Atrial fibrillation with RVR (rapid ventricular response) is an irregular electrical activity in the atria of the heart that leads to abnormal contraction there and in the ventricles. It is characterized by an excessively rapid heartbeat, but may or may not cause symptoms in some patients. There are different causes of atrial fibrillation, which is not a disease in its own right but a malfunction of the atrial cells' pacemaking. Complications include the gradual scarring of the atrial muscle, and become more probable if the problem becomes chronic.
The most common variety of cardiac arrhythmia, atrial fibrillation with RVR occurs when the electrical activity of the atria is erratic, causing more frequent ventricular contraction and increasing the heart rate. The normal heartbeat is called the sinus rhythm and is measured with an electrocardiogram (ECG). The ECG divides a single beat of the heart into six waves, each of which has a clearly defined order and duration. Excessive excitation of the atrial cells causes electrical waves to become spatially distinct and change their normal shape, resulting in an ECG display unique to this condition and used to diagnose it.
The rapid ventricular response accompanying some cases of atrial fibrillation occurs when cardiac muscle cells in the atria overcome their intrinsic pacemaker's signals, firing rapidly out of their normal pattern, an activity that then spreads to the ventricles. Atrial electrical signals must pass the heart's atrioventricular node (AV) in order for the contraction of a heartbeat to continue on to ventricular muscle. The AV node cannot convey all the rapid atrial electrical activity, so ventricular contraction rate remains lower than the atrial rate, but still is abnormally fast. Any ventricular rate greater than 100 beats per minute (bpm) can be called a rapid ventricular response.
Rapid heart rate or tachycardia can strain the heart, and patients may experience shortness of breath or chest pain. Sometimes, a heart quivering or fluttering is reported. Many instances are asymptomatic, though, and are only identified when a patient receives an ECG. This problem is not a condition in itself, but a consequence of other health disturbances. Lung disease, congestive heart failure, or a history of cardiovascular disease increase the risk of a patient having such complications.
Atrial fibrillation with RVR is more likely to cause health problems if it becomes a chronic condition than if it occurs only once. As the atrial walls become dilated over time, the sensors of the physiological feedback system that monitors blood pressure there are affected, and hypertension may result. Fibrosis of the atria, the formation of excessive fibrous tissue, occurs during prolonged atrial fibrillation due to the formation of scars. Further, the rapid ventricular response might lead to ventricular fibrillation, a life-threatening condition if the RVR causes the contraction rate to exceed 300 bpm.