Type 2 MI More Frequent, More Lethal Than Previously Appreciated

Patrice Wendling

April 11, 2016

CHICAGO, IL — Patients experiencing a first type 2 MI (T2MI), related to supply-demand inequity, rather than classical plaque rupture, have similar or worse prognosis than those with incident type 1 MI (T1MI), new research suggests[1].

The Catheter Sampled Blood Archive in Cardiovascular Diseases (CASABLANCA) study prospectively enrolled 1251 patients undergoing coronary or peripheral angiography. Over a median 3.4 years of follow-up, it found that T2MI patients had a higher rate of subsequent major adverse cardiovascular events (MACE) than those without T2MI (100 vs 17.6 events per 100 person-years; P<0.001) and similar to those with T1MI (78.9 per 100 years; P=0.41).

In adjusted analyses, T2MI patients were at roughly twofold greater risk for subsequent MACE (hazard ratio [HR] 1.90; P<0.001) and cardiovascular death (HR 2.16; P=0.001) and nearly threefold higher risk for subsequent all-cause death (HR 2.96; P<0.001) than those without T2MI, lead author Dr Hanna Gaggin (Massachusetts General Hospital, Boston) reported here at the American College of Cardiology (ACC) 2016 Scientific Sessions.

This study "really should cause clinicians to pause when a patient suffers a type 2 MI while under their care" and to consider what can be done to reduce risk "even before we have treatment strategies developed for type 2 MI," senior author Dr James Januzzi Jr (Massachusetts General Hospital, Boston) told heartwire from Medscape.

Currently there is no agreed-upon or evidence-based treatment strategy for T2MI patients due to supply-demand mismatch, but they are typically managed far more conservatively than classical T1MI due to coronary artery plaque rupture and thrombosis. Januzzi argues that these patients have more diffuse coronary artery disease than other MI types and should be on high-intensity statin therapy, antiplatelet therapy, and beta-blockers, or if not, have their medications adjusted.

"Ultimately it's going to take randomized trials of treatment intervention, presumably revascularization-based approaches, in order to better understand if we should be taking a type 2 MI urgently to the cath lab as we do with type 1 MI," he added.

Dr David Morrow (Brigham and Women's Hospital, Boston, MA), who was not involved in the study, told heartwire that the key message from CASABLANCA is to recognize the clinical importance of type 2 MI.

"The finding that the clinical outcomes in these patients are just as poor as in those with type 1 is important because I know in our hospital with our clinical trainees, they often dismiss type 2 MI as being clinically unimportant, and that's certainly not the case," he said.

Just Beginning to Scratch the Surface

While Morrow commended the authors for the robust clinical registry and prospectively adjudicating T2MI, he said that this patient population is just beginning to be characterized.  The prevalence of T2MI is also increasing with more sensitive assays for troponin but varies widely depending on the population.

In emergency-department patients, the incidence can reach 50% or more, while Morrow reported a T2MI incidence of only 0.3% using creatine kinase-MB in ACS patients who'd received revascularization. The T2MI incidence in CASABLANCA was 12.2% using troponin, which is comparable to the 7.1% reported in a recent Swedish cohort hospitalized for acute MI, he said.

As expected, T2MI patients in CASABLANCA had the diagnostic sine qua non of significant preexisting CAD, with most having at least 30% obstruction of a major coronary artery. But other clinical predictors support emerging data suggesting a complex medical phenotype, Januzzi said.

Patients with T2MI compared with those without T2MI were older (71.3 years vs 66.2 years); had more CV diagnoses including atrial fibrillation (31.6% vs 17%), heart failure (36.8% vs 18.2%), and prior MI (34.2% vs 22%); and had more non-CV diagnoses such as hypertension (86.2% vs 74%), diabetes (46.7% vs 25.2%), and chronic kidney disease (34.2% vs 10.5%).

Despite receiving more aggressive medical treatment, T2MI was more frequent than T1MI and was often recurrent, the authors noted.

Other baseline predictors of T2MI were elevations in N-terminal pro-B-type natriuretic peptide (NT-proBNP), cystatin C, a biomarker of renal dysfunction, and blood glucose.

Morrow agreed that like heart failure, there may be phenotypic subgroups within the heterogeneous mix of T2MI patients.

"You can take a relatively young patient who comes in with tachycardia and they have a heart rate of 170 and they develop demand myocardial injury in that setting, and that's a type 2 MI, but you can also have an 89-year-old patient who comes in with some other acute illness and in that setting has an increase in wall stress and myocardial injury and that's a type 2 MI," Morrow said. "Those patients and how you manage them are totally different.
"We need to figure out how to best manage these patients, and it's not taking them all to the cath lab and starting them on antithrombotic therapies, but we don't have the right answers yet," he added.

The study was funded in part by Siemens Diagnostics. Gaggin is supported in part by the Clark Fund for Cardiac Research Innovation. Januzzi is supported in part by the Roman W DeSanctis Clinical Scholar Endowment and the Hutter Family Professorship. Morrow reports consultant fees/honoraria from Abbott, BG Medicine, Daiichi Sankyo, DiaDexus, Eli Lilly, Gilead, GlaxoSmithKline, Instrumentation Laboratory, and Konica.

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