S. Muzzupappa

Warped-average template technique to track on a cycle-by-cycle basis the cardiac filling phases on left ventricular volume

The dynamic time warping approach is utilised to obtain a template from the left ventricular volume signal. The technique, by performing shrinking and enlarging of the temporal axes of two waveforms, indicates the best non-linear alignment between them. In this application this technique is used to track on a cycle-by-cycle basis the diastasis onset and offset thus allowing one to reliably measure temporal sub-intervals of the filling period.

Evaluation of respiratory influences on left ventricular function parameters extracted from echocardiographic acoustic quantification

This study was designed to assess, using the echocardiographic acoustic quantification technique, the influence of respiration on left ventricular (LV) function and its modifications connected with the ageing process, quantifying in a non-invasive way the respiratory contribution to the LV volume variability. An automated algorithm is applied to extract the beat-to-beat measurements of LV function parameters from the LV volume signal, obtained from recordings lasting a few minutes. Mean values, amount of variability and spectral content were studied in a population of 17 normal young (mean age 25 +/- 1 years) and 12 normal old (mean age 64 +/- 2 years) subjects. Mean values of the beat-to-beat measurements of LV function parameters were able to point out alterations connected with the ageing process in peak filling rate, peak atrial filling rate and peak ejection rate. Spectral analysis, applied to the extracted variability series, displayed a predominance of the high-frequency (HF) component corresponding to respiration in all LV function parameters; moreover, age related changes of HF variability were observed in peak ejection rate. The HF power spectrum component of beat to beat series extracted from the LV signal can provide a non-invasive assessment of the fluctuations in ventricular parameters associated with respiration.

Analysis of cardiac left-ventricular volume based on time warping averaging

The cardiac left-ventricular (LV) volume signal, obtained by acoustic quantification, is affected by noise and respiratory modulation, resulting in a large beat-to-beat variability that affects the computation of LV function indices. A new method is proposed to improve the evaluation of LV indices by applying a signal averaging technique based on dynamic time warping to consecutive LV volume waveforms. Volume signals obtained from ten normal young (NY) subjects (mean age±SD: 25±5 years) were used to evaluate the performance of this algorithm. To evaluate its clinical utility, the effects of ageing and pharmacologically induced changes on LV function were assessed by studying, respectively, ten normal (N) adult subjects (age 64±8 years) and ten patients with dilated cardiomyopathy during a control and low-dose dobutamine (10 μg kg−1 min−1) study. Indices of LV function were highly consistent, with a variability of less than 8%, even when only 16 beats were averaged, independently of their selection inside the whole recording. When compared with beat-to-beat measures, the averaging of 16 beats significantly reduced (by more than 50%) the interbeat variability of all indexes. Expected alterations in both diastolic and systolic function were evidenced both with ageing (peak filling atrial contraction and ejection rates: from 275±77 ml s−1, 76±30 ml s−1, 230±70 ml s−1, respectively, in NY, to 160±33 ml s−1, 125±39 ml s−1, 163±54 ml s−1 in N) and with dobutamine (peak filling and ejection rates from 160±72 ml s−1 and 183±86 ml s−1 respectively, in control, to 253±75 ml s−1 and 251±105 ml s−1 with dobutamine). Signal averaging with time warping allows fast and improved assessment of LV function.

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.

A case of subannular aortic aneurysm detected by transoesophageal echocardiography.

Subvalvular aortic aneurysm is a cardiac abnormality extremely uncommon in white adult patients. Accurate diagnosis can be made by transoesophageal echocardiography which is the modality of choice for non-invasive recognition of aortic and subaortic abnormalities. In this report we describe, in a 47-year-old white man with subvalvular aortic aneurysm associated to aortic bicuspid valve, the echocardiographic diagnosis and cardiac intervention of aortic valve replacement with surgical obliteration of the orifice.A good surgical result was confirmed by an echocardiographic transthoracic examination performed after 6 months.

Quantitative evaluation of regional left ventricular wall motion using color kinesis after percutaneous transluminal myocardial revascularization

cantly shortened in the 2 groups. The preprocedure lesion length did not differ in diabetic versus nondiabetic patients, but the lesion length at follow-up in the diabetic group was significantly longer than that in the nondiabetic group. • • • The most disappointing aspect of the present study was the high restenosis rate in diabetic patients after rotational atherectomy compared with that of nondiabetic patients. Teirstein et al2 reported a restenosis rate of 59% after rotational atherectomy in patients with diffuse coronary artery disease. The restenosis rate of diabetic patients in the present study was 72%, higher than Teirstein et al’s study.2 These results suggest that rotational atherectomy is not as effective for preventing restenosis in diabetic patients with diffuse coronary artery disease as it is in nondiabetic patients.

Time-warping averaging for quantitative evaluation of changes in LV function

Signal averaged acoustic quantification (SAAQ) with time-warping (TW) preserves the morphology of SAAQ waveforms allowing reliable noninvasive quantification of amplitude- and timing-indexes of left ventricular (LV) function, which cannot be assessed with simple signal averaging. We tested the ability of this technique to track pharmacologically induced changes in LV function during residual viability study. LV volume signals obtained (Sonos 5500) in 10 patients with dilated cardiomyopathy under control conditions and during low-dose dobutamine infusion (10 mcg/kg/min) were digitized at 300 Hz. In each subject and for each experimental condition LV volume signals were averaged (16 consecutive beats) with the TW technique. Averaged waveforms and time-derivatives were used to identify the phases of LV filling and calculate end-systolic and end-diastolic volumes, stroke, peak rapid and peak atrial filling rates, peak ejection rate, duration of heart cycle, systole, rapid filling and atrial filling phases. The calculated indices reflected the low-dose dobutamine-induced changes in LV function, evidencing variations both in rapid filling and systolic phases. Signal averaging with TW allows reliable calculation of indices of LV systolic and diastolic function, and can be used to monitor their changes related to residual viability examinations.

Poincare plots and symbolic dynamics patterns of left ventricular function parameters extracted from echocardiographic acoustic quantification

Throughout the echocardiographic acoustic quantification technique, a non-invasive estimate of left ventricular volume (VV) is obtained and acquired in real-time. An automated algorithm is applied to extract the beat-by-beat values of ventricular function parameters. Their beat-by-beat variability has been recently studied, together with heart period (RR) variability, by spectral techniques. In this study, we propose to investigate this variability by nonlinear techniques, such as Poincare plots (PPS) and symbolic dynamics (SyD) patterns. A group of 17 normal young subjects (NY, 25 /spl plusmn/ 1 years) and a group of 12 normal old subjects (NO, 64 /spl plusmn/ 2 years) were studied to observe if this approach could be able to detect modifications in VV function connected with the ageing process. Differences in RR, peak filling and peak ejection rate were evidenced by PPs indexes. SyD analysis evidenced different patterns: in RR a change from increasing/decreasing in NY to alternating pattern in NO was found, together with a change in SV pattern from random in NY to alternating in NO. Consistent alternating patterns were found in VV derivative parameters. In conclusion, PPs and SyD patterns seemed able to evidence differences between NY and NO ventricular function, otherwise not captured by linear analysis techniques.

Interaction between respiration and beat-by-beat ventricular parameters from acoustic quantification

In 8 patients with cardiac dilative myopathy and pseudo-normalized mitral Doppler pattern (DP, age 60/spl plusmn/2, mean/spl plusmn/SE), and in 11 age-matched control subjects (NL, age 61/spl plusmn/4), beat-by-beat end diastolic (EDV), end systolic (ESV), stroke (SV) ventricular volume (VV) measurements were obtained at rest for periods of at least 4 min by echocardiographic acoustic quantification (AQ) signal. RR intervals and respiration were recorded as well. In all subjects, spectral analysis showed a prevalence of high frequency (HF) components in all VV series, with an increased absolute power in DP (53/spl plusmn/12 ml/sup 2/ of HF SV variability compared to 16/spl plusmn/5 in NL). Folded scatter diagrams of the VV values vs the respiratory phase revealed consistent patterns. Parameters of a linear prediction model of SV were estimated by considering as inputs:1) three samples of respiration; 2) the previous sample of EDV slow trends, 3) the previous RR interval with a goodness of fit of 47/spl plusmn/4% in NL and 43/spl plusmn/6% in DP.