Procedural Volume and Outcomes After Primary Percutaneous Coronary Intervention for ST-Segment-Elevation Myocardial Infarction in Kerala, India: Report of the Cardiological Society of India-Kerala Primary Percutaneous Coronary Intervention Registry

Abstract

Background There are limited data to inform policy mandating primary percutaneous coronary intervention (PPCI) volume benchmarks for catheterization laboratories in low- and middle-income countries. Methods and Results This prospective state-wide registry included ST-segment-elevation myocardial infarction patients with symptoms of <12 hours, or with ongoing ischemia at 12 to 24 hours, reperfused with PPCI. From June 2013 to March 2016, we recruited 5560 consecutive patients. We categorized hospitals on the basis of annual PPCI volumes into low, medium, and high volume (<100, 100-199, and ≥200 PPCIs per year, respectively). Kaplan-Meier curves and Cox regression models were used to examine the association between PPCI volume and 1-year mortality. Among 42 recruiting hospitals, there were 24 (57.2%) low-volume, 8 (19%) medium-volume, and 10 (23.8%) high-volume hospitals. The median (25th-75th percentile) TIMI (Thrombolysis in Myocardial Infarction) ST-segment-elevation myocardial infarction risk score was 3 (2-5). Cardiac arrest before admission occurred in 4.2%, 2.1%, and 2.9% of cases at low-, medium-, and high-volume hospitals, respectively (P=0.02). Total ischemic time differed significantly among low-volume (median [25th-75th percentile], 3.5 [2.4-5.5] hours), medium-volume (median, 3.8 [25th-75th percentile, 2.58-6.05] hours), and high-volume hospitals (median, 4.16 [25th-75th percentile 2.8-6.3] hours) (P=0.01). Vascular access was radial in 61.5%, 71.3%, and 63.2% of cases at low-, medium-, and high-volume hospitals, respectively (P=0.01). The observed 1-year mortality rate was 6.5%, 3.4%, and 8.6% at low-, medium- and high-volume hospitals, respectively (P<0.01), and the difference did not attenuate after multivariate adjustment (low versus medium: hazard ratio [95% CI], 1.80 [1.12-2.90]; high versus medium: hazard ratio [95% CI], 2.53 [1.78-3.58]) (P<0.01). Conclusions Low- and middle-income countries, like India, may have a nonlinear relationship between institutional PPCI volume and outcomes, partly driven by procedural variations and inequalities in access to care.

Keywords: ST‐segment–elevation myocardial infarction; percutaneous coronary intervention; stents.

Figure 1. CONSORT diagram of exclusions from the primary angioplasty registry of Kerala.

PPCI indicates primary percutaneous coronary intervention; and STEMI, ST‐segment–elevation myocardial infarction.

Figure 2. Kaplan‐Meier curves for the entire cohort (n=5560), displaying the unadjusted relationship between hospitals, categorized according to the hospital‐level annual primary percutaneous coronary intervention volume, and all‐cause mortality at 30 days (inset box) and 1 year with a comparison between groups using log‐rank test.

Figure 3. Hazard ratios (HRs) of 30‐day all‐cause mortality between hospital groups, categorized into low‐, medium‐, and high‐volume, according to the annual institutional primary percutaneous coronary intervention (PCI) volume.

A indicates adjusted for sex, CI, confidence interval, TIMI (Thrombolysis in Myocardial Infarction) risk score, insurance coverage, living in poverty, family history, smoking status, culprit lesion in proximal left anterior descending artery, number of years catheterization laboratory was performing percutaneous coronary interventions, and year of enrollment. U, unadjusted.

Figure 4. Hazard ratios (HRs) of 1‐year all‐cause mortality between hospital groups, categorized into llow‐, medium‐, and high‐volume, according to the annual institutional primary percutaneous coronary intervention (PCI) volume.

A indicates adjusted for sex, TIMI (Thrombolysis in Myocardial Infarction) risk score, insurance coverage, living in poverty, family history, smoking status, culprit lesion in proximal left anterior descending artery, number of years catheterization laboratory was performing percutaneous coronary interventions, and year of enrollment. U, unadjusted.

Figure 5. Relationship between institutional annual primary percutaneous coronary intervention (PPCI) volume as a continuous variable and risk of the primary outcome (1‐year mortality).