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PubMedDate not supplied

[Electric cardioversion in the emergency service. Experience in 1000 cases].

We describe our experience with 1000 electric cardioversions performed at the emergency ward in the Hospital of Cardiology y Neumology, National Medical Center I.M.S.S. The objectives are: 1. Report our experience. 2. Investigate if digitalis treatment should be discontinued before the procedure. 3. Determine if all patients should be on anticoagulant therapy for elective cardioversion. 4. Indicate the optimal anesthetic drug with minimal side effects. A therapeutic procedure was performed in 73% of our cases and an elective one in the remaining 27%. Patients were grouped as ischemic heart disease 26%, rheumatic heart disease 24%, chronic obstructive pulmonary disease 14%, systemic hypertensive heart disease 13%, without clinical heart disease 6%, preexcitation syndrome 6%, adult congenital heart disease 4%, with implanted pacemaker 2%, pregnancy 2% and diverse myocardial diseases 2%. As a cardiac arrhythmias atrial fibrillation was the main cause 45%. Atrial flutter represented 25%, atrial paroxysmal tachycardia was 21% and ventricular tachycardia 9%. A cardioversion was performed in 43% of patients under digitalis treatment at therapeutic levels, without complications. Atrial flutter reverted to sinus rhythm in 98% of the procedures, and atrial fibrillation in 97%. Elective cardioversion in patients with atrial fibrillation was achieved with energies of 200 joules in 82% of the procedures (P less than 0.001) and in atrial flutter with 100 joules in 89% of the cases (P less than 0.001). The most frequent complications were atrial and junctional premature beats in 41% of the cases. We consider this procedure a safe one, effective at the energy levels described, with no need for discontinuation of digitalis therapy, with no mandatory previous anticoagulant therapy, and with no contraindications on pregnancy or implanted pacemakers.

Adolescent↗
PubMed2003

Rhythm discrimination by rate branch and QRS morphology in dual chamber implantable cardioverter defibrillators.

Morphology Discrimination is a discriminator based on QRS morphology analysis that has been recently implemented in dual chamber implantable cardioverter defibrillators (ICDs). Detected events are initially classified according to median atrial and ventricular rates (Rate Branch). Then, a series of discriminators (Morphology Discrimination, Stability, Sudden Onset) analyze the rhythm according to specific criteria and the number of discriminators required for VT diagnosis (i.e., requiring "any" or "all" of the specific discriminators to indicate VT). The discriminating accuracy of the algorithm was evaluated in 645 detections recorded during the follow-up of 25 patients. The overall specificity for 397 supraventricular arrhythmias was 73.5% (292/397) with the tachycardia diagnosis criteria set to "any" and 90.9% (361/397) with the tachycardia diagnosis criteria set to "all." Sensitivity for VT was 100% and 98.7% (231/234) with the tachycardia diagnosis criteria set to "any" and "all," respectively. With the tachycardia diagnosis criteria set to "any," specificity for atrial fibrillation was 88.6%, for atrial flutter 40.3%, for atrial tachycardia 0%, and for sinus tachycardia 97.0%. With the tachycardia diagnosis criteria set to "all," specificity for atrial fibrillation was 92.40%, for atrial flutter 93.5%, for atrial tachycardia 54.7%, and for sinus tachycardia 99.0%. The contribution of Morphology Discrimination was crucial to improve the specificity of the Rate Branch algorithm. The implementation of Morphology Discrimination in a dual chamber ICD with Rate Branch rhythm classification allows the attainment of high specificity and high sensitivity for ventricular tachyarrhythmias.

Aged↗
PubMed2004

Late recurrent arrhythmias after ablation of atrial fibrillation: incidence, mechanisms, and treatment.

OBJECTIVES: The aim of the study was to determine the incidence of atrial flutter and other arrhythmia recurrences (other than atrial fibrillation [AF]) during long-term follow-up after left atrial substrate modification by percutaneous radiofrequency (RF) ablation of AF. BACKGROUND: RF ablation is an effective treatment for patients with AF. However, late recurrent arrhythmias may complicate the patient's course. METHODS: One hundred fifty consecutive patients with paroxysmal or persistent AF were included in this prospective study. The incidence of arrhythmia recurrences after AF ablation was analyzed during long-term follow-up using repetitive 7-day ECG recording. RESULTS: In 28 of 150 patients (18.7%), stable regular arrhythmias other than AF were detected during follow-up. Left atrial flutter observed in 10 patients (6.7%) was treated by recompletion of the ablation lines in all 10 patients. Left atrial flutter was associated with recurrence of AF in all 10 patients. Nine of 10 patients (90%) were free from atrial flutter and 6 of 10 patients were free from AF after the second intervention. Typical right atrial flutter occurred in 10 patients (6.7%) and was treated successfully by percutaneous RF ablation without recurrence in all patients. Additionally, atrial flutter was documented during follow-up in 7 patients (4.7%); however, invasive electrophysiologic evaluation was not performed due to various reasons. CONCLUSIONS: Left atrial flutter is a relevant complication after RF catheter ablation of AF and was always associated with AF recurrence in our study population. Prevention of left atrial flutter can be achieved by induction of ablation lines as continuous and transmural as possible. However, left atrial flutter that does occur late after ablation is amenable to interventional treatment with good prospects of success.

Atrial Fibrillation↗
PubMed1996

[Late supraventricular arrhythmia complicating Fontan or cavopulmonary type procedures. Apropos of 7 cases].

The authors report 7 cases of late arrhythmias after atriopulmonary (5 cases) or total cavopulmonary (2 cases) bypass procedures. There were 6 cases of atrial flutter and one case of atrial tachycardia. The condition presented with cardiac failure in 5 cases. In 2 patients, atrial flutter caused syncope or dizziness. The arrhythmia was reduced by atrial stimulation (3 cases) or by cardioversion (1 case). Prevention of recurrence with oral amiodarone was effective in all cases but was responsible for secondary effects in 4 cases. In one patient, recurrence of atrial flutter was complicated by right atrial thrombosis with cerebral embolism. Five patients were reoperated after cardiac catheterisation and angiography. Surgery consisted of resection of a stenosis of the anastomosis in one case, and the transformation of atriopulmonary anastomosis into a total cavopulmonary bypass because of a very dilated right atrium without stenosis in 4 patients. The immediate postoperative period was complicated by a recurrence of the arrhythmia in 3 children not treated by antiarrhythmic therapy. At long-term, one patient died 6 months after withdrawal of amiodarone therapy of recurrence of atrial flutter. Five of the 6 survivors are treated with amiodarone or a betablocker; 3 have had pacemaker implantation for severe bradycardia. Late atrial arrhythmias complicating atrio- and cavopulmonary bypass procedures carry a risk of cardiac failure and sudden death. When diagnosed, the patient should be investigated for stenosis of the anastomosis but severe dilatation of the right atrium is often the only finding. After restoration of sinus rhythm, maintenance antiarrhythmic therapy should be continued indefinitely.

Amiodarone↗
PubMed2002

A population-based study of mortality among patients with atrial fibrillation or flutter.

PURPOSE: To determine the mortality associated with atrial flutter and atrial fibrillation in the general population. SUBJECTS AND METHODS: Using the Marshfield Epidemiologic Study Area, a database that captures nearly all medical care and deaths among its 58,820 residents, we identified patients diagnosed with atrial flutter or atrial fibrillation from July 1, 1991, through June 30, 1995. Patients were followed prospectively and compared with a group of controls without these arrhythmias. RESULTS: A total of 4775 person-years of follow-up were completed in 577 patients and 577 controls. Compared with controls, mortality among patients with atrial fibrillation or flutter was nearly 7.8-fold higher at 6 months (95% confidence interval [CI]: 4.1 to 15) and 2.5-fold higher (95% CI: 2.0 to 3.1; P < 0.0001) at the last follow-up (mean [+/- SD] of 3.6 +/- 2.3 years; range, 1 day to 7.3 years). At 6 months, mortality among patients with atrial flutter alone was somewhat greater than in controls and less than one third that of those with atrial fibrillation (with or without atrial flutter) (P = 0.02). At the last follow-up, however, mortality was greater among patients with atrial flutter (hazard ratio [HR] = 1.7; 95% CI: 1.2 to 2.6; P = 0.007), atrial fibrillation (HR = 2.4; 95% CI: 1.9 to 3.1; P < 0.0001), or both atrial arrhythmias (HR = 2.5; 95% CI: 1.9 to 3.3; P < 0.0001) when compared with controls in models that adjusted for cardiovascular risk factors. CONCLUSION: In the general population, both atrial flutter and atrial fibrillation are independent predictors of increased late mortality. The relatively benign course during the 6-month period after the initial diagnosis of atrial flutter suggests that early diagnosis and treatment of these patients may improve their long-term survival.

Aged↗
PubMed1993

Out-of-hospital symptomatic supraventricular arrhythmias. Epidemiological aspects derived from 10 years experience of the Florence Mobile Coronary Care Unit.

The epidemiologic features and the relative incidence of symptomatic supraventricular tachycardias in out-of-hospital settings are unknown. Rhythm disturbances account for 20% of the interventions performed by the Florence Mobile Coronary Care Unit (MCCU). Between November 1979 and December 1989, the MCCU rescued 1239 patients with recent onset (less than 24 hours) symptomatic supraventricular arrhythmias. 809 had atrial fibrillation, 376 paroxysmal supraventricular tachycardia (PSVT), 36 atrial flutter and 18 different atrial dysrhythmias. Women showed an overall predominance, more evident in patients with PSVT, and the incidence of the arrhythmias increased with age. Preexisting heart disease was more frequent in atrial fibrillation (41.1%) and atrial flutter (33.4%) in comparison to PSVT (27.6%). Similarly, a higher incidence of associated cardiovascular events (AMI, acute coronary insufficiency, pulmonary edema) was found in patients with atrial fibrillation and atrial flutter. Palpitations were the main complaint in each group, however, in atrial fibrillation and atrial flutter they were frequently associated with chest pain or dyspnea.

Adult↗
PubMed1985

[Intravenous amiodarone in the therapy of paroxysmal supraventricular tachycardias].

The Authors evaluated the effectiveness and the tolerance of intravenous Amiodarone in 50 cases of recent onset paroxysmal supraventricular tachyarrhythmias. Fifty consecutive patients, aged 17 to 84 (mean 52 years), presenting with paroxysmal supraventricular tachycardia (PSVT, 33 cases) or atrial flutter (11 cases) or atrial fibrillation (6 cases), were given 300 mg of Amiodarone intravenously within 2 min, followed in 4 patients by 150 mg after 15 min. All patients were monitored for 1 hour; ECG and blood pressure were recorded at fixed times. Within 15 min sinus rhythm was restored in 88% of PSVT, in 27% of atrial flutter and in 17% of atrial fibrillation cases; the other cases of atrial flutter and fibrillation always showed a 48-81% reduction of the average heart rate within 15 min. We have evidenced neither significant modifications of blood pressure and ECG parameters (P-Q, QRS and Q-T duration) nor particular side effects, except for 2 cases in which brief hot flushes were reported. The Authors believe Amiodarone to be an effective and well tolerated drug for the above mentioned arrhythmias, particularly promptly acting in PSVT cases, in whom sinus rhythm was restored within 15 min in 88% and within 1 hour in 100% of the cases.

Adolescent↗
PubMed1992

Role of anatomic architecture in sustained atrial reentry and double potentials.

To determine the role of anatomic architecture in atrial flutter, electrophysiologic findings were correlated with anatomic features in a modified model of atrial flutter with ligation of the crista terminalis. Crista ligation in the middle right atrium prolonged intraatrial conduction time in a rate-dependent manner in 12 dogs, particularly in the low right atrium. With burst atrial pacing, unidirectional block occurred either in the low right atrium or in the interatrial septal region near the superior vena cava, leading to initiation of atrial flutter. Atrial activation mapping revealed a slow conduction area in the low right atrium where conduction had been delayed by crista ligation. On the intact tissues between the venae cavae, double potentials were recorded, a finding indicative of functional block in the center of the reentrant circuit. The interdeflection time of double potentials changed with the activation sequence of atrial flutter. This change could be explained by assuming that the functional center of the reentrant circuit leaned on the right atrial free wall side. Anatomic study demonstrated that areas of slow conduction, unidirectional block, and functional block in the center of the reentrant circuit were closely related to the location of the intact crista terminalis. In conclusion, the intact portion of the crista terminalis played an important role in the genesis of atrial flutter after blockage of longitudinal conduction through the crista.

Animals↗
PubMed1977

Complex atrial dysrhythmias in a patient with congestive cardiomyopathy.

A patient with primary cardiomyopathy and long standing atrial fibrillation presented with atrial tachycardia and AV block. Atrial pacing sequentially converted the atrial tachycardia to atrial flutter (biatrial) and to the dissimilar atrial rhythms of right atrial fibrillation with left atrial flutter, right atrial flutter with left atrial electrical standstill and right atrial fibrillation with left atrial standstill. The clincial milieu and intracardiac recordings are presented.

Arrhythmias, Cardiac↗
PubMed2005

Electrical cardioversion for atrial fibrillation and flutter.

BACKGROUND: Atrial fibrillation increases stroke risk and adversely affects cardiovascular haemodynamics. Electrical cardioversion may, by restoring sinus rhythm, improve cardiovascular haemodynamics, reduce the risk of stroke, and obviate the need for long-term anticoagulation. OBJECTIVES: To assess the effects of electrical cardioversion of atrial fibrillation or flutter on the risk of thromboembolic events, strokes and mortality (primary outcomes), the rate of cognitive decline, quality of life, the use of anticoagulants and the risk of re-hospitalisation (secondary outcomes) in adults (>18 years). SEARCH STRATEGY: We searched the Cochrane CENTRAL Register of Controlled Trials (1967 to May 2004), MEDLINE (1966 to May 2004), Embase (1980 to May 2004), CINAHL (1982 to May 2004), proceedings of the American College of Cardiology (published in Journal of the American College of Cardiology 1983 to 2003), www.trialscentral.org, www.controlled-trials.com and reference lists of articles. We hand-searched the indexes of the Proceedings of the British Cardiac Society published in British Heart Journal (1980 to 1995) and in Heart (1995 to 2002); proceedings of the European Congress of Cardiology and meetings of the Joint Working Groups of the European Society of Cardiology (published in European Heart Journal 1983-2003); scientific sessions of the American Heart Association (published in Circulation 1990-2003). Personal contact was made with experts. SELECTION CRITERIA: Randomised controlled trial or controlled clinical trials of electrical cardioversion plus 'usual care' versus 'usual care' only, where 'usual care' included any combination of anticoagulants, antiplatelet drugs and drugs for 'rate control'. We excluded trials which used pharmacological cardioversion as the first intervention, and trials of new onset atrial fibrillation after cardiac surgery. There were no language restrictions. DATA COLLECTION AND ANALYSIS: For dichotomous data, odds ratios were calculated; and for continuous data, the weighted mean difference was calculated. MAIN RESULTS: We found three completed trials of electrical cardioversion (rhythm control) versus rate control, recruiting a total of 927 participants (Hot Cafe; RACE; STAF) and one ongoing trial (J-RHYTHM). There was no difference in mortality between the two strategies (OR 0.83; CI 0.48 to 1.43). There was a trend towards more strokes in the rhythm control group (OR 1.9; 95% CI 0.99 to 3.64). At follow up, three domains of quality of life (physical functioning, physical role function and vitality) were significantly better in the rhythm control group (RACE 2002; STAF 2003). AUTHORS' CONCLUSIONS: Electrical cardioversion (rhythm control) led to a non-significant increase in stroke risk but improved three domains of quality of life.

Adult↗
PubMed2002

A mathematical model of human atrioventricular nodal function incorporating concealed conduction.

This work develops a mathematical model for the atrioventricular (AV) node in the human heart, based on recordings of electrical activity in the atria (the upper chambers of the heart) and the ventricles (the lower chambers of the heart). Intracardiac recordings of the atrial and ventricular activities were recorded from one patient with atrial flutter and one with atrial fibrillation. During these arrhythmias, not all beats in the atria are conducted to the ventricles. Some are blocked (concealed). However, the blocked beats can affect the properties of the AV node. The activation times of the atrial events were regarded as inputs to a mathematical model of conduction in the AV node, including a representation of AV nodal concealment. The model output was compared to the recorded ventricular response to search for and identify the best possible parameter combinations of the model. Good agreement between the distribution of interbeat intervals in the model and data for durations of 5 min was achieved. A model of AV nodal behavior during atrial flutter and atrial fibrillation could potentially help to understand the relative roles of atrial input activity and intrinsic AV nodal properties in determining the ventricular response.

Atrial Fibrillation↗
PubMed2002

Noncontact three-dimensional mapping and ablation of upper loop re-entry originating in the right atrium.

OBJECTIVES: This study was aimed at delineating the reentrant circuit of right atrial (RA) upper loop re-entry using noncontact three-dimensional mapping. BACKGROUND: Various forms of atypical atrial flutter including lower loop re-entry and left atrial flutter have been demonstrated. However, little is known about upper loop re-entry in the RA. METHODS: The study population consisted of eight patients (65 +/- 12 years, seven men) with atypical atrial flutter. Right atrial activation during atrial flutter was visualized using a noncontact mapping system (EnSite-3000 with Clarity Software, St. Paul, Minnesota) for a three-dimensional reconstruction of the endocardial depolarization. The narrowest part of the re-entrant circuit was targeted using radiofrequency catheter ablation. RESULTS: Noncontact mapping showed macro-re-entry confined to the RA free wall with RA activation time accounting for 100% of the cycle length (214 +/- 21 ms) in all eight patients. Two patients had counterclockwise activation, and six patients had clockwise activation around the central obstacle, which was composed of the crista terminalis, the area of functional block, and superior vena cava. The lower turn-around points were located at the conduction gap in the crista terminalis. Radiofrequency linear ablation of the conduction gap in the crista terminalis was performed and eliminated atrial flutter in six patients without recurrence during a follow-up of 3.2 +/- 1.1 months. CONCLUSIONS: Atypical atrial flutter could arise from upper loop re-entry in the RA with conduction through the gap in the crista terminalis. Radiofrequency linear ablation of the conduction gap was effective in eliminating this atrial arrhythmia.

Aged↗
PubMed2003

Prognostic significance of atrial fibrillation/atrial flutter in patients with acute myocardial infarction treated with percutaneous coronary intervention.

Atrial fibrillation (AF) is a frequent complication after acute myocardial infarction (AMI) that has been associated with increased in-hospital and long-term mortality rates in the prethrombolytic and thrombolytic eras. Current therapies, including percutaneous coronary intervention (PCI), are effective in reducing mortality in patients with AMI. However, little is known concerning the incidence and prognostic significance of AF in patients with AMI who are treated with PCI. We evaluated 2,475 consecutive patients with AMI who underwent PCI within 24 hours after onset and who were enrolled in the Osaka Acute Coronary Insufficiency Study. Patients were categorized into 2 groups according to the presence of AF or atrial flutter. The incidence of AF was 12.0%. Patients with AF were older, were in higher Killip classes, had higher rates of previous myocardial infarction and previous cerebrovascular disease, had systolic blood pressure of <100 mm Hg and heart rates of > or =100 beats/min, multivessel disease, and had poorer reperfusion of the infarct-related artery than those without AF. Patients with AF had higher in-hospital (16.0% vs 6.7%, p <0.001) and 1-year (18.9% vs 7.9%, p <0.001) mortality than those without AF. Multivariate Cox regression analysis revealed that AF was an independent predictor of 1-year mortality (hazard ratio 1.64, 95% confidence interval 1.05 to 2.55) but was not a predictor of in-hospital mortality. AF is a common complication in patients with AMI who are treated with PCI and independently influences 1-year mortality.

Aged↗
PubMed1986

Analysis of arrhythmias based on atrial wall motion. Usefulness and feasibility of recording left and right atrial systole by echocardiography.

The usefulness and feasibility of recording atrial wall motion by M-mode echocardiography guided by two-dimensional examination was evaluated in three groups of consecutive patients: 7 with undefined tachyarrhythmias, 25 in sinus rhythm, and 20 with atrial flutter or fibrillation. Atrial systole was recorded in the left and right atrium in 58 and 98% of the patients, respectively (p less than 0.05). Six of the patients with undefined tachyarrhythmias exhibited electrocardiographic atrioventricular dissociation revealed by preceding echocardiography in all. The precise timing of left and right atrial systole could be recorded in patients in sinus rhythm; right atrial contraction preceded left atrial systole by 42 +/- 31 msec (mean +/- SD). Among patients with atrial flutter or fibrillation, one case of dissimilar atrial rhythms was revealed by echocardiography. Thus, recording of atrial wall motion is feasible in the majority of patients and provides information which is otherwise available only by esophagus ECG or by invasive means.

Adult↗
PubMed2001

Anticoagulants or antiplatelet therapy for non-rheumatic atrial fibrillation and flutter.

BACKGROUND: Atrial fibrillation (AF) carries a high risk of stroke and other thromboembolic events. Appropriate use of drugs to prevent thromboembolism in patients with AF involves comparing the patient's risk of stroke to the risk of hemorrhage from medication use. OBJECTIVES: To quantify risk of stroke, major hemorrhage and death from using medications that have been rigorously evaluated for prevention of thromboembolism in AF. SEARCH STRATEGY: Articles were identified through the Cochrane Collaboration's CENTRAL database and MEDLINE until December 1999. SELECTION CRITERIA: Included Randomized controlled trials of drugs to prevent thromboembolism in adults with non-postoperative AF. Excluded RCTS of patients with rheumatic valvular disease. DATA COLLECTION AND ANALYSIS: Data were abstracted by two reviewers. Odds ratios from all qualitatively similar studies were combined, with weighting by study size, to yield aggregate odds ratios for stroke, major hemorrhage, and death for each drug. MAIN RESULTS: Fourteen articles were included in this review. Warfarin was more efficacious than placebo for primary stroke prevention [aggregate odds ratio (OR) of stroke=0.30 [95% Confidence Interval (C.I.) 0.19,0.48]], with moderate evidence of more major bleeding [ OR= 1.90 [95% C.I. 0.89,4.04].]. Aspirin was inconclusively more efficacious than placebo for stroke prevention [OR=0.68 [95% C.I. 0.29,1.57]], with inconclusive evidence regarding more major bleeds [OR=0.81[95% C.I. 0.37,1.78]]. For primary prevention, assuming a baseline risk of 45 strokes per 1000 patient-years, warfarin could prevent 30 strokes at the expense of only 6 additional major bleeds. Aspirin could prevent 17 strokes, without increasing major hemorrhage. In direct comparison, there was moderate evidence for fewer strokes among patients on warfarin than on aspirin [aggregate OR=0.64[95% C.I. 0.43,0.96]], with only suggestive evidence for more major hemorrhage [OR =1.58 [95% C.I. 0.76,3.27]]. However, in younger patients, with a mean age of 65 years, the absolute reduction in stroke rate with warfarin compared to aspirin was low (5.5 per 1000 person-years) compared to an older group (15 per 1000 person-years). Low-dose warfarin or low-dose warfarin with aspirin was less efficacious for stroke prevention than adjusted-dose warfarin. REVIEWER'S CONCLUSIONS: The evidence strongly supports warfarin in AF for patients at average or greater risk of stroke, although clearly there is a risk of hemorrhage. Although not definitively supported by the evidence, aspirin may prove to be useful for stroke prevention in sub-groups with a low risk of stroke, with less risk of hemorrhage than with warfarin. Further studies are needed of low- molecular weight heparin and aspirin in lower risk patients.

Anticoagulants↗
PubMed2001

[Mode-switching algorithms: programming and usefulness].

BACKGROUND: Automatic mode switching is defined as the ability of a pacemaker to reprogram itself from tracking to non-tracking mode in response to atrial tachyarrhythmias, and to regain tracking mode as soon as the tachyarrhythmia terminates. In contrast to upper rate behavior, mode switching does not only limit atrial tracking at a certain rate but actively drives the ventricular pacing rate back to lower rate or sensor rate as long as the atrial tachyarrhythmia persists. In contrast to DDD with mode switch, AV synchrony may be lost in DDIR mode if the sinus rate exceeds the sensor rate. DDD pacing with mode switching represents a valuable option in patients with AV block and paroxysmal atrial tachyarrhythmias. It may prevent the transition from paroxysmal to permanent atrial fibrillation after AV node ablation to a higher extent than VVI(R) pacing. On the other hand, patients with sinus node disease and normal AV conduction may benefit from DDIR mode with long AV interval. Mode switching should provide a rapid, sensitive and specific detection of atrial tachyarrhythmias, fast switch to non-tracking mode without ventricular pacing at the upper rate limit, adequate ventricular rate during the atrial tachyarrhythmia, rapid, sensitive and specific detection of conversion to sinus rhythm and fast switch back to tracking mode. In addition, oscillations between DDD and DDI mode with sudden ventricular rate changes should be avoided. MODE-SWITCHING ALGORITHMS: To achieve these aims, different mode-switching algorithms have been developed which all show specific disadvantages: reliable but slow response to atrial tachyarrhythmias, fast but unspecific switch to non-tracking mode, mode oscillations, inclination to inadequate mode-switching due to ventricular far-field sensing, failure to perform modeswitching during atrial flutter or intermittent atrial undersensing. Some of these problems can be avoided by careful atrial lead implantation providing atrial signals above 2 mV and avoiding ventricular far-field signals. Programming of mode-switching related parameters (e.g. atrial rate and number of fast beats required for mode switch), atrial blanking times, and atrial sensitivity can solve some of the problems with mode switching. Clinical results show a strong influence of device programming and atrial undersensing on mode-switching performance. Some data suggest a superiority of fast mode-switching algorithms with regard to clinical symptoms. However, loss of AV synchrony during sinus rhythm due to premature or inadequate mode switching may limit the benefit of fast mode switching. FURTHER DEVELOPMENTS: Improved performance may be achieved by a combination of different mode-switching algorithms (e.g. one algorithm for detection of atrial fibrillation, another one for detection of atrial flutter). In addition, programmability of several algorithms (e.g. mean atrial rate, beat-to-beat, x out of y) within the same device and atrial cycle-dependent sensitivity adjustment similar to automatic gain control in implantable defibrillators may further increase the clinical use of automatic mode switching.

Algorithms↗
PubMed2007

Incidence and clinical relevance of supraventricular tachyarrhythmias in pulmonary hypertension.

BACKGROUND: In patients with severe pulmonary hypertension (PH), right ventricular function is a main determinant of clinical stability and outcome. Supraventricular tachyarrhythmias (SVTs) may compromise cardiac function and threaten prognosis in patients with PH, but the incidence and clinical relevance of SVTs in PH and chronic right ventricular failure have not been evaluated. METHODS: In a 6-year retrospective single-center analysis, 231 consecutive patients followed for pulmonary arterial hypertension, or inoperable chronic thromboembolic PH were studied for SVTs. Analysis included incidence, clinical consequences, treatment, and outcome. RESULTS: Thirty-one episodes of SVT were observed in 27 of 231 patients (cumulative incidence 11.7%, annual risk 2.8% per patient), including atrial flutter (n = 15), atrial fibrillation (n = 13), and AV nodal reentry tachycardia (n = 3). Supraventricular tachyarrhythmia onset was almost invariably associated with marked clinical deterioration and right ventricular failure (84% of SVT episodes). Outcome was strongly associated with the type of SVT and restoration of sinus rhythm. During follow-up, cumulative mortality was low (6.3%, follow-up 26 +/- 23 months) when sinus rhythm was restored (all cases of AV nodal reentry tachycardia and atrial flutter). In contrast, 9 of 11 patients with sustained atrial fibrillation died from right ventricular failure (cumulative mortality 82%, follow-up 11 +/- 8 months). CONCLUSIONS: In patients with PH, SVTs constitute a relevant problem, often resulting in clinical deterioration. Sustained atrial fibrillation may be associated with a high risk of death from right ventricular failure.

Adult↗
PubMed1997

Role of adenosine in the diagnosis and treatment of tachyarrhythmias in pediatric patients.

Tachyarrhythmias are common rhythm disturbances in infants and children. Despite the availability of diagnostic criteria arrhythmias are sometimes commonly misdiagnosed. Recent reports suggest that an endogenous purine nucleoside, adenosine, has a diagnostic effect in narrow QRS complex tachycardias, in addition to terminating supraventricular tachycardia involving the atrioventricular node. This report reviews the authors' experience with the use of adenosine for diagnosis of narrow and wide complex tachyarrhythmias in children. Adenosine was administered to 43 patients with several types of tachyarrhythmias (mean age, 8.3 +/- 5.24 years). Nineteen patients had structural or acquired heart disease. Of the 43 patients there were 28 (65%) several different types of narrow QRS complex tachycardia and 14 (33%) ventricular arrhythmias. One patient (2%) had long QT. Adenosine terminated supraventricular tachycardia, in 11 of 12 patients (92%), ventricular tachycardia in five of eight patients (63%), and transiently terminated premature ventricular contractions in two of six patients (33%). The diagnostic ability of adenosine was perfect in eight supraventricular tachycardia. In these eight cases the tachycardia mechanism was unclear before the administration of adenosine, which demonstrated three cases of sinus tachycardia, three of atrial flutter, one of atrial fibrillation and one of atrial fibrilloflutter. Confirmation of the primary diagnosis by adenosine was perfect in five tachyarrhythmias including three cases of atrial flutter, one of atrial fibrillation and one of ectopic atrial tachycardia. The average effective dose of adenosine was 212 micrograms/kg (range, 100-400 micrograms/kg). There were no serious side-effects except transient dyspnea, chest pain and flushing. These findings demonstrate adenosine to be helpful and safe in the diagnosis of tachyarrhythmias.

Adenosine↗