Intraventricular flow energy loss may be used to assess cardiac resynchronization therapy efficacy
The reduction of intraventricular flow energy loss (EL) through biventricular (BiV) pacing appears to be linked to a decrease in the plasma levels of brain natriuretic peptide (BNP), reports a poster presented at the recently concluded 2018 Congress of the Asian Pacific Society of Cardiology (APSC 2018) in Taipei, Taiwan.
In patients whose EL was reduced following BiV pacing, plasma BNP levels showed a significant decline of about –40 percent. In contrast, the EL-nonreduction group showed an approximately 15-percent increase in the plasma concentrations of BNP. The difference was statistically significant (p<0.05). [APSC 2018, abstract P050]
In addition, the percent change in systolic EL was significantly and positively correlated with the percent change in BNP for 1 month (ρ=0.65; p<0.05).
On the other hand, no significant differences in echocardiography findings were found between the EL-reduction and EL-nonreduction groups, which showed statistically similar left ventricular ejection fraction (25±4 percent vs 20±5 percent; p=0.07), left atrial dimension (49±7 vs 45±6 mm; p=0.18) and left ventricular end-systolic volume (159±51 vs 219±74 mL; p=0.34).
Changes in electrocardiography and echocardiography findings were likewise comparable between the two patient groups. For instance, there was no significant difference in the change in QRS duration of patients who did vs did not show EL reductions (–37±37 vs –26±35 ms).
There was also no significant difference in the change in velocity time integral between the EL-reduction and EL-nonreduction groups (1.9±2.1 vs –0.9±3.1 cm).
To obtain the above data, researchers recruited 11 patients who initiated cardiac resynchronization therapy (CRT) from January 2017 to March 2018. Of the participants, systolic EL reduction was observed in 4 (mean age 65.5±16.4 years; 75 percent male) while nonreduction was reported in 7 (mean age 58.7±14.4 years; 86 percent male).
Echocardiography and flow analysis with and without BiV pacing was performed over a median 7 days following implantation of device. Plasma BNP concentration was measured at baseline and at 1 month after CRT. Vector flow mapping was performed to measure EL, vortex area and circulation.
Both patient groups were statistically comparable at baseline. There were no significant differences in the prevalence of comorbidities such as hypertension (43 percent vs 25 percent; p=0.55) and diabetes mellitus (43 percent vs 50 percent; p=0.48), as with the baseline concentration of haemoglobin (13.3±1.4 vs 11.8±0.9 g/dL; p=0.07) and BNP (699±831 vs 1,359±1,194; p=0.22).
While the exact mechanism underlying the clinical efficacy of CRT is still unclear, the “[i]mprovement of energetic efficacy of [left ventricular] workload may be a factor,” proposed researchers. Future studies are however needed to confirm this.
The present findings show that in patients undergoing CRT, there is a link between EL reduction by BiV pacing and declining plasma BNP, said researchers, adding that “EL assessment may be a promising method to evaluate the efficacy of CRT.”