For 3 years in a row, updated guidelines on the use of cardiac resynchronization therapy (CRT) were published: in 2010 from the European Society of Cardiology (ESC),¹ 2011 from the Heart Failure Society of America,² and 2012 from the ACCF/American Heart Association (AHA).³ In the case of the ACC focused update, the writing committee stated that updates to the 2008 guidelines were necessary due to new data relating to the use of CRT and device follow-up. Most other recommendations from 2008 remained current.

Take-aways Recently, three sets of updated guidelines were released relating to the use of cardiac resynchronization therapy (CRT). The documents clarify and provide recommendations about which patients are most likely to benefit from CRT. While the recommendations are similar, there are some differences between the US and European documents as well as some unanswered questions.

The updated guidelines clarify and provide recommendations about which patients are most likely to benefit from CRT based on trials reported subsequent to the original guidelines, such as MADIT-CRT, RAFT, REVERSE, and MIRACLE ICD II. "These are patients who have previously been excluded from receiving CRT, but studies have shown they can benefit from this procedure," said Cynthia M. Tracy, MD, chair of the writing group. "The updated guidelines extend and clarify current best practices and will continue to evolve as technology advances."

Specific recommendations include:

• limitation of the class I indication to patients with QRS duration ≥150 ms;
• limitation of the class I indication to patients with left bundle-branch block (LBBB) pattern;
• expansion of the class I indication to New York Heart Association (NYHA) class II (and with LBBB with QRS duration ≥150 ms); and
• the addition of a class IIb recommendation for patients who have left ventricular ejection fraction (LVEF) ≤30%, ischemic etiology of heart failure, sinus rhythm, LBBB with a QRS duration ≥150 ms, and NYHA class I symptoms.

Based on current evidence, Mark S. Link, MD, Tufts University School of Medicine, Boston, said "Clearly, the patient most likely to benefit (from CRT) is a patient with a wide left bundle," defined as LBBB with a QRS greater than 150 ms. "This is the 'sweet spot'," he said, "the 'home run' of CRT therapy."

Concordance—Mostly
The ACCF/AHA writing committee acknowledged the other recently updated guidelines that address indications for CRT. For the patient categories in common between the Heart Failure Society of America document and the ACCF/AHA focused update, there is a good deal of agreement. Indeed, the ACCF/AHA guidelines were developed in collaboration with the Heart Failure Society of America, American Association for Thoracic Surgery, Society of Thoracic Surgeons, and Heart Rhythm Society.

However, differences can be found between the US guidelines and the ESC document. For example: in the ACCF/AHA document, CRT is recommended in NYHA class I patients who have LVEF ≤30%, have ischemic heart disease, are in sinus rhythm, and have a LBBB with a QRS duration ≥150 ms, but there is no similar recommendation in the ESC document.

Conversely, the ESC recommendations include patients with QRS duration <120 ms, but the ACCF/AHA guidelines have not recommended CRT for any functional class or ejection fraction with QRS durations <120 ms.

The ACCF/AHA guidelines committee elected to consider the presence of LBBB versus non-LBBB in the class of recommendations, on the basis of perceived differential benefit by functional class, QRS morphology, and QRS duration.

Overall, Dr. Link said, the new guidelines are sound, but he sees some holes in the data:

• Is there a subset of patients with narrower QRS who will benefit based on dyssynchrony indices?
• How can we select those with a RBBB who will benefit?
• Which patients are better served by CRT-pacemakers?
• Do patients with nonischemic cardiomyopathy and class I heart failure benefit from CRT?

References

1. Dickstein K, Vardas PE, Auricchio A, et al. Europace. 2010;12:1526-36.
2. Stevenson WG, Hernandez AF, Carson PE, et al. J Card Fail. 2012;18:94-106.
3. Tracy CM, Epstein AE, Darbar D, et al. J Am Coll Cardiol. 2013;61:e6-e75.

To listen to an interview with Mark S. Link, MD, about patient selection for CRT, visit youtube.cswnews.org. The interview was conducted by Douglas P. Zipes, MD.

Keywords: Cooperative Behavior, Writing, Myocardial Ischemia, Follow-Up Studies, Patient Selection, Ventricular Function, Left, Cardiomyopathies, Heart Failure, Bundle-Branch Block, Stroke Volume, Cardiac Resynchronization Therapy

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