MSCT evaluation on dynamic changes of aortic annulus during cardiac cycle / 中国介入影像与治疗学

Objective: To explore the dynamism of aortic annulus (AA) during cardiac cycle and the correlation with calcification with MSCT. Methods A total of 69 aortic stenosis patients (AS group) and 69 controls (normal control group) underwent MSCT. Dimensions of AA were assessed on both systolic and diastolic phase. For each phase, the long diameter, short diameter, area and perimeter of AA were measured, respectively. The features of annular dimension change and the relationship with calcium score were analyzed. Finally, the differences of dynamic of AA in different calcification grades were compared. Results The mean annular dimensions were significantly larger during systole than diastole (all P0.05). In AS group, the perimeter-derived diameter (DP) of AA was significantly larger than the area-derived diameter (DA) in both systolic and diastolic phase (P<0.001). The change rate of AA area was significantly higher than change rate of perimeter (P<0.001) during cardiac cycle. There were negative correlation between the calcium score of AA and the change of DA and Dp (r=-0.264, -0.302, P<0.05). The dynamic of AA had significant difference among different calcification grades (P<0.05). Conclusion: The morphology and structure of AA significantly changed during cardiac cycle, and the dynamic change of AA with severe calcification significantly reduced. Systolic multiparameter measurement might provide accurate anatomical data for transcatheter aortic valve replacement.

Aortic lumen diameter changes during systolic and diastolic periods: evaluation with ECG-gated computed tomography / 中华普通外科杂志

Objective To characterize the changes in the dimensions during systolic and diastolic periods in the aorta with ECG-gated multi-detector CTA scans.Methods The CT angiograms of 115 patients (78 males,mean age 55.2 ± 9.4 years;37 females,mean age 60.1 ± 8.5 years) both in systolic and diastolic periods were obtained on a 64-slice ECG-gated multi-detector CT scanner.The diameters were measured at four anatomic levels of the aorta.(Level A:1 mm proximal to the innominate artery;Level B:1 mm distal to the left common carotid artery;Level C:1 mm distal to the left subclavian artery;Level D:10cm distal to the left subclavian artery).On each level,the maximal and the minimal diameters were measured both in systolic and diastolic periods.Results The paired sample t test results showed a significant difference between the systolic and diastolic diameters in all individual subjects on every level (P ＜0.001).The mean maximum diameter changes were 1.95％ (range-2.0％ to 7.0％),2.12％ (range-3.0％ to 6.0％),1.88％(range-1.0％ to 8.0％)and2.47％(range-3.0％ to 10.0％)at level A,B,C and D,respectively.The mean minimum diameter changes were 1.43％ (range-3.0％ to 5.0％),2.67％ (range-2.0％ to 11.0％),1.75％ (range-14.0％ to 9.0％)and 2.99％ (range -2.0％ to 11.0％) at level A,B,C and D,respectively.Conclusions The differences of the aortic diameters between systolic and diastolic periods are significant.The pulsatility of aorta in Chinese population may be different from published Western literature.

Intraoperative management of critical arrhythmia / 대한마취과학회지

The incidence of intraoperative arrhythmia is extremely high, and some arrhythmias require clinical attention. Therefore, it is essential for the anesthesiologist to evaluate risk factors for arrhythmia and understand their etiology, electrophysiology, diagnosis, and treatment. Anesthetic agents reportedly affect normal cardiac electrical activity. In the normal cardiac cycle, the sinoatrial node initiates cardiac electrical activity through intrinsic autonomous pacemaker activity. Sequential atrial and ventricular contractions result in an effective cardiac pumping mechanism. Arrhythmia occurs due to various causes, and the cardiac pumping mechanism may be affected. A severe case may result in hemodynamic instability. In this situation, the anesthesiologist should eliminate the possible causes of arrhythmia and manage the condition, creating hemodynamic stability under proper electrocardiographic monitoring.

Numerical analysis of unsteady blood flow model of fluid-solid interaction in carotid artery / 介入放射学杂志

Objective To study the distribution of hemodynamics in carotid artery under the fluid-solid interaction at the typical point of time during a single cardiac cycle, and to explore the mechanism of the formation and development of carotid atherosclerotic plaque. Methods Numerical analysis the blood flow characteristics within a cardiac cycle in carotid artery was analyzed by using computational method of fluid dynamics. Based on the hemodynamic parameters, the influences of the cardiac systole and diastole on the blood flow distribution were analyzed. Results The distribution of blood flow in the carotid artery within a typical cardiac cycle was obtained. Compared with the findings in cardiac diastole, a larger area of blood stasis at the entrance of external carotid artery was observed. In this area, the flow velocity, the wall pressure and the wall shear stress were all lower, while the arterial wall deformation and von Mises equivalent stress were larger. Conclusion Under fluid-solid interaction, the low blood flow in carotid artery causes blood reflux, resulting in the deposition of lipid, fiber and other large molecular materials. The low wall pressure produced“negative pressure” effect, thus the normal blood flow is changed, the flow velocity becomes slow, and the blood supply of the brain becomes insufficient. The low wall shear stress destroys the blood flow near the wall, causing the increase of platelet activity and intimal hyperplasia. The larger arterial wall deformation variable and von Mises equivalent stress can cause stress concentration and increase vascular rupture risk.

Systolic and Diastolic Ratio and Rate Pressure Product in Anemia.

Anemia, a common clinical entity is associated with hyperdynamic circulation and may be involved in etiopathology of heart failure. So, the current study was carried out in 30 patients in the age group 20-40 years with hemoglobin level < 6 g/dl and of at least three month duration of anemia (using WHO definition) and compared with 30 age- and sex-matched healthy subjects. Duration of systole and diastole was estimated by recording of electrocardiogram, apex-cardiogram and phonocardiogram on polyrite with the paper speed of 50 mm/sec. Duration of cardiac cycle was reduced (18.22%) and heart rate was increased (p < 0.001) in anemia compared to controls. On comparison of duration of systole and diastole, there was more decrement in diastole (26.76%, p < 0.001) compare to systole (6.45%, p < 0.01) in anemia versus healthy subjects. Similarly, when fraction occupied by systole and diastole in cardiac cycle were compared, the systolic fraction was increased, diastolic fraction in cardiac cycle was reduced and systole/diastole ratio was increased (p < 0.001) in anemics compared to controls. Rate pressure product and double product were elevated (p < 0.001) in anemia versus controls, imposing mechanical load on heart. So, it is concluded that patients of severe anemia are at the brink of heart failure and should be treated promptly.

Study on Regulation of ECG Cycle Fluctuation / 航天医学与医学工程

Objective To investigate the regulation of fluctuation of beat to beat cardiac cycle.Methods A cardio-electric cycle consists of cardio-electric activity called P-T interval and cardio-electric resting TP segment,P-R interval and Q-T interval constitute P-T interval.The cardiac cycles fluctuate along with the time span fluctuation of sub waves and segments.This paper firstly extracted sub waves and segments based on signal processing methods,then discussed the contribution ratio of all waves and segments toward cardiac cycle fluctuation according to statistics.Results Experimental results indicated that the cardiac cycle fluctuation was mainly consistent with the change of TP segment.The P-T interval varied consistently with P-R interval foremost.Conclusion It is revealed that rule of cardiac cycle fluctuation is very useful for further research to figure out the cardiac function and mechanism.

Recovery of respiratory cardiac cycle variability after strenuous exercise / 体力科学

A study was conducted to examine the recovery of vagal activity after strenuous exercise based on changes in the magnitude of respiratory cardiac cycle variability, changes in the phase of this variability and the mechanism of the change. Six healthy male university students were studied for 5 h after exhaustive treadmill running. For cardiac cycle (RR) and blood pressure, the magnitude of respiratory variability and phase difference between respira-tory variability and respiration were measured. Respiratory period and tidal volume were maintained at 6 s and 21, respectively.<BR>1. The amplitude of respiratory RR variability decreased markedly after exercise and returned almost to normal after 2 h of recrvery. The phase of RR delayed with exercise, proceeded rapidly 2 h after exercise and progressively after that.<BR>2. The amplitude and phase of respiratory systolic blood pressure variability were almost stable before and after exercise.<BR>Based on these results, we conclude that vagal activity inhibited by strenuous exercise recovers about 2 h after the end of exercise. The delay in the phase of respiratory cardiac cycle variability with exercise may reflect inhibition of vagal activity.

Relationship between respiratory period and respiratory cardiac cycle variability. The influence of respiratory blood pressure variability / 体力科学

This study was undertaken to clarify the influence of respiratory blood pressure variability upon the relationship between respiratory period and respiratory cardiac cycle variability. In 4 healthy male university students respiratory period was varied over the range of 6-20 sec while tidal volume was maintained constant (21) and in 5 other male students tidal volume was varied over the range of 1.0-2.5<I>l</I> while respiratory period was maintained constant (6 sec) . For cardiac cycle (RR) and systolic and diastolic blood pressure (SBP and DBP), amplitude of respiratory variability and phase difference between respiratory variability and respiration were measured.<BR>1. Patterns of change of amplitude of RR and of SBP were similar when respiratory period was changed.<BR>2. When respiratory period was short (6sec), RR was nearly in phase with SBP. However, as respiratory period increased, the phases of RR and SBP had a tendency to proceed, with the tendency being more pronounced in the latter. Thus, when respiratory period was prolonged (20 sec), SBP led RR.<BR>3. Phase relationship between respiratory SBP variability and respiration did not change when tidal volume was changed.<BR>4. Respiratory DBP variability became more marked as respiratory period increased, and showed more marked phase shift than did respiratory SBP variability. Therefore, of those parameters DBP occurred earlier.<BR>Based on these results, it is concluded that respiratory RR variability is closely related to respiratory SBP variability when respiratory period is changed, but that the phase difference between RR and SBP reflects the effect of pulmonary stretch reflex which is dependent on respiratory period.

Relationship between respiratory period and respiratory arrhythmia / 体力科学

This study was undertaken to clarify the relationship between respiratory period and respiratory arrhythmia. Five healthy male university students voluntarily changed the respiratory period over a range of 3-30 seconds while maintaining tidal volume constant (; 21) . Maximum and minimum cardiac cycles (RRmax and RRmin) and amplitude of cardiac cycle variability (ΔRR), the difference between RRmax and RRmin, were measured from electrocardiogram and respiratory curve.<BR>1. Amplitude of cardiac cycle variability was small for shorter respiratory periods and increased with respiratory period, attaining maximum at respiratory periods of 8-14 seconds followed by decrease at longer respiratory periods.<BR>2. The time from the onset of inspiration to the minimum cardiac cycle was the same for respiratory periods of 8-14 seconds (about 3.6 seconds) .<BR>3. Phase difference between cardiac cycle variability and respiration was determined at each respiratory period. When the minimum or maximum cardiac cycle coincided with the onset of inspiration, this situation being defined as 0°, RRmin was delayed by 180°, 90°, and 0° at respiratory periods of 2.3, 14.4, and 26.5 seconds, respectively and by 360°, 270°, and 180° at respiratory periods of 2.7, 15.0, and 27.3 seconds, respectively.<BR>Based on these results, respiratory arrhythmia is concluded to be quite stable at respiratory periods of 8-14 seconds. At short respiratory periods, tachycardia was found to occur during inspiration and bradycardia during expiration. During long respiratory periods, bradycardia was noted during inspiration and tachycardia during expiration.