Clinical application of the conductance catheter technique in the adult human right ventricle

Right Ventricular Strain by Magnetic Resonance Feature Tracking Is Largely Afterload-Dependent and Does Not Reflect Contractility: Validation by Combined Volumetry and Invasive Pressure Tracings

Cardiac magnetic resonance (CMR) is currently the gold standard for evaluating right ventricular (RV) function, which is critical in patients with pulmonary hypertension. CMR feature-tracking (FT) strain analysis has emerged as a technique to detect subtle changes. However, the dependence of RV strain on load is still a matter of debate. The aim of this study was to measure the afterload dependence of RV strain and to correlate it with surrogate markers of contractility in a cohort of patients with chronic thromboembolic pulmonary hypertension (CTEPH) under two different loading conditions before and after pulmonary endarterectomy (PEA). Between 2009 and 2022, 496 patients with 601 CMR examinations were retrospectively identified from our CTEPH cohort, and the results of 194 examinations with right heart catheterization within 24 h were available. The CMR FT strain (longitudinal (GLS) and circumferential (GCS)) was computed on steady-state free precession (SSFP) cine CMR sequences. The effective pulmonary arterial elastance (Ea) and RV chamber elastance (Ees) were approximated by dividing mean pulmonary arterial pressure by the indexed stroke volume or end-systolic volume, respectively. GLS and GCS correlated significantly with Ea and Ees/Ea in the overall cohort and individually before and after PEA. There was no general correlation with Ees; however, under high afterload, before PEA, Ees correlated significantly. The results show that RV GLS and GCS are highly afterload-dependent and reflect ventriculoarterial coupling. Ees was significantly correlated with strain only under high loading conditions, which probably reflects contractile adaptation to pulsatile load rather than contractility in general.

Human biventricular electromechanical simulations on the progression of electrocardiographic and mechanical abnormalities in post-myocardial infarction

AIMS

Develop, calibrate and evaluate with clinical data a human electromechanical modelling and simulation framework for multiscale, mechanistic investigations in healthy and post-myocardial infarction (MI) conditions, from ionic to clinical biomarkers.

METHODS AND RESULTS

Human healthy and post-MI electromechanical simulations were conducted with a novel biventricular model, calibrated and evaluated with experimental and clinical data, including torso/biventricular anatomy from clinical magnetic resonance, state-of-the-art human-based membrane kinetics, excitation-contraction and active tension models, and orthotropic electromechanical coupling. Electromechanical remodelling of the infarct/ischaemic region and the border zone were simulated for ischaemic, acute, and chronic states in a fully transmural anterior infarct and a subendocardial anterior infarct. The results were compared with clinical electrocardiogram and left ventricular ejection fraction (LVEF) data at similar states. Healthy model simulations show LVEF 63%, with 11% peak systolic wall thickening, QRS duration and QT interval of 100 ms and 330 ms. LVEF in ischaemic, acute, and chronic post-MI states were 56%, 51%, and 52%, respectively. In linking the three post-MI simulations, it was apparent that elevated resting potential due to hyperkalaemia in the infarcted region led to ST-segment elevation, while a large repolarization gradient corresponded to T-wave inversion. Mechanically, the chronic stiffening of the infarct region had the benefit of improving systolic function by reducing infarct bulging at the expense of reducing diastolic function by inhibiting inflation.

CONCLUSION

Our human-based multiscale modelling and simulation framework enables mechanistic investigations into patho-physiological electrophysiological and mechanical behaviour and can serve as testbed to guide the optimization of pharmacological and electrical therapies.

Assessing Right Ventricular Function in the Perioperative Setting, Part II: What About Catheters?

An-depth assessment of right ventricular function is important in a many perioperative settings. After exploring 2-dimensional echo-based evaluation, other proposed monitoring modalities are discussed. Pressure-based methods of right ventricular appraisal is discussed. Flow-based assessment is reviewed. An overview of the state of current right ventricular 3-dimensional echocardiography and its potential to construct clinical pressure-volume loops in conjunction with pressure measurements is provided. An overview of right ventricular assessment modalities that do not rely on 2-dimensional echocardiography is discussed. Tailored selection of monitoring modalities can be of great benefit for the perioperative physician. Integrating modalities offers optimal estimations of right ventricular function.

Pressure Volume System for Management of Heart Failure and Valvular Heart Disease

PURPOSE OF REVIEW

To introduce the reader to the basics of pressure-volume (PV) analysis, its current role in management of heart failure and valvular disease, and the possibilities for future use.

RECENT FINDINGS

The recent introduction of FDA-approved miniaturized conductance catheters that can produce PV loops in the clinical setting has set the stage for the translation of this important research technique into clinical practice. The use of these catheters has shed important insights into the pathophysiology of many common conditions associated with heart failure including heart failure with preserved ejection fraction and right heart failure and has been utilized to assist in optimization of lead placement during cardiac resynchronization therapy. The use of PV loops has enhanced our understanding and diagnosis of common conditions associated with heart failure. In addition, it has shown promise as an adjunct to therapeutic procedures. Future directions may include the use of PV loops in the management of patients with heart failure requiring mechanical circulatory support and to help predict the utility of percutaneous valvular interventions.

Physiological insights of recent clinical diagnostic and therapeutic technologies for cardiovascular diseases

Diagnostic and therapeutic methods for cardiovascular diseases continue to be developed in the 21st century. Clinicians should consider the physiological characteristics of the cardiovascular system to ensure successful diagnosis and treatment. In this review, we focus on the roles of cardiovascular physiology in recent diagnostic and therapeutic technologies for cardiovascular diseases. In the first section, we discuss how to evaluate and utilize left ventricular arterial coupling in the clinical settings. In the second section, we review unique characteristics of pulmonary circulation in the diagnosis and treatment of pulmonary hypertension. In the third section, we discuss physiological and anatomical factors associated with graft patency after coronary artery bypass grafting. In the last section, we discuss the usefulness of mechanical ventricular unloading after acute myocardial infarction. Clinical development of diagnostic methods and therapies for cardiovascular diseases should be based on physiological insights of the cardiovascular system.

A novel single-beat approach to assess right ventricular systolic function

Clinical assessment of right ventricular (RV) contractility in diseases such as pulmonary arterial hypertension (PAH) has been hindered by the lack of a robust methodology. Here, a novel, clinically viable, single-beat method was developed to assess end-systolic elastance (E_es), a measure of right ventricular (RV) contractility. We hypothesized that this novel approach reduces uncertainty and interobserver variability in the estimation of the maximum isovolumic pressure (P_iso), the key step in single-beat methods. The new method was designed to include a larger portion of the RV pressure data and minimize subjective adjustments by the operator. Data were obtained from right heart catheterization of PAH patients in a multicenter prospective study ( data set 1) and a single-center retrospective study ( data set 2). To obtain P_iso, three independent observers used an established single-beat method (based on the first derivative of the pressure waveform) and the novel method (based on the second derivative). Interobserver variability analysis included paired t-test, one-way ANOVA, interclass correlation (ICC) analysis, and a modified Bland-Altman analysis. The P_iso values obtained from the two methods were linearly correlated for both data set 1 ( R² = 0.74) and data set 2 ( R² = 0.91). Compared with the established method, the novel method resulted in smaller interobserver variability ( P < 0.001), nonsignificant differences between observers, and a narrower confidence interval. By reducing uncertainty and interobserved variability, this novel approach may pave the way for more effective clinical management of PAH. NEW & NOTEWORTHY A novel methodology to assess right ventricular contractility from clinical data is demonstrated. This approach significantly reduces interobserver variability in the analysis of ventricular pressure data, as demonstrated in a relatively large population of subjects with pulmonary hypertension. This study may enable more accurate clinical monitoring of systolic function in subjects with pulmonary hypertension.

Diagnosing and treating the failing right heart

PURPOSE OF REVIEW

Right ventricular failure (RVF) is associated with significant morbidity and mortality. There is an increasing interest in proper assessment of right ventricle (RV) function as well as understanding mechanisms behind RVF.

RECENT FINDINGS

Within this article, we discuss the metabolic changes that occur in the RV in response to RVF, in particular, a shift toward glycolysis and increased glutaminolysis. We will detail the advances made in noninvasive imaging in assessing the function of the RV and review the methods to assess right ventricle-pulmonary artery coupling. We lastly investigate the role of new treatment options in the failing RV, such as β-blocker therapy.

SUMMARY

RVF is a complicated entity. Although some inferences on RV function and treatment can be made from our understanding of the left ventricle, the RV has unique features, anatomically, metabolically and embryologically, that require dedicated RV-directed research.

Determinants of right ventricular afterload (2013 Grover Conference series)

Right ventricular (RV) afterload consists of both resistive and capacitive (pulsatile) components. Total afterload can be measured directly with pulmonary artery input impedance spectra or estimated, either with lumped-parameter modeling or by pressure-volume analysis. However, the inverse, hyperbolic relationship between resistance and compliance in the lung would suggest that the pulsatile components are a predictable and constant proportion of the resistive load in most situations, meaning that total RV load can be estimated from mean resistive load alone. Exceptions include elevations in left atrial pressures and, to a lesser extent, chronic thromboembolic disease. The pulsatile components may also play a more significant role at normal or near-normal pulmonary artery pressures. Measures of coupling between RV afterload and RV contractility may provide important information not apparent by other clinical and hemodynamic measures. Future research should be aimed at development of noninvasive measures of coupling.

ESC Working Group on Myocardial Function Position Paper: how to study the right ventricle in experimental models

The right ventricle has become an increasing focus in cardiovascular research. In this position paper, we give a brief overview of the specific pathophysiological features of the right ventricle, with particular emphasis on functional and molecular modifications as well as therapeutic strategies in chronic overload, highlighting the differences from the left ventricle. Importantly, we put together recommendations on promising topics of research in the field, experimental study design, and functional evaluation of the right ventricle in experimental models, from non-invasive methodologies to haemodynamic evaluation and ex vivo set-ups.

Methods for measuring right ventricular function and hemodynamic coupling with the pulmonary vasculature

The right ventricle (RV) is a pulsatile pump, the efficiency of which depends on proper hemodynamic coupling with the compliant pulmonary circulation. The RV and pulmonary circulation exhibit structural and functional differences with the more extensively investigated left ventricle (LV) and systemic circulation. In light of these differences, metrics of LV function and efficiency of coupling to the systemic circulation cannot be used without modification to characterize RV function and efficiency of coupling to the pulmonary circulation. In this article, we review RV physiology and mechanics, established and novel methods for measuring RV function and hemodynamic coupling, and findings from application of these methods to RV function and coupling changes with pulmonary hypertension. We especially focus on non-invasive measurements, as these may represent the future for clinical monitoring of disease progression and the effect of drug therapies.

Advancements in pressure-volume catheter technology - stress remodelling after infarction

Microconductance catheters have been successfully applied to measure left ventricular (LV) function in the mouse to assess cardiac or pharmacological interventions for a number of years. New complex admittance methods produce an estimate of the parallel admittance of cardiac muscle that can be used to correct the measurement in real time. This contrasts with existing conductance technologies that require in vivo calibration using a bolus of hypertonic saline. Here, we report the application of this emerging technology in the context of myocardial infarction and LV remodelling. Using a combination of high-resolution ultrasound and LV conductance catheters, we compared measures of LV function using an admittance system and a traditional conductance-derived pressure-volume (PV) system. We subjected C57BL/6 mice to focal myocardial ischaemia-reperfusion by transient ligation of the left anterior descending coronary artery and assessed cardiac function with different systems to determine the reliability and accuracy of these methods to distinguish between normal and dysfunctional ventricle. We demonstrate that the admittance PV system, in our hands, provides a straightforward solution for assessing LV function in mice. Using this technique in combination with other established methods, we measured LV dysfunction following coronary artery occlusion and reperfusion, which can be ameliorated using a known preconditioning agent (CORM-3), and found that functional read-outs are representative of other methods. We have found that, especially in diseased tissue, LV pressure-volume loops derived from complex admittance provide a reproducible and reliable method of determining LV function without the need for technically challenging calibration. Our data suggest that admittance records accurate/physiological LV cavity volumes when compared with other invasive methods in the same animal. This emerging technology is both effective and reproducible for measuring LV function and dysfunction in the mouse, without the need for complicated interventions to calibrate the measurements or training in a new technology. This may mark the way towards a fast and accurate assessment of murine cardiac function in normal animals and disease models.

Imaging the right heart: the use of integrated multimodality imaging

During recent years, right ventricular (RV) structure and function have been found to be an important determinant of outcome in different cardiovascular and also pulmonary diseases. Currently, echocardiography and cardiac magnetic resonance (CMR) imaging are the two imaging modalities most commonly used to visualize the RV. Most structural abnormalities of the RV can be reliably described by echocardiography but due its complex geometrical shape, echocardiographic assessment of RV function is more challenging. Newer promising echocardiographic techniques are emerging but lack of validation and limited normal reference data influence their routine clinical application. Cardiac magnetic resonance is generally considered the clinical reference technique due to its unlimited imaging planes, superior image resolution, and three-dimensional volumetric rendering. The accuracy and reliability of CMR measurements make it the ideal tool for serial examinations of RV function. Multidetector computed tomography (MDCT) plays an important role in the diagnosis of pulmonary emboli but can also be used for assessing RV ischaemic disease or as an alternative for CMR if contra-indicated. Radionuclide techniques have become more obsolete in the current era. The different imaging modalities should be considered complimentary and each plays a role for different indications.

Right and left ventricular function after chronic pulmonary artery banding in rats assessed with biventricular pressure-volume loops

In many patients with congenital heart disease, the right ventricle (RV) is subjected to abnormal loading conditions. To better understand the state of compensated RV hypertrophy, which could eventually progress to decompensation, we studied the effects of RV pressure overload in rats. In the present study, we report the biventricular adaptation to 6 wk of pulmonary artery banding (PAB). PAB resulted in an RV pressure overload to ∼60% of systemic level and a twofold increase in RV mass ( P < 0.01). Systemic hemodynamic parameters were not altered, and overt signs of heart failure were absent. Load-independent measures of ventricular function (end-systolic pressure-volume relation, preload recruitable stroke work relation, maximum first time derivative of pressure divided by end-diastolic volume), assessed by means of pressure-volume (PV) loops, demonstrated a two- to threefold increase in RV contractility under baseline conditions in PAB rats. RV contractility increased in response to dobutamine stimulation (2.5 μg·kg−1·min−1) both in PAB and sham-operated rats in a similar fashion, indicating preserved RV contractile reserve in PAB rats. Left ventricular (LV) contractility at baseline was unaffected in PAB rats, although LV volume in PAB rats was slightly decreased. LV contractility increased in response to dobutamine (2.5 μg·kg−1·min−1), both in PAB and sham rats, whereas the response to a higher dose of dobutamine (5 μg·kg−1·min−1) was blunted in PAB rats. RV pressure overload (6 wk) in rats resulted in a state of compensated RV hypertrophy with preserved RV contractile reserve, whereas LV contractile state at baseline was not affected. Furthermore, this study demonstrates the feasibility of performing biventricular PV-loop measurements in rats.

Combined pulmonary stenosis and insufficiency preserves myocardial contractility in the developing heart of growing swine at midterm follow-up

This study was conducted to determine the effects of chronic combined pulmonary stenosis and pulmonary insufficiency (PSPI) on right (RV) and left ventricular (LV) function in young, growing swine. Six pigs with combined PSPI were studied, and data were compared with previously published data of animals with isolated pulmonary insufficiency and controls. Indexes of systolic function (stroke volume, ejection fraction, and cardiac functional reserve), myocardial contractility (slope of the end-systolic pressure-volume and change in pressure over time-end-diastolic volume relationship), and diastolic compliance were assessed within 2 days of intervention and 3 mo later. Magnetic resonance imaging was used to quantify pulmonary insufficiency and ventricular volumes. The conductance catheter was used to obtain indexes of the cardiac functional reserve, diastolic compliance, and myocardial contractility from pressure-volume relations acquired at rest and under dobutamine infusion. In the PSPI group, the pulmonary regurgitant fraction was 34.3 ± 5.8%, the pressure gradient across the site of pulmonary stenosis was 20.9 ± 20 mmHg, and the average RV peak systolic pressure was 70% systemic at 12 wk follow-up. Biventricular resting cardiac outputs and cardiac functional reserves were significantly limited ( P < 0.05), LV diastolic compliance significantly decreased ( P < 0.05), but RV myocardial contractility significantly enhanced ( P < 0.05) compared with control animals at 3-mo follow-up. In the young, developing heart, chronic combined PSPI impairs biventricular systolic pump function and diastolic compliance but preserves RV myocardial contractility.

Magnetic Resonance Imaging Analysis of Right Ventricular Pressure-Volume Loops

Background— The aims of this study were to validate MRI-derived right ventricular (RV) pressure-volume loops for assessment of RV myocardial contractility and then to apply this technique in patients with chronic RV pressure overload for assessment of myocardial contractility, ventricular pump function, and VA coupling.

Methods and Results— Flow-directed catheters were guided under MR fluoroscopy (1.5 T) into the RV for invasive pressure measurements. Simultaneously, ventricular volumes and myocardial mass were assessed from cine MRI. From sampled data, RV pressure-volume loops were constructed, and maximal ventricular elastance indexed to myocardial mass (E max_i ) was derived by use of a single-beat estimation method. This MRI method was first validated in vivo (6 swine), with conductance techniques used as reference. Bland-Altman test showed good agreement between methods (E max_i =5.1±0.5 versus 5.8±0.7 mm Hg · mL −1 · 100 g −1 , respectively; P =0.08). Subsequently, the MRI method was applied in 12 subjects: 6 control subjects and 6 patients with chronic RV pressure overload from pulmonary hypertension. In these patients, indexes of RV pump function (cardiac index), E max_i , and VA coupling (E max /E a ) were assessed. In patients with pulmonary hypertension, RV pump function was decreased (cardiac index, 2.2±0.5 versus 2.9±0.4 L · min −1 · m −2 ; P <0.01), myocardial contractility was enhanced (E max_I , 9.2±1.1 versus 5.0±0.9 mm Hg · mL −1 · 100 g −1 ; P <0.01), and VA coupling was inefficient (E max /E a , 1.1±0.3 versus 1.9±0.4; P <0.01) compared with control subjects.

Conclusions— RV myocardial contractility can be determined from MRI-derived pressure-volume loops. Chronic RV pressure overload was associated with reduced RV pump function despite enhanced RV myocardial contractility. The proposed MRI approach is a promising tool to assess RV contractility in the clinical setting.

Effects of Pulmonary Insufficiency on Biventricular Function in the Developing Heart of Growing Swine

Background— This study was conducted to determine the effects of chronic pulmonary insufficiency (PI) on right (RV) and left (LV) ventricular function in young growing swine.

Methods and Results— Six PI and 5 control animals were studied. PI was induced by transcatheter placement of stents across the pulmonary valve. Indices of systolic function (ejection fraction, cardiac output, and cardiac functional reserve), diastolic function (compliance), and myocardial contractility (the slope of the relationship of end-systolic pressure versus end-systolic volume [E max ] and the slope of the dP/dt max –end-diastolic volume relationship [M dP/dt ]) were assessed within 2 days of intervention and 3 months later. MRI was used to quantify PI and ventricular volumes. Conductance catheter techniques were used to obtain indices of contractility and diastolic compliance from pressure-volume relations at rest and under dobutamine infusion. In the PI group, pulmonary regurgitant fraction was 49.2±5.9% at 3-month follow-up. RV cardiac functional reserve was limited, diastolic function was preserved, and myocardial contractility was altered (E max =2.6±0.3 mm Hg/mL for the PI group versus 3.5±0.4 mm Hg/mL for control; P <0.01). LV cardiac functional reserve was limited, ventricular compliance decreased, and myocardial contractility was preserved.

Conclusions— In the young developing heart, chronic PI alters biventricular systolic function, RV myocardial contractility, and LV diastolic performance.

Reducing errors in parallel conductance measurement

Conductance (COND) measures left ventricle (LV) and right ventricle (RV) volume continuously during the cardiac cycle. COND measurement of the ventricle can be impaired by electrically conductive factors extrinsic to the heart that cause an artifactual increase in COND. This is known as parallel COND. A hypertonic saline injection has traditionally been used to measure parallel COND. The entry of hypertonic saline into the ventricle causes a rise (ascending region) in ventricular COND tracing, whereas its dissipation causes a fall (descending region). The hypothesis of this study is that parallel COND measurement can vary based on the region of COND tracing (ascending versus descending versus both) chosen for calculations. Parallel COND was measured in the LV (15 pigs and 5 sheep) and the RV (13 pigs and 5 sheep). In the LV, average +/- standard error of mean (SEM) parallel COND measured from the ascending region (55.4 +/- 9.2) was significantly different (p < 0.05) from the descending region and from both regions (72.2 +/- 10.3 and 66.4 +/- 9.2, respectively). Additionally, LV parallel COND measured from the descending region and from both regions were not different (p = NS; 72.2 +/- 10.3 and 66.4 +/- 9.2, respectively). In the RV, there was no significant difference (p = NS) among parallel COND calculated from ascending, descending, and both regions (102.9 +/- 8.1, 105.6 +/- 10.0, and 103.9 +/- 7.5, respectively). Average +/- SEM number of points used for parallel COND calculation (N) in the LV for each region (ascending versus descending versus both) were significantly different (p < 0.05) from one another (8 +/- 1 vs 11 +/- 1 vs 18 +/- 1). Similarly, N values used for the calculation of RV parallel COND in ascending versus descending versus both regions were significantly different (p < 0.05) from one another (6 +/- 1 vs 9 +/- 1 vs 14 +/- 1). In conclusion, there were significant differences in parallel COND calculation based on varying regions of LV COND. This was not true for the RV. To reduce errors that are caused by the differences cited here, one region should be used consistently to measure parallel COND. More study will be required to determine the optimal region of the COND tracing for the determination of parallel COND.

Right ventricular volume measurement: can conductance do it better?

The measurement of right ventricular volume will be reviewed with special reference to the conductance catheter technique. The historical development of the intracavitary impedance technique will be described along with the theory of the multielectrode conductance method. The major potential advantage of this technique is its ability to measure dynamic volume change during the cardiac cycle. This enables a real time beat to beat assessment of ventricular volume in addition to providing continuous recordings during loading manoeuvres performed on the ventricle. However, the conductance catheter technique is based on the assumption that the electric field produced by the catheter is homogeneous and parallel to the long axis of the ventricle, and the current, created by the excitation electrodes of the catheter, is contained within the ventricular cavity. The measurement of these two calibration factors (known as parallel conductance volume (V(C)) and dimensionless slope factor (alpha)), along with the effects of changes in blood resistivity and the orientation of the catheter on the measurement of absolute volume, will be described. Furthermore, some of the clinical applications of the technique in adults and children with heart disease will be outlined.

Differential response of the right and left ventricle to beta-adrenergic stimulation: an echo planar MR study in intact animals

PURPOSE

The purpose of this study was to compare the response in contractility of the right (RV) and left (LV) ventricle of the heart to beta-adrenergic stimulation using an echo planar MR technique.

METHOD

In six sheep, RV and LV pressure-volume (P-V) relationships were constructed simultaneously using intraventricular pressures and volumes measured with echo planar MRI at rest and during dobutamine stress. Contractility changes were quantified by assessment of the end-systolic P-V relationship (ESPVR) and the preload recruitable stroke work (PRSW).

RESULTS

Both the ESPVR the the PRSW showed a significant increase in contractility for both ventricles after dobutamine administration. The increase in contractility was significantly larger for the LV than for the RV, both measured wit the ESPVR (p < 0.0003) and the PRSW (p < 0.007).

CONCLUSION

This study shows the usefulness of echo planar MRI to assess myocardial contractility of both ventricles simultaneously. Furthermore, the study shows that beta-adrenergic stimulation has a significantly greater positive inotropic effect on LV contractility than on RV contractility.