PASSIVE COUNTERPULSATION: BIOMECHANICAL RATIONALE AND CLINICAL VALIDATION

Intra-aortic balloon counterpulsation (IABP) is the leading technique for cardiovascular support in most critical conditions. The beneficial effects of the procedure are widely known, but some drawbacks remain unsolved: high cost and controversial effect in presence of cardiac arrhythmia, both related to the control of intra-aortic balloon inflation and deflation. This paper describes the clinical validation of a completely passive solution (PIABP), which substitutes the time-controlled pumping system by a simple pressure-controlled reservoir. The test was performed on 10 patients, switching from IABP to PIABP and changing the reservoir pressure to obtain an optimal effect in terms of mean aortic pressure increase as an estimate of cardiac output. For each patient the reservoir pressure was increased in 10mmHg steps and the aortic pressure was recorded together with electrocardiogram. The PIABP showed a positive effect in all the patients, with a significant increase of the mean aortic pressure (þ6.5%, p < 0:05) and of the mean pressure of the aortic pulse diastolic phase (þ7%, p < 0:05). The change of heart rate between basal and optimal effect condition was not significant. Also an unexpected, significant increase of aortic maximal pressure (8%, p < 0:05) was found. The proposed passive solution cannot be a substitute of the active one in all the situation, but may be useful in border line conditions, where the IABP is no more necessary but a ventricular support is still desirable.