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PubMed1999

Ionic mechanisms of electrical remodeling in human atrial fibrillation.

OBJECTIVES: Atrial fibrillation (AF) is associated with a decrease in atrial ERP and ERP adaptation to rate as well as changes in atrial conduction velocity. The cellular changes in repolarization and the underlying ionic mechanisms in human AF are only poorly understood. METHODS: Action potentials (AP) and ionic currents were studied with the patch clamp technique in single atrial myocytes from patients in chronic AF and compared to those from patients in stable sinus rhythm (SR). RESULTS: The presence of AF was associated with a marked shortening of the AP duration and a decreased rate response of atrial repolarization. L-type calcium current (ICa,L) and the transient outward current (Ito) were both reduced about 70% in AF, whereas an increased steady-state outward current was detectable at test potentials between -30 and 0 mV. The inward rectifier potassium current (IKI) and the acetylcholine-activated potassium current (IKACh) were increased in AF at hyperpolarizing potentials. Voltage-dependent inactivation of the fast sodium current (INa) was shifted to more positive voltages in AF. CONCLUSIONS: AF in humans leads to important changes in atrial potassium and calcium currents that likely contribute to the decrease in APD and APD rate adaptation. These changes contribute to electrical remodeling in AF and are therefore important factors for the perpetuation of the arrhythmia.

Acetylcholine↗
PubMed1980

Initiation and termination of ventricular tachycardia by supraventricular stimuli. Incidence and electrophysiologic determinants as observed during programmed stimulation of the heart.

In 7 of 43 patients in whom a sustained ventricular tachycardia could be induced during programmed electrical stimulation by a single ventricular premature stimulus, an identical tachycardia could also be initiated by a single atrial premature stimulus. This phenomenon was observed only in those patients in whom the ventricular tachycardia could be induced by a single ventricular extrastimulus having a prematurity index (ratio between the longst ventricular premature stimulus interval resulting in tachycardia and th duration of the basic cycle length of the paced ventricular rhythm) above 54 percent. No single instance of initiation of ventricular tachycardia by atrial premature stimuli was observed in patients with a ventricular prematurity index below 54 percent or requiring more than one consecutive ventricular extrastimulus to have tachycardia initiated. Other features of patients showing initiation of ventricular tachycardia by atrial premature stimuli were a right bundle branch block configuration of the QRS complex during tachycardia in all seven patients and a relatively slow rate during tachycardia. In one patient ventricular tachycardia was terminated by a conducted atrial premature stimulus.

Adult↗
PubMed2000

Effect of Valsalva maneuver on surface electrocardiographic P-wave dispersion in paroxysmal atrial fibrillation.

The purpose of this study was to investigate the effect of the Valsalva maneuver on P-wave durations and dispersion. After the Valsalva maneuver, we found that maximum P-wave duration increased, minimum P-wave duration decreased, and P-wave dispersion increased in controls, whereas the opposite was true for unselected patients with paroxysmal AF. It was concluded that patients with paroxysmal AF performing the Valsalva maneuver normalized their P-wave dispersion, thereby correcting the inhomogeneous intra-atrial conduction.

Anti-Arrhythmia Agents↗
PubMed2005

Prediction of the recurrence of atrial fibrillation after successful cardioversion with P wave signal-averaged ECG.

BACKGROUND: The recurrence of atrial fibrillation (AF) was often observed after cardioversion. METHODS: In our study, a P wave triggered P wave signal-averaged ECG (P-SAECG) was performed on 118 consecutive patients 1 day after successful electrical cardioversion in order to evaluate the utility of this method to predict AF after cardioversion. We measured the filtered P wave duration (FPD) and the root mean square voltage of the last 20 ms of the P wave (RMS 20). RESULTS: During a 1-year follow-up, a recurrence was observed in 57 patients (48%). Patients with recurrence of AF had a larger left atrial size (41.9 +/- 4.0 vs 39.3 +/- 3.1 mm, P < 0.0003), a longer FPD (139.6 +/- 16.0 vs 118.2 +/- 14.1 ms, P < 0.0001), and a lower RMS 20 (2.57 +/- 0.77 vs 3.90 +/- 0.99 microV, P < 0.0001). A cutoff point (COP) of FPD > or =126 ms and RMS 20 < or =3.1 microV could predict AF with a specificity of 77%, a sensitivity of 72%, a positive value of 75%, a negative predictive value of 75%, and an accuracy of 75%. A stepwise logistic regression analysis of variables identified COP (odds ratio 9.97; 95% CI, 4.10-24.24, P < 0.0001) as an independent predictor for recurrence. CONCLUSIONS: We conclude that the probability of recurrence of AF after cardioversion could be predicted by P-SAECG. This method seems to be appropriate to demonstrate a delayed atrial conduction that might be a possible risk factor of reinitiation of AF.

Atrial Fibrillation↗
PubMed2005

Effect of reperfusion on P-wave duration and P-wave dispersion in acute myocardial infarction: primary angioplasty versus thrombolytic therapy.

BACKGROUND: Atrial fibrillation (AF) is a common arrhythmia occurring in about 10-20% of patients with acute myocardial infarction (AMI). P-wave dispersion (PWd) and P-wave duration (PWD) have been used to evaluate the discontinuous propagation of sinus impulse and the prolongation of atrial conduction time, respectively. This study was conducted to compare the effects of reperfusion either by thrombolytic therapy or primary angioplasty on P-wave duration and dispersion in patients with acute anterior wall myocardial infarction. METHODS: We have evaluated 72 consecutive patients retrospectively (24 women, 48 men; aged 58 +/- 12 years) experiencing acute anterior wall myocardial infarction (AMI) for the first time. Patients were grouped according to the reperfusion therapy received (primary angioplasty (PTCA) versus thrombolytic therapy). Left atrial diameter and left ventricular ejection fraction (LVEF) were determined by echocardiography in all patients. Electrocardiography was recorded from all patients on admission and every day during hospitalization. Maximum (P max) and minimum (P min) P-wave durations and P-wave dispersions were calculated before and after the treatment. RESULTS: There were not any significant differences between the groups regarding age, gender, left ventricular ejection fraction, left atrial diameter and volume, cardiovascular risk factors, and duration from symptom onset to treatment. P-wave dispersions and P-wave durations were significantly decreased after PTCA [Mean P max was 113 +/- 11 ms before and 95 +/- 17 ms after the treatment (P = 0.007)]. Mean PWd was 46 +/- 12 ms before and 29 +/- 10 ms after the treatment (P = 0.001). Also, P max and PWd were significantly lower in PTCA group (for P max 97 +/- 22 ms vs 114 +/- 16 ms and for PWd 31 +/- 13 ms vs 55 +/- 5 ms, respectively). CONCLUSIONS: Primary angioplasty reduces the incidence of AF by decreasing P max and P-wave dispersion.

Angioplasty, Balloon, Coronary↗
PubMed1983

[Sick sinus syndrome: comparative study of atrial and ventricular stimulation tests].

Subjects with a ventriculo-atrial block and normal sinus function exhibit acceleration of the sinus rhythm during incremental right ventricular pacing; this acceleration is nor observed or is hardly visible in patients with sinus node dysfunction. Incremental right ventricular pacing up to 150/min was performed in 16 patients with ventriculo-atrial block (Group A) referred for investigation of sinus node dysfunction and the results compared with the classical tests of atrial pacing (Strauss'graph, atrio-sino-atrial conduction time, sinus node recovery time). The same tests were carried out in 19 patients without sinus node dysfunction (Group B). In the latter group, sinus rhythm exceeded 80/min during right ventricular pacing at 150/min and the rate increased with respect to the basal rhythm was always greater than 10/min. In Group A premature atrial pacing gave abnormal results in 4 cases, sinus node recovery times were abnormal in 15 cases, and rapid right ventricular pacing abnormal in all cases (sinus rhythm less than 80/min and/or rate increase of less than 10/min). There was no relation between the increased sinus node recovery time and the degree of rate increase during rapid ventricular pacing. Incremental right ventricular pacing, therefore, seems to be a new method of investigating sinus node function but complementary studies are required to determine its limitations, the exact mechanism and to try to widen its application to subjects without ventriculo-atrial block.

Aged↗
PubMed2006

Disorganization of gap junction distribution in dilated atria of patients with chronic atrial fibrillation.

BACKGROUND: Atrial fibrillation (AF) is an arrhythmia associated with functional and morphological remodeling of atria. We investigated the distribution and the expression of connexins in atrial tissues from patients with chronic AF and left atrial dilatation (AD). METHODS AND RESULTS: Immunohistochemistry was performed in atrial tissues obtained during cardiac surgery from patients with chronic AF + AD (n = 11), sinus rhythm (SR, n = 11) and SR + AD (n = 4). In SR patients (control), the connexin (Cx) 43 labeling of the intercalated disks seen en-face was characterized by small central spots surrounded by larger spots at the periphery. In the left atria from AF + AD patients, the area of the intercalated disk was significantly enlarged. Although peripheral Cx43 labeling was preserved, there was a striking loss of central labeling spots. The area occupied by gap junctions was slightly but significantly larger than that of the control. The left atria from patients with SR + AD showed gap junction disorganization analogous to AF + AD. The labeling patterns of Cx40 were essentially similar to those of Cx43. Conclusions In chronic AF with AD, gap junctions at the intercalated disk are disorganized, resulting most likely from AD but not from AF itself. This gap junction remodeling might be involved in altered atrial conduction properties, but its potential arrhythmogenic role remains unclear.

Adult↗
PubMed1982

[Effect of ethmozine in patients with paroxysmal atrioventricular nodal tachycardias].

With the aid of the electrophysiological method ethmozine action on patients with paroxysmal atrioventricular nodal tachycardias has been studied. Tachycardia was arrested by ethomozine in 66.6% of patients. With the drug still acting stable tachycardia could not be elicited in 75% of cases. After ethmozine administration in 3 out of 14 patients complete block of impulse retrograde conduction in the atrioventricular node supervened, in the remaining 11 there was a significant increase in the refractory period (a mean of 124.5 ms) and a decrease in the level of Wenckebach's point of the ventriculo-atrial conducting system. The drug had practically no effect on the electrophysiological indices of the atrioventricular node for anterograde conduction. It is concluded that ethmozine is effective for arresting and, possibly, for preventing such disorders in this category of patients. Electrophysiological mechanism of this effect is the block of the echo-impulse of retrograde conduction in the atrioventricular node.

Adolescent↗
PubMed1982

[Disorders of formation and conduction of the cardiac impulse in hypertrophic and congestive primary myocardiopathy].

Little information is available regarding cardiac automatism and conduction disturbances in patients affected by congestive (CCM) or hypertrophic (HCM) cardiomyopathies. For this reason 29 patients with HCM (10 cases) and CCM (19 cases) and disturbances of sinus node automaticity or AV conduction underwent an electrophysiologic study. Eight patients affected by HCM were also submitted to cardiac catheterization. Sinus node function was normal in each of the HCM patients, and impaired in 6 of the 19 CCM patients. The intra-atrial conduction was prolonged in only one CCM case. One HCM and 2 CCM patients showed an impaired intranodal AV conduction. Thirteen patients (44%) showed a prolonged HV interval (3 HCM and 10 CCM patients). No calcific deposits on the aortic valve were discovered by X ray stratigraphic examination in any of the patients. In 6 cases a progression of the conduction disturbances was observed. Ventricular pre-excitation was present in 4 patients (13%).

Adolescent↗
PubMed1995

[Fetal arrhythmia. A case load of 4 years and a half].

In a 4 1/2 year period fetal, echocardiographic studies were performed on 1600 fetuses. In 55 with arrhythmia, 44 had supraventricular ectopic beats, resolved in all, and none had heart disease. Sustained arrhythmias occurred in 11 fetuses. Atrial flutter was present in 3 all with heart disease (Ebstein disease, right atrial tumour and WPW diagnosed after birth). Another 3 fetuses had supraventricular tachycardia (SVT), all with a normal heart. In the bradycardia group, 2 had complete heart block (CHB) associated with AVSD; 2 sinus bradycardia and one had non conducted atrial ectopic beats. Digoxin was the first choice drug for tachyarrhythmia therapy; association with Verapamil, Flecainide, Quinidine and Procainamide was used in 4 of the 6. One fetus with CHB received Orciprenaline with no results. Atrial flutter resolved or improved; in SVT 2 fetuses converted to sinus rhythm and one died in utero. All fetuses with CHB died in cardiac failure. Mortality was 27% (3 cases) in utero and global 36%. In our experience most fetal arrhythmias (90%) were transitory ectopic beats or non lasting bradycardia in normal heart and did not trigger other kinds of arrhythmias. In sustained arrhythmias, heart failure and heart disease had a negative effect on prognosis.

Arrhythmias, Cardiac↗
PubMed1988

Electrophysiological study of intravenous pinaverium bromide in cardiology.

Pinaverium bromide is a musculotropic spasmolytic agent which acts by inhibiting transmembrane calcium movements, an effect similar to that of verapamil. Because of this, an investigation was carried out to see if it had any electrophysiological effects in patients with various cardiac disorders. In an open study, 10 patients received 2 mg pinaverium bromide intravenously. In a double-blind study, 10 patients received 4 mg pinaverium bromide intravenously and 10 patients placebo. Patients included those with either normal or pathological basal conduction, such as bundle-branch block and 1st degree atrioventricular block. Measurements were made of electrophysiological parameters before and 10 minutes after injection. The results showed that neither of the two doses of pinaverium bromide had any effect on atrial excitability, sino-atrial conduction, node and trunk atrioventricular conduction or on intraventricular conduction. No significant difference was seen in comparison with placebo. Pinaverium bromide had no anti-arrhythmic properties in these studies. Local, cardiac and general clinical tolerability was good in all patients.

Aged↗
PubMed1985

Assessment of the antiarrhythmic profile of the new class I agent diprafenone.

The antiarrhythmic profile of the new compound diprafenone was evaluated using various dog models relevant to conditions in humans. In 8 animals, dose related effects on intracardiac conduction, atrial and ventricular refractoriness, fibrillation thresholds and on hemodynamics were determined. In this part of the study also the comparative actions of propafenone were assessed (8 animals). IN another 28 dogs the antiarrhythmic and antifibrillatory actions of diprafenone following short-term coronary occlusion and subsequent release were established. In additional 16 animals the effects of diprafenone on "delayed" reperfusion arrhythmias following release of coronary artery occlusion after 2 h and on stimulus-induced ventricular tachycardia in acute myocardial infarction were investigated. The results show: Diprafenone slows conduction through all parts of the AV-conduction system. The AH-interval is significantly prolonged, QRS-duration and ventricular repolarization are slightly lengthened, and both the atrial and ventricular refractory periods and fibrillation thresholds are markedly increased. Heart rate is slowed, aortic pressure and cardiac output are not significantly changed. Following acute short-term coronary artery occlusion, the incidence of ventricular fibrillation is reduced, and the drop in the ventricular fibrillation threshold is diminished. By contrast, the frequency of ventricular fibrillation after release of short-term occlusion is not influenced. "Delayed" reperfusion arrhythmias, however, are completely abolished, and initiation of ventricular tachycardia in myocardial infarction can be easily prevented. With a predominant local anesthetic mechanism of action and a potential additional beta-sympatholytic activity, the new compound displays close similarities to propafenone.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Sudden cardiac death while wearing a Holter monitor.

The Holter tapes of 61 patients (46 men, mean age +/- standard deviation 65 +/- 11 years) with sudden cardiac death while being monitored were analyzed. Thirty-eight patients were known to have coronary artery disease, 5 had cardiomyopathy, and 7 had aortic valve disease. Etiology remained unknown in 11 patients. Mean New York Heart Association functional class was 2.5 +/- 0.7. Thirty patients had received antiarrhythmic drugs and 32 had received digitalis. Sudden death occurred at rest in 73%. In the hours before death, repetitive ventricular arrhythmias were found in 50 patients (82%), with atrial fibrillation in 34%. Patients with bradyarrhythmic death (18%) had less complex ventricular activity compared to patients with tachyarrhythmic death (p less than 0.01). Lethal arrhythmias--monomorphic ventricular tachycardia, polymorphic ventricular tachycardia, torsades de pointes, primary ventricular fibrillation, and 1:1 conducting atrial tachycardia--were found in 26 (43%), 15 (25%), 5 (8%), 3 (5%), and 1 patient, respectively. The coupling interval of the final ventricular tachycardia correlated inversely with the initial frequency of ventricular tachycardia (p less than 0.05). For patients with tachyarrhythmic death, an increase of heart rate within the last 3 hours was noted (83 vs 89 beats/min, p less than 0.05). Ventricular premature complexes and the proportion of patients with greater than 2 couplets and greater than 2 triplets increased significantly only within the last hour before death.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1990

[Anterograde tachycardia caused by the antitachycardia mechanism in a DDD pacemaker].

If there is a demonstrable ventriculo-atrial conduction at the time of a DDD pacemaker implantation, the possibility of a pacemaker mediated tachycardia is always present. The latest technological advances tries to solve this problem by the refractory time programmability and specially by the automatic extension of the atrial refractory period. A new and special mode of premature ventricular contraction-synchronous atrial stimulus has been developed as an additional and more effective mechanism anti pacemaker mediated tachycardia. We present one case in which this anti pacemaker mediated tachycardia mode just unchains one tachycardia. The understanding of this tachycardia doesn't offer difficulties and the correction would be made by different steps.

Adult↗
PubMed2002

The electromechanical effects of pacing at different sites within the right atrium.

AIMS: To compare high right atrium (HRA) with right atrial appendage (RAA) pacing with respect to atrial electromechanical function. METHODS: Eleven patients undergoing elective electrophysiological studies were studied in order directly to compare atrial conduction acutely associated with HRA and RAA pacing. Twenty-five patients with chronically implanted, active fixation leads in the HRA were compared with an age and sex matched group of 25 patients with chronically implanted, passive fixation leads in the RAA. For both studies recordings were taken in sinus rhythm then repeated when paced. Measured time intervals were intra- and interatrial activation times. P wave duration and time to onset of atrial systolic blood flow. RESULTS: Right atrial pacing, when compared with sinus rhythm, significantly prolongs the interatrial activation time, the P wave duration and the time to onset of right and left atrial blood flow irrespective of site paced. Comparing the RAA group with the HRA group, there were no statistical differences for any of the measured parameters. CONCLUSION: High right atrial free wall or the right atrial appendage pacing, when compared with sinus rhythm, is significantly detrimental to atrial electromechanical function. There is, however, no demonstrable difference between the two sites.

Adult↗
PubMed1988

Electrophysiological effects of intravenous nicaïnoprol, a new antiarrhythmic agent, in 11 patients.

Nicaïnoprol, a new class 1 antiarrhythmic drug was given intravenously in a dose of 2 mg kg-1 of body weight (two patients) and 3 mg kg-1 of body weight (nine patients), and the clinical, electrocardiographic and electrophysiological effects were studied. Fifteen minutes after the end of drug administration, the PR interval was prolonged by 24.4% (P less than 0.001), and the QTc by 3.9% (P less than 0.01). The prolongation of QRS duration (+6%) was not significant. There was a slight (-3.9%) but non-significant decrease of the heart rate, with no alteration in sinus node function. Alteration of atrial conduction and atrioventricular (AV) conduction were due to an increase in the PA interval (+57.4%, P less than 0.05), the AH interval (+10.9%, NS) and the HV interval (+43.8%, P less than 0.01). The anterograde Wenckebach cycle length increased by 11% (P less than 0.01). The effective and functional atrial refractory periods increased respectively by 4.5% and 11.4% (P less than 0.05), and the effective refractory period of the AV node increased by 11.2% (P less than 0.05). None of the other electrophysiological variables changed significantly. A non-significant drop in blood pressure was noted between the second minute following injection (-9.4%) and the 15th minute (-3.4%), and two patients complained of dizziness; one of these two patients reported a heat flush with an oral burning. In conclusion, nicaïnoprol seems to possess the electrophysiological properties of some other class I antiarrhythmic drugs, and is clinically well tolerated.

Adult↗
PubMed2000

Catheter ablation of atrial flutter guided by electroanatomic mapping (CARTO): a randomized comparison to the conventional approach.

INTRODUCTION: Three-dimensional electroanatomic (CARTO) activation mapping of the cavotricuspid isthmus can be helpful to guide atrial flutter ablation, but to date has not been investigated in comparison to conventional strategies. The aim of the present study was to assess the efficacy of the CARTO navigation system, especially with respect to the fluoroscopy time required for successful atrial flutter ablation. METHODS AND RESULTS: Eighty patients with recurrent common-type atrial flutter were randomly assigned to temperature-controlled radiofrequency (RF) catheter ablation, either guided by conventional criteria (group 1) or additionally oriented on electroanatomic mapping (group 2). In all patients, similar multipolar catheters were inserted into the coronary sinus and placed at the tricuspid annulus, respectively. In group 2, positioning of the mapping electrode and delivery of RF pulses within the cavotricuspid isthmus was mainly oriented on the CARTO map to achieve the most linear and continuous RF lesions. Abolition of intra-atrial conduction verified by conventional criteria (group 1) and electroanatomic mapping (group 2) could be verified in all patients. The overall number of RF pulses (group 1: 16.7+/-6.5; group 2: 13.2+/-5.3) and mean procedure duration (group 1: 172.5+/-47.4 min; group 2: 169.3+/-47.3 min) were not different between the two groups, but mean fluoroscopy time was significantly shorter when the CARTO technology was used (group 1: 29.2+/-9.4 min; group 2: 7.7+/-2.8 min; P = 0.0001). Recurrence of atrial flutter was observed in 3 (9%) patients in each group after a mean follow-up of 8.5+/-2.8 months. CONCLUSION: Atrial flutter can be abolished effectively using the conventional technique as well as oriented on electroanatomic mapping. However, overall X-ray exposure can be significantly reduced by the CARTO-guided approach without prolongation of procedure duration.

Aged↗
PubMed2006

Cardiac arrhythmias in the fetus and newborn.

Arrhythmias are potentially life-threatening problems in the fetus and newborn. Appropriate management depends on accurate diagnosis. Atrioventricular re-entry is the most common type of supraventricular tachycardia in both the fetus and newborn. It should be distinguished from other types of tachycardia - such as atrial flutter, atrial ectopic tachycardia, permanent junctional re-entry tachycardia, and ventricular tachycardia. Neonatal and fetal bradycardias are less common clinical problems. Sustained bradycardia is most often caused by complete atrioventricular block. It can be mimicked by the more common but benign occurrence of non-conducted atrial premature beats.

Anti-Arrhythmia Agents↗