Noninvasive quantification of respiratory modulation on left ventricular size and stroke volume.

To noninvasively explore the complex interactions between heart rate, left ventricular (LV) stroke volume (SV) and respiration, different techniques were proposed and applied to the beat-to-beat measurements of end-diastolic (ED), end-systolic (ES) volumes and SV, obtained from echocardiographic acoustic quantification LV volume signal. Data were obtained from eight patients with dilated cardiomyopathy (DCM, age 60 +/- 2, mean +/- SE), and from 11 age-matched healthy volunteers (N, age 63 +/- 2). Spectral analysis showed an increase in HF power in DCM, both in ED (in ml2, 58 +/- 18 versus 19 +/- 5 in N) and in SV (in ml2, 55 +/- 12 versus 17 +/- 5 in N), together with an increase in total power (in ml2, ED: 119 +/- 31 in DCM versus 48 +/- 9 in N; SV: 88 +/- 17 in DCM versus 31 +/- 8 in N). Folded scattergrams evidenced higher amplitude oscillations in DCM (in ml, ES: 7.93 +/- 1.29; ED: 7.94 +/- 1.59; SV: 7.27 +/- 0.91) compared to N (in ml, ES: 4.08 +/- 0.64; ED: 3.56 +/- 0.65; SV: 3.63 +/- 0.43). Moreover, the prevalent effect of increased afterload generating SV reduction during inspiration was pointed out in N, while an intersubject dispersion in the relation between respiratory phase and LV dimension changes was found in DCM. Black-box model identification summarized these mechanisms by means of a few quantitative parameters.