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Introduction. This article provides an overview of the problem of sinus node dysfunction after surgical treatment for longstanding persistent atrial fibrillation and the methods for diagnosing the initial states of cardiac activity and conduction. Purpose. To identify predictors of initial sinus node dysfunction in patients with long-standing persistent atrial fibrillation. Material and Methods: The study comprised a total of 65 patients with long-standing persistent atrial fibrillation complicating mitral valve disease. The state of autonomic nervous system was analyzed in patients with long-standing persistent atrial fibrillation. The associations between the analyzed data and electrophysiological parameters were investigated. Results . The study allowed to identify the cutoff points for the contents of neurohumoral factors in the coronary circulation in patients with intact sinus node function and sinus node dysfunction. Prognostic criteria for the development of bradyarrhythmias in the postoperative period requiring pacemaker implantation were proposed and introduced into clinical practice.

Sinus node (SN) function is an important prognostic factor of atrial fibrillation (AF). However, AF ablation guideline has not recommended SN function test before ablation. SN function testing before AF ablation in patients with tachycardia‐bradycardia syndrome should be beneficial to determine further therapy strategies and prognosis.

There is growing awareness of the long-term impact of a Fontan circulation on the associated morbidity and mortality. Comparative data on the incidence of supraventricular arrhythmia and sinus node dysfunction following extracardiac conduit (EC) and lateral tunnel (LT) Fontans are controversial. We performed a meta-analysis pooling all available long-term results comparing the EC and LT Fontan, with a special focus on arrhythmia.We performed a systematic search of PubMed, Embase, and the Cochrane Library for articles reporting long-term results of Fontan comparing the EC and the LT Fontan.Twelve studies were selected with 3,330 patients (1,729 EC, 1,601 LT). Freedom from tachyarrhythmia was significantly higher in the EC group (92% versus 83% at 15 years; p0.0001), while there was no difference in term of bradyarrhythmias (p = 0.7). The survival was 93% and 89% at 20 years in the EC and LT groups, respectively (p = 0.007). The risk of thromboembolic events was 2.87% patient-years in the EC group versus 0.9% in the LT group (odds ratio, 2.15; 95% confidence interval, 0.95 to 4.85; p = 0.07).The EC Fontan confers long-term survival advantage over the LT Fontan without a higher rate of reoperations. The EC Fontan preserves the sinus node function and reduces significantly the incidence of long-term postoperative arrhythmia.

Background: KCNMA1 encodes the α-subunit of the large-conductance Ca 2+ -activated K + channel, K Ca 1.1, and lies within a linkage interval for atrial fibrillation (AF). Insights into the cardiac functions of K Ca 1.1 are limited, and KCNMA1 has not been investigated as an AF candidate gene. Methods: The KCNMA1 gene was sequenced in 118 patients with familial AF. The role of K Ca 1.1 in normal cardiac structure and function was evaluated in humans, mice, zebrafish, and fly. A novel KCNMA1 variant was functionally characterized. Results: A complex KCNMA1 variant was identified in 1 kindred with AF. To evaluate potential disease mechanisms, we first evaluated the distribution of K Ca 1.1 in normal hearts using immunostaining and immunogold electron microscopy. K Ca 1.1 was seen throughout the atria and ventricles in humans and mice, with strong expression in the sinus node. In an ex vivo murine sinoatrial node preparation, addition of the K Ca 1.1 antagonist, paxilline, blunted the increase in beating rate induced by adrenergic receptor stimulation. Knockdown of the K Ca 1.1 ortholog, kcnma1b , in zebrafish embryos resulted in sinus bradycardia with dilatation and reduced contraction of the atrium and ventricle. Genetic inactivation of the Drosophila K Ca 1.1 ortholog, slo , systemically or in adult stages, also slowed the heartbeat and produced fibrillatory cardiac contractions. Electrophysiological characterization of slo -deficient flies revealed bursts of action potentials, reflecting increased events of fibrillatory arrhythmias. Flies with cardiac-specific overexpression of the human KCNMA1 mutant also showed increased heart period and bursts of action potentials, similar to the K Ca 1.1 loss-of-function models. Conclusions: Our data point to a highly conserved role of K Ca 1.1 in sinus node function in humans, mice, zebrafish, and fly and suggest that K Ca 1.1 loss of function may predispose to AF.

Symptomatic bradycardia is usually caused by abnormalities of atrioventricular conduction or sinus node dysfunction. Reversible and irreversible causes must be considered.Temporary pacemakers are used in the emergency treatment in case of severe bradyarrhythmia.They help to bridge the acute phase until spontaneous restoration of atrioventricular or sinus node function or –if spontaneous restoration fails- until a permanent pacemaker system was implanted.In the following article we discuss the commonly used temporary pacemaker systems. We demonstrate their use and correct programming by an illustrated step by step explanation. For troubleshooting a flow chart was added.

In recent decades, invasive electrophysiological study (ES) has become an important instrument to evaluate patients with conduction disturbance and cardiac arrhythmias. Using catheters placed in heart chambers via central vein and/or central arterial access, ES may evaluate sinus node function, atrioventricular conduction, and tachyarrhythmias. Cardiac arrhythmias may not always be present in the baseline condition. Therefore, it is necessary to induce these arrhythmias by programmed pacing protocols. Commonly arrhythmias are seen as chaotic alterations of the normal heart conduction and of the normal heart rhythm, and then they are defined as cardiac rhythm disorders. Cardiac arrhythmias present with a common phenotype, characterized by irregularity of the cardiac rhythm and related clinical symptoms. In this setting, ES may be performed by using different diagnostic and pacing catheters and pacing protocols. Programmed pacing protocols involve incremental pacing, coupled with the introduction of single or multiple premature stimuli during one or more drive cycles. The pacing protocols are performed with a current output of twice the diastolic threshold or more, and at one or more sites. Therefore, a great discrepancy may exist between arrhythmia induction techniques in different laboratories. However, in the majority of cases, arrhythmias are due to specific arrhythmic electrical, anatomical, and/or electroanatomical circuits. These circuits respond to specific conduction properties of the systolic and diastolic electrical phases, which are reproducible and evocable by external triggers and by specific pacing techniques. Moreover, in the light of these observations, we have to stress the concept that induction and stimulation programs have to be selected and then paced to test the arrhythmic circuits for refractoriness and to trigger the conduction properties of the arrhythmic pathways. Therefore, we have to make arrhythmia induction protocols more uniform and as standardized as possible to avoid all possible bias. Indeed, how to induce arrhythmias by atrial and ventricular stimulation remains a relevant question that needs a specific and unique response. To respond to this question, we would like to introduce the concept that a pacing protocol to induce cardiac arrhythmias may be standard and programmed. As first, by programmed pacing, physicians may study the properties of the cardiac conduction system. This may be secondarily achieved by introduction of early stimuli to determine the conduction response, as a specific arrhythmia induction protocol. As discussed earlier, the type of induction and the chosen programmed stimulation protocol may be selected with regard to the type of arrhythmia the patient is suspected to have. In fact, re-entry tachycardias may usually be triggered using extrastimuli to stimulate the conduction pathways in slow conduction and fast conduction ways. Differently, automatic tachycardias not due to re-entry mechanisms may be more easily induced by burst pacing. In this chapter we would like to introduce pacing protocols to induce cardiac arrhythmias. Apart from the similarity of the diagnostic and pacing catheters, and in the setting of programmed stimulation protocols, the differences in the paced heart chambers and in the induced tachycardias teach us to separate the discussion of atrial stimulation from ventricular stimulation protocols. Therefore, we schematically divide the arrhythmia induction protocols into two separate chapter sections, discussing atrial stimulation protocols and ventricular stimulation protocols.

Medications that are routinely used in clinical practice to treat hypertension such as beta blockers or non-dihydropyridine calcium channel blockers can depress sinus node function, resulting in symptoms and electrocardiographic changes consistent with sinus node dysfunction. In some patients, medications are potentially a reversible cause of apparent sinus node dysfunction. We report a patient who was taking atenolol for hypertension presented with recurrent near syncopal spells due to atenolol-induced sinus node dysfunction manifested in the form of an interesting and rare arrhythmia known as Escape-capture bigeminy.

Sympathetic tone is important in cardiac arrhythmogenesis; however, methods to estimate sympathetic tone are either to invasive or require proper sinus node function that may be abnormal in disease states. Because of the direct and extensive connections among various nerve structures, it is possible for the sympathetic nerves in the various structures to activate simultaneously. Therefore, we hypothesized that nerve activity can be recorded from the skin and it can be used to estimate the cardiac sympathetic tone. Preclinical studies in canines demonstrated that nerve activity is detectable using conventional ECG electrodes and can be used to estimate cardiac sympathetic tone. Subsequent clinical studies further supported this concept. In addition to studying the autonomic mechanisms of cardiac arrhythmia, these new methods may have broad application in studying both cardiac and non-cardiac diseases.

it is well known that athletes have a resting sinus bradycardia—their resting heart rate can be half the normal value ([7][1])— and this is normally attributed to high vagal tone ([3][2]). This is a logical assumption, because we have known since 1921 from the work of the physiologist Otto Loewi

Aim: Atrial undersensing (AUS) in single-lead VDD pacemakers may be due to diminished P-wave amplitude secondary to local inflammation beneath the electrodes closer to atrial wall. The aim of this study was to assess the potential effect of distance between atrial electrode and atrial wall on immediate and long-term atrial sensing stability in VDD systems. Methods: A total of 275 patients with normal sinus node function who received VDD pacemakers were enrolled into the study and were followed up for a median duration of 33 months. During each control visit, a standard 12-lead electrocardiogram (ECG) was obtained and standard pacemaker function assessment was performed including testing for pacing threshold and atrioventricular synchrony. The distance between atrial electrode and atrial wall was measured from chest X-ray. Results: Of the 275 patients, AUS was detected in 59 patients. Univariate predictors of AUS were use of closely spaced bipolar ring atrial electrode (CSBR) (P = 0.01), wider atrial ring-spacing (P = 0.03), and atrial sensitivity programmed to a higher level (P = 0.001). Use of CSBR (P = 0.04) and atrial sensitivity ≥0.3 mV (P = 0.02) were observed to be the independent predictors for AUS. When the distance between atrial electrode and atrial wall was

The anti-arrhythmic effectiveness of propafenon (3 x 150 mg daily) combined with propranolol (3 x 20 mg daily) was compared with that of each drug alone in 15 patients with stable ventricular and (or) supraventricular extrasystoles. The frequency of extrasystoles decreased on propafenon alone by 70% (P less than 0.05), without further decrease on additional propranolol administration. Propranolol alone on average caused no significant decrease infrequency (35%). The most important ECG changes with the combined treatment consisted of a definite increase in P-Q interval by an average of 25% (P less than 0.01) while with propafenon alone it was 13%, with propranolol alone 19% . Propafenon plus propranolol decreased heart rate by a mean of 17% (P less than 0.01). The additive effect of both substances can lead to an inhibition of atrioventricular conduction and of sinus node function.

Resume Dans ce chapitre consacre a l'exploration electrophysiologique endocavitaire seront abordees les differentes etapes de l'examen, a l'exclusion de l'etude des tachycardies traitee dans d'autres chapitres de l'Encyclopedie Medico-Chirurgicale. La conduction a tous les etages est envisagee : etude de la fonction sinusale, de la conduction anterograde nodale, intrahisienne et infrahisienne ainsi que de la conduction retrograde.

VDD pacing provides the physiological benefits of atrioventricular synchronous pacing with the convenience of a single lead system, but is hampered by uncertainty regarding long term atrial sensing and potential development of sinus node disease. To examine the long-term reliability and complication rates of VDD pacing, we compared the outcome of 112 consecutive patients (age 70 ± 13 years, 59% men) with symptomatic AV block who received a single pass bipolar VDD system, to 80 patients (age 63 ± 16 years, 70% men) who received DDD pacing for the same indication. All patients were judged to have intact sinus node function based on submitted ECGs and monitoring results at the time of implant. Implant time was reduced in VDD patients compared to DDD patients (63 ± 20 vs 97 ± 36 minutes, P < 0.0001). Implant complications occurred in 5 (6%) DDD patients compared to 3 (3%) VDD patients (P = 0.15). The implant P wave was lower with VDD pacing compared to DDD patients (2.91 ± 1.48 vs 4.0 ± 1.7 mv, P < 0.0001), but remained stable during long-term follow-up in both groups. During 17.7 ± 10.0 months of follow-up in the VDD group, only two VDD patients were reprogrammed to VVIR mode, compared to three DDD patients. Physiological atrioventricular activation was maintained in 94%–99% of beats throughout the follow-up period in the VDD group. VDD pacing is an excellent strategy for treatment of patients with symptomatic AV block. The lower cost, high reliability, and abbreviated implantation time suggest that VDD pacing is a viable alternative to DDD pacing in patients with high degree AV block and normal sinus node function. (PACE 2004; 27:19–23)

Background: Adequate exposure of the mitral valve is a critical factor of success for either replacement or repair of the mitral valve. In the present study, we evaluated the merits of the extended vertical transseptal approach in comparison with the transseptal approach for mitral valve operations.Methods: A total of 72 consecutive patients operated on for mitral procedures were allocated to either group A (those operated on through an extended vertical transseptal approach [n = 38]) or group B (whose mitral valve exposure was achieved through a right atrium transseptal approach [n = 34]). The operation time, aortic cross-clamp time, first 24-hour drainage volume after the operation, and the rhythms pre- and postsurgery were compared between the 2 groups.Results: The mean operation time and mean cross-clamp time in group A were longer than that in group B and the drainage volume was greater in the first 24 hours, but the differences were not statistically significant. There was no surgical reexploration for bleeding in either group. For the 13 patients who had normal sinus rhythm preoperatively in group A, 2 (15.4%) developed episodes of atrial fibrillation and 1 (7.7%) developed temporary sinus bradycardia requiring temporary pacing in the immediate and early postoperative period. In group B, 2(15.4%) of patients with normal sinus rhythm before surgery developed atrial fibrillation that continued until 1 week after surgery.Conclusion: The extended vertical transseptal approach not only affords excellent exposure of the mitral valve, but also is safe for maintaining sinus node function compared with the transseptal approach.

Bei Patienten mit hohergradigem AV-Block und normaler Sinusknotenfunktion ermoglichen VDD-Schrittmachersysteme eine physiologische AV-synchrone Zweikammerstimulation mit nur einer Elektrode. Sie konkurrieren dabei mit DDD-Systemen. In dieser Arbeit werden die aktuellen Ergebnisse der VDD-Systeme bezuglich Implantation, atrialer Wahrnehmung und AV-Synchronitat, sowie Stabilitat der Sinusknotenfunktion vorgestellt, und teilweise den Ergebnissen der DDD-Stimulation gegenubergestellt. Daneben werden die ventrikularen Elektrodeneigenschaften und Kosten beider Systeme verglichen. Neue Entwicklungen zu Single-Lead-DDD-Systemen werden diskutiert. VDD-Systeme bieten den Vorteil um bis zu 40% kurzerer Implantations- und bis zu 55% kurzerer Durchleuchtungszeiten. Daneben besteht ein nicht signifikanter Trend zu weniger Komplikationen im Vergleich zur DDD-Implantation. Die Zuverlassigkeit der P-Wellen-Wahrnehmung und damit AV-Synchronitat betragt bei beiden Systemen im Mittel 99% und mehr. Mit dem Auftreten einer stimulationsbedurftigen Sinusknotenerkrankung ist nur in 1 bis 2% der Patienten zu rechnen. Damit ist die fehlende atriale Stimulation bei VDD-Systemen kaum bedeutsam. Fur die ventrikularen Elektrodeneigenschaften besteht kein Unterschied zwischen beiden Systemen. VDD-Systeme sind akut und langfristig kostengunstiger als DDD-Systeme. Die Ergebnisse aktueller Studien belegen, dass VDD-Systeme in der Schritmachertherapie des isolierten AV-Blocks etabliert sind. Sie sind den konkurrierenden DDD-Systemen ebenburtig, in einigen Aspekten sogar uberlegen.

We have developed a noninvasive transesophageal signal averaging technique for direct recording of sinus node electrogram. In this study, sinus node electrograms were recorded from 106 of 138 patients (77%), comparable to that (46%) recorded by conventional transesophageal technique, 59 were male and 47 were female ranging in age from 10-74 years (mean 44.2+/-12.4 years). The signals from lead I, surface averaged lead and esophagus averaged lead were amplified (up to 100 microV/cm), filtered (0.1-50 Hz), AD converted to 16-bit accuracy at a sampling rate of 2 KHz and averaged by using the three channel low-noise amplifier. The signal averaged esophageal sinus node potentials are deflections of low-amplitude and low-frequency preceding the P wave. Two morphologies, the domed wave (64 of 106 patients, 60%) and the smooth upstroke slope (42 of 106 patients, 40%), can be seen. The directly recorded sinoatrial conduction time was 82.3 +/-18.6 msec (mean+/-2 SD), ranged from 23-112 msec, amplitude was 3.8-27.7 microV and dv/dt was 0.42-1.92 mV/sec. The sinoatrial conduction time recorded by the transesophageal catheter technique was comparable to that (80.4+/-18. 1 msec) recorded by the transvenous catheter method perfectly. We think that signal averaged sinus node electrogram could be recorded in sinus rhythm in most patients with normal sinus node function and proper filter settings, high amplification and anti-drift technique are important in recording signal averaged esophageal sinus node electrogram.

Predictors of successful elimination of sinoatrial tachycardia (SAT) using radiofrequency current (RFC) were investigated in this report. Within 1991-1996 fourteen patients with SAT were subjected to electrophysiological study and radiofrequency catheter ablation (RFCA). Ten patients had sinoatrial reentrant tachycardia (SART), and four patients had chronic non-paroxysmal sinoatrial tachycardia (CNPSAT). The RFC (15-30 W, duration 10-30 sec) were applied during tachycardia in case of CNPSAT, and during sinus rhythm (SR) in case of SART. In 3 patients with SART RFC were delivered during tachycardia due to failing of RFC application, delivered during SR. During successful RFC attempts were noted: 1). In case of SART-transient development (3-6 sec) of SART (if RFC was delivered during SR), and acceleration of tachycardia rate with following termination of tachycardia (if application of RFC was performed during tachycardia); 2). In case of CNPSAT-transient development (4-7 sec) of low right atrial (3 patients) or junctional (1 patient) rhythm with rapid conversion to SR. All 14 patients have been free of tachycardia and have normal sinus node function during follow-up of 8-60 months. We conclude that predictors of successful elimination of SAT are: 1). In case of SART-acceleration of tachycardia rate before termination during RFC application (delivered during tachycardia), and transient development of SART during RFC application (delivered during SR); 2). In case of CNPSAT-transient development of low right atrial or junction rhythm (during application of RFC) with rapid conversion to SR.

The use of single lead, atrial synchronous ventricular (VDD) pacing in patients with high grade atrioventricular (AV) block and normal sinus node function is an acceptable alternative to dual chamber (DDD) pacing. Implantation and follow up procedures are simplified, and cost is usually reduced by more than the cost of an additional atrial lead. With the use of either diagonally arranged dipole or closely spaced ring electrodes, reliable atrial sensing can be achieved using differential atrial amplifier and high atrial sensitivity. Also oversensing is infrequently observed using provocation tests and dynamic recordings, clinical undersensing is unusual and minimized by programming to the highest atrial sensitivity. However, as atrial pacing is not possible, loss of AV synchrony and rate response may occur for unrecognized or progressive sinus node disease and lower rate limit. The development of single lead dual chamber pacing system may overcome this limitation. Recent studies have demonstrated that atrial pacing can be effective either with the use of a special pacing lead configuration or via floating atrial electrode with a novel stimulation method. Overlapping Biphasic Impulse (OLBI) can reduce atrial pacing threshold. Early clinical experience suggested that this new pacing method can provide effective and reliable atrial pacing with a relatively low incidence of diaphragmatic pacing. Thus the problem of atrial sensing is solved with a single pass lead but further long term evaluation is required to assess the efficacy and feasibility of new instrumentation for single lead dual chamber pacing.

Objective: The transseptal superior approach can offer an excellent view of the mitral valve but the incision almost always transects the sinus node artery. The purpose of this study was to evaluate the sinus node function after mitral operation by this approach. Patients and Methods: We reviewed the electrocardiograms of 76 patients who underwent mitral valve operations either via transseptal superior approach or via right lateral atriotomy. Nine patients who maintained the sinus rhythm for more than one year after surgery via the transseptal superior approach were selected for electrophysiological study to evaluate the sinus node function. Results and Conclusions: Postoperative electrocardiographic and electrophysiological studies revealed that the sinus node function after the transseptal superior approach was relatively well maintained for more than one year after the operation. The influence of the transseptal superior approach on the sinus node function in the mid-term postoperative period was apparently mild and did not cause a serious problem. However, some of the patients did show abnormal data in terms of sino-atrial conduction time and intrinsic heart rate. Therefore, further follow-up of the sinus node function is necessary in patients who underwent mitral surgery through the transseptal superior approach.

Cardiorespiratory autonomic control is in tight interaction with an intracardiac neural network modulating sinus node function. To gain novel mechanistical insights and to investigate possible novel targets concerning the treatment of inadequate sinus tachycardia, we aimed to characterize functionally and topographically the right atrial neural network modulating sinus node function. In 16 sheep 3-dimensional electro-anatomical mapping of the right atrium was performed. In five animals additionally magnetically steered remote navigation was used. Selective stimulation of nerve fibers was conducted by applying high frequency (200 Hz) electrical impulses within the atrial refractory period. Histological analysis of whole heart preparations by acetylcholinesterase staining was performed and compared to the acquired neuroanatomical mapping.We found that neural stimulation in the cranial part of the right atrium, within a perimeter around the sinus node area, elicited predominantly shortening of the sinus cycle length of -20.3 ? 10.1 % (n = 80, P

The original maze procedure that was described for the treatment of patients with atrial fibrillation was followed by an unacceptable incidence of two problems: (1) the frequent inability to generate an appropriate sinus tachycardia in response to maximal exercise and (2) occasional left atrial dysfunction. In an effort to overcome these problems, we modified the original technique (maze I) twice. The results of these modifications culminated in the maze III procedure, which is associated with a higher incidence of postoperative sinus rhythm, improved long-term sinus node function, fewer pacemaker requirements, less arrhythmia recurrence, and improved long-term atrial transport function. In addition, the maze III procedure is technically less demanding than either the maze I or maze II procedure. Therefore, the maze III procedure is now the technique of choice for the management of medically refractory atrial fibrillation. (J T HORAC C ARDIOVASC S URG 1995;110:473-84)

Abnormal Sinus Node Function. To understand abnormal sinus node function in clinical atrial arrhythmias, it is essential to understand the normal function of the sinus node. Much of our understanding of the sinus node comes from work done in rabbits. In small animals, the node is a thin structure and can be modeled in two dimensions. However, in canines and humans, the node is a more complex structure completely surrounded by myocytes. Recent data suggest that the node may be insulated from the surrounding atrial myocytes, except at a limited number of exit sites. A model of the node with discrete exit sites explains how atrial activation can be initiated from multiple sites simultaneously. Within the node there may exist specialized pathways that explain the complex conduction within the node. Multiple cell types, with different intrinsic rates, combined with the nonuniform distribution of autonomic receptors, provide a basis for understanding the dynamics of heart rate control and the initiation of atrial activation. In addition, this model of the sinus node provides a framework to propose novel mechanisms underlying various atrial arrhythmias, such as atrial premature depolarizations or sinus node reentry. (J Cardiovasc Electrophysiol, Vol. 14, pp. 215-217, February 2003)

We have applied a mathematical function to model sinus node recovery after atrial pacing at different cycle lengths in 13 autonomically denervated, anesthetized canines. This model provides “pure” indexes of sinoatrial conduction and of suppression of automaticity. We compared sinoatrial conduction computed from the model (SACTc) with sinoatrial conduction measured directly utilizing a catheter recording the sinus node electrogram (SACTd) to test the validity of the model. We used both the model and the sinus node electrogram to further define events after pacing. There was close agreement between SACTc and SACTd with correlation coefficients at pacing cycle lengths of 20 and 50% below resting of 0.86 (P < 0.0001) and 0.78 (P < 0.0001), respectively. We verified that the conventional sinus node recovery time is due both to suppression of automaticity and prolongation of sinoatrial conduction. Sinoatrial conduction time returned rapidly to normal over 1–3 beats, whereas automaticity recovered exponentially over 20–40 postpacing intervals. The model accurately describes postpacing phenomena and has the potential to provide a useful adjunct to the measurement of the sinus node electrogram for assessment of sinus node function in the experimental laboratory.

There are about 3 million people worldwide with pacemakers, and each year 600 000 pacemakers are implanted. With rare exception, implantation of a pacemaker does not change the recipient’s activities or lifestyle. Although most people who receive pacemakers are aged 60 years or older, people of any age, even children, may need pacemakers. Almost all pacemakers are implanted to treat slow heart beating, which is called “bradycardia.” At rest, the heart usually beats about 50 to 70 times each minute, and the heart rate may increase 2- to 3-fold during stress or exercise. If the heart beats too slowly, the brain and body do not get enough blood flow and a variety of symptoms may result. Extreme slowing or complete stopping of the heartbeat can be fatal. In other cases, people may have no symptoms but are at high risk for dangerously slow heart rates because of disturbances of the electrical system of the heart. A pacemaker may be recommended for these people before symptoms occur. The normal heartbeat is controlled by a natural pacemaker in the heart called the sinus node. The electrical signal generated by the sinus node spreads throughout the heart causing it to beat. The most common reason for pacemaker implantation is because the sinus node function becomes too slow from age, heart disease, or heart medications. The other leading cause for pacemaker implantation is failure of the normal electrical signal to reach …

The electrophysiology study is central to the field of cardiac electrophysiology. This chapter begins by describing maneuvers performed in a basic electrophysiology study. Indications for an electrophysiology study are then discussed. They include (1) evaluation of syncope, (2) diagnosis of an arrhythmia, (3) evaluation of patients with Wolff–Parkinson–White, and (4) risk stratification of sudden cardiac death. The role of EP studies in non-ischemic cardiomyopathies is also addressed.

洞機能正常例56例 (12～78歳) について加齢と洞機能および自律神経機能との関係を明らかにする目的で薬理学的自律神経遮断 (TAB) 前後で, 安静臥位時, 能動的坐位時に洞機能を測定した.TAB前では安静臥位時に比し能動的坐位時に洞周期 (SCL) , 全洞房伝導時間 (TSACT) , 修正洞結節回復時間 (CSRT) は有意に短縮し, 血漿ノルエピネフリン (NE) は有意に増加した.安静臥位ではTAB前に比しTAB後にSCL, TSACT, CSRTは有意に短縮した.内因性固有心拍数 (observed IHR) は力口齢と負の相関を示し, SCL, TSACT, CSRTはTAB前後とも加齢と正相関を示した.血漿NE測定, 体位変換法, TAB法にて評価した交感, 副交感神経活動度は加齢と有意な相関は認めなかった.以上のことより, 洞機能正常例における内因性洞機能 (洞自動能, 洞房伝導能) は加齢に伴い低下するが, 自律神経機能が正常に保持されるかぎり, 内因性洞機能の低下は代償され得ることが推察された.

In a 4-year interval, 3/55 (7.8%) heart transplant recipients developed (greater than 4 weeks) severe sinus node dysfunction. An epicardial ventricular pacemaker was implanted at 90, 40, and 38 days after operation. Follow-up ranged from 7 to 20 months. In two of the three cases, failure of stimulation or sensing was detected at the 3rd and 4th month after pacemaker implantation. Sinus rhythm reappeared in two of the three patients at the 2nd and 4th months after transplantation. Severe sinus node disease requiring pacemaker implantation can improve following the first 3 months after transplantation. Failure of stimulation or sensing may not be uncommon.

J.B. is a well-trained male with syncope due to paroxysmal AV nodal heart block who ultimately required a permanent pacemaker despite an initial attempt at cessation of training only. Baseline sinus node function was normal, but AV nodal conduction remained abnormal even after autonomic blockade supporting intrinsic AV nodal dysfunction. This case illustrates that vigorous physical training may unmask previously unrecognized intrinsic dysfunction of AV nodal conduction or, as previously reported for physical training induced sinus node dysfunction, cause AV nodal dysfunction. Simple cessation of training to treat this problem is often recommended but may not be adequate for some patients who remain at risk for recurrent syncope during the deconditioning period.

The sinus node is the primary pacemaker of the heart. A complex interplay of heterogeneities is assumed to be the basic mechanism that the sinus node can drive the heart. This interplay can be disturbed by e.g. diseases, drugs or mutations. In this work the effect of a mutation on the sinus node function were investigated. Therefore, measurement data of wild-type and mutant IKr channels were integrated with aid of optimization procedures into the heterogeneous sinus node model of Zhang et al. The measurement data shows a shift of the steady-state inactivation to more positive potentials. Simulated central sinus node cells lose their ability to depolarize spontaneously. Peripheral cell are also effected by the mutation. The main changes are the shortening of the action potential duration from 108 ms to 84 ms and the increase of auto-rhythmic frequency from 6.37 Hz to 7.62 Hz due to an increased mean IKr current. In a future study the bradycardial effect of this mutation will be shown in a tissue model.

Few case reports have described associations between autonomic failure and sick sinus syndrome.Only 1 report has presented the caseof a patient with pure autonomic failure accompanying sick sinus syndrome (Sakai et al., 1996), but electrophysiological studies (EPS) to evaluate sinus node function were not included. We therefore present herein thefirst case report of autonomic failure associated with Parkinson's disease and sick sinus syndrome, in which sinus node function was confirmed as normal by EPS.

This study evaluated prospective exercise correlates of sinus node function in young individuals. Subjects for this study were 25 children and young adults who required cardiac catheterization for a symptomatic arrhythmia. Measurements of sinus node function at elechophysiological catheterization were the sinus node recovery time (SNRT) and sinoatrial conduction time (SACT). Maximal exercise testing was performed using a Bruce treadmill protocol the day prior to cardiac catheterization. Exercise measurements included resting heart rate, peak heart rate, cardiac acceleration from rest to 3 minutes, from rest to 6 minutes, from rest to peak, and from 3 to 6 minutes, cardiac deceleration from peak to 1 minute postexercise, deceleration for each minute of recovery, recovery heart rates for each of 5 minutes postexercise, heart rate at which respiratory exchange ratio >1.0 and slope of the heart rate – VO2 curve. Exercise testing did not predict intracardiac measures of sinus node function either as a group (“normal” vs. “abnormal” groups) or individually.

The need for permanent pacemaker implantation was retrospectively reviewed in 436 consecutive cardiac transplant recipients at our center between 1985 and 1998. The incidence of pacemaker implantation was examined in three arbitrarily defined periods: period 1, 1985-1990, before a review of pacemaker implantation policy; period 2, 1991-1995, after a change in policy to delay pacemaker implantation resulting from the review; and period 3, 1996-1998, after audit of this policy change, and the introduction of a change in surgical technique, from the standard atrial anastomosis to the bicaval anastomosis. Pacemaker implantation was not required in any recipient after the change in surgical technique, suggesting that the bicaval technique preserves sinus node function much better than does the standard atrial anastomosis.

Background Even though current guidelines suggest the use of VDD pacemakers in patients with AV block and normal sinus node function, a DDD system is often preferred for fear of either long-term atrial undersensing or late sinus node dysfunction and the resultant need for system upgrades. Methods We evaluated the long-term follow-up of all VDD pacemakers implanted in our center between 1992 and 2001 regarding atrial sensing, maintenance of AV synchrony, incidence of atrial fibrillation (AF), or the need for system upgrade, respectively. Results 320 consecutive patients (56% men, age 75±13 years) received a VDD pacemaker for the following indications: third-degree AV block 54%, second-degree AV block 34%, fascicular block with first-degree AV block and syncope 6%, others 6%. 138 patients (43%) died during follow-up, 3.8±2.3 years after implantation. Follow-up duration was 6.1±2.5 years in the remaining patients. At the last follow-up, 268 pacemakers (84%) were programmed to the VDD mode, 47 pacemakers (15%) were permanently programmed to the VVI mode (AF 36, undersensing 7, others 4, respectively). In five patients a DDD upgrade was necessary for sinus node dysfunction (3) or lead defect (2). Lead revision was performed in 19 patients (6%) (ventricular lead dislocation 7, atrial undersensing 6, lead fracture 3, others 2, respectively). Conclusion VDD pacemakers have an excellent long-term performance in patients with AV block. They have a very low incidence of lead revisions for atrial undersensing (2%) and DDD upgrades for secondary sinus node dysfunction (1%).

Old age and a variety of cardiovascular disorders may disrupt normal sinus node function. Currently, this is successfully treated with electronic pacemakers, which, however, leave room for improvement. During the past decade, different strategies to initiate pacemaker function by gene therapy were developed. In the search for a biological pacemaker, various approaches were explored, including beta(2)-adrenergic receptor overexpression, down regulation of the inward rectifier current, and overexpression of the pacemaker current. The most recent advances include overexpression of bioengineered ion channels and genetically modified stem cells. This review considers the strengths and the weaknesses of the different approaches and discusses some of the different viral vectors currently used.

In heart failure patients with normal sinus node function, cardiac resynchronization therapy can be achieved with only two leads, one VDD type, and one left ventricular. This reduces the number of venous punctures, implanted leads, and possibly operation and fluoroscopic times and complication rates. We present two cases and discuss the advantages and limits of such a procedure.

Effects of enalapril on canine sinus node (SN) dysfunction induced by long-term rapid atrial pacing were investigated. Methods and Results: Seventeen beagles were pretreated with either placebo (group I, n = 9) or enalapril 1 mg/kg/day (group II, n = 8) and paced at 500/min from the right atrial appendage for 4 weeks. Every week, corrected sinus node recovery time (CSNRT) and sinus cycle length (SCL) were measured. Quantitative analysis of interstitial fibrosis (IF) and adipose tissue (AT) in the SN was performed with Masson's trichrome stain, and apoptosis of the sinus nodal cells were detected with terminal deoxynucleotidyl transferase nick end-labeling. In group I, rapid atrial pacing prolonged both CSNRT and SCL. After 4 weeks of pacing, CSNRT and SCL were significantly shorter in group II (CSNRT, 410 ± 37 msec; SCL, 426 ± 34 msec) than in group I (CSNRT, 717 ± 52 msec, P < 0.005; SCL, 568 ± 73 msec, P < 0.05). Both IF and AT of the SN were greater in group I (IF, 9.7 ± 1.9%; AT, 32.6 ± 5.9%) than in seven sham dogs (IF, 2.4 ± 0.9%, P < 0.05; AT, 4.0 ± 1.7%, P < 0.05) and in group II dogs (IF, 4.0 ± 2.0%, P < 0.05; AT, 4.0 ± 1.7%, P < 0.05). End-labeling assay was positive in three of nine dogs in group I, but negative in group II and sham dogs. Conclusions: Rapid atrial pacing impaired SN function through IF and AT of the SN. Enalapril prevented these pacing-induced degenerative changes and improved SN function.

Background Some studies have shown that patients with Brugada syndrome (BS) have atrioventricular conduction disturbance, but their sinus node function has not been evaluated. Methods and Results The patients group consisted of 59 male patients and 1 female patient with BS. Supraventricular and ventricular programmed electrical stimulation (PES) was performed. Ventricular fibrillation (VF) or sustained polymorphic ventricular tachycardia was induced by ventricular PES in 26 patients with BS (VF group), but was not induced in the other 34 patients (non-VF group). Sinus node function and conduction of the atrioventricular (AV) node in the control group, non-VF group and VF group were evaluated. Sinus node function was attenuated and the His - ventricle interval was prolonged in the VF group (corrected sinus node recovery time: 452±126 ms (VF group), 324±146 ms (non-VF group), Sino-atrial conduction time: 179±60 ms (VF group), 127±60 ms (non-VF group), His-ventricle interval: 41±9 ms (VF group), 35±8 ms (non-VF group)). Conclusion The function of both the sinus node and AV node are attenuated in patients with PES-induced VF. (Circ J 2004; 68: 473 - 476)

The association of atrial fibrillation (AF) with sinus node dysfunction has been known for many years [1–4]. These abnormal atrial electrophysiological features may result from the same organic substrate [1–4]. A considerable body of experimental and human studies in the past 5 years have shown shortening of atrial refractoriness and repolarization and abnormal adaptation to rate as well as conduction slowing as a result of rapid atrial rates of certain duration. These changes are referred as atrial electrical remodeling [5–11]. Short-term rapid atrial rates induce these alterations in atrial electrophysiology via functional changes in ion channels and transporters. However, longer periods of atrial tachycardia result in changes in specific ionic current densities (ICa INa) due to modified expression of the genes that determine the function of the responsible ionic channels [12–16].

We investigated the autonomic effects of short-term, single- and dual-chamber pacing by evaluating frequency-domain indexes of heart rate variability (HRV). The study group comprised 25 patients (mean age 62 +/- 7 years) without organic heart disease and with normal sinus node function who were implanted with a permanent dual-chamber DDD (n = 16) or VDD (n = 9) pacing system for transient high-degree atrioventricular block. Continuous overdrive pacing for 15 minutes slightly above the intrinsic rhythm was programmed to ensure complete capture in AAI, DDD, and VVI modes, and the atrioventricular delays were set to ensure permanent ventricular pacing in DDD and VDD modes. Components of frequency-domain measures of HRV (low frequency [LF], high-frequency [HF], and LF/HF ratio) were calculated in 5-minute intervals over a 30-minute period after cessation of each pacing mode. AAI pacing did not significantly affect LF and LF/HF measures, and presented the highest HF power. DDD and VDD modes led to similar responses with slightly increased fluctuations of LF and LF/HF power. VVI pacing triggered an acceleration in heart rate (p0.05), the most significant increases in LF power and in the LF/HF ratio, and the lowest HF power. Autonomic effects of pacing did not resolve with cessation of pacing. Atrial AAI pacing appears to have lesser effect on sympathovagal balance. Synchronous VDD and DDD stimulation favor a shift in autonomic balance toward sympathetic predominance. Asynchronous VVI pacing triggers both sympathetic overactivity and vagal withdrawal.

Objective: This study was designed to evaluate the safety and effectiveness of the combined superior-transseptal approach for mitral valve surgery.Methods: We compared the preoperative status, operative factors, and postoperative outcomes among patients having mitral valve operations with three atrial incisions. The incisions were transseptal (n = 40), combined superior-transseptal (n = 33), and left atrial (n = 22).Results: The cardiopulmonary bypass time and cross-clamp time were significantly higher in the superior-transseptal group compared with the transseptal group. No significant difference in blood loss was found among the three groups. The incidence of sinus node dysfunction in the early postoperative period was more common in the superior-transseptal group. The maintenance of sinus rhythm at the mid-term follow-up in patients with preoperative sinus rhythm was not significantly different among the three groups. On the other hand, a few patients in the superior-transseptal and transseptal groups with the preoperative sinus rhythm developed sick sinus syndrome requiring permanent pacemaker implantation.Conclusions: The use of the combined superior-transseptal approach was safe and effective, and was not associated with a higher incidence of rhythm disturbance. Because this approach provided an optimal exposure of the mitral valve and subvalvular apparatus, it has been positively adopted for use in patients undergoing complex and difficult mitral valve operation. To use this approach for patients undergoing mitral valve surgery through this approach, however, further follow-up study of the sinus node function is necessary.

Single-lead VDD pacing is an attractive alternative to DDD pacing in patients with high-degree AV block and normal sinus node function. It provides physiological AV synchronous stimulation with a single lead. Owing to easier implantation, VDD systems have shorten the operation time by up to 40% and reduce the intraoperative fluoroscopy time by up to 55%. Additionally, they showed a trend towards a reduction in perioperative complications compared with DDD systems, and also showed a reduction in cost. 1 Therefore, why are single-lead VDD systems used infrequently in patients with isolated high-degree AV block? First, concerns exist about testing for sinus node dysfunction and development of sinus bradycardia during long-term follow-up. Sinus bradycardia during VDD pacing may result in VVI stimulation or necessitate the implantation of an atrial lead. However, in properly selected patients, sinus node function remains stable in the vast majority of patients. 2 Secondly, scepticism exists about the reliability of atrial sensing, using a floating atrial dipole within the right atrium. When I (B.N.) personally had the first contact with single-lead VDD pacing at a presentation given by Seymour Furman in Munich in the year 1990, I asked him whether he really thought that this concept might work, he answered: ‘Just put it in, it works’. Many studies thereafter have shown that he was right. Reliable atrial sensing can be accomplished with the floating atrial dipole, achieving AV synchrony .99%, with the prerequisite that atrial sensitivity is programmed to very sensitive values. 3‐5

The purpose of this study was to evaluate the efficacy of atrial sensing in children with a single pass lead VDD pacing system and to compare it with the efficacy of atrial sensing in adult patients with the same pacing system. Although the feasibility of single pass lead VDD pacing system implantation in children was recently demonstrated, the efficacy of atrial sensing remains unclear. In addition, the effect of accelerated growth of children on the systems' efficacy has not been addressed. Atrial sensing followed by ventricular sensing and atrial sensing followed by ventricular pacing was prospectively evaluated in 13 children (age 0.5-15 years) and 24 adult patients (age 19-74 years). All had the same endocardial pacing system using a single pass lead. The children and adults had effective atrial sensing at a success rate of 94.00 +/- 9.687% and 96.04 +/- 4.64%, respectively, during mean follow-up of 3.5 years. The atrial electrogram amplitude was similar in both groups, 1.8 +/- 1.5 mV in children and 1.8 +/- 1.1 mV in adults. The adult patients more frequently exhibited ventricular sensing following atrial sensing. The ventricular pacing threshold and impedance were stable in both groups. When necessary, in children, the atrial sensing was corrected by adjusting the pacemaker's lower rate programming. Highly effective atrial sensing was demonstrated in children and adult patients with a single pass lead VDD pacing system. During a mean follow-up of 3.5 years, not only was the atrial electrogram amplitude stable, but the clinically relevant atrial sensing was highly effective, justifying endocardial pacing with single pass lead VDD pacing in children and adults with preserved sinus node function.

Sinus node function was evaluated in 4 patients with congenital long QT syndrome suffering from recurrent episodes of syncope and ventricular arrhythymias. Three of the 4 patients had bradycardia at rest on a 24-hour ECG. Sinus node function was examined by the atrial overdrive suppression test and the atrial premature stimulation test. Corrected sinus node recovery time (CSNRT) was prolonged in all patients. Total sinoatrial conduction time was also prolonged in 2 of the 4 patients. In all patients with abnormally high values, these values returned to normal after atropine administration, except in one patient. His prolonged CSNRT remained high after atropine administration, indicating abnormal automaticity such as that seen in sick sinus syndrome. These results show that sinus node function in congenital long QT syndrome is often associated with autonomic dysfunction, and sometimes with intrinsic disturbances of sinoatrial conduction.

Although several reports have stated that even therapeutic levels of lithium can induce sinus node dysfunction, the mechanism has not been fully elucidated. We present here two patients with sinus node dysfunction after long-term lithium therapy. Following lithium discontinuation, sinus node function recovered completely. After resuming lithium, however, irreversible sinus node dysfunction recurred and a permanent pacemaker was implanted in one patient. The serum concentration of lithium was within therapeutic levels. Nevertheless, hypothyroidism was associated with the sinus node dysfunction in both patients. Thus, thyroid function may play an important role in sinus node dysfunction induced by lithium. (PACE 1999; 22[Pt. I]-.954-957) lithium, sinus node dysfunction, hypothyroidism, sick sinus syndrome