Blog entry by Meguid El Nahas
De Vriese and colleagues in Belgium argue in teh january issue of KI that all patients on RRT should be screened for coronary artery disease (CAD). This implies that symptomatic but also asymptomatic patients should be screened.
Their argument is based on the fact that a very high prevalence of CAD in chronic dialysis patients including up to 53% in asymptomatic patients and 83% in those with diabetes. Also higher prevalence in older dialysis patients. Consequently, the majority of dialysis patients with angiographically documented CAD are asymptomatic (Ohtake et al).
They show data confirming the good predictive value of a positive Myocardial Perfusion Scintigraphy (MPS) for CAD. Adenosine, dipyridamole or dobutamine stresss MPS have all been shown to have high predictive values for CAD; the presence of reversible ischemia upon stress MPS closely correlating with the gold standard of coronary angiography (Rabbat et al, 2003).
The question that comes to mnd is why screen asymptomatic patients as data in non CKD patients shows that survival in such patients is not affected by intervention and therefore investigations not recommended. Furthermore, there is a good body of evidence that medical therapy? The authors argue that dialysis patients are at much higher risk of CAD and related mortality thus justifying screening and intervention. The published data, albeit limited, suggest that in dialysis patients with CAPD treated with PCI or CABG have a survival advantage compared to those on medication only.
The authors advocate screening all those on dialysis listed for transplantation arguing the high prevalence of asymptomatic patients justify such an approach rather than current guidelines recommending screening only in those with a histroy of revascularisation, a signficant reduction in LV function, or symptoms suggestive of CAD/CHF. Guidelines also recommend screening selected high risk patients which woukld automatically, in my view, include diabetic patients.
The authors advocate a large RCT that examines the incremental benefit of revascularisation in addition to medical therapy in asymptomatic dialysis patients.
I remain unconvinced on a cost/benefit analysis basis that all dialysis patients should be screened as their editorial review suggests a risk of asymptomatic CAD predmoninatly driven by diabetic patients on HD. It would therefore be more cost-effective to screen as currently recommended by international guidelines those at high risk: diabetics, history of CAD, those with an abnormal echocardiogram, etc...
It would be desirable to have a cheap and non invasive test/biomarkers that predicts the presence of subclinical CAD. Cartiac Troponins may prove to be such a test. Recent high sensitivity assays showed a considerable higher circulating levels in asymptoamtic CAD ESRD patients (Jacobs et al).
De Vriese et al. Should we screen for CAD in asymptomatic chronic dialysis patients. Kidney Int. 2012;81:143-151.
Ohtake et al. High prevalence of occult CAD in patients with CKD at th einitiation of renal replacement therapy. JASN 2005;16:1141-1148.
Rabbat et al. Prognostic value of myocardial perfusion studies in ESRD patients: a meta-analysis. JASN 2003; 14:431-439.
Jacobs et al. Hemodilayusis patients longitudinally assessed by highly sensitive cardiac troponin T and commercial cardiac Troponin T and I assays. Ann Clin Biochem 2009;46:283-290.