The Anglo-Scandinavian Cardiac Outcomes Trial - Blood Pressure Lowering Arm (ASCOT-BPLA) was made available early via the Lancet website late last week. The media have already picked up on this new study with the BBC and newspapers like the Telegraph reporting the headline findings of the trial.
Action: The outcomes of the study could be entirely driven by greater reductions in blood pressure that occurred in the Amlodipine arm. Until NICE release their new Guideline prescribers should continue to use the current NICE Hypertension Guideline. For more detail, read on.
Detail: This study was started about 6 years ago and compared the blood pressure lowering effects of Atenolol with Bendroflumethiazide to those of Amlodipine with Perindopril. The Primary Outcome of the trial was Non fatal MI (including silent MI) and fatal CHD. There was no statistical difference between the two arms of the study in this endpoint.
Where there was a statistical difference in the secondary outcomes, perhaps it would have been expected. For example there was less peripheral arterial disease and development of diabetes in the Amlodipine and Perindopril arm. This is to be expected due to the peripheral vasodilation effects of Amlodipine and Perindopril compared to Atenolol and Bendroflumethiazide. And we already know about the diabetes risk posed by the combination of Beta-blockers and Diuretics.
Some purists may be critical of the trial on two points, firstly that the Atenolol comparator arm is not reflective of current practice (the dose of Atenolol could be titrated to 100mg) and the fact that a post-hoc analysis was conducted that shows benefit for the Amlodipine arm (but this analysis was not defined at the start of the study). If these limitations in the study are accepted does it add anything new to the body of evidence in Hypertension?
At the same time the paper was released by the Lancet, they released another paper investigating the role of blood pressure and other variables in the results. This was perhaps seen as necessary because there was a difference in the blood pressures of the two arms of 2.7/1.9mmHg in favour of the Amlodipine arm. There were also favourable differences, towards the Amlodipine arm, for BMI, Triglyceride, creatinine, blood glucose and HDL.
Overall, this investigation found that correcting for these variables reduced the differences by about half for coronary events and by just under half for stroke events, and that neither were statistically significant after the correction.
NICE have released a statement detailing a collaborative project with the British Hypertension Society to review the BHS and NICE Hypertension guidelines following publication of this study. This process is likely to take six months.
Action: A detailed appraisal of the study reveals that it doesn't really add a great deal to our current knowledge. The outcomes of the study could be entirely driven by greater reductions in blood pressure that occurred in the Amlodipine arm. Until NICE release their new Guideline prescribers should continue to use the current NICE Hypertension Guideline.
- Prevention of cardiovascular events with an antihypertensive regimen of amlodipine adding perindopril as required versus atenolol adding bendroflumethiazide as required, in the Anglo-Scandinavian Cardiac Outcomes Trial-Blood Pressure Lowering Arm (ASCOT-BPLA): a mulitcentre randomised controlled study. ASCOT Investigators Lancet 2005;366:895-906.
- Role of blood pressure and other variables in the differential cardiovascular event rates noted in the Anglo-Scandinavian Cardiac Outcomes Trial-Blood Pressure Lowering Arm (ASCOT-BPLA). ASCOT Investigators Lancet 2005;366:907-903.
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