What is RVR AFib?
Atrial fibrillation (AFib) with Rapid Ventricular Response (RVR) is a heart rhythm disturbance with potentially dangerous complications. In AFib with RVR, the ventricles respond to the fibrillation chaotically and rapidly. The ventricular contractions can reach more than 100 BPM, leading to tachycardia. Prolonged tachycardia further increases some of the risks present only with AFib, like stroke, heart failure, and cardiomyopathies [1, 2].
RVR Afib vs SVT
Here are the key points regarding differentiating atrial fibrillation with rapid ventricular response (RVR AFib) from supraventricular tachycardia (SVT):
- RVR AFib is characterized by an irregular ventricular rate, while SVT typically has a more regular rhythm. Interval stability algorithms in ICDs can help distinguish between the two, with a variability of >80 ms suggesting AFib and inhibiting therapy delivery. [10]
- Entrainment from the right ventricular (RV) base can help differentiate atrioventricular nodal reentrant tachycardia (AVNRT), a type of SVT, from atrioventricular reentrant tachycardia (AVRT). A postpacing interval (PPI) minus tachycardia cycle length (TCL) of >110 ms and a corrected PPI-TCL of >95 ms from the RV base had sensitivities of 100% and specificities of 85-92% for diagnosing AVNRT. [11]
- RV apical electrogram (EGM) morphology analysis using wavelet algorithms can accurately distinguish SVT from ventricular tachycardia with 100% specificity, outperforming superior vena cava (SVC)-based EGMs (44% specificity). [12]
In summary, RVR AFib exhibits an irregular ventricular rate, while SVTs are more regular. Specific pacing maneuvers and EGM morphology analysis can further aid in distinguishing SVT subtypes.
Symptoms of AFib with RVR can be:
- heart palpitation
- shortness of breath
- dizziness
- chest pain
- or even fainting [2].
Early diagnosis is crucial and helps lower the risk of serious complications [2].
How does RVR AFib develop?
Rapid Ventricular Response (RVR) Atrial Fibrillation (AFib) develops due to abnormal electrical activity in the upper chambers (atria) of the heart. When these chambers fibrillate, pathological arrhythmia can lead to irregular contractions of the heart. Especially when the lower chambers (ventricles) respond in a fast manner to the atrial impulses, the pumping function of the heart can be seriously impaired [1].
The development of RVR AFib is not always clear. However, the rapid ventricular response can happen due to AFib, which arises on three main pathways.
One is due to structural changes in the heart. The heart anatomy can change in cardiomyopathy or due to depositions or fibrosis, like the one that occurs after a heart attack.
The second and third mechanisms by which AFib can develop are intertwined. One is the increased automaticity of the heart, and the other is changes in the electrical activity of the heart. In conditions like long QT syndrome and Brugada syndrome, the heart ion channels responsible for heart impulse transmission are impacted, leading to an increased heart rate.
Also, chronic stress can have this effect. A prolonged state of stress can lead to an increase in neuronal stimulation of the heart rate, leading to higher automaticity.
Regardless of the mechanism, certain risk factors increase the probability of AFib and an RVR, such as:
- age
- male gender
- genetics
- high blood pressure,
- high cholesterol levels [2],
- heart failure
- diabetes
- hyperthyroidism
- and alcohol.
Is RVR AFib dangerous?
Yes, AFib with Rapid Ventricular Response (RVR) can be dangerous. It is a heart rhythm disturbance that increases the risk for stroke and other serious complications [10]. When the ventricles beat too rapidly, they don't fill completely with blood from the atria, which can lead to inefficient blood pumping, potentially resulting in heart failure. This is especially common in individuals who already have another type of heart disease. RVR can also exacerbate conditions like congestive heart failure and cause chest pain [11].
How is RVR AFib treated?
The typical approach is heart rate control, and the first step includes pharmacological treatment. Common drugs prescribed are beta-blockers like propranolol and calcium-blockers like diltiazem [1].
The second step is arrhythmia control. Among the most commonly used antiarrhythmic medications are amiodarone, flecainide, propafenone, sotalol, and dofetilide [2]. They stabilize the electric activity of the heart and prevent fibrillation.
In difficult cases, the pharmacological treatment is followed by pacemaker implantation. These special devices allow them to simulate the heart permanently or only interfere when they sense tachycardia or fibrillation [1].
When the pacemaker is implanted, it can be supported by cardiac ablation. This special method allows the cutting of the malignant or any other electric circuit in the heart. It can be used as a singular treatment or in combination with the pacemaker. When used alone, the operator tries to cut all the malignant electric pathways that cause the chamber to fibrillate. In difficult-to-treat non-responsive AFib, cardiac ablation can be used to cut the normal electric pathways between the atria and the ventricle. After the cut, the heart has to rely on permanent, life-long pacing by a pacemaker [2].
In cases where the automaticity of the heart is increased, magnesium could be used for AFib/RVR as a complementary supplement. Magnesium has been shown to significantly reduce the heart rate [3].
What is SVT?
SVT, or supraventricular tachycardia, is a type of tachycardia that originates in the upper chambers of the heart (atria). Individuals with this condition experience sudden and fast heartbeats, which are felt as heart palpitations. SVT can persist for only a few minutes or many hours, and it can be episodical (come and go many times during the day or week) [4].
Among the triggers of SVT are stress, caffeine, alcohol, and smoking cigarettes. Alongside the heart palpitations, other symptoms are experienced, such as dizziness, shortness of breath, fainting, fatigue, and chest pain. SVT can affect anyone, but the first symptoms start most commonly in young adults [4].
How does SVT develop?
Supraventricular tachycardia (SVT) develops due to abnormalities in the electrical system of the heart. The exact development mechanisms of SVT are not fully understood.
However, the most commonly identified mechanism of SVT is a re-entry mechanism. During this phenomenon, the normal signal is conducted without problems, but at a certain point, often the atrioventricular node, it starts to circulate. This circulation, despite the normal natural pacing of the heart, causes an increase in the frequency of the signals transmitted down to the ventricles. It can be imagined that every signal that was emitted circles back in the atrium and is again transmitted down, causing another beat to happen [5].
Can SVT kill me?
Supraventricular tachycardia (SVT) is generally not life-threatening unless you have heart damage or other heart conditions. However, in extreme cases, an episode of SVT may cause unconsciousness or cardiac arrest [10]. A small number of patients with Wolff-Parkinson-White syndrome, a type of SVT, do have a tiny risk of sudden death [11]. In a study, 4.5% of 290 patients with aborted sudden death had SVT that deteriorated into ventricular fibrillation, a life-threatening heart rhythm [12]. Therefore, while SVT is typically not fatal, it can potentially lead to serious health conditions in certain circumstances.
How is SVT treated?
The treatment for SVT depends on the severity, frequency, and duration of the tachycardia. In mild cases, treatment might not be required, while in severe cases, steps must be taken to help the patient [6, 7].
An easy and effective treatment is a vagal massage or maneuver. Its performance allows it to solve up to 96% of all SVTs. The whole procedure is based on the simulation of the vagus nerve, which is responsible for a calming effect on the heart. There are a couple of actions that can make it activate. Among them are coughing a couple of times, holding the breath, and bearing down or putting the facts in cold water [8, 7].
After the diagnosis, it is important to adjust your lifestyle to get rid of the SVT simulators. Limitation of caffeine and smoking cessation are among the basic ones. Also, avoiding physical and emotional stress is important, as is sleeping enough [6, 7].
In cases where the SVT episodes are frequent and long-lasting, pharmacological treatment can also be considered. The most common drug given is adenosine. Sometimes other medications can be prescribed, like diltiazem, verapamil, or metoprolol [6, 7].
Another option for some recurring cases is catheter ablation. During this procedure, the re-entry pathway is destroyed, and the electric currents follow the normal way down to the ventricle [6, 9, 7].