LV-Only and LV-First Pacing Demonstrate Greater Improvements in Acute Hemodynamics Than Synchronous BiV Pacing in Heart Failure With Preserved Ejection Fraction

Background: Heart failure with a preserved ejection fraction (HFpEF) remains poorly understood with few options for treatment. Recent evidence identified regional delays in cardiac mechanical activation in HFpEF despite a narrow QRS and normal chamber size. We compared the acute effects of synchronous BiV pacing (VV0), BiV pacing with LV first (LVfirst) and LV only (LVonly) pacing on mechanical dyssynchrony and hemodynamics in HFpEF. Methods: HF patients with EF >50% and echocardiographic evidence of dyssynchrony were studied during cardiac catheterization. Patients were instrumented with temporary pacing catheters in the RA, LV and RV, and paced in VDD mode with AV timing selected to optimize transmitral flow during simultaneous BiV pacing. A pressure catheter provided continuous LV and aortic pressure. LVonly, LVfirst and VV0 pacing were compared to normal sinus rhythm (NSR). During LVfirst pacing, the LV was stimulated 45 ms before the RV. Regional mechanical delay (RMD) was measured in all pacing modes and during NSR. RMD is the time difference between the septal and lateral wall peak myocardial velocities. Results: Eleven patients participated (71 yo, 82% female, NYHA class of 2.5, BMI of 28 kg/m2). Patients had an EF of 74% and a narrow QRS (86 ms). LVonly and LVfirst significantly reduced systolic mechanical dyssynchrony, Ts-SD (standard deviation of time to peak systolic velocity of 12 ventricular segments) and RMD. However, E/E' significantly decreased only during LVonly. Paradoxically, all three pacing modes also showed a significant increase in LVEDP. LVonly and LVfirst also demonstrated improvements in several measures of systolic function. Conclusion: These data suggest that LV pre-excitation, achieved either by LV first or LV only pacing, may improve dyssynchrony in HFpEF patients with EF>50% and narrow QRS but with echo measures of dyssynchrony. Whether these acute improvements will lead to chronic therapeutic benefit in this population will require further study.