Methods

We retrospectively evaluated 243 consecutive patients who underwent CRT implantation from January 2009 to December 2012 at our centers for symptomatic drug-refractory heart failure (New York Heart Association class II to IV), LV systolic dysfunction with ejection fraction ≤35%, and QRS width ≥120 ms. Patients with a previously implanted right ventricular pacing system, either pacemaker or implantable defibrillator, were excluded from the study. Baseline QRS morphology was classified either as LBBB or right bundle branch block (RBBB) or nonspecific intraventricular conduction delay. An LBBB morphology was defined as QRS ≥120 ms; QS or rS complex in V1-V2; monophasic and notched or slurred R waves among I, aVL, V5, or V6; and absent Q waves in leads V5 and V6. Both RBBB and nonspecific intraventricular conduction delay morphologies were labeled as non-LBBB.

Implantation of transvenous CRT systems was performed according to standard techniques. To describe the LV myocardial segments, we used the same classification as Vardas et al. The veins from the lateral wall were considered as first choice for LV lead placement. A basal position was preferred and, whenever possible, the apical segment was avoided. When the initial target area was inaccessible or electrically unsuitable, the LV lead was placed as close as possible to the target site. A right atrial lead and a right ventricular lead were preferably positioned at the atrial appendage and at the apex, respectively. Before discharge, CRT devices were programmed as indicated by the current guidelines.

Within 2 weeks before and 6 months after CRT implantation, patients underwent a standard echocardiographic study (Vivid 7 system, General Electric Healthcare, Milwaukee, Wisconsin) according to the Guidelines of the American Society of Echocardiography and European Association of Echocardiography. At 6 months, an echocardiographic reduction of LV end-systolic volume ≥15% was considered as index of reverse remodeling and used to define a patient as responder to CRT. The clinical outcome was assessed using a composite clinical end point consisting of first hospitalization for worsening heart failure, all-cause mortality, and first episode of sustained and rapid ventricular tachyarrhythmias >200 beats/min detected and terminated or stored by the CRT device. All patients underwent regular follow-up at implanting centers, every 6 months or earlier, if clinically requested.

Statistical analyses were performed using Stata/SE 12.1 for Windows, (StataCorpLp, College Station, Texas); continuous variables were expressed as mean ± SD; categorical data were expressed as numbers (percentages). For group comparisons t test was used for continuous variables and the chi-square test for categorical variables. A receiver operating characteristic curve analysis was conducted to determine a cut-off value of QRS duration able to discriminate between responders and nonresponders in patients with LBBB. Univariate and multivariate logistic regression analysis were performed to evaluate risk factors associated with nonresponsiveness to therapy. Noncorrelated variables with p <0.1 at univariate analysis were included in the multivariate logistic regression model. The accuracy of the model was verified with Hosmer-Lemeshow goodness-of-fit test. Kaplan-Meier method was used to evaluate the influence of QRS duration on event free survival. All p values refer to 2-tailed tests of significance. A p <0.05 was considered significant.

Results

Baseline characteristics of the overall population are reported in Table 1 . Atrioventricular junction ablation was performed in 43 of 46 patients with atrial fibrillation because pharmacological rate control was ineffective. No patients had a LV lead in the great cardiac vein or in the middle cardiac vein. At 6-month follow-up evaluation, the overall New York Heart Association class was reduced from 2.87 ± 0.51 to 2.04 ± 0.82 (p = 0.0001) and LV ejection fraction increased from 25.4 ± 4.9% to 31.1 ± 8.1% (p = 0.0001).

At 6-month follow-up, according to our definition, 133 (55%) patients showed reverse remodeling and were considered responders to CRT. Baseline differences between responders and nonresponders are listed in Table 1 . Reverse remodeling was documented mostly in patients with LBBB (n = 101 of 169, 60%) rather than in patients without LBBB (n = 32 of 74, 43%; p = 0.025). The distribution of CRT responsiveness according to QRS duration was analyzed for patients with and without LBBB. The relation between QRS duration and CRT responsiveness in patients with LBBB was expressed by a “U shaped” curve, being nonresponders roughly clustered between 120 and 130 ms and above 180 ms; conversely, in patients without non-LBBB nonresponders were randomly distributed through the values of QRS duration ( Figure 1 ). The receiver operating characteristic curve analysis showed that 178 ms was the upper limit of QRS duration corresponding with the highest accuracy to predict echocardiographic nonresponsiveness to CRT in patients with LBBB (area under the curve = 0.67 [95% confidence interval 0.57 to 0.76]; Figure 2 ). In our study, 49 of 169 patients with LBBB morphology had a QRS duration ≥178 ms. At the univariate analysis an ischemic cause and a QRS≥178 ms were predictor of negative echocardiographic responsiveness to CRT in patients with LBBB and such variables remained independent predictor of failing responsiveness to CRT (area under the curve = 0.75) at the multivariate analysis, yielding a positive predictive value of 74% and a negative predictive value of 73% ( Table 2 ).

Distribution of responders ( gray bar ) and nonresponders ( black bar ) to CRT according to QRS duration divided into fraction by 5 ms categories, for patients without (A) and with (B) LBBB.

ROC curve for the identification of the most accurate value of QRS duration to predict a negative echocardiographic response to CRT for patients with LBBB. ROC = receiver operating characteristic.

Table 2

Predictors of echocardiographic nonresponsiveness to cardiac resynchronization therapy

	Univariate analysis		Multivariate analysis
	Odds ratio (95% CI)	p-value	Odds ratio (95% CI)	p-value
Age	1.01 (0.96-1.05)	0.63
Gender (male)	1.43 (0.71-2.90)	0.30
Ischemic etiology	1.92 (1.03-3.59)	0.04	2.00 (1.00-4.02)	0.05
Sinus rhythm	0.79 (0.35-1.78)	0.58
QRS duration (ms)	1.02 (1.01-1.04)	0.001
QRS≥178 ms	7.61 (3.59-16.15)	0.0001	7.75 (3.60-16.66)	0.0001
Left ventricular end-diastolic volume (mL)	1.00 (0.99-1.00)	0.54
Left ventricular end-systolic volume (mL)	1.00 (0.99-1.00)	0.19
Left ventricular ejection fraction (%)	1.03 (0.97-1.11)	0.27
Left ventricular lead pacing site	0.96 (0.50-1.87)	0.91

Only gold members can continue reading. Log In or Register to continue

Share this:

• Click to share on Twitter (Opens in new window)
• Click to share on Facebook (Opens in new window)

Related

Related posts:

1. Long-Term Outcomes and Causes of Death After Acute Coronary Syndrome in Patients in the Bologna, Italy, Area
2. Failure Rates of Single- Versus Dual-Coil Nonrecalled Sprint Quattro Defibrillator Leads
3. Impact of American-Style Football Participation on Vascular Function
4. Significance of Echocardiographic Assessment for Right Ventricular Function After Balloon Pulmonary Angioplasty in Patients With Chronic Thromboembolic Induced Pulmonary Hypertension

Stay updated, free articles. Join our Telegram channel

Join