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Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
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The paper evaluates the performance of an automatic adaptive time-frequency method to detect each cardiac cycle of a phonocardiogram (PCG) and extract average heart sounds and PCG cycles. The proposed method combines a global search of the PCG, in terms of the energy distribution of the most important components, with a local search relating to the specific events found within a cardiac cycle. The method is applied to 100 PCG recordings from 50 patients with an aortic bioprosthetic valve. The performance of the proposed method is compared with a commonly used semi-automatic method that is based on the combined analysis of an electrocardiogram (ECG) and the PCG signal. Results show that the proposed method clearly outperforms the semi-automatic method, especially in the case of patients with malfunctioning bioprostheses. By eliminating the need to record an ECG as the time-reference signal, this method reduces hardware overheads when analysis of PCG signals is the primary aim. It is also independent of subjective human judgment for selection of reference templates and threshold levels. Furthermore, the method is robust to artefacts, background noise and other kinds of signal interferences. With minor modifications, the procedure described could be applied to other types of biomedical signal in order to extract coherent transient components and identify specific events.
The cone-kernel distribution (CKD) is first applied to the analysis of the intracardiac and the thoracic first heart sound (S1) of dogs in various cardiac contractile states, and secondly to the S1 of patients with mitral mechanical prosthetic heart valves. The CKD of native S1 in dogs shows that the dominant components of S1 are generally concentrated in a band at around 50 Hz with a horizontal flat or a semi-lunar shape, independently of the myocardial contractile state. There is no significant systematic rising frequency component. The instantaneous frequency of S1 shows a good cross-correlation with the time derivative of the left ventricular pressure (dP/dt), but the maximum frequency is not proportional to the maximum of dP/dt. The CKD of S1 in patients with mitral mechanical prosthetic heart valves showed a pulse-like component with a high-frequency bandwidth, which is distinct from the low constant-frequency components of S1 produced by native heart valves.
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The vast majority of children with heart murmurs have an 'innocent' murmur. Differentiation of such murmurs from those due to structural cardiac disease, so called 'pathological' murmurs, is largely clinical. Pediatricians are capable of differentiating one from the other, provided a detailed evaluation is done. This article outlines the salient features of innocent murmurs that help us recognize them clinically.
We constructed and tested an inexpensive (less than $50) FM wireless, acoustically shielded, precordial radiostethoscope that enables the anesthetist to follow the heart tones and breath sounds of the patient regardless of the anesthetist's location in the operating room. We compared our acoustically shielded device with a similar, but acoustically unshielded, commercially available device. We found the sound quality of our radiostethoscope to be superior to that of the commercial device; the signal-to-noise ratio of our device was 7.6 for heart tones and 8.4 for breath sounds, whereas the commercial device had a signal-to-noise ratio of 2.7 and 3.9 for heart tones and breath sounds, respectively. Our device offers all of the advantages of a radiostethoscope and has the added advantages of low cost and high fidelity.
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A seven-month-old child with complex cyanotic heart disease desaturated dramatically following induction of anaesthesia. While a degree of hypoxaemia would have been acceptable in this infant, pulse oximetry detected an abrupt desaturation prompting the anaesthetist to consider other less common causes of cyanosis. This episode of desaturation subsided with the removal of a 12 french oesophageal stethoscope which had been inserted following induction. Further attempts to re-insert this oesophageal probe led to repeated episodes of desaturation. The most likely cause of this desaturation was a reduction in pulmonary blood flow due to compression by the oesophageal probe of an aorto-pulmonary collateral posterior to the oesophagus.
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