Acute alterations of pre- and afterload: Are Doppler-derived diastolic filling patterns able to differentiate the loading condition?

The net effects of acute changes in pre- and afterload on left ventricular filling, were examined by altering loading conditions in normal subjects. The specific purpose of this study was to investigate whether Dopplerderived transmitral flow patterns are able to differentiate the type of loading conditions. In 24 normal subjects (13 females, 11 males, mean age 44.1±11.5 years), the following Doppler variables were determined at baseline, after rapid volume infusion (preload increase), after nitroglycerin administration (preload decrease), during isometric exercise (afterload increase), and after application of a converting enzyme inhibitor (afterload decrease): the peak and integrated early (E, Ei) and late (A, Ai) diastolic flow velocities, their ratios (E/A, Ei/Ai), the percentage of atrial contribution (ACON), and the acceleration and deceleration times (Ac, dc) of early filling. Reduced preload and increased afterload led to similar filling patterns characterized by a significant E and Ei decrease (p<0.05, compared to baseline) accompanied by an A and Ai increase with a resultant reduction of E/A and Ei/Ai. Both changes increased the atrial contribution to filling and reduced Ac and dc. Increased preload only significantly increased E and Ei, while reduced afterload did not induce any significant changes. Different loading conditions alter Doppler-derived diastolic filling patterns. However, the transmitral flow profile is not specific enough to distinguish the manner in which loading conditions have been altered.     

Cerebral blood flow velocity: the influence of myocardial contractility on the velocity waveform of brain supplying arteries.

Indices of Doppler-derived velocity waveforms of arteries perfusing the brain are used as relative measures of neonatal brain blood flow. Using a dog model, we investigated the influence of changes in myocardial contractility, induced by dobutamine, on the blood flow velocity waveform of the vertebral artery. The following indices of the velocity waveform were investigated during control states and during 5 or 10 micrograms/kg/min dobutamine infusion: peak systolic flow velocity (PSFV), temporal mean flow velocity (TMFV), end-diastolic flow velocity (EDFV) and acceleration time (ACC-time). PSFV and ACC-time of the vertebral artery showed a strong relationship with myocardial contractile state. These results indicate that PSFV of an artery supplying the brain or indices which combine PSFV with MFV or EDFV should not be used for noninvasive assessment of brain blood flow or cerebral vascular resistance. ACC-time may prove to be very useful in assessing changes in myocardial contractile state.     

The effect of changes in afterload on Doppler echocardiographic indexes of left ventricular performance

To investigate the influence of changes in afterload on Doppler echocardiographic determination of peak aortic blood velocity, mean acceleration, and systolic velocity integral, eight dogs with their chests opened were studied in four inotropic states at varying levels of heart rate and mean aortic blood pressure. Data were collected in the control state, at two different levels of dobutamine administration (5 and 10 micrograms/kg/min intravenously), and after administration of propranolol (0.5 mg/kg intravenously). In each inotropic state, phenylephrine was infused intravenously to produce at least two successive steady state increases of 10 mm Hg or more in mean aortic blood pressure. Within a given animal, peak velocity emerged as the Doppler index most closely correlated with changes in Qmax, dQ/dt, and dP/dt (r = 0.94, 0.91, and 0.89, respectively). Mean acceleration also correlated closely with the invasive indexes (r = 0.87, 0.89, and 0.89). The effect of changes in mean aortic blood pressure on Doppler index measurements was not statistically significant in any of the inotropic states and did not affect the closeness of their correlation with the invasive indexes. We conclude that Doppler echocardiographic measurements of aortic blood peak velocity and mean acceleration remained as sensitive to changes in the inotropic state under conditions of varying increases in afterload as did the conventional invasive indexes tested.     

Optimized performance of the Abiomed BVS 5000: adjustment of the pump height based on Doppler control of the flow pattern

The Abiomed BVS 5000 is an automatic volume-driven paracorporeal pulsatile assist device providing left, right or biventricular support. The paracorporeal position allows optical adjustment of filling volumes of the device, which determines the output of the system. A procedure to adjust for maximal stable flow has not yet been established. In vitro measurements have been performed to assess the flow and pressure characteristics of the Abiomed BVS 5000 by raising the preload in 5 mmHg steps before running the system. Doppler probes were placed at the inflow and outflow lines of the pump. After setting the afterload at 80 mmHg the assist device was started. Two measurements were performed to find optimal flow (based on Doppler control and optical adjustment). (1) By Doppler control a stable flow pattern was found at a preload of 25 mmHg with a mean atrial pressure of 5 mmHg and a mean flow of 5.3 +/- 0.7 l/min (mean +/- standard deviation) at the inflow and outflow sites (the console flow was 4.8 +/- 0.4 l/min with a frequency of 61.8 +/- 2.0 l/min). (2) Optical adjustment of the pump height gave rise to a preload of 35 mmHg where we recorded a maximal atrial pressure of 107 +/- 5.8 mmHg, a maximal retrograde flow of -4.3 +/- 1.2 l/min at the inflow and -1.2 +/- 0.4 l/min at the outflow site. The mean flow at the inflow and outflow sites was 5.1 +/- 0.5 l/min (the console flow was 4.6 +/- 0.3 l/min with a frequency of 59.6 +/- 2.6 Hz). At an initial afterload of 60 and 40 mmHg the system showed the same qualitative behaviour, but the results were less accurate. Optical adjustment of the pump height may result in an atrioventricular valve insufficiency with undetected retrograde flow and high atrial pressures. We conclude that a Doppler flow probe must be placed at the inflow site to guarantee maximal stable flow.     

Concomitant use of beta-1 adrenoreceptor blocker and norepinephrine in patients with septic shock

BACKGROUND: Betablockade has been shown to have cardioprotective effects in patients under perioperative stress. Besides animal model of septic shock and a small cohort of septic patients, these benefits have not been studied in septic shock patients who require norepinephrine administration. METHODS: After correction of preload, an esmolol bolus (0.2-0.5?mg/kg) followed by continuous 24?h infusion was administered in septic patients with sinus or supraventricular tachycardia (HR?>?120/min). Exclusion criteria were severe LV systolic dysfunction, atrioventricular blockade and norepinephrine infusion at rates over 0.5?mg/kg/min. Monitoring with echocardiography and pulmonary artery catheter before, at 2, 6, 12, 24?h following the start and 6?h after ceasing of the esmolol drip. Patients were maintained normovolemic throughout the study and adjustments of concomitant norepinephrine infusion rates were made as required. RESULTS: Ten septic patients (mean age 54.4?±?18.7), APACHE II 21.5?±?6.2, CRP 275?±?78?mg/l, procalcitonin 14.5?±?10.1?mg/l, were given esmolol drip of 212.5?±?63.5?mg/h at start to 272.5?±?89.5?mg/h at 24?h. Heart rate decreased from mean 142?±?11/min to 112?±?9/min (p?相似文献   

Doppler flow velocity waveforms in the fetal ductus arteriosus during the first half of pregnancy: a reproducibility study.

Reproducibility of flow velocity waveform measurement in the fetal ductus arteriosus was studied in 52 normal pregnancies between 11 and 25 weeks of gestation. The flow velocity parameters studied were the peak systolic velocity, mean velocity, end-diastolic velocity, flow velocity integral and acceleration time. In each woman two consecutive measurements were performed with a time delay of 15 min. An acceptable reproducibility was achieved for all flow velocity parameters, except for the acceleration time and end-diastolic velocity.     

Role of preload and inotropy in stroke volume regulation at constant heart rate.

The relationship between preload and inotropy on left ventricular function was studied in anaesthetized open-chest dogs, by measuring left ventricular dimensions and stroke volume before and during saline infusion at different levels of inotropy. Left ventricular dimensions were continuously estimated by recording myocardial chord length (MCL) in the anterior wall of the left ventricle by ultrasonic technique. The effects of isoproterenol, a stimulator of adrenergic beta-receptors (high inotropy), and propranolol, an inhibitor of adrenergic beta-receptors (low inotropy), were examined during right atrial pacing at constant heart rate averaging 161 +/- 5 beats/min. Stroke volume was varied within the range 9.0 +/- 1.7 ml to 28.6 +/- 3.2 ml by increasing inotropy and preload. To increase preload, saline was infused intravenously until end-diastolic MCL increased by about 10% and left ventricular end-diastolic pressure was higher than 10 mmHg. At constant heart rate and blood volume, both before and during saline infusion, end-diastolic MCL was not influenced by isoproterenol or propranolol administration. End-systolic MCL was reduced by raising inotropy. The difference between end-diastolic and end-systolic MCL, the systolic myocardial shortening (MS), increased during saline infusion; the relative increase in MS was the same at high and low inotropy. On average, MS was more than 50% longer at high than at low inotropy, both before and after saline infusion. Thus, left ventricular end-diastolic volume is increased by saline infusion and end-systolic volume is reduced by increasing inotropy. Preload and inotropy exert independent effects on stroke volume.     

Validation of the myocardial performance index by echocardiography in mice: a noninvasive measure of left ventricular function.

BACKGROUND: The myocardial performance index (MPI) is a Doppler-based measure of left ventricular (LV) function. It is noninvasive, independent of LV shape, and does not require dimensional measurements. However, it has never been validated in mice. METHODS: A total of 29 anesthetized mice with LV pressure catheters underwent echocardiography (2-dimensional, M-mode, and Doppler) at baseline and during manipulations of beta-adrenergic tone, temperature, preload, and afterload. The maximum derivative of LV pressure with respect to time (dP/dt(max)) was compared with MPI, fractional shortening (FS), mean velocity of circumferential fiber shortening, and the FS/MPI ratio. RESULTS: MPI (baseline 0.44 +/- 0.07) correlated strongly with dP/dt(max) (R = -.779, P <.001), as did FS and mean velocity of circumferential fiber shortening. MPI differed significantly with contractility, preload, and afterload manipulation. FS/MPI showed the best correlation with dP/dt(max). CONCLUSIONS: MPI strongly correlates with dP/dt(max) over a range of hemodynamic conditions in mice. It can be used as a noninvasive index of LV function in this species.     

Effects of the specific bradycardic agent zatebradine on hemodynamic variables and myocardial blood flow during the early postresuscitation phase in pigs

Cardiopulmonary resuscitation (CPR) leads to an excessive stimulation of the sympathetic nervous system that may result in tachycardia and malignant arrhythmias in the postresuscitation phase. The attenuation of this reaction by a specific bradycardic agent has not been compared to beta-blockade and placebo. After 4 min of ventricular fibrillation, and 3 min of CPR, 21 pigs were randomized to receive 45 microg/kg epinephrine in combination with either a specific bradycardic agent (0.5 mg/kg zatebradine; n = 7), or a beta-blocker (1 mg/kg esmolol; n = 7), or placebo (normal saline; n = 7). Two minutes after drug administration, defibrillation was performed to restore spontaneous circulation (ROSC). Hemodynamic variables, left ventricular contractility, right ventricular function, and myocardial blood flow were studied at prearrest, and for 3 h after ROSC. In comparison with esmolol and placebo, zatebradine resulted in a significant reduction in heart rate during the postresuscitation period, and reduced the number of premature ventricular contractions in the first 5 min after ROSC. This reduction in heart rate was associated with a significantly higher right ventricular ejection fraction, stroke volume, and endocardial/epicardial perfusion ratio at 5 min after ROSC. In comparison with placebo, esmolol administration decreased heart rate only moderately, but significantly reduced right ventricular stroke volume and cardiac output at 5 min after ROSC. Although only one dose and only one administration pattern of zatebradine has been investigated, we conclude that zatebradine administration during CPR effectively reduced heart rate without compromising myocardial contractility during the postresuscitation phase in pigs.     

Effects of Enalaprilat on Regional Wall Stress in Patients with Angina Pectoris

Left ventricle (LV) cineventriculograms silhouettes in the right anterior oblique projection with simultaneous pressure micromanometry were assessed before and 10 min after administration of 1.25 mg enalaprilat intravenously to 10 patients with angina pectoris undergoing diagnostic cardiac catheterization. Cineventriculograms were divided into 20 areas using a modified Leighton's method for segmentalization of the LV and computed by the Janz's method for regional wall stress. Enalaprilat reduced preload and afterload in all cases. There was significant reduction in regional wall stress in 15 of the 20 segments after enalaprilat administration compared with baseline analysis. Segments without significant reduction in wall stress wee apical. There was significant reduction in global wall stress after enalaprilat. Thus, enalaprilat, in addition to improve hemodynamics decreasing both preload and afterload, reduces LV wall stress both regional and global. Clinical implications of these findings are in agreement with the wall stress reduction for prevention of ventricular remodeling with this agent in postinfarction patients.     

不同剂量艾司洛尔预防双腔支气管内插管时心血管反应的临床研究

目的观察不同剂量的艾司洛尔对预防双腔支气管内插管时心血管反应的临床效果及合适剂量。方法选择ASAⅠ～Ⅱ级开胸手术患者60例,随机分为三组,每组20人。A组：注射生理盐水10ml（对照组）,B组：静脉注射艾司洛尔0．5mg／kg,C组：静脉注射艾司洛尔1mg／kg,记录麻醉诱导前（基础值）、诱导后2min、插管后即刻、插管后2min、5min、10min的收缩压（SBP）、舒张压（DBP）、心率（HR）,计算各对应时点HR和收缩压（SBP）的乘积（RPP）。结果与基础值相比,诱导后2min三组SBP、DBP、HR和RPP均较基础值显著降低（P〈0．05）,B组降低的程度比A组更甚,但不及c组低;气管插管后即刻,A组、B组的SBP、DBP、HR和RPP显著升高（P〈0．05）,但B组增高的程度明显低于A组（P〈0．05）,而C组保持稳定;插管后2min、5min、10min三组SBP、DBP、HR和RPP随时间逐渐趋于基础值,但B、C组仍低于A组（P〈0．05）。结论应用0．5mg／kg和1mg／kg两种剂量的艾司洛尔均能有效抑制双腔支气管内插管引起的心血管反应,但1mg／kg艾司洛尔为合适剂量,且血流动力学稳定。     

机械-电反馈对心衰心室肌电重构的影响

目的:观察心衰时心室前后负荷改变基础上快速心室刺激导致的心室肌电生理特性的改变,探讨机械-电反馈对心室肌电重构的影响。方法:138只兔随机分为心衰组和正常组。在兔心外膜四个部位分别以220、240、260次/分为刺激频率测定单向动作电位时程(MAPD)及心室有效不应期(VERP)。并分别增加前后负荷后,再作上述测定。然后置电极于右房,以260次/分频率快速刺激30 min,重复测定。并以S1S2S3刺激方法诱发室颤,记录诱发率和持续时间。结果:心衰组在增加前或后负荷快速刺激后,均表现为MAPD90、VERP延长,四个部位之间差异明显。正常组虽有延长趋势,但统计学差异不明显。心衰组的室颤诱发率及平均持续时间显著高于正常各组,增加前、后负荷后更明显。结论:心衰时增加前、后负荷并快速心室刺激导致心室肌电重构的不均匀性明显增加,可能是心衰室性心律失常易于发生的原因。     

Symptomatic and hemodynamic recovery following dobutamine stress echo: benefit of low-dose esmolol administration

Objectives: We studied the use of esmolol in patients experiencing minor side effects of palpitations, anxiety, nervousness, and tremors associated with dobutamine stress echocardiography. Background: Dobutamine stress echocardiography is frequently used in the assessment of coronary artery disease. Esmolol administration may enhance patient comfort. Methods: Sixty consecutive patients who experienced minor side-effects during dobutamine stress echocardiography were given 0.3 mg/kg esmolol intravenously in the recovery period and compared retrospectively to sixty consecutive controls who underwent dobutamine stress echocardiography, who did not receive esmolol, during the same time period. Both groups were matched for age, ejection fraction, and peak dose of dobutamine. Heart rate and blood pressure were assessed during and after dobutamine administration. Results: Both groups had similar baseline blood pressure (mmHg) (142 ± 19/72 ± 14 vs 139 ± 20/72 ± 14) and heart rate (beats per minute) (75 ± 14 vs 75 ± 17) (esmolol and control respectively, p=ns), but peak heart rate was higher in the esmolol group (126 ± 14 vs. 116 ± 14, p<0.01). In the group who received esmolol, symptomatic relief paralleled the statistically significant decrease in heart rate which occurred within 1 minute of esmolol administration (99.7 ± 15.3 vs 108.5 ± 13.1 p<0.0001); the heart rate in the esmolol group remained significantly lower than the control group for 5 minutes following esmolol administration (92.0 ± 10.3 vs 96.7 ± 11.8 p<0.05). As a percentage of peak heart rate the esmolol group remained significantly lower than the control for 7 minutes (74% vs 80% p<0.05). Esmolol induced a significant reversal of dobutamine-induced diastolic hypotension (diastolic blood pressure at peak 66 ± 17 vs 8 min recovery 70 ± 12, p<0.03) that was not seen in controls (diastolic blood pressure at peak 64 ± 18 vs 8 min recovery 65 ± 14, p=ns). Systolic blood pressure and heart rate remained elevated in both groups 8 min into recovery compared to baseline, suggesting persistent dobutamine effect beyond the expected 2 min pharmacologic half-life of dobutamine. No side-effects from esmolol were seen despite it being used in 9 patients with EF $lt; 35%. Conclusions: Esmolol is effective and well tolerated for the management of dobutamine-related minor side-effects. The mechanism of benefit, in addition to heart rate reduction, may involve a reversal of dobutamine- induced diastolic hypotension. Blood pressure and heart rate recovery are slower than expected from previously published pharmacokinetic data.     

The sparing effect of low-dose esmolol on sevoflurane during laparoscopic gynaecological surgery

This double-blind, randomized, placebo-controlled study evaluated the sparing effect of esmolol on sevoflurane during laparoscopic gynaecological surgery in 54 patients between December 2009 and May 2010. The concentration of sevoflurane required to maintain adequate anaesthesia was determined. Patients received either a 0.5 mg/kg esmolol intravenous loading dose followed by infusion of 30 μg/kg per min or an identical volume of normal saline (placebo). During surgery the input concentration of sevoflurane was adjusted every 5 min to maintain systolic blood pressure within 15% of baseline and bispectral index at 50 - 60. Infusion of esmolol resulted in an 18.2% decrease in mean sevoflurane input concentration. Patients receiving esmolol had an earlier discharge from the postanaesthetic care unit and a lower mean fentanyl dose. In conclusion, intraoperative esmolol infusion decreased both the requirement for sevoflurane and postoperative administration of fentanyl.     

Preload recruitable stroke work relationship in the right ventricle: simultaneous assessment using conductance catheter and sonomicrometry

OBJECTIVE: To examine the suitability of the conductance catheter technique for assessment of right ventricular systolic myocardial performance by using preload recruitable stroke work, we compared variables obtained simultaneously by conductance catheter and sonomicrometry dimension techniques. In addition, linearity of volume relationships was studied during rapid preload alteration by bicaval occlusion. DESIGN: Prospective animal study. SETTING: University research laboratory. SUBJECTS: Anesthetized and ventilated swine (n = 9). INTERVENTIONS: Right intraventricular volumes were determined simultaneously by conductance catheter and sonomicrometry by using an ellipsoid shell subtraction model in open-chest swine. Animals were studied at the baseline state and under alterations of afterload, preload, and inotropy. Under each condition, steady-state recordings and transient bicaval occlusions were performed. Agreement of preload recruitable stroke work slope was assessed by using the Bland-Altman analysis, and second-order polynomials were fit to examine volume relationships during bicaval occlusions. MEASUREMENTS AND MAIN RESULTS: At steady state, the relationships for stroke-volumes and end-diastolic volumes were linear between the two methods. Altered physiologic conditions induced by the various interventions produced quantitatively similar changes in preload recruitable stroke work slope within an animal, although absolute values differed in some animals. Regression analysis of the preload recruitable stroke work slope revealed a significant intervention effect independent of the method used. During some bicaval occlusions, nonlinear relationships were observed similarly with both methods. CONCLUSIONS: These results suggest that changes in right ventricular systolic contractility assessed by the preload recruitable stroke work relationship were similar when measured by conductance catheter and sonomicrometry, although absolute values may differ in some animals.     

Influence of right ventricular pre‐ and afterload on right ventricular ejection fraction and preload recruitable stroke work relation

When right ventricular (RV) afterload is abnormally increased, it correlates inversely with right ventricular ejection fraction (RVEF). We tested, whether this would be different with normal afterload. Additionally, we investigated whether previous studies on the slope of RV preload recruitable stroke work (SW) relation, which used rather non‐physiological measures to change RV preload, could be transferred to more physiological loading conditions. RV volumes were determined by thermodilution in 16 patients with stable coronary artery disease and normal pulmonary artery pressure (PAP) at rest. Pre‐ and afterload were varied by body posture, nitroglycerin (NTG) application and by exercise at different body positions. At rest, the change from recumbent to sitting position decreased PAP, cardiac index (C_i), RV diastolic and systolic volumes, and RVEF. Additionally, mean pulmonary artery pressure (MPAP) correlated positively with both RVEF and cardiac index. After correction for mathematical coupling, the RV preload recruitable SW relation was: right ventricular stroke work index (RVSW_i) (10³ erg m^–2)= 8·1 × (RV end‐diastolic volume index ?4·9), with n=96, r=0·57, P≤0·001. Exercise abolished this correlation and led to an inverse correlation between RV end‐systolic volume (ESV) and RVSW. In conclusion, (i) RVEF correlates positively with RV afterload when afterload varies within normal range; (ii) the slope of the RV preload recruitable SW relation, which is obtained at steady state under normal loading conditions, is substantially flatter than previously described for dynamic changes of RV preload. With increasing afterload, preload loses its determining effect on RV performance, while afterload becomes more important. This puts earlier assumptions of an afterload independent RV preload recruitable SW relation into question.     

Effect of incremental positive end-expiratory pressure ventilation on right ventricular function in anesthetized pigs: A thermodilution study

The effects of positive end-expiratory pressure (PEEP) ventilation on right ventricular preload, after-load, and contractility under physiologic circumstances are controversial. We studied hemodynamics and right ventricular volumes (thermodilution) in 12 anesthetized pigs in which PEEP was increased by steps of 5 cm H₂O at 15 minute intervals (0 to 20 cm H₂O). At 20 cm H²O PEEP, cardiac output decreased by 2.0 ± 0.7 (mean ± SD) L/min, and mean arterial blood pressure by 50 ± 14 mm Hg. Heart rate increased by 39 ± 24 b/min. At 20 cm H₂O PEEP, right ventricular stroke volume fell by 25 ± 7 mL, end-diastolic volume by 50 ± 21 mL, end-systolic volume by 25 ± 17 mL, and ejection fraction by 17% ±0 10% (all p <.005). For mean values during PEEP, end-diastolic volume linearly and inversely related to central venous pressure. Stroke volume, ejection fraction, and end-systolic volume linearly and positively related to end-diastolic volume; relations did not differ from those without PEEP. Transmural mean pulmonary artery pressure linearly and positively related to cardiac output. Transmural systolic pulmonary artery pressure and central venous pressure linearly and positively related to endsystolic and end-diastolic volumes, respectively. We conclude that, during incremental PEEP ventilation up to 20 cm H₂O in anesthetized pigs with an intact baroreceptor reflex, a rise in intrathoracic pressure induces a linear fall in right ventricular preload and stroke volume at an unaltered pump function. Right ventricular ejection fraction and afterload diminish as a normal response to decreased preload. There are no effects on pulmonary vascular resistance, and right ventricular compliance and contractility, in spite of coronary hypotension and tachycardia.     

Non-invasive assessment of cardiac output in children.

BACKGROUND: Stroke distance, the systolic velocity integral of aortic blood flow, is a linear analogue of stroke volume; its product with heart rate is minute distance, analogous to cardiac output. OBJECTIVE: To investigate the feasibility of assessing cardiac output in children with a simple non-invasive Doppler ultrasound technique, and to determine the normal range of values. METHODS: Peak aortic blood velocity, stroke distance, and minute distance were measured through the suprasternal window in 166 children (mean age 9.6 years, range 2-14) using a portable non-imaging Doppler ultrasound instrument. RESULTS: The technique was well tolerated by all the children participating. Mean peak aortic blood velocity was 138 cm/s and was independent of age. Mean stroke distance was 31.8 cm and showed a small but significant increase with age; mean minute distance was 2490 cm and fell with age, as did heart rate. CONCLUSIONS: Suprasternal Doppler ultrasound measurement of stroke distance is a convenient, well tolerated, non-invasive technique for the assessment of cardiac output in children. The normal range of values during childhood has been established. The technique has great potential for assessing hypovolaemia in children.     

Myocardial Mechanics Before and After Ablation of Chronic Tachycardia

Chronic tachycardia has been shown to cause a congestive cardiomyopathy; however, previous methods of evaluating ventricular function are highly dependent on cardiac loading conditions. Mean velocity of fiber shortening and its relation to end-systolic wall stress (ESS) is a preload independent index of contractility that incorporates afterload. We reviewed 33 patients (aged 6 months to 20 years; mean 9.7 years) with ectopic atrial tachycardia (EAT) (n = 19), permanent functional reciprocating tachycardia (PfRT) (n = 12), or ventricular tachycardia (n = 2). who underwent nonpharniacological elimination of tachycardia; 28 by radiofrequency ablation and 5 surgically. Ventricular function was evaluated by echocardiographic measurements of shortening fraction, mean velocity of shortening corrected for heart rate (VcFc), and afterload as ESS. Contractility, expressed as the stress-velocity index, was determined by comparing the ESS/VcFc relation to the predicted normal VcFc for the measured ESS. Myocardial dysfunction was seen in 21 patients: 13 with EAT; 7 with PJRT; and 1 with ventricular tachycardia. In patients with EAT, the mean heart rate in tachycardia was significantly faster in those with dysfunction than in those without dysfunction (176.8 ± 32.2 vs 136.7 ± 28.2; P < 0.02). Of the 21 patients with dysfunction, full recovery was seen in 17 of 18 patients restudied after intervention (mean 17.5 ± 17.6 weeks), and the remaining patient improved markedly, but did not normalize entirely. Dysfunction, seen in 64% of young patients with chronic tachycardia, was due to depressed myocardial contractility, and is generally reversible within 3 months of definitive therapy.     

Doppler flow velocity waveforms in the fetal cardiac outflow tract: reproducibility of waveform recording and analysis

Reproducibility of flow velocity waveform recording and analysis was studied at fetal cardiac level (ductus arteriosus, pulmonary artery and ascending aorta) in 42 normal pregnancies. The flow velocity parameters studied were the peak systolic velocity (PSV), acceleration time (ACT), acceleration velocity (ACV), average velocity (AV) and flow velocity integral (FVI). In each patient, two consecutive measurements were performed (time delay 15 min) and of each measurement two hardcopies were analysed. A high reproducibility was achieved for the PSV, AV and FVI in all vessels studied; the coefficients of variation between readings of hardcopies were less than or equal to 3%, and the coefficients of variation between tests within patients were less than or equal to 7%. A moderate reproducibility was achieved for the ACT in the ascending aorta and pulmonary artery; the variation between tests was large for the ductus arteriosus. The reproducibility of the ACV was poor.