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Bifunctional agents for reperfusion arrhythmias: novel hybrid vitamin E/class I antiarrhythmics.

We have synthesized a series of hybrid compounds combining the pharmacophoric redox moieties of vitamin E and key features responsible for the antiarrhythmic properties of the class I antiarrhythmics procainamide and lidocaine. Procainamide analogue (2a) and lidocaine analogues (14a) and (14b) are very strong inhibitors of lipid peroxidation. All analogues tested at 100 or 30 microM enhanced the post ischemic recovery without inducing ventricular fibrillations while there was no evidence in our experiments for drug-induced pro-arrhythmia. In addition, they induced a widening of the QRS intervals. Our data suggest that the efficacy of the new compounds in preventing reperfusion arrhythmias could be attributed to their combined effects involving inhibition of free radical mediated damage coupled with antiarrhythmic properties.

Anti-Arrhythmia Agents↗

Comparison of cocaine and Na+ channel blockers on cardio-respiratory function in the rabbit.

The cardio-respiratory effects of cocaine were compared to various Na+ channel blocking Class I antiarrhythmics. Anesthetized rabbits were treated with various doses of either cocaine, quinidine, procainamide, lidocaine or flecainide. Cocaine produced clear decreases in blood pressure and heart rate. None of the other sodium channel blockers produced any change in blood pressure, and heart rate was decreased only slightly by procainamide and lidocaine. Cocaine produced larger increases in QRS duration than were observed for the four sodium channel blockers. All five drugs produced comparable increases in respiratory rate. Separate rabbits were pretreated with either the alpha-adrenoceptor antagonist phentolamine or the beta-adrenoceptor antagonist propranolol prior to cocaine. Phentolamine attenuated the blood pressure decrease following cocaine and propranolol attenuated the heart rate decrease following cocaine. These results suggest that the sodium channel blocking properties contribute only minimally to the overall effects of cocaine on blood pressure and heart rate. Further, the large effect of cocaine on QRS duration suggests that cocaine may act at sodium channels in a manner different from the other drugs. This unique effect of cocaine may contribute to the sudden death associated with cocaine use in some individuals.

Animals↗

Liquid chromatography in the monitoring of plasma levels of antiarrhythmic drugs.

High-performance liquid chromatography has been employed in the development of assay methods for six antiarrhythmic drugs, disopyramide, lidocain, tocainide, procainamide, aprinidine and quinidine. Liquid-solid chromatography has been used and separation times of about 5 min have usually been sufficient. Owing to the capacity of the liquid chromatographic system, sample preparation has been minimized to a single extraction and direct injection of a considerable part of the extract. The overall time of analysis is very short and the methods are well suited for monitoring of plasma levels of the antirrhythmic drugs and in some instances (procainamide and disopyramide) also for their main metabolites. UV detection at the optimal wavelength has permitted determinations down to 50 pmole (20 ng) in 1 ml of plasma for the amines with high absorbance.

Anilides↗

Effects of magnesium and potassium on Wolff-Parkinson-White syndrome.

To investigate the effects of electrolytes on anterograde conduction via accessory pathways, 12 patients with Wolff-Parkinson-White syndrome received, while in sinus rhythm, intravenous KCl (7 mEq in 200 mL of 0.9% NaCl), MgSO4 (10 mL 20% in 200 mL of 0.9% NaCl), NaCl (0.9%, 200 mL), and procainamide (maximal dose, 10 mg/kg of body weight over a 5-minute period) in a randomized fashion. NaCl had no effect on preexcitation. Procainamide abolished preexcitation in seven patients, of whom five had a similar response with MgSO4 and four with KCl. The finding that potassium and magnesium transiently abolish preexcitation in some Wolff-Parkinson-White patients deserves further study, especially during tachyarrhythmias in patients with accessory pathways.

Adolescent↗

Effects of antiarrhythmic drugs on variability of ventricular rate and exercise performance in chronic atrial fibrillation complicated with ventricular arrhythmias.

For conversion of atrial fibrillation to sinus rhythm and management of ventricular arrhythmias, antiarrhythmic drugs were frequently used. However, the effects of antiarrhythmic drugs on exercise performance and on the variability of ventricular rate were not available. This study included 37 patients who had chronic atrial fibrillation complicated with symptomatic ventricular arrhythmias. The patients were divided into three groups and received sotalol, propafenone, and procainamide, respectively. Before and after taking the drugs for 14 days, these patients received treadmill exercise test, 24 h Holter electrocardiogram, and tilt table test for evaluation of the exercise performance and the variability of ventricular rate (including the mean RR intervals, mRR, the standard deviation of RR intervals, SDRR, and the root mean square of the difference in successive RR intervals, rMSSD). All these antiarrhythmic drugs could suppress ventricular arrhythmia but only sotalol could significantly increase the exercise duration (374+/-50 to 476+/-55 s, P=0.02), and reduce the maximal heart rate (186+/-23 to 136+/-16 beats/min, P=0.01) during exercise test. Furthermore, only sotalol increased the mRR (777+/-60 to 885+/-66 ms, P=0.02), SDRR (190+/-40 to 216+/-48 ms, P=0.04) and rMSSD (223+/-48 to 253+/-40 ms, P=0.03) during 24 h Holter electrocardiogram. With head-up tilt, the mRR, SDRR and rMSSD all decreased significantly before drug therapy, and these changes were still present only after propafenone therapy. Therefore, comparisons among sotalol, propafenone and procainamide showed that sotalol increased the exercise performance and the variability of ventricular rate in patients who had chronic atrial fibrillation complicated with symptomatic ventricular arrhythmias.

Aged↗

Electrophysiologic characterization and postnatal development of ventricular pre-excitation in a mouse model of cardiac hypertrophy and Wolff-Parkinson-White syndrome.

OBJECTIVES: We sought to characterize an animal model of the Wolff-Parkinson-White (WPW) syndrome to help elucidate the mechanisms of accessory pathway formation. BACKGROUND: Patients with mutations in PRKAG2 manifest cardiac hypertrophy and ventricular pre-excitation; however, the mechanisms underlying the development and conduction of accessory pathways remain unknown. METHODS: We created transgenic mice overexpressing either the Asn488Ile mutant (TG(N488I)) or wild-type (TG(WT)) human PRKAG2 complementary deoxyribonucleic acid under a cardiac-specific promoter. Both groups of transgenic mice underwent intracardiac electrophysiologic, electrocardiographic (ECG), and histologic analyses. RESULTS: On the ECG, approximately 50% of TG(N488I) mice displayed sinus bradycardia and features suggestive of pre-excitation, not seen in TG(WT) mice. The electrophysiologic studies revealed a distinct atrioventricular (AV) connection apart from the AV node, using programmed stimulation. In TG(N488I) mice with pre-excitation, procainamide blocked bypass tract conduction, whereas adenosine infusion caused AV block in TG(WT) mice but not TG(N488I) mice with pre-excitation. Serial ECGs in 16 mice pups revealed no differences at birth. After one week, two of eight TG(N488I) pups had ECG features of pre-excitation, increasing to seven of eight pups by week 4. By nine weeks, one TG(N488I) mouse with WPW syndrome lost this phenotype, whereas TG(WT) pups never developed pre-excitation. Histologic investigation revealed postnatal development of myocardial connections through the annulus fibrosum of the AV valves in young TG(N488I) but not TG(WT) mice. CONCLUSIONS: Transgenic mice overexpressing the Asn488Ile PRKAG2 mutation recapitulate an electrophysiologic phenotype similar to humans with this mutation. This includes procainamide-sensitive, adenosine-resistant accessory pathways induced in postnatal life that may rarely disappear later in life.

AMP-Activated Protein Kinases↗

Proarrhythmic effects of antiarrhythmic drugs during programmed ventricular stimulation in patients without ventricular tachycardia.

The proarrhythmic effects of class IA antiarrhythmic drugs were prospectively evaluated during programmed ventricular stimulation in 24 consecutive patients with frequent ventricular premature beats whose baseline study, performed while no antiarrhythmic drugs were being taken, showed no inducible sustained ventricular arrhythmias. No patient had nonsustained (greater than 5 beats) or sustained ventricular tachycardia by history or baseline 24 hour ambulatory electrocardiographic monitoring. Sequential stimulation studies using up to three extra-stimuli were performed after administration of procainamide, quinidine and disopyramide on different days. Proarrhythmic response was defined as induction of one or more of the following: sustained monomorphic ventricular tachycardia; sustained polymorphic ventricular tachycardia; ventricular fibrillation; reproducibly inducible nonsustained monomorphic ventricular tachycardia. During 55 antiarrhythmic drug trials (24 of procainamide, 21 of quinidine, 10 of disopyramide) in the 24 patients, 6 patients had a proarrhythmic response: sustained monomorphic ventricular tachycardia in 3, ventricular fibrillation in 2, nonsustained monomorphic ventricular tachycardia in 1. Thus, 11% of drug trials resulted in a proarrhythmic response and 25% of patients had a proarrhythmic response to one of the drugs tested. A proarrhythmic response to one drug did not predict a similar response to another drug of the same class. The 6 patients with a proarrhythmic response did not differ significantly from the other 18 patients with regard to underlying heart disease, electrocardiographic or baseline 24 hour ambulatory electrocardiographic characteristics; however, they did have a higher incidence of digoxin usage (p less than 0.02), a shorter baseline right ventricular effective refractory period (p less than 0.01) and a smaller increment in effective refractory period during antiarrhythmic drug testing (p = 0.06).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

Metabolite formation pharmacokinetics: rate and extent of metabolite formation determined by deconvolution.

A two-step analytic procedure to determine the rate and extent of metabolite production following administration of the parent compound is described. The procedure provides the rate and extent of metabolite production as a function of time by application of the general model independent approach of deconvolution. The metabolite unit impulse response function is obtained by implicit deconvolution of the metabolite data with a truncated constant-rate metabolite input function. Then the obtained unit impulse response function is used in an analytic deconvolution with metabolite data following administration of the parent compound to obtain the rate and extent of metabolite production. The input function is also deconvolved with metabolite data to obtain the unit impulse response function appropriate for prediction of metabolite levels given a selected input of parent compound. The expected profile following administration of the consecutive infusions of parent drug is shown for both parent and metabolite. The rationale for selection of deconvolution methods is discussed. The approach is applied to data for procainamide and N-acetylprocainamide from three human subjects. The results indicate that from 27 to 39% of the procainamide was converted to N-acetylprocainamide in these subjects.

Acecainide↗

Efficacy and safety of N-acetylprocainamide in long-term treatment of ventricular arrhythmias.

Four patients with chronic ventricular arrhythmias, shown to respond over the short term to N-acetylprocainamide (NAPA), were treated for between 3 and 4 yr with NAPA, and 24-hr ambulatory ECGs were obtained monthly to monitor their responses. When the patients were ambulatory and receiving NAPA, the mean frequency of premature ventricular complexes averaged 70% (range 60% to 82%) below that recorded at 6-mo intervals when the patients were hospitalized and receiving placebo. Analysis of variance showed that NAPA exerted an antiarrhythmic effect in these patients and that tolerance to this effect did not develop with long-term therapy. Plasma NAPA concentrations required to achieve this level of response averaged 21 micrograms/ml (12 to 35 micrograms/ml) and were roughly twice as high as those which appeared to be maximally effective when the patients were hospitalized for their initial evaluation. NAPA therapy was associated with positive antibody titers in only one patient and seems less prone to cause drug-induced lupus erythematosus than procainamide, but NAPA shares the gastrointestinal and other side effects of procainamide.

Acecainide↗

N-substituted benzamides inhibit NFkappaB activation and induce apoptosis by separate mechanisms.

Benzamides have been in clinical use for many years in treatment against various disorders. A recent application is that as a sensitizer for radio- or chemotherapies. We have here analysed the mechanism of action of N-substituted benzamides using an in vitro system. We found that while procainamide was biologically inert in our system, the addition of a chloride in the 3' position of the benzamide ring created a compound (declopramide) that induced rapid apoptosis. Furthermore, declopramide also inhibited NFkappaB activation by inhibition of IkappaBbeta breakdown. An acetylated variant of declopramide, N-acetyl declopramide, showed no effect with regard to rapid apoptosis induction but was a potent inhibitor of NFkappaB activation. In fact, the addition of an acetyl group to procainamide in the 4' position was sufficient to convert this biologically inactive substance to a potent inhibitor of NFkappaB activation. These findings suggest two potential mechanisms, induction of early apoptosis and inhibition of NFkappaB mediated salvage from apoptosis, for the biological effect of N-substituted benzamides as radio- and chemo-sensitizers. In addition it suggests that N-substituted benzamides are potential candidates for the development of anti-inflammatory compounds using NFkappaB as a drug target.

Apoptosis↗

Intravenous administration of class I antiarrhythmic drugs induced T wave alternans in a patient with Brugada syndrome.

A 71-year-old man who experienced aborted sudden death was referred to our hospital. Coronary artery disease and cerebral accident were ruled out by conventional tests. The 12-lead ECG obtained at rest showed a right bundle branch block pattern and ST segment elevation in leads V1 to V3. Double ventricular extrastimuli at coupling intervals >180 msec induced ventricular fibrillation (VF) twice during electrophysiologic study. Intravenous administration of procainamide accentuated ST segment elevation in leads V1 to V3, and visible T wave alternans was induced in leads V2 and V3 at a dose of 450 mg. Initiation of T wave alternans was not associated with changes of the cardiac cycle or development of premature beats. When procainamide infusion was discontinued, T wave alternans disappeared before the elevated ST segment returned to the control level. Pilsicainide also accentuated ST segment elevation and induced similar T wave alternans in leads V2 and V3. Class I antiarrhythmic drug-related T wave alternans has been reported rarely in Brugada syndrome, but it may represent enhanced arrhythmogenicity of VF. We need to monitor closely and study the clinical implications of T wave alternans in Brugada syndrome.

Aged↗

Propylene glycol as a vehicle for percutaneous absorption of therapeutic agents.

Propylene glycol (PG) was evaluated as a vehicle for the in vivo percutaneous absorption of the hydrochloride salts of desipramine, nortriptyline, procainamide, and N-acetyl-procainamide. Each drug was administered topically to hairless (hr-1/hr-1) mice in water and in aqueous 10% and 50% PG. Mean drug concentrations in blood, brain, heart, liver, and lung were measured by high-pressure liquid chromatography after either two or three hours of topical absorption. The presence of PG generally enhanced the absorption of each drug, and the degree of enhancement appeared to be related to the percentage of PG in the dosing solution.

Acecainide↗

Lack of effect of amitriptyline in murine myotonia.

Amitriptyline, a tricyclic antidepressant, has been reported to diminish signs of human myotonic muscular dystrophy, but has not been examined in other myotonias. Normal and myotonic (ADRmto) mice were injected acutely with either amitriptyline, phenytoin, procainamide or 0.9% saline. In addition, two groups of myotonic mice were injected chronically with either 0.9% saline or amitriptyline for 28 days. Behavior, assessed before injection using a "drop test," was re-evaluated at 30-min intervals for up to 180 min postinjection, as well as at the end of the 28-day chronic trial. If improvement in behavior was noted, the mice were then evaluated with insertional needle electromyography (EMG) and in vitro contractility (maximal tetanic tension and relaxation time) studies. Neither acute nor chronic amitriptyline administration had any beneficial effect on behavior, EMG or contractile parameters in myotonic mice. Phenytoin abolished abnormal EMG activity and improved behavior. Procainamide improved behavior and contractility parameters but had no effect on EMG. These results confirm that the myotonic mouse is responsive to classic antimyotonic agents, but not to amitriptyline.

Amitriptyline↗

Frequency-dependent effects of several class I antiarrhythmic drugs on Vmax of action potential upstroke in canine cardiac Purkinje fibers.

Vmax of the action potential upstroke in canine cardiac Purkinje fibers was studied in the presence of seven class I antiarrhythmic drugs--lidocaine (4 micrograms/ml), mexiletine (4 micrograms/ml), propranolol (0.9 micrograms/ml), procainamide (30 micrograms/ml), quinidine (5 micrograms/ml), flecainide (4 micrograms/ml), and disopyramide (3.1 micrograms/ml)--at constant cycle lengths (CCL) and after abrupt changes in cycle length (ACCL). The time constant of Vmax recovery after ACCL at a basic cycle length of 500 ms was 0.09 +/- 0.01 s for lidocaine, 0.18 +/- 0.03 s for mexiletine, 1.35 +/- 0.20 s for propranolol, 4.4 +/- 0.8 s for procainamide, 8.3 +/- 1.2 s for quinidine, 11.0 +/- 0.9 s for flecainide, and 37.9 +/- 9.4 s for disopyramide. These values were similar to those reported by others in guinea pig papillary muscle, and, with the exception of flecainide, conformed to the scheme proposed by Courtney (J Mol Cell Cardiol 1980; 12:1273-86) based on the molecular weight and lipid solubility hypothesis. Each drug altered the Vmax differently at CCL from after ACCL at the same diastolic intervals. The magnitude of these differences and the range of diastolic intervals at which they were present varied among different drugs. These observations explain differences in the drug effects on the Vmax of the regularly and prematurely occurring depolarizations. In the presence of lidocaine and mexiletine, the recovery kinetics of Vmax were not altered by CCL within the 300-1,500-ms range, and the magnitude of Vmax depression was not influenced by action potential duration within the 200-270-ms range.

Action Potentials↗

Double-wave reentry in orthodromic atrioventricular reciprocating tachycardia: paradoxical shortening of the tachycardia cycle length with development of ipsilateral bundle branch block.

INTRODUCTION: Attempts to terminate reentrant tachyarrhythmias by rapid pacing may accelerate the tachycardia. One mechanism for acceleration is double-wave reentry, where two simultaneous wavefronts travel around the same circuit. METHODS AND RESULTS: We report pacing acceleration of AV reciprocating tachycardia (AVRT) due to double-wave reentry in a patient with Wolff-Parkinson-White syndrome. The patient had presented with atrial fibrillation and rapid conduction across a left lateral bypass tract. Intravenous procainamide was given during electrophysiologic study because of incessant atrial fibrillation and restored sinus rhythm. Orthodromic AVRT was induced and attempts to terminate the AVRT with right ventricular pacing initiated two alternate tachycardias, both with a left bundle branch block (LBBB) morphology. The first tachycardia, as expected for bundle branch block ipsilateral to the bypass tract, had a longer cycle length (CL) than the original tachycardia (366 msec compared to 297 msec). The second tachycardia had a paradoxically shorter CL, 238 msec compared to 297 msec. Electrogram analysis revealed that the circuit traversed by the accelerated LBBB tachycardia was the same as the slower LBBB tachycardia. The activation sequence revealed two independent wavefronts, traversing this common circuit. As described previously in experimental models, double-wave reentry was initiated when an antidromic-stimulated impulse blocked before colliding with the previous orthodromic impulse, thus allowing two orthodromic impulses to circulate within the circuit. CONCLUSION: We speculate that conduction slowing by procainamide combined with the intrinsic AV nodal delay resulted in the necessary increase in the excitable gap required to develop double-wave reentry. This is the first description of sustained double-wave reentry in humans.

Adult↗

ST segment elevation in the right precordial leads induced with class IC antiarrhythmic drugs: insight into the mechanism of Brugada syndrome.

We evaluated two patients without previous episodes of syncope who showed characteristic ECG changes similar to Brugada syndrome following administration of Class IC drugs, flecainide and pilsicainide, but not following Class IA drugs. Patient 1 had frequent episodes of paroxysmal atrial fibrillation resistant to Class IA drugs. After treatment with flecainide, the ECG showed a marked ST elevation in leads V2 and V3, and the coved-type configuration of ST segment in lead V2. A signal-averaged ECG showed late potentials that became more prominent after flecainide. Pilsicainide, a Class IC drug, induced the same ST segment elevation as flecainide, but procainamide did not. Patient 2 also had frequent episodes of paroxysmal atrial fibrillation. Pilsicainide changed atrial fibrillation to atrial flutter with 2:1 ventricular response, and the ECG showed right bundle branch block and a marked coved-type ST elevation in leads V1 and V2. After termination of atrial flutter, ST segment elevation in leads V1 and V2 continued. In this patient, procainamide and quinidine did not induce this type of ECG change. In conclusion, strong Na channel blocking drugs induce ST segment elevation similar to Brugada syndrome even in patients without any history of syncope or ventricular fibrillation.

Anti-Arrhythmia Agents↗

A segmental polynomial model of ventricular electrograms as a simple and efficient morphology discriminator for implantable devices.

BACKGROUND: The goal of this study is to construct a polynomial model of the ventricular electrogram (EGM) that faithfully reproduces the EGM and can be implemented in current, low computational power implantable devices. Such a model of ventricular EGMs is still lacking. METHODS: New Zealand White rabbits underwent chronic implantation of pacemakers through a left thoracotomy approach. Unipolar ventricular EGMs sampled at a frequency of 1 kHz were stored digitally in 1-minute segments before and after intravenous injection of isoproterenol or procainamide. Each cardiac cycle was divided into a QR and an RQ segment which were modeled separately using a 6th order polynomial equation. RESULTS: The 14 coefficients of each cardiac cycle were reproducible throughout the baseline recordings (r > or = 0.94, P < 0.002). Isoproterenol caused no changes in the coefficients of the QR segment but significantly altered all but one of the seven coefficients of the RQ segment (p(6)= 0.0039, p(5)= 0.017, p(4)= 0.00007, p(3)= 0.112, p(2)= 0.00016, p(1)= 0.0086, p(a)= 0.00003). Procainamide caused statistically significant changes in both QR segment (p(6)= 0.018, p(5)= 0.287, p(4)= 0.019, p(3)= 0.176, p(2)= 0.016, p(1)= 0.362, p(a)= 0.000044) and RQ segment (p(6)= 0.0028, p(5)= 0.036, p(4)= 0.002, p(3)= 0.058, p(2)= 0.022, p(1)= 0.718, p(a)= 0.0018) coefficients. CONCLUSION: Our data demonstrate the feasibility of a segmental polynomial equation that reproduces the phases of depolarization and repolarization of the rabbit EGM. This model is reproducible and demonstrates the expected changes with antiarrhythmic drug administration. If reproduced in humans, these findings can have wide applications in patients with implantable devices, ranging from morphologic discrimination of arrhythmias to early detection of metabolic derangements or drug effects.

Animals↗

Suppression of ventricular arrhythmias resulting from acute coronary artery ligation in rat by imipramine.

The potential antiarrhythmic activity of imipramine against ventricular arrhythmias induced by coronary artery ligation in rats has been investigated and compared with procainamide. Imipramide (1 and 5 mg/kg-1) or procainamide (5 and 10 mg/kg-1) or solvent were injected intravenously 30 min before ligation. Imipramine reduced the total number of ventricular ectopic beats as well as the incidence and duration of ventricular tachycardia and ventricular fibrillation. The drug did not significantly affect the blood pressure but reduced the heart rate. The antiarrhythmic activity of imipramine is postulated to be due to a quinidine-like effect and/or alpha-adrenergic blocking activity. The study confirms the potential utility of imipramine as an antiarrhythmic drug.

Animals↗