Cardiac cycle

About: Cardiac cycle is a research topic. Over the lifetime, 3290 publications have been published within this topic receiving 96159 citations.

Three-dimensional reconstruction of cardiac displacement patterns on the chest wall during the P, QRS and T-segments of the ECG by laser speckle inteferometry

Abstract: A noninvasive and noncontact technique based on the principle of laser speckle interferometry has been developed to record the cardiac displacements observed on the chest wall. These displacements are then reconstructed in the form of three-dimensional plots, during the P, QRS and T-waves of the ECG. A comparison of these patterns shows that the mechanical activity of each region varies significantly during these phases of cardiac cycle. As these displacements depend on the clinical status of the heart, its use with a cardiac patient shows the functional changes of the affected regions in the form of alteration of these patterns.

Functional anatomy of the heart of reptiles.

Abstract: Intravascular pressures, distributions of blood oxygen, dye-dilution curves, cineradiography, and electromagnetic flowmeters in major vessels suggest a highly directional flow oE systemic and pulmonary venous blood through reptilian hearts. The lacertilian right aortic arch contains blood from the pulmonary, and the left from the pulmonary or sometimes both pulmonary and systemic veins. Traces made of the pressure and blood flow show that the lacertilian and chelonian cava venosum and pulmonale are functionally distinct. Atrioventricular valves probably prevent regurgitation during ventricular systole and form an obstruction between the cava arteriosum and venosum during ventricular filling. The muscular ridge approaches the ventral ventricular wall at systole forming a functional ventricular septum. Low pulmonary vascular resistance favors pulmonary ejection before systemic. In Pseudemys the balance between pulmonary and systemic resistance causes a left-to-right shunt during respiration and a right-to-left shunt during diving; the latter probably reduces the expenditure of cardiac energy during hypoxia. Pressure traces and cineradiography indicate separation of systemic and pulmonary venous returns in alligators. The left ventricle perfuses both aortic arches and the right the pulmonary arch. Right ventricular pressure may exceed pulmonary pressure during ejection suggesting an impedance in the pulmonary outflow tract. Pulmonary resistance in crocodilians may increase during diving, instituting a right-to-left shunt.

Improving diagnostic accuracy of MDCT coronary angiography in patients with mild heart rhythm irregularities using ECG editing.

Abstract: OBJECTIVE. The objective of our study was to compare diagnostic accuracy of MDCT coronary angiography in a population of patients with mild heart rhythm irregularities before and after editing the ECG.SUBJECTS AND METHODS. Thirty-eight patients who underwent MDCT coronary angiography and conventional coronary angiography were enrolled in the study. The inclusion criterion was the presence of mild heart rhythm irregularities (i.e., premature beats; atrial fibrillation; mistriggering; or low heart rate, defined as 40 beats per minute or less) during the scan. All patients underwent MDCT with the following parameters: 16 detectors; collimation, 0.75 mm; gantry rotation time, 375 msec; 120 kV; and effective milliampere-second setting, 500–600. Images were reconstructed in two settings: before ECG editing and after ECG editing (i.e., arbitrary modification of temporal windows within the cardiac cycle at the site of mild heart rhythm irregularities). Data sets were scored for the presence of significant stenose...

Blood flow in pulmonary veins: II. The influence of events transmitted from the right and left sides of the heart.

Abstract: The wave form of blood flow in the large extra parenchymal pulmonary veins has an inverse relationship to the pressure wave form in the left atrium during each cardiac cycle. However, when vein flow from the lungs is separated from the left atrium by diverting it into a constant pressure reservoir, its wave form then resembles a lung capillary flow pulse, though delayed from it in time and reduced in amplitude. The pulsatility of flow in pulmonary veins separated from the left atrium is further reduced when transcapillary pressure is elevated by lung inflation. However, in the intact state, the relation between the pattern of pulmonary vein flow and left atrial pressure remains unaffected by lung inflation. It is postulated that the thin walled extraparenchymal pulmonary veins together behave as a collapsible reservoir which enables outflow from them to be determined by changes in left atrial pressure, in spite of variations of pulsatile flow into them from the lungs.

Sound Pressure Correlates of the Second Heart Sound: An Intracardiac Sound Study

Abstract: The sound pressure correlates of the second heart sound were studied in 22 patients during diagnostic cardiac catheterization. Simultaneous right ventricular and pulmonary artery pressures were recorded with equisensitive catheter-tip micromanometers together with the external phonocardiogram and ECG. In 12 patients having normal pulmonary vascular resistance (group 1), pulmonic closure sound was coincident with the incisura of the pulmonary artery pressure curve which in turn was separated from the right ventricular pressure trace by an interval denoted hangout. The duration of this interval varied (33-89 msec), was independent of pulmonary artery pressure or resistance and was felt to be primarily a reflection of the capacitance of the pulmonary vascular tree. The absolute value of this interval during inspiration was very similar to the splitting interval and, when subtracted from the Q-P 2 interval, the remaining interval (QRV) was almost identical to the Q-A 2 interval, indicating that the actual duration of right and left ventricular systole is nearly equal. Awareness of the existence of the hangout interval and its hemodynamic determinants offers a reasonable mechanism to explain the audible expiratory splitting of the second heart sound found in patients with idiopathic dilatation of the pulmonary artery following atrial septal defect repair and in one additional patient studied with mild valvular pulmonic stenosis. In nine patients with elevated pulmonary vascular resistance approaching systemic levels (group 2), the absolute value of the hangout interval was markedly reduced (15-28 msec) consistent with the decrease in capacitance of the pulmonary vascular bed and the increased pulmonary vascular resistance known to occur in pulmonary hypertension. In those patients where the duration of right and left ventricular systole were nearly equal, narrow splitting of the second heart sound was present. In those patients where selective prolongation of right ventricular systole occurred, the narrow hangout interval persisted, but the splitting interval was prolonged proportionate to the increased duration of right ventricular systole.