Concordance and discordance of drug responses in atrioventricular reentrant tachycardia

Whether the results of some drug studies could be used to predict the results of other drug studies was examined during serial electrophysiologic drug testing in patients with sustained atrioventricular reentrant tachycardia. The drugs studied were intravenous propranolol, 0.1 mg/kg; intravenous ouabain, 0.01 mg/kg; the combination of propranolol plus ouabain; intravenous procainamide, 0.75 to 1.5 g; oral quinidine, 1.2 to 2.4 g/day; and oral disopyramide, 0.8 to 1.6 g/day. Response was inability to induce sustained tachycardia after administration of a drug. Responses due to increased anterograde limb refractoriness. Six of 10 patients with response to propranolol plus ouabain versus 0 of 9 patients without response to this combination had response to propranolol alone (p less than 0.01). Seven of 14 patients with response to the combination versus 0 of 9 patients without response to the combination had response to ouabain alone (p less than 0.05). Responses due to increased retrograde limb refractoriness. Eight of 9 patients with response to procainamide versus 2 of 17 patients without response to this drug had response to quinidine (p less than 0.01). There was not a significant relation between response to procainamide and response to disopyramide, or between response to quinidine and response to disopyramide. Anterograde limb versus retrograde limb. There was not a significant relation between response to propranolol plus ouabain and response to any class I drug. In conclusion, there are relations between drug responses during electrophysiologic studies in patients with atrioventricular reentrant tachycardia. Thus, it should be possible to simplify these studies.

High-dose procainamide in chronic renal failure

A patient with chronic renal failure who experienced symptomatic ventricular tachycardia was treated successfully with procainamide (PA) after numerous dosage adjustments to optimize his clinical response and serum PA and NAPA concentrations. Efforts to maintain total combined serum levels at 20-30 micrograms/ml led to sustained ventricular ectopy whenever the serum PA levels decreased to less than 8 micrograms/ml.

The prevalence of antibodies to histones induced by procainamide in old people, in cancer patients, and in rheumatoid-like disease

Antibodies to histones were found to be most commonly responsible for the positive antinuclear antibody (ANA) test in asymptomatic patients treated with procainamide, in old people, in patients with neoplastic diseases, and in young women affected with a rheumatoid-like disease. Only in a very few patients were antibodies to dDNA and nucleoproteins demonstrated. Antibodies to nDNA were not found. The antibodies to histones were demonstrated by two methods: absorption of ANA-positive sera with a histone solution and subsequent performance of an ANA test; and acid elution of histones from thyroid sections followed by histone reconstitution.

[Treatment of paroxysmal forms of auricular fibrillation and atrial flutter in a cardiological hospital]

The results of treatment of paroxysmal forms of atrial fibrillation and flutter are analysed in a group of 503 patients with attacks lasting up to 3 weeks. The sinus rhythm was restored in 84.7% of patients, in only 3% of cases was electro-impulse therapy resorted to. In alcohol toxic form of atrial fibrillation and flutter potassium chloride was the most effective drug for restoration of the sinus rhythm in 47.1% of cases, and if used with cardiac glucosides in 64.7%. In atrial fibrillation and flutter of other etiology the method of choice was a combination of quinidine with isoptine either by itself, or after saturation of the body with potassium chloride (85% cases of sinus rhythm restoration).

Serum drug concentrations in patients with ischemic heart disease after administration of a sustained release procainamide preparation

Despite widespread marketing of a sustained release preparation of procainamide hydrochloride (PROCAN-SR, Parke-Davis), published literature demonstrating its efficacy in maintaining uniform serum drug levels over a 6-hour dosing interval is derived from only normal healthy volunteers. Thirty-three patients with ischemic heart disease, ages 30-88 years, were administered 1-4g/24 hours (mean dose 34 mg/kg/day) of PROCAN-SR in 4 equally divided doses on a Q6H schedule. After achievement of steady-state equilibrium drug concentration, procainamide and N-acetylprocainamide levels were determined by high-performance liquid chromatography on sera obtained from blood samples drawn 2, 3.5 and 5 hours after an oral dose. Mean maximal procainamide and N-acetylprocainamide serum concentrations were 4.6 +/- 1.8 microgram/ml and 4.2 +/- 2.1 micrograms/ml respectively. Mean minimal concentrations were 3.5 +/- 1.7 microgram/ml and 3.6 +/- 2.0 micrograms/ml respectively. The mean change in drug concentration was small (1.1 microgram/ml procainamide and 0.6 microgram/ml N-acetylprocainamide) with procainamide and N-acetylprocainamide concentrations varying only by 27 and 15 percent respectively. These data demonstrate in a population of patients with ischemic heart disease, that Q6H dosing with a sustained release procainamide hydrochloride preparation (PROCAN-SR, Parke-Davis) is associated with only a small acceptable variation between maximal and minimal serum procainamide and N-acetylprocainamide concentrations. This preparation should, therefore, offer greater patient convenience and compliance without sacrificing antiarrhythmic efficacy.

Inter- and intraatrial dissociation during spontaneous atrial flutter: evidence for a focal origin of the arrhythmia

Programmed electrical stimulation of the heart was performed in 2 patients with spontaneous atrial flutter. Patient 1 was a young man with paroxysmal atrial flutter that had proved resistant to drug therapy and who was studied during an episode of sustained flutter. In this patient rapid atrial pacing from the coronary sinus at a critical rate faster than the intrinsic flutter rate provoked local atrial fibrillation in the mid and low right atrium which persisted after termination of pacing. In spite of persistent local fibrillation in these regions, atrial flutter continued in the left atrium and the high right atrium. A second burst of pacing resulted in restoration of sinus rhythm. Patient 2 was an elderly woman with probable sick sinus syndrome who developed spontaneous atrial flutter during the course of an electrophysiologic investigation. During flutter intracavitary recordings from multiple sites in the atria revealed a pattern of 3:2 Wenckebach conduction between the left atrium and the high right atrium, with block of every third atrial depolarization at the latter site. These results indicate that atrial flutter may exist at some sites in the atria which are functionally dissociated from the remainder of the atrial tissue, thus supporting the hypothesis that flutter in some patients may be focal in origin.

Long-term intravenous infusion of antiarrhythmic drugs using a totally implanted drug delivery system

In vitro and in vivo testing was performed to establish the feasibility of a totally implantable pump system to deliver antiarrhythmic agents. In vitro flow characteristics suggested predictable day to day delivery with acceptably small variations in flow with changes in reservoir volume or temperature. During 3 months of in vitro testing, procainamide and bretylium were found suitable for long-term delivery. Delivery of lidocaine was limited by high viscosity and corrosion of steel elements within the pump. The pump was implanted in a subcutaneous pocket in four dogs. Procainamide (0.5 g/ml), delivered at 4 ml/day (70 mg/kg body weight per day), provided a mean steady state drug concentration of 5.3 micrograms/ml. Bretylium (50 mg/ml), delivered at 8 ml/day (13 mg/kg per day), provided a steady state concentration of 0.8 micrograms/ml (range 0.4 to 1.4). Long-term intravenous administration of therapeutic doses of bretylium and procainamide with this delivery system has been demonstrated in dogs and appears to be feasible in human subjects.

Evolving concepts of management of stable and potentially lethal arrhythmias

Recent studies indicate that the eradication of premature ventricular complexes (PVCs) by antiarrhythmic agents is an inadequate end point for estimating long-term protection against potentially lethal arrhythmias. In a study of survivors of prehospital ventricular fibrillation (VF), who have a 30% risk for recurrent VF during the first year of follow-up, we observed an apparent protection against recurrent VF by antiarrhythmic agents even if chronic PVCs were not suppressed by stable therapeutic plasma levels. To expand the data base pertinent to the relationships between PVCs and advanced arrhythmias, we studied six patients with chronic recurrent ventricular tachycardia (VT) and frequent PVCs between episodes of VT. Plasma levels of procainamide (PA) required to protect against recurrent VT averaged 9.4 +/- 3.4 microgram ml, compared with mean levels of 14.9 +/- 3.8 microgram/ml for 85% suppression of PVCs (p less than 0.01). PVC frequency decreased by a mean of only 36% (range -11% to -63%) at plasma levels of PA sufficient to prevent spontaneous VT. Concentration-response relationships between (PA) and PVC suppression were also compared in patients with PVCs during acute myocardial infarction and in patients with PVCs in stable chronic ischemic heart disease. In the former group of patients the mean plasma level of PA required to suppress 85% of the PVCs was 5.0 +/- 0.5 microgram/ml, and in the latter group was 9.3 +/- 0.7 microgram/ml (p less than 0.001). We conclude that the relationship between plasma levels of PA and PVC suppression is different in the two groups of patients, and furthermore, that a high degree of PVC suppression may not be a necessary end point for protecting patients against symptomatic recurrent VT or VF.

Drug-polymer combinations. Part 1: The preparation of sustained release drugs by combination with ion exchanging resins

The preparation of procainamide and propranolol resinates is described. By in vivo experiments with propranolol resinate as model substance the release rate as a function of crosslinking degree and particle size is studied. An in vitro test is carried out to compare the performance as prolonged release preparation of a resinate, e.g. procainamide resinate, with the action of the pure drug and of a Durette formulation.

Factors influencing procainamide total body clearance in the immediate postmyocardial infarction period

Fifteen acute myocardial infarction patients (only one of whom had evidence of significant renal dysfunction) received a constant-rate intravenous infusion of procainamide at one rate for a least 24 hours. Steady-state plasma levels achieved during these infusions were used to calculate total body clearance (C/B). Linear regression analysis of C/B versus a variety of clinical and laboratory patient characteristics yielded only body weight (or parameters derived from it) as a significant covariant (r = 0.713, P less than or equal to 0.005). Interestingly, the data from these 15 patients suggest that the presence of a significant degree of heart failure at the start of therapy did not result in a significant decrease in C/B (C/B = 5.9 ml/min/kg when class 0-I failure was present at the start of therapy and C/B = 5.5 ml/min/kg when class III-IV failure was present). If the data from five other patients who were studied previously are added to the group reported here, the conclusions reached would be the same. These data suggest that in patients with good renal and hepatic function, initial procainamide infusion rate could be selected on the basis of body weight and need not consider the initial presence of moderate heart failure. However, intense clinical monitoring for signs of impeding serious toxicity is strongly recommended since the observed regression line did not predict total body clearance accurately in 10-15 per cent of the patients studied.

Serial electrophysiologic testing of multiple drugs in patients with atrioventricular nodal reentrant paroxysmal tachycardia

Serial electrophysiologic testing of multiple drugs was performed in 21 patients with recurrent atrioventricular (AV) nodal reentrant paroxysmal supraventricular tachycardia (PSVT). All patients had reproducible sustained PSVT induced before drug administration. Serial daily PSVT induction was attempted after administration of i.v. ouabain (0.01 mg/kg) (16 patients), i.v. propranolol (0.1 mg/kg (17 patients), i.v. ouabain + propranolol (same dosages) (12 patients), i.v. procainamide (600-1000 mg) (17 patients) and oral quinidine (1600-2400 mg/day) (nine patients). In two of 21 patients (10%), no tested drug prevented induction of sustained PSVT. In 19 of 21 patients (90%), one or more drugs prevented induction of sustained PSVT: ouabain--seven patients, propranolol--seven patients, ouabain + propranolol--seven patients, procainamide--11 patients, quinidine--seven patients. The site of action of ouabain and/or propranolol was either the antegrade limb or the retrograde limb (RL) of the circus movement. The site of action of procainamide or quinidine was always the RL. These 19 patients were treated with oral drugs, based on results of serial testing. Eighteen patients were successfully followed for 6-50 months. In 13 of these 18 patients PSVT did not recur. Two patients (11%) had > 95% reduction in frequency of PSVT recurrences, and three (17%) did not respond to chosen oral drugs. Serial electrophysiologic testing of multiple drugs is feasible in patients with AV nodal reentrant paroxysmal tachycardia. Drug responses are variable. In most but not all patients, serial electrophysiologic testing defines effective prophylactic drug therapy. This method of defining prophylactic drug therapy appears most suitable for patients with poorly tolerated tachycardias that occur only sporadically.

Efficacy of intravenous procainamide infusion in converting atrial fibrillation to sinus rhythm. Relation to left atrial size

The efficacy of intravenous procainamide, infused at 30 mg/min to a maximum dose of 20 mg/kg, in converting atrial fibrillation was evaluated under electrocardiographic and blood pressure control in 21 patients. Nine patients had atherosclerotic heart disease, seven had valvular lesions, five had hypertension, and six had no apparent heart disease. Nine patients (converters), who reverted to sinus rhythm at a mean dose of procainamide of 13.3 +/- 3.6 mg/kg (mean plasma concentration, 7.4 +/- 3.9 micrograms/ml) had normal echocardiographic left atrial diameters. All but one of the remainder, the 12 non-converters, who received a mean drug dose of 13.1 +/- 3.5 mg/kg (mean plasma concentration 13.9 +/- 7.6 micrograms/ml), had atrial diameters exceeding 4.0 cm. QRS and QTc intervals were not altered significantly in converters, but were prolonged significantly in non-converters. No serious side effects from the infusion were encountered. Intravenous procainamide infusion appears to be a safe and rapidly effective method of converting recent-onset atrial fibrillation to sinus rhythm in patients with normal left atrial dimensions.

[Steady-state plasma and saliva concentrations of procainamide and N-acetyl-procainamide after a sustained release preparation]

With ordinary procainamide tablets a dosing interval of 3-4 hours must be chosen to achieve therapeutically useful plasma concentrations during the entire interval. The concentrations of procainamide and its N-acetylated metabolite, NAPA, have been studied in the plasma of 10 normal volunteers and 11 patients who were given a new sustained release preparation at 8 hour intervals. Blood samples were taken between two doses on the fourth day of treatment. Procainamide showed levels within the accepted therapeutic range during the entire dosing interval. A dose of 4.5 g per day per 70 kg body-weight is necessary in order to achieve adequate levels. NAPA concentrations did not fluctuate during the dosing interval and mean steady-state concentrations were influenced predominantly by the degree of renal function. Saliva to plasma concentration ratio, measured in four patients, showed huge inter- and intraindividual variability. Therefore, saliva concentrations measurements of procainamide and NAPA are of little clinical use.