The electrical impulses of atrium arise from the sinus node, subsequently pass through the right and left atrium, and finally arrive at the atrioventricular node. The P wave is the summation of the electrical current generated by depolarization due to its passage through the atrial conduction pathway. It provides many clinical clues that may be useful for diagnosis of atrial, ventricular, or valvular heart diseases. This review article briefly describes the clinical implications, mechanism of genesis, and normal and pathologic features of the P wave.
Atrioventricular Node ; Diagnosis ; Heart Atria ; Heart Valve Diseases ; Sinoatrial Node

The aim of present study is to investigate the effects of cGMP on hyperpolarization activated inward current (If), pacemaker current of the heart, in rabbit sino-atrial node cells using the whole-cell patch clamp technique. When sodium nitroprusside (SNP, 80 muM), which is known to activate guanylyl cyclase, was added, If amplitude was increased and its activation was accelerated. However, when If was prestimulated by isopreterenol (ISO, 1 muM), SNP reversed the effect of ISO. In the absence of ISO, SNP shifted activation curve rightward. On the contrary in the presence of ISO, SNP shifted activation curve in opposite direction. 8Br-cGMP (100 muM), more potent PKG activator and worse PDE activator than cGMP, also increased basal If but did not reverse stimulatory effect of ISO. It was probable that PKG activation seemed to be involved in SNP-induced basal If increase. The fact that SNP inhibited ISO-stimulated If suggested cGMP antagonize cAMP action via the activation of PDE. This possibility was supported by experiment using 3-isobutyl-1-methylxanthine (IBMX), non-specific PDE inhibitor. SNP did not affect If when If was stimulated by 20 muM IBMX. Therefore, cGMP reversed the stimulatory effect of cAMP via cAMP breakdown by activating cGMP-stimulated PDE. These results suggest that PKG and PDE are involved in the modulation of If by cGMP: PKG may facilitate If and cGMP-stimulated PDE can counteract the stimulatory action of cAMP.
1-Methyl-3-isobutylxanthine ; Guanylate Cyclase ; Heart ; Nitroprusside ; Sinoatrial Node*

Human heart rhythm is mainly regulated and controlled by the sinoatrial node. Fibrosis plays an important regulating role in adjusting the structural and functional integrity of the sinoatrial node pacemaker complex. In physiological state, the fibrosis degree of sinoatrial node is negatively correlated with heart rate, positively correlated with age and heart size, and can maintain a relatively stable heart rate. Pathological fibrosis of sinoatrial node can induce various types of arrhythmias which can result in sudden death. Determination of the mechanisms related to sinoatrial node pathological fibrosis could provide a target for clinical treatment of sinoatrial node fibrosis and diagnosis basis for forensic pathologists. This paper reviews the main mechanism of sinoatrial node pathological fibrosis, including abnormal activation of cardiac fibroblast cells in sinoatrial node, hyperplasia of epicardial adipose tissue, calcium clock disorder, artery stenosis, etc., introduces the test methods, diagnostic criteria as well as its role in sudden cardiac death and discusses the potential application, to provide reference for relevant research and application.
Arrhythmias, Cardiac ; Fibrosis ; Heart Rate ; Humans ; Sinoatrial Node

A simplified method of the cardiac conduction system (CCS) is evaluated by the study of 73 forensic cases. The sinoatrial node were observed in all cases (100.0%), atrioventricular node in 70 cases (95.9%) and penetrating bundle (His bundle) in 70 cases (95.9%). We divided the cases into three groups as the group of cardiac death (25 cases), non-cardiac death (24cases) and sudden unexpected death but undeterminable cause of death (24 cases) diagnosed after routine autopsy including routine cardiac examination and toxicological analysis and compared the type and incidence of CCS lesions in each groups. Narrowing of the sinoatrial (SA) or atrioventricular (AV) artery by fibromuscular hyperplasia (FMH) and fatty infiltration in SA or AV node were identified in all groups, lymphocytic infiltration in SA or AN node in cardiac and non-cardiac death group, hemorrhage and fibrosis of SA or AV node were identified in cardiac death group. FMH of the artery of SA or AN node occured more commonly in undeterminable cause of death group (45.1%) than in cardiac (16.0%) and non-cardiac group (20.8%) and severe narrowing (> or =75%) of the artery of SA or AV node was only present in undeterminable cause of death group (29.2%). The results led to the conclusion that this simple technique is very useful in detection of major abnor-malities of CCS with minimal effort and examination of the CCS in death which the routine autopsy and drug screen fail to provide a cause of death can yield a cause of death in a significant percentage of cases.
Arteries ; Atrioventricular Node ; Autopsy ; Cause of Death ; Death ; Death, Sudden* ; Fibrosis ; Hemorrhage ; Hyperplasia ; Incidence ; Sinoatrial Node

Nine patients of mean age 47.8 years, with suspected sinus node dysfunction, underwent extensive electrophysiological studies. Sinus bradycardia(6the electrophysiological study, AH and HV intervals were prolonged in 2/9 and 1/9 patients, respectively. Maximal sinus node recovery times were prolonged in 7/9 patients, ranging from 1,330 msec to 12,330msec. Sinoatrial conduction times measured by atrial premature stimulation technique were prolonged in 5/7 patients, ranging from 137msec to 310 msec. And sinoatrial conduction time measured by continuous pacing technique also revealed prolonged value in 4/6 patients ranging from 140 msec to 195 msec. The effective refractory periods, of atrium were prolonged in 6/8 patients (320 msec to 470 msec). The effective and functional refractory periods of AV node were prolonged in 3/8 patients (440 csec to 490 msec) and 4/8 patients (530 msec to 560 msec), respectively. Retrograde VA conduction could be observed in 3/7 patients and ventricular effective refractory periods were normal in 7/7 patients. Atrial flutter was induced in 1/9 patients by electric stimulation during electrophysiological study. Above data suggest that the electrophysiological study is very useful in assessing the sinus node function and other electrophysiological properties in sick sinus syndrome patients and also suggest that the data could be utilized in choosing the proper mode of artificial pacemaker for each patient.
Atrial Flutter ; Atrioventricular Node ; Electric Stimulation ; Humans ; Pacemaker, Artificial ; Sick Sinus Syndrome* ; Sinoatrial Node

The slowing down mechanism of heart rate during growth of the body after birth was studied in isolated rabbit heart and sinus node (SN) preparation with Langendorff perfusion method, conventional microelectrode recording and perforated patch for recording pacemaker current I(f). The radioimmunoassay was also used to measure the concentration of cAMP within SN cells. The results indicate that without the influence of nervous and humoral factors, the spontaneous heart rate would also become slower as the rabbit grew older, which is due to the decrease of spontaneous depolarized rate of phase 4 in SN cells. The negative directed shift of the threshold potential of I(f) and the decrease in cAMP concentration within SN cells may be responsible for the phenomenon. The results obtained suggest that besides the nervous and humoral factors which influence the heart rate, the changes in automaticity of SN cell itself may take part in the slowing down process as the body grows up.
Animals ; Cyclic AMP ; physiology ; Heart Rate ; In Vitro Techniques ; Microelectrodes ; Perfusion ; Rabbits ; Sinoatrial Node ; physiology

BACKGROUND: Extended transseptal approach can provide an excellent view of the mitral valve but the safety of this approach is controversial because this incision requires transection of the sinus node artery, which in most cases and can result postoperative arrhythmia. The purpose of this study was to evaluate perioperative and longterm conduction disturbances and the cardiac rhythms of patients who underwent an extended transseptal approach for mitral valve surgery. MATERIAL AND METHOD: Postoperative cardiac rhythms were analyzed in the 164 consecutive patients who received mitral valve replacements with a extended transseptal approach between March 1992 and July 2003. RESULT: Of the 84 patients in normal sinus rhythm, 34 (39%) had developed transient junctional rhythm and atrial fibrillation after operation, lasting less than 72 hours in most of cases. No intractable arrhythmias occurred. Most of these arrhythmia were not detected at the time of discharge and only 8 patients (9%) had atrial fibrillation at discharge. Postoperative PR intervals increased for 1 week, then decreased within 2 weeks postoperatively, and returned to normal range by 6 months postoperatively. During the postoperative period, 4 of the 78 patients with preoperative atrial fibrillation developed normal sinus thythm. CONCLUSION: The postoperative arrhythmias were temporary and showed no significant complications after extended transseptal approach for the mitral valve surgery.
Arrhythmias, Cardiac ; Atrial Fibrillation ; Coronary Vessels ; Humans ; Mitral Valve* ; Postoperative Period ; Reference Values ; Sinoatrial Node*

Atrial myxoma is the most common primary cardiac tumor, and surgical removal is the treatment of choice. Atrial flutter-fibrillation is common after the surgical excision of such tumors, whereas sinus node dysfunction is a rare complication. We detected postoperative sinus node dysfunction and atrial tachycardia after the excision of a left atrial myxoma in a 63-year-old woman. The patient underwent the implantation of a permanent pacemaker two weeks after the operation. The patient underwent successful catheter ablation of macroreentrant right atrial tachycardia 16 months after the operation with no recurrence of atrial tachycardia over the next four months.
Catheter Ablation ; Female ; Heart Neoplasms ; Humans ; Middle Aged ; Myxoma ; Recurrence ; Sick Sinus Syndrome ; Sinoatrial Node ; Tachycardia

Recent evidence indicates that the voltage (cyclic activation and deactivation of membrane ion channels) and Ca2+ clocks (rhythmic spontaneous sarcoplasmic reticulum Ca2+ release) jointly regulate sinoatrial node (SAN) automaticity. Since the intact SAN is a heterogeneous structure that includes multiple different cell types interacting with each other, the relative importance of the voltage and Ca2+ clocks for pacemaking may be variable in different regions of the SAN. Recently, we performed optical mapping in isolated and Langendorff-perfused canine right atria. We mapped the intracellular calcium (Cai) and membrane potentials of the intact SAN simultaneously. Using previously described criteria of the timing of the late diastolic Cai elevation (LDCAE) relative to the action potential upstroke to detect Ca2+ clock activity, we demonstrated that the sinus rate increased and the leading pacemaker shifted to the superior SAN with the robust LDCAE during beta-adrenergic stimulation. We also showed that the LDCAE was caused by spontaneous diastolic SR Ca2+ release and was closely related with heart rate changes. We conclude that the Ca2+ and voltage clocks work synergistically to generate SAN automaticity.
Action Potentials ; Calcium ; Heart Rate ; Membrane Potentials ; Membranes ; Sarcoplasmic Reticulum ; Sinoatrial Node ; Sympathetic Nervous System

Clinical EPS was performed in 16 normal adults without evidence of conduction disease on the surface standard 12 lead electrocardiogram in order to provide normal electrophysiological values of the sinus node function and AV conduction. EPS was also performed in 15 patients with sick sinus syndrome and 10 patients with AV conduction disturbance to evaluate the clinical usefulness of EPS in detecting sinus node dysfunction and AV conduction disturbance. The results were as follows. 1) The results of sinus node function test in the normal group were m-SNRT 853+/-198msec(range 800-1,560msec), c-SNRT 230+/-66msec(range 120-370msec), and %m -SNRT/SCL 127+/-11%(range 114-149%). 2) In 15 patients with SSS, the M-SNRT were ranged from 1,270 to 12,330msec and 10 patients(66%) had significantly increased m-SNRT exceeding 1,560msec. The c-SNRT were ranged from 230 to 10,730msec and 13 patients(83%) had significantly increased c-SNRT exceeding 370msec. The % m-SNRT/SCL were ranged from 136 to 770% and 12 patients(80%) had significantly increased % m-SNRT/SCL exceeding 150%. 3) The SACT in normal group were 84+/-14msec(range 70-105msec) measured by continuous atrial pacing method and 80+/-19 msec(range 60-115msec) measured by atrial extrastimulation method. 4) In SSS, the SACT measured by continuous atrial pacing method was ranged from 80 to 1,050msec and 11/12 patients(92%) had significantly increased SACT exceeding 112 msec. The SACT measured by atrial extrastimulation method was ranged from 90 to 310msec and 7/8 patients(88%) had significantly increased SACT exceeding 118 msec. 5) C-SNRT, % m-SNRT/SCL, and SACT were more useful in detecting sinus node dysfunction than m-SNRT. 6) The AV conduction intervals in normal group were PA interval 17+/-6(range 5-25msec), AH interval 96+/-18 msec(range 70-135msec), and HV interval 46+/-7msec(range 35-55msec). 7) Rapid atrial pacing induced Wenckebach type second degree AV block proximal to H at pacing rate of 90 to 190/min in 14/16 normal adults. 2 patients maintained intact AV conduction upto maximum pacing rate of 200/min. 8) His bundle electrogram showed the site of AV block in 9 of 10 patients with AV conduction disturbances. The sites of AV block were AV nodal area 1 case, intraHis bundle 4 cases, and infraHis bundle 4 cases. 9) EPS provided a good supportive information that was useful in selecting pacemaker therapy in a patient with chronic bifascicular block who revealed prolonged HV interval and infraHis bundle block at a pacing rate of 70min. 10) The refractory periods of AV conduction system in normal group were AERP 274+/-54msec (range 170-410msec), AVN-FRp 467+/-74msec(range 285-600msec), AVN-ERP 341+76msec(range 190-460), and V-ERP 280+/-25msec(range 240-320msec).
Adult ; Atrioventricular Block ; Electrocardiography ; Electrophysiologic Techniques, Cardiac ; Humans ; Sick Sinus Syndrome ; Sinoatrial Node*