Large-Scale Study Finds 'Flat-Line ECG' Predicts Poor Outcomes in Out-of-Hospital Cardiac Arrests

A comprehensive study conducted in Japan has shed light on the prognosis of patients experiencing out-of-hospital cardiac arrests characterized by a 'flat-line' or asystole on electrocardiograms. Asystole, recognized as the most critical form of cardiac arrest, indicates the heart has completely stopped beating and electrical activity has ceased, manifesting as a flat line on ECG.

The study analyzed data from over 60,000 adult patients who suffered out-of-hospital cardiac arrests between June 2014 and December 2020. Notably, Japanese emergency medical services (EMS) are mandated to continue resuscitative efforts in most cases, providing a unique opportunity to observe the impact of pre-hospital interventions on patient outcomes.

Among these patients, approximately 59.4% presented with asystole, with a median age of 77 years. A significant majority, 93.9%, received advanced life support procedures such as airway management and intravenous epinephrine administration. Despite aggressive treatments, only a small fraction—about 1.8%—survived after 30 days, and even fewer, roughly 0.2%, achieved a favorable neurological state.

The study revealed that advanced airway management increased the likelihood of survival by 45%, and the administration of intravenous epinephrine improved survival chances by 81%. However, neither procedure was associated with better neurological outcomes, highlighting the limited benefits of pre-hospital advanced interventions for asystole cases.

The researchers emphasized that many patients with asystole might be candidates for early termination of resuscitative efforts, especially since only a tiny percentage benefit neurologically from continued treatment. They advocate for the development of guidelines to better determine when to cease resuscitation, potentially improving resource allocation and patient care.

This research underscores the grim prognosis associated with flat-line ECG in cardiac arrest and raises important questions about the value of ongoing resuscitative efforts in these scenarios. The findings are crucial for emergency medicine professionals and policymakers aiming to optimize out-of-hospital cardiac arrest management.

Source: https://medicalxpress.com/news/2025-08-large-scale-reveals-flat-line.html