Evaluation of changes in cardiac output from the electrical impedance waveform in the forearm.

We tested the validity of regional impedance cardiography (RIC) for measuring changes in both cardiac output and stroke volume by comparing the values with a 2D ultrasound technique in response to the breath-hold manipulation. Among 13 subjects, changes in the maximum amplitude of the regional impedance waveform from the forearm conformed to those in stroke volume (r = 0.86, p < 0.001) and cardiac output (r = 0.76, p < 0.003) measured with the ultrasound technique in baseline and immediately after a 30 s breath-hold maneuver. We also found that the per cent change in cardiac output (r = 0.73, p < 0.005) and the per cent change in stroke volume (r = 0.84, p < 0.0003) by the echocardiography were both positively correlated with the per cent change in the peak impedance amplitude. In addition, both the change and the per cent change in the mean area under the impedance curve were consistent with those in the stroke volume, respectively. Accordingly, the regional electrical impedance waveform from lower limbs may be helpful in providing a non-invasive and continuous assessment of left ventricular output, especially during cardiac procedures.

Equivalent contractility indexes for the assessment of left ventricular systolic function in post-AMI human hearts.

We propose new contractility indexes, in the work, which are equivalent to the conventional contractility (Ees) determined with the slope of left ventricular (LV) end-systolic pressure-volume relation. Nineteen patients with acute myocardial infarction (AMI) were recruited in the study. They received thrombolytic therapy within 24 hours after the AMI event, and their LV pressures and volumes were measured with Millar and multi-electrode volume conductance catheters during catheterization examination at the first week and 3 months, respectively. The first equivalent contractility index (eEsv) submitted was defined as the Ees divided by the end-systolic volume (ESV) and normalized to 100 ml, the second (eEdv) as the Ees divided by the end-diastolic volume (EDV) and normalized to 100 ml, and the third (eEmv) as the Ees divided by the midrange of the LV volume and normalized to 100 m. Using linear regression methods, we found that a high correlation coefficient (r > 0.82) exists between the Ees and one of the three new contractility indexes. Furthermore, the eEsv but not Ees was significantly higher measured at 3 months than at one week after thrombolysis. In conclusion, an increase in the equivalent contractility eEsv implies the improvement of the left ventricular systolic function in the post-AMI human hearts long-term after thrombolytic intervention, as the size-dependence of contractility is taken into account.

Relationship between the left ventricular elastance and the effective arterial elastance in AMI patients after thrombolysis.

The purpose of the study is to investigate the effect of thrombolysis on the relationship between the left ventricular (LV) maximum elastance (Emax) and effective arterial elastance (Eart) in 20 patients with acute myocardial infarction (AMI). LV pressures and volumes of the patients were measured with Millar and multi-electrode volume conductance catheters during catheterization examination, respectively, at the first week and 3 months after the thrombolytic treatment. Emax was represented by the slope of the LV end-systolic pressure-volume relation, and Eart by the slope of the arterial end-systolic pressure-stroke volume relation. The results showed a linear Emax to Eart relation (r = 0.59) at the 1st week, but not 3 months (r =0.20), in those post-AMI patients. Moreover, the Emax was found to be linearly proportional to the Emax/Eart ratio at both the 1st week (r = 0.88) and 3 months (r = 0.85) after thrombolytic therapy. In summary, a 'stunt' hearts in the initial period after thrombolytic intervention reveals a linear relationship between the ventricular contractility and afterload, suggesting that the coupling of the left ventricle and arterial vasculature seems to be maintained.