Heart attack patients with a life-threatening complication called cardiogenic shock experience an improvement in survival at 6 months when treated with balloon angioplasty or coronary bypass surgery compared to patients who receive intensive medical care to stabilize their condition, according to a study funded by the National Heart, Lung, and Blood Institute (NHLBI).
The results of the SHOCK (Should we Emergently Revascularize Occluded Coronaries for Cardiogenic Shock) trial are published in the August 26 issue of The New England Journal of Medicine.
The investigators report that emergency "revascularization" with angioplasty or bypass surgery did not significantly reduce deaths of shock patients at 30 days (the primary end point of the study); however, after 6 months patients who had these procedures performed early had a 35 percent improvement in survival over patients who received intensive medical therapy, including clot-busting drugs. The improvement in survival was even greater – 57 percent – for patients under age 75 years.
"These results provide evidence that early treatment with bypass surgery or angioplasty can save the lives of heart attack patients with cardiogenic shock. Physicians should be strongly encouraged to consider emergency revascularization for these patients – even if it means referring them to another hospital that is better equipped to handle these procedures," said NHLBI Director Dr. Claude Lenfant.
Each year an estimated 71,000 hospitalized heart attack patients develop cardiogenic shock. This complication is the leading cause of death in patients hospitalized for heart attack. Relatively few patients with cardiogenic shock are currently treated with emergency bypass surgery or angioplasty. Such patients are extremely ill and physicians may be reluctant to subject them to relatively risky procedures – particularly since there has been conflicting evidence about the value of emergency revascularization for shock. Furthermore, many hospitals do not have adequate facilities to perform these procedures.
The SHOCK study is the largest randomized clinical trial of emergency revascularization for shock complicating heart attack conducted to date. Nearly 1,500 heart attack patients with shock at 30 sites around the world were screened for participation in the study. Patients were eligible if shock was caused primarily by dysfunction of the left ventricle, the heart's main pumping chamber, which leads to loss of blood flow to the body's vital organs. Such patients have extremely low blood pressure and they appear to be cold and clammy, mentally confused and do not produce adequate amounts of urine.
The investigators randomly assigned 152 patients to emergency balloon angioplasty or coronary bypass surgery. Procedures were to be performed as soon as possible – within 6 hours of assignment to the group. Another 150 patients were assigned to "medical stabilization" receiving a program of intensive medical therapy that included clot-busting drugs and "intraaortic balloon counterpulsation," a treatment in which a heart-assist device is inserted into the aorta to help pump the blood. The mean age of the patients was 66 years and 32 percent were women. Of the patients undergoing early revascularization, 64 percent had initial angioplasty and 36 percent had surgery as their first procedure.
The 30-day death rates were 47 percent for patients who had early revascularization and 56 percent for the initial stabilization group, a finding that was not statistically significant. However, this 30-day result is "clinically relevant and therapeutically worthwhile since it represents 93 lives saved per 1000 patients treated...more than double the number of lives saved by the administration of thrombolytic therapy within one hour after the onset of infarction (heart attack)," noted Dr. Thomas J. Ryan, chief (emeritus) of the Cardiology Section at Boston University, in an accompanying editorial.
At both 30 days and 6 months, patients under age 75 experienced the greatest benefit from early revascularization.
The SHOCK trial results were considered among the most important contributions to the recently revised Guidelines for the Management of Patients with Acute Myocardial Infarction. These guidelines, which now recommend early revascularization for shock patients under age 75, were released August 20, 1999 by the American College of Cardiology (ACC) and the American Heart Association. The guidelines are available on the ACC website: www.acc.org. Select Clinical Information to view the guidelines.
"The most striking finding from our study was the large benefit at 6 months for those under 75 years old. This equaled 20 more lives saved for every 100 patients with heart attack complicated by shock who were treated with emergency bypass or angioplasty," said Judith Hochman, M.D., SHOCK study chair and Director, Cardiac Care Unit and Cardiac Research at St. Luke's/Roosevelt Hospital Center in New York City.
"The overall preliminary 1-year results from SHOCK are equally encouraging and it is anticipated that the benefit of early revascularization will be sustained over the long term," said SHOCK co-author Dr. Patrice Desvigne-Nickens who is also the director of NHLBI's Heart Research Program.
Further analysis of the SHOCK data may yield clues to the mechanisms by which early angioplasty or bypass surgery increases survival of these patients, according to Dr. Ryan's editorial.
To schedule an interview with Dr. Desvigne-Nickens, call the NHLBI Communications Office at (301) 496-4236. To interview Dr. Hochman, call Brice Peyre, St.Luke's-Roosevelt Hospital Center, at (212) 523-4047 or page him at (917) 422-2235. To interview Dr. Ryan, call his office at (617) 638-8710.
NHLBI press releases, fact sheets, and other materials, including information about heart disease, can be found online at http://www.nhlbi.nih.gov.