AF and bad kidneys- a toxic combo!

One of the long term consequences of chronic conditions such as diabetes, high blood pressure and even severe obesity is the development of chronic kidney disease. In fact it is estimated that the number of patients with chronic kidney disease is more than doubling every decade. What is also a major concern is that as chronic kidney disease is an exceptionally inflammatory condition, it substantially increases the risk of virtually all forms of heart disease. One of the conditions that I have a real interest in and is seen significantly more commonly in patients with CKD is atrial fibrillation. In this blog, I wanted to summarise some of what we know about AF in CKD patients. If we look at the general population as a whole, AF is found in 1-2%. As people get older, it gets more prevalent. In those above the age of 80, the prevalence is almost 12%. Now if we look at patients with CKD and especially those on dialysis, we see the prevalence to be between 13-27% according to some studies. This means that AF is 10-20 fold more common in patients on dialysis. The worse the kidney disease the more prevalent the AF. It is also worth understanding that just because it hasn’t been diagnosed, does not mean it is not there and in such patients, an aggressive hunt for AF can show up a significant burden of undiagnosed AF. When AF is found, it is strongly correlated with underlying heart disease. If you look at the hearts of patients with CKD and AF, you are far more likely to find underlying coronary disease, heart failure, heart valve disease and even left ventricular hypertrophy (which refers to thickened strained stiff heart muscle). We also know that people who have chronic kidney disease and AF have worse outcomes. Mortality in patients with AF and CKD is doubled compared to those patients who have the same magnitude of chronic kidney disease but no AF (5% vs 2% mortality per year) . Additionally the development of AF also has an additional adverse impact on the kidneys. One of the problems associated with AF is the increased risk of strokes. Patients who have chronic kidney disease are at a higher risk of strokes anyway even if there is no AF. In fact the worse the kidney function the greater the risk of strokes. However when you combine the two, patients seem to be a significantly higher risk. The risk is increased in dialysis patients anywhere between 1.6 fold to 4.6 fold depending on which study you read. When AF is found anywhere, the first thing we do is calculate the CHADS2VASC score to estimate risk of stroke and if the risk is high we consider anticoagulation. Even though having kidney disease is not a risk factor on the CHADS2VASC score, it is generally acknowledged that the risks are higher regardless in patients with bad kidneys. Whilst anticoagulation is perhaps the most effective therapy for stroke prevention, kidney disease patients pose several challenges when it comes to anticoagulation. One of the risks associated with taking anticoagulation is the increased risk of bleeding. Patients with chronic kidney disease are at a higher risk of bleeding anyways so the risk harm associated with anticoagulation is increased in kidney disease patients. Many of the available anticoagulant agents are contraindicated in very severe kidney disease. This applies predominantly to the DOACs. The DOACs can still be used in milder forms of kidney disease but often require patients to take a lower dose. The only other available oral anticoagulant, Warfarin can however still be used but the dose needs very carefully monitoring.