Overview of Pharmacological Cardioversion
Cardioversion is a medical procedure used to return an irregular or abnormally fast heartbeat to its normal rhythm. Your heart usually beats at a steady pace due to a natural control center called the sinoatrial node. This node sends out messages to the right chamber (atrium) of your heart, then to a region called the atrioventricular node, and finally to the lower chambers (ventricles) of your heart. This creates a reliable, regular rhythm.
However, certain factors like changes in the physical structure of the heart, certain medications, or even tissue damage can disrupt this rhythm. The heart may then begin to beat too quickly, too slowly, or in an uneven pattern. When this happens, and the heart rate is either irregular or too fast, doctors may use cardioversion to restore a normal rhythm. If the heart rate is too slow, a process called cardiac pacing might be used to help speed it up.
Before starting treatment, doctors always look for possible reasons behind the abnormal rhythm, such as infection, blood clots in the lungs (pulmonary embolus), or a heart attack (myocardial infarction). This is important because addressing these underlying conditions may help fix the heart rhythm issue.
Anatomy and Physiology of Pharmacological Cardioversion
Cardioversion, a medical procedure that restores a normal heart rhythm, can be used for multiple types of abnormal heart rhythms. These include atrial fibrillation/flutter (AF), which causes your heart to beat irregularly and rapidly, and supraventricular tachycardias (SVT), where your heart speeds up unpredictably at the source of the heart’s electrical signal. Cardioversion is also applicable to ventricular tachycardia, a fast heart rate that starts in the heart’s lower chambers, or ventricles.
However, it’s worth mentioning that cardioversion isn’t suitable for all heart conditions. For instance, ventricular fibrillation, a life-threatening heart rhythm that results in a rapid, inadequate heartbeat, or unstable ventricular tachycardia, a fast, regular heartbeat that may lead to fainting or sudden cardiac arrest, aren’t typically treated with synchronized cardioversion.
Why do People Need Pharmacological Cardioversion
‘Cardioversion’ is a medical procedure used to return an irregular or fast heartbeat to a normal rhythm. There are three types of cardioversion that a doctor might consider, depending on a patient’s condition. If a person has low blood pressure, chest pain, confusion, or signals of a failing heart, the doctor may suggest immediately using ‘electrical cardioversion’. This process uses an electric shock to reset the heart’s rhythm.
Electrical cardioversion can also be used if the patient isn’t in immediate danger, but it does require sedation, meaning the patient will be put to sleep for the procedure. For patients who are stable and not in immediate danger, there are two other alternatives. ‘Supraventricular tachycardia’ refers to a fast heartbeat that originates in the upper parts of the heart. For patients with this condition, the doctor may suggest simple physical techniques that can help to slow down the heart rate.
For example, one technique is the ‘Valsalva maneuver’ – like straining as if you were going to the restroom – or a ‘carotid artery massage’, which involves applying gentle pressure to the large artery in your neck. These techniques can stimulate the vagus nerve, which can help to slow the heart rate.
‘Chemical cardioversion’ is another option, where medication is used to restore a normal heart rhythm. Whether or not this will be effective can depend on several factors, such as the cause and length of the irregular heartbeat.
When a Person Should Avoid Pharmacological Cardioversion
Treating a heart rhythm problem depends on how severe a patient’s condition is. For patients whose vital signs (like blood pressure and heart rate) are stable, doctors may use medicines to correct the problem, called pharmacological cardioversion. But if the patient’s vital signs are not stable (meaning they are hemodynamically unstable), which can be life-threatening, doctors will need to use electric shock treatment, known as immediate electrical cardioversion, to quickly get the heart back to its normal rhythm.
Equipment used for Pharmacological Cardioversion
There is a variety of medications that doctors can use to stabilize an irregular heartbeat in patients with abnormal heart rhythms. However, these methods can sometimes increase the risk of causing other heart rhythm problems. For instance, using some oral medications increases the chance of a very fast, irregular heartbeat by 2%. Therefore, to ensure your safety when undergoing this treatment, it must be carried out in a closely monitored area, like an intensive care unit. Also, in such settings, a machine to restart the heart, known as a defibrillator, must be within reach, and advanced life support equipment needs to be present in the room.
After the heart rhythm has successfully restored to normal, doctors will keep an eye on you for at least 24 to 48 hours or until a specific heart rhythm measure goes back to normal. This measure is known as the QT interval, which is a specific measurement on an ECG (a test that checks how your heart is working) that reflects how long it takes for your heart muscle cells to “recharge” between beats.
Different methods of medication can be used, either taken orally or given through a vein. As an outpatient (a patient who isn’t admitted to the hospital), you can receive intravenous (through the vein) medications. However, during the treatment, the doctor will monitor your heart rhythm and blood pressure continuously to ensure everything is running smoothly.
Who is needed to perform Pharmacological Cardioversion?
Using medication to correct an irregular heartbeat (which is known as pharmacological cardioversion) should be done by a heart doctor, or cardiologist, who has experience with heart rhythm problems (also known as arrhythmias). The cardiologist should know about the different medicines that can be used to treat heart rhythm problems and understand that these medicines can sometimes create new rhythm problems. This is a complex procedure, so it’s important for the cardiologist to be experienced and knowledgeable.
Preparing for Pharmacological Cardioversion
Converting an irregular or high heart rate to a normal rhythm using medication can be done either while the patient is admitted in the hospital, or as a standalone procedure without a hospital stay. However, most health experts suggest that this procedure should be carried out in a place where the patient’s health can be closely monitored.
It’s generally advised for patients to avoid eating before the procedure. During the procedure, heart and blood pressure monitors are used to keep a close eye on the patient’s heart function. Also, two intravenous (IV) lines (tubes that deliver medicines directly into a vein) will be put on the patient’s body. These setups are important to safely and efficiently complete the procedure.
How is Pharmacological Cardioversion performed
Narrow Complex Regular Tachycardia is a type of speedy heart rhythm. It originates from the top chambers of the heart, the atria. Its name comes from the fact that the heartbeat is regular and the electrical signals causing each heartbeat are of normal shape and size on an EKG (QRS complexes). The rate at which the heartbeats occur is often more than 150 per minute. If you have this, usually doctors give you a medicine called adenosine, which has to be given quickly because it only works for a very short time. They start with a 6 mg dose, which might be increased to 12 mg twice if the first dose doesn’t work. Other medicines, like Cardizem or Metoprolol, could also be used.
Regular Wide Complex Tachycardia is also a regular heart rhythm but the electrical signals causing each heartbeat look wider or enlarged on an EKG (QRS complexes). Various heart conditions can cause this rhythm. The treatment is similar to Narrow Complex Regular Tachycardia, starting with adenosine. If that doesn’t work, procainamide might be used, unless the condition is due to a particular type of drug overdose (tricyclic antidepressants).
Narrow Complex Irregular Tachycardia usually arises from conditions like atrial fibrillation or atrial flutter, which cause an irregular heartbeat. For these conditions, immediate treatment might not take place due to the risk of blood clots in the heart. This is especially the case if the irregular rhythm has been happening for more than 48 hours. The treatment usually involves controlling the heart rate and using blood thinners, sometimes followed by a procedure to alter the heart rhythm. As the success rate of using procainamide for altering the heart rhythm is around 60%, it should only be tried in the emergency department. Also, for a few weeks after the procedure, blood thinners might be used to reduce the risk of blood clots.
Irregular Wide Complex or Polymorphic Tachycardia refers to a heart rhythm where the beat is irregular or the shape of the heart’s electrical signals varies. This could be due to a combination of atrial fibrillation and disorders such as Wolff-Parkinson-White syndrome or atrial fibrillation with bundle branch block. It can also be caused by conditions such as torsades de pointes, and ventricular fibrillation. In Wolff-Parkinson-White syndrome, certain medications that affect the heart’s electrical system could be harmful, so cardiology advice should be sought. Medications like Procainamide or Amiodarone can be tried, but sometimes a procedure to restore a normal heart rhythm is needed. If it’s torsades de pointes, a high dose of magnesium usually helps to treat the condition.
What Else Should I Know About Pharmacological Cardioversion?
Pharmacological cardioversion is a procedure that restores normal heart rhythm using drugs. However, it does carry a small risk of causing blood clots that can lead to a stroke. This risk is tiny if your irregular heart rhythm (atrial arrhythmias) has been happening for less than 48 hours. But if your heart rhythm remains irregular for a long time, the risk of stroke becomes higher.
If you have persistent irregular heartbeats that have lasted more than 48 hours or for an unknown length of time, the doctor will usually give you a medicine to prevent blood clots (anticoagulation therapy) for at least 3 weeks before doing pharmacological cardioversion. It’s also important that this medicine is continued for 4 weeks after the procedure, as it takes several weeks for your heart (specifically the atria, the upper chambers of the heart) to recover their normal function and shape. During this time, doctors will monitor if your blood is thin enough to prevent clots but not so thin as to cause bleeding. This is measured by the INR rate, which should be maintained between 2 to 3.
Before the procedure, doctors may use a special type of ultrasound called a transesophageal echo (TEE) to check for any blood clots in your heart. However, this test must be interpreted carefully. There have been cases where blood clots caused problems even when this test didn’t show them. So, even if the TEE doesn’t show a clot, doctors will still continue with the anticoagulation therapy to prevent any possible risks.