Cardiac reflections and natural vibrations: force-frequency relation recording system in the stress echo lab

Exercise Stress Echocardiography for Stable Coronary Artery Disease: Succumbed to the Modern Conceptual Revolution or Still Alive and Kicking?

The modern conceptual revolution in managing patients with stable coronary artery disease (CAD), based on improvement in preventive and pharmacological therapy, advocates coronary artery revascularization only for smaller group of patients with refractory angina, poor left ventricular systolic function, or high-risk coronary anatomy. Therefore, our conventional wisdom about stress testing must be questioned within this new and revolutionary paradigm. Exercise stress echocardiography (ESE) is still a well-known technique for assessing known or suspected stable CAD, it is safe, accessible, and well-tolerated, and there is an widespread evidence base. ESE has been remarkably resilient throughout years of innovation in noninvasive cardiology. Its value is not to be determined over the short portion of diagnostic accuracy but mainly through its prognostic value evident in a wide range of patient subsets. It is coming very close to the modern profile of a leading test that should include, in addition to an essential accettable diagnostic and prognostic accuracy, qualities of low cost, no radiation exposure, and minor environmental traces. In this review, we will discuss advantages, diagnostic accuracy, prognostic value in general and special populations, cost-effectiveness, and changes in referral patterns of ESE in the modern era.

A Novel Broadband Forcecardiography Sensor for Simultaneous Monitoring of Respiration, Infrasonic Cardiac Vibrations and Heart Sounds

The precordial mechanical vibrations generated by cardiac contractions have a rich frequency spectrum. While the lowest frequencies can be palpated, the higher infrasonic frequencies are usually captured by the seismocardiogram (SCG) signal and the audible ones correspond to heart sounds. Forcecardiography (FCG) is a non-invasive technique that measures these vibrations via force sensing resistors (FSR). This study presents a new piezoelectric sensor able to record all heart vibrations simultaneously, as well as a respiration signal. The new sensor was compared to the FSR-based one to assess its suitability for FCG. An electrocardiogram (ECG) lead and a signal from an electro-resistive respiration band (ERB) were synchronously acquired as references on six healthy volunteers (4 males, 2 females) at rest. The raw signals from the piezoelectric and the FSR-based sensors turned out to be very similar. The raw signals were divided into four components: Forcerespirogram (FRG), Low-Frequency FCG (LF-FCG), High-Frequency FCG (HF-FCG) and heart sounds (HS-FCG). A beat-by-beat comparison of FCG and ECG signals was carried out by means of regression, correlation and Bland–Altman analyses, and similarly for respiration signals (FRG and ERB). The results showed that the infrasonic FCG components are strongly related to the cardiac cycle (R² > 0.999, null bias and Limits of Agreement (LoA) of ± 4.9 ms for HF-FCG; R² > 0.99, null bias and LoA of ± 26.9 ms for LF-FCG) and the FRG inter-breath intervals are consistent with ERB ones (R² > 0.99, non-significant bias and LoA of ± 0.46 s). Furthermore, the piezoelectric sensor was tested against an accelerometer and an electronic stethoscope: synchronous acquisitions were performed to quantify the similarity between the signals. ECG-triggered ensemble averages (synchronized with R-peaks) of HF-FCG and SCG showed a correlation greater than 0.81, while those of HS-FCG and PCG scored a correlation greater than 0.85. The piezoelectric sensor demonstrated superior performances as compared to the FSR, providing more accurate, beat-by-beat measurements. This is the first time that a single piezoelectric sensor demonstrated the ability to simultaneously capture respiration, heart sounds, an SCG-like signal (i.e., HF-FCG) and the LF-FCG signal, which may provide information on ventricular emptying and filling events. According to these preliminary results the novel piezoelectric FCG sensor stands as a promising device for accurate, unobtrusive, long-term monitoring of cardiorespiratory functions and paves the way for a wide range of potential applications, both in the research and clinical fields. However, these results should be confirmed by further analyses on a larger cohort of subjects, possibly including also pathological patients.

The prognostic value of stroke work/end-diastolic volume ratio during stress echocardiography

BACKGROUND

The ventricular stroke work (SW) refers to the work done by the left ventricle to eject the volume of blood during one cardiac cycle. The cath-lab relationship between SW and end-diastolic volume (EDV) is the preload-recruitable SW (PRSW). Recently a non-invasive single-beat PRSW (SBPRSW) has been proposed. However, the single beat formula needs mathematical skillness, and extra software. Aim of this study was to compare the non-invasive SBPRSW with the simpler non-invasive SW/EDVratio in the stress-echo lab.

METHODS

We studied 692 patients, age 62 ± 12 years, ejection fraction 50 ± 17%, with negative stress echo (SE)(exercise, n = 130, dobutamine, n = 124, dipyridamole, n = 438) and follow-up data. The PRSW was estimated at rest and at peak stress by the SBPRSW technique and compared with the SW/EDV. All patients were followed-up. Event rates were estimated with Kaplan-Meier curves.

RESULTS

SBPRSW and SW/EDV were linearly correlated at rest (r = 0.842, p < .001) and at peak stress (r = 0.860, p < .001). During a median follow-up of 20 months (first quartile 8, third quartile 40 months), 132 major events were registered: at receiver operating characteristic (ROC) analysis rest SBPRSW vs. SW/EDV (AUC 0.691 vs. 0.722) and peak stress (AUC 0.744 vs. 0.800) demonstrated both a significant prognostic power (all p < .001) with non-inferior survival prediction of the simpler SW/EDV ratio at Kaplan-Meier curves (Chi-square rest = 38, peak = 56) vs. SBPRSW (Chi-square rest = 14, peak = 42).

CONCLUSIONS

The data obtained with the non-invasive SBPRSW and by the simpler SW/EDV are highly comparable. PRSW with either SB or SW/EDV approach is effective in predicting follow-up events.

Spectral Decomposition and Sound Source Localization of Highly Disturbed Flow through a Severe Arterial Stenosis

For the early detection of atherosclerosis, it is imperative to explore the capabilities of new, effective noninvasive diagnosis techniques to significantly reduce the associated treatment costs and mortality rates. In this study, a multifaceted comprehensive approach involving advanced computational fluid dynamics combined with signal processing techniques was exploited to investigate the highly turbulent fluctuating flow through arterial stenosis. The focus was on localizing high-energy mechano-acoustic source potential to transmit to the epidermal surface. The flow analysis results showed the existence of turbulent pressure fluctuations inside the stenosis and in the post-stenotic region. After analyzing the turbulent kinetic energy and pressure fluctuations on the flow centerline and the vessel wall, the point of maximum excitation in the flow was observed around two diameters downstream of the stenosis within the fluctuating zone. It was also found that the concentration of pressure fluctuation closer to the wall was higher inside the stenosis compared to the post-stenotic region. Additionally, the visualization of the most energetic proper orthogonal decomposition (POD) mode and spectral decomposition of the flow indicated that the break frequencies ranged from 80 to 220 Hz and were correlated to the eddies generated within these regions.

Forcecardiography: A Novel Technique to Measure Heart Mechanical Vibrations onto the Chest Wall

This paper presents forcecardiography (FCG), a novel technique to measure local, cardiac-induced vibrations onto the chest wall. Since the 19th century, several techniques have been proposed to detect the mechanical vibrations caused by cardiovascular activity, the great part of which was abandoned due to the cumbersome instrumentation involved. The recent availability of unobtrusive sensors rejuvenated the research field with the most currently established technique being seismocardiography (SCG). SCG is performed by placing accelerometers onto the subject's chest and provides information on major events of the cardiac cycle. The proposed FCG measures the cardiac-induced vibrations via force sensors placed onto the subject's chest and provides signals with a richer informational content as compared to SCG. The two techniques were compared by analysing simultaneous recordings acquired by means of a force sensor, an accelerometer and an electrocardiograph (ECG). The force sensor and the accelerometer were rigidly fixed to each other and fastened onto the xiphoid process with a belt. The high-frequency (HF) components of FCG and SCG were highly comparable (r > 0.95) although lagged. The lag was estimated by cross-correlation and resulted in about tens of milliseconds. An additional, large, low-frequency (LF) component, associated with ventricular volume variations, was observed in FCG, while not being visible in SCG. The encouraging results of this feasibility study suggest that FCG is not only able to acquire similar information as SCG, but it also provides additional information on ventricular contraction. Further analyses are foreseen to confirm the advantages of FCG as a technique to improve the scope and significance of pervasive cardiac monitoring.

Noninvasive Determination of Blood Pressure by Heart Sound Analysis Compared With Intra-Arterial Monitoring in Critically Ill Children-A Pilot Study of a Novel Approach

OBJECTIVES

To develop a novel device to predict systolic and diastolic blood pressure based on measured heart sound signals and evaluate its accuracy in comparison to intra-arterial blood pressure readings.

STUDY DESIGN

Prospective, observational pilot study.

SETTING

PICU.

PATIENTS

Critically ill children (0-18 yr) undergoing continuous blood pressure monitoring via radial artery intra-arterial catheters were enrolled in the study after informed consent. The study included medical, cardiac, and surgical PICU patients.

INTERVENTIONS

Along with intra-arterial blood pressure, patient's heart sounds were recorded simultaneously by a highly sensitive sensor taped to the chest. Additional hardware included a data acquisition unit and laptop computer. Subsequently, advanced signal processing technologies were used to minimize random interfering signals and extract and separate S1 and S2 signals. A computerized model was then developed using artificial neural network systems to estimate blood pressure from the extracted heart sound analysis.

MEASUREMENTS AND MAIN OUTCOMES

We found a statistically significant correlation for systolic (r = 0.964; R = 0.928) and diastolic (r = 0.935; R = 0.868) blood pressure readings (n = 491) estimated by the novel heart-sound signal-based method and those recorded by intra-arterial catheters. The mean difference of the individually paired determinations of the blood pressure between the heart-sound-based method and intra-arterial catheters was 0.6 ± 7 mm Hg for systolic blood pressure and -0.06 ± 5 mm Hg for diastolic blood pressure, which was within the recommended range of 5 ± 8 mm Hg for any new blood pressure devices.

CONCLUSIONS

Our findings provide proof of concept that the heart-sound signal-based method can provide accurate, noninvasive blood pressure monitoring.

Myocardial contractility in the stress echo lab: from pathophysiological toy to clinical tool

Up-regulation of Ca2+ entry through Ca2+ channels by high rates of beating is involved in the frequency-dependent regulation of contractility: this process is crucial in adaptation to exercise and stress and is universally known as force-frequency relation (FFR). Disturbances in calcium handling play a central role in the disturbed contractile function in myocardial failure. Measurements of twitch tension in isolated left-ventricular strips from explanted cardiomyopathic hearts compared with non-failing hearts show flat or biphasic FFR, while it is up-sloping in normal hearts. Starting in 2003 we introduced the FFR measurement in the stress echo lab using the end-systolic pressure (ESP)/End-systolic volume index (ESVi) ratio (the Suga index) at increasing heart rates. We studied a total of 2,031 patients reported in peer-reviewed journals: 483 during exercise, 34 with pacing, 850 with dobutamine and 664 during dipyridamole stress echo. We demonstrated the feasibility of FFR in the stress echo lab, the clinical usefulness of FFR for diagnosing latent contractile dysfunction in apparently normal hearts, and residual contractile reserve in dilated idiopathic and ischemic cardiomyopathy. In 400 patients with left ventricular dysfunction (ejection fraction 30 ± 9%) with negative stress echocardiography results, event-free survival was higher (p < 0.001) in patients with ΔESPVR (the difference between peak and rest end-systolic pressure-volume ratio, ESPVR) ≥ 0.4 mmHg/mL/m2. The prognostic stratification of patients was better with FFR, beyond the standard LV ejection fraction evaluation, also in the particular settings of severe mitral regurgitation or diabetics without stress-induced ischemia. In the particular setting of selection of heart transplant donors, the stress echo FFR was able to correctly select 34 marginal donor hearts efficiently transplanted in emergency recipients. Starting in 2007, we introduced an operator-independent cutaneous sensor to monitor the FFR: the force is quantified as the sensed pre-ejection myocardial vibration amplitude. We demonstrated that the sensor-derived force changes at increasing heart rates are highly related with both max dP/dt in animal models, and with the stress echo FFR in 220 humans, opening a new window for pervasive cardiac heart failure monitoring in telemedicine systems.

Real time 3D echocardiography (RT3D) for assessment of ventricular and vascular function in hypertensive and heart failure patients

Background

Cardiac and systemic hemodynamics have been historically in the domain of invasive cardiology, but recent advances in real-time 3-Dimensional echocardiography (RT3D echo) provide a reliable measurement of ventricular volumes, allowing to measure a set of hemodynamic parameters previously difficult or impossible to obtain with standard 2D echo.

Aim

To assess the feasibility of a comprehensive hemodynamic study with RT-3D echo.

Methods

We enrolled 136 patients referred for routine echocardiography: 44 normal (N), 57 hypertensive (HYP), and 35 systolic heart failure patients (HF). All patients underwent standard 2D echo examination followed by RT3D echo examination, including measurement of left ventricular (LV) end-diastolic and end-systolic volumes and derived assessment of LV elastance (an index of LV contractility), arterial elastance (characterizing the distal impedance of the arterial system downstream of the aortic valve); ventricular-arterial coupling (a central determinant of net cardiovascular performance); systemic vascular resistances. Blood pressure was derived from cuff sphygmomanometer and heart rate from ECG.

Results

A complete 2D echo was performed in all 136 patients. 3D echo examination was obtained in 130 patients (feasibility = 95 %). Standard 2D echo examination was completed in 14.8 ± 2.2 min. Acquisition of 3D images required an average time of 5 ± 0.9 min (range 3.5-7.5 min) and image analysis was completed in 10.1 ± 2.8 min (range 6–12 min) per patient. Compared to N and HYP, HF patients showed reduced LV elastance (1.7 ± 1.5 mmHg mL^-1 m^-2, p <0.001 vs N = 3.8 ± 1.3 and HYP = 3.8 ± 1.3) and ventricular-arterial coupling (0.6 ± 0.5, p < 0.01 vs N = 1.4 ± 0.4 and HYP = 1.2 ± 0.4). Systemic vascular resistances were highest in HYP (2736 ± 720, p < .01 vs N = 1980 ± 432 and vs HF = 1855 ± 636 dyne*s/cm⁵). The LV elastance was related to EF (r = 0.73, p < 0.01) and arterial pressure was moderately related to vascular elastance (r = 0.54, p < 0.01). The ventricular-arterial coupling was unrelated to systemic vascular resistances (r = −0.04, p NS).

Conclusion

RT-3D echo allows a non invasive, comprehensive assessment of cardiac and systemic hemodynamics, offering insight access to key variables – such as increased systemic vascular resistances in hypertensives and reduced ventricular-arterial coupling in heart failure patients.

Ejection fraction change and coronary artery disease severity: a vasodilator contrast stress-echocardiography study

BACKGROUND

An important goal of noninvasive stress testing is the identification of patients with left main coronary artery or three-vessel disease, because coronary artery disease extension and severity are major prognostic factors in ischemic heart disease. Wall motion abnormalities during vasodilator stress echocardiography become apparent in more than one coronary territory only in a small number of patients with multivessel disease. The aim of this study was to assess the value of change in left ventricular ejection fraction change (ΔLVEF) to identify patients with multivessel obstructive coronary artery disease during dipyridamole stress echocardiography.

METHODS

All dipyridamole stress echocardiographic studies performed at the authors' institution from October 2007 through March 2010 were retrospectively reviewed, and 150 patients who underwent coronary angiography within the next 60 days were selected. Left ventricular end-diastolic volume and end-systolic volume were measured at baseline and at the end of high-dose dipyridamole; ΔLVEF was calculated as stress ejection fraction minus rest ejection fraction. Patients were divided into four groups (controls and patients with single-vessel, two-vessel, and three-vessel disease) on the basis of coronary angiographic results.

RESULTS

The mean LVEF increased significantly from rest to peak stress in all groups except the three-vessel disease group. Mean ΔLVEF was negative in patients with three-vessel or left main coronary artery disease (-2.8 ± 5.1%) and significantly lower compared with all other angiographic groups (10.2 ± 5.1% and 6.2 ± 4.1%, respectively, for single-vessel and two-vessel disease). The negative value of ΔLVEF for three-vessel disease was due mainly to increased end-systolic volume at peak stress. Receiver operating characteristic curves demonstrated excellent accuracy of ΔLVEF compared with change in wall motion score index in identifying patients with multivessel disease, with areas under the curves of 0.96 and 0.62, respectively.

CONCLUSIONS

ΔLVEF is significantly lower in patients with severe coronary artery disease compared with those with single-vessel or two-vessel disease; reduced ΔLVEF identifies high-risk patients, who are likely to benefit from a more aggressive therapeutic strategy.

Abnormal shortened diastolic time length at increasing heart rates in patients with abnormal exercise-induced increase in pulmonary artery pressure

Background

The degree of pulmonary hypertension is not independently related to the severity of left ventricular systolic dysfunction but is frequently associated with diastolic filling abnormalities. The aim of this study was to assess diastolic times at increasing heart rates in normal and in patients with and without abnormal exercise-induced increase in pulmonary artery pressure (PASP). Methods. We enrolled 109 patients (78 males, age 62 ± 13 years) referred for exercise stress echocardiography and 16 controls. The PASP was derived from the tricuspid Doppler tracing. A cut-off value of PASP ≥ 50 mmHg at peak stress was considered as indicative of abnormal increase in PASP. Diastolic times and the diastolic/systolic time ratio were recorded by a precordial cutaneous force sensor based on a linear accelerometer.

Results

At baseline, PASP was 30 ± 5 mmHg in patients and 25 ± 4 in controls. At peak stress the PASP was normal in 95 patients (Group 1); 14 patients (Group 2) showed an abnormal increase in PASP (from 35 ± 4 to 62 ± 12 mmHg; P < 0.01). At 100 bpm, an abnormal (< 1) diastolic/systolic time ratio was found in 0/16 (0%) controls, in 12/93 (13%) Group 1 and 7/14 (50%) Group 2 patients (p < 0.05 between groups).

Conclusion

The first and second heart sound vibrations non-invasively monitored by a force sensor are useful for continuously assessing diastolic time during exercise. Exercise-induced abnormal PASP was associated with reduced diastolic time at heart rates beyond 100 beats per minute.

WEB downloadable software for training in cardiovascular hemodynamics in the (3-D) stress echo lab

When a physiological (exercise) stress echo is scheduled, interest focuses on wall motion segmental contraction abnormalities to diagnose ischemic response to stress, and on left ventricular ejection fraction to assess contractile reserve. Echocardiographic evaluation of volumes (plus standard assessment of heart rate and blood pressure) is ideally suited for the quantitative and accurate calculation of a set of parameters allowing a complete characterization of cardiovascular hemodynamics (including cardiac output and systemic vascular resistance), left ventricular elastance (mirroring left ventricular contractility, theoretically independent of preload and afterload changes heavily affecting the ejection fraction), arterial elastance, ventricular arterial coupling (a central determinant of net cardiovascular performance in normal and pathological conditions), and diastolic function (through the diastolic mean filling rate). All these parameters were previously inaccessible, inaccurate or labor-intensive and now become, at least in principle, available in the stress echocardiography laboratory since all of them need an accurate estimation of left ventricular volumes and stroke volume, easily derived from 3 D echo.

Aims of this paper are: 1) to propose a simple method to assess a set of parameters allowing a complete characterization of cardiovascular hemodynamics in the stress echo lab, from basic measurements to calculations 2) to propose a simple, web-based software program, to learn and training calculations as a phantom of the everyday activity in the busy stress echo lab 3) to show examples of software testing in a way that proves its value.

The informatics infrastructure is available on the web, linking to http://cctrainer.ifc.cnr.it

Assessing functional mitral regurgitation with exercise echocardiography: rationale and clinical applications

Secondary or functional mitral regurgitation (FMR) represents an increasing feature of mitral valve disease characterized by abnormal function of anatomically normal leaflets in the context of the impaired function of remodelled left ventricles. The anatomic and pathophysiological basis of FMR are briefly analyzed; in addition, the role of exercise echocardiography for the assessment of FMR is discussed in view of its relevance to clinical practice.

Post-exercise contractility, diastolic function, and pressure: operator-independent sensor-based intelligent monitoring for heart failure telemedicine

BACKGROUND

New sensors for intelligent remote monitoring of the heart should be developed. Recently, a cutaneous force-frequency relation recording system has been validated based on heart sound amplitude and timing variations at increasing heart rates.

AIM

To assess sensor-based post-exercise contractility, diastolic function and pressure in normal and diseased hearts as a model of a wireless telemedicine system.

METHODS

We enrolled 150 patients and 22 controls referred for exercise-stress echocardiography, age 55 +/- 18 years. The sensor was attached in the precordial region by an ECG electrode. Stress and recovery contractility were derived by first heart sound amplitude vibration changes; diastolic times were acquired continuously. Systemic pressure changes were quantitatively documented by second heart sound recording.

RESULTS

Interpretable sensor recordings were obtained in all patients (feasibility = 100%). Post-exercise contractility overshoot (defined as increase > 10% of recovery contractility vs exercise value) was more frequent in patients than controls (27% vs 8%, p < 0.05). At 100 bpm stress heart rate, systolic/diastolic time ratio (normal, < 1) was > 1 in 20 patients and in none of the controls (p < 0.01); at recovery systolic/diastolic ratio was > 1 in only 3 patients (p < 0.01 vs stress). Post-exercise reduced arterial pressure was sensed.

CONCLUSION

Post-exercise contractility, diastolic time and pressure changes can be continuously measured by a cutaneous sensor. Heart disease affects not only exercise systolic performance, but also post-exercise recovery, diastolic time intervals and blood pressure changes--in our study, all of these were monitored by a non-invasive wearable sensor.

Comparison of the effect of pressure loading on left ventricular size, systolic and diastolic function in canines with left ventricular dysfunction with preserved and reduced ejection fraction

Background

Decompensated heart failure may present with severe hypertension in patients with preserved (PreEF) or reduced left ventricular (LV) ejection fraction (RedEF) and is clinically indistinguishable. Previously, we demonstrated that arterial pressure elevation increases LV filling pressures in a canine model of chronic LV dysfunction with PreEF or RedEF. It is not clear whether any differences in hemodynamics, LV volume or performance, or diastolic function can be demonstrated between canines with PreEF or RedEF in response to arterial pressure elevation. We hypothesized that the LV systolic, diastolic, and hemodynamic response to pressure loading would be similar in RedEF or PreEF.

Methods

We studied 25 dogs with chronic LV dysfunction due to coronary microsphere embolization with RedEF (35 ± 4%) and 20 dogs with PreEF (50 ± 3%). Arterial pressure was increased with methoxamine infusion and hemodynamics and echo-Doppler parameters of LV size, function, transaortic and transmitral pulsed Doppler prior to and with methoxamine infusion was obtained.

Results

Though LV filling pressures were similar at baseline, LV size was larger (p < 0.01) and ejection fraction lower in dogs with RedEF (p < 0.001). With methoxamine, there were similar increases in LV size, LV pressures, and index of myocardial performance with the ejection fraction reduced similarly. Diastolic parameters demonstrated similar tau increases, E/A reduction, and diastolic filling shortening in RedEF and PreEF dogs. A similar extent of isovolumic contraction and relaxation times and index of myocardial performance prolongation occurred with pressure loading.

Conclusion

Pressure loading in a canine model of LV dysfunction with PreEF and RedEF resulted in similar degrees of LV dilatation, increased filling pressures, and increased index of myocardial performance.

Arterial pressure changes monitoring with a new precordial noninvasive sensor

Background

Recently, a cutaneous force-frequency relation recording system based on first heart sound amplitude vibrations has been validated. A further application is the assessment of Second Heart Sound (S2) amplitude variations at increasing heart rates. The aim of this study was to assess the relationship between second heart sound amplitude variations at increasing heart rates and hemodynamic changes.

Methods

The transcutaneous force sensor was positioned in the precordial region in 146 consecutive patients referred for exercise (n = 99), dipyridamole (n = 41), or pacing stress (n = 6). The curve of S2 peak amplitude variation as a function of heart rate was computed as the increment with respect to the resting value.

Results

A consistent S2 signal was obtained in all patients. Baseline S2 was 7.2 ± 3.3 mg, increasing to 12.7 ± 7.7 mg at peak stress. S2 percentage increase was + 133 ± 104% in the 99 exercise, + 2 ± 22% in the 41 dipyridamole, and + 31 ± 27% in the 6 pacing patients (p < 0.05). Significant determinants of S2 amplitude were blood pressure, heart rate, and cardiac index with best correlation (R = .57) for mean pressure.

Conclusion

S2 recording quantitatively documents systemic pressure changes.

Diastolic time - frequency relation in the stress echo lab: filling timing and flow at different heart rates

A cutaneous force-frequency relation recording system based on first heart sound amplitude vibrations has been recently validated. Second heart sound can be simultaneously recorded in order to quantify both systole and diastole duration.

AIMS

1- To assess the feasibility and extra-value of operator-independent, force sensor-based, diastolic time recording during stress.

METHODS

We enrolled 161 patients referred for stress echocardiography (exercise 115, dipyridamole 40, pacing 6 patients).The sensor was fastened in the precordial region by a standard ECG electrode. The acceleration signal was converted into digital and recorded together with ECG signal. Both systolic and diastolic times were acquired continuously during stress and were displayed by plotting times vs. heart rate. Diastolic filling rate was calculated as echo-measured mitral filling volume/sensor-monitored diastolic time.

RESULTS

Diastolic time decreased during stress more markedly than systolic time. At peak stress 62 of the 161 pts showed reversal of the systolic/diastolic ratio with the duration of systole longer than diastole. In the exercise group, at 100 bpm HR, systolic/diastolic time ratio was lower in the 17 controls (0.74 +/- 0.12) than in patients (0.86 +/- 0.10, p < 0.05 vs. controls). Diastolic filling rate increased from 101 +/- 36 (rest) to 219 +/- 92 ml/m2* s-1 at peak stress (p < 0.5 vs. rest).

CONCLUSION

Cardiological systolic and diastolic duration can be monitored during stress by using an acceleration force sensor. Simultaneous calculation of stroke volume allows monitoring diastolic filling rate.Stress-induced "systolic-diastolic mismatch" can be easily quantified and is associated to several cardiac diseases, possibly expanding the spectrum of information obtainable during stress.