Utility of QRS width and echocardiography parameters in an integrative algorithm for selecting heart failure patients with cardiac dyssynchrony

Prevalence of cardiac dyssynchrony and correlation with atrio-ventricular block and QRS width in dilated cardiomyopathy: an echocardiographic study

INTRODUCTION

Cardiac dyssynchrony causes disorganised cardiac contraction, delayed wall contraction and reduced pumping efficiency. We aimed to assess the prevalence of different types of dyssynchrony in patients with dilated cardiomyopathy (DCM), and to establish the correlation between atrio-ventricular block and atrio-ventricular dyssynchrony (AVD), and between impaired intra-ventricular conduction and the existence of inter-ventricular dyssynchrony (inter-VD) and intra-left ventricular dyssynchrony (intra-LVD).

METHODS

We included 40 patients in New York Heart Association stage III or IV, admitted consecutively with DCM with severe left ventricular dysfunction (left ventricular end-diastolic diameter ≥ 60 mm and/or ≥ 30 mm/m(2)) and left ventricular ejection fraction < 35%. Electrocardiographic and echocardiographic data were evaluated in all patients. Patients were divided into two groups: group 1: eight patients, with a QRS duration ≥ 120 ms, and all presented with left bundle branch block; group 2: 32 patients with a narrow QRS < 120 ms.

RESULTS

Overall, the mean age was 54.7 ± 16.8 years and patients in group 1 were older (67.2 ± 13.6 vs 51.5 ± 15.8 years, p = 0.01). The prevalence of atrio-ventricular dyssynchrony (AVD), inter-VD and intra-LVD was respectively 40, 47.5 and 70%. Two patients (5%) did not exhibit dyssynchrony. AVD was present with a similar frequency in the two groups (37.5% in group 1 vs 40.6% in group 2, p = 0.8). There was no correlation of the magnitude of AVD with the duration of the PR interval (from the beginning of the P wave to the beginning of the QRS complex) (r(2) = 0.02, p = 0.37) or the QRS width (r(2) = 0.01, p = 0.38). A greater proportion of patients with inter-VD was observed in group 1 (87.5 vs 60%, p = 0.03). There was a trend towards a more important inter-ventricular mechanical delay according to QRS width (r(2) = 0.009, p = 0.06). The proportion of intra-LVD was similar in all groups, with a high prevalence (87.5% in group 1 and 65.6% in group 2, p = 0.39).

CONCLUSION

The assessment of cardiac dyssynchrony is possible in our country. Intra-ventricular mechanical dyssynchrony had a high prevalence in patients with DCM, irrespective of the QRS width. These data emphasise the usefulness of echocardiography in the screening of patients.

Relationship between fragmented QRS and response to cardiac resynchronization therapy

PURPOSE

Cardiac resynchronization therapy (CRT) is an effective treatment for heart failure (HF) with a wide QRS. Fragmented QRS (fQRS) on a 12-lead electrocardiography (ECG) has been shown to predict cardiac events in several patient populations. We aimed to investigate the relationship between fragmented wide QRS (f-wQRS) and left ventricular dyssynchrony and response to CRT.

METHODS

Fifty-three patients with HF undergoing CRT were studied. The presence of fQRS was assessed using standardized criteria. Dyssynchrony was defined as interventricular mechanical delay (IVMD) ≥40 ms and tissue Doppler velocity opposing-wall delay ≥65 ms. Echocardiographic response to CRT was defined by a ≥15 % reduction in left ventricular end-systolic volume at 6 months follow-up.

RESULTS

Fragmented wide QRS was present in 17 (32 %) patients. Interventricular and intraventricular dyssynchrony were highly prevalent in both patient groups with f-wQRS and nonf-wQRS (64.7 % vs 75 %, p = 0.44; 70.6 % vs 72.2 %, p = 0.25). Ischemic HF was significantly higher in patients with f-wQRS than patients with nonf-wQRS (64 % vs 33 %, p = 0.03). Reverse remodeling was developed in 32 (89 %) and 6 (35 %) of patients with nonf-wQRS and f-wQRS, respectively (p = 0.001). In multivariate analysis, significant associates of response to CRT were evaluated adjusting for etiology of cardiomyopathy, QRS width, IVMD, intraventricular delay, and f-wQRS. Lack of f-wQRS was the only predictor of response to CRT (OR 1.556, 95 % CI, 0.016-0.806, p = 0.028).

CONCLUSIONS

Presence of dyssynchrony is necessary but not sufficient to select appropriate candidates for CRT. Presence of f-wQRS on baseline ECG may play a role in identifying patients who may not respond to CRT.