Clinical and electrophysiologic effects of flecainide in patients with refractory ventricular tachycardia

A Possible Mechanism for Flecainide Induced Dizziness

OBJECTIVE

Flecainide is an oral class IC antiarrhythmic drug whose most common extracardiac adverse reactions are "dizziness" and "visual disturbances." We describe a case of flecainide associated- bilateral vestibulopathy and a literature review of this drug's effect on the vestibular system.

PATIENT

Sixty-nine-year-old man with a 3-month history of unsteadiness and dizziness after an increase in the dose of flecainide.

INTERVENTIONS

Otologic examination, video head-impulse test, vestibular evoked myogenic potentials, pure tone audiometry and high-resolution magnetic resonance imaging.

RESULTS

Otologic examination, including the head-impulse test, and vestibular testing revealed bilateral vestibulopathy.

CONCLUSIONS

Dizziness is a common extracardiac adverse reaction of Flecainide. Based on the clinical case that we present and the literature review carried out, we hypothesized that a possible mechanism by which flecainide might cause dizziness and visual disturbances is bilateral vestibulopathy.

Efficacy of class 1C antiarrhythmic agents in patients with inducible ventricular tachycardia refractory to therapy with class 1A antiarrhythmic drugs

The efficacy of class 1C antiarrhythmic agents was determined in 36 patients with inducible sustained monomorphic ventricular tachycardia during baseline electrophysiology study (EPS), who continued to have inducible monomorphic ventricular tachycardia during EPS on class 1A antiarrhythmic therapy. Of 12 patients who partially responded to class 1A drugs, 11 (91.7%) continued to have a partial response during EPS on class 1C therapy, whereas one patient did not respond. Of 24 nonresponders to class 1A therapy, 2 (8.3%) responded during EPS on class 1C therapy, 7 (29.2%) partially responded, and 15 (62.5%) did not respond. In the 24 nonresponders to class 1A therapy, 9 of 17 patients (53%) with left ventricular ejection fraction (EF) > or = 30% responded or partially responded to class 1C therapy, compared with none of 7 patients with EF < 30% (P < .05). The EPS on class 1C agents in patients who fail to respond to class 1A therapy may be warranted only in those with EF > or = 30%.

High-performance liquid chromatographic determination of the enantiomers of flecainide in human plasma and urine

A stereospecific high-performance liquid chromatographic method for the determination of (R,S)-flecainide acetate [(R,S)-N-(2-piperidylmethyl)-2,5-bis-(2,2,2-trifluoroethoxy)benzam ide acetate] in human plasma and urine is described. After addition of the internal standard [IS; (R,S)-N-(2-piperidylmethyl)-2,3-bis(2,2,2-trifluoroethoxy)- benzamide hydrochloride], a single-step extraction of alkalinized samples was performed with distilled diethyl ether. The organic layer was evaporated and the drug and IS were derivatized with 1-[(4-nitrophenyl)sulfonyl]-L-propyl chloride at 80 degrees C for 2 h. The diastereomeric derivatives of flecainide and IS were chromatographed on a C18 reversed-phase column with a mobile phase consisting of acetonitrile: water:triethylamine (45:55:0.2) at a flow rate of 1 mL/min. Flecainide diastereomers were separated with a resolution factor of 1.25 and detected by UV spectroscopy at a wavelength of 280 nm. An excellent linearity was observed between the peak area ratios (flecainide derivatives:IS) and plasma concentrations, and the intra- and interday coefficients of variation were always less than 9.8%. The lowest quantifiable concentration was set at 50 ng/mL for each enantiomer (CV of 4.9 and 4.4%), while the lowest limit of detection (signal:noise, 3:1) was on the order of a few nanograms. The assay was used to study the pharmacokinetics of flecainide enantiomers in a patient receiving (R,S)-flecainide therapy. The steady-state plasma time courses for the enantiomers were found to be parallel, but the difference between (R)- and (S)-flecainide concentrations was significant. The urinary excretion data were consistent with the plasma results. The method is suitable for therapeutic monitoring of flecainide enantiomers and for stereoselective pharmacokinetic studies in humans.

Acute effects of combination of IB and IC antiarrhythmics for the treatment of ventricular tachycardia

There are limited data on the effects of Class IB and IC antiarrhythmic drug combination for the treatment of ventricular tachycardia. The present study evaluated this combination in 12 patients who had sustained ventricular tachycardia (SuVT) during programmed electrical stimulation (PES) and failed IC antiarrhythmic therapy. Following combination of lidocaine and a IC agent (7 with encainide and 5 with flecainide), two had no inducible ventricular tachycardia (VT) and one had nonsustained VT (NSVT). In seven of nine patients who still had SuVT, the mean VT cycle length increased 40 +/- 25 msec post combination compared to IC antiarrhythmic therapy. Seven patients who had a favorable response to the initial combination (less than 10 beats of NSVT, or greater than or equal to 10 beats of VT with a greater than 100 msec increase in cycle length compared to baseline and no hemodynamic compromise) were then placed on IC + oral IB agent (5 with mexiletine, 2 with tocainide). Similar effects on VT inducibility and cycle length were observed following the oral combination. In conclusion, the addition of lidocaine to IC therapy produced favorable effects on induced ventricular tachycardia in 58% of patients compared to IC agent alone. Also, a positive PES response to lidocaine and IC therapy corresponded to a similar positive response when either mexiletine or tocainide was substituted for lidocaine.

Evaluation of the JT and corrected JT intervals as a new ECG method for monitoring doxorubicin cardiotoxicity in the dog

A comparison was made of the sensitivity of ECG, ultrastructural heart pathology, and plasma enzymes CK-MB and alpha-HBDH as methods to assess doxorubicin cardiotoxicity in adult beagle dogs given doxorubicin 30 mg/m2 i.v. once a week for three times. A progressive increase in JT and QT intervals, in corrected JT (JTc) and QT (QTc) intervals as well as a reduction in both T wave amplitude and RR duration, were observed in doxorubicin-treated dogs; the electrocardiogram (ECG) abnormalities were associated with doxorubicin-induced ultrastructural changes in cardiac tissue, consisting of dilation of the sarcoplasmic reticulum, multiform, flasklike invaginations of T-tubules containing electrondense material, and interruption of the junctional sarcoplasmic reticulum, which became more severe as the observation period progressed. On the contrary, doxorubicin treatment was associated with transient changes in plasma CK-MB and alpha-HBDH, which were unrelated to the severity of chronic cardiotoxicity. Overall results suggest that the monitoring of the ECG parameters related to the repolarization of the cardiac muscle, and particularly JT and JTc, might be regarded as a noninvasive method for the study of doxorubicin cardiotoxocity in the dog.