Measurement accuracy of cardiac output in humans: indicator-dilution technique versus geometric analysis by ultrafast computed tomography

Pulmonary CT perfusion robustly measures cardiac output in the context of multilevel pulmonary occlusion: a porcine study

BACKGROUND

To validate pulmonary computed tomography (CT) perfusion in a porcine model by invasive monitoring of cardiac output (CO) using thermodilution method.

METHODS

Animals were studied at a single center, using a Swan-Ganz catheter for invasive CO monitoring as a reference. Fifteen pigs were included. Contrast-enhanced CT perfusion of the descending aorta and right and left pulmonary artery was performed. For variation purposes, a balloon catheter was inserted to block the contralateral pulmonary vascular bed; additionally, two increased CO settings were created by intravenous administration of catecholamines. Finally, stepwise capillary occlusion was performed by intrapulmonary arterial injection of 75-μm microspheres in four stages. A semiautomatic selection of AFs and a recirculation-aware tracer-kinetics model to extract the first-pass of AFs, estimating blood flow with the Stewart-Hamilton method, was implemented. Linear mixed models (LMM) were developed to calibrate blood flow calculations accounting with individual- and cohort-level effects.

RESULTS

Nine of 15 pigs had complete datasets. Strong correlations were observed between calibrated pulmonary (0.73, 95% confidence interval [CI] 0.6-0.82) and aortic blood flow measurements (0.82, 95% CI, 0.73-0.88) and the reference as well as agreements (± 2.24 L/min and ± 1.86 L/min, respectively) comparable to the state of the art, on a relatively wide range of right ventricle-CO measurements.

CONCLUSIONS

CT perfusion validly measures CO using LMMs at both individual and cohort levels, as demonstrated by referencing the invasive CO.

RELEVANCE STATEMENT

Possible clinical applications of CT perfusion for measuring CO could be in acute pulmonary thromboembolism or to assess right ventricular function to show impairment or mismatch to the left ventricle.

KEY POINTS

• CT perfusion measures flow in vessels. • CT perfusion measures cumulative cardiac output in the aorta and pulmonary vessels. • CT perfusion validly measures CO using LMMs at both individual and cohort levels, as demonstrated by using the invasive CO as a reference standard.

CT coronary angiography as an alternative imaging method to ascertain cardiac output and its correlation with echocardiography

AIM

To assess the feasibility and accuracy of cardiac output (CO) obtained using a test bolus in patients scanned with single-source prospective-gated cardiac computed tomography (CT), and comparing it with CO obtained from unenhanced two-dimensional (2D) echocardiography using biplane Simpson's method.

MATERIALS AND METHODS

In the present study, 100 patients with a mean age of 55 ± 12 years who underwent coronary CT angiography with prospective electrocardiogram (ECG)-gated CT in which the scan delay was evaluated using a test bolus. The time-attenuation curves obtained from the test bolus were used to calculate the CO of the patients. The CO obtained was then compared with that obtained after follow-up 2D echocardiography using biplane modified Simpson method.

RESULTS

Linear regression was calculated between the CO and contrast enhancement: CO = -0.16(HUmax) + 7.65. The study showed good correlation between the two methods with r=0.77, p<0.001. On Bland-Altman analysis, no significant difference was noted between the two methods.

CONCLUSION

This less researched method for CO estimation appears feasible; however, the clinical usefulness of this parameter is uncertain in absence of further clinical and reference standard validation.

Avaliação de diferentes tempos de trânsito do meio de contraste intravascular em exames de tomografia computadorizada coronariana

Objective

To measure the transit times (TTs) of contrast agents among the injection site (antecubital vein), superior vena cava, pulmonary trunk, and ascending aorta, in coronary computed tomography angiography (CTA) examinations of outpatients with no history of cardiovascular or lung disease, thus defining reference values for those TTs.

Materials and Methods

The contrast TTs from the injection site (antecubital vein) to the superior vena cava, from the superior vena cava to the pulmonary trunk, and from the pulmonary trunk to the ascending aorta were measured by monitoring contrast enhancement in real time (bolus tracking). Cardiac output was measured by the geometric method during the CTA examination and was correlated with the contrast TT.

Results

Forty-three individuals were analyzed. The mean contrast TT was 13.1 s overall (from the antecubital vein to the ascending aorta), 3.0 s from the superior vena cava to the pulmonary trunk, and 7.2 s from the pulmonary trunk to the ascending aorta. There was a tendency toward a correlation between contrast TT and cardiac output (p = 0.055).

Conclusion

The reference values established here for contrast TTs among the superior vena cava, pulmonary trunk, and ascending aorta will serve as a basis for clinical evaluation.

Effect of Cardiac Phase on Cardiac Output Index Derived from Dynamic CT Myocardial Perfusion Imaging

Purpose: The aortic time-enhancement curve obtained from dynamic CT myocardial perfusion imaging can be used to derive the cardiac output (CO) index based on the indicator dilution principle. The objective of this study was to investigate the effect of cardiac phase at which CT myocardial perfusion imaging is triggered on the CO index measurement with this approach. Methods: Electrocardiogram (ECG) gated myocardial perfusion imaging was performed on farm pigs with consecutive cardiac axial scans using a large-coverage CT scanner (Revolution, GE Healthcare) after intravenous contrast administration. Multiple sets of dynamic contrast-enhanced (DCE) cardiac images were reconstructed retrospectively from 30% to 80% R-R intervals with a 5% phase increment. The time-enhancement curve sampled from above the aortic orifice in each DCE image set was fitted with a modified gamma variate function (MGVF). The fitted curve was then normalized to the baseline data point unaffected by the streak artifact emanating from the contrast solution in the right heart chamber. The Stewart−Hamilton equation was used to calculate the CO index based on the integral of the fitted normalized aortic curve, and the results were compared among different cardiac phases. Results: The aortic time-enhancement curves sampled at different cardiac phases were different from each other, especially in the baseline portion of the curve where the effect of streak artifact was prominent. After properly normalizing and denoising with a MGVF, the integrals of the aortic curve were minimally different among cardiac phases (0.228 ± 0.001 Hounsfield Unit × second). The corresponding mean CO index was 4.031 ± 0.028 L/min. There were no statistical differences in either the integral of the aortic curve or CO index among different cardiac phases (p > 0.05 for all phases).

Determination of cardiac output with dynamic contrast-enhanced computed tomography

Cardiac output (CO) is an important diagnostic and prognostic factor in the haemodynamic evaluation of patients. The gold standard for CO measurement, thermodilution, requires an invasive right-heart catheterisation (RHC). In this pilot study we aimed to determine the accuracy of non-invasive CO determination from dynamic contrast-enhanced computed tomography (CT) compared to thermodilution. Patients who underwent diagnostic or follow-up RHC due to suspected or known pulmonary vascular disease at our department and required a thoracic CT between June 2011 and August 2012 were included. CO was determined from CT attenuation-time curves in the pulmonary artery and the ascending aorta using a dynamic contrast-enhanced CT sequence. CO determined in N = 18 patients by dynamic CT in the pulmonary artery was in very good agreement with thermodilution data (r = 0.84). Bland-Altman analysis showed a systematic overestimation of 0.7 ± 0.6 l/min compared to thermodilution. Data from the ascending aorta also showed a good correlation, but with a larger scattering of the values. The average effective dose for the dynamic investigation was 1.2 ± 0.7 mSv. CO determined with dynamic contrast-enhanced CT in the main pulmonary artery reliably predicts the values obtained by thermodilution during RHC. This non-invasive technique might provide an alternative for repeated invasive right-heart catheter investigations in the follow-up of pulmonary arterial hypertension patients.

[Chest compression without ventilation during basic life support? Confirmation of the validity of the European Resuscitation Council (ERC) guidelines 2005]

Basic life support (BLS) refers to maintaining airway patency and supporting breathing and the circulation, without the use of equipment other than infection protection measures. The scientific advisory committee of the American Heart Association (AHA) published recommendations (online-first) on March 31 2008, which promote a call to action for bystanders who are not or not sufficiently trained in cardiopulmonary resuscitation (CPR) and witness an adult out-of-hospital sudden collapse probably of cardiac origin. These bystanders should provide chest compression without ventilation (so-called compression-only CPR). If bystanders were previously trained and thus confident with CPR, they should decide between conventional CPR (chest compression plus ventilation at a ratio of 30:2) and chest compression alone. However, considering current evidence-based medicine and latest scientific data both the European Resuscitation Council (ERC) and the German Resuscitation Council (GRC) do not at present intend to change or supplement the current resuscitation guidelines "Basic life support for adults". Both organisations do not see any need for change or amendments in central European practice and continue to recommend that only those lay rescuers that are not willing or unable to give mouth-to-mouth ventilation should provide CPR solely by uninterrupted chest compressions until professional help arrives. It is also stressed that the training of young people especially teenagers as lay rescuers should be promoted and the establishment of training programs through emergency medical organizations and in schools should be encouraged.

Optimization of cardiac MSCT contrast injection protocols: dependency of the main bolus contrast density on test bolus parameters and patients' body weight

RATIONALE AND OBJECTIVES

Our aim was to evaluate the correlation of test bolus (TB) curve parameters with main bolus (MB) contrast density for cardiac 16-slice computed tomography, and to correlate observed enhancement with patient body weight.

MATERIALS AND METHODS

Sixty patients with known or suspected coronary artery disease were included in a prospective double-blind study. Contrast material containing 300 mg iodine/mL (Iomeprol 300; Imeron 300, Bracco Imaging SpA, Milan, Italy) and 400 mg iodine/mL (Iomeprol 400; Imeron 400) was injected at a rate of 1 g of iodine/second. Contrast densities (Hounsfield units) of the MB were determined in the left cardiac system. The peak density (PD) of maximum attenuation and the area under the curve (AUC) of the TB curve were calculated for each patient. The dependency of MB contrast attenuation on these parameters and on patient body weight was evaluated.

RESULTS

Positive correlations (r = 0.52 and r = 0.56, respectively; P < .0001) were obtained between the PD and AUC of the TB curve with the mean density of the MB. Stronger correlations (r = 0.63 and r = 0.64, respectively; P < .0001) between PD and AUC of the TB curve and MB attenuation were found when patient body weight was included in the analysis.

CONCLUSIONS

Strong correlation of the PD and AUC of the TB curve with the mean density of the MB is observed when patient body weight is considered. Contrast injection protocols may be optimized, and variations of MB contrast density in the left ventricle and main coronary arteries reduced, by taking these TB parameters and the weight of the patient into account.

Contrast Bolus Optimization for Cardiac 16-Slice Computed Tomography

OBJECTIVES

The aims of our study were to compare contrast injection protocols with contrast media containing 300 and 400 mg iodine per milliliter for optimal contrast enhancement in cardiac multidector row computed tomography (CT) and to evaluate the correlation of test bolus curve parameters with the final contrast density of the main bolus.

MATERIALS AND METHODS

Sixty patients with known or suspected coronary artery disease were included in a prospective double-blind study. Patients were randomized to 2 groups. Group 1 received 83 mL of a contrast medium (CM) containing 300 mg of iodine (Iomeron 300, Bracco Imaging SpA, Milan, Italy) at a flow rate of 3.3 mL/s, whereas group 2 received 63 mL of the same agent containing 400 mg of iodine (Iomeron 400) at a flow rate of 2.5 mL/s. The test bolus volumes were 20 mL and 15 mL, respectively. Imaging was performed using a 16-slice CT system (16DCT; Somatom Sensation 16, Siemens Medical Solutions, Forchheim, Germany). Contrast densities (Hounsfield Units [HU]) were determined in the cardiac chambers and in the main coronary arteries. The peak density and area under the curve of the test bolus were calculated for each patient.

RESULTS

The mean contrast densities of the coronary arteries were 259.1 +/- 46.7 HU for group 1 and 251.6 +/- 51.0 HU, for group 2. No noteworthy differences between groups were noted for density measurements in the cardiac chambers or for the ratio of right-to-left ventricle density. Whereas a positive correlation was noted for both groups between the area under the curve of the test bolus and the mean density of the main bolus, a positive correlation between peak density of the test bolus and mean density of the main bolus was noted only for group 1.

CONCLUSION

Equivalent homogenous enhancement of the ventricular cavities and coronary arteries to that obtained using a CM with standard iodine concentration (Iomeron 300) can be achieved with lower overall volumes of administered CM and reduced injection flow rates when a CM with high iodine concentration (Iomeron 400) is used.

Left ventricular function studied with MDCT

Accurate determination of left ventricular (LV) myocardial function is fundamental for clinical diagnosis, risk stratification, and estimation of prognosis in patients with ischemic and nonischemic cardiomyopathy. Primarily, multi-detector-row spiral CT (MDCT) of the heart aimed at detecting coronary artery obstruction and cardiac morphology. Multiple studies have demonstrated that retrospectively, ECG-gated MDCT determination of LV volumes and consequently global LV function parameters is feasible in good agreement with established imaging modalities such as cineventriculography, echocardiography, and cine magnetic resonance imaging (CMR). Post-processing tools allow fast and semi-automatic determination of LV function parameters from MDCT data in analogy to known CMR evaluation approaches. Although MDCT is not considered to be first-line modality for LV function assessment, this technique provides accessory dynamic information in patients undergoing MDCT coronary angiography, contributing to combined assessment of cardiac morphology and function without need of additional radiation exposure. MDCT regional LV wall motion analysis at rest is feasible, but further improvement in temporal resolution seems mandatory to match results obtained from competing modalities. This paper will discuss the diagnostic potential of MDCT for assessment of LV function with regards to accuracy and clinical applications, as well as limitations, particularly in comparison with CMR as modality of reference.

Assessment of Mitral Valve Regurgitation at Electron-Beam CT: Comparison with Doppler Echocardiography

PURPOSE

To prospectively compare mitral valve regurgitation fractions calculated at electron-beam computed tomography (CT) (Doppler echocardiography as reference standard) and to evaluate accuracy of electron-beam CT volume and flow measurements compared with magnetic resonance (MR) imaging results.

MATERIALS AND METHODS

Institutional review board approval and informed consent were obtained. Volume and flow measurements were performed at electron-beam CT in 219 patients (197 men, 22 women; mean age, 61.5 years +/- 10.4 [standard deviation]), of whom 157 had known isolated mitral valve regurgitation. Regurgitation volume was calculated as the difference between left ventricular total and forward stroke volumes. Regurgitation fractions were compared with corresponding echocardiographic grades (grades 0-IV) by using Spearman rank correlation and a weighted kappa test. In 22 patients, CT volume and flow measurements were compared with MR results by using intraclass correlation.

RESULTS

Regurgitation fractions at CT correlated well with echocardiographic grading (rank correlation coefficient, r(S) = 0.82; P < .05). Mean regurgitation fractions for echocardiographic grades 0, I, II, III, and IV were 3.1% +/- 6.2, 12.7% +/- 9.9, 25.3% +/- 12.3, 40.4% +/- 11.5, and 55.9% +/- 13.7, respectively. The most suitable thresholds for differentiating echocardiographic grades were calculated regurgitation fractions of 6%, 20%, 30%, and 44%; with these thresholds, individual echocardiographic grades were differentiated (grades 0 vs I-IV, 0-I vs II-IV, 0-II vs III-IV, and 0-III vs IV, respectively) with sensitivities of 89%, 87%, 86%, and 93% and specificities of 81%, 87%, 92%, and 91%, respectively. There was perfect agreement in classification of mitral valve insufficiency between electron-beam CT and echocardiography in 134 (61%) patients and a mismatch by one grade in 72 (33%) and by two grades in 13 (6%) (kappa = 0.84). Intraclass correlation coefficients between CT and MR imaging for total and forward stroke volumes and regurgitation volume and fraction were 0.88, 0.79, 0.93, and 0.89, respectively.

CONCLUSION

Electron-beam CT provides quantitative information on severity of mitral valve regurgitation, but semiquantitative classification of regurgitation showed mismatch between electron-beam CT and Doppler echocardiography by at least one grade in more than one-third of all patients.

Quantification of Functional Mitral Valve Regurgitation in Patients With Congestive Heart Failure

OBJECTIVES

We sought to determine the agreement between electron-beam computed tomography (CT) and cardiac catheterization for the quantification of mitral regurgitation and to evaluate their association with echocardiographic assessment.

MATERIAL AND METHODS

Fifty patients with congestive heart failure were examined both by electron-beam CT and catheterization to calculate mitral regurgitation volume and fraction based on the difference between the left ventricular stroke and aortic flow volume. The severity of regurgitation was also compared with visual assessment by echocardiography (grade, 0-4+).

RESULTS

The mean values for the mitral regurgitation volume and fraction did not differ significantly between electron-beam CT and catheterization (mean differences: 0.2 mL/m2 and -0.9%, P > 0.05 each, limits of agreement: -14.0 to 14.4 mL/m2 and -26.3 to 24.5%, respectively) and showed a good correlation (r = 0.79 and r = 0.76, respectively; P < 0.05 each). Good levels of correlation were observed between echocardiographic severity grading and quantitative measurements of regurgitation volume and fraction, which were somewhat better between echocardiography and electron-beam CT (rS = 0.78 and rS = 0.84, respectively; P < 0.05 each) than between echocardiography and catheterization (rS = 0.72 and rS = 0.81, respectively; P < 0.05 each).

CONCLUSION

Our results suggest that electron-beam CT allows for quantification of mitral valve regurgitation with similar accuracy as cardiac catheterization. Measurements with both modalities correlated well with the results of echocardiographic assessment.

Relation of nonperfused myocardial volume and surface area to left ventricular performance in coronary microembolization

BACKGROUND

After occlusion of an epicardial artery, left ventricular (LV) dysfunction is closely related to the volume of nonperfused myocardium (NPM). The impact of coronary microembolization (ME) on LV function, however, is larger relative to the total volume of NPM. We hypothesized that the total surface area (SA), rather than the total volume, of NPM is the major determinant of ME-induced LV dysfunction.

METHODS AND RESULTS

We injected microspheres of 10-, 30-, or 100-microm diameter at each of 3 doses selectively into the left anterior descending coronary artery of 48 anesthetized pigs. Electron beam computed tomography (CT) was used to measure regional myocardial perfusion and changes in LV wall thickening (DeltaWT) and stroke volume (DeltaSV) after ME. At postmortem, a transmural "biopsy" of 1 to 2 cm3 of embolized myocardium was imaged by micro-CT, resulting in 3D images that provided volumes and SAs of the individual nonperfused foci. Additionally, in 9 pigs, creatine phosphokinase (CK) activity in embolized myocardium was measured as an index of washout of substances from the NPM. After ME, DeltaWT, DeltaSV, and CK washout were correlated more closely with the total SA (r=0.95, P<0.001; r=0.68, P<0.01; and r=0.88, P=0.01, respectively) than with the total NPM volume (r=0.59, P>0.05; 0.46, P>0.05; and r=0.69, P=0.04, respectively).

CONCLUSIONS

After coronary ME, LV dysfunction is more closely related to the total SA than to the total volume of nonperfused microregions in the myocardium.

Determination of Cardiac Output With Multislice Spiral Computed Tomography

OBJECTIVE

To validate and to determine the reproducibility of cardiac output (CO) measurements based on a test-bolus examination in multislice spiral computed tomography (MSCT) in comparison with invasively measured CO using the thermal dilution technique.

MATERIAL AND METHODS

In 8 swine, CO was determined by invasive thermal dilution technique and by analysis of enhancement data from dynamic MSCT test-bolus examinations. To assess reproducibility, all MSCT examinations were performed twice. Results were compared using Pearson's correlation coefficient and Bland-Altman plots.

RESULTS

Measure by thermal dilution technique CO was 3.71 +/- 1.12 L/min, whereas CO was 3.67 +/- 1.30 L/min using MSCT. Pearson's correlation coefficient was 0.89. The average deviation between MSCT and thermal dilution technique was 0.04 L/min with a standard deviation of 0.59 L/min. There was a good agreement between both MSCT measurements with a mean deviation of -0.03 L/min and a standard deviation of 0.51 L/min.

CONCLUSION

CO can reliably be determined from MSCT by means of indicator dilution technique. Measurements are reproducible and provide valuable information on the overall cardiovascular performance without application of additional contrast material or radiation. As this technique does not require time-consuming postprocessing it can be added to routine reporting.

Measurement of cardiac output from a test-bolus injection in multislice computed tomography

The aim of this study was to assess the feasibility of non-invasive determination of cardiac function from test-bolus data in multislice spiral computed tomography (MSCT). In 25 patients enhancement data gathered from a standardized test-bolus injection were analyzed. The test-bolus examination was performed prior to a retrospectively ECG-gated MSCT of the heart. A time-attenuation curve was obtained in the ascending aorta at the level of the pulmonary arteries. A gamma variate fit was applied to the curve in order to exclude recirculation and get pure first-pass data. Using the known amount of iodine injected, cardiac output (CO), and stroke volume (SV) were determined from integration of the fitted contrast enhancement curve using a reformation of the Stewart-Hamilton equation. Results were compared with CO and SV calculated from the geometric analysis of the retrospectively gated MSCT data using the ARGUS Software (Siemens, Forchheim, Germany). The CO and SV determined from test-bolus analysis and from geometric analysis correlated well with Pearson's correlation coefficients of 0.87 and 0.88, respectively. The standard deviation of the difference between both methods was 0.51 l/min for CO (8.6%) and 11.0 ml for SV (12.3%). Non-invasive quantification of CO seems to be feasible from a standard test-bolus injection. It provides valuable information on cardiac function without additional radiation or application of contrast material.

A Physiologically Based Approach for the Estimation of Recirculatory Parameters

Indicator dilution studies are used to provide estimates for several physiological parameters such as cardiac output as well as intra- and extravascular volumes. This study introduces a novel technique for the estimation of recirculatory parameters. A mathematical model based on a dispersion-convection partial differential equation (PDE), derived from the fractal geometry of the vascular tree and the hydrodynamics of the blood flow, is used to describe the spatiotemporal profile of tracers in the circulatory system. Initially, the equation is fitted to concentration-time (C,t) data of a tracer to derive the parameter estimates of the model equation; in a subsequent step, these estimates along with appropriate changes of the parameters of the PDE are used to generate the early concentration-time profile of a hypothetical appropriate tracer without recirculation. Thus, the area under the concentration-time curve of the first passage of the tracer is calculated and used for the estimation of various physiological parameters, including cardiac output, miscellaneous partial blood volumes, and the corresponding mean transit times. The procedure was applied successfully to literature data of various tracers from humans and dogs.

Quantification of mitral valve regurgitation by left ventricular volume and flow measurements using electron beam computed tomography: comparison with magnetic resonance imaging

PURPOSE

This study was designed to evaluate electron beam computed tomography (CT) for quantifying mitral regurgitation in comparison with magnetic resonance (MR) imaging as a reference method.

METHOD

Forty-three patients, among them 33 with known mitral regurgitation, underwent electron beam CT and MR imaging. Total left ventricular stroke volume (TSV), antegrade stroke volume (ASV), and mitral regurgitation volume (MRV) and fraction (MRF) were determined and compared between the two modalities. Additionally electron beam CT measurements were compared with the corresponding echocardiographic findings.

RESULTS

Significant differences between electron beam CT and MR imaging were found for measurements of TSV and MSV but not for ASV and MRF. There was a close linear correlation between both modalities for all parameters. Furthermore, there was good agreement between electron beam CT and echocardiography, although electron beam CT shows a tendency to overestimate mitral regurgitation slightly.

CONCLUSION

The results indicate that electron beam CT offers an additional procedure for quantifying mitral regurgitation and that it may be used as an alternative to MR imaging.

[Visualization by dynamic CT: invention of 2D-CT chronogram]

Dynamic computed tomography is one of the methods used for the functional analysis of blood flow information. We devised a simple method of visualization for dynamic CT. Re-sliced images were stacked as multi-slice images for the different acquisition times to show a continuous spatial arrangement with dynamic data. Images processed into re-sliced images termed 2D-CT Chronograms were observed in many directions and were useful for comprehending the blood flow function of the target organ. Time-density curves with motion dependency and color displays similar to those of ultrasound images are easily acquired from the 2D-Chronogram. We introduce some clinical applications of the 2-D Chronogram.

[Right ventricular function: physiological and physiopathological features]

Sinus and conus constitute the two cavities of the right ventricle. They are anatomically and functionally different. The sinus is a flow-generator and the conus a pressure-regulator. The coronary circulation of the right ventricle is provided by the right coronary artery and the left anterior descending artery. The right ventricle is perfused during systole and diastole. When oxygen demand increases, coronary arteries dilate and oxygen extraction rises. As for the left ventricle, right ventricular performance depends upon heart rate, rhythm, contractility and loading conditions. Ventricular interactions are very important for right ventricular function. Loading conditions and contractility of the left ventricle are of major significance for right ventricular performance. For the right ventricle, the end of the ejection is different from the end of the active contraction. The time between them allows to achieve ventricular emptying. This duration is linked to afterload. Presently, it is impossible to accurately and simply assess these conditions. Pressure and volume overloadings result in right ventricular failure. They are responsible for ventricular dilation and ischaemia with a decrease in cardiac output, generating a vicious circle. Treatment includes the removal of the cause, and the maintenance of systemic arterial pressure and biventricular contractility. It is difficult to assess the effects of intravenous vasodilators on right ventricular afterload.

Intracardiac echocardiography: in vitro and in vivo validation for right ventricular volume and function

To determine the feasibility and accuracy of intracardiac ultrasonography (ICUS) for the measurement of right ventricular (RV) volumes and function, a 10 MHz ICUS catheter was used in an in vitro and in vivo model. In the in vitro study, 16 sheep hearts were imaged. Sequential cross-sectional images from RV apex to base were recorded during a calibrated pullback. Volumes were calculated by applying Simpson's algorithm. ICUS-obtained volumes correlated well with actual volumes (standard error of estimate [SEE] = 2.3 ml, r = 0.98). For the in vivo study, a beating-heart canine model was used (31 hemodynamic stages in six dogs). Actual volumes were measured by an intracavitary balloon connected to an external column. Sequential cross-sectional images were recorded during the ICUS catheter pullback from apex to base of the RV, and volumes calculated by Simpson's algorithm. Good correlations were observed between ICUS and actual values for diastolic (SEE = 4.1 ml, r = 0.97), systolic (SEE = 3.4 ml, r = 0.96), and ejection fraction (SEE = 3.1%, r = 0.87) values. This new technique can accurately quantitate RV volumes, can function both in vitro and in vivo, and has the potential for increasing applications to questions of clinical and research interest.

Measurement of right ventricular volume in human explanted hearts using ultrafast cine computed tomography

The quantitative measurement of right ventricular (RV) volume has been attempted by a number of methods, including nuclear magnetic resonance imaging, contrast angiography, echocardiography, and radionuclide angiography. All of these methods have limitations. Ultrafast cine computed tomographic (CT) scan is a new technology that may have an important role in on-line ventricular volume measurements. Twelve human explanted hearts, fixed in formalin, were subjected to ultrafast cine CT scans to estimate RV volume. The volumes derived from the CT scans were compared with actual fluid volumes needed to fill the RV volume measurements. All measurements were conducted independently by two observers. Actual RV volumes in the 12 hearts ranged from 29.8 ml to 174.6 ml. A strongly significant correlation between actual volume and CT volume was seen (r = 0.99). Agreement between observers was also seen to be highly significant (r = 0.992). Limitations to accurate in vivo assessment due to bolus injection of contrast medium might include alterations in ventricular pressure change. Similarly, differentiation of the endocardial border with contrast may not be as sharp as that with an air-tissue interface. This study demonstrates that RV volumes can be reliably determined by ultrafast cine CT scans in explanted hearts. On-line systolic and diastolic volumes and thus stroke volume, ejection fraction, etc, can be accurately defined independent of cardiac orientation. This technique offers opportunities to study ventricular function under various conditions.