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

Perspective on Antiarrhythmic Drug Combinations

Physicians use multiple drugs in combination to treat hypertension, heart failure, diabetes mellitus, angina, hyperlipidemia, and many other cardiovascular conditions and risk factors. However, administering antiarrhythmic drugs (AAD) in combination is rarely discussed. Yet, the possibility of increasing efficacy and/or tolerance and/or safety of AADs (by adding mechanisms, offsetting adverse mechanisms, and/or using lower doses) exists. Unfortunately, this topic has not been reviewed in any contemporary cardiac literature of which we are aware, although information regarding AAD combinations has been published. In conclusion, and accordingly, this review discusses the possibility of using AAD combinations for both ventricular arrhythmias and atrial fibrillation, in which the rationale for such combinations, considerations for such combinations, and supporting literature are covered.

Quinidine in the Management of Recurrent Ventricular Arrhythmias: A Reappraisal

OBJECTIVE

This study aimed to review the utility of quinidine in patients presenting with recurrent sustained ventricular arrhythmia (VA) and limited antiarrhythmic drug (AAD) options.

BACKGROUND

Therapeutic options are often limited in patients with structural heart disease and recurrent VAs. Quinidine has an established role in rare arrhythmic syndromes, but its potential use in other difficult VAs has not been assessed in the present era.

METHODS

We performed a retrospective analysis of 37 patients who had in-hospital quinidine initiation after multiple other therapies failed for VA suppression at our tertiary referral center. Clinical data and outcomes were obtained from the medical record.

RESULTS

Of 30 patients with in-hospital quantifiable VA episodes, quinidine reduced acute VA from a median of 3 episodes (interquartile range [IQR]: 2 to 7.5) to 0 (IQR: 0 to 0.5) during medians of 3 days before and 4 days after quinidine initiation (p < 0.001). VA events decreased from a median of 10.5 episodes per day (IQR: 5 to 15) to 0.5 episodes (IQR: 0 to 4) after quinidine initiation in the 12 patients presenting with electrical storm (p = 0.004). Among the 24 patients discharged on quinidine, 13 (54.2%) had VA recurrence during a median of 138 days. Adverse effects in 9 of the 37 patients (24.3%) led to drug discontinuation, most commonly gastrointestinal intolerance.

CONCLUSIONS

In patients with recurrent VAs and structural heart disease who have limited treatment options, quinidine can be useful, particularly as a short-term therapy.

Acute electrophysiologic effects of intravenous amiodarone are independent of a sympatholytic action in humans

Previous experiments in animals demonstrated a novel sympatholytic action of acute intravascular amiodarone (AM). It is not known if this action also occurs in humans. Twelve male volunteers performed handgrip for 10 min before and after 300 mg intravenous (IV) AM over 60 min. The effect of handgrip was determined from changes in blood pressure (BP), heart rate (HR), and cardiac noradrenaline (NA) spillover. Changes in cardiac spillover of dihydroxyphenylglycol (DHPG), the metabolite of NA, were measured during AM infusion. The electrophysiological effects of AM were determined from changes to the A-H intervals during right atrial stimulation (100 beats/min). Handgrip increased HR (63 +/- 2 to 84 +/- 5 beats/min and 65 +/- 3 to 84 +/- 4 beats/min), systolic BP (141 +/- 4 to 179 +/- 6 mm Hg and 140 +/- 4 to 179 +/- 7 mm Hg), and cardiac NA spillover (11.9 +/- 4 to 44.3 +/- 13 ng/min and 17.3 +/- 4 to 55.5 +/- 11 ng/min) before and after AM, respectively (P < 0.02 in all groups). There was good correlation between increases in cardiac NA spillover and HR (r2 = 0.86) and systolic BP (r2 = 0.87). AM increased the A-H interval (95.5 +/- 18 to 107.8 +/- 20 ms, P < 0.02). There was no difference in hemodynamic or NA response to handgrip before or after the AM infusion. There was also no change in DHPG cardiac spillover during AM infusion. Acute IV AM did not exert a sympatholytic action in humans, with no attenuation in hemodynamic or NA response to handgrip or increase in DHPG production, despite producing an electrophysiologic response.

Amiodarone therapy for sustained ventricular tachycardia after myocardial infarction: long-term follow-up, risk assessment and predictive value of programmed ventricular stimulation

We determine the value of the programmed ventricular stimulation (PVS) and of clinical, angiographic and electrophysiologic variables in assessing the long-term risk of arrhythmia recurrence in a group of coronary artery diseased patients presenting with a first episode of monomorphic sustained ventricular tachycardia (VT) treated with amiodarone. Mortality and arrhythmia recurrence rates were retrospectively assessed in 55 consecutive patients with previous myocardial infarction presenting with a first VT episode. Results of left heart catheterization, echocardiography and time-domain signal-averaging were collected. Patients underwent PVS after amiodarone oral loading and were classified according to inducibility before being all discharged on amiodarone (200 mg daily). The mean follow-up was 42+/-31 months. Total and cardiac mortality rates were 29% (16 patients) and 23% (13 patients) respectively. Sudden death (SD) occurred in nine patients (16%). VT recurred in 13 patients (23%). Sustained monomorphic VT was inducible in 40 patients (72%) after amiodarone loading. Neither total mortality (10/40 vs. 6/15) nor cardiac mortality (3/40 vs. 1/15) were significantly different between inducible and non-inducible patients. Recurrent VT rate was 27% (11/40 patients) for the inducible group and 13% (2/15 patients) for the non-inducible group (NS). SD occurred in 6/40 inducible patients (15%) and in 2/15 non-inducible patients (13%) (NS). Arrhythmic events occurred in 42% (17/40) inducible patients vs. 26% (4/15) non-inducible patients (P=0.07). Parameters correlated with outcome were ejection fraction (EF) (5 SD/11 patients with EF <0.3 vs. 4/44 with EF >0.3, P=0.003), mitral insufficiency (MI) (4 SD/10 patients with MI vs. 4/44 patients without MI, P=0.004) and age (65+/-9 years for patients with VT recurrence vs. 58+/-9, P=0.02). Although the risk stratification can be improved, reliable and safe long-term prediction of recurrence of malignant ventricular arrhythmia in individual patients cannot be made. Consequently, the systematic implantation of a cardioverter-defibrillator in case of a first episode of sustained VT occurring in coronary artery disease patients should be further debated.

Combination of sotalol and quinidine in a canine model of torsades de pointes: no increase in the QT-related proarrhythmic action of sotalol

INTRODUCTION

Clinical treatment with a combination of Class IA and III antiarrhythmic drugs is not recommended, as they both favor bradycardia-dependent proarrhythmic events such as torsades de pointes (TdP). However, this theoretical additive effect on ventricular repolarization has never been demonstrated and could be questioned as other Class I drugs, such as mexiletine, a Class IB drug, limit the number of sotalol-induced TdP in dogs with AV block, suggesting the possibility of an antagonistic action of Class I properties against Class III effects.

METHODS AND RESULTS

We compared the electrophysiologic and proarrhythmic effects of sotalol (Class III) alone and combined with quinidine (Class IA) in a canine model of acquired long QT syndrome. Seven hypokalemic (K+: 3 +/- 0.1 mEq/L) dogs with chronic AV block had a demand pacemaker implanted and set at a rate of 25 beats/min. They were submitted to two (sotalol-alone and sotalol-plus-quinidine) experiments 48 hours apart using a randomized cross-over protocol. They were pretreated with quinidine (10 mg/kg + 1.8 mg/kg per hour) or saline infused throughout the experiment, and given sotalol (4.5 mg/kg + 1.5 mg/kg per hour) for 2 hours, 30 minutes after the beginning of the pretreatment infusion during both experiments. Ventricular and atrial cycle lengths were similarly increased by sotalol after quinidine or saline. The sotalol-induced prolongation of the QT interval was significantly shorter in quinidine-pretreated dogs (24 +/- 7 msec after quinidine vs 40 +/- 8 msec after saline). Fewer dogs developed TdP: significantly during the first hour of infusion (1/7 sotalol-plus-quinidine vs 6/7 sotalol-alone dogs, P < 0.05) but nonsignificantly during the second hour (3/7 vs 6/7).

CONCLUSION

In this model, the sotalol-plus-quinidine combination is at least no more arrhythmogenic than either of the drugs given alone.

Therapy of Sustained Ventricular Arrhythmias With Amiodarone: Prediction of Efficacy With Serial Electrophysiologic Studies

BACKGROUND: Programmed electrical stimulation early during amiodarone therapy has poor prognostic capabilities; and persistent inducibility has been associated with a favorable outcome in a majority of patients. These observations result from studies that differed significantly in methodology. METHODS AND RESULTS: The authors prospectively enrolled 121 patients in a standardized amiodarone dosing protocol in which amiodarone was the only antiarrhythmic agent. Electrophysiologic testing was done after 2 and 6 weeks to determine noninducibility, predictive value, and the significance of drug-induced prolongation of tachycardia cycle length. The mean age of the patients in the study was 63.2 +/- 11.5 years, and their ejection fraction was 32.8 +/- 11.9%. Coronary artery disease was present in 103 (85%). At 2 weeks 17 patients (14%) were no longer inducible, whereas 104 patients (86%) remained inducible. Patients in these groups were similar in age and ejection fraction. During follow-up evaluation, recurrences (35% vs 24%; P =.44) and sudden death (12% vs 13.5%) were similar in the two groups. Thirty-five of 95 patients (32%) with sustained monomorphic ventricular tachycardia had more than 100 ms prolongation of their cycle length, which was hemodynamically well tolerated (partial response), but 60 did not (nonresponse). Patients with a partial response were older (66.5 vs 61.1 years; P =.02) and had longer QRS durations (143.2 vs 129.4 ms; P =.03). They also had increased recurrences (37% vs 17%; P =.01) and more sudden deaths (23% vs 8%; P =.02). At 6 weeks 11 of 76 patients studied were noninducible. They had a lower recurrence rate than those who remained inducible (8% vs 27%; P =.02) but a similar number of sudden deaths (8% vs 16%; P =.27). Thirty-two patients partially responded, and 31 patients did not respond. During follow-up examination these two groups had a similar number of recurrences (25% vs 29%; P =.76) and sudden deaths (16% vs 16%). CONCLUSIONS: Noninducibility at 2 or 6 weeks of amiodarone therapy did not identify patients at low risk of sudden death. In inducible patients, tachycardia cycle length prolongation, even when well tolerated, was not a marker for favorable outcome. Electrophysiologically guided therapy, therefore, offers little benefit over empiric amiodarone.

Comparison of electrophysiologic effects of quinidine and amiodarone in sustained ventricular tachyarrhythmias associated with coronary artery disease

Fifteen patients with spontaneous ventricular tachyarrhythmias underwent electrophysiologic studies at baseline and during therapy with quinidine and amiodarone. In 9, ventricular tachycardia (VT) with a similar QRS morphology was induced with quinidine, amiodarone and under the control state. Both quinidine and amiodarone significantly increased QRS duration and the VT cycle length. Amiodarone increased the VT cycle length more than quinidine (85 vs 121 ms, p < 0.05). Amiodarone increased the percent QRS duration (during sinus rhythm, ventricular pacing and VT) significantly less than percent VT cycle length, whereas quinidine did so only at slow rates (at faster rates the percent increase in QRS duration is not different from the percent increase in VT cycle length). The percent increase in QRS duration produced by quinidine correlated significantly with the percent increase in VT cycle length (the best correlation was observed during pacing, r = 0.78). In contrast, no such significant correlations were obtained for amiodarone. Thus, amiodarone prolongs VT cycle length more than quinidine (at the doses used). The effects of quinidine on conduction in tissue mostly unrelated to tachycardia origin predict effects in the tachycardia cycle length. In contrast, the effects of amiodarone on the latter are more intense but not predicted by those on tissue unrelated to the tachycardia origin.

Prospective, randomized comparison of conventional and high dose loading regimens of amiodarone in the treatment of ventricular tachycardia

OBJECTIVES

The purpose of this prospective randomized study was to compare the electrophysiologic effects of conventional and high dose loading regimens of amiodarone in patients with sustained ventricular tachycardia.

BACKGROUND

Uncontrolled studies in which patients have been treated with an oral loading dose of 2 to 4 g/day of amiodarone have suggested that, compared with a conventional loading dose, this dosing regimen results in more rapid control of spontaneous ventricular tachycardia and ventricular tachycardia induced by programmed stimulation.

METHODS

Patients in whom sustained monomorphic ventricular tachycardia was inducible by programmed stimulation and who were refractory to class I antiarrhythmic medications were randomly assigned to receive either a conventional (n = 15) or a high (n = 17) loading dose of amiodarone. The conventional dose consisted of 600 mg twice a day for 10 days. The high dose regimen consisted of 50 mg/kg body weight per day on days 1 to 3, 30 mg/kg per day on days 4 and 5 and 600 mg twice a day on days 6 to 10. An electrophysiologic test was performed in the baseline state and after 3 and 10 days of therapy. An adequate response to amiodarone was defined as the inability to induce ventricular tachycardia or the ability to induce only relatively slow (cycle length > or = 350 ms) hemodynamically stable ventricular tachycardia.

RESULTS

After 3 days of therapy, 2 of 14 patients who received the conventional loading dose and 6 of 15 patients who received the high dose loading regimen had an adequate response to amiodarone (p = 0.08). After 10 days of therapy, four patients in each group had an adequate response to amiodarone (p = NS). Three patients who received the high dose and one patient who received the conventional dose of amiodarone had an adequate response after 3 days of therapy but not after 10 days of therapy. There were significant increases in the sinus cycle length, atrioventricular block cycle length, ventricular effective refractory period and ventricular tachycardia cycle length after 3 and 10 days of therapy compared with baseline values regardless of the dosing regimen. The extent of the effects of amiodarone on these variables after 3 and 10 days of therapy was similar with both dosing regimens.

CONCLUSIONS

The therapeutic and electrophysiologic effects of conventional and high dose loading regimens of amiodarone do not differ significantly after 3 or 10 days of therapy. High oral loading doses of amiodarone do not offer any significant clinical advantage over a conventional loading dose of amiodarone for controlling ventricular tachycardia induced by programmed stimulation.

Efficacy and safety of combination therapy with amiodarone and type I agents for treatment of inducible ventricular tachycardia

In a prospective study the efficacy of amiodarone in combination with the three Class I drugs mexiletine, flecainide, or encainide was evaluated consecutively in 12 patients with recurrent ventricular tachycardias (VT) by programmed stimulation. None of the tested drug combinations suppressed induction of sustained VT. The combination of amiodarone with Class IC drugs flecainide and encainide prolonged the cycle length of VT significantly, whereas the combination with mexiletine did not have the same degree of slowing on the VT cycle length. Several proarrhythmic effects occurred during the combination therapy with encainide: (1) frequent, spontaneous recurrences of hemodynamically well tolerated VT in four patients; (2) enhanced inducibility of VT in three patients; (3) impaired termination of VT in three patients. Though a marked increase in QRS and QTc intervals was observed by combined treatment with encainide, no significant correlation could be established between aggravation of arrhythmia and plasma levels of encainide, degree of QRS widening, JT or QTc prolongation. The only predictor for the occurrence of proarrhythmic events was found in left ventricular ejection fraction. These findings suggest that in patients refractory to amiodarone alone or a combination with mexiletine, the combined treatment of amiodarone with other Class IC drugs prolongs the VT cycle length but does not suppress induction of VT during programmed stimulation. Combination therapy of amiodarone with encainide was associated with a high incidence of proarrhythmic effects.

Cycle-length response of ventricular tachycardia associated with coronary artery disease to procainamide and amiodarone

We undertook this study to determine if the cycle-length response of ventricular tachycardia (VT) to procainamide and amiodarone is similar in the individual patient. We enrolled 40 patients with uniform, monomorphic VT at a baseline, drug-free electrophysiologic study, after procainamide infusion and during oral amiodarone therapy. We found a significant correlation (p less than 0.01) between VT cycle-lengths on the 2 agents as well as the percent change in cycle length from baseline. Only 60% of the patients exhibited VT rates within 10% between the 2 agents. Importantly, less than 20% of patients had further slowing of the VT rate (greater than 10% slowing) during amiodarone therapy as compared to procainamide. Thus, although the cycle-length response of VT to procainamide correlates with the cycle-length response to amiodarone, 40% of patients have a disparate response (greater than 10% difference in cycle length) to the 2 agents; additional slowing of VT rates in response to amiodarone beyond that seen with procainamide is unlikely. These results have important implications regarding the institution of amiodarone therapy and the need for repeat electrophysiologic testing during amiodarone therapy.

Safety and efficacy of amiodarone. The low-dose perspective

Amiodarone has been reported to be a remarkably safe and effective drug in the European and South American experience but American investigators have published conflicting data. Since this disparity may be explained by a different dosing schedule, we prospectively evaluated the safety and efficacy of a low dose regimen in a group of 68 patients with cardiac arrhythmia resistant to conventional therapy, of whom 57 had manifested either ventricular tachycardia or fibrillation. All were loaded either intravenously (17) or orally, and maintained on an oral dose of 200 to 600 mg/day (mean daily dose 317 +/- 114 mg) and followed for 4 to 58 months (22 +/- 11). Results indicated that amiodarone was a safe and effective antiarrhythmic drug when used in lower doses.