Dronedarone Versus Amiodarone in Preventing Premature Ventricular Contractions in an In Vitro Model of “Border Zone”:

Are antiarrhythmic agents indicated in premature ventricular complex-induced cardiomyopathy and when?

INTRODUCTION

Premature ventricular complexes (PVCs) are the most common ventricular arrhythmia that are encountered in the clinical practice. Recent data suggests that high PVC burden may lead to the development of PVC-induced cardiomyopathy (PVC-CM) even in patients without structural heart disease. Treatment for effective suppression of PVCs, can reverse PVC-CM. Both antiarrhythmic drugs (AADs) and catheter ablation (CA) are recognized treatment modalities for any cardiac arrhythmias. However, with increasing preference of CA, the role of AADs needs further defining regarding their efficacy, safety, indications and patient selection to treat PVC-CM.

METHODS

To ascertain the role of AADs to treat PVC-CM; whether they are indicated to treat PVC-CM, and if so, when, we interrogated PubMed and other search engines for English language publications with key words premature ventricular complexes (PVCs), cardiomyopathy, anti-arrhythmic drugs, catheter ablation, and pharmacological agents. All publications were carefully reviewed and scrutinized by the authors for their inclusion in the review paper. For illustration of cases, ethical standard was observed as per the 1975 Declaration of Helsinki, and the patient was treated as per the prevailing standard of care. Informed consent was obtained from the patient for conducting the ablation procedure.

RESULTS

Our literature search specifically the pharmacological treatment of PVC-CM with AADs revealed significant paradigm shift in treatment approach for PVCs and PVC-induced cardiomyopathy. No major large, randomized control trials of AADs versus CA for PVC-CM were found. We found that beta-blockers and calcium channel blockers are particularly effective in the treatment of PVCs originating from right ventricular outflow tract. For Class Ic AADs - flecainide and propafenone, small clinical studies showed Class Ic AADs to be effective in PVC suppression, but their usage was not recommended in patients with significant coronary artery disease. Mexiletine was found to have modest effect on PVC suppression. Studies showed sotalol to significantly reduce PVCs frequency in patients receiving both low and high doses. Studies also showed amiodarone to have higher successful PVC suppression, but not recommended as a first-line treatment for patients with idiopathic PVCs in the absence of symptoms and left ventricular dysfunction. For dronedarone, no major clinical data were available.

CONCLUSIONS

Based on the available data in the literature, we conclude that AADs play important role in the treatment of PVC-induced cardiomyopathy. However, appropriate patient selection criteria are vitally important, and in general terms AADs are indicated or polymorphic PVCs, epicardial PVCs; and when CA procedure is contraindicated, or not feasible or failed.

PAR1 contribution in acute electrophysiological properties of oral anticoagulants in rabbit pulmonary vein sleeve preparations

Whether oral anticoagulants, vitamin K antagonists (VKAs), and nonvitamin K oral anticoagulant (NOACs) frequently prescribed to atrial fibrillation (AF) patients, do themselves have a pro- or anti-arrhythmic effect have never been addressed. Transmembrane action potentials were recorded in an acute rabbit model of superfused pulmonary veins (PVs) sleeves preparations using standard microelectrode technique. Fluindione 10 μm (n = 6) increased the AP (action potential) duration (APD), induced a significantly V_max depression (from 95 ± 14 to 53 ± 5 V/s, P < 0.05), and 2 : 1 blocks during rapid atrial pacing thus evoking class I anti-arrhythmic properties, and prevented spontaneous trigger APs. Apixaban 10 μm (n = 6) increased the APD, significantly prolonged the effective refractory period (from 56.3 ± 4.2 to 72.0 ± 8.6 ms, P < 0.05), and prevented triggered APs occurrence. Fluindione and apixaban effects were suppressed with the addition of the protease-activated receptors 1 (PAR 1) agonist SFLLR-NH₂ . Warfarin 10 μm (n = 6) significantly abbreviated the early refractory period (from 56.3 ± 4.2 to 45.0 ± 2.2 ms, P < 0.05) and increased triggered APs occurrence that were successfully prevented by nifedipine but not by the addition of the protease-activated receptors 1 agonist SFLLR-NH₂ . In this acute rabbit PVs model, VKAs and NOACs, at physiological concentrations, exhibited very different pharmacological properties that influence PVs electrophysiology, implying PAR1, with fluindione and apixaban which exhibited more anti-arrhythmic properties, whereas warfarin exhibited more pro-arrhythmic properties.

Rapid and MR-Independent IK1 Activation by Aldosterone during Ischemia-Reperfusion

In ST elevation myocardial infarction (STEMI) context, clinical studies have shown the deleterious effect of high aldosterone levels on ventricular arrhythmia occurrence and cardiac mortality. Previous in vitro reports showed that during ischemia-reperfusion, aldosterone modulates K⁺ currents involved in the holding of the resting membrane potential (RMP). The aim of this study was to assess the electrophysiological impact of aldosterone on I_K1 current during myocardial ischemia-reperfusion. We used an in vitro model of “border zone” using right rabbit ventricle and standard microelectrode technique followed by cell-attached recordings from freshly isolated rabbit ventricular cardiomyocytes. In microelectrode experiments, aldosterone (10 and 100 nmol/L, n=7 respectively) increased the action potential duration (APD) dispersion at 90% between ischemic and normoxic zones (from 95±4 ms to 116±6 ms and 127±5 ms respectively, P<0.05) and reperfusion-induced sustained premature ventricular contractions occurrence (from 2/12 to 5/7 preparations, P<0.05). Conversely, potassium canrenoate 100 nmol/L and RU 28318 1 μmol/l alone did not affect AP parameters and premature ventricular contractions occurrence (except Vmax which was decreased by potassium canrenoate during simulated-ischemia). Furthermore, aldosterone induced a RMP hyperpolarization, evoking an implication of a K⁺ current involved in the holding of the RMP. Cell-attached recordings showed that aldosterone 10 nmol/L quickly activated (within 6.2±0.4 min) a 30 pS K⁺-selective current, inward rectifier, with pharmacological and biophysical properties consistent with the I_K1 current (NPo =1.9±0.4 in control vs NPo=3.0±0.4, n=10, P<0.05). These deleterious effects persisted in presence of RU 28318, a specific MR antagonist, and were successfully prevented by potassium canrenoate, a non specific MR antagonist, in both microelectrode and patch-clamp recordings, thus indicating a MR-independent I_K1 activation. In this ischemia-reperfusion context, aldosterone induced rapid and MR-independent deleterious effects including an arrhythmia substrate (increased APD₉₀ dispersion) and triggered activities (increased premature ventricular contractions occurrence on reperfusion) possibly related to direct I_K1 activation.

Dronedarone does not affect infarct volume as assessed by magnetic resonance imaging in a porcine model of myocardial infarction

Dronedarone has been demonstrated to be harmful in patients with recent decompensated heart failure. Furthermore, a PALLAS study reported that dronedarone therapy increases mortality rates in patients with permanent atrial fibrillation. Although a pathophysiological explanation for these finding remains to be elucidated, the long term effects of dronedarone on myocardial structure and stability have been suggested. The aim of the present study was to determine whether dronedarone therapy affects left ventricular (LV) function in a chronic model of myocardial infarction (MI). An anterior MI was induced in 16 pigs. Of these animals, eight pigs were then treated with dronedarone for 1 week prior to, and 4 weeks following MI, the remaining pigs served as controls. LV angiography was performed 4 weeks after MI to determine the LV ejection fraction (LVEF). A post‑mortem magnetic resonance imaging scan of the LV was then performed on the two groups (n=6) to determine the volume and size of the induced MI. Dronedarone therapy did not affect systemic and intracardiac hemodynamic parameters or LVEF during the follow‑up assessment. Of note, dronedarone had no negative effect on the total infarct volume and size and did not induce lethal proarrhythmic effects following the induced anterior MI. Therefore, the results suggested that dronedarone did not increase the volume or size of induced anterior MI and did not affect LV performance. Thus, dronedarone therapy was observed to be safe in a porcine model of anterior MI.

Electrophysiological and antiarrhythmic properties of potassium canrenoate during myocardial ischemia-reperfusion

INTRODUCTION

Recent clinical studies have reported the potential benefit of an early mineralocorticoid receptor (MR) blockade with potassium canrenoate (PC) on ventricular arrhythmias (VAs) occurrence in patients experiencing an ST-segment elevation myocardial infarction (STEMI). However, most of the electrophysiological properties of PC demonstrated to date have been investigated in normoxic conditions, and therefore, in vitro experiments during an acute myocardial ischemia-reperfusion were lacking.

MATERIALS AND METHODS

We used rabbit in vitro models and standard microelectrode technique to assess the electrophysiological impact of PC during myocardial ischemia-reperfusion, including right ventricle mimicking the "border zone" existing between normal and ischemic/reperfused areas (1 µmol/L, 10 and 100 nmol/L), isolated right ventricle, and sinoatrial node (SAN) experiments (1 µmol/L, respectively).

RESULTS

During ischemia-reperfusion, acute superfusion of PC 100 nmol/L prevented the increase in action potential (AP) duration at 90% of repolarization (APD90) dispersion between ischemic and nonischemic areas and in VAs occurrence induced by aldosterone 10 nmol/L (86 ± 3 vs 114 ± 4 milliseconds for aldosterone alone, P < .05). Potassium canrenoate also induced conduction blocks and significantly decreased Vmax during simulated ischemia (from 25 ± 5 to 12 ± 4, 14 ± 3, and 14 ± 5 V/s, respectively, for PC 1 µmol/L, 100, and 10 nmol/L, P < .05). Potassium canrenoate 1 µmol/L demonstrated cycle length (CL)-dependent effects on APD90 and on Vmax, and it also reduced SAN beating CL (from 446 ± 28 to 529 ± 24 millisecond, P < .05).

CONCLUSION

Our experimental study highlights new evidence for an antiarrhythmic impact of PC during myocardial ischemia-reperfusion via multiple channels modulation. These results are in line with recent clinical trials suggesting that an early MR blockade in STEMI may be preventive of VAs.