Chronicity of memory impairment in long-term out-of-hospital cardiac arrest survivors

Abstract

As a result of out-of-hospital defibrillation initiatives, many cities have an increasing population of out-of-hospital cardiac arrest survivors. We previously identified that one third of these patients suffer memory problems in the months after resuscitation. The pattern of memory impairment (impaired recall memory and intact recognition memory) is suggestive of hippocampal damage. In this study we followed up ten subjects who had previously been found to have memory impairment after their cardiac arrest. To assess the chronicity of this memory impairment, we re-tested memory function approximately 3 years after the index events. These subjects were compared with age and sex matched control subjects with previous myocardial infarction and no cardiac arrest. Memory was assessed using the Rivermead Behavioural Memory test (RBMT). To further assess recall and recognition memory we used the Doors and People test (DPT), which is specifically designed to identify deficits in these functions. RBMT scores declined significantly in both groups compared with the original assessment 8 months after cardiac arrest, possibly an effect of ageing-control group: mean (S.D.) 22.2 (1.4)-18.4 (2.9); cardiac arrest group: 16.1 (2.7)-14.6 (4.4). The inter-group difference in RBMT score remained significant (P=0.001). DPT scores were poor in the cardiac arrest group (mean (S.D.) total 5.8 (2.8)), compared with the control group (10.8 (3.4)) who scored normally. Both recall and recognition memory were poor in the cardiac arrest group. We conclude that the memory deficits that we previously observed in cardiac arrest victims are persistent. Both recall and recognition memory are affected, implying that non-selective brain injury may be the mechanism.