Atrial fibrillation: rate control often better than rhythm control

(1) The treatment aims in atrial fibrillation are to reduce patients' symptoms and to prevent both embolism and deterioration of any underlying heart disease. Therapy consists of anticoagulant or antiplatelet drugs, treatment of any underlying heart disease, and heart rate control. (2) Digoxin, betablockers, diltiazem and verapamil slow the heart rate but rarely restore sinus rhythm. Amiodarone, disopyramide, flecainide, quinidine and sotalol can be used to prevent relapse of atrial fibrillation after electrical cardioversion, but they all have potentially serious adverse effects. New trials of antiarrhythmic treatments have been published since our last review of this subject. (3) In one trial in 403 patients, amiodarone was more effective than sotalol and propafenone in restoring and maintaining sinus rhythm. After 15 months of follow-up, there were fewer strokes among patients treated with amiodarone, but there was no difference between the three drugs in the overall incidence of cardiovascular events. (4) A clinical trial with 4060 patients compared rhythm control (mainly with amiodarone, sotalol or propafenone; sometimes combined with electrical cardioversion) and rate control (with digoxin, betablocker, diltiazem or verapamil; systematically combined with anticoagulant therapy). The antiarrhythmic treatment restored sinus rhythm in more than half the patients in the long term. But rhythm control did not reduce the risk of death or serious cardiovascular events during a mean follow-up period of 3.5 years. Rhythm control caused more adverse events than rate control; subgroup analyses (weak evidence) suggest that rhythm control may also have caused more deaths among patients over 65 and among patients with coronary heart disease. (5) In another trial, electrical cardioversion followed by antiarrhythmic therapy (mainly sotalol) sustainably restored sinus rhythm in more than one-third of 522 patients. But, compared with rate control treatment plus anticoagulant therapy, rhythm control did not reduce the risk of cardiovascular events, and was associated with a larger number of serious adverse cardiac effects. (6) Other recent trials confirm the risk of serious adverse effects, including severe arrhythmia with sotalol (especially at the start of treatment), and adverse thyroid and pulmonary effects with amiodarone. (7) Combined radiofrequency ablation and cardiac stimulation improved symptoms in some patients with incapacitating atrial fibrillation who had not responded to other treatments. However, this approach carries a risk of serious adverse effects, and its impact on the risk of cardiovascular events and death is not known. (8) In practice, an attempt should be made to restore sinus rhythm with amiodarone and/or electrical cardioversion, in symptomatic, recent or paroxysmal atrial fibrillation in patients under 65 who have no signs or symptoms of coronary heart disease. In other situations, rate control is the first-line option, using digoxin, betablockers (other than sotalol) or calcium channel blockers (diltiazem or verapamil). Whatever the option, treatment must be combined with anticoagulant or antiplatelet therapy, and with treatment of any underlying heart disease.

Antiarrhythmic drug therapy of atrial fibrillation

In the post-AFFIRM era, treatment of AF has become the treatment of symptoms. In some patients, this will be simple rate control, but there remain a significant cohort of patients in whom rate control alone does not give acceptable symptom relief. In this group, antiarrhythmic therapy still has a role, and the AFFIRM trial indicates that this therapeutic strategy is without significant deleterious effect on mortality. The choice of antiarrhythmic agent must be individualized according to underlying cardiac pathologies and comorbidities, however. Most recently, the introduction of dofetilide has widened the therapeutic options in patients with severe heart disease, and the Canadian Trial of Atrial Fibrillation indicated the superior efficacy of amiodarone at low doses. The release/ development of newer Class III antiarrhythmic agents may offer hope for the benefits of amiodarone without the serious adverse effects with long-term therapy.

Simultaneous supraventricular tachycardias in both fetuses of a twin gestation

BACKGROUND

Fetal supraventricular tachycardia confers an increased risk of cardiac failure, hydrops, and eventual intrauterine death. Although protocols for prenatal anti-arrhythmic treatment are now well established, few published reports discuss this condition in the setting of multiple pregnancies.

CASE REPORT

A 20-year-old primigravida woman with a twin pregnancy presented at 31 weeks of gestation for routine obstetrical check-up which revealed simultaneous supraventricular tachycardia in both fetuses. She was treated with oral digoxin, resulting in successful cardioversion in both of the fetuses, which was maintained until they were delivered by caesarian section at 38 weeks gestation. However, several hours after birth, tachyarrhythmias recurred in each of the infants. Combined disopyramide therapy with digoxin was necessary to control their heart rates.

CONCLUSION

The treatment of arrhythmia in fetuses of a multiple gestation presents unique issues, particularly when diagnosed prior to fetal lung maturity.

Failure of Disopyramide to Improve Right Ventricular Outflow Tract Obstruction After Living-Donor Lobar Lung Transplantation

Right ventricular (RV) outflow tract obstruction (RVOTO) is an uncommon complication of lung transplantation in patients with pulmonary hypertension (PH) and both medical management and surgical intervention are required. A 28-year-old female with primary PH was referred and because she did not respond to medical treatment, living-donor lobar lung transplantation was performed. The operation was successful, but dyspnea and exercise intolerance developed during rehabilitation and transthoracic echocardiography revealed RVOTO. Intravenous disopyramide during cardiac catheterization reduced the pressure gradient from 35 mmHg to 16 mmHg without decreasing RV systolic pressure. However, electrical and hemodynamic parameters were adversely affected by disopyramide and thus, after cardiac catheterization, administration of fluid and a low dose of atenolol was started, and her symptoms improved. Transthoracic echocardiography showed improvement in the RVOTO. This case suggests that disopyramide should be avoided for patients with RVOTO following lung transplantation and that other negative inotropic agents, such as beta-blockers, are more effective for relief of RVOTO.

[Anti-arrhythmic therapy: diagnostic possibilities of signal-averaged electrocardiography and heart rate variability]

Effects of monotherapy with class IC, II and III antiarrhythmic drugs on parameters of signal averaged (SA) ECG and heart rate variability were studied in 88 patients (mean age 45.6+/-7.8 years). Class IC drugs (ethacizine, disopyramide) caused worsening of qualitative parameters of SA ECG and appearance of ventricular late potentials. Therapy with beta-adrenoblockers, amiodarone and sotalol in patients with ventricular arrhythmias was associated with improvement of parameters of SA ECG, lowering of sympathetic and augmentation of parasympathetic activity without sings of arrhrythmogenic and negative inotropic effects. Combination of noninvasive diagnostic methods including SA ECG, temporal and spectral analysis of heart rate variability, Holter ECG monitoring can facilitate selection of appropriate antiarrhythmic therapy and control of its efficacy.

[Relationship between duration of arrhythmia and subsequent preventive effect of disopyramide after cardioversion in patients with symptomatic paroxysmal and persistent atrial fibrillation]

OBJECTIVES

The relationship between the duration of arrhythmia and the subsequent long-term efficacy of disopyramide in preventing atrial fibrillation was investigated in patients with symptomatic paroxysmal and persistent atrial fibrillation.

METHODS

A total of 60 patients (39 men, 21 women, mean age 65 +/- 11 years) were given disopyramide (300 mg/day) after electrical and pharmacological cardioversion based on American Heart Association Task Force on Practice Guidelines. The patients were divided into two types based on the duration of atrial fibrillation: conversion within 48 hr (group A, n = 35) and more than 48 hr (group B, n = 25) after the episode. Mean follow-up period was 47.1 +/- 28.7 months.

RESULTS

Patient characteristics showed no statistically significant difference between groups A and B. The actuarial rates of maintenance of sinus rhythm at 1, 3, 6, 12, 18 and 24 months were 88.6%, 77.1%, 57.1%, 48.6%, 42.9% and 37.1%, respectively, in group A, and 72.0%, 44.0%, 28.0%, 16.0%, 12.0% and 8.0%, respectively, in group B. There was a significant difference in the rate at 24 months between groups A and B (p < 0.05). The periods for maintenance of sinus rhythm in groups A and B were 20.9 +/- 3.9 and 6.7 +/- 2.1 months, respectively, with a significant difference between groups A and B (p < 0.01).

CONCLUSIONS

The efficacy of disopyramide in preventing the recurrence of atrial fibrillation varies with the duration of the previous episode. These results demonstrate that it is important to convert to normal sinus rhythm earlier to prevent the recurrence of atrial fibrillation in the long term.

[Comparison of the efficacies of disopyramide, cibenzoline and aprindine for the termination of paroxysmal and persistent atrial fibrillation in elderly and non-elderly patients]

OBJECTIVES

The relationship between the efficacy of the anticholinergic action of disopyramide, cibenzoline and aprindine and age was examined in patients with paroxysmal and persistent atrial fibrillation.

METHODS

This prospective, randomized study included 278 patients (200 men, 78 women, mean age 61 +/- 11 years) divided into two groups; the non-elderly group (age below 60 years) and the elderly group (age over 60 years). Successful termination was defined as conversion of sinus rhythm within 30 min of intravenous administration of 50 mg disopyramide (n = 91), 70 mg cibenzoline (n = 93) or 100 mg aprindine (n = 94) in this prospective and randomized study.

RESULTS

No statistically significant difference was found in patient characteristics between the three agents. 1) The rate of conversion to sinus rhythm after disopyramide administration in the non-elderly group(37.8%) was significantly higher than that in the elderly group (17.4%, p = 0.0361). 2) The rate of conversion to sinus rhythm after cibenzoline administration in the non-elderly group (62.2%) tended to be greater than that in the elderly group (43.8%, p = 0.0972). 3) The rate of conversion to sinus rhythm after aprindine administration in the non-elderly group (25.6%) was not significantly higher than that in the elderly group (18.2%, p = 0.4474).

CONCLUSIONS

The anticholinergic action of antiarrhythmic agents has an effect on successful termination in non-elderly patients with paroxysmal and persistent atrial fibrillation.

Atrial fibrillation threshold predicted long-term efficacy of pharmacological treatment of patients without structural heart disease

AIMS

To ascertain if an electrophysiological study could predict long-term efficacy of anti-arrhythmic drugs in the treatment of lone atrial fibrillation.

METHODS AND RESULTS

Forty-four patients (36 males, 8 females, age 55.5 +/- 10.6) with paroxysmal atrial fibrillation were enrolled to undergo serial electrophysiological studies at the bedside. Two quadripolar catheters were inserted via the subclavian vein. Disopyramide (D: 2 mg/kg iv), cibenzoline (C: 1.4 mg/kg iv), aprindine (A: 2 mg/kg iv), pilsicainide (P: 2 mg/kg po) and flecainide (F: 3 mg/kg po) were tested. Atrial fibrillation threshold (AFT) was measured as the lowest current amplitude of rapid pacing (50 Hz for 1 s) to induce atrial fibrillation lasting more than 30 s. Before drug treatment, AFT was 3.9 +/- 0.3 mA. Pharmacological treatment raised AFT as follows: D 5.9 +/- 0.9 mA, C 7.6 +/- 1.2 mA, A 8.1 +/-1.1 mA, P 6.0 +/- 0.8 mA, F 7.3 +/- 1.1 mA. Recurrence of atrial fibrillation was observed during 1-year follow-up in 12% of cases when they were treated with a drug that raised AFT by 5 mA or more. On the other hand, the recurrence rate was 87% when patients were treated with a drug that raised AFT by less than 5 mA (P = 0.001).

CONCLUSION

AFT was a good predictor of long-term efficacy of pharmacological treatment against atrial fibrillation.

Effects of disopyramide and mexiletine on the terminal repolarization process of the in situ heart assessed using the halothane-anesthetized in vivo canine model

This study was designed to assess the effects of typical class I drugs on the terminal repolarization process of the in situ heart, which is a useful marker of the potential of drug-induced long QT syndrome. Disopyramide (0.3 and 3.0 mg/kg per 10 min, n = 6) or mexiletine (0.3 and 3.0 mg/kg per 30s, n = 6) was intravenously administered to halothane-anesthetized beagle dogs under the monitoring of multiple cardiovascular parameters. Antiarrhythmic concentrations were obtained with the high dose of each drug. The low dose of disopyramide or mexiletine hardly affected any of the electrophysiological parameters assessed. The high dose of disopyramide prolonged the monophasic action potential duration (MAP90) and effective refractory period (ERP) to a similar extent, thus displacing the terminal repolarization period backward, which might provide a potential proarrhythmic substrate, particularly at a slow heart rate. On the other hand, the high dose of mexiletine shortened the MAP90, but prolonged the ERP, resulting in the disappearance of the terminal repolarization period, which could prevent premature excitation with its associated conduction slowing. These electrophysiological effects of disopyramide and mexiletine on the terminal repolarization phase may at least in part explain their clinically described antiarrhythmic and proarrhythmic properties.

Strategy for the management of vasovagal syncope

The disorders of autonomic control associated with orthostatic intolerance are a diverse group of syndromes that can result in syncope and near-syncope. A basic understanding of the pathophysiology of these disorders is essential to diagnosis and proper treatment. It is especially important to recognise the difference between the effect of prolonged upright posture on a failing autonomic nervous system (a hyposensitive or dysautonomic response) and the vasovagal response (which may be a hypersensitive response). Vasovagal syncope is the most common abnormal response to upright posture and occurs in all age groups. The advent of tilt table testing has helped define a population with an objective finding during provocative testing that has enabled researchers to study the mechanism of vasovagal syncope and to evaluate the efficacy of treatments. In most patients, vasovagal syncope occurs infrequently and only under exceptional circumstances and treatment is not needed. Treatment may be indicated in patients with recurrent syncope or with syncope that has been associated with physical injury or potential occupational hazard. Based on study data, patients with vasovagal syncope can now be risk stratified into a high-risk group likely to have recurrent syncope and a low-risk group. Many patients with vasovagal syncope can be effectively treated with education, reassurance and a simple increase in dietary salt and fluid intake. In others, treatment involves removal or avoidance of agents that predispose to hypotension or dehydration. However, when these measures fail to prevent the recurrence of symptoms, pharmacological therapy is usually recommended. Although many pharmacological agents have been proposed and/or demonstrated to be effective based on nonrandomised clinical trials, there is a remarkable absence of data from large prospective clinical trials. Data from randomised placebo-controlled studies support the efficacy of beta-blockers, midodrine, serotonin reuptake inhibitors and ACE inhibitors. There is also considerable clinical experience and a consensus suggesting that fludrocortisone is effective. Encouraging new data suggest that a programme involving tilt training can effectively prevent vasovagal syncope. For patients with recurrent vasovagal syncope that is refractory to these treatments, implantation of a permanent pacemaker with specialised sensing/pacing algorithms appears to be effective. A number of larger clinical trials are underway which should help further define the efficacy of a number of different treatments for vasovagal syncope.

Population pharmacokinetics, protein binding and antiarrhythmic effects of disopyramide enantiomers in arrhythmic patients

Disopyramide (DP) is widely used as an antiarrhythmic agent. The antiarrhythmic effects of its enantiomers differ from each other and its metabolism and protein binding are also stereoselective. Population pharmacokinetic parameters of DP racemate, enantiomers (S(+)-DP, R(-)-DP), and their unbound concentrations (uDP, S(+)-uDP and R(-)-uDP) were analyzed using the nonlinear mixed effect model (NONMEM) program. Data were available from 108 points of 33 arrhythmic patients on maintenance therapy with DP racemate. We evaluated the factors to which pharmacokinetic parameters are attributed and the relationships between each serum concentration and the antiarrhythmic effect. A one-compartment model was fitted to the data using NONMEM. For DP, S(+)-DP and R(-)-DP, elimination rate constants (kes) were estimated as 0.0648, 0.0663 and 0.0691/h, respectively and the mean apparent volume of distribution (Vd/F) were estimated as 63.2, 54.1 and 71.6 l, respectively. Using the ke and Vd/F values estimated by NONMEM, time-concentration curves were well fitted to the observed data. Unbound fractions of both DP enantiomers showed nonlinearity and the binding ratio of S(+)-DP was 0.84 +/- 0.07, which was higher than that of R(-)-DP [0.70 +/- 0.11 (p < 0.01)]. Unbound fractions of both DP enantiomers correlated with alpha1-acid glycoprotein (AGP) (p < 0.01). On the other hand, using NONMEM, a significant proportion of the variability of Vd/F could be attributed only to AGP (p < 0.001). NONMEM was able to clarify the pharmacokinetic features in the protein binding of DP. Individual steady state concentrations were estimated by NONMEM using the Bayesian method. The average unbound concentrations of all nine responders were higher than those of the four non-responders, even though this difference was not significant. Unbound concentrations may reflect drug concentrations in the tissue, which suggests that these concentrations may indicate an antiarrhythmic effect rather than the total concentration.

Disopyramide-induced pneumonitis, diagnosed by lymphocyte stimulation test using bronchoalveolar lavage fluid

A 72-year-old man was admitted to our hospital with fever and cough. He had been on disopyramide treatment for nine days to control cardiac arrhythmia. On admission, chest X-ray examination revealed reticulonodular opacities in both lungs, and impending respiratory failure was evident. A differential cell count of the bronchoalveolar lavage fluid (BALF) showed a marked increase of lymphocytes. A lymphocyte stimulation test (LST) for disopyramide using BALF was positive, although the test using peripheral blood was negative. This case suggests that LST using BALF is useful for the diagnosis of drug-induced pneumonitis.

Medical therapy of neurocardiogenic syncope

Neurocardiogenic syncope, alternatively called vasovagal, vasodepressor, or neurally mediated syncope, is a clinical syndrome faced by many clinicians. Its pathophysiology is complicated and not fully understood. Multiple pharmacologic therapies have been evaluated, with no clear ideal agent. Decisions regarding tilt-table testing, selection of pharmacotherapy, and assessment of drug efficacy are not straightforward. This article attempts to assess these issues.

Efficacy of sequential antiarrhythmic treatment in sinus rhythm maintenance after successful electrocardioversion in patients with chronic non-valvular atrial fibrillation

BACKGROUND

Sequential use of antiarrhythmic drugs may improve prognosis in chronic atrial fibrillation (AF). We conducted a prospective study of the efficacy of sequential antiarrhythmic drug therapy in sinus rhythm (SR) maintenance after a successful electrocardioversion (CV) in pts with chronic AF.

MATERIAL AND METHODS

58 pts (64.3 +/- 4.3 years old) with chronic AF underwent CV. After SR restoration (Group I) pts received one of the following antiarrhythmic drugs (Drug I): propafenone, sotalol or disopyramide. In case of arrhythmia recurrence, second CV was performed and pts received another drug from those mentioned above (Drug II). If treatment proved to be unsuccessful pts received amiodarone (Drug III) and third CV was attempted. After first unsuccessful CV (Group II) pts received a loading dose of amiodarone and another CV was attempted. In case of SR restoration amiodarone was administered continuously.

RESULTS

After 12 months 81% pts were on SR; 85% pts received amiodarone continuously. After 1 year 6 (10%) pts presented with SR treated with Drug I (median 71 days); Drug II proved to be ineffective in all patients (median 27 days). 28 pts continued to receive amiodarone (no median).

CONCLUSIONS

Sequential antiarrhythmic drug therapy improves arrhythmia prognosis in AF within a 12-month observation period. Amiodarone seems to be the most effective antiarrhythmic drug also in pts who required second CV proceeded by amiodarone treatment to restore SR.

Transient appearance of antegrade conduction via an AV accessory pathway caused by atrial fibrillation in a patient with intermittent Wolff-Parkinson-White syndrome

A 55 year old man with intermittent Wolff-Parkinson-White (WPW) syndrome had an episode of atrial fibrillation (AF) that lasted for 117 days. After interruption of the AF a Delta wave appeared that lasted for two days and then disappeared. Exercise stress and isoprenaline infusion could not reproduce the Delta wave, but after another episode of AF which lasted for seven days a persistent Delta wave appeared that lasted for six hours. In an electrophysiological study performed on a day without a Delta wave, neither antegrade nor retrograde conduction via an accessory pathway was seen, but after atrial burst pacing (at 250 ms cycle length) for 10 minutes, a Delta wave appeared lasting for 16 seconds. Atrial electrical remodelling-that is, the shortening of the atrial effective refractory period caused by AF, is a possible mechanism of the appearance of the Delta wave.

Body surface distribution and response to drugs of ST segment elevation in Brugada syndrome: clinical implication of eighty-seven-lead body surface potential mapping and its application to twelve-lead electrocardiograms

INTRODUCTION

Body surface distribution and magnitude of ST segment elevation and their reflection in 12-lead ECGs have not been clarified in Brugada syndrome.

METHODS AND RESULTS

Eighty-seven-lead body surface potential mapping and 12-lead ECGs were recorded simultaneously in 25 patients with Brugada syndrome and 40 control patients. The amplitude of the ST segment 20 msec after the end of QRS (ST20) was measured from all 87 leads, and an ST isopotential map was constructed. The maximum ST elevation (maxST20) was distributed in an area of the right ventricular outflow tract in all Brugada patients, and it was larger than that in control patients (0.37 +/- 0.13 vs 0.12 +/- 0.04 mV; P < 0.0005). The maximum was observed on the level of the parasternal fourth intercostal space, on which the V1 and V2 leads of the standard 12-lead ECG were located, in 18 of the 25 Brugada patients in whom typical coved- or saddleback-type ST elevation was seen in leads V1 and V2. The maximum was located on the second intercostal space in the remaining seven Brugada patients in whom only a mild saddleback-type ST elevation was seen in leads V1 and V2 of the 12-lead ECG. Typical ST segment elevation was recognized in leads V1 and V2, which were recorded on the second or third intercostal space. ST elevation in Brugada patients was dramatically normalized by isoproterenol, a beta-adrenergic agonist (maxST20 = 0.17 +/- 0.08 mV; P < 0.0005 vs control conditions), and accentuated by disopyramide, an Na+ channel blocker (maxST20 = 0.50 +/- 0.15 mV; P < 0.0005 vs control conditions), without any change in the location of the maxST20.

CONCLUSION

Our data indicate that recordings of leads V1-V3 of the 12-lead ECG on the parasternal second or third intercostal space would be helpful in diagnosing suspected patients with Brugada syndrome. The data suggest that Na+ channel blockers are capable of accentuating ST elevation in leads V1-V3.

Is there a place for the late cardioversion of atrial fibrillation? A long-term follow-up study of patients with post-thyrotoxic atrial fibrillation

AIMS

As atrial fibrillation is associated with significant mortality and morbidity, restoration of sinus rhythm is desirable. However, previous data suggest that cardioversion should be restricted to patients in whom the fibrillation is of limited duration (<1-2 years) because of high relapse rates. It may be the frequent association with cardiac disease, rather than the duration of fibrillation itself, which determined the high relapse of earlier studies. The aim of this study was to investigate rates of cardioversion, maintenance of sinus rhythm and predictors of subsequent relapse in a homogeneous group of patients without evidence of any co-existent cardiac disease.

METHODS AND RESULTS

We report on a retrospective series of 106 patients with thyrotoxicosis-induced fibrillation but no other heart disease: 87% had been in atrial fibrillation for >12 months (median duration 28.5, interquartile range 15-47 months). Cardioversion was attempted using disopyramide and then electric shock. Ninety-eight patients were successfully cardioverted: at late follow-up, 80.6+/-37 months (mean+/-SD), 67% were in sinus rhythm.

CONCLUSION

Although a relationship between the duration of fibrillation and maintenance of sinus rhythm was found, the high proportion remaining in sinus rhythm, compared with other series, suggests this influence may be less important than the presence or absence of structural heart disease.

Dynamic outflow obstruction due to the transient extensive left ventricular wall motion abnormalities caused by acute myocarditis in a patient with hypertrophic cardiomyopathy: reduction in ventricular afterload by disopyramide

A 65-year-old woman was admitted to the coronary care unit because of acute pulmonary edema. Immediate 2-dimensional and Doppler echocardiograms revealed extensive left ventricular wall motion abnormalities and left ventricular hypertrophy with extreme outflow obstruction. Although an ECG showed ST-segment elevation in the anterolateral leads, a coronary arteriogram revealed normal epicardial arteries. Heart failure was relieved after diminishing the dynamic outflow obstruction with disopyramide administration. An endomyocardial biopsy from the right ventricle on the 8th hospital day showed borderline myocarditis. Wall motion abnormalities gradually normalized within 2 weeks. It is speculated that her pulmonary edema would not have been relieved so readily without the immediate reduction in ventricular afterload by disopyramide. These clinical changes over time were observed with serial echo-Doppler examinations.

Management of vasovagal syncope

Vasovagal syncope is a common disorder of autonomic cardiovascular regulation that can be very disabling and result in a significant level of psychosocial and physical limitations. The optimal approach to treatment of patients with vasovagal syncope remains uncertain. Although many different types of treatment have been proposed and appear effective based largely on small nonrandomized studies and clinical series, there is a remarkable absence of data from large prospective clinical trials. However, based on currently available data, the pharmacologic agents most likely to be effective in the treatment of patients with vasovagal syncope include beta blockers, fludrocortisone, and alpha-adrenergic agonists. In this article, we provide a summary of the various therapeutic options that have been proposed for vasovagal syncope and review the clinical studies that form the basis of present therapy for this relatively common entity.

Impact of plasmapheresis on disopyramide elimination

The impact of plasmapheresis on the disposition of disopyramide was investigated in a 16-year-old female with systemic lupus erythematosus. Determination of total disopyramide plasma concentrations immediately prior to and following a 4-h plasmapheresis treatment revealed a significant reduction (i.e., 1.77 to 0.7 mg/l or approximately 60%). However, reassessment of the total serum concentration after 1.5 h (i.e., post equilibrium) revealed a rebounding of the value to 1.64 mg/l. Associated with this reduction in total serum levels was a decrease in the protein-bound fraction of disopyramide from 69.5% (pre treatment) to 48.6% (post treatment) that corresponded to a commensurate reduction in the concentration of alpha1-acid glycoprotein (i.e., 119 mg/dl pre treatment to 48.9 mg/dl post treatment). Despite these alterations in disopyramide concentrations, the procedure removed only 2.7% of the disopyramide dose and was not associated with the appearance of a cardiac dysrhythmia.

Dispersion of filtered P wave duration by P wave signal-averaged ECG mapping system: its usefulness for determining efficacy of disopyramide on paroxysmal atrial fibrillation

INTRODUCTION

Although it is desirable to know drug efficacy before initiating antiarrhythmic therapy, there have been no methods for this evaluation. P wave signal-averaged ECG (P-SAECG) is useful to detect subtle changes in disturbance of atrial conduction. The purpose of this present study was to test whether P-SAECG mapping system would give any information on the efficacy of disopyramide on the prevention of paroxysmal atrial fibrillation (PAF).

METHODS AND RESULTS

P-SAECG was performed before disopyramide treatment, at 3 hours after a single dose of oral disopyramide (200 mg), and after 4 weeks of disopyramide treatment (300 mg/day). After measuring the filtered P wave duration by the vector magnitude and mapping methods, we calculated filtered P wave duration dispersion, difference between the maximal and minimal filtered P wave duration within 16 chest leads at these three time points. Filtered P wave duration and filtered P wave duration dispersion before treatment were longer in 32 patients with symptomatic PAF than in 31 healthy volunteers. Disopyramide was effective for suppression of PAF in 17 patients and ineffective in 15 patients after 4 weeks of treatment. Filtered P wave duration was similarly prolonged at 3 hours in the two groups, whereas filtered P wave duration dispersion at 3 hours after the disopyramide administration behaved differently; it decreased in all of the effective group and increased in all of the ineffective group. The effective patients were prospectively followed with the same treatment for 6 months. In 16 (94%) of these 17 effective patients, no PAF was documented and they remained to be asymptomatic.

CONCLUSIONS

Thus, measuring filtered P wave duration dispersion with the P-SAECG mapping method after a single administration may predict the long-term efficacy of disopyramide in patients with PAF.

Disopyramide improves hypoxia in patients with tetralogy of Fallot through a negative inotropic action

The hemodynamic and right ventricular volumetric effects of disopyramide were investigated in patients with tetralogy of Fallot (TF). Intracardiac pressure and oxygen saturation were measured, before and after intravenous administration of disopyramide (2 mg/kg) in 7 patients who had not had previous surgery. Right ventricular volume and the diameter of its outflow tract were analyzed in these 7 and in a further 4 patients with a previous shunt. Aortic oxygen saturation increased from 90.4+/-7.5 (mean+/-SD) to 94.1+/-5.5% (p<0.05) with an increase in pulmonary blood flow and pressure. The systolic pressure gradient between the main pulmonary artery and the right ventricle decreased from 59+/-8 to 42+/-9 mmHg (p<0.01). Aortic pressure fell from 77+/-5 to 67+/-4 mmHg (p<0.05). Systemic vascular resistance increased from 15.3+/-2.2 to 19.4+/-3.3 u x m2 (p<0.05). Pulmonary vascular resistance remained unchanged. The diastolic and systolic diameter indices of the right ventricular outflow tract increased from 17.8+/-3.8 to 20.5+/-3.4 and from 6.5+/-3.0 to 10.4+/-2.2 mm/m2, respectively (p<0.01), whereas the right ventricular ejection fraction decreased. Disopyramide improves systemic oxygen saturation in patients with TF through its negative inotropic action on the right ventricle.

Efficacy and safety of clonazepam in refractory neurally mediated syncope

Neurally mediated syncope is a complex syndrome that is often difficult to manage using currently available treatment strategies. The efficacy and safety of clonazepam was evaluated in 35 patients with refractory neurally mediated syncope. All patients had syncope (n = 33) or disabling presyncope (n = 2) and a positive head-up tilt table test (HUTT) despite treatment with one or more of the following therapies: beta-blocker, high-salt diet, fludrocortisone, elastic compression stockings, and disopyramide. Clonazepam was initiated at 0.5 mg/day and titrated in 0.25-0.5 mg/day increments for symptom control. Early (first 8 weeks) symptomatic response was achieved in 31 of 35 (89%) patients. Early HUTT reverted to negative in 29 of 35 (83%) patients. Two patients discontinued clonazepam during early follow-up due to side effects. Thirty-three patients received long-term clonazepam therapy. Twenty-five patients had late HUTT with 21 remaining negative. Of the eight patients who did not have late HUTT, one patient discontinued clonazepam prior to HUTT due to side effects. Seven patients refused late HUTT. All seven patients achieved symptomatic control on clonazepam with two requiring dose titration. Of the 21 patients with a negative late HUTT, 18 achieved symptomatic control with two of these patients requiring dose titration. Two patients who had only partial symptom control despite dose titration achieved total symptomatic control with the addition of disopyramide and beta-blockers. Two patients with a negative late HUTT discontinued clonazepam due to side effects. One patient had been symptomatically controlled while the other had recurrent symptoms with dose limiting side effects occurring after clonazepam dose titration. In the 4 patients with a positive late HUTT, 2 patients were symptomatically controlled, 1 patients required combination therapy with a beta-blocker to achieve symptomatic control, and 1 patient discontinued therapy due to side effects. Overall, 29 of 35 (83%) patients continue to receive clonazepam with symptom control. Based on intention-to-treat HUTT results, 21 of 35 (60%) patients were responders. Four patients required clonazepam dose titration and three required combination therapy with clonazepam plus disopyramide and/or a beta-blocker to achieve control. Clonazepam was discontinued in 6 patients, 5 for side effects and 1 following a transient ischemic attack. Clonazepam appears to be an effective therapeutic alternative in patients with refractory neurally mediated syncope. Based on our preliminary findings, a placebo controlled evaluation of clonazepam in neurally mediated syncope is warranted.