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Method to quantify late gadolinium enhancement helps predict outcomes of pulmonary vein isolation
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A novel method that quantifies late gadolinium enhancement enabled researchers to better predict recurrence of atrial fibrillation after pulmonary vein isolation.
The researchers analyzed 165 patients with paroxysmal or persistent AF (mean age, 60 years; 77% men; 57% with persistent AF) who underwent an initial ablation to treat AF.
According to the study background, recurrent AF after catheter ablation may be associated with the extent of left atrial late gadolinium enhancement (LGE) at baseline, but traditional intensity measurements have difficulty quantifying LGE.
Irfan M. Khurram, MD, from Einstein Medical Center, Philadelphia, and colleagues performed cardiac MRI using a 1.5 T scanner (Avanto, Siemens) after injecting patients with 0.2 mmol/kg gadolinium (gadopentetate dimeglumine; Magnevist, Bayer Healthcare), which enabled the processing of images to quantify the extent of LGE as a percentage of the left atrial myocardium.
They examined the association of baseline LGE extent with recurrence of AF. Mean follow-up was 10.2 months.
LGE extent predicted AF recurrence
During the study period, 38.2% of patients had a recurrence of AF, and after adjustment for confounders, LGE extent at baseline was independently associated with AF recurrence (HR per 10% increase in LGE = 1.5; 95% CI, 1.3-1.8), according to the researchers.
The greater the LGE extent, the greater the HR for AF recurrence, they found.
Regardless of age, left atrial volume, type of AF, prior congestive HF, prior coronary disease or prior peripheral vascular disease, a baseline LGE extent of more than 35% was associated with recurrence of AF (HR = 3.8; 95% CI, 2.1-6.8), Khurram and colleagues found.
Although the magnitude of association between baseline LGE of more than 35% and recurring AF was greater in those with persistent AF (HR = 6.5; 95% CI, 2.1-19.6) than in those with paroxysmal AF (HR = 3.6; 95% CI, 1.7-7.7), there was no statistical interaction between AF type and recurrence risk based on baseline LGE extent, they wrote.
“These findings suggest that patients with LGE 35% of [left atrial] myocardium should be considered as candidates for simple [pulmonary vein isolation] regardless of AF persistence,” they wrote.
Further work needed
In a related editorial, Mark D. O’Neill, MD, DPhil, FRCP, FHRS, and Henry Chubb, MD, MA, MRCP, MRCPCH, both from the division of imaging sciences and biomedical engineering at King’s College London, wrote: “There is a caveat that should be considered carefully in the interpretation of these figures, and this relates to ablation strategy. ... The [baseline LGE] may be a marker of distinct clinical entities, far more specific than the crude traditional dichotomization of AF into paroxysmal and persistent. ... Non-pulmonary vein drivers of AF have not been identified or ablated.”
O’Neill, also from the department of cardiology of St. Thomas Hospital, London, and Chubb concluded that “assessment of baseline atrial fibrosis by LGE MRI imaging remains an intriguing tool, but further work is required before it can be rolled out for every patient prior to ablation.” – by Erik Swain
Disclosure: The study was funded in part by Biosense Webster. One researcher reports receiving research funding via his institution from Biosense Webster and serving as a scientific adviser to Biosense Webster, CardioSolv and Medtronic. O’Neill reports receiving research support, honoraria and travel expenses from Biosense Webster and St. Jude Medical. Chubb reports no relevant financial disclosures.
Perspective
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Nathaniel Reichek, MD, FAHA, FACC
This is a potentially important paper for several reasons. The role of left atrial MRI LGE quantitation has been somewhat controversial, in part because most of the work has come from a single center and some other sites have not been able to use such imaging effectively. In addition, lack of a standardized way of measuring left atrial LGE has been an issue. While the sample size in this study is not large enough to answer every question on this topic, it does both confirm utility of a standardized method for measurement of LGE and the reliability of the basic observation that more pre-ablation LGE is associated with lower success rates.
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