Rate Of Change In Ventricular Pressure Research Articles

Reversal of Right Ventricular Hypertrophy and Dysfunction by Prostacyclin in a Rat Model of Severe Pulmonary Arterial Hypertension.

Prostacyclin analogs are among the most effective and widely used therapies for pulmonary arterial hypertension (PAH). However, it is unknown whether they also confer protection through right ventricle (RV) myocardio-specific mechanisms. Moreover, the use of prostacyclin analogs in severe models of PAH has not been adequately tested. To further identify underlying responses to prostacyclin, a prostacyclin analogue, treprostinil, was used in a preclinical rat Sugen-chronic hypoxia (SuCH) model of severe PAH that closely resembles the human disease. Male Sprague–Dawley rats were implanted with osmotic pumps containing vehicle or treprostinil, injected concurrently with a bolus of Sugen (SU5416) and exposed to 3-week hypoxia followed by 3-week normoxia. RV function was assessed using pressure–volume loops and hypertrophy by weight assessed. To identify altered mechanisms within the RV, tissue samples were used to perform a custom RNA array analysis, histological staining, and protein and transcript level confirmatory analyses. Treprostinil significantly reduced SuCH-associated RV hypertrophy and decreased the rise in RV systolic pressure, mean pulmonary arterial (mPAP), and right atrial (RAP) pressure. Prostacyclin treatment was associated with improvements in RV stroke work, maximum rate of ventricular pressure change (max dP/dt) and the contractile index, and almost a complete reversal of SuCH-associated increase in RV end-systolic elastance, suggesting the involvement of load-independent improvements in intrinsic RV systolic contractility by prostacyclin treatment. An analysis of the RV tissues showed no changes in cardiac mitochondrial respiration and ATP generation. However, custom RNA array analysis revealed amelioration of SuCH-associated increases in newly identified TBX20 as well as the fibrotic markers collagen1α1 and collagen 3α1 upon treprostinil treatment. Taken together, our data support decreased afterload and load-independent improvements in RV function following prostacyclin administration in severe PAH, and these changes appear to associate with improvements in RV fibrotic responses.

Comparing echocardiographic assessment of systolic function with catheterization data in patients with single right ventricles

Purpose Echocardiographic evaluation of systolic function in patients with single right ventricles (SRV) is important but remains challenging. Minimal data exist correlating echocardiographic indices with catheterization data in this population. The goal of this study was to evaluate which echocardiographic measurement correlated best with dP/dt (max) obtained by cardiac catheterization in SRV patients.Methods Patients with SRV physiology who underwent simultaneous echocardiography and cardiac catheterization were evaluated. Echocardiographic data included fractional area change % (FAC), displacement, TDI s’ wave, myocardial performance index (MPI), global systolic strain, and global SR s wave. Maximum positive rate of ventricular pressure change measured as dP/dt (max) was obtained from the cardiac catheterization report. Correlations of echocardiographic and catheterization variables were examined using the Pearson correlation.Results Twenty-seven SRV patients were studied. Median age at the time of the catheterization was 11.4 months (range 0 - 132 months). dP/dt (max) values ranged from 337-1860 mmHg/s with a median of 994 mmHg/s. Mean FAC was 27.15 ± 7.13%, displacement was 7.35 ± 2.88 mm, TDI s’ was 4.98 ±1.93 cm/sec, MPI was 0.41 ± 0.17, global strain was -14.85 ± 4.32%, and global SR s wave was -1.03 ± 0.34 sec-1. There were no significant correlations between dP/dt (max) and any of the echocardiographic measurements of systolic function in SRV patients.Conclusion In patients with SRV physiology, catheterization-derived dP/dt (max) did not correlate with echocardiographic measurements of systolic function. Larger studies are needed to determine which non-invasive parameter best describes systolic function in patients with SRV.

Assessment of Longitudinal Systolic Ventricular Dysfunction and Asynchrony Using Velocity Vector Imaging in Children With a Single Right Ventricle

Assessment of ventricular dysfunction and asynchrony is very important in predicting the outcome for children with a single right ventricle. However, the assessment is inaccurate and subjective because of the unusual ventricular shape. This study aimed to evaluate the feasibility and clinical value of velocity vector imaging for assessing longitudinal systolic ventricular dysfunction and intraventricular asynchrony in children with a single right ventricle. The study enrolled 36 children with a single right ventricle and 36 age-matched children with a normal heart. Peak systolic velocity, peak displacement, strain, strain rate, time to peak systolic velocity, and time to peak systolic strain were measured via velocity vector imaging using the Siemens Sequoia C512 echocardiography instrument. The maximum positive rate of ventricular pressure change (Max [dp/dt]) was obtained by cardiac catheterization for all the children with a single right ventricle. In the children with a single right ventricle, the maximal temporal differences and the standard deviations of the times to peak systolic velocity and peak systolic strain were higher (P < 0.01) than in the children with a normal heart. Moreover, the strain and strain rate values were significantly lower in all six segments (P < 0.05). The strain rate of the basal segment adjacent to the rudimentary chamber correlated best with Max (dp/dt) (r = 0.86; P < 0.01). Longitudinal systolic dysfunction and intraventricular asynchrony could be assessed accurately using velocity vector imaging in children with a single right ventricle.

Nitric Oxide Synthase Inhibition Weakens Beneficial Effects of Increased Plasma Viscosity on Cardiac Function in Hemodilution Model

This study tested the hypothesis that the inhibition of nitric oxide synthase negatively affects the beneficial effects of high viscogenic plasma expander (HVPE) on cardiac performance in a state of hemodilution. Five anesthetized hamsters were administered with N(G)‐nitro‐L‐arginine methyl ester (L‐NAME), nitric oxide synthase inhibitor, as a tested group whereas other five without L‐NAME infusion were used as a control group. Animals were performed an isovolemic hemodilution by 40% of estimated blood volume with dextran 2000 kDa, HVPE with viscosity 6.34 cP. L‐NAME administration followed by isovolemic hemodilution significantly decreased heart rate from 441±41 bpm at baseline to 355±27 bpm at 60 min after hemodilution. End‐systolic pressure increased 14% after L‐NAME infusion and maintained higher than baseline after hemodilution whereas it gradually decreased in animals without L‐NAME infusion. L‐NAME significantly decreased the maximum rate of ventricular pressure change, stroke volume and cardiac output after hemodilution compared to a control group. Systemic vascular resistance increased to 162% and 135% of baseline after L‐NAME infusion and 60 min after hemodilution which is particularly higher than a control group. These results indicate that nitric oxide induced by HVPE play a major role on cardiac function during an isovolemic hemodilution.

Simultaneous variation of ventricular pacing site and timing with biventricular pacing in acute ventricular failure improves function by interventricular assist

The goal of this work was to investigate the hemodynamic effects of simultaneous left ventricular (LV) pacing site (LVPS) and interventricular pacing delay (VVD) variation with biventricular pacing (BiVP) during acute LV failure. Simultaneously varying LVPS and VVD with BiVP has been shown to improve hemodynamics during acute right ventricular (RV) failure. However, effects during acute LV failure have not been reported. In six open-chest pigs, acute LV volume overload was induced by regurgitant flow via an aortic-LV conduit. Epicardial BiVP was implemented with right atrial and ventricular leads and a custom LV pacing array. Fifty-four LVPS-VVD combinations were tested in random order. Cardiac output was evaluated by aortic flow probe, ventricular systolic function by maximum rate of ventricular pressure change, and mechanical interventricular synchrony by normalized RV-LV pressure diagram area. Simultaneous LVPS-VVD variation improved all measures of cardiac function. The observed effect was different for each functional index, with evidence of LVPS-VVD interaction. Compared with effects of LVPS-VVD variation in a model of acute RV failure, hemodynamic changes were markedly different. However, in both models, maximum rate of ventricular pressure change of the failing ventricle was improved with synchronous interventricular contraction, suggesting that, in acute ventricular failure, BiVP can recruit the unstressed ventricle to support systolic function of the failing one. Thus simultaneously varying LVPS and VVD with BiVP during acute ventricular failure can improve cardiac function by "interventricular assist", with hemodynamic effects dependent on the type of failure. This supports the potential utility of temporary BiVP for the treatment of acute ventricular failure commonly seen after cardiac surgery.

Doppler myocardial performance index in assessment of ventricular function in children with single ventricles

Quantitative assessment of ventricular function in children with single ventricles is both difficult and subjective because of asymmetric ventricular geometry. The Doppler myocardial performance index (MPI) allows the assessment regardless of ventricular shape. This study was designed to evaluate the feasibility of MPI in assessing ventricular function in children with single ventricles before and after total cavopulmonary connection (TCPC). Subjects consisted of 161 pediatric patients with single ventricles and 80 normal children without heart disease. The maximum positive rate of ventricular pressure change (Max dp/dt) was obtained in 58 patients by cardiac catheterization. Sixty-eight children with single ventricles received TCPC. MPI was calculated from Doppler tracings of ventricular inflow and outflow, then MPI of single ventricles before and after surgery and normal heart were compared. Normal MPI value was 0.30+/-0.08 in the left ventricle and 0.26+/-0.08 in the right ventricle. Compared to normal children, MPI was significantly higher in 161 children with single ventricles (0.54+/-0.11, P<0.001). MPI correlated inversely with Max (dp/dt) (r=-0.77, P<0.01), and was positively related to age (r=0.54, P<0.01) in patients with single ventricles. MPI did not differ significantly before and after surgery in 68 patients with single ventricles (0.55+/-0.21 vs 0.51+/-0.20, P>0.05). However, MPI in 48 patients of <6 years old decreased significantly (0.55+/-0.21 vs 0.48+/-0.18, P<0.05), suggesting improved ventricular function. Compared to normal children, ventricular function is impaired in patients with single ventricles and may worsen with age. MPI provides an accurate method for assessing ventricular function in children with single ventricles before and after TCPC.

Short-term effects of ecadotril in dogs with induced congestive heart failure.

To evaluate short-term hemodynamic effects of ecadotril in a model of congestive heart failure in dogs. 6 conscious adult male dogs. Instruments were placed in dogs to measure left ventricular, aortic, and atrial blood pressures. Heart failure was induced by repeated coronary embolization with latex microspheres. Four times, and in random order, dogs were given vehicle or active drug (3, 10, or 30 mg/kg of body weight) orally. Hemodynamic variables, urine flow, and urinary electrolyte excretion were measured before and 30, 90, and 150 minutes, and 10 and 21 hours after drug administration. Changes in urine flow, heart rate, mean arterial pressure, or peak positive and negative rate of change in ventricular pressure were not apparent. Urinary sodium excretion significantly increased in response to the low and high doses of ecadotril but not in response to the 10 mg/kg dose. Left ventricular end diastolic pressure (LVEDP) consistently decreased in dose- and time-dependent manner. Maximal group-averaged reductions in LVEDP were 5.2, 8.1, and 10 mm Hg for the low, middle, and high doses, respectively. The magnitude of the decrease in LVEDP was not related to cumulative change in urine flow. Orally administered ecadotril reduced left ventricular filling pressures in these dogs by a mechanism that does not require a substantial diuretic effect. Ecadotril may be effective for alleviating clinical signs in dogs with left-sided heart failure and may be particularly beneficial for use in dogs that are refractory to traditional diuretic therapy.

Use of frog ventricle to examine mechanical and electrical activity of heart.

This report describes a Langendorff heart preparation, which utilizes frog rather than mammalian hearts to demonstrate both mechanical and electrical events of the cardiac cycle. The preparation is durable in that it can be maintained for several hours while being perfused with room-temperature solutions that are not supplemented with oxygen. Ventricular perfusion is achieved via a fluid-filled reservoir coupled to a truncus arteriosus catheter advanced into the ventricle. By varying the height of the reservoir relative to the heart, changes in ventricular pressure and the rate of ventricular pressure change during systole can be recorded by way of a side port on the catheter tubing. The former is indicative of Starling's law of the heart, whereas the latter is reflective of the contractility. Electrical activity of the heart can be observed by measuring injury potentials via a needle electrode inserted into the ventricle. These are extracellular potentials that reflect ventricular action potentials. In addition, surface electrodes placed on the ventricle can be used to detect an integrated ventricular electrocardiogram. Recording of ventricular pressure simultaneously with at least one of these two electrical recordings allows a direct comparison of electrical and mechanical events of the heart. In summary, the Langendorff frog heart preparation is economical in terms of both financial cost and simplicity; yet it enables a thorough examination of both electrical and mechanical properties of the heart either as a student lab exercise or as a classroom demonstration.

EFFECT OF VARYING CORONARY PERFUSION ON VENTRICULAR FUNCTION IN ISOLATED DOG HEARTS.

The effects of coronary perfusion on ventricular function have been studied in isolated ventricle preparations working under different conditions. Coronary flow, oxygen consumption, ventricular stroke work, rate of ventricular pressure change during isovolumetric contraction (dPC), and diastolic ventricular pressure (DVPm) and pressure/inflow ratio were determined. Maintenance of coronary flow and oxygen consumption in 5 experiments did not prevent irreversible changes in DVPm, stroke work, and dPC when the right ventricle was acutely overloaded. These ventricles did not accumulate water. Decreasing coronary perfusion pressure at constant arterial oxygen content in 11 experiments led to inconsistent changes in DVPm, stroke work and dPC. Decreasing arterial oxygen content at constant coronary perfusion pressure in 10 experiments led to increased DVPm but inconsistent changes in stroke work and dPC. There was an inverse relationship between DVPm and oxygen consumption in the variable perfusion experiments, but not in the overloading experiments. Ventricular function did not change significantly with time in 6 experiments in which the conditions of workload and coronary perfusion were kept constant. It was concluded that irreversible changes in performance of acutely overloaded ventricles could be independent of coronary flow, myocardial water content, or duration of experiment.