Study Design
This was a retrospective matched cohort study with a twelve month follow up duration from the index PCI. It utilised an existing data source of patients who received PCI with coronary stenting. The study consisted of two groups, an intervention group from 2020 who received a consult in the telehealth cardiology pharmacist clinic, and a control group of patients prior to 2020 who did not receive the intervention.
Telehealth Cardiology Pharmacist Clinic
The telehealth cardiology pharmacist clinic involves a 20-minute consultation with a pharmacist addressing a number of different care elements. The mode of delivery of the service, as well as patient and clinician acceptability has been assessed in a previous study. [11] A detailed best-possible medication history is taken with secondary source verification in line with the Society of Hospital Pharmacists Australia: Standards of Practice in Clinical Pharmacy. [12] Questions regarding cardiac symptoms and a functional assessment are completed, which align with the outcome measures defined in the Melbourne Interventionalist Group (MIG) assessment form. These questions are designed to understand the burden of cardiac symptoms as well as identifying any potential urgent referral points for patients. Education on cardiac health and treatment is provided in line with the National Heart Foundation of Australia National Cardiac Rehabilitation Quality Indicators. [13] Patients are consulted at one month, three months and twelve months post PCI. The format is repeated for each of the consultations, with a focus on building on patient knowledge of cardiac medications and health. Patients are specifically asked about adherence to each medication comprising OMT, with adherence defined as taking the medication more than 80% of the time. [14]
Study Setting
The study was based at a large public regional health service in Victoria, utilising data collected as part of the health services participation in the Victorian Cardiac Outcomes Registry (VCOR) and MIG, as well as data from the telehealth cardiology pharmacist clinic consult letters.
Study Participants
There are approximately 250 PCI and coronary stent patients who present to Grampians Health Ballarat annually. Patients who received PCI were enrolled into an opt-out registry maintained by the MIG. Data is collected at the time of PCI and at 30 days. Twelve-month follow up data was available for patients who received percutaneous coronary intervention with coronary stents in the 2015-2017 cohort. From 2017, routine twelve month follow up data was not collected.
Patients in the intervention arm had their baseline MIG data collected at time of PCI and at 30 days. Due to the lack of twelve-month MIG data, the telehealth cardiology pharmacist clinic report was used to check if OMT was present at twelve months.
In order to allow for comparison between control and intervention groups, set criteria were established to ensure twelve-month follow up data was available. It was the intention of this study to enrol all patients who received PCI for ACS during the study period of January 2020 to July 2020. All participants with ACS and PCI were included, even if they progressed to coronary artery bypass grafting. However, if no PCI was done, these patients were excluded.
Inclusion criteria for study:
- Adults aged 18 years or older
- Diagnosed with ACS requiring PCI with coronary stenting, inclusive of
- ST elevation Myocardial Infarction (STEMI)
- Non-ST elevation Myocardial infarction (NSTEMI)
- Unstable angina
- Patients who had twelve-month follow up data available for analysis (either via registry or clinic for control and intervention arms respectively)
- Patient or carer able to participate in telehealth consult or via phone (intervention arm only)
Exclusion criteria:
- Patients with ACS not treated with PCI who were transferred for surgical intervention
- PCI without stent deployment (balloon angioplasty only).
- Elective PCI for stable angina
- Patients with unsuccessful PCI that were escalated to surgical management
- Patients who chose to opt-out from registry or clinic at any time during the twelve-month follow up period
Study Outcomes
The primary outcome was the difference of self-reported Optimal Medication Therapy (OMT) (all four medication groups present) adherence at twelve months post coronary stenting between a matched cohort of patients who received the intervention and those who did not.
Secondary outcomes included the difference in Near-optimal Medication Therapy (NMT) (three medication groups present), Sub-optimal Medication Therapy (SMT) (less than three medication groups present), and individual medication groups (DAPT, statin, beta blocker and ACEI/ARB/ARNI) between control and intervention matched cohort.
Additionally, the difference in Major Adverse Cardiovascular Events (MACE) difference at twelve months between control and intervention matched cohort were investigated. MACE was defined as death, non-fatal myocardial infarction, stroke, or hospital readmission.
To validate the use of self-reported adherence within the study, self-reported adherence was compared to calculated medication possession ratio (MPR) via the patient’s primary pharmacy dispensing records. This outcome was only measured in the intervention group due to dispensing data availability.
Statistical Analysis
Cohort matching was used to reduce confounding between the control and intervention arms. [15] As this study is retrospective and non-randomised, the use of individual matching between cohorts provides a method to reduce confounding. [15] The matching criteria were selected due to both their availability within the data set as well as evidence in the literature regarding their significant correlation with changing adherence patterns between participants. [16-18]
In this study, matching was performed using individual matching across five criteria:
- Age stratification at time of percutaneous coronary intervention (PCI) [3]
- <50, 50-59, 60-69, 70-79, 80-89, >89
- Sex
- Type of Acute Coronary Syndrome (ACS)
- STEMI, NSTEMI, unstable angina
- Left ventricular dysfunction at PCI defined as by stratified ejection fraction [19]
Data matching was indexed at the time of the ACS event and baseline MIG data collected. Matching was performed using Stata® 17.
Based on previous studies, adherence to medications at twelve months post ACS event can vary between 45-75%. [3, 7] Based on a population size of approximately 100 patients to have ACS in the seven-month (January 2020 to July 2020) intervention period, with an alpha of 0.05 and beta of 0.2, the sample size would need to be 73-78 matched patient pairs.
For outcome calculations, McNemar’s chi-squared analysis for matched data was used between the control and intervention pairs. This was repeated across the primary and secondary outcomes involving matched data. For the adherence measure validation outcome, an R2 value was calculated between self-reported adherence scores and calculated MPR. A value of 0.75 or greater was considered a substantial correlation.