A propensity score-matched analysis indicates screening for asymptomatic coronary artery disease does not predict cardiac events in kidney transplant recipients

Coronary Artery Disease Assessment and Cardiovascular Events in Middle-Aged Patients on Hemodialysis

OBJECTIVE

To explore whether, in younger patients on dialysis with longer life expectancy, assessment of coronary artery disease (CAD) could identify individuals at higher risk of events and revascularization might improve outcomes in selected patients contrary to what had been observed in elderly patients.

METHODS

From August 1997 to January 2019, 2265 patients with stage 5 chronic kidney disease were prospectively referred for cardiovascular assessment. For this study, we selected 1374 asymptomatic patients aged between 18 and 64 years. After clinical risk stratification and cardiac scintigraphy by single-photon emission computed tomography, 866 patients underwent coronary angiography. The primary end point was the composite incidence of nonfatal/fatal major adverse cardiovascular events during a follow-up period of 0.1 to 189.7 months (median, 26 months). The secondary end point was all-cause mortality.

RESULTS

The primary end point occurred in 327 (23.8%) patients. Clinically stratified high-risk patients had a 3-fold increased risk of the primary end point. The prevalence of abnormal findings on perfusion scans was 29.2% (n=375), and significant CAD was found in 449 (51.8%) of 866 patients who underwent coronary angiography. An abnormal finding on myocardial perfusion scan and the presence of CAD were significantly associated with a 74% and 22% increased risk of cardiovascular events, respectively. In patients undergoing percutaneous coronary intervention or coronary artery bypass grafting (n=99), there was an 18% reduction in the risk of all-cause death relative to patients receiving medical treatment (P=.03).

CONCLUSION

In this cohort of middle-aged, asymptomatic patients on dialysis, assessment of CAD identified individuals at higher risk of events, and coronary intervention was associated with reducing the risk of death in selected patients.

The Minimisation of Cardiovascular Disease Screening for Kidney Transplant Candidates

Background: There is increasing evidence that cardiac screening prior to kidney transplantation does not improve its outcomes. However, risk aversion to perioperative events means that, in practice, testing remains common, limiting the availability of 'real-world' data to support any change. Our objective was to assess perioperative and 1-year post-transplant cardiovascular events in a kidney transplant candidate cohort who received minimal cardiovascular screening. Methods: The retrospective cohort study included all adult kidney-only transplant recipients in a single UK region between January 2015 and December 2021. Kidney transplant recipients asymptomatic of cardiac disease, even those with established risk factors, did not receive cardiac stress testing. The perioperative and 1-year post-transplant cardiovascular event incidences were examined. Logistic regression was used to identify variables of statistical significance that predicted cardiovascular or cerebrovascular events. Results: A total of 895 recipients fulfilled the inclusion criteria. Prior to transplantation, 209 (23%) recipients had an established cardiac diagnosis, and 193 (22%) individuals had a diagnosis of diabetes. A total of 18 (2%) patients had a perioperative event, and there was a 5.7% incidence of cardiovascular events 1 year post-transplantation. The cardiovascular mortality rate was 0.0% perioperatively, 0.2% at 3 months post-transplant, and 0.2% at 1 year post-transplant. Conclusions: This study demonstrates comparable rates of cardiovascular events despite reduced screening in asymptomatic recipients. It included higher risk individuals who may, on the basis of screening results, have been excluded from transplantation in other programmes. It provides further evidence that extensive cardiac screening prior to kidney transplantation is unlikely to be offset by reduced rates of cardiovascular events.

External Validation of Proposed American Heart Association Algorithm for Cardiovascular Screening Before Kidney Transplantation

BACKGROUND

Screening for cardiovascular disease is currently recommended before kidney transplantation. The present study aimed to validate the proposed algorithm by the American Heart Association (AHA-2022) considering cardiovascular findings and outcomes in kidney transplant candidates, and to compare AHA-2022 with the previous recommendation (AHA-2012).

METHODS AND RESULTS

We applied the 2 screening algorithms to an observational cohort of kidney transplant candidates (n=529) who were already extensively screened for coronary heart disease by referral to cardiac computed tomography between 2014 and 2019. The cohort was divided into 3 groups as per the AHA-2022 algorithm, or into 2 groups as per AHA-2012. Outcomes were degree of coronary heart disease, revascularization rate following screening, major adverse cardiovascular events, and all-cause death. Using the AHA-2022 algorithm, 69 (13%) patients were recommended for cardiology referral, 315 (60%) for cardiac screening, and 145 (27%) no further screening. More patients were recommended cardiology referral or screening compared with the AHA-2012 (73% versus 53%; P<0.0001). Patients recommended cardiology referral or cardiac screening had a higher risk of major adverse cardiovascular events (hazard ratio [HR], 5.5 [95% CI, 2.8-10.8]; and HR, 2.1 [95% CI, 1.2-3.9]) and all-cause death (HR, 12.0 [95% [CI, 4.6-31.4]; and HR, 5.3 [95% CI, 2.1-13.3]) compared with patients recommended no further screening, and were more often revascularized following initial screening (20% versus 7% versus 0.7%; P<0.001).

CONCLUSIONS

The AHA-2022 algorithm allocates more patients for cardiac referral and screening compared with AHA-2012. Furthermore, the AHA-2022 algorithm effectively discriminates between kidney transplant candidates at high, intermediate, and low risk with respect to major adverse cardiovascular events and all-cause death.

Screening and Management of Coronary Artery Disease in Kidney Transplant Candidates

Cardiovascular disease (CVD) is a major cause of morbidity and mortality in patients with chronic kidney disease (CKD), especially in end-stage renal disease (ESRD) patients and during the first year after transplantation. For these reasons, and due to the shortage of organs available for transplant, it is of utmost importance to identify patients with a good life expectancy after transplant and minimize the transplant peri-operative risk. Various conditions, such as severe pulmonary diseases, recent myocardial infarction or stroke, and severe aorto-iliac atherosclerosis, need to be ruled out before adding a patient to the transplant waiting list. The effectiveness of systematic coronary artery disease (CAD) treatment before kidney transplant is still debated, and there is no universal screening protocol, not to mention that a nontailored screening could lead to unnecessary invasive procedures and delay or exclude some patients from transplantation. Despite the different clinical guidelines on CAD screening in kidney transplant candidates that exist, up to today, there is no worldwide universal protocol. This review summarizes the key points of cardiovascular risk assessment in renal transplant candidates and faces the role of noninvasive cardiovascular imaging tools and the impact of coronary revascularization versus best medical therapy before kidney transplant on a patient's cardiovascular outcome.

Association of Pretransplant Coronary Heart Disease Testing With Early Kidney Transplant Outcomes

Importance

Testing for coronary heart disease (CHD) in asymptomatic kidney transplant candidates before transplant is widespread and endorsed by various professional societies, but its association with perioperative outcomes is unclear.

Objective

To estimate the association of pretransplant CHD testing with rates of death and myocardial infarction (MI).

Design, Setting, and Participants

This retrospective cohort study included all adult, first-time kidney transplant recipients from January 2000 through December 2014 in the US Renal Data System with at least 1 year of Medicare enrollment before and after transplant. An instrumental variable (IV) analysis was used, with the program-level CHD testing rate in the year of the transplant as the IV. Analyses were stratified by study period, as the rate of CHD testing varied over time. A combination of US Renal Data System variables and Medicare claims was used to ascertain exposure, IV, covariates, and outcomes.

Exposures

Receipt of nonurgent invasive or noninvasive CHD testing during the 12 months preceding kidney transplant.

Main Outcomes and Measures

The primary outcome was a composite of death or acute MI within 30 days of after kidney transplant.

Results

The cohort comprised 79 334 adult, first-time kidney transplant recipients (30 147 women [38%]; 25 387 [21%] Black and 48 394 [61%] White individuals; mean [SD] age of 56 [14] years during 2012 to 2014). The primary outcome occurred in 4604 patients (244 [5.3%]; 120 [2.6%] death, 134 [2.9%] acute MI). During the most recent study period (2012-2014), the CHD testing rate was 56% in patients in the most test-intensive transplant programs (fifth IV quintile) and 24% in patients at the least test-intensive transplant program (first IV quintile, P < .001); this pattern was similar across other study periods. In the main IV analysis, compared with no testing, CHD testing was not associated with a change in the rate of primary outcome (rate difference, 1.9%; 95% CI, 0%-3.5%). The results were similar across study periods, except for 2000 to 2003, during which CHD testing was associated with a higher event rate (rate difference, 6.8%; 95% CI, 1.8%-12.0%).

Conclusions and Relevance

The results of this cohort study suggest that pretransplant CHD testing was not associated with a reduction in early posttransplant death or acute MI. The study findings potentially challenge the ubiquity of CHD testing before kidney transplant and should be confirmed in interventional studies.

Cardiac Imaging and Management of Cardiac Disease in Asymptomatic Renal Transplant Candidates: A Current Update

Given the high cardiovascular risk accompanying end-stage kidney disease, it would be of paramount importance for the clinical nephrologist to know which screening method(s) identify high-risk patients and whether screening asymptomatic transplant candidates effectively reduces cardiovascular risk in the perioperative setting as well as in the longer term. Within this review, key studies concerning the above questions are reported and critically analyzed. The lack of unified screening criteria and of a prognostically sufficient screening cardiovascular effect for renal transplant candidates sets the foundation for a personalized patient approach in the near future and highlights the need for well-designed studies to produce robust evidence which will address the above questions.

Propensity Score and Instrumental Variable Techniques in Observational Transplantation Studies: An Overview and Worked Example Relating to Pre-Transplant Cardiac Screening

Inferring causality from observational studies is difficult due to inherent differences in patient characteristics between treated and untreated groups. The randomised controlled trial is the gold standard study design as the random allocation of individuals to treatment and control arms should result in an equal distribution of known and unknown prognostic factors at baseline. However, it is not always ethically or practically possible to perform such a study in the field of transplantation. Propensity score and instrumental variable techniques have theoretical advantages over conventional multivariable regression methods and are increasingly being used within observational studies to reduce the risk of confounding bias. An understanding of these techniques is required to critically appraise the literature. We provide an overview of propensity score and instrumental variable techniques for transplant clinicians, describing their principles, assumptions, strengths, and weaknesses. We discuss the different patient populations included in analyses and how to interpret results. We illustrate these points using data from the Access to Transplant and Transplant Outcome Measures study examining the association between pre-transplant cardiac screening in kidney transplant recipients and post-transplant cardiac events.

Screening for occult coronary artery disease in potential kidney transplant recipients: time for reappraisal?

Screening for occult coronary artery disease in potential kidney transplant recipients has become entrenched in current medical practice as the standard of care and is supported by national and international clinical guidelines. However, there is increasing and robust evidence that such an approach is out-dated, scientifically and conceptually flawed, ineffective, potentially directly harmful, discriminates against ethnic minorities and patients from more deprived socioeconomic backgrounds, and unfairly denies many patients access to potentially lifesaving and life-enhancing transplantation. Herein we review the available evidence in the light of recently published randomized controlled trials and major observational studies. We propose ways of moving the field forward to the overall benefit of patients with advanced kidney disease.

Performance versus Risk Factor-Based Approaches to Coronary Artery Disease Screening in Waitlisted Kidney Transplant Candidates

INTRODUCTION

Current screening algorithms for coronary artery disease (CAD) before kidney transplantation result in many tests but few interventions.

OBJECTIVE

The aim of this study was to study the utility of 6-minute walk test (6MWT), an office-based test of cardiorespiratory fitness, for risk stratification in this setting.

METHODS

We enrolled 360 patients who are near the top of the kidney transplant waitlist at our institution. All patients underwent CAD evaluation irrespective of 6MWT results. We examined the association between 6MWT and time to CAD-related events (defined as cardiac death, revascularization, nonfatal myocardial infarction, and removal from the waitlist for CAD), treating noncardiac death and waitlist removal for non-CAD reasons as competing events.

RESULTS

The 6MWT-based approach designated approximately 45% of patients as "low risk," whereas a risk factor- or symptom-based approach designated 14 and 81% of patients as "low risk," respectively. The 6MWT-based approach was not significantly associated with CAD-related events within 1 year (subproportional hazard ratio [sHR] 1.00 [0.90-1.11] per 50 m) but was significantly associated with competing events (sHR 0.70 [0.66-0.75] per 50 m). In a companion analysis, removing waitlist status from consideration, 6MWT result was associated with the development of CAD-related events (sHR 0.92 [0.84-1.00] per 50 m).

CONCLUSIONS

The 6MWT designates fewer patients as high risk and in need of further testing (compared to risk factor-based approaches), but its utility as a pure CAD risk stratification tool is modulated by the background waitlist removal rate. CAD screening before kidney transplant should be tailored according to a patient's actual chance of receiving a transplant.

Cardiac screening prior to renal transplantation-good intentions, rather than good evidence, dictate practice

Cardiovascular disease is the leading cause of death in kidney transplant recipients in many transplant registries. An analysis of transplant recipients from the United Kingdom using propensity score matching (PSM) suggests there are limited or no benefits to cardiovascular screening before transplant listing. We suggest that short of a randomized controlled trial (RCT) in this area, these data are sufficient to suggest that transplant centers should reflect on their current protocols for cardiovascular workup required before transplantation.