Vernakalant is a medication designed to manage heart rhythm disturbances in adults. Its primary role is to quickly restore a regular heart rhythm, known as normal sinus rhythm, in individuals experiencing recent-onset atrial fibrillation. This intravenous drug addresses a common cardiac condition.
How Vernakalant Acts on the Heart
Atrial fibrillation, often referred to as AFib, is a condition characterized by an irregular and rapid heartbeat originating in the heart’s upper chambers, called the atria. Instead of a coordinated contraction, the atria quiver chaotically, which can reduce the heart’s pumping efficiency. Vernakalant works by influencing the electrical activity within these atrial cells to help normalize their rhythm.
The drug achieves its effect by primarily blocking specific ion channels located in the atrial tissue. It targets potassium channels, such as the ultra-rapid delayed rectifier potassium current (IKur) and the transient outward potassium current (Ito), which are more active in the atria than in the ventricles. This selective blockade helps to prolong the refractory period of atrial cells, meaning they take longer to reset and be ready for another electrical impulse.
Vernakalant also affects atrial voltage-gated sodium channels, particularly during periods of rapid heart rate, which are common in AFib. This rate-dependent action means the drug becomes more effective when the heart rate is elevated, precisely when it is most needed. By inhibiting these sodium channels, vernakalant further helps to stabilize the electrical activity within the atria, making it less likely for the irregular impulses to persist. This dual mechanism, targeting both potassium and sodium channels with atrial selectivity and rate-dependence, helps restore a normal heart rhythm without significantly affecting the ventricles.
Who Can Receive Vernakalant and How It is Given
Vernakalant is indicated for the rapid conversion of recent-onset atrial fibrillation to a normal sinus rhythm in adults. This applies to non-surgery patients whose AFib has lasted less than seven days, or post-cardiac surgery patients with AFib of less than three days duration. It is considered for individuals without severe structural heart disease. Before administration, patients should be adequately hydrated, and low potassium levels should be corrected to at least 3.5 mmol/l.
Vernakalant should not be administered in several conditions due to potential risks. These contraindications include:
- Severe aortic stenosis
- Systolic blood pressure below 100 mmHg
- Severe heart failure (New York Heart Association Class III or IV, or left ventricular ejection fraction of 35% or less)
- Prolonged QT interval at baseline (greater than 440 milliseconds)
- Severe bradycardia
- Second or third-degree heart block (if no pacemaker is present)
- Use of other intravenous rhythm-control antiarrhythmic medications (Class I and Class III) within four hours prior to or after administration
- Acute coronary syndrome (including heart attack) within the last 30 days
- Hypertrophic obstructive cardiomyopathy
- Restrictive cardiomyopathy
- Constrictive pericarditis
- Clinically significant valvular stenosis
Vernakalant is always administered intravenously in a controlled medical setting, such as a hospital or emergency room. It is typically given as an initial infusion over 10 minutes. If a normal rhythm is not restored after 15 minutes, a second, slightly lower dose may be administered. Throughout this process, continuous cardiac monitoring and close observation of vital signs are maintained.
Managing Potential Side Effects
While effective, vernakalant can cause side effects, which are managed in the clinical setting. Common side effects include a taste disturbance, often described as metallic or bitter, which usually resolves after the infusion. Other reported effects are sneezing, nausea, headache, dizziness, and paresthesia (an abnormal sensation like tingling or numbness). These common reactions are transient and rarely lead to treatment discontinuation.
More serious side effects can occur, and medical staff closely monitor for these during and after administration. Hypotension (low blood pressure) is a serious side effect, and patients are monitored for sudden drops in blood pressure. Bradycardia (a slow heart rate) has also been reported, sometimes requiring intervention, especially if severe. If a significant drop in blood pressure or heart rate occurs during the initial infusion, the infusion is stopped, and a second dose is not given.
Other arrhythmias, such as atrial flutter or ventricular arrhythmias, have been observed, particularly in patients with pre-existing valvular heart disease, warranting close monitoring. Patients are observed for at least 15 minutes after the infusion, with vital signs and continuous cardiac rhythm monitoring, and often for two hours after the start of the infusion until clinical and ECG parameters are stable. The rapid metabolism and short half-life of vernakalant, around 3 to 5.5 hours, contribute to a quick offset of its effects, beneficial for managing adverse reactions.