At the Heart Rhythm congress (2–5 October 2011, Birmingham, UK), Tim Betts, cardiologist, Oxford Heart Centre, John Radcliffe Hospital, outlined a business case, to put to commissioners, for using the percutaneous left atrial appendage (LAA) occlusion device (Watchman, Boston Scientific) for stroke prevention in patients with atrial fibrillation.
According to Betts, the best way of presenting the LAA occlusion device as a cost-effective treatment is to compare its use with no treatment at all in patients with atrial fibrillation who have a CHADS2 (congestive heart failure, age≥75 years, diabetes, and stroke) score of two (or more) or who have absolute contraindications to warfarin.
The PROTECT-AF study (Holmes et al, Lancet 2009; 374:534–42) found that the device was non-inferior to warfarin and might provide an alternative strategy to warfarin for stroke prevention in patients with atrial fibrillation. Therefore, compared with no treatment, the LAA occlusion device would reduce the risk of stroke.
However, the cost per stroke prevented with the device depends on the patient’s initial CHADS2 score and their life expectancy. For example, Betts explained, in patients with a CHADS2 score of two or more, after one year, the number needed to treat to prevent one stroke was 37 and cost of the treatment was £241,000. By contrast, in patients with a CHADS2 score of six or more, after 10 years, the number needed to treat was 1.3 and using the device actually saved money compared with the cost of treating a stroke. Betts said: “Putting all the data together, the greatest cost efficiency is in patients with the greatest CHADS2 scores and the longest life expectancy. They are the ones who have the most to gain from the stroke reduction observed with the device.”
He added that in the current financial climate, a business case had do more than just show that a new treatment had a better quality adjusted life year (QALY) score than an existing treatment or no treatment. He said: “You have to introduce a new technology that is going to save money or take money from somewhere else. Regarding the Watchman device, it is probably one of the most cost-effective things I have come across. Admittedly, the calculations are preliminary but they are reasonably legitimate.”
Betts also provided responses for potential counter arguments that commissioners might use for refusing to pay for the Watchman device. One potential counter argument was that patients in the PROTECT-AF study received warfarin for 14 days prior to and 45 days following implantation of the device and therefore, there was no evidence that the device would be effective in patients who had contraindications to warfarin. He said: “For people with relative contraindications to warfarin, use warfarin for 60 days and then stop the warfarin 45 days after the operation. Alternatively, use dabigatran or low molecular weight heparin for 45 days post operation. If the patient has absolute contraindications, use dual antiplatelet therapy.” He added there was emerging data for just using dual antiplatelet therapy in this setting but admitted he was nervous about using the device without anticoagulation. “In the latest registry data, there were a couple of strokes in the follow-up period. However, it does not necessarily mean that the strokes were due to the device and the lack of anticoagulation.”
Another potential counter argument against using the Watchman device in patients with contraindications to warfarin would be to claim that such patients should be given aspirin instead. However, Betts said that there is no role for aspirin in stroke prevention in patients with atrial fibrillation at present. He said: “In patients who have a low risk of stroke, according to the European Society of Cardiology guidelines for atrial fibrillation, they should receive nothing rather than aspirin.” He added that the BAFTA study (Mant et al, Lancet 2007; 370:493-503), which studied the use of warfarin versus aspirin in an elderly community population with atrial fibrillation, found that the risk of severe bleeding with aspirin was the same as the risk of severe bleeding with warfarin and that this risk was actually higher in patients aged over 85 who were receiving aspirin compared with patients who were receiving warfarin. Additionally, the study showed that warfarin offered better protect against stroke compared with aspirin.