an ectopic focus within the ventricles. Patients with PVCs can be either asymptomatic or have severe disabling symptoms. The diagnostic workup for PVCs includes electrocardiogram (ECG) and 24-h Holter monitor to assess the QRS morphology and its frequency. A transthoracic echocardiogram (TTE) is done to look for structural heart disease and cardiomyopathy. Management of PVCs should be focused on identifying and treating the underlying causes, such as electrolyte abnormalities, substance use, and underlying structural heart disease. Beta-blockers are first-line therapy for symptomatic PVCs. Nondihydropyridine calcium channel blockers, classic antiarrhythmic agents, and amiodarone can be considered as second-line agents. Patients who are unable to tolerate medical therapy should undergo catheter ablation of the PVC focus to prevent PVC-induced cardiomyopathy. PVCs are common in clinical practice, and it is vital to identify patients at higher risk for PVC-induced cardiomyopathy to facilitate early intervention. Patients with no evidence of structural heart disease and infrequent PVCs should be monitored closely, while those who are symptomatic should be treated medically. For those who have failed medical therapy, catheter ablation of the PVCs focus is recommended. Catheter ablation has been shown to reduce PVCs burden and improve left ventricular ejection fraction (LVEF) in those with PVC-induced cardiomyopathy.

Permanent HIS bundle Pacing Feasibility in Routine Clinical Practice: Experience from an Indian Center

There is a paucity of experience regarding His bundle pacing (HBP) at laboratories initially attempting the procedure, especially in the Indian scenario. Patient who underwent HBP were selected for pacing therapy or in lieu of cardiac resynchronization therapy (CRT) at a single center. Among 22 patients attempted, 19 patients underwent successful implant, achieving selective HBP in 14 patients. There was a significant improvement in left ventricular ejection fraction (LVEF) (49.3 ± 9.3 vs. 36.7 ± 9.2) in the LV dysfunction subgroup (n = 6). Over a follow-up of 15 ± 6.5 months, thresholds were stable in all except one patient, and there was no requirement of lead revision. In summary, we found that HBP is a feasible option for achieving physiological pacing.

Prognostic role of non-sustained ventricular tachycardia detected with remote interrogation in a pacemaker population

Background

Non-sustained ventricular tachycardia (NSVT) can occur asymptomatically and can be incidentally detected in the internal records of pacemakers (PM). The clinical value of NSVT in the population of PM patients is still uncertain.

Our aim was to assess the prevalence of NSVT detected by remote PM control, to describe the clinical and demographic characteristics of patients with NSVT, and to assess the prognostic significance of NSVT in terms of both overall and cardiovascular mortality.

Methods

Consecutive patients followed with PM remote interrogations from September 2010 to December 2015 were included. The transmissions pertaining to the first 12 months of remote control were analysed and the patients were divided by those presenting NSVT and those without NSVT. The two groups were compared in terms of total mortality and cardiovascular mortality based on the administrative data provided by the regional administration of the Italian National Health System.

Results

The prevalence of NSVT in 408 patients (62% males, mean age 75.6; SD 10.6 years old) was 21% in a year. During a mean follow-up duration of 44 months, NSVT did not emerge as independently associated with overall mortality, but was associated with cardiovascular mortality in a competing risk regression model with older age, male gender, diabetes, chronic renal insufficiency, ischemic cardiomyopathy and chronic obstructive pulmonary disease.

Conclusions

We show that NSVT episodes recorded by remote control in a PM population are independently associated with cardiovascular mortality with possible implications for risk stratification and therapeutic options.

Premature Ventricular Complex-induced Cardiomyopathy

Premature ventricular complex-induced cardiomyopathy is a potentially reversible condition in which left ventricular dysfunction is induced by the occurrence of frequent premature ventricular complexes (PVCs). Various cellular and extracellular mechanisms and risk factors for developing cardiomyopathy in this context have been suggested but the exact pathophysiological mechanism remains unclear. The suppression of PVCs is usually indicated in symptomatic patients with frequent PVCs and also those with left ventricular dysfunction. Antiarrhythmic drugs are a useful non-invasive treatment to eliminate PVCs, but the side effect profile, including the risk of pro-arrhythmia, along with suboptimal clinical effectiveness, should be weighed against the usually more effective but not risk-free treatment with catheter ablation. The latter has progressively become first line therapy in many patients with PVC-induced cardiomyopathy and should be particularly considered in specific scenarios.

Right Ventricular Pacing Increases Risk of Appropriate Implantable Cardioverter-Defibrillator Shocks Asymmetrically: An Analysis of the ALTITUDE Database

BACKGROUND

Right ventricular pacing (RVP) increases risk of atrial fibrillation in patients with implantable cardioverter-defibrillators (ICDs), but ventricular proarrhythmia is less clear. We analyzed a large remote monitoring database to assess this question.

METHODS AND RESULTS

Patients with single- or dual-chamber ICDs, engaged in remote monitoring for at least 6 months and with unchanged tachycardia programming, were included. %RVP was derived for each weekly transmission. ICD electrograms preceding the first shock were adjudicated. Among 425 625 transmissions received from 8435 patients, 389 appropriate shocks occurred over a mean follow-up of 15.0±8.8 months. In a time-dependent Cox proportional hazards model, transmissions with 80% to 98% RVP were associated with a hazard ratio of 1.56 for an appropriate shock in the subsequent week compared with <1% RVP (95% CI, 1.01-2.41; P=0.04). By contrast, ≥98% RVP trended toward a lower risk of an appropriate shock (hazard ratio, 0.61; 95% CI, 0.33-1.12; P=0.108). Lifetime cumulative %RVP was closely correlated with weekly %RVP (R²=0.907) and was similarly associated with increased risk of appropriate shocks at 80% to 98% RVP (hazard ratio, 1.57; 95% CI, 1.01-2.44; P=0.046) but not at ≥98% RVP (hazard ratio, 0.49; 95% CI, 0.24-1.01; P=0.052). These results were driven by dual-chamber devices, but unaffected by PVC counts or programming. Male sex and age were also associated with appropriate ICD shocks.

CONCLUSIONS

Increasing frequency of RVP is associated with a progressively increased risk of appropriate ICD shocks until ≥98% RVP. RVP may have ventricular proarrhythmia because of competition of paced and intrinsic rhythm in ICD patients.

What About Tachycardia-induced Cardiomyopathy?

Long-standing tachycardia is a well-recognised cause of heart failure and left ventricular dysfunction, and has led to the nomenclature, tachycardia-induced cardiomyopathy (TIC). TIC is generally a reversible cardiomyopathy if the causative tachycardia can be treated effectively, either with medications, surgery or catheter ablation. The diagnosis is usually made after demonstrating recovery of left ventricular function with normalisation of heart rate in the absence of other identifiable aetiologies. One hundred years after the first reported case of TIC, our understanding of the pathophysiology of TIC in humans remains limited despite extensive work in animal models of TIC. In this review we will discuss the proposed mechanisms of TIC, the causative tachyarrhythmias and their treatment, outcomes for patients diagnosed with TIC, and future directions for research and clinical care.

Upgrade from ICD to CRT-D: clinical and haemodynamic impact of biventricular pacing in a patient with acquired long QT syndrome

Long QT syndrome (LQTS) is characterised by both the depolarisation and repolarisation disorder of cardiac muscle cells. Cardiac resynchronising therapy (CRT) is an important treatment option for patients with chronic heart failure (CHF) when echocardiographic and electrocardiographic criteria are met. Although CRT was introduced in clinical practice 10 years ago, doubts related to application of this treatment method persist because of its potential proarrhythmogenic effect. This is a case describing a 66-year-old Caucasian female with LQTS coexisting with a left bundle branch branch block (LBBB) and an implantable single-cavity cardioverter-defibrillator (ICD VR), who had repeated appropriate high-energy treatments. The upgrade to resynchronisation therapy defibrillator (CRT-D) significantly reduced frequency of ventricular tachycardia and the need for electrical therapies. The normalisation of the left ventricle size, as seen on echo examination, and the improvement of heart failure symptoms were also observed.

Frequency, origin, and outcome of ventricular premature complexes in patients with or without heart diseases

The objective of the present study was to investigate the relation of ventricular premature complex (VPC) burden, origin, and electrocardiographic characteristics with left ventricular function and survival. Of 1,589 study patients, 388 (25%), 610 (38%), and 591 (37%) had low (<1,000/24 hours), moderate (1,000 to 10,000/24 hours), and high (>10,000/24 hours) VPC burden, respectively. Twenty-three percent of study patients had a left ventricular (LV) ejection fraction <50% (8% in low-, 20% in moderate-, and 36% in high-VPC-burden groups, p <0.001). High VPC burden was associated with lower LV ejection fraction in the presence (r = -0.17, p <0.001) and absence (r = -0.20, p <0.001) of heart diseases. The Kaplan-Meier survival estimates showed a significant difference among the 3 VPC burden groups (p = 0.046). The survival rates were significantly lower for patients with a VPC coupling interval of ≥480 ms than those with a VPC coupling interval of <480 ms (p = 0.002) and lower for those with a VPC QRS duration of ≥150 ms than those with a VPC QRS duration of <150 ms (p <0.001). In conclusion, high VPC burden is detrimental to LV systolic function. Broader VPC QRS duration and longer VPC coupling interval adversely impact on long-term survival.

Relation of ventricular tachycardia/fibrillation to beta-blocker dose maximization guided by pacing mode analysis in nonpacemaker-dependent patients with implantable cardioverter-defibrillator

We hypothesized that uptitration of β blockade and adjustment of pacing parameters to achieve a prevalence of single chamber atrial inhibited rate-responsive (AAIR) pacing in patients with dual-chamber implantable cardioverter--defibrillators (ICDs) would result in maximization of β-blocker dosage and thus decrease appropriate ICD therapies. We included patients with ischemic or dilated cardiomyopathy and implanted ICDs without contraindications to β blockers and atrioventricular conduction disturbances. Two 6-month periods were compared: clinically guided phase (pacing function set at back-up dual-chamber rate-responsive pacing mode at a lower rate of about 40 beats/min) and pacing-guided phase, during which β-blocker dosage was titrated with a target of achieving >90% AAIR pacing (lower rate 60 beats/min). Sixty-one patients (64.2 ± 8.3 years old) were included. During the pacing-guided phase the target of ≥90% AAIR pacing was achieved in 80.3% of patients. Mean metoprolol dose during the clinically guided phase was 96.7 ± 29.4 versus 127.0 ± 39.6 mg/day in the pacing-guided phase (p <0.001). Appropriate ICD therapies were recorded in 35 patients (57.4%) during the clinically guided phase versus 20 (32.8%) during the pacing-guided phase (p <0.001; 1.15 and 0.48 appropriate ICD therapies per patient, respectively, p <0.001). In multivariate analysis, AAIR pacing and β-blocker dose were inversely related to appropriate ICD therapies. In conclusion, a pacing-guided approach for maximizing β-blocker doses guided by maximizing AAIR pacing in patients with ICDs may be beneficial compared to the conventional strategy. This pacing-guided approach led to higher daily β-blocker doses, which were correlated to fewer appropriate ICD therapies.

Permanent His-bundle pacing: seeking physiological ventricular pacing

AIMS

Right ventricular apical pacing can have deleterious effects and the His bundle has been widely reported to be an alternative site. This paper presents our experience with permanent His-bundle pacing (HBP).

METHODS AND RESULTS

Patients referred for pacemaker implants (regardless of block type) were screened to determine if temporary HBP corrected conduction dysfunctions (threshold < or =2.5 V for 1 ms) and provided infra-Hisian 1:1 conduction of at least 120 s/m. Of the 182 patients selected, HBP corrected conduction dysfunctions in 133 (73%) patients, 42 (32%) of whom were rejected for the permanent procedure due to high thresholds. His-bundle lead implantation was attempted in the remaining 91 patients and was successful in 59 (65% of all attempts, 44% of all possible cases).

CONCLUSION

In some patients, permanent HBP may be an alternative to right ventricular apical pacing.

Pacemaker-based analysis of atrioventricular conduction and atrial tachyarrhythmias in patients with primary sinus node dysfunction

BACKGROUND

Most patients with symptomatic sinus node disease (SND) receive DDDR pacemakers (PM) in order to cover SND and atrioventricular (AV) block from the outset. But the concern about adverse effects of right ventricular pacing (RVP) is increasing. So far, data on the incidence of AV block in SND are based on clinical events. The study undertakes to assess and appraise AV block and atrial tachyarrhythmias (AT) from memory and electrograms of a dual-chamber PM set to an AAIR-DDDR switch mode (AAISafeR).

METHODS

A dual-chamber PM incorporating the AAISafeR mode was implanted in 58 patients (70 +/- 10 years, 28 males) with SND, but without AV block >I. AV block and AT episodes were retrieved from the PM memory and validated from electrograms. AV block episodes were classified potentially relevant while comprising AV block III or AV block I/II during exercise.

RESULTS

The patients experienced a median of 90 (interquartile range 7-1,084) commutations. Possibly relevant AV block occurred in 32 patients (55%). Validation revealed high-quality PM-based categorization. The RVP prevalence was 0% (0-16%). The median AT prevalence was 0.03 (0-26) min/day. RVP was the only multivariate predictor of AT (P = 0.001).

CONCLUSIONS

Potentially relevant AV block occurs frequently in patients with SND. Nonetheless, the RVP prevalence is kept low through the AAISafeR mode. The protection of SND patients with demand-actuated ventricular pacing appears reasonable. The AT prevalence is low in SND patients treated by the AAISafeR mode. Even low RVP proportions appear to favor AT. Prospective evaluation is needed.

Temporary epicardial ventricular stimulation in patients with atrial fibrillation: acute effects of ventricular pacing site on bypass graft flows

OBJECTIVE

Data on coronary artery bypass grafts flows in patients with atrial fibrillation (AF) requiring epicardial ventricular pacing is lacking. This study aimed to evaluate the optimal epicardial ventricular pacing site in patients with AF following coronary artery bypass surgery (CABG).

METHODS

In 23 consecutive patients (mean age = 69.2 +/- 1.9 years, gender = 62% male, ejection fraction [EF]= 50.4 +/- 2.1%) monoventricular stimulations (VVI) were tested with a constant pacing rate of 100 bpm. The impact of ventricular pacing on bypass graft flow (transit-time flow probe) and pulsatility index (PI) were measured after lead placement on the mid paraseptal region of the right (RVPS) and the left (LVPS) ventricle, on the right inferior wall (RVIW), and on the right ventricular outflow tract (RVOT). In addition, hemodynamic parameters were measured. Patients served as their own control.

RESULTS

Comparison of all tested pacing locations revealed that RVOT stimulation provided the highest bypass grafts flows (59.9 +/- 6.1 mL/min) and PI (2.2 +/- 0.1) when compared with RVPS (51.3 +/- 4.7 mL/min, PI = 2.6 +/- 0.2), RVIW (54.0 +/- 5.1 mL/m; PI = 2.4 +/- 0.2), and LVPS (53.1 +/- 4.5 mL/min; PI = 2.3 +/- 0.1), respectively (p < 0.05). When analyzing patients according to their preoperative LV function (group I = EF > 50%; group II = EF < 50%), higher bypass graft flows were observed with RVOT pacing in patients with lower EF (p = n.s.).

CONCLUSIONS

Temporary RVOT pacing facilitates optimal bypass graft flows when compared with other ventricular pacing sites and should be the preferred method of temporary pacing in cardiac surgery patients with AF. Especially in patients with low EF following CABG, RVOT pacing may improve myocardial oxygen conditions for the ischemic myocardium and enhance graft patency in the early postoperative period.

Selective site pacing: rationale and practical application

Although it has become traditional to place permanent pacemaker leads at the right ventricular apex and right atrial appendage, pacing from these locations poorly mimics normal physiology. A growing evidence base shows that right ventricular apical pacing results in ventricular dyssynchrony and various adverse effects. Provocative data from early trials suggest that pacing from alternate sites in the right ventricle--His bundle pacing, para-Hisian pacing, septal right ventricular outflow tract pacing, and right ventricular midseptal pacing--may lead to improved results. Similarly, early data suggest that right atrial pacing near Bachmann's bundle may lead to superior outcomes when compared with pacing from the right atrial appendage. Several large-scale, randomized clinical trials are now under way to establish the future role of selective site pacing.