Bi-ventricular pacing improves pump function only with adequate myocardial perfusion in canine hearts with pseudo-left bundle branch block

Bi-ventricular (BiV) pacing is an effective therapy for the treatment of cardiac electromechanical (EM) dysfunction. The reason(s), however, for therapy non-response in approximately one-third of the subjects remains unclear, especially as it relates to myocardial perfusion and pacing location. In this study, we examined how acute BiV pacing response may be related to underlying myocardial perfusion coupled with pacing near or distant to the area of perfusion. In 10 open-chest anesthetized canines, coronary blood flow to the left ventricular (LV) anterior wall (AW: n = 5) and lateral wall (LW: n = 5) was controlled during four pacing conditions: right atrial, right ventricular (pseudo-left bundle branch block; [pseudo-LBBB]), BiV-LW and BiV-AW. Local EM function (piezo-electrical crystals and electrodes), along with global hemodynamic parameters, were measured during all pacing conditions at three coronary perfusion rates (≥0.40 mL/min/g, 0.20-0.40 mL/min/g and <0.20 mL/min/g). A positive BiV therapy response was assessed by a significant increase in the maximum cardiac output compared with the pseudo-LBBB condition. Despite no improvement in QRS duration, BiV-LW pacing improved LV function compared with the pseudo-LBBB pacing condition (P value <0.01). This improvement with BiV-LW pacing was seen above a certain myocardial perfusion threshold and was independent of any increases in regional coronary blood flow with BiV pacing. At lower myocardial perfusion rates, LV function was not improved with BiV pacing at any location. This study underscores the significance of even mild ischemia on BiV pacing response.

The effect of left ventricular pacing site on cardiac resynchronization therapy outcome and mortality: the results of a PROSPECT substudy

AIMS

Left ventricular pacing site (LV-PS) was prospectively collected to test the influence of the anatomical LV-PS on the outcome of cardiac resynchronization therapy (CRT) and mortality.

METHODS AND RESULTS

Four hundred and twenty-six patients with standard indications for CRT underwent echocardiographic and clinical evaluation before and after CRT implantation. The LV-PS was determined from fluoroscopy using the clockwise principle (CP). The LV-PS was categorized into three prospectively defined groups: between 3 and 5 o'clock and longitudinal basal/mid-position (Group A, 'optimal'); between 12 and 2 o'clock and longitudinal mid-apical anterior position (Group B, 'non-optimal'); and all other (Group C, 'other'). Of 333 patients, followed for 0.9 years (mean), adequate images were available to define the LV-PS. Left ventricular pacing site was Group A for 118 patients, Group B for 56, and Group C for 159. The three groups were comparable regarding gender, aetiology, and NYHA class; however, patients in Group A were younger. No relation was found between the LV-PS groups and CRT outcome or all-cause mortality. However, further exploratory subanalyses suggest that LV-PS may impact outcomes in non-ischaemic patients, those with left bundle branch block, and when LV-PS is apical in location.

CONCLUSION

Using the CP to define anatomical LV-PS, no relation was found between the LV-PS groups and CRT outcome and mortality. Exploratory analyses warrant further studies.

Correlation of body mass index and responder status in heart failure patients after cardiac resynchronization therapy: Does the obesity paradox exist?

Aims: We investigated the influence of body mass index (BMI) on the prevalence of responder status in chronic heart failure patients after cardiac resynchronization therapy (CRT).

Methods: Data on 169 patients with resynchronization therapy were analyzed. Patients were categorized on the basis of the BMI measured at device implantation according to the WHO classification, as normal (BMI: 18.5–24.9 kg/m2), overweight (BMI: 25–29.9 kg/m2) or obese (BMI:≥30 kg/m2). Patients were considered responders if left ventricular ejection fraction was increased by at least 5% at 6-month follow-up.

Results: The mean age in the study population was 60.9±10.86 years (females 29%). The BMI subgroups did not exhibit any significant differences in baseline characteristics (age, gender, left ventricular ejection fraction or NYHA class). Elevated BMIs were associated with higher prevalence of responder status (overweight: 71.4%, obese: 63.0%) relative to subjects with a normal BMI (44.7%) (p=0.015).

Conclusions: In this CRT population, overweight status was associated with a more favorable response to CRT, indicating that the response may possibly be influenced by factors other than those directly related to the heart status or the technical details of the CRT.