Now, new trial of mitral valve procedure will compare surgery with current drug therapy
ANN ARBOR, MI -- Surgery to repair a leaky heart valve can help even the sickest heart failure patients live longer, enjoy a better quality of life, and avoid or postpone a heart transplant, according to results published today by University of Michigan physicians. Now, the U-M is leading a trial to compare the operation directly with widely used drug-based therapy.
In a paper in the current issue of the Italian Heart Journal, the surgical technique is shown to have improved the condition of many heart failure patients who would have once been thought too sick for most surgery. The finding builds on earlier published data from the same U-M team.
The operation fixes the mitral valve, the muscular gateway to the chamber that pumps blood into the body, by placing a small flexible ring around the valve opening to tighten it. In the enlarged, damaged hearts of the heart failure patients in the study, the "valve job" improved heart pumping strength and blood output by more than 50 percent.
Statistically, the patients in the study faced an 80 percent chance of dying within a year if they didn't receive a heart transplant. Instead, eighty percent of the 92 patients were alive after one year, and 70 percent after two years. Some have lived more than five years since their operations. The finding raises the possibility that the operation might lessen the pressure on the nation's heart transplant system, and could help address the rising tide of heart failure cases.
"After several years of study, this approach continues to compare favorably with intensive drug therapy, based on historical data on survival and quality of life," says author and U-M cardiac surgery professor Steven Bolling, M.D. "But now we must compare it directly with the best of modern medical management for heart failure. Our current trial aims to accomplish that."
Called mitral valve repair, the operation is similar to a kind of surgery that is routinely performed on patients with lesser heart conditions. But for those with the two most severe classes of heart failure - an estimated 30 percent of the 4.6 million Americans with the disease - the surgery offers a rare chance to fix a cause of their problem, rather than symptoms. The only other surgical option for such patients, which removes a portion of the heart muscle, has a 60-percent operating-room death rate, compared with five percent 30-day mortality in the new study.
Heart failure most often arises as a result of other common diseases, including heart attack, narrowing of the arteries, high blood pressure and infection of heart muscle or valves. The weakened heart muscle deteriorates and cannot pump blood as efficiently, causing patients to feel tired and short of breath. Eventually, the heart fails. Heart transplant is often the only option.
In the new paper, Bolling and his colleagues report on the progress of 92 patients who underwent mitral reconstruction at the U-M between 1993 and 1999. All had heart failure resulting from cardiomyopathy, or heart muscle disease, and had mitral valves so leaky that they allowed as much as 70 percent of the blood flow back through the opening.
Many the patients's hearts had become severely enlarged to compensate for the muscle disease, stretching the area around the mitral valve so much that the valve's muscular flaps could not fully close. The valves usually overlap, sealing off the left atrium, or upper receiving chamber, from the left ventricle, or lower pumping chamber.
In addition to having leaky valves, the patients' left ventricles all had extremely weak pumping ability, propelling one-third the normal amount of blood into the body with each beat. Such low ejection fractions, as they are called, can cause further heart deterioration, clots in the left atrium that can travel to the brain and set off strokes, and other serious problems.
As a result of their condition, all of the patients were limited in their ability do everyday activities, causing them to be listed as Class III or Class IV heart failure patients. Class III patients can usually manage to make a bed or dress by themselves, but class IV patients can't even handle that strenuous a task.
The mitral valve reconstruction surgery aims to "overcorrect" for the leaky gateway, using a smaller-than-usual ring to reinforce the flaps. "This overcorrection enhances the effect of stopping backward flow and helps the left ventricle pump better," Bolling says. "It may also help weakened heart muscle heal. But it's not a cure. Patients must continue on medication, controlled diets and exercise regimes after surgery."
Two years after the operation, the surviving patients had recovered strength and ability, allowing them all to be reclassified as Class I or II heart failure patients. The amount of blood regurgitating, or flowing backward, through their mitral valve had been cut drastically, to an average of 13 percent. And their left ventricles were able to pump out a larger percentage of the blood that flowed into the chamber, because the remodeled valve area helped tighten the muscle of the entire ventricle.
Surgeons and cardiologists at U-M and nationwide will now test the surgery combined with conventional medical treatment against medical treatment alone in a multi-center trial named PREMIUM, short for Prospective Randomized Evaluation of Mitral Intervention started at the University of Michigan.
The study is supported by Baxter Healthcare Corp., Medtronic and St. Jude Medical, three manufacturers of the flexible annuloplasty rings used to reinforce the muscular flaps of the mitral valve. Prospective patients may call (734) 936-1900 to learn if they are eligible.
The PREMIUM trial will focus on those whose condition is most advanced. It will enroll more than 150 patients between the ages of 18 and 80 who have been diagnosed with Class III or Class IV congestive heart failure. Even patients who are not candidates for heart transplant, either because of age, diabetic condition, or Class III status, are eligible.
Patients must have moderate or severe mitral valve problems, with ejection fractions less than 30 percent, as compared with a normal 70 percent. They must have been on medications for at least three months.
The trial will compare surgery with the current optimal medical therapy, which includes drugs called ACE inhibitors and beta-blockers as well as digoxin and a diuretic. All patients will take such medications, and half of the patients in the randomized portion of the trial will be selected by lottery to undergo surgery. Another group of patients who elect to have the surgery instead of entering the lottery will also be followed and reported on.
The trial will feature strict observation to assess the effect of the two options over a long period. At the start of the trial, and at regular intervals until one or two years afterward, doctors will assess patients' ability to exercise; their heart pressure, volume, flow and regurgitation rates; their quality of life; the number of times they are hospitalized; and the cost of all their treatments. The trial may show not only how the surgery affects patients' survival and quality of life, but also how it affects their chances of needing a heart transplant.
Bolling says he hopes the trial will increase understanding of the mitral valve's importance to the entire heart's function, and to the overall failure of the heart. "The mitral valve is not just a door, it's an active mechanism that determines the power of the heart," he says. "It is integrated with the rest of the heart, and must work in concert with other components."
Note: Dr. Bolling acts as a consultant to all three companies sponsoring the trial.