Skip to main content

Think You Might Have AF? There's an App For That


WORCHESTER, Massachusetts — Innovative researchers have developed a smartphone-based application that allows patients to detect an irregular pulse caused by atrial fibrillation [1]. Two algorithms developed for the application that analyzed signals using an iPhone 4S successfully distinguished atrial fibrillation from sinus rhythm, report investigators.
"A number of patients who are referred to us have pretty symptomatic atrial fibrillation," said lead investigator Dr David McManus (University of Massachusetts Medical School, Worchester, MA). "So they are highly motivated to keep track of their episodes. We traditionally order Holter monitors and event monitors to capture the coming-and-going episodes of atrial fibrillation. I thought there was a potential role to leverage the fact that everybody has a smartphone and to use that as a means to do a sort of physiological assay of the patient."
The results of the study are published online December 7, 2012 in Heart Rhythm.
App Uses Camera and Flash to Measure Chaos in Pulse
To heart wire , McManus explained that patients often wear Holter and event monitors for up to 30 days in order to capture an atrial-fibrillation event, but some of the paroxysmal events are so infrequent that physicians might not even bother with the monitors. A phone-based rhythm-assessment tool would have positive implications for accessibility, allowing patients to record their pulse while the event is occurring to determine whether they are in fact having an episode of atrial fibrillation.
The application works using the smartphone camera and the flash to illuminate the fingertip when it is placed on top of the camera surface. Not unlike a pulse oximeter, which uses infrared light, the flash lens works to illuminate the finger as the camera records in real time the changes in the color of the fingertip. The changes in color act as a surrogate for blood flow, and this is in turn processed by a computer program embedded within the smartphone. Two algorithms--the root mean square of successive RR differences and Shannon entropy--analyze the degree of "chaos," or the variability of the pulse waveform.
"For the purposes of this study, we had patients keep their fingertip on the camera for two minutes, but we have that down now where we've shown that even one minute is sufficient," said McManus. "So it's a quick biopsy of person's pulse that appears to be highly accurate compared with a 12-lead ECG, which is what we used in this study."
In the study, 76 adults with persistent atrial fibrillation scheduled to undergo elective cardioversion were included in the analysis. All subjects who had a preprocedure ECG placed their finger on an iPhone 4S camera for two minutes while the program ran. Following cardioversion, patients successfully converted to normal sinus rhythm again reapplied their finger to the smartphone as another recording was obtained. The algorithms had excellent sensitivity (0.962), specificity (0.975), and accuracy (0.968) for the discrimination of an irregular pulse during atrial fibrillation from sinus rhythm.
"This is really the first step, showing that when it is used in the hospital setting, where a coach was showing them how to put their finger on the phone, people could successfully use this phone to know if they were in or out of atrial fibrillation," said McManus.
Young and Old, Patients Want This
To heart wire , McManus said that patients are clamoring for such an application, particularly those with diagnosed and treated atrial fibrillation who want to be on top of how many episodes of the arrhythmia they are having. They don't want to travel to the hospital or the doctor's office every time they suspect they might be having an episode, however. "Patients want this at their fingertips," he said. "They want something quick, they wanted something that's accurate, and they want something that allows them to communicate effectively with their doctor, all the more reason for it to be a phone-based program."
The application allows users to send the results directly to their physician via email and also provides summaries of atrial-fibrillation burden over selected time periods, a useful feature for physicians to determine whether another antiarrhythmic agent might be needed. Future issues remain, however, regarding how the application will fit into traditional testing, the approval process, who pays for it, and how it will get billed. While those market-based issues remain to be worked out, McManus believes the application fills an unmet need.
"I have to say that I have done a lot of clinical studies, but I had absolutely no problem recruiting patients for this one. Universally, they all said this is really cool."
 

Comments

Post a Comment

Popular posts from this blog

Missing Data Lead FDA Panel to Vote Against Rivaroxaban for ACS May 23, 2012 (Updated May 24, 2012) (Silver Spring, Maryland) — The missing data issues plaguing the ATLAS ACS 2 TIMI 51 trial of the factor Xa inhibitor rivaroxaban (Xarelto, Bayer Healthcare/Janssen Pharmaceuticals) have prevented the drug from earning the endorsement of the FDA Cardiovascular and Renal Drugs Advisory Committee. At its May 23 meeting, the panel voted six to four (with one abstention) against recommending that the FDA approve rivaroxaban for reducing the risk of thrombotic cardiovascular events in patients with acute coronary syndrome or unstable angina in combination with aspirin, aspirin plus clopidogrel, or ticlopidine. Janssen's application is based on the results of the ATLAS ACS 2 phase 3 and the ATLAS ACS TIMI 46 phase 2 trial. The placebo-controlled ATLAS ACS 2 showed rivaroxaban reduced the risk of both all-cause and cardiovascular mortality while increasing the risk of bleeding and intracranial hemorrhage, but the studies were hindered by early patient withdrawals and missing data. We Don't Know What We're Missing Based on the ATLAS ACS 2 results, FDA reviewer Dr Karen Hicks recommended approval of rivaroxaban for the requested indications except all-cause mortality. However, another FDA reviewer, Dr Thomas Marciniak, was adamant that the trial results are not interpretable because about 12% of the patients had incomplete follow-up, far higher than the 1% to 1.5% differences in the end-point rates between rivaroxaban and placebo. A total of 1294 subjects discontinued the trial prematurely, and the company was only able to contact 183, of which 177 were confirmed to be alive. Because of the patient dropouts, the company adopted a "modified intention-to-treat analysis," whereby patients were observed for 30 days after randomization or the global end date for the trial, instead of observing all the patients until the end of the trial as the FDA originally suggested. Marciniak criticized the sponsor's efforts to follow the patients and said that three patient deaths not counted in the modified intention-to-treat analysis may just be the "tip of the iceberg." Because the percentage of patients whose ultimate vital status remains unknown is much greater than the reported differences in mortality rates, the claimed mortality benefits are not reliable. The majority of the panel sided with Marciniak. For example, Dr Sanjay Kaul (University of California, Los Angeles) voted "no" because "there was enough uncertainty in the quality and robustness of the data that dissuaded me from voting yes. . . . The 'missingness' of the data doesn't invalidate it, but it certainly makes it hard to infer [the conclusion]." Dr Steven Nissen (Cleveland Clinic, OH) said that the decision to use the modified intention-to-treat analysis had a "profound impact" on the interpretability of the data. "It's saying we don't care what happens after 30 days, [and] that colored the trial in ways we couldn't recover from." Given the risk of major bleeding, "I want to see better evidence that this strategy of adding an Xa inhibitor or a direct thrombin inhibitor or something else to a good antiplatelet agent is robustly better for the patient," Nissen said. He recommends that the companies run a new trial of the 2.5 twice-daily dose of rivaroxaban using a strict intention-to-treat approach, but, he said, "I don't expect the death benefit to be too robust." Several panelists said they were concerned that the patients who dropped out of the trial were disproportionately likely to have a bleeding event, which led them to quit the trial, or a "protopathic" event, as statistician Dr Scott Emerson (University of Washington, Seattle) put it. "We're worried that an impending event is what is changing their behavior. We see that all the time in clinical trials--that regularly measured end points do not pick up [all of] the events," he said. He said that since the company was only able to contact 183 of the over 1200 patients who dropped out, it is possible that the dropouts skew the outcomes comparison of the trial. "Differential event rates after dropout are the number-one thing we're afraid of, so you have to explore it" in a statistical sensitivity analysis of the potential impact of these unknown outcomes. "It would not surprise me if, at the end of the day, these data did not hold up under a proper sensitivity analysis," he said. "What I want to know is, among the people who had events, how differential was the follow-up, but I can tell you by just looking at it, there was a very slightly different amount of follow-up of the people in the treatment arm. But I don't know whether everyone in the treatment arm was cured and they were trekking in the Himalayas and everyone in the placebo arm went home to die. I don't know that that's not the case." Dr Maury Krantz (University of Colorado, Denver) voted in favor of approval but said he does not know how rivaroxaban would perform in general clinical practice, especially when used with aspirin and clopidogrel. "I felt very much torn by this. This isn't a simple paradigm shift. It means going to triple therapy, which is really a three-headed monster in many ways. I think that what you're going to see in practice, if this is not done carefully with the proper labeling and secondary studies, is really dramatic magnification of bleeding and perhaps minimization of the efficacy benefit."

May 23, 2012   (Updated May 24, 2012)  (Silver Spring, Maryland)  —  The missing data issues plaguing the  ATLAS ACS 2 TIMI 51   trial of the factor Xa inhibitor  rivaroxaban  (Xarelto, Bayer Healthcare/Janssen Pharmaceuticals) have prevented the drug from earning the endorsement of the  FDA  Cardiovascular and Renal Drugs Advisory Committee. At its May 23 meeting , the panel voted six to four (with one abstention) against recommending that the FDA approve rivaroxaban for reducing the risk of thrombotic cardiovascular events in patients with acute coronary syndrome or unstable angina in combination with aspirin, aspirin plus  clopidogrel , or  ticlopidine . Janssen's application is based on the results of the ATLAS ACS 2 phase 3 and the  ATLAS ACS TIMI 46   phase 2 trial. The placebo-controlled ATLAS ACS 2 showed rivaroxaban reduced the risk of both all-cause and cardiovascular mortality while increasing the ri...
Post a Comment
Read more

Antidepressants Linked to Higher Diabetes Risk in Kids

Pediatric patients who use antidepressants may have an elevated risk for type 2 diabetes, the authors of a new study report. In a retrospective cohort study of more than 119,000 youths 5 to 20 years of age, the risk for incident type 2 diabetes was nearly twice as high among current users of certain types of antidepressants as among former users, Mehmet Burcu, PhD, and colleagues report in an article  published online October 16 in  JAMA Pediatrics . The risk intensified with increasing duration of use, greater cumulative doses, and higher daily doses of these antidepressants. The findings point to a growing need for closer monitoring of these products, including greater balancing of risks and benefits, in the pediatric population, the authors caution. They undertook the study because, despite growing evidence of an association between antidepressant use and an increased risk for type 2 diabetes in adults, similar research in pediatric patients was scarce. "To our know...
Post a Comment
Read more

Contact Precautions May Have Unintended Consequences

Contact precautions, including gloves, gowns, and isolated rooms, have helped stem the transmission of hospital pathogens but have also had some negative consequences, according to findings from a new study. Healthcare worker (HCWs) visited patients on contact precautions less frequently than other patients and spent less time with those patients when they did visit, report Daniel J. Morgan, MD, from the University of Maryland School of Medicine and the Veterans Affairs (VA) Maryland Health Care System, Baltimore, and colleagues. Moreover, patients on contact precautions also received fewer outside visitors. "Less contact with HCWs suggests that other unintended consequences of contact precautions still exist," Dr. Morgan and coauthors write. "The resulting decrease in HCW contact may lead to increased adverse events and a lower quality of patient care due to less consistent patient monitoring and poorer adherence to standard adverse event prevention methods (such...
Post a Comment
Read more