Chest radiography is a poor predictor of left ventricular lead position in patients undergoing cardiac resynchronization therapy: comparison with multidetector computed tomography.

BACKGROUND: Optimal left ventricular (LV) lead position is thought to be a major predictor of response in patients undergoing cardiac resynchronization therapy (CRT). While the post-implant posterior-anterior (PA) and lateral chest X-ray (CXR) is commonly used to determine the position of the LV lead, the accuracy to which the CXR can correctly localize the LV lead is unknown. METHODS: We collected data on 47 consecutive patients (mean age 64 years, 60% men and LV ejection fraction 23%, 49% ischemic cardiomyopathy) that underwent CRT between 2004 and 2007, who had both a post-implant CXR as well as a contrast-enhanced multi-detector computed tomography (MDCT) of the chest for any reason. The positions of the LV lead on CXR and MDCT were interpreted in a blinded fashion, independent of each other. The accuracy of the CXR in localizing various LV lead positions, with MDCT as the gold standard, was recorded. RESULTS: On CXR, the LV lead tip position was as follows: basal (4%), mid-ventricular (66%), and apical (30%) and anterior (2%), lateral (34%), and posterior (64%). On MDCT, the LV tip position was: basal (28%), mid-ventricular (60%), and apical (13%) and anterior (13%), lateral (19%), and posterior (68%). Compared to the MDCT gold standard, the percentage of LV lead positions the CXR correctly classified correctly were: 100% basal, 39% mid-ventricular, and 29% apical and 0% anterior, 12% lateral, and 77% posterior. Taking both PA and lateral views into consideration, the LV lead position was misclassified by CXR in 62% cases. CONCLUSION: Using MDCT as a gold standard, the routine post-implant CXR performs very modestly in terms of accurate LV lead positioning.

QRS fragmentation is not associated with poor response to cardiac resynchronization therapy.

BACKGROUND: QRS fragmentation (fQRS) has been shown to be a marker of scar in patients with left ventricular dysfunction. Whether fQRS is associated with progressive left ventricular remodeling and increased mortality in patients receiving cardiac resynchronization therapy (CRT) is unclear. METHODS: We reviewed the preimplant and follow-up echocardiograms in 233 patients undergoing the new implantation of a CRT device between December 2001 and November 2006. Patients were included if they had a pre-CRT ECG with appropriate filter settings (filter 0.16-100 or 0.16-150 Hz, 25 mm/s, 10 mm/mV), a left ventricular ejection fraction (LVEF) ≤40%, and New York Heart Association class II-IV symptoms on standard medical therapy. The 12-lead electrocardiogram (ECG) was interpreted by two blinded reviewers for the presence of fQRS. Remodeling end points, including changes in LVEF and left ventricular end-diastolic (LVEDV) and systolic (LVESV) volumes, were compared between patients with and without contiguous fQRS, and an assessment of all-cause mortality was made. RESULTS: Two hundred thirty-two patients met inclusion criteria, of which 50 demonstrated fQRS in contiguous leads. There was no difference in improvement in LVEF (%) (7.9 ± 12.9 vs 6.8 ± 11.0, P = 0.60) or reduction in LVEDV (mL) (-30.1 ± 57.2 vs -15.7 ± 47.6) or LVESV (mL) (-33.7 ± 58.1 vs -22.7 ± 50.6, P = 0.40) between patients with and without contiguous fQRS. At a mean follow-up of 4.4 ± 1.9 years, there were a total of 89 deaths, 22 (44.0%) in patients with contiguous fQRS and 67 (36.8%) without (log rank P = 0.31). CONCLUSIONS: QRS fragmentation is not a predictor of progressive ventricular remodeling or mortality in heart failure patients undergoing CRT.

The QRS narrowing index predicts reverse left ventricular remodeling following cardiac resynchronization therapy.

BACKGROUND: The relationship between QRS narrowing and response to cardiac resynchronization therapy (CRT) has been controversial. OBJECTIVE: We sought to analyze the relationship between QRS narrowing and reverse remodeling in patients undergoing CRT, taking into account potential confounders including pre-CRT QRS duration and underlying QRS morphology. METHODS: We reviewed pre- and postimplant electrocardiograms and echocardiograms in a cohort of 233 patients undergoing the new implantation of a CRT device between December 2001 and September 2006. For inclusion in the final cohort, patients had New York Heart Association classes II-IV heart failure, left ventricular ejection fraction (LVEF) ≤ 40%, and QRS duration ≥120 ms. Response to CRT was defined as a reduction in left ventricular end-systolic volume (LVESV) of ≥10%. A multivariate model was constructed to determine the relationship between QRS change and response to CRT. RESULTS: Patients with QRS narrowing had significantly greater reductions in left ventricular end-diastolic volume (LVEDV) (mL) (-26.5 ± 52.5 vs -4.8 ± 44.0, P = 0.002) and LVESV (mL) (-34.0 ± 55.5 vs -9.9 ± 45.8, P = 0.002) and improvement in LVEF (%) (8.9 ± 12.8 vs 4.5 ± 9.0, P = 0.007) than patients without narrowing. In univariate analysis, female gender (P = 0.0002), percent QRS narrowing from baseline (P = 0.008), lack of nitrate (P≤0.0001) and antiarrhythmic medication use (P = 0.01), lack of a nonspecific intraventricular conduction delay (=0.02), nonischemic cardiomyopathy (P = 0.003), and lower pre-CRT LVEDV (P = 0.006) and LVESV [P = 0.01]) were associated with responders. In a multivariate model, QRS narrowing, indexed to the baseline QRS duration, remained strongly associated with response (odds ratio 0.08 [0.01-0.56], P = 0.01). CONCLUSIONS: After adjusting for potential confounders, QRS narrowing, indexed to baseline QRS duration, is associated with enhanced reverse ventricular remodeling following CRT.