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Cardiac cycle
About: Cardiac cycle is a research topic. Over the lifetime, 3290 publications have been published within this topic receiving 96159 citations.
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TL;DR: The result indicates that the myocardial oxygen consumption is predominantly determined by the total mechanical energy generated during systole, or the systolic pressure-volume area, independent of how thetotal mechanical energy is converted effectively to external mechanical work during the cardiac cycle.
Abstract: We have found that myocardial oxygen consumption is linearly correlated with the systolic pressure-volume area in the canine left ventricle. This pressure-volume area is a specific area in the pressure-volume diagram that is circumscribed by the end-systolic pressure-volume relation line, the end-diastolic pressure-volume relation curve, and the systolic segment of the pressure-volume trajectory. This area is equivalent to the total mechanical energy generated by ventricular contraction, consisting of the external mechanical work and the mechanical potential energy. In the present study, we specifically changed the course of the diastolic segment of the pressure-volume trajectory without changing the systolic segment of the pressure-volume trajectory and the systolic pressure-volume area. Although the fractions of external mechanical work and mechanical potential energy in the pressure-volume area were markedly changed, the simultaneously measured left ventricular oxygen consumption remained unchanged. This result indicates that the myocardial oxygen consumption is predominantly determined by the total mechanical energy generated during systole, or the systolic pressure-volume area, independent of how the total mechanical energy is converted effectively to external mechanical work during the cardiac cycle.
26 citations
TL;DR: The effect of acute digitalization on the cardiovascular dynamics in patients with complete heart block with a fixed ventricular rate and the effect of digitalized on the contribution of atrial systole to ventricular filling at a fixed Ventricular rate are described.
Abstract: THE hemodynamic consequences of acute digitalization in man have been reported in a few studies with controversial results. It has been stated that digitalis has little or no effect on the cardiovascular events in the absence of manifestations of heart failurel-' while it significantly improves cardiac function in the failing heart.'2 This paper describes the effect of acute digitalization on the cardiovascular dynamics in patients with complete heart block with a fixed ventricular rate and the effect of digitalization on the contribution of atrial systole to ventricular filling at a fixed ventricular rate.
26 citations
TL;DR: Evaluating the waveforms of left atrial area changes obtained by automated boundary detection with newly developed acoustic quantification technology suggests that automatic boundary detection may assist in serial non-invasive measurement ofleft atrial size to assess disease states and treatments.
Abstract: OBJECTIVE--To evaluate the waveforms of left atrial area changes obtained by automated boundary detection with newly developed acoustic quantification technology. DESIGN--All subjects had measurements of left atrial areas taken in the apical four chamber, parasternal long axis, and parasternal short axis views using both conventional echocardiographic methods and automatic boundary detection on two occasions separated by at least a week. On the second visit measurements were also repeated in healthy volunteers after acute intravenous volume loading with 1 litre of saline over 2-5 minutes. SETTING--A university medical school echocardiographic laboratory. SUBJECTS--12 healthy male volunteers and 8 patients with cardiac disease (5 with congestive heart failure, 1 with mitral stenosis, and 2 with hypertensive left ventricular hypertrophy, and dilated left atria). RESULTS--There was close correlation between conventionally derived left atrial areas and those obtained by automatic boundary detection, particularly in the apical four chamber view (r = 0.98). Both inter and intra observer variabilities (coefficient of variation) for left atrial areas measured by automatic boundary detection were good (4.7-14.2% and 8.1-18.6% respectively). The reproducibility (coefficient of variation) for derived indices of left atrial function, however, was much poorer (10.4-104.8% and 12.5-88% respectively). After acute volume loading significant increases in left atrial area were observed at all stages in the cardiac cycle. CONCLUSIONS--These data demonstrate that although the reproducibility of left atrial functional indices is poor, instantaneous left atrial cavity measurements with automatic boundary detection are reproducible. This suggests that automatic boundary detection may assist in serial non-invasive measurement of left atrial size to assess disease states and treatments.
26 citations
TL;DR: The results suggest that sustained ventricular tachycardia is frequently associated with stable reentrant pathways through areas of critically slow conduction, and specific, orderly and reproducible patterns were seen more often than chaotic “localized fibrillation.”
Abstract: Sustained ventricular tachycardia, consisting of a regular rhythm with 100 or more consecutive ectopic beats, was studied in 14 dogs anesthetized with sodium pentobarbital 4 days after occlusion of the left anterior descending coronary artery. Electrocardiograms were recorded as well as composite (epicardial) and electrode catheter (endocardial) electrograms from the area of infarction. Sustained ventricular tachycardia was induced by atrial or ventricular pacing, or both (180 to 360/min) in 3 of 21 untreated dogs and 11 of 19 dogs treated with methylprednisolone (30 mg/kg body weight, intravenously) given at the time of coronary occlusion. Sustained ventricular tachycardia with two or more QRS configurations occurred in nine dogs, and seven dogs showed both right and left bundle branch block patterns. Ventricular tachycardia was associated with continuous electrical activation in composite epicardial electrograms that bridged interectopic intervals and showed regular patterns of electrical activation that were reproducible with each cardiac cycle. Interectopic activation patterns were distinctive for each QRS pattern. In some instances portions of activation patterns for two different configurations were similar; however, the electrographic configuration immediately before the onset of the QRS complex always differed. During ventricular tachycardia, spontaneous alterations in QRS configuration were observed in two dogs and were induced by atrial or ventricular pacing in five dogs. In all cases changes in QRS configuration during sustained ventricular tachycardia were preceded by changes in diastolic activation patterns. The results suggest that sustained ventricular tachycardia is frequently associated with stable reentrant pathways through areas of critically slow conduction. In this experimental preparation, specific, orderly and reproducible patterns were seen more often than chaotic “localized fibrillation.” Different QRS configurations after changes in interectopic patterns of continuous electrical activation are consonant with changes in specific reentrant pathways through the region of slow conduction.
26 citations
TL;DR: Acute LPA angulation is associated with adverse haemodynamic performance and should be particularly addressed during the reconstruction of pulmonary artery in the repair of tetralogy of Fallot.
Abstract: OBJECTIVES: To study the effect of the angulation between the left pulmonary artery (LPA) and the main pulmonary artery on pulmonary haemodynamics METHODS: A 3D model of patient-specific pulmonary artery (PA) was reconstructed as an original model Four models with descendent LPA angulation equalled to 120°, 110°, 100° and 90°, were reconstructed by computer-aided design for the virtual simulation of the pulmonary flow under different surgical strategies Computational fluid dynamics was introduced to calculate the pulmonary blood flow in five models Streamlines, wall shear stress, energy loss and flow distribution ratio were calculated and compared to determine the better haemodynamics in the pulmonary artery RESULTS: Vortices were formed at the lower wall of the opening of right PA and LPA in models with LPA angles equal to or less than 100° (Models 3 and 4) Relative high wall shear stress areas at the lateral and lower wall of LPA opening had an ascendant tendency as the angle declined Decreased flow distribution ratio to left lung (original model: 058, Model 1: 063, Model 2: 0586, Model 3: 0564, Model 4: 055) and increased energy loss (original model: 3852 mV, Model 1: 2394 mV, Model 2: 3843 mV, Model 3: 4309 mV, Model 4: 4398 mV) in a cardiac cycle were noted as the angle reduced CONCLUSIONS: Acute LPA angulation is associated with adverse haemodynamic performance This should be particularly addressed during the reconstruction of pulmonary artery in the repair of tetralogy of Fallot
26 citations