Risk factors for cardiovascular events among Asian patients without pre-existing cardiovascular disease on the renal transplant wait list

INTRODUCTION: For suitable end-stage renal failure (ESRF) patients, renal transplantation gives better long term survival and quality of life as compared to dialysis. Prior to entry into the renal transplant wait list, potential candidates are screened for the presence of cardiovascular disease. However, the waiting time on the transplant list is long, and interval screening for cardiac fitness for surgery is not well defined. We aim to study the risk factors for the development of a cardiovascular event (CVE) and the time interval from recruitment to onset of a CVE that resulted in their removal from the transplant wait list. METHODS: A retrospective study of all patients registered under the cadaveric renal transplant waiting list in Singapore General Hospital (SGH) from 16(th) April 1987 to 31(st) October 2010. We identified patients who developed a CVE among this cohort. We compared the demographics and clinical characteristics of patients who experienced a CVE versus those who did not. Univariable and multivariable cox regression were performed to investigate the significant variables for the development of a CVE. The time to development of CVE was estimated using Kaplan Meier estimation and log-rank test was used to compare the time to CVE between those with diabetes mellitus and those without. RESULTS: 1265 patients were enrolled in this study. 273 patients dropped out of the wait list due to medical reasons or death, of which 38.8% were due to CVE. The mean and median time duration from recruitment into the waiting list to development of a CVE was 14.42 (95% CI 13.72 to 15.11) and 15.69 (95% CI 13.86 to 17.51) years respectively. For patients with diabetes mellitus, this was 8.22 (95% CI 6.30 to 10.14) and 8.16 (95% CI 4.95 to 11.36) years respectively. Factors associated with an increased risk of developing a CVE included male gender (adjusted HR 2.21, 95% CI 1.43 to 3.41, p<0.001), presence of diabetes mellitus (adjusted HR 5.13, 95% CI 2.85 to 9.24, p<0.001) and patients who were either not working or working part-time as compared to their full-time counterparts (adjusted HR 1.76, 95% CI 1.14 to 2.72, p=0.010). In addition, hazard ratio for CVE significantly increased with advancing age quartile (p<0.001 by log rank test for trend). CONCLUSION: A significant proportion of patients exited from the renal transplant wait list due to a CVE. Being male, age 37 years old or more, presence of diabetes mellitus and non-working or part-time workers as compared to full-time workers were found to increase the risk of developing a CVE during the wait period for transplantation. The presence of diabetes mellitus significantly shortened the time to development of a CVE.