Day 1 at ESC 2012: Controversies in cardiac resynchronization therapy

Aug 25, 2012 16:18 EDT

Heart-rhythm doctors are spoiled; we have at our disposal an array of highly successful treatments. Huge leaps in technology over the past decade have made it "normal" to succeed against arrhythmia. One particular therapy stands out above the rest—cardiac resynchronization therapy (CRT). For feel-good stories in the practice of medicine, CRT has it all.

Start with the patients: CRT-eligible patients feel awful. They need help. Then consider the procedure: It's challenging without being frustrating. Even when we struggle with difficult venous anatomy, we persist because of the reward: the potential for a Lazarus-like transformation. When this happens as a result of your surgery, and it does, it's hard not to feel really good.

That's why I chose to cover the CRT controversies session on the first day of the European Society of Cardiology 2012 Congress.

Let's get to the three notable abstracts:

CRT-P vs CRT-D:

My favorite abstract of the morning delved into the thorny issue of whether to implant a CRT device with or without a backup defibrillator. It's a topic that heart-rhythm doctors seem to avoid.

Provocatively titled, Backup defibrillation therapy is unnecessary for cardiac resynchronization therapy functional responders, Dutch researchers looked back at 142 patients implanted with CRT-D devices. They identified 42 functional CRT responders—those whose EF improved to greater than 35% (which would place them outside of defibrillator-indications). The remaining "nonfunctional responders" formed the comparison group. CRT responders did well, with no deaths, heart-failure hospitalization, or appropriate ICD shocks reported. That compared with seven deaths, 15 hospitalizations for heart failure, and 15 appropriate shocks in the nonresponder group. Both groups had an 8% incidence of inappropriate shocks. Inappropriate shocks were a point of emphasis in the presentation. The researchers concluded CRT responders have a good prognosis and may not need concomitant defibrillator therapy, although they appropriately emphasized the limits of this single-center experience.

As is often the case, a good study leads to a lively question-and-answer exchange. Session chairperson Prof B Merkely (Hungary) asked: "Which device do you implant in a 72-year-old female with nonischemic cardiomyopathy, NYHA class 3 symptoms, EF 32%, typical LBBB and QRS duration of 160 ms?" He knows this patient is likely to be a superresponder to CRT. He also knows the data supporting a mortality advantage of ICDs in female patients with nonischemic cardiomyopathy is less than robust. Again, the youthful Dutch presenter was flawless. "I'd put in the CRT-D. . . . Our study is too small to go against guidelines." Dr Merkely had made his point.

A few of my thoughts: At least in the US, the thinking holds that if we are operating; why not implant the most advanced device? Why not offer the "insurance policy" of having an ICD? Why use a lesser (or "downgraded") device?

This line of reasoning assumes the feature-intensive CRT-D device is superior. A debatable topic indeed—witness Sprint Fidelis, Riata, and the poor prognosis of ICD shocks. What's more, the only trial directly comparing CRT-P and CRT-D devices, the Companion Trial, revealed very small absolute differences in mortality. I found this quote in the 2008 ACC/HRS/AHA guidelines document:

[In COMPANION], CRT-D reduced mortality by 36% compared with medical therapy, but there was insufficient evidence to conclude that CRT-P was inferior to CRT-D.

The role of AV junction ablation in patients implanted with CRT devices:

This is also an important and common scenario in clinical cardiology. In AF patients, a common reason for nonresponse to CRT is that the ventricular response exceeds the lower pacing rate of the device. There are only two options for controlling the ventricular rate in AF: AV nodal blockers or AV junction ablation. Medical therapy is limited by inefficacy or side effects, and AV junction ablation has as its chief downside, the permanency of AV block and pacer dependence. That said, we all know how well AV node ablation can work. A recent review article published in the Journal of the American College of Cardiology concluded that AV node ablation, compared with medical therapy, improved mortality and functional class in patients with AF treated with CRT.

To the abstract: A group of Spanish researchers compared 155 patients with AF who had CRT devices implanted. Two equally divided (but nonrandomized) groups were followed over an average of three years. There were no differences in any outcomes. Most importantly, AV node ablation did not result in a higher mortality. Not surprisingly, the researchers found impaired kidney function, advanced heart failure, and EF <25% as independent predictors of mortality.

It's a small study, but it's from the real world and it is consistent with the recent meta-analysis. These data act to reassure AV node ablators that we are not doing harm. I'm drawn to studies like this because I like evidence that shows that what we thought was a good idea actually turned out to be so.

Does CRT benefit patients with mild LV dysfunction?

Most of the evidence base supporting CRT comes from clinical trials that enrolled patients with moderate to severe impairment of LV function (EF <35%). There are not a lot of data on patients with mild LV dysfunction, although many of us can report anecdotal success stories in symptomatic patients with less-than-horrible echocardiograms.

Dr Michael Gold presented an interesting analysis of the previously reported REVERSE trial. Recall that REVERSE is the only randomized trial of CRT that included patients with LVEF up to 40%. The substudy presented today included 263 (of 610 total) patients in REVERSE who had an LVEF of 30% to 40%. They measured echo parameters, quality-of-life (QoL) measures and six-minute-walk test in 77 patients with CRT programmed "off" and 186 with CRT "on."

Similar to the overall findings of REVERSE, CRT benefited patients with only mild LV dysfunction and mild heart failure (class 1 or 2). Specifically, CRT resulted in better QoL scores and more reverse remodeling. These findings led to the conclusion that further study of the potential benefit of CRT earlier in the course of heart failure is warranted.

Intervening early in the course of disease—that sounds like good idea.

That's it for today. See you tomorrow.

JMM