PROMPT: LV Pacing Doesn't Prevent Remodeling After Large MI

Deborah Brauser

September 02, 2015

LONDON, UK — Single- or dual-site biventricular pacing in the peri-infarct zone does not improve outcomes for patients who have experienced a recent large MI, suggests new research[1].

The Post–Myocardial Infarction Remodeling Prevention Therapy (PROMPT) study showed that participants randomized to receive a cardiac resynchronization therapy defibrillator (CRT-D) with LV pacing alone or with right ventricular (RV) pacing had no significant differences in remodeling 18 months later, the primary end point, compared with those who didn't receive any implant. There were also no differences in secondary end points, which included mortality or HF hospitalization.

Dr Gregg Stone

The findings were presented by Dr Gregg W Stone (Columbia University Medical Center, New York City) here at the European Society of Cardiology (ESC) 2015 Congress and simultaneously published in the European Heart Journal.

He told heartwire from Medscape that these patients presented about 8 hours after their infarct, "and although they all had primary PCI, it was too late for them. They ended up with large infarcts," said Stone.

"This is a very high-risk group of patients with few optimal therapeutic options," he said. However, he noted that there have now been two negative randomized trials looking at this therapy in this difficult population. "And I don't anticipate in the future there being a third."

No Significant Differences

A total of 126 participants, all of whom had a large first MI (creatinine phosphokinase >3000 U/L) and QRS duration <120 msec, were enrolled within 10 days of their symptom onset between December 2010 and October 2013. They were randomized 1:1:1 to a CRT-D with LV and RV pacing, CRT-D with LV pacing only, or no implant at all (controls, n=45). For this analysis, the two pacing groups were combined (n=81).

The investigators used Protecta XT or Consulta CRT-Ds (Medtronic), "with LV leads implanted in the peri-infarct zone with 2D echo guidance," reported Stone. A total of 98.7% of device implant attempts were successful.

At the 18-month follow-up, the pooled pacing group had an adjusted mean change in LV end-diastolic volume (LVEDV) of 16.7 mL (95% CI 8.9–23.9) vs 15.3 in the control group (P=0.92). There were also no differences in LVEDV or ejection fraction throughout the study.

In addition, change in the six-minute-walk test, quality-of-life measures (using both Minnesota Living with HF and EQ-5D scores), and NYHA class showed no significant between-group differences. Death or hospitalization was also similar for the pacing and control groups (17.4% vs 21.7%, respectively, P=0.59).

Stone noted that this was a small study with a mix of anterior and nonanterior infarcts. Plus, "even though they all had large infarcts, some had very large infarcts. So we're just not powered to say if this would have worked in some subgroups of patients."

Dr Kim Williams

After a press briefing, comoderator Dr Kim Williams (Rush University Medical Center in Chicago, IL), current president of the American College of Cardiology, told heartwire that PROMPT had an interesting concept.

"Unloading the ventricle by starting early. . . . We do understand that mechanically that's the time when there's going to be the lowest pressure, the lowest afterload. That makes sense; but it didn't work," said Williams.

"It may be that the pacing causes its own set of dyssynchrony," he said, adding that it might be worthwhile to measure dyssynchrony using gated single photo-emission computed tomography (SPECT) or three-dimensional echocardiograph. "That might inform how well you're actually doing that procedure of unloading."

Feisty Discussion

Dr Frank Ruschitzka

During a hot-line session, official discussant Dr Frank Ruschitzka (University of Zurich, Switzerland) started his talk by saying "sometimes you win, sometimes you lose" and that it's "kind of a quirky, crazy idea" to pace infarct tissue.

"But we need this kind of crazy, outside-of-the-box thinking," said Ruschitzka. "However, after two trials and no signal, I think this will be the end of peri-infarct pacing, sadly enough."

During his response time, Stone answered, "We actually didn't think this was a crazy idea. There's a lot of experimental evidence that would suggest that you could decrease wall stress and remodeling."

He also noted that in the earlier Prevention of Myocardial Enlargement and Dilation Post-Myocardial Infarction (MENDMI) trial, "there was a trend toward reductions in patients with large infarcts. So we had good rationale to do this study."

However, "while MENDMI did show a signal, we didn't even see a signal," said Stone. "So I pretty much think this puts this concept to rest."

The study was funded by Medtronic. Stone reported no relevant financial disclosures; disclosures for the coauthors are listed in the article. Ruschitzka had no relevant financial relationships.

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