Showing papers on "Cardiac cycle published in 2001"

Implantable medical device for measuring mechanical heart function

Abstract: An implantable device for measuring mechanical heart function of selected heart chambers using a heart contraction detection system that includes a magnetic field sensor. The system may be used for monitoring signs of acute or chronic cardiac heart failure, to enable diagnosis of the condition of the heart, to prescribe appropriate therapies, and to assess delivered pacing therapies. Distance measurements within the heart are made using the magnetic field sensor which is implanted at a sensor site in or on one of the right or left ventricle. A magnet implanted at a site relative to the other of the left or right heart ventricle is sufficiently spaced at a distance that fluctuates with expansion and contraction of the ventricles. The magnetic field sensor provides a sensor output signal having a signal magnitude proportional to the magnetic field strength of the magnet, and which is indicative of changing cardiac dimensions.

Coronary artery motion during the cardiac cycle and optimal ECG triggering for coronary artery imaging.

Abstract: rationale and objectives. Our purpose was to investigate the motion characteristics of the coronary arteries and determine optimal electrocardiographic (ECG) trigger time during the cardiac cycle to minimize motion artifacts. methods. Contrast-enhanced multislice movie studies of electron beam tomography (EBT) images were performed on 70 subjects. The EBT datasets, which covered an entire cardiac cycle at 58-ms intervals, were acquired for a short-axis view of the heart with ECG triggering. The pixel values along x and y axes were measured at multiple intervals during the cardiac cycle to establish the motion distance and velocity of three major coronary arteries. results. Coronary artery motion varied greatly throughout the cardiac cycle in three major coronary arteries and increased with the patient’s baseline heart rate. The greatest and lowest velocities of coronary arterial movement during the cardiac cycle were determined. Based on the lowest velocity of right coronary artery movement during the cardiac cycle, the optimal ECG trigger times were located at approximately 35% (31.4%–37.6%) or 70% (68.7%–71.4%) of the R-R interval in patients whose resting heart rate was ≤70 beats per minute (bpm); at 50% (47.2%–61.1%) of the R-R interval in the 71- to 100-bpm group; and at 55% (52.8%–59.1%) of the R-R interval in the >100-bpm group. Our data demonstrated that the motion characteristics of the left circumflex artery were quite similar to those of the right coronary artery and that the left anterior descending coronary artery had no significant differences in motion throughout the cardiac cycle. A minimum scan speed of 35.4 to 75.5 ms per slice is needed to completely diminish cardiac motion artifacts (in-plane coronary artery motion with conclusions. For coronary artery screening, the optimal ECG trigger time should be determined according to the patient’s heart rate, thus greatly reducing motion and motion artifacts during 100-ms acquisitions.

Minimal force-frequency modulation of inotropy and relaxation of in situ murine heart

Abstract: 1 The normal influence of heart rate (HR) on cardiac contraction and relaxation in the mouse remains uncertain despite its importance in interpreting many genetically engineered models. Prior in vivo data have repeatedly shown positive effects only at subphysiological heart rates, yet depressed basal conditions and use of load-dependent parameters probably have an impact on these results. 2 Open-chest mice of various strains (n = 16, etomidate/urethane anaesthesia) were instrumented with a miniaturized pressure-volume catheter employing absolute left ventricular (LV) volume calibration. HR was slowed (< 400 beats min−1) using ULFS-49, and atrial or ventricular pacing was achieved via an intra-oesophageal catheter. Pressure-volume data yielded cardiac-specific contractile indexes minimally altered by vascular load. 3 At a resting HR of 600 beats min−1, peak pressure-rise rate (dP/dtmax) was 16 871 ± 2941 mmHg s−1 (mean ±s.d.) and the relaxation time constant was 3.9 ± 0.8 ms, similar to values in conscious animals. Within the broad physiological range (500-850 beats min−1), load-insensitive contractile indexes and relaxation rate varied minimally, whereas dP/dtmax peaked at 600 ± 25 beats min−1 and decreased at higher rates due to preload sensitivity. Contraction and relaxation were enhanced modestly (13-15 %) at HRs of between 400 and 500 beats min−1. 4 The minimal force-frequency dependence was explained by rapid calcium cycling kinetics, with a mechanical restitution time constant of 9 ± 2.7 ms, and by dominant sarcoplasmic reticular buffering (recirculation fraction of 93 ± 1 %). 5 The mouse normally has a very limited force-frequency reserve at physiological HRs, unlike larger mammals and man. This is important to consider when studying disease evolution and survival of genetic models that alter calcium homeostasis and SR function.

Cardiac resynchronization system employing mechanical measurement of cardiac walls

Abstract: Methods and devices are disclosed for employing mechanical measurements to synchronize contractions of ventricular wall locations. Accelerometers that may be placed within electrode leads are positioned at ventricular wall locations, such as the left ventricle free wall, right ventricle free wall, and the anterior wall/septum wall. The accelerometers produce signals in response to the motion of the ventricular wall locations. A processor may then compare the signals to determine a difference in the synchronization of the ventricular wall location contractions. The difference in synchronization can be determined in various ways such as computing a phase difference and/or amplitude difference between the accelerometer signals. One or more stimulation pulses may be provided per cardiac cycle to resynchronize the contractions as measured by the accelerometers to thereby constantly and automatically optimize the cardiac resynchronization therapy.

Modulation of the human nociceptive flexion reflex across the cardiac cycle.

Abstract: Carotid baroreceptor stimulation has been shown to dampen pain. This study tested, in 40 normotensive adults, the hypothesis that pain is lower during systole when arterial baroreceptor stimulation is maximal than diastole when stimulation is minimal. The sural nerve was stimulated electrocutaneously to obtain a nociceptive flexion reflex (NFR) threshold, and then stimulation was delivered for 28 trials at 100% NFR threshold at seven intervals after the R-wave. Nociceptive responding was indexed by electromyographic (EMG) activity elicited in the biceps femoris. Significant variations in EMG activity occurred across the cardiac cycle, with less activity midcycle, indicating that the NFR response was attenuated during systole compared to diastole. Stimulation of baroreceptors by natural changes in blood pressure during the cardiac cycle dampened nociception, and accordingly, the data support the arterial baroreflex mechanism of hypertensive hypoalgesia.

Visualization of flow patterns distal to aortic valve prostheses in humans using a fast approach for cine 3D velocity mapping.

Abstract: The fluid dynamic performance of mechanical heart valves differs from normal valves and thus is considered related to late clinical complications in patients. Since flow patterns evolving around heart valves are complex in space and time, flow visualization based on time-resolved 3D velocity data might add important information regarding the performance of specific valve designs in vivo. However, previous cine 3D techniques for three-directional phase-contrast velocity mapping suffer from long scan duration and therefore might hamper assessment in patients. A hybrid 3D phase-contrast sequence combining segmented k-space acquisition with short EPI readout trains is presented with its validation in vitro. The technique was applied to study flow patterns downstream from a bileaflet aortic prosthesis in six patients. Navigator echoes were incorporated for respiratory motion compensation. Before flow visualization, spurious phase errors due to concomitant gradient fields and eddy currents were corrected. Flow visualization was based on particle paths and animated velocity vector plots. Dedicated algorithms for particle path integration were implemented to account for the considerable motion of the ascending aorta during the cardiac cycle. A distinct flow pattern reflecting the valve design was observed closest to the valve during early flow acceleration. Reverse flow occurred adjacent to high velocity jets and above the hinge housings. Later in systole, flow became confined to the central vessel area and reverse flow along the inner aortic curvature developed. Further downstream from the valve, flow patterns varied considerably among patients, indicating the impact of varying aortic anatomy in vivo. It is concluded that MR velocity mapping is a potential tool for studying 3D flow patterns evolving around heart valve prostheses in humans. J. Magn. Reson. Imaging 2001;13:690–698. © 2001 Wiley-Liss, Inc.

Strain rate imaging in normal and reduced diastolic function: Comparison with pulsed doppler tissue imaging of the mitral annulus

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.)

Regulation of Cardiomyocyte Mechanotransduction by the Cardiac Cycle

Abstract: Background—Overloading the left ventricle in systole (pressure overload) is associated with a distinct morphological response compared with overload in diastole (volume overload). Methods and Results—We designed a novel computer-controlled experimental system that interfaces biaxially uniform strain with electrical pacing, so that cellular deformation can be imposed during a specified phase of the cardiac cycle. Cardiomyocytes were exposed to strain (4%) during either the first third (systolic phase) or last third (diastolic phase) of the cardiac cycle. Strain imposed during the systolic phase selectively activated p44/42 mitogen-activated protein kinase (MAPK) and MAPK/extracellular signal–regulated protein kinase kinase (MEK1/2, an activator of p44/42 MAPK) compared with strain imposed during the diastolic phase. In contrast, there was no difference in activation of p38 and c-Jun NH2-terminal kinases induced by strain imposed during the systolic phase (5.8- and 3.3-fold versus control, n=4) compared wit...

Coronary MR angiography: selection of acquisition window of minimal cardiac motion with electrocardiography-triggered navigator cardiac motion prescanning--initial results.

Abstract: The authors developed an electrocardiography-triggered M-mode navigator-echo technique to help monitor cardiac motion and identify the period of minimal cardiac motion in the cardiac cycle. Coronary magnetic resonance angiography was performed in eight healthy adult volunteers and one patient with heart disease. To minimize cardiac motion effects, trigger delays were estimated with the navigator-echo technique and two empirical formulas. The quality of images obtained with the different delay times was compared for clarity of depiction of the coronary arteries. Image quality was best with the delay calculated with the navigator-echo technique.

The information content of Doppler ultrasound signals from the fetal heart.

Abstract: Knowledge of the content of Doppler ultrasound signals from the fetal heart is essential if the performance of fetal heart rate (FHR) monitors based upon this technology is to be improved For this reason instrumentation was constructed to enable the simultaneous collection of Doppler audio signals and the transabdominal fetal ECG (for signal registration), with a total of 22 recordings being made with an average length of around 20 minutes These data demonstrate the transient nature of the Doppler audio data with wide variations in the signal content observable on a beat-to-beat basis Short-time Fourier analysis enabled the content of the Doppler signals to be linked to six cardiac events, four valve and two wall motions, with higher frequency components being associated with the latter This differing frequency content together with information regarding the direction of movement that can be discerned from Doppler signals provided a potential means of discriminating between these six events (which are unlikely to all contribute to the Doppler signal within the same cardiac cycle) Analysis of 100 records showed that wall contractions generate the most prominent signals, with atrial contraction recognisable in all records and ventricular wall contraction in 95% (although its amplitude is only around 30% of that of the atrial signal) Valve motion, with amplitudes between 15 and 25% that of the atrial wall signal, were visible in 75% of records These results suggest means by which the six events that contribute to the Doppler signal may be distinguished, providing information that should enable an improvement in the current performance of Doppler ultrasound-based FHR monitors

Atrioventricular plane displacement correlates closely to circulatory dimensions but not to ejection fraction in normal young subjects.

Abstract: The complex myocardial fiber architecture of the left ventricle (LV) enables long-axis motion (annular excursion), short-axis motion and also a small torsional deformation throughout the cardiac cycle. The contribution of the long-axis motion has proven to be important in generating ventricular filling and emptying, and the analysis of annular excursion has become a well established diagnostic tool for the assessment of ventricular function. Cardiac motion can be accurately described with modem non-invasive imaging teclmiques, and this is important ground for deeper understanding and more reliable diagnosis of cardiovascular disease. The focus of this thesis was to provide new insights into cardiac pump function using variables originating from the annular excursion and dynamic changes in shape, applying both established and novel echocardiographic imaging approaches.The traditional method of evaluating systolic ventricular fimction according to the total annular excursion overestimates the excursion amplitude in relation to true systolic fimction. A novel method presented here, measurement of the systolic annular excursion, more accurately reflects the timing of true systole, and was applied both in patients with heart disease and in healthy subjects. To date, the form of asynchronous myocardial motion called postsystolic shortening (PSS) has mainly been observed in the setting of myocardial ischemia. The significance of PSS in hypertensive heart disease remains incompletely described. We found that a subgroup of hypertensive patients with PSS along the LV long-axis had signs of more severe cardiac involvement unrelated to the level of blood pressure. Endurance trained subjects showed a larger LV long-axis motion as compared to strength trained and untrained controls. Mitral annular (MA) excursion correlated strongly to LV stroke volume, end-diastolic volume and maximal oxygen consumption per body weight, but weakly to LV ejection fraction. These findings provide further evidence of the importance of annular excursion to normal cardiac performance. In order to assess the contribution of MA excursion and shape dynamics to total LV volume change in humans, a novel 4-dimensional transesophageal echocardiography teclmique was developed. The excursion of the annulus accounted for an important portion (19±3%) of the total LV filling and emptying in healthy human subjects. Furthermore, our findings elucidate an atrial influence on MA physiology in humans, as well as a sphincter-like action of the MA. These temporal changes may facilitate ventricular filling by annular expansion during early and mid diastole, and aid competent valve closure during the marked decrease in annular area during late diastole and early systole.

Maximum atrial tracking rate for cardiac rhythm management system

Abstract: A cardiac rhythm management system includes an operational mode in which ventricular pacing pulses are delivered at a rate that tracks a sinoatrial rate up to an appropriate maximum atrial tracking rate (MATR) value determined by the system. In one example, the MATR value is based on a patient activity level and a hemodynamic maximum rate (HMR) determined from a QRS-to-S2 interval, where S2 is an accelerometer-generated fiducial correlative to aortic valve closure (AVC). In a further example, a correlation between the QRS-to-S2 interval and heart rate is established, and the MATR is based on the patient activity level and heart rate. In a further example, a lower rate threshold for providing antitachyarrhythmia therapy is modified based on the MATR. For example, when the MATR exceeds a default value of the antitachyarrhythmia therapy lower rate threshold, the threshold tracks the MATR. In another example, the MATR is based on an active time between a QRS complex and a heart impedance signal maximum slope during the same cardiac cycle.

Effect of P-Wave Timing During Supraventricular Tachycardia on the Hemodynamic and Sympathetic Neural Response

Abstract: Background—Previous studies have shown the importance of the timing of atrial and ventricular systole on the hemodynamic response during supraventricular tachycardia (SVT). However, the reflex changes in autonomic tone during SVT remain poorly understood. Methods and Results—Eleven patients with permanent dual-chamber pacemakers were enrolled in the study. Arterial blood pressure (BP), central venous pressure (CVP), and peripheral muscle sympathetic nerve activity (SNA) were recorded during DDD pacing at a rate of 175 bpm (cycle length 343 ms) with an atrioventricular (AV) interval of 30, 200 and 110 ms, simulating tachycardia with near-simultaneous atrial and ventricular systole, short-RP tachycardia (RP PR). Each pacing run was performed for 3 minutes separated by a 5-minute recovery period. All patients demonstrated an abrupt fall in BP, an increase in CVP, and an increase in SNA regardless of the AV interval. The decreases in SBP, DBP, and MAP and the increase in CVP w...

Clinical aspects of left ventricular diastolic function assessed by Doppler echocardiography following acute myocardial infarction.

Abstract: LV systolic function and dilation after Ml have been extensively studied and have been related to heart failure and cardiac mortality. In recent years, it has been increasingly apparent that LV diastolic dysfunction contributes to signs and symptoms of heart failure and LV diastolic dysfunction is associated with increased mortality rates in patients chronic heart failure independent of systolic function. LV diastolic dysfunction is difficult to assess on basis of clinical examination including chest radiography and electrocardiography. LV diastolic filling has traditionally been evaluated by cardiac catherization with direct measurement of filling pressures and relaxation. However, the invasive approach describing LV compliance and relaxation as the major determinants of LV diastolic function, is not feasible and suitable for routine investigations of diastolic function. Two-dimensional and Doppler echocardiography has become a well accented practical and safe non-invasive method for diagnosis of LV diastolic dysfunction. Combined invasive and echocardiographic studies have shown that analysis of mitral and pulmonary venous flow velocities relate to invasively measured filling pressures and relaxation rate in cardiac diseases. Based on Doppler analysis of mitral and pulmonary venous flow three abnormal LV filling patterns are identified: impaired relaxation, "pseudonormalization" and restrictive. These LV filling patterns have been related to symptoms, relaxation rate, filling pressure and prognosis in patients with restrictive and dilated cardiomyopathy. The Doppler flow profiles are influenced by several factors including age, heart rate, load conditions and valve heart diseases which must be taken into consideration during evaluation. During the last decade information about LV diastolic function assessed non-invasively by Doppler echocardiography has gained in patients with CAD. Myocardial ischemia induced by brief coronary artery occlusion or pacing leads to abnormal myocardial relaxation which can be reversed to normal by restoring normal myocardial blood flow. The diastolic abnormality is present within seconds and a characteristic impaired relaxation filling pattern are identified by mitral and pulmonary venous flow analysis. Diastolic dysfunction has been recognized during the early as well during the post-MI phase with or without LV systolic dysfunction. In the acute phase both an abnormal relaxation pattern and restrictive LV filling pattern are present which has been related to in-hospital heart failure. The identification of a pseudonormal or restrictive LV filling pattern are associated with later readmission to hospital with heart failure and cardiac death. Abnormal relaxation filling is the most pronounced filling pattern after one year which might be related to the remodeling process including compensatory hypertrophy, scarring of the infarct zone leading to a non-uniform relaxation of the LV. Remodeling of the LV following a MI is subject to several factors which might involve diastolic function. This is supported by the presence of an impaired relaxation and restrictive filling pattern are associated with progressive LV dilatation following Ml. Furthermore, the LV remodeling process following the very early phase includes the scarring process with collagen deposition in the infarcted and non-infarcted myocardium. The extent and quality of the repair process involving collagen deposition are believed to influence the remodeling process. Increased collagen deposition in the subacute phase of Ml indicated by elevated values of the collagen marker PIIINP is found to be related to LV dilation, depressed systolic function and restrictive LV filling. Development of a restrictive filling in patients with increased collagen deposition might be due to increasing LV volume but also to increased myocardial stiffness. Regarding prognosis diastolic dysfunction seems to be an important marker of outcome as abnormal diastolic properties are related to progressive LV dilatation, development of heart failure and cardiac death following MI. The beneficial effects of BB on morbidity and mortality in post-MI patients are well established. Recently, it has been demonstrated that BB has beneficial effects on progressive CHF and cardiac mortality in patients with chronic heart failure and moderate to severe systolic dysfunction. The mechanisms behind these effects are not fully understood. However, improvement of both systolic and diastolic function during BB therapy are demonstrated in patients with CHF. A few studies in patients with MI indicates that long-term BB therapy improves LV diastolic function which seems to be followed by improvement in systolic function. BB has the potential to lengthening diastole, improving subendocardial myocardial perfusion and affecting symptomatic amd neurohumoral activation following MI which might affect LV systolic and diastolic function and thereby improving outcome. Functional capacity following Ml is a well known predictor for outcome in MI patients. LV diastolic function a closely related to exercise capacity in contrast to measures of systolic function. BB therapy in patients with mild to moderate systolic dysfunction seems to improve exercise capacity which is related to improvement in LV diastolic function. Thus, BB improves exercise capacity and diastolic function by increasing LV compliance which might have prognostic implications. Even though LV systolic and diastolic dysfunction coexist, few two-dimensional and Doppler echocardiographic variables combine measurements of both phases of the cardiac cycle. Recently, the MPI has been suggested as a measure of combined systolic and diastolic myocardial performance which is based on Doppler time intervals of the systolic and diastolic phases. The MPI is easily obtained, reproducible, non-geometric and seems less dependent on heart rate and load conditions compared to traditional Doppler measurements. In patients with MI is has shown to reflect disease severity and contain prognostic information. The assessment of MPI seems therefore to be a relevant attractive alternative to established measurements of LV function following MI.

Implantable cardiac device providing repetitive non-reentrant ventriculo-atrial synchronous (RNRVAS) rhythm therapy using VA interval extension and method

Abstract: A system and method detects and terminates a repetitive non-reentrant ventriculo-atrial synchronous (RNRVAS) rhythm. The system and method is particularly adapted for use in an implantable cardiac stimulation device including a pulse generator that delivers atrial and ventricular pacing stimulation pulses to a heart which implements an AV delay and an atrial escape interval. The system includes a sensing circuit that senses cardiac activity of the heart and a detector responsive to the sensing circuit that determines if an RNRVAS rhythm is present. When an RNRVAS rhythm is present, a therapy control circuit lengthens the atrial escape interval for at least one cardiac cycle. In addition, the VA delay interval may be shortened by the same amount to maintain a consistent ventricular pacing rate.

Conversion of umbilical arterial Doppler waveforms to cardiac cycle triggering signals: a preparatory study for online motion-gated three-dimensional fetal echocardiography.

Abstract: To remove motion artefacts, a device was built to convert “noisy” umbilical arterial Doppler waveforms (UADWs) from an ultrasound (US) system into sharp ECG R-wave-like cardiac cycle triggering signals (CCTSs). These CCTSs were then used to gate a simultaneous (online) 3-D acquisition of sectional fetal echocardiograms from another US system. To test the conversion performance, a study was carried out in sheep fetal twins. Pulmonary arterial flow waveforms (PAFWs) from implanted probes were traced, in the meantime, to determine the reference cardiac cycle. Interference caused by running the two nonsynchronised US systems was controlled to three degrees (not-noticeable, moderate, and severe), together with high (≥ 40 cm/s) and low (

Normal pericardial fluid in the fetus: color and spectral Doppler analysis.

Abstract: Objectives To estimate the incidence of sonographic identification of pericardial fluid in normal fetuses and to evaluate the flow pattern of pericardial fluid by using color and spectral Doppler techniques. Methods We evaluated 27 normal fetuses for the presence of pericardial fluid by using gray-scale two-dimensional and M-mode ultrasound, and color and spectral Doppler techniques. Results Pericardial fluid was detected in 52% of cases by two-dimensional and M-mode ultrasound and in 81% of cases by color Doppler. The pericardial fluid moved towards the ventricles during systole and towards the atria during diastole. In 9 of 22 fetuses with pericardial fluid identified by color Doppler, spectral waveforms were obtained. The waveforms confirmed the bidirectional flow pattern identified at color Doppler. In six cases there was monophasic systolic and biphasic diastolic flow. In the remaining three cases, the flow was monophasic during both systole and diastole. Conclusions Pericardial fluid can be identified with color Doppler in the majority of normal fetuses. It characteristically shows bidirectional flow as it moves with ventricular systole and diastole. Spectral waveforms can be obtained from the pericardial fluid. The presence of pericardial fluid per se should not be considered as abnormal. Color-coded pericardial fluid should not be mistaken for coronary artery blood flow. Copyright © 2001 International Society of Ultrasound in Obstetrics and Gynecology

Temporal dynamics of blood flow effects in half-Fourier fast spin echo (1)H magnetic resonance imaging of the human lungs.

Abstract: A cardiac-triggered half-Fourier single-shot turbo spin echo (HASTE) technique is currently the method of choice for MR imaging of the lung parenchyma without the use of exogenous contrast agents. In this study, we specifically examined the effects of the cardiac cycle on the HASTE signal intensity of the lungs. Images were obtained from six healthy human volunteers at an end expiration breath-hold using a HASTE sequence and a variable cardiac-triggered delay time. Analysis of the data sets showed a 30% decrease in the lung signal intensity during systole, and a 15% decrease during mid-diastole. These decreases correlate with phases of the cardiac cycle when the blood flow in the lungs is expected to be greatest. Misregistration artifacts, particularly from the pulmonary arteries and aorta, are worse during these periods of signal decrease. To minimize cardiac dependent signal losses, HASTE lung imaging should be performed after systole but before rapid filling of the ventricles.J. Magn. Reson. Imaging 2001;14:411–418. © 2001 Wiley-Liss, Inc.

Disturbed atrioventricular electromechanical function long after Mustard operation for transposition of great arteries: a potential contributing factor to atrial flutter.

Abstract: Objective: The objectives were to study atrial and ventricular electromechanical function in patients long after Mustard repair for transposition of great arteries and to identify possible causes and physiologic disturbances in those with recurrent atrial flutter. Methods: Electromechanical atrial and ventricular function was assessed in 22 patients (11 women) aged 27 ± 5 years, 10 to 29 (mean 24) years after initial Mustard operation with electrocardiography and echocardiography. The study subjects involved 12 patients with documented atrial flutter and the remaining 10 without history of atrial arrhythmia served as controls. All patients were studied while in sinus rhythm. Results: There was no difference in age, gender, or age at original Mustard surgery between the 2 patient groups. The P wave and QRS duration were significantly broader in patients compared with controls (128 ± 14 ms vs 100 ± 10 ms, P P P P P P P P r = 0.79, P Conclusion: Right ventricular dysfunction is present long after Mustard operation for transposition of great arteries whether flutter occurs. However, in patients with history of atrial flutter, evidence of left ventricular dysfunction, significant tricuspid regurgitation, impaired right atrial electrical and mechanical function, and reversed onset of atrial systole is also present. The consistent association of the disturbed atrial and ventricular electromechanical behavior suggests a multifactorial etiology for atrial arrhythmia.

Magnetic resonance imaging needing a long waiting time between pre-pulses and imaging pulse train

Abstract: In the black blood method using a double inversion pulse, images in the systole of the cardiac cycle can be captured in a reliable manner even in the presence of a cycle-to-cycle variance in the heart beat cycle. A pulse sequence of the black blood method composed of a double inversion pulse DIV and an imaging pulse train SEQ ima is used. This sequence is applied in sync with an ECG signal of a subject to be imaged, and magnetic resonance imaging is thereby performed. The double inversion DIV is applied in sync with an R-wave:R 1 appearing on the ECG signal at a given timing, with a first delay time td 1 (fixed value), and the imaging pulse train SEQ ima is applied in sync with the following R-wave:R 2 with a second delay time td 2 (fixed value: set in accordance with the systole). A variance of the cardiac cycle is absorbed in an inversion time BBTI.

Method and monitor for monitoring diastolic relaxation of a heart ventricle

Abstract: In a monitor for monitoring diastolic relaxation of a ventricle of a heart, an impedance signal is measured in a ventricle of the heart and the occurrence of a notch in the impedance signal coincident with the entry of blood into the monitored ventricle is detected by forming a time derivative of the impedance signal and generating a loop by plotting impedance values of the impedance signals with respect to related time derivative values to form a loop for each cardiac cycle of the heart, and comparing the generated loop to a loop template representing a normal loop for the subject, to identify deviations in the loop from normal deviations in timing and shape of the notch.

Decrease in coronary vascular volume in systole augments cardiac contraction.

Abstract: Coronary arterial inflow is impeded and venous outflow is increased as a result of the decrease in coronary vascular volume due to cardiac contraction. We evaluated whether cardiac contraction is i...