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From the Editor's Desk
It is with great pleasure I welcome the readers to the first edition of Pulse-a quarterly newsletter from HVCA. Through this newsletter we aim to cover the latest and the greatest news from the world of cardiovascular medicine and bring the "pulse" of our practice to you, the reader.
Ashish Pershad, M.D. FACC
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Latest Update on treatment of carotid artery disease - Stenting versus CEA. The debate continues...
Carotid artery atherosclerosis is an important cause of stroke in the United States. Stenting and carotid endarterectomy are two treatment options for carotid artery stenosis. CREST, a major clinical trial was published this year in the New England Journal of Medicine in May 2010. In this trial stenting and endarterectomy were compared head to head in symptomatic and asymptomatic patients who were followed for 4 years.
In the CREST Trial, the composite primary end point of any stroke, MI, or death during the periprocedural period or ipsilateral stroke on follow-up, stenting was associated with a 7.2% rate of these events vs 6.8% with surgery, a nonsignificant difference.
However, individual risks varied. At 30 days, the rate of stroke was significantly higher with stenting at 4.1%, vs 2.3% with surgery, although major stroke was not different, at less than 1% in both groups. Conversely, MI was higher with CEA at 2.3% vs 1.1% with stenting, again a statistically significant difference.
"I think these CREST results show that physicians now have two ways to treat carotid artery disease, the tried and true surgical approach and the new kid on the block, carotid stenting," opined Dr. Nathan Laufer, a pioneer of carotid stenting in the Southwest region of the US.
For symptomatic patients, he noted, "results with both procedures are excellent with regard to safety and durability out to four years." Similarly, for asymptomatic patients, "both procedures are exceptionally safe and, again, exceptionally durable."
At HVCA, Drs. Laufer and Pershad perform carotid artery stenting for patients with symptomatic and asymptomatic carotid artery stenosis. To schedule an appointment for any of your potential patients with carotid disease please call (602) 307 0070.
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Focused Update on CV drugs and recent BLACK BOX warnings
Plavix Black-box warning:
The US FDA today announced it is requiring a boxed warning to be added to the anticoagulant clopidogrel (Plavix, Bristol-Myers Squibb/Sanofi-Aventis) to caution that poor metabolizers of the drug may not receive its full benefits. The boxed warning also states that tests are available to determine the genetic profile of a key liver enzyme and predict whether a patient will ineffectively convert clopidogrel to its active form. It advises clinicians to consider other antiplatelet medications or alternative dosing strategies for clopidogrel in poor metabolizers.
However, the FDA noted that while higher doses of clopidogrel increase antiplatelet response in poor metabolizers, an appropriate dose regimen for these patients has not been established in a clinical-outcomes trial.
A liver enzyme called CYP2C19 is primarily responsible for converting clopidogrel into an active metabolite that will protect patients from blood clots. Some patients, however, have alleles, or variations, that code for alternate versions of this enzyme that can't metabolize the drug.
Roughly 3% of the population are poor clopidogrel metabolizers. However, this metabolism inefficiency varies by ethnicity, affecting 2% of whites, 4% of blacks, and 14% of Chinese.
The ACC and AHA issued a clinical alert just 12 weeks after the FDA black-box warning on Plavix (clopidogrel), stating that routine genetic or platelet-function testing is not recommended when using antiplatelet therapy. They do leave the door open a crack, however, and allow for such testing in patients believed to be at moderate or high risk for poor outcomes, to be used at the physician's discretion.
This is different from the interaction noted recently between PPI drugs and Plavix. The largest meta-analysis to date on whether treatment with proton-pump inhibitors adversely affects cardiovascular outcomes in patients receiving clopidogrel still provides no firm answers; more research is necessary.
Dr. Suzanne Sorof, an expert at HVCA in platelet biology when asked in a local media interview in the Arizona Republic concluded that any risk is likely small and that those on clopidogrel with a high likelihood of gastrointestinal bleeding should still receive a PPI.
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How Atrial Fibrillation has Evolved
Atrial fibrillation (AF) remains the number one cardiac arrhythmia in North America, both in the number of patients affected and the frequency of events associated. Approximately 1% of individuals in the 60s are affected and the prevalence rises to 10-12% in individuals over 80 years old. In most patients, AF is initially paroxysmal; whereas other patients (predominantly with underlying heart disease) may have persistent, long-standing persistent or even permanent atrial fibrillation. Atrial fibrillation remains a significant burden on our health care system because of the number of patients affected, impact of stroke, and the overall cost of both inpatient and outpatient therapy.
The major comorbidity associated with AF is that of thromboembolic-events such as a stroke. Because of stroke risk, most patients require some form of anticoagulation therapy, either in the form of aspirin or warfarin. Therapy should be based on the ACC/AHA/ESC guidelines for atrial fibrillation using the CHADS2 scoring system (LV dysfunction, hypertension, Age > 75, diabetes and/or prior stroke or TIA). One point is assessed for each risk factor and two points for prior stroke or TIA. This data stems from large mortality studies. Minor risk factors to be considered are female gender, presence of coronary artery disease, age greater than 65 and thyrotoxicosis. Some have argued to assign a half-point for each of these. Despite clear guidelines for thromboembolic risk prevention, many patients do not receive the appropriate therapy.
The drug therapy for AF should focus on rate or rhythm control. Many patients have a rapid ventricular response during AF, which is predominantly responsible for symptoms. This may result in a tachycardia-induced cardiomyopathy. Rate control is important to prevent the sequelae of LV dysfunction and improve ones quality of life. Guidelines recommend resting heart rates during AF be less than 90 to 100 beats per minute, with exercise heart rates maintained to be less than 110 to 120 beats per minute.
Restoration of sinus rhythm may be the most effective means of rate control. Over the last 30 years several studies have been performed to evaluate the effectiveness of antiarrhythmic drug (AAD) therapy for maintenance of sinus rhythm. The average efficacy rate at maintenance of sinus rhythm at one year for most patients treated with AADs is 30-50%. This has been corroborated by several trials including AFFIRM, RACE, STAF and others. Results overall have been disappointing. Most recently the data from the ATHENA trial have encouraged the use of drug therapy in AF. Comparison of dronaderone to placebo in more than 4,500 patients showed a 24% reduction in CV hospitalization or mortality, a 29% decrease in CV mortality, and a 26% decrease in CV hospitalization with active therapy at 22+/- 5 months of follow-up. The control rate with this drug is less than that of amiodarone, but one has to evaluate the potential for long-term side effects associated with amiodarone usage.
The role of atrial fibrillation ablative therapy is still second-line therapy. This has been endorsed by the AHA, ACC and HRS. The need is to decrease or eliminate AF in symptomatic patients. Patients who have failed to respond to one or more AAD may be a good candidate for atrial fibrillation ablation therapy. The success rates depend on type of AF, left atrial size and/or the presence of left ventricular dysfunction. The most important factor is to prevent stroke or other peripheral thromboembolic events.
Ongoing large multicenter trials such as CABANA (Catheter Ablation Versus Antiarrhythmic Drug Therapy in Atrial Fibrillation) seek to establish a mortality benefit and a reduction in stroke risk. The study will examine the benefit of ablation versus drug therapy in approximately 3,000 patients with AF enrolled in 140 centers around the world.
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