Clinical pharmacokinetics of antiarrhythmic drugs

Extracorporeal Treatment in Phenytoin Poisoning: Systematic Review and Recommendations from the EXTRIP (Extracorporeal Treatments in Poisoning) Workgroup

The Extracorporeal Treatments in Poisoning (EXTRIP) Workgroup conducted a systematic literature review using a standardized process to develop evidence-based recommendations on the use of extracorporeal treatment (ECTR) in patients with phenytoin poisoning. The authors reviewed all articles, extracted data, summarized findings, and proposed structured voting statements following a predetermined format. A 2-round modified Delphi method was used to reach a consensus on voting statements, and the RAND/UCLA Appropriateness Method was used to quantify disagreement. 51 articles met the inclusion criteria. Only case reports, case series, and pharmacokinetic studies were identified, yielding a very low quality of evidence. Clinical data from 31 patients and toxicokinetic grading from 46 patients were abstracted. The workgroup concluded that phenytoin is moderately dialyzable (level of evidence = C) despite its high protein binding and made the following recommendations. ECTR would be reasonable in select cases of severe phenytoin poisoning (neutral recommendation, 3D). ECTR is suggested if prolonged coma is present or expected (graded 2D) and it would be reasonable if prolonged incapacitating ataxia is present or expected (graded 3D). If ECTR is used, it should be discontinued when clinical improvement is apparent (graded 1D). The preferred ECTR modality in phenytoin poisoning is intermittent hemodialysis (graded 1D), but hemoperfusion is an acceptable alternative if hemodialysis is not available (graded 1D). In summary, phenytoin appears to be amenable to extracorporeal removal. However, because of the low incidence of irreversible tissue injury or death related to phenytoin poisoning and the relatively limited effect of ECTR on phenytoin removal, the workgroup proposed the use of ECTR only in very select patients with severe phenytoin poisoning.

Initial Experience With a Multidisciplinary Strategy for Initiation of Propranolol Therapy for Infantile Hemangiomas

Objectives. To outline a safe, standardized protocol for outpatient initiation of propranolol therapy for infantile hemangiomas.

Study Design. Retrospective review.

Setting. Academic tertiary care pediatric hospital.

Subjects and Methods. Forty-nine infantile hemangioma patients were offered propranolol therapy and included in the study. Any patients requiring hospital admission were excluded. Screening consisted of cardiology evaluation, including electrocardiography and, when indicated, echocardiography. Target initiation dose was 2 to 3 mg/kg/d divided into 3 doses. Blood pressure and heart rate were initially monitored at baseline and 1 and 2 hours in clinic following initial dosing. A 3-hour time point was later added. Families received standardized instructions regarding home heart rate monitoring, side effects, and fasting.

Results. Outpatient propranolol therapy was safely initiated in 39 of 44 patients (89%). Five patients required brief admission: 1 with clinical signs/symptoms of heart failure, 3 having airway involvement, and 1 for social reasons. Propranolol administration transiently reduced blood pressure; the maximal decrease occurred at 2 hours, prompting addition of a 3-hour time point to ensure recovery. No patients exhibited symptomatic hypotension, bradycardia, or heart failure.

Conclusions. In most children with infantile hemangiomas, propranolol therapy can be safely initiated as an outpatient. Careful cardiovascular evaluation by an experienced clinician is essential for pretreatment evaluation, inpatient admission (when necessary), blood pressure and heart rate monitoring following initial dosing, and parent education. This standardized multidisciplinary outpatient initiation plan reduces the cost of initiating therapy compared with inpatient strategies while still providing appropriate monitoring for potential treatment complications. Further evaluation of propranolol therapy efficacy at the current dosing and duration of treatment continues.

Management of supraventricular tachyarrhythmias

Supraventricular tachyarrhythmias are common and treatment is based on the frequency and hemodynamic severity caused by these arrhythmias. Empiric therapy with currently available medications often satisfactorily controls symptomatic arrhythmias. Nonpharmocologic therapy with permanent antitachycardia pacemakers, percutaneous catheter ablation or surgery can be effective for selected patients with medically refractory supraventricular tachyarrhythmias after thorough electrophysiologic evaluation. In selected patients with life-threatening supraventricular tachyarrhythmias due to the WPW syndrome, surgical ablation is the therapy of choice.

Comparative efficacy and safety of oral mexiletine and quinidine in benign or potentially lethal ventricular arrhythmias

The antiarrhythmic efficacy and safety of oral mexiletine hydrochloride and quinidine sulfate were compared at 29 clinical centers in a double-blind, parallel-group trial involving 491 patients with benign or potentially lethal ventricular arrhythmias. Responders were defined as those who had at least a 70% reduction in the frequency of ventricular premature complexes (VPCs) that persisted for 12 weeks, and who experienced no intolerable side effects that required discontinuation of therapy. Of the patients available for analysis, 71 of 232 (31%) in the mexiletine and 73 of 225 (32%) in the quinidine group met these criteria. The dose range used for mexiletine was 200 to 400 mg every 8 hours, and that for quinidine 200 to 400 mg every 6 hours. More than half of the patients in each group were successfully treated with the smallest dose (200 mg every 8 hours mexiletine vs 200 mg every 6 hours for quinidine). Quinidine significantly prolonged the QT interval, whereas mexiletine did not. Proarrhythmic reactions were recorded in 18 of 221 (9%) patients taking quinidine and 10 of 217 (5%) patients taking mexiletine. There was no difference in the incidence of adverse reactions between the 2 groups; in both, the most common side effects were related to the gastrointestinal and central nervous systems. Mexiletine thus represents an alternative to quinidine for the treatment of patients with ventricular arrhythmias.

Comparison of intravenous mexiletine and lidocaine for the treatment of ventricular arrhythmias

The efficacy and safety of intravenous loading of mexiletine was compared to lidocaine in patients with ventricular premature depolarizations (VPDs). Seventeen men and five women, average age 63 years, completed this randomized parallel study. Twelve patients received mexiletine intravenously at (5 to 10 mg/min) until greater than or equal to 95% VPD suppression was achieved or a total of 450 mg of drug was given. The average loading dose of mexiletine was 4.4 mg/kg, at an infusion rate of 0.1 mg/kg/min. Ten patients received lidocaine (1 mg/kg) given over 3 minutes, with a second similar bolus given if after 10 minutes greater than or equal to 95% VPD suppression was not achieved. Total VPDs were determined for the 60 minutes before drug administration, during drug infusion, and 60 minutes thereafter. Eleven of 12 (92%) patients receiving mexiletine were full responders (greater than or equal to 95% suppression) and one was a partial responder (greater than or equal to 75% greater than or equal to 95% suppression). Five of 10 lidocaine patients (50%) were full responders, three (30%) were partial responders, and two failed to respond. At peak suppression, mexiletine reduced mean VPD from 37 +/- 33/5 minutes (mean +/- S.D.) to 0.8 +/- 0.9/5 minutes (p less than 0.01) and lidocaine decreased mean VPDs from 28 +/- 47/5 minutes to 4.7 +/- 2.2/5 minutes (p less than 0.01). Mexiletine resulted in greater suppression of VPDs than lidocaine in terms of mean percent reduction (96% vs 68%, p less than 0.01). All lidocaine patients had therapeutic plasma levels (range 1.6 to 3.5 micrograms/ml).(ABSTRACT TRUNCATED AT 250 WORDS)

Flecainide versus quinidine for conversion of atrial fibrillation to sinus rhythm

The effectiveness and safety of flecainide and quinidine for conversion of atrial fibrillation (AF) to sinus rhythm were compared. Sixty consecutive patients were treated with either flecainide (up to 2 mg/kg intravenously and then orally) or quinidine (up to 1.2 g orally). There was no statistical difference in age, left atrial size, duration of the arrhythmia and underlying cardiac diseases between the 2 groups. The overall conversion rate to sinus rhythm was 63% (38 patients): AF was converted in 18 patients (60%) treated with quinidine and 20 (67%) with flecainide. If AF lasted less than 10 days, the conversion rate was 86% in the flecainide group and 80% in the quinidine group (difference not significant). When AF lasted more than 10 days the rate was 22% in the flecainide group and 40% in the quinidine group. Adverse effects were more frequent in the quinidine group (27%) (gastrointestinal disturbances) than in the flecainide group (7%) (conduction disturbances), but they were less severe in the quinidine group. Thus, flecainide given intravenously appeared to be as effective as quinidine given orally for conversion of AF of recent onset (within 10 days). However, quinidine should probably remain the preferred drug for conversion of AF of long duration (more than 10 days) to sinus rhythm. Adverse effects occurred less often with flecainide therapy, but they were more severe.

Emergency treatment of tachyarrhythmias

The diagnosis, clinical aspects, and emergency treatment of the most common cardiac arrhythmias, including atrial flutter and fibrillation, paroxysmal supraventricular tachycardia, the Wolff-Parkinson-White syndrome, ventricular tachycardia, and torsades de pointes, are discussed. The use of the antiarrhythmic drugs most frequently utilized in clinical practice is described.

Short-term myocardial uptake of lidocaine and mexiletine in patients with ischemic heart disease

Determination of short-term myocardial drug uptake and subsequent redistribution was performed in 27 patients with ischemic heart disease for the antiarrhythmic agents lidocaine and mexiletine, using frequent simultaneous measurements of drug concentration in aortic and coronary sinus blood, combined with measurement of coronary sinus blood flow after intravenous bolus injection of the drug. Maximal myocardial drug content per unit resting coronary sinus blood flow (MDC:F) was significantly greater in patients in whom coronary sinus pacing at 100 beat/min was performed during the initial period of drug uptake. Maximal myocardial drug content occurred after 2.4 +/- 0.2 (SEM) for lidocaine and after 5.5 +/- 0.6 min for mexiletine (p less than .001), and pacing did not affect time to maximum myocardial drug content. In nonpaced, but not paced, patients maximal MDC:F was greater in the lidocaine group than that in the mexiletine group. The subsequent efflux of lidocaine from the myocardium was more rapid that that of mexiletine in both paced and nonpaced groups.

Adjunctive therapy of phenytoin overdose--a case report using plasmaphoresis

Phenytoin is widely used as an anticonvulsant. In overdose situations phenytoin demonstrates saturable metabolic kinetics making treatment difficult. Phenytoin's high protein binding makes it a poor candidate for hemodialysis or hemoperfusion. We report a case of an attempted suicide in which plasmaphoresis was used in an attempt to lower plasma levels and reduce toxicity. A review of the use of plasmaphoresis in acute intoxications is included.

Comparative efficacy and safety of oral tocainide and quinidine for benign and potentially lethal ventricular arrhythmias

The antiarrhythmic efficacy and safety of oral tocainide hydrochloride and quinidine sulfate were compared in a double-blind, 3-center, parallel trial involving 133 patients with benign and potentially lethal ventricular arrhythmias. Baseline demographic, etiologic, functional and ventricular arrhythmia data were not significantly different between the 2 groups. Two weeks of an initial placebo period were followed by 8 weeks of active drug treatment, concluding with 4 weeks of washout. Frequent 24-hour ambulatory electrocardiographic monitoring was used to judge efficacy. Ten of 27 patients (37%) receiving tocainide and 12 of 24 patients (50%) receiving quinidine had a 75% reduction with drug treatment compared with the initial placebo period (p greater than 0.25). Total abolition of ventricular tachycardia occurred in 6 of 16 patients (37%) receiving tocainide and 6 of 13 patients (43%) receiving quinidine (p greater than 0.25). Conditions that required discontinuation of therapy occurred in 18 of 67 patients (27%) receiving tocainide and 16 of 66 (24%) receiving quinidine (difference not significant). More patients had dizziness during tocainide treatment and diarrhea during quinidine treatment. Quinidine caused a prolongation in the QT interval (0.03 second); tocainide caused a slight reduction (0.01 second). No important changes in vital signs or laboratory measurements were observed in left ventricular ejection fraction when measured. Thus, tocainide, the new oral analog of lidocaine, appears to be as safe as quinidine but is slightly less effective in suppressing ventricular arrhythmias.

Long-term antiarrhythmic therapy. Problem of low drug levels and patient noncompliance

Maintenance of adequate serum blood levels is crucial to successful antiarrhythmic therapy. Serum levels of four antiarrhythmic agents (long-acting procainamide, quinidine sulfate, quinidine gluconate, and disopyramide) were determined in 98 consecutive ambulatory patients receiving long-term oral therapy. Medication dosages, dosing intervals, and time elapsed from last dosage until blood sampling were determined. Seventy-five patients (76.5 percent) had subtherapeutic blood levels (with mean levels less than 50 percent of the suggested minimum), and only 22 patients (22.5 percent) had therapeutic levels. Even among the 61 patients who claimed to have taken their medications within the six hours prior to blood sampling, 43 (70 percent) had subtherapeutic levels. These ratios held among all subgroups studied. Physicians should be aware of the high proportion of patients receiving long-term oral antiarrhythmic therapy with inadequate serum blood levels when planning therapeutic regimens.

Evaluation of quinidine short and long-acting in control of arrhythmias

Twenty-one patients with arrhythmias responsive to quinidine were studied both with regard to consistency of response as determined by repeat Holter Monitoring and in half of these patients a comparison of short and long-acting quinidine was made. Holter Monitoring demonstrated greater than 60% reduction of ectopic activity in all but one patient and reproducibility varied by less than 10% in nineteen of twenty-one patients. Nine of eleven patients showed the same response to long-acting quinidine as compared to short-acting. Eight of nine patients having significant numbers of ectopic pairs showed a significant reduction with quinidine therapy, both short-acting and long-acting.

Electrophysiologic effects of flecainide acetate on sinus node function, anomalous atrioventricular connections, and pacemaker thresholds

The acute electrophysiologic effects of i.v. flecainide acetate (2 mg/kg body weight) were assessed in 71 patients undergoing electrophysiologic study. Ten patients underwent investigation for sinus node dysfunction. Sinus cycle length shortened slightly, from 980 +/- 292 to 931 +/- 276 ms (p less than 0.01). Uncorrected or corrected sinus node recovery times or sinoatrial conduction time (according to the methods of Strauss and Narula) did not change in 6 patients with normal sinus node function and in 3 of 4 patients with abnormal sinus node function at rest. In the remaining patient maximal sinus node recovery time increased from a value at rest of 5,185 ms to 23,460 ms after flecainide. In the same patient sinoatrial conduction times at rest increased from 159 ms (Strauss method) and 143 ms (Narula method) to 1,398 and 1,455 ms, respectively, after flecainide. Thirty-three patients underwent electrophysiologic evaluation of anomalous atrioventricular (AV) pathways and reentrant tachycardias. Flecainide significantly prolonged accessory AV pathway anterograde and retrograde refractoriness. Anterograde accessory pathway block occurred in 33% of patients and retrograde accessory pathway block in 44%. Flecainide was successful in the acute termination of 86% of orthodromic atrioventricular reentrant tachycardias. In 15 patients with dual AV nodal pathways, only retrograde "fast" AH pathway refractoriness was significantly increased by flecainide, which was successful in the acute termination of 88% of intra-AV nodal reentrant tachycardias. In 28 patients who underwent endocardial pacing threshold assessment before and after i.v. flecainide, the acute threshold rose by a maximum of 117%, whereas the chronic threshold rose by a maximum of 83%.(ABSTRACT TRUNCATED AT 250 WORDS)

Flecainide versus quinidine: results of a multicenter trial

In this multicenter trial, the efficacy and safety of flecainide, a new antiarrhythmic agent, were compared with those of quinidine, a standard antiarrhythmic agent in the United States. A randomized, parallel, placebo-controlled design was used. Flecainide was more effective than quinidine (p less than 0.0001) in reducing ventricular premature complexes, couplets and ventricular tachycardia. Flecainide continued to be effective in reducing ventricular arrhythmias during a 12-month follow-up period. The incidence of side effects was similar for the 2 drugs in both short- and long-term studies. Therefore, flecainide should be an excellent drug to use in treating patients with ventricular arrhythmias classified as either benign or potentially malignant.

Cardiac arrhythmias. Emergency management

Cardiac arrhythmias often call for emergency treatment, and often it is the primary care physician who must respond quickly and effectively. In this article, Dr Brent reviews the various types of arrhythmias and the methods available for dealing with them on an emergency basis. According to one peer reviewer, this article contains "the information that the clinician should have at the tips of his or her fingers at all times."

Ten years of experience with amiodarone

Arrhythmias may be controlled in most patients with recurrent supraventricular tachycardia or atrial fibrillation with small to moderate maintenance doses of amiodarone (100 to 400 mg/day). Moderate doses (400 mg/day) are also highly effective in suppressing "warning" ventricular arrhythmias in patients with chronic ischemic heart disease, particularly if the goal of treatment is to eliminate ventricular couplets, runs of ventricular tachycardia (VT), and the "R on T" phenomenon. Treatment and prevention of sustained recurrent VT and the malignant arrhythmias of chagasic myocarditis require, however, doses of about 800 mg/day, which may be higher than those needed for ischemic heart disease complicated by VT and ventricular fibrillation. Clinical studies suggest an elimination half-life for amiodarone of about 30 days (range 15 to 100 days). Thus there is a pretherapeutic latency period that varies according to the type of arrhythmia and the doses employed. The maximal effects (as well as the most significant adverse effects) are not attained before 90 to 150 days of treatment, and the antiarrhythmic protection may persist for varying intervals, up to 150 days or more, after the drug has been discontinued. Side effects are not negligible but are generally dose dependent. Despite these side effects, many patients have been treated by us with amiodarone for as long as 5 to 8 years--and for up to 10 years in some cases. Amiodarone appears to be one of the most promising drugs for the possible prevention of ventricular fibrillation and sudden death.

Flecainide versus quinidine for treatment of chronic ventricular arrhythmias. A multicenter clinical trial

The antiarrhythmic efficacy and safety of oral flecainide acetate and quinidine sulfate were compared in a double-blind, 16-center parallel trial involving 280 patients with chronic premature ventricular complexes (PVCs). Eighty-five percent of the flecainide patients had at least 80% suppression of PVCs, vs 57% of the quinidine patients (p less than 0.0001). Sixty-eight percent of the flecainide patients met the above criterion and also had complete suppression of couplets and beats of ventricular tachycardia, vs 33% of the quinidine patients (p less than 0.0001). PR and QRS intervals were prolonged by flecainide without clinical consequence, but they were not substantially affected by quinidine (p less than 0.0001). Quinidine prolonged JT (QT minus QRS) intervals significantly more than flecainide (p less than 0.05). Nineteen of 141 flecainide patients and 21 of 139 quinidine patients discontinued therapy because of side effects (p greater than 0.50). Flecainide side effects included dizziness, blurred vision, headache and nausea. Quinidine side effects included diarrhea, nausea, headache and dizziness. Flecainide was more effective than quinidine in suppressing chronic ventricular arrhythmias (especially complex forms), and thus is an important new antiarrhythmic agent.

Bioavailability and saturation of the presystemic metabolism of oral lorcainide therapy initiated in three different dose regimens

The feasibility of giving a supplementary starting dose of the antiarrhythmic drug lorcainide, in order to minimalize the impact of the extensive, but saturable first-pass metabolism, was evaluated. Twenty-five adult patients were given 100 mg lorcainide tablets according to one of 3 different dosage schedules: Eight patients took one tablet at 0, 12 and 24 h, 8 took 1 tablet at 0, 1, 12 and 24 h and 9 took 1 tablet at 0, 2, 12 and 24 h. Levels of lorcainide and its metabolite, nor-lorcainide, during treatment were determined by gas-liquid chromatography. The results show that giving a second tablet 1 or 2 h after the first may produce faster saturation of the pre-systemic metabolism of lorcainide in the liver.

Ventricular ectopy: etiology, evaluation, and therapy

Ventricular ectopy occurs commonly. Its significance is related to the degree of complexity and the associated cardiac substrate. Coronary artery disease is the most frequent underlying cause, followed by cardiomyopathy and valvular disease. Symptomatic ventricular arrhythmias require treatment, whereas benign simple ventricular ectopy does not; however, the treatment of asymptomatic high-grade ventricular ectopy remains controversial. Therapy first must be directed toward the cardiac disease. Evaluation of the patient includes Holter monitoring, echocardiography, radionuclide studies, exercise testing, cardiac catheterization, and electrophysiologic testing. Programmed stimulation is useful in the diagnosis and prognosis of ventricular tachycardia, as well as in the evaluation of drug regimen efficacy. After treatment of ischemia and/or failure, specific antiarrhythmic agents, conventional and investigational, alone or in combination, are systematically selected. Should medical therapy alone be insufficient, consideration is given to surgical procedures such as subendocardial resection or ventriculotomy, often in combination with bypass grafting, aneurysmectomy, or valvular replacement. Electronic devices, including pacemakers or automatic internal defibrillators, may also be useful in certain selected cases. Suggested guidelines are proposed for a standardized approach, although therapy for each patient must still be individualized.

Short- and long-term therapeutic efficacy of quinidine sulfate for the treatment of chronic ventricular arrhythmias

To determine the efficacy and tolerance of oral quinidine sulfate in the treatment of chronic ventricular arrhythmias using contemporary definitions of drug efficacy, 20 ambulatory patients underwent a short-term, placebo-controlled, double-blind trial consisting of four days of quinidine therapy at 400 mg every 6 hours. A long-term trial was conducted in 12 additional patients where ventricular ectopic frequency during two weeks of placebo therapy was compared with that during eight weeks on quinidine sulfate at 300 mg every 6 hours. Quinidine efficacy was determined by 48 hours of Holter monitoring. Blood levels were within the therapeutic range in both trials. Side effects consisted of diarrhea, which occurred in 15 per cent of patients on the short-term and 25 per cent of patients on the long-term trial. Drug effect defined as a statistically significant (P less than 0.025) reduction in chronic premature ventricular complexes occurred in 70 per cent of patients on the short-term trial and in 67 per cent of patients on the long-term trial. In both trials, all patients with ventricular tachycardia had statistically significant suppression. Statistically significant reduction in ventricular couplets occurred in all patients on the short-term trial but in only 73 per cent of the patients on the long-term trial. These data can be used as reference standards for quinidine sulfate in new antiarrhythmic drug comparison trials.

The electropharmacology of acute drug testing using pacemakers

Acute drug testing in patients is useful to select prophylactic treatment for life-threatening or intractable tachycardias. This is generally done by induction of tachycardias with pacing. Acute studies that depend on temporary insertion of pacing electrodes do not determine efficacy in the same sense as longer term clinical drug trials because of the biased population referred for testing with pacemakers. However, the pharmacologic activity of compounds can be tested in terms of electrical functions such as conductivity and refractoriness not merely of the heart in general, but also of the arrhythmogenic focus. Such data can be directly applied to patients with similar arrhythmias, obviating the confusion often caused by interspecies and disease differences.

Assessment of oral quinidine effects on sinus node function in sick sinus syndrome patients

The effects of therapeutic doses of orally administered quinidine sulfate on sinus rhythmicity and automaticity were observed in 11 patients with sick sinus syndrome (SSS). Evaluation of sinus node (SN) function was undertaken by assessing sinus nodal recovery time (SNRT), treadmill exercise testing, and 24-hour ambulatory ECG monitoring before and after quinidine administration (25 mg/kg) (range 800 to 1600 mg daily). Corrected SNRT ranged from 100 to 1320 msec (average 551) before quinidine and was not significantly (p greater than 0.05) altered after quinidine to 346 to 660 msec (average 481). Further, quinidine did not induce accelerated infrasinus pacemaker activity. Spontaneous sinus rate evaluated with ambulatory monitoring revealed average rate of 57 bpm (range 53 to 63) before quinidine without significant increase to average 59 bpm (range 52 to 80) after quinidine therapy. Similarly, the maximal SN response to exercise was not significantly affected by quinidine (average 129 bpm before and 129 bpm after drug therapy). It is concluded that therapeutic doses of quinidine do not exert adverse effects on SN function in SSS patients. Chronic oral quinidine therapy can therefore be used safely with caution in patients with chronic SN disease when indicated for control of tachyarrhythmias.

Encainide: a new and potent antiarrhythmic agent

Encainide is a potent Class I antiarrhythmic drug that prolongs conduction in the His-Purkinje system. It produces only minimal hemodynamic changes in the normal or depressed left ventricle. Studies to date demonstrate excellent effectiveness against ventricular arrhythmia, and in comparative studies with quinidine, encainide was superior in reducing the frequency and complexity of ventricular premature beats in patients late after myocardial infarction.

Effects of antiarrhythmic drugs on atrioventricular conduction in patients with acute myocardial infarction

Three hundred fifty-eight of 429 (83%) consecutive patients with acute myocardial infarction (MI) and a normal PR interval received various antiarrhythmic drugs (AD), including lidocaine and/or procainamide, quinidine, digoxin, propranolol or disopyramide. There was no significant difference in the incidence of progression to any degree of atrioventricular (AV) block or to higher degrees of AV block (Mobitz II or third-degree AV block) between those treated and not treated with AD: 38 of 358 (11%) and six of 358 (1.7%) with AD vs 11 of 71 (15%) and two of 71 (2.8%) in the untreated group, respectively. Similarly, there was no significant difference in progression between treated and untreated patients with anterior MI, 14 of 144 (10%) vs five of 32 (16%); inferior MI, 21 of 111 (19%) vs five of 26 (19%), or subendocardial MI, three of 103 (3%) vs one of 12 (8%). Bundle branch block (BBB) (without AV block) was initially present in 89 of 249 (21%). The incidence of AV block (seven of 24, 30%) was higher in treated patients with newly acquired BBB (27 patients) than in the untreated patients (none of three, p less than 0.05). The commonly used ADs did not adversely affect AV conduction in patients with acute MI with narrow QRS and either normal, first-degree, or Mobitz I AV block. Moreover, no subset of patients grouped by infarct location, specific AD used, or BBB (except perhaps for those with newly acquired BBB) appeared to be at risk of development of AV block during AD therapy.

The elderly patient in the coronary care unit. II. Incidence and treatment of arrhythmias

In 1976, 130 patients aged 70 or older were admitted to the Coronary Care Unit (CCU) at Toronto Western Hospital. Arrhythmias were noted in all but 24 percent. Digoxin was given to 53 patients, lidocaine to 24, propranolol to 28, and quinidine to 11. In 2 patients, cardioversion by direct current was required for supraventricular arrhythmias. In 26 patients, temporary pacemakers were used. Of 13 patients who experienced at least one cardiac arrest in the CCU, 10 survived to be discharged to the ward. In total, only 12 of the 130 elderly patients died in the hospital, and in only 3 of these was arrhythmia the primary cause of death. The treatment of arrhythmias in the elderly is as successful and rewarding as in younger patients. Indications for the various antiarrhythmic drugs are similar. Except for digoxin, the dosages of such drugs for the elderly are the same as those for younger patients. Adverse effects apparently are not more common in the elderly.

Antiarrhythmic drug therapy in survivors of prehospital cardiac arrest: comparison of effects on chronic ventricular arrhythmias and recurrent cardiac arrest

We studied the long-term effects of membrane-active antiarrhythmic agents on chronic ventricular arrhythmias in patients who have survived prehospital cardiac arrest. Among 16 patients treated with a dose-adjusted, plasma level-monitored antiarrhythmic regimen, eight have survived for longer than 12 months and eight have had recurrent cardiac arrests (RCAs). Monthly Holter monitor tapes (HM) recorded during the 4 months before the eight RCAs were compared with monthly HM tapes matched for time of entry and duration of follow-up in the eight patients who did not have RCAs. Transient or persistent complex ventricular ectopic depolarizations (VEDs) have been recorded on 47 of the 63 monthly HM tapes (75%). The difference between VEDs in the RCA patients (mean 153 VEDs/hr, median 19 VEDs/hr) and VEDs in the patients who have not had RCA (mean 122 VEDs/hr, median 8 VEDs/hr) was not significant (p less than 0.2); nor was there a predictable relationship between therapeutic plasma levels of antiarrhythmic agents and the frequency and complexity of chronic asymptomatic VEDs (therapeutic levels--mean 104 VEDs/hr, median 6 VEDs/hr; subtherapeutic levels--mean 184 VEDs/hr, median 21 VEDs/hr). Differences were not significant (p greater than 0.1). In contrast, all eight RCA patients had unstable plasma levels (21 of 31 determinations subtherapeutic) while six of the eight patients who have not had RCA had consistently therapeutic levels (p less than 0.01). Thus, adequate plasma levels of antiarrhythmic agents may protect against RCA, despite failure to suppress VEDs predictably. The apparent dissociation between predictable suppression of chronic VEDs and protection against RCA suggests that clinical effectiveness of these agents may not be best measured by their effect on chronic VEDs.

High-dose propranolol therapy in the management of supraventricular tachycardia

Five patients, age 3 weeks to 11 years, presented with supraventricular tachycardia that remained uncontrolled following adequate digitalization. Four of these patients underwent invasive electrophysiologic studies to determine the mechanism of the arrhythmias. Of these four patients, three had concealed Wolff-Parkinson-White syndrome, and one patient had evidence of dual A-V nodal pathways. Propranolol was added to the medical treatment and was administered orally in doses ranging from 7 to 14 mg/kg/day (average 9 mg/kg/day). All five children remain free of their tachycardia except for one patient who occasionally has supraventricular tachycardia with febrile illnesses. No adverse reactions to these high doses of propranolol were encountered.

New antiarrhythmic agents: amiodarone, aprindine, disopyramide, ethmozin, mexiletine, tocainide, verapamil

The present status, clinical experience, side effects, clinical pharmacology and electrophysiologic actions of seven new antiarrhythmic agents are reviewed. The drugs selected for comment are amiodarone, aprindine, disopyramide, ethmozin, mexiletine, tocainide and verapamil. Each drug has been shown to have clinical efficacy in suppressing cardiac arrhythmias.