Stroke risk in AF
Assessing risk of stroke in patients with atrial fibrillation is essential so that appropriate thromboprophylaxis can be started. There are numerous schemes to stratify stroke risk but most have modest predictive value, said Professor Greg Lip (Birmingham, UK). The well-known CHADS2 scheme has limitations: it does not include many risk factors and it classifies a large proportion of people as “moderate” risk. Nonetheless, it is
simple to use and well validated.
“If you want a quick and easy method, I’d still strongly recommend it, and if the score is 2 or above, go ahead and anticoagulate. There is no need to debate this anymore.”
For the future, the artificial low/moderate/high risk strata might be abandoned and a patient with no risk factors will have no thromboprophylaxis while someone with any risk factor is given anticoagulant. “There will come a time when we will give anticoagulant to all patients with one or more risk factors.” Not only does AF increase stroke risk, when stroke occurs in association with AF, mortality and morbidity are higher than in stroke patients without AF. Women are at nearly five–fold higher risk of stroke in AF than men. Key to improving antithrombotic treatment in AF patients will be the development of oral anticoagulants that are easier to use than warfarin, with no need for monitoring. The first AF trial with one of these new drugs has just been reported. This was the RE-LY trial with the direct thrombin inhibitor dabigatran.
“This landmark trial will certainly change our thinking about how to approach stroke prevention in AF over the next few years.”
Dabigatran 150mg twice daily significantly reduced stroke compared with warfarin with similar risk of major bleeding, while dabigatran 110mg twice daily had a similar rate of stroke to warfarin but significantly reduced major bleeding. Clinicians will need to wait for formal license approval of use of dabigatran in AF. In the meantime, the key to safe and effective use of warfarin is to try to keep within the target INR range of 2-3.
Diagnosing hypertension
Diagnosis of hypertension requires accurate blood pressure measurement: whatever method is used there is need for multiple readings using a calibrated and validated sphygmomanometer, said Dr Richard McManus (Birmingham, UK). Routine measurement is often flawed. For one thing, readings are often rounded-up and
this can clearly have an effect on diagnosis for patients on either side of the 140/90mm Hg threshold. Blood pressure varies over 24 hours and varies with ambient temperature, and hypertension must not be diagnosed on the basis of a first reading. In a study in which blood pressure was measured six times, at one-minute intervals, in 1500 patients, systolic pressure dropped by 12mmHg, becoming stable after the fifth reading.
“If you only took the first two readings, which would fit with some guidelines, you are missing the fact that for many people blood pressure is settling over time.”
Multiple measurements, either at home or by ambulatory blood pressure monitoring (ABPM), are more likely to capture “usual” blood pressure. However, it is important to be aware that patients with normal blood pressure in the surgery can have raised blood pressure with ambulatory/ home measurements, and vice versa.
Antiplatelet Therapies in ACS
Discussing novel antiplatelet agents – prasugrel and ticagrelor – in acute coronary syndrome, Professor Steen Dalby Kristensen (Aarhus, Denmark) said it is now apparent that some patients have a low response to the widely used clopidogrel. This appears to be related to poor metabolism of the pro-drug.
Two newer antiplatelet drugs, prasugrel and ticag relor, act as clopidogrel as inhibitors of the platelet P2Y12 receptor. Prasugrel (also a prodrug) is more potent than clopidogrel, and it has a more uniform response and faster onset. It is marketed for ACS patients undergoing percutaneous coronary intervention. In the TRITON-TIMI 38 trial, prasugrel was shown to have greater efficacy than clopidogrel. However, there was an increased risk of bleeding in certain groups.
“Patients with prior stroke or TIA should not use the drug, and we should probably use a reduced dose in patients aged over 75 or with low bodyweight.”
All three drugs act as inhibitors of the platelet P2Y12 receptor. Unlike clopidogrel and prasugrel, ticagrelor is a reversible platelet inhibitor. This might be an advantage in some circumstances but could also be a problem.
“The challenge in the real world will be compliance. Patients have to take this drug twice daily and if they stop taking it after a day they will be unprotected.”
In the PLATO trial, which was reported at the preceding ESC Congress, ticagrelor was more effective than clopidogrel, with no difference in bleeding. Ticagrelor is not yet licensed.
