Search

The aim of the present work is to establish a protocol for monitoring the cardiac activity measuring the skin surface vibrations of the main neck vessels, caused by vascular wall motion in carotid artery. The method is based on the optical recording of the movements of the neck by means of laser Doppler interferometry. The ECG signal and the velocity of vibration of the skin in correspondence of the carotid artery (named optical vibrocardiography: VCG) have been simultaneously recorded on five healthy subjects. Standard heart rate variability tests have been carried out. The capability of VCG signals to be used as a surrogate of the ECG in assessing both cardiac rate and heart rate variability (HRV) has been tested using time and spectral descriptors, and specific statistical analysis. Mean differences have been found lower than 3.13%. Optical vibrocardiography might be a simple approach to the clinical practice of cardiovascular screening, in particular in harsh environment, such as MR clinical practice, where ECG recordings are corrupted by artefacts and ECG cables might represent an hazard for the patients.

In the present work we use a compact and low-cost laser sensor based on self-mixing effect for non-invasive non-contact analysis of heart beat, by measuring the vibrations of the skin surface caused by vascular wall motion in carotid, radial and dorsal pedal arteries. The electrocardiography (ECG) and optical vibrocardiography (VCG) signals are simultaneously acquired and analyzed. VCG can be exploited for testing medical parameters beyond the heart rate, such as artery deformation, vessel elasticity and blood pulse characteristics.

Laser Doppler vibrometry has been recently applied for non-contact monitoring of the cardiac activity, both in terms of cardiac rate and heart rate variability, measuring the velocity of the skin surface of the chest wall and the neck (optical Vibrocardiography, VCG). To go further insight in the analysis of VCG recordings, in this study authors have compared heart sounds by digital Phonocardiography (PCG) with the motion of the skin on the chest wall by optical VCG, the final aim being the identification of some events of cardiac mechanics in the VCG signals. PCG and VCG traces were synchronously recorded on 10 healthy subjects, along with ECG. To reach this goal, multiresolution analysis together with Hilbert transforms for envelope calculation on PCG and VCG have been applied, temporal and morphological features were extracted from the signals. Data collection and signal processing allowed us to identify some events of cardiac mechanics, correlating the heart sounds relative to the closure of the mitral valve, and the following closure of the aortic and pulmonary valve with characteristic deflections identifiable on VCG traces.

We present an optical non-contact method for heart beat monitoring, based on the measurement of chest wall movements induced by the pumping action of the heart, which is eligible as a surrogate of electrocardiogram (ECG) in assessing both cardiac rate and heart rate variability (HRV). The method is based on the optical recording of the movements of the chest wall by means of laser Doppler interferometry. To this aim, the ECG signal and the velocity of vibration of the chest wall, named optical vibrocardiography (VCG), were simultaneously recorded on 10 subjects. The time series built from the sequences of consecutive R waves (on ECG) and vibrocardiographic (VV) intervals were compared in terms of heart rate (HR). To evaluate the ability of VCG signals as quantitative marker of the autonomic activity, HRV descriptors were also calculated on both ECG and VCG time series. HR and HRV indices obtained from the proposed method agreed with the rate derived from ECG recordings (mean percent difference

1. Precordial low-frequency vibrocardiograms were studied in 32 patients with aortic insufficiency.2. Each deflection of the apical tracing had a definite correlation with the clinical status of the left ventricular overloading. With the severity of the disease an atrial upstroke increased, an ejection downstroke decreased and a mid-systolic abnormal outward movement (bulge) appeared or increased. Grades of apex beat had also a correlative relationship with the functional status of this disease.3. The difference of apical tracing between our record and another report in aortic insufficiency was discussed and demonstrated.4. The atrial deflection of the cases with Austin Flint murmur would supply interesting data, compared with mitral stenosis.

This book originates from a course on phonographic and mechanographic methods in cardiology (1973). Discussions among the faculty, self-assessment exercises and other "noninvasive" procedures are also included. The criteria adopted in the choice of these techniques are not explained. For instance, as noted by Luisada, the kymographic methods (radarkymography), are not even mentioned; yet contrast cardiography and echocardiography focus in part on motion of limited segments of the endocardial surface. "Vibrocardiography" comprises a broad enough and wellcircumscribed area: it would have been better to limit the content of this text to vibrographic methods. These methods are not new. Much is new, however, in knowledge and in techniques; also, the need for objectivity is unquestionable. There is good reason then for offering to nonspecialists an opportunity for learning and training. I doubt however that a faculty of strict specialists— frequently committed investigators— is the best vehicle for this purpose; even more