Indices Of Contractile Function Research Articles

Ergogenic effect of ischemic preconditioning is not directly conferred to isolated skeletal muscle via blood.

Ischemic preconditioning (IPC) in humans has been demonstrated to confer ergogenic benefit to aerobic exercise performance, with an improvement in the response rate when the IPC stimulus is combined with concurrent exercise. Despite potential performance improvements, the nature of the neuronal and humoral mechanisms of conferral and their respective contributions to ergogenic benefit remain unclear. We sought to examine the effects of the humoral component of ischemic preconditioning on skeletal muscle tissue using preconditioned human serum and isolated mouse soleus. Isolated mouse soleus was electrically stimulated to contract while in human serum preconditioned with either traditional (IPC) or augmented (AUG) ischemic preconditioning compared to control (CON) and exercise (ERG) preconditioning. Force frequency (FF) curves, twitch responses, and a fatigue-recovery protocol were performed on muscles before and after the addition of serum. After preconditioning, human participants performed a 4km cycling time trial in order to identify responders and non-responders to IPC. No differences in indices of contractile function, fatiguability, nor recovery were observed between conditions in mouse soleus muscles. Further, no human participants improved performance in a 4-km cycling time trial in response to traditional nor augmented ischemic preconditioning compared to control or exercise conditions (CON 407.7 ± 41.1s, IPC 411.6 ± 41.9s, ERG 408.8 ± 41.4s, AUG 414.1 ± 41.9s). Our findings do not support the conferral of ergogenic benefit via a humoral component of IPC at the intracellular level. Ischemic preconditioning may not manifest prominently at submaximal exercise intensities, and augmented ischemic preconditioning may have a hormetic relationship with performance improvements.

ECHOCARDIOGRAPHIC ASPECTS OF ASSESSMENT OF MITRAL INSUFFICIENCY IN PATIENTS WITH ACUTE MYOCARDIAL INFARCTION WITH REDUCED LEFT VENTRICULAR EJECTION FRACTION.

The aim is to analyze patients with acute myocardial infarction with reduced ejection fraction in order to determine risk factors for mitral insufficiency. Materials and methods: The study included 149 patients with acute myocardial infarction. Among the patients, there were 113 males (75.8%) and 36 females (24.2%). The age of the patients ranged from 43 to 86 years. Echocardiography was performed using a Phillips Epiq 7 machine. Patients were examined three times: upon admission to the hospital, after revascularization, and six months after discharge. Patients received transthoracic echocardiography, which was used to determine the presence and degree of mitral regurgitation. Results: According to the results of the study, it was found that the presence of concomitant somatic pathology worsens the course of an acute myocardial infarction, in turn increasing the likelihood of valvular pathology. An increase in left ventricular volume indicators, such as end-diastolic volume, end-systolic volume, end-diastolic index, and the index of contractile function (ejection fraction) contributes to the development of mitral valve insufficiency. Conclusions: The presence of mitral regurgitation in patients with acute myocardial infarction and reduced left ventricular ejection fraction worsens the course of the disease and negatively affects the prognosis.

Impact of the Severity of Mitral Stenosis on the LV Systolic function as assessed by 2D Strain using Speckle tracking

Abstract Background Rheumatic heart disease remains a considerable cause of cardiovascular morbidity and mortality in developing countries and mitral stenosis is the most common valve affection of rheumatic heart disease worldwide.The left ventricular ejection fraction is the most widely used index of contractile function, but due to the visual component, assessment of endocardial excursion is subjective leading to inter-observer variability.Speckle-tracking echocardiography is an imaging technique developed as a method to objectively quantify myocardial function and analyzes cardiac motion and deformation by tracking naturally occurring speckle patterns in the myocardium. Objective To evaluate the effect of the severity of mitral stenosis on LV systolic function as assessed by speckle tracking. Patients and Methods This study was a case-control study involving 80 individuals which included 60 patients having mitral stenosis who presented to the outpatient clinics of Ain Shams University Hospitals and 20 healthy volunteers, The patients suffering from mitral stenosis were subdivided into 3 sub-groups: GROUP(1) 20 Patients having severe mitral stenosis (MV Area less than 1 cm²) GROUP (2) 20 Patients having moderate mitral stenosis (MV Area more than 1 cm² and less than 1.5 cm²) GROUP(3) 20 Patients having mild mitral stenosis (MV Area more than 1.5 cm²) A Control group involved 20 healthy volunteers recruited from health care workers in Ain Shams University hospitals. Results Study included 60 patients,16 males (26.7%) and 44 females (73.3%), with mean age of 41.30 ± 8.64 years. Patients living in rural Areas were 34 (57.7%) while those in urban areas were 26 (43.3%).Which was significant.There was no significant difference between gender or habitat and the severity of mitral Stenosis.There was a strong significance between the duration of the disease and its severity. The more the duration of mitral Stenosis, the more severe the mitral stenosis.A strong positive relation was noticed between the severity of mitral stenosis and both RVSP and LA diameter, while a strong negative relation between severity of mitral stenosis and GLPS. GLPS was affected in severe mitral stenosis only. Conclusion Subtle LV systolic dysfunction is present in large number of patients with severe mitral stenosis even in patients with normal ejection fraction by conventional 2D echocardiography.There was a significant relationship between the duration of mitral stenosis and its severity. The longer the duration of mitral stenosis, the more severe the mitral stenosis.Speckle tracking echocardiography (STE) can play a great role in identification of higher risk subgroups in whom earlier and more aggressive intervention could have a significant impact on their prognosis.

Distinct hemodynamic responses to (pyr)apelin-13 in large animal models.

This study tested the hypothesis that (pyr)apelin-13 dose-dependently augments myocardial contractility and coronary blood flow, irrespective of changes in systemic hemodynamics. Acute effects of intravenous (pyr)apelin-13 administration (10 to 1,000 nM) on blood pressure, heart rate, left ventricular pressure and volume, and coronary parameters were measured in dogs and pigs. Administration of (pyr)apelin-13 did not influence blood pressure (P = 0.59), dP/dtmax (P = 0.26), or dP/dtmin (P = 0.85) in dogs. However, heart rate dose-dependently increased > 70% (P < 0.01), which was accompanied by a significant increase in coronary blood flow (P < 0.05) and reductions in left ventricular end-diastolic volume and stroke volume (P < 0.001). In contrast, (pyr)apelin-13 did not significantly affect hemodynamics, coronary blood flow, or indexes of contractile function in pigs. Furthermore, swine studies found no effect of intracoronary (pyr)apelin-13 administration on coronary blood flow (P = 0.83) or vasorelaxation in isolated, endothelium-intact (P = 0.89) or denuded (P = 0.38) coronary artery rings. Examination of all data across (pyr)apelin-13 concentrations revealed an exponential increase in cardiac output as peripheral resistance decreased across pigs and dogs (P < 0.001; R2 = 0.78). Assessment of the Frank-Starling relationship demonstrated a significant linear relationship between left ventricular end-diastolic volume and stroke volume across species (P < 0.001; R2 = 0.70). Taken together, these findings demonstrate that (pyr)apelin-13 does not directly influence myocardial contractility or coronary blood flow in either dogs or pigs.NEW & NOTEWORTHY Our findings provide much needed insight regarding the pharmacological cardiac and coronary effects of (pyr)apelin-13 in larger animal preparations. In particular, data highlight distinct hemodynamic responses of apelin across species, which are independent of any direct effect on myocardial contractility or perfusion.

P621Variation of global longitudinal strain (2D STE) with passive leg lifting maneuver: a marker of myocardial functional reserve?

Abstract Introduction In a normal heart, the passive leg lifting maneuver (LLM) will result in an increase in myocardial contractility, according to the mechanistic concept of the Frank-Starling law. With the progression of myocardial disease this ability is impaired and the myocardial functional reserve (mFR) is reduced (Figure1 – Panel A). The variation of left ventricular global longitudinal strain (as an index of contractile function) with LLM may thus represent a marker of left ventricular mFR. Purpose To assess the variation of left ventricular global longitudinal strain (LV GLS) with LLM as a marker of mFR in a healthy population and in patients with myocardial disease (hypertrophic myocardiopathy - HCM and systolic dysfunction patients – SystDysf. Methods and results We evaluated the variation of LV GLS by 2-dimensional Speckle Tracking Echocardiography (2D-STE), in response to passive LLM, in a population of 103 individuals (54 healthy individuals, 28 HCM patients and 21 left ventricular SystDysf patients). Clinical, demographic and echocardiographic parameters (including LV longitudinal mechanics obtained with 2D-STE before and after LLM) were described. The population had a mean age of 46±18 years and 55% were women. Increased venous return to the heart during LLM was confirmed by an increase in the maximal diameter of the inferior vena cava (15,1±3,6 vs 20,6±3,8 mm, p&lt;0.001). There was a significant variation of LV GLS in healthy individuals submitted to LLM (−20,58±3,0 vs −21,5±2,6%, p=0,02, Δ 0,6%, 95% CI 0,1–1,1%). Regarding the HCM and SystDysf groups, no significant change in LV GLS was observed with LLM (−13,2±2,8 vs −12,3±2,9%, p=0,12, Δ +0,6%, 95% CI −1,4 to 0,18% and −10,2±2,5 vs 10,2±2,7%, p=0,79, Δ 0,08%, 95% CI −0,7 to 0,5%, respectively). Figure 1 (Panel B) Conclusion To our knowledge, this is the first report describing the use of LV GLS and LLM to assess mFR in this clinical setting. The absolute increase of LV GLS in the healthy population suggests that this may be a reliable method and a sensitive marker to assess the mFR. Conversely, patients with HCM and with SystDysf show poor or no response to the LLM, suggesting, as expected, a low myocardial functional reserve. Given the non-invasiveness and cost-effectiveness nature of this technique, we suggest that this maneuver could pose a feasible way to assess mFR. Further studies are needed to validate this technique and to assess the role of mFR by 2D-STE as a prognostic marker.

Biatrial performance in children with hypertrophic cardiomyopathy: CMR study

ObjectivesTo investigate biatrial mechanics and their relation with left ventricular outflow tract (LVOT) obstruction (LVOTO), the degree of hypertrophy, indices of ventricular diastolic function and fibrosis in children with hypertrophic cardiomyopathy (HCM).MethodsFifty-five consecutive, prospectively recruited children with HCM (mean age 12.5 ± 4.6 years, 69.1% male), 19 (34.5%) of whom had LVOTO, underwent cardiac magnetic resonance and echocardiography with quantification of phasic components of biatrial function, biventricular diastolic function and fibrosis. Twenty healthy, sex-matched subjects served as controls.ResultsWe found a significant increase of left atrial (LA) and right atrial (RA) volumes and reduction in the majority of indices of contractile function, strains and strain rates (p < 0.05) in children with HCM compared with controls. Nearly all of the LA dynamics markers attained a significant association with the LVOT gradient (p < 0.05), the RA volumes and contractile functions were affected by LV fibrosis and mass (p < 0.05), and the RA mechanical components were related to the degree of LVOTO (p < 0.05). The minority of biatrial dynamics markers were associated with indices of ventricular diastolic function.ConclusionsThe majority of biatrial volumetric and functional indices were severely compromised in children with HCM compared with controls. The degree of LVOTO appears to trigger LA volumetric and LA and RA mechanical malfunction. On the other hand, the deterioration of RA volumetric components was linked to LV fibrosis and mass.Key Points• Biatrial function was severely compromised in children with HCM.• Left atrial malfunction was associated with the degree of LVOTO.• Fibrosis and LV mass were related to RA volumetric and contractile dysfunction.• The degree of LVOTO was linked to right atrial mechanical abnormalities.

Clinical Impact of Changes in Hemodynamic Indices of Contractile Function During Treatment of Acute Decompensated Heart Failure

BackgroundThe objective of this work was to determine the impact of improving right ventricular versus left ventricular stroke work indexes (RVSWI vs LVSWI) during therapy for acute decompensated heart failure (ADHF). Methods and ResultsCox proportional hazards regression and logistic regression were used to analyze key factors associated with outcomes in 175 patients (mean age 56.7 ± 13.6 years, 29.1% female) with hemodynamic data from the Evaluation Study of Congestive Heart Failure and Pulmonary Artery Catheterization Effectiveness trial. In this cohort, 28.6% and 69.7%, respectively, experienced the outcomes of death, transplantation, or ventricular assist device implantatation (DVADTX) and DVADTX or HF rehospitalization (DVADTXHF) during 6 months of follow-up. Increasing RVSWI (ΔRVSWI) from baseline to discharge was associated with a decrease in DVADTXHF (hazard ratio [HR] 0.923, 95% confidence interval [CI] 0.871–0.979) per 0.1 mm Hg⋅L⋅m−2 increase); however, increasing LVSWI (ΔLVSWI) had only a nonsignificant association with decreased DVADTXHF (P = .11) In a multivariable model, patients with ΔRVSWI ≤1.07 mm Hg⋅L⋅m−2 and ΔLVSWI ≤4.57 mm Hg⋅L⋅m−2 had a >2-fold risk of DVADTXHF (HR 2.05, 95% CI 1.23–3.41; P = .006). ConclusionCompared with left ventricular stroke work, increasing right ventricular stroke work during treatment of ADHF was associated with better outcomes. The results promise to inform optimal hemodynamic targets for ADHF.

Cardiac mechanics and dysfunction with anthracyclines in the community: results from the PREDICT study

BackgroundOur objective was to determine the relevance of changes in myocardial mechanics in diagnosing and predicting cancer therapeutics-related cardiac dysfunction (CTRCD) in a community-based population treated with anthracyclines.MethodsQuantitative measures of...

The influence of β-endorphin on the functional activity of the isolated heart of rat. The role of δ-opioid receptors

The purpose of research is to learn the influence of β-endorphin on the functional activity indicators of the isolated heart of rat and to evaluate the role of opioid receptors. Materials and methods. The research was performed on isolated hearts of males nonlinear white rats. Perfusion of the heart was performed on the Langendorff System at constant flow. Register indicators are volume rate of coronary perfusion, perfusion pressure, the pressure in the left ventricle, pulse pressure, heart rate, speed of changing the pressure developed by the left ventricle. Additionally was calculated integral indicator minute performance of the left ventricle corresponding to the area under the curve of change of pressure in the left ventricle per a minute, index of contractile function and the integral indicator of the average performance of the left ventricle per one contraction. Results and discussion. It was identified depressant effect of β-endorphin in slightly declining trend to decrease of myocardial contractility indicators in a concentration range from 6.3x10 -10 to 6.3x10 -18 M. In the presence of a blocker of δ-opioid receptor naltrindole inhibitory effect of β-endorphin identified in isolated use, practically was not manifested. Thus, the peripheral δ-opioid receptors of cardiomyocytes mediate the decrease of myocardial contractility caused by β-endorphin using. Conclusions. β-endorphin in physiological concentrations has a depressing effect on functional parameters of the isolated heart of rat. Stimulation of δ-opioid receptors is one of the mechanisms leading to formation of the negative inotropic effect of β-endorphin as a component of local cardiac activity regulation.

Mechanical restitution curves — a possible load independent assessment of contractile function

The time constant of mechanical restitution (T((MRC))), proposed to reflect changes in calcium release and uptake, has been shown to increase in left ventricular (LV) failure, and might have a potential as an index of contractile function. However, in vivo studies of the effect on T((MRC)) of changing loading conditions in the normal and failing heart have not been reported. Consequently, in this study, we tested the hypothesis that the increase in T((MRC)) in vivo is independent of preload and afterload. Left ventricular pressure-volume loops were assessed at baseline in eight open chest pigs using the combined pressure-volume conductance catheter technique during right atrial pacing at 120b/min. Mechanical restitution curves (MRC) were constructed during four different loading conditions in all eight animals: uninfluenced load, reduced preload (balloon catheter in v. cava inferior), increased afterload (balloon catheter in descending aorta), and increased preload combined with reduced afterload (aortocaval shunting). Acute LV failure was then induced by microembolization through the left main coronary artery, and the experimental protocol was repeated. Contractile response was defined as the maximal first derivative of pressure (dP/dt(max)), and T((MRC)) was calculated using a least square approximation algorithm. Hemodynamic data 30min after microembolization showed decreased mean arterial pressure (98+/-14-67+/-10mmHg, (mean+/-SD) P<0.0001) and dP/dt(max) (1482+/-193-1001+/-125mmHg/s, P=0.001). Stroke volume decreased from 30+/-5 to 20+/-5ml (P<0.0001) compared to baseline, and preload recruitable stroke work decreased from 52+/-7 to 31+/-10mmHg (P=0.002). T((MRC)) increased in all eight animals after induction of LV failure at all loading conditions. There was no difference between the different loading conditions at baseline, nor at LV heart failure, but T((MRC)) increased significantly after the induction of heart failure (ANOVA, two ways). We have shown that the left ventricular T((MRC)) increases after developed heart failure. The increase in T((MRC)) was independent on loading conditions and thus have a potential for a contractility index.

Role of reverse mode Na +/Ca 2+ exchanger in the cardioprotection of metabolic inhibition preconditioning in rat ventricular myocytes

This study determined the role of the reverse mode Na +/Ca 2+ exchanger (NCX) in cardioprotection of metabolic inhibition preconditioning in isolated ventricular myocyctes. Activity of the reverse mode NCX was assessed by changes of [Ca 2+] i upon withdrawal of extracellular Na +. [Ca 2+] i was measured by spectrofluorometry, using Fura-2 as Ca 2+ indicator. The amplitude of contraction and exclusion of trypan blue by myocytes served as indices of contractile function and viability, respectively. Firstly, NCX activity significantly decreased during simulated reperfusion after severe metabolic inhibition (index ischaemia) in myocytes subjected to metabolic inhibition preconditioning. This inhibitory effect on NCX activity correlated with the enhancing effect of metabolic inhibition preconditioning on cell viability following ischaemic insult. Treatment myocytes with E4031, an activator of reverse mode NCX, during index ischaemia and reperfusion attenuated the enhancing effects of metabolic inhibition preconditioning on cell contraction and viability. Secondly, NCX activity was significantly higher at the end of metabolic inhibition preconditioning. More importantly, E4031 pretreatment mimicked the beneficial effects of metabolic inhibition preconditioning in myocytes and ischaemic preconditioning in the isolated perfused heart, respectively, and these effects were abolished by KB-R7943, an inhibitor of reverse mode NCX. The results indicate that increased reverse mode NCX activity during preconditioning triggered cardioprotection, and reduced reverse mode NCX activity during reperfusion after index ischaemia conferred cardioprotection.

Noninvasive Analysis of Myocardial Function Using High-Resolution Doppler Tissue Echocardiography in Rats

The widespread use of rodent models of cardiovascular disease has demanded improved methods of assessing myocardial function. Recently, invasive measurement of cardiac function using conductance catheterization has become available for assessing ventricular performance in small animals. 1-3 However, although pressure-volume loop analysis has become the gold standard, it is impractical for longitudinal assessment of disease or interventions. The ideal method under these circumstances would be noninvasive, an accurate index of contractile function, resistant to the influence of load, and reproducibly measurable in small animals. Doppler tissue echocardiography (DTE) is a new modality that has been widely used to assess cardiac function noninvasively. 4,5 Many indices of systolic function have been described but, as might be expected, ejection-phase indices have been shown to be load dependent. This limits their applicability to the assessment of intrinsic myocardial contractility. We have recently demonstrated that myocardial isovolumic acceleration (IVA), derived by DTE, is a relatively load-independent index of systolic ventricular function that is also capable of describing the force-frequency relationships in both the right ventricle and left ventricle (LV) in porcine models and human beings. 6,7 DTE has previously been used to assess cardiac function in rodent models. For example, myocardial systolic and diastolic velocity gradients were shown to be abnormal in a rat model of myocardial hypertrophy. 8 However, interpretation of such data obtained with conventional probes, which are limited in terms of both spatial and temporal resolution, is difficult. Furthermore, as in studies of larger animals and human beings, interpretation of noninvasively acquired data can only be complete when the load dependency of the index is understood. To our knowledge, there are no systematically obtained data regarding the load dependency of systolic indices of function measured by DTE. This study assesses the use of DTE indices in small rodents. Using a high-resolution probe, we investigated IVA, isovolumic velocity (IVV), and systolic wall velocity (SW) of the LV myocardium together with simultaneous conductance catheter recording of pressure and volume. We examined contractile function to determine the influence of alterations in preload and afterload, and measured the response of these indices to inotropic change.

Does local anesthetic stereoselectivity or structure predict myocardial depression in anesthetized canines?

Background and Objectives: It is unclear whether the susceptibility to myocardial depression from an accidental intravascular local anesthetic (LA) administration is associated with LA stereoselectivity or structure. By using direct left ventricular pressure monitoring and echocardiographic indices of contractile function in anesthetized, ventilated dogs, we compared the cardiac depressant effects of bupivacaine, ropivacaine, levobupivacaine, and lidocaine. Methods: Open-chest dogs were randomized to receive escalating incremental infusions of the 4 local anesthetics until cardiovascular collapse. We assumed a concentration relationship for potency of 4:1 for lidocaine/bupivacaine, ropivacaine, and levobupivacaine. Results: All LAs produced concentration-dependent increases in left ventricular end diastolic pressure (LVEDP) and decreases in dP/dtmax, ejection fraction % (EF), fractional shortening (%) (FS), and cardiac output (CO). When comparing the long-acting agents, the effect was least for ropivacaine. The effective concentration estimates for ropivacaine that produced 35% reductions in dP/dtmax and FS were 4.0 μg/mL (95% confidence intervals [CI95]: 3.1 to 5.2 μg/mL) and 3.0 μg/mL (CI95: 2.1 to 4.2 μg/mL), respectively. The concentrations of levobupivacaine that produced these same end points of contractile dysfunction were significantly less: 2.4 μg/mL (CI95: 1.9 to 3.1 μg/mL) and 1.3 μg/mL (CI95: 0.9 to 1.8 μg/mL), respectively, and these were not different from bupivacaine. As expected, the concentrations of lidocaine that produced 35% reductions in dP/dtmax and FS were significantly greater than the longer acting agents; 8.0 μg/mL (CI95: 5.7 to 11.0 μg/mL) and 5.5 μg/mL (CI95: 3.5 to 8.7 μg/mL), respectively. Conclusions: This study suggests that smaller molecular size and possibly a piperidine-free structure as opposed to stereoselectivity may be the more important factor in reducing the risk of LA-induced myocardial depression. Reg Anesth Pain Med 2002;27:460-468.

Assessment of myocardial contractile reserve during dobutamine stress echocardiography in patients with coronary artery disease by the novel index of contractile function: myocardial acceleration during isovolumic contraction

Assessment of myocardial contractile reserve during dobutamine stress echocardiography in patients with coronary artery disease by the novel index of contractile function: myocardial acceleration during isovolumic contraction

Noninvasive assessment of the force frequency relationship by a novel tissue doppler-based index of contractile function: myocardial acceleration during isovolumic contraction in an animal experiment

Noninvasive assessment of the force frequency relationship by a novel tissue doppler-based index of contractile function: myocardial acceleration during isovolumic contraction in an animal experiment

Sialyl Lewis X oligosaccharide preserves myocardial and endothelial function during cardioplegic ischemia

Background. Neutrophil adhesion to endothelium contributes to myocardial reperfusion injury after cardiac operation. Initial neutrophil-endothelial interactions involve selectins, which bind Sialyl-Lewis X on neutrophils. Blockade of selectin-mediated neutrophil-endothelial interactions with CY-1503, a synthetic analogue of Sialyl-Lewis X, might reduce reperfusion injury after myocardial ischemia. Methods. The efficacy of CY-1503 to attenuate global myocardial reperfusion injury was assessed in isolated blood-perfused neonatal lamb hearts that had 2 hours of cold cardioplegic ischemia. CY-1503 (40 mg/L) or saline vehicle was added to blood perfusate before ischemia. Contractile function (developed pressure, dP/dt) and coronary vascular endothelial function (acetylcholine response) were assessed at base line and during reperfusion. Myocardial neutrophil accumulation was assessed by myeloperoxidase quantification. Results. Compared to controls, treatment with CY-1503 improved recovery of all indices of contractile function, preserved coronary vascular endothelial function, and reduced myocardial neutrophil accumulation. Conclusions. In isolated neonatal lamb hearts that underwent hypothermic cardioplegic ischemia, CY-1503 administration reduced myocardial neutrophil accumulation and preserved endothelial and contractile function. Selectin blockade of leukocyte-endothelial interactions might attenuate reperfusion injury and enhance myocardial protection during cardiac surgical procedures.

Myocardial effects of repeated electrical defibrillations in the isolated fibrillating rat heart.

Although substantial myocardial cell injury has been reported after high-energy electrical defibrillation, only minimal injury with transient functional defects seems to develop at energy levels not exceeding those required to reverse ventricular fibrillation. Because multiple electrical shocks are often delivered in clinical settings during attempts to reverse ventricular fibrillation, we investigated the effects of repetitive shocks on postresuscitation myocardial dysfunction by using an isolated rat heart model of ventricular fibrillation. Prospective and randomized. Cardiopulmonary resuscitation research laboratory. Twenty-seven Sprague-Dawley rats. Hearts were harvested and perfused at a constant flow of 10 mL/min by using a modified Krebs-Henseleit solution equilibrated with 95% oxygen and 5% CO2. Ventricular fibrillation (VF) was induced by a 0.05-mA current delivered to the right ventricular endocardium and the perfusate flow was stopped. After 10 mins, the perfusate flow was resumed at 20% of baseline flow and maintained for 15 additional minutes before returning to baseline flow after 25 mins of VF (VF25 mins). Twenty-seven hearts were randomized to receive from VF22 mins to VF25 mins either 0 epicardial shocks, 6 epicardial shocks, or 12 epicardial shocks. Isovolumic indices of left ventricular function were obtained by using a latex balloon advanced through the mitral valve into the ventricular cavity. After defibrillation, indices of contractile function rapidly returned to baseline without differences among groups. The isovolumic end-diastolic pressure, however, remained elevated throughout the postresuscitation interval. A left shift of the diastolic pressure-volume curves without changes in their slope was observed at 10 mins after resuscitation with partial return to baseline by 30 mins postresuscitation. The shifts were significantly greater in hearts that received 12 shocks. These findings indicate that repetitive low-energy electrical shocks do not accentuate postischemic systolic dysfunction in the isolated fibrillating rat heart but adversely affect postischemic diastolic dysfunction by reducing the unstressed left ventricular end-diastolic volume.

Exercise echocardiographic assessment in severe mitral regurgitation.

In chronic severe mitral regurgitation, minimum morbidity and mortality is achieved by applying surgical correction before left ventricular dysfunction becomes irreversible. This requires detection of subtle signs of early ventricular decompensation, for which isotonic stress echocardiography is more accurate than is use of resting indices of contractile function alone. We perform serial 6-monthly stress echocardiography for patients with severe mitral regurgitation, and recommend surgery when the exercise end-systolic volume index or ejection fraction reaches the cutoff values in Table 4 or if there is a clear adverse trend. Exercise echocardiography is more accurate than is exercise electrocardiography for detecting concomitant coronary disease prior to revascularization. Stress testing is also an objective measure of symptoms. Color-Doppler stress echocardiography can detect those patients whose mitral regurgitation worsens (or even develops de novo) with exercise, which can explain unexpected symptoms. Stress echocardiography, therefore, provides a comprehensive and cost-effective evaluation of patients with mitral regurgitation that combines functional, diagnostic, and prognostic information.

Single-beat determination of preload recruitable stroke work relationship: derivation and evaluation in conscious dogs

OBJECTIVESTo derive and evaluate a method of estimating the slope (Mw) of the preload recruitable stroke work (PRSW) relationship between left ventricular stroke work (SW) and end-diastolic volume (EDV) from a single beat.BACKGROUNDMwis a load-insensitive index of contractile function, but its clinical application has been limited by the need to record multiple beats over a wide volume range.METHODSPressure-volume loops were recorded over a variable preload and afterload range by vena caval and aortic constrictions in 12 conscious dogs instrumented with epicardial dimension transducers and micromanometers. Single-beat Mw(SBMw) was determined as the ratio SW/(EDV − Vw), where the volume-axis intercept of the PRSW relationship (Vw) (EDV at zero SW) was estimated as k·EDVB+ (k− 1)LVwall, kis the ratio of the epicardial shell volumes corresponding to Vwand baseline EDV (EDVB) and LVwallis wall volume.RESULTSIn the first six dogs, kwas found to be essentially constant at 0.7, SBMwestimates were insensitive to wide preload variation, and the relationship between SBMwand multibeat Mwdetermined during caval and aortic constrictions did not differ significantly from the line of identity. When the same constant kvalue was applied to SBMwestimation in a different group of six dogs, SBMwdid not differ significantly from multibeat Mw(83 ± 12 erg·cm−3·103and 77 ± 12 erg·cm−3·103, respectively), neither changed significantly during aortic constriction and both increased significantly with calcium infusion (107 ± 18 erg·cm−3·103and 95 ± 19 erg·cm−3·103, respectively, both p < 0.05). Single-beat Mwwas less load-dependent, more reproducible and a more sensitive index of inotropic state than two previously described single-beat indexes, single-beat elastance and maximum power divided by EDV2.CONCLUSIONSMwcan be determined accurately from a single, steady-state beat in the normal canine heart and is sensitive to inotropic alterations while being insensitive to wide variations in preload and afterload. Single-beat Mwestimation should facilitate noninvasive, load-independent assessment of contractile function.

Acute Right Ventricular Dilatation in Response to Ischemia Significantly Impairs Left Ventricular Systolic Performance

Background—Right ventricular (RV) dilatation that occurs as a consequence of RV infarction is thought to produce hemodynamic instability by reducing left ventricular (LV) preload and compliance. We hypothesized that these geometric changes may also adversely affect LV systolic performance. Methods and Results—Twelve 40-kg pigs were studied. Integrated conductance catheters and micromanometers were placed in both the LV and RV to allow simultaneous recordings of pressure and volume and derivation of indices of contractile function. RV ischemia was induced by balloon occlusion of the proximal right coronary artery (RCA) under 3 conditions: 1) with the pericardium intact, 2) with the pericardium intact and inotropic support, and 3) with the pericardium wide open. With an intact pericardium, RCA occlusion produced a decrease in LV end-diastolic volume associated with a marked decline in the contractile function. With the pericardium open, the same ischemic insult resulted in both LV and RV dilatation, which p...