Dynamic effects of intravenous procainamide infusion on the electrophysiological properties during atrial fibrillation.
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Although the mechanism of atrial fibrillation (AF) is still controversial, multiple wandering reentry is considered the primary mechanism in most AF. It has been suggested that prolongation of the wavelength would make it impossible for the reentry to continue and would lead to the termination of the AF. In the present study a dynamic fluctuation in the electrophysiological properties was observed with procainamide infusion during AF. In 12 patients, both the local electrogram and monophasic action potentials (MAP) during AF were recorded from the right atrium before, during and after infusion of procainamide (10 mg/kg). The minimum AF cyclelength (CLmin), MAP duration at 90% repolarization (MAPD90) and widths of the intraatrial potentials (WAP) were measured with custom-made computer software. The conduction velocity index (CVI) was determined from the WAP. The wavelength index (WLI=CVIxCLmin) and postrepolarization refractoriness (PRR= CLmin-MAPD90) were calculated. In 6 patients, AF was terminated by procainamide infusion (group A), but not in the other 6 patients (group B). Group A patients showed a biphasic change in the parameters following procainamide infusion. In phase I, the CLmin, MAPD90 and PRR increased, while the CVI decreased, and the WLI remained unchanged. In phase II, the PRR, CVI and WLI increased and the AF was terminated. No restoration of the CVI nor increase in the WLI were observed in group B. The biphasic fluctuation in the CVI and the remarkable increase of the PRR and WLI were observed before termination of AF by procainamide infusion. (+info)
Amitriptyline and procainamide inhibition of cocaine and cocaethylene degradation in human serum in vitro.
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Amitriptyline (AMI) and procainamide (PA) have been reported to inhibit the activity of human plasma butyrylcholinesterase, an enzyme important in the metabolic degradation of cocaine (COC) and its ethyl analogue cocaethylene (CE). Because both AMI and PA may be used in the treatment of COC intoxication and abuse, the effect of high pharmacological concentrations of these compounds on the degradation of COC and CE in pooled human serum was studied. AMI (1.8 micromol/L) modestly inhibited the degradation of COC by 4.2% and of CE by 4.0%. PA (42.5 micromol/L) profoundly inhibited degradation of COC by 42.7% and of CE by 47.2%. In contrast, lithium carbonate (1 mmol/L, control) showed no inhibition of degradation of either COC or CE. These results suggest that AMI and PA may prolong the half-life of COC and CE in human serum. (+info)
Doppler sonographic evaluation of left atrial function after cardioversion of atrial fibrillation.
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Restoration of sinus rhythm is not always followed by immediate return of effective atrial contraction. Left atrial mechanical function can be assessed by Doppler echocardiography; in the present study we measured the atrial ejection force, which is a noninvasive Doppler-derived parameter that measures the strength of atrial contraction. The aim of the present study was to evaluate the influence of clinical and echocardiographic parameters: duration and cause of atrial fibrillation, different modality of cardioversion, and left atrial size with respect to the delay in the return of effective atrial contraction after cardioversion. Seventy patients were randomly chosen to undergo cardioversion by either direct current shock or intravenously administered procainamide hydrochloride. The 52 patients who had sinus rhythm restored underwent a complete Doppler echocardiographic examination 1 h after the restoration of sinus rhythm and after 1 day, 7 days, and 1 month. The relation between clinical variables and atrial ejection force was tested. Atrial ejection force was greater immediately and 24 h after cardioversion in patients who underwent pharmacologic therapy compared to patients treated with direct current shock (11.3+/-3 versus 5+/-2.9 dynes; P<0.001). In both groups atrial ejection force increased over time. The mode of cardioversion was significantly associated with recovery of left atrial mechanical function by day 1 in univariate and multivariate analysis (odds ratio, 0.14; 95% confidence interval, 0.02-1.2). The other variable associated with the delay in the recovery of atrial function was a dilated left atrium (odds ratio, 0.16; 95% confidence interval, 0.12-1.6). Atrial ejection force is a noninvasive parameter that can be easily measured after cardioversion and gives accurate information about the recovery of left atrial mechanical function. The recovery of left atrial function was influenced by the mode of cardioversion and left atrial size. (+info)
Electrical restitution and spatiotemporal organization during ventricular fibrillation.
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Despite recent advances in our understanding of the mechanism for ventricular fibrillation (VF), important electrophysiological aspects of the development of VF still are poorly defined. It has been suggested that the onset of VF involves the disintegration of a single spiral wave into many self-perpetuating waves. It has been further suggested that such a process requires that the slope of the electrical restitution relation be >/=1. The same theory anticipates that a single spiral wave will be stable (not disintegrate) if the maximum slope of the restitution relation is <1. We have shown previously that the slope of the restitution relation during rapid pacing and during VF is >/=1 in canine ventricle. We now show that drugs that reduce the slope of the restitution relation (diacetyl monoxime and verapamil) prevent the induction of VF and convert existing VF into a periodic rhythm. In contrast, a drug that does not reduce the slope of the restitution relation (procainamide) does not prevent the induction of VF, nor does it regularize VF. These results indicate that the kinetics of electrical restitution is a key determinant of VF. Moreover, they suggest novel approaches to preventing the induction or maintenance of VF. (+info)
Procainamide inhibition of human hepatic degradation of cocaine and cocaethylene in vitro.
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Procainamide (PA), a cardioactive drug, inhibited the degradation of both cocaine (COC) and cocaethylene (CE) when either was incubated in human liver homogenates for 3 h at 37 degrees C. PA appeared to enhance the formation of CE when COC and ethanol (ETOH) were incubated together in liver homogenate. These observations are clinically significant because cardiotoxicity is common after COC abuse and because PA may be administered to individuals who use COC alone and with ETOH. (+info)
Inhibitory effects of procainamide on rabbit platelet aggregation and thromboxane B2 production in vitro.
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AIM: To study the influences of procainamide (PA) on thrombin-induced rabbit platelet aggregation and thromboxane B2 (TXB2) production in vitro. METHODS: Turbidimetry and radioimmunoassay were used. RESULTS: PA 8.5, 34, 136, and 544 mumol.L-1 inhibited thrombin-induced platelet aggregation and TXB2 production, and the inhibitory rates were 45% +/- 37%, 48% +/- 32%, 88% +/- 23%, 92% +/- 15% and 53% +/- 24%, 65% +/- 26%, 90% +/- 6%, 95% +/- 6%, respectively. There was positive correlation between PA concentration and efficiency of inhibition of platelet aggregation and TXB2 production, and also between the inhibition % of platelet aggregation and that of production of TXB2. The three linear equations and main parameters were Y = 0.2075X-4.9157, r = 0.9985; Y = 0.9546X-34.6724, r = 0.9921; Y = 0.8202X + 19.7062, r = 0.9921. CONCLUSION: PA inhibited thrombin-induced platelet aggregation and TXB2 production in rabbits. (+info)
Effect of procainamide on ultrastructure of blood platelet in rabbits.
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AIM: To study the effect of procainamide (PA) on the ultrastructure of blood platelets. METHODS: Arachidonic acid was added to PA-treated platelet-rich plasma to induce platelet aggregation. The 50-nm sections were examined with a transmission electron microscope. RESULTS: PA 8.5-136 mumol.L-1 markedly inhibited changes of pseudopods, alpha-granules, dense granules, glycogens, open canalicular system, and dense tubular system. CONCLUSION: PA markedly inhibited the changes of ultrastructure of blood platelet and releasing response. (+info)
Mechanism of procainamide-induced prevention of spontaneous wave break during ventricular fibrillation. Insight into the maintenance of fibrillation wave fronts.
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BACKGROUND: Ventricular fibrillation (VF) is maintained by 2 mechanisms: first by reentry formation and second by spontaneous wave break or wave splitting. We hypothesized that spontaneous wave break results from a critical shortening of the action potential duration (APD) during VF and that its prevention by procainamide eliminates spontaneous wave break. METHODS AND RESULTS: The endocardial surfaces of 7 isolated, perfused swine right ventricles were mapped with a 3.2x3.8 cm plaque with 477 bipolar electrodes. Activation pattern during VF was visualized dynamically while simultaneously recording epicardial action potentials with a glass microelectrode. APD restitution curves were constructed during VF (dynamic) and during S(1)S(2) protocols. At baseline, VF was maintained by 5.3+/-1 wavelets. Procainamide (PA) at 10 microgram/mL decreased the number of wavelets to 3.5+/-1 (P<0.05). At baseline VF was maintained by spontaneous wave break and by new reentrant wave front formation. PA eliminated spontaneous wave break during VF while having no effect on reentry formation. PA increased the cycle length of the VF (148.5+/-41.2 ms vs 81+/-10 ms, P<0.01) and the core area of the reentry from 5.8 to 14.5 mm(2) (P<0.05). Dynamic APD restitution curve during VF showed that PA eliminated the initiation of activation with APDs shorter than 30 ms. The effects of PA on cellular properties and wave front dynamics were reversed during 60 minutes of drug-free perfusion. CONCLUSIONS: Critically short APDs during VF promote spontaneous wave break. Their elimination with PA, however, maintains VF by generating new reentrant wave front. (+info)