Student: Te Kiriwera Wicksteed
Supervisors: Suzanne Pitama, Vicky Cameron
Sponsor: Health Research Council
The Hauora Manawa/Community Heart study is a 5 year HRC funded project that is looking at the prevalence of cardiovascular risk factors in a Maori community. The first stage of the study has just been completed looking at a rural Maori population (Wairoa, Hawkes Bay). 256 participants were recruited and all survey and clinical data is now being correlated.
The aim of this project was to document the prevalence of left ventricular hypertrophy in this community. Left ventricular hypertrophy (LVH) is thickening of the muscle of the left ventricle of the heart. It occurs in response to stress on the heart and is associated with an increased risk of future cardiovascular event. The most sensitive diagnostic tool is echocardiogram, an ultrasound scan of the heart.
The next goal was to explore the calculated risk factors associated with LVH- sex and age, body mass index (BMI), weight, height, systolic and diastolic blood pressure, fat free mass (FFM) and calculated cardiovascular risk (using Best Practice software).
Participants were not included if the clinical data collected from them was not complete. This included participants who were unable to have fat free mass recordings due to pregnancy or lack of mobility, and those whose echo measurements could not be obtained. This left a study population of 239 people. Of the 239, 59% were female. The age group ranged from 20-65.
The diagnosis of LVH was made by echocardiogram using the American Society of Echocardiography (ASE) criteria. Once the prevalence of LVH had been documented, the calculated risk factors were put into a database for analysis. This data required cleaning before analysis could be done. The data was entered into EpiInfo (statistical analysis software) to examine relationships between the risk factors. Further analysis was undertaken looking specifically at the relationship between left ventricular mass (as a marker of LVH) and other calculated risk factors. The data was also used to examine the profiles of risk factors of the populations with and without LVH.
The prevalence of LVH in this community was 52/239 (22%). There was a strong relationship between left ventricular mass (LVM) and weight, and BMI, however the strongest correlation was between LVM and fat free mass. This is consistent with recent research. It is interesting to note that there was not a strong relationship between blood pressure and LVM, however this may be accounted for through appropriate medication for hypertension. There was not a strong relationship between LVM and height or calculated cardiovascular risk.
When comparing the population with LVH and the population without LVH there are significant differences in the risk factors. In general, the LVH population has a higher BMI, higher blood pressure and higher fat free mass than the population without LVH but there was no difference in height. In addition, the estimated cardiovascular risk (% risk of a cardiovascular event within 5 years) was significantly higher in those with LVH.
This project identified that the prevalence of those who had LVH within this cohort was 22%. Currently there is no data on prevalence rates in New Zealand. This study identified that there were statistically significant differences between the population who had identified LVH and those that did not have LVH present (in accordance with the echo findings). More complex analysis will be undertaken to explore possible further correlations between risk factors and also to look at confounding variables