Cardiac cycle

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

Cardiac motion of coronary arteries: variability in the rest period and implications for coronary MR angiography.

Abstract: PURPOSE: To measure the duration of the rest period in the cardiac cycle, a parameter vital to data acquisition in coronary magnetic resonance (MR) angiography. MATERIALS AND METHODS: Motion of coronary arteries was measured in 13 patients by using breath-hold, biplane, conventional angiography, with frontal and lateral projections of the left and right coronary arteries acquired at 30 frames per second. The time courses of the coordinates of bifurcations of proximal parts of the coronary arteries were measured, from which the rest period (motion < 1 mm in orthogonal axes), velocity, displacement range, motion correlation, and reproducibility from heartbeat to heartbeat were estimated. RESULTS: Both the motion pattern and the amplitude varied substantially from patient to patient. The rest period varied from 66 to 333 msec (mean, 161 msec) for the left coronary artery and from 66 to 200 msec (mean, 120 msec) for the right coronary artery. CONCLUSION: The rest period for coronary arteries in the cardiac cy...

Non-invasive assessment of the atrial cycle length during atrial fibrillation in man: introducing, validating and illustrating a new ECG method

Abstract: Objectives: Atrial fibrillation (AF) in man has previously been shown to include a wide variety of atrial activity. Assessment of the characteristics of this arrhythmia with a commonly applicable tool may therefore be important in the choice and evaluation of different therapeutic strategies. As the AF cycle length has been shown to correlate locally with atrial refractoriness and globally with the degree of atrial organization, with, in general, shorter cycle length during apparently random AF compared to more organized AF, we have developed a new method for non-invasive assessment of the AF cycle length using the surface and the esophagus (ESO) ECG. Methods and Results: From the frequency spectrum of the residual ECG, created by suppression of the QRST complexes, the dominant atrial cycle length (DACL) was derived. By comparison with multiple intracardiac simultaneously acquired right and left AF cycle lengths in patients with paroxysmal AF, we found that the DACL in lead V1, ranging from 130 to 185 ms, well represented a spatial average of the right AF cycle lengths, whereas the DACL in the ESO ECG, ranging from 140 to 185 ms, reflected both the right and the left AF cycle length, where the influence from each structure depended on the atrial anatomy of the individual, as determined by MRI. In patients with chronic AF, the method was capable of following changes in the AF cycle length due to administration of d,l-sotalol and 5 min of ECG recording was sufficient for the DACL to be reproducible. Conclusions: We conclude that this new non-invasive method, named ‘Frequency Analysis of Fibrillatory ECG’ (FAF-ECG), is capable of assessing both the magnitude and the dynamics of the atrial fibrillation cycle length in man.

Myocardial elastography—a feasibility study in vivo

Abstract: Early detection of cardiovascular diseases has been a very active research area in the medical imaging field. Assessment of the local and global mechanical functions is one of the major goals of accurate diagnosis. In this study, we investigated the feasibility of elastography for estimation and imaging of the local cardiac muscle displacement and strain in a human heart in vivo. In its noninvasive applications, elastography has been typically used to determine local tissue strain through the use of externally applied compression. For our study, we utilized the cardiac muscle motion during a cardiac cycle as the mechanical stimulus, and acquired successive radiofrequency (RF) data frames of the septal and posterior walls over a few cardiac cycles in parasternal and apical views, respectively. High-quality cine-loop elastograms were obtained due to high frame rates and the resulting low decorrelation noise. Furthermore, the strain contrast was higher in the parasternal case, when only the posterior wall was imaged, and strain estimation was more robust in the apical view. High repeatability of the results was observed through elastographic measurements over several cardiac cycles. Finally, an M-mode version of elastography was used to follow part of the interventricular septum or the posterior wall over the course of two cardiac cycles. Not only do these preliminary results show that elastography is feasible in cardiac applications in vivo, but also that it can provide new information regarding cardiac motion and mechanical function. Future prospects include assessment of the role of elastography in detection of ischemia and infarction.

Studies on Cardiac Dimensions in Intact, Unanesthetized Man

Abstract: A method is described which permits measurement of relative changes in the external dimensions of individual cardiac chambers throughout the cardiac cycle in intact, unanesthetized man. It consists of suturing multiple radiopaque silver-tantalum clips to the surface of the heart at the time of cardiac operations. In the postoperative period, cine-radiograms are obtained and the distances between clips are measured on each individual frame. This technique has been found to be safe and has been employed in 68 patients without any complications. As a result of studies in eight patients utilizing biplane serial exposures, the effects of rotation of the heart in the sagittal plane during the cardiac and respiratory cycles were determined precisely. If clips were properly placed on the heart, the possible errors resulting from such rotation were found to be quite small. During inspiration right ventricular dimensions increased, while the opposite occurred during expiration and during the Valsalva maneuver. Left...