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

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

Atrial fibrillation is the most common of all cardiac arrhythmias. It is associated with significant morbidity and mortality and is frequently resistant to medical therapy. On the experimental and clinical study, the presence of macroreentrant circuits and the absence of either microreentrant circuits or evidence of atrial automaticity suggests that atrial fibrillation should be amenable to surgical ablation. The results of the maze III procedure are 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. We had experienced 4 patients with chronic atrial fibrillation. For the first time, Hioki procedure had been performed in the first patient with ASD and atrial fibrillation, regular sinus rhythm showed on postoperative EKG, but junctional rhythm and bradycardia developed postoperative 3 years. The maze III procedure for the rest with mitral valvular disease and atrial fibrillation had been done, followed by regular sinus rhythm for 2 patients and atrial fibrillation for 1 patient, managed with amiodarone, on immediate postoperative state. Echocardiogram documented good contraction of right atrium and hardly contraction of left atrium for 2 patients with regular sinus rhythm postoperative 3 months.
Amiodarone ; Arrhythmias, Cardiac ; Atrial Fibrillation* ; Bradycardia ; Electrocardiography ; Heart Atria ; Humans ; Incidence ; Mortality ; Recurrence ; Sinoatrial Node

BACKGROUND: The most widely utilized indexes of sinus node dysfunction are the sinus node recovery time (SNRT) and the corrected sinus node recovery time (CSNRT), which generally require catheterization. Adenosine has negative chronotropic effect on the sinoatrial node. Non-invasive and reliable sinus node function test with intravenous adenosine was investigated. METHODS AND RESULT: The clinical value of rapid intravenous injection of adenosine for assessing sinus node dysfunction was examined in 14 patients with sick sinus syndrome (SSS) and 31 controls. After prophylactic insertion of a temporary pacemaker in the right ventricle, overdrive suppression test was conducted using the standard technique and CSNRT was measured to evaluate the sinus node function. Then, the CSNRT after administration of an intravenous bolus of adenosine (6 mg and 12 mg) was measured. Post-adenosine corrected sinus node recovery time (ADO: SNRT) was calculated by subtracting the basal sinus cycle length from the longest sinus cycle length. When ADO: SNRT over 550 msec was assumed as an indicator of sinus node dysfunction, intravenous injection of 6 mg of adenosine had a sensitivity of 85% and specificity of 100%, and 12 mg of adenosine had a sensitivity of 100% and specificity of 90% for detection of sick sinus syndrome. There were significant differences in ADO: SNRT between patient and control group (6 mg 1501+/-1081 msec vs 64+/-109 msec; 12 mg 4005+/-2055 msec vs 216+/-315 msec, respectively). CONCLUSION: he ADO: SNRT was a highly sensitive and specific index for diagnosing sick sinus syndrome, and should be considered as an alternative to invasive testing in patients with suspected sick sinus syndrome.
Adenosine* ; Catheterization ; Catheters ; Diagnosis* ; Heart Ventricles ; Humans ; Injections, Intravenous ; Sensitivity and Specificity ; Sick Sinus Syndrome* ; Sinoatrial Node

Hyponatremia is the most common electrolyte abnormality in hospitalized patients and often presents no symptoms. The association between sinus node dysfunction and hyponatremia has rarely been reported. We describe a 77-year-old woman who developed reversible sinus node dysfunction accompanied by pulmonary edema that was associated with hyponatremia.
Aged ; Female ; Humans ; Hyponatremia* ; Pulmonary Edema* ; Sick Sinus Syndrome* ; Sinoatrial Node*