Haemodynamic effects of cardiac resynchronization therapy using single-vein, three-pole, multipoint left ventricular pacing in patients with ischaemic cardiomyopathy and a left ventricular free wall scar: the MAESTRO study.

AIMS: The clinical response to cardiac resynchronization therapy (CRT) is variable. Multipoint left ventricular (LV) pacing could achieve more effective haemodynamic response than single-point LV pacing. Deployment of an LV lead over myocardial scar is associated with a poor haemodynamic response to and clinical outcome of CRT. We sought to determine whether the acute haemodynamic response to CRT using three-pole LV multipoint pacing (CRT3P-MPP) is superior to that to conventional CRT using single-site LV pacing (CRTSP) in patients with ischaemic cardiomyopathy and an LV free wall scar. METHODS AND RESULTS: Sixteen patients with ischaemic cardiomyopathy [aged 72.6 ± 7.7 years (mean ± SD), 81.3% male, QRS: 146.0 ± 14.2 ms, LBBB in 14 (87.5%)] in whom the LV lead was intentionally deployed straddling an LV free wall scar (assessed using cardiac magnetic resonance), underwent assessment of LV + dP/dtmax during CRT3P-MPP and CRTSP. Interindividually, the ΔLV + dP/dtmax in relation to AAI pacing with CRT3P-MPP (6.2 ± 13.3%) was higher than with basal and mid CRTSP (both P < 0.001), but similar to apical CRTSP. Intraindividually, significant differences in the ΔLV + dP/dtmax to optimal and worst pacing configurations were observed in 10 (62.5%) patients. Of the 8 patients who responded to at least one configuration, CRT3P-MPP was optimal in 5 (62.5%) and apical CRTSP was optimal in 3 (37.5%) (P = 0.0047). CONCLUSIONS: In terms of acute haemodynamic response, CRT3P-MPP was comparable an apical CRTSP and superior to basal and distal CRTSP. In the absence of within-device haemodynamic optimization, CRT3P-MPP may offer a haemodynamic advantage over a fixed CRTSP configuration.

Induction by direct current pulse versus 50-Hz pacing on ventricular fibrillation and defibrillation.

BACKGROUND: Ventricular fibrillation (VF) induced by different modes of induction may have different characteristics and defibrillation thresholds. This study compares the cycle lengths and defibrillation of VF induced by direct current (DC) pulses vs 50 Hz. METHOD: We compared induction by DC pulses and 50-Hz pacing in this single-centre observational study of 259 consecutive patients with implantable cardioverter defibrillators in 2007-2008. Patients with inadequate defibrillation safety margin (DSM), defined as unsuccessful defibrillation at 25 J, were identified. RESULTS: Of the 259 patients, 132 underwent induction with DC pulses and 127 with 50-Hz pacing. DC pulses induced VF of shorter cycle lengths (207 ± 16 vs 231 ± 24 ms, p < 0.001) compared to 50-Hz pacing. There were 17 patients (6.6%) with inadequate DSM-13/132 (9.8%) with DC pulse vs 4/127 (3.1%) with 50-Hz pacing (p < 0.001). The induced VF cycle lengths were shorter in patients with inadequate DSM (186 ± 25 vs 221 ± 21 ms, p < 0.001). On multivariate analysis, only the induced VF cycle length (p = 0.002) was independently associated with inadequate DSM. CONCLUSION: VF of shorter cycle lengths is independently associated with inadequate DSM. DC pulses are associated with greater proportion of patients with inadequate DSM as it induces VF of shorter cycle lengths compared to 50-Hz pacing.