Normal Sinus Node Research Articles

Corrected sinus node recovery time as a screening test in patients with typical atrial flutter post-ablation to predict pacemaker implantation.

The objective of the study was to establish the prognostic value of CSNRT regarding the necessity for pacemaker implantation in patients with atrial flutter (AFL) post-ablation. This prospective cohort study, conducted at the National Institute of Cardiology "Ignacio Chavez" in Mexico City, assessed patients who had undergone ablation procedures to correct AFL, posterior to which an autonomic blockade was performed, and CSNRT was measured. The sample for this investigation was 40 patients. These were subdivided into two study groups depending on their requirement of pacemaker implant post-ablation (Pacemaker P, No Pacemaker NP). Sinus node (SN) dysfunction was diagnosed in 13 (32.5%) of the 40 participants, 10 (71.43%) of which required a pacemaker implant, while only 4 participants (28.57%) with normal SN function required pacemakers. Ten out of the 14 patients (71.43%) who required a pacemaker had an elevated CSNRT > 500 ms (p ≤ 0.01). Post-ablation CSNRT mean was 383.54 ms ± 67.96 ms in the NP group versus 1972.57 ms ± 3423.56 ms in the P group. Furthermore, SN pause in the P group had a mean of 1.86 s ± 0.96 s versus the NP group with 1.196 s ± 0.52 s. CSNRT has the potential to be a quantitative prognostic tool for the assessment of future pacemaker implants in patients with AFL post-ablation. This could aid in the timely diagnosis of sinus node dysfunction, which could, in the long run, result in the reduction of cardiac functional capacity loss due to cardiac remodeling.

Abstract 10897: Severe Atrial Dysfunction and Sick Sinus Syndrome in a Patient With Scn5a Mutation

Introduction: SCN5A mutations are associated with numerous cardiovascular conditions, including dilated cardiomyopathy, atrial fibrillation, and sick sinus syndrome. Specific variants in patients with severe atrial dysfunction may be associated with increased risk of stroke even in young patients. Case: This case describes a previously healthy 38-year-old male of French descent who presented with intermittent palpitations and presyncope associated with atrial flutter followed by prolonged conversion pauses up to 7.5 seconds, then followed by junctional bradycardia. Echocardiogram showed a mildly dilated left atrium. Electrophysiology study demonstrated extensive scarring in the left atrium with normal sinus node function and right atrial voltage. No atrial fibrillation was noted. He was also found to have typical atrial flutter and mitral flutter. He underwent cavotricuspid isthmus ablation and mitral annular flutter ablation. Due to his vagal-mediated pauses and junctional rhythm, he also underwent cardioneuroablation aimed at partial denervation. Following this, he had further episodes of junctional rhythm on the days after exercise. He underwent further total cardioneuroablation and was found to have progressive scarring at the sinus node area and sinus node dysfunction, so a permanent pacemaker was placed. He underwent genetic testing which demonstrated SCN5A heterozygous missense pathogenic variant c.2823G>A. Conclusion: The SCN5a gene encodes the alpha subunit of the cardiac sodium channel, which is responsible for initiation and propagation of action potentials. SCN5A variants are associated with a number of cardiovascular conditions. There are reports of stroke in young French patients with severe atrial dysfunction and SCN5A mutations, including variant c.2823G>A, demonstrating that severe atrial dysfunction is a risk factor for stroke regardless of CHADS2VASc score, and specific SCN5A mutations may be associated with increased risk of stroke. Given these reports and absence of relevant guidelines, apixaban was continued indefinitely for prevention of stroke. At follow-up two months later, the patient resumed physical activity and reported symptomatic improvement, without any episodes of syncope or near syncope.

Sinus node sparing novel hybrid approach for treatment of inappropriate sinus tachycardia/postural sinus tachycardia: multicenter experience

BackgroundThe ideal treatment of inappropriate sinus tachycardia (IST) and postural orthostatic tachycardia syndrome (POTS) still needs to be defined. Medical treatments yield suboptimal results. Endocardial catheter ablation of the sinus node (SN) may risk phrenic nerve damage and open-heart surgery may be accompanied by unjustified invasive risks.MethodsWe describe our first multicenter experience of 255 consecutive patients (235 females, 25.94 ± 3.84 years) having undergone a novel SN sparing hybrid thoracoscopic ablation for drug-resistant IST (n = 204, 80%) or POTS (n = 51, 20%). As previously described, the SN was identified with 3D mapping. Surgery was performed through three 5-mm ports from the right side. A minimally invasive approach with a bipolar radiofrequency clamp was used to ablate targeted areas while sparing the SN region. The targeted areas included isolation of the superior and the inferior caval veins, and a crista terminalis line was made. All lines were interconnected.ResultsNormal sinus rhythm (SR) was restored in all patients at the end of the procedure. All patients discontinued medication during the follow-up. After a blanking period of 6 months, all patients presented stable SR. At a mean of 4.07 ± 1.8 years, normal SN reduction and chronotropic response to exercise were present. In the 51 patients initially diagnosed with POTS, no syncope occurred. During follow-up, pericarditis was the most common complication (121 patients: 47%), with complete resolution in all cases. Pneumothorax was observed in 5 patients (1.9%), only 3 (1.1%) required surgical drainage. Five patients (1.9%) required a dual-chamber pacemaker due to sinus arrest > 5 s.ConclusionsPreliminary results of this multicenter experience with a novel SN sparing hybrid ablation of IST/POTS, using surgical thoracoscopic video-assisted epicardial ablation combined with simultaneous endocardial 3D mapping may prove to be an efficient and safe therapeutic option in patients with symptomatic drug-resistant IST and POTS. Importantly, in our study, all patients had a complete resolution of the symptoms and restored normal SN activity.

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.

Repair of Superior Sinus Venosus Atrial Septal Defect Using a Modified Two-Patch Technique

Surgical repair of superior sinus venosus atrial septal defect associated with partial anomalous pulmonary venous connection is usually performed with either a two-patch technique or the Warden procedure. However, both techniques can lead to superior vena cava or pulmonary vein stenosis, as well as sinus node dysfunction. To prevent these complications, we have utilized a modified two-patch technique. Between January 2000 and December 2015, 44 patients underwent modified two-patch repair of superior sinus venosus atrial septal defect associated with partial anomalous pulmonary venous connection at our institution. The technique utilizes the right atrial appendage to patch the superior vena cava and avoid superior vena cava obstruction. Patients' data were collected from reviewing hospital charts and clinic records. Mean age was 10.3 years (range, 0.68 to 61 years). There was no hospital mortality. Six patients (13.6%) had sinus node dysfunction after surgery. All of them recovered their normal sinus node function at a mean follow-up period of 45.7 months. No superior vena cava or pulmonary vein stenosis was observed at long-term follow-up. A modified two-patch technique is a valid alternative to other methods of superior sinus venosus atrial septal defect and partial anomalous pulmonary venous connection repair, and prevents late systemic/pulmonary venous pathway obstruction while maintaining sinus rhythm.

Sinus Node Sparing Novel Hybrid Approach for Treatment of Inappropriate Sinus Tachycardia/Postural Orthostatic Sinus Tachycardia With New Electrophysiological Finding

The ideal treatment of Inappropriate Sinus Tachycardia (IST) and Postural Orthostatic Tachycardia Syndrome (POTS) still needs to be defined. Medical treatment yields suboptimal results, endocardial ablation of the sinus node (SN) may risk phrenic nerve damage and open heart surgery may be accompanied by unjustified invasive risks. We describe our first experience of 50 consecutive patients (41 females, 22.83 ± 3.91 years) having undergone a novel hybrid thoracoscopic ablation for drug resistant IST (n = 39, 78%) or POTS (n = 11, 22%). The SN was identified with the help of 3D mapping. Surgery was performed through 3 (5 mm) ports from the right side. A minimally invasive approach with a radio frequency bipolar clamp was utilized to a new target sparing the SN region, to isolate the superior and the inferior caval veins, and a crista terminalis line was made. All lines were interconnected. Normal SR was restored in all patients at the end of the procedure. All patients discontinued medication during the follow-up. After a blanking period of 6 months all patients presented stable SR. At a mean of 28.4 ± 1.2 months, normal SN ruction and chronotropic response to exercise was present. In the 11 patients initially diagnosed with POTS, no syncope occurred. During the follow-up, pericarditis was the most common complication (39 patients; 78%) with complete resolution in all cases. In conclusions the preliminary results of our first experience with a SN sparing novel hybrid ablation of IST/POTS, using surgical thoracoscopic video-assisted epicardial ablation combined with concomitant endocardial 3D mapping may prove an efficient and safe therapeutic option in patients with symptomatic drug resistant IST and POTS. Importantly, in our study all patients had a complete resolution of the symptoms and restored normal SN activity.

Cardiac Rhythm Disturbances in Heterotaxy Syndrome.

Heterotaxy syndrome is associated with complex cardiac malformations and cardiac conduction system abnormalities. Those with right atrial isomerism (RAI) have dual sinus nodes and dual atrioventricular nodes predisposing them to supraventricular tachycardia (SVT). Those with left atrial isomerism (LAI) lack a normal sinus node and are at risk of sinus node dysfunction (SND) and atrioventricular block (AV block). We report the occurrence and risk factors associated with arrhythmias in heterotaxy syndrome. A retrospective review of all heterotaxy syndrome patients born and treated at our institution between 2000 and 2014 was performed. A total of 40 patients were identified; 16/40 (40%) with LAI and 24/40 (60%) with RAI. There were 12 deaths during follow-up [LAI 3/16 (19%), RAI 9/24 (38%); p = 0.30]. Twenty-one patients had arrhythmias during a mean follow-up period of 5.4 years; 14/16 (87%) in LAI and 7/24 (29%) in RAI (p < 0.001). Freedom from arrhythmia at 1,3,5years of age was 75.0%, 37.9%, 22.7% in LAI, and 83.3%, 77.5%, 69.6% in RAI, respectively(p = 0.00261). LAI had a three-fold increase in developing arrhythmias. Left atrial isomerism was the only factor identified to be associated with arrhythmia occurrence. Arrhythmias were commonly seen in heterotaxy syndrome particularly in left isomerism with more than half of the patients having arrhythmias by 3years of age. Atrial situs was the only risk factor identified to be associated with arrhythmias, and close follow-up is warranted in these patients.

Behavior of leadless AV synchronous pacing during atrial arrhythmias and stability of the atrial signals over time-Results of the MARVEL Evolve subanalysis.

The MARVEL study demonstrated at a single time point that accelerometer (ACC)-based atrial sensing improves atrioventricular (AV) synchrony (AVS) in patients with AV block and a Micra pacemaker (Medtronic, Minneapolis, MN, USA). The purpose of the MARVEL Evolve substudy was to assess the performance over time. This prospective single-center study compared AVS and ACC signals at two visits ≥6months apart. Custom software was temporarily downloaded into the Micra at each visit and AVS was measured during 30min at rest. Nine patients from the MARVEL study were enrolled. The mean (±standard deviation) age was 82.3±6.0 years old, 67% were male, and a Micra was implanted for 6.0±6.4 months. High-degree AV block was present in four patients, whereas five with predominantly intrinsic conduction required intermittent pacing for bradycardia. The mean interval between visits was 7.1±0.6 months. Seven patients had normal sinus node function at both visits and were included in a paired analysis. Both ACC signal amplitude (visit 2-visit 1=1.4 mG; 95% confidence interval [CI] [-25.8 to 28.4 mG]; P=0.933) and AVS (visit 1: 90.8%, 95% CI [72.4, 97.4] and visit 2: 91.4%, 95% CI [63.8, 98.5]; P=0.740) remained stable. Three patients had spontaneous atrial tachycardia. During atrial fibrillation, no atrial contraction was detected or tracked. During atrial flutter, intermittent tracking resulted in a ventricular rate of 60±8beats per minute (bpm); there was no ventricular pacing>100bpm. ACC signals amplitude and performance of AVS pacing were stable over time. During atrial arrhythmias, the AV synchronous pacing mode behaved safely.

3881Restoration of normal sinus node physiology in a model of sick sinus syndrome; Tbx18 overexpression improves heart rate, rate stability and adrenergic response

3881Restoration of normal sinus node physiology in a model of sick sinus syndrome; Tbx18 overexpression improves heart rate, rate stability and adrenergic response

Prediction of Sinus Node Dysfunction in Patients with Paroxysmal Atrial Fibrillation and Sinus Pause

Background and Objectives: Sinus pause association of paroxysmal atrial fibrillation (PAP) is generally considered a sinus node dysfunction (SND) known as tachycardia-bradycardia syndrome (TBS). Cure of tachyarrhythmias in some patients with prolonged pauses on termination of tachyarrhythmia resulted in an improvement in sinus node function and/or a return to normal ranges thus avoiding the need for permanent pacing. The purpose of this study was to investigate the electrophysiological and clinical characteristics as well as their sinus node function in patients with prolonged pauses and PAP. Methods and Results: Of 1266 PAP patients undergoing radiofrequency catheter ablation (RFCA), 122 patients with pauses (>2 s) were studied. The mean maximum symptomatic prolonged pause on termination of tachycardias was 2.67 ± 1.4 s (2.0–12.6 s). SND developed in 32 patients. There was no difference between the patients with and without SND in terms of the age and sex. Patients were divided into two groups based on the intracardiac electrophysiology study after the RFCA procedure. Eleven patients (8 men, 3 women; age 30–72 years, mean 48.2 ± 9.3 years) were placed in a normal sinus node function (NSF) group, and 17 patients (12 men, 5 women; age 37–75 years, mean 62.2 ± 7.5 years) were in an SND group. There was no significant difference in gender, left atrial dimension, left ventricular ejection fraction, blood pressure, or the longest pause between the two groups. RFCA was successful in 28 patients. Electrophysiological data show that corrected sinus node recovery time (CSNRT) was 409 ± 152 ms in NSF group patients and 558 ± 178 ms in SND group before the ablation procedure (P 2 cycle lengths in 12 patients. In the multivariate analysis, prolonged pauses on termination of tachyarrhythmia, frequency of pauses, and mean heart rate after ablation were independent predictors of SND. Conclusions: (1) Catheter ablation of atrial fibrillation (AF) is effective in treating paroxysmal AF-related TBS; (2) in some patients, there is progressive improvement of sinus node function after elimination of AF, an indication that these sinus pauses may be a manifestation of tachycardia-mediated remodeling of the sinus node, and that permanent pacemaker implantation is unnecessary; (3) among the extrinsic and intrinsic causes of SND, intrinsic causes are seldom reversible and some causes of extrinsic SND may be reversible; and (4) prolonged pauses on termination of PAF, frequency of pauses (>2.0 s), and mean heart rate after ablation were independent predictive factors of SND.

Anatomy and pathology of the sinus node.

The aim of this study is to review the key features of anatomy of the sinus node of the human sinus node and its pathological variations as reported in the literature and supplemented with our observations. The sinus node is located adjacent to important structures such as the right phrenic nerve and the nodal artery. Although intimately related to its matrix of fibrous tissue, the nodal cells are in contact with atrial myocardium through nodal extensions. Nodal cell numbers decrease with age as part of the normal aging process. Pathological changes include diminished size of node and nodal cell replacement with fibro-fatty tissues. The location of the normal sinus node is well recognised. There is variation in the relationship of the node and its arterial supply to the terminal crest and the cavo-atrial junction.

Kaya et al. Is it a typical crosstalk: Need for re-implantation?

I have read with attention the case report by Kaya et al. entitled “Is it a typical crosstalk: Need for re-implantation?” [1] The authors described atrial lead malfunction in a patient with a dual-chamber pacemaker. The right atrial lead tip was in close proximity to the tricuspid valve, but was it located in the ventricle or atrium? Pacing of the ventricle and the low sensitivity for detection of atrial activation suggest that the tip is located in the ventricle with far-field atrial activity sensation. Changing the pacemaker mode to VDD is a good approach in cases of normal sinus node function and loss of atrial lead capture, especially if atrial sensing is stable. In this case, Short AV delay is a good way to reduce the risk of R on T phenomenon which is theoretically possible if a ventricular ectopy is sensed by the atrial lead before the ventricular lead, which may cause inappropriate ventricular spiking after programmed AV delay. But as an AV delay optimization improves hemodynamics and clinical parameters in patients treated with a dual-chamber-pacemaker, if this short AV delay causes atrioventricular dyssynchrony, with a stable P-wave sensation by atrial lead, a DDD mode with an active ventricular safety pacing may be a better option for this case. [2] It should be noted that ventricular safety pacing is not an option when the device is operating with VDD mode. Lastly, if P-wave sensing is not stable and the patient still has dyspnea at follow-up, atrial lead replacement should be considered. The author has no conflict of interest to declare.

Revisiting heart activation-conduction physiology, part I: atria

This discussion paper re-examines the conduction-activation of the atria, based on observations, with respect to the complexity of the heart as an organ with a brain, and its evolution from a peristaltic tube. The atria do not require a specialized conduction system because they use the subendocardial layer to produce centripetal transmural activation fronts, regardless of the anatomical and histological organization of the transmural atrial wall. This has been described as "two-layer" physiology which provides robust transmission of activation from the sinus to the AV node via a centripetal transmural activation front. New productive insights can come from re-examining the physiology, not only during sinus rhythm but also during atrial tachycardias, in particular atrial flutter and atrial fibrillation (AF). During common flutter, the areas of slow conduction, in the isthmus and following trabeculations, particularly the subendocardial layer confines conduction through the trabeculations which supports re-entry. During experimental or postoperative flutter, the circular 2D activation around the obstacle follows the physiological transmural activation. Understanding this physiology offers insights into AF. During acute or protracted AF, the presence of stationary or drifting rotors is characteristic and consistent with normal physiological 2D atrial activation, suggesting that suppressing physiological transmural activation of AF will permanently restore normal sinus node atrial activation. In contrast, during permanent AF, normal 2D activation is abolished; the presence of transmural, serpentine, and chaotic atrial activation suggests that the normal physiological activation pattern has been replaced by a new, irreversible variety of atrial conduction that is a new physiology, which is consistent with evolution of complex systems.

Influence of racemic higenamine on the sinus node

The aim of this study was to explore the mechanism of racemic higenamine in the treatment of sick sinus syndrome (SSS). A total of 40 New Zealand rabbits were randomly divided into normal sinus node and damaged sinus node (SND) groups, and each group was randomly divided into treatment and control groups (n=10). The SND model was established by formaldehyde wet dressing of the sinus node area. The treatment groups were administered an intravenous infusion of 0.04 mg/kg racemic higenamine via the marginal ear vein within 5 min. The electrophysiological indicators of sinoatrial function, including the sinus node recovery time (SNRT), corrected sinus node recovery time (CSNRT), total sinoatrial conduction time (TSACT) and sinus cycle length (SCL), were determined before and 20 min after medication and the changes in these indicators were evaluated. The two control groups were administered 10 ml physiological saline. Following the administration of racemic higenamine, the SNRT, CSNRT, TSACT and SCL in the normal sinus node and SND groups were significantly shortened compared with those in the control groups (P<0.01). The electrophysiological influence of racemic higenamine on sinoatrial function in the SND group was significantly greater than that in the normal sinus node group (P<0.01), and its effect in the treatment of arrhythmia caused by a damaged sinus node was statistically significant (P<0.05). The main electrophysiological mechanism of racemic higenamine in the treatment of SSS was the enhancement of sinus node self-discipline and improvement of sinoatrial and atrioventricular conduction function.

Sleep-disordered breathing predicts sinus node dysfunction in persistent atrial fibrillation patients undergoing pulmonary vein isolation

BackgroundThe indications for catheter ablation have been expanded to include persistent atrial fibrillation (AF) to enable a high degree of sinus rhythm maintenance. We occasionally encounter patients undergoing pacemaker implantation in whom sick sinus syndrome became clinically evident after ablation. This study investigated whether underlying sinus node dysfunction (SND) during persistent AF can be predicted before deciding the indications for ablation. Methods and resultsIn total, 87 consecutive patients with persistent AF who underwent catheter ablation between January 2010 and July 2011 were enrolled in the study. Nocturnal polysomnography as well as transthoracic and transesophageal echocardiography were performed in all patients before ablation. We used the double Lasso catheter and electroanatomical mapping-guided extensive encircling pulmonary vein isolation (EEPVI) method. We performed electrophysiological studies after EEPVI, and SND was defined as a corrected SN recovery time of ≥550ms. SND was detected in 42 (48%) patients (SND group); the other patients showed normal sinus node function (NSN group). The apnea/hypopnea index (AHI) was significantly greater in the SND group than in the NSN group (25.7±13 vs. 17.5±11, p=0.002). Multivariate analysis revealed that moderate to severe sleep-disordered breathing (defined as AHI≥15) was an independent predictor of SND after catheter ablation for persistent AF. ConclusionThe results suggest that underlying SND in patients with persistent AF can be predicted by evaluating sleep-disordered breathing before catheter ablation.

Understanding the Atrioventricular Dissociation

A 56-year old male patient was addressed to our intensive cardiac care unit with a diagnosis of “complete atrioventricular (AV) block”, 4 days following surgical treatment of symptomatic obstructive hypertrophic cardiomyopathy including large septal resection and mitral valve replacement. We noted no relevant medical history. On physical examination, at admission, the patient presented normal hemodynamic, regular heart rate about 60 bpm, no signs of right heart failure. An abnormal transient jugular vein pulse was noted. The EKG on admission is presented in Fig. 1. Do you agree with the diagnosis of complete AV block? Diagnosisof considered “complex”EKG features appears tobe reserved for cardiologists or even to electrophysiologists, although good sense and simple logical approach allowmaking the diagnosis yourself in a number of cases. Let‘s go for a typical case of a suspected AV conduction disorder following cardiac surgery. First, let’s review some elementary considerations on the cardiac conduction physiology. Sinoatrial node is a part of a specialized type of myocardial network which has the particularity of being also pacemaker myocyte cells. This specialized network is represented by sinoatrial node, AV node, His and bundle branch as well as distal Purkinje fibers. Unlike the rest of themyocytes, these pacemaker cells may initiate action potential through spontaneous diastolic depolarization. Because of a higher depolarization slope, the impulse initiated from sinoatrial node depresses the activity of subsidiary pacemaker sites, and also automatically generates electrical pulses that spread as waves of electrical excitation over the atria and then to ventricles via AV node. Interruption of the conduction at any level enables subsidiary pacemakers to emerge usually at a slower rate (the lower andmore distal is the block, the slower is the rate). On the opposite, enhanced automaticity in any part of this specialized myocardial network may overdrive normal sinus node activity, particularly when the latest is slower.

Arrhythmias After Heart Transplantation: Mechanisms and Management

Heart transplantation (HT) has significantly altered the treatment paradigm for end-stage heart disease. With current surgical techniques and postoperative immunosuppression, 1-year survival after HT is ≈90%, 5-year survival is ≈70%, and median survival exceeds 10 years.[1][1]–[3][2] These

Single-lead VDD pacing--a serious alternative for atrioventricular synchronous pacing in patients with atrioventricular block?

This editorial refers to ‘Long-term follow-up of DDD and VDD pacing: a prospective non-randomized single-centre comparison of patients with symptomatic atrioventricular block’ by S. Marchandise et al ., on page 496 For >20 years, single-lead VDD pacemakers have been implanted in patients with atrioventricular (AV) block and normal sinus node function.1 A single tripolar or quadripolar passive fixation lead is placed in the apex of the right ventricle for unipolar or bipolar ventricular sensing and pacing. Two sensing rings floating in the right atrium are used for bipolar sensing of the atrial potential. Due to lacking wall contact of the atrial dipole in most patients, atrial potential amplitudes are lower than those of fixed atrial electrodes. Thus, a high atrial sensitivity allowed by a differential sensing amplifier is usually needed for AV synchronous pacing in single-lead VDD devices. Since atrial pacing is not possible, a sinus node disease is a contraindication for VDD pacing and has to be ruled out before implantation. Several registries and randomized trials have shown an equivalent therapeutic efficacy of single-lead VDD pacing2–4 compared with DDD pacemakers. Long-term complications5 and costs of AV synchronous pacing therapy may be reduced by single-lead VDD pacemaker implantation.6,7 Despite these encouraging results, single-lead VDD pacing did not get beyond a ‘niche’ therapy for AV synchronous pacing.8 The concern about …

Usefulness of Hemodynamic Sensors for Physiologic Cardiac Pacing in Heart Failure Patients

The rate adaptive sensors applied to cardiac pacing should respond as promptly as the normal sinus node with an highly specific and sensitive detection of the need of increasing heart rate. Sensors operating alone may not provide optimal heart responsiveness: central venous pH sensing, variations in the oxygen content of mixed venous blood, QT interval, breathing rate and pulmonary minute ventilation monitored by thoracic impedance variations, activity sensors. Using sensors that have different attributes but that work in a complementary manners offers distinct advantages. However, complicated sensors interactions may occur. Hemodynamic sensors detect changes in the hemodynamic performances of the heart, which partially depends on the autonomic nervous system-induced inotropic regulation of myocardial fibers. Specific hemodynamic sensors have been designed to measure different expression of the cardiac contraction strength: Peak Endocardial Acceleration (PEA), Closed Loop Stimulation (CLS) and TransValvular Impedance (TVI), guided by intraventricular impedance variations. Rate-responsive pacing is just one of the potential applications of hemodynamic sensors in implantable pacemakers. Other issues discussed in the paper include: hemodynamic monitoring for the optimal programmation and follow up of patients with cardiac resynchronization therapy; hemodynamic deterioration impact of tachyarrhythmias; hemodynamic upper rate limit control; monitoring and prevention of vasovagal malignant syncopes.

Prediction of Underling Sinus Node Dysfunction during Chronic Atrial Fibrillation before Catheter Ablation Using Apnea/Hypopnea Index

Background: Indication of ablation has been expanded to include chronic atrial fibrillation (CAF) for enabling high degree of sinus rhythm maintenance. We have encountered patients undergoing pacemaker implantation, in whom sick sinus syndrome became clinically evident after ablation. The study aims to investigate whether underling sinus node dysfunction (SND) during CAF can be predicted before deciding the indication for ablation. Methods and Results: Sixty consecutive patients with CAF who underwent ablation between January to December 2010 were enrolled in the study. Nocturnal polysomnography as well as echocardiography was performed for all patients before ablation. We used the double Lasso catheter and electro anatomical mapping guided extensive encircling pulmonary vein isolation (EEPVI). We performed electrophysiological studies after EEPVI, and SND was defined as corrected SN recovery time of ≥550 ms. SND was detected in 26 (43%) patients (SND group); the other patients showed normal sinus node function (NSN group). The apnea/hypopnea index (AHI) was significantly greater in the SND group than in the NSN group (25.7±13 vs 15.8±10, P=0.0022). On multivariate analysis, sleep apnea syndrome (SAS) was an independent predictor of SND after ablation for CAF. Conclusion: This study suggested that underlying SND in CAF patients can be predicted by evaluating SAS before ablation.