What is the clinical evidence from this study?

Study design: Observational. Population: Heart failure with a narrow QRS complex (n=123). Intervention: Cardiac resynchronization therapy (CRT). Primary outcome: Response to CRT (reduction ≥15% in left ventricular end-systolic volume at 6 months follow-up).

September 23, 2010Open Access

Association of intraventricular mechanical dyssynchrony with response to cardiac resynchronization therapy in heart failure patients with a narrow QRS complex

Key Result

Intraventricular mechanical dyssynchrony measures, specifically opposing wall delay (≥75 ms) and anteroseptal posterior wall delay (≥107 ms), predicted CRT response in narrow QRS heart failure.

Study Design

Type

Observational (n=123)

Multicenter

Yes

Structured PICO

Does intraventricular mechanical dyssynchrony predict response to cardiac resynchronization therapy in heart failure patients with a narrow QRS complex?

Population

123 consecutive heart failure patients with a narrow QRS complex (<120 ms) undergoing cardiac resynchronization therapy

Intervention

Cardiac resynchronization therapy (CRT) with echocardiographic assessment of mechanical dyssynchrony

Outcome

Response to CRT, defined as a reduction ≥15% in left ventricular end-systolic volume at 6 months follow-upsurrogate

Intraventricular measures of mechanical dyssynchrony, specifically opposing wall delay and anteroseptal posterior wall delay, may predict echocardiographic response to CRT in heart failure patients with a narrow QRS complex.

Abstract

AIMS: current criteria for cardiac resynchronization therapy (CRT) are restricted to patients with a wide QRS complex (>120 ms). Overall, only 30% of heart failure patients demonstrate a wide QRS complex, leaving the majority of heart failure patients without this treatment option. However, patients with a narrow QRS complex exhibit left ventricular (LV) mechanical dyssynchrony, as assessed with echocardiography. To further elucidate the possible beneficial effect of CRT in heart failure patients with a narrow QRS complex, this two-centre, non-randomized observational study focused on different echocardiographic parameters of LV mechanical dyssynchrony reflecting atrioventricular, interventricular and intraventricular dyssynchrony, and the response to CRT in these patients. METHODS AND RESULTS: a total of 123 consecutive heart failure patients with a narrow QRS complex (<120 ms) undergoing CRT was included at two centres. Several widely accepted measures of mechanical dyssynchrony were evaluated: LV filling ratio (LVFT/RR), LV pre-ejection time (LPEI), interventricular mechanical dyssynchrony (IVMD), opposing wall delay (OWD), and anteroseptal posterior wall delay with speckle tracking (ASPWD). Response to CRT was defined as a reduction ≥15% in left ventricular end-systolic volume at 6 months follow-up. Measures of dyssynchrony can frequently be observed in patients with a narrow QRS complex. Nonetheless, for LVFT/RR, LPEI, and IVMD, presence of predefined significant dyssynchrony is <20%. Significant intraventricular dyssynchrony is more widely observed in these patients. With receiver operator characteristic curve analyses, both OWD and ASPWD demonstrated usefulness in predicting response to CRT in narrow QRS patients with a cut-off value of 75 and 107 ms, respectively. CONCLUSION: mechanical dyssynchrony can be widely observed in heart failure patients with a narrow QRS complex. In particular, intraventricular measures of mechanical dyssynchrony may be useful in predicting LV reverse remodelling at 6 months follow-up in heart failure patients with a narrow QRS complex, but with more stringent cut-off values than currently used in 'wide' QRS patients.