Now, a national study based on data from 37,233 patients casts a shadow on this practice of "part-time" emergency angioplasty.
In the Jan. 17 Circulation, a team led by University of Michigan and Yale University cardiologists reports that patients are less likely to die during their hospital stay, and will receive faster treatment, if they have their emergency angioplasty at hospitals where it is the "default" treatment, used on the vast majority of heart attack patients.
By contrast, the in-hospital death risk and risk of delayed treatment were both higher for angioplasty patients treated at hospitals where emergency angioplasty was used in a minority of heart-attack patients. On the whole, they were significantly more likely to die before leaving the hospital, and waited an average of 20 minutes longer for treatment, than those treated at hospitals where most heart attack patients received angioplasty. Many waited far longer than the 90 minute "window" during which emergency angioplasty is thought to have an edge over clot-busting drugs.
Surprisingly, the study also suggests that hospitals' level of "specialization" in emergency angioplasty has more to do with patient survival than the sheer number of emergency angioplasties performed there each year. Previous studies have shown that patients do better when they receive angioplasties and other such treatments at hospitals where many such procedures take place each year.
"In the case of emergency angioplasty, for hospitals it seems that it's not just how many you do, but how used to doing them you are," says lead author Brahmajee Nallamothu, M.D., MPH, an assistant professor of internal medicine at the U-M Medical School, researcher at the VA Ann Arbor Healthcare System and member of the U-M Cardiovascular Center. "The overall commitment to doing emergency angioplasties, and the protocols and staffing that come out of that commitment, appear to be key." The bottom line for anyone having a heart attack, he adds, is still to call 911 and let the emergency medical staff decide which hospital to choose.
The study was funded by a National Heart, Lung and Blood Institute grant led by Harlan Krumholz, M.D., a professor at Yale University School of Medicine, and used data from the National Registry of Myocardial Infarction collected from 2000 to 2002.
"This study has direct policy implications for hospitals trying to decide what services to provide," says Krumholz. "It seems best to decide on a single approach to the care of patients with heart attacks and stick to it."
The new paper, the authors say, suggests that hospitals where the "default" emergency heart attack treatment is clot-busting drugs (fibrinolytics) may want to focus on optimizing that approach, or determine better ways to institute emergency angioplasty protocols and staffing for around-the-clock care.
Nallamothu notes that public policy can also play a role – such as the state of Michigan's recent requirement that hospitals newly licensed to perform emergency angioplasty without on-site cardiac surgery be able to do it around the clock, 7 days a week. Increasingly in Michigan, small and mid-sized hospitals are making the effort to get a state license for emergency angioplasty without having a heart surgeon available as backup – which brings with it regular monitoring of patient outcomes.
The authors stress that their findings bolster prior findings by teams at U-M, Yale and other institutions showing that angioplasty patients do better if treated at hospitals, and by doctors, that perform many of the procedures each year. Says Nallamothu, however, "Procedure volume is only a surrogate for other measures of quality, and we hope this study helps illuminate the role of specialization."
Funding for the NRMI study that yielded the data for the new paper was provided by Genentech, which makes two fibrinolytic drugs used to treat acute heart attack. The company provided access to the NRMI data at no charge, and approved the study protocol before the analysis.
Further information on the study:
The patients were treated at 463 hospitals, which the authors divided into four categories. Hospitals in the most-specialized group performed emergency angioplasty on more than 88.5 percent of the heart attack patients. Those in the least-specialized group provided emergency angioplasty to less than 34 percent of their heart attack emergency patients. The other two groups were in between.
The biggest difference in survival and time-to-treatment for angioplasty patients was seen between the highest and lowest groups. But there was a noticeable, though not statistically significant, difference between the highest group and the next two groups. There were no significant differences among the groups in death risk or treatment time for patients given clot-busting drugs.
All the patients had a form of heart attack known as STEMI, and all had arrived at the hospital within 12 hours of the start of their symptoms. None were transferred from an acute-care hospital, or had conditions that would have kept them from getting either angioplasty or clot-busting drugs.
Emergency angioplasty and other catheter-based treatments are known as primary percutaneous coronary interventions, or PPCI, and have become the "default" treatment at most major medical centers. In order to offer such treatments around the clock, many large hospitals have created standard protocols to determine quickly if a patient is having the type of heart attack for which angioplasty works best, give medications that can help improve their response, and get them to a fully-staffed procedure room called a cardiac catheterization lab within minutes of their arrival.
The time from hospital arrival to the inflation of the angioplasty balloon within the blocked artery is called "door to balloon" time, and national guidelines currently recommend that hospitals aim for times under 90 minutes. Angioplasty can be performed on most patients, but a sizable fraction of heart attack patients have medical conditions or take drugs that keep them from receiving the other standard artery-opening treatment, fibrinolytics. For patients without these underlying factors, fibrinolytics do work well – especially if given within 30 minutes of arrival at the hospital, an interval known as "door to needle" time. And nearly any hospital can offer fibrinolytics around the clock.