Thursday, March 30, 2006
--Hope this is helpful-
Tuesday, March 28, 2006
Monday, March 27, 2006
Sunday, March 26, 2006
Thursday, March 23, 2006
So what is "microvolt t-wave alternans testing (MTWA)?" Well, the test is performed by placing special high-resolution electrodes designed to reduce electrical interference on a patient's chest prior to a period of controlled exercise. These electrodes detect TINY beat-to-beat changes in a portion of the EKG (the "T-wave") that represents a "resetting" current after the heart is stimulated. The changes are in the order of one millionth of a volt ("microvolt" range). A special mathmatical method of detecting these changes called "spectral analysis" is used to measure the timing change and amplitude change of the electrical signals. A positive test was present if the MTWA onset heart rate was <=110, negative if the maximum MTWA onset heart rate was >=105 and all others considered indeterminate. Indeterminate tests occurred because of noise (slightly less than 10% of the time), skipped heart beats (ectopy), inability to achieve a heart rate of 105, or inability to sustain t-wave alternans during testing.
One of the better recent prospective studies to evaluate T-wave alternans was recently published by Bloomfield et al. in the Journal of the American College of Cardiology (Vol 47, No 2, 456-63): "Microwave T-wave Alternans and the Risk of Death or Sustained Ventricular Arrhythmias in Patients with Left Ventricular Dysfunction." This is a follow-up investigation that expands the applicability of the test published in Circulation in 2004 which looked at just ischemic cardiomyopathy patients (weak heart muscles from coronary disease). In Bloomfield et al.'s recent study, 549 patients were studied, only 1/2 of which had ischemic coronary heart disease. In this study, either positive or indeterminate tests were lumped together and compared to a negative test. Bottom line: A negative test means there is a 2.5% chance of death or arrhythmia in 2 years, vs a 12.3% (positive test) to 17.5% (indeterminate test) risk of death or cardiac arrhythmia.
What was interesting was the numbers.... 549 patients (average ejection fraction 25%), 189 had normal (negative) tests (with 4 events), 360 patients had abnormal MTWA tests (with 47 events). "Abnormal" MTWA tests included either positive (162 patients) or indeterminant (198 patients) tests.
So will ICD implant rates in patient's with low EF be decreased if this test is widely deployed? I don't think so. Given the LARGER total number of patients with positive or indeterminate tests, relative to the number of patients with negative tests in this study. If this test is widely implemented in stress labs, while the patients with negative tests might be spared an ICD, the increased screening using this test might actually INCREASE the number of implanted devices, since far more patients will have positive or indeterminate tests AND CMS seems to be willing to pay for the testing.....
I guess the next question is will smaller cardiology offices be willing to shell out the $30,000 to purchase this machine and the $75 for electrode patches per test? You have to do a lot of T-wave alternans testing to see a return on that investment if the CMS reimbursement rate is low....
Tuesday, March 21, 2006
I had a wonderful opportunity to meet the wonderful mother and daughter team of Terri and 4 year old Gemma, (seen here) both of whom have Crohn's disease. Crohn's disease is one form of inflammatory bowel disease, an autoimmune disorder (where the body considers some of its own cells to be "foreign") and is thought in some cases to be linked to a genetic mutation of gene called NOD2/CARD15 and is marked by recurrent bouts of inflammation anywhere in the gastrointestinal tract. Although there is no known cure, there are lots of therapies that are effective in reducing the bouts of inflammation. It is estimated the Crohn's disease effects 500,000 people in the United States alone. They are busy advocating on behalf of folks with all forms of inflammatory bowel disease. They are seen with our "Semi-Colon" t-shirts from MedTees.com which they use to raise awareness and "bring out of the closet" the difficult issues associated with these diseases and to urge continued support of research into this disease. Importantly, they are also working to prevent cuts in research funding at the National Institute of Health, which is estimated to be reduced bu one million dollars in fiscal year 2007. Terri also participates in this Parents of Kids with Inflammatory Bowel Disease support group. Check them out, lend your support, and learn more about this illness from the Crohn's and Colitis Foundation of America.
Thursday, March 16, 2006
Bioabsorbable magnesium-alloy stent safe to implant
March 13, 2006
Atlanta, GA - An interventional strategy that aims to eventually do away with the stent altogether has shown promising, albeit very early, results. Presenting data on a new bioabsorbable magnesium-alloy stent, investigators showed that the bare-metal stent met its primary end point, with a major adverse cardiac event (MACE) rate of 23.8% at four months.
Speaking with heartwire, lead investigator Dr Raimund Erbel (University Clinic, Essen, Germany) said that after four months, despite the complete disappearance of the stent, "the vessel lumen is nicely opened and we have not seen elastic recoil as a problem."
The results of the study, known as the Clinical Performance and Angiographic Results of the Coronary Stenting and Absorbable Metal Stents trial, known as PROGRESS-AMS, were presented during an i2 Summit late-breaking clinical-trials session here at the American College of Cardiology 2006 Scientific Sessions. The PROGRESS study was a prospective, multicenter, consecutive, nonrandomized trial evaluating the clinical feasibility of the stent, made by Biotronik in Berlin, Germany, in the treatment of a single de novo lesion in a native coronary artery.
Cool stuff. Now stents might not interfere with CT scans and MRI's.... just need to have a little drug ellution added to prevent restenosis...
Wednesday, March 15, 2006
Tuesday, March 07, 2006
Monday, March 06, 2006
Sunday, March 05, 2006
You can listen to it here. Love to get your feedback....
Saturday, March 04, 2006
The bad news is that over one quarter of the patients had recurrent atrial fibrillation (26%) and often troublesome atypical atrial flutters (6%) requiring a repeat procedure (not a big surprise, given the chronicity of the arrhtyhmia and the size of the atria involved). It is also important to realize that this study was performed collectively in two of the larger a-fib ablation centers worldwide, and results are not likely to be replicated as easily by low-volume centers. Nonetheless, it was encouraging that no other significant complications occurred in this study.
Bottom line: Afib ablation is coming, albeit slowly, and will take lots of patience and perserverence to achieve a 74% cure rate. Hence 26% of folks still will NOT be cured with this technique. We still need better tools, but the technology and techniques continue to improve. My hat's off to these centers and their work...
Wednesday, March 01, 2006
"Catheter ablation for atrial fibrillation has been set as second-line therapy for all patients in the treatment guidelines scheduled to be released later this year by the American College of Cardiology, the American Heart Association, and the European Society of Cardiology. By the new guidelines, patients have to fail only one drug before they become eligible for catheter ablation. This recommendation applies to all patients with atrial fibrillation, including those with concurrent heart failure, oronary artery disease, or hypertension..."
Any why not first line therapy? Well, not all folks agree on the safety and efficacy data, but there seems to be some consensus that centers with a higher volume of procedures have better outcomes.
The placement seems appropriate to me, since often patients can greatly reduce their number of episodes non-invasively with medical therapy before venturing into an ablation procedure. Also, the requirement that only ONE antiarrhythmic drug needs to be tried (especially if that drug is amiodarone, flecanide, sotalol or propafenone), permits the patient to seek non-pharmachologic therapies earlier, if desired. Note that in the substudy of the AFFIRM trial, amiodarone was the most effective antiarrhythmic medication of those listed above...