Ventricular flutter and ventricular fibrillation are life-threatening arrhythmias. They are most common in coronary artery disease and in the terminal stages of various diseases. Additionally, antiarrhythmic drugs, especially those that prolong the QT interval and cause Torsades de Pointes, severe hypoxia, ischemia, pre-excitation syndrome with atrial fibrillation and rapid ventricular rates, and electrical injuries can also trigger these conditions.
ECG features
Ventricular flutter appears as a sinusoidal pattern with large, regular amplitudes. The QRS complexes are monomorphic with a frequency of 150 - 300 bpm (usually over 200 bpm), sometimes difficult to distinguish from ventricular tachycardia. In ventricular fibrillation, the waveform, amplitude, and frequency are extremely irregular, making it impossible to identify QRS complexes, ST segments, or T waves. The duration is short, and without prompt intervention, cardiac electrical activity rapidly ceases within minutes.
Figure 1 Ventricular flutter and ventricular fibrillation
In lead II, continuous oscillations resembling a sine wave are observed at a frequency of 250 bpm, with no discernible QRS complexes, ST segments, or T waves, indicating ventricular flutter.
In lead III, irregular oscillations with varying shapes and amplitudes are present at a frequency of approximately 300 bpm, with the absence of QRS-T complexes, indicating ventricular fibrillation.
Clinical manifestations
Ventricular flutter and fibrillation can cause dizziness, followed by loss of consciousness, convulsions, apnea, and even death. During an episode, the ventricular activation sequence is disrupted, causing rapid and weak regular or irregular activity of the ventricular myocardium, severely impairing ventricular ejection. This leads to no cardiac output, absence of heart sounds and pulse, and undetectable blood pressure, resulting in cessation of blood perfusion to the heart, brain, and peripheral tissues. The atria may continue to beat independently or at the frequency of ventricular fibrillation for a period. Ultimately, cardiac electrical activity ceases.
The treatment for ventricular flutter and fibrillation can be seen in cardiac arrest and sudden cardiac death.