Recent evidence indicates that the voltage clock (cyclic activation and deactivation of membrane ion channels) and Ca2+ clocks (rhythmic spontaneous sarcoplasmic reticulum Ca2+ release) jointly regulate sinoatrial node (SAN) automaticity. However, the relative importance of the voltage clock and Ca2+ clock for pacemaking was not revealed in sick sinus syndrome. Previously, we mapped the intracellular calcium (Cai) and membrane potentials of the normal intact SAN simultaneously using optical mapping in Langendorff-perfused canine right atrium. We demonstrated that the sinus rate increased and the leading pacemaker shifted to the superior SAN with robust late diastolic Cai elevation (LDCAE) during beta-adrenergic stimulation. We also showed that the LDCAE was caused by spontaneous diastolic sarcoplasmic reticulum (SR) Ca2+ release and was closely related to heart rate changes. In contrast, in pacing induced canine atrial fibrillation and SAN dysfunction models, Ca2+ clock of SAN was unresponsiveness to beta-adrenergic stimulation and caffeine. Ryanodine receptor 2 (RyR2) in SAN was down-regulated. Using the prolonged low dose isoproterenol together with funny current block, we produced a tachybradycardia model. In this model, chronically elevated sympathetic tone results in abnormal pacemaking hierarchy in the right atrium, including suppression of the superior SAN and enhanced pacemaking from ectopic sites. Finally, if the LDCAE was too small to trigger an action potential, then it induced only delayed afterdepolarization (DAD)-like diastolic depolarization (DD). The failure of DAD-like DD to consistently trigger a sinus beat is a novel mechanism of atrial arrhythmogenesis. We conclude that dysfunction of both the Ca2+ clock and the voltage clock are important in sick sinus syndrome.
Animals ; Arrhythmia, Sinus/physiopathology ; Atrial Fibrillation/physiopathology ; Bradycardia/physiopathology ; Calcium/*physiology ; Calcium Channels/*physiology ; Dogs ; Humans ; Sick Sinus Syndrome/physiopathology ; Sinoatrial Node/physiology/*physiopathology

To investigate the effects of gradually guided breathing on respiratory sinus arrhythmia (RSA), 15 healthy men's simultaneous ECG and respiratory signals during the guided breathing process (14 beats/min-12.5 beats/ min--1 beats/min--9.5 beats/min--8 beats/minute--7 beats/min) were acquired. Based on the frequency domain and time domain methods, the effects of respiratory rate on RSA were studied. A general tendency increase features the three parameters of RSA as respiratory rate decreased. RSA represents the reflection control of respiratory system to cardiovascular system. The results suggested that the function of the reflection control of respiratory system to cardiovascular system increaseed with guided breathing decreasing. The conclusion indicates that the cardiovascular system could be improved by regulating the mode of respiration.
Adult ; Arrhythmia, Sinus ; physiopathology ; Electrocardiography ; Humans ; Male ; Music ; Respiration ; Respiratory Rate ; physiology

As is known in literature, the Base-scale Entropy Measure is useful for analyzing short-term heart rate variability signals. In this study, the method is applied to detect cardiac arrhythmias, including sinus and atrial arrhythmia. We detect and analyze normal sinus rhythm (NSR), atrial premature contraction (APC) and sinus bradycardia (SBR) signals. The selected data of NSR are obtained from the MIT-BIH normal sinus database, while others are from the MIT-BIH arrhythmia database. The results show the Base-scale Entropy can also detect sinus and atrial arrhythmia.
Algorithms ; Arrhythmia, Sinus ; diagnosis ; physiopathology ; Atrial Premature Complexes ; diagnosis ; physiopathology ; Electrocardiography ; Entropy ; Humans ; Signal Processing, Computer-Assisted

Arrhythmia, Sinus ; physiopathology ; therapy ; Atrial Fibrillation ; physiopathology ; therapy ; Electric Countershock ; methods ; Humans ; Male ; Middle Aged ; Treatment Outcome

Respiratory sinus arrhythmia (RSA) is known as fluctuations of heart rate associated with breathing. It has been increasingly used as a noninvasive index of cardiac vagal tone in psychophysiological research recently. Its analysis is often influenced or distorted by respiratory parameters, posture and action, etc. This paper reviews five methods of quantification, including the root mean square of successive differences (RMSSD), peak valley RSA (pvRSA), cosinor fitting, spectral analysis, and joint timing-frequency analysis (JTFA). Paced breathing, analysis of covariance, residua method and msRSA per liter tidal volume are adjustment strategies of measurement and analysis of RSA in this article as well. At last, some prospects of solutions of the problems of RSA research are given.
Algorithms ; Arrhythmia, Sinus ; physiopathology ; Artifacts ; Calibration ; Electrocardiography ; methods ; Humans ; Respiration ; Signal Processing, Computer-Assisted ; Tidal Volume ; physiology ; Vagus Nerve ; physiology

This study sought to disclose whether Hurst index can be used as a criterion for distinguishing sinus and atrial arrhythmia signals. Normal sinus rhythm beats, atrial premature contraction (APC) beats, and sinus bradycardia (SBR) signals, were taken from the MIT-BIH standard database. Hurst index method was used to distinguish the two kinds of arrhythmia. The results showed that the Hurst exponents of three kinds of signals were larger than 0.5, but they were in different value region. The data indicated that the long-term relevant character was the best for normal signal, better for sinus bradycardia, and the worst for atrial premature beats. So Hurst index is a useful identification criterion for distinguishing sinus and atrial arrhythmia signals.
Algorithms ; Arrhythmia, Sinus ; diagnosis ; physiopathology ; Atrial Premature Complexes ; diagnosis ; physiopathology ; Bradycardia ; diagnosis ; physiopathology ; Diagnosis, Differential ; Electrocardiography ; Humans ; Signal Processing, Computer-Assisted

Time irreversibility is a fundamental property of nonequilibrium systems. It is significant to measure the trend of change of time irreversible index under different physiological and pathological state of electrocardiosignal. We analyzed and tested the heart rate variability (HRV) signals of the normal sinus rhythm, atrial contraction, sinus bradycardia in the MIT-BIH standard database using the multiscale time irreversiblity method. It was shown that the time irreversiblity index of the normal heart rhythm, atrial premature beats and bradycardia were in the decreasing trend. The results would be helpful to clinical diagnosis as a secondary means.
Arrhythmia, Sinus ; physiopathology ; Atrial Premature Complexes ; physiopathology ; Bradycardia ; physiopathology ; Electrocardiography ; methods ; Heart Rate ; physiology ; Humans ; Signal Processing, Computer-Assisted ; Time Factors

To explore the energy proportion of the QRS complexes in the electrocardiogram (ECG), a new method, wavelet analysis, has been presented. Using wavelet transform of ECG, we can calculate the energy proportion of QRS complexes in multiple scales. The electrocardiograms (ECGs) were used as the experimental data, which were collected from a young (21-34 yr) group and an elderly (68-81 yr) group of healthy subjects, as well as from a group of arrhythmia patients (66-81 yr). the data analysis was performed with the energy proportion of the QRS complexes in the ECG using Mexican-Hat as a mother wavelet in multiple scales. Results showed that the energy proportion of the QRS complexes had no changes with ages increasing (P > 0.44), but in the same age group, the arrhythmia patients' energy proportion of the QRS complexes near 17Hz are obviously less than that in the healthy group (P < 0.01), so the energy proportion of the QRS complexes calculated by wavelet analysis can be used as a feature index to judge whether a person is a sinus arrhythmia patient or not.
Adult ; Aged ; Aged, 80 and over ; Arrhythmia, Sinus ; diagnosis ; physiopathology ; Arrhythmias, Cardiac ; physiopathology ; Electrocardiography ; methods ; Female ; Humans ; Male ; Middle Aged ; Wavelet Analysis ; Young Adult

BACKGROUNDLong-term maintenance of sinus rhythm after successful conversion of chronic atrial fibrillation (CAF), often ameliorates patients' symptoms, reduces the risk of ischemic stroke and improves cardiovascular hemodynamics. This prospective study aims to evaluate the long-term efficacy and safety of very low-dose amiodarone (100 mg daily) for the maintenance of sinus rhythm after successful direct-current (DC) cardioversion in patients with CAF and rheumatic heart disease (RHD) post intervention.

METHODSThis study was a randomized prospective trial. One day after successful DC cardioversion (remained normal sinus rhythm) in patients with CAF and RHD post intervention for more than six months and adequate anticoagulation, all were randomly administered either amiodarone 200 mg daily in group A or amiodarone 100 mg daily in group B.

RESULTSA total of 76 patients (40 men and 36 women) were examined from February 1998 to December 1999. The mean age of the patients was (66 +/- 10) years, and the mean follow-up was (67 +/- 8) months (range 61 to 84 months). Actuarial rates of the maintenance of sinus rhythm were similar in the two groups after 5 years of follow-up. Four patients (11%) in group A but none in group B experienced significant adverse effects that necessitated withdrawal of amiodarone. No death occurred during the study period.

CONCLUSIONA very low dose of amiodarone results in adequate long-term efficacy and is safe for maintaining sinus rhythm in patients with CAF and RHD post intervention after successful DC cardioversion.

Aged ; Amiodarone ; administration & dosage ; adverse effects ; Anti-Arrhythmia Agents ; administration & dosage ; Arrhythmia, Sinus ; drug therapy ; Atrial Fibrillation ; drug therapy ; physiopathology ; Chronic Disease ; Cohort Studies ; Electric Countershock ; methods ; Female ; Humans ; Male ; Middle Aged ; Prospective Studies

Arrhythmia, Sinus ; physiopathology ; Arrhythmias, Cardiac ; physiopathology ; surgery ; Atrioventricular Node ; anatomy & histology ; physiology ; Catheter Ablation ; Electrophysiologic Techniques, Cardiac ; Electrophysiology ; Heart ; anatomy & histology ; physiology ; Heart Atria ; anatomy & histology ; Heart Conduction System ; physiology ; Humans ; Models, Cardiovascular ; Wolff-Parkinson-White Syndrome ; physiopathology