Cognitive impairment is common among individuals with heart failure (HF). While the mechanisms linking cognitive dysfunction and heart failure are still being elucidated, structural brain changes and reduced cerebral perfusion have been implicated as important contributors. However, the limited research investigating these potential mechanisms has yielded mixed results. The current study examined the relationships among cardiac output, cerebral blood flow, and cognition, with a specific focus on cardiac output as a potential moderator of cognitive impairment.
A total of 100 older adults with HF completed a comprehensive neuropsychological battery, a measurement of cardiac function (i.e., cardiac output), and transcranial Doppler ultrasonography to quantify cerebral blood flow indices (i.e., mean flow velocity and pulsatility index of the anterior, middle, and posterior cerebral arteries). Hierarchical multiple regression was used to determine whether cardiac output moderated the relationship between cerebral blood flow and cognitive performance in the domains of memory, executive function, attention/psychomotor speed, and language.
A moderating effect of cardiac output was only observed for the relationship between mean flow velocity of the anterior cerebral artery for memory and executive performance. However, these results did not exhibit the expected pattern as higher levels of cardiac output with increasing mean flow velocity of the anterior cerebral artery was associated with decreased executive function and no change in memory performance. Moreover, cardiac output was not found to be a significant individual predictor of performance within these models, and blood flow velocity was only associated with memory performance.
These findings suggest the associations among cardiac output, cerebral blood flow, and cognition in HF are more complex than originally suspected. It is possible these relationships were obscured by the relatively intact cognitive function of the current sample. In addition, an important disease by time interaction may have been missed due to the cross-sectional nature of the study. Future longitudinal work examining more precise measures of cardiac and cerebrovascular functioning are warranted to clarify their relationship with cognition among individuals with HF.