Left Ventricular Pump Function after Long-Term Treatment with Ventricular Pacing compared to Atrial Synchronous Pacing
The effect of VVI and VAT pacing on the left ventricular pump function was determined by cardiac catheterization after long-term treatment in 9 patients with high degree heart block. Measurements were made in supine at rest, with the patients legs elevated, during steady state work and the procedure was ended with a period of stepwise increase in load of 10 W × 1 min-1 until exhaustion (Wmax). Function curves were constructed by plotting stroke work index (SWI) and left ventricular power index (LVPI) against left ventricular end-diastolic pressure (LVEDP).
Cardiac output (CO) increased with VAT vs VVI pacing at rest by 22% (5.5 vs 4.5 l/min, p < 0.01). An increased stroke volume constituted the difference (75 vs 63 ml, p < 0.05). The ventricular rate being the same. At Wmax CO increased with VAT vs VVI by 40% (10.2 vs 7.3 l/min, p < 0.01). Atrial rate (AR), systolic aortic pressure (SP) and systemic vascular resistance (SVR) was reduced during exercise with VAT vs VVI pacing. The function curves with SWI vs LVEDP demonstrated a shift to the right with a significant decrease in SWI during exercise with VAT vs VVI, whereas LVPI vs LVEDP showed a shift to the left with a significant increase in LVPI at Wmax with VAT vs VVI. The changes in function curves, as the reduction in AR, SP and SVR appear to be constituted by a decrease in sympathetic activity with the VAT vs VVI.
The present study demonstrates that hemodynamic advantages with VAT pacing are still obtainable after several years of prior VVI pacing.
KeywordsCardiac Output Atrial Rate Stroke Work Index Increase Stroke Volume Systolic Aortic Pressure
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