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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: A technique to image CS caliber over the duration of the cardiac cycle is developed and the echo visualization of CS‐related structures, such as tributary veins and the Thebesian valve, are demonstrated.
Abstract: The coronary sinus (CS) can be imaged echocardiographically as a small tubular sonolucency in the posterior atrioventricular groove. To date, its importance to echocardiographers has been that CS dilatation usually signifies a persistent left superior vena cava. Recently, we developed a technique to image CS caliber over the duration of the cardiac cycle. CS contraction accompanies the P wave on the electrocardiogram, in sinus rhythm or in various arrhythmias. CS contraction is always absent in atrial fibrillation. In sinus rhythm, CS contraction may be attenuated or absent if congestive heart failure, with marked venous congestion, is present. Thus, this attenuation is a potentially valuable echocardiographic sign of elevated central venous pressure. We demonstrate the echo visualization of CS-related structures, such as tributary veins and the Thebesian valve. The potentially useful concept of the CS as a "miniventricle" is discussed. CS blood flow can be recorded by interrogation in the right heart inflow view. The pattern of CS antegrade flow and the exceptional situation of retrograde systolic CS flow from a posteriorly directed tricuspid regurgitant jet are demonstrated.

27 citations

Journal ArticleDOI
Jörg Blobel1, H Baartman, P. Rogalla, Jürgen Mews, Alexander Lembcke 
TL;DR: In this article, the authors used a linear trend function to estimate the blurring of the imaged coronary arteries, independent of the actual heart rate, with respect to the R-R interval.
Abstract: The use of the CT scanner for cardiac imaging is mainly influenced by the spatial and temporal resolution that can be achieved with the applied technologies and procedures. The data acquisition with 16 x 0.5 mm scan slice thickness and a special multisegment image reconstruction procedure are a new combination for accurate imaging of the cardiac morphology. A 0.5 mm slice thickness and an overlapping pitch < 0.35 generate an isotropic image voxel of 0.35 x 0.35 x 0.35 mm. The object size of a coronary artery with a diameter of 2.5 mm amounts to a relative spatial blurring factor K (d) of approximately 15 %. The segment reconstruction with 4 segments from 4 consecutive cardiac cycles requires the optimum acquisition time of 50 ms for one frame. The relative exposure factor K (t) with reference to the R-R interval is an appropriate measure to validate the influence of coronary artery movement on the image quality at different heart rates. This relative exposure varies between 10 % and 20 % for a heart rate of 40 to 140 beats per minutes (bpm) and its mean is approximated by a linear trend function with K (t) = 14 %. A constant value in this linear trend function means a constant "blurring" of the imaged coronary arteries, independent of the actual heart rate. Thus, computed tomographic examinations can be carried out for heart rates between 40 and 140 bpm without using beta-blocking medication. Case studies of the 3D reconstruction and curved reformatting of coronary arteries with stents and calcifications show the achievable image quality at different heart rates.

27 citations

Journal ArticleDOI
TL;DR: Results of the present study indicate that decrease or absence of reversed atrial flow and decrease in the first phase of ventricular flow were noticeable in patients in Groups 2, 3, and 4, and the second phase of pulmonary venous flow was significantly decreased in patients with mitral obstruction.
Abstract: The factors affecting pulmonary venous flow were studied in a group of 50 patients divided into four groups. Group 1 consisted of 14 normal subjects. Group 2 consisted of 10 patients with pure mitral stenosis and normal sinus rhythm. Group 3 consisted of 15 patients with pure mitral stenosis and atrial fibrillation. Group 4 consisted of 11 patients with atrial fibrillation alone. Pulmonary venous flow, atrial septal motion, and mitral valve flow were obtained by transesophageal echocardiography. Pulmonary wedge pressure or left atrial pressure was measured invasively in all patients. We observed that pulmonary venous flow had a reversed flow during atrial contraction and a biphasic flow in the ventricular phase. The first phase of flow occurred during ventricular systole, corresponding to the beginning of atrial relaxation. The second phase of flow, during ventricular diastole, occurred consistently after the rapid filling wave of mitral flow. The beginning of the second phase, corresponding to maximal relaxation of the atrial septum, reached a maximum corresponding to the beginning of atrial contraction. Results of the present study also indicate that decrease or absence of reversed atrial flow and decrease in the first phase of ventricular flow were noticeable in patients in Groups 2, 3, and 4. The second phase of pulmonary venous flow was significantly decreased in patients with mitral obstruction (Groups 2 and 3), but was maintained when the mitral valve was normal (Group 4). In six patients undergoing percutaneous mitral valvuloplasty, the ventricular phase of pulmonary venous flow increased. We concluded that the pulmonary venous flow is influenced by dynamic changes in the left atrium and in mitral valve motion. The atrial reversal flow and the first phase in pulmonary venous flow are strongly related to the change in left atrial pressure, atrial contraction, and suction effect of the atrium. The second phase is related to mitral valve motion.

27 citations

Journal ArticleDOI
TL;DR: In this small series of patients with atrial fibrillation, congestive heart failure and a prolonged QRS duration, LVP and BVP provided similar hemodynamics effects at rest whereas BVP was associated with better hemodynamic effects during exercise and fewer premature ventricular complexes.
Abstract: Background: Left ventricular pacing (LVP) and biventricular pacing (BVP) have been proposed as treatments for patients with advanced heart failure complicated by discoordinate contraction due to intraventricular conduction delay. For patients in sinus rhythm, BVP works in part by modulating the electronic atrial-ventricular time delay and thus optimizing contractile synchrony, the contribution of atrial systole, and reducing mitral regurgitation. However, little is known of the mechanisms of BVP in heart failure patients with drug-resistant chronic atrial fibrillation. Hypothesis and Methods: LVP differs from BVP because hemodynamic and clinical improvement occurs in association with prolongation rather than shortening of the QRS duration. We sought to determine if LVP or BVP improves mechanical synchronization in the presence of atrial fibrillation. Thirteen patients with chronic atrial fibrillation, severe heart failure and QRS ≥140 ms received (after His bundle ablation) a pacemaker providing both LVP and BVP. The mean age was 62 ± 6 years and left ventricular ejection fraction was 24 ± 8%. After a baseline phase of one month with right ventricular pacing, all patients underwent in random order 2 phases of 2 months (LVP and BVP). At the end of each phase, an echocardiogram, a hemodynamic analysis at rest and during a 6-minute walking test and a cardio-pulmonary exercise test were performed. Results: LVP and BVP provided similar performances at rest (p = ns). The 6-minute walking test revealed similar performances in both pacing modes but patients were significantly more symptomatic at the end of the test with LVP (p = 0.035). The cardio-pulmonary exercise test showed higher performances with BVP (92 ± 34 Watts) vs. LVP (77 ± 23; p = 0.03). LVP was associated with significantly more premature ventricular complexes recorded during the 6 minute walking test (49 ± 71) than BVP (10 ± 23; p = 0.04). Conclusions: In this small series of patients with atrial fibrillation, congestive heart failure and a prolonged QRS duration, LVP and BVP provided similar hemodynamic effects at rest whereas BVP was associated with better hemodyamic effects during exercise and fewer premature ventricular complexes. Although the mechanisms for the observed differences are uncertain, it is possible that there is worsening of right ventricular function due to a rise in left-to-right electromechanical delay during exercise. Increased catecholamines release might contribute to the lower exercise tolerance and greater number of premature ventricular complexes recorded during exercise observed during LVP compared to BVP. Recommendations: Patients with atrial fibrillation, heart failure and QRS prolongation who are candidates for His-bundle ablation and cardiac resynchronization therapy may respond better to BVP rather than to LVP.

27 citations

Journal ArticleDOI
TL;DR: The continuous pressure-volume relationships throughout the cardiac cycle were evaluated in children with tetralogy of Fallot, isolated ventricular septal defect, and patent ductus arteriosus, with marked increase in stroke volume.
Abstract: The continuous pressure-volume relationships throughout the cardiac cycle were evaluated in children with tetralogy of Fallot, isolated ventricular septal defect, and patent ductus arteriosus. Biplane cineangiocardiography and simultaneous left ventricular pressures were utilized for data acquisition. Normal pressure-volume loops demonstrated only small changes in left ventricular volume during the isovolumic periods. In tetralogy of Fallot, there was a decrease in left ventricular volume during the interval of the "isovolumic" contraction with 12 to 43% of the total stroke volume being ejected during this phase. A decrease in left ventricular volume during this time was also found in large ventricular septal defects; however, volume changes during this interval were minimal in those patients judged to have small defects. With large left-to-right shunts of comparable magnitude, the relative area of the pressure-volume loop was greater in patent ductus arteriosus as compared with ventricular defects. Both ...

27 citations


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