Effect of biventricular pacing during a ventricular sensed event

Acute echocardiographic and electrocardiographic effects of triggered left ventricular pacing

Cardiac resynchronization therapy (CRT) is an essential pillar in the therapy of heart failure patients with reduced ejection fraction (HFrEF) presenting with broad left bundle branch block (LBBB) or pacemaker dependency. To achieve beneficial effects, CRT requires high bi-ventricular (BiV) pacing rates. Therefore, device-manufacturers designed pacing algorithms which maintain high BiV pacing rates by a left ventricular (LV) pacing stimulus immediately following a right ventricular sensed beat. However, data on clinical impact of these algorithms are sparse. We studied 17 patients implanted with a CRT device providing triggered left ventricular pacing (tLVp) in case of atrioventricular nodal conduction. Assessment of LV dyssynchrony was performed using echocardiographic and electrocardiographic examination while CRT-devices were set to three different settings: 1. Optimized bi-ventricular-stimulation (BiV); 2. Physiological AV nodal conduction (tLVp-off); 3. Physiological AV nodal conduction and tLVp-algorithm turned on (tLVp-on). QRS duration increased when the CRT-device was set to tLVp-off compared to BiV-Stim, while QRS duration was comparable to BiV-Stim with the tLVp-on setting. Echocardiographic analysis revealed higher dyssynchrony during tLVp-off compared to BiV-Stim. TLVp-on did not improve LV dyssynchrony compared to tLVp-off. QRS duration significantly decreased using tLVp-algorithms compared to physiological AV nodal conduction. However, echocardiographic examination could not show functional benefit from tLVp-algorithms, suggesting that these algorithms are inferior to regular biventricular pacing regarding cardiac resynchronization. Therefore, medical treatment and ablation procedures should be preferred, when biventricular pacing rates have to be increased. TLVp-algorithms can be used in addition to these treatment options.

Atrial fibrillation in cardiac resynchronization therapy

Patients with atrial fibrillation (AF) were largely excluded from the major clinical trials of cardiac resynchronization therapy (CRT), despite the presence of AF in up to 40% of patients receiving CRT in clinical practice. AF appears to attenuate the response to CRT, by the combination of a reduction in biventricular pacing and the loss of atrioventricular synchrony. In addition, remodeling secondary to CRT may influence the progression of AF. Management options for patients with AF and CRT include rate control, with drugs or atrioventricular node ablation, or rhythm control, with electrical cardioversion and antiarrhythmic therapy, or AF catheter ablation. The evidence for these therapies in patients with CRT is largely limited to observational studies or inferred from randomized studies in the general heart failure population. In this review, we explore the complex interaction between AF, heart failure, and CRT and discuss the evidence for the treatment options in this difficult patient cohort.

[Management of premature ventricular ectopy in cardiac resynchronization therapy : Treatment strategies for an optimized cardiac resynchronization]

Cardiac resynchronization therapy (CRT) is an integral part in the treatment of chronic heart failure. However, a high degree of biventricular pacing is essential for the effectiveness of this therapy. In addition to atrial fibrillation, premature ventricular contractions (PVC) are a common cause of reduced biventricular stimulation in CRT. In addition to the prognostically unfavorable reduction of biventricular pacing, PVC are generally associated with reduced outcome in the presence of structural heart disease. Options to increase biventricular stimulation percentage by reprogramming the CRT devices are limited in the majority of cases. Due to the mutual relationship between cardiomyopathy and ventricular arrhythmias, adequate heart failure therapy is essential for the reduction of ventricular ectopy. In addition to beta-blocker therapy, specific antiarrhythmic medication is mostly limited to class III antiarrhythmic drugs due to the structural heart disease usually present in CRT patients. Catheter ablation is superior to pharmacological therapy especially in the field of idiopathic PVC, but promising data are also available for catheter ablation of PVC in structural heart disease and CRT nonresponders.

Maximizing biventricular pacing in patients with rate-controlled atrial fibrillation using ventricular sense response

In patients with atrial fibrillation (AF), cardiac resynchronization therapy (CRT) is challenging because the ventricular rate of conducted AF exceeds the biventricular pacing rate. In the current report, we present a patient who received a CRT device that was programmed to ventricular sense response (VSR) on with VVI 40 beats per minute to allow the AF to be paced as fusion beats. We found that the pacing configuration resulting in the narrowest QRS in this patient was VVI 40 with VSR biventricular fusion pacing during AF. VSR mode allows for CRT delivery without the need to artificially increase heart rate.

Left univentricular pacing for cardiac resynchronization therapy

This review describes the rationale and published evidence for left univentricular pacing for cardiac resynchronization therapy, gives an overview of the existing optimization algorithms featuring this mode, and discusses future perspectives.

Device rounds: T-wave oversensing: A cause of loss of cardiac resynchronization therapy

A CRT-D patient presented with loss of biventricular pacing associated with heart failure symptoms. The electrocardiogram showed sinus rhythm with alternating wide unpaced and narrower paced QRS complexes. Device interrogation showed T-wave oversensing on all paced biventricular beats, with the following sinus P-wave not tracked due to it falling in the post-ventricular atrial refractory period, leading to intrinsic conduction. Device reprogramming from true bipolar (RV tip to RV ring) sensing to integrated bipolar (RV tip to RV coil) resolved the problem without having to decrease sensitivity values, allowing biventricular pacing close to 100% to resume with improvement of symptoms. T-wave oversensing is a frequently recognised cause of inappropriate therapy in implantable cardioverter defibrillators, but less frequently as a cause of loss of biventricular pacing in CRT-Ds. We review the different non-invasive strategies to overcome this problem.

Left ventricular performance during triggered left ventricular pacing in patients with cardiac resynchronization therapy and left bundle branch block

PURPOSE

To assess the acute effect of triggered left ventricular pacing (tLVp) on left ventricular performance and contraction pattern in patients with heart failure, left bundle branch block (LBBB), and cardiac resynchronization therapy (CRT).

METHODS

Twenty-three patients with pre-implant QRS complex >150 ms, QRS complex narrowing under CRT, and sinus rhythm were included ≥3 months after CRT implantation. Echocardiographic assessment of left ventricular ejection fraction (LVEF), global peak systolic longitudinal strain (GLS), and contraction pattern by 2D strain was performed during intrinsic conduction, tLVp, and BiV pacing and compared as paired data. Echocardiographic analysis was done blinded with respect to pacing mode.

RESULTS

LVEF was significantly higher during BiV pacing (47 ± 11 %) compared with intrinsic conduction (43 ± 13 %, P = 0.001) and tLVp (44 ± 13 %, P = 0.001), while there was no difference between intrinsic conduction and tLVp (P = 0.28). GLS was higher during BiV (14 ± 3) than during intrinsic conduction (13 ± 3, P = 0.01) and tLVp (13 ± 3, P = 0.03). Difference in time-to-peak contraction between the basal septal and lateral walls was shorter during BiV pacing (-3 ± 44 ms) than during intrinsic conduction (129 ± 66, P < 0.001) and tLVp (118 ± 118 ms, P < 0.001), with no difference between tLVp and intrinsic conduction (P = 0.56). The electrocardiogram showed change in frontal axis from intrinsic conduction in only 2 (9 %) patients during tLVp and in 20 (87 %) patients during BiV pacing.

CONCLUSIONS

The acute effect of tLVp on LV systolic function and contraction pattern is significantly lower than the effect of BiV pacing and not different from intrinsic conduction in patients with LBBB and CRT.

The Burden and Morphology of Premature Ventricular Contractions and their Impact on Clinical Outcomes in Patients Receiving Biventricular Pacing in the Multicenter Automatic Defibrillator Implantation Trial-Cardiac Resynchronization Therapy (MADIT-CRT)

INTRODUCTION

Premature ventricular contractions (PVCs) frequently occur in patients with left ventricular dysfunction. However, there are limited data regarding the burden and morphologic characteristics of PVCs in patients receiving cardiac resynchronization therapy.

METHODS AND RESULTS

Patients enrolled in the Multicenter Automatic Defibrillator Implantation Trial-Cardiac Resynchronization Therapy (MADIT-CRT) with >5000 PVCs on a predevice implant 12-lead, 24-hour Holter were identified. The putative PVC site of origin for the most dominant PVC was characterized and their effects on clinical outcomes were evaluated. A total of 146 patients were identified to have >5000 PVCs on Holter of which 75 (51%) had PVCs originating from a non-outflow tract site. Other sites included the left ventricular outflow tract (LVOT), right ventricular outflow tract (RVOT), and the sinus of Valsalva. In multivariate analysis, the risk for HF/Deatd was similar in patients with Outflow tract PVCs when compared to patients with Non-outflow tract PVCs (HR 1.4, 95% CI 0.7-2.8, P = 0.3). The degree of echocardiographic reverse remodeling was similar in patients with outflow tract versus Non-outflow tract PVCs. One-third of patients with nonischemic cardiomyopathy were found to have PVCs originating from the RVOT.

CONCLUSIONS

In patients with mild symptoms of heart failure, there is no difference in the risk of HF or death in patients with outflow versus non-outflow tract PVCs. One-third of patients with NICM have frequent PVCs originating from the RVOT.

Far-field atrial sensing by the left ventricular channel of a biventricular device

BACKGROUND

The left ventricular (LV) channel of Biotronik biventricular devices used for cardiac resynchronization therapy (CRT) is designed with the capability of sensing via the LV lead. Therefore a displaced LV lead in a coronary vein could sense far-field atrial signals and interfere with CRT.

METHODS

The Biotronik troubleshooting archives containing data of approximately 700 transvenous CRT-D cases (D = defibrillator) were examined for atrial far-field sensing by the LV channel. We selected three cases from the archives to demonstrate the typical features of LV sensing of far-field atrial activity.

RESULTS

We found 3 typical cases of far-field atrial sensing by the LV channel. The LV lead was displaced in 2 cases and possibly in the third patient. Two cases exhibited short intervals between LV sensed events (LVs-LVs = 207-218 ms), a finding typical of this form of far-field atrial sensing by an LV lead. In the third case, short LVs-LVs intervals were not observed because spontaneous LV activation failed to generate an LVs marker (corresponding with the terminal LVs marker in a short LVs-LVs interval). LV activity was unsensed during the blanking period of the LV upper rate interval initiated by the first LVs that actually generated by far-field oversensing. This response was also observed intermittently in a patient who presented with short LVs-LVs intervals.

CONCLUSIONS

Far-field atrial oversensing by the LV channel of a CRT-D device occurs mostly with LV lead displacement. The diagnosis is important because it interferes with the delivery of therapeutic CRT but it is not life-threatening. Oversensing can be easily corrected by simple reprogramming of the device or LV lead repositioning if there is high LV pacing threshold.

Ventricular safety pacing, ventricular sense response, and ventricular tachycardia

The ventricular sense response (VSR) algorithm enforces biventricular pacing on ventricular sensing to maximize biventricular pacing in patients with atrial fibrillation. This report describes a case of recurrent ventricular tachycardia that may be facilitated by this enforced pacing algorithm.