When a child's heart stops, onset time of abnormal rhythms is crucial

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Furthermore, not all ventricular fibrillation (VF) is the same, said study co-investigators Vinay Nadkarni, M.D., and Peter A. Meaney, M.D., M.P.H., specialists in Critical Care Medicine at The Children's Hospital of Philadelphia. They added that VF is more likely to be fatal if it is not the initial heart rhythm detected at the start of cardiac arrest, but instead develops later during the arrest, typically during resuscitation.

A research team from the American Heart Association's National Registry of Cardiopulmonary Resuscitation (CPR) analyzed records from more than 1,000 children who suffered cardiac arrests while in the hospital. The largest study by far of outcomes from VF in children, it appears in the June 1 issue of the New England Journal of Medicine. Researchers from Children's Hospital and from the University of Arizona led the study, which included records from 159 participating hospitals.

"This landmark in-hospital study challenges prevailing paradigms in pediatric cardiac critical care," said senior author Robert A. Berg, M.D., of the Steele Children's Research Center at the University of Arizona. "Abnormal rhythms were thought to be uncommon during cardiac arrests in children, occurring less than 10 percent of the time, but we found the occurrence to be 27 percent. When physicians applied shocks promptly from defibrillators, many of these children survived, and the vast majority of the survivors have good neurological outcomes."

"Secondly," continued Dr. Berg, "we learned that cardiac arrests due to initial shockable rhythms often have good outcomes, whereas cardiac arrests with shockable rhythms developing during resuscitation typically have poor outcomes. Now we have to learn what we can do to improve outcomes from the latter cases."

Of the 1,005 children who suffered in-hospital cardiac arrest, more than one in four (272 patients) had documented VF or tachycardia (rapid heart beats) that require shocks at some point during the arrest. In 104 of those patients VF or tachycardia occurred initially, while in 149 patients it occurred at a subsequent time during the arrest. Of the children with initial abnormal rhythms, 35 percent survived to hospital discharge, compared to 11 percent of children with subsequent abnormal rhythms.

The largest group of patients with cardiac arrest, 733 children, had no documented VF or tachycardia. A majority of the group, 602 patients, was known to have asystole (no heart contractions) or no pulse at the start of cardiac arrest. This group had intermediate outcomes: 27 percent survived to hospital discharge.

The researchers were surprised that this group with no VF had better outcomes than children with subsequent VF. Unlike patients with VF, shock delivery with defibrillators does not help patients with asystole or pulseless rhythms.

The question of why survival outcomes from subsequent VF were so low is interesting and requires more research, according to the researchers. One possible explanation, said Dr. Berg, is that children with subsequent VF have more severe underlying heart disease. Another possibility is that clinicians are less aware of the possibility of subsequent VF, and may not diagnose and treat it until it is recognized very late in resuscitation efforts. If this is the case, he added, better recognition, diagnosis and treatment of subsequent VF might improve survival.

The authors point out that, although outcomes may vary, the majority of children with cardiac arrest do not survive to hospital discharge. However, they stress that "CPR and advanced life support are certainly not futile," even among the group with the worst outcomes — children with subsequent VF and tachycardia.

Based partly on data reported by the National Registry of CPR, the American Heart Association recently issued new guidelines for CPR and emergency cardiovascular care, both for children and adults. "Our findings reinforce the concept that CPR with early recognition of shockable rhythms remains a most important aspect of successful cardiac resuscitation," added Dr. Nadkarni, "but clearly, we need to continue to develop, teach and implement better strategies using registries and networks that help us to discern key aspects of cardiac arrest."

Children's Hospital of Philadelphia