Characteristics and risk of coronary-related events following hospitalisation for chronic coronary disease
Authors: Nedkoff L , Robinson K , Hung J , Wright F L , Briffa T , Chew D P , Herrington S , Katzenellenbogen J M , Sohel F , Lopez D , Hickling S , Murray K 
Published: May 2023

Abstract

Funding Acknowledgements
Type of funding sources: Public Institution(s). Main funding source(s): Western Australian Department of Health.

Background
Chronic coronary heart disease (CCD) is associated with a high healthcare burden and expenditure in Western societies, yet population-level data on CCD are limited. Use of hospitalisation data to investigate CCD epidemiology has not been well explored. Our aim was to describe characteristics of patients hospitalised with CCD and to estimate the long-term risk of coronary outcomes in this cohort.

Method
We used Western Australian state-wide linked hospitalisation/mortality data to identify all hospitalisations for CCD, comprised stable angina (SA, ICD-10-AM I20.1-I20.9) and chronic ischaemic heart disease (IHD, I25) from 2002 – 2017. Index admissions were defined as the first SA or chronic IHD admission in the study period. 14-years of hospitalisation history data were used to identify prior medical history, including admissions for acute coronary syndromes (ACS) +/- angiography, PCI and CABG. Kaplan-Meier survival analyses were used to estimate risk of readmission for coronary outcomes and procedures using up to 15-years of follow-up from linked morbidity/mortality data.

Results
There were 32,557 index SA and 29,505 index chronic IHD admissions from 2002-2017. SA index case number declined by -3.9%/year while chronic IHD admissions increased steadily (+5.3%/year, age-adjusted). The mean age was 66 years for SA and chronic IHD index admissions, with women on average 3 years younger than men; median length of stay was 3 days. Women comprised a higher proportion of SA admissions (37.8%) than chronic IHD (26.9%, p&lt;0.0001). SA admissions were more likely to be emergency admissions (45.6% vs 13.4%) and have comorbidities including diabetes, hypertension and stroke. Patients with a chronic IHD admission were more likely to undergo angiography only (65.3% vs 46.7%) or revascularisation (20.6% vs 12.9%) during the index admission. Around 1/3 of SA and chronic IHD patients had a prior ACS admission (n=9964 and 8291 respectively); around half of these prior ACS admissions occurred in the 1-year preceding the index SA and chronic IHD admissions (Figure), with the majority occurring in the 90 days immediately prior to the index admission. Following an index SA or chronic IHD admission, the risk of ACS within the initial year of follow-up was 9.4% in men and 8.6% in women with SA, and 5.6% in chronic IHD men and women. This risk increased to &gt;20% in both groups with 15 years of follow-up. The 15-year risk of CVD mortality was 4.3% in men and 4.2% in women following a chronic IHD admission; similar long-term risks were seen following SA admissions.

Conclusion
The heterogeneity in clinical profile and outcomes between patients admitted for SA versus chronic IHD requires cautious interpretation of hospitalisation data to inform the epidemiology of CCD. However, while mortality risk is low, the risk of ACS readmission is high, indicating significant ongoing morbidity and healthcare burden of CCD.