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PubMed2003

Relation of coronary flow pattern to myocardial blush grade in patients with first acute myocardial infarction.

BACKGROUND: Analysis of myocardial blush grade (MBG) and coronary flow velocity pattern has been used to obtain direct or indirect information about microvascular damage and reperfusion injury after percutaneous transluminal coronary angiography for acute myocardial infarction. OBJECTIVE: To evaluate the relation between coronary blood flow velocity pattern and MBG immediately after angioplasty plus stenting for acute myocardial infarction. DESIGN: The coronary blood flow velocity pattern in the infarct related artery was determined immediately after angioplasty in 35 patients with their first acute myocardial infarct using a Doppler guide wire. Measurements were related to MBG as a direct index of microvascular function in the infarct zone. RESULTS: Coronary flow velocity patterns were different between patients with absent myocardial blush (n = 14), reduced blush (n = 7), or normal blush (n = 14). The following variables (mean (SD)) differed significantly between the three groups: systolic peak flow velocity (cm/s): absent blush 10.9 (4.2), reduced blush 14.2 (6.4), normal blush 19.2 (11.2); p = 0.036; diastolic deceleration rate (ms): absent blush 103 (58), reduced blush 80 (65), normal blush 50 (19); p = 0.025; and diastolic-systolic velocity ratio: absent blush 4.06 (2.18), reduced blush 2.02 (0.55), normal blush 1.88 (1.03); p = 0.002. In a multivariate analysis MBG was the only variable with a significant impact on the diastolic deceleration rate (p = 0.034,) while age, infarct location, time to revascularisation, infarct vessel diameter, and maximum creatine kinase had no significant impact. CONCLUSIONS: The coronary flow velocity pattern in the infarct related epicardial artery is primarily determined by the microvascular function of the dependent myocardium, as reflected by MBG.

Aged↗
PubMed2003

Portable spectral Doppler echocardiographic device: overcoming limitations.

BACKGROUND: There is evidence that new portable echocardiographic devices are useful in evaluating heart anatomy and function, but a lack of Doppler modes has up to now been an important limitation in obtaining haemodynamic data. OBJECTIVES: To report the Doppler capabilities of a new hand held echocardiographic device. DESIGN: Blinded comparison of two types of echocardiography machine. SETTING: Tertiary care centre. PATIENTS: 98 consecutive patients were randomly imaged with the hand held device, with a standard platform as reference. OUTCOME MEASURES: Pulsed wave transmitral Doppler inflow tract velocities, deceleration time, and continuous wave Doppler measurements of aortic ejection and tricuspid regurgitation peak velocities were recorded. RESULTS: There was excellent agreement between the hand held device and standard echocardiography for the evaluation of diastolic E and A waves, E/A ratio, and deceleration time with pulsed wave Doppler (intraclass correlation coefficients of 0.97, 0.93, 0.90, and 0.78, respectively). In addition, good agreement was found between continuous wave Doppler measurements of aortic ejection and tricuspid regurgitation velocities (intraclass correlation coefficients of 0.96 and 0.80). However, there was a significant difference between patients with tricuspid regurgitation measured with the hand held device (25.5%) and by standard echocardiography (65.3%), resulting in misdiagnosis of eight patients with pronounced pulmonary hypertension. CONCLUSIONS: New hand held devices with Doppler capabilities overcome previous limitations in evaluating haemodynamic variables. With colour Doppler they are now suitable for the complete evaluation of valvar disease and diastolic function. However, important limitations remain in the evaluation of pulmonary pressures.

Aortic Valve Stenosis↗
PubMed2005

Myocardial performance index for assessment of left ventricular outcome in successfully recanalised anterior myocardial infarction.

OBJECTIVE: To investigate whether the myocardial performance index (MPI) can predict left ventricular functional outcome in patients with early recanalisation after anterior acute myocardial infarction (MI) and to determine when the index should be measured. DESIGN: MPI was measured serially by two dimensional Doppler echocardiography after successful percutaneous coronary intervention (PCI). Left ventricular function was evaluated by echocardiography and left ventriculography. To assess coronary microvascular damage, the coronary flow velocity pattern was measured immediately after PCI with a Doppler guidewire. SETTING: Hiroshima City Asa Hospital. PATIENTS: 32 consecutive patients with their first anterior acute MI who had complete occlusion of left anterior descending coronary artery. INTERVENTIONS: Successful PCI within six hours of symptom onset. MAIN OUTCOME MEASURES: Left ventricular anterior wall motion score index (A-WMSI), left ventricular end diastolic pressure (LVEDP), left ventricular ejection fraction (LVEF), and left ventricular end diastolic volume (LVEDV). RESULTS: There was a significant negative correlation between MPI on day 2 and the coronary diastolic deceleration time (r = -0.66, p < 0.002), as well as a significant positive correlation with the coronary diastolic deceleration rate (r = 0.74, p < 0.0001). MPI on day 2 was significantly correlated with the short and long term changes of A-WMSI and with the short term changes of LVEDP. Furthermore, MPI on day 2 was significantly correlated with the short and long term changes of LVEF (r = -0.52, p < 0.003, and r = -0.64, p < 0.0008, respectively) and of LVEDV (r = 0.51, p < 0.003, and r = 0.41, p < 0.05, respectively). CONCLUSIONS: Doppler derived MPI on day 2, representative of the early coronary microvascular state, can predict the left ventricular functional outcome after early successful recanalisation of a patient's first anterior acute MI.

Aged↗
PubMed1984

Analysis of blood flow in pulmonary hypertension with the pulsed Doppler flowmeter combined with cross sectional echocardiography.

Blood flow patterns were analysed at nine points in the pulmonary area using the pulsed Doppler technique combined with cross-sectional echocardiography in 53 patients with heart disease and 10 healthy subjects. In subjects with a normal pulmonary artery pressure the blood flow pattern in systole showed a gradual acceleration and deceleration with a rounded summit in mid systole, designated the round type. In patients with pulmonary hypertension it showed a rapid acceleration and early deceleration with a sharp peak in early systole, designated the triangular type. The acceleration time index, defined as the ratio of the time interval from the beginning to the peak of ejection to the ejection time, showed a significant inverse correlation with mean pulmonary artery pressure. In pulmonary hypertension a prominent reverse flow occurred in the right posterior part of the pulmonary trunk during mid-systole and early diastole, indicating the presence of a vortex. Similar flow patterns were also seen in patients with idiopathic pulmonary artery dilatation. The factors responsible for the triangular type were principally the reduced capacitance and increased impedance of the pulmonary vascular tree. Those responsible for the reverse flow were the curved path of the blood flow and dilatation of the pulmonary artery.

Adult↗
PubMed1992

Adjustment for the influence of age and heart rate on Doppler measurements of left ventricular filling.

OBJECTIVE: To determine the normal range of pulsed Doppler measurements of left ventricular filling adjusted for age and heart rate. DESIGN: Multiple regression was used to measure the effects of age and heart rate on pulsed Doppler indices of left ventricular filling in normal subjects. These regression equations were used to calculate a predicted normal value and 95% confidence interval (95% CI) for any subject from his age and heart rate. PARTICIPANTS: 61 subjects with no evidence of cardiovascular disease, aged 20 to 90 years, with a resting heart rate of 47-89 beats/min. RESULTS: The effect of a 10 year increase in age was peak atrial filling velocity +15% (95% CI 12.0% to 18.5%); peak early filling velocity -3.2% (-6.0% to 0%); isovolumic relaxation time +6.2% (3.9% to 8.4%); acceleration time -3.8% (-6.0% to -1.5%); deceleration time +7.9% (5.1% to 10.8%). The effect of a 10 beat/min increase in heart rate was: peak atrial filling velocity +5.5% (1.2% to 10.1%); peak early filling velocity -4.0% (-8.1% to 2.0%); isovolumic relaxation time -2.5% (-4.6% to 0.6%); acceleration time -3.1% (-6.4% to 0.4%); deceleration time -1.8% (-4.0% to 3.8%). CONCLUSION: For any individual, comparison of the predicted normal measurement and 95% CI with the observed measurement allows an assessment of the effects of disease on left ventricular filling that is independent of age and heart rate.

Adult↗
PubMed1995

M mode and Doppler echocardiographic assessment of left ventricular diastolic function in primary antiphospholipid syndrome.

BACKGROUND: High titres of serum antiphospholipid antibodies are a possible pathogenic factor for cardiac lesions in patients with systemic lupus erythematosus. OBJECTIVE: To test the hypothesis of a causal link between high titres of antiphospholipid antibodies in the serum and myocardial involvement in patients without systemic lupus erythematosus. PATIENTS AND DESIGN: 18 patients with primary antiphospholipid syndrome (recurrent fetal loss, arterial and/or venous thrombosis, high titres of antiphospholipid antibodies, and no criteria for systemic lupus erythematosus) were prospectively studied by cross sectional, M mode, and pulsed Doppler echocardiography, and compared with 18 healthy controls. The pulsed Doppler indices of left ventricular diastolic function included isovolumic relaxation time and four mitral outflow indices: peak velocity of early flow, peak velocity of late flow, early to late peak flow velocity ratio, and rate of deceleration of early flow. Four computerised M mode indices were also measured: peak rate of left ventricular enlargement in diastole, peak rate of posterior wall thinning, peak velocity of lengthening of the posterior wall, and velocity of circumferential chamber lengthening. RESULTS: Compared with controls, patients with primary antiphospholipid syndrome had higher values for isovolumic relaxation time and peak velocity of late mitral outflow and lower values for early to late mitral peak outflow velocity ratio, rate of deceleration of early mitral outflow, peak rate of left ventricular enlargement in diastole, peak rate of posterior wall thinning, peak velocity of lengthening of the posterior wall and velocity of circumferential chamber lengthening. CONCLUSION: This abnormal pattern reflects an impairment of myocardial relaxation and filling dynamics of the left ventricle in patients with primary antiphospholipid syndrome who were free of any clinically detectable heart disease. These data suggest that high serum titres of antiphospholipid antibodies may be associated with subclinical myocardial damage.

Adult↗
PubMed1996

ACE inhibitors unmask incoordinate diastolic wall motion in restrictive left ventricular disease.

OBJECTIVE: To assess the effect of ACE-inhibition on left ventricular filling and wall motion in patients with a clinical diagnosis of heart failure. DESIGN: Prospective examination of left ventricular systolic and diastolic function using M mode echocardiography and pulsed and continuous wave Doppler before and three weeks after starting an ACE inhibitor. SETTING: A tertiary referral centre for cardiac disease equipped with non-invasive facilities. SUBJECTS: 30 outpatients with a clinical diagnosis of heart failure in whom treatment with an ACE inhibitor was started; age 61 (SD 11) years; 27 male; 3 female; 21 healthy controls of similar age. RESULTS: Left ventricular cavity was dilated both at end systole and end diastole, and fractional shortening reduced. Although mean isovolumetric relaxation time (IVRT) and transmitral E (early) to A (late) filling velocity (E/A) ratio were not different from normal, a value of 1.0 on the normal frequency plot of the E/A ratio divided the patients bimodally into two groups: 20 patients (group A) with E/A ratio > 1.0 and 10 patients (group B) < 1.0. In group A patients, IVRT was short as was transmitral E wave deceleration time compared to normal (P < 0.001), fulfilling the criteria of restrictive left ventricular physiology. Left ventricular wall motion during IVRT was coordinate and left ventricular end diastolic pressure was raised on the apex-cardiogram (P < 0.001). In group B, E wave deceleration time was longer, relaxation incoordinate, and apexcardiogram normal. With an ACE inhibitor: in group A, left ventricular dimensions fell at end diastole (P < 0.05) and end systole (P < 0.01) but fractional shortening did not change; long axis total excursion (P < 0.01) and peak rate of shortening (P < 0.05) both increased; IVRT increased (P < 0.001) with the appearance of markedly incoordinate wall motion, minor axis lengthening, and long axis shortening (P < 0.001 for both); A wave amplitude also consistently increased (P < 0.001); finally, transmitral E wave velocity fell and A wave velocity increased. ACE inhibition did not alter any of the left ventricular minor and long axis or transmitral Doppler variables in patients in group B. CONCLUSIONS: Patients with a clinical diagnosis of heart failure differ in their presentation and response to ACE inhibition according to baseline haemodynamics. In restrictive left ventricular physiology, ACE inhibition reduces cavity size and prolongs IVRT, compatible with a fall in left atrial pressure. At the same time, ventricular relaxation becomes very delayed and incoordinate, greatly reducing early diastolic left ventricular filling velocity. Thus ACE inhibition unmasks major diastolic abnormalities in patients with restrictive left ventricular disease.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed2005

Out on a limb: risk factors for arm fracture in playground equipment falls.

OBJECTIVES: To investigate and quantify fall height, surface depth, and surface impact attenuation as risk factors for arm fracture in children who fall from playground equipment. DESIGN: Unmatched case control study. SETTING: Five case hospitals and 78 randomly selected control schools. PARTICIPANTS: Children aged less than 13 years in Victoria, Australia who fell from school playground equipment and landed on their arm. Cases sustained an upper limb fracture and controls had minor or no injury. A total of 402 cases and 283 controls were included. INTERVENTIONS: Children were interviewed in the playground as soon as possible after their fall. MAIN OUTCOME MEASURES: Falls were recreated on site using two validated impact test devices: a headform (measuring peak G and HIC) and a novel anthropometric arm load dummy. Equipment and fall heights, as well as surface depth and substrate were measured. RESULTS: Arm fracture risk was greatest for critical equipment heights above 1.5 m (OR 2.39, 95% CI 1.49 to 3.84, p<0.01), and critical fall heights above 1.0 m (OR 2.96, 95% CI 1.71 to 5.15, p<0.01). Peak headform deceleration below 100G was protective (OR 0.67, 95% CI 0.45 to 0.99, p = 0.04). Compliance with 20 cm surface depth recommendation was poor for both cases and controls. CONCLUSIONS: Arm fracture-specific criteria should be considered for future standards. These include surface and height conditions where critical headform deceleration is less than 100G. Consideration should also be given to reducing maximum equipment height to 1.5 m. Improved surface depth compliance and, in particular, guidelines for surface maintenance are required.

Accidental Falls↗
PubMed1998

The effect of unilateral posteroventral pallidotomy on the kinematics of the reach to grasp movement.

OBJECTIVE: To assess postoperative effects of unilateral posteroventral pallidotomy on the organisation of upper limb movement. METHODS: A three dimensional kinematic system (ELITE, B/T/S/ Italy) was used to record reach to grasp movements to objects of either small (0.7 cm) or large (8 cm) diameter placed at a reaching distance of either 20 or 30 cm. Four patients with Parkinson's disease were assessed in "off" (12 hours without medication) and "on" (1 hour after administration of medication) preoperatively and postoperatively. RESULTS: Duration of the movement and the time spent in arm deceleration were significantly reduced after surgery. However, movement patterning according to object size was adversely affected. Postoperatively, all four patients showed an abnormal pattern of a longer movement duration, and three showed a longer time of reaching arm deceleration, for reach to grasp movements to the large object than for those to the small object. CONCLUSION: Posteroventral pallidotomy seems to be beneficial in reducing bradykinesia of upper limb movements but may have "costs" to movement patterning, particularly for reach to grasp movements to objects of differing sizes. This study raises interesting questions about the role of the globus pallidus interna in coordinating stimulus bound visual information with appropriate motor patterning.

Aged↗
PubMed1995

Representation of hand position prior to movement and motor variability.

Pointing accuracy of six human subjects was measured in two blocked conditions where the hand was either never visible (T: target only) or only visible in static position prior to movement onset (H+T: hand+target). It was shown in condition H+T that, viewing the hand prior to movement greatly decreased end-point variability compared with condition T. This effect was associated with a significant modification of the movement kinematics: the H+T condition induced a shortened acceleration phase with a corresponding lengthened deceleration phase, compared with the T condition. These results led us to the hypothesis that viewing the hand prior to movement onset allowed a decrease of pointing variability through a feedback process. This hypothesis was further tested by turning the target off during the deceleration phase of the movement at half peak velocity. It was shown that turning the target off had no effect upon the T condition but induced a significant increase of pointing variability in the H+T condition. This result suggests that vision of the static hand enhances the proprioceptive localization of the limb and allows for a better visual to kinesthesic feedback.

Adult↗
PubMed2000

Contribution of NK(2) tachykinin receptors to propulsion in the rabbit distal colon.

The role of the tachykinin neurokinin (NK)(2) receptors on rabbit distal colon propulsion was investigated by using two selective NK(2)-receptor antagonists, MEN-10627 and SR-48968. Experiments on colonic circular muscle strips showed that contractile responses to [beta-Ala(8)]NKA-(4-10) (1 nM-1 microM), a selective NK(2)-receptor agonist, were competitively antagonized by MEN-10627 (1-100 nM), whereas SR-48968 (0.1-10 nM) caused an insurmountable antagonism, thus confirming the difference in the mode of action of the two compounds. Colonic propulsion was elicited by distending a mobile rubber balloon with 0.3 ml (submaximal stimulus) or 1.0 ml (maximal stimulus) of water. The velocity of anal displacement of the balloon (mm/s) was considered the main propulsion parameter. At low concentrations (1.0-100 nM and 0.1-10 nM, respectively), MEN-10627 and SR-48968 facilitated the velocity of propulsion, whereas at high concentrations (100 nM and 1 microM, respectively) they decelerated propulsion. The excitatory and inhibitory effects of both antagonists were observed only with submaximal stimulus. We focused on the hypothesis that the facilitatory effect on propulsion may result from blockade of neuronal NK(2) receptors and the inhibitory effect from suppression of the excitatory transmission mediated by NK(2) receptors on smooth muscle cells. In the presence of N(G)-nitro-L-arginine (300 microM), a nitric oxide synthase inhibitor, MEN-10627, at a concentration (10 nM) that was found to accelerate propulsion in control experiments inhibited the velocity of propulsion. In the presence of threshold (1-10 nM) or full (1 microM) concentration of atropine, which inhibited to a great extent the velocity of propulsion, the inhibitory effect of MEN-10627 (1 microM) was markedly increased. In conclusion, in the rabbit distal colon NK(2) receptors may decelerate propulsion by activating a nitric oxide-dependent neuronal mechanism and may accelerate it by a postjunctional synergistic interaction with cholinergic muscarinic receptors.

Animals↗
PubMed2006

Validation of the wall motion score and myocardial performance indexes as novel techniques to assess cardiac function in mice after myocardial infarction.

The aim of this study was to determine the feasibility and accuracy of wall motion score index (WMSI) and myocardial performance index (MPI) for measuring regional and global left ventricular (LV) function with use of high-resolution echocardiography after myocardial infarction (MI) in mice. In 48 mice, myocardial infarction was induced by ligation in the middle of the left anterior descending coronary artery. Echocardiography was performed under anesthesia at baseline and 1 mo after MI. WMSI was analyzed by a 16-segment model on short-axis views, and wall motion was scored as 1 for normal, 2 for hypokinetic, 3 for akinetic, 4 for dyskinetic, and 5 for aneurysmal. WMSI was calculated as the sum of scores divided by the total number of segments. MPI was calculated on the basis of isovolumetric contraction time (IVCT), isovolumetric relaxation time (IVRT), and ejection time (ET): MPI = (IVCT + IVRT)/ET. We measured LV ejection fraction (LVEF), end-systolic and end-diastolic volumes (ESV and EDV), fractional shortening (FS), and infarct size (IS). LVEF at 4 wk after MI was reduced at 32.8 +/- 9.0%. Linear correlation analyses showed that WMSI (1.6 +/- 0.3) correlated with LVEF (r = -0.84, P < 0.0005), FS (r = -0.43, P = 0.003), and IS (34.3 +/- 15.3%, r = 0.86, P < 0.0005). MPI (0.67 +/- 0.09) correlated with LVEF (r = -0.67, P < 0.0005) and IS (r = 0.72, P < 0.0005). MPI also correlated with mitral inflow velocity (r = -0.68, P < 0.0005) and deceleration time (r = -0.42, P = 0.003). Stepwise regression analysis revealed that WMSI was independently associated with IS. IS, FS, mitral inflow velocity, and deceleration time were independent determinants of MPI. In conclusion, echocardiographic assessments of WMSI and MPI in mice are feasible and correlate strongly with two-dimensional measurement of LV function and IS. These novel parameters provide additional noninvasive assessment of regional and global LV function in mice after MI.

Animals↗
PubMed1976

Temporal relationships of barosensory attenuation in conscious rabbits.

Electrical stimulation of anterior or posterior hypothalamus with 10-s trains elicited heart rate and blood pressure decreases. Presentation of anterior hypothalamic stimulation coincident with or 5, 10, or 15 s prior to 5-s train stimulation of aortic nerve (AN) summated with depressor-decelerator responses to AN stimulation. The summating effect was more pronounced for heart rate than for blood pressure. Simultaneous onset of AN and posterior hypothalamic stimulation did not influence AN responses. In contrast, when AN stimulation was delayed until 5, 10, or 15 s after onset of posterior hypothalamic stimulation, small, moderate, and full attenuation of AN responses occurred, respectively. Since AN and posterior hypothalamic stimulation each led to depressor-decelerator responses, attenuation of AN responses cannot be attributed to simple summation of cardiovascular responses elicited by intracranial and aortic nerve stimulation.

Animals↗
PubMed2006

Regular heartbeat dynamics are associated with cardiac health.

The human heartbeat series is more variable and, hence, more complex in healthy subjects than in congestive heart failure (CHF) patients. However, little is known about the complexity of the heart rate variations on a beat-to-beat basis. We present an analysis based on symbolic dynamics that focuses on the dynamic features of such beat-to-beat variations on a small time scale. The sequence of acceleration and deceleration of eight successive heartbeats is represented by a binary sequence consisting of ones and zeros. The regularity of such binary patterns is quantified using approximate entropy (ApEn). Holter electrocardiograms from 30 healthy subjects, 15 patients with CHF, and their surrogate data were analyzed with respect to the regularity of such binary sequences. The results are compared with spectral analysis and ApEn of heart rate variability. Counterintuitively, healthy subjects show a large amount of regular beat-to-beat patterns in addition to a considerable amount of irregular patterns. CHF patients show a predominance of one regular beat-to-beat pattern (alternation of acceleration and deceleration), as well as some irregular patterns similar to the patterns observed in the surrogate data. In healthy subjects, regular beat-to-beat patterns reflect the physiological adaptation to different activities, i.e., sympathetic modulation, whereas irregular patterns may arise from parasympathetic modulation. The patterns observed in CHF patients indicate a largely reduced influence of the autonomic nervous system. In conclusion, analysis of short beat-to-beat patterns with respect to regularity leads to a considerable increase of information compared with spectral analysis or ApEn of heart-rate variations.

Adult↗
PubMed1997

Stretch-induced enhancement of mechanical power output in human multijoint exercise with countermovement.

The relation between the eccentric force developed during a countermovement and the mechanical power output was studied in squatting exercises under nominally isotonic load (50% of 1-repetition maximum). The subjects (n = 5) performed squatting exercises with a countermovement at varied deceleration rates before lifting the load. The ground reaction force and video images were recorded to obtain the power output of the body. Net muscle moments acting at hip, knee, and ankle joints were calculated from video recordings by using inverse dynamics. When an intense deceleration was taken at the end of downward movement, large eccentric force was developed, and the mechanical power subsequently produced during the lifting movement was consistently larger than that produced without the countermovement. Both maximal and mean power outputs during concentric actions increased initially with the eccentric force, whereas they began to decline when the eccentric force exceeded approximately 1.4 times the sum of load and body weight. Video-image analysis showed that this characteristic relation was predominantly determined by the torque around the knee joint. Electromyographic analyses showed no consistent increase in time-averaged integrated electromyograph from vastus lateralis with the power output, suggesting that the enhancement of power output is primarily caused by the prestretch-induced improvement of an intrinsic force-generating capability of the agonist muscle.

Adult↗
PubMed2005

Fetal acidosis and hypotension during repeated umbilical cord occlusions are associated with enhanced chemoreflex responses in near-term fetal sheep.

This study examined the hypothesis that repeated episodes of brief but severe hypoxia would not attenuate the chemoreflex-mediated rapid initial fall in fetal heart rate (FHR) and, further, that greater hypoxic stress, as shown by hypotension and metabolic acidosis, would be associated with an enhanced chemoreflex response. Chronically instrumented, near-term fetal sheep received 1 min total umbilical cord occlusion either every 5 min for 4 h (1:5 group; n = 8) or every 2.5 min (1:2.5 group; n = 8) until mean arterial blood pressure fell to <20 mmHg on two successive occlusions. Umbilical cord occlusion caused variable decelerations, with sustained hypertension in the 1:5 group and little change in acid-base status (pH 7.34 +/- 0.03 after 4 h). In contrast, the 1:2.5 group showed progressive hypotension and metabolic acidemia (pH 6.92 +/- 0.04 after the last occlusion). The 1:2.5 group showed a significant increase in the rate of initial fall in FHR during the occlusion series, which was greater than the 1:5 group in the last 30 min of the occlusion series (9.4 +/- 1.4 vs. 3.5 +/- 0.3 beats.min(-1).s(-1); P < 0.01), with a greater fall in FHR (71.9 +/- 6.5 vs. 47.0 +/- 8.7 beats/min; P < 0.05). In summary, this study demonstrated that repetitive laborlike cord occlusions, which led to severe fetal compromise, were associated with an increase in the slope and magnitude of the initial FHR deceleration. These findings support the concept of the chemoreflex as a central, robust component of fetal adaptation to severe hypoxia.

Acidosis↗
PubMed2005

Isovolumic pressure-to-early rapid filling decay rate relation: model-based derivation and validation via simultaneous catheterization echocardiography.

Transmitral Doppler echocardiography is the preferred method of noninvasive diastolic function assessment. Correlations between catheterization-based measures of isovolumic relaxation (IVR) and transmitral, early rapid filling (Doppler E-wave)-derived parameters have been observed, but no model-based, causal explanation has been offered. IVR has also been characterized in terms of its duration as IVR time (IVRT) and by tau, the time-constant of IVR, by approximating the terminal left ventricular IVR pressure contour as Pt= Pinfinity + P(o)e(-t/tau), where Pt is the continuity of pressure, Pinfinity and Po are constants, t is time, and tau is the time constant of IVR. To characterize the relation between IVR and early rapid filling more fully, simultaneous (micromanometric) left ventricular pressure and transmitral Doppler E-wave data from 25 subjects undergoing elective cardiac catheterization and having normal physiology were analyzed. The time constant tau was determined from the dP/dt vs. P (phase) plane and, simultaneous Doppler E-waves provided global indexes of chamber viscosity/relaxation (c), chamber stiffness (k), and load (xo). We hypothesize that temporal continuity of pressure decay at mitral valve opening and physiological constraints permit the algebraic derivation of linear relations relating 1/tau to both peak atrioventricular pressure gradient (kxo) and E-wave-derived viscosity/relaxation (c) but does not support a similar, causal (linear) relation between deceleration time and tau or IVRT. Both predicted linear relations were observed: kxo to 1/tau (r = 0.71) and viscosity/relaxation to 1/tau (r = 0.71). Similarly, as anticipated, only a weak linear correlation between deceleration time and IVRT or tau was observed (r = 0.41). The observed in vivo relationship provides insight into the isovolumic mechanism of relaxation and the changing-volume mechanism of early rapid filling via a link of the respective relaxation properties.

Cardiac Catheterization↗
PubMed2004

Echocardiographic parameters discriminating myocardial infarction with pulmonary congestion from myocardial infarction without congestion in the mouse.

Our aim was to establish parameters describing systolic and diastolic function in mice after myocardial infarction (MI) that distinguish MI with pulmonary congestion from MI without congestion. Echocardiography, left ventricular (LV) catheterization, and infarct size measurements were performed on days 3, 5, 7, and 14 after ligation of the left coronary artery in C57BL/6 mice. Sham-operated mice were used as controls (Sham). MI mice with lung weight normalized to tibial length >125% of the average in the corresponding Sham group were considered to have pulmonary congestion (MIchf). MI mice with a smaller increase were called MI nonfailing (MInf). An infarct >40% of total LV circumference measured in two-dimensional long axis distinguished MIchf from MInf on both an average and an individual basis. Mean maximum rate of rise of LV pressure, LV fractional shortening, and posterior wall shortening velocity were significantly lower in MIchf compared with Sham at all time points and to MInf at 7 days. The diastolic parameters mitral flow deceleration velocity, LV end-diastolic pressure, and maximum rate of decline in LV pressure (LVdP/dtmin) discriminated the MIchf groups from Sham at all time points. Mitral flow deceleration velocity and LVdP/dtmin separated MIchf from MInf at 7 days. In addition to distinguishing all the groups on an average basis, left atrial diameter distinguished all MIchf animals from Sham and MInf. In conclusion, significantly increased left atrial diameter and infarct size >40% of total LV circumference may serve as major criteria for heart failure with pulmonary congestion after MI in mice.

Animals↗