Original article
Cardiovascular
Beat-to-Beat Effects of Intraaortic Balloon Pump Timing on Left Ventricular Performance in Patients With Low Ejection Fraction

https://doi.org/10.1016/j.athoracsur.2004.07.073Get rights and content

Background

Intraaortic balloon counterpulsation (IABP) timing errors during arrhythmia may result in afterload increases which may negatively influence left ventricular (LV) ejection and LV mechanical dyssynchrony. The aim of our study was to determine beat-to-beat effects of properly timed IABP, premature IAB inflation, and late IAB deflation on LV performance and LV mechanical dyssynchrony in heart failure patients undergoing cardiac surgery.

Methods

In 15 patients, LV pressure-volume relations and LV dyssynchrony were measured by conductance volume catheter. Properly timed IABP was evaluated at a 1:1 assist ratio within a 10 seconds time-span. Premature IAB inflation and late IAB deflation were evaluated at a 1:4 assist ratio.

Results

Properly timed 1:1 IABP acutely decreased LV end-systolic volume by 6.1% (p < 0.0001) and LV end-systolic pressure by 17.5% (p < 0.0001) due to decreased aortic impedance. Stroke volume (SV) increased by 14% (p < 0.0001), which correlated markedly with a decrease of LV mechanical dyssynchrony (p < 0.0001). The largest SV increases occurred in patients with lowest contractile state. Premature IAB inflation decreased SV by 20% (p < 0.0001) due to abrupt increase of LV afterload during late ejection. Late IAB deflation increased SV and stroke work by 18% (p < 0.0001) and 16% (p < 0.01) respectively, due to increased afterload during early ejection and decreased afterload during late ejection.

Conclusions

Left ventricular performance during IABP is causally related to changes in LV afterload, and the timing of these changes in relation to contraction or relaxation phases, to LV mechanical dyssynchrony and to contractile state.

Section snippets

Patients

Fifteen patients, New York Heart Association (NYHA) class II–IV, 48 to 64 years old, EF 21.5% ± 8.5%, undergoing cardiac surgery requiring prophylactic IABP, were studied. Eight patients underwent LV aneurysmectomy (6 patients with coronary artery bypass graft [CABG]), 6 patients underwent CABG (1 with mitral valve repair), and 1 patient underwent mitral valve repair. Open chest hemodynamic evaluations of acute effects of IABP were performed before cardiopulmonary bypass.

The study protocol was

Hemodynamic Response to Conventionally Timed IABP

The acute effects of proper IABP timing at a 1:1 assist ratio are illustrated by two typical examples (Fig 1). The largest decreases in LV pressure, LV end-systolic volume (ESV), LV end-diastolic volume (EDV) and concomitant increases in SV are observed within 4 assisted beats. Decreases in LVESV and LV end-systolic pressure (ESP) delineate the end-systolic P-V relationship and its slope, the Ees, representing a load independent index of contractile state. The average hemodynamic responses to

Comment

This study demonstrates acute beneficial effects of properly timed IABP at a 1:1 ratio in heart failure patients. Decreases in aortic impedance resulted in instantaneous increases in SV by LV afterload reduction with concomitant decreases in LVESV, LVEDV, and LV mechanical dyssynchrony. The decreases in LVESV and LVESP delineated the slope (Ees) of the end-systolic P-V relationship. The largest increases in SV occurred in the patients with the lowest contractile state.

Premature IAB inflation

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