Ashraf W Khir | PubMed Health

PubMed2005

Intra-aortic balloon pumping: does posture matter?

BACKGROUND: The effect of the posture of semirecumbent patients on the hemodynamics and performance of intra-aortic balloon (IAB) were studied in vivo and in vitro. METHODS: An IAB was inserted into a glass tube filled with saline, fully inflated and deflated using an intra-aortic balloon pump (IABP). Three successive cycles were filmed at 125 frames/s with the tube positioned at various angles between 0 degrees (horizontal) and 90 degrees (vertical). Pressure and flow were measured distal to both ends of the balloon. In parallel, coronary left anterior descending (LAD) flow velocity and aortic pressure were recorded in 6 patients using IABP, postcardiac surgery in the intensive care unit. Recordings were made when the patient was lying horizontally (recumbent) and when the patient's torso was inclined at 30 degrees to the horizontal (semirecumbent). RESULTS: With the tube horizontal, the inflation was effectively uniform along the length of the balloon. At all other angles, the higher end of the balloon inflated first, and mean pressure and flow measured distal to the higher end of the balloon were less than those measured at 0 degrees . Mean aortic pressure and LAD flow decreased by 10 +/- 2% (P = 0.001) and 15 +/- 3% (P = 0.001), respectively, when the patient was semirecumbent compared to when the patient was recumbent. CONCLUSION: The decreased mean aortic pressure and LAD flow velocity suggests that unless patients using IABP are required to be semirecumbent, it may be best to position them horizontally to gain the full benefits of balloon counter pulsation to the coronary circulation.

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PubMed2003

Intra-aortic balloon pumping: effects on left ventricular diastolic function.

OBJECTIVE: The intra-aortic balloon pump is the most widely used form of temporary cardiac assist and often utilised in patients before and after cardiac surgery. Several effects of balloon counter-pulsation have been reported previously, but its effect on left ventricular diastolic function has not been thoroughly investigated. The aim of this study is to examine the effect of the intra-aortic balloon pump on left ventricular wall motion and transmitral flow. METHODS: We studied 20 patients in the intensive care unit, less than 36 h following cardiac surgery. We recorded left anterior descending coronary artery and transmitral E-wave flow velocities using transesophageal echocardiography pulsed Doppler. We also recorded left ventricular long axis free-wall movement using M-mode. The intra-aortic balloon pump was set to full augmentation and recordings were made at pumping cycles 1:1, 1:2, 1:3, and when the pump was on stand-by, leaving a minimum of 5 min between the pumping modes to allow the return to control conditions. In order to eliminate time effects, the sequence of recording was varied between patients using a 4 by 4 Latin-square. RESULTS: The peak diastolic left anterior descending coronary artery and transmitral E-wave flow velocities, and left ventricular free-wall early diastolic lengthening velocity increased significantly with intra-aortic balloon pumping cycles 1:1, 1:2 and 1:3 compared to their value with the pump on stand-by, all P < 0.001. The increase in peak transmitral E-wave flow velocity correlated with the increase in peak left anterior descending coronary artery diastolic flow velocity (r = 0.74, P = 0.02), and with the increase in left ventricular free-wall early diastolic lengthening velocity (r = 0.80, P < 0.001). CONCLUSION: Using the intra-aortic balloon pump post-cardiac surgery significantly increases peak diastolic left anterior descending coronary artery flow velocities and left ventricular free-wall early diastolic lengthening velocity, whose increase explains the increase in peak transmitral E-wave velocity. Although coronary flow is epicardial and mitral flow is intracardial, their close relationship suggests an improvement in left ventricular diastolic function with intra-aortic balloon pump.

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