Narrowing filtered QRS duration on signal-averaged electrocardiogram predicts outcomes in cardiac resynchronization therapy patients with nonischemic heart failure.

BACKGROUND: To evaluate the impact of changes in the filtered QRS duration (fQRS) on signal-averaged electrocardiograms (SAECGs) from pre- to postimplantation on the clinical outcomes in nonischemic heart failure (HF) patients under cardiac resynchronization therapy (CRT). METHODS: We studied 103 patients with nonischemic HF and sinus rhythm who underwent CRT implantation. SAECGs were obtained within 1 week before and 1 week after implantation and narrowing fQRS was defined as a decrease in fQRS from pre- to postimplantation. Echocardiography was performed before and 6 months after CRT implantation. The primary outcome was death from any cause. The secondary outcomes were hospitalization due to worsened HF and occurrence of ventricular tachyarrhythmias. RESULTS: Of the 103 CRT patients, 53 (51%) showed narrowing fQRS. Left ventricular end-diastolic volume and end-systolic volume were significantly reduced (both p < .001), and the left ventricular ejection fraction was significantly increased (p < .001) after CRT in patients with narrowing fQRS, but not in patients with nonnarrowing fQRS. During a median follow-up period of 33 months, patients with narrowing fQRS exhibited better survival than patients with nonnarrowing fQRS (p = .007). A lower incidence of hospitalization due to worsened HF (p < .001) and a lower occurrence of ventricular tachyarrhythmias (p = .071) were obtained in patients with narrowing fQRS. After adjusting for confounding variables, narrowing fQRS was associated with a low risk of mortality (HR 0.27, p = .006). CONCLUSION: Our results suggested that narrowing fQRS on SAECG after CRT implantation predicts LV reverse remodeling and long-term outcomes in nonischemic HF patients.

Association between sleep apnea and overnight hemodynamic changes in hospitalized heart failure patients with and without paroxysmal nocturnal dyspnea.

BACKGROUND: Paroxysmal nocturnal dyspnea (PND) is a common symptom for patients with acute decompensated heart failure (ADHF). Some symptoms of PND are similar to those of sleep apnea (SA) which might be associated with overnight worsening hemodynamics in failing hearts. However, the association between PND, SA, and overnight change in hemodynamics in patients with heart failure remains uncertain. METHODS: We studied 28 consecutive patients with reduced ejection fraction who were hospitalized with ADHF. Plasma atrial natriuretic peptide (ANP) levels were measured before and after overnight sleep study. PND was defined as having an episode of PND prior to hospitalization for ADHF. RESULTS: Ten (36%) patients had a history of PND. Respiratory disturbance index (the frequency and severity of sleep apnea) was an independent factor associated with a history of PND (odds ratio 1.24, 95% confidence interval 1.05-1.47, p=0.011). In those without PND, plasma ANP levels decreased from before sleep to after waking, whereas in those with PND it increased (p=0.011). In addition, overnight change in plasma ANP levels was independently associated with respiratory disturbance index (p=0.035). CONCLUSION: These results thus suggest that in patients with ADHF, SA might be a predisposing cause of PND in association with overnight worsening hemodynamics.

Low-dose dobutamine induces left ventricular mechanical dyssynchrony in patients with dilated cardiomyopathy and a narrow QRS: a study using real-time three-dimensional echocardiography.

AIMS: The effects of inotropic agents on left ventricular (LV) synchrony in heart failure patients are still unknown. The purpose of this study was to investigate the effects of dobutamine on LV mechanical dyssynchrony and LV systolic performance in patients with dilated cardiomyopathy (DCM) and a narrow QRS using real-time three-dimensional echocardiography (RT3DE). METHODS AND RESULTS: Thirty-three patients with idiopathic DCM and a narrow QRS underwent low-dose dobutamine stress echocardiography (LDSE) with RT3DE. A time-global LV volume curve and time-regional LV volume curves were derived from RT3DE. Regional LV stroke volumes were summed in each stage, and the dobutamine-induced increase in the sum of regional LV stroke volumes was considered as the sum of regional contractile reserve. Systolic dyssynchrony index (SDI) was calculated as follows: (standard deviation of time to minimal volume for regional LV segments)×100/RR duration. Among the 33 patients, low-dose dobutamine increased global LV stroke volume (SV) in 28 (85%), but decreased global LVSV in the remainder (15%). The sum of regional contractile reserve was modestly correlated with the dobutamine-induced increase in global LVSV (R=0.57, p<0.001). In contrast, low-dose dobutamine increased SDI in 14 (42%) patients without a significant change in QRS duration, and there was an inverse correlation between the increase in SDI and the increase in global LVSV induced by dobutamine (R=-0.67, p<0.001). CONCLUSIONS: Dobutamine may induce LV mechanical dyssynchrony in a substantial proportion of patients with DCM and a narrow QRS. In such cases, regional LV contractile reserve does not fully contribute to an increase in global LVSV.