Ventricular Fibrillation (VF) Frequency Calculator
Estimate the electrical oscillation rate during chaotic rhythms.
Calculation Results
How to Calculate Heart Rate in Ventricular Fibrillation
Calculating a "heart rate" in the traditional sense during Ventricular Fibrillation (VF) is clinically impossible because the heart is not contracting in a coordinated manner. In VF, there are no identifiable P waves, QRS complexes, or T waves. Instead, the ventricles merely quiver, resulting in a pulseless state.
However, medical professionals often analyze the Fibrillation Frequency or Fibrillatory Wave Rate to distinguish between "Coarse VF" and "Fine VF." This frequency provides insight into the duration of the arrest and the likelihood of successful defibrillation.
Important Note: A patient in Ventricular Fibrillation has a clinical pulse rate of 0. This calculator measures the electrical frequency of the quivering, not a mechanical heart rate.
The 6-Second Strip Method for VF
To estimate the frequency of the electrical activity during VF, clinicians use the following steps:
Obtain a 6-second EKG strip: This is the standard length for rhythm analysis.
Count the "Peaks": Identify the number of chaotic upward deflections (fibrillatory waves) within that 6-second window.
Apply the Formula: Multiply the number of peaks by 10 to get the estimated frequency per minute.
VF Classification by Frequency and Amplitude
Coarse VF: Characterized by larger, more vigorous waves (usually >3mm). This often indicates a recent onset of VF and a higher probability of successful shocks. Frequency is typically higher.
Fine VF: Characterized by small, low-amplitude waves (<3mm). This suggests the heart has been in VF for a longer period and has depleted much of its metabolic energy (ATP). It can eventually lead to asystole.
Mathematical Formula Used
The calculation for electrical frequency in disorganized rhythms is:
Frequency (waves/min) = (Counted Waves / Strip Duration in Seconds) × 60
Example Calculation
If you count 45 small fibrillatory peaks on a standard 6-second rhythm strip:
Waves: 45
Time: 6 seconds
Calculation: (45 / 6) = 7.5 waves per second.
Final Frequency: 7.5 × 60 = 450 waves per minute.
This would be classified as a high-frequency VF, typically seen in the early stages of cardiac arrest.
function calculateVFRate() {
var waves = document.getElementById("waveCount").value;
var seconds = document.getElementById("stripDuration").value;
var resultDiv = document.getElementById("vfResult");
var frequencyText = document.getElementById("vfFrequencyText");
var classificationText = document.getElementById("vfClassification");
var w = parseFloat(waves);
var s = parseFloat(seconds);
if (isNaN(w) || isNaN(s) || s <= 0 || w < 0) {
alert("Please enter valid positive numbers for waves and duration.");
return;
}
var frequency = (w / s) * 60;
var roundedFreq = Math.round(frequency);
resultDiv.style.display = "block";
frequencyText.innerHTML = "Estimated Electrical Frequency: " + roundedFreq + " fibrillatory waves per minute.";
var classification = "";
if (roundedFreq > 400) {
classification = "This frequency is consistent with Rapid/Coarse VF. This often suggests a high metabolic state of the myocardium, typically seen early in cardiac arrest.";
} else if (roundedFreq 200) {
classification = "This frequency is consistent with Intermediate VF.";
} else {
classification = "This frequency is consistent with Fine VF. Fine VF may be harder to defibrillate and often indicates a prolonged duration of arrest or myocardial exhaustion.";
}
classificationText.innerHTML = "Clinical Context: " + classification;
}