Test on viability of heart muscle identifies patients who will benefit from angioplasty after clot-lysing therapy for an acute heart attack

Emergency angioplasty (balloondilation of the coronary vessel) is the preferred treatment for patients with an acute heart attack. Because of its limited availability worldwide, the majority of patients who are admitted to the hospital with a heart-attack are treated with clot-lysing drugs (thrombolysis).

Although this treatment improves the chance of surviving considerably, during the recovery phase many patients (20-30%) are confronted with new episodes of chest-pain sometimes resulting in a new heart-attack. These complaints are often caused by a significant narrowing that is still present in the coronary artery after clot-lysing therapy. Although clot-lysing therapy is capable of opening occluded coronary arteries and saving heart muscle, it will not remove the narrowing that was already present before the heart-attack took place. Patients with recurrent complaints often need to undergo coronary angiography (heart catheterisation) with the intention to perform balloondilation (angioplasty) of the infarct-related coronary artery in order to remove the narrowing and to protect the initially saved viable heart muscle. (The infarct-related artery is the vessel that was occluded and caused the heart attack).

Although some studies have shown that elective angioplasty performed after thrombolysis can lower the risk of recurrent heart-attacks, this is not generally accepted as a standard strategy. Because two-third of the patients have an uneventful clinical course without recurrent complaints, many patients do not need angioplasty (a procedure that carries a small, but not negligible risk) and do well with medical, non-invasive treatment. Therefore, current treatment strategies after thrombolysis include an ischemia-guided approach. (Ischemia means: insufficient oxygen supply to the heart muscle). As part of this approach angioplasty is only performed in patients who have signs or symptoms indicative for an impending new heart-attack (ischemia). In this setting it is of great importance to know which patients are at risk for developing a new heart-attack after they have been treated with thrombolysis. Because currently used methods are not sufficient to predict which patients will develop a new heart-attack, it is clear that we have to improve our ability to detect these high-risk patients. In the VIAMI-study an improved method has been studied.

The VIAMI study

In the VIAMI study a new method was used to predict the risk of a new heart attack. The method involved is a viability test using an ultrasound technique. It was already shown in pilot-studies that with this technique it was possible to identify patients with a heart-attack who are at high risk of suffering a second heart attack. Patients in whom it could be demonstrated that remaining viable heart muscle was present in the area of the heart-attack, had a high risk of getting a new (threatening) heart-attack, whereas patients without viable heart muscle did not have such recurrent problems. The ultrasound technique that was used to detect viable heart-muscle is called dobutamine echocardiography (cardiac ultrasound). During this test a heart-muscle stimulating drug called dobutamine is administered to the patient. During the infusion of dobutamine the heart is studied with ultrasound to look for improvement of the area where the heart attack took place. Improvement in function of the heart muscle indicates the presence of viable heart muscle.

Methods

The VIAMI trial studied the benefits of an angioplasty procedure in patients with viable heart muscle after clot-lysing therapy. For this reason, patients who were admitted to the hospital with a heart-attack and were treated with thrombolysis underwent viability testing with the ultrasound technique. Also, patients who were too late for clot-lysing therapy were allowed to participate in the study. When viable heart muscle was found patients were randomized to an angioplasty procedure or to a conservative treatment. In the first group angioplasty was performed as soon as possible. In the second group angioplasty was only to be performed in case of new signs and/or symptoms of a threatening heart attack. The two patient groups were followed for 6 months to look at survival and recurrent complaints (ischemia). The patients who had no viable heart muscle were studied as a registry group.

Results

Two hundred and sixteen (216) patients showed viability and were randomised. Seventy five (75) patients had no viability and served as registry group. The primary interest of the study was to look at the occurrence of death or a new (threatening) heart-attack during 6 months follow-up.

The analysis shows that in the patients with residual viable heart muscle, angioplasty of the infarct-related coronary artery significantly reduces the risk of a recurrent (threatening) heart-attack. In the conservatively managed group 15.5% of patients developed recurrent heart problems, whereas only 6.6% of patients in the angioplasty group had a recurrent heart problem. This means that viability can identify the high-risk patient and that angioplasty can lower this risk considerably (by 59 percent).

The patient group without viability had a low rate of recurrent (threatening) heart-attacks (5.3%), confirming that the absence of viable heart muscle is associated with a low risk. These patients do not need an invasive procedure per se.

Conclusions of the study

The data from the VIAMI-study show that after clot-lysing therapy (and also when patients were too late for such treatment) a relatively simple bedside method like cardiac ultrasound combined with a heart-muscle stimulating drug is able to identify high-risk patients. Not only is shown that ‘viable' patients are at increased risk for a new (threatening) heart-attack, but it is also shown that angioplasty of the infarct-related artery is an effective treatment for these patients. After angioplasty these patients have a long-term uneventful clinical course, with a significantly better prognosis than patients in whom angioplasty is performed only when new signs or symptoms of ischemia occur.