We observed gradual and substantial increases between 1992 and 2005 in the postdischarge use of β-blockers, angiotensin-modifying agents and statins among elderly patients with myocardial infarction. The use of β-blockers and angiotensin-modifying agents approximately doubled over the study period, and the use of statins increased 18-fold. Furthermore, at the population level, the use of each of these therapies appears to have reached a plateau.
A novel contribution of our study is that it examined the association of physician and hospital characteristics with temporal changes in the use of evidence-based drug therapies. Although we did not find a consistent pattern across the 3 classes of medications, we found an association between physician and hospital characteristics and the rate of increase in the postdischarge use of each of the 3 medication classes over time. For example, in 1992 β-blocker use was higher among patients attended by cardiologists than among those attended by noncardiologists. However, the rate of increase in the prescribing of β-blockers was greater among general internists and other specialists than among cardiologists, such that postdischarge rates were converging between the different specialties by the end of the study period.
The temporal increase in postdischarge statin use was greater among patients attended by cardiologists than among those attended by noncardiologists. An explanation for this difference may be the temporality of the availability of evidence. Evidence for statin use in myocardial infarction patients accumulated in the 1990s, which comprised the early part of our study period. In contrast, evidence for β-blocker use in this population accumulated in the 1980s, before our study period. Thus, cardiologists may have been aware of the evidence for β-blockers, while it took longer for this evidence to disseminate among noncardiologists. Finally, the temporal rate of increase in postdischarge use of angiotensin-modifying agents was greater among cardiologists than among internists and other specialists. Evidence for the use of angiotensin-modifying agents accumulated during the study period, and cardiologists may have had a better awareness of this evidence.
The overall trends in our study are similar to those of a recent study that examined the trends in quality of care provided to myocardial infarction patients in 4 US states between 1992 and 2001.19
That study found improvements, among all patients and ideal candidates, in prescribing at discharge of ASA, β-blockers and ACE inhibitors between 1992 and 2001. Importantly, only a minority of patients were identified as ideal candidates for each therapy. In 2000/01, among all patients, the discharge rates of prescribing ASA, β-blockers and angiotensin-converting enzyme inhibitors were 79.4%, 71.4% and 64.6%, respectively. Among ideal candidates, prescribing rates were 87.4%, 80.3% and 74.8%, respectively.
Our findings are also relevant to policy-makers and clinicians interested in quality improvement for cardiac care. The steady, as opposed to abrupt, increase in the rates of use of drug therapies for the secondary prevention of myocardial infarction over our 14-year study period suggests that changing physician prescribing behaviour is a process that happens slowly over time and that it is achievable with sustained reinforcement. Multiple clinical trials and observational studies that expanded the indications and documented the underuse of these therapies were published during the study period. Our results suggest that these studies likely had a cumulative effect that eventually resulted in close to saturation levels of therapy for secondary prevention.
When restricted to agents for which evidence was disseminated during the study period (angiotensin-modifying agents and statins), our study provides some evidence that cardiologists adapt evidence-based medication use more rapidly than noncardiologists. Furthermore, physicians who cared for a low number of patients with myocardial infarction tended to adopt evidence-based care more slowly than those who cared for many such patients. Finally, teaching hospitals adopted the use of statins more rapidly than nonteaching hospitals. Our findings suggest that there is a need to identify methods to stimulate more rapid uptake of evidence-based drug therapies by physicians practising in nonteaching hospitals, as well as by noncardiologists and physicians who care for a low number of patients with myocardial infarction. Providing low-volume physicians with mentors and encouraging academic institutions to partner with nonteaching hospitals may result in a more rapid uptake of evidence. Finally, we speculate that the development and rapid dissemination of standardized discharge checklists by cardiovascular specialists could improve the uptake of evidence-based practices by groups in which uptake has been historically slower.
Bradley and colleagues conducted a qualitative study to identify factors associated with an increase in β-blocker use after myocardial infarction.20
They found that hospitals with greater temporal improvements in β-blocker use had 4 characteristics not found in hospitals with less or no temporal improvement: shared goals for improvement, substantial administrative support, strong physician leadership advocating β-blocker use and use of credible data feedback.20
The final element suggests that hospital report cards that include hospital-specific postdischarge rates of medication use among myocardial infarction patients, similar to one published earlier in Ontario,21
may help to improve evidence-based prescribing.
There are limitations to our study. First, we used administrative data, which did not allow us to exclude patients who had contraindications to the therapies under consideration. However, as found elsewhere,19
it is likely that postdischarge medication use is even higher among ideal patients for whom therapy is indicated and who have no contraindications than it is in the entire population of patients with myocardial infarction. Furthermore, our use of administrative data allowed us to examine use of prescription medications by all elderly patients with myocardial infarction in our jurisdiction. The data for our study were from a population-based database of incident hospital admissions of patients with myocardial infarction in Ontario. Therefore, our data are comprehensive and not restricted to only tertiary centres or to a registry that is subject to voluntary enrolment.
A second limitation is that we reported the percentage of patients who filled a prescription. We were unable to capture prescriptions that were not filled by the patient. Therefore, our results likely underestimate postdischarge prescribing.
A third limitation is that our analyses were restricted to patients aged 65 and older. Earlier studies have shown that prescribing of evidence-based therapies after myocardial infarction decreases with increasing age.6,7,11
Thus, the use of these therapies is likely even higher among younger patients.
Prescriptions for β-blockers, angiotensin-modifying agents and statins are currently filled by about 80% of elderly patients with myocardial infarction after discharge from hospital. However, there was moderate variation in hospital-specific rates of use of these therapies, with about half of all hospitals prescribing these medications to less than 80% of patients. Furthermore, the rate of increase in use of evidence-based drug therapies use depended on physician and hospital characteristics.
@@ See related research, page 901, related commentary, page 875, and related review, page 909