Cardiovascular consequences of cooling in critical care

This commentary discusses a paper by Filseth and colleagues in a previous issue of Critical Care. The authors describe the cardiovascular effects of induced hypothermia, focusing particularly on post-hypothermic ventricular function. The findings indicate that the treatment resulted in reduced systolic but unchanged diastolic left ventricular function with compensatory effects on heart rate and systemic vascular resistance. The novel aspects of this study are the registration of ventricular function using sophisticated, load-independent indices in a clinically relevant, large animal model during the entire cooling and re-warming trajectory of hypothermia therapy

Balloon sizing in surgical ventricular restoration: What volume are we targeting?

Cardiolog

Effects of critical coronary stenosis on global systolic left ventricular function quantified by pressure-volume relations during dobutamine stress in the canine heart

AbstractObjectives. In this study we quantified the effects of a critical coronary stenosis on global systolic function using pressure-volume relations at baseline and during incremental dobutamine stress.Background. The effects of coronary stenosis have previously been analyzed mainly in terms of regional (dys)function. Global hemodynamics are generally considered normal until coronary flow is substantially reduced. However, pressure-volume analysis might reveal mechanisms not fully exposed by potentially load-dependent single-beat parameters. Moreover, no systematic analysis by pressure-volume relations of the effects of dobutamine over a wide dose range has previously been presented.Methods. In 14 dogs left ventricular volume and pressure were measured by conductance and micromanometer catheters, and left circumflex coronary flow by Doppler probes. Measurements in control and with left circumflex stenosis were performed at baseline and at five levels of dobutamine (2.5 to 20 μg/kg/min). The end-systolic pressure-volume relation (ESPVR) dP/dtMAX− vs. end-diastolic volume (dP/dtMAX− VED) and the relation between stroke work and end-diastolic volume (preload recruitable stroke work [PRSW]) were derived from data obtained during gradual caval occlusion.Results. In control, dobutamine gradually increased heart rate up to 20 μg/kg/min, the inotropic effect blunted at 15 μg/kg/min. With stenosis, the chronotropic effect was similar, however, contractile state was optimal at approximately 10 μg/kg/min and tended to go down at higher levels. At baseline, the positions of ESPVR and PRSW, but not of dP/dtMAX− VED, showed a significant decrease in function with stenosis. No differences between control and stenosis were present at 2.5 μg/kg/min; the differences were largest at 15 μg/kg/min.Conclusions. Pressure-volume relations and incremental dobutamine may be used to quantify the effects of critical coronary stenosis. The positions of these relations are more consistent and more useful indices than the slopes. The positions of the ESPVR and PRSW show a reduced systolic function at baseline, normalization at 2.5 μg/kg/min and a consistent significant difference between control and stenosis at dobutamine levels of 5 μg/kg/min and higher

Interventional creation of an atrial septal defect and its impact on right ventricular function: An animal study with the pressure-volume conductance system

Background: The aim of our study was to assess the suitability of different interventional techniques to create an atrial septal defect (ASD) and to evaluate the short-term effects of right ventricular (RV) volume overload on RV contractility in the growing swine. Methods: Thirteen ASD and six control animals were studied. An ASD was created by balloon dilatation (BD) of the fossa ovalis (n = 4) or by implantation of a multi-perforated Amplatzer Septal Occluder (n = 4) or a patch-less nitinol device (n = 5). After 4.8 (3.9&#8211;6.0) weeks, the amounts of left-to-right shunting (Qp/Qs) and RV contractility (end systolic elastance &#8212; Ees) were assessed. Results: In the ASD group, a significant left-to-right shunt could be documented (Qp/Qs 1.5 &#177; &#177; 0.4). However, a shunt was absent in the BD subgroup (Qp/Qs 1.1 &#177; 0.1). In animals with devices implanted, a significant relationship between the post-mortem ASD area and Qp/Qs was found (r = 0.68, p < 0.05). Compared to controls, RV contractility was not significantly impaired at rest and during dobutamine in ASD animals (Ees: 0.40 &#177; 0.20 vs 0.54 &#177; 0.12 and 0.75 &#177; 0.29 vs 1.04 &#177; 0.24 mm Hg/mL, p = NS for both). Conclusions: Device implantation is necessary to create a patent ASD resulting in significant left-to-right shunting. In an experimental ASD model, a five week period of chronic RV volume overload does not alter RV contractility significantly. (Cardiol J 2011; 18, 3: 289&#8211;296

Noninvasive estimation of left ventricular filling pressures in patients with heart failure after surgical ventricular restoration and restrictive mitral annuloplasty

ObjectiveDoppler echocardiography, including tissue Doppler imaging, is widely applied to assess diastolic left ventricular function using early transmitral flow velocity combined with mitral annular velocity as a noninvasive estimate of left ventricular filling pressures. However, the accuracy of early transmitral flow velocity/mitral annular velocity in patients with heart failure, particularly after extensive cardiac surgery, is debated. Global diastolic strain rate during isovolumic relaxation obtained with 2-dimensional speckle-tracking analysis was recently proposed as an alternative approach to estimate left ventricular filling pressures.MethodsWe analyzed diastolic function in patients with heart failure after surgical ventricular restoration and/or restrictive mitral annuloplasty. Echocardiography, including tissue Doppler imaging and speckle-tracking analysis, was performed to determine early transmitral flow velocity/atrial transmitral flow velocity, isovolumetric relaxation time, deceleration time, early transmitral flow velocity/mean mitral annular velocity, strain rate during isovolumic relaxation, and early transmitral flow velocity/strain rate during isovolumic relaxation. These noninvasive indices were correlated with relaxation time constant Tau, peak rate of pressure decline, and left ventricular end-diastolic pressure obtained in the catheterization room using high-fidelity pressure catheters.ResultsTwenty-three patients were analyzed 6 months after restrictive mitral annuloplasty (n = 8), surgical ventricular restoration (n = 4), or a combined procedure (n = 11). The strongest correlation with invasive indices, in particular left ventricular end-diastolic pressure, was found for strain rate during isovolumic relaxation (r = −0.76, P < .001). Early transmitral flow velocity/mean mitral annular velocity did not correlate significantly with any of the invasive indices. Strain rate during isovolumic relaxation (cutoff value < 0.38 s−1) accurately predicted left ventricular end-diastolic pressure of 16 mm Hg or more with 100% sensitivity and 93% specificity.ConclusionsIn a group of patients with heart failure who were investigated 6 months after cardiac surgery, early transmitral flow velocity/mean mitral annular velocity correlated poorly with invasively obtained diastolic indexes. Global strain rate during isovolumic relaxation, however, correlated well with left ventricular end-diastolic pressure and peak rate of pressure decline. Our data suggest that global strain rate during isovolumic relaxation is a promising noninvasive index to assess left ventricular filling pressures in patients with heart failure after extensive cardiac surgery, including restrictive mitral annuloplasty and surgical ventricular restoration

Cardiac power output accurately reflects external cardiac work over a wide range of inotropic states in pigs

BACKGROUND: Cardiac power output (CPO), derived from the product of cardiac output and mean aortic pressure, is an important yet underexploited parameter for hemodynamic monitoring of critically ill patients in the intensive-care unit (ICU). The conductance catheter-derived pressure-volume loop area reflects left ventricular stroke work (LV SW). Dividing LV SW by time, a measure of LV SW min- 1 is obtained sharing the same unit as CPO (W). We aimed to validate CPO as a marker of LV SW min- 1 under various inotropic states. METHODS: We retrospectively analysed data obtained from experimental studies of the hemodynamic impact of mild hypothermia and hyperthermia on acute heart failure. Fifty-nine anaesthetized and mechanically ventilated closed-chest Landrace pigs (68 ± 1 kg) were instrumented with Swan-Ganz and LV pressure-volume catheters. Data were obtained at body temperatures of 33.0 °C, 38.0 °C and 40.5 °C; before and after: resuscitation, myocardial infarction, endotoxemia, sevoflurane-induced myocardial depression and beta-adrenergic stimulation. We plotted LVSW min- 1 against CPO by linear regression analysis, as well as against the following classical indices of LV function and work: LV ejection fraction (LV EF), rate-pressure product (RPP), triple product (TP), LV maximum pressure (LVPmax) and maximal rate of rise of LVP (LV dP/dtmax). RESULTS: CPO showed the best correlation with LV SW min- 1 (r2 = 0.89; p < 0.05) while LV EF did not correlate at all (r2 = 0.01; p = 0.259). Further parameters correlated moderately with LV SW min- 1 (LVPmax r2 = 0.47, RPP r2 = 0.67; and TP r2 = 0.54). LV dP/dtmax correlated worst with LV SW min- 1 (r2 = 0.28). CONCLUSION: CPO reflects external cardiac work over a wide range of inotropic states. These data further support the use of CPO to monitor inotropic interventions in the ICU

Biventricular function in exercise during autonomic (thoracic epidural) block

Background Blockade of cardiac sympathetic fibers by thoracic epidural anesthesia (TEA) was previously shown to reduce right and left ventricular systolic function and effective pulmonary arterial elastance. At conditions of constant paced heart rate, cardiac output and systemic hemodynamics were unchanged. In this study, we further investigated the effect of cardiac sympathicolysis during physical stress and increased oxygen demand. Methods In a cross-over design, 12 patients scheduled to undergo thoracic surgery performed dynamic ergometric exercise tests with and without TEA. Hemodynamics were monitored and biventricular function was measured by transthoracic two-dimensional and M-mode echocardiography, pulsed wave Doppler and tissue Doppler imaging. Results TEA attenuated systolic RV function (TV SMODIFIER LETTER PRIME: - 21%, P < 0.001) and LV function (MV SMODIFIER LETTER PRIME: - 14%, P = 0.025), but biventricular diastolic function was not affected. HR (- 11%, P < 0.001), SVI (- 15%, P = 0.006), CI (- 21%, P < 0.001) and MAP (- 12%, P < 0.001) were decreased during TEA, but SVR was not affected. Exercise resulted in significant augmentation of systolic and diastolic biventricular function. During exercise HR, SVI, CI and MAP increased (respectively, + 86%, + 19%, + 124% and + 17%, all P < 0.001), whereas SVR decreased (- 49%, P < 0.001). No significant interactions between exercise and TEA were found, except for RPP (P = 0.024) and MV E DT (P = 0.035). Conclusion Cardiac sympathetic blockade by TEA reduced LV and RV systolic function but did not significantly blunt exercise-induced increases in LV and RV function. These data indicate that additional mechanisms besides those controlled by the cardiac sympathetic nervous system are involved in the regulation of cardiac function during dynamic exercise

Перспективи розвитку світової енергетики й забезпечення енергетичної безпеки України

Проблеми забезпечення енергетичної безпеки (ЕнБ) безпеки були та залишаються головними складовими забезпечення національної безпеки та загального сталого розвитку

Echocardiographic Assessment of Embryonic and Fetal Mouse Heart Development: A Focus on Haemodynamics and Morphology

Background. Heart development is a complex process, and abnormal development may result in congenital heart disease (CHD). Currently, studies on animal models mainly focus on cardiac morphology and the availability of hemodynamic data, especially of the right heart half, is limited. Here we aimed to assess the morphological and hemodynamic parameters of normal developing mouse embryos/fetuses by using a high-frequency ultrasound system. Methods. A timed breeding program was initiated with a WT mouse line (Swiss/129Sv background). All recordings were performed transabdominally, in isoflurane sedated pregnant mice, in hearts of sequential developmental stages: 12.5, 14.5, and 17.5 days after conception (n=105). Results. Along development the heart rate increased significantly from 125 ± 9.5 to 219 ± 8.3 beats per minute. Reliable flow measurements could be performed across the developing mitral and tricuspid valves and outflow tract. M-mode measurements could be obtained of all cardiac compartments. An overall increase of cardiac systolic and diastolic function with embryonic/fetal development was observed. Conclusion. High-frequency echocardiography is a promising and useful imaging modality for structural and hemodynamic analysis of embryonic/fetal mouse hearts