Case Report: Pacing With Closed Loop Stimulation

Neurocardiogenic syncope (NCS) in patients who are refractory to conventional measures such as pharmacological treatment and/or implantation of standard pacemakers can be trying to both patient and physician. Quality of life as well as the importance of preventing serious injury as a result of syncopal events are major concerns. In patients with trigger-mediated vasovagal syncope, it is sometimes especially difficult to control symptoms with conventional therapy. The Evia pacemaker (BIOTRONIK, Berlin, Germany) (Figure 1) is equipped with closed loop stimulation (CLS), a novel sensor system that can help restore correct autonomic tone, and also offers a decade of battery longevity. CLS pacing may provide earlier intervention in the progression of this disorder, and recent observations have demonstrated CLS pacing to be an effective therapeutic modality in a select group of patients with recurrent, severe NCS refractory to standard treatment modalities. When compared against standard pacing systems, CLS appeared to offer these patients a much greater degree of symptomatic relief.¹ We present here a case of situational syncope causing significant morbidity, and successful control with CLS-based pacing.

Case Report

A 50-year-old man with a history of hypertension, diabetes, chronic obstructive pulmonary disease and obstructive sleep apnea was admitted through the emergency room after experiencing multiple episodes of syncope associated with recurrent coughing fits during an exacerbation of his pulmonary disease. The patient recalled coughing in bed and awakening on the floor with facial trauma. Telemetry monitoring initially revealed sinus rhythm with brief episodes of atrial tachycardia. Recent echocardiography demonstrated normal left ventricular function, mild concentric left ventricular hypertrophy, and was without significant valvulopathy. A tilt table test did not reproduce the patient’s symptoms. No significant vasodepressor or cardioinhibitory response was elicited. Recommendations were then made to consider a course of outpatient rhythm monitoring. While still hospitalized and awaiting further testing, however, telemetry revealed bradycardia with short pauses correlating with brief syncopal episodes during coughing fits. This occurred off any rate-slowing medications. Given his clear trigger-mediated symptoms, only brief bradycardia observed during episodes, its association with significant trauma, and anticipated difficulty in controlling triggers in the setting of baseline pulmonary disease, it was concluded that implantation of a CLS-outfitted pacemaker would provide the most reasonable management strategy. A BIOTRONIK Evia permanent pacemaker was implanted without complications and the patient was subsequently discharged. The patient was seen in outpatient clinic two weeks post procedure and reported feeling well without further syncope. At three-month follow-up, the patient again reported feeling well without subsequent events.

Discussion

NCS is a term that encompasses trigger-mediated, situational, vasovagal, and other forms of dysautonomic syncope. In the classic vasovagal response, peripheral venous blood pooling leads to reduced ventricular filling. This reduction leads to an increase in sympathetic tone, causing an increase in myocardial contraction. Baroreceptors are then activated, triggering an increased vagal output. This leads to a relative bradycardia and increased peripheral vasodilatation. The ultimate result of this rate slowing and hypotensive effect is syncope. It has been demonstrated, however, that many patients exhibit a significant fall in blood pressure that far precedes a decline in heart rate.² Standard pacing in an attempt to prevent these episodes in classic vasovagal syncope have therefore met limited success, as increasing a patient’s heart rate may provide no immediate correction to the preceding drop in blood pressure which contributes to the syncopal response. With the development of closed loop stimulation, the detection of the vasovagal response is established earlier in its progression and the corrective action of increasing heart rate is activated to stabilize blood pressure and prevent syncope. The CLS system is the only sensor FDA approved to respond to emotional stress. This advanced algorithm provides a more natural response to the body’s demands, regulating heart rate according to physiological needs including stress, and increasing mental acuity as a result. CLS gathers localized intracardiac impedance signals over the cardiac cycle and is able to monitor the inotropic state of the heart. These signals provide information regarding myocardial wall motion changes in the vicinity of any standard right ventricular pacing lead. Heart contractility is directly correlated to cardiac output and therefore to heart rate. By measuring changes in the heart’s contractile state, CLS automatically adjusts to changes in a patient’s lifestyle, activity and drug regimens. This makes CLS a true “closed loop” rate response algorithm (Figure 2). In order to establish proper physiologic pacing, CLS records multiple impedance data points throughout a ventricular contraction of every heart beat. All CLS devices are outfitted with an accelerometer. This accelerometer is used purely to determine if a patient is in motion or at rest and does not contribute to the response of the CLS algorithm. The patient’s heart contractility dynamic (or inotropic state) at rest is reflected by continuously updated, moving average reference wave curves. The area differential between the immediate impedance and resting rate moving average curves is used to determine the patient’s physiologic paced rate. An exertion threshold rate (ETR) can then be targeted for a prescribed level of sensor responsiveness (Figure 3). The new integrated circuit in Evia consumes 50% less energy than previous generations and is designed with 33% fewer components, resulting in substantial size reduction and a decade of longevity. Increased battery life also helps to reduce the long-term risks associated with multiple generator changes. The REPLACE registry³ has clearly helped to define these real risks associated with device replacement and upgrade procedures. Maximizing battery longevity has become an important strategy in device selection, and this is especially important in younger patients to limit the number of procedures needed throughout the course of their lifetime. BIOTRONIK’s Home Monitoring is also available with the Evia pacemaker. With wireless capability using a GSM-based, truly mobile transmitter, our patient is now able to be closely monitored while out living his life. Through earlier detection of serious arrhythmic events and the potential to significantly reduce the number of clinical follow-up visits, the system is geared towards maximizing patient safety and convenience.⁴ Our patient, the first on Long Island to receive an Evia pacemaker, has successfully resumed his life and is enjoying the many benefits of this novel device.

References

1. Kanjwal K, Karabin B, Kanjwal Y, Grubb B. Preliminary observations on the use of closed-loop cardiac pacing in patients with refractory neurocardiogenic syncope. J Interv Card Electrophysiol 2010;27(1):69–73. 2. Occhetta E, Bortnik M, Audoglio R, Vassanelli C, for the INVASY Study Investigators. Closed loop stimulation in prevention of vasovagal syncope. Inotropy Controlled Pacing in Vasovagal Syncope (INVASY): a multicentre randomized, single blind, controlled study. Europace 2004;6(6):538–547. 3. Gleva M, Holcomb R, Mela T, et al. Complication rates associated with pacemaker and implantable defibrillator generator replacement: results from the REPLACE registry. Presented at HRS 2009 Late Breaking Clinical Trials and in publication. 4. Varma N, Epstein A, Irimpen A, et al. Efficacy and safety of automatic remote monitoring for implantable cardioverter-defibrillator follow-up: the TRUST trial. Circulation 2010,122:325–332.

Editor’s Note: This article underwent peer review by one or more members of EP Lab Digest’s editorial board. Disclosure: The authors have no conflicts of interest to report.