Ventricular fibrillation electrocardiogram

 Ventricular fibrillation Microchapters

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Overview

The electrocardiographic findings in ventricular fibrillation comprise of poorly identifiable QRS complexes and absent P waves. The heart rate is >300 beats per minute and it is irregular. The pattern is bizarre with a wandering baseline.

Electrocardiogram

• In summary ventricular fibrillation is described as a grossly irregular wave with marked variability in the electrocardiographic shape.[1]
• Ventricular rate is usually higher than 300 per minute.
• Cycle length is usually less than 200 milliseconds.

Characteristics of the Ventricular Fibrillation Waveform

Ventricular fibrillation can be described in terms of its electrocardiographic waveform appearance. All waveforms can be described in terms of certain features, such as amplitude and frequency. Researchers have looked at the frequency of the ventricular fibrillation waveform to see if it helps to elucidate the underlying mechanism of the arrhythmia or hold any clinically useful information. More recently, Gray has suggested an underlying mechanism for the frequency of the waveform that has puzzled investigators as possibly being a manifestation of the Doppler effect of rotors of fibrillation.[2] Analysis of the fibrillation waveform is performed using a mathematical technique known as Fourier analysis.

Power Spectrum

The distribution of frequency and power of a waveform can be expressed as a power spectrum in which the contribution of different waveform frequencies to the waveform under analysis is measured. This can be expressed as either the dominant or peak frequency, i.e., the frequency with the greatest power or the median frequency, which divides the spectrum into two halves. Frequency analysis has many other uses in medicine and in cardiology, including analysis of heart rate variability and assessment of cardiac function, as well as in imaging and acoustics.[3][4]

EKG Examples

Shown below is an EKG with a heart rate of more than 300 per minute, no clearly identifiable QRS complexes and absent P waves depicting ventricular fibrillation.

Copyleft image obtained courtesy of Wikipedia, http://en.ecgpedia/wiki/File:Lead_II_rhythm_generated_ventricular_fibrilation_VF.JPG

Shown below is an EKG with an irregular heart rhythm, unrecognizable QRS duration, absent P waves and bizarre waveforms depicting ventricular fibrillation .

Copyleft image obtained courtesy of ECGpedia, http://en.ecgpedia.org/wiki/File:Rhythm_ventricular_fibrillation.png

Shown below is an EKG initially depicting sinus rhythm, which then converts into a ventricular fibrillation wave pattern of irregular rhythm and unrecognizable QRS and P waves in all the leads. The patient had an inferior wall myocardial infarction and has developed ventricular fibrillation as depicted in the EKG.

Copyleft image obtained courtesy of ECGpedia, http://en.ecgpedia.org/wiki/File:ECG_SR_to_VF_in_INF_MI.jpg

Shown below is an EKG monitor strip depicting the induction of ventricular fibrillation with paced beats and a low energy T wave shock. This is followed by termination of the ventricular fibrillation by the device and then return to sinus rhythm. The tracing was made during testing of the implanted defibrillator in a middle-aged woman with ventricular tachycardia and a structurally normal heart. Note the QT interval in this patient of 500 ms which is long for the heart rate of 60/min.

Copyleft image obtained courtesy of ECGpedia, http://en.ecgpedia.org/wiki/File:E00031733.jpg