Local Myocardial Contractility Research Articles

Simulated Effects of Acute Left Ventricular Myocardial Infarction on Mitral Regurgitation in an Ovine Model.

Ischemic mitral regurgitation (IMR) occurs from incomplete coaptation of the mitral valve (MV) after myocardial infarction (MI), typically worsened by continued remodeling of the left ventricular (LV). The importance of LV remodeling is clear as IMR is induced by the post-MI dual mechanisms of mitral annular dilation and leaflet tethering from papillary muscle (PM) distension via the MV chordae tendineae (MVCT). However, the detailed etiology of IMR remains poorly understood, in large part due to the complex interactions of the MV and the post-MI LV remodeling processes. Given the patient-specific anatomical complexities of the IMR disease processes, simulation-based approaches represent an ideal approach to improve our understanding of this deadly disease. However, development of patient-specific models of left ventricle-mitral valve (LV-MV) interactions in IMR are complicated by the substantial variability and complexity of the MR etiology itself, making it difficult to extract underlying mechanisms from clinical data alone. To address these shortcomings, we developed a detailed ovine LV-MV finite element (FE) model based on extant comprehensive ovine experimental data. First, an extant ovine LV FE model (Sci. Rep. 2021 Jun 29;11(1):13466) was extended to incorporate the MV using a high fidelity ovine in vivo derived MV leaflet geometry. As it is not currently possible to image the MVCT in vivo, a functionally equivalent MVCT network was developed to create the final LV-MV model. Interestingly, in pilot studies, the MV leaflet strains did not agree well with known in vivo MV leaflet strain fields. We then incorporated previously reported MV leaflet prestrains (J. Biomech. Eng. 2023 Nov 1;145(11):111002) in the simulations. The resulting LV-MV model produced excellent agreement with the known in vivo ovine MV leaflet strains and deformed shapes in the normal state. We then simulated the effects of regional acute infarctions of varying sizes and anatomical locations by shutting down the local myocardial contractility. The remaining healthy (noninfarcted) myocardium mechanical behaviors were maintained, but allowed to adjust their active contractile patterns to maintain the prescribed pressure-volume loop behaviors in the acute post-MI state. For all cases studied, the LV-MV simulation demonstrated excellent agreement with known LV and MV in vivo strains and MV regurgitation orifice areas. Infarct location was shown to play a critical role in resultant MV leaflet strain fields. Specifically, extensional deformations of the posterior leaflets occurred in the posterobasal and laterobasal infarcts, while compressive deformations of the anterior leaflet were observed in the anterobasal infarct. Moreover, the simulated posterobasal infarct induced the largest MV regurgitation orifice area, consistent with experimental observations. The present study is the first detailed LV-MV simulation that reveals the important role of MV leaflet prestrain and functionally equivalent MVCT for accurate predictions of LV-MV interactions. Importantly, the current study further underscored simulation-based methods in understanding MV function as an integral part of the LV.

ST-elevation myocardial infarction in patients with type 2 diabetes mellitus. Influence of the SGLT2 inhibitor dapagliflozin

Background. Patients with type 2 diabetes mellitus (T2DM) have a 2-fold higher risk of deve­loping coronary heart disease and mortality than those without carbohydrate metabolism disturbances. The reason for such negative trends is the occurrence of metabolic stress due to hyperglycemia and insulin resistance, which causes disturbance in energy metabolism and ischemic damage to cardiomyocytes. The purpose of the study is to improve the effectiveness of rehabilitation treatment and assess the dynamics of quality of life in patients with ST-elevation myocardial infarction (STEMI) and T2DM who are at high risk of develo­ping cardiac complications during the inpatient treatment by including the sodium-glucose transport protein 2 (SGLT2) inhibitor dapagliflozin in the comprehensive therapy. Materials and methods. The study group consisted of 38 patients with STEMI and T2DM who received dapagliflozin in addition to percutaneous coronary intervention (PCI). The control group included 37 patients with STEMI and T2DM who received only standard protocol treatment after PCI. In addition to general clinical examinations and assessment of quality of life using the EuroQol Group EQ-5D-5L questionnaire (1990), echocardiography was performed to determine general and local myocardial contractility by the Simpson method; plasma levels of glucose, insulin were evaluated, and insulin resistance was determined by the HOMA-IR. Results. Patients with STEMI and T2DM after PCI most often developed reperfusion syndrome with left ventricular failure and rhythm disturbances. Under the influence of standard medical treatment, a significant clinical and functional improvement was observed, but postinfarction remodeling progressed with impaired systolic and diastolic function and the development of heart failure syndrome, as well as treatment-resistant atrial and ventricular fibrillation paroxysms, supraventricular and ventricular extrasystoles, and bundle branch block. In patients of the study group with STEMI and T2DM on the comprehensive treatment with the SGLT2 inhibitor dapagliflozin, a significant decrease in the frequency of rhythm and conduction disturbances was noted on the se­cond day of observation, as well as a decrease in postinfarction left ventricular remodeling, which ultimately manifested in a statistically significant improvement of myocardial contractility (ejection fraction increased by 6.7 %) and a decrease in diastolic dysfunction. There was also a significant decrease in the frequency and severity of reperfusion arrhythmias, which was achieved due to the cardiometabolic effect of the SGLT2 inhibitor dapagliflozin. Conclusions. The inclusion of the SGLT2 inhibitor dapagliflozin in the comprehensive treatment led to a significant improvement in central cardiac hemodynamic parameters and a decrease in the frequency and severity of reperfusion arrhythmias and acute left ventricular failure, which contributed to the improvement in quality of life.

Cardiac structural and functional changes in ischemia-reperfusion injury of myocardium

The aim is to study the effect of microvascular reperfusion injury (RI) of myocardium on structural and functional changes of heart in patients with acute coronary syndrome with ST segment elevation (STE-ACS) and endovascular revascularization. Materials and Methods. The study included 146 patients with STE-ACS (mean age 54 ± 10 years, 89 % men). Depending on the presence of microvascular RI, according to CMR, performed on 5 ± 3 days after myocardial infarction, patients were divided into groups: the first group included 73 patients (50 %) with microvasculature lesions, the second group consisted of 73 patients (50 %) without microvasculature lesions. All patients underwent endovascular myocardial revascularization within 12 hours of symptoms onset. The assessment of structural and functional parameters of heart was performed by CMR with contrast enhancement on 5 ± 3, 30 and 90 days, by echocardiography on 1-2 days, 1, 6 and 12 months after myocardial infarction. Results. In our study microvascular RI was accompanied by a significant size of infarction, a high transmurality index (TI), a large size of edema and a low myocardial salvage index, was associated with LV dilatation, a decrease in global and local myocardial contractility during the 12 months post-infarction period (p < 0.05). The risk of developing pathological remodeling of left ventricle with microvascular RI size >1.2 % of LV mass is OR=6.25, 95 % CI 2.25–17.35 (p < 0.001), myonecrosis size on day 5 ± 3 of MI >11.7 % of LV mass (OR=10.1, 95 % CI 4.72–21.69, p < 0.001), TI > 64.3 (OR=5.63, 95 % CI 2.37–13.39, p < 0.001), edema size >24.7 % of LV mass (OR = 2.33, 95 % CI 1.09–4.97, p < 0.02). Conclusion. Microvascular RI of myocardium is associated with pathological remodeling of the left ventricle.

Detection of symptom-related coronary arteries in patients with coronary artery disease using real-time three-dimensional stress echocardiography with adenosine triphosphate

Aim 1) To develop normative values of global and regional left ventricular longitudinal deformation (LVLD) during real time three-dimensional stress echocardiography with adenosine triphosphate (ATP) and utilization of automated function imaging technology (4D Stress-Echo + LVLD with ATP); 2) to compare the effectiveness of detection of symptom-related coronary arteries during 4D Stress-Echo with ATP using: a) traditional visual assessment of regional myocardial contractility and b) step-by-step analysis of segmental LVLD.Material and Methods 15 healthy subjects and 32 patients with coronary artery disease (CAD) were examined after coronary angiography. All individuals underwent 4D Stress-Echo + LVLD with ATP (Vivid E95, General Electric).Results The normative values of global LVLD at three stages of the pharmacological stress-test (before, during and after ATP infusion) were –19.5 (95% CI: -20.4 – -19.0), –21.6 (95% CI: -22.8 – -20.4) and –19.5 (95% CI: -20.3 – -18.6), respectively; the values of LVLD in each of the 17 segments of left ventricular myocardium in healthy subjects were also determined. In patients with CAD visual control of contractility during stress test revealed dynamic decrease in local thickening of the myocardium, appearance of new zones of contractility disorders and expansion of previously noted in 31.2% of cases, while analysis of deformation detected the appearance of new zones of deformation disturbances and expansion of previously found – in 68.7% (р = 0.0055). Stress-induced worsening of myocardial deformation during ATP infusion in the zones of blood supply of left anterior descending coronary artery, circumflex artery and right coronary artery (with presence of hemodynamically significant stenoses and occlusions detected during coronary angiography) were found in 28.0, 77.7 and 65.2% respectively (р1-3 = 0.0194; р1-2 = 0.0019; р2-3 = 0.2864).Conclusion The normal values of global and segmental LVLD for each stage of 4D Stress-Echo + LVLD with ATP were determined. 4D Stress-Echo + LVLD with ATP can significantly increase the effectiveness of symptom-related coronary arteries identification in patients with CAD in comparison with traditional Stress-Echo with visual assessment of local myocardial contractility.

Impact of comorbid chronic heart failure with preserved left ventricular ejection fraction on the management of elderly cancer patients before and after total resections

To determine the predictors of safe enhanced recovery after surgery in elderly cancer patients with comorbid chronic heart failure (CHF) and preserved left ventricular ejection fraction (LVEF). There were 75 patients over 65 years old (mean 73.6±5.6 years) with cancer of abdominal and pelvic organs and comorbid cardiovascular diseases for the period from January 2018 to July 2020. All patients underwent total resections with enhanced postoperative recovery at the Petrovsky National Research Centre of Surgery. CHF with preserved LVEF was diagnosed in 42 (56%) patients (NYHA class I - 20 patients, class II - 19 patients, class III - 3 patients). ACE/ARA/neprilysin inhibitors were described in 74.7% of patients, beta-blockers - 70.7%, calcium channel blockers - 37.3%, diuretic therapy - 21.3%, antithrombotic therapy - 62.7%, statins - 54.7%, antiarrhythmic therapy - 12%. Preoperative correction of cardiac therapy was required in 60% of patients. Mean LVEF was 58.5±6.8%, pulmonary artery systolic pressure - 29±7.8 mm Hg, impairment of local myocardial contractility was observed in 6.7% of patients. Serum NT-proBNP level was 534.5±63.9 pg/ml, LDL-C - 3.3±1.1 mmol/l, GFR - 65.95±17.1 ml/min/1.73m2, glycated hemoglobin 6.37±0.67%. Perioperative risk of cardiovascular complications within 30-day postoperative period was assessed using the Revised Cardiac Risk Index (RCRI) score (6% in 59 patients, 10.1% in 11 patients, and 15% in 5 patients). Incidence of cardiovascular complications in early postoperative period was 4%, postoperative 30-day mortality rate - 1.3%. Our small study of surgical treatment of elderly cancer patients with comorbid CHF with preserved LVEF demonstrates the need for a personalized assessment of preoperative clinical and instrumental data to optimize cardiac therapy and perioperative monitoring. Multidisciplinary approach reduces perioperative mortality and cardiovascular morbidity from 7.2% to 4%.

Prophylaxis of Reperfusion Complications in Treatment of Acute Myocardial Infarction in Type 2 Diabetes Mellitus Patients

Purpose — to identify the possibility of improving the outcome of multimodality treatment of acute myocardial infarction (AMI) in type 2 diabetes mellitus (DM) patients by use of a succinate-containing drug.Materials and methods. The results of examination and treatment of 86 men aged 40 to 70 years with clinical diagnosis of AMI and concomitant type 2 DM were analyzed. The patients were split into two groups depending on use of the succinate-containing drug. Patients of the control group (38 men, 58.3±7.1 years old) received the standard treatment that included percutaneous coronary intervention (PCI). In the main group under study (48 men, 57.6±7.6 years old), the standard therapy complex was complemented with administration of a succinate-containing drug (1.5% succinic acid solution), which was administered first 30–60 minutes prior to PCI intravenously at a dose of 10–12 ml/kg; then, daily once a day, for 5 days at a dose of 5–6 ml/kg. Peculiarities of the AMI clinical course, dynamics of myocardial contractility, values of acid-base balance (ABB), glucose and lactate content, lipid peroxidation (LPO) and antioxidant system (AOS), rheological properties of the blood were evaluated.Results. During AMI type 2 DM patients developed compensated metabolic lactic acidosis and oxidative distress that manifested in considerable activation of LPO and insufficient activity of the enzymatic component of AOS, blood viscosity grew, elasticity of red blood cells fell. Decreased local and global myocardial contractility was noted as well. During PCI in this category of patients, cardiac rhythm disorders developed in 47.4% of cases, 23.7% of which were life threatening, such as multifocal ventricular extra systole and ventricular fibrillation. Conclusion. Administration of a succinate-containing drug during performance of PCI provided correction of the lipid peroxidation processes and rheological properties of the blood in the population studied, facilitated improvement of left ventricle’s systolic and diastolic function, reduced the risk of reperfusion complications.

PREVALENCE OF CARDIAC RISK FACTORS IN PATIENTS WITH ABDOMINAL AORTIC ANEURYSM

Introduction. According to the literature, 27 to 65 % of patients with abdominal aortic aneurysm also suffer from coronary heart disease. Mortality from coronary heart disease after surgical treatment for abdominal aortic aneurysm according to some data exceeds 20 %.Objective: improvement of results of treatment of patients with combined lesions of coronary arteries and aneurysm of the abdominal aortaSubjects and method. A retrospective analysis of case histories of 100 patients hospitalized in our clinic diagnosed with «abdominal aortic aneurysm» for examination. Of all patients, 37 % were diagnosed with significant coronary artery lesions. The average ejection fraction was 58.2 ± 5.4 %, 13 % of the study diagnosed significant violations of local myocardial contractility. 16 % of patients had previous myocardial infarction, 7 % – a permanent form of atrial fibrillation. 4 % of patients complained of chest pain during exercise. Hypertension was present in 100 % of patients, the average maximum systolic blood pressure was 176 ± 24.5 mmHg.Results. Hospital mortality was 2 % (all patients were non-operated on coronary arteries and had no significant coronary pathology). There were no significant complications (cardiac, neurological, respiratory) in the early postoperative period. The average length of hospital stay was 9.8 ± 1.99 bed days.Conclusions. Determination of cardiac status before surgery for abdominal aortic aneurysm is the most important moment of stratification of the risk of perioperative complications. Coronary angiography in patients with abdominal aortic aneurysm is a mandatory point of diagnosis, allowing to identify cardiac risk factors.

GW28-e0166 Can we use high intensity reflected motion signals (RIMS) for assessment of local myocardial contractility?

GW28-e0166 Can we use high intensity reflected motion signals (RIMS) for assessment of local myocardial contractility?

CHANGE OF LOCAL MYOCARDIAL CONTRACTILITY DUE TO SELECTION OF DIFFERENT ARRHYTHMIA TREATMENT STRATEGIES IN PATIENTS WITH ISCHEMIC HEART DISEASE AND PAROXYSMAL ATRIAL FIBRILLATION

Aim. To study the change of local myocardial contractility in patients with ischemic heart disease (IHD) and paroxysmal atrial fibrillation (AF) during treatment with amiodarone 200 mg daily compared with bisoprolol therapy 5 mg daily. Material and methods. A total of 47 IHD patients with persistent AF were enrolled in the study. Sinus rhythm (SR) was restored during the first 24 hours after admission in all the patients. After SR restoration patients were randomly allocated into two groups receiving either amiodarone 200 mg/day during 6 months for SR maintenance (group 1) or bisoprolol 5 mg daily for ventricular rate (VR) control (group 2). To estimate a local myocardial systolic function all the patients were undergone steady-state radionuclide ventriculography in the first 24 hours after SR restoration and 6 months later. Results. Sinus rhythm saving at amiodarone therapy within 6 months led to an improvement of the local myocardial contractility of the left ventricle with a significant increase in normokinesis zones from 79 (58.1%) to 92 (67.6%), hypokinesis and akinesia zones reduction from 46 (33.8%) to 41 (30.2%) and from 11 (8.1%) to 3 (2.2%) (p<0.05), respectively. Achieving the target values of ventricular rate during the remaining episodes of AF in patients of group II did not significantly affect the local left ventricle contractility. Conclusion. 6-month SR maintenance with amiodarone intake in IHD patients with persistent AF resulted in significant reduction of akinesia zones and increase in the number of normokinesia segments.

Clinical effectiveness of bilateral recanalization of chronic coronary artery occlusion

Aim. To assess the short- and long-term angiographic and clinical effectiveness of endovascular bilateral recanalization of chronic coronary artery occlusion (CCAO), compared to conservative therapeutic strategy. Material and methods. The study included 56 patients with coronary heart disease and CCAO. Angina Functional Class (FC) was assessed clinically and in electrocardiography tests. Local and global myocardial contractility was assessed using echocardiography. Group I (n=36) included CCAO patients who underwent an attempt of bilateral percutaneous coronary angioplasty; Group II (n=20) included CCAO patients who were treated conservatively. Clinical effectiveness of the treatment was assessed at 12 months. Results. At baseline, 16 and 20 Group I patients had FC III and II, respectively. Out of 36 attempts of bilateral recanalization, 27 were successful, based on the angiography results. All these 27 cases were also clinically successful in the short term, and 20 in the long term. Global myocardial contractility increased from 54±3% to 56,9±4% (p=0,03). In Group II, 10 and 10 patients had baseline FC III and II, respectively. The long-term stabilisation of clinical status was observed in 15 patients, with the mean levels of left ventricular ejection fraction of 53,9±2,4% (p=0,9). Observed complications of coronary angioplasty did not result in clinically significant ischemic and haemorrhagic events, while the clinical improvement was substantially more pronounced, compared to Group II. Conclusion. Bilateral CCAO recanalization is a technically demanding procedure, requiring an extensive surgical expertise and experience, and linked to a higher risk of complications. However, it could be used when the antegrade access is impossible; the anaesthesiological risk of coronary artery bypass graft surgery is high; and the patient refuses the cardiac surgery intervention.

Exercise tissue Doppler echocardiography with strain rate imaging in healthy young individuals: feasibility, normal values and reproducibility

The study was done to determine the clinical feasibility and reproducibility of tissue Doppler echocardiography (TDE) with strain rate imaging (SRI) at rest and under physical exercise in healthy young individuals and to report normal values for parameters of regional myocardial function under exercise. Forty-five young volunteers (age 9-29 years) underwent echocardiography with TDE/SRI at rest and during a bicycle exercise test (2 W/kg body weight). Velocities could be obtained in 93% of segments, whereas strain rate was measurable at least in 80% of segments. Inter- and intraobserver variability for measurement of velocities under exercise was 14% and 9%, respectively for strain rate 28% and 20%. Except for peak strain, values for all other parameters were higher during exercise with the clearest response in the left lateral and the right ventricular wall. (1) Tissue Doppler with strain rate imaging is a practical and robust method for assessment of regional function of both ventricles under exercise. (2) Systolic motion, local myocardial relaxation and contractility increased significantly under physical exercise. These normal values obtained from healthy young subjects can serve as a reference database for further clinical studies.

Investigating myocardial motion by MRI using tissue phase mapping

Velocity-encoded phase contrast magnetic resonance imaging (MRI) provides a tool to quantify regional myocardial wall motion of the entire heart. It allows the acquisition of three-directional velocity vector fields with high spatial resolution that reflect the temporal evolution of myocardial velocities over the cardiac cycle. In contrast to other imaging modalities such as echocardiography left ventricular performance can be assessed without limited anatomical or functional coverage. Compared to other techniques that quantify local myocardial contractility (e.g. implanted ultrasonic crystals) by means of regional displacement, phase contrast MRI provides information about local and global left ventricular velocities (i.e. motion) by utilizing the intrinsic motion sensitivity of MRI. The resultant motion components of contraction, expansion, rotation, lengthening, and shortening of the left ventricle are described in high spatial and temporal detail. Phase contrast measurements were performed in 12 healthy volunteers with a respiratory-gated technique in order to achieve a high temporal resolution of 13.8ms to demonstrate the detailed assessment of global and regional myocardial motion. Data revealed details in left ventricular motion patterns that were previously not seen in phase contrast measurements and are only known from echocardiography. For all volunteers, characteristic myocardial motion patterns and locally different radial (i.e. contraction and expansion), rotational (i.e. twisting and untwisting) and longitudinal (i.e. lengthening and shortening) motion components could be detected with high accuracy. The phase contrast MRI technique for high temporal resolution velocity mapping is therefore very promising for the investigation and better understanding of the myocardial motion in normal subjects and patients with disturbed left ventricular performance and may validate further testing of different models of cardiac structure.

THE INFLUENCE OF LONG-TERM THERAPY WITH PERINDOPRIL ON THE HEART INOTROPIC FUNCTION IN PATIENTS WITH CHRONIC POSTINFARCTION ANEURISM

Aim. To study the influence of long-term therapy with perindopril on the heart inotropic function in patients with chronic postinfarction aneurism. Material and methods. 21 patients suffering ischemic heart disease with postinfarction cardiosclerosis, chronic aneurism of left ventricle and chronic heart failure of functional class III-IV according to NYHA were observed. All patients took perindopril, 2-4 mg daily. Before and after 6 months of therapy myocardial contractile function of left and right ventricles was studied by balanced radioventriculography with segmental and phase analysis of histogram. Results. In patients with chronic postinfarction aneurism significant structural and functional abnormalities were revealed: reduction of left ventricular ejection fraction up to 17,8 ± 3,2 %, the same for right ventricular up to 22,1±4,4 %, their considerable dilation with reduction of filling and expulsion velocity. After 6 months of therapy with perindopril improvement of clinic status of patients, tendency towards increase of both ventricles general ejection fraction, enlargement of maximal filling velocity and filling velocity during 1/3 of diastole as well as tendency to reduction of both ventricles end diastolic and systolic volumes were registered. In left ventricle there were normokinetic zones in 35 (21%) segments, hypokinetic zones in 24 (14%), akinetic zones in 54 (32%) and dyskinetic zones in 17 (10%) segments. In right ventricle there were normokinetic zones in 45 (27%) segments, hypokinetic zones in 62(37%), akinetic zones in 54 (32%) and dyskinetic zones in 7 (4%) segments. After 6 months of therapy with perindopril tendency towards improvement of local myocardial contractility was registered. Conclusion. In patients with chronic postinfarction aneurism deterioration of general and local myocardial contractility were registered. Accurate link between left ventricle local myocardial contractility and localization of aneurism were not revealed. After 6 months of therapy with perindopril tendency towards improvement of general and local myocardial contractility of both ventricles was registered.

Ischaemic preconditioning causes increased myocardial vascular resistance but no myocardial contractility changes in pigs after OPCAB

The coronary vascular resistance (CVR) after off pump coronary bypass (OPCAB) surgery has never been clarified and ways of preventing stunning are wanted. We wished to investigate the effect of ischaemic preconditioning (IPC) on the CVR and stunning in the postoperative period after OPCAB. In 20 pigs (80 kg), 7 piezo-electric crystals were placed on the left ventricle to assess global and local myocardial contractility. Coronary vascular resistance was measured as the relation between perfusion pressure and coronary artery blood flow. IPC was obtained in ten pigs with one period of 10 min of coronary occlusion, followed by 15 min of reperfusion and 20 min of ischaemia. Ten control animals were exposed to 20 min of ischaemia only. Reperfusion was allowed for 120 min. The CVR was higher in the IPC group (measured by the slopes of the curves in the reperfusion period) (IPC: -0.33 (CI: (-0.62)-(-0.03)); 0.31 (CI: (-0.03)-(0.67)), P<0.005. There was no difference in the local myocardial contractility (slopes of the curves in the reperfusion period) (IPC: -0.004+/-0.01; -0.005+/-0.01). In conclusion, there was no alteration in myocardial contractility, but increased CVR in the early reperfusion period in animals preconditioned before sustained ischaemia.

Intracoronary application of C1 esterase inhibitor improves cardiac function and reduces myocardial necrosis in an experimental model of ischemia and reperfusion.

Myocardial injury from ischemia can be aggravated by reperfusion of the jeopardized area. The precise underlying mechanisms have not been clearly defined, but proinflammatory events, including complement activation, leukocyte adhesion, and infiltration and release of diverse mediators, probably play important roles. The present study addresses the possibility of reducing reperfusion damage by the application of C1 esterase inhibitor (C1-INH). Cardioprotection by C1-INH 20 IU/kg IC was examined in a pig model with 60 minutes of coronary occlusion, followed by 120 minutes of reperfusion. C1-INH was administered during the first 5 minutes of coronary reperfusion Compared with the NaCl controls, C1-INH reduced myocardial injury (48.8 +/- 7.8% versus 73.4 +/- 4.0% necrosis of area at risk, P < or = .018). C1-INH treatment significantly reduced circulating C3a and slightly attenuated C5a plasma concentrations. Myocardial protection was accompanied by reduced plasma concentration of creatine kinase and troponin-T. C1-INH had no effect on global hemodynamic parameters, but local myocardial contractility was markedly improved in the ischemic zone. In the short-axis view, 137 degrees of the anteroseptal region showed significantly improved wall motion at early and 29 degrees at late reperfusion with C1-INH treatment. C1-INH significantly protects ischemic tissue from reperfusion damage, reduces myocardial necrosis, and improves local cardiac function.

Is local myocardial contractility related to endocardial acceleration signals detected by a transvenous pacing lead?

The availability of sensors monitoring cardiac function parameters may offer many interesting new applications in cardiac pacing. A microaccelerometer sensor (BEST, Biomechanical Endocardial Sorin Transducer) located at the tip of a pacing lead (PL) has been developed by Sorin Biomedica. The signal detected by the accelerometer, peak endocardial acceleration (PEA), was shown to reflect cardiac contractility and to be related to the dP/dt signal. Whether the PEA detected by the BEST sensor in different cardiac locations is the expression of local acceleration forces or reflects the whole heart contractility has not yet been demonstrated in humans. Endocardial acceleration and PEA were evaluated in five patients (4 males, 1 female, mean age 68 years) who underwent cardiac catheterization. Sinus rhythm was present in four patients and chronic atrial fibrillation was present in one. The BEST PL was introduced through the left subclavian vein and PEA signals were recorded: (1) at the apex of the right ventricle (RV), (2) within the coronary sinus (CS), (3) at the right atrial appendage (RAA), and (4) floating in the right atrium. The PEA signals were recorded simultaneously with surface ECG, intracardiac electrograms, and RV pressure. At each recording site, PEA signals with significant amplitude were always recorded during the preejection period, during the isovolumic contraction phase, independently of the recording site and cardiac rhythm. The PEA amplitude was higher in the RV (mean value 1.32 g) and it decreased in the RAA and CS (0.75 and 0.45 g, respectively). The same behavior of PEA was observed during sinus rhythm or atrial fibrillation. The amplitude and the timing of the PEA signals detected by the BEST accelerometer were independent of the recording site and atrial rhythm; they appeared to be strictly related to the global ventricular contractility. These results suggest that the BEST could be used either as an effective sensor in closed loop pacing systems, or primarily as a diagnostic hemodynamic sensor.

Nitric oxide does not modulate myocardial contractility acutely in in situ canine hearts.

The study was designed to assess the influence of nitric oxide (NO) on myocardial contractility in vivo. The left anterior descending coronary artery (LAD) of 28 anesthetized, open-chest dogs was perfused with arterial blood via an extracorporeal circuit. In the LAD bed, segmental shortening (SS), an index of local myocardial contractility, was measured with ultrasonic crystals. Coronary blood flow (CBF) was measured by Doppler flow transducer and used to calculate myocardial oxygen consumption (MVO2). Studies were performed with coronary perfusion pressure (CPP) constant (n = 23) or with CBF constant (n = 5). Measurements were obtained 1) during intracoronary infusions of the NO donors sodium nitroprusside (SNP, 80 ng/min) and nitroglycerin (NTG, 40 micrograms/min) and of a stimulator of endogenous NO release, acetylcholine (ACh, 20 micrograms/min), and 2) after inhibition of basal NO synthase activity with either NG-nitro-L-arginine methyl ester (L-NAME, 300 micrograms/min ic for 15 min) or NG-monomethyl-L-arginine (L-NMMA 2mg/min ic for 15 min). Decreases in SS (-38%) and MVO2 (-42%) during intracoronary isoflurane infusion verified responsiveness of preparation to negative inotropic agents. With CPP constant, SNP, NTG, and ACh caused increases in CBF (177, 28, and 280%, respectively) with no changes in SS or MVO2. Neither L-NAME nor L-NMMA affected SS, MVO2, or CBF. With CBF constant, the SNP- and ACh-induced decreases in CPP were accompanied by no changes in SS. In conclusion, NO had no direct influence on myocardial contractility or oxygen demand under baseline conditions, or when its local concentration was increased acutely with SNP, NTG, or ACh. An augmented SS secondary to increased CBF per se, i.e., Gregg's phenomenon, did not obscure potential negative inotropic effects of SNP and ACh with CPP constant.

Effect of Intracoronary Infusions of Amrinone and Dobutarnine on Segment Shortening, Blood Flow, and Oxygen Consumption in In Situ Canine Hearts

Previous in vivo studies assessing the effects of amrinone on myocardial contractility used intravenous infusions, and thus were complicated by varying cardiac loading conditions. Accordingly, the present study was performed in 15 open-chest, anesthetized (fentanyl and midazolam) dogs using infusions of amrinone and dobutamine directly into the left anterior descending artery (LAD). In the LAD bed, percentage of segment shortening (%SS), an index of local myocardial contractility, was assessed with ultrasonic crystals. Coronary blood flow was measured electromagnetically and used to calculate myocardial oxygen consumption and infused drug concentrations. Amrinone and dobutamine were infused separately into the LAD at rates yielding calculated arterial blood concentrations in the clinical range (100, 150, and 200 micrograms/min, and 2.5, 5.0, and 7.5 micrograms/min, respectively). A mixture of amrinone and dobutamine was also infused into LAD and changes in %SS compared with the sum of the their individual effects. In six of the dogs, an extracorporeal system was used to maintain constant coronary blood flow during amrinone infusions. Amrinone and dobutamine caused individually increases in %SS that were comparable (range, 20%-45%). Myocardial oxygen consumption increased in parallel with %SS for both amrinone and dobutamine. For amrinone, coronary blood flow increased more than myocardial oxygen consumption, resulting in a modest (at highest dose approximately 10%) decrease in oxygen extraction; whereas for dobutamine, coronary blood flow increased in proportion to myocardial oxygen consumption, resulting in no change in oxygen extraction.(ABSTRACT TRUNCATED AT 250 WORDS)

A non-linear elastic model of contraction of local myocardium (a): evaluation of peak a as a new index of local myocardial contractility

A non-linear elastic model of contraction of local myocardium (a): evaluation of peak a as a new index of local myocardial contractility

Myocardial Oxygen Consumption and Segmental Shortening during Selective Coronary Hemodilution in Dogs

Experiments were conducted in 33 open chest, anesthetized dogs to evaluate direct effects of hemodilution on myocardial oxygenation and contractile function. The left anterior descending coronary artery (LAD) was perfused selectively from a controlled pressure reservoir with either normal arterial blood or arterial blood diluted with lactated Ringer's solution. Systemic hemodynamic parameters were held stable. In the LAD bed, values were obtained for coronary blood flow (CBF) with an electromagnetic flowmeter, myocardial oxygen consumption (MVO2) using the Fick principle, and percentage segmental shortening (%SS), an index of local myocardial contractility, by sonomicrometry. Studies were conducted with LAD perfusion pressure (PP) set at control (100 mm Hg) and at 50% of that level to simulate coronary insufficiency (CI). CI abolished coronary reactive hyperemia after release of a 90-second occlusion, indicating exhausted vasodilator reserve capacity. With PP at control, reductions in LAD hematocrit to as low as 10% had no effect on MVO2 or %SS, because increases in blood flow were sufficient to offset induced falls in arteriovenous oxygen content difference. However, during CI, a more modest reduction in hematocrit to 17% caused reductions in both MVO2 and %SS, because of inadequate flow responses during hemodilution. The following conclusions can be made: 1) Extreme hemodilution is well tolerated by the normal heart with a stable work requirement and; 2) Relatively modest hemodilution may compromise myocardial oxygenation and contractile function when in the presence of exhausted or severely depleted vasodilator reserve capacity.