Role of closed loop stimulation pacing (CLS) in vasovagal syncope

Rate-Responsive Cardiac Pacing: Technological Solutions and Their Applications

Modern cardiac pacemakers are equipped with a function that allows the heart rate to adapt to the current needs of the patient in situations of increased demand related to exercise and stress ("rate-response" function). This function may be based on a variety of mechanisms, such as a built-in accelerometer responding to increased chest movement or algorithms sensing metabolic demand for oxygen, analysis of intrathoracic impedance, and analysis of the heart rhythm (Q-T interval). The latest technologies in the field of rate-response functionality relate to the use of an accelerometer in leadless endocavitary pacemakers; in these devices, the accelerometer enables mapping of the mechanical wave of the heart's work cycle, enabling the pacemaker to correctly sense native impulses and stimulate the ventricles in synchrony with the cycles of atria and heart valves. Another modern system for synchronizing pacing rate with the patient's real-time needs requires a closed-loop system that continuously monitors changes in the dynamics of heart contractions. This article discusses the technical details of various solutions for detecting and responding to situations related to increased oxygen demand (e.g., exercise or stress) in implantable pacemakers, and reviews the results of clinical trials regarding the use of these algorithms.

Paroxysmal Nonepileptic Events in Children: A Video Gallery and a Guide for Differential Diagnosis

Purpose

of review Paroxysmal Non-Epileptic Events (PNEEs) are a heterogeneous group of time-limited events, characterized by changes in motor or behavioral activity beginning abruptly and ending in a short time. Due to their manifestation, these conditions can clinically simulate seizures.

Recent findings:

These episodes belong to different categories including syncopal events, psychiatric disorders, movement disorders, and many others. PNEEs are a common cause of diagnostic mistakes and families’ concerns and the risk of useless and sometimes even injurious treatment is considerable. The high frequency of these manifestations in clinical practice makes PNEEs a diagnostic challenge for clinicians.

Sensors for rate-adaptive pacing: How they work, strengths, and limitations

Chronotropic incompetence is the inability of the sinus node to increase heart rate commensurate with increased metabolic demand. Cardiac pacing alone may be insufficient to address exercise intolerance, fatigue, dyspnea on exertion, and other symptoms of chronotropic incompetence. Rate-responsive (adaptive) pacing employs sensors to detect physical or physiological indices and mimic the response of the normal sinus node. This review describes the development, strengths, and limitations of a variety of sensors that have been employed to address chronotropic incompetence. A mini-tutorial on programming rate-adaptive parameters is included along with emphasis that patients' lifestyles and underlying medical conditions require careful consideration. In addition, special sensor applications used to respond prophylactically to physiologic signals are detailed and an in-depth discussion of sensors as a potential aid in heart failure management is provided.

Closed-looped stimulation cardiac pacing for recurrent vasovagal syncope: A systematic review and meta-analysis

BACKGROUND

Vasovagal syncope (VVS) is defined by transient loss of consciousness with spontaneous rapid recovery. Recently, a closed-loop stimulation pacing system (CLS) has shown superior effectiveness to conventional pacing in refractory VVS. However, systematic review and meta-analysis has not been performed. We assessed the impact of CLS implantation and reduction in recurrent VVS events by a systematic review and a meta-analysis.

METHODS

We comprehensively searched the databases of MEDLINE and EMBASE from inception to September 2017. Included studies were published prospective or retrospective cohort, randomized controlled trial, and case-control studies that compared VVS events between recurrent, severe, or refractory cardioinhibitory VVS patient implanted with CLS and conventional pacing. Data from each study were combined using the random-effects, generic inverse variance method of DerSimonian and Laird to calculate odds ratios and 95% confidence intervals.

RESULTS

Six studies from November 2004 to October 2017 were included in this meta-analysis involving 224 recurrent, severe, or refractory cardioinhibitory VVS patients implanted with CLS and 163 recurrent, severe, or refractory VVS patients implanted with conventional pacing. CLS significantly reduced recurrent VVS events compared to conventional pacing (pooled odds ratio = 0.23, 95% confidence interval: 0.13-0.39, P = 0.000, I 2 = 36.5%) as well as subgroup of four randomized controlled trial studies (pooled odds ratio = 0.28, 95% confidence interval: 0.17-0.44, P = 0.000, I 2 = 39.2%).

CONCLUSION

Closed-loop stimulation significantly reduced recurrent VVS events up to 80% when compared to conventional pacing. Our study suggests that CLS is an effective tool for preventing syncope recurrences in patients with recurrent, severe, or refractory cardioinhibitory VVS.

Role of implantable loop recorders in patients with postural orthostatic tachycardia syndrome

INTRODUCTION

We previously reported on a subgroup of postural orthostatic tachycardia syndrome (POTS) patients who may also have features of neurocardiogenic syncope as well. In this subgroup of patients, we found syncope and presyncope were predominant clinical features. To understand the mechanism of syncope in this subgroup, we identified 39 patients who underwent loop recorder insertion.

METHODS

We reviewed charts of 450 patients who had POTS and syncope seen at the University of Toledo Medical Center from 2003 to 2017. Thirty-nine patients had at least four episodes of syncope in the last 6 months and were included for this study. All of these patients had a prior evaluation with a Holter and an event monitor which were inconclusive.

RESULTS

Thirty-nine patients, 33 (85%) women, aged 20-46 years, were included in this study. All patients demonstrated prolonged asystole (>6 seconds) or severe bradycardia (heart rate < 30 beats/min) during their syncope on implantable loop recorder (IRL). Fifteen patients demonstrated an asystole of >10 seconds and also had prolonged and convulsive syncope. All patients had abrupt syncope without any warning sign. All patients underwent dual-chamber pacemaker implantation using a closed loop stimulation algorithm. Syncope were completely eliminated in all patients following pacemaker implantation; however, they continued to have orthostatic tachycardia.

CONCLUSION

POTS patients with unusually frequent syncope should be considered for ILR implantation if other monitoring modalities like 48-hour Holter monitor or event recorder are inconclusive. ILR may identify a subgroup of POTS patients who may benefit from pacemaker implantations.