Large dose procainamide therapy for ventricular tachyarrhythmia

Electropharmacologic effect of a standard dose of intravenous procainamide in patients with sustained ventricular tachycardia

BACKGROUND

Patients with inducible sustained ventricular tachycardia (VT) sometimes receive intravenous procainamide during electrophysiologic testing. Unfortunately, the responses to intravenous and subsequent oral drug therapy are variable and may be discordant.

HYPOTHESIS

It was the aim of this study to determine whether this variability might be explained by heterogeneity in the electropharmacologic response, even in a homogeneous population.

METHODS

We studied 42 patients who had spontaneous malignant ventricular arrhythmia and were inducible to sustained monomorphous VT during electrophysiologic testing. Each received 15 mg/kg of intravenous procainamide followed by a 2 mg/min infusion. Serum levels were drawn immediately following programmed stimulation. The mean procainamide level was 6.7 +/- 1.4 mcg/ml with an N-acetyl procainamide level of 1.0 +/- 0.5 mcg/ml. The 14 procainamide responders (5 of whom were noninducible and 9 whose VT cycle length increased > 100 ms) and the 28 nonresponders had similar procainamide and NAPA levels (6.5 +/- 1.4 vs. 6.7 +/- 1.4 mcg/ml).

RESULTS

There was no significant difference in baseline clinical parameters, His to ventricular electrogram (HV) interval, effective refractory period, or VT cycle length. Prolongation of the effective refractory period and infra His conduction time occurred to a similar extent in responders and nonresponders.

CONCLUSION

We conclude that procainamide has a consistent dose-response relationship with respect to refractoriness and conduction in patients with malignant arrhythmias. However, acute antiarrhythmic efficacy of procainamide cannot be predicted by clinical factors, drug levels, or drug-induced changes in common electrophysiologic parameters.

Therapeutic Levels of Intravenous Procainamide in Neonates: A Retrospective Assessment

STUDY OBJECTIVES

To evaluate dosing and pharmacokinetic parameters of intravenous continuous-infusion procainamide in neonates, and to identify dosage regimens and factors leading to therapeutic procainamide levels and minimal adverse events.

DESIGN

Retrospective, observational study.

SETTING

Pediatric hospital.

PATIENTS

. Twenty-one patients (seven preterm, 14 full term) younger than 30 days who received continuous-infusion procainamide therapy for more than 15 hours or had two consecutive therapeutic procainamide levels obtained while receiving therapy between June 1, 2002, and December 31, 2005.

MEASUREMENTS AND MAIN RESULTS

Data on demographics, dosing, drug levels, and adverse effects were collected. Doses that achieved therapeutic levels were documented, and procainamide clearance was calculated and evaluated with regard to renal function and gestational age in patients who were at steady state. Mean clearance and mean N-acetylprocainamide (NAPA):procainamide ratios were compared between preterm and term neonates. No patients experienced hemodynamic instability or other adverse effects due to procainamide. Procainamide was given as a mean +/- SD 9.6 +/- 1.5-mg/kg bolus in 20 of 21 patients before continuous infusion. The mean +/- SD dose at which two therapeutic levels were achieved was 37.56 +/- 13.52 microg/kg/minute. Procainamide clearance was 6.36 +/- 8.85 ml/kg/minute and correlated with creatinine clearance (r=0.78, p<0.00001) and age at day of sampling (r=0.49, p<0.00001). The NAPA:procainamide ratio at steady state was 0.84 +/- 0.53; two patients were determined to be fast acetylators (ratio > 1). Preterm infants had lower mean clearance rates (p<0.001) but higher NAPA:procainamide ratios (p<0.01) than those of term infants. Five patients experienced seven supratherapeutic levels while receiving therapy; four of these patients were preterm, and all had creatinine clearances less than 30 ml/minute/1.73 m(2). Three patients had four pairs of levels obtained after discontinuation of procainamide, and elimination rate constant and half-life were calculated.

CONCLUSION

Procainamide can be safely used in neonates, with no short-term adverse effects. The dosage regimen for intravenous procainamide required to achieve therapeutic levels in neonates is similar to that of older infants and children. Doses may need to be reduced in premature infants and in those with renal dysfunction.

Procainamide-induced psychosis: a case report and review of the literature

OBJECTIVE

To describe a case of procainamide-induced psychosis in an adult treated for atrial fibrillation.

CASE SUMMARY

A 45-year-old Native American woman developed acute psychosis within 72 hours of initiating procainamide for atrial fibrillation. Symptoms abated within 24 hours of discontinuing procainamide. Serum procainamide/N-acetylprocainamide concentrations were therapeutic throughout treatment. Sotalol was started without recurrence of symptoms.

DISCUSSION

Psychosis is a rare complication of treatment with procainamide, but the exact mechanism for this adverse event is not fully understood. Seven cases implicating procainamide as the cause of acute psychosis are reported in the literature. Cases of psychosis involving other antiarrhythmic agents have also been reported.

CONCLUSIONS

Healthcare personnel should be aware of this adverse event related to procainamide and other antiarrhythmic agents.

The pharmacokinetics and pharmacodynamics of procainamide in horses after intravenous administration

Six horses were administered either 15 or 20 mg/kg body weight (b.w.) procainamide (PA) as an intravenous (i.v.) dose over 10 min. The plasma concentrations of PA and N-acetylprocainamide (NAPA) as well as the pharmacodynamic effect (prolongation of the QT interval) were monitored. The PA plasma concentrations could be described by a one-compartment model with a t1/2 of 3.49 +/- 0.61 h. The total body clearance of PA was 0.395 +/- 0.090 l/hr/kg and the volume of distribution was 1.93 +/- 0.27 l/kg. As observed after PA administration, NAPA (an active metabolite) had a t1/2 longer than PA of 6.31 +/- 1.49 h. Peak NAPA concentrations (1.91 +/- 0.51 micrograms/ml) occurred at 5.2 h after the PA i.v. dose. The ratio of area under the curves for NAPA to PA was 0.46 +/- 0.15 which is similar to that expected in humans classified as slow acetylators. Percentage change in the QT interval was examined with respect to PA and PA + NAPA plasma concentrations. For PA, % delta QT = 41.2 log (PA) - 13.26 and correlations (r) ranged from 0.77 to 0.91 among the horses. In the case of PA+ NAPA, % delta QT = 57.3 log (PA + NAPA) - 31.83 and ranged from 0.77 to 0.90. No evidence of toxicity was noted with respect to changes in the PR interval.

Serial electropharmacologic studies in patients with ischemic heart disease and sustained ventricular tachyarrhythmias: when is drug testing sufficient?

Serial testing of antiarrhythmic drugs by programmed electrical stimulation can be costly in time, expense and risk. The purpose of this study was to evaluate the results of serial electropharmacologic tests for similarities that might obviate the need for protracted drug testing. Serial electropharmacologic testing was performed in 283 patients with coronary artery disease and clinical sustained ventricular tachycardia (VT) or fibrillation (VF). Drug tests were defined as concordant if sustained VT or VF could be consistently induced, or failed to be consistently induced during all such trials in a given patient. The following drugs were included for testing: procainamide, quinidine and disopyramide (class IA); phenytoin, mexiletine and tocainide (class IB); and flecainide and encainide (class IC). All patients were serially tested with > or = 2 (mean and median, 3) antiarrhythmic agents regardless of results from drug-free testing or initial acute drug testing. Overall, the results of serial drug trials directed by programmed stimulation were concordant in more than two thirds of patients. Concordance was comparably high whether patients were serially tested with drugs within the same antiarrhythmic class, or with drugs from differing classes, and was not related to patients' clinical or electrophysiologic characteristics. Protracted serial electropharmacologic testing does not appear necessary for predicting successful or unsuccessful antiarrhythmic drug therapy in survivors of clinical VT or VF. Single drug testing can identify most patients whose arrhythmia will or will not respond to medications.

Effect of high-current stimulation in patients with sustained ventricular tachycardia rendered noninducible by antiarrhythmic drugs

Successful antiarrhythmic drug therapy for sustained ventricular tachycardia (VT) is presumed to be related to effects on myocardium within the re-entrant circuit. To test the hypothesis that prevention of VT induction may be related to effects on myocardium other than that directly involved in the tachycardia circuit, high-current stimulation was used to achieve shorter coupling intervals in 22 patients with sustained uniform VT that was rendered noninducible by antiarrhythmic agents during stimulation at twice threshold. Sustained uniform VT was induced in 10 patients in response to high-current stimulation (group 1), including 4 tachycardias with the same morphology observed in the baseline study. There were no inducible arrhythmias in 12 patients (group 2). Patients were receiving several different antiarrhythmic regimens, but there was no particular drug associated with the induction of VT using high-current stimulation. There was no statistically significant difference between groups 1 and 2 in baseline VT cycle length (247 +/- 41 vs 253 +/- 44 ms), drug-induced increase in effective refractory period (20 +/- 15 vs 16 +/- 7%), QRS duration (25 +/- 10 vs 20 +/- 17%) or maximal current strength delivered (10.9 +/- 5.3 vs 9.3 +/- 4.0 mA). There was no significant difference in local activation with high-current stimulation between groups 1 and 2. In conclusion, sustained uniform VT was induced in 45% (10 of 22) of patients whose arrhythmias were rendered noninducible by antiarrhythmic agents during programmed stimulation at twice threshold.(ABSTRACT TRUNCATED AT 250 WORDS)

Iontophoretic transmyocardial drug delivery. A novel approach to antiarrhythmic drug therapy

BACKGROUND

Antiarrhythmic drugs often fail to achieve therapeutic effects without toxic systemic levels. Direct transport of drugs into the myocardium may circumvent this problem and may also provide new insights into antiarrhythmic drug effect on arrhythmogenic tissues. In a canine model, procainamide (PA) was delivered iontophoretically using pulsed current synchronized with the ventricular depolarization via an implantable defibrillator patch electrode that was modified to contain a 3.6-ml chamber. Myocardial tissue concentrations of PA were evaluated in 7-day myocardial infarcts (n = 16) that were exposed to 10 minutes of iontophoretic PA delivery and compared with passive diffusion (n = 5) and intravenous (n = 16) PA. These dogs were followed for 3 hours. The infarcted tissue PA levels were compared with normal myocardium. Coronary and systemic blood levels of PA, effective refractory period (ERP), diastolic threshold, and efficacy of ventricular tachycardia (VT) suppression were evaluated throughout the follow-up period.

METHODS AND RESULTS

Three hours after 10 minutes of iontophoretic, passive, and intravenous PA, the epicardial layer concentration in the center of the infarcted zone was 840 +/- 853 micrograms/g, 93 +/- 90 micrograms/g, and 15 +/- 8 micrograms/g of tissue, respectively. In the endocardial layer, the PA concentrations with iontophoresis were 38 +/- 57 micrograms/g and were significantly higher than those achieved with either passive diffusion 38 +/- (4 +/- 2 micrograms/g) or with intravenous delivery (11 +/- 5 micrograms/g) (p less than 0.05). Epicardial tissue PA concentrations 3 hours after iontophoresis, passive diffusion, and intravenous PA in the normally perfused tissues were 14 +/- 13 micrograms/g, 3 +/- 2 micrograms/g, and 16 +/- 8 micrograms/g of PA, respectively. Venous blood levels were 2 +/- 3 micrograms/ml 3 hours after iontophoresis, 1 +/- 1 microgram/ml 3 hours after passive PA delivery, and 11 +/- 7 micrograms/ml with intravenous administration (p less than 0.05 intravenous versus passive and iontophoresis). Iontophoretic delivery of PA resulted in 22 +/- 29 msec ERP prolongation intramurally in the infarcted zone with no significant normal tissue ERP prolongation. Passive delivery of PA produced no significant changes in ERP. After intravenous infusion, the ERP in the infarcted zone increased by 35 +/- 29 msec and 13 +/- 12 msec in the normal tissue. Sustained monomorphic VT was induced in 20 animals. In one of these animals, only nonsustained VT could be induced at baseline; however, after intravenous PA, VT could be induced and remained inducible throughout the 3-hour follow-up period. In the iontophoretic delivery group, PA suppressed VT in all of the animals, with termination time ranging from 20 seconds to 7 minutes. In three cases, sustained monomorphic VT could be reinduced, two after 60 minutes and one after 120 minutes. However, in seven dogs, VT could not be induced during the 3-hour follow-up period. None of the dogs in which PA was delivered iontophoretically into the infarcted myocardium developed VT that was not induced before delivery of the drug. Intravenous PA administration resulted in VT suppression in one of 10 dogs. In two dogs, VT could not be induced before intravenous infusion of PA. However, after intravenous PA, VT could be induced. Immunohistochemical mapping of the PA within the infarcted tissue revealed transmural PA distribution.

CONCLUSIONS

These data show that 1) the delivery of high transmural concentrations of PA directly into infarcted myocardium is both feasible and effective...

Usefulness of the electrophysiology laboratory for evaluation of proarrhythmic drug response in coronary artery disease

Two potential manifestations of proarrhythmic responses to type IA antiarrhythmic agents in the electrophysiology laboratory were evaluated in 122 patients with chronic coronary artery disease and previous myocardial infarction: (1) conversion of uniform nonsustained ventricular tachycardia (VT) into sustained VT after drug administration, and (2) induction of sustained VT by fewer extrastimuli after drug administration. Forty-two patients were evaluated for nonsustained VT. Eighty patients were evaluated for sustained VT: 30 of these had spontaneous sustained VT only while receiving empiric therapy with quinidine or procainamide, whereas the remaining 50 developed spontaneous VT in the absence of antiarrhythmic drugs. All patients underwent programmed stimulation in the baseline state and after procainamide. Four patients had conversion of induced uniform nonsustained VT into the same morphology, but sustained VT after procainamide administration. These responses only occurred in patients evaluated for nonsustained VT. Over 90% of patients presenting with sustained VT had uniform sustained VT induced at the baseline study and after procainamide, regardless of whether the spontaneous arrhythmia occurred only in the presence or absence of antiarrhythmic drugs. There was no significant difference in the change in mode of induction from baseline to procainamide study, regardless of whether patients had developed spontaneous VT only in the presence or absence of antiarrhythmic drugs. One patient with no inducible VT at the baseline study had inducible uniform sustained VT after procainamide administration, and 1 patient with inducible VT at baseline developed spontaneous sustained uniform VT after procainamide administration. Both patients had developed spontaneous sustained VT only while receiving therapy with type IA agents.(ABSTRACT TRUNCATED AT 250 WORDS)

Practical optimisation of antiarrhythmic drug therapy using pharmacokinetic principles

The optimisation of antiarrhythmic drug therapy is dependent on the definitions and methods of short term efficacy testing and the characteristics of those drugs used for rhythm disturbances. The choice of an initial antiarrhythmic drug dosage is highly empirical, and will remain so until the measurement of free concentrations, enantiomeric fractions and genetic phenotyping becomes routine. However, the clinician can devise an efficient initial dosage for efficacy testing procedures based on pharmacokinetic principles and disposition variables in the literature. In this regard, a nomogram for commonly used agents and dosages was constructed and is offered as a guide to accomplish this goal. Verification of the accuracy and usefulness of this nomogram in a prospective manner in patients with symptomatic tachyarrhythmias is still required. On a long term basis, dosage regimens can be modified by the use of pharmacokinetic principles and patient-specific target concentrations, in accordance with the methods used to monitor arrhythmia recurrence and drug-related side effects.

Day-to-day reproducibility of antiarrhythmic drug trials using programmed extrastimulus techniques for ventricular tachyarrhythmias associated with coronary artery disease

Forty-nine patients with coronary artery disease and documented clinical sustained ventricular tachycardia (VT) or ventricular fibrillation (VF) were studied twice in the drug-free state and twice during treatment with an identical antiarrhythmic medication at therapeutic plasma concentrations using an identical programmed electrical stimulation protocol. Tested drugs included procainamide, quinidine, disopyramide and phenytoin. During their 2 paired tests, 11 patients had nearly identical therapeutic plasma concentrations of antiarrhythmic agents (group I) and 38 patients had therapeutic plasma concentrations, but with more variation in drug levels between otherwise identical paired drug tests (group II). Overall, 71% of patients had inducible sustained VT or VF during drug testing. Induced ventricular arrhythmias were not reproducible in 45% of group I patients, despite restudy at nearly identical therapeutic plasma concentrations of an identical antiarrhythmic agent. Induced arrhythmias were also not reproducible in 16% of group II patients. This variability could not be attributed to the electrophysiologic characteristics of the patients studied. Drug trials directed by programmed stimulation should be cautiously interpreted because time-associated changes can mimic a change attributed to a beneficial or deleterious drug effect.

Inducible monomorphic sustained ventricular tachycardia in the conscious pig

Sustained monomorphic ventricular tachycardia (VT) is of clinical importance but has not been readily modeled in conscious animals. Eleven pigs had myocardial infarction induced by pulling snares previously placed around the left anterior descending (LAD) coronary artery. Six days after occlusion, bipolar pacing catheters were inserted in the right ventricular apex for induction of VT. Testing was repeated in conscious pigs on 6 out of 8 to 19 days after infarction. Monomorphic VT was induced in each animal during each session, using three to four extrastimuli. VT was terminated by burst pacing in 74% of trials; average VT rate was 362 +/- 26 beats/min. VT was prevented in four of eight animals by procainamide and in five of eight animals by magnesium, but was not prevented by lidocaine or metoprolol. The model may be useful in the study of potentially malignant ventricular tachyarrhythmias, important prodromes for sudden death.

Rate-dependent changes in intraventricular conduction produced by procainamide in anesthetized dogs. A quantitative analysis based on the relation between phase 0 inward current and conduction velocity

Antiarrhythmic drug effects on maximal upstroke velocity (Vmax) are frequency dependent, which implies that the effects of these drugs on conduction should also be rate dependent. Previous in vivo studies have been limited by assumptions about unchanging propagation pathway, and by the empirical use of a first-order recovery model. To explore time-dependent antiarrhythmic drug-induced conduction slowing in vivo, we used 56-electrode epicardial mapping in chloralose-anesthetized dogs with formalin-induced atrioventricular block. Interval-dependent changes in conduction time were assessed under control conditions and then after three loading and maintenance infusions of procainamide. Under control conditions, epicardial activation time (86 +/- 26 msec at a basic cycle length of 300 msec) was unchanged (87 +/- 24 msec) by pauses up to 6.6 +/- 2.2 seconds. Procainamide caused conduction slowing that dissipated as a function of recovery interval, with 94 +/- 6% recovery over a maximum pause of 6.7 +/- 1.5 seconds, but did not alter activation pattern. Drug-induced changes in conduction were evaluated by use of a mathematical model assuming phase 0 inward current proportional to conduction velocity squared. Conduction changes were better fitted by this "quadratic model" (least sum of squared deviations 3.9 x 10(-3) by mapping in five dogs, 2.7 x 10(-2) by use of QRS duration in nine dogs) than by a monoexponential model (sum of squared deviations 5.7 x 10(-3) by mapping, 3.4 x 10(-2) with QRS; p less than 0.01 vs. quadratic model for each). As predicted by theoretical analysis, recovery time constants from the quadratic model were similar to time constants for procainamide-induced changes in Vmax in vitro, and significantly longer than values obtained with a monoexponential model. Drug-induced changes in QRS duration were highly correlated with simultaneous changes measured by epicardial mapping (r = 0.95, p less than 0.001), indicating that QRS duration is a valid index of drug effects on ventricular conduction. We concluded that procainamide causes interval-dependent changes in ventricular conduction in vivo that are consistent with a proportional relation between phase 0 inward current and the square of conduction velocity. These observations have important potential implications for the dose-dependent and heart rate-dependent effects of antiarrhythmic drugs.

Efficacy of procainamide on ventricular tachycardia: relation to prolongation of refractoriness and slowing of conduction

The effect of procainamide on intraventricular conduction and refractoriness, and the prevention of induction of ventricular tachycardia (VT) were studied in 29 patients who had remote myocardial infarction and inducible sustained monomorphic VT. AFter intravenous administration of 15 mg/kg procainamide, induction of VT was suppressed in seven (24%) patients (responders), while in 22 (76%) VT was still inducible (nonresponders). The percent change in paced QRS duration at a cycle length (CL) of 400 msec produced by procainamide was significantly less in responders than in nonresponders: 29.8 +/- 3.9% versus 38.9 +/- 10.8% (p = 0.0020). The percent change in the right ventricular effective refractory period (ERP) at CLs of 600 and 400 msec was significantly greater in responders than in nonresponders: 14.6 +/- 6.9% versus 7.9 +/- 7.3% (p = 0.0414) for ERP at a CL of 600 msec and 15.1 +/- 7.0% versus 8.0 +/- 7.4% (p = 0.0386) for ERP at a CL of 400 msec. Stepwise discriminant analysis showed that greater percent increase in ERP at a CL of 400 msec and lesser percent increase in paced QRS duration at a CL of 400 msec were significantly independent markers for the responders. These findings suggest that lesser slowing of conduction and greater prolongation of refractoriness by procainamide tend to abolish reentry within the reentrant circuit. Greater slowing of conduction and lesser prolongation of refractoriness tend to stabilize a reentrant circuit, and promote the continued induction of VT.

Sudden cardiac death: etiologies, pathogenesis, and management

Sudden death claims an estimated 350,000 lives per year in the United States. When death occurs within 1 hour of the onset of symptoms, 90% are the result of ventricular tachyarrhythmias. The majority of victims are middle-aged men with coronary artery disease, but in approximately 25%, sudden death is the presenting manifestation of their problem. In some populations, the detection of premature ventricular complexes (PVCs) by ambulatory monitoring is predictive of an increased risk of sudden death. However, the arrhythmia that best predicts this risk is unclear, and ambient arrhythmias are only a modest marker of this risk. Therapy to suppress asymptomatic PVCs has not been shown to be effective in preventing sudden death, and in some cases, lethal arrhythmias can be prevented without significant effects on ambient arrhythmias. Other risk markers such as depressed left ventricular function and the presence of low-amplitude, long-duration, late potentials recorded on a signal averaged electrocardiogram are more powerful predictors of risk than are PVCs. These latter findings in particular support the presence of areas of slow electrical conduction (a requirement for reentrant mechanism arrhythmias) and suggest that an abnormal electrical environment or "substrate" is the most important factor in this problem. The management of patients at risk for sudden death is controversial. While postinfarct survivors with arrhythmias constitute a population at increased risk, the absolute risk is only about 5% in the first year and has not been shown to be improved by conventional antiarrhythmic drugs. Small study size, arrhythmia variability, ill-defined end points, and proarrhythmia may partially explain this apparent lack of efficacy. The prophylactic use of antiarrhythmic drugs other than beta-blockers to prevent sudden death in asymptomatic populations at risk is therefore of unproven benefit. By contrast, patients who have survived a life-threatening arrhythmia unrelated to an acute myocardial infarction have an approximately 30% risk of recurrence in the following year. In these patients, the use of ambulatory monitoring to guide therapy is limited by the high incidence of false-negative responses (lethal arrhythmia recurrence despite ambient arrhythmia suppression) and the lack of frequent spontaneous arrhythmias in many patients. In this patient population, electrophysiological testing can be used to prognosticate recurrence and gain insight into arrhythmia mechanism, stability, and hemodynamic tolerance. The technique is also useful in guiding both pharmacological and nonpharmacological therapy.(ABSTRACT TRUNCATED AT 400 WORDS)

A comparison of sotalol and procainamide in symptomatic ventricular tachycardia

The effects of oral sotalol were compared with 1000 and 1500 mg of procainamide in 23 patients with sustained ventricular tachycardia. The predictive value of an induction study after procainamide was assessed. The mean age of the study group was 62 +/- 12 years, and the mean ejection fraction was 32 +/- 16%. The cycle length (CL) of the induced tachycardia, the coupling interval (CI) of the first extrastimulus (in ms), and the number of noninducible (NI) patients are given in the table below. (table; see text) One patient developed torsades during the loading period of sotalol and is included in the number requiring cardioversion (DC). Important proarrhythmic effects (spontaneous occurrence of tachycardia) were seen twice after procainamide. Induction suppression by procainamide predicted success with sotalol (p = 0.0013).

CONCLUSION

Ventricular tachycardia seems to be less often inducible after oral sotalol than after procainamide. The success of procainamide during programmed electrical stimulation predicts the same for sotalol. If ventricular tachycardia remains inducible after oral sotalol, it is faster than after procainamide but slower than the baseline tachycardia. Both drugs slightly prolong refractoriness.

Rapid assessment of rate and antiarrhythmic drug effect on the myocardium using asymmetric biphasic pulse stimulation

An asymmetric biphasic pulse which stimulates the heart and neutralizes the poststimulation polarization at the electrode-myocardial interface permitting the recording of the evoked endocardial response (EER) up to approximately 1 ms poststimulation with the same electrode used for stimulation is described. Using this mode of cardiac stimulation in 20 dogs the effects on the EER of increasing heart rate and antiarrhythmic drugs, procainamide (PA) and N-acetylprocainamide (NAPA), were studied. EERs were recorded during bipolar and unipolar pacing rates of 120, 150, and 200/min before and during a five step PA or NAPA infusion which resulted in progressively increasing PA and NAPA plasma concentrations (Cps), 1.7-32.5 mg/l for PA and 8.1-116.1 mg/l for NAPA. The effects of progressively increasing heart rates were: The T wave amplitude and QS area increased with increases in rate; during pacing at 120, 150, and 200/min, the T wave amplitudes were 7.6 +/- 2.3, 8.2 +/- 2.1, and 9.8 +/- 2.5 mV and the QS areas were 905 +/- 204, 995 +/- 199, and 1101 +/- 231 mVms. The QT interval and QST area decreased with increases in rate; during pacing at 120, 150, and 200/min, the QT intervals were 265 +/- 61, 249 +/- 57, and 226 +/- 52 ms and the QST areas were 288 +/- 198, 221 +/- 154, and 154 +/- 52 mVms. The effects of the antiarrhythmic drugs, PA and NAPA, on the EER were: PA prolonged both the QS duration and QT interval at low Cp (type Ia antiarrhythmic drug property); at a therapeutic PA Cp of 15.0 +/- 0.2 mg/l and a heart rate of 120/min the percent increase of the QS duration was 12 +/- 4% (P = 0.001) and that of the QT interval was 20 +/- 6% (P less than 0.001). The prolongation of the QS duration by PA was rate dependent, the faster the rate the greater the prolongation. NAPA prolonged the QT interval at low Cp, while the QS duration was not significantly effected at low or therapeutic Cps (type III antiarrhythmic drug property); at a therapeutic NAPA Cp of 15.9 +/- 1.6 mg/l and a heart rate of 120/min the percent increase of the QS duration was 1 +/- 1% (NS) and that of the QT interval was 13 +/- 9% (P = 0.018). Our results show that the use of an asymmetric biphasic pulse allows for pacing and recording of an EER, QS and T waves, with a single electrode.(ABSTRACT TRUNCATED AT 400 WORDS)

Drug therapy for survivors of sudden cardiac death

The proliferation of standard as well as novel community based systems for resuscitation of victims of out-of-hospital cardiac arrest has provided a large group of sudden cardiac death survivors who present a therapeutic challenge. The nature and severity of the underlying heart disease must be delineated. Particularly, myocardial ischemia and congestive heart failure must be controlled. Prior to considering device therapy of surgical intervention, pharmacologic therapy should be evaluated. Baseline electrophysiological studies determine the applicability of serial pharmacologic testing. In patients with inducible VT/VF, serial electrophysiological testing can identify drug regimens that prevent the arrhythmia in approximately 40% of patients. In an additional 20% of patients, regimens which slow the ventricular tachycardia and significantly reduce the arrhythmia related mortality can be identified. Three to 5-year follow-up has shown such an approach can reduce the sudden death mortality in these patients to less than 3% per year. It has been suggested that certain medication, most notably amiodarone, electrophysiological testing has not been useful in assessing efficacy. Several recent studies, however, have shown that electrophysiological testing is indeed useful even in evaluating the efficacy of amiodarone. In patients in whom ventricular tachycardia/ventricular fibrillation cannot be prevented or significantly slowed, medical therapy is generally ineffective and the sudden death mortality is 20% to 40% per year. In such patients, other therapeutic modalities should be considered.

Prediction of successful suppression of sustained ventricular tachyarrhythmias by serial drug testing from data derived at the initial electrophysiologic study

This study investigated whether data available after the initial electrophysiologic study in patients with sustained ventricular tachyarrhythmia could identify those patients in whom serial drug testing is likely to be efficacious. One hundred six patients with inducible sustained ventricular tachyarrhythmia, whose initial study included short-term drug testing with intravenous procainamide, were evaluated. The baseline arrhythmia induced (in the absence of all antiarrhythmic drugs) was monomorphic tachycardia with a cycle length greater than 200 ms in 81 patients and ventricular flutter or fibrillation in the remaining 25 patients. After intravenous infusion of procainamide (1,250 +/- 300 mg), a ventricular tachyarrhythmia could still be induced in 80 patients during testing with up to three extrastimuli. Serial drug testing with one to four trials of oral conventional and investigational agents was then undertaken. Evaluation of 15 clinical, hemodynamic and electrophysiologic variables by stepwise logistic regression identified two independent predictors of successful response to oral antiarrhythmic drugs: 1) noninducibility of ventricular tachycardia after intravenous procainamide (p less than 0.001), and 2) left ventricular ejection fraction greater than or equal to 40% (p less than 0.05). Subgroup analysis combining each of these variables identified patients with a high, intermediate or low probability of finding a successful oral drug regimen. Patients whose arrhythmia was suppressed by intravenous procainamide had a 100% likelihood (if left ventricular ejection fraction was greater than or equal to 40%) or an 87% likelihood (if ejection fraction was less than 40%) of responding to an oral regimen.(ABSTRACT TRUNCATED AT 250 WORDS)

Worsening of ventricular tachycardia by amiodarone

The details of worsening of ventricular tachycardia in 8 (4.1%) of 194 patients receiving treatment with amiodarone are reported. Two forms of amiodarone-induced tachycardia were recognized: first, the development of new tachycardias (three patients) and second, a change in the pattern of recurrence of clinical tachycardia (five patients). In retrospect, the time from the initiation of amiodarone to the initial documentation of worsening ranged from 1 to 23 days (mean +/- SD, 9.4 +/- 8.2 days) and the time from the initiation of therapy to the recognition of worsening ranged from 6 to 26 days (14.6 +/- 10.1 days). Seven patients survived the worsening of tachycardia and one died. The total dose of amiodarone received and the duration of administration did not correlate with time to manifestation or time to resolution of worsening. This report emphasizes that worsening of ventricular tachycardia as a result of amiodarone is often difficult to differentiate from inadequate drug loading or early recurrence of 2 patient's clinical tachycardia. Further, because of the pharmacokinetics of the drug, the manifestations of worsening may be prolonged. In the cases reported, it ranged from 2 to 26 days (7.9 +/- 8.3 days), which is longer than previously reported. Because of the potential for amiodarone to cause life-threatening worsening of ventricular tachycardia and in accordance with current results, a period of in-hospital monitoring of at least 10 days at the start of therapy with amiodarone is recommended.

Pharmacodynamics of intravenous procainamide as used during acute electropharmacologic testing

No previous studies have determined the pharmaco-dynamics of intravenous procainamide when administered in a dose of 15 mg/kg and at a rate of 50 mg/min, as is common practice during electropharmacologic testing. In this study, 30 patients received procainamide in this fashion; the right ventricular effective refractory period and the QRS duration at a ventricular pacing rate of 120/minute were then determined every minute for 20 minutes. Ten patients received no maintenance infusion of procainamide (group A), 10 received a 4 mg/min maintenance infusion (group B) and 10 received an 8 mg/min maintenance infusion (group C). Ten additional patients received no procainamide and served as control subjects (group D). The plasma procainamide concentration was measured at 1, 5, 10, 15 and 20 minutes after the loading dose was administered. A stable plasma procainamide concentration was not present in group A, B, or C until 15 minutes after infusion of the loading dose. The effective refractory period and QRS duration increased compared with baseline at 1 minute, decreased between 1 and 10 minutes and then remained essentially unchanged between 10 and 20 minutes in all 3 treatment groups. Concentration-effect relation was linear in each treatment group. The plasma procainamide concentrations in group C were significantly greater than in group A; however, the effects on refractoriness and QRS duration were similar in both groups. These findings indicate that with a procainamide dosing method commonly used during electropharmacologic testing, the plasma procainamide concentration decreases significantly during the first 15 minutes after the loading dose is administered.(ABSTRACT TRUNCATED AT 250 WORDS)

Procainamide, disopyramide and quinidine: discordant antiarrhythmic effects during crossover comparison in patients with inducible ventricular tachycardia

A crossover comparison of intravenous procainamide, disopyramide and quinidine was made in 32 patients. All three drugs had dosage-related effects on electrocardiographic intervals, refractory periods and cycle length of ventricular tachycardia. Significant linear relations between serum drug levels and changes in refractory periods and ventricular tachycardia cycle length were also observed. Ventricular tachycardia was no longer inducible on at least one drug in 11 patients but concordance of this effect on both of the others was 36% and on either of the others it was 45%. Ventricular tachycardia remained inducible on at least one drug in 28 patients and concordance of this effect on both of the others was 75% and on either of the others was 79%. Continued inducibility on quinidine, the drug producing the greatest electrophysiologic effects, was the best individual predictor of continued inducibility on the others. Subdivision of continued inducibility into easier to induce, inducibility unchanged, or harder to induce dramatically decreased concordance of this effect. Thus the antiarrhythmic effects of these drugs are discordant in individual patients despite electrophysiologic similarities. Nevertheless, continued inducibility after high dosages of any one of these drugs is clinically useful for screening for continued inducibility on the others and this is dose-related rather than drug specific.

Procainamide in the dog: antiarrhythmic plasma concentrations after intravenous administration

Procainamide hydrochloride was administered to ouabain-intoxicated dogs to determine an antiarrhythmic plasma concentration of procainamide. Ventricular arrhythmias were produced in dogs following intravenous injections of ouabain. After a sustained ventricular tachycardia was achieved, procainamide was administered and plasma samples collected for assay. Plasma procainamide was assayed by fluorescence polarization immunoassay. Procainamide was administered at increasingly higher constant rate infusions in order to achieve intermittent, steady-state plasma concentrations. Infusion rates were calculated on the basis of previous pharmacokinetic information. All six dogs that received procainamide converted to a normal sinus cardiac rhythm after attaining a mean plasma concentration of 33.8 micrograms/ml with a range of 48.5 micrograms/ml-25.0 micrograms/ml. It was observed that the computer-generated prediction of plasma concentrations based upon previous pharmacokinetic data produced an underestimate of the actual plasma concentrations. These data may suggest that plasma concentrations of procainamide for controlling some cardiac arrhythmias in dogs may be higher than plasma concentrations cited for human patients.

The Inotropic Actions of N-Acetylprocainamide: Blockade and Reversal by Propranolol

The inotropic actions of N-acetylprocainamide (NAPA) were studied in chloralose-urethane anesthetized dogs. Myocardial contractile force was measured with a Walton-Brodie strain gauge sutured to the right ventricle. A low-dose NAPA infusion (12 mg/kg i.v.) increased myocardial force by a maximum of 11.6±2.4% (mean±SEM), whereas a high dose of NAPA (60 mg/kg i.v.) increased myocardial force by 33.3±2.6% at the peak of the effect. The high-dose NAPA infusion also caused significant reductions in heart rate and blood pressure, while the low-dose NAPA infusion lacked significant chronotropic or hypotensive actions. Pretreatment with propranolol (0.5 mg/kg i.v. loading, followed by a 10 μg/kg/min infusion) did not block the positive inotropic actions of NAPA 12 mg/kg, but these actions were blocked in dogs pretreated with both propranolol and atropine (1 mg/kg). On the other hand, pretreatment with propranolol blocked and reversed the inotropic actions of NAPA 60 mg/kg, and potentiated its negative chronotropic effects. Thus, the positive inotropic actions of NAPA are indirect and more than one mechanism is involved; a component due to direct action related to the lengthening of cardiac repolarization is not discounted. At low doses, the increase in myocardial force seems related to NAPA's vagolytic properties, whereas at high doses the positive inotropic actions appear to be catecholamine-mediated. Furthermore, a negative inotropic action of high-dose NAPA is apparent after beta-adrenergic receptor blockade.

Effects of incremental doses of procainamide on ventricular refractoriness, intraventricular conduction, and induction of ventricular tachycardia

The short-term effects of incremental doses of procainamide (7.5, 15, 22.5, and 30 mg/kg) on right ventricular effective refractory period, intraventricular conduction, and induction of ventricular tachycardia were determined in 31 patients who had a history of sustained, unimorphic ventricular tachycardia. QRS duration during incremental ventricular pacing was used as an index of rate-dependent changes in intraventricular conduction. The mean plasma procainamide concentrations corresponding to the incremental doses were 5.5 +/- 1.2 (+/- SD), 9.0 +/- 1.6, 12.6 +/- 2.2, and 16.3 +/- 3.2 mg/liter. Each incremental dose of procainamide up to a dose of 30 mg/kg resulted in a significant increment in right ventricular effective refractory period and each dose up to 22.5 mg/kg potentiated a rate-dependent prolongation of QRS duration. After the 7.5 mg/kg dose of procainamide, induction of ventricular tachycardia was suppressed in eight of 31 patients. After higher doses of procainamide, induction of ventricular tachycardia was suppressed in two additional patients. In three of 10 patients in whom the induction of ventricular tachycardia was suppressed by 7.5, 15, or 22.5 mg/kg of procainamide, sustained unimorphic ventricular tachycardia was again inducible after a higher dose of procainamide. In three of 31 patients, only nonsustained ventricular tachycardia was inducible after a 7.5 to 22.5 mg/kg dose of procainamide; however, in two of these three patients, sustained ventricular tachycardia was again inducible after administration of a higher dose of procainamide. In conclusion, during electropharmacologic testing with procainamide, it is worthwhile to test a dose of 7.5 mg/kg, because this dose is often effective in patients who respond to this drug. However, the results of this study indicate that procainamide may be effective in suppressing the induction of sustained ventricular tachycardia at a relatively low plasma concentration, but not at a higher plasma concentration. Therefore, during long-term therapy with procainamide it may be important to avoid plasma procainamide concentrations not only lower, but also higher than the concentration that results in the suppression of induction of tachycardia.

Amiodarone versus amiodarone and a type IA agent for treatment of patients with rapid ventricular tachycardia

Induction of rapid ventricular tachycardia or fibrillation during therapy with amiodarone is associated with an increased risk of sudden death. To determine whether the addition of a type IA antiarrhythmic agent to therapy would improve outcome, 37 patients in whom ventricular tachyarrhythmia of a cycle length less than 350 msec was induced after 14 +/- 2 days of amiodarone were randomly assigned to therapy with amiodarone alone (group 1, 20 patients) or amiodarone plus type IA agent (group 2, 17 patients). Type IA therapy consisted of procainamide in 13 patients and quinidine in four procainamide-intolerant patients. To assess the short-term effects of a type IA agent on inducibility of ventricular tachyarrhythmia, cycle length, and hemodynamic tolerance, 16 of 20 patients in group 1 and all patients in group 2 underwent repeat programmed stimulation after the intravenous administration of procainamide during amiodarone therapy (mean procainamide serum concentration 7.2 +/- 2.0 micrograms/ml). Procainamide prevented induction of sustained arrhythmia in only two of 33 patients. Procainamide increased the cycle length of induced ventricular tachycardia from 283 +/- 30 to 352 +/- 46 msec (p less than .001). After the addition of procainamide, 16 of 31 patients vs 10 of 37 patients on amiodarone alone had an induced arrhythmia that was tolerated hemodynamically (p less than .05). There were no differences between groups 1 and 2 with respect to patient or arrhythmia characteristics, response to short-term procainamide, or duration of follow-up. The mean follow-up for all patients was 14 +/- 10 months.(ABSTRACT TRUNCATED AT 250 WORDS)

Clinical electrophysiology, efficacy and safety of chronic oral cibenzoline therapy in refractory ventricular tachycardia

The electrocardiographic (ECG) and electrophysiologic (EP) effects, clinical efficacy and safety of oral cibenzoline therapy were evaluated using a twice-daily dosing regimen in patients with refractory ventricular tachycardia (VT). Twenty patients underwent EP studies in the control (drug-free) state and after cibenzoline therapy using an incremental dose-titration protocol. Oral cibenzoline (2.4 to 5.8 mg/kg/day) was administered in doses of 130, 160 or 190 mg at 12-hour intervals. ECG and EP variables, 24-hour ambulatory ECG monitoring and programmed electrical stimulation studies were obtained in the control state and after 11 +/- 4 days of cibenzoline therapy. Cibenzoline therapy prolonged the mean PR interval (from 179 +/- 29 to 201 +/- 36 ms, p less than 0.001), the mean QRS duration (from 107 +/- 21 to 130 +/- 25 ms, p less than 0.001), and the mean QTc interval (from 422 +/- 25 to 460 +/- 42 ms, p less than 0.001). It increased the mean HV interval (from 50 +/- 17 to 65 +/- 20 ms, p less than 0.01) and mean right ventricular effective refractory period (from 245 +/- 24 to 266 +/- 27 ms, p less than 0.01). After cibenzoline therapy, 5 patients (25%) had suppression of inducible sustained VT during programmed electrical stimulation. High-degree atrioventricular block occurred in 2 patients. Chronic cibenzoline therapy (mean follow-up 24 +/- 3 months) remained effective in long-term suppression of VT in 4 patients. Two patients had to discontinue therapy because of gastrointestinal intolerance. Cibenzoline is effective in suppression of refractory VT in selected patients using a twice-daily dosing schedule.

Antiarrhythmic drug efficacy at electrophysiology testing: predictive effectiveness of procainamide and flecainide

In an effort to assess the ability of procainamide to predict effectiveness of antiarrhythmic agents at programmed electrical stimulation (PES) testing, we compared the result of procainamide at PES testing with that of all of the other agents studied. One hundred fifty-three patients underwent PES studies because of either sustained or nonsustained ventricular tachycardia (VT). Procainamide prevented VT induction in 79 of 153 patients. Seventy-four of the remaining 153 were inducible for VT on procainamide, with 55 of these being protected by another antiarrhythmic agent (p less than 0.001). If procainamide failed to prevent VT induction, other conventional and experimental agents were equally as likely to be effective in preventing VT induction. Analysis of flecainide acetate as a predictor of efficacy was also evaluated. Fifty-five patients received flecainide and 29 of these were protected at PES testing; 26 of these patients were also protected with another agent. When VT was inducible in patients who received flecainide, 15 of these 26 patients were protected by another agent, either conventional or experimental (p less than 0.01). Thus, if procainamide or flecainide prevented VT induction they accurately predicted effectiveness of other drugs; however, when they did not prevent VT induction, they served as a poor predictor of the possible effectiveness of other drugs. Serial drug testing at PES studies with multiple conventional and experimental drugs increases the likelihood of finding an effective antiarrhythmic agent.

Electropharmacologic testing in sustained ventricular tachycardia associated with coronary heart disease: value of the response to intravenous procainamide in predicting the response to oral procainamide and oral quinidine treatment

Twenty patients with inducible, sustained ventricular tachycardia (VT) were prospectively evaluated to determine whether the response to intravenous procainamide administration, as assessed by programmed ventricular stimulation, predicted the response to oral procainamide and oral quinidine treatment. Six patients (30%) responded to intravenous procainamide (fewer than 10 beats of inducible VT). Ten of 20 patients (50%) responded to oral quinidine and 5 (25%) responded to oral procainamide. Mean drug serum levels were 11.3 +/- 2.1 micrograms/ml for intravenous procainamide, 5.4 +/- 0.8 micrograms/ml for oral quinidine and 11.7 +/- 3.4 micrograms/ml for oral procainamide. There was no significant difference in serum levels between those who responded and those who did not. Fifteen patients (75%) had a concordant drug response for intravenous and oral procainamide. Ten patients (50%) had a concordant response for intravenous procainamide and oral quinidine. Fifteen patients (75%) had a concordant drug response for oral procainamide and oral quinidine. Thus, in patients with sustained VT, the response to intravenous procainamide does not reliably predict the response to oral quinidine or oral procainamide, and serial day drug testing with these agents is necessary. Furthermore, high-dose quinidine therapy may be more effective in controlling VT in these patients than procainamide.

Efficacy of combination therapy with mexiletine and a type IA agent for inducible ventricular tachyarrhythmias secondary to coronary artery disease

The efficacy of combination therapy using a type IA agent (quinidine or procainamide) and a type IB agent (mexiletine) in suppressing inducible sustained ventricular tachyarrhythmias was studied in 23 patients undergoing serial drug testing with programmed stimulation. All patients had coronary artery disease (CAD) with previous myocardial infarction and abnormal left ventricular function (mean ejection fraction 35%). Fifty-five percent of the patients presented with syncope or cardiac arrest. In 19 patients therapy had failed during empiric trials of 1 to 3 antiarrhythmic agents. All 23 patients had inducible sustained ventricular tachyarrhythmias (18 had uniform morphology sustained ventricular tachycardia (VT) and 5 had ventricular fibrillation [VF]) during control electrophysiologic study, and therapy had failed with a type IA agent and mexiletine alone. The combination therapy of mexiletine and the type IA agent prevented induction of any ventricular tachyarrhythmias in 8 of 23 patients. In 15 patients, the combination significantly prolonged the tachycardia cycle length and reduced the symptoms associated with the induced arrhythmia. Patients more likely to respond to the combination had shorter cycle lengths and polymorphic configuration of the control-induced arrhythmia. The increased efficacy of the combination therapy could not be attributed to higher plasma drug levels for the combination, as there was no significant difference in plasma levels for each drug when given alone or in combination. Thus, the increased efficacy most likely reflects a synergistic electropharmacologic effect of the 2 agents.(ABSTRACT TRUNCATED AT 250 WORDS)

Limitations of failure of procainamide during electrophysiologic testing to predict response to other medical therapy

To determine whether failure of procainamide to prevent initiation of ventricular tachyarrhythmias during electrophysiologic testing predicted failure of other antiarrhythmic regimens, 81 consecutive patients with coronary artery disease whose ventricular tachyarrhythmias remained inducible during procainamide administration were studied. Overall, 26 (12%) of 216 subsequent drug studies were successful and at least one effective drug regimen was identified in 22 (27%) of the 81 patients. Drug success was significantly related to the arrhythmia induced at baseline study; 7% of drug studies were successful in patients with sustained ventricular tachycardia, 24% in patients with ventricular fibrillation, and 29% in patients with nonsustained ventricular tachycardia. An effective drug regimen was found in 11 (19%) of 59 patients with sustained ventricular tachycardia, 4 (50%) of 8 patients with ventricular fibrillation and 7 (50%) of 14 patients with nonsustained ventricular tachycardia. In patients with sustained ventricular tachycardia, failure of procainamide to suppress the arrhythmia correlated with failure of other agents used singly but not in combination. This study supports the view that when procainamide fails to prevent initiation of the arrhythmia in patients with inducible sustained ventricular tachycardia it is unlikely that other individual standard agents will be effective. However, combination regimens may suppress the arrhythmia and should be evaluated. In patients with nonsustained ventricular tachycardia, all agents should be evaluated because failure to respond to procainamide does not predict subsequent responses to other agents either alone or in combination.

Concentration-dependent clearance of procainamide in normal subjects

Four normal volunteers each received two intravenous doses of PA. The mean low dose was 3.30 mg kg-1 (infused over 20 minutes) while the mean high dose was 12.5 mg kg-1 (infused over 60 minutes). Blood samples were collected for 12 hours and urine was collected for 48 hours after each dose. PA concentrations were determined by both HPLC and fluorescent immunoassay methods. The reported concentrations and pharmacokinetic parameters are from the HPLC data unless otherwise indicated. The mean peak serum PA concentrations resulting from the low and high doses were 3.18 and 9.07 micrograms ml-1, respectively. Total PA clearance averaged 763 ml min-1 and 577 ml min-1 while renal clearance averaged 360 ml min-1 and 318 ml min-1 after the low and high doses, respectively. Concentration-dependent decreases in nonrenal PA clearance ranged from 31 to 43 percent (p less than 0.05) in the four subjects. Total clearance decreases ranged from 4.7 to 36 per cent (p less than 0.05). Differences between doses in renal clearance, elimination rate constant, and volume of distribution were not statistically significant. This study demonstrates that the nonrenal and total clearances of PA are concentration-dependent in normal subjects at therapeutic plasma PA concentrations and suggests that the total clearance changes are of sufficient magnitude to be clinically important.

Ventricular arrhythmias in severe heart failure: incidence, significance, and effectiveness of antiarrhythmic therapy

Forty-three patients receiving maximal medical therapy for severe chronic heart failure from dilated cardiomyopathies (28 ischemic, 15 idiopathic) and ventricular premature beats (VPBs) on the 12-lead ECG had baseline 24-hour ambulatory ECG monitoring. Complex VPBs (multiform, repetitive--couplets, R on T phenomenon) and asymptomatic, nonsustained ventricular tachycardia were present in 38 patients (88%) and 22 patients (51%), respectively. Twenty-three patients (group I) were placed on long-term antiarrhythmic therapy (20 patients received procainamide and the remaining quinidine). Twenty patients (group II) did not receive antiarrhythmic therapy. At baseline, no significant differences between the two groups were noted for age, functional class, type of cardiomyopathy, medical therapy for heart failure, cardiothoracic ratio, radionuclide ejection fraction, or rate and complexity of the ventricular arrhythmias on the 24-hour ambulatory ECG tracings. At a mean follow-up period of 16 months (range 1 to 37), there were 16 deaths, 10 (62%) of which were sudden and unexpected. No significant differences in the incidence of sudden death and overall mortality were noted between the two groups. Among patients with nonsustained ventricular tachycardia, those who died suddenly had a lower mean left ventricular ejection fraction (0.15 +/- 0.01) when compared to the survivors (0.23 +/- 0.02; p less than 0.01). It is concluded that patients with severe heart failure have a high mortality from both sudden and nonsudden cardiac death, incidence of complex VPBs is very high, sudden death is more common when the left ventricular function is severely compromised, and apparently, therapeutic plasma levels of conventional antiarrhythmic drugs do not protect this group of patients from dying.

The utility of aprindine blood levels in the management of ventricular arrhythmias

Sixty-four patients with a history of ventricular tachycardia and ventricular fibrillation refractory to conventional therapy received aprindine to abolish recurrent episodes of symptomatic ventricular tachycardia. Fifty-six patients became asymptomatic and were followed up for a mean period of 23 months. Aprindine dose was adjusted to minimize adverse reactions but still control arrhythmia. Survival analysis was performed for the group with aprindine levels greater than 1.5 micrograms/ml and the group with levels of 1.5 micrograms/ml or less. At the end of the study, 65% of the patients with a high level were alive and asymptomatic as compared with only 35% of the patients with a low level (p less than 0.036). In patients at risk of recurrent sudden cardiac death, high aprindine levels maintained after abolition of symptomatic ventricular tachycardia were associated with improved survival.

Intravenous quinidine: relations among concentration, tachyarrhythmia suppression and electrophysiologic actions with inducible sustained ventricular tachycardia

A computer simulation was used to devise quinidine sulfate infusions to produce pseudo-steady-state concentrations in the low (8 microM/liter) and high (14 microM/liter) therapeutic ranges, avoiding high peak concentrations. Using this infusion, efficacy and electrophysiologic actions of quinidine sulfate were assessed in 21 patients with sustained inducible ventricular tachycardia (VT) when concentrations were 12.6 +/- 11 microM/liter (mean +/- standard deviation) and 18 +/- 9 microM/liter. Although mean concentrations approximated target levels, there was substantial individual variation. A reciprocal linear relation (r = 0.8, p less than 0.01) was noted between resultant serum concentrations and drug-free ejection fraction (EF). Transient hypotension occurred early in 3 patients, 2 of whom had a normal left ventricular (LV) EF. No hemodynamic compromise was seen in patients with LVEFs of less than 30%. Induced VT was suppressed in 5 patients at low concentrations and in an additional 4 at high concentrations (total 9 of 21, 42%). Concentration-dependent changes in the ventricular effective refractory period of the beat induced by S3 paralleled antiarrhythmic efficacy. Independent of response or lack of response to intravenous quinidine, 17 patients received gradually increasing oral quinidine dosages adjusted to reproduce plasma levels that had been effective during intravenous administration, or to maximal well-tolerated dosage (if side effects occurred). VT was still inducible during oral treatment in 4 of 5 patients in whom VT had been suppressed during the intravenous infusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparative electrophysiologic effects of intravenous and oral procainamide in patients with sustained ventricular arrhythmias

Thirty-three patients with sustained ventricular arrhythmias underwent electrophysiologic testing after intravenous and again after oral procainamide administration. Two groups were identified: group 1 included 15 patients with concordant serum procainamide concentrations with less than a 3 micrograms/ml difference after intravenous (mean 8.6 +/- 2.7) and oral (mean 8.8 +/- 2.7) procainamide administration, with mean N-acetylprocainamide concentrations of 1.0 +/- 0.6 and 6.2 +/- 2.8 micrograms/ml, respectively. Group 2 included 18 patients with discordant serum procainamide concentrations after intravenous (mean 9.5 +/- 5.9 micrograms/ml) and oral (mean 14.1 +/- 5.2 micrograms/ml) procainamide, with mean N-acetylprocainamide concentrations of 0.9 +/- 0.5 and 10.7 +/- 5.7 micrograms/ml, respectively. In group 1, response to programmed stimulation was the same after intravenous and oral procainamide administration, with no inducible ventricular arrhythmia in 5 of 15 patients. In group 2, 3 of 18 patients had no inducible arrhythmia after intravenous compared with 7 of 18 patients after oral procainamide administration. There was a different response to programmed stimulation after oral compared with intravenous procainamide in 6 of 18 patients in group 2 but in none of 15 patients in group 1 (p = 0.02). The effective procainamide concentration was greater than the ineffective concentration in five of the six patients with a discordant response, and the effective route of administration was oral in five of the six patients. The change in ventricular refractoriness in group 1 was similar after intravenous (28 +/- 23 ms) and oral (29 +/- 19 ms) procainamide, whereas in group 2, refractoriness was increased more after oral (33 +/- 21 ms) than intravenous (20 +/- 17 ms) procainamide administration and paralleled the difference in procainamide concentration.(ABSTRACT TRUNCATED AT 250 WORDS)

Procainamide: clinical pharmacology and efficacy against ventricular arrhythmias

Procainamide (PA) has been a mainstay of treatment against acute and chronic supraventricular and ventricular arrhythmias for more than 30 years. PA's clinical pharmacology has been studied extensively and its bioavailability (75-95%); volume of distribution (1.5-2.5 liters per kg), plasma protein-binding (15-25%), half-time for elimination (3-7 hours), and metabolism are known. PA's efficacy against acute ventricular arrhythmias and chronic stable VPDs is associated with plasma drug concentrations of 4 to 10 micrograms per ml; but much higher plasma concentrations may be required against sustained ventricular arrhythmias. From 30 to 60% of a PA dose is excreted as the metabolite, N-acetylprocainamide (NAPA), and PA's metabolism is determined genetically (fast or slow acetylation phenotype). Studies in patients with VPDs indicate that NAPA is also antiarrhythmic, although the contribution of NAPA to the antiarrhythmic effect after PA is not known. Studies in patients with the systemic lupus-like syndrome from PA show that NAPA is not associated with this. Investigations comparing efficacy and adverse effects of PA with those of new antiarrhythmic agents available for clinical trials are indicated in the future.

Therapy with conventional antiarrhythmic drugs for ventricular arrhythmias

Conventional antiarrhythmic drugs are an important tool for the clinical cardiologist for the treatment of ventricular arrhythmias. Knowledge of the different properties of these drugs will help decrease the incidence of adverse effects and increase the frequency of successful therapy.