The vast majority of heart attack patients treated at U.S. hospitalsinitially receive a shot of thrombolytics to clear out blocked arteriesand the drug of choice is Genentech Inc.'s Activase, or tissueplasminogen activator (tPA).
Balloon angioplasty, an alternative surgical procedure, is performedonly about 10 percent of the time as a primary therapy. And only 20percent of American medical centers have qualified doctors and theequipment to perform the operation.
However, new research data presented this week at an AmericanCollege of Cardiology conference in New Orleans suggestangioplasty may be more beneficial and cost effective in someinstances than thrombolytics.
Douglas Weaver, professor of medicine at the University ofWashington in Seattle, described some of the findings as"provocative," but said more comparison studies are needed.
Weaver, who was not involved in the angioplasty trials, has beenamong investigators participating in studies to identify the mosteffective clot busters. Those on-going trials are dubbed the GlobalUtilization Strategy for Thrombolysis of Occluded Arteries(GUSTO) studies.
"It will be a long time before angioplasty has any significant impacton tPA," said Matthew Geller, an analyst with Oppenheimer & Co. inNew York.
But Barbara Hoffman, an independent biotechnology analyst inDenver, said the recent angioplasty research "won't be helpful toGenentech's sales of tPA."
A biotechnology beneficiary of the angioplasty studies, Hoffmanobserved, could be Centocor Inc.'s ReoPro, which was approved bythe FDA last December for use in high risk angioplasty patients.ReoPro, a platelet inhibitor, is used following angioplasty to preventblood clots from reforming.
The angioplasty studies "won't be positive for thrombolytics,"Hoffman observed, "but they would be positive for ReoPro."
The angioplasty research presented in New Orleans was coordinatedby doctors at William Beaumont Hospital in Royal Oak, Mich. Thestudies are called Primary Angioplasty in Myocardial Infarction(PAMI) and the data were from the second of two PAMI trials.
"Two years ago in a head-to-head comparison [in PAMI-1] we foundthat mortality with tPA was 6.5 percent and with angioplasty it was2.5 percent," said William O'Neill, an investigator on the PAMIstudies and the director of cardiovascular disease at BeaumontHospital. The PAMI-1 studies involved 395 patients at 12 medicalcenters.
O'Neill said PAMI-2 was designed to demonstrate angioplasty'seffectiveness on a widespread basis. It did not, however, involve ahead-to-head comparison with Activase.
About 1,100 patients participated at 25 medical centers in the U.S.and five hospitals in Japan, Argentina, Brazil and Spain. Mortalitywas 2.9 percent and the studies showed angioplasty was a more cost-effective treatment than clot dissolvers in heart attack patientscharacterized as low risk.
"For low risk patients," O'Neill said, "the total cost was $3,000 lessfor angioplasty than tPA."
The cost comparison, he added, was based on length ofhospitalization and need for ancillary tests. The hospital stay for low-risk patients receiving angioplasty was three days, compared with atypical seven to 10 days for those being treated with clot busters.
The angioplasty patients also did not require treatment in an intensivecare unit and follow-up stress tests and echocardiograms were notnecessary. Mortality for the low risk patients was 0.4 percent.
O'Neill added that in association with the angioplasty procedure, aheart catheterization was done, enabling physicians to identify lowand high risk patients. In high risk patients, he said, the mortality withangioplasty, plus use of a balloon pump, was 3.5 percent.
O'Neill said the PAMI studies demonstrate the superiority ofangioplasty and he expects Genentech, whose Activase sales accountfor 70 percent of thrombolytic market in the U.S., "to pull out allstops to disprove" the results.
Although Weaver observed that the PAMI trials have shownangioplasty is at least as effective as thrombolytics and superior forsome patients, he said, "It's not time for all of us to change ourpractice."
Weaver was impressed by some angioplasty study findings, such asstratification of patients into low and high risk groups, early hospitaldischarges and the overall mortality rate. He suggested larger trialsinvolving angioplasty and thrombolytics are needed.
The GUSTO II trials, which mainly involve testing of anticoagulantsagainst heparin, include a part comparing angioplasty to tPA in 1,000patients.
However, Weaver said he has some concerns about the guidelines forthose studies, which are being conducted in Europe. n
-- Charles Craig
(c) 1997 American Health Consultants. All rights reserved.