The present study aimed to determine the impact of a patient’s place of residence on rates of cardiac catheterization and on long-term rates of all-cause mortality and readmission to hospitals in Nova Scotia. Following adjustment for differences between patients in terms of age, sex, comorbid illness and estimated income level, place of residence in areas remote from the single tertiary cardiac care centre in Nova Scotia emerged as being independently associated with lower rates of cardiac catheterization within the first six months following admission, as well as higher long-term rates of readmission to the hospital for any cardiac cause. No differences were noted regarding long-term rates of all-cause mortality.
Our findings confirm those of studies (2
) in other provincial jurisdictions across Canada with regard to regional variation in rates of cardiac catheterization following an acute MI. However, we were unable to attribute such regional variation to differences in socioeconomic status, an association that has been demonstrated in earlier studies from Ontario and Quebec (5
). Rather, place of residence emerged as an independent predictor of rates of cardiac catheterization following an acute MI. This is similar to findings from the United States (20
) in which decreased distance between the patient’s residence and the nearest cardiac revascularization services was found to be predictive of increased rates of invasive cardiac care.
The relationship that we documented between residence in either UAs or RAs, and reduced rates of and prolonged wait times for cardiac catheterization may reflect barriers in access to care that exist at the level of the health care provider. We have shown that patients in Nova Scotia who were admitted closest to or at the QEII Health Sciences Centre were more likely to be admitted under a cardiologist. Prior studies from the United States (21
) have shown that patients with an acute MI who were admitted under a cardiologist were more likely to undergo coronary angiography and subsequent coronary revascularization. This appears to hold true in Nova Scotia, where rates of cardiac catheterization were highest in areas in which patients were more likely to be cared for primarily by a cardiologist. We hypothesized that the reduced rates of cardiac catheterization seen in patients from UAs or RAs would be associated with increased rates of noninvasive testing but found that this was not the case because patients with the highest rates of cardiac catheterization were also those with the highest rates of noninvasive testing.
Alternatively, patient-specific factors may have influenced whether a patient sought advanced cardiac care and, ultimately, underwent cardiac catheterization. A recent study by Alter et al (6
) demonstrated that a patient’s socioeconomic status, as measured by self-reported income and education levels, influenced his/her access to cardiac services as well as his/her perception of the care received. It may be postulated that patients living in closer proximity to the tertiary cardiac care centre represented a group of people who were more motivated to seek out the highest level of care available to them, thus causing higher rates of cardiac catheterization in this group. Conversely, patients from more remote areas, particularly elderly patients, may have been less inclined to travel to the tertiary care centre, either because they were unwilling to undergo more aggressive treatment or because they were satisfied with the care available to them at their local hospital.
Following cardiac catheterization, rates of subsequent PCI or CABG and wait times from the point of catheterization to the point of revascularization did not differ by place of residence. This likely reflects the relatively uniform approach to revascularization employed by practitioners in Nova Scotia and the effectiveness of a peer-reviewed cardiovascular surgery conference system practised at the QEII Health Sciences Centre, where patients who are referred for surgery are impartially reviewed by a panel of cardiovascular specialists that determines surgical eligibility and priority based on such criteria as coronary anatomy, stress-test results and functional status, regardless of place of residence (23
In the present study, long-term survival was found to be similar across the three geographical groups. Studies in both Canada and the United States have repeatedly shown that the impact of increased rates of cardiac catheterization on long-term survival is negligible (3
). However, randomized clinical trials have demonstrated reduced rates of symptom recurrence, readmission to the hospital and, in some instances, rates of mortality, in patients admitted with an acute MI who were managed with an early invasive strategy, compared with those who were managed conservatively (26
). In their meta-analysis of 23 randomized trials comparing the results of primary PCI with those of thrombolytic therapy in patients with ST segment elevation acute MI, Keeley et al (29
) touted the benefits of primary PCI in reducing mortality and morbidity, both in the short term and in the long term. It is possible that the lack of a mortality benefit in patients from MAs despite their higher rates of cardiac catheterization reflects the absence of a comprehensive primary PCI program at the QEII Health Sciences Centre during the study period relative to other cardiac care centres in Canada (13
In the present study, rates of readmission to the hospital for any cardiac cause over time were significantly increased in patients living outside of MAs, likely reflecting the reduced rates of and delays in access to cardiac catheterization experienced by affected patients. However, other factors may have played a pivotal role in determining whether a patient was readmitted to the hospital. First, although the use of evidence-based cardiovascular medications in Nova Scotia is rising and approaching reasonable levels for certain drug classes (30
), we found significant variation in prescription rates of disease-modifying cardiovascular medications across the three geographical strata, which may, in turn, explain the differing readmission rates. Second, the level of follow-up with either a specialist or a nonspecialist after initial discharge from the hospital may have varied considerably across geographical groupings and subsequently impacted the patient’s eventual need for readmission (31
). Finally, the threshold for readmission to the hospital, particularly for diagnoses other than acute coronary syndrome, may have been lower in peripheral, nontertiary care centres in which health care providers may have been less comfortable managing such conditions on an outpatient basis.
The present study is the first to employ a province-wide, population-based, disease-specific registry to examine the effect of clinical and non-clinical factors on access to invasive cardiac services and long-term outcomes following an acute MI. It provides valuable insights into the role that place of residence plays in determining the level of care that a patient with an acute MI receives and the potential deleterious effect that it may have on rates of readmission to the hospital over time. However, the present study is not without its limitations. First, there may be issues surrounding data accuracy, in particular as they pertain to the reporting of comorbid illnesses. Residents of MAs were younger and had a higher income but, surprisingly, they possessed a greater burden of comorbid illness. Patients from RAs were expected to have the highest burden of comorbid illness and patients from MAs were expected to have the lowest. While this finding may reflect the migration of individuals with advanced comorbid illnesses (eg, patients with renal failure requiring dialysis) to areas in which specialized expertise and services exist, it may also be the result of under-reporting or under-diagnosis of comorbid conditions such as hypercholesterolemia and hypertension among residents of UAs and RAs. This limitation is likely not exclusive to clinical registries. In the present study, the distribution of comorbid illnesses across geographical groupings only served to underestimate the differences in risk-adjusted rates of readmission seen between residents of UAs and RAs, and residents of MAs. Second, a clinical registry, while more detailed than an administrative dataset, is still not fully comprehensive. Therefore, one cannot ensure that all potentially important confounding variables have been adjusted for and that the differences seen in long-term outcomes are the result of residual confounding. Finally, individual-level data concerning socioeconomic status, including personal income, education and occupation level, were lacking, thereby necessitating the use of ecologic-level markers of socioeconomic status. While the use of ecologic-level measures of socioeconomic status in health outcomes research has previously been validated (17
), a number of more recently published studies have indicated that treatment of ecologic-level measures as patient-level factors may yield erroneous conclusions and that such measures should be treated as group-level or contextual-level variables rather than patient-level variables (5