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Abstract
Cardiovascular absolute risk (CVAR) assessment involves a multifactorial approach to determine a person’s numerical risk of experiencing a cardiovascular event in a given time period. Using this approach allows treatment, including pharmacological therapy, to be targeted to those at highest risk. CVAR assessment is widely recommended by guidelines, but to date its use has shown only modest improvement in prescribing for high risk patients. This thesis aimed to investigate what impact CVAR assessment had on prescribing of cardiovascular medications in Australian general practice, and to understand how general practitioners (GPs) utilised CVAR assessment.
The thesis involved two phases. The first phase was a pilot study that utilised a before and after study design evaluating a CVAR assessment intervention. The second phase used a mixed methods approach, involving a cluster randomised controlled trial (RCT) with an embedded qualitative component. The RCT tested a complex intervention incorporating GP training, CVAR assessment of patients and practice support. The qualitative component involved interviews with GPs and patients.
The pilot study recruited six GPs and 54 patients and found minimal impact of the intervention on GP prescribing. The RCT, involving 36 GPs and 1074 patients, showed no significant difference between groups in the prescription of antihypertensive and/or lipid-lowering medications. Regression analysis indicated that GPs based prescribing on targets for blood pressure and lipids rather than CVAR scores. This suggested single risk factors were still influential in determining management decisions. Imputation analysis of patients on medications at baseline indicated the potential for CVAR assessment to reduce prescribing among low risk patients, although this seldom occurred.
The interviews confirmed that, for most GPs, utilising CVAR assessment did not influence their decision making about prescribing. They did, however, find it useful to educate and motivate patients. For a minority, the process was valuable for prescribing decisions, but overall the intervention was insufficient to significantly change existing approaches to CV risk management. These findings helped explain the outcomes of the RCT as well as identifying issues that impeded the adoption of CVAR assessment. This thesis demonstrated the difficulty in shifting GPs to a CVAR approach for pharmacological decision making.