Efficacy of type 1C antiarrhythmic agents for treatment of resistant atrial fibrillation

In order to determine the efficacy of type 1C agents (flecainide, encainide, propafenone) in patients with atrial fibrillation who have failed to maintain sinus rhythm with type 1A agents (quinidine, procainamide, disopyramide), 147 patients, that were admitted into the John Dempsey Hospital with new or recurrent atrial fibrillation between 1987-1991, were studied retrospectively. Out of the total, 29 patients converted spontaneously to sinus rhythm, 14 patients were left in atrial fibrillation, and 104 patients were given a type 1A antiarrhythmic. Sixty-five of these patients remained in sinus rhythm (54% converted on drug alone, 46% required electrical cardioversion) for at least 6 months. Of the remaining 39 patients, 28 were given a type 1C antiarrhythmic; 13 were successfully converted (61% chemical, 39% electrical) to and remained in sinus rhythm for at least 6 months; the remaining 15 either failed to convert or reverted to atrial fibrillation. New onset atrial fibrillation had a significantly lower incidence of congestive heart failure (10%) than recurrent atrial fibrillation (33%; P < 0.01). No differences in digoxin, beta blocker use, or other clinical characteristics were seen either between type 1A or type 1C successes or failures. Similarly, echocardiographic dimensions did not predict success or failure with either class of agent. In conclusion, type 1C antiarrhythmics for suppression of recurrent atrial fibrillation represent a reasonable therapeutic alternative for suppression of atrial fibrillation in patients who have failed type 1A agents. Prognostic factors predicting success or failure remain undetermined.

A placebo-controlled trial of intravenous and oral disopyramide for prevention of neurally mediated syncope induced by head-up tilt

OBJECTIVES

A double-blind randomized trial was designed to determine the efficacy of intravenous and oral disopyramide phosphate in preventing neurally mediated syncope induced by a head-up tilt test.

BACKGROUND

Neurally mediated syncope is a frequent cause of syncope and may be induced by head-up tilt testing. Recent uncontrolled trials have suggested that disopyramide may be an effective therapy in patients with neurally mediated syncope.

METHODS

Twenty-two consecutive patients with recurrent neurally mediated syncope and two or more successive positive head-up tilt test responses were randomly allocated to receive either intravenous disopyramide or placebo. Head-up tilt testing at 60 degrees was performed for 15 min. If presyncope or syncope was not provoked, isoproterenol infusion was started at a rate of 1 microgram/min and the rate gradually increased until a 25% increase in heart rate was achieved. Eleven patients were subsequently randomized in crossover fashion to receive oral disopyramide (800 mg/day) or placebo during 1 week. The primary end point was prevention of syncope or presyncope provoked by head-up tilt testing.

RESULTS

Head-up tilt test results were positive for syncope in 12 (75%) of 16 patients receiving intravenous placebo and in 12 (60%) of 20 patients receiving disopyramide (p = 0.55 Fisher exact test, 95% confidence interval [CI] -14% to 40%). In the intravenous phase, complete crossover was achieved in 15 patients. Head-up tilt test results during this phase were positive in 13 patients (87%) receiving placebo and in 12 patients (80%) receiving disopyramide (p = 0.50 Fisher exact test, 95% CI -19% to 32%) and were positive in all patients receiving their initially randomized drug or placebo. In the oral phase, head-up tilt results were positive in only two patients (18%) assigned to placebo and in three patients (27%) receiving disopyramide (p = 0.54 Fisher exact test, 95% CI -42% to 24%). A mean follow-up time of 29 +/- 8 months was obtained in 21 of the 22 patients. Syncope recurred in 3 (27%) of the 11 patients receiving disopyramide and 3 (30%) of the 10 patients not treated pharmacologically (p > 0.05).

CONCLUSIONS

Intravenous disopyramide was ineffective for the prevention of neurally mediated syncope provoked by head-up tilt testing. No significant effect was observed after oral therapy with disopyramide. There was a striking decrease in the incidence of positive tilt test results over time regardless of intervention, thus discouraging the use of head-up tilt as the single method of assessing therapeutic efficacy. Recurrence of syncope after the investigative protocol was infrequent over long-term follow-up regardless of treatment group.

[Antiarrhythmic treatment after reduction of atrial fibrillation by external shock]

Among the drugs recommended to prevent recurrences of atrial fibrillation after external electric shock, antiarrhythmic agents of classes Ia (quinidine, disopyramide), Ic (cibenzoline, flecainide, propafenone) and III (sotalol) seem to have the same effectiveness in maintaining the sinus rhythm in about 50 percent of the cases after 6 months and one year. Amiodarone, seldom used as first-line treatment, appears to be the most effective drug. The percentage of side-effects requiring discontinuation of treatment is the same for all drugs (about 10 percent). All these drugs have potential proarrhythmic effects. In case of recurrence electric shocks can be repeated in some special cases. The therapeutic strategy according to the clinical context (atrial fibrillation of vagal nerve or catecholergic origin, normal or altered left ventricular function) is discussed.

Supraventricular tachycardia and pre-excitation syndromes: pharmacological therapy

Tachyarrhythmias which originate above the bifurcation of the bundle of His or incorporate tissue proximal to it are classified as supraventricular tachyarrhythmias (SVT). Primary treatment of SVT attempts to influence the underlying disease. Therapy is subdivided into drug therapy, electrotherapeutic tools (e.g. antitachycardia pacemakers, catheter ablation) and antiarrhythmic surgery. Antiarrhythmic agents which slow conduction and suppress premature beats are efficient for emergency and long-term treatment of supraventricular tachycardias. We evaluated some of the most relevant antiarrhythmic drugs for SVT including propafenone, diprafenone, cibenzoline, lorcainide and sotalol; in addition, usage and efficacy of quinidine/verapamil, disopyramide, amiodarone, ajmaline, adenosine and flecainide are summarized. The principles for acute management of tachycardia episodes with narrow and broad complexes are outlined. The reason for the selection as well as the efficacy in the termination of the tachycardias is described for different antiarrhythmic agents including verapamil, adenosine, ajmaline, propafenone and flecainide.

Clinical evaluation of the use-dependent QRS prolongation and the reverse use-dependent QT prolongation of class I and class III antiarrhythmic agents and their value in predicting efficacy

We measured the QRS duration during a treadmill exercise test and the QT interval using a 24-hour Holter electrocardiogram at various heart rates to identify use-dependent QRS prolongation and reverse use-dependent QT prolongation of class I and III antiarrhythmic drugs. Use-dependent QRS prolongation was detected in 61%, 53%, and 64% of patients receiving disopyramide, mexiletine, and pilsicainide, respectively. Reverse use-dependent QT prolongation was found in 40% and 70% of patients receiving disopyramide and E4031. Drugs suppressed > or = 75% of the total premature ventricular contractions in all patients who had both use-dependent QRS prolongation and reverse use-dependent QT prolongation, in 79% of patients with use-dependent QRS prolongation alone, in 70% with reverse use-dependent QT prolongation alone, and in 11% with neither use-dependent QRS prolongation nor reverse use-dependent QT prolongation. Use-dependent QRS prolongation and reverse use-dependent QT prolongation were identified noninvasively and were useful in evaluating antiarrhythmic efficacy.

Acute dose-response effects of intravenous disopyramide in hypertrophic obstructive cardiomyopathy

To evaluate the acute hemodynamic effects of intravenous disopyramide in hypertrophic obstructive cardiomyopathy (HOCM), 25 patients (12 men, 13 women) with an average age of 40 years (range 18 to 70 years) were evaluated while undergoing cardiac catheterization-angiography. Biplane left ventricular angiography was performed with standard intracardiac-systemic hemodynamics, including resting and provoked (after ventricular premature beat) left ventricular outflow tract gradients, by using simultaneous LV and aortic pressures as disopyramide was being administered (total dose 100 mg, bolus 10 mg every 3 minutes). Average baseline thermodilution cardiac output equalled 4.5 +/- 1.2 L/min, with all 25 subjects demonstrating systolic anterior motion of the mitral apparatus (mild, 3 [12%]; moderate, 8 [32%]; severe, 14 [64%]). Although heart rate originally slowed during disopyramide administration, average heart rate increased during the final stages (before, 78 +/- 15 vs after, 82 +/- 13 beats/min; p < 0.05). Systemic aortic pressures increased during intravenous disopyramide (before, 107 +/- 21/71 +/- 19 mm Hg vs after, 120 +/- 28/81 +/- 13 mm Hg; p < 0.05), with a decline in LV end-diastolic pressure (before, 19 +/- 7 vs after, 16 +/- 6 mm Hg; p < 0.01). Maximum LV systolic pressures decreased (before, 193 +/- 32 vs after, 146 +/- 29 mm Hg; p < 0.01), with a substantial reduction in resting LV outflow tract gradients (before, 86 +/- 34 vs after, 27 +/- 20 mm Hg; p < 0.001) in conjunction with less inducible obstruction (before, 124 +/- 33 vs after, 64 +/- 33 mm Hg; p < 0.001). Only minor electrocardiographic changes were seen during disopyramide infusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of cardiac pacing with drug therapy in the treatment of neurocardiogenic (vasovagal) syncope with bradycardia or asystole

BACKGROUND

The efficacy of permanent cardiac pacing in patients with neurocardiogenic (or vasovagal) syncope associated with bradycardia or asystole is not clear. We compared the efficacy of cardiac pacing with that of oral drug therapy in the prevention of hypotension and syncope during head-up tilt testing.

METHODS

Among 70 patients with a history of syncope in whom hypotension and syncope could be provoked during head-up tilt testing, 22 had bradycardia (a heart rate < 60 beats per minute, with a decline in the rate by at least 20 beats per minute) or asystole along with hypotension during testing. There were 9 men and 13 women, with a mean (+/- SD) age of 41 +/- 17 years. Head-up tilt testing was repeated during atrioventricular sequential pacing (in 20 patients with sinus rhythm) or ventricular pacing (in 2 patients with atrial fibrillation). Regardless of the results obtained during artificial pacing, all the patients subsequently had upright-tilt testing repeated during therapy with oral metoprolol, theophylline, or disopyramide.

RESULTS

During the initial tilt test, 6 patients had asystole and 16 had bradycardia along with hypotension. Despite artificial pacing, the mean arterial pressure during head-up tilt testing still fell significantly, from 97 +/- 19 to 57 +/- 19 mm Hg (P < 0.001); 5 patients had syncope, and 15 had presyncope. By contrast, 19 patients who later received only medical therapy (metoprolol in 10, theophylline in 3, and disopyramide in 6), 2 patients who received both metoprolol and atrioventricular sequential pacing, and 1 patient who received only atrioventricular sequential pacing had negative head-up tilt tests. After a median follow-up of 16 months, 18 of the 19 patients who were treated with drugs alone (94 percent) remained free of recurrent syncope or presyncope, whereas the patient treated only with permanent dual-chamber pacemaker had recurrent syncope.

CONCLUSIONS

In patients with neurocardiogenic syncope associated with bradycardia or asystole, drug therapy is often effective in preventing syncope, whereas artificial pacing is not.

[Two cases of idiopathic ventricular fibrillation with interesting electrocardiographic findings]

We encountered two cases of ventricular fibrillation (VF) without overt heart disease. The first case we report is that of a 47-year-old man, and the second case is a 39-year-old man. VF occurred in the night unrelated to myocardial ischemia or myocarditis. Their basic ECGs showed normal sinus rhythm, but neither QT prolongation nor abnormal Q wave was seen. But we could see IRBBB and ST segment elevation in the V1-2 lead not only in the acute phase, but also in the chronic phase. Abnormal findings were not found in noninvasive cardiac examinations, nor in cardiac catheterization and histological examinations. In the second case, VF was induced by electrical stimulation, and Disopyramide was found to be effective for the prevention of VF. The patient in the first case died suddenly two years after his first attack. Both cases have interesting ECG findings, and it may be that they play on important role in discovering the etiology of sudden cardiac death.

[Efficacy and tolerability of sustained-release disopyramide in the treatment of cardiac arrhythmia. Results of a study with 593 patients]

In the context of an open multicentre study, 593 patients participated in the evaluation of sustained release disopyramide (*) in the treatment of cardiac arrhythmias. One hundred and seventy one (29%) had a ventricular arrhythmia, 382 (64%) a supraventricular arrhythmia and 40 (7%) an atrial and ventricular arrhythmia. Two hundred and seventy patients (46%) had underlying cardiac disease. Disopyramide was administered at the mean daily dose of 462 +/- 95 mg. The effectiveness of treatment was assessed after 3 and 6 months by Holter in the group treated for ventricular arrhythmias, the responder rate was 52.6% at three months and 58.1% at 6 months. It was significantly (p < 0.001) greater in the group treated for supraventricular arrhythmias (71.3% at 3 months and 82.1% at 6 months). The Holter responder rate in patients aged over 65 (70.5% at 6 months) was high and general and cardiac acceptability similar to that in younger patients. Adverse events led to the interruption of treatment in 8.2% of patients. Thus the effectiveness/acceptability ratio of SR disopyramide makes it entirely appropriate for the treatment of cardiac arrhythmias, even in the elderly.

Delayed restoration of atrial function after conversion of atrial flutter by pacing or electrical cardioversion

It is often suggested but never proven that atrial function is not affected during atrial flutter, nor after its conversion to normal sinus rhythm. To evaluate this hypothesis, a prospective study was performed in 22 patients (age range 20 to 88 years) with atrial flutter. Diastolic transmitral flow was analyzed with echo-Doppler before and after conversion. After randomization, conversion was attempted with overdrive pacing or up to two 50 J shocks. If the initial method was unsuccessful, a 200 J shock was administered. All patients were converted to sinus rhythm with this protocol. Shortly after conversion (at 1 and 6 hours), atrial contribution to ventricular filling was absent in 4 of 22 patients. In the remaining 18 patients, atrial contribution to ventricular filling was small. Atrial contribution to transmitral flow improved from 20 to 27% within 24 hours (p < 0.01) and increased further to 38% at 6 weeks (p < 0.005). Peak velocity of late diastolic filling increased from 0.28 m/s after 1 hour to 0.39 m/s after 24 hours (p < 0.0001) and improved even further during later follow-up. In 1 patient, an effective atrial systole was not observed until the 14th day. Cardiac output did not change significantly during the study period. No differences were observed between the conversion modalities. In conclusion, atrial dysfunction is present immediately after conversion of atrial flutter to normal sinus rhythm. This dysfunction occurs also after overdrive pacing and can last > 1 week. The findings suggest that stasis in the atria can remain temporarily present after successful conversion of atrial flutter to sinus rhythm.

Recurrent unexplained syncope in the elderly: the use of head-upright tilt table testing in evaluation and management

OBJECTIVE

To investigate the usefulness of head-upright tilt table testing for vasovagal episodes in the evaluation and management of elderly patients with recurrent idiopathic syncope.

DESIGN

Prospective survey.

SETTING

Electrophysiology laboratory of a university hospital.

PATIENTS

Twenty-five patients (11 male, 14 female; mean age 73 +/- 6 years) with recurrent unexplained syncope and seven control subjects with other causes of syncope (4 male, 3 female; mean age 70 +/- 4 years).

METHODS

Each patient underwent head-upright tilt table testing for 30 minutes with or without an infusion of isoproterenol (1-3 micrograms/min given intravenously) in an attempt to provoke bradycardia, hypotension, or both.

MAIN RESULTS

Syncope occurred in nine patients (36%) during the baseline tilt and in seven patients (28%) during isoproterenol infusion (total positives 64%). None of the controls had syncope during the test. All of the patients who had positive test results eventually became tilt table negative with therapy, and over a mean follow-up period of 24 months, no further syncopal episodes have occurred.

CONCLUSIONS

Head-upright tilt table testing combined with isoproterenol infusion may be a useful tool in the diagnosis of vasovagal syncope in the elderly and in the evaluation of preventive therapy.

Treatment of myotonia with antiarrhythmic drugs

The effects of disopyramide, phenytoin, mexiletine, and tocainide were compared in 30 patients with myotonic disorders. The severity of myotonia was assessed by clinical and electromyographic criteria at the end of each treatment phase lasting four weeks. Mexiletine (MXT) and tocainide (TCD) were found to be the most potent antimyotonic agents. The antimyotonic efficacy of MXT and TCD is explained by their fast-blocking effect on voltage-dependent sodium channels in the muscle membrane. The benefits of myotonia control with pharmacological agents must be weight against the risk of therapy in the individual patient. Because of the risks of hematologic problems, TCD is not recommended by us for the treatment of myotonia.

Mexiletine and disopyramide suppress ventricular premature contractions (VPC) irrespective of the relationship between the VPC and the underlying heart rate

The effects of mexiletine (300 mg/day, 24 patients) and disopyramide (300 mg/day, 20 patients) on ventricular premature contractions (VPCs) were studied using a 24-hour ambulatory electrocardiogram. The VPC frequency was evaluated as a function of the underlying heart rate (HR). The VPC-HR correlation was classified into 2 major types, depending on whether the frequency of the VPC increased with the increased HR (positive type) or not (nonpositive type). The effects of the drugs were assessed based on the VPC-HR correlation and on the percent reduction of the VPC frequency. Mexiletine and disopyramide significantly decreased the frequency of the VPCs of both the positive and nonpositive types. Each drug was assumed to be effective when the percent reduction of the VPC frequency exceeded 70%. Mexiletine (300 mg/day) was 58.5% effective in positive type patients and 33.3% effective in nonpositive type patients, with a total efficacy of 45.8%. Disopyramide was effective in 50% of total cases with 44.4% in positive type patients and 54.5% in nonpositive type patients. However, the efficacy of these drugs on the 2 different types of VPCs was the same statistically. The findings strikingly contrasted those obtained with diltiazem and atenolol, which predominantly suppressed VPCs of the positive type which share similar characteristics with a triggered activity in vitro. We conclude that the mode of action of class I antiarrhythmics on the VPCs differs from that of class II or IV antiarrhythmics, as viewed from the VPC-HR relationship, and that the difference probably comes from the different arrhythmogenesis for positive and nonpositive types of VPCs, in addition to the different electrophysiological actions of mexiletine and disopyramide.

Steady-state pharmacokinetics and bioavailability of total and unbound disopyramide in children with cardiac arrhythmias

We studied the pharmacokinetics of the total (protein-bound plus -unbound and unbound forms of disopyramide (DP) at steady-state in six children (aged 5.2 to 12.2 years) with cardiac arrhythmias who had received repeated oral DP therapy. Maximum concentrations after the oral dose were reached at 2.5 +/- 1.1 h (mean +/- SD) for both total and unbound DP. The bioavailabilities calculated from total and unbound plasma concentration-time curves were 99 +/- 23 and 89 +/- 27% of the dose, respectively. These parameters seen in our children are similar to those reported from adult subjects. The mean elimination half-lives (t1/2), volumes of distribution, and total body clearances (CL) of total and unbound DP were 3.15 +/- 0.64 and 2.50 +/- 0.37 h, 1.02 +/- 0.25 and 2.60 +/- 0.38 L/kg, and 3.79 +/- 0.82 and 13.12 +/- 2.60 ml/min/kg, respectively. These mean CL and t1/2 values are considerably greater and shorter, respectively, than those reported from adult subjects. The findings indicate that the greater doses of DP per kg of body weight reportedly required for attaining a therapeutic plasma drug level in pediatric age patients should be due to a greater drug CL in children than in adults. A sustained-release preparation of DP may be required for pediatric patients to minimize a large fluctuation of plasma drug levels during the dosing intervals.

The effect of pretreatment with moricizine on early arrhythmia resulting from myocardial ischemia in rats

Moricizine (moracizine) is a new class I antiarrythmic drug which is undergoing a large scale clinical trial at present. A rat model was used to compare the effects of moricizine (5 mg/kg i.v.), disopyramide (DSP 5 mg/kg i.v.) and mexiletine (MXT 5 mg/kg i.v.) on early ventricular arrhythmias occurring within 30 min after ligation of the left coronary artery. After intravenous administration, all three drugs slowed the heart rate significantly (p less than 0.01), and compared to the control group only moricizine significantly increased the systolic, diastolic and mean arterial blood pressures. The total number of premature ventricular complexes were as follows; control group (n = 9); 1666 +/- 250 beats, moricizine group (n = 7); 1645 +/- 417 beats (NS), DSP group (n = 10); 325 +/- 155 beats (p less than 0.01 vs control) and MXT group (n = 10); 733 +/- 147 beats (p less than 0.01 vs control). The incidence of primary ventricular fibrillation, was significantly reduced by DSP and MXT (10% reduction and 20% reduction respectively) (p less than 0.05), while moricizine (incidence 80%) had no effect in comparison to the control group (incidence 90%). Death due to arrhythmia was completely abolished by DSP and MXT; although moricizine showed a slight tendency to increase the mortality rate, but the difference was not significant. In conclusion, moricizine has no obvious protective effect on early ventricular arrhythmias resulting from coronary artery occlusion in rats.

[Prospective course of therapy arresting attacks of atrial fibrillation in patients with preexcitation syndromes]

A comparative study of antiarrhythmic drugs was performed in 81 patients with atrial fibrillation attacks in the presence of preexcitation syndrome. The first intravenous administration of cordarone was effective in 84.06%, disopyramide--in 69%, ajmaline in 44.8, verapamil in 42.1, novocaine amide in 39.4 and ethacizin in 38.5% of the patients. The first oral administration of quinidine and kinilentin arrested 80.4% of arrhythmia attacks, disopyramide 66.7% propranolol and mexitil 37.5 and 33.3%, respectively. Prospective evolution of antiarrhythmic therapy manifested with decreased therapeutic efficacy of the drugs from 55.7 to 26.2% in the whole group during the period of 1-5 years.

[A comparison between amiodarone and disopyramide in a delayed-release formulation in the prevention of recurrences of symptomatic atrial fibrillation]

In order to compare the efficacy in preventing recurrencies of symptomatic atrial fibrillation of amiodarone (A.) and slow release disopyramide (D.RET.), 76 consecutive patients with recent onset atrial fibrillation (1 to 24 hrs.) were enrolled. In 20 (26%) conversion to sinus rhythm was obtained by electrical cardioversion, and in 56 (74%) by oral quinidine loading. Forty-one patients (group A) were assigned at random to treatment with D.RET. (250 mg twice daily) and 35 patients (group B) to amiodarone treatment (1200 mg daily for 10 days, and subsequently 200 mg daily). The two groups were similar as to age, sex and cardiac pathology. Patients were followed as to clinical condition, standard and dynamic ECG after one and three months and every three months subsequently for an average of 13.2 months (group A) and 14.1 months (group B). Six group A patients (14%) were excluded from follow-up on account of side effects which arose during the first week of treatment. Crises of symptomatic atrial fibrillation occurred in 20 patients of group A (57%) and in 11 (32%) group patients; this difference is statistically significant (p less than 0.05). Four (10%) group A patients stopped taking the drug due to side effects of an anticholinergic type, and three (8.5%) patients developed hyperthyroidism during follow-up. The authors therefore come to the conclusion that amiodarone is more effective than slow-release disopyramide in preventing recurrencies of atrial fibrillation; besides untoward side effects are less frequent with amiodarone.

Effect of propranolol and disopyramide on left ventricular function at rest and during exercise in hypertrophic cardiomyopathy

In 19 patients with hypertrophic cardiomyopathy (15 males, 4 females, mean age 49.2 +/- 10.8 years) left ventricular function was studied with radionuclide ventriculography at rest and during exercise in a crossover design without intervention and after disopyramide and propranolol treatment. 15 of the 19 patients had a resting or latent intraventricular gradient of more than 30 mm Hg. Left ventricular function at rest and during exercise was evaluated before medication, 90 min after oral administration of 200 mg disopyramide or 160 mg propranolol and after 3 weeks of oral therapy with disopyramide 200 mg 2 times a day or propranolol 80 mg 4 times a day. After long-term treatment with disopyramide, resting ejection fraction decreased from 72 +/- 12 to 69 +/- 14% (p less than 0.01) and peak ejection rate (PER) decreased from 3.46 +/- 135 to 3.24 +/- 65 end-diastolic volume (EDV).s-1 (p less than 0.01). Peak filling rate (PFR) at rest decreased from 3.01 +/- 0.8 to 2.77 +/- 0.63 EDV.s-1 (p less than 0.05). Time to peak filling rate (TPFR) at rest and during exercise after acute and chronic therapy did not change compared to control values. Acute and long-term administration of propranolol lead to a significant reduction in heart rate at rest and during exercise.(ABSTRACT TRUNCATED AT 250 WORDS)

Clinical study on coupling interval of ventricular premature contraction in patients with organic heart disease

The characteristics of the coupling interval (CI) of ventricular premature contraction (VPC) were studied in 100 patients with frequent VPCs using 24 h ambulatory ECG recording. All R-R intervals were registered on computer to determine the mean value of CIs (Mean CI) and the standard deviation of CIs (SD-CI). We compared the Mean CI and the SD-CI between idiopathic VPCs and VPCs with organic heart disease (OHD). In addition, we evaluated the efficacy of disopyramide (DP) and mexiletine (MX) and we examined the relationship between the efficacy of these drugs and the characteristics of CI. The Mean CI of VPCs with OHD was longer than that of idiopathic VPCs (530 vs. 494 msec, p less than 0.05). The SD-CI of VPCs with OHD was larger than that of idiopathic VPCs (54.1 vs. 39.3 msec, p less than 0.01). In all treated cases, the drug efficacy was not different between DP (11/18, 61%) and MX (9/19, 47%). However when we isolated cases of OHD, we found a tendency that DP (9/12, 75%) was more effective than MX (7/16, 44%). In cases where DP was administered, the Mean CI of VPCs was not different between effective and ineffective cases, while in cases where MX was administered, the Mean CI of ineffective cases had a tendency to be longer than that of effective cases (552 vs. 506 msec, p less than 0.1).(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of transcatheter cardioversion on chronic lone atrial fibrillation

The effectiveness and safety of internal transcatheter cardioversion on chronic lone atrial fibrillation were examined in ten patients resistant to external electrical (400 joules) and pharmacological cardioversion. Transcatheter cardioversion was performed by pulling back the atrioventricular junction catheter just inferior to the site of the His-bundle recording and delivering the shock between a proximal electrode (cathode) and backplate (anode). Transcatheter cardioversion restored sinus rhythm in all of the ten patients. The only complication observed was transient atrioventricular block after the shock and this was treated by temporary pacing. However, atrial fibrillation recurred in five patients at 30, 27, 52, 1, and 6 days, respectively. A second attempt at transcatheter cardioversion was performed in those patients an was successful in three patients. During a follow-up period ranging from 12 to 22 months, eight patients continued in sinus rhythm. Thus, transcatheter cardioversion is considered effective and safe in selected patients with chronic lone atrial fibrillation in whom external cardioversion was unsuccessful.

Repetitive nonsustained monomorphic ventricular tachycardia aborted by methoxamine and sleep "heart rate dependent ventricular tachycardia"

Methoxamine, an alpha adrenoreceptor agonist, and sleep abolished repetitive nonsustained monomorphic ventricular tachycardia in a 41-year-old man without detectable underlying heart disease. Detailed pacing studies revealed that the occurrence of ventricular tachycardia was totally dependent on the basic heart rate. Sleep and the alpha adrenoreceptor agonist abolished the ventricular tachycardia by slowing the basic heart rate. Verapamil, propranolol, and disopyramide were able to decrease the upper limit of the tachycardia-initiating heart rate, but none of them were able to increase the lower limit (75/min). Failure to increase the lower limit of the tachycardia-initiating heart rate was a major reason why these conventional antiarrhythmic drugs were unable to suppress his daytime episodes of repetitive ventricular tachycardia.