The Effect of IABP Ventricular Contractility of the Normal and Ischemic Canine Heart Assessed in Situ by T-Emax
Intra-aortic balloon pumping (IABP) has been shown to be effective in supporting the failing circulation through two alternating hemodynamic effects, i.e., a diastolic augmentation, and a reduction of the impedance to left ventricular ejection. These effects improve the myocardial oxygen supply/demand ratio and thereby increase cardiac performance (Norman and Igo, 1985). 0f the three determinants, i.e., preload, after-load and contractile state, only the last reflects the intrinsic performance of the myocardium. For a better understanding of the effectiveness and the physiological mechanism of IABP, the effects of IABP on the contractile state of the in situ heart must be fully elucidated. It is not surprising that there have been some confusing and contradictory reports from previous studies (Mullins et al., 1971; Rose et al. 1979; Grover et al., 1979; Norman an Igo, 1985), since most of the indices used to assess the contractile state during IABP are described as load- and heart rate-dependent Munch and Downey, 1981; Norman and Igo, 1985). However, the slope (Emax) of the End-Systolic Pressure Volume Relation (ESPVR) was proposed as an index of ventricular contractility, being independent of preload and after load (Suga et al., 1973; Suga and Sagawa, 1914; Sagawa, 1978). In addition, the transient slope of the end-systolic pressure-volume line (T-Emax) was reported to be a useful index for assessment of left ventricular contractility of the in situ canine heart (Igarashi and Suga, 1986). To our knowledge, T-Emax has not been used so far to evaluate the effect of IABP on either normal or ischemic heart. The present study was undertaken to elucidate the effect of IABP on T-Emax of both normal and ischemic canine heart in situ. For comparison, we also investigated simultaneously the changes of the maximum rate of rise of left ventricular pressure (dP/dtmax), an isovolumic phase index of contractility commonly used by previous authors (Mullins et al., 1971,; Grover et al., 1979; Okada and Nakamura, 1986) to assess contractility changes caused by IABP.
KeywordsAortic Pressure Regional Ischemia Aortic Flow Canine Heart Aortic Occlusion
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- Munch D F and Downey J M (1981) Regulation of Myocardial contractility, in: Cardiac Pharmacology, pp 3, Academic Press.Google Scholar
- Norman J C and Igo S R (1985) Mechanical circulatory assistance: established (IABP) and evolving (LVAD). A narrative summary. Thorac Car-diovasc Surgeon. 33:133.Google Scholar
- Okada M and Nakamura K (1986) Intraaortic balloon pumping — current status of IABP and artificial heart in Japan. Jpn J Thorac Surg 39:172.Google Scholar
- Sagawa K (1978) The ventricular pressure-volume diagram revisited. Cir Res 43:677.Google Scholar
- Suga H, Sagawa K and Shoukas A A (1973) Load independence of the instantaneous pressure-volume ratio of canine left ventricle and effects of epinephrine and heart rate on the ratio. Cir Res 32:314.Google Scholar
- Suga H and Sagawa K (1974) Instantaneous pressure-volume relationships and their ratio in the excised, supported canine left ventricle. Cir. Res. 35: 117.Google Scholar
- Sunagawa K, Maughan W L and Sagawa K (1983) Effect of regional ischemia on the left ventricular end-systolic pressure-volume relationship of isolated canine hearts. Cir Res 52:170.Google Scholar