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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 results suggest that “inotropy‐sensing” via measurement of intracardiac impedance is highly accurate and seems to be a promising sensor principle for physiological rate adaptation in a closed‐loop pacing system.
Abstract: OSSWALD, S., et al.: Closed-Loop Stimulation Using Intracardiac Impedance as a Sensor Principle: Correlation of Right Ventricular dP/dtmax and Intracardiac Impedance During Dobutamine Stress Test. Changes of the unipolar right ventricular impedance during the cardiac cycle are related to the changing content of blood (low impedance) and tissue (high impedance) around the tip of the pacing electrode. During myocardial contraction, the impedance continuously increases reaching its maximum in late systole. This impedance increase is thought to correlate with right ventricular contractility, and thus, with the inotropic state of the heart. In the new Inos2 DDDR pacemaker, integrated information from the changing ventricular impedance (VIMP) is used for closed-loop regulation of the rate response. The aim of this study was to analyze the effect of increasing dobutamine challenge on RV contractility and the measured impedance signals. In 12 patients (10 men, 68 ± 12 years) undergoing implantation of an Inos2 DDDR pacemaker (Biotronik), a right ventricular pigtail catheter was inserted for continuous measurements of RV-dP/dtmax and simultaneous VIMP signals during intrinsic and ventricular paced rhythm. Then, a stress test with a stepwise increase of intravenous dobutamine (5–20 μg/kg per min) was performed. To assess the relationship between RV contractility and measured sensor signals, normalized values of dP/dtmax and VIMP were compared by linear regression. There was a strong and highly significant correlation between dP/dtmax and VIMP for ventricular paced (r2= 0.93) and intrinsic rhythm (r2= 0.92), although the morphologies of the original impedance curves differed quite substantially between paced and intrinsic rhythm in the same patient. Furthermore, VIMP correlated well with sinus rate (r2= 0.82), although there were at least four patients with documented chronotropic incompetence. We conclude, that for intrinsic and ventricular paced rhythms sensor signals derived from right ventricular unipolar impedance curves closely correlate with dP/dtmax, and thus, with a surrogate of right ventricular contractility during dobutamine stress testing. Our results suggest that “inotropy-sensing” via measurement of intracardiac impedance is highly accurate and seems to be a promising sensor principle for physiological rate adaptation in a closed-loop pacing system.

89 citations

Journal ArticleDOI
TL;DR: The goals of this study were to establish normal values for these measurements and to study the changes with minimal diastolic dysfunction, and to add information about the physiology and pathophysiology of diastole.
Abstract: Objectives: The pixel velocity values obtained by color Doppler tissue imaging (DTI) can be processed to velocity gradients as a measure of longitudinal strain rate with a technique termed strain rate imaging (SRI). Color mapping of strain rate does show the spatial-temporal relations of the diastolic phases. The phases of early filling and late filling during atrial systole can be seen to consist of a stretch wave in the myocardium, propagating from the base to the apex. Diastolic function is characterized by both peak strain rate and propagation velocity of this wave. The goals of this study were to establish normal values for these measurements and to study the changes with minimal diastolic dysfunction. Methods: Twenty-eight healthy control subjects and 26 patients with hypertension and normal systolic function were studied. The patients had normal blood pressure on treatment, normal ejection fraction, minimal hypertrophy, and moderately prolonged deceleration and isovolumic relaxation times. Real-time SRI color cineloops, ordinary echocardiography and Doppler recordings, and pulsed wave DTI from the mitral ring were acquired and processed. Results: Patients showed a reduction of systolic and early diastolic tissue velocities and strain rates and no significant increase in late diastolic tissue velocity and strain rate. Propagation velocity of diastolic strain during both early and late filling phases was reduced in the patients. The combination of changes in peak strain rate and propagation velocity of strain rate corresponded with changes in DTI. Conclusion: Diastolic deformation of the ventricle can be shown as a complex series of events, with temporal sequences in the ventricle. The peak strain rate and the propagation velocities of strain rate can describe the two main diastolic events: early and late filling. In reduced diastolic function, both are reduced during early filling. The velocities of the mitral ring are the result of this combination. This adds information about the physiology and pathophysiology of diastole. (J Am Soc Echocardiogr 2001;14:264-74.)

89 citations

Journal ArticleDOI
TL;DR: It is established that longitudinal movement of IVUS transducers within coronary vessels occurs during the cardiac cycle, and IVUS images are best obtained with electrocardiographic gating.

89 citations

Journal ArticleDOI
TL;DR: This study demonstrated a significant individual dynamic change in the dimensions of the aortic root, independent of gender, age, height and weight, which is highly unpredictable.
Abstract: Cardiac pulsatility and aortic compliance may result in aortic area and diameter changes throughout the cardiac cycle in the entire aorta. Until this moment these dynamic changes could never be established in the aortic root (aortic annulus, sinuses of Valsalva and sinotubular junction). The aim of this study was to visualize and characterize the changes in aortic root dimensions during systole and diastole with ECG-gated multidetector row computed tomography (MDCT). MDCT scans of subjects without aortic root disease were analyzed. Retrospectively, ECG-gated reconstructions at each 10% of the cardiac cycle were made and analyzed during systole (30–40%) and diastole (70–75%). Axial planes were reconstructed at three different levels of the aortic root. At each level the maximal and its perpendicular luminal dimension were measured. The mean dimensions of the total study group (n = 108, mean age 56 ± 13 years) do not show any significant difference between systole and diastole. The individual dimensions vary up to 5 mm. However, the differences range between minus 5 mm (diastolic dimension is greater than systolic dimensions) and 5 mm (vice versa). This variability is independent of gender, age, height and weight. This study demonstrated a significant individual dynamic change in the dimensions of the aortic root. These results are highly unpredictable. Most of the healthy subjects have larger systolic dimensions, however, some do have larger diastolic dimensions.

89 citations

Journal ArticleDOI
TL;DR: It is concluded that MR velocity mapping can enable noninvasive measurement of coronary venous outflow and global left ventricular perfusion and may become clinically useful in assessment of coronary blood flow reserve.
Abstract: Velocity and volumetric flow of left ventricular venous outflow in the distal coronary sinus were measured with magnetic resonance (MR) velocity mapping techniques in 24 healthy men A total of 16-21 velocity maps were acquired throughout the cardiac cycle To determine the accuracy of the MR velocity-mapping pulse sequence, measurements were obtained with a flow phantom Mean blood flow was 144 mL/min +/- 62 (standard deviation); mean velocity, 21 cm/sec +/- 10; and mean cross-sectional area, 12 cm2 Phasic measurements revealed a biphasic flow pattern in the coronary sinus, with a first peak in systole (257 mL/min +/- 174) and a second peak in early diastole (1,090 mL/min +/- 487) The cross-sectional area varied between 05 cm2 +/- 02 at end diastole and 19 cm2 +/- 06 in systole, a finding that suggests a capacitance function for venous outflow Mean blood flow measurements were in agreement with measurements obtained invasively in previous studies It is concluded that MR velocity mapping can enable noninvasive measurement of coronary venous outflow and global left ventricular perfusion and may become clinically useful in assessment of coronary blood flow reserve

89 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202377
2022178
202169
202068
201979
201876