At what rate we will say 'atrial fibrillation with fast ventricular rate'?

generally it is presumed that if ventricular rate is > 100 & ECG showing atrial fibrillation v label it as 'atrial fibrillation with fast ventricular rate'.But medicine deals with evidence not works on presumption.do u know any source where the definition is written?

Syed - I see where you are going with your question. I have never seen any source defining a "rapid ventricular response" as being >= any particular heart rate. Even the definitive cardiology texts - Braunwald and Topol - do not give a specific definition. However, that is not to say that we don't have any guidelines to go by.

The best places to look for this kind of information are the ACC/AHA guidelines. The 2006 guidelines for the management of patients with atrial fibrillation uses the phrase "rapid ventricular response" many times without explicitly defining it. BUT it does talk about the definition of "adequate rate control", so we can infer that anything faster than what is "adequate" can be defined as "rapid".

From the guidelines: "The definition of adequate rate control has been based primarily on short-term hemodynamic benefits and has not been well studied with respect to regularity or irregularity of the ventricular response to AF, quality of life, or symptoms or development of cardiomyopathy. No standard method for assessment of heart rate control has been established to guide management of patients with AF. Criteria for rate control vary with patient age but usually involve achieving ventricular rates between 60 and 80 beats per minute at rest and between 90 and 115 beats per minute during moderate exercise.

For the AFFIRM trial, adequate control was defined as an average heart rate up to 80 beats per minute at rest and either an average rate up to 100 beats per minute over at least 18-h ambulatory Holter monitoring with no rate above 100% of the maximum age-adjusted predicted exercise heart rate or a maximum heart rate of 110 beats per minute during a 6-min walk test. In the RACE trial, rate control was defined as less than 100 beats per minute at rest. Only about 5% of patients from these large clinical trials required AV ablation to achieve heart rate control within these limits."

Based on this, an average heart rate of 100bpm seems a reasonable cut-off for defining someone as having atrial fibrillation with a rapid ventricular response. I know you were probably looking for a more definitive answer, but that is the extent of what can be found in the literature. Hope that helps!

Tachycardia is defined as greater than 100bpm as you correctly mentioned and that is technically fast ventricular rate.

This is not a hard and fast, black and white, rule and I sincerely doubt you would be tested on such...99 is fine, 101 is not. No, it doesn't work that way.

Firstly most of the time afib seems to run at generally fast rates between 120 to 140, though this is variable too and it can be seen as high as 200. So if someone were creating a case study, they would not use 101 as a rate (though it indisputably would be an abnormally fast rate), they would use 138 bpm to depict a more realistic picture.

In really treating patients, you need to take in context with whatever else is going on.

For instance, if given rate control medication (CCB or B-blocker), then the rate runs down to 32, then of course 100 is preferrable. On the other hand if a person has severe heart disease and any heart rate over 85 is going throw them into acute coronary syndrome, then you do what you need - maybe even rate control medication with external pacing until the problem can be more permanently fixed.

I hope this helps. Good luck.