A study conducted at the Carlos III National Center for Cardiovascular Research (CNIC) has shed new light on ventricular fibrillation — one of the most dangerous cardiac arrhythmias and a leading cause of sudden cardiac death.

The findings were published in the journal Cardiovascular Research.

Ventricular fibrillation (VF) occurs when the heart’s electrical activity becomes chaotic, preventing the heart from pumping blood effectively. This causes an immediate disruption of blood flow to the brain and other vital organs. Survival rates for out-of-hospital cardiac arrest caused by VF remain extremely low, at less than 10%.

Researchers analyzed the heart’s electrical signals during VF-induced cardiac arrest and discovered that these signals contain important information not only about the condition of the heart itself, but also about damage to other organs, including the brain.

One of the most important findings was that the right ventricle tolerates a lack of blood supply and oxygen better than the left ventricle. This difference creates electrical “gradients” within the heart — variations in electrical activity that reflect the degree of tissue damage.

The researchers also found that these differences are especially pronounced between the inner layer of the heart (the endocardium) and the outer layer (the epicardium), as well as between the epicardial layers of the right and left ventricles.

The greater resilience of the right ventricle appears to be linked to the longer preservation of its electrical activity, indicating stronger metabolic resistance to ischemia — a condition caused by oxygen deprivation in tissues.

The key discovery is that a standard surface electrocardiogram (ECG) recorded during cardiac arrest may help predict a patient’s chances of neurological recovery after resuscitation. In other words, the heart’s electrical signal may indirectly reflect the extent of brain injury.

Study leader David Filgueiras Rama said these findings could help doctors assess a patient’s prognosis earlier during the acute phase of cardiac arrest.

Additional computer models developed in collaboration with the Polytechnic University of Valencia confirmed the results.

According to the researchers, understanding why the left ventricle is more vulnerable to ischemia could eventually help scientists develop new methods to protect the heart during cardiac arrest and improve the effectiveness of resuscitation.

The authors emphasize that treating ventricular fibrillation remains one of the greatest challenges in modern cardiology, and progress in this field will depend heavily on interdisciplinary approaches combining clinical research, engineering models, and physiology.