Electrical injury is a serious public health problem. Heart is one of the most frequently affected organs. Electrical injury can cause life-threatening cardiac complications such as asystole, ventricular fibrillation, and myocardial rupture. In this case report, we present a 20-yr-old male patient with sick sinus syndrome that developed years after electrical injury.
Adult ; Atropine/diagnostic use ; Electric Injuries/complications* ; Electrocardiography ; Exercise Tolerance ; Human ; Male ; Pacemaker, Artificial ; Sick Sinus Syndrome/etiology* ; Sick Sinus Syndrome/physiopathology ; Sick Sinus Syndrome/therapy ; Sinoatrial Node/physiopathology ; Time Factors

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

PURPOSE: The identification of sick sinus syndrome (SSS) in patients with atrial flutter (AFL) is difficult before the termination of AFL. This study investigated the patient characteristics used in predicting a high risk of SSS after AFL ablation. MATERIALS AND METHODS: Out of 339 consecutive patients who had undergone radiofrequency ablation for AFL from 1991 to 2012, 27 (8%) had SSS (SSS group). We compared the clinical characteristics of patients with and without SSS (n=312, no-SSS group). RESULTS: The SSS group was more likely to have a lower body mass index (SSS: 22.5+/-3.2; no-SSS: 24.0+/-3.0 kg/m2; p=0.02), a history of atrial septal defects (ASD; SSS: 19%; no-SSS: 6%; p=0.01), a history of coronary artery bypass graft surgery (CABG; SSS: 11%; no-SSS: 2%; p=0.002), and a longer flutter cycle length (CL; SSS: 262.3+/-39.2; no-SSS: 243.0+/-40; p=0.02) than the no-SSS group. In multivariate analysis, a history of ASD [odds ratio (OR) 3.7, 95% confidence interval (CI) 1.2-11.4, p=0.02] and CABG (7.1, 95% CI 1.5-32.8, p=0.01) as well as longer flutter CL (1.1, 95% CI 1.0-1.2, p=0.04) were independent risk factors for SSS. CONCLUSION: A history of ASD and CABG as well as longer flutter CL increased the risk of SSS after AFL ablation. While half of the patients with SSS after AFL ablation experienced transient SSS, heart failure was associated with irreversible SSS.
Atrial Flutter/physiopathology/*surgery ; Catheter Ablation/*adverse effects ; Female ; Humans ; Male ; Middle Aged ; Multivariate Analysis ; Odds Ratio ; Risk Factors ; Sick Sinus Syndrome/*etiology/physiopathology ; Treatment Outcome

OBJECTIVETo study the effect of Kangxin Fulu Recipe (KFR) on electrophysiological functions of the sinoatrial node in rabbits with sick sinus syndrome (SSS).

METHODSSixty big ears white rabbits were randomly divided into six groups, i.e., the normal group, the model group, the atropine group, the high dose KFR group, the middle dose KFR group, and the low dose KFR group, ten in each group. SSS model was established by injecting formaldehyde to the sinoatrial node except those in the normal group. Changes in AA interval, the sinoatrial conduction time (SACT), the sinus node recovery time (SNRT), and the corrected sinus node recovery time (CSNRT) were measured before and after modeling, seven days before and after gastrogavage.

RESULTS(1) The AA interval and SACT could be significantly shortened in the high dose KFR group, the middle-dose KFR group, and the atropine group (P<0.05, P<0.01). Better effects were obtained in the former two groups (P<0.05). (2) SNRT and CSNRT could be shortened in the high dose KFR group and the atropine group, with no statistical difference between the two groups (P>0.05).

CONCLUSIONThe electrophysiological mechanism of KFR might possibly be correlated with accelerating the recovery of sinus node autorhythmicity and conduction functions.

Animals ; Disease Models, Animal ; Drugs, Chinese Herbal ; pharmacology ; Heart Rate ; drug effects ; Rabbits ; Sick Sinus Syndrome ; physiopathology ; Sinoatrial Node ; drug effects ; physiopathology

OBJECTIVETo determine the feasibility on the left ventricular systolic synchronism and cardiac function evaluation in patients with permanent cardiac pacing by real-time three-dimensional echocardiography.

METHODSFifteen patients with sick sinus syndrome post dual-chamber pacemaker implantation were enrolled in this study. Pacemakers were programmed to AAI, DDD, and VVI respectively. After pacing for 5 minutes in each mode, participants were examined with real-time three-dimensional echocardiography. Images in different pacing modes were obtained and analyzed by the off-line Qlab 4.2 software. Parameters including global and 17-segmental volume-time curves (VTCs), dispersion of time to minimal regional volume for 16, 12, and 6 left ventricular segments (Tmsv16-s, Tmsv12-s, Tmsv6-s), and maximal difference of time to minimal regional volume for l6, 12 and 6 left ventricular segments (Tmsv16-dif, Tmsv12-dif, Tmsv6-dif), end diastolic volume (EDV), end systolic volume (ESV), left ventricular ejection fraction (LVEF) were measured respectively. Parameters of peak filling rate (PFR), regional end diastolic volume (rEDV), regional end systolic volume (rESV), and regional ejection fraction (rEF) were also calculated.

RESULTSLeft ventricular systolic synchronism as reflected by VTCs, Tmsv16-s, Tmsv12-s, Tmsv6-s, Tmsv16-dif, Tmsv12-dif and Tmsv6-dif as well as parameters reflecting ventricular function, i.e., LVEF, PFR were significantly better in AAI mode than in DDD and VVI models (all P < 0.05). All above indexes were similar between DDD and VVI models (all P > 0.05). rEFs of left inferior wall in base, septum in base and apex were significantly lower in DDD and VVI models compared that in AAI mode (P < 0.05).

CONCLUSIONReal-time three-dimensional echocardiography can objectively and accurately evaluate left ventricular systolic synchronism and cardiac function in patients with permanent cardiac pacing and AAI mode is superior to DDD and VVI models.

Adult ; Aged ; Cardiac Pacing, Artificial ; Echocardiography, Three-Dimensional ; methods ; Female ; Heart Ventricles ; diagnostic imaging ; Humans ; Male ; Middle Aged ; Sick Sinus Syndrome ; diagnostic imaging ; physiopathology ; Ventricular Function, Left

PURPOSE: The optimal pacing mode with either single chamber atrial pacemaker (AAI or AAIR) or dual chamber pacemaker (DDD or DDDR) is still not clear in sinus-node dysfunction (SND) and intact atrioventricular (AV) conduction. MATERIALS AND METHODS: Patients who were implanted with permanent pacemaker using AAI(R) (n = 73) or DDD(R) (n = 113) were compared. RESULTS: The baseline characteristics were comparable between the two groups, with a mean follow-up duration of 69 months. The incidence of death did not show statistical difference. However, the incidence of hospitalization for congestive heart failure (CHF) was significantly lower in the AAI(R) group (0%) than the DDD(R) group (8.8%, p = 0.03). Also, atrial fibrillation (AF) was found in 2.8% in the AAI(R) group, which was statistically different from 15.2% of patients in the DDD(R) group (p = 0.01). Four patients (5.5%) with AAI(R) developed AV block, and subsequently switched to DDD(R) pacing. The risk of AF was lower in the patients implanted with AAI(R) than those with DDD(R) [hazard ratio (HR), 0.84; 95% confidence interval, 0.72 to 0.97, p = 0.02]. CONCLUSION: In patients with SND and intact AV conduction, AAI(R) pacing can achieve a better clinical outcome in terms of occurrence of CHF and AF than DDD(R) pacing. These findings support AAI(R) pacing as the preferred pacing mode in patients with SND and intact AV conduction.
Aged ; Atrial Fibrillation/complications/physiopathology ; Atrioventricular Node/*physiopathology ; Cardiac Pacing, Artificial ; Cohort Studies ; Female ; Follow-Up Studies ; Heart Failure/complications ; Humans ; Male ; Middle Aged ; Proportional Hazards Models ; Retrospective Studies ; Sick Sinus Syndrome/*physiopathology ; Treatment Outcome