The American Heart Association estimates that over 350,000 individuals suffer out-of-hospital cardiac arrests every year in the United States and that the average survival rate with good neurologic function is 8.3 percent. For a specific subset of these cases, researchers at the U.Va. Health System have devised a tool to predict patients’ neurologic outcomes.
According to cardiologist Dr. Chris Rembold, professor of internal medicine and physiology, there are several possible outcomes of a cardiac arrest. In the first case, the cardiac arrest could be witnessed and the patient could get their heart shocked back into rhythm right away, wake up and be fine. Second, the patient could be shocked into normal cardiac rhythm but not wake up immediately. In a final situation, the patient could die or continue to have cardiac problems following resuscitation attempts.
In the case that the patient returns to a normal cardiac rhythm but does not regain consciousness, a therapy called Targeted Temperature Management can be used to protect a patient’s neurologic function. According to Dr. Lawrence Gimple, a professor of medicine and cardiology and the director of Clinical Cardiology, TTM involves cooling patients to protect against neurologic damage, and then slowly warming the patient back up.
Dr. Alex Parker, a cardiovascular medicine fellow working on Gimple’s team, explained that they were searching for a way to predict which patients would benefit from TTM.
“We treated patients who have made unexplainable recovery after surviving an arrest, and others who are left with either devastating neurologic injury or die,” Parker said. “We became interested in finding a tool that would predict which patients would benefit from temperature management, and which patients that would have poor outcomes regardless of temperature management.”
Gimple and his team developed a simple tool, called C-GRApH, to provide more information to families and physicians about a patient’s chances of survival with a good neurologic outcome based on five easily identifiable parameters. Each letter stands for a different variable — coronary artery disease, glucose, rhythm, age and pH.
According to Parker, the five variables that they determined to be most predictive of a poor outcome “were a known history of coronary artery disease, glucose greater than 199, a non-shockable rhythm at arrest, age greater than 45 and arterial pH less than or equal to 7.0.”
Using these parameters, scores are calculated as a whole number on a scale of 0 to 5, with a lower score corresponding to a greater chance of survival with good neurologic function, Gimple said. Higher scores are indicative of a much greater chance of an unfavorable outcome, while mid-range scores do not provide as much insight.
The most important way that this tool differs from past ones is that it relies exclusively on objective data that can be easily collected.
“Other scores people have done have asked the question, ‘How long was the patient unconscious?’ [and] ‘How long was CPR done?’ and the fact is if you ask the family that was there how long it lasted for, they'll say ‘Well it lasted forever,’ so they have no idea how long that time was,” Gimple said. “So when you try to use parameters like that, it's much more difficult. But C-GRApH is using objective numbers and pieces of medical information that are typically known, and that's how the score is calculated.”
Measures such as arterial blood pH and blood glucose are indicative of how long a patient might have been unconscious, and are data points that are routinely collected in emergency rooms for patients who have suffered cardiac arrest, Gimple said.
While this tool was developed using information from University patients, it was also able to accurately predict outcomes for a cohort of patients from Cleveland, proving its predictive value regardless of demographic differences, according to Gimple.
Gimple also cautioned that the tool was meant only to provide information and perspective, and not to prescribe specific courses of action to physicians or families, as that had not yet been studied.
"It is not a tool that tells doctors what to do or tells families what to do,” Gimple said. “It simply provides information and perspective.”
One of the most important implications of their work, besides providing more information to physicians and families, is the future directions for the research to take, Gimple said. Other studies could look at whether specific therapies would benefit patients with certain C-GRApH scores or if the inclusion of certain biomarkers in the score could provide greater specificity.
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