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  • Title: Acute effect of rapid ventricular pacing and volume loading on total vascular capacitance.
    Author: Ogilvie RI, Zborowska-Sluis D.
    Journal: Can J Cardiol; 1992 Dec; 8(10):1071-8. PubMed ID: 1288839.
    Abstract:
    OBJECTIVE: Rapid right ventricular pacing (RRVP) at 250 beats/min plus a saline volume load produces acute heart failure manifested by a limited increase in cardiac output in response to the volume load and increased right atrial, pulmonary artery and capillary wedge pressures. The effects on vascular capacitance are unknown. DESIGN: Three groups of six anesthetized splenectomized dogs were subjected to RRVP alone at 250 beats/min for 40 mins volume loading alone with intravenous 0.9% sodium chloride 40 mL/kg over 10 mins or volume loading followed by RRVP for 15 mins. Vascular capacitance, unstressed volume and compliance were determined from pressure-volume curves using transient circulatory arrests induced by acetylcholine before and 40 mins after starting the interventions. RESULTS: Neither RRVP nor volume loading alone produced acute heart failure or altered total vascular compliance. Fifteen minutes of RRVP after the volume load induced heart failure, reduced compliance (3.4 +/- 0.5 to 2.5 +/- 0.3 mL/mmHg/kg, P < 0.05), increased central blood volume (7.7 +/- 0.7 to 10.6 +/- 0.5 mL/kg, P < 0.01) and reduced the unstressed vascular volume to 57 +/- 10 mL/kg, compared with 77 +/- 9 mL/kg (P < 0.01) after the volume load alone. Stressed blood volume was increased similarly with either volume loading alone (20.1 +/- 2.0 to 30.0 +/- 1.7 mL/kg, P < 0.01) or volume loading plus RRVP (23.5 +/- 3.8 to 30.2 +/- 4.9 mL/kg, P < 0.01). The reduction in unstressed volume rather than an increase in stressed volume was the major peripheral change associated with acute heart failure induced by volume loading plus RRVP. CONCLUSION: RRVP reduced vascular capacitance by a reduction in unstressed volume. Acute volume loading of this smaller vascular compartment resulted in redistribution centrally and acute heart failure.
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