Barcelona, Spain - Percutaneous revascularization of residual viable myocardium identified by dobutamine echocardiography after acute-MI thrombolytic therapy significantly reduces the risk of ischemic events compared with a more conservative strategy of PCI only if symptoms recur, concludes a randomized study [1].

Dr Gerrit Veen

"Viability testing should become a standard tool in the clinical evaluation of patients in the early phase after thrombolytic therapy," according to Dr Gerrit Veen (VU University Medical Center, Amsterdam, the Netherlands), who presented the Viability-Guided Angioplasty after Acute Myocardial Infarction (VIAMI) trial today here at the World Congress of Cardiology 2006. "In patients in whom you can demonstrate viability, revascularization should be considered before hospital discharge."

In an interview with heartwire, Veen observed that such selective revascularization potentially brings the ultimate clinical effectiveness of thrombolytic therapy closer to what is possible when PCI is used as the primary reperfusion strategy. Such primary PCI is considered to be more protective against recurrent ischemic events, he noted, but requires timely access to a cardiac catheterization laboratory and is less widely used than lytic reperfusion in most of the world. Viability-guided intervention can be a "second-best" alternative strategy "in all settings where primary PCI is not readily available."

Of the VIAMI trial's 291 patients treated for acute MI at 12 centers in the Netherlands, about half received thrombolytic therapy; the remainder presented too long after symptom onset to be eligible for thrombolytics. All underwent low-dose dobutamine-echocardiographic testing within 48 to 72 hours. The 216 patients who demonstrated viability in previously threatened myocardium were randomized to receive PCI of the infarct-related artery or to watchful waiting with PCI only in the event of symptoms suggesting recurrent ischemia. Percutaneous intervention consisted of coronary stenting accompanied by the antiplatelet agent abciximab.

The hazard ratio for the composite primary end point of death, reinfarction, or unstable angina at six months was 0.41 for the group that went straight to PCI (95% CI 0.19-0.96).

VIAMI: Six-month outcomes in patients with viable infarct-zone myocardium after thrombolytic therapy

End point	PCI, n=106 (%)	Watchful waiting, n=110 (%)	p
Event-free survival*	93.4	84.5	0.04
Death	1.9	0.9	NS
Recurrent MI	1.9	2.7	NS
Unstable angina	2.8	11.8	0.012
Elective revascularization	0	17.3	<0.0001

Dr Freek W Verheugt

According to Dr Freek W Verheugt (University Medical Centre St Radboud, Nijmegen, the Netherlands), who was not involved in VIAMI, viability-guided intervention represents an important enhancement of thrombolytic therapy in that it helps limit invasive procedures to those most likely to benefit. "But it also works the other way around—if you find there is no viability in the myocardium, you can spare the patient the PCI," he told heartwire.

In VIAMI, the event-free survival rate at six months was 94.7% among the 75 patients showing no infarct-zone viability, a confirmation of their low-risk status and an indication that they would have been unlikely to benefit much from intervention, according to Veen.

Dr Carlo Di Mario (Royal Brompton Hospital & Imperial College, London, UK), the featured discussant for Veen's VIAMI presentation, cautioned that the trial's inclusion of patients treated with thrombolytics and of those ineligible for the drugs, "two very heterogeneous groups with different coronary and myocardial pathologies," complicated its interpretation.

But Veen observed for heartwire that patients presenting too late for thrombolytic therapy frequently experience spontaneous reperfusion and therefore can still have viable myocardium that could be protected by revascularization. He said the VIAMI data "clearly show" that the key determinant of whether invasive therapy is likely to provide further benefit is infarct-zone viability. "That is what indicates the risk."

VIAMI was supported in part by grants from Eli Lilly, Boehringer Ingelheim, and Bristol-Myers-Squibb.