Transitioning disopyramide to mavacamten in obstructive hypertrophic cardiomyopathy: A case series and clinical guide

BACKGROUND

Hypertrophic cardiomyopathy (HCM) is a genetic disorder for which first-line treatments for obstructive HCM (oHCM) include beta-blockers, non-dihydropyridine calcium channel blockers, and disopyramide for refractory cases. Mavacamten, a selective cardiac myosin inhibitor, is indicated for symptomatic oHCM to improve functional capacity and symptoms. Use of disopyramide and mavacamten together is not recommended due to concerns of additive negative inotropic effects. Transitioning from disopyramide to mavacamten may be preferred to avoid adverse effects and frequent administration, however, the best approach for making the transition has not been established.

CASES

We present a series of seven patients with oHCM who transitioned from disopyramide to mavacamten and underwent echocardiograms mandated by a Risk Evaluation and Mitigations Strategies program. Two methods were employed. The first approach, involving washout of disopyramide before starting mavacamten, resulted in worsening of heart failure symptoms in the first two cases. The second approach, involving tapering disopyramide when starting mavacamten, was successfully implemented in the last five cases, with no adverse effects or worsening of systolic dysfunction.

CONCLUSION

Our method of tapering disopyramide when starting mavacamten using a stepwise approach is feasible and safe. Our report fulfills an unmet need by serving as a guide for other clinicians who seek to transition their patients from disopyramide to mavacamten.

Disopyramide is a safe and effective treatment for children with obstructive hypertrophic cardiomyopathy

BACKGROUND

Left ventricular outflow tract obstruction (LVOTO) is present in 1/3 of children with Hypertrophic Cardiomyopathy (HCM). Disopyramide improves symptoms associated with LVOTO and delays surgical intervention in adults, but it is not licensed in children.

AIM

To describe a single-centre thirty-year experience of using disopyramide to treat LVOTO-related symptoms in a paediatric HCM cohort.

METHODS

Clinical data were collected for all patients meeting diagnostic criteria for HCM (<18 years) at the time of initiation, 6 months after, and last follow-up or end of disopyramide treatment. It included demographics, clinical history, 12‑lead electrocardiography, and echocardiography. Comparisons between baseline and 6 month follow up, and end of follow up respectively were performed.

RESULTS

Fifty-one patients with HCM were started on disopyramide at a mean age 10.2±5.3 years. At 6 months, of those previously symptomatic, 33(86.8%) reported an improvement of symptoms and 12(31.6%) were asymptomatic. PR interval, corrected QT interval and maximal LVOT gradient had not significantly changed, but fewer participants were noted to have systolic anterior motion of the mitral valve 31 (72.1%) vs. 26 (57.80%). Patients were followed up for a median of 1.9 years (IQR 0.83-4.5). Nine patients (17.6%) reported side effects, and eleven patients (33.3%) with initial improvement in symptoms reported a return or worsening of symptoms requiring a change in medication (n = 4, 12.1%) or left ventricular septal myomectomy (n = 7, 21.2%) during follow up.

CONCLUSION

Disopyramide is a safe and effective treatment for LVOTO-related symptoms in childhood obstructive HCM. Any delay in the need for invasive intervention, particularly during childhood, is of clear clinical benefit.

Left ventricular outflow tract pressure gradient changes after carvedilol-disopyramide cotherapy in a cat with hypertrophic obstructive cardiomyopathy

Disopyramide reduces the left ventricular outflow tract (LVOT) pressure gradient and improves symptoms in humans with hypertrophic obstructive cardiomyopathy (HOCM). However, the efficacy of disopyramide in cats has not been reported. We treated a cat with HOCM with carvedilol and disopyramide cotherapy and monitored the changes in LVOT flow velocity and N-terminal pro B-type natriuretic peptide (NT-proBNP) concentration. A 10-month-old neutered male Norwegian Forest cat was referred with a moderate systolic cardiac murmur. Echocardiography revealed thickening of the left ventricular wall, systolic anterior motion of the mitral valve leaflets, and turbulent aortic flow in the LVOT at systole. The LVOT flow velocity was 5.6 m/s. The plasma NT-proBNP concentration exceeded 1,500 pmol/L. The cat was diagnosed with HOCM and the β-blocker carvedilol was started and gradually increased to 0.30 mg/kg, bid. After 57 days, the LVOT flow velocity (4.8 m/s) and plasma NT-proBNP concentration (870 pmol/L) had decreased but remained elevated. Therefore, disopyramide was added at 5.4 mg/kg po bid and increased to 10.9 mg/kg po bid after 22 days. After 141 days of carvedilol and disopyramide treatment, the systolic anterior motion of the mitral valve leaflets had disappeared and the LVOT flow velocity and plasma NT-proBNP concentration had decreased to 0.7 m/s and 499 pmol/L, respectively. No adverse effect has been observed during the follow-up. Disopyramide might relieve feline LVOT obstruction after only partial response to a beta-blocker. Further large-scale studies are required to investigate the efficacy and safety of disopyramide use in cats with moderate to severe HOCM.

In silico assessment of the effects of quinidine, disopyramide and E-4031 on short QT syndrome variant 1 in the human ventricles

Aims

Short QT syndrome (SQTS) is an inherited disorder associated with abnormally abbreviated QT intervals and an increased incidence of atrial and ventricular arrhythmias. SQT1 variant (linked to the rapid delayed rectifier potassium channel current, I_Kr) of SQTS, results from an inactivation-attenuated, gain-of-function mutation (N588K) in the KCNH2-encoded potassium channels. Pro-arrhythmogenic effects of SQT1 have been well characterized, but less is known about the possible pharmacological antiarrhythmic treatment of SQT1. Therefore, this study aimed to assess the potential effects of E-4031, disopyramide and quinidine on SQT1 using a mathematical model of human ventricular electrophysiology.

Methods

The ten Tusscher et al. biophysically detailed model of the human ventricular action potential (AP) was modified to incorporate I_Kr Markov chain (MC) formulations based on experimental data of the kinetics of the N588K mutation of the KCNH2-encoded subunit of the I_Kr channels. The modified ventricular cell model was then integrated into one-dimensional (1D) strand, 2D regular and realistic tissues with transmural heterogeneities. The channel-blocking effect of the drugs on ion currents in healthy and SQT1 cells was modeled using half-maximal inhibitory concentration (IC₅₀) and Hill coefficient (nH) values from literatures. Effects of drugs on cell AP duration (APD), effective refractory period (ERP) and pseudo-ECG traces were calculated. Effects of drugs on the ventricular temporal and spatial vulnerability to re-entrant excitation waves were measured. Re-entry was simulated in both 2D regular and realistic ventricular tissue.

Results

At the single cell level, the drugs E-4031 and disopyramide had hardly noticeable effects on the ventricular cell APD at 90% repolarization (APD₉₀), whereas quinidine caused a significant prolongation of APD₉₀. Quinidine prolonged and decreased the maximal transmural AP heterogeneity (δV); this led to the decreased transmural heterogeneity of APD across the 1D strand. Quinidine caused QT prolongation and a decrease in the T-wave amplitude, and increased ERP and decreased temporal susceptibility of the tissue to the initiation of re-entry and increased the minimum substrate size necessary to prevent re-entry in the 2D regular model, and further terminated re-entrant waves in the 2D realistic model. Quinidine exhibited significantly better therapeutic effects on SQT1 than E-4031 and disopyramide.

Conclusions

The simulated pharmacological actions of quinidine exhibited antiarrhythmic effects on SQT1. This study substantiates a causal link between quinidine and QT interval prolongation in SQT1 and suggests that quinidine may be a potential pharmacological agent for treating SQT1 patients.

Can pharmacologic gradient reduction decrease mortality in hypertrophic cardiomyopathy?

Pharmacologic therapy is the first line approach to relieve symptoms in obstructive hypertrophic cardiomyopathy. There are no randomized trials to evaluate their effect on prognosis. Gradient reduction by surgical septal myectomy is associated with excellent prognosis, but not all patients have symptoms severe enough to require surgery; and, guidelines recommend operation only for patients with high gradients and symptoms unresponsive to pharmacologic therapy. The combination of disopyramide and beta-blockade is effective in reducing resting gradients (though not to the extent of surgery). This review examines the question of whether pharmacologic reduction of gradient in asymptomatic patients or those with milder symptoms might decrease HCM-related mortality.

Hemodynamic and electrocardiographic effects of disopyramide in patients with ventricular arrhythmia

Antiarrhythmic and hemodynamic effects of i.v. disopyramide phosphate (1.7 mg/kg b.wt. over 2 min) have been studied in nine patients, several in various degrees of cardiac decompensation, with sinus rhythm and persistent ventricular ectopic beats (VEBs). In one case with primary cardiomyopathy, with greater than 30 VEBs/min, disopyramide (DE) abolished the arrhythmia for 30 min, but precipitated brief dysponea. Other side-effects were tolerable and mainly attributable to anticholinergic effects of the drug. DE either abolished or significantly reduced the arrhythmia in all cases. For 30 min, only one patient showed VEBs, and in three patients no VEBs were seen for three hours. Changes in cardiac output and pulmonary artery (PAP) and central aortic pressures were measured in eight patients. Negative inotropic effects were indicated in seven by an increased diastolic PAP/stroke volume ratio and in seven by a decreased central aortic (dp/dt)max. Patients with high control values for diastolic PAP showed marked reductions in cardiac output, stroke volume and stroke work. In predicting myocardial depressant effects of DE, the control values for diastolic PAP seemed to be superior to central venous pressure, cardiac index and systolic time intervals. Mean arterial pressure measured 5 and 10 min after drug administration showed no significant change, indicating that vasoconstrictor reflexes were well preserved, and a pressure level significantly above the control value was reached from the 20th min. It is concluded that DE is potent in suppressing VEBs but exerts negative inotropic effects that may be of clinical importance. The optimal antiarrhythmic dose is probably lower than that used in the present study.

Propafenone versus disopyramide for treatment of chronic symptomatic ventricular arrhythmias. A multicenter study

The efficacy and safety of propafenone, 150 mg four times daily, were compared with those of disopyramide, 100 mg four times daily, in a randomized single-blind, cross-over study in 38 patients with symptomatic premature ventricular complexes (PVCs). The 24-hour ambulatory ECG, employed for assessing antiarrhythmic efficacy, was analyzed blindly. The median reduction in the number of PVCs was higher with propafenone than with disopyramide (91.4% vs. 63.5%, respectively, p less than 0.01). A reduction of at least 80% was achieved by propafenone in 22 (59%) and by disopyramide in 16 patients (43%) (NS). Ventricular tachycardias (VTs) were abolished by propafenone in eight out of 11, and by disopyramide in five out of nine patients with VTs (NS) a possible proarrhythmic effect was seen in three patients during disopyramide and in one patient during propafenone treatment. Micturition disturbances (p less than 0.001) and a dry mouth (p less than 0.01) were more commonly associated with disopyramide than with propafenone. In conclusion, in the given dosages, propafenone was superior to disopyramide in suppressing PVCs and had fewer side-effects.

Kinetics of hemodynamic and electrocardiographic changes following intravenous disopyramide

Changes in hemodynamic and ECG variables following disopyramide (1.7 mg = 3.9 mmol/kg b.wt.) were studied in 9 patients with ventricular arrhythmias. All patients displayed a marked reduction in the number of ventricular ectopic beats, all except one exhibiting complete abolition of the arrhythmia for at least 30 min. QT and QRS intervals showed statistically significant prolongations, and thereafter decreased exponentially with time. Above a certain concentration threshold that varied between the patients, systolic time intervals and aortic (dp/dt)max showed linear changes with increasing drug serum levels. Changes in diastolic pulmonary artery pressure showed no simple relationship with disopyramide concentration or time after injection. In 3 out of 4 patients studied, there was a good correlation between the lowest level of disopyramide that elicited both an antiarrhythmic effect and a demonstrable decrease in cardiac contractility.

Acute intervention studies in patients with myocardial infarction using atenolol, propranolol, oxprenolol and disopyramide phosphate

The value of beta-blockade and of disopyramide phosphate in the immediate treatment of patients with suspected acute myocardial infarction was assessed in two placebo controlled trials. In the first study 388 patients with suspected acute myocardial infarction were randomly allocated to treatment with propranolol, atenolol, or placebo, and when analysed on an initial intention to treat basis there was no significant difference between the three groups in respect of the mortality at one year. In addition, there was no evidence to suggest that either atenolol, or propranolol reduced the incidence of 'serious' ventricular arrhythmias in the coronary care unit. In the second study 473 patients with suspected acute myocardial infarction were randomly allocated to treatment with oxprenolol, disopyramide phosphate, or placebo. Again no significant differences were seen with respect to the mortality at six weeks. There was, however, a significantly increased incidence of heart failure in the group which received disopyramide phosphate. Patients who received this drug also showed a reduced number of dysrhythmic episodes on 24-hour ECG recordings, but this trend did not achieve statistical significance. These results suggest that none of the three beta-blockers tested nor disopyramide phosphate is likely to reduce the mortality from acute myocardial infarction when given prophylactically, although disopyramide phosphate does reduce the incidence of 'serious' ventriicular arrhythmias.

Disopyramide plasma levels in cardiac patients on maintenance therapy

The antiarrhythmic agent disopyramide, in a dosage of 200 mg/8 h, was given to 7 cardiac patients. The drug was fairly rapidly absorbed, and the mean peak plasma concentration (3.5 microgram/ml) was measured 1 h after administration of the first dose. The mean biological half-life (7.8 h) was slightly prolonged compared to that reported in normal volunteer subjects. Mean steady state plasma concentrations within the therapeutic range were attained 24--32 h after the start of medication. The fluctuations in the plasma levels were in the order or 30 percent; however, a wide spread of the values was observed. The drug was well tolerated.

Disopyramide in ventricular tachycardia

Administration of disopyramide phosphate (DE) i.v. in two doses, 30 min apart, to a patient with ventricular tachycardia was accompanied by no, or only slight, changes in systemic arterial pressure (SAP), cardiac output (Q), stroke work (SW), and pulmonary artery diastolic pressure (PADP). Heart rate fell from 123 to 103/min. Following reversion to sinus rhythm, which occurred 60 min after the second dose of DE at a serum concentration greater than 4.3 mug/ml, Q ans SW showed significant increases above their control values. PADP fell from 20 to 6 mmHg whereas the mean SAP remained largely unchanged. There seemed to be no adverse effects of drug administration. In this patient, recurrent attacks of ventricular tachycardia not responding to conventional antiarrhythmic treatment could be prevented by oral DE in a dose of 800 mg/day.

In vivo Effects of Mutant HERG K+Channel Inhibition by Disopyramide in Patients with a Short QT-1 Syndrome: A Pilot Study

INTRODUCTION

Quinidine has been evaluated in patients with a short QT-1 syndrome caused by an IKr gain-of-function mutation of HERG. Recently, in vitro data with disopyramide showed an even stronger effect on the N588K mutant current. The aim of the present study was to test the in vivo effects of disopyramide in patients with short QT-1 syndrome caused by a N588K mutation in HERG.

METHODS AND RESULTS

Repetitive ECGs were recorded in two female patients with short QT-1 syndrome with a N588K-HERG mutation off drugs, on oral quinidine, and on oral disopyramide. One patient underwent exercise testing on drugs to determine the QT interval to heart rate relation, whereas the QT interval was calculated to the peak of the T wave in lead V3. In the same patient, drug-induced changes in ventricular effective refractory periods were determined by programmed ventricular stimulation via the ICD lead. Disopyramide increased the QT interval from QTc 329 ms/QTc 315 ms, respectively, off drugs to QTc 358 ms/QTc 333 ms in both patients and restored the heart rate dependence of the QT interval toward normal subjects (-0.39 ms/bpm off drugs, -0.58 ms/bpm on disopyramide vs. 1.29 +/- 0.33 ms/bpm in normal subjects). The ventricular effective refractory period increased under disopyramide by 40 ms.

CONCLUSION

These preliminary observations suggest that oral disopyramide may be a suitable alternative to quinidine for prolonging the QT interval and ventricular effective refractory periods in patients with short QT-1 syndrome. Further studies of this pharmacologic approach are warranted.

Pathophysiology of hypertrophic cardiomyopathy determines its medical treatment

Physicians treating hypertrophic cardiomyopathy (HCM) are faced with unique management challenges. Understanding pathophysiology and overall good prognosis forms the basis for medical treatment. Treatment is tailored by the presence or absence of outflow tract gradient and individual symptoms. In all patients, formal stratification for sudden death risk is necessary, with consideration of defibrillator implantation in patients deemed to be at high risk. In patients with no or only mild symptoms the approach of watchful waiting is often appropriate. For symptomatic patients with non-obstructed disease medical treatment with calcium channel blockers and beta-blockers is aimed to improve heart failure symptoms, and ischemia. Verapamil is the most often used, with likely benefit of relieving ischemia. Obstruction, most commonly due to systolic anterior motion of the mitral valve (SAM) and mitral-septal contact, occurs in >/=50% of all HCM patients, worsening symptoms and increasing mortality. Successful medical treatment of obstruction with negative inotropes slows acceleration of left ventricular ejection with delay in SAM, ultimately yielding a lower pressure gradient. Beta -blockers are the first line treatment in obstructive HCM predominantly by mitigating provocable gradients. The magnitude of symptom relief with verapamil is similar to the effect of beta -blockade. Disopyramide combined with beta -blockade is thought by some to be the most effective medical treatment of obstruction, and has been shown to be safe and not pro-arrhythmic. Most symptomatic HCM patients with significant obstruction at rest or provocation can be successfully managed with long-term medication alone.

Increased AAI mode pacing threshold after termination of atrial fibrillation by acute administration of disopyramide phosphate

AIMS

We studied changes in atrial pacing threshold after termination of atrial fibrillation (AF) by acute administration of disopyramide phosphate (DP) to elucidate the suitable setting for atrial pacing output before AF termination.

METHODS AND RESULTS

Four patients with sick sinus syndrome implanted with AAI mode pacemakers were examined. Disopyramide phosphate (2 mg/kg body weight) was injected intravenously for termination of a total of eight AF episodes. The maximal pacing threshold after AF termination (5.2+/-0.8 V at 0.45 ms) was significantly higher than that at baseline (1.3+/-0.2 V at 0.45 ms; P<0.01) and the average increment was 433+/-68%. During a period free from AF, an acute administration of DP did not increase the atrial pacing threshold and serum disopyramide levels were not toxic.

CONCLUSION

The increased atrial pacing threshold observed after AF termination cannot be explained by the action of DP alone. However, our results suggest that atrial pacing output should be set at the maximum value before DP is administered to induce AF termination in patients with AAI pacemaker-dependent bradyarrhythmias.

Cough reflex by ventricular premature contractions

A 72-year-old man was referred for further assessment of a chronic cough. He noticed an association between the episodes of coughing and palpitations. Electrocardiography (ECG) revealed normal sinus rhythm and sporadic unifocal ventricular premature contractions (VPCs). Each cough was preceded by a premature beat. Continuous wave Doppler echocardiography revealed a VPC-induced transient increase in the pulmonary artery blood flow. He was successfully treated for VPCs with oral disopyramide, resulting in subsidence of both the coughing and palpitations. We suspect that the VPC-induced hemodynamic changes in the pulmonary circulation might be responsible for coughing in our patient. Premature contractions should be considered as a possible cause of chronic dry cough in the clinical setting.

Repolarization dynamics in patients with idiopathic ventricular fibrillation: pharmacological therapy with bepridil and disopyramide

The electrocardiographic parameters relating occurrence of ventricular fibrillation (VF) episodes in patients with idiopathic VF (IVF) are still unknown. The aim of this study was to clarify efficacy of pharmacological therapy in patients with IVF with respect to repolarization dynamics. The study group consisted of 8 men (age 43.6 +/- 9.1 years) with IVF (Brugada type 5 patients, prominent J wave in the inferior leads 3 patients) who had documented spontaneous episodes of VF, 7 of whom had implantable cardioverter defibrillators. The relation between QT and RR interval was analyzed from 24-hour Holter ECG using an automatic analyzing system before and after pharmacological therapy (bepridil 5 and disopyramide 3). From QT-RR linear regression lines, QT intervals were determined at RR intervals of 0.6 second [QT(0.6)], 1.0 second [QT(1.0)], and 1.2 seconds [QT(1.2)]. Pharmacological therapy increased the slope of QT-RR regression line from 0.105 +/- 0.020 to 0.144 +/- 0.037 (P < 0.05). Accordingly, QT(1.0) and QT(1.2) became longer after drug therapy [QT(1.0), 0.382 +/- 0.016 seconds vs 0.414 +/- 0.016 seconds (P < 0.01); QT(1.2), 0.403 +/- 0.017 seconds vs 0.442 +/- 0.021 seconds (P < 0.01)]. However, QT(0.6) did not change after drug administration. Before drug therapy the average episodes of VF were 5.5 +/- 5.8 (range 1 to 17) during the observation period of 19.3 +/- 17.6 months (range 6 to 60 months). After drug therapy, 6 patients had no episode of VF for 24 to 120 months (66.0 +/- 38.5 months). Two patients had a single episode of VF for 12- and 96-month follow-ups. Pharmacological therapy decreased the frequency of VF episodes in association with prolongation of QT intervals at slower heart rates. Not only J wave and ST elevation but also shorter QT intervals at slower heart rates may represent an electrophysiological substrate for development of VF episodes in these specific IVF patients.

[Atrial flutter and fibrillation]

This article summarizes current understandings and therapies for both arrhythmias. Atrial flutter is most often arising from a macroreentry circuit in the right atrium or around scar tissue in case or previous cardiothoracic surgery. As a macroreentrant tachycardia it is regular and can lead to higher heart rates, especially if occurring with 1:1 conduction. In contrast atrial fibrillation, especially when occurring paroxysmal at the beginning, is arising from triggers within the pulmonary veins. Ablation strategies to electrically isolate those triggers have a treatment success rate of 80%, which is much more than can be achieved with antiarrhythmic medication (success rates 30-50%). Emergency treatment of both arrhythmias include cardioversion and pacemaker implantation with AV node ablation if necessary.

Phase I and pharmacokinetic study of amrubicin, a synthetic 9-aminoanthracycline, in patients with refractory or relapsed lung cancer

Amrubicin is a novel synthetic 9-aminoanthracycline derivative and is converted enzymatically to its C-13 hydroxy metabolite, amrubicinol, whose cytotoxic activity is 10-100 times that of amrubicin. We aimed to determine the maximum tolerated dose (MTD) of amrubicin and to characterize the pharmacokinetics of amrubicin and amrubicinol in previously treated patients with refractory or relapsed lung cancer. The 15 patients were treated with amrubicin intravenously at doses of 30, 35, or 40 mg/m(2) on three consecutive days every 3 weeks for a total of 43 courses. Neutropenia was the major toxicity (grade 4, 67%). The MTD was 40 mg/m(2), with the specific dose-limiting toxicities being grade 4 neutropenia persisting for >4 days, febrile neutropenia, or grade 3 arrhythmia in the three patients treated at this dose. A patient with non-small-cell lung cancer showed a partial response, and ten individuals experienced a stable disease. The area under the plasma concentration versus time curve (AUC) for amrubicin and that for amrubicinol increased with amrubicin dose. The amrubicin AUC was significantly correlated with the amrubicinol AUC. The recommended phase II dose of amrubicin for patients with lung cancer refractory to standard chemotherapy is thus 35 mg/m(2) once a day for three consecutive days every 3 weeks.

Atrial Pacing Failure Following Termination of Atrial Fibrillation by Acute Administration of Disopyramide Phosphate

Atrial pacing failure occurred after termination of atrial fibrillation by acute administration of disopyramide phosphate in a 71-year-old woman implanted with an AAI pacemaker for sick sinus syndrome. The atrial pacing threshold showed an 810% increase; however, the serum concentration of disopyramide corresponded to therapeutic level. Infusion of the same dose of disopyramide phosphate used during the period of atrial pacing rhythm did not increase the atrial pacing threshold. In the present patient, we supposed that atrial pacing failure did not occur by the effect of disopyramide alone, but rather was a reciprocal action in response to atrial fibrillation.

Multicenter study of the efficacy and safety of disopyramide in obstructive hypertrophic cardiomyopathy

OBJECTIVES

In this study we assessed the long-term efficacy and safety of disopyramide for patients with obstructive hypertrophic cardiomyopathy (HCM).

BACKGROUND

It has been reported that disopyramide may reduce left ventricular outflow gradient and improve symptoms in patients with HCM. However, long-term efficacy and safety of disopyramide has not been shown in a large cohort.

METHODS

Clinical and echocardiographic data were evaluated in 118 obstructive HCM patients treated with disopyramide at 4 HCM treatment centers. Mortality in the disopyramide-treated patients was compared with 373 obstructive HCM patients not treated with disopyramide.

RESULTS

Patients were followed with disopyramide for 3.1 +/- 2.6 years; dose 432 +/- 181 mg/day (97% also received beta-blockers). Seventy-eight patients (66%) were maintained with disopyramide without the necessity for major non-pharmacologic intervention with surgical myectomy, alcohol ablation, or pacing; outflow gradient at rest decreased from 75 +/- 33 to 40 +/- 32 mm Hg (p < 0.0001) and mean New York Heart Association functional class from 2.3 +/- 0.7 to 1.7 +/- 0.6 (p < 0.0001). Forty other patients (34%) could not be satisfactorily managed with disopyramide and required major invasive interventions because of inadequate symptom and gradient control or vagolytic side effects. All-cause annual cardiac death rate between disopyramide and non-disopyramide-treated patients did not differ significantly, 1.4% versus 2.6%/year (p = 0.07). There was also no difference in sudden death rate, 1.0%/year versus 1.8%/year (p = 0.08).

CONCLUSIONS

Two-thirds of obstructed HCM patients treated with disopyramide could be managed medically with amelioration of symptoms and about 50% reduction in subaortic gradient over >/=3 years. Disopyramide therapy does not appear to be proarrhythmic in HCM and should be considered before proceeding to surgical myectomy or alternate strategies.

Deglutition-induced atrial fibrillation

We present the case of 38-year-old woman who experienced palpitations on swallowing, which were later found to be atrial fibrillation. Her symptoms improved on treatment with disopyramide and verapamil. Within 9 months, she was weaned from both medications without recurrence of symptoms.

Pharmacological treatment of reflex syncope

Patient education, identification of possible triggers of syncope and reassurance are a central feature of the management of patients with reflex syncope. Patients should be advised as to the importance of adequate hydration and taught physical countermaneuvers to enhance cardiac venous return. These maneuvers are sufficient for most patients, however, for a small number of patients who continue to have recurrent syncopal events, pharmacological intervention may be considered. Volume expansion can be enhanced with salt and fludrocortisone. Agents from diverse pharmacological classes have been used to attenuate the reflex response, enhance vasoconstriction and attenuate vagal outflow. Alpha adrenoreceptor agonists, anticholinergic agents, theophylline, beta adrenoreceptor antagonists, serotonin reuptake inhibitors and disopyramide are the most widely studied. None of these agents has shown a consistent therapeutic benefit in clinical trials.

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.