Index Of Myocardial Oxygen Consumption Research Articles

#2567 ASSOCIATION OF IMBALANCE OF MYOCARDIAL OXYGEN SUPPLY/DEMAND WITH MYOCARDIAL INJURY IN END STAGE KIDNEY DISEASE PATIENTS

Abstract Background and Aims It is well known that oxygen transport ability is impaired in patients with anemia, low hemoglobin (Hb) level, whereas the double product (DP, bpm*mmHg), consisting of the systolic blood pressure (SBP) multiplied by the heart rate (HR), is an index of myocardial oxygen consumption. The combination of these two markers could be a potential marker for balance of myocardial oxygen supply and demand. Therefore, we hypothesized that the balance of these two markers may lead to myocardial damage in end-stage kidney disease (ESKD) patients who is susceptible to vulnerable heart in oxygen balance. The purpose of this study is to examine the association of balance of DP and Hb with myocardial injury in ESKD patients. Method A single-center, cross-sectional study has conducted. From December 2010 to November 2021, 327 consecutive ESKD patients started maintenance hemodialysis (HD). Among them, 44 patients met the exclusion criteria as follows: (1) missing data of cardiac troponin T (cTnT); (2) complicating acute cardiac syndrome; (3) death during hospitalization for HD initiation, a total of 283 ESKD patients were enrolled into the study finally. The patients were divided four groups according to the high or low of Hb level of 9 g/dL and DP 12500, a median of our patients, and named low-DP/high-Hb; G1, low-DP/low-Hb; G2, high-DP/high-Hb; G3, and high-DP/low-Hb; G4. The patients with G1 group were defined as a well oxygen balanced group, whereas those with G4 was defined as an imbalance of oxygen supply and demand group. Based on the results of previous study, cTnT cut off for myocardial injury was serum cTnT ≧0.15 ng/mL. Odds ratio (OR) for myocardial injury was calculated in each group compared with well oxygen balanced group by logistic regression analysis. Results Median age was 72 years, 71% of them were male, 52.6% had diabetes. Mean Hb level was 9.09 ± 1.61, and median DP was 12144 (25% tile 10540, 75% tile 14688). Median cTnT was 0.083 (25% tile 0.057 and 75% tile 0.13), and 20.4% of patients were defined as suffering from myocardial injury latently. In the adjusted model, the odds for myocardial injury was significantly increasing in high-DP compared with low-DP (OR: 1.87, p = 0.049), while low-Hb did not show significant increment of odds for myocardial injury compared with high-Hb. As shown in the Table 1, compared to well-balanced group (G1), OR increased by exposing only high-DP (G3), however it was not statistically significant (OR 1.20, p = 0.68). Interestingly, by exposing with high-DP with low-Hb simultaneously (G4), synergistic increased OR was found compared with well-balanced (G1) group (OR 3.07, 95%CI 1.24-7.62, p = 0.015). Furthermore, these associations were enhanced and weakened if Hb cut-off level became to be lower (Hb 8 g/dL) and higher (Hb 10 g/dL), as shown in Tables 2, 3. Conclusion Imbalance of oxygen supply (Hb) and demand (DP) was associated with myocardial injury in incident HD patients. Appropriate control of anemia, SBP and HR may have possibility to prevent myocardial injury. Especially we need to pay attention more to the Hb level if BP and HR control is insufficient. Tables 1, 2, 3. Odds ratio for cTnT≧0.15 in four groups divided by DP and Hb (adjusted for age, male, CRP, albumin, diabetes mellitus).

Effects of Hyperoxia on Coronary Circulation in Patients with Peripheral Artery Diseases (PAD)

It is well‐known that hyperoxia evokes different effects in patients with different dieaseas conditions. Studies from this lab and others have shown that hyperoxia is a potent coronary vasoconstrictor. Recently, we found that hyperoxia exaggerates systolic blood pressure (BP) response in patients with PAD. The aim of this study is to characterize the coronary circulatory effects of hyperoxia in PAD patients and healthy controls. We recruited 20 PAD patients (14M, 6F, 66 ± 6yrs), and 16 age‐matched control subjects (10M, 6F, 65 ± 8yrs). The ankle‐brachial pressure index (ABI) in the most affected limbs of the patients was 0.58 ± 0.15, compared to the controls ABI of 1.04 ± 0.09. For the hyperoxia procedure the subjects breathed room air for three minutes and 100% oxygen for five minutes. BP and heart rate (HR) were monitored during baseline and hyperoxia. The rate pressure product (RPP), an index of myocardial oxygen consumption, was calculated as the product of systolic BP and HR. Transthoracic Coronary Echocardiography was used to record early and late peak coronary blood flow velocities (CBV1 and CBV2) in the left anterior descending artery. Early and late coronary vascular conductances (peak coronary blood velocity/diastolic blood pressure, CVC1 and CVC2) and coronary perfusion time fraction (CPTF, coronary perfusion time/R‐R interval) were calculated. All data was compared across time and between groups using Repeated Measures Analyses of Variance (RMANOVA).ResultsAt the baseline, RPP and coronary parameters (CBV2, CVC1, and CVC2) were higher in the PAD group compared to controls, also the PAD group showed significantly shorter CPTF. During hyperoxia, CBV1, CBV2, CVC1, and CVC2 decreased to varying degrees in both groups. However, no significant interactions were observed for RPP and all coronary parameters during hyperoxia between the groups (Table). Our findings suggest that the effect of hyperoxia on coronary circulation was not significantly different between PAD and healthy controls.

Effects of Tanshinone on Hemodynamics and Expression of NF- B and Myeloperoxidase in Rats with Spinal Cord Ischemia-Reperfusion Injury

Spinal cord ischemia-reperfusion injury (SCII) can cause spinal nerve injury and loss of function. Tanshinone IIA has antioxidant activity. However, the effect of tanshinone on SCII rats remains unclear. SD rats were randomly divided sham operation group (sham group), SCII group and tanshinone group. Heart rhythm (HR), mean blood pressure (MAP), and myocardial oxygen consumption index (RPP) hemodynamic parameters were analyzed. Rat neurological function scores were performed by the Tarlov method. The glutamate detection kit was used to detect the content of glutamate, superoxide dismutase (SOD) and myeloperoxidase (MPO). NF-κ B protein expression was assessed by Western blot. The expressions of tumor necrosis factor-α (TNF-α) and interleukin6 (IL-6) were analyzed by ELISA. In SCII group, HR, MAP, RPP, and neurological function score as well as SOD activity were significantly decreased with increased MPO, glutamate, TNF-α and IL-6 secretion as well as elevated NF-κ B expression compared with sham group (P < 0 05). After tanshinone treatment, HR, MAP, RPP, and neurological function score as well as SOD activity were all significantly increased along with decreased MPO, glutamate, TNF-α and IL-6 secretion, as well as reduced NF- κB expression compared with SCII group (P < 0 05). Tanshinone can improve the oxidative stress, reduce the secretion of inflammatory factors, and improve hemodynamics which is possibly through regulating NF-κ B expression.

Enteral Tranexamic Acid Decreases Proteolytic Activity in the Heart in Acute Experimental Hemorrhagic Shock.

The mechanisms for cardiac injury after hemorrhagic shock (HS) are unresolved. We hypothesize that remote organ damage can be caused by uncontrolled pancreatic proteolytic activity, as enteral protease inhibition improves outcomes in experimental HS. Uncontrolled proteolysis in the heart may disrupt cardiac metabolism and adrenergic control with subsequent deleterious outcomes. To test this hypothesis, the heart rate-pressure product (RPP) as an index of myocardial oxygen consumption and the levels of fatty acid transporter proteins CD36 and FATP6 as surrogates for metabolic activity in the heart were measured in rats subjected to experimental HS (n = 6/group) with and without the enteral protease inhibitor tranexamic acid (TXA). Plasma troponin I and heart fatty acid-binding protein (HFABP) concentrations were measured as indices of myocardial damage. Expression of the adrenergic receptors β1, α1D, and β2 was also measured in the heart to determine the possible effects of shock with and without enteral TXA on the adrenergic control of heart function. Hemorrhagic shock was induced by reduction in mean arterial blood pressure to 35 mm Hg for 2 hours before reperfusion of shed blood. The RPP was maintained in shocked animals treated enterally with TXA but not in those subjected to HS alone; this group also demonstrated decreased HFABP and plasma troponin I levels. Serine protease (trypsin, chymotrypsin, and elastase) and matrix metalloproteinase (MMP)-2 and MMP-9 activity was elevated in cardiac tissue and plasma after HS and abrogated by enteral TXA. Levels of CD36, FATP6, β1, α1D, and β2 were also increased after HS in cardiac tissue, and the increases were mitigated by TXA treatment. These results suggest that increased proteolytic activity may contribute to cardiac injury after HS. Enteral TXA prevents these changes, indicating a potential therapeutic option in the management of shock with resultant cardiac injury.

Development of Novel Cardiac Indices and Assessment of Factors Affecting Cardiac Activity in a Bivalve Mollusc Chlamys farreri.

Cardiac activity has been widely used in marine molluscs as an indicator for their physiological status in response to environmental changes, which is, however, largely less studied in scallops. Here, we monitored cardiac performance of Zhikong scallop Chlamys farreri using an infrared-based method, and evaluated the effects of several biotic (shell height, total weight, and age) and environmental factors (circadian rhythm and temperature) on scallop heart rate (HR), amplitude (HA), and rate-amplitude product (RAP). Results revealed that size has a significant effect on both HR (negative) and HA (positive), but RAP values are similar in different sized scallops. Age also affects scallop cardiac performance, significantly for HR, but not for HA or RAP. Circadian rhythm affects cardiac activity, with significant elevation of HR, HA and RAP during 1:00–8:00 and 17:00–19:00. With seawater temperature elevation, HR peaks at 30.03 ± 0.23°C, HA at 15.08 ± 0.02°C, and RAP at 15.10 ± 0.19 and 30.12 ± 0.28°C. This suggests HR is a good indicator for thermal limit, whereas HA may indicate optimal growth temperature, and RAP could be an index of myocardial oxygen consumption to indicate myocardium stress. Our study provides basic information on the factors that may affect scallop cardiac performance. It also elucidates the feasibility of HA and RAP as cardiac indices in marine molluscs.

The effect of blood flow restriction along with low-intensity exercise on cardiac structure and function in aging rat: Role of angiogenesis

AimsLow-intensity aerobic training along with limbs blood flow restriction can improve mass and strength of skeletal muscle, but its effects on aging heart structure and performance is unidentified. We investigated the effects of this model of training on myocardial function, histology and angiogenesis in old male rats. Main methodsAnimals randomly were divided into control (Ctl), sham-operated (Sh), limbs blood flow restriction (BFR), sham-operated plus 10 weeks low intensity treadmill exercise (Sh + Ex), and BFR plus exercise (BFR + Ex) groups. Finally, blood pressure, heart physiological and stereological parameters, myocardial oxygen consumption index and expression of vascular endothelial growth factor (VEGF) and its receptors (Flt-1 and kdr) were assessed. Key findingsBFR + Ex group had significantly lower heart rate (P < 0.05 vs. Ctl and Sh groups), rate-pressure product (RPP) and left ventricular end diastolic pressure (P < 0.05 and P < 0.01 vs. untrained groups, respectively). BFR + Ex group also had greater +dp/dt max (P < 0.01) and −dp/dt max (P < 0.05) than untrained groups. A significant increase in volumes of left ventricle and myocytes (P < 0.05, vs. Ctl and Sham), ventricular hypertrophy index and capillaries length density (P < 0.05 vs. untrained groups) were observed in BFR + Ex group.The level of VEGF and Flt-1 proteins and their mRNAs increased in the BFR + Ex group compared to Ctl, Sh and BFR (P < 0.01) and Sh + Ex (P < 0.05) groups. The kdr mRNA and its protein level were significantly higher in the BFR + Ex group. SignificanceFindings suggest that BFR plus exercise through improving the angiogenesis, physiological cardiac remodeling and oxygen demand/supply matching can promote cardiac performance in the elderly rats.

Determination of Optimal Coronary Flow for the Preservation of "Donation after Circulatory Death" in Murine Heart Model.

Donation after circulatory death donors (DCD) have the potential to increase the number of heart transplants. The DCD hearts undergo an extended period of warm ischemia, which mandates the use of machine perfusion preservation if they are to be successfully recovered for transplantation. Because the minimum coronary artery flow needed to meet the basal oxygen demand (DCRIT) of a DCD heart during machine perfusion preservation is critical and yet unknown, we studied this in a DCD rat heart model. Adult male rats were anesthetized, intubated, heparinized, and paralyzed with vecuronium. The DCD hearts (n = 9) were recovered 30 minutes after circulatory death whereas non-DCD control hearts (n = 12) were recovered without circulatory death. Hearts were perfused through the aorta with an oxygenated Belzer Modified Machine Perfusion Solution (A3-Bridge to Life Ltd. Columbia, SC) at 15°C or 22°C starting at a flow index of 300 ml/100 g/min and decreasing by 40 ml/100 g/min every 10 minutes. Inflow (aortic) and outflow (inferior vena cava) perfusate samples were collected serially to assess the myocardial oxygen consumption index (MVO2) and O2 extraction ratio. The DCRIT is the minimum coronary flow below which the MVO2 becomes flow dependent. The MVO2, DCRIT, and oxygen extraction ratios were higher in DCD hearts compared with control hearts. The DCRIT for DCD hearts was achieved only at 15°C and was significantly higher (131.6 ± 7 ml/100 g/min) compared with control hearts (107.7 ± 8.4 ml/100 gm/min). The DCD hearts sustain warm ischemic damage and manifest higher metabolic needs during machine perfusion. Establishing adequate coronary perfusion is critical to preserving organ function for potential heart transplantation.

Application of combined femoral & paravertebral nerve block in the hip joint operation

Objective To evaluate the application value of combined femoral and thoracolumbar paravertebral nerve blocks in the hip joint operations of elderly patients.Methods Sixty five patients aged over 70 undergoing hip joint operation were randomly divided into general anesthesia group (GA) and paravertebral nerve block (PVB) group.In the PVB group,each patient received a combined femoral nerve-thoracolumbar paravertebral nerve block with the aid of a neurostimulator,and a 10 ml mixture of 0.75％ bupivacaine and 2％ lidocaine was used in each block.In the GA group,a total intravenous general combined anesthesia was applied to each patient.Mean arterial pressures (MAP),heart rates (HR) and myocardial oxygen consumption indexs were recorded 30 minites after the surgery started and when it finished.In addition,indwelling catheter management,visual analogue scale scores,resuscitation room indexes,and lower respiratory tract infections in the intensive care unit (ICU) were evaluated postoperatively.Results There were no differences in demographic data,ASA status,operation time,preoperative MAP,HR and myocardial oxygen consumption index of patients between the two groups.MAP,HR and myocardial oxygen consumption index of two groups 30 minites after the start of operations were lower than those of preoperative baseline values,respectively (P＜0.05),and the HR and myocardial oxygen consumption index of GA group were both lower than those of the PVB group (P＜0.05),the HR of GA group and PVB group were (68±11) beats/min and (80±11) beats/min,the myocardial oxygen consumption index of GA group and PVB group were (8 807±1 883) and (10 362±2 433).MAP,HR and myocardial oxygen consumption index in the PVB group was obviously lower than the GA group postoperatively (P＜0.05),MAP(88±12) mmHg(1 mmHg=0.133 kPa) vs (101±15) mmHg,HR(75±11) beats/min vs (84±19) beats/min,myocardial oxygen consumption index,(9 706±2 009) vs (12 687±4 119),respectively,and preoperatively (which was of no statistical significance).The length of ICU stay,infections of lower respiratory tracts,and the need for urinary catheters for patents in the PVB group were significant lower than those in Group GA (P＜0.05).Conclusions We conclude that the combined femoral-thoracolumbar parave rtebral nerve block can be safe and effective for the hip surgery,associated with minor physiological disturbance,lower myocardial oxygen consumption index,and higher postoperative comfort and safety. Key words: Paravertebral nerve block; General anesthesia; Hip joint operation; Elderly patient

Endothelial cell‐targeted over‐expressing ET‐1 leads to increased blood pressure and decreased heart rate in aged mice (LB655)

Endothelin‐1 (ET‐1) is a 21 amino acid vasoconstrictor and implicated in the regulation of hypertention. Recently, our colleagues found that transgenic mice (TET‐1) with endothelial ET‐1 over‐expression developed hypertention in young mice by changing vascular properties. However, the effects of over‐expressing endothelial ET‐1 on cardiovascular system in aged mice are still unclear. Therefore, this study investigated the blood pressure and heart rate of TET‐1 aged mice and non‐transgenic (NTg) aged mice (1.5‐2 years old). A non‐invasive tail cuff measurement showed that a significant elevation of both systolic (115.1 ± 2.935 vs 103.5 ± 1.846 mmHg, p&lt;0.01) and diastolic (85.81 ± 2.303 vs 74.56 ± 2.029 mmHg, p&lt;0.05) in conscious TET‐1 aged mice comparing to NTg counterpart, indicating over‐expressed endothelial ET‐1 cause both systolic and diastolic hypertension in aged mice. And, aged TET‐1 mice showed a significantly decreased heart rate to aged NTg mice (616.7 ± 20.14 vs 670.9 ± 11.57 beats per minute (bpm), p&lt;0.05). Moreover, Rate‐pressure product is a sensitive index of myocardial oxygen consumption, and it was not altered in TET‐1 mice (71085 ± 3258 vs 69337 ± 1233 bpm*mmHg, p&gt;0.05), implicating over‐expressed endothelial ET‐1 would change cardiovascular properties by mechanisms of mutual compensation between blood pressure and heart rate. These findings provide evidence for roles of endothelial ET‐1 in altering cardiovascular system in aged mice. This study also implicates clinical importance of endothelial ET‐1 as a therapeutic target for hypertension in the elderly.Grant Funding Source: Supported by the departmental fund, Department of Anaesthesiology, The University of Hong Kong

Right Heart Failure: An Ischemic Model and Restraint Therapy for Treatment

Right heart failure is poorly understood and treated. In left heart failure, ventricular restraint can reverse pathologic left ventricular remodeling. The effect of restraint in right heart failure, however, is not known. We hypothesize that ventricular restraint can be applied selectively to the right ventricle (RV) to promote RV reverse remodeling. Right heart failure was induced by right coronary artery ligation in a sheep model. Eight weeks later, a saline-filled epicardial balloon was placed around the RV surface for restraint. Restraint level was defined by measuring balloon luminal pressure at end-diastole. Maximum balloon pressure was determined by the amount of balloon pressure required to decrease systemic mean arterial pressure by 10 mm Hg. We determined end-diastolic transmural myocardial pressure, indices of myocardial oxygen consumption, and RV diastolic compliance at 4 different restraint levels. After coronary ligation, RV ejection fraction (EF) decreased from 0.574±0.04 to 0.362±0.03 (p<0.05). End-diastolic RV volume increased from 70.8 mL/m2±9 to 82.2 mL/m2±7 (p<0.05) by magnetic resonance imaging. After application of restraint to the RV only, RV transmural pressure decreased significantly by 27%. Greater levels of restraint also improved RV EF (0.347±0.06 to 0.473±0.05) but did not change RV end-diastolic volume. A model of ischemic right heart failure was successfully created. Selective RV restraint results in improved mechanical efficiency, decreased wall stress, and improved EF. The benefits of restraint in right heart failure warrant further investigation.

Susceptibility to life-threatening ventricular arrhythmias in an animal model of paradoxical sleep deprivation

BackgroundAccording to some reports regarding the increase of cardiac events following sleep deprivation, our study was conducted to clarify the effects of rapid eye movement (REM) sleep deprivation on susceptibility to lethal ventricular arrhythmias in rat. MethodsThe animal groups included the control group; the sham 48 and sham 72 groups (without sleep deprivation); and the test 48 and test 72 groups, who experienced REM sleep deprivation for 48h and 72h, respectively. For induction of cardiac arrhythmia, aconitine was infused via the tail vein of the animals. ResultsAfter 72h of REM sleep deprivation, the blood pressure (BP) levels and the QTc interval of the electrocardiogram (ECG) were significantly increased (P<.05 and P<.01, respectively). However, the sleep deprivation had no significant effect on the heart rate (HR), myocardial oxygen consumption index, and plasma corticosterone level. Furthermore, sleep deprivation increased the latency times of premature ventricular contraction (PVC), ventricular tachycardia (VT), and also the PVC number; however, it did not increase the number, duration, and severity of VT and ventricular fibrillation (VF). ConclusionOur findings suggest that 72h of REM sleep deprivation is associated with increased risk for hypertension and QT interval prolongation under nonstressful conditions; however, it does not increase the susceptibility to lethal ventricular arrhythmia in rat.

English

The aim of this study was to investigate the effect of dexmedetomidine (DEX) maintenance on myocardial oxygen consumption during extubation for generally-anesthetized old patients under bispectral index (BIS) monitoring. A total of 40 patients who were subjected to thyroid operation and laparoscopic cholecystectomy under general anesthesia (ASA I or II) were randomized into the experimental (n = 20) and control (n = 20) groups. General anesthesia was induced using midazolam, etomidate, sufentanil, and vecuronium bromide and was maintained using propofol, remifentanil, and&nbsp;atracurium besilate. The experimental group received micropump infusion of DEX at 0.2 ug kg-1&nbsp;h-1&nbsp;from 30 min before the end of operation to the end of extubation. The control group was given physiological saline with the same volume during the same period. BIS monitors were connected. Hemodynamic indexes [systolic blood pressure&nbsp;(SBP),&nbsp;diastolic arterial blood pressure&nbsp;(DBP), and heart rate (HR)] were recorded, and myocardial oxygen consumption index&nbsp;and the recovery time of consciousness were determined. HR of the experimental group decreased from 65 &plusmn; 8 to 60 &plusmn; 5 times/min at 10 min after micropump infusion, whereas that of the control group increased from 73 &plusmn; 10 to 85 &plusmn; 12 times/min, showing a significant difference (P&nbsp;&lt; 0.01). Both groups did not show significant changes in HR during the following maintenance period. The two groups showed significant differences in SBP, DBP, HR, and BIS at 1, 5, and 10 min during extubation period (P&nbsp;&lt; 0.05). They did not show any significant difference in extubation score, the recovery time of consciousness, or extubation time (P&nbsp;&gt; 0.05). BIS-guided DEX has a stable effect on myocardial oxygen consumption in generally-anesthetized old patients during extubation period. It has no obvious influences on extubation score and the recovery time of consciousness. Thus, 0.2 ug kg-1&nbsp;h-1&nbsp;is a proper DEX micropump infusion rate. &nbsp; Key words:&nbsp;Bispectral index, dexmedetomidine, myocardial oxygen consumption.

Double Product Reflects the Predictive Power of Systolic Pressure in the General Population: Evidence from 9,937 Participants

The double product (DP), consisting of the systolic blood pressure (SBP) multiplied by the pulse rate (PR), is an index of myocardial oxygen consumption, but its prognostic value in the general population remains unknown. We recorded health outcomes in 9,937 subjects (median age, 53.2 years; 47.3% women) randomly recruited from 11 populations and enrolled in the International Database on Ambulatory blood pressure in relation to Cardiovascular Outcomes (IDACO) study. We obtained the SBP, PR, and DP for these subjects as determined through 24-hour ambulatory monitoring. Over a median period of 11.0 years, 1,388 of the 9,937 study subjects died, of whom 536 and 794, respectively, died of cardiovascular (CV) and non-CV causes, and a further 1,161, 658, 494, and 465 subjects, respectively, experienced a CV, cardiac, coronary, or cerebrovascular event. In multivariate-adjusted Cox models, not including SBP and PR, DP predicted total, CV, and non-CV mortality (standardized hazard ratio [HR], ≥ 1.10; P ≤ 0.02), and all CV, cardiac, coronary, and stroke events (HR, ≥ 1.21; P < 0.0001). For CV mortality (HR, 1.34 vs. 1.30; P = 0.71) and coronary events (1.28 vs. 1.21; P = 0.26), SBP and the DP were equally predictive. As compared with DP, SBP was a stronger predictor of all CV events (1.39 vs. 1.27; P = 0.002) and stroke (1.61 vs. 1.36; P < 0.0001), and a slightly stronger predictor of cardiac events (1.32 vs. 1.22; P = 0.06). In fully adjusted models, including both SBP and PR, the predictive value of DP disappeared for fatal endpoints (P ≥ 0.07), coronary events (P = 0.06), and stroke (P = 0.12), or DP was even inversely associated with the risk of all CV and cardiac events (both P ≤ 0.01). In the general population, we did not observe DP to add to risk stratification over and beyond SBP and PR.

Restraint to the left ventricle alone is superior to standard restraint

In standard ventricular restraint therapy, a single level of restraint is applied to the entire ventricular surface. We showed previously that at high restraint levels, cardiac tamponade develops because of the thin-walled right ventricle, even while the left ventricle remains unaffected. We now hypothesize that applying restraint exclusively to the left ventricle permits higher levels of restraint, resulting in increased benefit to the left ventricle. The acute effect of restraint applied to the left ventricle alone was analyzed in healthy and cardiomyopathic sheep hearts. Restraint therapy was applied by fluid-filled epicardial balloons placed solely around the left ventricle. Restraint level was defined by the measured balloon luminal pressure at end diastole. At incrementally higher restraint levels (0, 3, 5, 8, 10, 12, and 14 mm Hg), transmural myocardial left ventricular pressure (P(tm) = Left ventricle pressure - Balloon pressure) and indices of myocardial oxygen consumption were measured in healthy sheep (n = 5) and in sheep with heart failure (n = 6). Increasing restraint from 0 to 14 mm Hg decreased transmural myocardial pressure by 48.8% (P ≤ .02) and the left ventricle tension-time index by 39.1% (P ≤ .01), and the pressure-volume area decreased by 58.4% (P ≤ .01). Similarly, stroke work decreased by 57.9% (P ≤ .03). Systemic hemodynamics were unchanged. There was no difference in the trend for all indices between animals that were healthy and those with heart failure. We showed previously that, with standard restraint, right ventricle tamponade develops at high restraint levels, limiting restraint therapy. We now show that restraint applied to the left ventricle alone permits increased restraint levels, without causing right ventricle or left ventricle tamponade, for greater therapeutic benefit. We conclude that partial left ventricle restraint may be more effective than standard restraint.

Comparative study of rate pressure product in obese women with non obese women.

Background and Objective: Nowadays Obesity is considered as global epidemic. It exacerbates a large number of health problems. Obese people are at risk of impaired cardiac performance, commonly seen in women. So our study aimed to assess the Rate pressure product in obese women and to compare the same with non obese women aged 35-55years. As above mentioned parameters are associated with increased risk for cardiovascular diseases Methods and Material: Study A comparative cross sectional study including 140 women (70- obese , 70- non obese) of age 35-55years. The study group was divided into four according to BMI Group I ( BMI 25-29.9 kg/m2), Group II( BMI 30-34.9 kg/m2) , Group III( BMI 35 – 39.9 kg/m2) , Group IV (BMI > 40 kg/m2) including Control( BMI < 25 kg / m 2 ) . Anthropometric parameters like height (cm), weight (Kg), WHR, BMI were recorded. After 20 mins of rest in supine position ECG and brachial SBP, DBP were recorded. HR was calculated by using formula 1500/R-R. The rate pressure product was calculated as = SBP X HR. As RPP is an index of myocardial oxygen consumption. Results: We found statistically significant higher values of RPP in group IV when compared to control group. Also found statistically insignificant increase in values of RPP in groups I, II, III. Conclusion: obesity is a significant predictor of increased MVO2 and decreased efficiency. This may cause increase in fatty acid metabolism & decrease in cardiac efficiency in obese women.

English

In this study, we assessed the effect of &ldquo;Tai Chi Quan&rdquo; exercise on heart function of aged people. A total of 66 old people (mean age, 72.81&nbsp;&plusmn;&nbsp;7.27 years) was recruited for the study in November 2009. All subjects were asked to practice &ldquo;Tai Chi Quan&rdquo; for one hour, every day. This study had continued for 1 year. Some physiological indexes were measured in November 2009 (beginning point) and December 2010 (ending point), respectively. Results showed that &ldquo;Tai Chi Quan&rdquo; exercise could significantly increase cardiac output, stroke index and myocardial oxygen consumption index in aged practicers. It can be concluded that &ldquo;Tai Chi Quan&rdquo; exercise can improve heart function of aged people. &nbsp; Key words:&nbsp;&ldquo;Tai Chi Quan&rdquo;, elderly, heart.

Body metabolic rate and electromyographic activities of antigravitational muscles in supine and standing postures

We measured metabolic (oxygen uptake, carbon dioxide production, respiratory ratio), cardio-circulatory (heart rate, systolic and diastolic arterial blood pressure, rate-pressure product, an index of myocardial oxygen consumption calculated by multiplying heart rate by systolic pressure) and electromyographic (integrated electromyographic activities of two antigravitational muscles of the lower limb, soleus and gastrocnemius) variables on 12 young healthy subjects in supine and standing positions at rest. We found statistically significant increments of oxygen uptake, carbon dioxide production, heart rate and integrated electromyographic activities in standing versus supine position. Rate-pressure product increased but not significantly, and no other significant changes were detected. We conclude that postural changes influence metabolic rate, antigravitational muscle reflex activities, and heart rate. A significant positive correlation was found between oxygen uptake and carbon dioxide production and integrated electromyographic activities of antigravitational muscles, while the same was not found for cardio-circulatory variables. These results suggest that the increased metabolic rate in standing position is, at least in part, due to antigravitational muscle tone.

Cerebral and myocardial blood flow responses to hypercapnia and hypoxia in humans

In humans, cerebrovascular responses to alterations in arterial Pco(2) and Po(2) are well documented. However, few studies have investigated human coronary vascular responses to alterations in blood gases. This study investigated the extent to which the cerebral and coronary vasculatures differ in their responses to euoxic hypercapnia and isocapnic hypoxia in healthy volunteers. Participants (n = 15) were tested at rest on two occasions. On the first visit, middle cerebral artery blood velocity (V(P)) was assessed using transcranial Doppler ultrasound. On the second visit, coronary sinus blood flow (CSBF) was measured using cardiac MRI. For comparison with V(P), CSBF was normalized to the rate pressure product [an index of myocardial oxygen consumption; normalized (n)CSBF]. Both testing sessions began with 5 min of euoxic [end-tidal Po(2) (Pet(O(2))) = 88 Torr] isocapnia [end-tidal Pco(2) (Pet(CO(2))) = +1 Torr above resting values]. Pet(O(2)) was next held at 88 Torr, and Pet(CO(2)) was increased to 40 and 45 Torr in 5-min increments. Participants were then returned to euoxic isocapnia for 5 min, after which Pet(O(2)) was decreased from 88 to 60, 52 and 45 Torr in 5-min decrements. Changes in V(P) and nCSBF were normalized to isocapnic euoxic conditions and indexed against Pet(CO(2)) and arterial oxyhemoglobin saturation. The V(P) gain for euoxic hypercapnia (%/Torr) was significantly higher than nCSBF (P = 0.030). Conversely, the V(P) gain for isocapnic hypoxia (%/%desaturation) was not different from nCSBF (P = 0.518). These findings demonstrate, compared with coronary circulation, that the cerebral circulation is more sensitive to hypercapnia but similarly sensitive to hypoxia.

Effect of postconditioning with electrical stimulation of vagus never on myocardial ischemia reperfusion injury in rats

Objective To evaluate the effect of postconditioning with electrical stimulation of vagus never on myocardial ischemia reperfusion injury in rats. Methods Forty male Sprague-Dawley rats aged 8 weeks and weighing 250 g-350 g were randomly allocated into four groups (n=10 in each group):sham group (S group), ischemia reperfusion group (IR group), ischemia preconditioning group( IPC group)and postconditioning with electrical stimulation of vagus never group( POES group). The myocardial ischemia reperfusion model was preparated by ligation of left anterior descending coronary artery (LAD) for 30 min followed by 120 min reperfusion. During process of ischemia and reperfusion, HR and MAP were recorded and the rate pressure product (RPP) at each measuring point was calculated as the index of myocardial oxygen consumption. Arrhythmia was recorded during ischemia and initial period of reperfusion. At the end of reperfusion, blood samples were collected to assay serum concentrations of CK-MB, and cTnI. At the end of experiment, the infarct sizes was assessed from excised hearts by Evans blue and triphenyltetrazolium chloride (TTC) staining. Results The infarct size (IS%) was (72±9)% in IR group, (36±13)% in IPC group and (47±12)% in POES group, respectively, and serum concentration of cTnI was(0.99±0.14) μg/L in IR group, (0.37±0.08) μg/L in IPC group and (0.40±0.08) μg/L in POES group. Serum concentration of CK-MB was(110±13) μg/L in IR group, (38±8) μg/L in IPC group and(42±7)μg/L in POES group. Compared to the IR group, the IS% and serum concentrations of cTnI and CK-MB in IPC and POES groups were significantly reduced, rate of ventricular arrhythmia during initial period of reperfusion in the IPC and POES groups were also significantly reduced. Compared to IPC group, the IS% was significantly increased in the POES group. Conclusion Postconditioning with electrical stimulation of vagus never can attenuate myocardial ischemia reperfusion injury in rats. However, cardioprotection provided by postconditioning with electrical stimulation of vagus never is weaker than that by ischemia preconditioning. Key words: Ischemia reperfusion injury; Ischemia preconditioning; Postconditioning; Electric stimulation of vagus never

Effect of Heart tablets on cardiac hemodynamics and myocardial oxygen consumption in anesthetized dogs

To observe the pharmacological effects of Heart tablets on cardiac function and its mechanism, the effects on cardiac hemodynamics and myocardial oxygen consumption in anesthetized dogs were observed. Observe the effect of Heart tablets on coronary blood flow, cardiac output, myocardial oxygen consumption and other indicators in normal anesthetized dogs. The Heart tablets can increase femoral arterial blood pressure, while no effect is found on the heart rate, standard II ECG PR interval, QRS interval, QT interval, T wave and other parameters. The tablets can expand coronary artery and peripheral vessel, increase coronary blood flow, lower coronary resistance and increase cardiac blood supply capacity, improve left ventricular function, ameliorate cardiovascular adaptability, increase dp/dt(max), enhance myocardial activity and have a positive regulatory role in heart. At the meantime raise the cardiac output and stroke volume were raised, so that blood pressure can be increased, while the total peripheral resistance was decreased. The coronary vein sinus oxygen content were significantly increased and myocardial oxygen consumption index and myocardial oxygen utilization were reduced. The tablets can adjust and improve the cardiovascular system.