CDU Executive Editor
DENVER — Around 95% of those struck by sudden cardiac arrest (SCA) die.
A new group, the Sudden Cardiac Arrest Coalition, would like to reverse this — to 90% saved with the use of defibrillation very quickly after the heart stops because of an electrical “short” in the heart’s system.
That was, pragmatically speaking, the rather unrealistic projection by the coalition of the potential survival from SCA, its formation un-veiled at a press conference at the scientific sessions of the Heart Rhythm Society (HRS; Washington) in May.
But given the number of medical and healthcare associations forming the SCA Coalition — nearly 30, and likely to grow — a sustained effort in this sector could at least somewhat improve the dismal 5% rate of SCA survival.
That is, if it gets the necessary federal funding that it plans to ask for.
Citing the huge mortality rate from SCA, Dwight Reynolds, MD, outgoing president of HRS, said that initiatives that are able to reduce that figure “to 75% even, that’s a dramatic savings of lives in this country,” based on 250,000 deaths from SCA annually in the U.S.
The “U.S. government,” he added, “is the best hope for arming us, reaching the public to provide the level of awareness that can make a difference.”
A statement by the coalition said that it will seek the funding “to develop and implement a comprehensive education and research program for SCA [that will] include a resolution to create a national Sudden Cardiac Arrest Week … to focus on this deadly killer.”
Juliet Johnson, a spokesperson for the coalition, told Cardiovascular Device Update that the group will offer “omnibus legislation” to Congress for the money to support various programs to improve public awareness and research, but the financing amount it will ask for was an undisclosed wild card. The group’s representatives said it was “still crafting” what amount of additional funding it will request.
Garnering public support
The coalition backed its push for funding with public opinion. At the press conference it presented surveys indicating — once respondents were made aware of the specifics of SCA risk — that about 94% support greater emphasis on SCA awareness and education; and about 77% agreed that more federal funding is needed for these efforts.
A survivor of SCA, Judy Sudmeir, a Denver nurse, was on hand to say this was her “third birthday,” marking the years since she suffered SCA and was given rapid CPR and defibrillation, and noting that 650 people die each day in the U.S. as the result of SCA.
But the current therapies of AEDs and ICDs are frequently considered cost-ineffective because SCA hits so suddenly and with so little warning - as well as occurring mostly in the home, and when no witness is present, even if an AED were available for use, suggesting the need for broad ICD use.
Acknowledging these problems, Reynolds said that the “signs and symptoms [of SCA] are not often easily seen — most of the time there is no warning of an arrhythmia.” But he also said that SCA is “not a random event; most victims have some kind of heart disease or some other event,” providing some forewarning.
The coalition obviously may be a boon to AED and ICD manufacturers in promoting broader use of these technologies, but it should especially hearten those developing research on early risk stratification for SCA.
“We don’t always have the tools at our disposal to detect those who are at high risk,” Reynolds said, specifically citing the need for “a cost-effective screening tool to find people in general population” with increased risk based on genetic markers.
While he said that ICDs are 98% effective, he acknowledged the dual problem of not being able to identify those who would most benefit from the devices, and ICDs are implanted in many people who never need them. Thus, he said, “We’re striving with the tools that we have today, not to be putting defibrillators in those who are not at high risk [so as to] implant fewer defibrillators than is optimal.
Absent: diagnostics predicting SCA
The lack of tools to effectively predict those who will suffer SCA — and those most likely to benefit from an ICD — was pointed up fairly dramatically at the HRS conference by the rather obvious paucity of studies in this area. (Only four studies were listed in the abstract index under “Risk factor.”)
Additionally, the few studies reported on still depend on evaluating patients who have already experienced a heart “event” of some sort.
Following is a sampling of these studies — from among several hundred overall — that were interesting, but so technically specific and limited to such narrow populations over relatively short periods, that they appear to provide only the narrowest of pathways to what the SCA Coalition needs in terms of preventing SCA in the near term. This is an observation likely to be made by government budget authorities and may raise continuing doubts concerning the cost-effectiveness of making any inroads vs. this lethal event.
• In a Finnish study, researchers combined bicycle ergometer exercise testing with T-wave alternans (TWA) to predict mortality in 1,047 patients referred for exercising testing but not having an MI. TWA is a noninvasive method for analyzing beat-to-beat variance in the T-wave portion of the ECG, and is most often used to determine risk of death following MI. Digital ECGs were recorded and TWA was analyzed with a method called time-domain modified moving average. The maximum TWA value at heart rate was derived and analyzed for its ability to stratify risk for all-cause cardiovascular death and for risk of sudden cardiac death.
In a 44-month follow-up, 59 of those enrolled died of either SCA or as the result of some other heart failure. Analysis showed that the relative TWA risk was 7.4 for sudden cardiac death, 6 for cardiovascular mortality, and 3.3 for all-cause mortality. The researchers concluded that the testing method “powerfully predicts mortality” in a population undergoing exercise testing combined with TWA.
• A study from Poland used microvolt TWA (MTWA, a TWA variant measuring one-millionth of a volt) to determine if it can be used as a universal marker for “cardiac events” after acute MI. The researchers said that when it looked at all of the negative events from a population of 115 post-MI patients who had suffered negative events — deaths, sudden deaths, reinfarctions, ventricular tachycardia and rehospitalizations — the only common factor was “a not negative MTWA,” and thus a “powerful predictor” of such events, but not predictive of which events are the worst — sudden death.
• A Japanese study appeared to offer a specific negative concerning a combination of TWA systems for identification of risk. The researchers studied the use of MTWA as an index of risk for ventricular arrhythmias or sudden cardiac death and combined this with ambulatory ECG-based tracking of TWA (called A-TWA), which is also used for risk stratification. The study employed the two methods, using the same voltage power, to look at 68 patients with serious cardiac disorders or syncope but found no linear correlation between the two methods.
• Another study out of the University of Utah (Salt Lake City) examining the prediction of death following an MI, used two new predictive systems: heart rate turbulence (HRT) and deceleration capacity (DC). The study enrolled 2,292 patients that had acute revascularization and found 185 deaths in this population in a five-year follow-up.
The researchers said that the methods of analysis correlated with the high risk of left ventricular ejection fraction (LVEF) — with depressed LVEF being a high-risk predictor — and so the two methods are “feasible” for identifying those patients at highest risk for death, the research report concludes.
• Sleep apnea has long been associated with cardiovascular disease and perhaps sudden SCA. Researchers from two universities in Japan said that sleep apnea clearly has been proven to be associated with death in those with CHF, but that there has been no definitive relationship shown to cause sudden death in these CHF patients. The study followed 95 patients with CHF receiving treatment for sleep apnea, with an average of 17 months follow-up, and it reported 18 patients of the group dying, 10 experiencing ventricular tachyarrhythmia.
It said the results supported the need for the management of sleep apnea in these patients, and that the risk factors identified were independent of hemodynamic parameters.
Therapy window shrinks
Another point made by the SCA Foundation was the importance of providing therapy for SCA as soon as possible, and describing an even narrower window of success than previous estimates. While use of an AED has generally been said to be needed within the first 10 minutes after SCA onset, the coalition presenters described the most effective window for successful survival of SCA as four to six minutes (given the mental and physical deficits that have been seen as the result of resuscitation providing survival, but outside that four- to six-minute window).
Though highlighting the mortality resulting from SCA, the coalition clearly was attempting to emphasize its survivability. The foundation has launched an online registry for survivors of SCA, calling it “the nation’s first.”
Michael Sayre, MD, of The Ohio State University Medical Center (Columbus), said in a statement that the registry — at www.sca-aware.org — “will give sudden cardiac arrest survivors and their families an opportunity to find others who have been through similar life-changing events, share their experiences and help one another in the healing process.”
Other goals include fostering “awareness initiatives designed to help improve survival rates” and serving as a research tool by providing information concerning “location of arrest, types of interventions and outcomes.”