Validation of an instrument to measure cognitive function in patients with heart failure

Thesis (Ph.D.)--University of Rochester. School of Nursing, 2007.Background: Heart Failure (HF) patients are reported to have twice the risk of having cognitive deficits compared to the general population. Cognitive deficit in HF is subtle and reversible. Cognitive deficit has a significant impact on HF patients’ choices for planning their lifestyle, financial, legal and personal affairs. Cognitive deficit also may decrease compliance and cause delay in seeking health care, which potentially could increase the risk of mortality and morbidity and thus increase health care cost due to frequent hospitalization. Although cognitive deficit is common among people with HF, cognitive screening is not routinely performed due to lack of a simple screening tool and the misconception that cognitive changes are part of normal aging. Objective: To compare the Montreal Cognitive Assessment (MoCA) with the Mini Mental Status Examination (MMSE) regarding their reliability and appropriateness as tools to measure cognitive function in persons with HF, and to validate both measures against physiologic measures of cerebral perfusion. Design: Cross sectional Setting and Sample: Ninety community dwelling adults aged 50 and above with a clinical diagnosis of HF, cared for by cardiologists affiliated with a tertiary university hospital, who met the inclusion criteria were enrolled from January to June of 2007. Measurement: Participants were simultaneously administered the MMSE and the MoCA along with questionnaires to measure covariates including: co-morbidity, depression, disability, and the six-minute walk test. Clinical and demographic data were collected via a questionnaire developed for the study. Cerebral perfusion was measured using transcranial doppler to obtain cerebral perfusion pressure (CPP) and impedance cardiograph to obtain cardiac index (CI). Results: Participants were predominately men 59 (66%), Caucasian (78%), aged 50-89 with mean age 62 (SD + 9 years), 54 % were in NYHA class II, and 32 % in NYHA class III, 80% were in HF stage C, and 77% had low ejection fraction (<40%). Hierarchical multiple regression and logistic regression analyses revealed no significant correlation between cerebral perfusion measures (CPP & CI) and cognitive measures (MMSE & MoCA). However, the MoCA was found to be more sensitive than the MMSE in identifying subtle cognitive changes. Forty nine (54.4%) of the participants scored below the cut of score of 26 on the MoCA suggesting mild cognitive impairment and 15 (16.7%) scored less than 22 on the MoCA suggesting severe cognitive impairment while, only two participants (2.2 %) scored less than 24 on the MMSE. Sixty two of the participants (68.9%) scored poorly on the Visuo-spatial/executive domain, short term memory (61.1%), and delayed recall (86.7%) supporting current literature on domains of subtle cognitive changes seen in HF. Language deficit was reported among HF patients as poor IQ or learning skills by Mauro and colleagues, which were identified among 64.4% of the participants in our study. The MoCA also demonstrated an increased sensitivity of 96% and specificity 78% when using a cutoff score of < 22 with good area under the receiver operating characteristic curve (ROC curve =0.804). The non-association between cerebral perfusion measures (CPP & CI) and cognitive measures (MMSE & MoCA) could mean that the cognitive function in this sample may have different etiologies than cerebral perfusion or influenced by various exogenous factors that affect endothelial phenotype such as vascular endothelial growth factor, B-type natriuretic peptide or BNP, and cytokines which were not measured. Also, we attempted to measure CPP before it crossed the ischemic threshold to explore whether this was related to subtle cognitive dysfunction. Hence, we recruited community dwelling HF patients. The results indicate that the MoCA actually may have identified subtle cognitive symptoms while the CPP was still with in the normal range on these stable community dwelling HF patients. Protective benefit of angio-tension enzyme inhibitors (ACEI) on cognition may have played a role for the non-significant results since, 90% of the participants were on ACEI compared to 75 % reported as National average. Implication: This study demonstrated that the MoCA may be a sensitive tool to assess subtle cognitive changes in persons with HF. This study prompts further exploration with an appropriately designed longitudinal study to validate the MoCA as an appropriate tool to assess subtle cognitive changes in HF